Richard Peet, J.D., Ph.D.

MOTIVATION TO EXERCISE

Can We Adjust Our Microbiome to Stay Fit?

If the results of recent research in mice are applicable to humans, it may well be possible to add certain types of bacteria to our gut microbiome to increase our motivation to exercise. Studies with mice revealed that certain bacteria in the gut microbiome contributed to increased physical activity. Since exercise is so important to physical and mental health in humans, motivating people to get off the couch and work up a sweat must be an important part of any health plan.

Why are some mice motivated to exercise? The researchers studied a population of mice in the lab https://doi.org/10.1038/s41586-022-05525-z. Some mice spend a lot of time on the treadmill in their cages. For the sake of simplicity, we’ll call these rodents the jocks. In contrast, other mice avoided the treadmill; we’ll call them the couch potatoes. The scientists asked, “why are some mice motivated to exercise a lot, while others are less active?” The researchers didn’t find differences in genetics, the DNA blueprint of the mice, between jocks and the couch potatoes. However, they did find differences in the gut microbiome; jocks had bacteria not present in the gut microbiome of the couch potatoes. The scientists identified the jock bacteria as members of the genera Eubacterium and Coprococcus. I know, the names of these bacteria are very disappointing, but they are capable of some very cool things. When the scientists introduced the right Eubacterium and Coprococcus bacteria into the gut of mice that lacked a gut microbiome, these bacteria enhanced exercise performance compared to germ free mice.

How do jock bacteria motivate mice to exercise? The researchers found that the jock gut bacteria produced molecules that sent signals to the mouse brain inhibiting the breakdown of dopamine. Normally dopamine levels in the brain are regulated by an enzyme that breaks it down, but the jock bacteria sent signals to the brain to stop production of this enzyme, thereby increasing dopamine levels. Dopamine is a neurotransmitter, found in mice and humans, well
known to motivate movement and exercise.

How do jock bacteria in the mouse gut send signals to the brain motivating exercise? This is where the story gets bizarre but very fascinating. The research scientists determined that the jock bacteria produce molecules with a chemical structure similar to “endocannabinoids” that interact with a receptor in the mouse endocannabinoid system (eCS) signaling the brain to stop reducing the quantity of dopamine. The endocannabinoid interacts with a receptor in the eCS,
and this receptor then sends a signal through the afferent nerve system that connects the gut, and other peripheral organs, to the brain through the spinal cord. Endocannabinoid? Wait a minute. Are you talking about Cannabis plant and cannabinoids?

What are endocannabinoids and the endocannabinoid system? The eCS is a well-kept secret. Every day your body produces molecules called endocannabinoids. These substances interact with some of the same receptor sites as the molecules produced by the Cannabis plant, the chemicals contained in marijuana. Cannabinoids are molecules called terpenes that have a very different chemical structure than the human-produced endocannabinoids. Endocannabinoids are lipid-based molecules. Yet, cannabinoids and endocannabinoids interact with many of the same receptors in the eCS. Human-produced endocannabinoids and the eCS play an important role in controlling homeostasis, a fancy word that means biological balance. The eCS plays an important role in everything from controlling appetite to inflammation. The scientists found that the endocannabinoid-like molecules produced by jock bacteria interact with the same endocannabinoid receptor, CB1, as the psychoactive THC molecules in the Cannabis plant. The jock-produced endocannabinoids do not make us high, but do increase dopamine levels in the brain thereby motivating us to exercise.

Can I motivate myself to exercise with jock bacteria? The scientific research, while done with mice, may be relevant to humans. In the future, it may be possible to take probiotics comprised of jock bacteria to produce molecules to motivate us to exercise. It may be possible to take postbiotics, comprised of bacteria-produced endocannabinoids, to motivate us to exercise. While most folk think it takes will power, discipline, and energy to exercise, in the future, we
may get help from probiotics and postbiotics.

I would like to thank my friend Michael B. Reiner, Ph,.D. for editing some of these blogs.  Any errors in the blogs are solely my responsibility.