appetite regulation Flashcards
what is an orexigen?
A substance (hormone or drug) that increases food intake - appetite stimulant
when is an orexigen undesirable?
when its an unwanted side effect of medication (increases weight gain)
when can an orexigen be useful?
in cachexia treatment or AIDS/cancer
what is an anorexigen?
Substance (hormone or drug) that inhibits food intake
Activates specific neuronal pathways to alter eating behaviour
in what ways can food be broken down in the GI tract?
o Mastication (chewing) in the oral cavity along with breakdown via amylase production in the mouth o Stomach acid breaks down food o Proteases o Mechanical movements e.g. rhythmic gastric contractions
how is food broken down in the duodenum?
bile acids
pancreatic enzymes
where are most nutrients taken up?
small intestine
what is GPR120 and what is its relevance?
medium to long chain FA receptor. People without this receptor have a tendency to gain weight –> obese phenotype
what do enteroendocrine cells do and how?
sense the luminal environment
have GPCRs on the EEC surface which is how food intake is relayed to the rest of the body
name adaptations of the EECs and how are these useful?
long processes - can reach out through the lumen
triangular shape with a wider base - wide base has more secretory granules that contain hormones and peptides that regulate food intake
what parts of the GI tract does the vagus nerve innervate?
stomach
small intestine
proximal colon
what activates chemoreceptors on the vagus nerve?
activated by mediators released by EEC cells
Respond to nutrients, hormones, pH, osmolality
what activates mechanoreceptors on the vagus nerve?
o Gastric distension causes satiety
o Meal size
what controls the short term homeostatic control of appetite?
vagus nerve
what controls the long term control of appetite?
hypothalamus
what type of hormone is leptin?
adipokine - hormone made by adipose tissue
anorexigenic hormone
what does leptin do?
Satiety signal that affects all organs in the body but acts specifically in the hypothalamus
o Inhibits NPY/AgRP neurones
o Activates POMC/CART neurones
what do leptin levels correlate with?
body fat
what are leptin levels in obese people and why?
obese people have high leptin levels bc they have leptin resistance
where is CCK synthesised?
I cells of the duodenum
what is CCK released in response to and what does it do?
- Released in response to fat and protein
- Slows gastric emptying, releases bile and pancreatic enzymes
- Activates vagus nerve activates feeling of satiety
what is PYY3-36?
Anorexigenic hormone released from L cells in the GI tract
what is PYY3-36 released in response to and what does it do?
- Released in response to high fat/protein
- Infusions lead to enhanced satiety
- Directly inhibits NPY neurones and activates POMC neurones
- Decreased food intake
when are PYY3-36 levels elevated?
• Elevated during bariatric surgeries
