Department of Sports Medicine, Medical Clinic, University Hospital Tübingen, Tübingen, Germany.
Interfaculty Research Institute for Sport and Physical Activity, Eberhard Karls University of Tübingen, Tübingen, Germany.
Physiol Rep. 2020 Oct;8(20):e14609. doi: 10.14814/phy2.14609.
Physical activity and exercise induce a complex pattern of adaptation reactions in a broad variety of tissues and organs, particularly the cardiovascular and the musculoskeletal systems. The underlying mechanisms, however, specifically the molecular changes that occur in response to training, are still incompletely understood. Animal models help to systematically elucidate the mechanisms of exercise adaptation. With regard to endurance-based running exercise in mice, two basic regimens have been established: forced treadmill running (FTR), usually consisting of several sessions per week, and voluntary wheel running (VWR). However, the effects of these two programs on skeletal muscle molecular adaptation patterns have never been directly compared. To address this issue, in a pilot study, we analyzed the effects of two ten-week training regimens in juvenile, male, C57BL/6 mice: moderate-intensity forced treadmill running three-times-a-week, employing a protocol that has been widely used in similar studies before, and voluntary wheel running. Our data suggest that there are similarities, but also characteristic differences in the molecular responses of different skeletal muscle species to the two training regimens. In particular, we found that VWR induces a significant fiber type shift toward more type IIX fibers in the slow, oxidative soleus muscle (p = .0053), but not in the other three muscles analyzed. In addition, while training-induced expression patterns of the two metabolic markers Ppargc1a, encoding Pgc-1α (peroxisome proliferator-activated receptor gamma coactivator 1-alpha) and Nr4a3 (nuclear receptor subfamily 4 group A member 3) were roughly similar, downregulation of the Mstn (myostatin) gene and the "atrogene" Fbox32 could only be observed in response to VWR in specific muscles, such as in the gastrocnemius (p = .0015 for Mstn) and in the tibialis anterior (p = .0053 for Fbox32) muscles, suggesting that molecular adaptation reactions to the two training regimens show distinct characteristics.
体力活动和运动在广泛的组织和器官中引起复杂的适应反应模式，特别是心血管和肌肉骨骼系统。然而，潜在的机制，特别是对训练的反应发生的分子变化，仍然不完全清楚。动物模型有助于系统地阐明运动适应的机制。关于小鼠基于耐力的跑步运动，已经建立了两种基本方案：强制跑步机跑步（FTR），通常每周包括几次会议，和自愿轮式跑步（VWR）。然而，这两种方案对骨骼肌分子适应模式的影响从未被直接比较过。为了解决这个问题，在一项初步研究中，我们分析了两种为期十周的训练方案在幼年雄性 C57BL/6 小鼠中的效果：中等强度的强制跑步机跑步，每周三次，采用一种在类似研究中广泛使用的方案，和自愿轮式跑步。我们的数据表明，两种不同的训练方案对不同骨骼肌的分子反应既有相似之处，也有特征性的差异。特别是，我们发现 VWR 在慢氧化比目鱼肌（p =.0053）中引起明显的纤维类型向更多的 IIX 型纤维的转变，但在其他三种分析的肌肉中没有。此外，虽然训练诱导的两个代谢标志物 Ppargc1a（编码 Pgc-1α（过氧化物酶体增殖物激活受体γ共激活因子 1-α）和 Nr4a3（核受体亚家族 4 组 A 成员 3）的表达模式大致相似，但 Mstn（肌肉生长抑制素）基因和“atrogene”Fbox32 的下调只能在 VWR 下观察到在特定的肌肉中，如腓肠肌（Mstn 的 p =.0015）和胫骨前肌（Fbox32 的 p =.0053），这表明两种训练方案的分子适应反应具有明显的特征。
