Results
We found that native (-SH) and total thiol (-SH+-S-S-) levels were lower in patients with CKD (stage 3-5) and HD compared with the control subjects (230.7±59.9 and 202.6±79.7 µmol/L; 267.7±66.4, and 264.9±98.6 µmol/L respectively). However, disulfide levels were higher in patients with CKD and HD compared with the control subjects (18.5±7.4 and 31.2±12.3 µmol/L, respectively). Moreover, disulfide levels were significanlty high in the patients receiving HD compared with both patients with CKD (stage 3-5) and control subjects (31.2±12.3µmol/L, 18.5±7.4 µmol/L and 16.3±4.8 µmol/L respectively). Disulfide levels in HD patients increased significantly compared with patients with CKD and control subjects (p=0.001). In addition, plasma IMA levels were significantly different between control and CKD (stage 3-5) and control and HD groups (p = 0.001, Table 1).
Native and total thiol levels showed negative correlation with IMA, blood urea nitrogen (BUN), and creatinine levels (r=-0.628, p=0.001; r=-0.747, p=0.001, r=-0.732, p=0.001). In addition, it showed positive correlation with glomerular filtration rate (GFR) (r= 0.835, p=0.001; r=0.824, p=0.001). There was no correlation between disulfide levels and age and GFR (Table 2). In patients receiving HD, native and total thiols in pre-and post-dialysis were significantly different (p=0.001), but disulfide levels did not significantly change (p=0.0152) by a single dialysis session. Serum albumin and CRP levels were significantly different before and after the dialysis session (p=0.001, Table 3). Therefore, we also calculated adjusted native thiol, total thiol, and disulfide levels based on albumin concentrations in HD patients both before and after the dialysis. After albumin correction, there was no significant difference anymore in the native and total thiol levels of pre- and post- dialysis patients (p=0.143, p=0.567), however significant difference was observed in the disulfide levels (p=0.001, Table 4).