Chronic exposure to interleukin-6 causes hepatic insulin resistance in mice.
Interleukin (IL)-6 is one of several proinflammatory cytokines associated with the insulin resistance of obesity and type 2 diabetes. There is, however, little direct evidence in vivo for a causative role of IL-6 in insulin resistance. Here, a 5-day constant subcutaneous infusion of hIL-6 before portal vein insulin challenge resulted in impairment of early insulin receptor signaling in the liver of mice. Importantly, the sixfold elevation of IL-6 attained with constant infusion was similar to levels reached in obesity. Consistent with an hepatic response to IL-6, STAT3 phosphorylation was increased in livers of IL-6-treated mice at 5 days. Chronic infusion of IL-6 also reduced hepatic insulin receptor autophosphorylation by 60% and tyrosine phosphorylation of insulin receptor substrates-1 and -2 by 60 and 40%, respectively. IL-6 had no effect on the mass of these proteins. IL-6 also decreased refeeding-dependent glucokinase mRNA induction by approximately 40%. Insulin tolerance tests revealed reduced insulin sensitivity. In contrast to hepatic insulin receptor signal transduction, 5-day IL-6 exposure failed to suppress skeletal muscle insulin receptor signal transduction. These data suggest that chronic IL-6 treatment selectively impairs hepatic insulin signaling in vivo, further supporting a role for IL-6 in hepatic insulin resistance of obesity.
Klover
Peter J
PJ
Department of Pathology and Laboratory Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York 14642, USA.
Zimmers
Teresa A
TA
Koniaris
Leonidas G
LG
Mooney
Robert A
RA
D000818:Animals; D005941:Glucokinase / Q000235:genetics; D007263:Infusions, Parenteral; D007329:Insulin Antagonists / Q000494:pharmacology*; D055504:Insulin Receptor Substrate Proteins; D007333:Insulin Resistance / Q000502:physiology*; D015850:Interleukin-6 / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D047908:Intracellular Signaling Peptides and Proteins; D008099:Liver / Q000187:drug effects / Q000502:physiology; D051379:Mice; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology; D010750:Phosphoproteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D012333:RNA, Messenger / Q000235:genetics; D011972:Receptor, Insulin / Q000037:antagonists & inhibitors / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects*; D014158:Transcription, Genetic / Q000187:drug effects
D007329:Insulin Antagonists; D055504:Insulin Receptor Substrate Proteins; D015850:Interleukin-6; D047908:Intracellular Signaling Peptides and Proteins; C526295:Irs1 protein, mouse; C526298:Irs2 protein, mouse; D010750:Phosphoproteins; D012333:RNA, Messenger; D005941:Glucokinase; D011972:Receptor, Insulin