By Lillian So Chan with Manny W Radomski, PhD
New research using both mice and human models provides the first evidence of the mechanism by which gut microbes may modulate high-intensity endurance athletic performance.
Lactate homeostasis is a critical determinant of athletic performance. It is an end product of energy use in the muscle cells. Accumulation increases muscle acidity and interferes with muscle function. But after returning to the liver, lactate can turn back into glycogen to support further muscle energy demand.
When a team of American and Canadian researchers set out to identify gut bacteria associated with athletic performance and recovery status, they found, in the gut microbiomes of Boston Marathon runners, variable but significant increases in a bacteria species (Veillonella) that specializes in breaking down lactate.
The researchers showed that these gut microbes are converting lactate into propionate, a short-chain fatty acid. The propionate is absorbed in the colon and contributes to the synthesis of glucose in the liver.
These increases were found both when surveying the same individual, pre- and post-races, and when comparing athletes to sedentary controls.
In another distinct set of gut microbiome samples from post-training elite runners and rowers, enriched genes that encode proteins involved in the pathway used by Veillonella to convert lactate to propionate were also found.
The researchers further demonstrated that even though circulating lactate in the blood can cross into the gut lumen (the passage space through the gut), its levels did not decrease with Veillonella colonization.
In contrast, mice colonized with Veillonella or administered propionate supplement increased their run-to-exhaustion treadmill time.
That means gut microbial production of propionate, rather than lactate clearance, underlies the effects of performance improvements in the study.
They suggest that gut microbes modulate athletic performance by turning the exercise by-product lactate into the performance-enhancing molecule propionate. Dietary fiber consumption is known to naturally generate most of the propionate found in our gut.
Exhausting the body’s glucose storage limits endurance exercise, compromising performance. Effective shift of energy supply in working muscles from glucose to fatty acid for endurance performance is a hallmark of the trained muscles of elite athletes.
A team of researchers from USA, Switzerland, and Australia show that this key metabolic adaptation in endurance sports is dependent on muscle peroxisome proliferator-activated receptors (PPARs), and stimulation of the PPARs is activated by gut microbes.
In humans, the family of cell nuclear receptors includes 48 transcriptional factors (proteins involved in converting DNA to RNA, which initiate and regulate the transcription of genes). They are activated by their specific ligands (binding molecules) to regulate diverse developmental, inflammatory, and metabolic processes.
A group among this family called peroxisome proliferator-activated receptors (PPARs), is expressed in the gut, muscle cells, and fat tissues, among others. They control lipid homeostasis and the transportation and deposit of lipids in the liver, muscle, and fat tissues. They also improve fatty acid metabolism, insulin resistance, and thermogenesis.
Metabolites produced by gut microbes are absorbed by the cells lining our gut wall and transported to the liver, fat tissues, heart, blood vessels, and other organs. In these organs, the metabolites act as ligands for the PPARs, activating them to regulate whole-body and gut immune response, including maintaining the integrity of the gut wall barrier, and carbohydrate and fat metabolism for energy.
In this new study, researchers show that activation of PPARs in muscle suppresses the breakdown of glucose and glucose consumption. Preserving glucose delayed the onset of glucose depletion and almost doubled the running duration of mice in the study from about 90 to 180 minutes.
Researchers suggest that the findings of this study have implications for future research in the therapeutic activation of PPARs, either genetically or pharmacologically.
Lillian So Chan is the founding editor of WellnessOptions, a print magazine and website, and author of the book WellnessOptions Guide to Health published by Penguin Books. With over thirty years of experience in journalism and editing, Lillian has established unique editorial directions for several award-winning publications. She has worked for Maclean’s, Canada's largest news magazine, and served as a Governor and Deputy Chairperson of the Board of Governors at the Simon Fraser University, British Columbia, Canada.
He served as Scientific Advisor to the Chief of Air Staff, Defence Canada; Board Director of the Canadian Defence Research and Development Executive Committee; member on the NATO Research and Technology Agency’s Human Factors and Medicine Panel.
He is the former Editor-in-Chief of the Undersea Biomedical Research Journal and serves as a referee for the Aviation, Space, and Environmental Medicine Journal.
He has published on diving and aerospace medicine, human performance and protection, stress endocrinology, sleep, tropical medicine, and circadian disorders. Manny is a co-editor of WellnessOptions magazine and journal.
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