Evaluation of a multi-parameter biomarker set for oxidative damage in man: increased urinary excretion of lipid, protein and DNA oxidation products after one hour of exercise

The objective of the present study was to evaluate a comprehensive set of urinary biomarkers for oxidative damage to lipids, proteins and DNA, in man. Eighteen moderately trained males (mean age 24.6+/-0.7) exercised 60min at 70% of maximal O2 uptake on a cycle ergometer. Urine fractions for 12 h were collected 1 day before, and for 3 consecutive days after exercise. As biomarkers of lipid peroxidation, 8 aldehydes (i.e. propanal, butanal, pentanal, hexanal, heptanal, octanal, nonanal and malondialdehyde-MDA)and acetone were analyzed in urines by gas chromatography with electron capture detection (GC-ECD). As a biomarker of protein oxidation, o,o'-dityrosine was analyzed in urine samples by a recently developed isotope dilution HPLC-atmospheric pressure chemical ionization (APCI)-tandem-mass spectrometry (HPLC-APCI-MS/MS) methodology. As a biomarker of oxidative DNA damage, urinary excretion of 8-hydroxy-2'-deoxyguanosine (8-OHdG) was measured by an ELISA method. On the day of exercise, significant increases were observed in urinary excretions of acetone (p < 0.025, n = 18) and butanal (p < 0.01, n = 18) in the 12h daytime fractions compared to the daytime fraction before exercise. The urinary acetone excretion was also significantly (p < 0.05) increased on the 1st day after exercise. Octanal and nonanal were increased in the daytime urine fraction on the 2nd day after exercise. However, these increases were of borderline significance (p = 0.09 and p = 0.07, respectively). Significantly elevated urinary o,o'-dityrosine amounts were observed in the daytime fraction on the day of exercise (p < 0.025) and on the 1st day after exercise (p = 0.07) compared to the before exercise daytime fraction. Excretion of urinary 8-OHdG was statistically significantly increased in the daytime fractions on the day of exercise (p = 0.07) and on the 1st day after exercise (p < 0.025) compared to before exercise daytime fraction. Increases in urinary excretions of acetone, propanal, pentanal, MDA and 8-OHdG significantly correlated with training status (hours of exercise/week) of the volunteers, while o,o'-dityrosine did not. To our knowledge, the present study is the first to evaluate a multi-parameter non-invasive biomarker set for damage to three main cellular targets of ROS. It shows that 1 h of exercise may already induce oxidative damage in moderately trained individuals and that the chosen urinary biomarkers are sensitive enough to monitor such damage.