| Part I Experiment study on nonalcoholic fatty liver model made byinjecting oxytetracycline intraperitoneallyObjective: To investigate an economical and effective method to establish nonalcoholic fatty liver(NAFL) animal model.Methods: 40 SD rats were randomly allocated into control group (n=10) and model group (n=30). The rats of control group were fed with standard diet; while the rats of model group were fed with fat-rich diet and injected oxytetracycline intraperitoneally once five days in a 10mg/100g dose. 10 rats which were selected randomly in the model group were killed respectively at the 2nd, 4th and 8th weekend of the experiment and 10 rats in the control group were killed at the 8th weekend of the experiment. The liver index was measured and the serum alanine aminotransferase(ALT), aspartate aminotransferase(AST), triglyeride(TG), total cholesterol(TC), malondialdehyde(MDA), superoxide dismutase(SOD) and hepatic TG, TC, MDA, SOD were measured respectively and the liver pathological change was evaluated by light microscopy after HE staining and masson staining.Results: At the 2nd , 4th and 8th weekend the serum ALT, AST, TG, TC and MDA increase, SOD decreases, the hepatic TG, TC and MDA increase, SOD decreases, and the liver index also increases in the model group compared with the normal group at the 8th weekend (p<0.05), steatohepatitis was observed in the model group at the 2nd week and the 4th weekend, the liver fibrosis can be found at the 8thweekend.Conclusion: The method of injecting oxytetracycline intraperitoneally and taking fat-rich food is effective and economical to establish nonalcoholic fatty liver model of rat in short time.Part II The mRNA expression of PPAR , PPARγ and CYP2E1 in rat withnonalcoholic fatty liver disease and analysis of their correlationObjective: To investigate the mRNA expression of PPAR α, PPARγ and CYP2E1 in the liver of rats with nonalcoholic fatty liver disease and analyze their correlation.Methods: 20 SD rats were randomly divided into control group (n=10) and model group (n=10). The rats of model group were fed with fat-rich diet and injected oxytetracycline intraperitoneally. All the rats were killed at the 8th weekend of the experiment. The hepatic TG, TC, MDA and SOD were measured respectively and the liver pathological change was evaluated by light microscopy after HE staining. The expression of PPAR α , PPARγ and CYP2E1 mRNA in liver was examined by semi-quantitativ reverse translation polymerase chain reaction and their correlation were analyzed.Results: Compared with the normal group, in the model group the hepatic TG, TC and MDA increase, SOD decreases,and in the liver tissue the expression of PPARαmRNA was decreased(P<0.05), the expression of CYP2E1 mRNA was increased(P<0.05), the change of the expression of PPARγ mRNA was not obvious.(P > 0.05) , Related analysis showed PPAR a mRNA correlated with CYP2E1 mRNA, TG, TC and MDA in the liver and the scores of inflammation of liver negatively(P<0.05), and did with SOD in the liver positively (P<0.05) ; CYP2E1 mRNA correlated with MDA in the liver and the scores of inflammation ofliver positively (P<0.05), and did with SOD in the liver negatively (P<0.05),Conclusion: During the course of development of the NAFLD, PPARaand CYP2E1 play an important role. They participated in the lipid peroxidation and inflammatory reaction in the liver. PPAR inhibts the expression of CYP2E1. Part III Effects of Silymarin on Nonalcoholic Steatohepatitis of rat and itspartly Mechanisms of ActionObjiective: To investigate the effect of silymarin on nonalcoholic steatohepatitis of rat and its partly mechanisms of action.Methods: Thirty SD rats were randomly and medially divided into three groups (control group, model group and silymarin group) , and the rat nonalcoholic steatohepatitis model was induced by feeding on fat-rich food and injecting oxytetracycline intraperitoneally, the rats in silymarin group were treated with silymarin(100 mg/kg ? d-1). After eight weeks, all the rats were sacrificed. The serum alanine aminotransferase(ALT), aspartate aminotransferase(AST), triglyeride(TG), total cholesterol(TC), malondialdehyde(MDA), superoxide dismutase(SOD) and hepatic TG, TC, MDA, SOD were measured. The levels of liver peroxisome proliferator activated receptor α (PPARa) mRNA were measured by semi-quantitative reverse translation polymerase chain reaction, and PPARα protein were determined by western-blot respectively.Results: Compared with the control group, the levels of the serum ALT, AST, TG, TC, MDA and hepatic TG, TC, MDA of the model group rats were markedly higher, while the serum and hepatic SOD were significantly lower. PPARa mRNA and PPARa protein levels in liver was decreased (P<0.01) . Compared with the model group, the levels of the serum ALT, AST, TG, TC, MDA and hepatic TG, TC, MDAof the silymarin group rats were markedly lower, while the serum and hepatic SOD were significantly higher. The levels of PPAR α mRNA and prtein in liver was increased (P<0.01) .Conclusion: Silymarin is effective in treating rat nonalcoholic fat liver, one mechanism of treating nonalcoholic fat liver is Silymarin can promote hepatic PPARa mRNA and PPARa protein expression.
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