Appetite Flashcards
How is the hypothalamus involved in feeding
Integrates the peripheral satiety signals
Name 6 things that the hypothalamus influences in order to regulate metabolic rate
- Pituitary function
- Feeding
- Stress response
- Water balance
- Sleep-wake cycle
- Thermoregulation
What is the main centre for appetite regulation in hypothalamus
Arcuate nucleus
What 2 systems make up the arcuate nucleus
NPY/ Agouti related peptide
Cocaine related transcript and pro-opiomelanocortin
What % is BMI heriditable
30-70
Where is agouti related peptide (AgRP) found
In the hypothalmus co-current with cells producing NPY
Effect of insulin levels on AgRP?
Insulin causes drop in AgRP levels
What is meant by orexigenis
Appetite stimulating
What is meant by anorexigenic
Appetite inhibiting
What molecules are orexigenic
NPY
AgRP
MCH
What molecules are anorexigenic
POMC
CART
What is Pomc
Proopiomelanocortin
What does POMC modify to become? What is action of the modified molecule?
Melanocortins
Binds to metlanocortin receptors
Give an example of melanocortin receptor
MCR4
What happens to mice and humans who are deficient in POMC
Develop hyperphagia and obesity
What is considered the predominant POMC derived product which controls energy balance
Alpha-melanocyte-stimulating-hormone
In what percentage of the following groups is an MC4R mutation found
a) obese adults
b) obses children
a) 0.5-2.5%
b) 5%
Is serotonin anorexigenic or orexigenic?
Anorexigenic
Which receptors does serotonin/ 5HT act
Htr1b and HTr2c
What happens when serotonin acts on its receptors
- Increases signalling from POMC neurones
- Decreases AgRP neuron signalling
Where is ghrelin secreted from
Stomach
Where are ghrelin receptors found
NPY neurons
Action of ghrelin
Stimulates NPY
Increases food intake both directly and via vagal nerve
Does PYY 3-36 inhibit or increase food intake
Inhibit
Describe the process by which PYY 3-36 inhibits food intake
- PYY 3-36 synthesised in gut
- PYY reaches hypothalamus
- PYY inhibits NPY neurones and stimulates POMC neurones
- Food intake declines
Where is glucagon like peptide released from
L cells in the gut lining
What is the action of GLP-1
Interacts to inhibit NpY and stimulates PoMC
What receptor does PYY act on
Y2R receptor
What is the action of PYY
Inhibits NpY and stimulates PoMC`
What does CCK stand for
Cholecystokinin
Where is CCK secreted from?
Type 1 enteroendocrine cells in duodenum and small intestine
Does CCK supress or improve appetite
Supresses
Where is the hormone leptin secreted from
Adipose tissue
What two genetic defects to do with leptin have been identified
- Defective leptin [ob]
- Defective receptor [db]
Describe the phenotype of ob/ob and db/db mice (9)
- Obese
- Increased appetite
- Insulin resistance and diabetes
- Hyperlipidaemia
- Hypertension
- Hypothermia
- Infertility
- Over expression of orexigenics
- Decreased expression of POMC
What is the effect of leptin and insulin on AGRP levels
Decrease in AGRP levels
What happens if you inject congenitally leptin deficient children with leptin
Normalisation of body weight and fat mass
What controls level of malonyl CoA?
AMPK
Calcium regulated
Effect of cannabinoids on appetite and consumption of food
Increase appetite and consumption of food
What is the receptor for cannabinoids in the brain
CB1
What is the impact of CB1 activity in hunger centre
Increases palatability of food
