Diabetes, Vol 40, Issue 3 310-314, Copyright © 1991 by American Diabetes Association
Newly identified pancreatic protein islet amyloid polypeptide. What is its relationship to diabetes?
KH Johnson, TD O'Brien and P Westermark
Department of Veterinary Pathobiology, University of Minnesota, St. Paul 55108.
Islet amyloid polypeptide (IAPP) or amylin is a newly identified 37-amino
acid COOH-terminal-amidated polypeptide that is the major protein
constituent of amyloid deposits in insulinomas and amyloid deposits in
pancreatic islets of non-insulin-dependent (type II) diabetic humans and
adult diabetic cats. IAPP is stored with insulin in beta-cell secretory
vesicles and is cosecreted with insulin in response to glucose and several
secretagogues. IAPP has been demonstrated in normal pancreatic islets of
many species, but IAPP-derived amyloid develops commonly in the islets of
only a few species (e.g., humans and cats), especially in association with
age-related diabetes. IAPP from the human and cat inherently contains a
short amyloidogenic sequence that is not present in species that do not
form islet amyloid. Studies in animals indicate that an aberration in the
synthesis or processing of IAPP, leading to a local increase in
concentration of IAPP in the islet, is also required to facilitate the
conversion of IAPP to amyloid. The formation of islet amyloid may
contribute to the development of type II diabetes by causing disruption of
islet cells and by replacement of islets. It has also been proposed that an
abnormality of IAPP homeostasis underlies the pathogenesis of type II
diabetes. A significant causal relationship between IAPP and type II
diabetes is based on reports that IAPP inhibits glucose-stimulated insulin
release by beta-cells and that IAPP inhibits insulin-stimulated rates of
glycogen synthesis and glucose uptake by skeletal muscle cells.(ABSTRACT
TRUNCATED AT 250 WORDS)