Obesity is associated with increased circulating interleukin-6 (IL-6), which may contribute to hepatic insulin resistance by impairing insulin receptor signaling. This study was designed to assess the impact of the systemic absence of IL-6 on the development of insulin resistance and glucose intolerance in an obese mouse model. Systemic insulin, glucose, and pyruvate tolerance tests were performed in IL-6 knockout (IL6KO) mice that had been crossed with a genetically obese (leptin receptor-deficient mouse model [Lep db]) mouse model. Real-time reverse transcriptase polymerase chain reaction and Western blot analysis assessed cellular and molecular markers of insulin signaling, inflammation, and metabolism. Absence of IL-6 did not improve systemic glucose or insulin tolerance, but Lep db × IL6KO mice displayed a smaller blood glucose increase following a pyruvate challenge. These results suggest that loss of IL-6 in the context of obesity may locally reduce hepatic glucose production from a gluconeogenic precursor. Hepatic insulin-dependent insulin receptor autophosphorylation, Akt activation, and FoxO1 phosphorylation were similar between Lep db × IL6KO mice and Lep db controls. Basal gene expression of the gluconeogenic enzyme phosphoenolpyruvate carboxykinase was reduced in male Lep db × IL6KO mice relative to Lep db controls; but gene expression of another regulatory enzyme, glucose-6-phosphatase, remained unaltered. Absence of IL-6 reduced gene expression of serum amyloid A and RelA in female Lep db mice, but did not alter hepatic triglyceride accumulation or lipogenic gene expression. Overall, our results suggest that IL-6 may be detrimental in obesity by contributing to elevated hepatic glucose output.
ASJC Scopus subject areas
- Endocrinology, Diabetes and Metabolism