The Acute Effects of Exercise on Saliva-Derived Regional Mitochondrial DNA from Trained Runners

ABSTRACT Introduction/Purpose Research has identified two regions within mitochondrial deoxyribonucleic acid (mtDNA), which seem to be more (major arc; mtMAJ) and less (minor arc; mtMIN) prone to oxidation and mtDNA lesion formation. Oxidation of mtDNA base pairs can result in reduced copy number and has been linked to chronic diseases. Interestingly, exercise can also induce acute copy number reductions; however, in a healthy population, there seems to be a restorative effect (i.e., gaining mtDNA copy numbers) that occurs within a couple of hours to days after exercise. Few have investigated these regional mtDNA changes in trained runners (>90th fitness percentile). Typical mtDNA procedures are invasive and inconvenient, requiring muscle biopsies, and/or blood draws; therefore, a simpler, less invasive method of specimen collection is appealing. The purpose of this study was to examine how salivary-derived molecular (mtMAJ and mtMIN), hormonal (cortisol), and oxidative (8-hydroxy-2′-deoxyguanosine (8-OHdG)) markers change after acute exercise. Methods Trained runners ( n = 7; 52 ± 12 miles·wk −1 run in the past year; 28.8 ± 3.3 yr old; height, 1.76 ± 0.07 m; weight, 67.9 ± 11.3 kg; maximum oxygen consumption, 62.4 ± 5.7 mL·kg −1 ·min −1 ) completed a 60-min treadmill run at 70% peak oxygen consumption. Saliva samples were collected before exercise, 30 min after exercise (30Post), and 6 h after exercise (6hPost) and analyzed for changes in regional mtDNA via real-time quantitative polymerase chain reaction and stress (cortisol and 8-OHdG) markers using competitive enzyme-linked immunosorbent assays. Results mtMIN copy number decreased 30Post (−44.5%, P = 0.04) and 6hPost (−45.3% P = 0.03), but mtMAJ copy numbers were unchanged after exercise ( P = 0.44). Neither of the stress-related saliva biomarkers changed after exercise (cortisol, P = 0.13; 8-OHdG, P = 0.77). Conclusions Saliva-derived DNA findings point to mtMIN, supposedly the more stable of the two regions, as a greater contributor to copy number reductions within our cohort of trained runners. These results contribute to the understanding of aerobic exercise’s influence over saliva-derived, regional mtDNA dynamics.