Tam B T, Pei X M, Yu A P, Sin T K, Leung K K, Au K K, Chong J T, Yung B Y, Yip S P, Chan L W, Wong C S, Siu P M
Department of Health Technology and Informatics, Faculty of Health and Social Sciences, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China.
Acta Physiol (Oxf). 2015 Jun;214(2):221-36. doi: 10.1111/apha.12503. Epub 2015 Apr 21.
Acute exercise is known to activate autophagy in skeletal muscle. However, little is known about how basal autophagy in skeletal muscle adapts to chronic exercise. In the current study we aim to, firstly, examine whether long-term habitual exercise alters the basal autophagic signalling in plantaris muscle and, secondly, examine the association between autophagy and fibre-type shifting.
Adult female Sprague-Dawley rats aged 2 months were randomly assigned to control and exercise groups. Animals in exercise group were kept in cages equipped with free access running wheels to perform habitual exercise for 5 months. Animals in the control group were caged in the absence of running wheels. Animals were sacrificed after the 5-month experimental period. Plantaris muscle tissues were harvested for analysis.
We showed that long-term habitual exercise enhanced basal autophagy, but without altering expressions of autophagy proteins in plantaris muscle. Interestingly, sirtuin protein, a possible regulator of autophagy, was upregulated in plantaris muscle. Furthermore, we suspected that different types of muscle fibre adapted to chronic exercise in different ways. Long-term habitual exercise resulted in fibre-type shifting from type IIX to IIA in both gastrocnemius muscle and plantaris muscle. Intriguingly, our analysis demonstrated that LC3-II protein abundance is positively correlated with the proportion of type IIA fibre whereas it was negatively correlated with the proportion of type IIX fibre in plantaris muscle. PGC-1α protein abundance was positively associated with the proportion of type IIA fibre and LC3-II in plantaris muscle.
These results suggest that basal autophagy is enhanced in plantaris muscle after long-term habitual exercise and associated with fibre-type shifting.
已知急性运动可激活骨骼肌中的自噬。然而，关于骨骼肌中的基础自噬如何适应长期运动，我们知之甚少。在本研究中，我们旨在，首先，研究长期习惯性运动是否会改变比目鱼肌中的基础自噬信号，其次，研究自噬与纤维类型转变之间的关联。
将2个月大的成年雌性Sprague-Dawley大鼠随机分为对照组和运动组。运动组的动物饲养在配备有自由转动跑轮的笼子里，进行习惯性运动5个月。对照组的动物饲养在没有跑轮的笼子里。在5个月的实验期后处死动物。采集比目鱼肌组织进行分析。
我们发现长期习惯性运动增强了基础自噬，但未改变比目鱼肌中自噬蛋白的表达。有趣的是，自噬的一种可能调节因子——沉默调节蛋白在比目鱼肌中上调。此外，我们怀疑不同类型的肌纤维以不同方式适应长期运动。长期习惯性运动导致腓肠肌和比目鱼肌的纤维类型从IIX型转变为IIA型。有趣的是，我们的分析表明，在比目鱼肌中，LC3-II蛋白丰度与IIA型纤维的比例呈正相关，而与IIX型纤维的比例呈负相关。PGC-1α蛋白丰度与比目鱼肌中IIA型纤维和LC3-II的比例呈正相关。
这些结果表明，长期习惯性运动后比目鱼肌中的基础自噬增强，且与纤维类型转变相关。
