Blockade of interleukin 6 signalling ameliorates systemic insulin resistance through upregulation of glucose uptake in skeletal muscle and improves hepatic steatosis in high-fat diet fed mice

Background & AimsMice fed high-fat diet (HFD) demonstrate obesity-related systemic insulin resistance (IR). Aim of this study is to clarify the role of interleukin (IL)-6 in IR in vivo focusing on skeletal muscle, adipose tissue and liver. MethodsPlasma markers of IR and hepatic IL-6 signalling were examined in eight-week HFD feeding C57/BL6 mice. Furthermore, IR-related molecules in skeletal muscles, adipose tissues and livers were investigated following a single injection of anti- IL-6 receptor neutralizing antibody (MR16-1) in two-week HFD feeding mice. To investigate the role of IL-6 in hepatic steatosis by prolonged HFD, hepatic triglyceride accumulation was assessed in eight-week HFD feeding mice with continuous MR16-1 treatment. ResultsHigh-fat diet for both 2 and 8weeks elevated plasma IL-6, insulin and leptin, which were decreased by MR16-1 treatment. A single injection of MR16-1 ameliorated IR as assessed by glucose and insulin tolerance test, which may be attributable to upregulation of glucose transporter type 4 via phosphorylation of AMP-activated protein kinase as well as upregulation of peroxisome proliferator-activated receptor alpha in livers and, particularly, in skeletal muscles. MR16-1 also decreased mRNA expression of leptin and tumour necrosis factor-alpha and increased that of adiponectin in adipose tissue. High-fat diet for 8weeks, not 2weeks, induced hepatic steatosis and increased hepatic triglyceride content, all of which were ameliorated by MR16-1 treatment. ConclusionsBlockade of excessive IL-6 stimulus ameliorated HFD-induced IR in a skeletal muscle and modulated the production of adipokines from an early stage of NAFLD, leading to prevention of liver steatosis for a long term.