Gender-related reference intervals of urinary 8-oxo-7,8-dihydro-2 '-deoxyguanosine determined by liquid chromatography-tandem mass spectrometry in Serbian population

Abstract

Objectives: Although there are many nucleobase modifications, 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) is one of the dominant form of oxidative modifications of DNA. Urinary 8-oxodG is potentially the best non-invasive biomarker of oxidative stress. Defining reference interval for urinary 8-oxodG is a prerequisite for its clinical use as biomarker. Design and methods: Reference population included 229 healthy Serbian adults (130 males and 99 females). The spot urinary 8-oxodG was determined using high performance liquid chromatography and tandem mass spectrometry (HPLC-MS/MS). Urinary creatinine was measured by the kinetic Jaffe method. Results: Analytical performances of the HPLC-MS/MS: CVs within and between-run variations were 5.6% and 2.6%; LOD and LOQ were 1.65 nmol/L and 330 nmol/L; mean recovery and relative accuracy were 96% and 97%. Creatinine level was higher in males than in females, but no gender difference in 8-oxodG level was observed. Upon the adjustment of 8-oxodG to creatinine (8-oxodG/creatinine), higher values were obtained in females (1.38 +/- 0.65 nmol/mmol) than in males (1.05 +/- 0.48 nmol/mmol). Distribution of 8-oxodG/creatinine in spot urine sample was log-normal and gender-related reference intervals (estimated as the 2.5th-97.5th percentiles) were 0.45-2.22 nmol/mmol for males, and 0.54-3.11 nmol/mmol for females. Body mass index (BMI) affects excretion of the 8-oxodG in males, independently of urinary creatinine, while in females it does not. Therefore, BMI might contribute to the gender-related differences of 8-oxodG/creatinine in spot urine samples. Conclusions: This is the first established gender-related reference intervals of spot urinary 8-oxodG/creatinine. Our results contribute to the full validation of 8-oxodG as biomarker of oxidative stress.