热量限制通过AMPK-SIRT1-线粒体通路延缓小鼠骨骼肌衰老

目的 观察热量限制对老化进程中小鼠骨骼肌线粒体等生物学性状的影响,探讨热量限制生物效应的分子机制.方法 13月龄C57BL/6雄性小鼠30只,按照简单随机抽样法分为自由进食组和热量限制组,每周按照自由进食组前1周平均摄食量的60％饲养热量限制小鼠.热量限制12周后,测量骨骼肌衰减指数、胫前肌等肌纤维密度及相对横截面积,透射电镜观察骨骼肌线粒体变化,Western blot检测PGC1 α、AMPKα、p-AMPKα及SIRT1等的表达,并比较老年鼠与成年鼠的表达差异.结果 ①与自由进食组比较,热量限制组骨骼肌衰减指数变化不明显,胫前肌等肌纤维密度显著升高(P＜0.01),相对横截面积降低(P＜0.01);②电镜观察显示:与自由进食组比较,热量限制组骨骼肌线粒体长度和宽度均增加(P＜0.05,P＜0.01),相对密度增加(P＜0.01),PGC1α表达升高(P＜0.05);③与自由进食组比较,热量限制组骨骼肌AMPK的磷酸化水平升高(P＜0.01),同时SIRT1表达也升高(P＜0.05);④与成年鼠比较,老年鼠骨骼肌AMPK磷酸化水平下降(P＜0.05),SIRT1和PGC1α的表达也均下降(P＜0.05).结论 热量限制能显著促进老化进程中骨骼肌线粒体的生成及活性,这一作用可能通过激活AMPK信号途径实现.

Calorie restriction delays skeletal muscle aging through AMPK-SIRT1-mitochondria pathway in mice

Objective To observe the effects of calorie restriction (CR) on the biological characteristics of mouse skeletal muscle mitochondria during the aging process,and explore the molecular mechanism of the biological effects of CR.Methods Thirty C57BL/6 male mice,13 months old,were randomly divided into 2 groups:free eating (ad libitum,AL) group and CR group,and the CR group was fed with 60％ consumption of the AL group.After 12 weeks of CR,the sarcopenia index of skeletal muscle,and the myofiber density and cross section area in tibialis anterior muscle were measured.The changes of skeletal muscle mitochondria were observed with transmission electron microscopy.The expression levels of AMPKα,p-AMPKα,SIRT1,and PGC1α were detected by Western blotting,and those of AMPKα and SIRT1 in the normal adult mice and aged mice were compared.Results Compared with the AL group,the sarcopenia index did not change significantly,the myofiber density was increased significantly (P ＜ 0.01),and the relative cross-sectional area was decreased (P ＜ 0.01) in the CR group.Electron microscope observation showed that the length and width of skeletal muscle mitochondria in the CR group were significantly increased (P ＜ 0.05,P ＜ 0.01),the relative density was significantly increased (P ＜ 0.01),and the expression of PGClα was significantly increased (P ＜ 0.05).The phosphorylation of AMPK in skeletal muscle was enhanced by CR,and the expression levels of SIRT1 and PGC1α were significantly increased (P ＜ 0.05).Compared with the normal adult mice,the phosphorylation of AMPK and the expression of SIRT1 and PGC1α in the aged mice were significantly decreased (P ＜ 0.05).Conclusion CR can significantly promote the biogenesis and activity of mitochondria in the aging skeletal muscle,which may be regulated by activating AMPK signaling pathway.