Monday, January 14, 2008

New celular insights into how muscles grow when doing exercise

Researchers at CRG have showed in an article published in January in Cell Metabolism that satellite cells (stem cells present in muscles) and the inflammatory molecule interleukin 6 (IL-6) are essential for the growth of the adult muscle fibers in response to a physical effort.

Skeletal muscles are formed by individual fibers, each containing several nuclei with genetic material. As muscles work more and more intensely, their mass increases and they incorporate new nuclei. However, the mechanisms responsible for this process have been difficult to determine for a long time.

The group directed by Pura Muñoz-Cánoves, with the collaboration of Luis Serrano, both of them at CRG, have now discovered that the muscles of mice who work intensely show an increase in IL-6 after one day. Furthermore, this increase in the cytokine, which is maintained for two weeks before decreasing again, induces the proliferation of satellite cells. Curiously high levels of IL-6 had previously been implied in the process of muscle wear out, says Muñoz-Cánoves. “An excess of IL-6 is not good, but its local and transient expression is needed for the muscle growth”.

According to Muñoz-Cánoves “these data will facilitate the discovery of new methods to restore the loss of muscle mass in old people or in those affected with diseases such as cancer or AIDS, as well as people with certain immobility”.

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