薯蓣皂苷元通过mTOR/SREBP-1c/HSP60/MCAD/SCAD信号通路缓解高脂饮食诱导的大鼠NAFLD

Diosgenin alleviates NAFLD induced by a high-fat diet in rats via mTOR/SREBP-1c/HSP60/MCAD/SCAD signaling pathway

研究薯蓣皂苷元对非酒精性脂肪肝病(nonalcoholic fatty liver disease,NAFLD)模型大鼠肝组织中雷帕霉素靶蛋白(mammalian target of rapamycin,mTOR)、甾醇调节元件结合蛋白-1c(sterol regulatory element-binding protein-1c,SREBP-1c)、热休克蛋白60(heat shock protein,HSP60)、中链酰基辅酶A脱氢酶(medium-chain acyl-CoA dehydrogenase,MCAD)、短链酰基辅酶A脱氢酶(short-chain acyl-CoA dehydrogenase,SCAD)表达的影响,探讨薯蓣皂苷元缓解NAFLD的作用机制。40只雄性SD大鼠,按照随机数表法分为5组:对照组、高脂饮食组、薯蓣皂苷元低剂量组(150 mg·kg^(-1)·d^(-1))、薯蓣皂苷元高剂量组(300 mg·kg^(-1)·d^(-1))、辛伐他汀组(4 mg·kg^(-1)·d^(-1)),每组8只,其中对照组大鼠给予普通饲料喂养,其余4组大鼠给予高脂饮食喂养,喂食8周后,高脂饮食喂养组大鼠的体质量显著增加,此后,每天以相应剂量薯蓣皂苷元或辛伐他汀连续灌胃给药8周。生化法检测血清中甘油三酯(triglyceride,TG)、总胆固醇(total cholesterol,TC)、谷丙转氨酶(alanine transaminase,ALT)及谷草转氨酶(aspartate transaminase,AST)水平;酶法检测肝脏中TG、TC水平;油红O染色检测肝脏脂质蓄积情况;苏木素-伊红(hematoxylin-eosin,HE)染色检测肝组织病理形态变化;实时荧光定量聚合酶链反应和蛋白免疫印迹法分别检测大鼠肝组织中mTOR、SREBP-1c、HSP60、MCAD、SCAD的mRNA和蛋白表达水平。结果显示,与对照组相比,高脂饮食组大鼠体质量、食物摄入量、肝指数以及血清TG、TC、ALT、AST水平和肝脏TG、TC水平显著升高,肝脏脂质蓄积显著增多,肝脏结构紊乱,脂肪变性明显,肝脏mTOR、SREBP-1c的mRNA和蛋白表达水平显著升高,而HSP60、MCAD、SCAD的mRNA和蛋白表达水平显著降低;与高脂饮食组比较,各治疗组大鼠体质量、食物摄入量、肝指数以及血清TG、TC、ALT、AST水平和肝脏TG、TC水平显著降低,肝脏脂质蓄积显著减少,肝脏脂肪变性明显改善,肝脏mTOR、SREBP-1c的mRNA和蛋白水平显著降低,HSP60、MCAD、SCAD mRNA和蛋白水平显著升高。薯蓣皂苷元高剂量组的治疗效果优于薯蓣皂苷元低剂量组和辛伐他汀组。薯蓣皂苷元可能通过抑制mTOR、SREBP-1c的表达,促进HSP60、MCAD、SCAD的表达,以减少肝脏脂质合成、改善线粒体功能、促进脂肪酸β氧化,发挥防治NAFLD的作用。

This study aims to observe the effects of diosgenin on the expression of mammalian target of rapamycin(mTOR),sterol regulatory element-binding protein-1c(SREBP-1c),heat shock protein 60(HSP60),medium-chain acyl-CoA dehydrogenase(MCAD),and short-chain acyl-CoA dehydrogenase(SCAD) in the liver tissue of the rat model of non-alcoholic fatty liver disease(NAFLD) and explore the mechanism of diosgenin in alleviating NAFLD.Forty male SD rats were randomized into five groups:a control group,a model group,low-(150 mg·kg^(-1)·d^(-1)) and high-dose(300 mg·kg^(-1)·d^(-1)) diosgenin groups,and a simvastatin(4 mg·kg^(-1)·d^(-1)) group.The rats in the control group were fed with a normal diet,while those in the other four groups were fed with a high-fat diet.After feeding for 8 weeks,the body weight of rats in the high-fat diet groups increased significantly.After that,the rats were administrated with the corresponding dose of diosgenin or simvastatin by gavage every day for 8 weeks.The levels of triglyceride(TG),total cholesterol(TC),alanine transaminase(ALT),and aspartate transaminase(AST) in the serum were determined by the biochemical method.The levels of TG and TC in the liver were measured by the enzyme method.Oil-red O staining was employed to detect the lipid accumulation,and hematoxylin-eosin(HE) staining to detect the pathological changes in the liver tissue.The mRNA and protein levels of mTOR,SREBP-1c,HSP60,MCAD,and SCAD in the liver tissue of rats were determined by real-time fluorescence quantitative polymerase chain reaction(RT-qPCR) and Western blot,respectively.Compared with the control group,the model group showed increased body weight,food uptake,liver index,TG,TC,ALT,and AST levels in the serum,TG and TC levels in the liver,lipid deposition in the liver,obvious hepatic steatosis,up-regulated mRNA and protein expression levels of mTOR and SREBP-1c,and down-regulated mRNA and protein expression levels of HSP60,MCAD,and SCAD.Compared with the model group,the rats in each treatment group showed obviously decreased body weight,food uptake,liver index,TG,TC,ALT,and AST levels in the serum,TG and TC levels in the liver,lessened lipid deposition in the liver,ameliorated hepatic steatosis,down-regulated mRNA and protein le-vels of mTOR and SREBP-1c,and up-regulated mRNA and protein levels of HSP60,MCAD,and SCAD.The high-dose diosgenin outperformed the low-dose diosgenin and simvastatin.Diosgenin may prevent and treat NAFLD by inhibiting the expression of mTOR and SREBP-1c and promoting the expression of HSP60,MCAD,and SCAD to reduce lipid synthesis,improving mitochondrial function,and promoting fatty acid β oxidation in the liver.