高脂饮食通过p-AMPK/mTOR信号通路下调小鼠肝细胞自噬水平

High-fat diet suppresses hepatic autophagy via p-AMPK/mTOR signal channel in mice

目的探讨高脂饮食对小鼠肝细胞自噬的影响并分析其可能机制。方法将C57BL小鼠随机分为2组,每组n=15,给予常规饮食(NC)或高脂饮食(HFD)喂养,8、12和16周后每组随机处死5只小鼠,测体质量、肝质量、内脏脂肪质量;油红(Oil-Red-O)染色测肝脂质沉积;Western blot检测肝脏自噬相关蛋白LC3Ⅱ/LC3Ⅰ、P62和自噬调控信号通路蛋白p-mTOR和p-AMPK的表达。结果 8周时,HFD组小鼠出现腹型肥胖,16周时小鼠体质量、内脏脂肪质量及肝脂滴沉积较NC组明显增加(P<0.01);HFD组8周时肝脏LC3Ⅱ表达较NC组增加(P<0.05);而12及16周肝脏LC3Ⅱ表达较NC组显著降低(P<0.05);P62表达较NC组明显增加(P<0.05)。与NC组相比,HFD组各时间点肝脏p-AMPK表达均减少,而p-mTOR蛋白表达均显著增加。结论高脂饮食初期小鼠肝细胞自噬短暂增加,但长期高脂饮食可导致肝细胞自噬水平显著下调甚至衰竭,肝细胞自噬水平下调与高脂饮食抑制肝细胞p-AMPK表达及增加p-mTOR的活性有关。

Objective To investigate the effects of high fat diet on hepatic autophagy in mice and analyze the possible mechanism. Methods C57 BL male mice were fed with either normal diet or high-fat diet（ HFD） for 8,12 or16 weeks. The mice were sacrificed after measuring the body weight. The mesentery and epididymal fat tissue weight,the liver weight and the hepatic lipid accumulation were detected. The expression of hepatic AMP-activated protein kinase（ AMPK） and mammalian target of rapamycin（ m TOR） protein and autophagic markers including LC3Ⅱ,P62 protein were measured by Western blot. Results HFD-fed mice displayed significantly heavier body weight at 16 weeks and significantly heavier intra abdominal fat weight and lipid overaccumulation in liver at 8,12,16 weeks（ all P〈0. 01）. Western blot showed hepatic LC3Ⅱ expression was up-regulated mildly in HFD fed mice at8 weeks（ P〈0. 05）,but the change dramatically was reversed,hepatic LC3Ⅱ was significantly lower in HFD fed mice at 12,16 weeks,as well as P62 was increased in HFD fed animals（ all P 0. 05）. HFD suppressed phosphorylation of AMPK and increased phosphorylation of m TOR levels in liver at 8,12,16 weeks,compared to thenormal-diet fed mice.Conclusions Our data demonstrate that hepatic autophagy is in dynamic change in high-fat diet mice,long term high-fat diet severely suppressed hepatic autophagy,which is associated with decreased p-AMPK and increased p-mTOR.