University of Alaska Fairbanks, Institute of Arctic Biology, PO Box 757000 Fairbanks, AK 99775, USA.
J Exp Biol. 2022 Nov 1;225(21). doi: 10.1242/jeb.244659. Epub 2022 Nov 11.
The metabolic rate (ṀO2) of eurythermal fishes changes in response to temperature, yet it is unclear how changes in mitochondrial function contribute to changes in ṀO2. We hypothesized that ṀO2 would increase with acclimation temperature in the threespine stickleback (Gasterosteus aculeatus) in parallel with metabolic remodeling at the cellular level but that changes in metabolism in some tissues, such as liver, would contribute more to changes in ṀO2 than others. Threespine stickleback were acclimated to 5, 12 and 20°C for 7 to 21 weeks. At each temperature, standard and maximum metabolic rate (SMR and MMR, respectively), and absolute aerobic scope (AAS) were quantified, along with mitochondrial respiration rates in liver, oxidative skeletal and cardiac muscles, and the maximal activity of citrate synthase (CS) and lactate dehydrogenase (LDH) in liver, and oxidative and glycolytic skeletal muscles. SMR, MMR and AAS increased with acclimation temperature, along with rates of mitochondrial phosphorylating respiration in all tissues. Low SMR and MMR at 5°C were associated with low or undetectable rates of mitochondrial complex II activity and a greater reliance on complex I activity in liver, oxidative skeletal muscle and heart. SMR was positively correlated with cytochrome c oxidase (CCO) activity in liver and oxidative muscle, but not mitochondrial proton leak, whereas MMR was positively correlated with CCO activity in liver. Overall, the results suggest that changes in ṀO2 in response to temperature are driven by changes in some aspects of mitochondrial function in some, but not all, tissues of threespine stickleback.
温水鱼类的代谢率（ṀO2）会随温度变化而变化，但线粒体功能的变化如何导致ṀO2 变化尚不清楚。我们假设，在三刺鱼（Gasterosteus aculeatus）中，随着细胞水平代谢重塑，ṀO2 会随驯化温度升高而升高，但肝脏等某些组织的代谢变化对ṀO2 变化的贡献会大于其他组织。三刺鱼被驯化到 5、12 和 20°C 7 到 21 周。在每个温度下，分别量化标准代谢率（SMR）和最大代谢率（MMR）以及绝对需氧量（AAS），同时量化肝脏、氧化型骨骼肌和心肌中的线粒体呼吸率，以及肝脏、氧化型和糖酵解型骨骼肌中柠檬酸合酶（CS）和乳酸脱氢酶（LDH）的最大活性。SMR、MMR 和 AAS 随驯化温度升高而升高，所有组织中线粒体磷酸化呼吸率也随之升高。5°C 时 SMR 和 MMR 较低，与肝脏、氧化型骨骼肌和心脏中线粒体复合物 II 活性较低或无法检测，以及对复合物 I 活性的依赖程度增加有关。SMR 与肝脏和氧化型肌肉中的细胞色素 c 氧化酶（CCO）活性呈正相关，但与线粒体质子泄漏无关，而 MMR 与肝脏中的 CCO 活性呈正相关。总体而言，研究结果表明，代谢率（ṀO2）对温度变化的响应是由某些组织中线粒体功能的某些方面变化驱动的，而不是所有组织。
