Association of Mitochondrial DNA Copy Number with Risk of Progression of Kidney Disease

Background and objectives Mitochondrial DNA copy number is a biomarker of mitochondrial function, which has been hypothesized to contribute to pathogenesis of CKD through podocyte injury, tubular epithelial cell damage, and endothelial dysfunction. The prospective association of mitochondrial DNA copy number with CKD progression has not been previously evaluated. Design, setting, participants, & measurements Chronic Renal Insufficiency Cohort study participants had serum levels of mitochondrial DNA copy number calculated from probe intensities of mitochondrial single nucleotide polymorphisms genotyped on the Illumina HumanOmni 1-Quad Array. CKD progression was defined as kidney failure or halving of eGFR from baseline. Cox proportional hazards models were used to calculate hazard ratios for mitochondrial DNA copy number and risk of CKD progression. Results Among 2943 participants, mean age was 58 years, 45% were women, and 48% self-identified as Black. There were 1077 patients who experienced CKD progression over a median follow-up of 6.5 years. The incidence rate of CKD progression was highest for those in the lowest tertile of mitochondrial DNA copy number (tertile 1, 58.1; tertile 2, 50.8; tertile 3, 46.3 per 1000 person-years). Risk for CKD progression was higher for participants with lower levels of mitochondrial DNA copy number after adjustment for established risk factors (for tertile 1 versus 3, hazard ratio, 1.28 [95% confidence interval, 1.10 to 1.50]; for tertile 2 versus 3, hazard ratio, 0.99 [95% confidence interval, 0.85 to 1.16]; trend P =0.002). Similar results were seen among those with albuminuria (for tertile 1 versus 3, hazard ratio, 1.24; 95% confidence interval, 1.05 to 1.47), but there were no statistically significant associations among individuals without albuminuria (for tertile 1 versus 3, hazard ratio, 1.04; 95% confidence interval, 0.70 to 1.53; interaction P <0.001). Conclusions These findings suggest lower mitochondrial DNA copy number is associated with higher risk of CKD progression, independent of established risk factors among patients with CKD.