Involvement of visfatin in palmitate-induced upregulation of inflammatory cytokines in hepatocytes.

ABSTRACT

Free fatty acids (FFAs) lead to the activation of inflammatory pathways related to the induction of insulin resistance. Visfatin is known to play a role in obesity-related metabolic diseases and inflammatory conditions. Here, the role of visfatin in FFA-induced inflammation was investigated in hepatocytes. The following factors were examined (1) the protein and messenger RNA (mRNA) expression of visfatin in the liver tissue of insulin-resistant rats and in (2) in HepG2 cells treated with palmitate, (3) the palmitate-induced mRNA expression and protein synthesis of interleukin-6 and tumor necrosis factor-α in HepG2 cells transfected with visfatin-specific small interfering RNA, and (4) the expression of visfatin in HepG2 cells treated with a nuclear factor-κB (NF-κB) inhibitor (SN50) and infected with Ad-IκBα. The protein and mRNA levels of visfatin were significantly higher in insulin-resistant rat liver tissue compared with the control group. Visfatin expression and protein synthesis significantly increased in HepG2 cells treated with palmitate in a time- and concentration-dependent manner. Visfatin-specific small interfering RNA significantly decreased the palmitate-induced mRNA expression and protein synthesis of interleukin-6 and tumor necrosis factor-α. A NF-κB inhibitor induced the downregulation of visfatin in HepG2 cells following treatment with palmitate. HepG2 cells infected with Ad-IκBα showed decreased expression of visfatin following treatment with palmitate. The expression of visfatin is closely associated with the expression of proinflammatory cytokines in FFA-induced inflammation and is significantly decreased by NF-κB inhibition in HepG2 cells. Visfatin may play a role in FFA-induced inflammation in hepatocytes through the NF-κB pathway.