Researchers say increasing levels of the peptide musclin could improve exercise endurance.
Investigators found that increasing blood circulation of a peptide called musclin improves exercise capacity by triggering production of mitochondria in muscle cells.
First author Ekaterina Subbotina, PhD, of the University of Iowa, and colleagues publish their findings in the Proceedings of the National Academy of Sciences.
To reach their findings, the team genetically engineered mice so they were deficient in musclin. The absence of musclin reduced the exercise capacity of the mice, meaning they were unable to exercise for as long or as hard as normal mice.
This indicates musclin works as an "exercise factor" - a hormone-like substance that is produced by skeletal muscle in response to exercise and released into the bloodstream.
Increasing musclin levels improved exercise performance in 1 week
Subbotina and colleagues then infused the genetically modified mice with musclin, comparing their exercise performance with that of musclin-deficient mice that received a placebo.
In just 1 week, the researchers found the exercise capacity of the musclin-infused mice returned to normal; the rodents were able to run for faster and longer on a treadmill than control mice.
On further investigation, the team discovered that musclin signaling stimulates the production of mitochondria within muscle cells; mitochondria are referred to as the cells' "powerhouses," providing them with the energy they need to function.
The researchers conclude that it is the increase in mitochondria production that enhanced the physical capacity of the genetically engineered mice.
They note that musclin may also play an important role in muscle health in very low-level exercise; they found that even when the genetically modified mice were sedentary, they still demonstrated lower exercise endurance than normal mice.
Overall, the researchers believe their findings could bring benefits for individuals who find it hard to engage in physical activity.
Senior author Dr. Leonid Zingman, of the Carver College of Medicine at Iowa, adds:
"Exercise is an extremely powerful way to improve people's health, but unfortunately, increasing physical activity can be really difficult in many circumstances.
We don't want to replace exercise by using this exercise factor, but if we can learn more about the mechanism it might help us to increase exercise tolerance and make it easier for people to actually exercise. And if it is easier, people may exercise more."
In October, a report published in the journal Trends in Pharmacological Sciences suggested it may one day be possible to replace physical activity with a simple pill that mimics the benefits of exercise.