The skeletal muscle is a highly plastic tissue. Its ability to respond to external stimuli and challenges allows it to face the functional needs of the organism. In the goldfish Carassius auratus, a model of hypoxia resistance, exposure to reduced oxygen is accompanied by an improvement of the swimming performance, relying on a sustained contractile behavior of the skeletal muscle. At the moment, limited information is available on the mechanisms underlying these responses.

We here evaluated the effects of short- (4 days) and long- (20 days) term exposure to moderate water hypoxia on the goldfish white skeletal muscle, focusing on oxidative status and mitochondrial dynamics. No differences in lipid peroxidation, measured as 2-thiobarbituric acid-reacting substances (TBARS), and oxidatively modified proteins (OMP) were detected in animals exposed to hypoxia with respect to their normoxic counterparts. Exposure to short-term hypoxia was characterized by an enhanced SOD activity and expression, paralleled by increased levels of Nrf2, a regulator of the antioxidant cell response, and HSP70, a chaperone also acting as a redox sensor. The expression of markers of mitochondrial biogenesis (TFAM) and abundance (VDAC) and of the mtDNA/nDNA ratio was similar under normoxia and under both short- and long-term hypoxia, thus excluding a rearrangement of the mitochondrial apparatus. Only an increase of PGC1α (a transcription factor involved in mitochondrial dynamics) was detected after 20 days of hypoxia. Our results revealed novel aspects of the molecular mechanisms that in the goldfish skeletal muscle may sustain the response to hypoxia, thus contributing to adequate tissue function to organism requirements.

骨骼肌是一种高度可塑性的组织。它对外部刺激和挑战做出反应的能力使其能够面对有机体的功能需求。在金鱼鲫鱼（一种耐缺氧模型）中，暴露于减少的氧气中会伴随着游泳性能的改善，这依赖于骨骼肌的持续收缩行为。目前，有关这些反应背后机制的信息有限。

我们在这里评估了短期（4天）和长期（20天）暴露于中度水缺氧对金鱼白色骨骼肌的影响，重点关注氧化状态和线粒体动力学。在暴露于缺氧的动物​​中，与正常含氧量的动物相比，没有检测到以 2-硫代巴比妥酸反应物质 (TBARS) 和氧化修饰蛋白 (OMP) 测量的脂质过氧化差异。暴露于短期缺氧的特点是 SOD 活性和表达增强，同时 Nrf2（抗氧化细胞反应的调节剂）和 HSP70（也充当氧化还原传感器的伴侣）水平增加。线粒体生物合成 (TFAM) 和丰度 (VDAC) 标记物以及 mtDNA/nDNA 比率的表达在常氧条件下以及短期和长期缺氧条件下相似，因此排除了线粒体装置的重排。缺氧 20 天后，仅检测到 PGC1α（一种参与线粒体动力学的转录因子）增加。我们的结果揭示了金鱼骨骼肌可能维持缺氧反应的分子机制的新方面，从而有助于满足生物体需求的足够的组织功能。