耐力訓練對骨骼肌肌纖維類型與細胞凋亡關係的影響

Effect of endurance exercise training on the relationship between myosin heavy chain isoforms and apoptosis in skeletal muscle

"目的：探討耐力運動訓練後，腓腸肌（gastrocnemius）與比目魚肌（soleus）不同重鏈肌凝蛋白（myosin heavy chain，MyHC）異構物與細胞凋亡現象及粒腺體訊息傳遞分子mRNA基因表現量的關係。方法：將8週齡雄鼠（Sprague-Dawley）隨機分成控制組（n＝6）及運動組（n＝6），運動組在動物跑步機上進行10週之耐力運動訓練。結果：耐力運動訓練增加腓腸肌及比目魚肌之檸檬酸合成酶活性（p＜.05）；腓腸肌增加MyHC I、MyHC IIa與MyHC IIx及減少MyHC IIb的比率（p＜.05），比目魚肌增加MyHC I及減少MyHC IIa的比率（p＜.05）；減少腓腸肌與比目魚肌之細胞凋亡現象（p＜.05），而且比目魚肌細胞凋亡現象低於腓腸肌（p＜.05）；腓腸肌增加B細胞淋巴瘤／白血病2（B-cell leukemia／lymphoma2，Bcl-2）及減少細胞凋亡誘發因子（apoptosis inducing factor，AIF）mRNA表現量（p＜.05），比目魚肌增加Bcl-2、Bcl-2-性關聯蛋白（Bcl-2-associated X protein，Bax）與熱休克蛋白70（heat shock protein 70，HSP70）及減少劊白酶9（caspase-9）與AIF等mRNA表現量（p＜.05）。結論：（一）耐力運動訓練增加腓腸肌及比目魚肌之MyHC I比率，與骨骼肌細胞凋亡現象及其粒腺體訊息傳遞分子mRNA基因表現量下降有關，此現象對比目魚肌的影響大於腓腸肌。（二）耐力運動訓練後之比目魚肌，除了可降低粒腺體誘發細胞凋亡訊息傳遞分子mRNA基因表現量外，同時也會增加抗細胞凋亡分子之mRNA基因表現量，在腓腸肌無此現象。Purpose: To examine the relationship between myosin heavy chain (MyHC) isoforms and apoptosis in the gastrocnemius and soleus after endurance exercise training. Methods: Male Sprague-Dawley rats were randomly assigned to an untrained (CON, n = 6) or an endurance training group (ET, n = 6). The ET exercised on a treadmill for 10 weeks. Results: After endurance exercise traning, citrate synthase activity was increased in both gastrocnemius and soleus (p < .05). In gastrocnemius, the content of MyHC I, MyHC IIa and MyHC IIx were increased while MyHC IIb was decreased (p < .05). In soleus, the content of MyHC I was increased while MyHC IIa was decreased (p < .05). Apoptotic index was decreased in both gastrocnemius and soleus. Also, the apoptotic index of soleus was lower than the gastrocnemius after endurance training (p < .05). B-cell leukemia/lymphoma 2 (Bcl2) mRNA was up-regulated while apoptosis inducing factor (AIF) mRNA was down-regulated in gastrocnemius of ET. Bcl-2, Bcl-2-associated X protein (Bax) and heat shock protein 70 (HSP 70) mRNA were up-regulated while caspase-9 and AIF mRNA were down-regulated in soleus of ET. Conclusions: 1) Decreased apoptosis and down-regulated the mRNA expression of mitochondrial dependent apoptotic signaling were correlated with that the content of MyHC I increased in both gastrocnemius and soleus after endurance exercise training that is more sensitive to influence soleus than gastrocnemius. 2) Endurance exercise training not only down-regulated the mRNA of mitochondrial dependent apoptotic signaling but up-regulated the mRNA of anti-apoptosis in soleus that didn't occur in gastrocnemius."