Islet amyloid polypeptide: the cause of type-2 diabetes?
Islet amyloid polypeptide (IAPP or amylin), first identified as the peptide deposited as amyloid in type-2 diabetic pancreas and insulinoma, turns out to be a peptide produced in the pancreatic beta-cell secretory granule that is costored and coreleased with insulin. Experimental evidence suggests that, under certain conditions, IAPP can counter insulin action in peripheral tissue and inhibit insulin release from the pancreas. IAPP therefore appears to respond to the same physiologic stimuli as insulin, but has opposing biologic actions. The role of IAPP, both in normal physiology and in pathology, remains unclear, but current evidence suggests against a role as a circulating hormone in favor of a paracrine or autocrine modulator of insulin secretion.
Bretherton-Watt
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Royal Postgraduate Medical School, Hammersmith Hospital, London, UK.
Bloom
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