Gut Microbes May Affect Motivation to Exercise

National Institutes of Health

Exercise provides many health benefits, including protection from many diseases. Some people seem to enjoy physical activity more than others. But the mechanisms affecting people’s motivation to exercise are not well understood.

An NIH-funded team of researchers, led by Dr. Christoph Thaiss at the University of Pennsylvania, set out to identify factors affecting exercise performance in mice. Their study appeared in Nature on December 14, 2022.

The researchers first measured how long mice running on a treadmill took to exhaust themselves and how much the mice voluntarily ran on a wheel. They found that the makeup of the gut microbiome—the trillions of microbes living in the gut—predicted these values better than genetic, metabolic, or behavioral traits. When the researchers used antibiotics to eliminate gut microbes, the mice got exhausted earlier and ran less on the wheel.

Motivation is controlled in part by a region of the brain known as the striatum. Neurons in the striatum are activated by the neurotransmitter dopamine. Dopamine activation provides a feeling of reward. The team found that dopamine levels in the striatum increased after exercise in normal mice, but not in microbiome-depleted mice. Treating mice with a drug that blocks dopamine signaling had the same effect on exercise as depleting the microbiome. Conversely, a drug that activates dopamine signaling restored exercise capacity in microbiome-depleted mice.

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