Effect of exercise intensity on Nrf2 signalling in young men

Introduction: The transcription factor Nrf2 is the master regulator of antioxidant defence. Recent data indicate a single bout of moderate-intensity stationary cycling at a constant workload upregulates Nrf2 signalling in young, but not older men; however, the role of exercise intensity on Nrf2 activation has not been tested. We hypothesised that a high-intensity interval session would elicit a greater Nrf2 response than moderate aerobic exercise. Methods: Nrf2 signalling in response to two 30-min cycling protocols (high-intensity interval and constant workload) was compared in young men (25 +/- 1y, n = 16). Participants completed exercise trials in random order with blood collected pre-, immediately post-, and 30-mins post exercise. Five participants completed a control trial without any physical activity. Nrf2 signalling was determined by measuring protein expression of Nrf2 in whole cell and nuclear fractions. Plasma 8-isoprostanes as well as peripheral mononuclear cell glutathione reductase (GR) and superoxide dismutase activity were measured as markers of oxidative stress. Results: The exercise trials elicited significant increases in nuclear Nrf2 (p < .01), but increases in whole cell Nrf2 did not reach statistical significance. GR activity and plasma 8-isoprostanes increased significantly in response to exercise (p < .05), and GR response was higher in the high-intensity trial (p < .05). Conclusion: Our findings indicate that acute aerobic exercise elicits activation of nuclear Nrf2, regardless of exercise intensity, but that higher-intensity exercise results in greater activity of GR. Future experiments should explore the effect of exercise mode and duration on Nrf2 signalling, and the role of intensity in compromised populations.