Role of Skeletal Muscle Mitochondrial Supercomplexes in Exercise Intolerance

摘要 肺动脉高压与生活质量差、功能耐受性受损和肺动脉高压限制相关。 体力活动。尽管有最佳的PH治疗方法，但患者报告疲劳、功能下降 能力，生活质量下降。运动不耐受（即最大摄氧量降低）与 骨骼肌（SkM）线粒体功能和细胞呼吸。最近的研究表明， 电子传递链复合体结构的变化可显著改变线粒体呼吸 和能源生产。单个电子传递链复合物结合成大分子量 超复合物（SC）提高呼吸效率，减少破坏性活性氧，并提高ATP的产生。 SC可以由复合物I和复合物III和IV的多个单元直接缔合以允许直接电子传递到复合物I。 转移在初步研究中，我们发现SkM在PH大鼠中大大降低了I/III/IV 超复杂的组装，这与最大跑步机确定的最大摄氧量降低有关 运动能力我们的中心假设是，减少线粒体SC在SkM有助于运动 增加SC可减轻PH引起的SkM功能障碍。我们将测试这个 假设使用一个完善的大鼠肺动脉高压模型，概括了 病理生理方面以及运动不耐受观察PH患者。在目标1，我们将 评估PH诱导的SkM线粒体SC形成的变化和呼吸系统的相关变化 在临床前PH模型和PH患者中的功能、线粒体含量和嵴结构。此外 我们将证实这些变化确实存在于PH患者的人SkM样品中。在目标2中，我们 确定分离的SkM中线粒体功能和SC组装改变的分子机制 纤维和分化的初级SkM肌管从控制和PH动物最后在目标3中，我们将 确定通过运动或药物治疗增加SkM中线粒体超复合物的形成是否会导致 改善功能容量（即VO 2 max）。这将是第一个研究来评估线粒体的作用， SC在与慢性疾病（如PH）相关的运动不耐受中的作用，以及 直接靶向SC组装以减轻SkM功能障碍。

ABSTRACT Pulmonary hypertension is associated with poor quality of life, impaired functional tolerance and limitation of physical activity. Despite optimal available therapy for PH, patients report fatigue, decreased functional capacity, and worsening quality of life. Exercise intolerance (i.e. reduced VO2 max) is associated with reduced skeletal muscle (SkM) mitochondrial function and cellular respiration. Recent studies have demonstrated that changes in organization of electron transport chain complexes can significantly alter mitochondrial respiration and energy production. Binding of individual electron transport chain complexes into large molecular weight supercomplexes (SC) increases respiration efficiency, reduces damaging ROS, and improves ATP production. SC can consist of complex I and multiple units of complex III and IV in direct association to allow direct electron transfer. In preliminary studies, we have found that SkM in rats with PH have greatly reduced I/III/IV supercomplex assembly and this is associated with reduced VO2 max determined by maximal treadmill exercise capacity. Our central hypothesis is that reduction in mitochondrial SC in SkM contributes to exercise intolerance in PH, and that increasing SC can alleviate PH-induced SkM dysfunction. We will test this hypothesis using a well-established rat model of pulmonary hypertension that recapitulates the pathophysiological aspects as well as exercise intolerance observed in patients with PH. In Aim 1, we will evaluate PH-induced changes in SkM mitochondrial SC formation and associated changes in respiratory function, mitochondrial content, and cristae architecture in a preclinical PH model and PH patients. In addition we will verify these changes are indeed present in human SkM samples from PH patients. In Aim 2, we will determine molecular mechanisms underlying altered mitochondrial function and SC assembly in isolated SkM fibers and differentiated primary SkM myotubes from control and PH animals Finally in Aim 3, we will determine if increasing mitochondrial supercomplex formation in SkM by exercise or drug therapy results in improved functional capacity (i.e. VO2 max). These will be the first studies to evaluate the role of mitochondrial SC in exercise intolerance associated with chronic medical condition such as PH, and the first studies to directly target SC assembly to alleviate SkM dysfunction.