The endoplasmic reticulum in pancreatic beta cells of type 2 diabetes patients

Abstract

Aims/hypothesis Pancreatic beta cells have highly developed endoplasmic reticulum (ER) due to their role in insulin secretion. Since ER stress has been associated with beta cell dysfunction, we studied several features of beta cell ER in human type 2 diabetes. Methods Pancreatic samples and/or isolated islets from non-diabetic controls (ND) and type 2 diabetes patients were evaluated for insulin secretion, apoptosis (electron microscopy and ELISA), morphometric ER assessment (electron microscopy), and expression of ER stress markers in beta cell prepared by laser capture microdissection and in isolated islets.Results Insulin release was lower and beta cell apoptosis higher in type 2 diabetes than ND islets. ER density volume was significantly increased in type 2 diabetes beta cells. Expression of alpha-mannosidase (also known as mannosidase, alpha, class 1A, member 1) and UDP-glucose glycoprotein glucosyl transferase like 2 (UGCGL2), assessed by microarray and/or real-time reverse transcriptase polymerase chain reaction (RT-PCR), differed between ND and type 2 diabetes beta cells. Expression of immunoglobulin heavy chain binding protein (BiP, also known as heat shock 70 kDa protein 5 [glucose-regulated protein, 78 kDa] [HSPA5]), X-box binding protein 1 (XBP-1, also known as XBP1) and C/EBP homologous protein (CHOP, also known as damage-inducible transcript 3 [DDIT3]) was not higher in type 2 diabetes beta cell or isolated islets cultured at 5.5 mmol/l glucose (microarray and real-time RT-PCR) than in ND samples. When islets were cultured for 24 h at 11

Palmitate induces a pro-inflammatory response in human pancreatic islets that mimics CCL2 expression by beta cells in type 2 diabetes

“…Human islets exposed in vitro to palmitate activate the three branches of the ER stress response under the control of PRKR-like endoplasmic reticulum kinase (PERK), activating transcription factor 6 (ATF6) and inositol-requiring 1 (IRE1) [10]. Markers of oxidative [11] and ER stress [8,12,13] are present in islets of type 2 diabetic patients, suggesting these stress responses may indeed play a role in the development and progression of the disease.…”

A local glucagon-like peptide 1 (GLP-1) system in human pancreatic islets

“…Islet isolation and culture Islets were prepared by enzymatic digestion and gradient separation [22,23], and suspended in M199 culture medium (Sigma Chemicals, St Louis, MO, USA) supplemented as detailed elsewhere [22,23]. Islets with a diameter ≥100 μm were handpicked and studied within 3 days of isolation.…”

“…Whole-cell lysate (A-431, SC-2201; Santa Cruz Biotechnologies, Santa Cruz, CA, USA) was used as positive control. Islet glucagon and GLP-1 content was measured from four nondiabetic and three type 2 diabetic preparations after overnight acid-ethanol (1.5% HCl, 79% ethanol [95% pure], 19.5% water) extraction [22,23].…”

“…Quantitative RT-PCR studies The expression of genes encoding insulin, glucagon, PC1/3 and PC2 was assessed by quantitative RT-PCR experiments in alpha and beta cell fractions from eight non-diabetic and three type 2 diabetic islet preparations, according to methods detailed elsewhere [22,23,25]. Briefly, after RNA extraction and reverse transcription, mRNA levels of the genes of interest were quantified and normalised to β-actin in a bioanalyser (7700; Applied Biosystems, Foster City, CA, USA).…”

Increased insulin demand promotes while pioglitazone prevents pancreatic beta cell apoptosis in Wfs1 knockout mice

“…In addition to genetic factors, processes involving glucotoxicity and/or lipotoxicity are likely to be contributory [4]. Endoplasmic reticulum (ER) stress has also recently emerged as a candidate mechanism [5][6][7].…”