Chronic kidney disease is associated with increased levels of renalase in serum and decreased in erythrocytes

INTRODUCTION Renalase is a novel flavin adenine dinucleotide-dependent amine oxidase with catecholamine-degrading activity. The kidneys are the main source of this enzyme. OBJECTIVE In this study, we examined the concentrations of renalase in the serum, urine, and erythrocytes of patients with chronic kidney disease (CKD). PATIENTS AND METHODS We enrolled 155 white patients with CKD and 30 healthy controls. Renalase concentrations were measured using an enzyme-linked immunosorbent assay. RESULTS Serum renalase levels were higher in patients with CKD than in controls: median (Q1-Q3), 103 ng/ml (55.6-166 ng/ml) vs 17.7 ng/ml (16.3-21.8 ng/ml); P <0.001. Renalase levels in erythrocytes were lower in patients with CKD than in controls (median [Q1-Q3], 122 ng/ml [67.2-189 ng/ml] vs 254 ng/ml [166-293 ng/ml]; P <0.001). Urinary renalase levels did not differ between patients with CKD and controls (median [Q1-Q3], 147 ng/ml [102-193 ng/ml] vs 144 ng/ml [116-170 ng/ml]; P = 0.78). Urinary and erythrocyte renalase concentrations were negatively correlated with estimated glomerular filtration rate (eGFR). A multivariate general linear model analysis adjusted for age, sex, and eGFR of CKD patients showed that higher plasma dopamine and total protein concentrations were independent predictors of higher serum renalase levels (beta = 0.32, P <0.001 and beta = 0.25, P <0.001, respectively). CONCLUSIONS Our results indicate that serum renalase concentrations are elevated in patients with CKD, whereas renalase concentrations in urine and erythrocytes are correlated with impaired kidney function.