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.
Wheeler et al (1995) Functional expression of the rat pancreatic islet glucose-dependent Insotropic polypeptide receptor: ligand binding and intracellular signaling properties. Endocrinol. 136 4629 PMID: 7664683
Meier et al (2002) Gastric inhibitory polypeptide: the neglected incretin revisited. Regul.Peptides 107 1 PMID: 12137960
Hansen et al (2016) N‐terminally and C‐terminally truncated forms of glucose‐dependent insulinotropic polypeptide are high‐affinity competitive antagonists of the human GIP receptor. Br. J. Pharmacol. 173 826 PMID: 26572091