Lecture 20: Regulation of Food Intake

Question 1

What are the feeding/satiety centers in the hypothalamus?

Answer 1

Lateral nucleus
Ventromedial nucleus
Paraventricular nucleus 
Dorsomedial nucleus
Arcuate nucleus

Question 2

What pathways are regulated by the arcuate nucleus?

Answer 2

Anorexigenic (satiety pathway)
Orexigenic (hungry pathway)

*antagonize each other

Question 3

Describe the anorexigenic pathway

Answer 3

Satiety factors: Insulin, Leptin, CCK, stomach distension > POMC neurons release a-MSH > binds to MCR-4 > decrease food intake

Question 4

Describe the orexigenic pathway

Answer 4

Ghrelin > AGRP/NPY neurons release AGRP and NPY > NPY binds to Y1R, AGRP binds to MCR-4 > increase food intake

Question 5

What happens if there are mutations in POMC and MCR4?

Answer 5

loss of feelings of satiety > can lead to obesity

Question 6

Genetic causes of obesity: affected genes
Leptin or leptin receptor gene deficiency
Melanocortin 4 receptor gene mutation
Prader Willi syndrome
Proopiomelanocortin (POMC) deficiency

Answer 6

• leptin gene
• MC4R gene
• partial deletion of chromosome 15 (paternally expressed genes)
• POMC genes

Question 7

What is the pathway of satiety signals for inducing satiety?

Answer 7

satiety signals > vagus N. (nolose ganglion) > NTS in medulla > Arcuate nucleus in hypothalamus > anorexigenic pathway > satiety

Question 8

What happens when Vagus N. is blocked?

Answer 8

lose input from satiety signals = can’t figure out if you’re full or not

Question 9

What are the roles of the other appetite centers in terms of regulating appetite?

Answer 9

Lateral nucleus: hunger center (releases MCH and orexins to stimulate hunger pathway)
Ventromedial nucleus: satiety center
Dorsomedial nucleus & Paraventricular nucleus: take input to the cerebral cortex/brainstem

Question 10

Ghrelin:

How does it affect appetite and how does it do it?

Answer 10

Ghrelin > GHSR on neurons > release of NPY > increase appetite

Effects: increased appetite, gastric motility, acid secretion, adipogenesis

Question 11

Insulin:

How does it affect appetite and how does it do it?

Answer 11

Insulin inhibits NPY and stimulates POMC > increase satiety

Question 12

CCK:

How does it affect appetite and how does it do it?

Answer 12

-increases satiety and metabolism

I cells in duodenum > release CCK > Vagus N. > NTS > arcuate nucleus > decrease Ghrelin, gastric emptying, increase distension

Question 13

PYY:

How does it affect appetite and how does it do it?

Answer 13

-increases satiety and metabolism

L cells in ileum > PYY > bind to Y2R in hyp > inhibit NPY and stimulate POMC

Question 14

Leptin:
How does it affect appetite and how does it do it?

What kind of obesity does leptin reduce fat mass in?

Answer 14

-increases satiety and metabolism

Adipose > leptin > inhibit NPY and stimulate POMC

congenital leptin deficiency. regular obesity patients do not respond to exogenous leptin

Question 15

GLP-1 (glucagon like peptide - 1)

Answer 15

• GLP-1 is an incretin that increases after eating and decreases when fasting
• active after eating - decreases food intake, glucagon secretion and gastric emptying
• L cells > GLP 1 with oxyntomodulin

Question 16

Pancreatic peptide
Glucagon
Amylin

Answer 16

• F Islet cells > PP > decrease food intake
• a islet cells > decrease food intake
• B cells > insulin + amylin > NPY inhibition > decrease food intake

Question 17

Anorexia nervosa

Answer 17

• reduced fat mass leads to reduced basal and pulsatile leptin secretion
• Ghrelin resistance - can’t feel hunger
• increased PYY - suppresses appetite