Effect of insulin resistance on fatty liver in high-fat diet-fed mice / 中国病理生理杂志

ABSTRACT

[ ABSTRACT] AIM:To study the influence of insulin resistance on fatty liver in the mice fed with high-fat diet (HFD).METHODS:Male 8-week-old C57BL/6J mice were randomly divided into HFD group (with 60% calories by high saturated fatty acid) and control group (with chow diet).The mice in both groups were fed for 12 weeks.The body weight, liver weight, serum triglyceride (TG) and total cholesterol (TC), and blood glucose and insulin levels were meas-ured.Hyperinsulinemic euglycemic clamp experiment was applied to reflect insulin sensitivity .The lipid deposition in the liver was analyzed by HE staining , Sudan IV staining and measurement of liver fat content .The phosphorylation levels of IRS1 and Akt, and the protein levels of SREBP-1 and FAS were determined by Western blot to reflect the activities of insu-lin signaling and lipid synthesis .RESULTS:Compared with control group , the body weight and liver weight were signifi-cantly increased in HFD group .TG and TC contents in serum and liver tissues were remarkably increased in HFD group . High-fat diet induced insulin resistance , as evidenced by increased serum insulin levels , reduced glucose infusion rate and decreases in IRS1 and Akt phosphorylation levels .In livers of HFD group, HE staining showed that the cytoplasm of hepa-tocytes was filled with vacuoles .Sudan IV staining also displayed that many different sizes of red lipid drops existed in the hepatocytes , and the protein levels of SREBP-1 and FAS were significantly increased .In primary normal hepatocytes with exogenous oleic acid intervention for 48 h, the phosphorylation levels of IRS 1 and Akt were reduced , and the protein ex-pression of SREBP-1 and FAS was significantly increased in a dose-dependent manner .CONCLUSION: Feeding with HFD leads to insulin resistance , resulting in activation of lipid synthesis and accumulation of lipid deposition in the liver , thus inducing fatty liver .