Lec 14 - Gut hormones Flashcards by Kirti Grover

2 types of enteroendocrine cells (EEC)

open EEC = has microvilli to sample the lumen
closed EEC = no access to lumen, recieve input from eihter blood or neurotransmitters from motor neurons

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what do EECs do

release hormones in response to nutrints in gut lumen

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what type of hromone are most GI hromones

peptides that bind to GPCRs

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3 types of gut peptide hromones

gastrins = regulate digestive process
secretins = induce hormone release
motilins = regulate gastric motility

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the 3 phases of hromone release

cephalic phase
gastric phase
intestinal phase

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Cholecystokinin (CCK): where released from

I cells in duodenum

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Cholecystokinin (CCK): when released

stimulated by fat and protein in intestinal lumen

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Cholecystokinin (CCK): what receptor

CCK 1 receptor

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Cholecystokinin (CCK): effects

decreased gastric motility
delayed gastric emptying
increased satiety (smaller meals BUT eat more frq, so food intake is acc the same = not used to treat obesity)

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Glucose dependent insulinotropic polypeptide (GIP): wehre released from

K-cells in duodenum

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Glucose dependent insulinotropic polypeptide (GIP): released why

stimulated by sugar and fat

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Glucose dependent insulinotropic polypeptide (GIP): effects

Incretin horome release to increase insulin secretion from pancreatic beta cells

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Glucose dependent insulinotropic polypeptide (GIP): what type of hormone

endocrine

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Glucose dependent insulinotropic polypeptide (GIP): where does it act

on GIPR on beta cells in pancreas
- GIPR also throughout the body

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Glucose dependent insulinotropic polypeptide (GIP): why doesnt it reduce food intake on its own effectively

doesnt reach the CNS cuz degraded so fast

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Glucose dependent insulinotropic polypeptide (GIP): what do long acting GIPRA allow

long acting GIP agonists
allow bidning to GIPR in brainstem = reduce food intake and body weight

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Glucagon like peptide-1 (GLP-1): where released

L - cells in ileum and jejunum

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Glucagon like peptide-1 (GLP-1): when released

in cephalic phase = stimulated by neural input from brain
post-prandially is stimulated by sugar

Glucagon like peptide-1 (GLP-1): effects

an incretin hromone: inc insulin release
decreases glucagon release
ileal brake = inhibit gastric emptying,

Glucagon like peptide-1 (GLP-1): what type of hromone

endrocrine and neural

Glucagon like peptide-1 (GLP-1): what does it do in the CNS

acts on ARC and AP to increase satiety

Glucagon like peptide-1 (GLP-1): what receptor

GLP-1R

Glucagon like peptide-1 (GLP-1): effects on vagal afferent neurons

triggers vago-vagal reflex
decreases gastric emptying
increases satiation

enzyme that cleaves GLP-1, giving it a short half life

DPP4

what are gliptins

DPP-4 inhibitors = inc circulating GLP-1

what are exendins

analogues of GLP-1 that are resistant to DPP4

primary fucntion of leptin

signals sufficiency of adipose stores to permit various biological functions

leptin deficiency symptoms

obese hyperphagic

leptin receptor>

LepR 5 types, located peripherallly and centrally receptor tyrosine kinases

what does receptor tyrosine kinases trigger

JAK/STAT signalling pathways

Leptin: what type of signalling

neural and endocrine

how does leptin affect orexigenic and anorexignic signals

- attenuates orex - potentiates anorex = induces satiety

effect of circulating leptin binding to LepR in arcuate nucleus

- inhibits AgRP/NPY - stimulates POMC neurons = release of aMSH = reduced food intake = increased energy expendature

what might hyperleptinaemia lead to

leptin resistance

leptin resistancce as a cause of obesity

rare but can have congenital defect in leptin gene OR leptin receptor defects

Ghrelin: released from where

- Pd1 cells in stomach - X/A cells in enteroendocrine - episilon cells in islets of langerhans literally wtf is that

Ghrelin: when stimulated

cephalic phase empty stomach is major trigger for ghrelin

Ghrelin: main function

the only HUNGER hormone appetite stimulus increases gastric motility increases gastric acid secretion

Ghrelin: effects of adminstering exogenous ghrelin

stim feelings of hunger causes hunger pains, by contracting gi tract muscles

Ghrelin: how does it signal

neural and endocrine pathways

Ghrelin: what receptor

growth hormone secretagogue receptor (GHSR)

Ghrelin: where are GHSR

either: - vagal/sympathetic afferent neurons (neural) - target tissues e.g. brain (endocrine)

how does leptin control ghrelin

High adiposity = high leptin = inhibition of ghrelin = decreases hunger And vice versa

Ghrelin: in terms of endorcrine control, what does it act on

the GHSR in arcuate nucleus: - stimulates AgRP/NPY neurones - inhibits POMC neurons