Table 3.

Summary of the action of selected gastrointestinal hormones, insulin and leptin and how they are altered in obesity ⁹

Gut hormone	Gastrointestinal site of secretion	Action on gastrointestinal system	Effect on appetite	Changes in obesity
Ghrelin	X/A-cells in gastric fundus	Increases gastric motility	Increases appetite	Reduced pre-prandial peak levels and reduced postprandial suppression
Peptide YY3-36	L-cells in distal intestine	Inhibits gallbladder secretions, inhibits gastric emptying, inhibits pancreatic secretions, enterogastrone effect.	Decreases appetite	Reduced fasting and postprandial secretion
					Glucagon-like peptide-1	L-cells in distal intestine	Inhibits gastric emptying, inhibits gastric secretions, promotes pancreatic beta-cell growth, incretin effect.	Decreases appetite	Reduced postprandial secretion
Oxyntomodulin	L-cells in distal intestine	Inhibits gastric secretions, inhibits gastric emptying, incretin effect.	Decreases appetite	–
					Cholecystokinin	I cells in small intestine, co-localises with PYY in L-cells of distal intestine	Promotes gallbladder contraction, increases pancreatic secretions, inhibits gastric secretions, inhibits gastric emptying.	Decreases appetite	Not implicated

Peripheral hormone	Site of secretion	Effect on appetite	Changes in obesity
Insulin	Pancreas (beta-cells)	Decreases appetite	Hyperinsulinaemia, insulin resistance
				Leptin	Adipocytes	Decreases appetite	Hyperleptinaemia, leptin resistance