What is insulin secretion?

Updated: Jan 02, 2019
  • Author: Saranya Buppajarntham, MD; Chief Editor: Eric B Staros, MD  more...
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Answer

Answer

In normal physiology, insulin secretion is induced by elevated plasma glucose levels. Glucose diffuses to beta cells through glucose transporter 2 (GLUT2) and activates the glycolysis pathway, leading to elevated adenosine triphosphate (ATP) levels. Increasing ATP levels induce ATP-sensitive K+ channels to shut down and subsequently stimulate depolarization of the beta-cell membrane. Then, voltage-gate Ca2+ channels are opened to increase cytosolic Ca2+ and trigger insulin exocytosis. [6] However, high insulin levels in a hypoglycemic state have been found in a hypersecretory state; an example is insulinoma, in which insulin is secreted in at a high rate independent from the plasma glucose level.

Interestingly, oral administration of glucose is more effective in increasing insulin secretion than intravenous glucose (called "incretin effect"). Carbohydrate meals potentiate insulin secretion through multiple gastrointestinal hormones (incretin hormones), including cholecystokinin, glucagonlike peptide-1 (GLP-1), and gastric-inhibiting polypeptide (GIP). [6, 9]


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