Regulation of Food Intake Flashcards
where are the neuronal centers that control feeding and satiety located?
within the hypothalamus
how does the hypothalamus receive signals from the GI tract?
via the vagus nerve
where does most of the integration signaling regulating food intake and energy expenditure happen?
in the arcuate nucleus
what neurons are involved in the anorexigenic pathway?
pro-opiomelanocortin (POMC) neurons or CART
what stimulates the POMC/CART neurons?
insulin, leptin, and CCK
what happens when insulin, leptin, or CCK stimulate the POMC/CART neurons?
they will release alpha-MSH
where does the alpha-MSH bind to in the anorexigenic pathway?
on their receptors- MCR-4 on the second order neurons in the paraventricular nucleus
what is the result of alpha-MSH binding to the MCR-4 receptors
decreased food intake and an increase in energy expenditure
what neurons are involved in the orexigenic pathway?
AGRP and NPY
what stimulates the AGRP and NPY neurons?
Ghrelin
what inhibits the AGRP and NPY neurons?
insulin, leptin, and CCK
what does NPY bind to?
its receptor- Y1R on the second order neuron in the PVN
what is AGRP an antagonist of?
MCR-4
what happens when NPY binds to its Y1R receptor on the second order neuron in the PVN?
it will result in an increase in food intake
what have some cases of obesity been related to?
mutations in the POMC and MCR-4 genes
what is the finding with prader-willi syndrome?
partial deletion of chromosome 15
what are the symptoms of prader willi syndrome?
small hands and feet, hyperphagia, and paradoxically elevated ghrelin
several peptides that stimulate satiety and decrease feeding activate what?
receptors on vagal afferents
where do the vagal afferents travel?
to the nucleus tractus solitarius and then to the hypothalamus
what kind of information do the vagal afferents carry?
gastric distention, levels of gut hormone, type of lumenal content
what is considered to be the hunger center?
the lateral hypothalamic areas (LHA)
what is considered to be the satiety center?
the ventromedial hypothalamic nucleus
what is ghrelin secreted by?
endocrine cell in the stomach
what does ghrelin stimulate?
neurons that release NPY
what is the only known orexogenic gut hormone?
ghrelin
what is ghrelin release associated with?
increased appetite- it appears to initiate the feeding response
where does insulin bind?
to receptors in the POMC and NPY systems
what happens when insulin binds to the POMC system?
it is going to stimulate it
what happens when insulin binds to the NPY system?
it is going to inhibit it
what is the action of insulin?
it is going to decrease appetite and increase metabolism
what is CCK released by?
I cells in the duodenum
what does release of CCK do?
elicits satiety
what is the mechanism of CCK release?
it is going to act on the vagus nerve, which then travels to the NTS, and then to the hypothalamus circuit
what are the actions of CCK?
it is going to cause an inhibition of the release of ghrelin; it is also going to increase gastric distention and therefore decrease gastric emptying
what is PYY release by?
L cells of the ileum and the colon following a meal
what does PYY bind to?
Y2R in the hypothalamus
what is the action of PYY?
it is going to inhibit NPY neurons and it is going to release the inhibition of POMC neurons (so it promotes the anorexigenic pathway)
what is leptin secreted by?
cells in adipose tissue
what does leptin bind to?
receptors in POMC and NPY systems
what happens when leptin binds to the NPY pathway?
it is going to inhibit it
what happens when leptin binds to the POMC pathway?
it is going to stimulate the POMC pathway
what are the actions of leptin?
it is an appetite-supressing hormone; it causes decreased appetite, increased metabolism, and decreased ghrelin release
obesity in humans is often associated with what type of levels of leptin?
high leptin levels and failure to respond to exogenous leptin (leptin resistance)
What type of regulation is adiposity signals (leptin) involved in?
long-term regulation of energy balance
what is glucagon-like peptide co-secreted with?
PYY from L cells in the intestin
when do the levels of glucagon-like peptide rise and fall?
levels rise after a meal and fall during fasting
what are the actions of glucagon-like peptide?
reduce food intake, suppresses glucagon secretion, and delays gastric emptying
where is oxyntomodulin released from?
released from L cells of the intestine in response to ingested food
what is the effect of oxyntomodulin?
anorectic effect
where is pancreatic peptide (PP) secreted from?
from cells in the pancreatic islets of Langerhans
what is the action of pancreatic peptide?
it decreases food intake directly through Y4R in the brainstem and the hypothalamus; may also act via the vagus nerve to produce anorectic effects
what is the action of glucagon?
increase blood glucose levels and insulin secretion and reduces food intake
where is amylin stored and released from?
stored and released with insulin in response to food intake
what is the effect of amylin?
anorectic effects (inhibition of NPY release)
what is anorexia nervosa characterized by?
self-starvation and excessive weight loss
what biological factors are related to anorexia nervosa?
polymorphisms in genes involved in eating attitudes; basal and pulsatile secretion of leptin is reduced; ghrelin resistance; elevated levels of PYY
