Hyperthermia With Mild Electrical Stimulation Protects Pancreatic β-Cells From Cell Stresses and Apoptosis

  1. Eiichi Araki1
  1. 1Department of Metabolic Medicine, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
  2. 2Department of Molecular Medicine, Faculty of Life Sciences, Global COE “Cell Fate Regulation Research and Education Unit,” Kumamoto University, Kumamoto, Japan
  1. Corresponding author: Eiichi Araki, earaki{at}gpo.kumamoto-u.ac.jp.
  1. T.K., K.S., and R.M. contributed equally to this work.

Abstract

Induction of heat shock protein (HSP) 72 improves metabolic profiles in diabetic model mice. However, its effect on pancreatic β-cells is not known. The current study investigated whether HSP72 induction can reduce β-cell stress signaling and apoptosis and preserve β-cell mass. MIN6 cells and db/db mice were sham-treated or treated with heat shock (HS) and mild electrical stimulation (MES) (HS+MES) to induce HSP72. Several cellular markers, metabolic parameters, and β-cell mass were evaluated. HS+MES treatment or HSP72 overexpression increased HSP72 protein levels and decreased tumor necrosis factor (TNF)-α–induced Jun NH2-terminal kinase (JNK) phosphorylation, endoplasmic reticulum (ER) stress, and proapoptotic signal in MIN6 cells. In db/db mice, HS+MES treatment for 12 weeks significantly improved insulin sensitivity and glucose homeostasis. Upon glucose challenge, a significant increase in insulin secretion was observed in vivo. Compared with sham treatment, levels of HSP72, insulin, pancreatic duodenal homeobox-1, GLUT2, and insulin receptor substrate-2 were upregulated in the pancreatic islets of HS+MES-treated mice, whereas JNK phosphorylation, nuclear translocation of forkhead box class O-1, and nuclear factor-κB p65 were reduced. Apoptotic signals, ER stress, and oxidative stress markers were attenuated. Thus, HSP72 induction by HS+MES treatment protects β-cells from apoptosis by attenuating JNK activation and cell stresses. HS+MES combination therapy may preserve pancreatic β-cell volume to ameliorate glucose homeostasis in diabetes.

Footnotes

  • Received August 7, 2011.
  • Accepted January 10, 2012.

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  1. Diabetes vol. 61 no. 4 838-847
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