Mitochondrial dysregulation in skeletal myocytes is considered a major factor in aged sarcopenia. In this study, we aimed to study the effects of peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) on Sestrin2-mediated mechanistic target of rapamycin complex 1 (mTORC1) in aged skeletal muscles. C2C12 myoblasts were stimulated by 50 μM 7β-hydroxycholesterol (7β-OHC) to observe the changes of DNA damage, mitochondrial membrane potential (Δψm), mitochondrial ROS and PGC-1α protein. The PGC-1α silence in the C2C12 cells was established by siRNA transfection. The levels of DNA damage, Δψm, mitochondrial ROS, Sestrin2 and p-S6K1/S6K1 proteins were observed after the PGC-1α silence in the C2C12 cells. Recombinant Sestrin2 treatment was used to observe the changes of DNA damage, Δψm, mitochondrial ROS and p-S6K1/S6K1 protein in the 7β-OHC-treated or PGC-1α siRNA-transfected C2C12 cells. Wild-type (WT) mice and muscle-specific PGC-1α conditional knockout (MKO) mice, including young and old, were used to analyse the effects of PGC-1α on muscle function and the levels of Sestrin2 and p-S6K1 in the white gastrocnemius muscles. Recombinant Sestrin2 was administrated to analyse its effects on muscle function in the old WT mice and old MKO mice. 7β-OHC treatment induced DNA damage, mitochondrial dysfunction and decrease of PGC-1α protein in the C2C12 cells. PGC-1α silence also induced DNA damage and mitochondrial dysfunction in the C2C12 cells. Additionally, PGC-1α silence or 7β-OHC treatment decreased the levels of Sestrin2 and p-S6K1/S6K1 protein in the C2C12 cells. Recombinant Sestrin2 treatment significantly improved the DNA damage and mitochondrial dysfunction in the 7β-OHC-treated or PGC-1α siRNA-transfected C2C12 cells. At the same age, muscle-specific PGC-1α deficiency aggravated aged sarcopenia and decreased the levels of Sestrin2 and p-S6K1 in the white gastrocnemius muscles when compared to the WT mice. Recombinant Sestrin2 treatment improved muscle function and increased p-S6K1 levels in the old two genotypes. This research demonstrates that PGC-1α participates in regulating mitochondrial function in aged sarcopenia through effects on the Sestrin2-mediated mTORC1 pathway.

中文翻译：

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PGC-1α 通过影响 Sestrin2 介导的 mTORC1 通路参与调节老年肌少症的线粒体功能

骨骼肌细胞线粒体失调被认为是老年肌少症的主要因素。在这项研究中，我们旨在研究过氧化物酶体增殖物激活受体γ共激活剂-1α (PGC-1α) 对衰老骨骼肌中 Sestrin2 介导的雷帕霉素复合物 1 (mTORC1) 机制靶点的影响。用50 μM 7β-羟基胆固醇（7β-OHC）刺激C2C12成肌细胞，观察DNA损伤、线粒体膜电位（Δψm）、线粒体ROS和PGC-1α蛋白的变化。通过 siRNA 转染建立 C2C12 细胞中的 PGC-1α 沉默。沉默PGC-1α后，观察C2C12细胞中DNA损伤、Δψm、线粒体ROS、Sestrin2和p-S6K1/S6K1蛋白的水平。采用重组Sestrin2处理观察7β-OHC处理或PGC-1α siRNA转染C2C12细胞中DNA损伤、Δψm、线粒体ROS和p-S6K1/S6K1蛋白的变化。使用野生型（WT）小鼠和肌肉特异性PGC-1α条件敲除（MKO）小鼠（包括年轻和年老）来分析PGC-1α对肌肉功能以及Sestrin2和p-S6K1水平的影响。白色腓肠肌。给予重组Sestrin2，分析其对老年WT小鼠和老年MKO小鼠肌肉功能的影响。 7β-OHC 处理诱导 C2C12 细胞中 DNA 损伤、线粒体功能障碍和 PGC-1α 蛋白减少。 PGC-1α沉默还诱导C2C12细胞中的DNA损伤和线粒体功能障碍。此外，PGC-1α沉默或7β-OHC处理降低了C2C12细胞中Sestrin2和p-S6K1/S6K1蛋白的水平。重组 Sestrin2 治疗显着改善了 7β-OHC 处理或 PGC-1α siRNA 转染的 C2C12 细胞中的 DNA 损伤和线粒体功能障碍。在同一年龄，与 WT 小鼠相比，肌肉特异性 PGC-1α 缺乏会加重老年肌少症，并降低白色腓肠肌中 Sestrin2 和 p-S6K1 的水平。重组 Sestrin2 治疗改善了旧两种基因型的肌肉功能并增加了 p-S6K1 水平。这项研究表明，PGC-1α 通过影响 Sestrin2 介导的 mTORC1 通路参与调节老年肌少症的线粒体功能。