Faculty of Sport & Health Science, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga, 525-8577, Japan.
Faculty of Sport & Health Science, Ritsumeikan University, 1-1-1 Nojihigashi, Kusatsu, Shiga, 525-8577, Japan; Graduate School of Human and Environmental Studies, Kyoto University, Kyoto, Japan.
Biochem Biophys Res Commun. 2020 May 14;525(4):921-927. doi: 10.1016/j.bbrc.2020.02.152. Epub 2020 Mar 12.
Although several studies have implied that a hypoxic environment may be a factor that influences muscle hypertrophy, scant attention has been paid to the effect of oxygen molecules on the morphological characteristics of muscle. The purpose of the present study was to examine the effect of semisevere (i.e., 5%) to moderate (i.e., 10% or 15%) hypoxic environments on the morphological characteristics of skeletal muscle and the associated mechanisms. C2C12 skeletal muscle cells were divided into various groups, namely, the normoxia group (20.9% O) and hypoxia groups (5% O, 10% O, and 15% O), and cell growth and the expression of associated proteins in the hypoxia groups were compared with those in the normoxia group. The myotube diameter and cell differentiation index were determined on day 6 by immunocytochemical analyses. The expression of proteins associated with muscle cell differentiation (MyoD and myogenin) and muscle hypertrophy (mTOR and p70s6K) were analyzed by Western blotting. We found that compared with normoxia, a 5% oxygen environment inhibited differentiation and caused muscle atrophy. However, compared with normoxia, a 10% oxygen environment promoted muscle differentiation, and 10% oxygen and 15% oxygen environments induced muscle hypertrophy. Compared with normoxia, a 10% oxygen environment promoted myogenin and the expression of mTOR, p70s6K, and the metabolic signal AMPK. We concluded that a hypoxic environment, if not too severe, may promote muscle differentiation and hypertrophy by increasing the expression of proteins associated with muscle cell differentiation and hypertrophy.
虽然有几项研究表明，缺氧环境可能是影响肌肉肥大的一个因素，但很少有人关注氧分子对肌肉形态特征的影响。本研究旨在探讨中等到轻度缺氧环境（即 5%或 10%或 15%）对骨骼肌形态特征的影响及其相关机制。C2C12 骨骼肌细胞被分为不同的组，即常氧组（20.9%O）和缺氧组（5%O、10%O 和 15%O），并比较了缺氧组与常氧组细胞生长和相关蛋白的表达。第 6 天通过免疫细胞化学分析测定肌管直径和细胞分化指数。通过 Western blot 分析与肌肉细胞分化（MyoD 和 myogenin）和肌肉肥大（mTOR 和 p70s6K）相关的蛋白表达。结果发现，与常氧相比，5%氧环境抑制分化并导致肌肉萎缩。然而，与常氧相比，10%氧环境促进肌肉分化，10%氧和 15%氧环境诱导肌肉肥大。与常氧相比，10%氧环境促进了 myogenin 以及 mTOR、p70s6K 和代谢信号 AMPK 的表达。我们得出结论，缺氧环境如果不太严重，可能通过增加与肌肉细胞分化和肥大相关的蛋白表达来促进肌肉分化和肥大。
