Glucose-Dependent Insulinotropic Polypeptide in Incretin Physiology: Role in Health and Disease.

Glucose-dependent insulinotropic polypeptide (GIP) is a 42-amino acid hormone that is synthesized and released from upper intestinal enteroendocrine K-cells in response to the ingestion of glucose or fat. The structure of GIP places it in the secretin/vasoactive intestinal polypeptide family of gastrointestinal regulatory peptides. Although originally named "gastric inhibitory polypeptide" on the basis of its ability to inhibit gastric acid secretion, GIP accounts for 60%-80% of the postprandial insulin response, consistent with the notion that this regulatory peptide constitutes the principal physiological incretin.