Resistin is a pro-inflammatory adipokine produced by the white adipose tissue (WAT) adipocytes and macrophages. Obesity results in chronic inflammation of the WAT, marked by an increase in resistin and other inflammatory cytokines, and by infiltrating leukocytes. Elevated resistin levels are believed to play a major role in the development of insulin resistance in the peripheral tissues. Adenylyl cyclase-associated protein 1 (CAP1) was recently identified as a receptor for resistin. In the present study we aimed to investigate whether CAP1 mediates resistin actions which may affect insulin sensitivity in the liver. As a model we used BNL CL.2 mouse liver cell line. Concentration- and time-dependent experiments demonstrated that resistin upregulated TNFα, SOCS3, IL-1α, and IL-6 mRNA expression maximally when used in concentration of 12.5 ng/ml for 6 hours. In order to determine the CAP1 involvement in mediating resistin actions in the liver, we transfected BNL CL.2 cells with CAP1 siRNA and performed a real-time PCR array measuring the expression of 84 key genes involved in insulin signaling, adipokine signaling, and inflammation. Results demonstrated that resistin upregulated mRNA expression of IL-6; this effect was ameliorated when CAP1 was downregulated. Knock-down of CAP1 facilitated mRNA expression of genes involved in insulin signaling and adipokine signaling pathways, while it resulted in downregulation of infiltrating leukocyte markers expression. Taken together these results indicate that CAP1 is a mediator of resistin actions in the liver.
D. Avtanski: None. A. Garcia: None. P. Thangeswaran: None. B. Caraballo Bordon: None. L. Poretsky: None.