Plasma and urinary F 2 -isoprostane markers of oxidative stress are increased in cats with early (stage 1) chronic kidney disease

Abstract

Objectives Oxidative stress contributes to chronic kidney disease (CKD) progression in humans and rodent models; F 2 -isoprostanes (F 2 -IsoPs) are established biomarkers of oxidative stress. Our primary aim was to evaluate plasma F 2 -IsoPs in cats with International Renal Interest Society stage 1 and 2 CKD, compared with healthy cats, and to determine whether plasma and urinary F 2 -IsoPs are equivalent biomarkers. The secondary aim was to assess whether consumption of a renal diet enriched in omega-3 fatty acids led to improvements in plasma and urinary F 2 -IsoPs. Methods Plasma and urinary F 2 -IsoPs were measured in 24 cats with stage 1 or 2 CKD, and 12 unaffected controls aged ⩾6 years. Twelve CKD cats were re-evaluated after feeding a commercial renal diet for at least 4 weeks. Results Median plasma F 2 -IsoPs were significantly higher in stage 1 CKD (96.2 pg/ml), early stage 2 CKD (83.2 pg/ml) and late stage 2 CKD (80.8 pg/ml) compared with healthy cats (22.8 pg/ml; P = 0.03−0.002). Median urinary F 2 -IsoPs were significantly higher in cats with stage 1 CKD (231.2 pg/mg) compared with healthy cats (152.5 pg/mg) or cats with late stage 2 CKD (124.8 pg/mg; P = 0.01). Plasma F 2 -IsoPs remained increased, while urinary F 2 -IsoPs fell with transition from stage 1 to stage 2 CKD. Feeding a commercial renal diet led to significant decreases in plasma F 2 -IsoPs in the small group of cats with stage 1 CKD (25−75% decrease) compared with cats with stage 2 CKD (20% decrease to 53% increase; P = 0.01). Conclusions and relevance Oxidative stress is prominent in cats with stage 1 CKD. Plasma and urinary F 2 -IsoPs are not interchangeable biomarkers in cats with stage 2 CKD. Placebo-controlled studies are indicated to evaluate dietary or pharmacologic doses of omega-3 fatty acids on redox stress and progression of renal dysfunction in cats with stage 1 CKD.