We knew that the bacteria found in our intestine and that are part of our microbiota or intestinal flora together with other microorganisms –viruses, protozoa, fungi, archaea…– affect our physical and mental health. But science is discovering new connections between these microbes and how we feel. Now, new research has revealed that they also influence our motivation to exercise and our sports performance.
The study has been carried out in mice by scientists at the Perelman School of Medicine at the University of Pennsylvania (USA) and has found that certain species of intestinal bacteria activate nerves in the intestine to induce the desire to exercise. Their results, published in Nature, reveal the gut-to-brain pathway that explains why some bacteria increase the desire to go out and train.
The researchers, led by Dr. Christoph Thaiss, a professor of microbiology at the University of Pennsylvania, gathered around 200 mice and set them to run, on a treadmill or on a treadmill. The performance of the animals was very different, and when they were classified by their genetic inheritance, they found no relationship between their genes and their sports performance, so they investigated other potential causes, such as the metabolome (set of metabolites generated by the organism), your metabolism or your gut microbiome (set of gut microbes and their genetic interactions).
“Sensory neurons transmit a signal to the brain that raises dopamine levels, the main neurotransmitter involved in generating the motivation to exercise”
They observed that while the first two factors were not correlated with the level of physical activity and that the differences in the running performance of the mice were largely attributed to the presence of certain species of gut bacteria in the rodents that performed better . They found that genetics seemed to explain only a small part of the performance differences, with differences in gut bacteria populations appearing to be substantially more important.
The researchers administered a cocktail of broad-spectrum antibiotics to the animals to test their effects, since treatments with these drugs are known to deteriorate the intestinal flora as a side effect, and they observed that the performance of those that had been medicated was much better. low, up to 50% lower than before taking the drugs and compared to mice that had not taken the drugs. Many didn’t even go near the treadmill or get on the wheel.
A pathway that connects intestinal bacteria with the desire to train
Dr Thaiss explained: “What we discovered is a pathway that connects the gut microbiome to an area of the brain called the striatum, which is critical for generating motivation.” “The microbiome produces specific metabolites that are detected by the neurons that innervate the intestine. These neurons are activated during exercise and molecules derived from the microbiome enhance this activation. Sensory neurons then transmit a signal to the brain, which results in elevated dopamine levels in the striatum. Dopamine, in turn, is the main neurotransmitter involved in generating the motivation to exercise.
The striatum is a key node in the brain’s motivation and reward network, so the researchers concluded that additional dopamine in this brain area during exercise increases performance by enhancing the desire to exercise. This would be the circuit that connects intestinal bacteria with the desire to train, although for now it has only been studied in mice. “If we can confirm the presence of a similar pathway in humans, it could offer an effective way to increase people’s exercise levels to improve overall public health,” said Dr. Thaiss, lead author of the study.
“This gut-to-brain motivation pathway might have evolved to connect nutrient availability and gut bacteria population status with readiness to engage in prolonged physical activity,” says study co-author J. Nicholas Betley, Associate Professor of Biology in the School of Arts and Sciences at the University of Pennsylvania. “This line of research could become a whole new branch of exercise physiology.”
The findings of these scientists open new avenues of research on the subject. For example, the experiments showed evidence that the best-performing mice experienced a more intense ‘runner’s high’, which in this case was measured by a decrease in pain sensitivity, suggesting that this phenomenon would also be controlled, by least in part, by gut bacteria.
The team’s next goal is to carry out new studies to confirm the existence of this pathway from the intestine to the brain in people, since it could not only offer cheaper and safer diet-based alternatives to encourage people to run and to optimize the performance of elite athletes, but it could also contribute to the development of simpler methods to modify motivation and mood in people with addiction or depression problems.
.
