Regulation of Food Intake

Question 1

Neuronal centers controlling feeding

Answer 1

• All in hypothalamus
• Lateral nucleus (LH)
• Ventromedial nucleus (VM)
• Paraventricular nucleus (PV)
• Dorsomedial nucleus (NM)
• Arcuate nucleus (Arc)

Question 2

Anorexigenic Pathway

Answer 2

• Stimulated by leptin, insulin, CCK
• a-melanocortin (a-MSH) released by POMC neurons
• a-MSH binds to MCR-4

Question 3

Orexigenic Pathway

Answer 3

• Ghrelin stimulates
• Hunger stimulates NPY – NPY binds Y1R
• AGRP also released

Question 4

AGRP special feature

Answer 4

Antagonist of MCR-4 (inhibits anorexigenic pathway)

Question 5

Where does integration signaling regulating food intake occur?

Answer 5

Arcuate Nucleus

Question 6

How do the anorexigenic and orexigenic pathways regulate each other?

Answer 6

• Antagonism
• Peptides stimulating a-MSH inhibit NPY
• AGRP is an antagonist for MCR-4

Question 7

Obesity and mutations?

Answer 7

Specifically to POMC and MCR-4 genes

Question 8

Ghrelin mechanism

Answer 8

• Secreted in stomach by endocrine cells
• Binds to GHSR
• Stimulates neurons releasing NPY

Question 9

Ghrelin actions

Answer 9

• Increase appetite, gastric motility, gastric acid secretion, adipogenesis
• Decrease insulin?

Question 10

Insulin mechanism

Answer 10

• Binds receptors in POMC (stimulates) and NPY (inhibits) systems

Question 11

Insulin actions

Answer 11

• Decreases appetite
• Increases metabolism
• DM 1 pts have decreased insulin w/ increased food

Question 12

CCK

Answer 12

• I cells in duodenum

- Elicits satiety

Question 13

CCK mechanism

Answer 13

• Acts on vagal – NTS – hypothalamus – decreases ghrelin

- Decreases gastric emptying – increases gastric distention

Question 14

PPY

Answer 14

• L cells in ileum and colon post-prandially
• Binds Y2R in hypothalamus
• Inhibits NYP neurons
• Releases inhibition of POMC

Question 15

Leptin

Answer 15

• Secreted by cells in adipose tissue
• Binds receptors in POMC (stimulates) and NPY (inhibits)
• Decreases appetite, ghrelin release
• Increases metabolism

Question 16

Issues associated with leptin in children

Answer 16

Congenital leptin deficiency causes childhood obesity (can be treated w/ subq admin of leptin)

Question 17

Issues associated with leptin in adults

Answer 17

• Pt w/ high leptin levels (but body fails to respond)

* Leptin resistance

Question 18

Glucagon-like peptide-1 (GLP-1)

Answer 18

• 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

Question 19

Oxyntomodulin

Answer 19

• Proglucagon derived peptide
• L cells in response to ingested food
• Anorectic effect

Question 20

Pancreatic peptide

Answer 20

• From cells in islets of Langerhans
• Decreases food intake via Y4R in brainstem/hypo
• Could act via vagus n. to produce anorectic effect too

Question 21

Glucagon

Answer 21

• a cells in pancreatic islets
• Increase blood glucose and insulin secretion
• Reduces food intake

Question 22

Amylin

Answer 22

• Stored/released w/ insulin in response to food intake

- Anorectic effect (via NPY inhibition)

Question 23

Anorexia Nervosa

Answer 23

• Self-starvation and excessive weight loss

- Pt. becomes severely malnourished, has endocrinological/cardiological dysfunctions

Question 24

Biological factors and AN

Answer 24

• 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)