JNK and tumor necrosis factor-alpha mediate free fatty acid-induced insulin resistance in 3T3-L1 adipocytes

J Biol Chem. 2005 Oct 21;280(42):35361-71. doi: 10.1074/jbc.M504611200. Epub 2005 Aug 5.

Abstract

Lipid infusion and high fat feeding are established causes of systemic and adipose tissue insulin resistance. In this study, we treated 3T3-L1 adipocytes with a mixture of free fatty acids (FFAs) to investigate the molecular mechanisms underlying fat-induced insulin resistance. FFA treatment impaired insulin receptor-mediated signal transduction and decreased insulin-stimulated GLUT4 translocation and glucose transport. FFAs activated the stress/inflammatory kinases c-Jun N-terminal kinase (JNK) and IKKbeta, and the suppressor of cytokine signaling protein 3, increased secretion of the inflammatory cytokine tumor necrosis factor (TNF)-alpha, and decreased secretion of adiponectin into the medium. RNA interference-mediated down-regulation of JNK blocked JNK activation and prevented most of the FFA-induced defects in insulin action. Blockade of TNF-alpha signaling with neutralizing antibodies to TNF-alpha or its receptors or with a dominant negative TNF-alpha peptide had a partial effect to inhibit FFA-induced cellular insulin resistance. We found that JNK activation by FFAs was not inhibited by blocking TNF-alpha signaling, whereas the FFA-induced increase in TNF-alpha secretion was inhibited by RNA interference-mediated JNK knockdown. Together, these results indicate that 1) JNK can be activated by FFAs through TNF-alpha-independent mechanisms, 2) activated JNK is a major contributor to FFA-induced cellular insulin resistance, and 3) TNF-alpha is an autocrine/paracrine downstream effector of activated JNK that can also mediate insulin resistance.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • 3T3-L1 Cells
  • Adipocytes / metabolism
  • Adiponectin / metabolism
  • Animals
  • Biological Transport
  • Blotting, Western
  • Cell Differentiation
  • Deoxyglucose / metabolism
  • Down-Regulation
  • Enzyme Activation
  • Enzyme-Linked Immunosorbent Assay
  • Fatty Acids, Nonesterified / metabolism*
  • Genes, Dominant
  • Glucose / metabolism
  • Glucose Transporter Type 4
  • I-kappa B Kinase / metabolism
  • Inflammation
  • Insulin / metabolism
  • Insulin Resistance*
  • JNK Mitogen-Activated Protein Kinases / metabolism
  • Lipids / chemistry
  • MAP Kinase Kinase 4 / metabolism
  • MAP Kinase Kinase 4 / physiology*
  • Mice
  • Protein Transport
  • RNA Interference
  • Signal Transduction
  • Suppressor of Cytokine Signaling 3 Protein
  • Suppressor of Cytokine Signaling Proteins / metabolism
  • Time Factors
  • Tumor Necrosis Factor-alpha / metabolism
  • Tumor Necrosis Factor-alpha / physiology*

Substances

  • Adiponectin
  • Fatty Acids, Nonesterified
  • Glucose Transporter Type 4
  • Insulin
  • Lipids
  • Slc2a4 protein, mouse
  • Socs3 protein, mouse
  • Suppressor of Cytokine Signaling 3 Protein
  • Suppressor of Cytokine Signaling Proteins
  • Tumor Necrosis Factor-alpha
  • Deoxyglucose
  • I-kappa B Kinase
  • JNK Mitogen-Activated Protein Kinases
  • MAP Kinase Kinase 4
  • Glucose