Okano T, Yoshida K, Nakamura A, Sasazawa F, Oide T, Takeda S, Ikeda S
Third Department of Medicine, Shinshu University School of Medicine, Matsumoto, Japan.
Muscle Nerve. 2005 Aug;32(2):191-9. doi: 10.1002/mus.20351.
The aim of this study was to examine the effects of chronic running exercise on degenerative-regenerative processes in the hindlimb muscles of dystrophin-deficient mdx mice. The number of large-sized degenerative-regenerative groups (DRGs) was markedly decreased, whereas that of small-sized DRGs was unchanged by exercise. Expression of insulin-like growth factor-1 (Igf1), as well as a myogenic factor MyoD (Myod1), was downregulated in mdx muscles by exercise. The downregulation of Igf1 may well correlate with the decrease in the population of early regenerating fibers, which existed predominantly in DRGs, because IGF-1 was mainly localized in these fibers. Our data indicate that chronic exercise may accelerate the active cycle of degeneration-regeneration in mdx skeletal muscles. This means that mdx skeletal muscles can temporarily cope with work-induced injury by enhancing muscle regeneration and repair, but we speculate that an early decline of IGF-1 will accelerate age-dependent muscle wasting and weakness in the later stage of life in mdx mice.
本研究的目的是研究慢性跑步运动对肌营养不良蛋白缺乏的mdx小鼠后肢肌肉退变-再生过程的影响。大型退变-再生组（DRGs）的数量显著减少，而小型DRGs的数量在运动后未发生变化。运动使mdx肌肉中胰岛素样生长因子-1（Igf1）以及肌源性因子MyoD（Myod1）的表达下调。Igf1的下调很可能与主要存在于DRGs中的早期再生纤维数量的减少相关，因为IGF-1主要定位于这些纤维中。我们的数据表明，慢性运动可能会加速mdx骨骼肌退变-再生的活跃周期。这意味着mdx骨骼肌可以通过增强肌肉再生和修复来暂时应对工作引起的损伤，但我们推测，IGF-1的早期下降将加速mdx小鼠生命后期与年龄相关的肌肉萎缩和无力。
