| 1 To create a rat model of insulin- resistant fatty liver Objective To create a rat model of insulin- resistant fatty liver. Methods Fourteen male Wistar rats were randomly divided into a high–fat diet group and a normal control group. The high–fat diet rats were fed a high-fat diet (45% of energy from fat) for 8 weeks, and the normal control a standard diet (19% of energy from fat). Insulin sensitivity was measured with glucose infusion rate (GIR) by the euglycermic hyperinsulinemia clamp technique. The aminotransferase, TG, TC, FFA,SOD and MDA were measured by biochemical methods , and insulin was measured by radioimmunoassay, tumor necrosis factor-α(TNF-α) by ELISA. The assessment of hepatic steatosis, inflammatory activity and fibrosis in all rats were scored according to criteria under light microscope, and ultrastructural changes of rat livers were observed by electron microscope. Results GIR of rats fed the high-fat diet was significantly lower than normal control group (6.31±1.28 VS 10.22±1.47,P﹤0.01) .Liver index and epidiymal fat were markedly higher than normal control group(P﹤0.01 and P﹤0.05). All high-fat diet rats had a significant elevated levels of serum aminotransferase , insulin, TG, FFA , hepatic TG, TC,FFA, TNF-α and MDA, and low SOD. Histological changes demonstrated that rats fed the high-fat diet developed diffuse macrovesicular steatosis, lobular inflammatory- cell infiltration, slight fibrosis and abnormal mitochondria, however those fed the standard diet had normal livers. Conclusions Fatty liver and insulin resistance model was successfully developed in rats fed a high-fat diet for 8 weeks ,which had a mimic pathological and metabolic changes of fatty liver in patients with obesity or type 2 diabetes . It provided a realistic experimental tool for elucidating pathogenesis and screening effective drug of non-alcoholic fatty liver disease. 2 The effect of high-fat diet on hepatic insulin signalling molecular in rats Objective To explore the effect of high-fat diet on hepatic insulin signalling molecular IRS-1, IRS-2 in rats. Methods After the rats fed high-fat diet and standard diet for 8 weeks, hepatic mRNA and protein content of IRS-1 and IRS-2 were measured by RT-PCR and Western blotting. Results Compared with the normal control, hepatic IRS-1mRNA and IRS-1 protein content in high-fat diet group were reduced by 28%(P﹤0.01) and 32%(P﹤0.01),respectively. Similarly, hepatic IRS-2mRNA and IRS-2 protein content in high-fat diet group were reduced by 30%(P﹤0.01) and 27%(P﹤0.05),respectively. Conclusions High-fat diet resulted in a significant decrease in mRNA expression and protein content of hepatic insulin signalling molecular IRS-1 and IRS-2 in rats, which might be one of the molecular mechanisms of insulin resistance induced by high-fat diet. Objective To study the effect of insulin resistance and oxidative stress on development of fatty liver, and investigate the effect two" hits" on the pathogenesis of non-alcoholic fatty liver disease. Methods Thirty male Wistar rats were randomly assigned to normal control group and model control group, 7 rats in each group, metformin-treated group and vitamin E- treated group, 8 rats in each group. The normal control group fed a standard diet , the other groups fed high-fat diet .Metformin-treated group and vitamin E- treated group had been administered with metformin (200mg·kg-1·d-1 )and vitamin E(200mg·kg-1·d-1 )for 8 weeks. Insulin sensitivity was measured with GIR by the euglycermic hyperinsulinemia clamp technique. The levels of aminotransferase, insulin ,TG, TC, FFA, SOD, MDA, and TNF-α were detected. The mRNA expression of hepatic TNF-α and UCP2 were detected by RT-PCR, and protein content of UCP2 and CYP2E1 were measured by immunohistochemistry. The assessment of steatosis, inflammatory activity and fibrosis in all rats were scored under light microscope. Results Compared with the vitamin E- treated and the model control group , in metformin-treated group, GIR increased significantly ( P﹤0.05),on... |
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