We all know that exercise is good for health. However, some find it more difficult than others to motivate themselves to play sports and until now it was not well known why. A new study in mice confirms that the mechanism behind motivation to play sports may have to do with gut microbes.
As demonstrated by the results of the research led by scientists from the Perelman School of Medicine of the University of Pennsylvania published this Wednesday (12.14.2022) in the journal Nature, an important factor that stimulates the practice of exercise, both competitive and recreational, is the motivating pleasure derived from prolonged physical activity. This is triggered by exercise-induced neurochemical changes in the brain.
This article describes a gut-brain connection that improves athletic performance by increasing dopamine neurotransmitter signaling during physical activity. The scientists discovered that the differences in running performance within a large group of laboratory mice were largely due to the presence of certain species of gut bacteria in those animals with the highest performance.
“If we can confirm the presence of a similar pathway in humans, we could offer an effective way to increase people’s exercise levels to improve overall public health,” summarizes lead author Christoph Thaiss.
Genetics only plays a small role
To search for the factors that determine exercise performance, the team recorded genome sequences, gut bacterial species, bloodstream metabolites, and other data from genetically diverse mice. Next, they measured the amount of daily voluntary running on the wheel that the animals performed, as well as their endurance. They analyzed the data using machine learning, looking for the attributes of the mice that could best explain the considerable inter-individual differences in running performance.
The team was surprised to find that genetics seemed to explain only a small part of these performance differences, while inequalities in gut bacteria populations seemed to be substantially more important.
In fact, they found that giving mice broad-spectrum antibiotics to kill off their gut bacteria cut their running performance in half. The researchers discovered that two closely related bacterial species with better performance, “Eubacterium rectale” and “Coprococcus eutactus”, produce metabolites known as fatty acid amides.
The latter stimulate receptors called CB1 endocannabinoids on sensory neurons in the gut, which connect to the brain via the spinal cord. This stimulation causes levels of the neurotransmitter dopamine to rise during exercise, in a region of the brain called the striatum, a critical node in the brain’s reward and motivation network.
The findings open up new avenues of scientific inquiry, according to the authors.
For example, the experiments showed that the best-performing mice experienced a more intense “runner’s high”—measured in this case by a reduced sensitivity to pain—suggesting that this phenomenon is also controlled, at least in part. by intestinal bacteria.
In addition to offering potential cheap, safe, and diet-based ways to get ordinary people running and optimize performance for elite athletes, exploring this pathway could also provide easier methods for changing motivation and mood in contexts such as addiction and depression, details J. Nicholas Betley, another of the signatories.
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