title: Insulin stimulates interleukin-6 and tumor necrosis factor-alpha gene expression in human subcutaneous adipose tissue.
abstract: High circulating levels of interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha) are found in patients with hyperinsulinemia. Insulin stimulates release of IL-6 from adipocyte cultures, and it stimulates IL-6 gene expression in insulin-resistant, but not control, rat skeletal muscle. In addition, TNF-alpha may be involved in the pathogenesis of insulin resistance. Therefore, we studied the effect of insulin on IL-6 and TNF-alpha gene expression in human skeletal muscle and adipose tissue. Nine healthy young volunteers participated in the study. They underwent a 6-h hyperinsulinemic euglycemic clamp at a fixed insulin infusion rate, with blood glucose clamped at fasting level. Blood samples drawn at 0, 1, 2, 3, 4, 5, and 6 h were analyzed for IL-6 and TNF-alpha. Muscle and fat biopsies, obtained at 0, 2, 4, and 6 h, were analyzed for IL-6 and TNF-alpha mRNA with real-time PCR. IL-6 mRNA increased 11-, 3-, and 5-fold at 2, 4, and 6 h, respectively, in adipose tissue (ANOVA P = 0.027), whereas there was no significant effect of insulin on skeletal muscles. Plasma IL-6 increased during insulin stimulation. TNF-alpha mRNA increased 2.4-, 1.4-, and 2.2-fold in adipose tissue (ANOVA P = 0.001) and decreased 0.74-, 0.64-, and 0.68-fold in muscle tissue (ANOVA P = 0.04). Plasma levels of TNF-alpha were constant. In conclusion, the finding that insulin stimulates IL-6 and TNF-alpha gene expression in adipose tissue only and inhibits the TNF-alpha production in skeletal muscles suggests a differential regulation of muscle- and adipose tissue-derived IL-6 and TNF-alpha.
authors.affiliation: Department of Infectious Diseases, The Copenhagen Muscle Research Centre, Rigshospitalet, DK-2100 Copenhagen, Denmark.
authors.forename: Rikke
authors.initials: R
authors.lastname: Krogh-Madsen
authors.forename: Peter
authors.initials: P
authors.lastname: Plomgaard
authors.forename: Pernille
authors.initials: P
authors.lastname: Keller
authors.forename: Charlotte
authors.initials: C
authors.lastname: Keller
authors.forename: Bente Klarlund
authors.initials: BK
authors.lastname: Pedersen
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D000328:Adult; D015870:Gene Expression / Q000187:drug effects*; D015309:Glucose Clamp Technique; D006801:Humans; D007328:Insulin / Q000494:pharmacology*; D015850:Interleukin-6 / Q000097:blood / Q000235:genetics*; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D040521:Subcutaneous Tissue / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics* / Q000378:metabolism
chemical_list: D007328:Insulin; D015850:Interleukin-6; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha