French researchers taking the fight to sarcopenia.

Researchers in France have uncovered a molecular switch that may control and one day help reverse sarcopenia, the dramatic loss of muscle seen with ageing.

The condition increases the risk of falls, hospitalisation and death, and was classified as a disease by the World Health Organisation in 2016. Australia followed suit earlier this year.

“Sarcopenia is defined by a progressive and general loss of mass, strength and quality of the whole musculature from the age of 50,” says France Piétri-Rouxel, from the Centre de Recherche en Myologie at Sorbonne Université in Paris.

“It may lead to a decrease of more than 30% of initial muscle mass at the age of 80,” she says.

Piétri-Rouxel, a co-author of the new study published in the journal Science Translational Medicine, explains that muscles have to contract to stay strong, something triggered by the nerves that supply them. The process is called “excitation-contraction” coupling.

But it’s a classic case of use it or lose it – when muscles don’t contract, they simply waste away. That can happen through disuse, if the person is bedridden or has their limb in a cast for example, or if the nerve is damaged.

The muscles do fight back, however, when they are denied stimulation. The body makes more of something called growth differentiation factor 5 (GDF5), which tries to put a floor under the amount of muscle lost.

The team suspected that muscles could be downsizing with age because the GDF5 back up plan fails, so they set about testing the idea in a series of very clever experiments in mice.

Read the full story in Cosmos magazine here