Obesity and the endocrine control of food intake Flashcards
What is the arcuate nucleus (in rodents) called in humans?
Infundibulum nucleus
Usually refer to arcuate nucleus because most test are done on rodents
How is POMC cut up in the arcuate nucleus? How is this different to in the rest of the body?
Normally POMC is cut up to MSH and ACTH
But in arcuate nucleus it is cut up differently to make alpha-MSH
What part of the brain balances energy in vs energy out aka body weight homeostasis? How does it do this?
Hypothalamus via neural input from the periphery and other brain regions, as well as hormones eg ghrelin, PYY and leptin
Where does the arcuate nucleus sit?
Just above the fenestrated capillaries in the median eminence
Why is the arcuate nucleus not completely protected by the blood brain barrier? What does this lead to
Due to the capillaries it sits on are fenestrated leading to access to the peripheral hormones
What is the major mechanism for the arcuate nucleus to monitoring and integrating peripheral nucleus state
Stimulating - NPY/Agrp neuron
Inhibitory - POMC neuron
How do NPY/Agrp neurons affect appetite?
Increase appetite
How do POMC neurons affect appetite?
Decrease appetite
What type of CNS mutations can cause morbid obesity?
POMC deficiency and MC4-R mutations
What does leptin do?
Activates POMC and inhibits NPY/AgRP -> decreasing food intake and increasing thermogenesis
What are levels of leptin like when there are different levels of body fat?
Low when there is low body fat and high when there is high body fat - it is coded in body fat
Where does leptin circulate?
In plasma in concentrations proportional to fat mass
What happens to leptin in obesity
Most fat humans have high leptin - obesity due to leptin resistance: hormone is present but doesn’t signal effectively
What happens to the body if there is no leptin?
Hyperphagia, lowered energy expenditure, sterility - body starves itself if you have no leptin - it is an anti-starvation hormone
What does the presence of leptin in the body tell the brain?
One has sufficient fat reserves for normal function - but high leptin has little effect
How does insulin regulate food intake?
It circulates at levels proportional to body fat via receptors on the hypothalamus.
What happens if you administer insulin centrally into the hypothalamus
Reduces food intake
Why does basal insulin correlate accurately with BMI
More body weight put on - more tendency for insulin resistance, so pancreas works harder to make insulin and shifts your insulin release during the early stages
Where are insulin receptors particularly found?
In the hypothalamus
What is the body’s largest endocrine organ?
GI tract
What does the GI tract release?
It releases more than 20 different regulatory peptide hormones
What do gut hormones influence
processes including gut motility, secretion of other hormones, appetite and body weight.
What influences gut hormone release
gut nutrient content - what you’ve eaten, how much, what is it made up of?
What does cholecystokinin affect
Gall bladder contraction, GI motility, pancreatic exocrine secretion
