The Effects Of Blackcurrant Supplementation On Oxidative Stress And Antioxidant Activity Surrounding Repeated Exercise-Heat Exposures

PURPOSE: Evaluate the influence of blackcurrant (BC) supplementation on biomarkers reflective of oxidative stress and antioxidant responses surrounding exercise in the heat pre-heat acclimation (HA) and post-HA. METHODS: In a multi-year crossover study, 9 participants (2 M,7F; mean ± standard deviation [SD]: 24 ± 3 years, 48.8 ± 7.7 ml·kg-1·min-1)completed 5 days of HA with no BC (CON) and again with 784 mg of BC·day-1 (BC). Two tests of heat tolerance (HTT1 and HTT2) were conducted pre-HA and post-HA (ambient temperature: ~40 °C). Blood biomarkers of oxidative stress (8-hydroxy 2 deoxyguanosine (8-OHdG) and malondialdehyde (MDA)), and the antioxidant response (glutathione peroxidase (GPx)) were quantified before and after exercise pre-HA and post-HA. Rectal temperature (Trec) was continuously monitored during exercise. Dependent samples T-Test (p < 0.05) were used to compare biomarker means (i.e., relative percent (%) change from baseline) and Trecmeans between BC and CON at each timepoint. RESULTS: There were no significant differences in the relative % change of 8-OHdG concentrations from baseline between BC and CON at any timepoint (p > 0.05). There were multi-directional differences in the relative % change of MDA concentrations after exercise at pre-HA HTT1 (mean ± SD: BC: 14.45 ± 48.40%, CON: -7.46 ± 53.95%, p = 0.038), pre-HA HTT2 (BC: 68.39 ± 30.31%, CON: 24.39 ± 47.69%, p = 0.031) and post-HA HTT1 (BC: 44.59 ± 85.38%, CON: -9.75 ± 43.33%, p = 0.041). The relative % change of GPx activity from baseline was altered after exercise at pre-HA HTT2 (BC: -10.45 ± 3.52%, CON: 3.30 ± 9.81%, p = 0.026) and before exercise post-HA HTT1 (BC: -9.34 ± 3.70%, CON: 3.44 ± 4.15%, p = 0.013). Trec values were similar between BC and CON at all time points (p > 0.05). CONCLUSIONS: Surrounding HA, BC supplementation corresponded with increased systemic changes in MDA concentrations after exercise and decreased GPx activity before and after exercise. BC may reduce the damaging oxidative load resulting from exertional-heat stress and future investigation of additional biomarkers is warranted for confirmation. The variability in biochemical responses to HA from baseline demonstrate the importance of personalized dietary strategies surrounding exercise in the heat for naïve and acclimated individuals to combat exertional-heat stress. Supported by: DoD BA200299