维生素E对非酒精性脂肪性肝病小鼠肝脏SIRT1、PGC-1α表达的影响

Effect of Vitamin E on the Expression of SIRT1 and PGC-1α in Mice with Nonalcoholic Fatty Liver Disease

目的观察维生素E(Vit E)对非酒精性脂肪性肝病(NAFLD)小鼠肝脏SIRT1和PGC-1α表达的影响,探讨Vit E在NAFLD小鼠中抗氧化应激的作用机制。方法采用高脂饮食24周建立C57BL/6小鼠NAFLD模型,于造模第7周起以50 mg·kg^(-1)·d^(-1)Vit E灌胃干预18周,HE和Masson染色观察肝组织病理学变化;生化法检测血清丙氨酸氨基转移酶(ALT)、天冬氨酸氨基转移酶(AST)水平,黄嘌呤氧化酶法检测肝脏总超氧化物歧化酶(SOD)、MnSOD水平,硫代巴比妥酸法检测肝脏丙二醛(MDA)含量;Real-time PCR和免疫组化法检测肝组织沉默信息调节蛋白1(SIRT1)、过氧化物酶体增殖物激活受体γ辅激活因子1α(PGC-1α)mRNA和蛋白的表达。结果长期高脂饮食可诱导小鼠肝组织脂肪变、炎症及纤维化,形成NAFLD,NAFLD模型组小鼠血清ALT、AST水平较正常组显著增高(P<0.05),肝组织SIRT、PGC-1α基因mRNA和蛋白表达均较正常组明显减少(P<0.01);肝组织总SOD、MnSOD水平较正常组明显降低(P<0.01),MDA含量较正常组明显增多(P<0.05);应用Vit E干预后能一定程度减轻肝组织炎症程度和纤维化程度;Vit E组小鼠血清ALT、AST水平较模型组显著下降(P<0.01、P<0.05),肝组织SIRT1、PGC-1α基因mRNA和蛋白表达均较模型组显著增强(P<0.05),肝组织总SOD和MnSOD水平也较模型组明显增高(P<0.05),MDA含量则较模型组明显下降(P<0.05)。结论 Vit E通过调节SIRT1/PGC-1α信号通路关键因子的表达,纠正高脂饮食诱导的NAFLD小鼠氧化与抗氧化体系的失衡,减轻肝脏炎症损伤,防止NAFLD的进展。

OBJECTIVE To investigate the effect of vitamin E （Vit E） on the expression of SIRT1 and PGC-1α in mice with nonalcoholic fatty liver disease（ NAFLD）, and to explore its role in the resistance against the oxidative stress. METHODS As ani- mal models of NAFLD, Male C57BL/6 mice were fed with high-fat diets for 24 weeks, the model mice was administered Vit E （50 mg·kg^-1·d^-1） intragastricaUy for 18 weeks from 7th week of modeling. The pathological changes in liver were determined by HE and Masson staining. The serum levels of alanine aminotransferase （ALT） and aspartate aminotransferase （AST） analyzed using automatic biochemical instrumentation. The levels of liver superoxide-dismutase （SOD） and MnSOD were tested by xanthine oxidase assay. Total content of malondialdehyde （MDA） in liver homogenate was tested by thiobarbituric acid （TBA） method. The mRNA and protein levels of silent mating type information regulation 2 homolog 1 （ SIRT1 ） and peroxisome proliferator-activated receptor gamma coactivator-1 alpha （PGC-1α） were tested by Real-time PCR and immunohistochemistry assay respectively. RESULTS Long-term high-fat diet induced NAFLD with the progression from liver steatosis, inflammatory response to fibrosis. The levels of serum ALT and AST in the rats of the NAFLD group were significantly higher than those of the normal group （ P 〈 0. 05 ）. The transcript and protein levels of liver SIRT1 and PGC-1α were significantly decreased compared with the normal group. The total contents of liver SOD and MnSOD were much lower than those of the normal group, while the MDA level increased significantly（P 〈 0. 05）. The administration of Vit E to some extent reduced inflammation and fibrosis. After Vit E treatment, the levels of serum ALT and AST were significantly lower than those of the model group（P 〈0. 01, P 〈0. 05）. The mRNA and protein levels of liver SIRT1 and PGC-lct became higher than those of the model group（P 〈 0. 05 ）. Then liver SOD and MnSOD levels were significantly increased compared with the model group （P 〈 0. 05） while MDA content was reduced（P 〈 0. 05 ）. CONCLUSION Vitamin E corrects the imbalances of the oxidative and antioxidative system in mice models of high-fat diet-induced NAFLD by regulating the expression levels of the key factors of the SIRT1/PGC-1α signaling pathway, which reduces inflammation damage in liver and prevents the progression of NAFLD.