title: Insulin antagonizes interleukin-6 signaling and is anti-inflammatory in 3T3-L1 adipocytes.
abstract: Adipose tissue secretes different adipokines, including interleukin-6 (IL-6), that have been implicated in the insulin resistance and inflammatory state characterizing obesity. We examined the putative cross-talk between insulin and IL-6 in adipose cells and found that insulin exerts an inhibitory effect on the IL-6 signaling pathway by altering the post-translational modifications of the signal transducer and activator of transcription 3 (STAT3). Insulin reduces the tyrosine phosphorylation and increases the serine phosphorylation of STAT3, thereby reducing its nuclear localization and transcriptional activity. Signaling through the MEK/MAPK pathway plays an important role as treatment with the MEK inhibitor PD98059 reduces the effects of insulin on IL-6 signaling. We also show that the protein tyrosine phosphatase SHP2 is activated upon insulin signaling and is required for the dephosphorylation of STAT3 and that insulin exerts a synergistic effect with IL-6 on suppressor of cytokine signaling 3 expression. As a consequence, the IL-6-induced expression of the inflammatory markers serum amyloid A 3 and haptoglobin are significantly decreased in cells incubated with both IL-6 and insulin. Thus, insulin exerts an important anti-inflammatory effect in adipose cells by impairing the IL-6 signal at several levels.
authors.affiliation: Lundberg Laboratory for Diabetes Research, Department of Molecular and Clinical Medicine, The Sahlgrenska Academy at Göteborg University, SE-413 45 Göteborg, Sweden.
authors.forename: Christian X
authors.initials: CX
authors.lastname: Andersson
authors.affiliation: Lundberg Laboratory for Diabetes Research, Department of Molecular and Clinical Medicine, The Sahlgrenska Academy at Göteborg University, SE-413 45 Göteborg, Sweden.
authors.forename: Victoria Rotter
authors.initials: VR
authors.lastname: Sopasakis
authors.affiliation: Lundberg Laboratory for Diabetes Research, Department of Molecular and Clinical Medicine, The Sahlgrenska Academy at Göteborg University, SE-413 45 Göteborg, Sweden.
authors.forename: Emelie
authors.initials: E
authors.lastname: Wallerstedt
authors.affiliation: Lundberg Laboratory for Diabetes Research, Department of Molecular and Clinical Medicine, The Sahlgrenska Academy at Göteborg University, SE-413 45 Göteborg, Sweden. Electronic address: ulf.smith@medic.gu.se.
authors.forename: Ulf
authors.initials: U
authors.lastname: Smith
mesh_terms: D041721:3T3-L1 Cells; D017667:Adipocytes / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D018836:Inflammation Mediators / Q000502:physiology*; D007328:Insulin / Q000502:physiology*; D015850:Interleukin-6 / Q000502:physiology; D007424:Intracellular Fluid / Q000378:metabolism; D051379:Mice; D010766:Phosphorylation; D050796:STAT3 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D000093242:Interleukin-6 Inhibitors
chemical_list: D000894:Anti-Inflammatory Agents, Non-Steroidal; D018836:Inflammation Mediators; D007328:Insulin; D015850:Interleukin-6; D050796:STAT3 Transcription Factor; D000093242:Interleukin-6 Inhibitors; C494087:Stat3 protein, mouse