Aging is associated with metabolic decline and reduction in mitochondrial function in skeletal muscle which can be delayed by physical activity. Moreover, exercise training has been shown to prevent age-associated decline in mitochondrial function and fragmentation of the mitochondrial network in mouse skeletal muscle. However, whether lifelong endurance exercise training exerts the same effects in human skeletal muscle is still not clear. Therefore, the aim of the present study was to examine the effect of volume-dependent lifelong endurance exercise training on mitochondrial function and network connectivity in older human skeletal muscle. Skeletal muscle complex I+II-linked mitochondrial respiration per tissue mass was higher, but intrinsic complex I+II-linked mitochondrial respiration was lower in highly trained older than in young untrained, older untrained and older moderately trained men. Mitochondrial volume and connectivity were higher in highly trained older than in untrained and moderately trained older subjects. Furthermore, protein content of the ADP/ATP exchangers ANT1 + 2 and VDAC was higher and of the mitophagic marker Parkin lower in skeletal muscle from the highly trained older than from untrained and moderately trained older subjects. In contrast, H2O2 emission in skeletal muscle was not affected by either age or exercise training, but SOD2 protein content was higher in highly trained older than in untrained and moderately trained older subjects. This suggests that healthy aging does not induce oxidative stress or mitochondrial network fragmentation in human skeletal muscle, but high-volume exercise training increases mitochondrial volume and network connectivity, thereby increasing oxidative capacity in older human skeletal muscle.

中文翻译：

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衰老和终身运动训练对人体骨骼肌线粒体功能和网络连接的影响

衰老与骨骼肌中的代谢下降和线粒体功能降低有关，这可以通过身体活动来延迟。此外，运动训练已被证明可以防止与年龄相关的线粒体功能下降和小鼠骨骼肌线粒体网络的断裂。然而，终生耐力运动训练是否对人体骨骼肌产生同样的影响尚不清楚。因此，本研究的目的是检查体积依赖性终身耐力运动训练对老年人骨骼肌线粒体功能和网络连接的影响。每组织质量的骨骼肌复合物 I+II 相关线粒体呼吸较高，但训练有素的老年人比未受过训练的年轻人低内在复合物 I+II 相关线粒体呼吸，年长的未受过训练的人和年长的适度训练的人。受过良好训练的老年人的线粒体体积和连通性高于未受过训练和适度训练的老年人。此外，ADP/ATP 交换器 ANT1 + 2 和 VDAC 的蛋白质含量更高，而线粒体自噬标记物 Parkin 在骨骼肌中的含量较低，来自训练有素的老年人比未受过训练和适度训练的老年人骨骼肌。相比之下，骨骼肌中的 H2O2 排放量不受年龄或运动训练的影响，但训练有素的老年人的 SOD2 蛋白含量高于未受过训练和适度训练的老年人。这表明健康的老龄化不会在人体骨骼肌中引起氧化应激或线粒体网络断裂，但高强度运动训练会增加线粒体体积和网络连通性，