Exercising is healthy, but not always appealing. Research led by Guadalupe Sabio from the National Cancer Research Center (CNIO) may have found a “switch” that activates the desire to get moving, as it shows that during exercise the muscle activates proteins which encourage further activity. The paper is published in Science Advances.
“We have discovered how muscle itself regulates interest in exercise through a signaling pathway between muscle and brain that we didn’t know about, and which is one of those responsible—as there must be several—for the fact that, when we exercise, we experience the impulse to train even more,” explains Sabio, head of CNIO’s Interaction between Organs in Metabolic Diseases Group.
The article also shows that the proteins produced by muscle through exercise regulate each other. Thus, they prevent the desire to exercise from eventually harming the body.
The results are based on data obtained in animal models and also in humans (volunteers who performed controlled exercise, and patients with obesity). This suggests the identified signaling pathway “plays a crucial role in regulating physical activity in both mice and humans,” and “highlights the potential therapeutic significance of this pathway in treating obesity and metabolic diseases,” write the authors.
First co-authors of the study are Leticia Herrera and Cintia Folgueira, researchers at the National Center for Cardiovascular Research (CNIC).
Three proteins that influence the desire for physical activity
The group observed that when muscles contract repeatedly and intensely, due to exercise, the pathways of two proteins of the same family are activated: p38α and p38γ. Interest in physical activity is greater or lower depending on how much each of these two proteins is activated, the study shows.
There is also a third protein involved: interleukin 15 (IL-15). The authors observed that activation of p38γ by exercise induces the production of IL-15, and that this protein has a direct effect on the part of the cerebral cortex that controls movement, the motor cortex.
The increase of IL-15 in blood functions as a signal to the brain to enhance motor activity, which makes the animals voluntarily become more active.
“In this study, we revealed that exercise-induced activation of muscle p38γ leads to the production of IL-15, which subsequently enhances spontaneous physical activity. Furthermore, we observed the presence of this p38γ/IL-15 axis in humans after exercise, underscoring the clinical relevance of this signaling pathway in promoting exercise behavior within the population,” say the authors.