13. Endocrine control of appetite

Question 1

Which nucleus plays a role in control of appetite?

Answer 1

Arcuate nucleus within the hypothalamus

Question 2

What do primary neurons in the arcuate nucleus sense?

Answer 2

Sense metabolite and hormone levels

Question 3

What are the divisions of the primary neurones in the arcuate nucleus?

Answer 3

Excitatory (orexigenic neurons) and inhibitory (anorexigenic neurons) types

Question 4

How do excitatory primary neurons affect appetite and which hormones do they release?

Answer 4

Stimulate appetite via the release of two peptides:

• neuropeptide Y (NPY)
• agouti-related peptide (AgRP)

Question 5

How do inhibitory primary neurons affect appetite and which hormones do they release?

Answer 5

Suppress appetite by releasing pro opiomelanocortin (POMC)

Question 6

What are the products of cleavage of POMC, and which is involved in regulation of appetite?

Answer 6

β-endorphin, adrenocorticotropic hormone (ACTH), α-melanocyte stimulating hormone (α-MSH)

• α-MSH and β-endorphin promote satiety
• α-MSH suppresses appetite
• β-endorphin Produces feelings of tiredness and euphoria after a meal

Question 7

What receptor does α-MSH act on?

Answer 7

melanocortin 4 receptors

Question 8

Give examples of hormones that feedback to the arcuate nucleus.

Answer 8

• ghrelin
• PYY
• leptin
• amylin
• insulin

Question 9

When is ghrelin released?

Answer 9

When the stomach is empty

- released from cells lining stomach wall

Question 10

Which arcuate neurons does ghrelin have an effect on and what effect does it have?

Answer 10

Stimulates excitatory primary neurones and therefore stimulates appetite

Question 11

What inhibits ghrelin release?

Answer 11

Filling of stomach inhibits ghrelin release

Question 12

What is PYY and where is it released from?

Answer 12

Peptide Tyrosine Tyrosine

Short (36-amino acid) peptide hormone released by cells in the ileum and colon in response to feeding

Question 13

Which arcuate neurons does PYY have an effect on and what effect does it have?

Answer 13

Inhibits the excitatory primary neurones of the acrcuate nucleus and stimulates the inhibitory neurones
- suppress appetite

Question 14

What type of hormone is leptin and where is it released from?

Answer 14

Peptide hormone released from adipose tissue.

Question 15

Which arcuate neurons does leptin have an effect on and what effect does it have?

Answer 15

1) Stimulates the inhibitory (POMC) neurones
2) Inhibits the excitatory (AgRP/NPY) neurones in
arcuate nucleus

• suppress appetite

Question 16

What effect does leptin have on mitochondria?

Answer 16

induces expression of uncoupling proteins in

mitochondria. Energy therefore dissipated as heat

Question 17

What effect does insulin have on appetite?

Answer 17

• Suppresses appetite by similar mechanism as leptin

* Seems to be less imp

Question 18

What type of hormone is amylin and where is it released from?

Answer 18

peptide hormone released form beta cells in pancreas

Question 19

What are the effects of amylin?

Answer 19

suppress appetite, decrease glucagon secretion and slow gastric emptying

Question 20

What is pramlintide?

Answer 20

A synthetic analogue of amylin approved for treatment of type 2 diabetes

Question 21

What is the association between PYY and obesity?

Answer 21

There is a blunted PYY response following food intake in obese humans —> crave more food still

Question 22

What is the association between leptin and obesity?

Answer 22

• A lack of leptin production or insensitivity to leptin has been associated with obesity
• treated with leptin injection

Question 23

What are primary neurones attached to in the arcuate nucleus?

Answer 23

Primary neurones synapse with secondary neurones in other regions of the hypothalamus and the signals they receive are integrated to alter feeding behaviour via the vagus nerve