Background: Oxidative stress is considered to be a unifying link between diabetes mellitus (DM) and its complications, including nephropathy. There have been many reports on increased production of oxidants and decreased level of antioxidants in diabetic patients. The dialysis procedure contributes to oxidative stress. An increase in oxidative stress may contribute to the development of oxidative protein damage in diabetic patients. Our aim was to reveal the effects of diabetes and hemodialysis (HD) on oxidative modifications of plasma proteins.
Methods: We measured reactive carbonyl derivates (PCO), protein thiol (P-SH), and reduced glutathione (GSH) levels in Type 2 diabetic (DM) and diabetic hemodialysed patients (DHD) and in healthy control participants.
Results: Protein carbonyl (PCO) content increased significantly in all patient groups relative to the controls. The dialysis procedure caused an additional increase in PCO levels in DHD patients before and after dialysis compared with the level in DM patients. There was a significant decrease in P-SH levels in DHD patients compared with the level in healthy participants and DM patients. There was no significant difference in the whole blood GSH levels between the DM patients and control participants. It was significantly higher in DHD patients in comparison to the DM patients.
Conclusions: We conclude that PCO level increases in DM patients, and this increase is more profound in DHD patients, indicating that both diabetes and dialysis contribute to increased protein oxidation. The low P-SH level in DHD patients, but not in DM patients, suggests that dialysis is responsible for this decrease. We propose plasma PCO derivate as a novel specific marker for oxidative protein damage.