High glucose predisposes gene expression and ERK phosphorylation to apoptosis and impaired glucose-stimulated insulin secretion via the cytoskeleton

PLoS One. 2012;7(9):e44988. doi: 10.1371/journal.pone.0044988. Epub 2012 Sep 14.

Abstract

Chronic high glucose (HG) inflicts glucotoxicity on vulnerable cell types such as pancreatic β cells and contributes to insulin resistance and impaired insulin secretion in diabetic patients. To identify HG-induced cellular aberrations that are candidate mediators of glucotoxicity in pancreatic β cells, we analyzed gene expression in ERoSHK6, a mouse insulin-secreting cell line after chronic HG exposure (six-day exposure to 33.3 mM glucose). Chronic HG exposure which reduced glucose-stimulated insulin secretion (GSIS) increased transcript levels of 185 genes that clustered primarily in 5 processes namely cellular growth and proliferation; cell death; cellular assembly and organization; cell morphology; and cell-to-cell signaling and interaction. The former two were validated by increased apoptosis of ERoSHK6 cells after chronic HG exposure and reaffirmed the vulnerability of β cells to glucotoxicity. The three remaining processes were partially substantiated by changes in cellular morphology and structure, and instigated an investigation of the cytoskeleton and cell-cell adhesion. These studies revealed a depolymerized actin cytoskeleton that lacked actin stress fibers anchored at vinculin-containing focal adhesion sites as well as loss of E-cadherin-mediated cell-cell adherence after exposure to chronic HG, and were concomitant with constitutive ERK1/2 phosphorylation that was refractory to serum and glucose deprivation. Although inhibition of ERK phosphorylation by PD98059 promoted actin polymerization, it increased apoptosis and GSIS impairment. These findings suggest that ERK phosphorylation is a proximate regulator of cellular processes targeted by chronic HG-induced gene expression and that dynamic actin polymerization and depolymerization is important in β cell survival and function. Therefore, chronic HG alters gene expression and signal transduction to predispose the cytoskeleton towards apoptosis and GSIS impairment.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / metabolism
  • Animals
  • Apoptosis / genetics*
  • Cell Adhesion / genetics
  • Cell Division / genetics
  • Cell Line
  • Cell Proliferation
  • Cell Survival / genetics
  • Cytoskeleton / metabolism*
  • Extracellular Signal-Regulated MAP Kinases / metabolism*
  • Gene Expression Regulation*
  • Glucose / metabolism*
  • Insulin / metabolism*
  • Insulin Secretion
  • Insulin-Secreting Cells / metabolism*
  • Mice
  • Phosphorylation
  • Signal Transduction

Substances

  • Actins
  • Insulin
  • Extracellular Signal-Regulated MAP Kinases
  • Glucose

Grant support

This work was funded by the Agency for Science, Technology and Research – Biomedical Research Council (A*STAR BMRC) and partially supported by grants from the National Medical Research Council of Singapore (NMRC1218/2009; NMRC/EDG/0056/2009 to G.L.). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.