St-Jean-Pelletier Félix, Pion Charlotte H, Leduc-Gaudet Jean-Philippe, Sgarioto Nicolas, Zovilé Igor, Barbat-Artigas Sébastien, Reynaud Olivier, Alkaterji Feras, Lemieux François C, Grenon Alexis, Gaudreau Pierrette, Hepple Russell T, Chevalier Stéphanie, Belanger Marc, Morais José A, Aubertin-Leheudre Mylène, Gouspillou Gilles
Département de Sciences de l'activité Physique, Faculté des Sciences, UQAM, Quebec, Canada.
Groupe de Recherche en Activité Physique Adaptée, Québec, Canada.
J Cachexia Sarcopenia Muscle. 2017 Apr;8(2):213-228. doi: 10.1002/jcsm.12139. Epub 2016 Sep 2.
The exact impact of ageing on skeletal muscle phenotype and mitochondrial and lipid content remains controversial, probably because physical activity, which greatly influences muscle physiology, is rarely accounted for. The present study was therefore designed to investigate the effects of ageing, physical activity, and pre-frailty on skeletal muscle phenotype, and mitochondrial and intramyocellular lipid content in men.
Recreationally active young adult (20-30 yo; YA); active (ACT) and sedentary (SED) middle-age (50-65 yo; MA-ACT and MA-SED); and older (65 + yo; 65 + ACT and 65 + SED) and pre-frail older (65 + PF) men were recruited. Muscle biopsies from the vastus lateralis were collected to assess, on muscle cross sections, muscle phenotype (using myosin heavy chain isoforms immunolabelling), the fibre type-specific content of mitochondria (by quantifying the succinate dehydrogenase stain intensity), and the fibre type-specific lipid content (by quantifying the Oil Red O stain intensity).
Only 65 + SED and 65 + PF displayed significantly lower overall and type IIa fibre sizes vs. YA. 65 + SED displayed a lower type IIa fibre proportion vs. YA. MA-SED and 65 + SED displayed a higher hybrid type IIa/IIx fibre proportion vs. YA. Sedentary and pre-frail, but not active, men displayed lower mitochondrial content irrespective of fibre type vs. YA. 65 + SED, but not 65 + ACT, displayed a higher lipid content in type I fibres vs. YA. Finally, mitochondrial content, but not lipid content, was positively correlated with indices of muscle function, functional capacity, and insulin sensitivity across all subjects.
Taken altogether, our results indicate that ageing in sedentary men is associated with (i) complex changes in muscle phenotype preferentially affecting type IIa fibres; (ii) a decline in mitochondrial content affecting all fibre types; and (iii) an increase in lipid content in type I fibres. They also indicate that physical activity partially protects from the effects of ageing on muscle phenotype, mitochondrial content, and lipid accumulation. No skeletal specific muscle phenotype of pre-frailty was observed.
衰老对骨骼肌表型、线粒体及脂质含量的确切影响仍存在争议，这可能是因为很少考虑到对肌肉生理有重大影响的身体活动。因此，本研究旨在调查衰老、身体活动和虚弱前期对男性骨骼肌表型、线粒体及肌细胞内脂质含量的影响。
招募了休闲活跃的年轻成年人（20 - 30岁；YA）；活跃（ACT）和久坐（SED）的中年男性（50 - 65岁；MA - ACT和MA - SED）；以及老年（65岁及以上；65 + ACT和65 + SED）和虚弱前期老年男性（65 + PF）。采集股外侧肌的肌肉活检样本，以在肌肉横截面上评估肌肉表型（使用肌球蛋白重链同工型免疫标记）、线粒体的纤维类型特异性含量（通过定量琥珀酸脱氢酶染色强度）以及纤维类型特异性脂质含量（通过定量油红O染色强度）。
与YA相比，只有65 + SED和65 + PF的总体和IIa型纤维尺寸显著更小。与YA相比，65 + SED的IIa型纤维比例更低。与YA相比，MA - SED和65 + SED的IIa/IIx混合型纤维比例更高。无论纤维类型如何，久坐和虚弱前期但不活跃的男性的线粒体含量均低于YA。与YA相比，65 + SED而非65 + ACT的I型纤维脂质含量更高。最后，在所有受试者中，线粒体含量而非脂质含量与肌肉功能、功能能力和胰岛素敏感性指标呈正相关。
总体而言，我们的结果表明，久坐男性的衰老与以下情况相关：（i）肌肉表型的复杂变化，优先影响IIa型纤维；（ii）线粒体含量下降，影响所有纤维类型；（iii）I型纤维中脂质含量增加。结果还表明，身体活动可部分保护肌肉免受衰老对肌肉表型、线粒体含量和脂质积累的影响。未观察到虚弱前期的骨骼特异性肌肉表型。
