Valencik: Satiety Lecture Flashcards by Megan Foggia

suppress appetite

anorexigenic

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increase appetite

orexigenic

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satiation vs satiety

cessation of hunger vs sensation of being full

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Gut hormones that stimulate insulin secretion

incretins

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Gastric parietal cells that release gastric acid

oxyntic cells

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What are two long-term signals for hunger/satiety?

leptin & insulin

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Long term signal
Secreted in proportion to fat stores.
Eat less, less body fat, less of this signal is produced
However, body adapts by:
Minimizing energy usage
Increasing appetite

leptin

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Long term signal

Decreases appetite

insulin

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Factors involved in short-term signaling of hunger/satiety

GI tract hormones - modulated by size/number of meals
Ghrelin - makes you hungry
CCK, PYY - make you full

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5 neural centers that regulate food intake

lateral nuclei
ventromedial nuclei (VMN)
paraventricular nuclei (PVN)
dorsomedial nuclei (DMN)
arcuate nuclei (ARC)

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The feeding center
When stimulated, hunger increases a lot
When destroyed, there is no urge to eat

lateral nuclei

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The satiety center
When stimulated, there is no urge or a refusal to eat
When destroyed, you have a crazy appetite & may continue to eat until you are obese

ventromedial nuclei

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Lesions in this nucleus lead to excessive eating

paraventricular nuclei

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Lesions in this nuclei depress eating

dorsomedial nuclei

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Site where multiple hormones released from the GI & adipose tissue converge to regulate eating & energy consumption

arcuate nuclei

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Two types of neurons found in the arcuate nuclei

anorexigenic –> POMC/CART

orexigenic –> AgRP/NYP

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What happens when you stimulate POMC/CART neurons?

production of alpha MSH which binds to MCR-3/4 & decreases food intake & increases sympathetic activity/energy expenditure

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POMC/CART neurons release (blank) leading to the activation of melanocortin (blank) and (blank) receptors on the PVN.
Simultaneously, (blank) peptide is released and binds an unknown receptor.
They stimulate the PVN regulation pathways that (blank) eating and (blank) energy expenditure

MSH-alpha;
MCR3 and MCR4;
CART;
inhibit;
stimulate

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Orexigenic neurons release (blank) and (blank) in response to low energy stores.
(blank) is an antagonist of MCR-4 blocking the signaling by α-MSH in the PVN.
AgRP stimulates the release of (blank) resulting in inhibition of POMC.

AgRP; NYP
AgRP;
GABA;

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What is the end result of stimulation of AgRP/NYP neurons?

NYP binds to Y1 receptor, alpha-MSH is blocked from binding to MCR-4;
the PVN are not subject to α-MSH binding to MCR-4 and appetite increases, food intake increases, and energy expenditure decreases

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Binds to the Y1 receptor and inhibits neuronal function via hyperpolarization thereby interfering with VMN satiety
Preferentially stimulates to desire for CARBOHYDRATES
Reduces fatty acid oxidation, promotes carbohydrate oxidation, and fatty acid synthesis

NYP

Orexigenic
ARC restricted
Colocalizes with NPY neurons in the ARC.
Functional relationship with NPY. Expression is similarly modulated under identical physiological conditions.
Antagonism with melanocortins in eating and body weight control.

AgRP (Agouti-Related peptide)

Hypothalamic neuroendocrine protein.
Part of a family—the pancreatic polypeptide family hormones.
2 gut hormones, pancreatic polypeptide (PP) and peptide tyrosine-tyrosine (PYY) are other members of the family.
Highest levels are found in the ARC.
One of the most potent orexigenic factors.
When you lose weight, it increases.
Stimulates a craving for carbohydrates

NYP

What happens to NYP levels when you lose weight? What does it stimulate a craving for?

they increase; carbohydrates

Found in the lateral and posterior hypothalamic areas with axonal projections throughout the brain. Receptors are distributed throughout the CNS. Believed to have a role in the emotional & motivational aspects of feeding behavior. Increase wakefulness & suppress REM sleep. Do many things.

orexins

Anorexigenic peptides released in response to food (make you full)

``` Glucagon-like peptide-1 (GLP-1) Cholecystokinin (CCK) Peptide tyrosine tyrosine (PYY) Pancreatic polypeptide (PP) Oxyntomodulin (OXM or OXY) Insulin Leptin ```

Released in response to hunger (make you want to eat)

Ghrelin Galanin Cortisol

Regulates overall body weight by limiting food intake. Directly correlate with body fat. Promotes the synthesis of α-MSH (anorexigenic) suppressing hunger. Reduces the inhibitory effects of local orexigenic neuropeptide-Y (NPY) on POMC nuclei and suppresses hunger initially but in the long run NPY levels return to normal

Leptin

What does leptin do to food intake & energy expenditure?

decreases food intake | increases sympathetic activity & energy expenditure

Thought to mainly regulate BMR Increases insulin sensitivity & fatty acid oxidation Activity is inhibited by adrenergic stimulation & glucocorticoids Levels are reduced in obese individuals & increased in patients with anorexia nervosa

adiponectin

The largest endocrine organ | Releases hormones, peptide neurotransmitters & growth factors

the gut

Examples of gut hormones

``` GLP-1 oxyntomodulin CCK ghrelin pancreatic polypeptide PYY ```

Hormones that stimulate a decrease in blood glucose levels by increasing insulin secretion from the pancreas. Give two examples.

Incretins: glucagon-like peptides, glucose-dependent insulinotropic peptide (GIP)

These are examples of incretins, which decrease blood glucose levels They potentiate glucose-dependent insulin secretion Inhibit glucagon secretion Inhibit gastric acid secretion Inhibit gastric emptying Decrease appetite

glucagon-like peptides

This is an incretin (decreases blood glucose by increasing insulin secretion from the pancreas) Expressed by enteroendocrine K cells of the duodenum & proximal jejunum

glucose-dependent insulinotropic peptide

Overall, what do GLP-1 & GIP do?

decrease appetite & food intake | decrease body weight

A 37 amino acid peptide derived from proglucagon containing the entire 29 amino acids of glucagon. Synthesized and released in the enteroendocrine L cells of the distal gut. Secreted in response to food intake within 5-10 minutes. Has incretin activity. Is thought to use the GLP-1 receptor. In the brain it suppresses ghrelin effects.

oxyntomodulin

Expressed mainly in the duodenum and jejunum. Several active forms (4 major forms) In human plasma it is the CCK-33 form. Increases within 15 minutes after eating and peaks at 25 but the half life is only 1-2 minutes. Binds to GPCRs Synergistic with leptin

CCK (cholecystokinin)

When CCK binds to GPCRs, what happens?

gallbladder contracts pancreatic enzymes are released gastric emptying is inhibited

What are the three pancreatic polypeptide family hormones?

``` 2 gut hormones: pancreatic polypeptide peptide tyrosine tyrosine CNS hormone: Neuropeptide Y (NPY) ```

It does not cross the blood brain barrier. It is expressed in the distal GI. It increases after about 6 hours in proportion to caloric intake. It increases in response to ghrelin, motilin & gastric distention. It decreases ghrelin expression.

pancreatic polypeptide

Pancreatic polypeptide increases in response to (blank x3) and decreases (blank) expression

ghrelin, motilin, & gastric distension; | ghrelin

Produced and secreted from enteroendocrine L-cells of the ileum and colon. Food composition is a potent regulator. Fat leads to the highest levels. Is a potent agonist of Y1 but predominantly the Y2 receptor (increases POMC and decreases NPY) Reduces ghrelin, gut motility, delays in gastric emptying, inhibits pancreatic bicarbonate and protein secretion and inhibits gallbladder contraction. It has satiety effects via actions on the ARC nuclei in the hypothalamus.

protein tyrosine tyrosine

Protein tyrosine tyrosine has (blank) effects via actions of the (blank) nuclei in the hypothalamus

satiety; arcuate

Endogenous agonist of growth hormone Secretagogue receptor stimulates the release of growth hormone. Makes you hangry.

Ghrelin

Where is ghrelin secreted? What is essential for the binding of ghrelin & its effects on food intake?

secreted by stomach, small intestine & colon | must be octanolyated (n-octanoic acid side chain)

Ghrelin's major effect is at the hypothalamus at the (blank) nucleus, where it stimulates (blank) and (blank) causing increased (blank) release inhibiting POMC nuclei

arcuate; NPY; AgRP; GABA

Orexigenic 29 AA peptide Expressed in the gut and brain (wide distribution) and binds GALR1 in the hypothalamus. GAL results in a stimulatory effect on feeding Its effect is small and short lived compared to NPY. It does not impact food preference.

Galanin

Major hormones produced when you're hangry =(

ghrelin

Major hormones produced when you're full =)

insulin (from pancreas) leptin (from adipose tissue) CCK, PYY (from intestine)