DIFFERENTIAL EXPRESSION OF ISLET AMYLOID POLYPEPTIDE (AMYLIN) AND INSULIN IN EXPERIMENTAL DIABETES IN RODENTS

An increased ratio of islet amyloid polypeptide (IAPP) to insulin for mRNA and peptide content in pancreatic extracts and for secretion has been observed in experimental diabetes, suggesting a differentially re gulated IAPP and insulin expression. Therefore, we investigated the is let expression of IAPP and insulin in streptozotocin and alloxan diabe tic rats and mice, using in situ hybridization and immunocytochemistry . A low dose of streptozotocin equivalently reduced IAPP and insulin m RNA levels to approximately 45% of controls. In contrast, a high dose of streptozotocin or alloxan reduced IAPP mRNA levels significantly le ss than those of insulin mRNA (streptozotocin: 24 vs. 15%, P = 0.011; alloxan: 15 vs. 6%, P < 0.0001). In situ hybridization and immunocytoc hemistry revealed expression of IAPP in experimental diabetes to occur predominantly in insulin cells. Thus, LAPP and insulin gene expressio n are differentially regulated in experimental diabetes in rodents and IAPP is predominantly expressed in insulin cells.