线粒体乙醛脱氢酶2在有氧运动抑制衰老骨骼肌细胞凋亡中的作用及机制

Physical exercise is currently considered the primary countermeasure to sarcopenia through attenuating age-related increase in myocyte apoptosis. However, the underlying cellular and molecular mechanisms are not well understood. We used an unbiased proteomic approach reveal the overall mechanism of the aerobic exercise improved sarcopenia. As a biomarkers, mitochondrial aldehyde dehydrogenase 2 (ALDH2) was identified further. Recent evidence has insinuated that loss of ALDH2 enzyme in the knockout mice cause accumulation of mitochondrial 4-HNE, which may contribute to skeletal muscle oxidative damage and mitochondrial dysfunction. The previous study confirmed that 4-HNE is closely related to age-related increase in myocyte apoptosis. It may thus be speculated that ALDH2 deficiency augments skeletal muscle 4-HNE levels, exacerbates muscle cell mitochondrial damage and apoptosis, the aerobic exercise may be inhibit myocyte apoptosis through upregulating the activity and expression of ALDH2. The present study is designed to evaluate the impact of ALDH2 activity on age-related increase in myocyte apoptosis and ALDH2 inhibitor was administrated，confirming that ALDH2 plays a pivotal positive role in mediating the aerobic exercise against myocyte apoptosis. Culture L6 muscle cells in vitro, to investigate the effect of ALDH2 on autophagy, apoptosis, mitochondrial damage, reveal which ALDH2 act via pathways. This project is the first study evaluating ALDH2-mediated protection of myocyte apoptosis by the aerobic exercise on both a cellular and a molecular level.

体育运动可通过抑制肌细胞凋亡来防治肌肉减少症，但具体机制不清。我们前期实验从蛋白质组学角度揭示了有氧运动改善肌肉减少症的整体机制，筛选出生物标示物线粒体乙醛脱氢酶2(ALDH2)。已知ALDH2基因缺失导致的4-羟基壬烯醛(4-HNE)积累会引起骨骼肌氧化损伤和线粒体功能失调。研究证实老龄骨骼肌4-HNE增加与肌细胞凋亡有关。据此推测“衰老肌细胞凋亡与ALDH2活性下调有关，有氧运动经ALDH2抑制肌细胞凋亡来防治肌肉减少症”。为了证实该假说，本课题进一步观察不同鼠龄大鼠骨骼肌ALDH2活性与肌细胞凋亡关联，给予ALDH2抑制剂，证实ALDH2介导有氧运动的保护作用。体外培养大鼠骨骼肌细胞，探讨ALDH2对自噬、线粒体损伤和凋亡的影响，证明ALDH2发挥作用依赖的信号级联。本课题首次在器官、细胞及分子水平上探讨ALDH2介导有氧运动抑制肌细胞凋亡及其机制，为肌肉减少症的防治提供理论基础。

本项目采用双能X射线（DEXAs）、超声心动图、反转录酶-聚合酶链锁反应（RT-PCR）、蛋白质印迹（Western blot）、透射电镜和蛋白质组学等手段研究持续性耐力运动（MICT）和高强度间歇训练（HIIT）对增龄大鼠体成分、心功能、骨骼肌结构和功能及其内在机制的影响，结果发现：（1）衰老大鼠体成分、运动表现的衰减与机体氧化应激、低度慢性炎症、脂肪细胞因子分泌改变有关；与MICT相比，HIIT更显著抑制氧化应激和炎症介质的释放，并改善脂肪和循环脂肪因子分泌；2）一方面，HIIT通过IGF-1/SIRT3轴上调衰老骨骼肌SOD2活性，防止骨骼肌氧化损伤；另一方面，HIIT通过激活脂联素/AMPK信号上调自噬活性和线粒体生物合成，进而改善线粒体质量控制并抑制细胞凋亡；3）MICT和HIIT对增龄大鼠腓肠肌ALDH2代谢底物4-HNE生成均有明显抑制作用，这与腓肠肌ALDH2蛋白表达增加有关，与心肌和比目鱼肌的ALDH2蛋白表达无关；4）蛋白质组学发现，MICT和HIIT能共同改善衰老骨骼肌中参与调控钙离子稳态、收缩机能、线粒体氧化磷酸化、再生和凋亡、细胞外基质信号等功能的蛋白表达；MICT特异性调控内质网应激；HIIT特异性调控脂联素信号通路，本项目首次从蛋白质组学角度揭示HIIT和MICT抵抗肌肉减少症的特异和共同作用机制，为深入研究其内在机制提供了数据支撑。