Exercise-induced muscle molecule shown to build bone: study

A recently identified molecule produced by skeletal muscle in response to exercise has been shown to increase bone mass for the first time, a study said Monday.

Exercise is a well-known stimulus for new bone formation, but it has remained unclear how muscle "talks" to bone, despite their close proximity, according to the study published in the U.S. journal Proceedings of the National Academy of Sciences.

"This is a novel finding, and offers promise in the lab, and in the clinic," co-lead study author Mone Zaidi, professor of the Icahn School of Medicine, said in a statement.

"It establishes for the first time a molecule released from muscle during exercise can act directly on long bones to increase their strength. These are the bones utilized during exercise, and also the ones most likely to break."

In the experiment, young male mice, chosen because researchers could best see bone accrual at this age, were injected with the recently identified signaling molecule known as irisin.

The researchers found saw significant increases in the injected mice's bone mass and strength, specifically cortical bone, which is a dense and compact type of bone tissue that constitutes about 80 percent of skeletal weight.

Trabecular, or spongy bone, the body's reservoir for calcium, was largely not affected.

The results showed that "irisin is fundamental to muscle-bone communication, and likely translates the well-known skeletal anabolic action of exercise by directly stimulating new bone synthesis by osteoblasts," said the collaborative study between researchers at the Icahn School of Medicine and Italy's universities of Ancona and Bari.

The findings, according to the study, could lead to the development of future therapies for sarcopenia, the gradual loss of muscle mass seen as one gets older, and osteoporosis, a disease in which bones become weak and brittle and more likely to break. Enditem