Abstract
The etiology, risk factors, and management of sarcopenia and metabolic dysfunction-associated steatotic liver disease (MASLD) are comparable, which prompted the investigators to search for a particular diagnostic or prognostic biomarker that was involved in both disorders. Peptides or proteins known as myokines, or exerkines, are produced and secreted by contracted muscles. Myokines work similarly to hormones in their actions. One common clinical hallmark of sarcopenia and MASLD is physical inactivity, which is associated with alterations in the levels of myokines. Irisin is a positive regulator of muscle size that is elevated in the biological fluids during exercise. Significantly low levels were observed in the pathological conditions associated with physical inactivity. The serum levels of irisin are significantly higher in MASLD patients, while their levels were lower in risk factors of MASLD, e.g., diabetes mellitus, obesity, and insulin resistance. In sarcopenia with obesity (sarcopenic obesity) or with a normal build, serum irisin levels are significantly lower than in healthy subjects. Therefore, serial determination of irisin levels that showed a transition from higher to lower levels in MASLD indicated the development of sarcopenia in those patients.