The Endocrine Control of Food Intake

Question 1

Describe the hypothalamus structure

Answer 1

Paraventricular nucleus -> 3rd ventricle
lateral hypothalamus beside the paraventricular nucleus
Ventromedial hypothalamus beside the 3V
Arcuate nucleus alongside the bottom of 3V

Question 2

Describe the arcuate nucleus

Answer 2

Key in regulation of food intake
Incomplete blood brain barrier - allows access to peripheral hormones
Integrates peripheral and central feeding signals

Question 3

What are the neuronal populations of the acute nucleus

Answer 3

Stimulatory - NPY/Agrp neuron Inhibitory - POMC neuron

Both extend to other hypothalamic and extra-hypothalamic regions

Question 4

Which CNS mutation affect appetite

Answer 4

POMC deficiency and MC4-R mutations -> morbid obesity

Question 5

What brain regions are involved in appetite regulation

Answer 5

Prefrontal cortex
Cortex
Amygdala
Nucleus Accumbens
Brainstem

Question 6

When are leptin levels high and low

Answer 6

Low in low body fat

High in high body fat

Question 7

What is the action of leptin

Answer 7

Activates POMC and inhibits NPY/AgRP neurons.

Question 8

What is the effect of central or peripheral administration of leptin

Answer 8

Decrease in food intake and increase in thermogenesis

Question 9

How is leptin associated with obesity

Answer 9

Leptin resistance
Most fat humans have high leptin
Leptin is ineffective as a weight control drug

Question 10

What are the effects of an absence of leptin

Answer 10

Hyperphagia
Lowered energy expenditure
Sterility

Question 11

What are the associations between insulin and food intake

Answer 11

Insulin circulates at levels proportional to body fat
Receptors in the hypothalamus
Central administration reduces food intake
May co-ordinate glucose and energy homeostasis

Question 12

How many hormones does the gut release and what are the processes influenced by

Answer 12

> 20 regulatory peptide hormones

Gut motility, secretion of other hormones, appetite

Question 13

What is the release of gut hormones regulated by

Answer 13

Gut nutrient content

Question 14

Which hormones are released by the stomach and what do they stimulate

Answer 14

Ghrelin - hunger, growth hormone release

Gastrin - acid secretion

Question 15

Which hormones are released by the duodenum and what do they stimulate

Answer 15

Cholecystokinin - gall bladder contraction, GI motility, pancreatic exocrine secretion

Secretin - pancreatic exocrine secretion

GIP - Incretin activity

Motion - GI motility

Question 16

Which hormones are released by the pancreas and what do they stimulate

Answer 16

Insulin + glucagon - glucose homeostasis

Pancreatic polypeptide - Gastric motility, satiation

Amylin - glucose homeostasis, gastric motility

Question 17

Which hormones are released by the colon and what do they stimulate

Answer 17

GLP-1 - incretin activity, satiation

GLP-2 - GI motility and growth

Oxyntomodulin - satiation, acid secretion

PYY 3-36 - satiation

Question 18

Describe the structure of ghrelin and its daily levels

Answer 18

28 amino acids

Fluctuates throughout the day and is highest at breakfast, lunch and dinner

Question 19

Explain how ghrelin achieves its affect on food intake

Answer 19

simulates NPY/Agrp neurons (arcuate nucleus)
Inhibits POMC neurons
Increases appetite
Increased food intake

Question 20

Which cells secrete PYY and GLP-1

Answer 20

L cells in the colon

Question 21

Explain how PYY 3-36 achieves its affect on food intake

Answer 21

Inhibits NPY release
Stimulates POMC neurons
Decreases appetite
Decreased food intake

Question 22

Describe GLP-1

Answer 22

Glucagon-like-peptide-1
Characterised incretin role to stimulate glucose-stimulated insulin release
Reduced food intake

Question 23

Describe the processing of pro-glucagon in intestinal L-cells

Answer 23

Gut hormone coded for by the preproglucagon gene and released post-prandially
Prohormone convertase 1 converts GLP-1 to the active agonist
After half life (1min) it becomes inactive (DP-IV)

Question 24

What is saxenda

Answer 24

Long-acting glucagon-like-peptide-1 receptor agonist (liraglutide)
Double the dose used for T2DM

Question 25

What are the 3 types of satiety action

Answer 25

Post-prandial - reduces food intake after a meal

Chronic - gut disease - chronic elevation to suppress appetite

Acute nausea - toxic ingestion - acutely very high levels

Question 26

What are the comorbidities associated with obesity

Answer 26

Depression 
Stroke
MI
Sleep apnoea
Hypertension 
Diabetes 
Bowel cancer 
Osteoarthritis 
Peripheral vascular disease
Gout

Question 27

Describe the thrifty gene hypothesis

Answer 27

Specific genes are selected to increase metabolic efficiency and fat storage
Plentiful food and little exercise -> the genes predispose the carrier to obesity and diabetes

Question 28

Describe the adaptive drift hypothesis

Answer 28

Following a normal distribution of body weight - fat are eaten, thin starve
Humans then learned to defend against predators so the obese were not selected against
Putting on fat led to a genetic drift
Those who inherit this gene put on weight

Question 29

What can leptin administration restore

Answer 29

LH pulsatility in leptin deficient children

LH pulsatility in women with amenorrhoea

Question 30

What is the association with PYY and calories

Answer 30

More calories -> more PYY