Sarcopenia, a condition of low muscle mass, quality and strength, is commonly found in cirrhotic patients and is associated with adverse clinical outcomes including: reduction in quality of life, increased mortality and post-transplant complications. In chronic liver disease (CLD) it is most commonly defined through the measurement of the skeletal muscle index of the third lumbar spine. A major contributor to sarcopenia in CLD is the imbalance in muscle protein turnover, which likely occurs due to a decrease in muscle protein synthesis and an elevation in muscle protein breakdown. This imbalance is assumed to arise due to a number of factors including: accelerated starvation, hyperammonemia, amino acid deprivation, chronic inflammation, excessive alcohol intake and physical inactivity. In particular, hyperammonemia is a key mediator of the liver-gut axis and is known to contribute to mitochondrial dysfunction and an increase in myostatin expression. Currently, the use of late-evening snacks, branched-chain amino acid supplementation and physical activity have been proposed to help the management and treatment of sarcopenia. However, little evidence exists to comprehensively support their use in clinical settings. A number of new, pharmacological strategies, including myostatin inhibition and the nutraceutical Urolithin A have recently been proposed to treat age-related sarcopenia, and may also be of use in CLD. This review highlights the potential molecular mechanisms contributing to sarcopenia in CLD alongside a discussion of existing and potential new treatment strategies.

中文翻译：

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慢性肝病中的肌肉减少症：机制和对策

肌肉减少症是一种肌肉质量、质量和力量低下的疾病，常见于肝硬化患者，并与不良临床结果相关，包括：生活质量下降、死亡率增加和移植后并发症。在慢性肝病 (CLD) 中，它最常通过测量第三腰椎的骨骼肌指数来定义。CLD 中肌肉减少症的一个主要因素是肌肉蛋白质周转不平衡，这可能是由于肌肉蛋白质合成减少和肌肉蛋白质分解增加所致。这种不平衡被认为是由多种因素引起的，包括：加速饥饿、高氨血症、氨基酸剥夺、慢性炎症、过量饮酒和缺乏运动。特别是，高氨血症是肝肠轴的关键介质，已知会导致线粒体功能障碍和肌肉生长抑制素表达增加。目前，已提出使用宵夜、补充支链氨基酸和体育锻炼来帮助管理和治疗肌肉减少症。然而，几乎没有证据可以全面支持它们在临床环境中的使用。最近提出了许多新的药理学策略，包括肌肉抑制素抑制和营养药物 Urolithin A 来治疗与年龄相关的肌肉减少症，并且也可能用于 CLD。本综述强调了导致 CLD 肌肉减少症的潜在分子机制，同时讨论了现有和潜在的新治疗策略。