Lipid hydroperoxides in sarcopenia and muscle wasting: mechanisms and intervention

对退伍军人健康的意义：三分之二的退伍军人年龄在55岁或以上。石棺减少症 是一种影响大约25%70岁以上美国人口的综合症，其特征是 骨骼肌质量和力量的进行性丧失，不良后果的风险增加，如 身体残疾，生活质量差，甚至死亡。此外，骨质疏松症的发展可能导致 二次健康状况，如停用、营养不良、跌倒、骨折和糖尿病。除了身体上的 伴随着石棺减少的病人的疾病，石棺减少贡献了超过185亿美元 占医疗保健总支出的比例。在呈现另一种健康状况的受试者中，骨质疏松症的患病率更高。 健康受试者的健康状况，包括精神疾病，如抑郁症，在 退伍军人。目前还没有有效的治疗石棺减少症的方法，因为潜在的机制不是 完全阐明了。目的：本研究的目的是测试去神经是否会导致脂质的产生。 过氧化氢(LOOHs)，通过酶12/15-脂氧合酶(12/15-Lox)或通过直接氧化 脂质，导致神经肌肉连接(NMJ)中断和线粒体功能障碍，从而启动肌肉 萎缩，肌肉蛋白质分解，虚弱。研究计划：在具体目标1中，我将测试其效果 低氧清除剂Liproxstatin-1对线粒体功能的影响 衰老小鼠的结构和功能、蛋白质代谢以及肌肉质量和功能的维持。具体而言 目的2，我将测试肌肉特异性基因缺失的效果，12/15-Lox是一种产生二十烷类化合物的酶 和氧脂，对维持衰老小鼠的肌肉质量和功能。最后，在具体目标3中，我将 测试肌肉特异性过表达谷胱甘肽过氧化物酶4(Gpx4)的效果 膜内LOOHs对维持衰老小鼠肌肉质量和功能的作用。我们将使用 结合药理学方法、遗传小鼠模型和新的研究技术来测试 中心假说。预期结果：我所有的具体目标都集中在减少骨骼肌上 LOOHs(酶产生或直接氧化脂质)对年龄相关的去神经的反应。我 假设我的干预措施将改善骨骼肌萎缩和后肢肌肉功能障碍 降低衰老小鼠脂质过氧化，改善线粒体功能，降低蛋白质含量 降级，并保持NMJ的完整性。我的初步数据清楚地表明，LOOH的生成量增加了 在衰老肌肉中，LOOH的产生与失神经模型中的肌肉质量损失密切相关 萎缩。要发生骨骼肌质量下降，蛋白质降解率必须大于 蛋白质合成。因此，我的干预措施必须降低蛋白质降解率和/或提高降解率 失神经肌肉的蛋白质合成。有多条证据表明线粒体健康 对维持骨骼肌质量和功能很重要。我的初步数据显示 Gpx4在加速性骨质疏松症模型中的过表达改善了线粒体功能，这可能是 减少肌肉质量损失。因此，我们假设，减少肌肉中的LOOHs将改善线粒体 对衰老小鼠的作用。最后，失神经可以在周围传播氧化应激和NMJ破坏。 纤维。我们预测，减少肌肉中的LOOHs将减缓周围纤维的NMJ降解。 培训计划：我的短期目标是描述LOOH导致的石棺减少的机制和 在氧化应激、衰老、稳定同位素的使用、使用遗传动物模型和科学研究方面的培训 沟通。我将通过与我的指导团队的会议相结合的方式接受培训， 会议、演讲、正式课程和进行实验。我概述的培训计划将 请允许我实现成为一名独立的退伍军人管理局科学家的长期目标。

SIGNIFICANCE TO VETERANS HEALTH: Two-thirds of all veterans are 55 years of age or older. Sarcopenia is a syndrome that effects approximately 25% of the U.S. population over the age of 70 characterized by progressive loss of skeletal muscle mass and strength with an increased risk of adverse outcomes such as physical disability, poor quality of life and even death. Further, the development of sarcopenia may lead to secondary health conditions such as disuse, malnutrition, falls, fractures and diabetes. In addition to the physical ailments that accompany patients that suffer from sarcopenia, sarcopenia contributes to over $18.5 billion dollars of total health care expenditures. The prevalence of sarcopenia is higher in subjects presenting another health condition than in healthy subjects including mental conditions such as depression that are common among veterans. There are currently no effective treatments for sarcopenia because underlying mechanisms are not fully elucidated. OBJECTIVES: The objective of this study is to test if denervation induced generation of lipid hydroperoxides (LOOHs), through the enzyme 12/15-Lipoxygenase (12/15-Lox) or through direct oxidation of lipids, leads to neuromuscular junction (NMJ) disruption and mitochondrial dysfunction that initiates muscle atrophy, muscle protein breakdown, and weakness. RESEARCH PLAN: In Specific Aim 1, I will test the effect of reducing LOOHs via treatment with the LOOH scavenger liproxstatin-1 on mitochondrial function, NMJ structure and function, protein turnover, and maintenance of muscle mass and function in aged mice. In Specific Aim 2, I will test the effect of muscle specific genetic deletion of 12/15-Lox, an enzyme that generates eicosanoids and oxylipins, on the maintenance of muscle mass and function in aged mice. Finally, in Specific Aim 3, I will test the effect of muscle specific overexpression of glutathione peroxidase 4 (GPx4), an enzyme that reduces LOOHs within membranes, on the maintenance of muscle mass and function in aged mice. We will use a combination of pharmacological approaches, genetic mouse models, and novel research techniques to test the central hypothesis. ANTICIPATED OUTCOMES: All of my Specific Aims focus on reducing skeletal muscle LOOHs (either enzymatically generated or direct oxidation of lipids) in response to age-related denervation. I hypothesize that my interventions will ameliorate skeletal muscle atrophy and dysfunction in hindlimb muscle from aged mice by reducing lipid peroxidation, improving mitochondrial function, reducing rates of protein degradation, and maintaining NMJ integrity. My preliminary data clearly shows that LOOH generation is elevated in aged muscle, and that LOOH generation is strongly correlated to muscle mass loss in models of denervation atrophy. For skeletal muscle mass loss to occur, rates of protein degradation have to be greater than rates of protein synthesis. Therefore, my interventions have to reduce rates of protein degradation and/or increase rates of protein synthesis in denervated muscle. There are multiple lines of evidence that shows mitochondrial health is important for the maintenance of skeletal muscle mass and function. My preliminary data shows that overexpression of GPx4 in a model of accelerated sarcopenia improves mitochondrial function, which may reduce muscle mass loss. Therefore, we hypothesize that reducing LOOHs in muscle will improve mitochondrial function in aged mice. Finally, denervation can propagate oxidative stress and NMJ disruption in surrounding fibers. We predict that reducing LOOHs in muscle will slow NMJ degradation of the surrounding fibers. TRAINING PLAN: My short-term goals are to delineate the mechanisms of LOOH driven sarcopenia and receive training in oxidative stress, aging, the use of stable isotopes, using genetic animal models, and scientific communication. I will receive this training through a combination of meetings with my mentoring team, conferences, presentation, formal courses, and performing experiments. The training plan I have outlined will allow me to achieve my long-term goal of becoming an independent VA scientist.