A protein that is produced in human muscle cells during exercise may be the key to preventing age-related physical decline, after tests revealed that elderly mice were able to sprint like young pups after being injected with the compound. Physical performance was seen to increase drastically in mice of all ages following treatment, indicating that the protein may be an important ally in the quest to increase health during all stages of life and into old age.

Publishing their findings in the journal Nature Communications, the study authors explain how they set out to examine the role of mitochondrial DNA in physical performance and aging. Mitochondria are organelles that regulate metabolism and provide cells with energy, and are thought to be derived from ancient bacteria that became assimilated into our cells at some point in our evolutionary history.

Because of this, mitochondria have their own genome that is distinct from that of the cell itself. It was recently discovered that the mitochondrial genome codes for a protein called MOTS-c, which enters the cell nucleus during times of stress in order to regulate the cell’s genome and help it resolve the situation.

To conduct their study, the researchers first collected samples of muscle tissue and blood plasma from human volunteers before, during and after working out on an exercise bike. Analysis showed that MOTS-c increased 12-fold in muscle cells, and by 50 percent in blood plasma, as a result of this physical exertion. In their write-up, the authors suggest that the protein promotes “adaptive responses to exercise-related stress conditions,” such as metabolic imbalance and heat shock.

They then then sought to determine how MOTS-c impacts the physical capacity of performance of young, middle-aged and elderly mice. To achieve this, they injected three groups of mice – aged two, 12 and 22 months – with the protein, and observed how this affected their ability to run on a treadmill and balance on a rotating rod.

Mice of all ages performed significantly better after receiving MOTS-c, and were able to run faster and for longer than untreated mice, while also displaying superior grip and balance. Even mice that had been fed on a high-fat diet displayed major improvements while also gaining less weight than those that didn’t receive MOTS-c injections, backing up a previous study which suggested that the protein may protect against obesity and diabetes.

“The older mice were the human equivalent of 65 and above and once treated, they doubled their running capacity on the treadmill,” explained study author Changhan Lee in a statement. “They were even able to outrun their middle-aged, untreated cohorts.”

Amazingly, 17 percent of the aged mice were able to increase their running speed to a sprint after being injected with 15 milligrams of MOTS-c per kilogram of body weight each day for two weeks, while none of their untreated counterparts managed to go faster than walking pace. Strength also increased in elderly mice that received the protein, as did stride length, signifying a more robust and powerful gait.

Of the young mice who received this dose, 100 percent were able to achieve a running speed of 23 meters per minute, compared to just 16.6 percent of those who received one-third of this dose or no MOTS-c at all.

The results of this study increase our understanding of the importance of the mitochondrial genome in supporting healthy aging, and suggest that MOTS-c could one day be used to increase health span – or the number of years spent in good health – in humans.