High Glucose Induces Dysfunction in Insulin Secretory Cells by Different Pathways: A Proteomic Approach

Abstract

Chronic hyperglycemia is a hallmark of type 2 diabetes and can contribute to progressive beta cell dysfunction and death. The aim of the present study was to identify pathways mediating high glucose-induced beta cell demise by a proteomic approach. INS-1E cells were exposed to 25 mM glucose for a sustained period of 24 h. Protein profiling of INS-1E cells was done by two-dimensional difference gel electrophoresis, covering the pH ranges 4-7 and 6-9 (n = 4). Differentially expressed proteins (P < 0.05) were identified by MALDI-TOF/TOF and proteomic results were confirmed by functional assays. High glucose levels impaired glucose-stimulated insulin secretion and decreased insulin content. 2D-DIGE analysis revealed 100 differentially expressed proteins that were involved in different pathways. Chaperone proteins were down-regulated, protein biosynthesis and ubiquitin-related proteasomal degradation were attenuated and perturbations in intracellular trafficking and vesicle transport and secretion could be observed. Moreover, several pathways were confirmed by functional assays and a direct role for eEF2 in insulin biosynthesis was demonstrated. The present findings provide new insights in glucotoxicity and identify key target proteins for the prevention and treatment of beta cell dysfunction in type 2 diabetes.

Deletion of C/EBP homologous protein (Chop) in C57Bl/6 mice dissociates obesity from insulin resistance

“…In this view, we have previously shown that changes in mRNA levels initiating the unfolded protein response are not translated into protein changes. Moreover, we stated an important role for post-translational modifications in the regulation of ER stress [26,27]. Activation of ER stress induces an increased release of NEFA, adipokines and inflammatory mediators [28,29], triggering infiltration and activation of macrophages in adipose tissue, contributing to insulin resistance [30,31].…”

Cellular responses of novel human pancreatic β-cell line, 1.1B4 to hyperglycemia

“…[16][17][18][19][20][21][22] Basal insulin release at 5.6 mM glucose was not affected by hyperglycemia but the secretory response to 16.7 mM glucose was impaired by 48 and 72 h exposure to 25 mM glucose. We also observed that insulin release from 1.1B4 cells chronically exposed to hyperglycemia for 48 and 72 h was significantly reduced in response to alanine, GLP-1, KCl, elevated Ca 2+ , or forskolin.…”

Pancreatic islet proteome profile in Zucker fatty rats chronically treated with a grape seed procyanidin extract

“…GSPE decreased protein levels of the chaperones Hspd1, Hsp90b1, and Hspa5, proteins that promote protein folding and degradation (Kriegenburg, Ellgaard, & Hartmann-Petersen, 2011); and of protein disulfide-isomerase A3 (Pdia3), involved in ER-associated degradation. Chaperones Hspa5 and Hsp90b1, as well as Pdia3, were also decreased in the beta-cell line INS-1E when severe ER stress was induced or when they were treated with high glucose, indicating a defective UPR (Ahmed et al, 2010;D'Hertog et al, 2010;Maris et al, 2010). GSPE treatment also increased Polyubiquitin-B (Ubb), a molecule that targets misfolded proteins for degradation (Kriegenburg et al, 2011).…”