Hypobaric hypoxic stress leads to oxidative stress, inflammation, and disturbance in protein turnover rate. Aggregately, this imbalance in redox homeostasis is responsible for skeletal muscle protein loss and a decline in physical performance. Hence, an urgent medical need is required to ameliorate skeletal muscle protein loss. The present study investigated the efficacy of ursolic acid (UA), a pentacyclic triterpene acid to ameliorate hypobaric hypoxia (HH)-induced muscle protein loss. UA is a naturally occurring pentacyclic triterpene acid present in several edible herbs and fruits such as apples. It contains skeletal muscle hypertrophy activity; still its potential against HH-induced muscle protein loss is unexplored. To address this issue, an in vivo study was planned to examine the beneficial effect of UA supplementation on HH-induced skeletal muscle loss. Male Sprague Dawley rats were exposed to HH with and without UA supplementation (20 mg/kg; oral) for 3 continuous days. The results described the beneficial role of UA as supplementation of UA with HH exposure attenuated reactive oxygen species production and oxidative protein damage, which indicate the potent antioxidant activity. Furthermore, UA supplementation enhanced Akt, pAkt, and p70S6kinase activity (Akt pathway) and lowered the pro-inflammatory cytokines in HH exposed rats. UA has potent antioxidant and anti-inflammatory activity, and it enhanced the protein content via upregulation of Akt pathway-related proteins against HH exposure. These three biological activities of UA make it a novel candidate for amelioration of HH-induced skeletal muscle damage and protein loss.

中文翻译：

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熊果酸通过上调 Akt 通路改善低压缺氧诱导的骨骼肌蛋白丢失：使用大鼠模型的实验研究

低压缺氧应激导致氧化应激、炎症和蛋白质周转率的紊乱。总的来说，这种氧化还原稳态失衡是造成骨骼肌蛋白质损失和身体机能下降的原因。因此，迫切需要改善骨骼肌蛋白质损失的医疗需求。本研究调查了熊果酸 (UA) 的功效，一种五环三萜酸改善低压缺氧 (HH) 诱导的肌肉蛋白丢失。UA 是一种天然存在的五环三萜酸，存在于几种可食用的药草和水果（如苹果）中。它含有骨骼肌肥大活性；它对 HH 诱导的肌肉蛋白质损失的潜力仍未得到探索。为了解决这个问题，计划进行一项体内研究，以检查补充 UA 对 HH 诱导的骨骼肌损失的有益作用。雄性 Sprague Dawley 大鼠在有和没有 UA 补充剂（20 mg/kg；口服）的情况下连续 3 天暴露于 HH。结果描述了 UA 作为补充 UA 与 HH 暴露的有益作用减弱了活性氧的产生和氧化蛋白损伤，这表明了有效的抗氧化活性。此外，UA 补充剂增强了 Akt、pAkt 和 p70S6 激酶活性（Akt 途径）并降低了 HH 暴露大鼠的促炎细胞因子。UA 具有有效的抗氧化和抗炎活性，它通过上调 Akt 通路相关蛋白对抗 HH 暴露来提高蛋白质含量。