Serum renalase inversely related to heart rate variability in dialysis patients

Heart rate variability(HRV) is a noninvasive technique for autonomic nerve activity assessment and an indirect index of adrenergic cardiovascular drive. Renalase is the only known enzyme degrading circulatory catecholamines, participating in regulations of the cardiovascular and sympathetic nervous systems. This study aims at the relation between serum renalase and HRV indexes in dialysis patients. There were 14 hemodialysis(HD)cases, 16 continuous ambulatory peritoneal dialysis(PD) cases, and 16 healthy volunteers enrolled in this study.All the subjects underwent 24 h Holter testing by using a dynamic electocardiogram monitor system to determine HRV parameters, and serum renalase levels were measured. The standard deviation of normal to normal R-R intervals(SDNN, a measure of beat-to-beat variability), root mean square successive difference(RMSSD), and the proportion derived by dividing NN50(the number of interval differences of successive normal to normal intervals greater than 50 ms) by the total number of NN intervals(pNN50) were determined to assess HRV. Both HD and PD patients presented increased maximum heart rate(Max-HR), minimum heart rate(Min-HR) and average heart rate(Ave-HR), and presented decreased SDNN, RMSSD and pNN50 relative to healthy controls. Serum levels of renalase were highly negatively correlated with Ave-HR(correlation coefficient r =-0.68, probability P 0.01), while positively correlated with SDNN(r = 0.64, P 0.01) in both the HD and PD groups. Serum level of renalase was positively correlated with 24 h urine volume(r = 0.73, P 0.01) in PD patients. Renalase might be reciprocally related to HRV and inversely related to Ave-HR in dialysis patients, which will help to probe into renalase's physiology and may pave the way to explore renalase replacement therapy in patients with end stage renal disease(ESRD).