miR-26b-5p responds to aerobic exercise intervention for concussion recovery in adolescent athletes: a pilot trial

Background: Guidelines for sport-related concussion (SRC) management recommend aerobic exercise treatment. Salivary microRNAs (miRNAs) associate with exercise and concussion; therefore, we investigated their expression in adolescents with SRC during prescribed exercise. Methods: Before and after intervention, athletes with SRC (n = 32, 15.78 ± 1.5 y/o, 66% male, 5.26 ± 3.56 days from injury) and controls (n = 28, 15.96 ± 1.7 y/o, 68% male) provided saliva samples and completed clinical exams. High (5 days/week, 30 min) or low (3 days/week, 20 min) volumes of aerobic exercise were assigned. RT-qPCRs were performed to assess 13 pre-selected miRNAs. Results: miRNAs 1246, 944, 151a-3p, and 26b-5p were reduced (p = 0.0002, 0.0024, 0.0015, 0.0002, CI mean difference: [−4.55, −1.54] [−4.58, −1.08] [−4.77, −1.24] [−5.64, −1.92], respectively) compared to controls. The expression of 182-5p, 532-3p, and 26b-5p increased with exercise volume in concussed participants (p = 0.0035, 0.0035, 0.0020, CI for exercise coefficient: [0.000100, 0.000396] [0.000060, 0.000237] [0.000107, 0.000373], respectively), but not in controls. Conclusion: miRNAs 1246, 944, and 151a-3p may be concussion biomarkers unaffected by aerobic exercise. miR-26b-5p, associated with concussion and exercise volume, may be a useful biomarker to monitor adherence to exercise prescriptions for SRC recovery.