NEW YORK, N.C., June 15 (UPI) -- A protein produced by the bones can rejuvenate the function of muscle, researchers found in experiments with mice, suggesting new ways to increase the amount of exercise people get as they age -- which may help keep them more healthy.
Researchers at Columbia University report old mice injected with the protein osteocalcin, which is produced by bones, could run as far as their younger counterparts in experiments, an effect that appears to be the same in humans.
Osteocalcin makes up 1 to 2 percent of the bone's mineralized matrix, though researchers at Columbia found in previous studies the protein appears in the bloodstream and acts like a hormone in organs. They also noticed the amount of osteocalcin in the bloodstream doubles during exercise -- suggesting a greater role than previously understood.
The researchers have also previously found osteocalcin helps regulate blood sugar and has positive effects on male fertility, mood and memory, all of which they say means osteocalcin has a significant role in the body and could help with physical activity as it relates to aging, especially osteoporosis.
More than half of all Americans over age 50 -- about 44 million people -- have osteoporosis, according to the International Osteoporosis Foundation.
"Bone is not just a victim of aging through osteoporosis, but it may be an active determinant in preventing many deleterious manifestations of aging as long as osteocalcin is being produced," Dr. Gerard Karsenty, a professor of medicine and genetics and development at Columbia University, said in a press release.
For the study, published in the journal Cell Metabolism, researchers compared the running skills of young and old mice, measuring the effects of injecting them with osteocalcin -- and finding it drastically increased the amount of running both groups of mice could do.
An average young mouse can run about three-quarters of a mile on an exercise wheel before getting tired, with older mice capable of roughly half that. When researchers gave normal young mice extra osteocalcin, however, they ran 20 percent farther, similar to young mice incapable of producing the protein running between 20 and 30 percent shorter a distance than their normal brethren.
With older mice, the effect was significantly stronger. Injecting osteocalcin into the muscles of old mice improved their running distance by 100 percent, helping 15-month-old mice exhibit the exercise capacity of 3-month-old mice.
While the researchers say there is no way to know if the same effect could be seen in humans, other studies suggest osteocalcin acts the same way in humans -- increasing the amount of glucose and fatty acid skeletal muscle can take in and consume during exercise -- suggesting some type of treatment could be derived from the knowledge.
The researchers add that, considering how important and beneficial exercise is to health, the potential to increase the ability of older people to be physically active may provide an opportunity to delay aging or at least soften its effects.
"Exercise is very beneficial to us, so it's important to try to find things to help older people get more of it," Karsenty said. "Increasing osteocalcin -- or mimicking its effects -- may be one way to do that."
