Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, PE, Canada.
Department of Biomedical Sciences, Atlantic Veterinary College, University of Prince Edward Island, PE, Canada.
Free Radic Biol Med. 2023 Nov 1;208:602-613. doi: 10.1016/j.freeradbiomed.2023.09.018. Epub 2023 Sep 18.
Mitochondrial reactive oxygen species (ROS) homeostasis is intricately linked to energy conversion reactions and entails regulation of the mechanisms of ROS production and removal. However, there is limited understanding of how energy demand modulates ROS balance. Skeletal muscle experiences a wide range of energy requirements depending on the intensity and duration of exercise and therefore is an excellent model to probe the effect of altered energy demand on mitochondrial ROS production. Because in most fish skeletal muscle exists essentially as pure spatially distinct slow-twitch red oxidative and fast-twitch white glycolytic fibers, it provides a natural system for investigating how functional specialization affects ROS homeostasis. We tested the hypothesis that acute increase in energy demand imposed by exhaustive exercise will increase mitochondrial HO emission to a greater extent in red muscle mitochondria (RMM) compared with white muscle mitochondria (WMM). We found that native HO emission rates varied by up to 6-fold depending on the substrate being oxidized and muscle fiber type, with RMM emitting at higher rates with glutamate-malate and palmitoylcarnitine while WMM emitted at higher rates with succinate and glyceral-3-phosphate. Exhaustive exercise increased the native and site-specific HO emission rates; however, the maximal emission rates depended on the substrate, fiber type and redox site. The HO consumption capacity and activities of individual antioxidant enzymes including the glutathione- and thioredoxin-dependent peroxidases as well as catalase were higher in RMM compared with WMM indicating that the activity of antioxidant defense system does not explain the differences in HO emission rates in RMM and WMM. Overall, our study suggests that substrate selection and oxidation may be the key factors determining the rates of ROS production in RMM and WMM following exhaustive exercise.
线粒体活性氧（ROS）的动态平衡与能量转换反应密切相关，需要调节 ROS 产生和清除的机制。然而，对于能量需求如何调节 ROS 平衡，人们的了解还很有限。骨骼肌的能量需求范围很广，具体取决于运动的强度和持续时间，因此是探究能量需求变化对线粒体 ROS 产生影响的理想模型。由于在大多数鱼类中，骨骼肌基本上由纯粹的空间分离的慢肌纤维（红肌纤维）和快肌纤维（白肌纤维）组成，因此它为研究功能特化如何影响 ROS 动态平衡提供了一个天然系统。我们假设，通过剧烈运动施加的急性能量需求增加，将导致红肌线粒体（RMM）中的线粒体 HO 排放比白肌线粒体（WMM）增加更多。我们发现，HO 的天然排放速率取决于所氧化的底物和肌肉纤维类型，差异最大可达 6 倍，谷氨酸-苹果酸和棕榈酰肉碱更有利于 RMM 中的 HO 排放，而琥珀酸和甘油-3-磷酸则更有利于 WMM 中的 HO 排放。剧烈运动增加了 HO 的天然和特异性排放速率；然而，最大排放速率取决于底物、纤维类型和氧化还原位点。与 WMM 相比，RMM 中的 HO 消耗能力和单个抗氧化酶的活性（包括谷胱甘肽和硫氧还蛋白依赖的过氧化物酶以及过氧化氢酶）更高，这表明抗氧化防御系统的活性并不能解释 RMM 和 WMM 中 HO 排放速率的差异。总的来说，我们的研究表明，底物选择和氧化可能是决定剧烈运动后 RMM 和 WMM 中 ROS 产生速率的关键因素。
