Fecal transplants from elite athletes improve metabolic health in mice

University of Rennes researchers have discovered that transplanting gut microbiota from elite athletes into mice improves mouse insulin sensitivity and increases their muscle glycogen stores.

Findings reveal that high aerobic exercise capacity corresponds with a distinct gut bacterial profile rich in short-chain fatty acid producing species like Prevotella copri and Phascolarctobacterium succinatutens. Rather than diversity, it was this specialized microbial composition that drove the metabolic benefits in the mice.

Aerobic exercise capacity, measured by metrics such as maximal oxygen consumption and fat oxidation, is a recognized indicator of metabolic health and mortality risk.

Previous studies in both humans and mice have suggested potential links between physical activity, gut microbiota composition, and short-chain fatty acid (SCFA) production. Yet, existing human studies have often failed to control for key confounding factors such as diet and body mass index, leaving the specific role of gut bacteria in aerobic performance unclear.

In the study, “Atypical gut microbial ecosystem from athletes with very high exercise capacity improves insulin sensitivity and muscle glycogen store in mice,” published in Cell Reports, researchers applied a combination of clinical phenotyping, metagenomic sequencing, and fecal microbiota transplantation (FMT) to investigate the relationship between gut microbiota and physical performance traits.

A total of 50 healthy, normal-weight male participants were enrolled, with a wide range of aerobic capacities, from inactive individuals to elite cyclists and soccer players. Food intake and body composition were carefully matched across groups to isolate the effects of exercise capacity on gut microbial communities.

Microbial DNA from fecal samples was extracted and sequenced to analyze bacterial composition, density, diversity, and metabolic function. Participants underwent both maximal and submaximal exercise testing. Fecal microbiota from selected human donors was then transplanted into antibiotic-pretreated mice to assess changes in insulin sensitivity and glycogen storage.

Gut bacterial diversity and density were reduced in athletes with the highest aerobic capacities, yet these same individuals exhibited significantly higher fecal SCFA concentrations, particularly propionate and valerate. Participants with high levels of Prevotella copri and Phascolarctobacterium succinatutens, two SCFA-associated bacterial species, showed a distinctive gut ecosystem correlated with better fat oxidation rates and higher energy expenditure during exercise.

Mice that received fecal microbiota from high-capacity human donors demonstrated improved insulin sensitivity and greater muscle glycogen content compared to controls. In contrast to previous assumptions, higher microbial diversity was not required for these metabolic benefits to occur.

While the mice receiving gut microbiota from these high‑capacity donors showed marked gains in insulin sensitivity and glycogen storage, their actual treadmill running endurance did not improve. This suggests that while some health benefits associated with elite athletes can be acquired by managing microbiota (fecal transplant), actual athleticism is not as easily transferable.

Improving insulin sensitivity and metabolic health with microbiota transplants could provide a positive therapeutic intervention. Future research including human-to-human transplants would better illustrate the effectiveness and longevity of such treatments.

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