ABSTRACT
Chronic renal failure [CRF] is a worldwide public health problem. It is a progressive disease characterized by gradual and persistant impairment of both glomrerular filtration and tubular functions, so the kidneys are no longer able to keep normal internal environment. Oxidative and carbonyl stresses are considered among the mechanisms involved in the pathogenesis of CRF. Oxidative stress is known as imbalance between reactive oxygen species and antioxidants in favour of the former, while carbonyl stress is characterized as an overload of reactive carbonyl compounds [RCOs]. Both oxidative stress and carbonyl stress can cause damage to important biological structures e.g. proteins, carbohydrates, lipids, and nucleic acids resulting in the generation of new compounds and modified structures which can serve as markers of these mechanisms such as advanced glycation end products [AGEs] and advanced oxidation protein products [AOPPs]. AOPPs are proteins, predominantly albumin and its aggregates, that are damaged by oxidative stress. The present work aimed to study the effects of two different renal replacement modalities, peritoneal dialysis [PD] and hemodialysis [HD], on oxidation products of glucose, lipids, and proteins in patients with end stage renal disease [ESRD.] It also aimed at studying the effects of these therapies on the antioxidant defenses of these patients. The present study was conducted on 20 patients with ESRD. Patients were divided into two groups; group I consisted of 10 patients maintained on continuous intermittent peritoneal dialysis [PD] thrice weekly, and group II consisted of 10 patients maintained on bicarbonate hemodialysis [HD] thrice weekly. 10 healthy volunteers of matched age and sex served as a control group. All patients and control subjects were subjected to the following investigations; serum malondialdehyde [MDA] serum AOPPs, blood glutathione [GSH], erythrocyte glutathione peroxidase [GPx] and superoxide dismutase [SOD] activities, plasma vitamins A and C, serum vitamin E and beta carotene. For all patients, these markers were measured before the start of dialysis and 4 weeks after the first dialysis session. For control volunteers, these markers were measured only once. There was significant increase in the predialysis values of MDA and AOPPs when all ESRD patients were compared with the control group. There was also significant decrease in the predialysis values of GSH, GPx, SOD, vitamins A, E, and C, and beta carotene when all ESRD patients were compared with the control group. There was significant increase in the postdialysis values of MDA and AOPPs and significant decrease in the postdialysis values of GSH, GPx, SOD, vitamins A, E, and C, and beta carotene compared to their corresponding predialysis values in both PD and HD groups. There was no significant percentage change in all studied markers between PD and HD except GPx and vitamin C where the percentage change was significant. This study also revealed significant positive correlation between serum levels of MDA and AOPPs and significant negative correlation between each of them in one hand and all the antioxidant markers except for vitamin E in the post dialysis phase in the other hand. It is concluded that both PD and HD therapies, as practiced currently, are associated with increased oxidative stress. AOPPs are new uremic toxins that appear to be important components in the complex pathophysiology of oxidative stress and inflammation and therefore should be taken as a potential target to interrupt the vicious circle of oxidation and inflammation in uremia. AOPPs can be also used as a marker of oxidative stress. Prevention of oxidative stress in dialysis patients might focus on improving the biocompatibility of the dialysis system and supplementation of deficient patients with antioxidants