The critical role of gut microbiota dysbiosis in skeletal muscle wasting: a systematic review

Aims Skeletal muscle wasting is affected by the gut microbiota dysbiosis through multiple pathways, including inflammatory process, defected immune system, and anabolic resistance. We aimed to systematically review the studies investigating the gut microbiota composition in sarcopenic and cachexic humans and animals. Methods We carried out a comprehensively systematic search using relevant keywords on PubMed, Web of Science, and Scopus databases until July 2021. Original human observational research and animal studies related to our research topics published in English were selected. Results Seven human studies and five animal studies were included. Three human studies were case-control, whereas the other four were cross-sectional studies that investigated three different conditions, including age-related sarcopenia, as well as liver cirrhosis and cancer cachexia. The principal alteration in age-related sarcopenia and liver cirrhosis-induced sarcopenia was a reduction in short-chain fatty acids (SCFAs) -producing bacteria. Lachnospiraceae family, consisting of Lachnospira, Fusicatenibacter,Roseburia, and Lachnoclostridium, significantly decreased in age-related sarcopenia, while in liver cirrhosis-induced sarcopenia, the alpha diversity of gut microbiota decreased compared with the control group. Moreover, Enterobacteriaceae, which has a pro-inflammatory effect increased in muscle-wasted animals. Conclusion This systematic review presents associations between the gut microbiota alterations and skeletal muscle wasting as a consequence of various pathologies, including aging sarcopenia, renal failure, and cancer cachexia in both human and animal studies.