Gastric inhibitory polypeptide (GIP, glucose-dependent insulinotropic peptide) (Moody AJ et al, 1984) is a member of the secretin family of hormones. It is synthesized and secreted from endocrine cells in the small intestine. GIP induces insulin secretion, which is primarily stimulated by hyperosmolarity of glucose in the duodenum. Gastric inhibitory polypeptide receptors are found on beta-cells in the pancreas (Volz A et al, 1995). Their effects are mediated by coupling to the G protein alpha s subunit, which stimulates adenylyl cyclase which can increase intracellular cAMP levels (Bollag RJ et al, 2000).