Nonessential Amino Acid Metabolism in Healthy Adult Males

Leah CooperDepartment of Pediatrics, University of British

Columbia & Child and Family Research Institute, BC Children's Hospital

Outline

Background Protein Amino Acids Indicator Amino Acid Oxidation

Technique Objective & Hypothesis Methods

3 Steps in Study Results Conclusion Future Directions

Background - Protein

Structural component of the body

Enzymes, Hormones, Neurotransmitters, Transport Molecules

Made of 20 Amino Acids Need all 20 in correct

proportions for protein synthesis to occur in the body

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Background – Amino Acids

www.thehealthsite.com www.rpi.edu

Background - Evolution

http://www.nature.com/scitable/topicpage/an-evolutionary-perspective-on-amino-acids-14568445

Background - Nitrogen

Play many metabolic roles in the body

The requirement for total nitrogen is the primary determinant of total protein requirement

If total amino nitrogen is inadequate, synthesis of nonessential amino acids and thus protein is less than maximal

Some nonessential amino acids (NEAA) may supply nitrogen better than others

Rose et al. (1948) showed increased growth by 70-75% in rats fed essential amino acids (EAA) + NEAA

Rechcigl et al. (1957) showed different growth rates in rats

Glutamate gave the largest increase in growth Followed by Alanine, Aspartate, Asparagine, Proline, and Glutamine Smallest increases in growth were Glycine and Serine

Background – Nitrogen Supply

Background - Indicator Amino Acid Oxidation Technique

Previous Methods (N balance) were long in duration, very invasive and impractical

The stable isotope based IAAO is rapid, minimally invasive and accurate

IAAO measures the oxidation of the tracer 13C-PHE to 13CO2 in breath

Oxidation is inversely proportional to protein synthesis

High Oxidation = Low Protein Synthesis

Objective: To determine the metabolic demand of 9 of the NEAA using the indicator amino acid oxidation (IAAO) method in healthy adult males

Hypothesis: There will be a hierarchy among the 9 NEAA, more specifically Alanine, Arginine, Asparagine, Aspartate, Glutamine, Glutamate, Glycine, Proline, and Serine, to supply Nitrogen to the body for the de novo synthesis of the other NEAA and for protein

Methods

Preliminary Study

Adaptation

Study Day

Preliminary Study

Target Population: Healthy adult males Between the ages 20-40 classified as normal body weight

and BMI (18.5-25 kg/m2) Background Information:

Medical & Dietary histories Anthropometric measurements Body composition Resting energy expenditure (REE) Informed consent

Methods

Preliminary Study

Adaptation

Study Day

2 days prior to each study day Adaptation diets contain a

protein intake of 1.0 g/kg and a caloric intake of 1.7 × REE

Provided as 6 milkshakes.

Adaptation

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Methods

Preliminary Study

Adaptation

Study Day

10 Study Days Randomized

Diet: The Base Diet (0.34

g/kg/day) Only EAA

The Base Diet + 1 NEAA (0.73 g/kg/day) 50:50 ratio of EAA:

NEAA 5th Meal starts the

isotope tracer protocol with an oral dose of L-1-13C- Phenylalanine

Study Day Diet

Base +

ALA

BASE (EAA

)

Base +

SER

Week 1

Week 2

Base +

GLN

BASE +

PRO

Base +

ARG

Week 4

Week 5

Etc…for 10 weeks

Study Day 1 Study Day 2 Study Day 3

Study Day 4 Study Day 5 Study Day 6

Study Day Sampling

Sample Collection Breath and Urine

Baseline Isotopic Steady State

Carbon dioxide production (VCO2)

13CO2 oxidation values analyzed using repeated measures ANOVA (Graphpad PRISM)

Sample Analysis & Statistics

Multi-flow Continuous Isotope Ratio Mass Spectrometer

BASE

ALAN

INE

ARGIN

INE

ASPA

RTATE

ASPA

RAGIN

E

GLUTA

MAT

E

GLUTA

MIN

E

GLYCIN

E

SERIN

E

PROLI

NE0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Means ± SD

Tra

cer

Oxid

ati

on

*

Results – 50 Study Days

• The first study to look at NEAA in humans

•We suggest all NEAA can satisfy the metabolic demand for total nitrogen.

Conclusion

Determine whether a difference in NEAA metabolic demand exists in more vulnerable populations

Future Directions

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Acknowledgments

Dr. Rajavel Elango Lab members Ajinomoto Inc. Co. Child and Family

Research Institute University of British

Columbia All my participants!

Rose, W.C., Oesterling, M.J., and Womack, M. (1948). Comparative growth on diets containing ten and nineteen amino acids with further observations upon the role of glutamic and aspartic acids. J Biol Chem 176: 753-762.

Rechcigl Jr., M., Loosli, J. K., Williams, H. H. (1957). The net utilization of non-specific nitrogen sources for the synthesis of non-essential amino acids I. Growth and nitrogen utilization. J Nutr 63: 177-192.

Millward DJ. Methodological considerations. Proc Nutr Soc 2001;60: 3–5.

Food and Agriculture Organization of the United Nations. Energy and Protein Requirements (1991).

References

QUESTIONS ??Thank you for listening !!

Study Diet

Study Day Base Diet