title: Diurnal variation of urinary markers of nucleic acid oxidation.
abstract: OBJECTIVE
  Urinary 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) and 8-oxo-7,8-dihydroguanosine (8-oxoGuo) are biomarkers of oxidative stress with clinical potential in a variety of diseases. As part of their clinical validation, this study aimed to investigate whether the urinary excretion of 8-oxodG and 8-oxoGuo undergoes diurnal variation and to evaluate the validity of 6-hour sampling as well as creatinine corrected spot urine sampling.
  
  
  METHODS
  A total of 23 healthy study subjects collecting their 24-h urine in four fractions covering 6 hours each. Urinary 8-oxodG and 8-oxoGuo levels were quantified using a modified version of UPLC-MS/MS.
  
  
  RESULTS
  No significant difference in excretion levels between the 12-h diurnal and 12-h nocturnal state or between the four 6-h periods during the day was found for either biomarker. A strong linear relationship between the excretion levels in each of the 6-h periods and the 24-h excretion level was shown for both biomarkers. Creatinine correction of the 6-h levels reduced the biological variation of the excretion levels and weakened the linear relationship with the uncorrected 24-h excretion level for both biomarkers. The correlations were strengthened when the 24-h excretion level was expressed per kg body weight.
  
  
  CONCLUSIONS
  The results showed that 8-oxodG and 8-oxoGuo did not undergo diurnal variation in the study population overall and hence that the time of sampling is not crucial. Furthermore, 6-h sampling can be used as a substitute for 24-h sampling, and creatinine corrected sampling may be rational due to the reduction in biological variation of the biomarkers and the reasonable correlation with body weight-adjusted 24-h levels.
authors.affiliation: Laboratory of Clinical Pharmacology, Copenhagen University Hospital Rigshospitalet, and Department of Clinical Pharmacology, Copenhagen University Hospital Bispebjerg , Denmark.
authors.forename: Ida S
authors.initials: IS
authors.lastname: Grew
authors.forename: Vanja
authors.initials: V
authors.lastname: Cejvanovic
authors.forename: Kasper
authors.initials: K
authors.lastname: Broedbaek
authors.forename: Trine
authors.initials: T
authors.lastname: Henriksen
authors.forename: Morten
authors.initials: M
authors.lastname: Petersen
authors.forename: Jon T
authors.initials: JT
authors.lastname: Andersen
authors.forename: Espen
authors.initials: E
authors.lastname: Jimenez-Solem
authors.forename: Allan
authors.initials: A
authors.lastname: Weimann
authors.forename: Henrik E
authors.initials: HE
authors.lastname: Poulsen
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000652:urine*; D002940:Circadian Rhythm / Q000502:physiology*; D003404:Creatinine / Q000652:urine; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000652:urine; D005260:Female; D006151:Guanosine / Q000031:analogs & derivatives* / Q000652:urine; D006801:Humans; D008297:Male; D008875:Middle Aged; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D015203:Reproducibility of Results
chemical_list: D015415:Biomarkers; D006151:Guanosine; C046215:8-hydroxyguanosine; D000080242:8-Hydroxy-2'-Deoxyguanosine; D003404:Creatinine; D003849:Deoxyguanosine
keywords: 8-oxo-7,8-dihydro-2ʹ-deoxyguanosine; 8-oxo-7,8-dihydroguanosine; 8-oxoGuo; 8-oxodG; diurnal variation