8-Hydroxy-2'-deoxyguanosine and malondialdehyde in plasma and their association with disease severity in 20 cats with chronic kidney disease.

Abstract

Oxidative stress is associated with the development and progression of chronic kidney disease (CKD) in humans. The aim of this study was to evaluate the concentrations of oxidative stress markers, 8-hydroxy-2'-deoxyguanosine (8-OHdG) and malondialdehyde (MDA), in the plasma and urine of cats with different stages of CKD. Plasma and urine samples were collected from cats with CKD that were referred to the Veterinary Medical Center of the University of Tokyo between April 2019 and October 2022. Plasma and urine samples were collected from healthy cats (n = 6 at most), cats with stage 2 CKD (n = 8) and stage 3-4 CKD (n = 12), and cats with idiopathic cystitis (disease control, n = 5). Plasma and urine concentrations of 8-OHdG and MDA were measured using ELISA and thiobarbituric acid reactive substances assay kits, respectively. The median plasma 8-OHdG concentrations were 0.156 ng/ml (<0.125-0.210 ng/ml) in the healthy group, <0.125 ng/ml (range <0.125 ng/ml) in the idiopathic cystitis group, 0.246 ng/ml (range 0.170-0.403 ng/ml) in cats with stage 2 CKD and 0.433 ng/ml (range 0.209-1.052 ng/ml) in cats with stage 3-4 CKD. Concentrations in stage 3-4 CKD were significantly higher than those in the healthy and disease control groups. Plasma MDA concentrations were low in the healthy and disease control groups and significantly higher in cats with stage 3-4 CKD. In every cat with CKD, plasma 8-OHdG and MDA concentrations were positively correlated with plasma creatinine concentrations (8-OHdG, rs = 0.68; MDA, rs = 0.67). Urinary 8-OHdG/urinary creatinine (u-CRE) and urinary MDA/u-CRE levels did not differ significantly between the groups; however, it was difficult to evaluate them because of the small sample size. This report shows that plasma 8-OHdG and MDA concentrations increase with the severity of feline CKD. These markers may be useful for assessing oxidative stress in cats with CKD.