Appetite regulation Flashcards
Define Adiposity
Level of body fat
What is an Adipostat?
Produced by adipose tissue; circulating levels are proportional to body fat
Give 2 examples of an adipostat
Leptin
Insulin
Name 3 areas of the hypothalamus related to hunger regulation
Ventromedial
Lateral
Arcuate nucleus
Which area of the brain is responsible for appetite regulation?
Hypothalamus
What is meant by the ‘set point’ of body weight?
With unlimited & free choice of food an animal’s body weight will be defended about a set point.
Starvation causes weight loss
Force feeding causes weight gain
Which areas of the hypothalamus are affected directly by blood glucose levels?
Ventromedial
Lateral
An increase in blood glucose;
Will turn on which area of hypothalamus?
To have what effect?
Ventromedial
Satiety
A decrease in blood glucose;
Will turn on which area of hypothalamus?
To have what effect?
Lateral
Hunger
A mouse with Ventromedial HT lesion.
What will happen to body weight and set point?
Weight gain
Increased set point
A mouse with Lateral HT lesion.
What will happen to body weight and set point?
Weight loss
Decreased set point
Leptin is encoded for by which gene?
Ob gene
On which area of the hypothalamus does Leptin act primarily?
Arcuate nucleus
What changes would be expected following a decrease in Leptin levels?
(after weight loss)
Increased food intake Decreased temperature Decreased energy expenditure Decreased reproductive function Increased parasympathetic activity (rest & digest)
What changes would be expected following an increase in Leptin levels?
(after weight gain)
Lower food intake
Lower energy expenditure
Increased sympathetic activity
What type of peptides are released from the Arcuate Nucleus in response to high Leptin levels?
Anorexigenic peptides
ee. CART, aMSH
What is an anorexigenic?
Peptide that inhibits feeding behaviour
Give 2 examples of anorexigenic peptides
aMSH
(alpha-melanocyte stimulating hormone), secreted by the POMC nuclei of the Arcuate nucleus.
CART
(Cocaine and amphetamine related transcript)
What area of the HT do Orexigenic peptides act on?
Lateral hypothalamus
Are Orexigenic peptide release a response to increased or decreased Leptin levels?
Decreased Leptin levels
Name 2 Orexigenic peptides
NPY
(Neuropeptide Y)
AgRP
(Agouti-related peptide)
What effect do Orexigenic peptides have on feeding behaviour?
They activate feeding behaviour
What effects do aMSH and AgRP have on the Melanocortin Receptor?
MCR4
aMSH activates the receptor
AgRP blocks the receptor
What is the most common cause of inherited obesity?
MCR4 mutation
Present in 1-2.5% of obese people
What effect does leptin treatment have on a person with congenital leptin deficiency?
Effective form of treatment
Causes weight loss
What effect does leptin treatment have on most overweight people?
No effect
Majority of obese people have normal leptin genes; they commonly have high circulating leptin levels
What hormone signals hunger?
Ghrelin
Where is Ghrelin produced, and how is it regulated?
Stomach
Regulated by calorie intake
Where does Ghrelin act?
Arcuate nucleus of HT
What happens to Ghrelin levels in obesity?
Ghrelin levels are reduced
Targetting the Ghrelin pathway to treat obesity has been ineffective. Ghrelin levels are low at the appropriate times in obesity
Which nerve signals satiety?
Vagus
What activates the Vagus nerve to signal satiety?
Stomach distension
CCK; relesed by gut epithelia in response to fatty meal
What area of the HT produces orexigenic and anorexigenic peptides?
Arcuate nucleus
What area of the brain does the Vagus nerve stimulate in response to being full?
Nucleus of the solitary tract
Which comuunicates with the HT
What happens to serotonin levels during appetite
Serotonin levels are increased in anticipation of a meal and peak during a meal, especially if carb rich
Name a drug that promotes satiety
Sibutramine (reductil)
How does Sibutramine work?
Serotonin and Noradrenaline reuptake inhibitor
Increases satiety & reduces metabolic supression that occurs with weight loss
Withdrawn, CV risks
What is the reward hormone?
Dopamine
From where is dopamine released?
VTA; ventral tegmental area
How does the Dopaminergic reward system affect appetite?
Causes consumption of palatable foods.
How do endocanabinoids cause hunger?
Released post-synaptically
Block volt-gated Ca2+ channels
Prevent neurotransmitter release
