146b - Appetite Regulation and Energy Expenditure

Question 1

Which neuropeptides are anorexogenic? (2)

How does leptin affect them?

Answer 1

POMC

CART

Leptin stimulates POMC, CART, which binds MC4R

• > satiety, decreased food intake
• Anorexogenic = decreased appetite

Question 2

What is the effect of a mutation in the MC4 receptor? (MC4R)

Answer 2

MC4R is part of the signaling pathway that tells us that we are full

If mutated, no feeling of fullness

• -> hungry all the time
• -> obesity

Leptin -> increased AgRP, POMC -> bind MC4R

Question 3

List the GI peptides that regulate appetite (4)

Answer 3

• GLP-1
• Amylin
• PYY
• Ghrelin

They inform our brain about our food intake status

Question 4

When trying to lose weight, why is exercise less effective as a treatment than dietary restriction?

Answer 4

Net calorie burn is usually not significant enough to cause a meaningful difference in energy balance

(Net calorie burn = calories burned during exercise - what would have been burned just sitting on the couch)

Question 5

What is the primary hormone from fat cells that signals overall energy stores?

Answer 5

Leptin

• Produced by fat tissue
• Correlates with amount of body fat

Question 7

What condition is associated with leptin resistance?

What are the implications?

Answer 7

Obesity

• Fat stores increase and extra leptin is released
• However, receptors are satruated; we cannot sense extra body fat

Leptin is more effiecient at signaling depletion of energy stores (dropping when weight is lost) than signaling energy surplus (increasing when weight is gained)

Question 8

Which neuropeptides are orexigenic? (2)

How does leptin affect these hormones?

Answer 8

AgRP

NPY

Inhibited by leptin;
low leptin = increased AgRP, NPY -> increased appetitie

• Orexigenic = appetite stimulating
• AgRP and NPY inhibit MC4R (catabolic)
  
  • Leptin inhibits AgRP and NPY to remove the inhibition on MC4R

Question 9

Describe the hypothalamic response to a high fat diet

Answer 9

High fat diet ->

• Microcleal and astrocyte activation
• -> Inflammation
• -> Resistance of AgRP and POMC to leptin signaling
  
  • Normally, leptin inhibits AgRP and POMC
• -> hungry all the time

Question 10

Which hormone regulates day to day energy intake?

Answer 10

Ghrelin

• Regulatory sensor within the GI tract
• Causes us to feel hungry when energy intake is low

(G-ut derived for G-hrelin for G-rowing hungry on the daily)

Question 11

Which cells produce leptin?

Answer 11

Fat cells (adipocytes)

• Fat cells release leptin - function to signal long-term energy stores
• A decrease in leptin -> icnreased appetite
  
  • One reason people feel hungry all the time when they lose weight

Question 12

Which nutrients stimulate GLP-1, GLP-2, PYY release? (4)

Answer 12

Glucose

Amino acids

Short chain fatty acids

Long chain fatty acids