Division of Geriatrics, Department of Medicine, Duke University Medical Center, Durham, NC 27709, USA.
Am J Clin Nutr. 2010 Apr;91(4):1123S-1127S. doi: 10.3945/ajcn.2010.28608A. Epub 2010 Feb 17.
Loss of skeletal muscle mass occurs during aging (sarcopenia), disease (cachexia), or inactivity (atrophy). This article contrasts and compares the metabolic causes of loss of muscle resulting from these conditions. An understanding of the underlying causes of muscle loss is critical for the development of strategies and therapies to preserve muscle mass and function. Loss of skeletal muscle protein results from an imbalance between the rate of muscle protein synthesis and degradation. Cachexia, sarcopenia, and atrophy due to inactivity are characterized by a loss of muscle mass. Each of these conditions results in a metabolic adaptation of increased protein degradation (cachexia), decreased rate of muscle protein synthesis (inactivity), or an alteration in both (sarcopenia). The clinical consequences of bedrest may mimic those of cachexia, including rapid loss of muscle, insulin resistance, and weakness. Prophylaxis against bedrest-induced atrophy includes nutrition support with an emphasis on high-quality protein. Nutritional supplementation alone may not prevent muscle loss secondary to cachexia, but, in combination with the use of an anabolic agent, it may slow or prevent muscle loss.
骨骼肌量在衰老（肌肉减少症）、疾病（恶病质）或不活动（萎缩）期间会发生丢失。本文对比并比较了这些情况下肌肉丢失的代谢原因。了解肌肉丢失的根本原因对于制定策略和治疗方法以维持肌肉量和功能至关重要。骨骼肌蛋白丢失是由于肌肉蛋白合成和降解率之间的不平衡造成的。恶病质、不活动引起的肌肉减少症和萎缩的特征是肌肉量的减少。这些情况中的每一种都会导致蛋白质降解增加（恶病质）、肌肉蛋白合成率降低（不活动）或两者都改变（肌肉减少症）的代谢适应。卧床休息的临床后果可能类似于恶病质，包括肌肉迅速减少、胰岛素抵抗和虚弱。预防卧床休息引起的萎缩包括营养支持，重点是高质量蛋白质。单独的营养补充可能无法预防恶病质引起的肌肉丢失，但与使用合成代谢剂结合使用，可能会减缓或预防肌肉丢失。
