Uric acid shown to contribute to increased oxidative stress level independent of xanthine oxidoreductase activity in MedCity21 health examination registry

Uric acid has both antioxidant and pro-oxidant properties in vitro by scavenging and production of reactive oxygen species (ROS). This cross-sectional study examined whether uric acid possesses effects on oxidative stress under physiological conditions independent of xanthine oxidoreductase (XOR), which is involved in uric acid and ROS production. Serum uric acid level was measured, while plasma XOR activity was determined using our high-sensitive assay in 192 participants (91 males, 101 females) who underwent health examinations and were not taking an antihyperuricemic agent. For antioxidant potential and oxidative stress level, biological antioxidant potential (BAP) and derivative of reactive oxygen metabolites (d-ROMs) in serum, respectively, were measured. Median uric acid level and plasma XOR activity were 5.6 mg/dL and 26.1 pmol/h/mL, respectively, and BAP and d-ROMs levels were 2112.8 μmol/L and 305.5 Carr U, respectively. Multivariable regression analyses revealed no significant association of serum uric acid level with BAP level, whereas serum uric acid level showed a significant association with d-ROMs level independent of plasma XOR activity (p = 0.045), which was prominent in females (p = 0.036; p for interaction = 0.148). Uric acid might contribute to increased oxidative stress independent of XOR activity by increasing ROS production, without affecting ROS scavenging, especially in females.