Correlation of oxidative stress biomarkers and peritoneal urea clearance with mitochondrial DNA copy number in continuous ambulatory peritoneal dialysis patients

Background/Aims: The influence of oxidative stress and peritoneal clearance on alterations in mitochondrial DNA (mtDNA) copy number in continuous ambulatory peritoneal dialysis (CAPD) patients was investigated. Methods: Ninety-one CAPD patients (age, 30-57 years) and 99 age-matched healthy subjects were enrolled. Biochemical variables, plasma thiobarbituric-acid-reactive substances (TBARS), free thiol levels and mtDNA copy number in peripheral leukocytes were measured. Results: CAPD patients showed higher TBARS levels, lower free thiol levels and a higher mtDNA copy number than control subjects. Plasma TBARS levels and peritoneal urea clearance were significant factors contributing positively to leukocyte mtDNA copy number (p = 0.024, R² = 0.238). The CAPD patients were further categorized into 4 groups depending on whether the TBARS and free thiol plasma levels were above or below the mean values for these parameters. Patients with higher TBARS levels and lower free thiol levels had a significantly higher number of leukocyte mtDNA copies than patients with lower TBARS levels and higher free thiol levels (multi-covariate ANOVA, p = 0.008). Conclusion: This study demonstrated that CAPD patients have higher oxidative stress than healthy subjects; such elevated oxidative stress and peritoneal urea clearance have a positive correlation with mtDNA copy number in peripheral leukocytes.