Nephrol Dial Transplant ( 1997) 12: 2312–2317
Nephrology Dialysis Transplantation
Erythropoietin and oxidative stress in haemodialysis: beneficial effects of vitamin E supplementation J.-P. Cristol, J.-Y. Bosc, S. Badiou, M. Leblanc, R. Lorrho, B. Descomps and B. Canaud Departments of Biochemistry and Nephrology, Lapeyronie Hospital, Montpellier, France
Abstract. Oxidative stress can produce profound alterations to cellular membrane lipids, impairing cell metabolism and viability. This phenomenon, previously observed in haemodialysis patients, has been proposed as a significant factor in regard to haemodialysis-related shortened red blood cells ( RBC ) survival. In the present study, several parameters associated with oxidative stress were evaluated in a group of haemodialysis patients either receiving erythropoietin therapy (n=12, mean erythropoietin dose 88±24 U/kg/week) or not receiving such therapy (n=30), and in 38 controls. Malonyldialdehyde (MDA, nmol/ml ), an end-product of lipid peroxidation, and RBC antioxidant systems were measured, including RBC a-tocopherol ( RBC vitamin E, mg/l ), RBC glutathione (GSH, nmol/mgHb), and RBC superoxide dismutase activity (SOD, U/mgHb). Plasma vitamin E concentrations were also evaluated. Finally, oral vitamin E supplementation (500 mg daily), an exogenous antioxidant, was administered for 6 months to seven patients from the dialysis group receiving erythropoietin while oxidative parameters were repeatedly evaluated and erythropoietin requirements monitored, in order to appreciate the therapeutic relevance of an antioxidant supplementation. An elevation of serum MDA was observed in all haemodialysis patients and a significant decrease in RBC vitamin E, despite normal serum vitamin E levels. Furthermore, the reduction in RBC vitamin E was more important in patients treated with erythropoietin. Vitamin E supplementation resulted in a significant increase in RBC vitamin E (from 0.3±0.1 to 1.2±0.2 mg/l of pellet) and a reduction in erythropoietin dose (from 93±24 to 74±26 U/kg/week) while maintaining stable haemoglobin concentrations. These results suggest that the oxidative stress could be one of the resistance factors to erythropoietin response in haemodialysis and that vitamin E supplementation could have a sparing effect on erythropoietin dosage requirement.
Correspondence and offprint requests to: Jean-Paul Cristol MD PhD, Department of Biochemistry, Lapeyronie Hospital, 34295 Montpellier, France.
Key words: antioxidant; erythropoietin; haemodiafiltration; lipid peroxidation; oxidative stress; vitamin E
Introduction Oxidative stress corresponds to an imbalance between the production of reactive oxygen species (ROS ), mainly the superoxide anion (O o−), hydroxyl radical 2 (OHo), peroxyl radicals (LOOo ), and hydrogen peroxide ( H O ), and protective mechanisms [1,2]. Several 2 2 enzymatic systems can detoxify ROS: copper/zinc superoxide dismutase (Cu/Zn SOD) catalyses the conversion of O o− to H O and works concomitantly 2 2 2 with hydroperoxide-removing enzymes such as catalases and a selenoprotein, glutathion peroxidase (GPX ). In addition, some micronutrients can prevent ROS harmful effects by non-enzymatic modes: reduced glutathion (GSH ), a-tocopherol (TocoH ) or vitamin E, which leads to the formation of alpha-tocopheroxyl radicals ( Tocoo), and finally ascorbic acid or vitamin C, which can regenerate TocoH from Tocoo. Haemodialysis, far from improving the oxidative stress associated with chronic renal failure, enhances this metabolic disorder. First, bioincompatibility represents an important source of ROS formation: namely O2o− and its metabolites (H O and OHo) [3,4], and 2 2 hydroperoxides released enzymatically from arachidonic acid [5,6 ]. Second, several antioxidative defences are altered in haemodialysis patients: a reduction in the activity of Cu/Zn SOD in erythocytes [7–9] and of GPX in plasma [7,10]. Third, several hydrophilic and lipophilic vitamins are altered in uraemia; vitamin E concentration in erythrocytes and mononuclear cells are low despite normal plasma levels [11–13]; furthermore, ascorbic acid (vitamin C ) depletion is observed in patients undergoing haemodialysis [8,14,15]. Indeed, most markers of oxidative stress are elevated: lipid peroxidation products (such as malonyldialdehyde MDA) [9 ], advanced glycosylation end-products (AGE ) [16 ], advanced oxidation proteins [17 ], and enhanced susceptibility to LDL oxidation [18 ]. Since membrane lipids are generally considered as the preferential targets of most oxidative processes,
© 1997 European Renal Association–European Dialysis and Transplant Association
Vitamin E supplementation in haemodialysis patients
lipid peroxidation results in profound structural and functional cellular alterations. Such a phenomenon could be involved to explain the shortened RBC survival recognized in haemodialysis [19–22 ] and could also become a limitating factor in regard to the erythropoietin response. The purpose of the present study was to determine oxidative stress parameters in haemodialysis patients treated with or without erythropoietin, and to evaluate the impact of a supplementation with vitamin E on their response to erythropoietin therapy.
Subjects and methods Patients Forty two chronic haemodialysis patients (mean age of 60±10 years) on renal replacement therapy for more than 1 year were included in this study after informed consent. Twelve patients of the whole group were regularly receiving subcutaneous erythropoietin (Eprex, Janssen–Cilag, Boulogne-Billancourt, France) at a mean dose of 88±24 U/kg/week. Patients treated with erythropoietin were systematically supplemented with parenteral iron (20 mg/session, Maltofer, Laboratoires Lucien, Neuilly-sur-Seine, France) to maintain or replete their reserves. All patients were treated by on-line post-dilutional haemodiafiltration ( Fresenius 2008, Bad Homburg, Germany) using 1.8 m2 polysulphone membrane haemodiafilter ( HF80, Fresenius, Bad Homburg, Germany) at a mean blood flow of 350±10 ml/min, a mean dialysate flow rate of 600 ml/min, and an ultrafiltration rate of 111±10 ml/min. The dialysate was ultrapure as previously described; the infusate was produced from the dialysate by a two-step ultrafiltration . There was no significant difference between subgroups in regard to age, dialysis dose as assessed by single-pool Kt/V, haemoglobin levels, and serum iron ( Table 1). However, ferritin levels were significantly higher in erythropoietin-treated patients. The results of lipid metabolism and oxidative stress parameters obtained in dialysis patients were compared to a control group of 38 healthy volunteers ( 55±9 years) ( Table 2).
Table 2. Lipid status in the two subgroups of haemodialysis patients at baseline and in the control group Patients
Number Cholesterol (mmol/l ) (N, 4.1–5.7 ) Triglycerides (mmol/l ) (N, 0.6–1.7 ) HDL cholesterol (mmol/l ) (N, 1.2–2.0 ) Apo A ( g/l ) (N, 1.1–2.0 ) ApoB (gl/l ) (N, 0.6–1.4 )
N, normal range values in our laboratory; Epo, erythropoietin; *P