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Gut bacteria impact motivation to exercise in mice

Researchers have identified a gut-to-brain pathway in mice that may be the key to unlocking the motivation to exercise. The study, published in Nature, identified a microbiome dependent pathway that induced neurochemical changes in the brain. This may make it easier to harness the benefits of exercise.

A gut-to-brain motivation pathway

Exercise is undoubtedly beneficial to your health. But getting motivated to exercise is often the most difficult part.

Researchers at the Perelman School of Medicine at the University of Pennsylvania used mice studies to show that some gut bacteria affect the desire to exercise. The researchers discovered that the stimulation of nerves by specific bacterial metabolites in the gut led to an increased desire to exercise. The metabolites stimulated sensory nerves that connect the gut to the ventral striatum (the motivation-controlling region in the brain).

Nicholas Betley, co-author and Associate Professor of Biology at the University of Pennsylvania’s School of Arts and Sciences said, “This gut-to-brain motivation pathway might have evolved to connect nutrient availability and the state of the gut bacterial population to the readiness to engage in prolonged physical activity.”

Experimental approach

The researchers analysed genome sequences, gut microbiota, metabolites in the bloodstream, energy and metabolism in mice using machine learning approaches (figure 1). This allowed them to determine the factors that affected exercise performance in mice. The amount of voluntary wheel running and endurance performed by the mice were used to assess their exercise performance.

Figure 1. Experiment protocol. Genetically diverse mice were profiled across different factors and assessed for exercise performance. Source: Published in Nature.

The researchers discovered that the differences in exercise performance were largely explained by gut microbiota rather than genetic diversity. To confirm this, the researchers reassessed running performance after removing the gut bacteria using antibiotics. The running performance reduced by 50%.

Two bacterial species were identified as the performance-drivers: Eubacterium rectale and Coprococcus eutactus. The bacteria produced endocannabinoid metabolites. The metabolites stimulated receptors on sensory neurons that innervated the gut. These nerves connect the gut to the brain via the spine in mice. When the metabolites stimulated the nerves during exercise, dopamine was released in the ventral striatum. The researchers hypothesised that the increased dopamine in this region improved exercise performance by enhancing the underlying motivation to exercise.

The key to exercise is through your gut

The study has many applications in a potentially new branch of exercise physiology. If the same gut-to-brain pathway is identified in humans, public health initiatives might become geared to gut health.

Christoph Thaiss, senior author and Assistant Professor of Microbiology at Penn Medicine said, “If we can confirm the presence of a similar pathway in humans, it could offer an effective way to boost people’s levels of exercise to improve public health generally. Apart from possibly offering cheap, safe, diet-based ways of getting ordinary people running and optimizing elite athletes’ performance, the exploration of this pathway might also yield easier methods for modifying motivation and mood in settings such as addiction and depression.”

More on these topics

Bacteria / Brain / Gut / Machine Learning / Microbiome