Relationship between breath isoprene excretion and oxidative stress responses to submaximal exercise / 体力科学

The physiological functions of expiratory isoprene, which is abundantly contained in human breath, are not well known. Recently, breath isoprene has been proposed to be related to oxidative stress, although no direct evidence has been reported. Therefore, the purpose of this study was to investigate the relationship between breath isoprene and oxidative stress status. Ten healthy male subjects performed a 20-min submaximal step-load cycling exercise, the intensity of which corresponded to a 60% peak oxygen uptake after a 10-min rest. Breath isoprene excretion during the exercise was calculated from the product of minute ventilation and isoprene expiratory concentration. To evaluate the oxidative stress, we collected blood samples from the subject’s fingertips before and immediately after the end of the exercise, and then diacron reactive oxygen metabolites (d-ROMs), which is an index of oxidative stress level, and biological antioxidant potential (BAP), which is an index of antioxidant potential, were measured. The breath isoprene concentration at the rest was significantly positively correlated with the ratio from BAP to d-ROMs (BAP/d-ROMs), which is an index of latent antioxidant potential (r = 0.63, P < 0.05). Furthermore, the change in breath isoprene excretion from before to after the exercise was significantly negatively correlated with the change in d-ROMs (r = -0.73, P < 0.05) and positively correlated with the change in BAP/d-ROMs (r = 0.88, P < 0.01). These results suggest that isoprene might play a role in the control of oxidative stress.

The effects of physical training on antioxidative status under exercise-induced oxidative stress

This study investigated the effect of physical training and oxidative stress on the antioxidative activity and on plasma lipid profile. Forty eight rats were given either a physical training or no training for 4 weeks and were then subdivided into 3 groups: before-exercise (BE); during-exercise (DE); after-exercise (AE). The antioxidative activity was evaluated with the activities of catalase in plasma and superoxide dismutase (SOD), the ratio of reduced glutathione/oxidized glutathione (GSH/GSSG) and the level of malondialdehyde (MDA) in liver. The plasma concentrations of triglyceride (TG), total cholesterol (TC), high-density lipoprotein-cholesterol (HDL-C)) were also compared. Compared to those of non-training group, catalase activities of training group were lower before exercise but higher during and after exercise. SOD activities were higher regardless of exercise. GSH/GSSG ratio was higher before exercise but was not significantly different during exercise and even lower after exercise. There were no differences between non-training group and training group in MDA levels regardless of exercise. Compared to those of non-training group, atherosclerotic index of training group was lower after exercise and there were no significant differences before and during exercise. There were no differences between non-training group and training group in HDL-C regardless of exercise. These results suggest that moderate physical training can activate antioxidant defenses and decrease the atherosclerotic index and this beneficial effect is evident under exercise-induced oxidative stress.