Regulation of Food Intake Flashcards
Neuronal centers controlling feeding
- All in hypothalamus
- Lateral nucleus (LH)
- Ventromedial nucleus (VM)
- Paraventricular nucleus (PV)
- Dorsomedial nucleus (NM)
- Arcuate nucleus (Arc)
Anorexigenic Pathway
- Stimulated by leptin, insulin, CCK
- a-melanocortin (a-MSH) released by POMC neurons
- a-MSH binds to MCR-4
Orexigenic Pathway
- Ghrelin stimulates
- Hunger stimulates NPY – NPY binds Y1R
- AGRP also released
AGRP special feature
Antagonist of MCR-4 (inhibits anorexigenic pathway)
Where does integration signaling regulating food intake occur?
Arcuate Nucleus
How do the anorexigenic and orexigenic pathways regulate each other?
- Antagonism
- Peptides stimulating a-MSH inhibit NPY
- AGRP is an antagonist for MCR-4
Obesity and mutations?
Specifically to POMC and MCR-4 genes
Ghrelin mechanism
- Secreted in stomach by endocrine cells
- Binds to GHSR
- Stimulates neurons releasing NPY
Ghrelin actions
- Increase appetite, gastric motility, gastric acid secretion, adipogenesis
- Decrease insulin?
Insulin mechanism
- Binds receptors in POMC (stimulates) and NPY (inhibits) systems
Insulin actions
- Decreases appetite
- Increases metabolism
- DM 1 pts have decreased insulin w/ increased food
CCK
- I cells in duodenum
- Elicits satiety
CCK mechanism
- Acts on vagal – NTS – hypothalamus – decreases ghrelin
- Decreases gastric emptying – increases gastric distention
PPY
- L cells in ileum and colon post-prandially
- Binds Y2R in hypothalamus
- Inhibits NYP neurons
- Releases inhibition of POMC
Leptin
- Secreted by cells in adipose tissue
- Binds receptors in POMC (stimulates) and NPY (inhibits)
- Decreases appetite, ghrelin release
- Increases metabolism
Issues associated with leptin in children
Congenital leptin deficiency causes childhood obesity (can be treated w/ subq admin of leptin)
Issues associated with leptin in adults
- Pt w/ high leptin levels (but body fails to respond)
* Leptin resistance
Glucagon-like peptide-1 (GLP-1)
- Proglucagon derived peptide
- Cosecreted w/ PPY in L cells
- Incretin
- Increases post-meal/ falls during fasting
- Reduces food intake, suppresses glucagon secretion, delays gastric emptying
Oxyntomodulin
- Proglucagon derived peptide
- L cells in response to ingested food
- Anorectic effect
Pancreatic peptide
- From cells in islets of Langerhans
- Decreases food intake via Y4R in brainstem/hypo
- Could act via vagus n. to produce anorectic effect too
Glucagon
- a cells in pancreatic islets
- Increase blood glucose and insulin secretion
- Reduces food intake
Amylin
- Stored/released w/ insulin in response to food intake
- Anorectic effect (via NPY inhibition)
Anorexia Nervosa
- Self-starvation and excessive weight loss
- Pt. becomes severely malnourished, has endocrinological/cardiological dysfunctions
Biological factors and AN
- Leptin secretion may be reduced, along w/ reductions in fat mass
- Ghrelin resistance may be present
- Elevated PYY (which may contribute to decreased nutrient intake and disordered eating)
