Islets Of Patients Research Articles

Inhibitory Effect of Islet Amyloid Polypeptide of Glucose-Induced Proinsulin Biosynthesis in Rat Insulinoma Cells

Islet amyloid polypeptide (IAPP) has been recently identified as the principal constituent of amyloid deposits in pancreatic islets of patients with type 2 (non-insulin-dependent) diabetes mellitus and causes insulin resistance in some target cells. In addition, glucose-induced insulin secretion is inhibited by IAPP. We studied the effect of IAPP on proinsulin biosynthesis in rat insulinoma (RINr) cells. Glucose at concentrations of 0, 15, 30, 60, 100, and 300 mg/dl stimulated proinsulin biosynthesis in a dose-responsive and and actino-mycin D-inhibitable manner after 6 h of incubation. At a glucose concentration of 300 mg/dl, IAPP decreased the mean responses of proinsulin biosynthesis to 61.2 and 29% at concentrations of 0.1 and 1 microM, respectively, compared with the IAPP-free control. In conclusion, IAPP inhibits glucose-induced proinsulin biosynthesis in RINr cells. IAPP might play an important role in the pathogenesis of type 2 diabetes mellitus.

Amylin expression in the pancreatic beta-cell.

Amylin, or Islet Amyloid Polypeptide (IAPP), is a 37 amino acid peptide that is secreted from the pancreatic β-cell. It’s discovery resulted from the analysis of amyloid deposits that are found in the islets of patients with noninsulin-dependent diabetes mellitus (NIDDM). These extracellular protein deposits have the characteristic Congo Red staining found in amyloid in other organs and were initally noted in the early 1900’s. However, due to the insolubility of the islet amyloid and the isolated deposition in the diabetic pancreas the structure of the primary component of the amyloid was not determined until 1986. At that time two groups succeeded in purifying and sequencing the peptide that constituted the majority of the deposit.1,2 The sequence of the peptide revealed that it was similar, but not identical, to calcitonin gene related peptide (CGRP). The terms, diabetes associated peptide and IAPP, were initially used to refer to the peptide. Later the term amylin was proposed by Leighton and Cooper based on the premise that the peptide had hormone-like activity.3

Morphometry of the pancreatic islets in patients with insulinomas and gastrinomas: H. Schwarting, G. Osse, M. Sippel, R. Arnold and W. Creutzfeldt

Morphometry of the pancreatic islets in patients with insulinomas and gastrinomas: H. Schwarting, G. Osse, M. Sippel, R. Arnold and W. Creutzfeldt