Ceramide Mediated Oxidative Stress in Muscle Loss with Aging and Disuse

描述(申请人提供)：背景：骨质疏松症的特征是肌肉质量下降和虚弱，导致虚弱和行动不便。在住院和卧床休息期间，长时间的肌肉停用会加速骨质疏松症的进展。石棺减少症及其相关的并发症在美国是一个巨大的公共卫生问题。然而，石棺减少的机制尚未阐明。肌肉氧化应激升高抑制蛋白质合成并增加蛋白质分解，已被认为是废用时肌肉萎缩的媒介。虽然肌肉萎缩过程中氧化应激的来源尚未确定，但线粒体产生的活性氧物种(ROS)可能起到一定作用。在肌肉长时间不活动期间，ROS产生的调节机制在很大程度上仍不清楚。然而，有证据表明，肌肉脂神经酰胺可能起到一定作用。目的：本研究的目的是确定神经酰胺在衰老和废用情况下线粒体ROS的产生和肌肉萎缩中的作用。方法：采用小鼠后肢模型，建立幼龄和老年小鼠肌肉萎缩模型。通过使用不同的实验范式专门操作骨骼肌中神经酰胺的含量(myriocin治疗，DES-1KO)或过氧化氢(MCAT过度表达)，我们将能够更仔细地辨别它们在废用萎缩中的作用。肌肉性能，包括疲劳性和最大强度将被确定，因为神经酰胺也被证明可以调节疲劳和力量损失。我们将招募肌源性低体能和非肌源性高体能老年人，以确定肌肉质量、功能和肌肉活检衍生神经酰胺种类和线粒体生物能量学之间的关系。意义：拟议的研究将首次为动物和人类提供新的翻译证据，证明心肌细胞内神经酰胺有助于线粒体ROS的产生、骨骼肌减少和身体功能丧失。

DESCRIPTION (provided by applicant): Background: Sarcopenia is characterized by loss of muscle mass and weakness, leading to frailty, and impaired mobility. Prolonged muscle disuse, as occurs during hospitalization and bed rest, can accelerate the progression sarcopenia. Sarcopenia and its related co-morbidities are an enormous public health problem in the U.S. However, the mechanisms underlying sarcopenia have not been elucidated. Elevated muscle oxidative stress inhibits protein synthesis and increases protein breakdown, and has been identified as a mediator of muscle atrophy during disuse. While the source of oxidative stress during muscle atrophy has not been identified, reactive oxygen species (ROS) produced by mitochondria may play a role. The regulators of ROS production during prolonged muscle inactivity remains largely unknown. However, evidence suggests that the muscle lipid ceramide may play a role. Aim: The aim of this study is to determine the role of ceramide in mitochondrial ROS production and muscle atrophy in the context of aging and disuse. Methods: A hind limb model will be used to induce muscle atrophy in young and old mice. By specifically manipulating either ceramide content (myriocin treatment, DES-1 KO) or H2O2 (mCAT over-expression) within skeletal muscle using different experimental paradigms, we will be able to more carefully discern their roles in disuse atrophy. Muscle performance, including fatigability and maximal strength will be determined, as ceramide has also been shown to mediate fatigue and loss of strength. We will recruit sarcopenic low physically functioning and non-sarcopenic high physically functioning elderly individuals to define the relationships between muscle mass, function and muscle biopsy-derived ceramide species, and mitochondrial bioenergetics. Significance: The proposed studies will provide, for the first time, novel translational evidence i both animals and humans that intramyocellular ceramides contribute to mitochondrial ROS production, sarcopenia and loss of physical function.