A hormone released from bones enhances muscle function during exercise, giving old mice the capabilities of young ones.
Gerard Karsenty of Columbia University Medical Center in New York City and his colleagues found that blood concentrations of a hormone called osteocalcin increased during aerobic exercise in mice, monkeys and people. The hormone helped muscles to adapt to exercise by increasing their uptake and use of glucose and other nutrients. Mice that lacked the gene for osteocalcin had diminished exercise capacity.
Blood concentrations of osteocalcin declined as animals aged, and administering the hormone to 15-month-old mice gave them the exercise capacity of 3-month-old animals.