GLUT4 repression in response to oxidative stress is associated with reciprocal alterations in C/EBP alpha and delta isoforms in 3T3-L1 adipocytes

Dorit Pessler-Cohen, Phillip Pekala, Julia Kovsan, Asnat Bloch-Damti, Assaf Rudich, Nava Bashan

Research output: Contribution to journalArticlepeer-review

35 Scopus citations

Abstract

Insulin responsiveness of adipocytes is acquired during normal adipogenesis, and is essential for maintaining whole-body insulin sensitivity. Differentiated adipocytes exposed to oxidative stress become insulin resistant, exhibiting decreased expression of genes like the insulin-responsive glucose transporter GLUT4. Here we assessed the effect of oxidative stress on DNA binding capacity of C/EBP isoforms known to participate in adipocyte differentiation, and determine the relevance for GLUT4 gene regulation. By electrophoretic mobility shift assay, nuclear proteins from oxidized adipocytes exhibited decreased binding of C/EBPα-containing dimers to a DNA oligonucleotide harboring the C/EBP binding sequence from the murine GLUT4 promoter. C/EBPδ-containing dimers were increased, while C/EBPβ-dimers were unchanged. These alterations were mirrored by a 50% decrease and a 2-fold increase in the protein content of C/EBPα and C/EBPδ, respectively. In oxidized cells, GLUT4 protein and mRNA levels were decreased, and a GLUT4 promoter segment containing the C/EBP binding site partially mediated oxidative stress-induced repression of a reported gene. The antioxidant lipoic acid protected against oxidation-induced decrease in GLUT4 and C/EBPα mRNA, but did not prevent the increase in C/EBPδ mRNA. We propose that oxidative stress induces adipocyte insulin resistance partially by affecting the expression of C/EBPα and δ, resulting in altered C/EBP-dimer composition potentially occupying the GLUT4 promoter.

Original languageEnglish
Pages (from-to)3-12
Number of pages10
JournalArchives of Physiology and Biochemistry
Volume112
Issue number1
DOIs
StatePublished - 1 Feb 2006

Keywords

  • Adipocyte dedifferentiation
  • Electrophoretic mobility shift assay (EMSA)
  • GLUT1
  • GLUT4
  • GLUT4 promoter
  • Hydrogen peroxide
  • Insulin resistance
  • Lipoic acid

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