| [ Summary ] |
Sarcopenia is the degenerative loss of skeletal muscle mass, quality, and strength. Sarcopenia is common in patients with cirrhosis, with an estimated prevalence of 40‒70 %. Sarcopenia reduces survival, quality of life, and post‒liver transplant outcomes in patients with cirrhosis. Sarcopenia occurs due to a reduction in protein synthesis, an increase in proteolysis, or a combination of the two. Skeletal muscle hyperammonemia in cirrhosis induces transcriptional up‒regulation of myostatin and increases autophagy, both of which contribute to sarcopenia. Leucine, a potent direct activator of mammalian target of rapamycin (mTOR), increases muscle protein synthesis. However, plasma and skeletal muscle concentrations of leucine and other branched chain amino acids (BCAA) are decreased in patients with cirrhosis. In older individuals, reduced testosterone is thought to contribute to muscle loss. Serum testosterone is reduced in men with cirrhosis, and levels fall as liver disease advances. Proinflammatory cytokines such as interleukin‒6 (IL‒6) and tumor necrosis factor‒alpha (TNF‒α), increase in patients with chronic liver disease and play important roles in modulating signaling pathways during skeletal muscle loss. The causes of sarcopenia in patients with chronic liver disease are multi‒factorial. |