Regulation of Food Intake Flashcards
What are neuronal centers that conttrol feeding and satiety?
- lateral nucleus
- ventromedial nucleus
- paraventricular nucleus
- dorsomedial nucleus
- arcuate nucleus
Where are the centers that control feeding and satiety located?
hypothalamus
What is key to maintaining energy balance?
cross-talk between neural and hormonal regulation via hypothalamus
What signals converge in hypothalamus?
neural from GI tract
chemical from nutrients in blood
GI hormones
adipose tissue
cerebral cortex (small, taste, sight)
Where is most of the integration of signaling that regulates food intake and energy expenditure?
arcuate nucleus of hypothalamus
What is the anorexigenic pathway of the arcuate nucleus?
first part of arcuate nucleus pathway
–> alpha-melanocortin (a-MSH) released by POMC neurons
–> bind to MCR-4 present in second order neurons
*****DECREASE food intake
What is the orexigenic pathway of the arcuate nucleus?
second part of arcuate nucleus pathway
–> neuropeptide Y (NPY) stimulated by hunger signals
–> bind Y1R
–> AGRP released which is an antagonist of MCR-4
**INCREASE food intake
What is related to mutations in POMC and MCR-4 genes?
some cases of obesity
Do the arcuate nucleus pathways antagonize each other?
Yes–> what activates one inhibits the other
Describe the appetite-inhibiting pathway
POMC (appetite-inhibiting neurons) release a-MSH–> bind MC4 receptors on second-order neurons to inhibit food intake and increase metabolism
Describe the appetite-stimulating pathway
hunger signals stimulate release of neuropeptide Y–> bind Y1 receptors to increase feeding behavior and storage of calories
What is an antagonist of the MC4 receptor?
AgRP released by NPY
Peptides that stimulate satiety and decrease feeding activate receptors on?
Vagal afferents
What circuit produces responses related to feeding behavior and metabolism?
Vagus–>NTS–>hypothalamus
When does the amount of material in the stomach no longer influence meal size?
when vagal activity is blocked
–>also eliminates effects of satiety hormones
What is crucial in interpretation and relaying of peripheral signals from vagus N?
NTS
–> nucleus tractus solitarius
What percent of vagal fibers are afferent?
75%
What is the purpose of the vagal–>NTS–>hypothalamus pathway?
alter feeding behavior and metabolic responses
What is able to regulate food intake in response to peripheral signals even in absence of higher brain center input?
NTS (hindbrain)
What nucleus contains neurons that project to cerebral cortex and areas of brainstem?
PVN
What is the hunger center?
Lateral hypothalamic area
What peptides do the lateral hypothalamic neurons release?
orexigenic peptides
–> MCH, orexins A and B
What is the satiety center?
ventromedial hypothalamic nucleus
Hormones released from what areas regulate feeding behavior?
GI tract
Pancreas
Adipose tissue
Describe Ghrelin in feeding behavior
- secreted in stomach, bind to growth hormone secretagogue receptors
- stimulate neurons that release NPY
- increase appetite, gastric motility and acid secretion, adipogenesis
- decrease insulin secreition
- initiates feeding response
Describe insulin in feeding behavior
- bind receptors in POMC and NPY systems
- —–>inhibits NPY, + POMC
- decreases appetite
- increases metabolism
Describe insulin effects in Type 1 DM related to food intake
increased food intake is associated with decreased insulin in type 1 DM
Describe CCK in feeding behavior
Released by I cells in duodenum
- elicits satiety by acting on vagal-NTS-hypo pathway
- ———> decreases ghrelin
- decreases gastric emptying
- ——->increases gastric distention
Describe PYY in feeding behavior
Released by L cells of ileum and colon after meal
-binds YR2 in hypothalamus to INHIBIT NPY neurons and + POMC neurons
Describe Leptin in feeding behavior
Secreted by adipose tissue
- bind receptors on POMC and NPY systems
- ——> inhibits NPY
- —–> + POMC
- *Appetite-suppressing hormone
- ———> decreases appetite and ghrelin release
- ——-> increases metabolism
Injection of what hormone in obese children reduces fat mass, hyperinsulinemia and hyperlipidemia?
Leptin
Obesity in general is associated with high _____ levels and failure to respond to exogenous ____
leptin
–>AKA leptin resistance
What is released from pancreatic B cells?
Insulin
What is the site of action of insulin r/t feeding behavior?
hypothalamus
What hormone decreases appetite and increases metabolism?
insulin
What hormone is released from fat cells and endocrine cells of the stomach?
leptin
What are the sites of action of leptin?
Hypothalamus and Vagal Afferents
What are the effects of leptin on the hypothalamus?
Increase POMC
Decrease NPY and AgRP
What decreases appetite and ghrelin release, increases metabolism?
leptin
What is secreted from I cells of duodenum?
CCK
What is the site of action of CCK in feeding behavior?
Vagal afferents
What decreases appetite and gastric emptying?
CCK
What is secreted from L cells of ileum and colon?
PYY
What are the sites of action of PYY?
Hypothalamus
Stomach
What are the effects of PYY on the hypothalamus?
decrease NPY and AgRP
Increase POMC
What decreases appetite and gastric emptying, increases metabolism?
PYY
What is secreted from endocrine cells of stomach, hypothalamus, LI and SI?
Ghrelin
What are the sites of action of ghrelin?
Hypothalamus
Vagal afferents
What are the effects of ghrelin on the hypothalamus?
Increase NPY, AgRP
What increases appetite, decreases metabolism and leptin release?
Ghrelin
What is the difference between fat and gut peptide signal in the modulation of food/energy?
Adiposity signals–> long-term regulation of energy balance
Gut peptides–> modulate food intake on meal-by-meal basis
What reduces food intake, suppresses glucagon secretion and delays gastric emptying?
Glucagon-like peptide 1 (GLP-1)
What is co-secreted with PYY from L cells in intestine and is also an incretin?
GLP-1
How are GLP-1 levels affected by meals and fasting?
rise after meal, fall during fasting
–>d/t reduces food intake and inhibits glucagon
What is released from L cells of intestine in response to ingested food/caloric intake?
Oxyntomodulin
–>anorectic effect
What decreases food intake directly through Y4R in brainstem and hypothalamus?
Pancreatic peptide
Where is pancreatic peptide secreted from?
pancreatic islets of Langerhans
What can act on the vagus nerce to produce anorectic effects?
pancreatic peptide
What is stored and released with insulin in response to food intake and inhbits NPY release?
Amylin
What molecules have anorectic effects?
Amylin
Pancreatic Peptide
Oxyntomodulin
Define anorexia nervosa
self-starvation and excessive weight loss
What are some biological factors that support habits of patients with anorexia nervosa?
- morphs in genes involved in eating attitudes and behavior
- secretion of leptin reduced
- ghrelin resistance
- elevated levels of PYY (contributes to decreased nutrient intake)
What are genetic causes of obesity?
- Leptin receptor gene deficiency
- MC4R receptor gene mutation
- Prader Willi syndrome
- POMC deficiency
What causes early-onset SEVERE obesity, hyperphagia, and infertility?
Leptin deficiency
What causes early-onset SEVER obesity, hyerinsulinemia and is the MOST COMMON cause of genetic obesity
MC4R mutation
What is the most common known genetic cause of obesity?
MC4R gene mutation
food inhibition pathway
What leads to severe obesity and MR in children with paradoxically elevated ghrelin?
Prader-Willi syndrome
–>partial deletion chromosome 15
What is related to obesity, red hair, jaundice and adrenal insufficiency?
POMC deficiency
food inhibition pathway
