Ceramide Mediated Oxidative Stress in Muscle Loss with Aging and Disuse

描述（由申请人提供）：背景：肌肉减少症的特征是肌肉量减少和无力，导致虚弱和活动能力受损。在住院和卧床休息期间，肌肉长期不使用可加速肌肉减少症的进展。在美国，肌少症及其相关合并症是一个巨大的公共卫生问题。然而，肌少症的潜在机制尚未阐明。升高的肌肉氧化应激抑制蛋白质合成和增加蛋白质分解，并已确定为肌肉萎缩的中介在废用。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（ROS）可能起作用。在长时间肌肉不活动时ROS产生的调节因子在很大程度上仍然未知。然而，有证据表明，肌肉脂质神经酰胺可能起作用。目的：本研究的目的是确定神经酰胺在衰老和废弃的情况下线粒体ROS产生和肌肉萎缩中的作用。方法：采用后肢模型诱导小鼠后肢肌肉萎缩。通过使用不同的实验范式特异性地操纵骨骼肌内神经酰胺含量（肉豆蔻素处理，DES-1 KO）或H2O2 （mCAT过表达），我们将能够更仔细地识别它们在废用性萎缩中的作用。肌肉表现，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。我们将招募肌肉减少低身体功能和非肌肉减少高身体功能的老年人，以确定肌肉质量，功能和肌肉活检来源的神经酰胺种类以及线粒体生物能量学之间的关系。意义：这些研究将首次在动物和人类身上提供新的转化证据，证明细胞内神经酰胺有助于线粒体ROS的产生、肌肉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.