An April 2021 study by the University of Pittsburgh said, 

"Although there are no proven treatments for sarcopenia [age-related loss of skeletal muscle mass and function] yet, there are some pharmaceutical treatments entering clinical trials. Interestingly, many of these act on mechanisms that also involve a protein called Klotho," 

"Evidence suggests that Klotho levels gradually decline with age, and so we wanted to test whether supplementation with Klotho may attenuate the development of sarcopenia."

"Our data suggest that treatment with Klotho may be more effective in slowing the progression of sarcopenia at an earlier time point, rather than rescuing advanced age-related disease, by which time the gene responses seem to be more random," 

"It will be interesting in future studies to determine whether boosting Klotho levels at a younger age could prevent muscle declines into old, and even oldest-old, age.”