GIP (Gastric Inhibitory Polypeptide) is derived from a 153-amino acid proprotein encoded by the GIP gene and circulates as a biologically active 42-amino acid peptide. GIP is released by the K cells of the duodenum and jejunum in response to food intake and while it is weak inhibitor of gastric acid secretion, its main role is to stimulate insulin release. Type 2 diabetics are not responsive to GIP and have lower levels of GIP secretion after a meal when compared to non-diabetics. In mice, absence of GIP receptors correlates with resistance to obesity.
