Sarcopenia in patients with non-alcoholic fatty liver disease: is it a clinically significant entity?

Sarcopenia, described as the loss of muscle mass and/or strength, is gaining importance as it can be increasingly related to many chronic diseases. It is also associated with chronic liver disease, and recently it has been more frequently linked to non-alcoholic fatty liver disease (NAFLD) in particular. Both sarcopenia and NAFLD are subject to complex and intermingled pathophysiological processes, of which some are in common. Furthermore, it is presently unclear if sarcopenia directly contributes to NAFLD or vice versa. The mechanisms that are involved may include obesity, insulin resistance, vitamin D deficiency, aging, physical inactivity and certain cytokines. Current clinical evidence is subject to an important heterogeneity in methods and definitions, with additionally also a relative overrepresentation of evidence in Asian ethnicities. Nonetheless, all studies so far point towards the same association between sarcopenia and NAFLD, including an association with NAFLD-severity and NAFLD-related fibrosis. Since the field is in its infancy, clear definitions and further research are needed to aid to improve understanding of the association between NAFLD and sarcopenia. This can eventually lead to additional potential therapeutic interventions. This review attempts to give an overview of the current published literature that links sarcopenia to NAFLD, followed by a discussion of the presumably involved pathophysiological factors, and ends by discussing current unmet needs.