Increase in Endoplasmic Reticulum Stress–Related Proteins and Genes in Adipose Tissue of Obese, Insulin-Resistant Individuals

  1. Guenther Boden1,
  2. Xunbao Duan2,
  3. Carol Homko1,
  4. Ezequiel J. Molina3,
  5. WeiWei Song1,
  6. Oscar Perez2,
  7. Peter Cheung1 and
  8. Salim Merali2
  1. 1Division of Endocrinology, Diabetes, and Metabolism and the Clinical Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania
  2. 2Department of Biochemistry, Temple University School of Medicine, Philadelphia, Pennsylvania
  3. 3Department of Surgery, Temple University School of Medicine, Philadelphia, Pennsylvania
  1. Corresponding author: Guenther Boden, bodengh{at}tuhs.temple.edu

Abstract

OBJECTIVE—To examine fat biopsy samples from lean insulin-sensitive and obese insulin-resistant nondiabetic individuals for evidence of endoplasmic reticulum (ER) stress.

RESEARCH DESIGN AND METHODS—Subcutaneous fat biopsies were obtained from the upper thighs of six lean and six obese nondiabetic subjects. Fat homogenates were used for proteomic (two-dimensional gel and MALDI-TOF/TOF), Western blot, and RT-PCR analysis.

RESULTS—Proteomic analysis revealed 19 differentially upregulated proteins in fat of obese subjects. Three of these proteins were the ER stress–related unfolded protein response (UPR) proteins calreticulin, protein disulfide-isomerase A3, and glutathione-S-transferase P. Western blotting revealed upregulation of several other UPR stress–related proteins, including calnexin, a membrane-bound chaperone, and phospho c-jun NH2-terminal kinase (JNK)-1, a downstream effector protein of ER stress. RT-PCR analysis revealed upregulation of the spliced form of X-box binding protein-1s, a potent transcription factor and part of the proximal ER stress sensor inositol-requiring enzyme-1 pathway.

CONCLUSIONS—These findings represent the first demonstration of UPR activation in subcutaneous adipose tissue of obese human subjects. As JNK can inhibit insulin action and activate proinflammatory pathways, ER stress activation of JNK may be a link between obesity, insulin resistance, and inflammation.

Footnotes

  • Published ahead of print at http://diabetes.diabetesjournals.org on 20 June 2008.

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    • Accepted June 13, 2008.
    • Received May 5, 2008.
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  1. Diabetes vol. 57 no. 9 2438-2444
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