Abstract
White matter tracts are known to be susceptible to injury following concussion. The objective of this study was to determine whether contact play in sport could alter white matter metabolite levels in female varsity athletes independent of changes induced by long-term exercise. Metabolite levels were measured by single voxel proton magnetic resonance spectroscopy (MRS) in the prefrontal white matter at the beginning (In-Season) and end (Off-Season) of season in contact (N = 54, rugby players) and non-contact (N = 23, swimmers and rowers) varsity athletes. Sedentary women (N = 23) were scanned once, at a time equivalent to the Off-Season time point. Metabolite levels in non-contact athletes did not change over a season of play, or differ from age matched sedentary women except that non-contact athletes had a slightly lower myo-inositol level. The contact athletes had lower levels of myo-inositol and glutamate, and higher levels of glutamine compared to both sedentary women and non-contact athletes. Lower levels of myo-inositol in non-contact athletes compared to sedentary women indicates long-term exercise may alter glial cell profiles in these athletes. The metabolite differences observed between contact and non-contact athletes suggest that non-contact athletes should not be used as controls in studies of concussion in high-impact sports because repetitive impacts from physical contact can alter white matter metabolite level profiles. It is imperative to use athletes engaged in the same contact sport as controls to ensure a matched metabolite profile at baseline.
Highlights
There is growing concern that repetitive mild traumatic brain injuries from concussion put athletes at an increased risk of cognitive dysfunction (Montenigro et al, 2017; Gangolli et al, 2019) and long-term neurodegeneration (McCrory et al, 2013)
When comparing changes during and after the sports season, myo-inositol and glutamate were found to be lower and glutamine was found to be higher in contact (Rugby) athletes compared to non-contact (Rowers and Swimmers) athletes
Metabolite levels in female varsity non-contact swimmers and rowers did not differ from age matched sedentary women except for a slightly lower myo-inositol level in the non-contact athletes
Summary
There is growing concern that repetitive mild traumatic brain injuries from concussion put athletes at an increased risk of cognitive dysfunction (Montenigro et al, 2017; Gangolli et al, 2019) and long-term neurodegeneration (McCrory et al, 2013). Metabolite Levels Differ in Contact-Athletes (McGroarty et al, 2020) Such impacts are generally thought to be inconsequential, but may lead to subtle changes in brain metabolism and function (Manning et al, 2020). Elevated Glx/Cr (Bari et al, 2018) in the GM of females (Age 14–18) and reduced N-acetyl aspartate (Mayer et al, 2015; Panchal et al, 2018) in white matter (WM) and GM in both sexes (Age 15–33) have been observed after a season of play Taken together, these studies demonstrate alterations in the metabolite profile of contact athletes in the absence of concussion. This study did not include a group to control for an exercise effect across seasons of play
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