13. Endocrine control of appetite Flashcards
Which nucleus plays a role in control of appetite?
Arcuate nucleus within the hypothalamus
What do primary neurons in the arcuate nucleus sense?
Sense metabolite and hormone levels
What are the divisions of the primary neurones in the arcuate nucleus?
Excitatory (orexigenic neurons) and inhibitory (anorexigenic neurons) types
How do excitatory primary neurons affect appetite and which hormones do they release?
Stimulate appetite via the release of two peptides:
- neuropeptide Y (NPY)
- agouti-related peptide (AgRP)
How do inhibitory primary neurons affect appetite and which hormones do they release?
Suppress appetite by releasing pro opiomelanocortin (POMC)
What are the products of cleavage of POMC, and which is involved in regulation of appetite?
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
What receptor does α-MSH act on?
melanocortin 4 receptors
Give examples of hormones that feedback to the arcuate nucleus.
- ghrelin
- PYY
- leptin
- amylin
- insulin
When is ghrelin released?
When the stomach is empty
- released from cells lining stomach wall
Which arcuate neurons does ghrelin have an effect on and what effect does it have?
Stimulates excitatory primary neurones and therefore stimulates appetite
What inhibits ghrelin release?
Filling of stomach inhibits ghrelin release
What is PYY and where is it released from?
Peptide Tyrosine Tyrosine
Short (36-amino acid) peptide hormone released by cells in the ileum and colon in response to feeding
Which arcuate neurons does PYY have an effect on and what effect does it have?
Inhibits the excitatory primary neurones of the acrcuate nucleus and stimulates the inhibitory neurones
- suppress appetite
What type of hormone is leptin and where is it released from?
Peptide hormone released from adipose tissue.
Which arcuate neurons does leptin have an effect on and what effect does it have?
1) Stimulates the inhibitory (POMC) neurones
2) Inhibits the excitatory (AgRP/NPY) neurones in
arcuate nucleus
- suppress appetite
What effect does leptin have on mitochondria?
induces expression of uncoupling proteins in
mitochondria. Energy therefore dissipated as heat
What effect does insulin have on appetite?
- Suppresses appetite by similar mechanism as leptin
* Seems to be less imp
What type of hormone is amylin and where is it released from?
peptide hormone released form beta cells in pancreas
What are the effects of amylin?
suppress appetite, decrease glucagon secretion and slow gastric emptying
What is pramlintide?
A synthetic analogue of amylin approved for treatment of type 2 diabetes
What is the association between PYY and obesity?
There is a blunted PYY response following food intake in obese humans —> crave more food still
What is the association between leptin and obesity?
- A lack of leptin production or insensitivity to leptin has been associated with obesity
- treated with leptin injection
What are primary neurones attached to in the arcuate nucleus?
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
