Scientists reveal on October 10 in an article published at bioRxiv.org that marathon runners appear to rely on myelin, the fatty tissue coiled around nerve fibers, for energy during a race. Brain scans of runners show that this tissue appears to substantially shrink in the day or two after a marathon. The brain fat returns to almost prerace levels two weeks following the race. According to the research, the athletes’ high energy expenditure during running may require them to replenish their energy reserves in order to maintain proper brain function.
Mustapha Bouhrara, a neuroimaging scientist at the National Institute on Aging in Baltimore, adds, “This is definitely an intriguing observation.” “The idea that myelin lipids are used as fuel during prolonged exercise is quite plausible.”
He adds the work may have therapeutic ramifications if the study authors’ observations turn out to be accurate. Comprehending the quick recovery of runners’ myelin may provide insights into the development of possible treatments, such as those for those who have lost myelin due to ageing or neurodegenerative diseases.
Myelin, a tissue that coats nerve fibers and functions as an insulator similar to rubber covering an electrical wire, is found throughout a large portion of the human brain. Because of this insulation, electrical signals can travel quickly between nerve cells, which is essential for brain function.
Although fatty tissue appears to be a simple substance with a simple function, neurobiologist Klaus-Armin Nave of the Max Planck Institute for Multidisciplinary Sciences in Göttingen, Germany, believes there is probably more to it than that. “Myelin sheathes were long believed to be assembled, inert structures of insulation that don’t change much after they’re made,” he explains.
Evidence now exists that myelin is a dynamic structure that changes in size and abundance in response to cellular circumstances. We refer to this concept as myelin plasticity. It’s well researched, according to Nave.
He claims that on a regular basis, fatty molecules and other myelin sheath constituents flip, dissolving and reassembling the insulating substance. According to studies by Nave’s group, when sugar, the brain’s usual energy source, is in short supply, brain cells in mice may be able to access these in-flux fats.
Carlos Matute, a neurobiologist at the University of the Basque Country in Leioa, Spain, and the Achucarro Basque Center for Neuroscience, questioned whether these fats could help support the brains of endurance athletes. As a marathon runner, he had always been interested in how people’s minds functioned when intense exercise depleted their bodies’ energy stores.
Four marathon runners had their brains scanned using an MRI machine in the days leading up to the race, and two more runners had their brains scanned two weeks later. The crew saw a decrease in the brain’s myelin content a day or two following the race. According to Matute, this indicated a thinning of the myelin sheathed around nerve fibers. Two weeks later, the myelin had thickened around the nerve fibers and was mostly back.
According to Bouhrara, that’s a sharp drop followed by a quick recovery—a dramatic outcome that makes him stop. Water trapped between myelin layers was utilized by Matute and associates as a stand-in for myelin content. More myelin is indicated by more of this water. But dehydration’s consequences cannot be completely ruled out, according to Bouhrara. After a race, runners who are dehydrated may simply have dried out brain tissue.
Matute has heard this before when he has presented his statistics to peers. “We don’t think this is the case.” Days after the event, his staff checked the racers, giving them time to rehydrate, he said. Furthermore, the brain volumes of the runners did not significantly change before or after the marathon. According to Matute, dehydrated brains would likely be smaller. “We observed that there is absolutely no brain shrinkage.”
His team is currently tracking the trajectory of their discoveries to determine whether the myelin dip causes any changes in brain function and how long it takes for full recovery.