Characterisation of extracellular redox enzyme concentrations in response to exercise in humans.

Redox enzymes are ubiquitous proteins that modulate intracellular redox balance and can be secreted in response to cellular oxidative stress, potentially modulating systemic inflammation. Both aerobic and resistance exercise are known to cause acute systemic oxidative stress and inflammation; however, how redox enzyme concentrations alter in extracellular fluids following bouts of either type of exercise is unknown. Recreationally active males (n=26, age 28 ± 8 years) took part in either: 1) two separate energy-matched cycling bouts: one of moderate intensity (MOD) and a bout of high intensity interval exercise (HIIE) or 2) a resistance exercise protocol. Alterations in plasma (study 1) and serum (study 2) peroxiredoxin (PRDX)-2, PRDX-4, superoxide dismutase-3 (SOD3), thioredoxin (TRX-1), TRX-reductase and Interleukin (IL)-6 were assessed before and at various timepoints after exercise. There was a significant increase in SOD3 (+1.5 ng/mL) and PRDX-4 (+5.9 ng/mL) concentration following HIIE only, peaking at 30- and 60-min post-exercise respectively. TRX-R decreased immediately and 60-min following HIIE (-7.3 ng/mL) and MOD (-8.6 ng/mL) respectively. In non-resistance trained males, no significant changes in redox enzyme concentrations were observed up to 48 hours following resistance exercise, despite significant muscle damage. IL-6 concentration increased in response to all trials, however there was no significant relationship between absolute or exercise-induced changes in redox enzyme concentrations. These results collectively suggest that HIIE, but not MOD or eccentric exercise increase the extracellular concentration of PRDX-4 and SOD3. Exercise-induced changes in redox enzyme concentration do not appear to directly relate to systemic changes in IL-6 concentration.