Brain-Gut Axis

Nota:

• Cholecocystokinin frp, endocrine cells in small intestine, to inhibit gastric secretion stimulates pancreatic hCo3 secretion, stim gall bladder and cause satiety Peptide YY (PYY) from colon, it inhibits appetite via hypothalamus in the brain. Ghrelin (growth hormone releasing) from stomach, stimulates appetite via hypothalamus

1. Short Term

   Nota:

   • Others includes PYY, ghrelin and leptin
   1. Insulin

      Nota:

      • Standard. Hormone released from pancreas in response to increased blood glucose. Activates insulin receptors and promote glucose uptake
   2. CCK

      Nota:

      • Hormone released in small intestine, in response to fat.. Activates CCK receptors in vagal afferents.. Satiety Potentiated by gastric distension
   3. Peptide YY

      Nota:

      • Chain of 36 amino acid hormone released from colon. Activates Y receptors in brain. Leads to inhibition of food intake
   4. Ghrelin

      Nota:

      • Opposite of PYY, its also 36aa. released from oxyntic cells. Activate receptors in hypothalamus and stimulates food intake
2. Long Term

   Nota:

   • Allow maintenance of optimal body weight over long term.
   1. Leptin

      Nota:

      • Hormone released from adipose cells. Plasma levels proportional to BMI and fat mass. Can cross  BBB via a saturable process. Receptors located at hypothalamus Obese people made loads of leptin but not responding due to receptor desensitisation.

Nota:

• Multiple inputs changes feeding behaviour  Appetite control involves a complex interplay between hormonal and mechanoreceptor information reaching the brain. It is homeostatic.

1. Regulation

Nota:

• Nutrition in early life is linked to risk of obesity, diabetes and HBP in adulthood. Obesity gradient uses BMI, more than 30 is considered obese.

1. Factors influencing

   Nota:

   • Genes Environmental factors such as exercise food intake, culture(sleep) or BMR