Obesity 2: control of appetite Flashcards
What is satiation
Feeling of fullness that terminates meal
What is satiety
Feeling of repletion that inhibits further meals
What controls food intake
Hypothalamus
What region of the brain controls hunger and appetite
Arcuate nucleus (ARC) within the hypothalamus
What does the release of NPY and AgRP from the arcuate nucleus in the hypothalamus stimulate and what does this do
Orexigenic neurons in paraventricular nucleus
-Leads to a stimulation of food intake
What does the release of POMC and CART from the ARC in the hypothalamus stimulate and what does this do
Anorexigenic neurones in the paraventricular nucleus (PVN)
-LEads to inhibition of food intake
How can POMC and CART affect orexigenic neutrons
Inhibit them
How can NPY and AgRP affect anorexigenic neutrons
Inhibit them
What does POMC undergo and where does it act on to inhibit food intake
Undergoes post translational modification to generate melanocortins which act at melanocortin receptors
How does AgRP inhibit the effects of POMC
Endogenous antagonist of the melanocortin-4 receptor
What effect does Leptin (released from adipose tissue) have on neurotransmitters from the ARC
Stimulate release of POMC and CART
Inhibit release of NPY and AgRP
Inhibits appetite
What effect does PYY have on appetite and how does it do this
Inhibits appatite
Either acts straight on the ARC
or
Acts on pancreas which releases insulin which acts on ARC and switches off appetite
What effect does CCK have on appetite and how
It either acts directly on the brain or stimulates the vagus nerve which acts on the brain and inhibits appetite
Which hormones inhibit appetite
Leptin
PYY
CCK
Which hormones increase appetite
Ghrelin
What effect does gastric distension have on food intake
Leads to a release of gut peptides from the enteroendocrine cells
Which hormones are released from the enteroendocrine cells which inhibit food intake when there is gastric distension
CCK
Glucagon-like peptide 1 (GLP1)
Oxyntomodulin
Peptide YY (PYY3-36)
Apolipoprotein A-IV
Enterostatin
When are leptin levels decreased
When there’s decreased food intake
Where is ghrelin produced
GIT
What does Ghrelin do
Make you feel hungry
Where is PYY secreted from and what is it stimulated by
Distal GIT
- dependent on nutrient intake (more protein than fat or carbs)
- also stimulated by CCK, gastric acid, bile
Where does active PYY act and what does it do
NPY Y2 receptors
-MImics the effect of NPY and so stops further release of NPY
What does PYY do to food intake in lean and obese people
Decreases food intake
How is there negative feedback with NPY
NPY released from presynaptic neurone and this acts on Y1 and Y2 receptors. NPY goes back to the presynaptic membrane and attaches to the Y2 receptor. This inhibits further release of NPY
What inhibits appetite stimulating neurons
Leptin
PYY
INsulin
(NPY and AgRP)
What stimulates appetite inhibiting neurons
Leptin
POMC and CART
What stimulates release of NPY and AgRP
Grehlin
What reward processes are involved in appetite
Opioid receptors (endorphins)
Cannabinoid receptors
Dopamine and dopamine receptors
What does bupropion do
It is a dopamine reuptake inhibitor. Inhibition of this reuptake leads to an increase in the amount of dopamine in the synapse, leading to a prolonged activation of the dopamine receptor.
Aids weight loss
How does orlistat act
Inhibits gastric and pancreatic lipase which decreases absorption
HOw should orlistat be taken
Before each main meal
Cobined with a low fat diet
What is the side effect of orlistat
- Steatorrhea
- Reduced absorption of fat therefore need to monitor fat soluble vitamin status
Who can you give orlistat to
BMI>30
BMI>28 if other risk factors e.g. type2 diabetes, hypercholesterolaemia, hypertension
What is saxenda and what does it do
GLP1 agonist
-Appetite suppression-increased secretion of POMC/CART
What can GLP1 do
Reduce high fat food intake by suppressing dopamine signalling effect on reward pathway
Who can you give saxenda to and when should you be careful
If BMI>30 or lower if concurrent disease
Care with type 2 diabetes as patient may already be on a GLP1 agonist
What is mysimba
Obesity drug which has an effect on reward pathways
