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).
It has been reported that retinol-binding protein 4(RBP4) is associated to adiposity,insulin resistance,and type 2 diabetes.Meanwhile,circulating RBP4 levels are also affected by renal function.The aim of the present study is to investigate whether serum levels of RBP4 are primarily associated with different stages of chronic kidney disease(CKD) or type 2 diabetes,if there is more potential relevance between RBP4 and renal replacement therapy.The serum levels of RBP4 were assessed by commercial competitive enzyme-linked immunosorbent assay(ELISA)kit in 212 patients with the CKD stages 1—5 and in 24 healthy controls,while its correlation with clinical and metabolic parameters was analyzed.The serum level of RBP4 had a strong correlation with estimated glomerular filtration rate(e GFR)(P < 0.001).Stratified by e GFR and treatment,no more differences in RBP4 serum concentration were detected between type 2 diabetic and non-diabetic subjects [CKD stages 1—5,non-dialysis(ND),hemodialysis(HD) and peritoneal dialysis(PD);P > 0.05 for all].The elevation of RBP4 become higher in HD than in PD and ND in CKD5 patients(P = 0.008 and P = 0.04,respectively),while there was no significant difference between PD and ND groups.Multivariate linear regression analysis demonstrated three independent predictors of e GFR(β =-0.676,P < 0.001),C-reactive protein(CRP)(β =-0.573,P < 0.001) and creatine(β = 0.509,P = 0.024) in the study population.The study results demonstrated that the serum level of RBP4 was negatively related to the e GFR,whether diabetes mellitus(DM) affected the blood concentration of RBP4 or not.And the serum level of RBP4 exhibited significant difference in different renal replacement therapies.
