Muscles produce a protein that helps them recover after an effort and that increases the ability to exercise, according to research from the University of Hong Kong that has analyzed how muscle fibers are restored after physical activity.
A drug or nutritional supplement that acts like this protein, called BDNF, could help frail people gain muscle strength, people who tire quickly to do more physical activity, and people who play sports to recover faster from exertion, the researchers say. authors of the research. There are already analogs of the BDNF protein in development, although none have been approved so far.
Physical activity "causes metabolic stress" in the muscles, the researchers write in the journal Science Signaling, in which they present the results this week. This stress leads to the accumulation of reactive oxygen species (such as free radicals) and the depletion of energy reserves, made up of lipids and glycogen.
Research has shown that physical activity also causes the production of BDNF in the muscles and that this protein is key in recovery after exertion. Specifically, high levels of BDNF promote rapid recovery and make muscles more resistant to exertion.
Although the research was carried out in mice, "we believe that BDNF has the same important function in the muscles of mice and humans", biochemist Chi Bun Chan, director of the research, told La Vanguardia. "The structure of BDNF and its intracellular action is very similar between mice and humans," says Chan. In addition, "BDNF also increases after exercise in humans, the same as we have seen in mice."
The researchers found that, in mice in which the muscle cells cannot produce BDNF, the muscles have a reduced ability to recover after an effort. These animals do not increase their endurance even if they exercise. But if the mice are given a BDNF analogue as a nutritional supplement, there are "increases in the time spent running, in the maximum speed at which they run and in the ability to hang," they report in Science Signaling. This increase in physical activity takes place without increasing the muscle mass or strength of the mice, which indicates that BDNF increases the muscles' resistance to exercise.
BDNF triggers a cascade of biochemical reactions in muscles. Researchers have shown that BDNF activates another protein called PPAR-delta, and that the latter, in turn, activates multiple genes that modify muscle and increase exercise capacity.
Until now, the BDNF protein had been studied mainly for its action in the brain, where it is essential for the growth and functioning of neurons, and for cognitive functions, such as memory. BDNF deficiency has been associated with Alzheimer's, depression and schizophrenia, which has fueled interest in developing therapies that boost this protein.
The BDNF analog used in the University of Hong Kong experiments is a flavonoid called 7,8-dihydroxyflavone (or 7,8-DHF) found in some plants. According to Chi Bun Chan, "it could be used to improve the exercise capacity of people for whom physical activity is recommended, such as obese people". The director of the research warns that "it is not a substitute for exercise, but an aid to have a healthy life".
On the other hand, "elderly people have less BDNF, and low levels of BDNF have been associated with more frailty," adds Chan. "The results could explain, in part, why the muscles of the elderly atrophy. Using BDNF or a similar substance as medicine could help improve muscle strength in the elderly."
In people who practice sports, concludes the research director, "taking a BDNF analogue could reduce the time needed to recover after each activity". In the study "we did not observe any side effects on the health of mice that took 7,8-DHF continuously for more than six months".
