Molecular mechanisms of oxidative stress in aging muscle

描述（由申请人提供）：随着年龄的增长，我们在50岁以后每年损失大约1-2%的肌肉质量。这种与年龄相关的肌肉萎缩，称为肌肉减少症，相对知之甚少，影响虚弱的严重程度，并对个人健康和生活质量有显着影响。虽然肌肉减少症的具体机制尚不清楚，但衰老肌肉中的能量不足已被强烈暗示为肌肉萎缩和凋亡性细胞死亡的前体，这表明线粒体功能障碍可能在肌肉减少症的进展中起重要作用。先前的研究表明，随着年龄的增长，线粒体氧化功能能力下降，这与线粒体复合物I和复合物III中氧化剂的产生增加有关。然而，骨骼肌线粒体的年龄相关变化的表征已经复杂的实现，存在两个不同的群体的线粒体：肌原纤维间线粒体（IFM），这是在肌原纤维之间的平行行，和肌膜下线粒体（SSM），这是位于质膜下。IFM可能是肌肉收缩期间ATP的主要来源，因此我们认为它们更有可能随着年龄的增长而积累氧化损伤。我们的中心假设是，IFM表现出更大的自由基泄漏在复杂的I和III和氧化损伤，这是负责增加线粒体功能障碍，骨骼肌萎缩和收缩功能下降，所有这些都可以放大II型肌肉相比，I型肌肉。在拟议的实验中，我们将获得年轻，中年和老年大鼠，确定骨骼肌收缩功能，细胞凋亡和I型和II型肌肉中肌减少症的程度，我们将从两种纤维类型中分离IFM和SSM，并测量生物能量学的关键参数。在第二系列实验中，我们将检查相同的因素和变量，但增加了两种已被证明可以延长寿命的良好特征的干预措施：卡路里限制和终身车轮运行，以确定这些干预措施显着改善与年龄相关的氧化损伤，线粒体功能障碍和肌肉损失的机制。这可能为肌少症的潜在机制提供证据，也可能提供线粒体功能障碍对肌细胞功能和收缩性产生负面影响的第一个直接证据。

DESCRIPTION (provided by applicant): With age we lose muscle mass at approximately 1-2% per year past the age of 50. This age-related muscle atrophy, termed sarcopenia, is relatively poorly understood, impacts the severity of frailty, and has significant effects on individual health and quality of life. While the specific mechanisms underlying sarcopenia are unknown, energy deficits in aging muscle have been strongly implicated as precursors to muscle atrophy and apoptotic cell death, suggesting that mitochondrial dysfunction may play a significant role in the progression of sarcopenia. Previous studies have shown decreased mitochondrial oxidative functional capacity with age, which was associated with increased oxidant production in mitochondrial complex I and complex III. However, characterization of age-related changes to skeletal muscle mitochondria has been complicated by the realization that two distinct populations of mitochondria exist: interfibrillar mitochondria (IFM), which are found in parallel rows between the myofibrils, and subsarcolemmal mitochondria (SSM), which are located beneath the plasma membrane. IFM are likely the primary source of ATP during muscle contraction, and we believe they are therefore more likely to accumulate oxidative damage with age. Our central hypothesis is that IFM exhibits a greater free radical leak in complex I and III and oxidative damage, and that this is responsible for increased mitochondrial dysfunction, skeletal muscle atrophy and decreased contractile function, all of which could be amplified in type II muscle compared with type I muscle. In the proposed experiments, we will obtain young, mid-aged and old rats, determine skeletal muscle contractile function, apoptosis and the extent of sarcopenia in type I and type II muscle, and we will isolate IFM and SSM from both fiber types and measure key parameters of bioenergetics. In a second series of experiments, we will examine the same factors and variables, but with addition of two well-characterized interventions that have been shown to extend life span: calorie restriction and life-long wheel running, to determine the mechanisms by which these interventions significantly ameliorate age-related oxidative damage, mitochondrial dysfunction and muscle loss. This could provide evidence for the mechanisms underlying sarcopenia, and may also provide the first direct evidence that mitochondrial dysfunction has a negative impact on muscle cell function and contractility.