LOS ANGELES — Loss of muscle mass is a fact of life starting in middle age — we lose about 1 percent a year in a phenomenon called sarcopenia.

Researchers say they’ve not only discovered the cause of that loss but may have found a drug that could help it as well.

The online study, released recently in the journal Cell Metabolism, maintains that sarcopenia happens because of calcium seepage from the ryanodine receptor channel complex, a group of proteins found in muscle cells. A domino effect follows: The leaks kick off a chain reaction resulting in muscle fibers not being able to fully contract.

Lead author Dr. Andrew Marks, director of the Wu Center for Molecular Cardiology at Columbia University Medical Center, said in a news release that sarcopenia and muscular dystrophy may have ryanodine receptor leakage in common.

“This is a completely new concept,” he said, “that the damage that occurs in aging is very similar to what happens in muscular dystrophy. Thus as we age we essentially develop an acquired form of muscular dystrophy.”

But an experimental drug called S107 might shore up those muscles.

Marks said, “Our results suggest that you can improve muscle function by fixing leaky calcium channels. And in fact, treating aged mice with S107 enhanced muscle strength without increasing muscle size, at least during the four-week treatment period.”

In the interest of full disclosure, Marks is a consultant for ARMGO Pharma Inc., which, according to the release, is looking at ryanodine receptors “to improve exercise capacity in muscle diseases.”