Biomarkers of oxidative stress to nucleic acids: Background levels and effects of body mass index and life-style factors in an urban paediatric population

The aims of the present study were to establish the background levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo), 8-oxo-7,8-dihydroguanosine (8-oxoGuo), 8-oxo-7,8-dihydroguanine (8-oxoGua) among a group of healthy Italian children, and to evaluate the contribution of some potential interfering/confounding factors to the urinary (u) levels of these biomarkers of oxidised guanine derivatives. The levels of 8-oxodGuo, 8-oxoGuo, 8-oxoGua, and u-cotinine in urine samples from 159 healthy children (5-11years) recruited in a cross-sectional study were measured via liquid chromatography-tandem mass spectrometry. Data regarding the anthropometric and life-style characteristics of the participants were obtained from questionnaires. The 5th-95th percentiles of the levels of 8-oxodGuo, 8-oxoGuo, and 8-oxoGua for all children were 2.4-13.9, 3.8-19.9 and 5.4-79.5μg/L and 2.9-12.6, 4.8-15.2, and 5.1-93.4μg/g creatinine, respectively. Significant correlations were found between the level of 8-oxoGuo and that of 8-oxoGua and 8-oxodGuo but not between the level of 8-oxoGua and that of 8-oxodGuo in all children and in both the male and female subgroups. Multiple linear regression analyses revealed the independent effect of the investigated variables on 8-oxodGuo, 8-oxoGuo, and 8-oxoGua. u-Creatinine was the most significant predictor of the urinary excretion of both 8-oxoGuo and 8-oxodGuo, age displayed a significant positive independent effect on the level of 8-oxoGuo, whereas the weight status according to the BMI was negatively associated with the level of 8-oxodGuo. None of the chosen independent variables influenced the levels of 8-oxoGua.