Metabolic stress, IAPP and islet amyloid.

ABSTRACT

Amyloid forms within pancreatic islets in type 2 diabetes from aggregates of the ß-cell peptide islet amyloid polypeptide (IAPP). These aggregates are toxic to ß-cells, inducing ß-cell death and dysfunction, as well as inciting islet inflammation. The ß-cell is subject to a number of other stressors, including insulin resistance and hyperglycaemia, that may contribute to amyloid formation by increasing IAPP production by the ß-cell. ß-Cell dysfunction, evident as impaired glucose-stimulated insulin secretion and defective prohormone processing and exacerbated by metabolic stress, is also a likely prerequisite for islet amyloid formation to occur in type 2 diabetes. Islet transplants in patients with type 1 diabetes face similar stressors, and are subject to rapid amyloid formation and impaired proinsulin processing associated with progressive loss of ß-cell function and mass. Declining ß-cell mass is predicted to increase metabolic demand on remaining ß-cells, promoting a feed-forward cycle of ß-cell decline.