1 به نام خدا. CONTROL OF FOOD INTAKE AND APPETITE 2

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خدا نام به

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CONTROL OF FOOD INTAKE AND APPETITE

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What’s the underlying cause?

Fast forward 15 years to 2030 Humans are sicker than ever

Life expectancy has decreased and productivity is down

Obesity

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Traditionally, a distinction has been made between

homeostatic & nonhomeostatic control of appetite and food

intake

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Deviation from homeostatic control

physiologic nonphysiologic

obesity

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CENTRAL CONTROLS OF FOOD INTAKE AND APPETITE

Coordination by the

Hypothalamus

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The hypothalamus is widely recognized as the

in the control of food intake and appetite

“gate keeper”

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the lateral hypothalamus as the

“hunger center” and

the medial hypothalamus as the

“satiety center”

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A network of communicationamong the gut,

pancreas, adipose tissue, brainstem, and hypothalamus is well

established

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Additionally, further communication

exists between the

hypothalamus and higher cortical centers

pertaining tofood memory of food, with resulting

overall coordinated

control of food intake

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Role of the Brainstem

is the main organ responsible for facilitating the communication between peripheral signals

of food intake and hypothalamic nuclei

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The arcuate nucleus (ARC) is thought to be the

main hypothalamic

area controlling food intake

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Within the ARC, two groups of neurons are pivotalin regulating food intake

One group of neurons contains

neuropeptide Y (NPY), and most of these also contain

Agouti-related peptide (AgRP)

The second group is formed by neurons containing pro-opiomelanocortin

(POMC)

Activation of these neurons

enhances food ntake

(orexigenic)

Activation of these neurons

reduces food intake

(anorexigenic)

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NPY

is the most powerful central stimulant of

appetite

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Neuropeptides Implicated in the Control ofFood Intake

• Agouti-Related Peptide• Cocaine- and Amphetamine-Regulated Transcript

• Hypothalamic Releasing Hormones• Orexins• Melanin-Concentrating Hormone• Brain-Derived Neurotrophic Factor• Ciliary Neurotrophic Factor• Central Neurotransmitters

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PERIPHERAL CONTROLS OF FOOD INTAKEAND APPETITE

Nutrient, hormonal signals from the gastrointestinal system, endocrine

organs, and adipose tissueall have essential roles in influencing

food intake and appetite

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These peripheral signals target areas of the hypothalamus to regulate

appetite They include signals conveying afeeling of fullness (satiety signals)

and hunger (orexigenic signals)

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meal size

These signals can control

&

meal number

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Neural Signals

Orosensory and Optic Stimuli

Orosensory and optic stimuli provide the brain with

sensory information regarding the

nature of foodThese stimuli include

appearance, taste, smell, and textural stimuli

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The information isused by the brain to decision

to eat or not eat to continue or to stop eating

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Gastric Distention

Volume-related postprandial gastric distention results in satiety during a meal

bariatric surgical

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Nutrient Signals

Most nutrient signals exert their effects on the gastrointestinal

system and the brain and induce the secretion of gastrointestinal

hormones and appetite regulation

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Gut Hormones

• the largest endocrine organ

• secretes more than 30 different regulatory

peptide hormones

• digestion and absorption

• affect short-term feelings of hunger and satiety

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These hormones are

the subject of extensive research, given their

potential as

physiologic antiobesity therapies

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Cholecystokinin (CCK)

• It is released postprandially• slowed gastric emptying

• CCK reduces food intake

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Ghrelin• Increases appetite• “hunger hormone”• considered as one of the most powerful

physiologic orexigenic agents • increases food intake and body weight

in rodents• Plasma ghrelin levels are also noted to

increase on weight loss (regain weight )

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Peptide YY (PYY)

• released postprandially• PYY administration decreases food

intake• Obese patients demonstrate a blunted

postprandial rise in PYY• PYY-based antiobesity agents are

currently under development

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Glucagon-like Peptide-1(GLP-1)

• reduces food intake• released postprandially • reduces gastric emptying• analogs of GLP-1 are used in the

treatment of type 2 diabetes• currently undergoing clinical trials for

the treatment of obesity

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Pancreatic Hormones

• major function is to control glucose homeostasis (Insulin & Glucagon)

• pancreatic polypeptide and amylin, also affect appetite ( are satiety signal and reduces food intake)

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Hormones from Adipose Tissue (leptin)

• a circulating protein produced by adipocytes (fat cells)

• is a signal from the adipose tissue to the brain that reflects the state of energy stores

• increased by overfeeding• absence of leptin lead to severe obesity

• Leptin acts on ARC LepR to stimulate POMC neurons and inhibit NPY/AgRP neurons to decrease food intake

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Other HormonesThyroid hormones, gonadal steroids

and glucocorticoids regulate metabolic rate, reproductive state and stress

responses, respectively These processes rely on adequate

energy supplies. Therefore, it is not surprising that hormones regulating these processes are also

involved in theendocrine regulation of appetite

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Signals from the Immune System

Anorexia or decreased food intake during infectious,

inflammatory, and neoplastic disease states is very evident.

Anorexia appears to result from the action of cytokines in the brain

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Hedonic Mechanisms

visual, smell, and taste

signals can override satiety signals to maintain

food intake

The word “hedonic” relates to pleasant (or unpleasant)

sensations

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CONCLUSION

The regulation of food intake and appetite occurs through

the integration of various

central and peripheral signals

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These signals interact at the level of the

brainstem and hypothalamus to produce an overall response of

hunger or fullness

Additionally,

these neuronal networks are hugely modified by other influences such as sensory

inputs, food memory, rewarding aspects

of food, and numerous environmental and emotional factors

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This modification is a particular feature of modernhuman eating behavior and

may underpin the dysregulationof energy balance that is

responsible for the current

obesity epidemic

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By means of ever-expanding current research , it is hoped that our understanding of the complex and intricate signaling pathways governing appetite control will improve and pave the way for

better antiobesity drug treatments

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