Plasma Xanthine Oxidoreductase Activity Associated with Glycemic Control in Patients with Pre-Dialysis Chronic Kidney Disease

Introduction: Xanthine oxidoreductase (XOR) activity plays an important role as a pivotal source of reactive oxygen species, which is associated with cardiovascular disease (CVD) events. Patients with CKD have increased risk of CVD events. In the present study, factors associated with plasma XOR activity in pre-dialysis CKD patients were investigated. Methods: In this cross-sectional study, plasma XOR activity in 118 pre-dialysis CKD patients (age 68 [57–75] years; 64 males, 26 with diabetes mellitus [DM]) was determined using a newly established highly sensitive assay based on ( 13 C 2 , 15 N 2 ) xanthine and liquid chromatography/triple quadrupole mass spectrometry. Results: Plasma glucose, hemoglobin A1c, and estimated glomerular filtration (eGFR) were significantly and positively correlated with plasma logarithmically transformed XOR (ln-XOR) activity. In multiple regression analyses, eGFR and hemoglobin A1c or plasma glucose were significantly, independently, and positively associated with plasma ln-XOR activity after adjusting for several confounders. Plasma XOR activity was significantly higher in CKD patients with (n = 26) than in those without (n = 92) DM (62.7 [32.3–122] vs. 25.7 [13.4–45.8] pmol/h/mL, p < 0.001). A total of 38 patients were taking uric acid-lowering drugs. Multiple regression analysis of CKD patients not administered uric acid-lowering drugs (n = 80) showed no significant association between eGFR and plasma ln-XOR activity. In contrast, association between glycemic control and plasma ln-XOR activity was significant even in CKD patients without uric acid-lowering drug treatment. Conclusions: These results indicate the importance of glycemic control in CKD patients in regard to decreased XOR, possibly leading to a decrease in CVD events.