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Researchers led by Duke-NUS Medical School identified a pathway connecting the gene DEAF1, the FOXO protein family and mTORC1 activity in aging muscle. In fruit flies and mice, exercise helped lower DEAF1 and restore protein maintenance, but the findings have not established the same effects in humans.
Researchers led by Duke-NUS Medical School have identified a molecular pathway through which exercise helped aging muscles maintain and repair tissue in fruit flies and mice. The study links the gene DEAF1 and the growth-regulating pathway mTORC1 to the balance between making proteins and clearing damaged ones, but it does not establish that the mechanism works the same way in people.
The study, conducted with researchers from Singapore General Hospital and Cardiff University, found that DEAF1 levels can rise as muscles age. In the animals studied, this increase was associated with excessive activity in mTORC1, a pathway that helps regulate protein production and muscle maintenance. When the balance is disrupted, cells may make proteins while becoming less effective at removing damaged ones.
The researchers also examined the role of FOXO proteins, which help regulate gene activity and cellular maintenance. Their findings indicate that FOXO activity declines with age, weakening control over DEAF1. The resulting chain — reduced FOXO regulation, higher DEAF1 and excessive mTORC1 activity — may contribute to impaired muscle repair, according to the study.
Exercise activated regulatory proteins that lowered DEAF1 in the animal models, helping bring mTORC1 activity toward a healthier balance. The researchers said this supported the cells’ ability to clear damaged proteins while continuing to make new ones. The work was published in the Proceedings of the National Academy of Sciences; the supplied report does not specify the exercise protocol or how large the effects were.
A Cellular Link Between Exercise and Repair
The findings offer a possible explanation for why physical activity can support muscle health with age: it may influence not only muscle growth but also the internal processes that maintain muscle cells. That distinction matters because muscle weakness can affect mobility, independence and recovery, while muscle tissue also has a role in regulating blood sugar.
The study may also help explain why older people do not all respond to exercise in the same way. The researchers reported that exercise was less able to restore normal repair when DEAF1 was extremely elevated or FOXO activity was very low. This points to biological differences as one possible factor, not a proven explanation for variation in human outcomes. The results do not show that exercise reverses muscle aging in people or establish a new treatment.
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How the Muscle Pathway Works
Muscle cells need to produce proteins for growth and function while also removing proteins that are damaged or no longer useful. The study focuses on mTORC1, which helps direct protein production, and asks what causes this system to become imbalanced in aging muscle.
Researchers have associated excessive mTORC1 activity and the accumulation of damaged proteins with muscle deterioration, but the study says the mechanism driving that imbalance was not clear. Its proposed explanation centers on DEAF1 and FOXO regulation. The evidence described in the report comes from fruit flies and mice, so whether the same chain operates in human muscle, and how much it contributes to age-related weakness, remains to be tested.
“Exercise can reverse this process, correcting the imbalance. Physical activity activates certain proteins which lower DEAF1 levels, bringing the growth pathway back into balance.”
— Assistant Professor Tang Hong-Wen, the study’s lead author at Duke-NUS
Human Effects Still Need Testing
The report describes experiments in fruit flies and mice, not clinical evidence that exercise reverses muscle aging in humans. It does not provide enough detail to assess the exercise regimen, the magnitude or duration of the effects, or whether particular forms of activity produced different results.
It also remains unclear how often older adults have the levels of DEAF1 or FOXO activity that limited the response in the animal experiments. The proposed pathway may inform future research, but the findings do not show that targeting DEAF1 or mTORC1 would safely or effectively treat age-related muscle loss.
Testing the Pathway in People
The next step is to determine whether the same DEAF1–FOXO–mTORC1 pathway operates in human muscle and whether changes in it correspond to measurable differences in strength, repair or response to exercise. The report does not announce a human trial or give a timetable for one.
Further studies would also need to establish which exercise conditions affect the pathway and whether the apparent limits seen in the animal models apply to older people. Until then, the findings are a biological explanation to investigate, not a basis for promising that exercise can reverse muscle aging in every individual.
Key Questions
What did the researchers discover?
They identified a proposed pathway in which declining FOXO activity allows DEAF1 levels to rise, increasing mTORC1 activity and disrupting protein maintenance in aging muscle. Exercise helped counter this process in fruit flies and mice.
Does the study prove exercise reverses muscle aging in people?
No. The reported experiments were conducted in fruit flies and mice. Human effects have not been established by this study.
What does DEAF1 do in the study?
As muscle aged in the animal models, higher DEAF1 was linked to excessive mTORC1 activity and a less balanced cycle of protein production and removal. Exercise lowered DEAF1 in the experiments.
Why might some older people respond differently to exercise?
The researchers found that exercise was less able to restore normal repair when DEAF1 was extremely elevated or FOXO activity was very low. Whether this explains differences among older adults remains uncertain.
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