Copyright by Silvia Esquivel Muñoz 2013

Copyright

by

Silvia Esquivel Muñoz

2013

The Dissertation Committee for Silvia Esquivel Muñoz certifies that this is the

approved version of the following dissertation:

PSYCHOSOCIAL INFLUENCES OF

ACCULTURATION AND ACCULTURATIVE STRESS ON

LEPTIN, ADIPONECTIN, AND GESTATIONAL DIABETES IN MEXICAN AMERICAN

WOMEN DURING PREGNANCY

Committee: ____________________________________ Eileen K. Kintner, Supervisor ____________________________________ Heather Becker ____________________________________ Alexandra Garcia ____________________________________ Diane Tyler ____________________________________ R. Jeanne Ruiz

PSYCHOSOCIAL INFLUENCES OF ACCULTURATION AND ACCULTURATIVE

STRESS ON



by

Silvia Esquivel Muñoz, BSN, MSN

Dissertation

Presented to the Faculty of the Graduate School of

The University of Texas at Austin

in Partial Fulfillment

of the Requirements

for the Degree of

Doctor of Philosophy

The University of Texas at Austin

December 2013

Dedication

I would like to dedicate this dissertation to the most self-less and caring individual I have

had the privilege to have in my life, Don Juan Esquivel, for embodying the true

meaning of unconditional love and respect. Everything I have accomplished has been

because of his selfless acts and support. He will never be forgotten and will always be

admired.

v

Acknowledgments

I would like to express my full gratitude to everyone who made this possible.

Ernesto Muñoz, for giving me his full support, patience and always believing in me.

My mother Margarita Esquivel and all my family for reminding me Que, Si Se Puede.

Dr. Jeanne Ruiz, for awakening my curiosity, nurturing my imagination, guiding me

through the scientific process, making me believe that the possibilities are endless,

sharing her data, and making this study possible.

Dr. Eileen Kintner, for directing my thought process, always keeping me on task,

reminding me to think like a scientist, and nurturing my confidence.

Dr. Heather Becker, Dr. Alexandra Garcia, Dr. Diane Tyler, for participating in the

dissertation committee, reading the chapters, offering guidance, and support.

The University of Texas at Austin School of Nursing Doctoral Program Faculty, for

fostering scientific learning, teaching future scientists, promoting research, and nursing

science.

Dr. Julie Zuñiga, my good friend who shared her own experiences with the doctoral

program and gave me insight on what was coming ahead.

S. Maggie McCray, my colleague and friend who sat next to me at work and listened to

every school story, listened without judgment, and reminded me it was all possible.

vi

PSYCHOSOCIAL INFLUENCES OF

ACCULTURATION AND ACCULTURATIVE STRESS ON



Silvia Esquivel Muñoz Ph. D

The University of Texas at Austin, 2013

Supervisor: Eileen Kintner

The purpose of this biobehavioral study was to explore relationships between

psychosocial stressors of acculturation, acculturative stress, and metabolic markers of

leptin and adiponectin in Mexican American women with and without GDM. A case

control design was used for this secondary analysis which included a sample of 38

pregnant women with GDM and 38 healthy controls without GDM, who were matched on

age and BMI status. Subjects completed two surveys—the Multidimensional

Acculturation Scale II (MASII) and the Multidimensional Acculturative Stress Inventory

(MASI)—which measured acculturation and acculturative stress. Descriptive statistics,

Pearson r correlations, and independent sample t-tests were used to analyze the data.

The results from this study indicated that significant relationships do exist between some

of the variables of interest; however, there were no overall significant differences found

between women with and without gestational diabetes. These mixed results may be an

indicator of a need to further explore these concepts.

vii

TABLE OF CONTENTS

ABSTRACT ............................................................................................................................. vi LIST OF TABLES .................................................................................................................... x LIST OF FIGURES .................................................................................................................. xi CHAPTER I. INTRODUCTION ................................................................................................ 1

Diabetes ............................................................................................................................ 1 Altered Glucose Metabolism .............................................................................................. 3 Purpose ............................................................................................................................. 6 Significance to Nursing ...................................................................................................... 7 Assumptions ...................................................................................................................... 7 Conceptual Framework ..................................................................................................... 8 Concepts ........................................................................................................................... 12

Gestational Diabetes Mellitus .................................................................................... 12 Psychosocial Stress .................................................................................................. 13

Acculturation .................................................................................................... 14 Acculturative Stress ......................................................................................... 14

Metabolic Responses ................................................................................................ 15 Leptin ............................................................................................................... 15 Adiponectin ...................................................................................................... 16

Research Questions .......................................................................................................... 16 Summary ........................................................................................................................... 17

CHAPTER II. REVIEW OF THE LITERATURE ....................................................................... 19

Hypothalamic-Pituitary-Adrenal Axis .................................................................................. 19 Psychosocial Stress .......................................................................................................... 20 Stress in Mexican American Women ................................................................................. 25

Acculturation ............................................................................................................. 25 Acculturative Stress .................................................................................................. 27

Metabolic Response to Stress ........................................................................................... 29 Leptin ........................................................................................................................ 36 Adiponectin ............................................................................................................... 38

Gestational Diabetes ......................................................................................................... 40 Summary ........................................................................................................................... 41

CHAPTER III. METHODS ...................................................................................................... 43

Institutional Review Board Approval .................................................................................. 43 Research Design ............................................................................................................... 43

Sampling Procedures ................................................................................................ 44 Case-control Sample ................................................................................................ 45 Recruitment of Subjects for the Parent Study ........................................................... 46 Securing Informed Consent ...................................................................................... 46

viii

Ethical Considerations ....................................................................................................... 47 Protecting human rights of subjects ......................................................................... 47 Balancing benefits and risks of a study .................................................................... 48

Measures .......................................................................................................................... 48

Multidimensional Acculturative Stress Inventory (MASI) .......................................... 49 Multidimensional Acculturation Scale II (MAS II) ...................................................... 49 Leptin ........................................................................................................................ 51 Adiponectin ............................................................................................................... 52

Data Collection Procedures .............................................................................................. 52 Survey Data .............................................................................................................. 52 Physiologic Data ....................................................................................................... 52

Data Analysis ................................................................................................................... 53 Physiologic Data ....................................................................................................... 53

Threats to Design Validity ................................................................................................. 55 Statistical Validity ..................................................................................................... 55 Internal Validity ........................................................................................................ 55 Construct Validity ..................................................................................................... 56 External Validity ....................................................................................................... 56

Summary .......................................................................................................................... 56 CHAPTER IV. RESULTS ........................................................................................................ 57

Description of Sample ...................................................................................................... 57 Demographic Statistics ............................................................................................. 57

Gestational Diabetes Group ............................................................................. 57 Healthy Control Group (Non-Gestational Diabetes) .......................................... 58

Biologic Characteristics ............................................................................................. 60 Measures .................................................................................................................. 62

Multidimensional Acculturation Scale (MAS II) ................................................. 62 Multidimensional Acculturative Stress (MASI) .................................................. 62 Leptin ............................................................................................................... 64 Adiponectin ...................................................................................................... 64

Research Questions ......................................................................................................... 65 Research Question 1 ................................................................................................ 65 Research Question 2.1 ............................................................................................. 73 Research Question 2.2 ............................................................................................. 73

Summary ........................................................................................................................... 75

CHAPTER V. DISCUSSION AND SUMMARY ...................................................................... 76

Interpretation of Findings .................................................................................................. 76 Psychosocial Stress .................................................................................................. 76 Metabolic Response ................................................................................................. 78 Gestational Diabetes................................................................................................. 80

Limitations ........................................................................................................................ 81 Self-Report Measures ............................................................................................... 81

ix

Sample Size ............................................................................................................ 81 Matching Techniques ................................................................................................ 82

Application to the Development of Nursing Theory ........................................................... 82 Implications for Nursing Practice ...................................................................................... 83 Recommendations for Future Research ........................................................................... 85 Summary .......................................................................................................................... 86

APPENDIX A .......................................................................................................................... 88 APPENDIX B .......................................................................................................................... 97 REFERENCES ........................................................................................................................ 98

x

LIST OF TABLES

TABLE 1.1 Definitions of Concepts Contained in the Psychosocial Stress and

Metabolic Response in Gestational Diabetes Mellitus Model ..............................10 TABLE 2.1 Summary of Studies on Acculturation and Acculturative Stress in Mexican

Americans ..............................................................................................................22

TABLE 2.2 Summary of Studies Investigating Leptin and Adiponectin in Gestational

Diabetes.................................................................................................................31

TABLE 4.1 Demographic Characteristics of Women with and without Gestational

Diabetes.................................................................................................................59

TABLE 4.2 Biologic Characteristics of Women with and without Gestational Diabetes

...............................................................................................................................61

TABLE 4.3 MASII and MASI Subscale Survey Scores ...........................................................63

TABLE 4.4a Correlations among Study Variables ....................................................................71

TABLE 4.4b Correlations among Study Variables ....................................................................72

TABLE 4.5 Independent t-test Analysis of Difference between Women with and

Without Gestational Diabetes................................................................................74

xi

LIST OF FIGURES

FIGURE 1.1 Psychosocial Stress and Metabolic Response in Gestational Diabetes

Model .....................................................................................................................11

1

CHAPTER I

INTRODUCTION

This chapter addresses the need for this research by describing the health

problem and summarizing the impact of altered glucose metabolism. The purpose of the

study and its significance for nursing are presented. Assumptions are delineated and the

conceptual framework is specified. Next, concepts are defined and hypotheses are

presented for relationships among the concepts. Finally, the research questions are

posed.

Diabetes

Diabetes is a metabolic disease characterized by hyperglycemia resulting from

defects in insulin secretion, insulin action, or both (American Diabetes Association

[ADA], 2011), and is the seventh leading cause of death in United States (Centers for

Disease Control and Prevention [CDC], 2011). Type 2 diabetes (T2DM) accounts for

between 90% and 95% of those with diabetes, and encompasses individuals who have

both insulin resistance and relative insulin deficiency (ADA, 2011). Alterations in glucose

metabolism lead to high levels of glucose in the blood, which places the body at risk for

altered processes that can cause complications of T2DM including cardiovascular

disease, renal and neurological diseases, blindness, and lower limb amputations (CDC,

2011). Some of the major risk factors for T2DM include obesity, Hispanic ethnicity, and

history of Gestational Diabetes Mellitus (GDM).

GDM is any degree of glucose intolerance with onset or first recognition during

pregnancy (ADA, 2011). GDM consists of a combination of insulin resistance and beta

cell dysfunction that leads to altered carbohydrate metabolism (Retnakaran et al., 2003).

Approximately 7% of all pregnancies are complicated by GDM, resulting in more than

2

200,000 cases annually (ADA, 2011; CDC 2011). It is estimated that between 35% and

60% of women who had GDM will develop T2DM within 10 to 20 years of the pregnancy

(ADA, 2011; CDC. 2011). The combination of the risk factors of high prevalence of

obesity and Hispanic ethnicity places Mexican American women with a history of GDM

at very high risk for later development of T2DM.

Diabetes is more common in Hispanics, affecting 11.8% of this population

compared to 7.1% of non-Hispanic White Americans (CDC, 2011). Prevalence of

diabetes among Mexican Americans has reported to be even greater—14% (CDC,

2011). Hispanic Americans also are at increased risk for diabetes complications due to

increased poverty and lack of health insurance (CDC, 2011; Black, 2002).

In 2010, Hispanics accounted for the majority of the nation’s increase in

population (Passel, Cohn, & Lopez, 2011). The population increase was largely due to

migration and high birth rates among Hispanics (Lawrence, 2010). The U.S. Census

projects that people of Hispanic descent will become the largest minority group in the

country by 2050, with Mexican Americans comprising the vast majority of this group

(Passel et al., 2011). This population shift and changes in the needs of this growing

population group will likely create a demand for changes in our current health system.

Obesity and physical inactivity are major risk factors for both T2DM and GDM

(ADA, 2011; Black, 2002). Obesity is thought to induce insulin resistance and altered

glucose metabolism (Wellen & Hotamisligil, 2005). Obesity also is associated with a

state of chronic subclinical inflammation that can affect metabolic and immune pathways

(Wellen & Hotamisligil, 2005). Mexican American women are at increased risk for

obesity compared to non-Hispanic White Americans (Black, 2002). Mexican American

women of childbearing age have a high prevalence of obesity, with about 45%

3

considered obese and 70% being overweight (CDC, 2011; Flegal, Carroll, Ogden, &

Curtin, 2010).

Mexican American women comprise a vulnerable population and are at

increased risk for obesity, GDM, T2DM, and psychosocial stress related to poverty,

acculturation, and acculturative stress (Gallo, Jimenez, Shivpuri, Espinosa de los

Monteros & Mills, 2010; Wellen & Hotamisligil, 2005). The projected population growth

among Mexican Americans will create an increased demand for the delivery of culturally

appropriate health care for a population that is misunderstood and vulnerable, especially

women of childbearing years. Understanding how acculturation and acculturative stress

affect childbearing Mexican American women can potentially help health care providers

establish a risk profile for earlier recognition of GDM, thus decreasing fetal exposure to

the GDM environment and decreasing or preventing future T2DM in pregnant women

with GDM and their children.

Altered Glucose Metabolism

Women who develop gestational diabetes mellitus (GDM) have up to a 60% risk

of developing T2DM later in life (ADA, 2011; Lawrence, 2010). Fetuses exposed to the

GDM environment have higher rates of obesity and are at increased risk for T2DM as

adults (Lawrence, 2010; Otero et al., 2006). Diabetes is characterized by altered glucose

metabolism that decreases the production of insulin and resistance to the existing insulin

(ADA, 2011). Pregnant women are screened for GDM during the latter part of the

second trimester, which potentially exposes the fetus to the effects of altered glucose

metabolism over the first 24–28 weeks of gestation. Although biological influences of

GDM have been studied (Lawrence, 2010; Otero et al., 2006; Wellen & Hotamisligil,

2005), little is known about psychosocial influences on GDM; specifically, chronic

4

psychosocial stressors of acculturation and acculturative stress and their influence on

metabolic processes.

Mexican Americans experience increased prevalence of psychosocial stress

related to acculturation and acculturative stress, making them vulnerable to disease.

Stress in Mexican American women who are actively engaged in acculturation is

referred to as acculturative stress (Caplan, 2007). Acculturation is defined as a dynamic

and multi-faceted process by which individuals from one culture acquire traits or

acclimate to a new culture (Johnson, Carroll, Fulda, Cardarelli, & Cardarelli, 2010;

Schwartz & Zamboango, 2008). Acculturative stress is defined as the psychosocial and

physiological impact of adapting to a new culture as a result of changes in environment,

language, and finances (Torres, 2010). The impact of psychosocial stress, in particular,

distancing from extended family members and culture of origin, can potentially result in

mental health problems such as anxiety and depression (Hovey & Magana, 2000).

Physiologic stress can lead to inflammation, resulting in cell injury. Inflammation is a

cascade of biochemical reactions that attempt to heal and remove harmful stimuli and

restore cells to their normal function (McCance & Huether, 2002). Because inflammation

can cause changes in the insulin signaling pathways and result in altered glucose

metabolism, it has been implicated in diabetes (Wellen & Hotamisligil, 2005).

Physiological stress can also alter the metabolic markers of leptin and

adiponectin (Bouloumie, Curat, Miranville, & Sengenes, 2007). Leptin is a hormone

produced in white adipose tissue that has adipokine and cytokine properties (Otero et

al., 2006). As a pleiotropic hormone, it has a role in regulating energy homeostasis,

appetite, fat disposition, metabolism, and fertility (Bouloumie, Curat, Miranville, &

Sengenes, 2007; Henson & Castracane, 2005). Elavated levels of leptin are related to

5

obesity, inflammation, and risk for cardiovascular disease (Bouloumie, Curat, Miranville,

& Sengenes, 2007). Leptin is released in response to the amount of energy stored in the

adipose tissue (Bluther & Mantzoros, 2004). There are leptin receptors in the brain, liver,

ovaries, and skeletal muscle that stimulate neuro-endocrine, immune, and inflammatory

responses (Otero et al., 2006; Bluther et al., 2004). Leptin plays an important role in

controlling appetite and regulating food intake by signaling satiety in the brain

(Bouloumie, Curat, Miranville, & Sengenes, 2007). Additionally, leptin acts on monocytes

and macrophages to release pro-inflammatory cytokines that can cause changes to

vasculature, oxidative stress, and platelet aggregation (Bouloumie et al., 2007).

Obesity is characterized by elevated serum leptin levels primarily due to leptin

resistance or the body’s inability to respond to leptin (Otero et al., 2006). The resistance

is related to faulty leptin transport and saturation of leptin receptors resulting in high

levels of leptin (Otero et al., 2006). Elevated leptin levels have been linked to obesity,

hypertension, diabetes, and heart disease (Bouloumie et al., 2007). During pregnancy,

elevated leptin has been linked to GDM, preeclampsia, intrauterine growth restriction,

and the fetal origins of adult disease (Henson & Castracane, 2005; Kautzky-Willer,

2001). Investigations of leptin serum concentrations across pregnancy indicate that leptin

levels are positively correlated with BMI as well as insulin resistance both before and

during the pregnancy (Henson & Castracane, 2005; Kautzky-Willer, 2001). In contrast,

another study suggested that women with GDM may exhibit lower leptin levels

compared to their healthy counterparts (Festa, Shnawa, Krugluger, Schernthaner, &

Haffner, 1999).

Adiponectin is a polypeptide hormone secreted by the adipocytes in adipose

tissue, which has anti-inflammatory, anti-atherogenic, and insulin sensitizing properties

6

(Huang et al, 2007). Adiponectin prevents early inflammatory responses by preventing

the differentiation and maturation of white blood cells needed in the inflammatory

response (Huang et al, 2007). Adiponectin also affects the release and expression of

other anti-inflammatory mediators such as interleukin-10 (IL-10), which in turn limits anti-

inflammatory and immunosuppressive properties (Huang, et al., 2007). Adiponectin

further acts as an anti-atherogenic molecule by preventing aggregation of endothelial

cells and macrophages in vascular walls (Han et al., 2007). Macrophage suppression

also prevents vascular stenosis and decreases uptake of low-density cholesterol (Han et

al, 2007). Finally, adiponectin helps inhibit gluconeogenesis, which results in lower blood

glucose levels and a decrease in insulin resistance (Han et al., 2007).

High levels of adiponectin have been found to be protective against T2DM and

GDM, making adiponectin an important hormone in diabetes prevention. Dysregulation

of adiponectin and low levels of this hormone are predictive of GDM (Han et al., 2007;

Weerakeit et al, 2006). Increased adipose tissue decreases or stops the secretion of

adiponectin, which results in low adiponectin levels and loss of its beneficial properties.

Low adiponectin levels are also present in obese individuals (Han et al., 2007; Weerakeit

et al., 2006).

Purpose

The purpose of this study is twofold:

1. To explore relationships between the psychosocial stressors of acculturation

and acculturative stress in Mexican American women with and without

gestational diabetes.

2. To examine differences in the metabolic markers of leptin and adiponectin in

Mexican American women with and without gestational diabetes.

7

Mexican American women comprise a vulnerable population and are at

increased risk for obesity, GDM, T2DM, and psychosocial stress related to poverty,

acculturation and acculturative stress (Gallo et al., 2010; Wellen & Hotamisligil, 2005).

Exploring whether the psychosocial factors of acculturation and acculturative stress have

an impact on metabolic markers such as gestational diabetes, leptin, and adiponectin

will aid in supporting the importance of the delivery of culturally competent care.

Significance to Nursing

Nursing is a scientific discipline that promotes the well-being of the whole person

within historical, cultural, and social contexts that shape an individual’s response to her

environment (Fitzpatrick & Whall, 1989). Leininger’s theory of transcultural nursing

(1978,1985) proposed that culturally sensitive care begins with recognizing that

individuals are the sum of their historical, cultural, and social experiences. Betty Neuman

(1982) theorized that individuals actively seek to maintain a balance in the

interrelationship of stressors and environment in order to achieve health. Any

dysregulation of this balance can lead to altered health. Struggles and disharmony can

result in negative outcomes and an inability for the individual to attain optimal health

(Fitzpatrick & Whall, 1989). Leinininger’s theory of transcultural nursing and Neuman’s

systems model can help investigate relationships between psychosocial stress (e.g.,

acculturation and acculturative stress) and metabolic alterations in leptin, adiponectin,

and gestational diabetes.

Assumptions

The following assumptions provided the foundation for this study:

1. Women are unique individuals possessing a range of normal responses to

their environment.

8

2. Women desire to remain free of disease and want to promote the health of

their families.

3. Women are physiologically programmed to respond to environmental

stressors.

4. Repeated exposure to stressors alters homeostasis and physiological

processes.

5. Culture affects women’s responses to their environment.

6. The process of acculturation and acculturative stress can be stressful events

in persons not equipped or ready to confront change.

7. Acculturation and acculturative stress are psychosocial stressors.

These assumptions provided the foundation for specification of the Psychosocial

Stress and Metabolic Response in Gestational Diabetes Model. The model is based on

the allostatic load model (McEwen, 1988) and is consistent with Leininger’s theory

(1978, 1985), which states that culture and social contexts are major factors that

influence individuals’ responses to health. Neuman’s (1982) systems approach to

understanding stress responses and principles also was incorporated into the model.

The allostatic load model describes the physiological expense of a disruption of the

response systems to stress. It illustrates the physiological interrelationships that can lead

to dysregulation, which causes bodily functions to decline (McEwen, 1988). Thus, it

demonstrates that acculturation and acculturative stress are important factors that can

place individuals at risk for altered physiologic responses.

Conceptual Framework

A modified version of the allostatic load model was used to guide this

investigation of the relationships between the psychosocial markers of acculturation and

9

acculturative stress, the metabolic markers of leptin and adiponectin, and their

relationship in women with and without gestational diabetes mellitus. Definitions of the

model’s concepts are presented in Table 1 and relationships among the concepts are

illustrated in Figure 1.

10

Table 1.1 Definitions of Concepts Contained in the Psychosocial Stress and Metabolic Response

in Gestational Diabetes Mellitus Model

Concept Definition

Acculturation The process of transitioning and adapting from one culture into another culture.

Acculturative Stress

Stress that originates from stressors encountered during the process of acculturation, which can include anxiety, depression, feelings of marginality and alienation, heightened psychosomatic symptoms, and identity confusion.

Adaptation The biological process by which the body adjusts to repetitive external demands and threats.

Adiponectin A polypeptide hormone produced in adipose tissue that has anti-inflammatory, anti-atherogenic, and insulin sensitizing properties.

Allostasis The ability of the body to achieve homeostasis after a physiologic disruption.

Allostatic Load The physiological expense of the disruption of the response systems to stress.

Gestational Diabetes Mellitus (GDM)

Diabetes that occurs during pregnancy, generally diagnosed late in the second trimester.

Leptin A pleiotropic hormone produced in adipose tissue that plays a role in regulating energy homeostasis, appetite regulation, fat disposition, and metabolic, and fertility processes.

Metabolic Response

The physical and chemical processes that maintain body functions, including the anabolic and catabolic processes needed to sustain life.

Psychosocial Stress

Stress originating from personal, social, cultural, and external factors, and which elicit the biological response to stress.

Stress A multidimensional reaction that consists of psychosocial and physiologic factors that permit individuals to respond to a perceived threat.

11

Figure 1. Psychosocial Stress and Metabolic Response in Gestational Diabetes Model adapted from the Allostatic Load Model by McEwen, 1998. Chronic psychosocial stress leads to allostatic load, creating altered metabolic responses that can lead to gestational diabetes.

12

The chronic stressors of acculturation and acculturative stress experienced by

Mexican American women were integrated into the model of physiologic phenomena of

allostasis and allostatic load to highlight their potential impact on the metabolic response

of leptin, adiponectin, and GDM. The Psychosocial Stress and Metabolic Response in

Gestational Diabetes Model proposes that repetitive activation of the stress response,

which is seen in the process of acculturation and acculturative stress, disrupts the

metabolic responses, which results in changes in leptin and adiponectin levels and

potentially increased risk for GDM. Furthermore, disruption in allostasis or balance of the

stress response creates changes in immune and metabolic processes, which places the

body at increased risk for T2DM, cardiovascular disease, and mental health problems

(McEwen, 1998).

Concepts

Gestational Diabetes Mellitus

Gestational Diabetes Mellitus was defined as diabetes that occurs during

pregnancy and is detected late in the second trimester of pregnancy, between 24 and 28

weeks gestation. Clinically, women are screened with a 1-hour 50-gm glucose tolerance

test between 24–28 weeks gestation. Women who have values greater than 139 mg/dL

require a diagnostic 3-hour glucose 100-gm tolerance test. Two elevated values out of

four are diagnostic for GDM (Kapustin et al., 2008; Esakoff, Cheng, & Caughey, 2005).

Gestational diabetes is a major risk factor for T2DM; it is estimated that 35%–60% of

women who had diabetes during their pregnancy will develop T2DM within 10 to 20

years of the pregnancy (CDC, 2011). T2DM is a metabolic disease that affects glucose

metabolism resulting in a persistent state of hyperglycemia secondary to pancreatic beta

13

cell dysfunction and the cellular resistance to the effect of insulin that can lead to

vascular and neurological complications including stroke, neuropathies, amputations,

blindness, and kidney disease (McCance & Huether, 2002).

Psychosocial stress

Stress was theoretically defined as a multidimensional reaction that consists of

psychosocial and physiologic factors that elicit a response a threat (Selye, 1973).

Stressful events are mediated by the woman’s appraisal of the threat and available

coping mechanisms, including psychosocial, social, and cultural forces that enable the

woman to respond (Glanz & Schwartz, 2008; Selye 1973). Stress occurs when the

psychosocial and physiologic demands of the threat exceed the psychosocial and

physiologic coping mechanisms potentially resulting in allostatic load (McEwen, 1998).

The stress response consists of a cascade of physiological responses that maintain the

normative environment. The hypothalamic-pituitary-adrenal axis (HPA-axis) responds

with a cascade of neuroendocrine reactions that stimulate response systems to maintain

homeostasis (Vedhara & Irwin, 2007; McEwen, 1998). Over time, the repeated demands

on the body create a path towards adaptation. Chronic stress occurs when repeated

insults maintain the HPA-axis in a state of persistent activation, which creates a

hypersensory environment that can lead to a derangement of the physiologic harmony

and result in blunted stress responses (McEwen, 1998; Selye, 1973;). The hypersensory

state also leads to allostatic load that can harm the body’s normal functions and cause

changes in glucose metabolism, fat storage, and affective processes (Vedhara & Irwin,

2007; McEwen, 1998). Chronic stressors related to work, financial burdens, and

caregiving are associated with higher allostatic load that can contribute to physiological

dysregulation in Mexican American women (Gallo et al., 2010).

14

Psychosocial stress was defined as stress that originates from personal, social,

and external factors that elicit biological responses to stress. Because it causes changes

to the connectivity of brain networks, psychosocial stress has been strongly associated

with impaired affective (mood) functioning, including depression and anxiety (Liston,

McEwen, & Casey, 2009). Increased psychosocial stressors, such as maternal anxiety

during pregnancy, have been associated with altered infant development at 12 months

(Davis & Sandman, 2010). Additionally, psychosocial stress has been associated with

poor pregnancy outcomes, including increased risk for low birth weight (Hobel,

Goldstein, & Barrett, 2008). In this study, acculturation and acculturative stress were

used as indicators of psychosocial stress.

Acculturation. Acculturation was defined as the process of transitioning and

adapting from one culture into another culture (Carter-Porkras et al., 2008). During this

process, individuals experience change and are exposed to a state of stress that

requires them to use previously learned coping strategies to help them regain a state of

balance (Ward, 2006). Reaching balance may not always be possible, resulting in

altered coping mechanisms that lead to dysfunction. Acculturation among Mexican

Americans has been associated with poor health outcomes, including higher rates of

obesity, diabetes, and mental illness (Carter-Pokras, et al., 2006; Kaester, Pearson,

Keene, & Geronimus, 2009).

Acculturative Stress. Acculturative stress was defined as stress that originates

from stressors encountered during the process of acculturation. This type of stress often

includes anxiety, depression, heightened psychosomatic symptoms, identity confusion,

and feelings of marginality and alienation (Berry & Williams, 1991). Acculturative stress

can result in negative health outcomes and place individuals at risk for disease.

15

Acculturative stress is a significant positive predictor for depressive symptoms that affect

well-being among college students (Iturbide, Raffaelli, & Carlo, 2009).

Metabolic Responses

Metabolic responses were defined as the physical and chemical processes that

maintain body functions, including the anabolic and catabolic processes needed to

sustain life. Chronic stress can impair normal physiologic functions and interfere with

metabolism, growth, reproduction, and immune responses (Kyrou & Tsigos, 2009).

During stress, the body is programmed to activate the HPA-axis, which results in the

release of a series of hormones that help restore homeostasis. Repetitive activation can

result in HPA-axis failure and lead to altered hormonal pathways that render the stress

response system ineffective. Chronic stress is associated with elevated cortisol levels,

which puts individuals at risk for visceral fat deposits and obesity (Anagnostis, Athyros,

Tziomalos, Karagiannis, & Mikhailidis, 2009). Visceral fat is associated with metabolic

syndrome, diabetes, and cardiovascular disease. Leptin and adiponectin are hormones

that originate from the cells of adipose tissue. In this study, the adipocytes leptin and

adiponectin were used as markers of metabolic response to evaluate if chronic stress

affects these hormones.

Leptin. Leptin was defined as a pleiotropic hormone that has a role in regulating

energy homeostasis, appetite, fat disposition, metabolism, and fertility processes

(Bouloumie, Curat, Miranville, & Sengenes, 2007; Otero et al., 2006). High leptin levels

have been associated with obesity, diabetes, and mental health problems (Bouloumie et

al., 2007). Leptin levels can be quantified by an enzyme-linked immunosorbent assay

(ELISA).

16

Adiponectin. Adiponectin was defined as a polypeptide hormone produced in

adipose tissue that has anti-inflammatory, anti-atherogenic, and insulin sensitizing

properties. Low adiponectin levels have been associated with insulin resistance,

diabetes, and atherosclerosis (Linh, Pedersen, & Richelsen, 2006). Adiponectin levels

can be quantified by an enzyme-linked immunosorbent assay (ELISA).

Concepts contained in the Psychosocial Stress and Metabolic Response in

Gestational Diabetes Mellitus Model include acculturation, acculturative stress, levels of

leptin and adiponectin, and GDM. Definitions are provided in Table 1. Relational

statements proposed by the model and depicted in Figure 1 are:

1. Psychosocial stress is related to the process of acculturation and

acculturative stress.

2. Psychosocial stress is related to allostatic load.

3. Psychosocial stress is associated with changes in metabolic response.

3. Metabolic response is associated with changes in leptin and adiponectin

levels.

4. Changes in leptin and adiponectin levels are associated with gestational

diabetes mellitus.

Research Questions

The following research questions reflective of the specific aims were posed:

Specific Aim #1: To explore relationships between the psychosocial stressors

(i.e., acculturation and acculturative stress) and metabolic markers (i.e., leptin and

adiponectin levels) in Mexican American women with and without gestational diabetes.

17

Research Question 1. Is there a significant relationship between levels of the

psychosocial markers of acculturation and acculturative stress, and levels of the

metabolic markers of leptin and adiponectin?

Specific Aim #2: To examine differences in the levels of the metabolic markers

of leptin and adiponectin in Mexican American women with and without gestational

diabetes.

Research Question 2.1. Is there a significant difference in the levels of the

psychosocial markers of acculturation and acculturative stress between women

with and without gestational diabetes?


metabolic markers of leptin and adiponectin between women with and without

gestational diabetes?

Summary

Psychosocial stressors of acculturation and acculturative stress may alter the

metabolic response over time, which can result in abnormal glucose metabolism that can

lead to GDM and to potential future T2DM. Mexican American women have a greater

prevalence of GDM and Type 2 Diabetes Mellitus than White Americans. Earlier

identification of GDM would help decrease fetal exposure to the GDM environment and

have the potential to decrease or prevent future T2DM in both mother and child.

This chapter addressed the health problem of gestational diabetes mellitus in

Mexican American women and summarized the impact of altered glucose metabolism.

The purpose of the study and its significance for nursing were presented. Assumptions

were delineated and the conceptual framework was specified. Next, key concepts were

18

defined and relationships among these concepts hypothesized. Finally, the research

questions were posed.

19

CHAPTER II

REVIEW OF THE LITERATURE

This chapter presents a review of research literature on psychosocial stress,

metabolic response, and gestational diabetes in Mexican American women of

childbearing years. An overview of the hypothalamic-pituitary-adrenal axis (HPA axis)

stress response is discussed, and the major markers for psychosocial stress in Mexican

American women (i.e., acculturation and acculturative stress) are highlighted. The major

markers for metabolic response (i.e., leptin and adiponectin) also are described.

Hypothalamic-Pituitary-Adrenal Axis

The body responds to short-term episodes of stress by the process of adaptation.

This process also is known as allostasis (McEwen, 1998). Allostasis is the body’s ability

to achieve stability after a perceived threat. The body is able to reach allostasis by

creating a stable environment during high levels of stress by activating the stress

response (McEwen, 1998). The hypothalamic-pituitary-adrenal axis (HPA axis)

stimulates stress response systems that use the neurological, cardiovascular, and

endocrine systems simultaneously to counteract threats by releasing hormones that

target specific organs (Juster, McEwen & Lupien, 2010).

The hypothalamus acts as the central regulator of the stress response and

initiates a series of interactions that lead to behavioral and peripheral changes, which

help the body readjust to a state of homeostasis (Tsigos & Chrousos, 2002). Allostasis

helps regulatory systems change over time to adapt to the demands of the environment

(Power & Schulkin, 2012). During repetitive and long-term activation of the HPA-axis,

such as that experienced in chronic stress, dysregulation occurs, which places the

response systems at risk for allostatic load.

20

Allostatic load is a state of dysfunction that results from wear and tear on the

body and brain from chronic over-activity or inactivity of the physiological systems

involved in the stress response (McEwen, 1998). This state of physiologic overload

makes the body vulnerable to disease (Power & Schulkin, 2012) and has been linked

with cardiovascular disease, T2DM, and mental health problems (Keastner, Pearson,

Keene & Geronimus, 2009). Allostatic load from chronic stress also has been implicated

in poor pregnancy outcomes including intrauterine growth restriction, preterm delivery,

and preeclampsia (Lantendreese, 2009). Repeated activation of the HPA-axis disrupts

the hormonal mechanism by failing to fully disable the stress response, taxes the body,

and maintains the body in a hypersensory state that eventually fails to reach allostasis,

leading to allostatic load. Allostatic load can be quantified by using psychosocial and

physiologic markers that help determine risk for disease (Seeman, Singer, Rowe,

Horwitz & McEwen, 1997).

Psychosocial Stress

Psychosocial stress was defined as stress that originates from personal, social,

and other external factors that elicit biological responses (Liston, McEwen, & Casey,

2009). Psychosocial stress has been strongly associated with impaired mental

functioning (e.g., depression and anxiety) that results from changes in the connectivity of

brain networks (Liston, McEwen, & Casey, 2009). Increased psychosocial stressors,

such as maternal depression and anxiety during pregnancy, have been associated with

altered infant development at 12 months (Davis & Sandman, 2010). Additionally,

psychosocial stress has been associated with poor pregnancy outcomes including

increased risk for low birth weight (Hobel, Goldstein, & Barrett, 2008).

21

Many Mexican American women who have immigrated to the United States

experience psychosocial stressors including acculturation and acculturative stress,

putting them at risk for psychosocial stress. A literature review and synthesis that

identified studies examining acculturation and acculturative stress as markers of

psychosocial stress in Hispanics including Mexican American women is summarized.

A systematic literature review was conducted to explore the information available

on acculturation and acculturative stress. The electronic search engines used to find

articles for this review were PubMed and CINAHL. The search terms used for this review

were acculturation, acculturative stress, Mexican Americans, Latinos, and Hispanic.

Using these terms, PubMed and CINAHL generated a total of 244 articles. Next, these

articles were examined for inclusion criteria, which included peer-reviewed articles and

research studies published in the past five years; this resulted in 43 articles. Next, from

these articles, those that were not peer-reviewed, that focused on animal studies,

descriptive articles, dissertations, and review articles were eliminated. After excluding

these publications, only 10 articles were identified as being relevant to this study.

Information for the studies reviewed is provided in Table 2.1.

22

Table 2.1

Summary of Studies on Acculturation and Acculturative Stress in Mexican Americans

Author, Year

Purpose Design Sample Results Conclusion

Buscemi, Williams, Tappen, & Blais, 2012

To identify relationships between acculturation and health in Hispanic elders.

Descriptive Correlational

N= 132

Acculturation had a significant positive influence on mental health but not on physical health status.

Individuals with greater acculturation reported better mental health but not physical health.

Torres, Driscoll, & Voell, 2012

To investigate the role of acculturative stress in the relationship between discrimination and distress and to examine the ability of acculturation to serve as a moderator between perceived discrimination and distress.

Cross Sectional

N = 669

Acculturative stress mediates the perceived discrimination-psychosocial distress relationship; perceived discrimination is moderated by Anglo-orientation.

Perceived discrimination was related to increased acculturative stress and psychosocial distress.

Perez-Escamilla, 2011

To examine the evidence for a link between acculturation, nutrition, and health disparities in Latinos.

Systematic Literature Review

8 studies

Associations were found between acculturation, nutrition, and health disparities..

These relationships are not linear; longitudinal studies are needed for further evaluation.

Ceballos & Palloni, 2010

To evaluate the “acculturation paradox” and investigate the selective return migration hypothesis on birth outcomes.

Cross Sectional

N = 539

Length of stay in the U.S. had a significant, nonlinear relationship with birth outcomes; acculturation was not significantly relationship to birth outcomes.

The “Acculturation Paradox” has little effect on birth outcomes. Birth outcomes are more likely affected by the selective return migration mechanism.

23

Table 2.1 continued


Author, Year Purpose Design Sample Results Conclusion

Johnson, Carroll, Fulda, Cardarelli, & Cardarelli, 2010

To investigate the relationship between acculturation and self-reported health.

Cross Sectional

N = 135

Mexican-oriented participants were about 3 times more likely to report fair to poor self-reported health compared to Anglo-oriented participants.

Acculturation levels in Mexican Americans had an effect on their self-reported health.

Negy, Hammons, Reig-Ferrer, & Carper, 2010

To examine the relationship between acculturative stress and marital distress in immigrant women and explore acculturation, ethnic identity, and social support.

Cross Sectional

N = 95 Acculturative stress was significantly associated with higher marital distress; acculturative stress significantly predicted marital distress, while social support mediated the relationship between acculturative stress and marital distress.

Social support is an important factor in acculturative stress and marital distress.

Torres, 2010 To investigate the ability of acculturation, acculturative stress, and coping to predict different levels of depression in Latinos.

Cross Sectional

N = 148

The high depression group significantly endorsed an Anglo orientation and English competency.

The pressures and demands of acculturation pose an increased risk for mental health problems.

24

Table 2.1 continued


Author, Year


Iturbide, Raffaelli, & Carlo, 2009

To investigate whether different ethnic identity components moderate the association between acculturative stress and psychosocial adjustment in Mexican American college students.

Cross Sectional

N = 148

Ethnic affirmation/belonging moderated the relationship between acculturative stress and depression; acculturative stress was negatively correlated with self-esteem and positively with depression.

Acculturative stress is an important factor to consider when evaluating well-being of Mexican origin college students.

Campos, Schetter, Walsh & Schenker, 2007

To examine whether Mexican and Anglo orientation in pregnant women demonstrate different patterns associated with stress, pregnancy anxiety, and infant birth weight.

Cross Sectional

N = 1064

Acculturation was significantly associated with greater perceived stress, but was not significantly associated with pregnancy anxiety and low birth weight.

Acculturation is multidimensional and is influenced by other psychosocial factors.

Carter-Pokras, 2008

To compare health status indicators between U.S. and Mexican-born Mexican Americans using proxy measures of acculturation.

Systematic Literature Review

90 studies

U.S.-born Mexican Americans have higher morbidity and mortality compared to Mexico-born immigrants.

The longer individuals reside in the U.S. the more likely they are to engage in behaviors that are not health promoting.

25

Stress in Mexican American Women

Acculturation

Acculturation is a multidimensional process that occurs when individuals who are

transitioning into a new culture attempt to adopt the cultural traits and social patterns of

the dominant culture (Carter Porkras et al., 2008; Hovey, 2000). As they experience the

acculturation process, women undergo a state of stress and use previously learned

coping strategies to help them regain a state of balance (Ward, 2006). However, these

previously learned coping strategies may not always be sufficient to help women adapt

to the new environment. As a result, they may be forced to find new coping mechanisms,

which, in turn, can create chaos and disharmony as they slowly transition into the new

culture. Acculturation among Mexican Americans has been associated with poor health

outcomes including higher risk for obesity, mental distress, and diabetes (Carter-Pokras

et al., 2008; Kaester, Pearson, Keene, & Geronimus, 2009). In contrast, some

researchers have concluded that although more acculturated individuals may not report

better physical health, some report better mental health compared to less acculturated

individuals (Buscemi, Williams, Tappen, & Blais, 2012).

Acculturation also has been linked to depression and systemic inflammation

(Raison, Capuron, & Miller, 2006). Evidence suggests that more acculturated women

have a higher risk for depression, inflammation, and obesity (Ruiz, Stowe, Goluszko,

Clark, & Tan, 2007). A study that investigated acculturation and depression in Latinos

concluded that those experiencing higher levels of depression significantly endorsed an

Anglo orientation and reported greater English competency (Torres, 2010). The author

concluded that the pressures and demands of acculturation increase the likelihood of

mental health problems in this population.

26

Other studies have suggested that the relationship between acculturation and

health outcomes was not as clear. A study that evaluated acculturation, nutrition, and

health disparities in Latinos concluded that acculturation is associated with poor diet and

obesity. The author, however, was not convinced that these results were due to

acculturation, but rather may have been the result of other socioeconomic and

demographic factors such as income and nativity (Perez-Escamilla, 2011). He also

concluded that the relationship was not linear and required further evaluation through

longitudinal studies and more sophisticated statistical techniques.

Indicators of health status of U.S. and Mexico-born Mexican Americans vary, with

U.S.-born Mexican Americans having higher morbidity and mortality rates compared with

Mexico-born immigrants (Carter-Porkras, 2008). The authors believe that the longer

individuals reside in the U.S., the more likely they are to engage in behaviors that are not

health promoting including excess alcohol use, smoking, and drug use. Ceballos and

Palloni (2010) proposed that the negative effects seen with acculturation, specifically

related to birth outcomes, were due to the selective return hypothesis. This hypothesis

suggests that because healthier women are more likely to migrate these women also

have better birth outcomes because they began their pregnancy in better health.

Similarly, unhealthy women are more likely to stay in one place longer and exhibit poor

health outcomes because they were already in poor health. Migration may be a

demanding and possibly difficult event that those in good health are more likely to

consider.

In a study that examined acculturation as a moderator between perceived

discrimination and distress, the authors found that perceived discrimination is moderated

by Anglo behavioral orientation but not by Latino behavioral orientation (Torres, Driscoll,

27

& Voell, 2012). Anglo behavioral orientation is consistent with higher level of

acculturation and longer U.S. residence. Furthermore, a study that evaluated

relationships between acculturation and health in Hispanic elders aged 55-98 found that

acculturation had a significant influence on mental health status but not on physical

health status (Buscemi, Williams, Tappen, & Blais, 2012). In their study, individuals with

greater levels of acculturation reported better mental health but not physical health

although the literature reports that more acculturated Hispanics have better health

practices (Buscemi, Williams, Tappen, & Blais, 2012). Similarly, when investigating the

relationship between acculturation and self-reported health in Mexican Americans,

Mexican-oriented subjects were about three times more likely to report fair to poor health

as Anglo-oriented subjects (Johnson, Carroll, Fulda, Cardarelli, & Cardarelli, 2010). The

study concluded the process of acculturation and possibly the process of adapting to the

new environment resulted in perceptions of poor health.

Acculturative Stress

Acculturative stress was defined as stress that originates from stressors

encountered during the process of acculturation; it often includes anxiety, depression,

feelings of marginality and alienation, heightened psychosomatic symptoms, and identity

confusion (Berry & Williams, 1991). Acculturative stress can place individuals at risk for

negative health outcomes. Acculturative stress has been found to be a significant

positive predictor for depressive symptoms among college students when exploring

psychological factors that affect well-being (Iturbide, Raffaelli, & Carlo, 2009). In a study

that investigated the role of acculturative stress in perceived discrimination and

psychosocial distress, the authors (Torres, Driscoll, & Voell, 2012) found that

acculturative stress mediated the perceived discrimination-psychosocial distress

28

relationship. They concluded that perceived discrimination was related to increased

acculturative stress and psychosocial distress.

The process of acculturation is challenging, makes individuals feel vulnerable,

and places them at risk for acculturative stress. Acculturative stress can negatively affect

family relationships. A study that investigated the relationship between acculturative

stress and marital distress in immigrant women and explored acculturation, ethnic

identity, and social support found that acculturative stress was significantly associated

with and was a significant predictor of higher marital distress (Negy, Hammons, Reig-

Ferrer, & Carper, 2010). These authors also found that social support mediated the

relationship between acculturative stress and marital distress. These findings highlight

the importance of evaluating acculturative stress as a potential risk factor for altered

family functioning.

Hovey and Magana (2000) associated high levels of acculturative stress with

anxiety and depression in Mexican farm workers. Finch, Hummer, Kolody, and Vega

(2001) found that acculturative stress resulting from discrimination contributed to

negative ratings of health. The study concluded that individuals who experience

acculturative stress report not feeling well.

Allostatic load has been linked to chronic stress and has been implicated in

cardiovascular disease, T2DM, and mental health problems (Keastner, Pearson, Keene

& Gernonimus, 2009). Psychosocial stress, such as seen with acculturation and

acculturative stress, is a form of chronic stress (Berry & Sam, 1997) that can potentially

lead to allostatic load causing a derangement of the stress response (McEwen, 1998).

Although studies continue to explore the effects of acculturation and acculturative stress,

there is sufficient evidence to support that this form of psychosocial stress can have

29

negative effects, indicating that further studies are needed to explore whether

acculturation and acculturative stress can place the body in a state of allostatic load.

Metabolic Response to Stress

Metabolic responses were defined as physical and chemical processes that

maintain bodily functions, including anabolic and catabolic processes needed to sustain

life. Chronic stress can impair normal physiologic functions and interfere with

metabolism, growth, reproduction, immune response, and mental health (Kyrou &

Tsigos, 2009). During stress, the body is programmed to activate the HPA-axis, which

results in the release of a series of hormones that help restore homeostasis. Repeated

activation of the HPA-axis can result in hormonal failure and lead to altered hormonal

pathways that render the stress response system ineffective. Chronic activation of the

HPA-axis results in altered metabolic responses that lead to increased visceral adiposity

and decreased lean body mass (Tsigos & Chrousos, 2002). Chronic stress also is

associated with elevated cortisol levels, which place an individual at risk for visceral

adipose accumulation (Anagnostis, Athyros, Tziomalos, Karagiannis, & Mikhailidis,

2009), a condition that is associated with metabolic syndrome, diabetes, and

cardiovascular disease. Because leptin and adiponectin are hormones that originate

from the cells of adipose tissue, an increase in visceral adiposity may place persons at

risk for altered metabolic status. In the current study, the adipocytes leptin and

adiponectin were used as markers of the metabolic response to evaluate whether

chronic stress affects these hormones.

Women who develop GDM are in an altered metabolic state marked by

subclinical inflammation years before they exhibit signs and symptoms of disease, which

places them at risk for altered glucose metabolism, metabolic syndrome, and

30

cardiovascular disease (Di Cianni, 2007; Winzer, et al., 2004). Women who previously

had GDM have evidence of endothelial dysfunction, which is associated with insulin

resistance and pro-inflammatory cytokines (Winzer et al., 2004). Additionally, because

the level of insulin resistance and production is greatly affected by body mass, obese

women have greater insulin resistance than normal weight women (Volpe et al., 2007).

Obesity is a major contributing factor for GDM and is related to pro-inflammatory and

angiopathy processes (Winzer, 2004). There is evidence that pro-inflammatory cytokines

are present in adipose tissue, which significantly increases inflammation and risk for

insulin resistance, GDM, and T2DM (Wellen & Hotamisligil, 2005; Dandona et al., 2004).

Some markers implicated in both GDM and T2DM are the adipokines leptin and

adiponectin.

A systematic literature review and synthesis was conducted to explore the

information available on the relationship of the adipokines leptin and adiponectin and

GDM. The electronic search engines used to find articles for this review were PubMed

and CINAHL. The search terms used for this review were leptin, adiponectin, and

gestational diabetes. PubMed and CINAHL generated a total of 54 articles on this topic.

Inclusion criteria encompassed peer-reviewed articles and research studies published in

the past 10 years. Articles that were not peer-reviewed, animal studies, descriptive

articles, dissertations, and review articles were not included. After excluding all studies

that did not meet the desired criteria, only 13 articles were identified as being relevant to

this study. Information for the studies reviewed is provided in Table 2.2.

31

Table 2.2

Summary of Studies Investigating Leptin and Adiponectin in Gestational Diabetes


Lopez-Tinoco et al., 2012

To evaluate the relationships between cytokine concentrations, components of metabolic syndrome, and cardiovascular risk in women with GDM.

Case Control

N = 126 n = 63 cases n = 63 controls

Women with GDM had significantly higher BMIs, higher levels of leptin, and significantly lower levels of adiponectin.

Women with GDM have a cytokine profile that includes high concentrations of leptin, low levels of adiponectin, and higher pre-gravid weight.

Skavarca, Tomazic, Krhin, Blagus & Janez, 2012

To evaluate associations between concentrations of adipokines and insulin resistance at different stages of glucose tolerance.

Cross Sectional

N = 74 n = 25 normal n = 19 intermediate glucose tolerance n = 30 GDM; Evaluated at 24–28 weeks gestation

There were significant differences in insulin resistance between the three groups. No significant differences were seen in adipokine concentrations.

Adiponectin and leptin were not associated with degree of glucose tolerance in pregnancy.

Horosz, Bomba-Opon, Szymanska, Wielgos, 2011

To compare adiponectin, leptin, and insulin resistance in women with and without gestational diabetes.

Case Control

N = 134 n = 86 cases n = 48 controls

Adiponectin levels were significantly lower in the GDM group; leptin levels were not significantly different between the groups; insulin resistance was significantly higher in the GDM group.

Women with GDM have lower levels of adiponectin and higher levels of insulin resistance.

32

Table 2.2 continued


Author, Year


Saucedo et al., 2011

To investigate the relationship between adipokines and insulin resistance during pregnancy and PP in women with GDM.

Prospective Longitudinal

N = 120 n = 60 GDM women n = 60 healthy women; Evaluated at 30 weeks gestation, and at 6 weeks and 6 months PP

GDM women had higher insulin resistance compared to healthy controls. No differences in levels of adipokines were seen during pregnancy, at 6 weeks, and at 6 months PP. Women with GDM had persistent leptin and insulin resistance; progressively impaired glucose tolerance was found in women with prior GDM.

Women with prior GDM have higher levels of insulin resistance, higher levels of leptin, and glucose intolerance.

Retnakaran et al., 2010a

To evaluate the risk of early progression to pre-diabetes and diabetes in women with varying levels of glucose intolerance in pregnancy.


N = 325 Evaluated at 3 months and 12 months PP

At 12 months, 10% of the subjects progressed to impaired glucose tolerance, compared to 17% with prior GDM. At 3 months, although all had NGT, progressors had higher BMIs and leptin levels and lower adiponectin levels.

Normal glucose tolerance test at 3 months PP does not provide assurance of low risk for pre-diabetes progression.

33

Table 2.2 continued


Author, Year


Retnakaran et al., 2010b

To evaluate if adiponectin, leptin, and CRP levels during pregnancy are related to PP metabolic defects that link GDM with T2DM.


N = 487 n = 137 GDM n = 91 IGT n = 259 NGT Evaluated at 28–31 weeks gestation and 3-months PP

Adiponectin levels were lowest and CRP levels highest in women with prior GDM; no differences were found in leptin levels. Low adiponectin levels were also related to PP beta cell function and predicted PP insulin sensitivity and beta cell function.

Low adiponectin levels during pregnancy predict insulin resistance, beta cell function, and fasting glucose and may play a role in the progression of GDM to T2DM.

Choi et al., 2008

To investigate if adipokine concentrations are associated with abnormal glucose tolerance in women with prior GDM.

Cross Sectional

N = 157 n = 17 NGT n = 72 GDM NGT n = 60 GDM IGT n = 8 GDM-DM Evaluated at 2 months PP

Adiponectin levels were the lowest in the GDM DM group and were inversely correlated with parameters of insulin resistance. No differences were found in leptin levels.

Severity of glucose intolerance in women with prior GDM is associated with low adiponectin levels.

Xue-Lian, Hui-xia & Yi, 2008

To investigate which occurs first in GDM— changes

in adipokines or abnormal glucose metabolism.

Nested Case Control

N = 32 n = 22 GDM n= 10 GIGT n = 20 Healthy controls; Evaluated at 14–20 weeks gestation

Women with GDM had significantly higher levels of leptin and lower levels of adiponectin.

Changes in adipokines occurred prior to evidence of altered glucose metabolism.

34

Table 2.2 continued


Author, Year


Pirc et al., 2007

To compare concentrations of glucose, insulin, leptin, and adiponectin in umbilical cord blood of babies of women without GDM, mild GDM without treatment, and mild GDM with treatment.

Randomized Controlled Trial

N = 228 n = 36 Mild GDM Treatment n = 49 Mild GDM Routine Care n = 133 Controls

Cord plasma glucose was statistically higher in women receiving routine care compared to controls; cord serum insulin and insulin to glucose ratio were similar in the 3 groups; leptin was statistically lower in the GDM treated group compared to routine care, and significantly different in controls. Adiponectin was lower in both GDM groups compared to controls.

Fetal adipo-insular (fat-insulin) axis is affected by treatment in women with mild GDM.

Ategbo et al., 2006

To investigate hormone and cytokine profile of macrosomic babies born to mothers with GDM.

Case Control

N = 119 n = 59 GDM cases n = 60 controls Mothers with GDM and newborns were evaluated immediately after delivery and aged matched with healthy women and newborns

Women with GDM had lower adiponectin levels and higher levels of leptin and inflammatory cytokines.

GDM is linked to down regulation of adiponectin and up regulation of leptin and inflammation. Fetal macrosomia is associated with down-regulation of adipokines.

35

Table 2.2 continued



McLachlan, O’neal, Jenkins & Alford, 2006

To investigate the role of adiponectin, TNF-α, leptin, and CRP in insulin resistance in pregnancy and relationship to insulin secretion and action.

Case Control N = 38 n = 19 cases n = 19 controls

Only leptin was correlated with SI; no changes were seen with adiponectin.

The influence of leptin and adiponectin on SI might be attributed to other factors in pregnancy.

Winzer et al., 2004

To investigate plasma concentration of parameters of subclinical inflammation and adipocytokines in women with pGDM at both 3-and 12-months post- delivery.

Cross Sectional; Prospective Longitudinal

N = 108 n = 89 women with pGDM at 3 and 12 months post-delivery n = 19 normal controls

Women with pGDM had lower levels of adiponectin, decreased insulin sensitivity, but increased leptin levels and subclinical inflammation parameters.

Women with pGDM have lower concentrations of adiponectin independent from degree of obesity and insulin sensitivity.

Ranheim et al., 2004

To evaluate if adiponectin represents a link between endocrine function of adipose tissues and GDM by comparing levels in women with and without GDM.

Case Control N = 51 n = 22 cases n = 29 controls

Women with GDM had lower levels of adiponectin compared to non-GDM women. Leptin levels did not differ between the groups.

Low adiponectin is associated with GDM.

Note: BMI = body mass index; CRP = c-reactive protein; GDM = gestational diabetes mellitus; GDM-DM =

type 2 diabetes after gestational diabetes; GIGT = gestational impaired glucose tolerance; IGT = impaired

glucose tolerance; NGT = normal glucose tolerance; pGDM = prior gestational diabetes mellitus; PP =

postpartum; SI = insulin sensitivity; TNF-α = tumor necrosis factor – alpha; T2DM = type 2 diabetes mellitus;

Wks = weeks

36

Leptin

Leptin is a hormone secreted by adipose tissue that plays a role in regulating

energy homeostasis, appetite regulation, fat disposition, and metabolic and fertility

processes (Bouloumie, Curat, Miranville, & Sengenes, 2007; Henson & Castracane,

2005). Leptin has an influence on several bodily functions, including the hypothalamus,

pancreas, liver, and skeletal and adipose tissues. In the hypothalamus, leptin acts as a

satiety (fullness) signal and alerts the body to regulate food intake and energy

expenditure. In skeletal, adipose and liver tissues, leptin acts on fatty acid oxidation,

lipolysis, and lipogenesis. In the pancreas, leptin modulates insulin secretion. Leptin

further plays a role in inflammation by altering vascular wall reaction and platelet

aggregation; it also has pro-inflammatory and immune-stimulatory effects (Bouloumie,

Curat, Miranville, & Sengenes, 2007). Elevated leptin is associated with obesity and is

positively correlated with BMI (Fried, Ricci, Russell, & Laferrere, 2000). In pregnancy,

leptin levels progressively increase with gestation, and the rise in leptin levels is

correlated with the rise of the pregnancy hormone human chorionic gonadotropin

(Henson & Castracane, 2006).

During pregnancy, elevated leptin levels have been linked to GDM,

preeclampsia, intrauterine growth restriction, and the fetal origins of adult diabetes

(Henson & Castracane, 2005; Kautzky-Willer, 2001). In a study in women with GDM that

evaluated the relationships between cytokine concentrations, components of metabolic

syndrome, and cardiovascular risk, women with GDM had significantly higher BMIs and

higher levels of leptin, an indication of altered metabolic status and a potential link to

metabolic and cardiovascular disease (Lopez-Tinoco et al., 2012).

37

In contrast, in a study that evaluated associations between concentrations of

adipokines and insulin resistance at different stages of glucose tolerance in pregnant

women, the authors did not find significant differences in adipokine concentrations. They

concluded that adipokines were not associated with the degree of glucose tolerance in

pregnancy (Skavarca, Tomazic, Krhin, Blagus & Janez, 2012). Similarly, in a study that

investigated the role of adiponectin, TNF-α, leptin, and CRP in insulin resistance in

pregnancy and their relationship to insulin secretion and action, the researchers

concluded that leptin and adiponectin may not be the primary factors influencing insulin

sensitivity, but rather that insulin resistance may be caused by other factors related to

the pregnancy (McLachlan, O’Neal, Jenkins & Alford, 2006). Further, in a study that

compared leptin and insulin resistance in women with and without gestational diabetes,

although leptin was not found to be significantly different in the two groups, insulin

resistance was significantly higher in the GDM group (Horosz, Bomba-Opon,

Szymanska, Wielgos, 2011). Another study that investigated the relationship between

adipokines and insulin resistance during pregnancy and the postpartum period reported

that women with GDM had higher insulin resistance compared to normal women and did

not find differences in adipokines between the two groups during pregnancy (Saucedo et

al., 2011). However, these researchers did find that at six weeks and six months

postpartum, the women who had GDM had persistently elevated leptin concentrations,

insulin resistance, and glucose intolerance. These findings support the need for long-

term investigation of the role of leptin on insulin resistance and glucose intolerance in

women who experienced prior GDM.

38

Adiponectin

Adiponectin is a protein secreted by adipose tissue that has a role in glucose

regulation and insulin resistance. It has anti-inflammatory, anti-atherogenic, cardio-

protective, and insulin sensitizing properties that may be protective against obesity-

related diseases including T2DM (Szmitko, Teoh, Stewart, & Verma, 2007; Wellen &

Hotamisligil, 2005). Adiponectin helps to maintain a healthy vascular system and has

protective effects against endothelial dysfunction, plaque initiation and progression, and

plaque rupture and thrombosis. In contrast, low adiponectin levels promote vasculature

dysfunction by activating endothelial damage, plaque formation and progression, as well

as rupture and thrombosis of plaques. Adiponectin’s insulin sensitizing properties are

related to its ability to reduce tissue triglyceride content and up-regulation of insulin

signaling, which results in improved insulin sensitivity in the liver and skeletal muscles

(Kadowaki & Yamauchi, 2005).

Studies have suggested that low levels of adiponectin are predictive of GDM,

while higher levels may be protective against GDM (Weerakeit et al, 2006). Studies have

demonstrated that obesity, which is often characterized by an inflammatory process, is

marked by low adiponectin levels (Lopez-Tinoco et al.; Weerakeit et al., 2006). Lower

levels of adiponectin have been reported in women with prior GDM. A study that

measured adiponectin concentrations in the first trimester of pregnancy to identify a

relationship for subsequent GDM found that women who developed GDM exhibited

lower levels of adiponectin at 11 weeks and 28 weeks gestation (Georgiou et al., 2008).

Heitritter et al. (2004) reported similar findings in women one year after a pregnancy

complicated by GDM. They found that women with prior GDM had lower levels of

adiponectin compared to women without prior GDM. Both of these studies suggest that

39

lower levels of adiponectin are associated with altered glucose metabolism, which is

likely due to the loss of its beneficial glucose regulating functions.

A study that compared adiponectin and insulin resistance in women with and

without gestational diabetes found that adiponectin was significantly lower and insulin

resistance was significantly higher in the GDM group (Horosz, Bomba-Opon,

Szymanska, & Wielgos, 2011). These findings are consistent and support that low

adiponectin levels are associated with loss of insulin regulating properties. A longitudinal

study that evaluated the risk of early progression to pre-diabetes and diabetes in women

with varying levels of glucose intolerance during pregnancy reported that at three

months postpartum, women with prior GDM had higher BMIs, higher levels of leptin, and

lower levels of adiponectin; all the study participants had normal glucose tolerance. In

addition, at 12 months postpartum, 10% of the study population progressed to impaired

glucose tolerance, compared to 17% of participants with prior GDM. The researchers

concluded that the normal glucose tolerance test at 3 months postpartum does not

provide assurance of low risk for pre-diabetes progression (Retnakaran et al., 2010a).

When evaluating whether adiponectin, leptin, and c-reactive protein (CRP) levels

during pregnancy are related to postpartum metabolic defects that link GDM with T2DM,

studies have found that adiponectin levels were lowest and CRP levels were highest in

women with prior GDM. Low adiponectin levels also were related to postpartum beta cell

function and predicted postpartum insulin sensitivity and beta cell function (Retnakaran

et al., 2010b). These findings suggest that low adiponectin levels during pregnancy may

be predictive of factors that play an important role in the progression of GDM to T2DM.

40

Gestational Diabetes

Gestational diabetes was defined as diabetes that occurs during pregnancy.

GDM generally is detected late in the second trimester of pregnancy between 24 and 28

weeks of gestation. Clinically, women are screened with a 1-hour 50-gm glucose

tolerance test at between 24 and 28 weeks gestation. Women with values greater than

139 mg/dL require a diagnostic 3-hour glucose 100-gm tolerance test. Two elevated

values out of four tests are diagnostic for GDM (Kapustin et al., 2008; Esakoff, Cheng, &

Caughey, 2005). Because gestational diabetes complicates a pregnancy, requires strict

management to avoid maternal and fetal complications. Women with GDM have an

increased risk for preeclampsia, shoulder dystocia, and cesarean section delivery

(Hayes, 2009). Fetal complications include fetal macrosomia (birth weight 4000 grams or

greater), neonatal hypoglycemia (blood sugar less than 45 ng/dL), congenital

abnormalities, increased risk for prenatal mortality, and risk for obesity and T2DM as

adults (Kapustin et al., 2008). To manage this condition, women require intensive

counseling on diet, glucose monitoring, weight management, and recommended

physical activities. Women who are not able to maintain and control their recommended

glucose levels will require medical management including oral medication or insulin.

Women who develop GDM have an altered metabolic state marked by subclinical

inflammation for years before they develop signs and symptoms of diabetes, which puts

them at risk for altered glucose metabolism, metabolic syndrome, and cardiovascular

disease (Di Cianni, 2007; Winzer et al., 2004). Women with previous GDM also have

evidence of endothelial dysfunction, which is associated with insulin resistance and pro-

inflammatory cytokines (Winzer et al., 2004). In addition, because the level of insulin

41

resistance and production is greatly affected by body mass, obese women have greater

insulin resistance than normal weight women (Volpe et al., 2007).

There also is evidence that pro-inflammatory cytokines are present in adipose

tissue, significantly increasing inflammation and risk for insulin resistance, GDM, and

T2DM (Wellen & Hotamisligil, 2005; Dandona et al., 2004). Some markers implicated in

GDM and T2DM are the adipokines leptin and adiponectin. A study that investigated the

temporal order changes in adipokines and abnormal glucose metabolism found that

women with GDM had significantly higher levels of leptin and lower levels of adiponectin

and that these changes occurred prior to evidence of altered glucose metabolism or

GDM (Xue-Lian, Hui-xia & Yi, 2008).

Metabolic responses are essential to meet the physiological demands of the

body (Kyrou & Tsigos, 2009). Leptin and adiponectin are two adipokines that are known

to contribute to metabolic responses and which have been associated with metabolic

alterations including obesity and glucose metabolism (Kyrou & Tsigos, 2009). Chronic

stress has been known to contribute to increases in cortisol, the stress hormone that has

been known to increase visceral adipose tissue, potentially altering the normal metabolic

responsibilities of these hormones (Anagnostis, Athyros, Tziomalos, Karagiannis, &

Mikhailidis, 2009). The literature supports that alterations in leptin and adiponectin are

found in women with GDM and glucose intolerance.

Summary

Studies on acculturation and acculturative stress suggest that both acculturation

and acculturative stress are life altering experiences that can place individuals at risk for

chronic stress. Studies on leptin and adiponectin suggest that alterations in these

metabolic hormones can yield disruption of the normal physiology of the body. Although

42

there is extensive literature on how each of these concepts affects individuals and

human physiology, little is known about how the chronic stressors of acculturation and

acculturative stress, in combination with changes in the metabolic markers of leptin and

adiponectin, may affect or contribute to gestational diabetes mellitus and altered

metabolic function indicating allostatic load. Thus, this study intends to explore the

relationships between psychosocial stress and metabolic response in Mexican American

women with and without gestational diabetes.

This chapter presented a review of research literature addressing psychosocial

stress, metabolic response, and gestational diabetes in Mexican American women of

childbearing age. An overview of the HPA-axis stress response was discussed, and the

major markers for psychosocial stress in Mexican American women (e.g., acculturation

and acculturative stress) were highlighted. The major markers for metabolic response—

leptin and adiponectin—were described. Gestational diabetes in Mexican American

women of child-bearing years was reviewed.

43

CHAPTER III

METHODS

This chapter addresses the research approach and methodology used in this

study. Institutional Review Board approval, research design, sampling and recruitment

procedures, and informed consent are discussed. Procedures for data collection,

analyses and interpretation of results are described. Finally, potential threats to validity

are acknowledged and addressed.

Institutional Review Board Approval

Institutional Review Boards (IRBs) develop protocols to protect the ethical issues

that can arise when conducting research (Sieber & Stanley, 1988). Conducting

responsible research consists of having respect, integrity, and protecting research

ethics. Ethical considerations in research include having voluntary participation of

subjects, informed consent, confidentiality, anonymity, and explaining any potential

harms of the study (Polonski & Waller, 2005). In this study, these ethical considerations

were considered as part of the parent study as well as the secondary analysis and

efforts were made to comply with IRB policies. The principal investigator of the parent

study, Dr. Jeanne Ruiz, received IRB approval from the University of Texas at Austin.

For this study, IRB approval was resubmitted and obtained for the secondary analysis.

Research Design

The research design describes the methodology and procedures that will be

used to address the research questions of interest. The current study was a secondary

analysis of the prospective, observational study funded by the National Institutes of

Health #5R01NR007891, “Preterm Birth: Psychoneuroimmunology in Hispanics,” which

was conducted by Dr. Jeanne Ruiz. The purpose of the study was to examine the impact

44

of acculturation in Hispanic women on preterm birth and to assess the role of

psychosocial, physiologic, and genetic mediating factors for explaining the relationships

between acculturation and birth outcomes.

A secondary analysis is research to address new questions that is conducted on

data already collected by another researcher and reanalyzed to address those additional

questions (Polit & Tatano Beck, 2008). A case-control, descriptive, correlation design

was used to address the current research questions. A purposive sample of Mexican

American women aged 14–45 who were between 22 and 24 weeks pregnant was

recruited for the parent study.

Sampling Procedures

The parent study used a non-probability convenience sampling procedure to

recruit a total of 518 study participants. Participants in the parent study were pregnant

Mexican American women who had resided in the United States for at least 10 years

and who were receiving their obstetrical care at obstetrical clinics in east and central

Texas. Women who had lived in the U.S. for fewer than 10 years were excluded

because previous studies have found that consistent with the “Hispanic Paradox,”

women who had recently immigrated had similar or better health outcomes than the non-

Hispanic white population (Palloni & Morenoff, 2001; Franzini; Ribble, & Keddie, 2000).

Inclusion criteria for the parent study included the following:

Ability to provide informed consent

Ability to read and speak English or Spanish

Pregnant at 22–24 gestational weeks with a singleton, intrauterine pregnancy as

confirmed by accurate last normal menstrual period or ultrasound to confirm

dating

45

Self-identified as Hispanic

Age between 14–45 years

If age 17 or younger, ability to obtain parental consent

Exclusion criteria for women included:

Inability to read either English or Spanish

Known uterine or cervical abnormalities

Multiple gestations: twins or triplets

Kidney disease, pyelonephritis in the current pregnancy, or chronic hypertension

Heart disease, coronary artery disease, history of peri-partum cardiomyopathy

Autoimmune disorders: lupus, antiphospholipid syndrome

Type 1 or Type 2 diabetes

Asthma requiring use of steroid inhaler

Pre-eclampsia at time of data collection

Oral steroid use one month prior to the time of enrollment

Congenital anomalies as determined on fetal ultrasound, especially those leading

to hydramnios, trisomies, major structural anomalies as neural tube defects,

ventral wall defects, or congenital heart disease

Blood group isoimmunization

Active cervico-vaginal bleeding or placenta previa

Self-report of an ethnicity other than Hispanic

Previous participation in the study.

Case-control Sample

The secondary analysis consisted of a case-control design where GDM cases

from the parent study were matched and compared with non-GDM cases. The database

46

from the parent study was examined and using a chart audit, participants who had GDM

were selected. Next, a new database was created, and the 38 participants with GDM

were manually matched according to age and BMI to participants who did not develop

GDM during the pregnancy. The total sample for the sub-study included 76 participants

aged 21–43 years. No minors were included in the sub-sample since there were no

participants with GDM younger than 18 years of age.

Recruitment of Subjects for the Parent Study

Clinic staff, nurses, nurse practitioners, and physicians at participating obstetrical

clinics in east and central Texas were asked to direct potential participants who were

less than 22 weeks pregnant to the bilingual recruiter. The trained recruiter approached

potential participants during their obstetric visit to ask about their interest in participating

in the study. If the participant agreed, the recruiter provided the potential eligible

participants with the telephone number to enroll in the study and scheduled a time for

the data collection appointment. The research office telephone was managed by the

research nurse, who would further screen the interested participants, determine

eligibility, and confirm the appointment for data collection.

Securing Informed Consent

Informed consent is an ethical principal requiring researchers to disclose

potential risks and benefits involved in the propose study (Polit & Tatano Beck, 2008).

Informed consent should include disclosure, capacity, and voluntary participation.

Consent was received from the participants for the parent study according to IRB

protocol. IRB-approved consent forms were provided to all potential study participants.

Potential participants were required to read the first two lines of the consent to the

recruiter to verify literacy. Participants then were given the opportunity to read the

47

consent form themselves or have the research nurse read the consent form to them. For

participants younger than 18 years of age, assent was obtained from the participant and

consent was obtained from their parent. The research nurse was available to answer

any questions regarding the study. The secondary analysis conducted for this study did

not include participants younger than 18 years of age.

Ethical Considerations

Protecting Human Rights of Subjects. A major responsibility of all researchers

is to protect the human rights of study subjects. Researchers must abide by the

guidelines set forth by the Belmont Report, which delineates important ethical principles

needed for the conduct of responsible research. These principles include respect for

persons, beneficence, and justice (Belmont Report, 1979). Research participation should

at all times be voluntary with participants viewed as autonomous; if autonomy is to be

lost, special consideration for protection should be considered. To protect confidentiality

of the potential subjects, participants for the parent study were approached for

discussion regarding the study only in private areas and only those individuals who were

interested were enrolled. All participants were informed that participation in the study

was voluntary and that they could withdraw from the study at any time. Contact

information and demographic information for participants was obtained in a private

office. Data were collected in a private examination room to ensure maximum privacy

during the time the participant completed the questionnaires and blood was collected. To

ensure anonymity, each participant was assigned an identification number and all

instruments and specimens were labeled accordingly. A master list with participants’

names and codes was created. Access to the master list of participants’ names and

codes was restricted to the Principal Investigator, project coordinator, and research

48

nurse. The master list was kept in a locked cabinet separate from the data collected. All

information collected was independent from their prenatal care visit.

Balancing Benefits and Risks of a Study. According to IRB policies, optimizing

benefits and minimizing risks is important in all research studies. The information gained

from the parent study advanced the state of the science related to the etiology of

preterm labor. There were no direct benefits for participants taking part in the parent

study. Potential risks for the parent study included fatigue from participating in at least

105 minutes of data collection, emotional stress from answering personal questions, and

pain and bruising during and after blood collection. Risks were addressed as follows:

1. Participants were encouraged and given the opportunity to take breaks during

the data collection.

2. Participants who scored high on the depression scale were referred for

counseling.

3. Blood collection was performed by an experienced research nurse using a

small gauge needle.

No additional risks were anticipated for the current study. The parent study

received full IRB approval and after IRB approval submission for the current study, the

Office of Research Support (ORS) at the University of Texas at Austin determined that

this secondary analysis was excempt from further IRB requirements. Please refer to

Appendix B for the letter from ORS.

Measures

Research measures used to operationalize the concepts of interest have a vital

role in research projects (Polit & Tatano Beck, 2008). They are used to collect the data

needed to answer the research questions. Research instruments should be reliable and

49

valid. The self-report instruments used in this study included: the Multidimensional

Acculturative Stress Inventory (MASI) and the Multidimensional Acculturation Scale II

(MAS II).

Multidimensional Acculturative Stress Inventory (MASI). The MASI is a 36-

item instrument that measures the level of stress related to Spanish and English

competency pressures and pressures for and against acculturation (Rodriguez, Myers,

Bingham Mira, Flores, & Garcia-Hernandez, 2002). Level of stress is rated on 6-point

Likert-type scale with item responses ranging from (0) does not apply, (1) not at all

stressful to (5) extremely stressful. The measure generates four subscales, Spanish

Competency Pressure, English Competency Pressure, Pressure to Acculturate, and

Pressure Against Acculturation. Items from each of the subscales are averaged to obtain

a stress rating for each of the subscales. The reported reliabilities (Cronbach’s α) for

each of the subscales ranged from .77–.93 (Rodriguez et al., 2002). The validity for this

instrument was demonstrated using a factor analysis where the four factors explained

64.4% of the variance and were significantly correlated in the appropriate directions with

the selected criterion measures of acculturation, such as generational status and length

of U.S. residence (Rodriguez et al., 2002). This instrument was tested on 174 Mexican

origin adults aged 18–69 (M = 31.59, SD = 11.02), including 117 women who resided in

the Los Angeles, California, greater metropolitan area. Internal consistency reliability

(Cronbach’s α) for each subscale in this sample ranged from .79–.95. The Pearson r

correlations for the subscales ranged from .29–.50. See Appendix A for the detailed

survey.

Multidimensional Acculturation Scale II (MAS II). The MAS II is a 22-item

instrument used to assess acculturation by identifying Anglo American or Mexican

50

American involvement and identification in each culture and English and Spanish

language proficiency. Item responses in the MAS II are rated on a 6-point Likert-type

scale ranging from (0) does not apply and (1) not well/not at all/can’t speak or

understand to (5) very well/very much/very fluent. These subscales identify the

participant’s cultural identity as either Anglo or Mexican American with language

preference English or Spanish language. Items from the English proficiency and the

Anglo American identification subscales are summed and averaged to create an

American identity mean score. Items from the Spanish language proficiency and the

Mexican American identification subscales are summed and averaged to create a

Mexican identity mean score. The instrument has a reported reliability (Cronbach’s α) of

.96 for the language proficiency subscales and .90 for the ethnic identity subscale

(Rodriguez, Bingham Mira, Paez, & Myers, 2007). Validity of this instrument was

demonstrated with correlations of commonly accepted acculturation indicators of

generational status and length of U.S. residence. First generation included participants

born in Mexico, second generation included participant’s mother having been born in

Mexico and the participant having been born in the U.S., third generation included

participant’s grandmother having been born in Mexico and participant and mother having

been born in U.S., fourth generation included participant’s great-grandmother having

been born in Mexico and the participant and participant’s mother and grandmother being

born in U.S. As expected, generational status was significantly correlated with the

English language proficiency (r = .56, p < .01), Spanish language proficiency (r = - .74, p

< .01), and Anglo identity (r = .32, p < .01) subscales. Also as expected, length of U.S.

residency was significantly correlated with the English language proficiency (r = .73, p <

.01), Spanish language proficiency (r = - .63, p < .01), and Anglo identity (r = .42, p <

51

.01) subscales. Neither indicator was significantly correlated with the Mexican cultural

identity subscale (r = -.07, p >.05; r = -.03, p > .05). This instrument was tested on 248

adults aged 18–69 of Mexican origin (M = 36.44, SD = 11.93), including 124 women

from the Los Angeles greater metropolitan area. Internal consistency reliability

(Cronbach’s α) for each subscale in this sample ranged from .80–.96. The Pearson r

correlations for the subscales ranged from -.08–.52.

Leptin. Leptin was defined as a pleiotropic hormone that plays a role in

regulating energy homeostasis, appetite regulation, fat disposition, and metabolic and

fertility processes (Otero et al., 2006; Bouloumie et al., 2007). Leptin was

operationalized by enzyme linked immunosorbent assay. Assay plates were purchased

from the American Laboratory Products Company, Salem, New Hampshire (ALPCO),

and the ELISA procedure was followed according to manufacturer’s specifications.

ELISA is a biochemical technique used to measure protein levels (Vedhara & Irwin,

2005). The ELISA test kit was purchased from ALPCO reports leptin mean detectible

dose (MDD) with a range of .020 –.128 ng/ml with sensitivity of 0.057 based on leptin

standard curves (ALPCO, 2005). Mean detection dose and sensitivity is comparable to

other kits on the market (Neogen, 2012). Mean detection dose and sensitivity for ALPCO

kit was determined by the National Committee on Clinic Laboratory Standards

(NCCCLS) protocol and inter-assay (between assays) and intra-assay (within assays)

precisions were verified and comparable to other kits on the market (ALPCO, 2012).

ALPCO (2012) reported leptin levels for lean women of 7.4 ng/mL. Leptin levels are

directly proportional to BMI and are higher in pregnancy ranging from 117.4–163.8

ng/mL with the highest levels seen during the second trimester (Hardie, Trayhurn,

52

Abramobvich, & Fowler, 1997). Higher levels of leptin are attributed to the weight and

hormonal changes for pregnancy (Hardie, Trayhurn, Abramobvich, & Fowler, 1997).


adipose tissue that has anti-inflammatory, anti-atherogenic, and insulin sensitizing

properties. Adiponectin was operationalized by enzyme linked immunosorbent assay.

The ELISA test kit was purchased from ALPCO reports adiponectin MDD range of .075–

4.8 ng/mL and sensitivity of 0.019 ng/mL based on adiponectin standard curve and

strong correlations (r = .99) when compared to other commercial kits (ALPCO, 2013).

Data Collection

Survey Data. During the data collection visit, the research nurse collected vital

signs (i.e., blood pressure, pulse, temperature), weight, calculated gestational age, and

administered the pen and pencil questionnaires. The participants filled out a

demographic information sheet and completed the questionnaires. Questionnaires and

demographic data sheets were all kept in a secured cabinet in the research offices. The

estimated time for the pen and paper questionnaires was 90 minutes. The nurse then

collected the blood sample from the participant. The order of the protocol was

implemented to help the participant become familiar with the study environment and help

decrease stress prior to blood collection.

Physiologic Data. Peripheral venous blood was drawn from the antecubital area

using a butterfly vacutainer needle into a syringe by the research nurse. This was done

between 1 p.m. and 3 p.m. to help control for the diurnal patterns of certain markers.

Participants were instructed not to eat two hours prior to data collection to control for the

effects of eating or fasting on the markers under study. The research nurse verified their

last dietary intake was within the instructed time. The estimated time for physiologic data

53

collection was 15 minutes. The 30 mL of blood collected were centrifuged; the plasma

was transferred into smaller aliquots, frozen, and stored in a secured, temperature

controlled freezer at -80°C in the biobehavioral laboratory at the University of Texas at

Austin until the blood was ready for the assays.

Data Analysis

Data analysis was conducted using the Statistical Package for the Social

Sciences (SPSS) Version 19 (IBM, 2011). Responses for the MAS II and MASI surveys

were electronically entered into spreadsheet format and exported into SPSS. The

existing laboratory values from the parent study were entered by the research nurse into

the database after the laboratory technician completed the laboratory procedures. All

data were manually verified for accuracy. Laboratory data for this study were entered

and verified in the same manner. The database for the parent study was filtered and all

participants who had GDM were extracted. The 38 participants with diagnosed GDM

from the parent study were manually matched according to age and BMI with

participants from the parent study who did not develop GDM, and a new SPSS database

was created and used for data analysis.

Physiologic Data

Leptin and adiponectin were quantified by enzyme linked immunosorbent assay

(ELISA). ELISA is a biochemical technique used to measure protein levels (Vedhara &

Irwin, 2005). The assays consisted of an adipokine-specific monoclonal antibody that

detects the presence and level of the adipokine of interest.

All data were verified for accuracy. Frequency tables were generated for all

variables. Descriptive, parametric, and and correlation statistics were used to analyze

the data (Polit & Tatano Beck, 2008). Data analysis was conducted systematically and

54

verified data that it met the pertinent assumptions related to the statistical tests of

interest. Descriptive statistics are used to describe and summarize data (Polit & Tatano

Beck). They enable researchers to summarize the characteristics of the sample.

Descriptive statistics generated for the subsample included the mean, standard

deviation, and frequencies. Correlational statistics explored relationships between

variables. Independent t-tests were conducted to analyze differences between two

means.

The research questions reflective of their specific aims and planned analyses

were as follows:

Specific Aim #1: To explore relationships between the psychosocial stressors

(i.e., acculturation and acculturative stress) and metabolic markers (i.e., leptin and

adiponectin) in Mexican American women with and without gestational diabetes.

Research Question 1. Is there a significant relationship between levels of the

psychosocial markers of acculturation and acculturative stress and the metabolic

markers of leptin and adiponectin? Planned analysis: Pearson r Correlation

Specific Aim #2: To examine differences in the metabolic markers of leptin and

adiponectin in Mexican American women with and without gestational diabetes.


psychosocial markers of acculturation and acculturative stress between women

with and without gestational diabetes? Planned Analysis: Independent samples

t-test.

Research Question 2.2. Is there a significant difference in the metabolic

markers of leptin and adiponectin between women with and without gestational

diabetes? Planned Analysis: Independent samples t-test.

55

Threats to Design Validity

Statistical Validity

Statistical validity relates to the study results and represents the true differences

belong to the study design and not those that occur as a result of random error (Brink &

Wood, 2001). The MAS II and MASI have established reliability over time. This study is

limited to data that was already collected in the parent study; additional instrumentation

was not used. In this secondary analysis, statistical power is limited due to the small

sample size. Because the sampling techniques used in this study were non-probability,

possible error introduced during sampling cannot be measured, thus limiting the validity

of the results. To address this threat, systematic and consistent data collection methods

were used by the parent study for questionnaire administration and blood specimen

collection and storage.

Physiologic data results for the biomarkers were dependent on proper storage

and handling of the stored blood as well as time elapsed since collection. Strict

temperature controls were maintained for the freezers at all times, and the assays were

completed in batches of 50 as soon as information was collected from 50 participants.

Statistical and normal distribution assumptions were addressed.

Internal Validity

Internal validity is the degree that the study’s results are attributed to the

research design and not to systematic error (Polit & Tatano Beck, 2008). Internal validity

was controlled by reducing testing effect by using the shortest valid instruments to

measure the concepts of interest, thus reducing the burden on the participant.

Participants were given detailed instructions on the questionnaires to ensure

questionnaires were appropriately completed. The research nurse was available to

56

answer all questions during data collection and reviewed each questionnaire to ensure

completion.

Construct Validity

Construct validity is the degree to which inferences can be made that the

instruments used in the study appropriately measure the theoretical concepts of the

study (Brink & Wood, 2001). The instruments were validated by using two commonly

used indicators of acculturation: generational level and length of U.S. residency. Both

instruments demonstrated significant correlations indicating construct validity.

External Validity

External validity is the degree to which the study’s results can be generalized to a

sample outside the one studied (Polit & Tatano Beck, 2008). The findings in this study

may not be generalizable to all Mexican Americans residing in the United States but will

be applicable to those residing in Central Texas who have characteristics similar to the

sample.

Summary

This chapter addressed the research approach and methodology used in this

study. Institutional review board approval, research design, sampling and recruitment

procedures, and informed consent were discussed. Procedures for data collection and

analysis and interpretation of results were described. Finally, potential threats to validity

were acknowledged and addressed.

57

CHAPTER IV

RESULTS

This chapter presents the results of this secondary study by answering the

research questions posed in Chapter I using the statistical methods outlined in Chapter

III. The sample is described by reporting frequency distributions of demographic data.

Then, frequency distributions of scores for survey instruments and values for laboratory

tests are presented. The research questions were answered through performing

parametric tests, specifically calculating Pearson r correlations and conducting

independent sample t-tests.

Description of Sample

Frequencies were calculated to provide a description of the sample. These

included the following demographic characteristics: country of birth, language

preference, generational level, marital status, regional background, educational level,

income, age, and years of residence in the United States. Description of the biological

variables include height, weight, pre-pregnancy weight and BMI, systolic blood pressure,

leptin and adiponectin levels, and leptin-adiponectin ratio.

Demographic Characteristics

The sample consisted of a total of 76 Mexican American women, 38 with GDM

and 38 healthy controls without GDM. Individual and biologic characteristics are reported

by group. The groups were overall very similar.

Gestational Diabetes Group. The age range for the GDM group was 21–42

years (M = 29.79, SD = 5.62); these women had a reported range of U.S. residence of

8–39 years (M = 23.42, SD = 8.15). Approximately, 55% of the group had been born in

the U.S., and 46% were born in Mexico. A total of 71% reported having a preference for

58

the English language, while 29% reported having a Spanish language preference.

Frequencies and percent for generational level, marital status, regional background,

education, and income are reported in Table 4.1.

Healthy Control Group (Non-Gestational Diabetes). The age range for the

healthy control (non-GDM) group was aged 21–43 years (M = 29.82, SD = 5.68); these

women had a reported range of U.S. residency of 7–39 years (M = 23.11, SD = 8.35). A

total of 61% of the group had been born in the U.S., and 39% were born in Mexico.

Frequencies and percent for generational level, marital status, regional background,

education, and income are reported in Table 4.1.

59

Table 4.1

Demographic Characteristics of Women with and without Gestational Diabetes

Demographic

Characteristic

GDM Group Healthy Control (Non GDM)

Group

n % Range M SD n % Range M SD

Country of birth

U.S. 21 55 23 61

Mexico 17 45 15 39

Language preference

English 27 71 25 66

Spanish 11 29 12 32

Generational level

1st 14 37 20 53

2nd

16 42 3 8

3rd

2 5 5 12

4th 5 13 9 24

Marital status

Married 22 58 23 60

Single 16 42 15 40

Regional background

Houston, TX 13 34 17 44

Pasadena, TX 18 47 14 36

Galveston, TX 2 5 0 0

Austin, TX 5 13 7 18

Education (years)

< 12 14 37 6 15

12 9 24 16 42

13-15 9 24 8 21

≥ 16 2 5 3 8

Income

< $11,999 5 13 5 13

$12,000–$24,999 10 26 6 16

$25,000–$49,999 14 37 14 37

≥ $50,000 3 8 6 16

Age (years) 38 100 21–42 29.79 5.62 38 100 21–43 29.82 5.68

Years U.S. Residence 38 100 8–39 23.42 8.15 38 100 7–39 23.11 8.35

60

Biologic Characteristics

Biologic characteristics examined for this study included height, weight, pre-

pregnancy weight and BMI, leptin, adiponectin, and leptin-adiponectin ratio. For the

GDM group, these women’s measured height ranged from 58–69 inches (M = 62.82, SD

= 2.58) and their weight ranged from 123–276 pounds (M = 196.76, SD = 39.11).

Reported pre-pregnancy weight ranged from 97– 288 pounds (M = 183.16, SD = 46.23)

and their calculated pre-pregnancy BMI ranged from 18.02–55.65 (M = 32.65, SD =

8.27). ELISSA quantified leptin levels ranged from 21.94–355.58 ng/mL (M = 92.82, SD

= 78.99) and adiponectin levels ranged from 2.08–10.38 ng/mL (M = 6.20, SD = 1.96).

The mean for the calculated leptin-adiponectin ratio for the GDM group was 16.88 (SD =

14.76).

For the healthy control (non-GDM) group, their measured height ranged from 55–

67 inches (M = 62.32, SD = 2.55), and their weight ranged from 108–295 pounds (M =

194.75, SD = 43.25). Reported pre-pregnancy weight ranged from 93–285 pounds (M =

180.32, SD = 43.25) and the calculated pre-pregnancy BMI ranged from 19.39–55.65 (M

= 32.58, SD = 7.68). ELISSA quantified leptin levels ranged from 7.66–309 ng/mL (M =

108.75, SD = 72.77) and adiponectin levels ranged from 0.21–14.97 ng/mL (M = 6.81,

SD = 2.82). The mean for the calculated leptin-adiponectin ratio for the Non-GDM group

was 31.49 (SD = 85.94). Biologic characteristics for each group are presented in Table

4.2.

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Table 4.2

Biologic Characteristics of Women with and without Gestational Diabetes

Biologic Characteristic

GDM Group Healthy Control (Non GDM) Group

n % Range M SD n % Range M SD

Height (inches) 38 100 58–69 62.82 2.58 38 100 55–67 62.32 2.55

Weight (pounds) 38 100 123–276 196.76 39.11 38 100 108–295 194.75 43.25

Pre-pregnancy weight 38 100 97–288 183.16 46.23 38 100 93–285 180.32 43.25

Pre-pregnancy BMI 38 100 18.02–55.65 32.65 8.27 38 100 19.39–55.65 32.58 7.68

BMI < 20 3 8 1 3

BMI 20-24.9 3 8 5 13

BMI 25-29.9 9 24 10 26

BMI > 30 23 60 22 58

Leptin 38 100 21.94–355.58 92.82 78.99 37 97 7.66–309.00 108.75 72.77

Adiponectin 38 100 2.08–10.38 6.20 1.96 38 100 0.21–14.97 6.81 2.82

Leptin-adiponectin ratio 38 100 2.59–70.27 16.88 14.76 38 100 0.53–539.76 31.49 85.94

Note. Overall leptin levels ranged from 21.94 to 355.58 and were all included in data analysis. Levels were verified with laboratory and there were no indicators the results were flawed. When excluding high levels of leptin, no significant differences were observed; therefore, due to small sample size all levels were included. Adiponectin levels ranged from 0.21 to 14.97. Levels were verified with laboratory. Laboratory notes indicated one sample may have contained an interfering substance resulting in close to undetectable levels. This value was replaced by the corresponding subgroup’s mean value for adiponectin. When excluding the replaced value, no significant results were observed.

62

Measures

The survey instruments used in this study to measure acculturative stress and

acculturation were the self-report instruments: Multidimensional Acculturation Scale II

(MAS II) and the Multidimensional Acculturative Stress Inventory (MASI). ELISSA

technique from ALPCO was used to quantify leptin and adiponectin.

Multidimensional Acculturation Scale II (MAS II). The MAS II is a 22-item self-

report survey consisting of four subscales used to measure acculturation. Frequencies

and scores for each subscale are provided in Table 4.3.

Multidimensional Acculturative Stress Inventory (MASI). The MASI is a 36-

item self-report survey consisting of four subscales used to measure acculturative

stress. Frequencies and scores for each of the subscales are provided in Table 4.3.

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Table 4.3

Subscale Survey Scores

Survey Scale

Gestational Diabetes Non Gestational Diabetes

n Range M SD n Range M SD

Multidimensional Acculturation Scale II (N = 22)

Subscale

English proficiency 6 0–30 24.81 7.59 6 0–30 24.25 7.93

Spanish proficiency 5 3–25 19.49 7.11 5 1–25 19.08 6.68

American culture identity 5 12-25 19.89 3.65 5 5–25 18.76 5.07

Mexican culture identity 6 13–30 25.62 4.27 6 12–30 23.71 5.14

Multidimensional Acculturative Stress Scale (N = 36)

English competency pressure 8 0–40 5.05 9.06 8 0–19 3.74 4.97

Spanish competency pressure 8 0–17 4.42 5.40 8 0–17 3.92 4.80

Pressure to acculturate 11 0–29 5.95 6.45 11 0–23 5.34 5.52

Pressure against acculturation 9 0–15 4.43 4.40 9 0–17 3.68 4.13

Note. N = number of total survey questions, n = number of survey questions per subscale

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Leptin. Leptin was defined as a pleiotropic hormone that plays a role in

regulating energy homeostasis, appetite regulation, fat disposition, metabolic and fertility

processes (Otero et al., 2006; Bouloumie, Curat, Miranville, & Sengenes, 2007). ELISA

is a biochemical technique used to measure protein levels (Vedhara & Irwin, 2005).

ALPCO reports a leptin mean detectible dose of (MDD) 0.50 ng/mL with a sensitivity of

0.42. Mean reported leptin levels in lean women were 7.4 ng/mL (ALPCO, 2010). Leptin

levels for the GDM group ranged from 21.94–355.58. The mean measured leptin for the

GDM group was 92.82 (SD = 78.99). Leptin levels for the healthy controls (non GDM)

group ranged from 7.66–309.00 with the mean measured leptin of 108.75 (SD = 72.77).

Levels were verified with laboratory and there were no indicators the results were

flawed. When excluding high levels of leptin during data analysis, no significant

differences were observed when excluding and including the high levels; therefore, due

to small sample size all levels were included for the final analysis.


adipose tissue that has anti-inflammatory, anti-atherogenic and insulin sensitizing

properties. Adiponectin was operationalized by enzyme linked immunosorbent assay.

Adiponectin levels for the GDM group ranged from 2.08–10.38 with a mean adiponectin

level 6.20 (SD = 1.96). Adiponectin levels for the healthy control (non-GDM) group

ranged from 0.21–14.97 with a mean adiponectin of 6.81 (SD = 2.82). Serum

adiponectin range for this study is consistent with other studies that have reported

adiponectin ranges from 2–20 (Lihn, Pederson, & Richelsen, 2005). Adiponectin levels

were verified with laboratory. Laboratory notes indicated one sample from the non-GDM

group possibly contained an interfering substance resulting in close to undetectable

65

levels. This value was replaced with the non-GDM group’s mean value for adiponectin.

When excluding the replaced value, no differences were observed.

Research Questions

This section answers the research questions posed in Chapter I. The research

questions were formulated to address the major purposes of this study which were to

explore relationships between the psychosocial stressors of acculturation and

acculturative stress in Mexican American women with and without gestational diabetes,

and to examine whether differences exist in the metabolic markers of leptin and

adiponectin in Mexican American women with and without gestational diabetes. Survey

instruments were used to measure the psychosocial markers of acculturation and

acculturative stress. The ELISA technique was used to measure the metabolic markers

of leptin and adiponectin.

Research Question 1

Is there a relationship between levels of the psychosocial markers of

acculturation (i.e., English proficiency, Spanish proficiency, American cultural identity,

Mexican cultural identity) and acculturative stress (i.e., English competency pressure,

Spanish competency pressure, pressure to acculturate, pressure against acculturation),

and the metabolic markers of leptin and adiponectin?

MAS II

Pearson r correlations were used to answer this question. Findings are reported

for each of the subscales of acculturation in addition to the common indicators of

acculturation (i.e., preferred language, residency index).

English proficiency. There was a statistically significant, positive correlation

found between English proficiency and weight (r = .27, p < .01) and leptin level (r = .26,

66

p < .05). There was a statistically significant, negative correlation between English

proficiency and residency index (r = -.83, p < .01); preferred language (r = -.69, p < .01),

No statistically significant correlations were found between English proficiency

and the following variables:

gestational diabetes

pre-pregnancy weight

pre-pregnancy BMI

newborn weight

adiponectin

leptin/adiponectin ratio

Spanish proficiency. There was a statistically significant, positive correlation

found between Spanish proficiency and residency index (r = .45, p < .01) and preferred

language (r = .31, p < .01).

No statistically significant correlations were found between Spanish language

proficiency and the following variables



pre-pregnancy BMI

weight

newborn weight

American culture identity. There was a statistically significant, positive

correlation between American culture identity and leptin (r = .27, p < .05) There was a

statistically significant, negative correlation between American culture identity and

resident index (r = -.47, p < .01), preferred language (r = -.48, p < 01).

67

No statistically significant correlations were found between American cultural

identity and the following variables:



pre-pregnancy BMI

weight

newborn weight.

Mexican culture identity. There was a statistically significant, positive

correlation found between Mexican cultural identity and newborn weight (r = .26, p <

.05). There was a statistically significant, negative correlation found between English

proficiency and preferred language (r = -.23, p < .01).

No statistically significant correlations were found between Mexican cultural

identity and the following:



pre-pregnancy BMI

weight

residency index

leptin

adiponectin


BMI group

MASI

68

Pearson r correlations were used to answer this question. Findings are reported

for each of the subscales for acculturative stress.

English competency pressure. There was a statistically significant, positive

correlation between English competency pressure and residency index (r = .61, p < .01)

and preferred language (r = .47, p < .01).

No statistically significant correlations were found between English language

competency pressure and



pre-pregnancy BMI

weight

newborn weight

leptin

adiponectin


BMI group

Spanish language competency pressure. No statistically significant

correlations were found between Spanish language competency pressure and



pre-pregnancy BMI

weight

newborn weight

resident index

69

preferred language

leptin

adiponectin


BMI group

Pressure to acculturate. No statistically significant correlations were found

between pressure to acculturate and



pre-pregnancy BMI

weight

newborn weight

residency index

preferred language

leptin

adiponectin


BMI group

Pressure against acculturation. No statistically significant correlations were

found between pressure against acculturation and



pre-pregnancy BMI

weight

70

newborn weight

resident index

preferred language

leptin

adiponectin


BMI group

Values for the Pearson r correlation coefficients are presented in Tables 4.4a

and 4.4b.

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Table 4.4a

Correlations among Study Variables

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

1. Gestational diabetes — .03 -.01 .03 .13 -.02 -.08 .04 -.21 .08 .01 -.10 .11 -.15 -.02

2. Pre-pregnancy weight — .84** .93** .14 -.26* -.35** .20 -.02 .19 .16 -.16 .02 -.09 -.01

3. Pre-pregnancy BMI — .84** .05 -.27* -.31** .14 -.04 .12 .06 -.13 .05 -.04 .02

4. Weight — .21 -.35** -.36** .27** -.11 .21 .17 -.20 .07 -.11 .01

5 Newborn weight — .06 .02 .04 .09 .14 .26* -.02 -.19 -.05 -.17

6 Resident index — .81** -.83** .45** -.47** -.12 .61** -17 .15 .01

7 Preferred language — -.69** .31** -.48** -.23** .47** -.12 .06 -.04

Multidimensional Acculturation Scale II

8 English proficiency — -.29* .50** .22 -.58** .05 -.08 -.04

9 Spanish proficiency — .08 .33** .24* -.63** .05 -.22

10 American culture identity — .52** -.22 -.03 -.04 -.05

11 Mexican culture identity — -.11 -.38 -.03 -.21

Multidimensional Acculturative Stress Inventory

12 English competency pressure — -.04 -.59** .33**

13 Spanish competency pressure — .23 .59**

14 Pressure to acculturation — .74**

15 Pressure against acculturation —

** p < 0.01. * p < 0.05.

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Table 4.4b

Correlations among Study Variables

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

1 Leptin — -.10 .89** .-10 .52** .45** .38** .26* -.02 .27* .16 -.18 .01 .02 .53

2 Adiponectin — -.38** -.17 -.23 -.27* -.26* -.06 .04 -.11 .05 -.01 .09 -.09 -.11

3 Leptin-adiponectin ratio — -.12 .53** .50** .39** .22 -.10 .16 .13 -.18 -.06 .05 .09

4 Gestational diabetes — .03 .03 -.02 .04 .03 .13 .20 .09 .05 .05 .09

5 Weight — .93** .71** .27** -.11 .21 .17 -.20 .07 -.11 .01

6 Pre-pregnancy weight — .79** .20 -.02 .19 .16 -.16 .02 -.09 -.01

7 BMI group — .04 -.21 .08 .01 -.10 .11 -.15 -.02


8 English proficiency — -.29* .50** .22 -.58** .05 -.08 -.04

9 Spanish proficiency — -.08 .33** .24* -.63** .05 -.22

10 American culture identity — .52** -.22 -.03 -.04 -.05

11 Mexican culture identity — -.11 -.38 -.03 -.21


12 English competency pressure — -.04 .59** .33**

13 Spanish competency pressure — .23 .59**

14 Pressure to acculturation — .74**

15 Pressure against acculturation —

** p < 0.01. * p < 0.05

73

Research Question 2.1.

Is there a significant difference in the levels of the psychosocial markers of

acculturation and acculturative stress between women with and without gestational

diabetes?

Independent t-tests were used to answer this question. These revealed that there

was no significant difference between women with and without gestational diabetes in

the levels of the psychosocial markers of acculturation (English language proficiency,

Spanish language proficiency, American cultural identity, Mexican cultural identity) and

acculturative stress (English language competency pressure, Spanish language

competency pressure, pressure to acculturate, and pressure against acculturation). T-

test results are presented in Table 4.5.

Research Questions 2.2.

Is there a significant difference in the metabolic markers of leptin and adiponectin

between women with and without gestational diabetes?

Independent t-tests were used to answer this question. These revealed that there

was no significant difference between women with and without gestational diabetes in

the levels of the metabolic markers of leptin, adiponectin, and in the leptin/adiponectin

ratio. T-test results are presented in Table 4.5.

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Table 4.5

Independent t-test Analysis of Difference between Women with and without Gestational Diabetes

Gestational Diabetes (n = 38)

Non-Gestational Diabetes (n = 38)

M

SD M SD t df p

Pre-pregnancy weight 183.16 46.23 180.32 43.95 -.28 74 .78

Pre-pregnancy BMI 32.65 8.27 32.58 7.68 -.04 74 .97

Leptin 93.82 78.99 108.75 72.77 .86 74 .39

Adiponectin 6.20 1.96 6.98 2.60 1.47 74 .15

Leptin-adiponectin ratio 18.88 14.76 17.74 14.63 .26 74 .80


English proficiency 24.81 7.59 24.25 7.93 -.31 73 .76

Spanish proficiency 19.49 7.11 19.08 6.68 -.26 73 .80

American cultural identity 19.89 3.65 18.76 5.07 -1.10 73 .27

Mexican cultural identity 25.62 4.27 23.71 5.14 -1.75 73 .09


English competency pressure 5.05 9.06 3.74 4.97 -.78 73 .44

Spanish competency pressure 4.42 5.40 3.92 4.80 -.42 73 .67

Pressure to acculturate 5.95 6.45 5.34 5.52 -.44 73 .66

Pressure against acculturation 4.43 4.40 3.68 4.13 --.76 73 .45

75

Summary

The results from this study answered the research questions posed and indicated

that significant relationships do exist between some of the variables of interest; however,

there were no overall significant differences found between women with and without

gestational diabetes. These mixed results may be an indicator of a need to further

explore these concepts.

This chapter presented the results of this study by answering the research

questions posed in Chapter I using statistical methods outlined in Chapter III. The

sample was described by reporting frequency distributions of demographic data. Then,

frequency distributions of scores for survey instruments and values for laboratory tests

were provided. Parametric tests including Pearson r correlations and t-tests were used

to answer the research questions.

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CHAPTER V

DISCUSSION AND SUMMARY

This chapter begins by reviewing the purpose and research questions presented

in Chapter 1 before interpreting the findings presented in Chapter 4. Study limitations are

presented and addressed. Applications to theory development, implications to nursing

practice, and recommendations for future research are considered.

This biobehavioral study was a secondary analysis of the NIH-funded study,

Preterm Birth: Psychoneuroimmunology in Hispanics. This study explored relationships

between the psychosocial stressors of acculturation and acculturative stress in Mexican

American women with and without gestational diabetes and examined whether

differences exist in the metabolic markers of leptin and adiponectin in Mexican American

women with and without gestational diabetes.

Interpretation of Findings

Findings in this study were mixed. Small to moderate significant correlations

were found between some of the psychosocial variables and physiological variables, but

overall there were no significant relationships between the psychosocial variables

(acculturation and acculturative stress), metabolic variables (leptin and adiponectin), and

gestational diabetes or differences in women with and without gestational diabetes.

Psychosocial Stress

Acculturation is a multi-factorial and dynamic process that has been linked to

high risk of obesity (Oza-Frank & Cunningham, 2010). The findings support the current

literature (Oza-Frank & Cunningham, 2010; Perez-Escamilla & Putnik, 2007) and

indicate a positive relationship between acculturation and body weight among this group

of Mexican American women. Findings indicated that the longer women reside in the

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U.S. and the more acculturated they report becoming, the heavier their weight. Existing

research attributes overweight and obesity among first generation Americans to the

demands of the transition into the American mainstream culture including the stress

associated with departure from their country of origin, social isolation, language

difficulties, financial difficulties and discrimination (Akresh, 2007). Dietary and physical

activity patterns which contribute to the changes in weight are also thought to change as

individuals adapt to their new culture (Akresh, 2007). The new dietary patterns of high

fat, high sugar diet, along with more sedentary physical activity patterns eventually get

transferred to the next generation, making successive generations more vulnerable to

overweight and obesity.

In contrast, acculturative stress was not significantly associated with weight or

gestational diabetes. However, research indicates that acculturative stress is a powerful

concept that has been associated with negative effects on individuals including poor

psychological functioning, depression, and anxiety (Torres, Driscoll, & Voell, 2012;

Iturbide, Raffaelli, & Carlo, 2009). As a chronic stressor, acculturative stress can be a

direct result of the acculturation process. During the process of acculturation, individuals

can adapt to the host culture using different strategies including integration, assimilation,

separation or marginalization. Separation and marginalization are considered the most

challenging and can place individuals for higher risk for acculturative stress (Berry &

Sam, 1997). Acculturative stress is highly dependent on an individual’s appraisal of the

acculturation experience itself. Individuals must choose what characteristics they want to

keep from their own culture and what they want to adopt from the host culture (Caplan,

2007; Berry & Sam, 1997). Acculturative stress models depict the concept on a

continuum where individuals can select to keep characteristics of their country of origin,

78

to identify more closely with the host society, or do both making the concept difficult to

investigate (Berry & Sam, 1997).

Equally challenging to investigate and related to stress, this study proposed

allostatic load as a potential contributor to altered metabolic response. Unfortunately,

without a solid relationship with acculturative stress, one of the major markers of stress

in this study, further investigation is needed to examine this study’s proposed

relationship of the body reaching allostatic load as a result of the changes of the

acculturation process, mostly influenced by acculturative stress. Allostatic load is difficult

to examine in pregnant women because some of its markers, such as cholesterol and

waist hip ratio, cannot adequately be measured during pregnancy. Future longitudinal

studies could further pursue this hypothesis by including more clearly defined and

measurable allostatic load markers such as cortisol, norepinephrine, epinephrine,

dehydroepiandrosterone (DHEA), cholesterol, waist hip ratio, glycosylated hemoglobin,

and blood pressure in women during the pre-conception period, throughout the

pregnancy, and then postpartum (Geronimus, Hicken, Keene, & Bound, 2006; Seeman,

McEwen, Rowe, & Singer, 2001). Examination of markers such as cholesterol and waist

hip ratio would be limited to the pre-pregnancy and postpartum periods. Having allostatic

load information for the pre-conception period, different pregnancy trimesters, and

postpartum periods would provide valuable information on biological risks associated

with the process of acculturation and acculturative stress in relation to allostatic load

markers.

Metabolic Response

The study of adipokines in metabolic response is an emerging science that is

actively establishing a credible body of evidence supporting the role of adipokines in

79

disease, and implicating leptin and adiponectin in altered metabolic responses (Kyrou &

Tsigos, 2009). This study supports prior findings that suggest that leptin levels are

associated with weight. Generally, overweight and obese individuals have overall higher

levels of leptin and other pro-inflammatory compounds, which place them at risk for

altered metabolic responses—specifically metabolic syndrome, cardiovascular disease,

and diabetes (Kyrou & Tsigos, 2009). Our data describes a significant, positive direct

relationship between weight and leptin levels, which supports prior findings.

Although the science of the physiology of the metabolic response is still evolving,

little is known about how psychosocial factors influence these responses. Few research

studies have investigated the impact of how the transition of adapting to U.S.

mainstream culture affects levels of leptin and other physiologic responses. This study

further examined the relationship of leptin with the psychosocial influences of

acculturation and acculturative stress. The study contributes a novel and important

finding by finding a significant association between English proficiency and American

culture identity and levels of leptin. This small but significant finding supports the need to

expand the science on the biological influences of acculturation and the need for

culturally sensitive care that begins with assessing modifiable risk factors and providing

appropriate interventions to ease the transition of individuals adapting to the American

culture.

By identifying modifiable risk factors associated with the acculturation process,

such as social isolation, depression, and anxiety, advanced practice nurses can

implement cognitive behavioral interventions designed to alleviate these symptoms.

Additionally, implementing weight loss and exercise programs for weight management

80

can help alleviate the risk of weight gain, which has been found among first generation

Americans adjusting to the American culture.

Gestational Diabetes Mellitus

A surprising finding of this study was a lack of significant relationships and

differences in women with and without gestational diabetes related to weight and levels

of leptin and adiponectin. Overweight and obesity are established risk factors for

gestational diabetes and other metabolic alterations (Yogev & Visser, 2009). While

previous studies have supported strong associations between gestational diabetes and

weight, this finding was not demonstrated in this sample. It is possible that this

association was not clearly delineated because the sample was matched by weight.

Because of this approach, there was not enough variability in the women’s weight that

would allow us to determine any differences. Perhaps a random selection technique for

the non GDM group would have provided more diversity in weight ranges making

differences more evident. Similarly, the literature supports that there are differences in

leptin and adiponectin levels in women with and without gestational diabetes. However,

this study did not find any significant differences between the two groups (Ategbo 2006;

Winzer et al., 2004). Gestational diabetes has been implicated in pregnancy

complications that affect both the mother and baby. Because it is usually diagnosed

during the third trimester of pregnancy, it creates prolonged fetal exposure during

vulnerable periods of fetal development (Yogev & Visser, 2009). Prevention and early

recognition of glucose intolerance is vital in women of childbearing age at risk for

gestational diabetes to prevent prolonged fetal exposure. To help diagnose gestational

diabetes early, further research is needed to investigate what other markers may be

implicated in its development.

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Limitations

This study met its aims and answered the research questions posed. However,

several limitations exist that restrict generalizability of the findings.

Self-Report

This study relied on self- report for demographic and survey data. Self-report

survey studies can be limiting due to the nature of the participants’ willingness to answer

questions truthfully and accurately since personal biases may exist. Additionally,

participants’ may not fully understand or fail to disclose lack of understanding of the

questions of interest making their responses inaccurate. Demographic data reported

country of birth and generational level did not match as expected. This could be

attributed to inconsistent participant self-report, personal introspective, and/or lack of

understanding of the question.

Sample size

The sample size in this study was small, which affected its power and overall

generalizability. A larger sample size with a broader range of women’s weight and more

equitable generational levels (i.e., greater participation of second generation participants

for the non-GDM group) could have provided more information, as well as an opportunity

to use more advanced statistical analyses to evaluate the complex relationships

investigated. Evidence supports that people in the transitional stages of acculturation,

such as those of the second generation, are more likely to be actively struggling with the

acculturation process and may develop worse health problems compared with earlier

and later generations (Perez-Escamilla & Putnik, 2007). In addition, because the

relationships among the concepts explored in this study are multifactorial, dynamic, and

complex, inclusion of mediators or moderators that may affect the psychosocial and

82

physiologic processes may be useful for explaining potential relationships among the

variables.

Matching techniques

Matching the women with and without gestational diabetes on weight was

limiting. Because weight is a major contributor to metabolic response, having a primarily

obese sample that was matched by weight, biological information was unavailable on

normal weight women. Matching on weight compromised the variability of the sample

and limited the findings by decreasing the data available on normal weight women.

Having a more diverse weight range in the women without gestational diabetes would

have provided useful information. Obesity, as a major contributor to metabolic response,

may also possibly have obscured other existing relationships. Recruiting more normal

weight women for both groups may have been a better technique to meet the goals of

this study. Furthermore, random selection of the non-GDM would have

Despite these limitations, the study’s findings revealed valuable information and

informed the science on gestational diabetes. Statistically significant, preliminary

Pearson r correlations were obtained, which warrant further exploration of the concepts

of interest.

Application to the Theory Development

Theory development in professional nursing is important for the growth of nursing

science. This study was influenced by Leininger’s theory of transcultural nursing (1978;

1985), which proposed that culturally sensitive care begins with recognizing that

individuals are the sum of their historical, cultural, and social influences. It also was

based on Neuman’s systems model (1982), which proposed that individuals seek to

maintain a balance in the interrelationships of stressors and environment in order to

83

achieve health. This study’s conceptual model also was guided by McEwen’s allostatic

load theory (1988), which specifies that the physiological cost of individuals’ adaptation

to stressors can lead to a decline of physiological function, resulting in allostatic load

which can increase risk of disease.

Consistent with Leininger’s and Neuman’s theories, this study’s findings of

significant associations between the psychosocial (i.e., resident index, preferred

language, English language proficiency, American cultural identity) and biological

(weight, leptin level) variables supports that cultural influences are associated with

physiological processes. This finding warrants further investigation of these dynamic and

complex relationships to advance the science. Specifically, investigating whether the

psychosocial variables (i.e., acculturation, acculturative stress) have an impact on

physiologic responses leading to maladaptation of the stress response as seen in

McEwen’s allostatic load theory would support the use of the psychosocial stressors of

acculturation and acculturative stress as markers of allostatic load.

Implications for Nursing Practice

As the country is transformed into a society where Mexican Americans are the

largest minority group, the U.S. health care system will need to be prepared to make

changes in the delivery of health care. Nurses, physicians, health care administrators,

and legislators will need to respond appropriately by planning how effective, culturally

appropriate health care will be delivered to a vulnerable population.

As posed by the Hispanic paradox (Palloni & Morenoff, 2001; Franzini; Ribble, &

Keddie, 2000), first generation Americans have comparable to better health outcomes as

non-Hispanic White Americans, making preventive care and health promotion vital to

first generation Americans’ transition into American culture. Maintaining the health of this

84

generally healthy population by implementing health promotion strategies such as weight

management, exercise, stress management, smoking avoidance and/or cessation, and

regular health screening in first generation Americans can result in keeping them free of

disease and provide opportunities for early recognition of disease. If they continue to

adopt health promoting behaviors as they age, transition, and adjust to the U.S.

mainstream culture, the group is likely to remain healthy. In addition, promoting healthy

behaviors in first generation Americans may result in healthier subsequent generations

as the elders impart their healthy behaviors to new generations.

First generation childbearing women are an excellent group to target for health

education and preventive care. Reaching these women, specifically women who are at

risk for GDM and later T2DM, during the pre-conception and prenatal care periods with

health education to prevent disease, weight management, mental health, and disease

risk assessments and screening will have an impact on their conception, pregnancy, and

their future health and that of their child. Targeting this group of women can help us

foster the positive influences of acculturation by supporting their opportunities to have

better access to health care, including greater use of preventive care and improved

educational opportunities. Ultimately, these types of services can contribute to better

health, higher earning potential and upward mobility (Perez-Escamilla, 2011; Akresh,

2007).

Advanced practice nurses are trained in health promotion and disease

prevention, making them important contributors in the planning of delivery of this type of

care. It is imperative that advanced practice nurses participate in research to investigate

the impact of psychosocial stress on metabolic response, plan and evaluate effective

interventions for appropriate care, disseminate health promotion information, participate

85

in establishing and evaluating efficient health promotion programs, as well as work at the

bedside promoting overall health and implementing preventive health care.

Recommendations for Future Research

This biobehavioral study provided insights into how cultural influences might alter

biological processes. The following research questions are worthy of being explored in

future research:

1. What is the relationship between level of acculturation and body mass index,

blood pressure, fasting blood sugar, glycosylated hemoglobin, triglycerides,

and waist circumference in normal, overweight, and obese women

contemplating pregnancy within one year?

2. What is the relationship between acculturative stress and markers of

allostatic load (i.e., cortisol, norepinephrine, epinephrine, and

dehydroepiandrosterone [DHEA])?

3. Is gestational diabetes a long-term predictor for metabolic syndrome? What is

the predictive value of gestational diabetes on metabolic syndrome?

4. Is acculturation useful as a measure of allostatic load?

5. What are the relationships among acculturation, stress, depression, and

anxiety?

6. What is the relationship between acculturation and dietary intake in

childbearing women?

7. Is acculturation a predictor of inflammatory response as measured by C-

reactive protein and tumor necrosis alpha?

8. Is acculturation a predictor of changes in metabolic response?

86

9. Are leptin and adiponectin levels different in normal weight women with and

without gestational diabetes during the different trimesters of pregnancy?

10. What are the relationships among leptin, adiponectin, C-reactive protein,

tumor necrosis alpha in normal, overweight, and obese women?

Summary

Although findings indicated that acculturation had no direct impact on

development of GDM in Mexican American women, acculturation was positively

associated with weight and leptin levels. The relationship between acculturative stress

and allostatic load requires additional investigation to provide insight on whether

acculturative stress can be used to quantify biological risks associated with the

development of GDM in Mexican American women.

As the U.S. transitions to a society where individuals who were historically

considered minorities become the majority, our health care system will face multiple

challenges as it adapts to provide high quality, culturally appropriate care for all.

Governments and policy makers will need to review and adapt policies to meet the

needs of these people. Advanced practice nurses and nurse researchers need to

continue to investigate and provide quality health care to foster holistic wellness and

promote accountability in individuals. Most importantly, individuals will need to become

accountable for their health and the health of their families, be active participants in their

communities, and take responsibility for their health by choosing behaviors that can lead

to better health outcomes.

This chapter reviewed the purpose and research questions that were presented

in Chapter 1, interpreted the findings presented in Chapter 4, presented and addressed

87

study limitations, discussed applications to theory development and implications for

nursing practice, and proposed recommendations for future research.

88

Appendix A.

Survey Instruments

89

90

91

92

93

94

95

96

97

Appendix B

Letter from Office of Research Support

98

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