New research has identified a type of bacteria found in the microbiomes of elite athletes that contributes to improved capacity for exercise. These bacteria, members of the genus Veillonella, are not found in the guts of sedentary people who are less active.
By taking a closer look at the bacteria, the researchers from Joslin Diabetes Center in Boston, Massachusetts, determined that Veillonella metabolizes lactic acid produced by exercise and converts it into propionate, a short chain fatty acid. The human body then utilizes that propionate to improve exercise capacity. The results were reported in the international journal Nature Medicine on June 24, 2019.
“Having increased exercise capacity is a strong predictor of overall health and protection against cardiovascular disease, diabetes, and overall longevity,” said Dr. Aleksandar D. Kostic, a co-author of the paper.
“What we envision is a probiotic supplement that people can take that will increase their ability to do meaningful exercise and therefore protect them against chronic diseases including diabetes,” he added in a press release.
The work began in 2015 with fecal samples from Boston Marathon runners. Dr. Jonathan Scheiman, then a researcher in the lab of George Church at Harvard Medical School, collected samples during a time span of a week before the marathon to a week afterwards. He also collected samples from sedentary individuals. He then brought the samples to Kostic, who analyzed them to determine the species of bacteria in both cohorts.
“One of the things that immediately caught our attention was this single organism, Veillonella, that was clearly enriched in abundance immediately after the marathon in the runners. Veillonella is also at higher abundance in the marathon runners [in general] than it is in sedentary individuals,” noted Kostic.
They confirmed the link to improved exercise capacity in mouse models, where they saw a marked increase in running ability after supplementation with Veillonella.
Next, they wanted to figure out how it worked.
“As we dug into the details of Veillonella, what we found was that it is relatively unique in the human microbiome in that it uses lactate or lactic acid as its sole carbon source,” said Kostic. Lactic acid is produced by the muscles during strenuous exercise. The Veillonella bacteria are able to use this exercise by-product as their main food source.
“Our immediate hypothesis was that it worked as a metabolic sink to remove lactate from the system, the idea being that lactate build-up in the muscles creates fatigue,” he stated. However, after talking to Dr. Sarah Lessard, a clinical researcher at Joslin, and others in the exercise physiology field, the idea that lactate build-up causes fatigue was found to be incorrect. This caused them to rethink their hypothesis.
The researchers returned to the lab to figure out what could be causing the increase in exercise capacity. They ran a metagenomic analysis, meaning they tracked the genetics of all the organisms in the microbiome community, to determine what events were triggered by Veillonella’s metabolism of lactic acid. They noted that the enzymes associated with conversion of lactic acid into the short chain fatty acid propionate were at much higher abundance after exercise.
Then the question in the minds of the researchers was that maybe it’s not the removal of lactic acid, but the generation of propionate. They did some experiments to introduce propionate into mice [via enema] and test whether that was sufficient for this increased running ability phenotype. And it proved to be correct.
The team now plans to investigate the mechanisms of how propionate affects exercise capacity in collaboration with Lessard.
“The microbiome is such a powerful metabolic engine. This is one of the first studies to directly show a strong example of symbiosis between microbes and their human host,” said Kostic.
“It’s very clear. It creates this positive feedback loop. The host is producing something that this particular microbe favors. Then in return, the microbe is creating something that benefits the host. This is a really important example of how the microbiome has evolved ways to become this symbiotic presence in the human host,” he said.