Islet amyloid polypeptide--hen or egg in type 2 diabetes pathogenesis?

Islet amyloid polypeptide (IAPP or amylin) was first identified as the major peptide constituent of amyloid deposited in the islets of Langerhans in patients with type-2 diabetes mellitus or in insulinomas. It was subsequently shown that IAPP is produced by the pancreatic beta-cells, co-stored and co-released with insulin. IAPP is homologous with the neuropeptide calcitonin gene-related peptide (CGRP) and has therefore been assumed to have a function as an endocrine, paracrine or autocrine hormone. This has prompted the search for its physiological function as well as a putative pathogenic role in type 2 diabetes mellitus.