Probiotic Bacteria Slowed Muscle Loss in Mice

Muscles shrink with age, and there are no effective drugs to stop it. In mice, certain probiotic bacteria now slowed this kind of muscle loss. The treated animals had more muscle mass, thicker muscle fibers and performed better.

The researchers first looked for bacterial strains that make a lot of one particular enzyme. In the gut, it breaks down bile acids, the digestive juices made by the liver. Two strains of Bifidobacterium animalis worked best. They were tested in mice whose muscle loss was triggered by dexamethasone, a cortisone-like drug. The bacteria changed the gut flora and the mix of bile acids. This points to a signal running from gut to muscle: a messenger from the small intestine activates docking sites on muscle, and less muscle protein gets broken down.

The team also made a fermented milk with the two strains. It met quality standards and scored better in taste and sensory testing. The mice lost muscle because of a drug, though, not because of aging. Whether the bacteria or the fermented milk help people keep their muscles was not tested.