Division of Clinical Physiology, Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden.
Unit of Clinical Physiology, Karolinska University Hospital, Stockholm, Sweden.
Am J Physiol Regul Integr Comp Physiol. 2020 Jul 1;319(1):R50-R58. doi: 10.1152/ajpregu.00061.2020. Epub 2020 May 20.
The current study explored whether the marked hypertrophic response noted with a short-term unilateral concurrent exercise paradigm was associated with more prominent changes in myonuclei accretion, ribosome biogenesis, and capillarization compared with resistance exercise alone (RE). Ten men (age 25 ± 4 yr) performed aerobic and resistance exercise (AE + RE) for one leg while the other leg did RE. Muscle biopsies were obtained before and after 5 wk of training and subjected to fiber-type specific immunohistochemical analysis, and quantification of total RNA content and mRNA/rRNA transcript abundance. Type II fiber cross-sectional area (CSA) increased with both AE + RE (22%) and RE (16%), while type I fiber CSA increased mainly with AE + RE (16%). The change score tended to differ between legs for type I CSA ( = 0.099), and the increase in smallest fiber diameter was greater in AE + RE than RE ( = 0.029). The number of nuclei per fiber increased after AE + RE in both fiber types, and this increase was greater ( = 0.027) than after RE. A strong correlation was observed between changes in number of nuclei per fiber and fiber CSA in both fiber types, for both AE + RE and RE ( > 0.8, < 0.004). RNA content increased after AE + RE (24%, = 0.019), but the change-scores did not differ across legs. The capillary variables generally increased in both fiber types, with no difference across legs. In conclusion, the accentuated hypertrophic response to AE + RE was associated with more pronounced myonuclear accretion, which was strongly correlated with the degree of fiber hypertrophy. This suggests that myonuclear accretion could play a role in facilitating muscle hypertrophy also during very short training periods.
本研究旨在探讨与单独进行抗阻运动（RE）相比，短期单侧同时进行的运动是否会引起更为明显的肌核蓄积、核糖体生物发生和毛细血管生成变化，从而导致更为明显的肥厚反应。10 名男性（年龄 25±4 岁）进行单侧的有氧和抗阻运动（AE+RE），而对侧腿仅进行 RE。在 5 周的训练前后采集肌肉活检标本，并进行纤维类型特异性免疫组织化学分析以及总 RNA 含量和 mRNA/rRNA 转录物丰度的定量分析。AE+RE 和 RE 均可使 II 型纤维横截面积（CSA）增加（分别增加 22%和 16%），而 I 型纤维 CSA 主要通过 AE+RE 增加（增加 16%）。I 型 CSA 的两腿之间的变化评分存在差异（ = 0.099），AE+RE 组的最小纤维直径增加大于 RE 组（ = 0.029）。两种纤维类型的肌纤维中核数均在 AE+RE 后增加，且这种增加大于 RE 组（ = 0.027）。在两种纤维类型中，AE+RE 和 RE 后，核数与纤维 CSA 的变化之间均存在很强的相关性（>0.8，<0.004）。AE+RE 后 RNA 含量增加（24%， = 0.019），但两腿之间的变化评分没有差异。毛细血管变量通常在两种纤维类型中均增加，两腿之间没有差异。结论：AE+RE 引起的肥大反应增强与更为显著的肌核蓄积有关，而肌核蓄积与纤维肥大的程度密切相关。这表明，在非常短的训练期间，肌核蓄积也可能在促进肌肉肥大中发挥作用。
