A recently identified molecule produced by skeletal muscle in response to exercise has been shown to increase bone mass, according to a study published online ahead of print September 29 in the Proceedings of the National Academy of Sciences. “This is a novel finding, and offers promise in the lab, and in the clinic,” said co-lead study author Mone Zaidi, MD, PhD, Professor of Medicine and of Structural and Chemical Biology at the Icahn School of Medicine at Mount Sinai, and Director of the Mount Sinai Bone Program in New York. “It establishes for the first time [that] 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.”
Mone Zaidi, MD, PhD
In this study, young male mice, chosen because researchers could best see bone accrual at this age, were injected with irisin. In the injected mice, researchers saw significant increases in bone mass and strength, specifically cortical bone. The action of the recently identified signaling molecule, irisin, was mediated primarily through bone growth.
The study suggests 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.
According to the study authors, identifying irisin as a molecule responsible for muscle-bone connectivity during exercise could lead to the development of future therapies for sarcopenia and osteoporosis.
“These diseases often occur together, and both muscle and bone loss are common medical problems in the elderly that cause significant disability. Understanding this molecular connection between muscle and bone gives us hope for treating age-related bone and muscle loss at the same time, with the same agent,” said Dr. Zaidi.