Mechanisms of exercise-induced muscular hypertrophy : A study with venous-occlusion models.

我们之前已经证明，低强度阻力训练与适度的血管闭塞相结合时，会导致肌肉尺寸和力量的增加。阐明其机制不仅有助于了解运动性肌肉肥大的共同机制，而且有助于开发新的运动方法，大大减少机械应力。为此，我们开发了两种类型的运动模型（动物和人体模型）。在动物模型中，用加热的金属针手术挤压闭塞大鼠后肢肌肉的主要静脉。静脉血流量的慢性限制2周引起的后肢肌肉的湿重和干重以及总蛋白质含量增加，但比目鱼肌除外。在跖肌，肌纤维的所有类型（类型I，IIa和IIb/X）显示出增加其横截面积（CSA）。此外，还观察到发生了肌纤维类型向更快亚型的转变。浓度 关于我们 糖原、乳酸、一氧化氮（NO）、HSP-72和活性肝细胞生长因子（HGF）含量增加，而肌生成抑制素含量减少。NOS-1表达增加，IGF-I表达有增加趋势，但无统计学意义。在人体模型中，对膝伸肌进行低强度阻力运动（一次重复最大值的30%），每天两次，持续2周。即使在如此短的训练时间内，肌肉横截面积（增加10%）和力量也会增加，并且在匹配良好的条件下对活检样本（外侧静脉）进行分析。I型和II型纤维均显示肥大，但II型纤维倾向于显示CSA的较大增加。基因芯片分析显示，IGF-I/II、卵泡抑素样肽、小窝蛋白和细胞外基质相关蛋白表达增加，而肌生成抑制素表达明显减少。结果表明，在运动过程中减少氧气输送起着重要的作用，并影响与肌肉卫星细胞增殖有关的因素。少

We have previously shown that low-intensity resistance training cause increases in muscular size and strength when combined with moderate vascular occlusion. Elucidating its mechanism likely contributes not only to understand the common mechanisms of exercise-induced muscular hypertrophy but also to develop new exercise methods with much reduced mechanical stress. For this purpose, we developed two types of exercise model (animal and human models). In the animal model, major veins from hindlimb muscles of the rats were surgically crush-occluded with a heated metal needle. The chronic restriction of venous blood flow for 2 weeks caused in hindlimb muscles increases in wet and dry weights and total protein content, except for the soleus muscle. In the plantaris muscle, muscle fibers of all types (types I, IIa and IIb/x) showed an increase in their cross-sectional area (CSA). In addition, transitions of muscle-fiber types directed towards faster subtypes were observed to occur. The concen … More trations of glycogen, lactate, nitric oxide (NO), HSP-72 and active form of hepatocyte growth factor (HGF) increased, whereas that of myostatin decreased. Expressions of NOS-1 increased, whereas that of IGF-I tended to increase without significance. In the human model, low-intensity resistance exercise for knee extensor muscles (30% of one-repetition maximum) was performed twice daily for 2 weeks. Even with such short period of training, increases in muscle cross-sectional area (by〜10%) and strength occurred, and analyses for biopsy samples (v.lateralis) were made in a well-matched condition. Both type I and II fibers showed hypertrophy, though type II fibers tended to show a larger increase in CSA. DNA microarray analysis showed that expressions of IGF-I/II, follistain-like peptide, caveolin and extracellular matrix-related proteins increased, whereas that of myostatin considerably decreased. The results suggest that reduced oxygen delivery during exercise plays an important part and affects the factors relating to the proliferation of muscle satellite cells. Less