Islet Amyloid Polypeptide (IAPP) A short review

Abstract

Within the mature IAPP molecule the amino acid sequence 23-29 shows considerable amino acid heterogenicity among various mammalian species. the amino acid composition of human IAPP in this specific region promotes the development of pancreatic islet amyloidosis, a phenomenon related to the ability to develop type II diabetes in that particular species. However, as type II diabetes is an inherited disease affecting a subpopulation of humans, not only the gene coding mature IAPP, but also one or several other hereditary factors of unknown origin are needed for the disease to develop. We have established a radioimmunoassay for plasma measurements of IAPP. During screening investigations of a large material of endocrine tumors we found a patient with extremely elevated plasma levels of IAPP, about 20 000pmol/l. Immunohistochemical investigations confirmed the IAPP content and also revealed amyloid deposits. While performing an oral glucose tolerance test insulin levels remained unchanged whereas there was an increase in the glucose and IAPP levels. It is thus concluded that IAPP can be used as a tumor marker in pancreatic islet cell tumors and that high plasma levels of IAPP can inhibit glucose stimulated insulin secretion.