incretin
An incretin is a gut hormone that tells the pancreas “food is coming” before blood sugar even rises very far. Eat a meal, and cells in your intestine release these messengers within minutes, priming the insulin response so glucose gets handled quickly.
The key observation is the “incretin effect”: glucose taken by mouth triggers far more insulin than the same amount of glucose injected into a vein. The difference is roughly 50 to 70 percent of the insulin released after a meal, and it exists because oral nutrients stimulate the intestine to release incretins, which then amplify insulin secretion from beta cells. The two main human incretins are GLP-1 and GIP, both released by enteroendocrine cells in the gut wall.
A practical caveat: the incretin effect is blunted in type 2 diabetes, partly because the body responds poorly to GIP. This insight drove the development of GLP-1-based drugs, which restore and exaggerate incretin signaling to lower blood sugar and reduce appetite.
After a bowl of rice, the intestine releases GLP-1 and GIP, which reach the pancreas and make beta cells secrete more insulin than the rising glucose alone would command.
Oral nutrients amplify insulin via incretins — the incretin effect.
Incretins are quickly degraded by the enzyme DPP-4; this is why one drug class (DPP-4 inhibitors, the “gliptins”) works by blocking that enzyme so natural incretins last longer.