Incretin
A class of gut hormones released after eating that stimulate insulin secretion in a glucose-dependent manner. The two main incretins are GLP-1 and GIP, both of which are targets for peptide-based diabetes and obesity therapies. The incretin effect accounts for up to 70% of post-meal insulin secretion.
Technical Context
The incretin effect was discovered when researchers observed that oral glucose produced 2-3 times greater insulin secretion than the same glucose load given intravenously (the incretin effect accounts for approximately 50-70% of post-meal insulin response). GLP-1 (from L-cells) and GIP (from K-cells) are the two identified incretins. Both are rapidly degraded by DPP-4 — GLP-1 has a half-life of 1-2 minutes, GIP approximately 5-7 minutes. In type 2 diabetes, the incretin effect is diminished: GIP's insulinotropic action is impaired (though GIP secretion may be normal or increased), while GLP-1's action is largely preserved but secretion may be reduced. This differential impairment partly explains why GLP-1 receptor agonists are more effective than DPP-4 inhibitors for glucose lowering.