Definition
A gut hormone released after eating that amplifies glucose-dependent insulin secretion; mainly GLP-1 and GIP.
Incretins are hormones secreted by the intestine in response to nutrients that enhance insulin release from pancreatic beta cells. The incretin effect describes the observation that oral glucose produces a substantially larger insulin response than the same amount of glucose given intravenously. The two principal incretins are GLP-1, from L cells in the lower intestine, and GIP, from K cells in the upper small intestine. Both act through class B GPCRs and are glucose-dependent, stimulating insulin mainly when glucose is elevated. Both are rapidly inactivated by the enzyme DPP-4. Incretin biology underlies GLP-1 receptor agonists, DPP-4 inhibitors and the newer multi-receptor agonists studied in metabolic research.