Tincknell James B, Kugler Benjamin, Spicuzza Haley, Yan Huimin, You Tongjian, Zou Kai
bioRxiv. 2023 Jun 29:2023.06.28.546902. doi: 10.1101/2023.06.28.546902.
Mitochondrial quality control processes are essential in governing mitochondrial integrity and function. The purpose of the study was to examine the effects of 10 weeks of HIIT on the regulatory protein machinery of skeletal muscle mitochondrial quality control and whole-body glucose homeostasis in diet-induced obese mice. Male C57BL/6 mice were randomly assigned to a low-fat diet (LFD) or high-fat diet (HFD) group. After 10 weeks, HFD-fed mice were divided into sedentary and HIIT (HFD+HIIT) groups and remained on HFD for another 10 weeks (n=9/group). Graded exercise test, glucose and insulin tolerance tests, mitochondrial respiration and regulatory protein markers of mitochondrial quality control processes were determined by immunoblots. Ten weeks of HIIT enhanced ADP-stimulated mitochondrial respiration in diet-induced obese mice (P < 0.05) but did not improve whole-body insulin sensitivity. Importantly, the ratio of Drp1(Ser ) over Drp1(Ser ) phosphorylation, an indicator of mitochondrial fission, was attenuated in HFD-HIIT compared to HFD (-35.7%, P < 0.05). Regarding autophagy, skeletal muscle p62 content was lower in HFD group than LFD group (-35.1%, P < 0.05), however, such reduction was disappeared in HFD+HIIT group. In addition, LC3B II/I ratio was higher in HFD than LFD group (15.5%, P < 0.05) but was ameliorated in HFD+HIIT group (-29.9%, P < 0.05). Overall, our study demonstrated that 10 weeks of HIIT was effective in improving skeletal muscle mitochondrial respiration and the regulatory protein machinery of mitochondrial quality control in diet-induced obese mice through the alterations of mitochondrial fission protein Drp1 activity and p62/LC3B-mediated regulatory machinery of autophagy.
线粒体质量控制过程对于维持线粒体的完整性和功能至关重要。本研究的目的是探讨10周高强度间歇训练（HIIT）对饮食诱导肥胖小鼠骨骼肌线粒体质量控制调节蛋白机制及全身葡萄糖稳态的影响。雄性C57BL/6小鼠被随机分为低脂饮食（LFD）组或高脂饮食（HFD）组。10周后，高脂饮食喂养的小鼠被分为久坐组和HIIT（HFD+HIIT）组，并继续高脂饮食10周（每组n=9）。通过免疫印迹法测定分级运动试验、葡萄糖和胰岛素耐量试验、线粒体呼吸以及线粒体质量控制过程的调节蛋白标志物。10周的HIIT增强了饮食诱导肥胖小鼠中ADP刺激的线粒体呼吸（P < 0.05），但未改善全身胰岛素敏感性。重要的是，与高脂饮食组相比，高脂饮食-HIIT组中线粒体分裂指标Drp1（Ser ）与Drp1（Ser ）磷酸化的比值降低（-35.7%，P < 0.05）。关于自噬，高脂饮食组骨骼肌p62含量低于低脂饮食组（-35.1%，P < 0.05），然而，这种降低在高脂饮食+HIIT组中消失。此外，高脂饮食组中LC3B II/I比值高于低脂饮食组（15.5%，P < 0.05），但在高脂饮食+HIIT组中得到改善（-29.9%，P < 0.05）。总体而言，我们的研究表明，10周的HIIT通过改变线粒体分裂蛋白Drp1活性以及p62/LC3B介导的自噬调节机制，有效改善了饮食诱导肥胖小鼠的骨骼肌线粒体呼吸和线粒体质量控制的调节蛋白机制。
