Vitamin E-bonded cellulose membrane, lipoperoxidation, and anemia in hemodialysis patients

Effect of Vitamin E-Coated Dialysis Membranes on Anemia in Patients with Chronic Kidney Disease: An Italian Multicenter Study

Background

Increased oxidant stress is increasingly recognized as a crucial factor in anemia in patients with chronic kidney disease. Vitamin E-coated membranes (VECMs) consist of a multilayer membrane with liposoluble vitamin E on the blood surface allowing direct free radical scavenging at the membrane site, which is of potential clinical benefit. Our objective was to examine the effect of VECMs on anemia in chronic hemodialysis (HD).

Methods

We enrolled 172 stable chronic HD patients (94 men, 78 women, age 65.4 ± 13.4 years) in an open-label multicenter study. They were shifted from their previous dialyzer to VECM for 1 year. Hemoglobin (Hb) levels and recombinant human erythropoietin (rHuEpo) dosage were analyzed after 4, 8, and 12 months on the VECM and compared with baseline values using paired tests.

Results

Hb significantly increased from 10.9 ± 1.2 g/dL at baseline to 11.7 ± 1.2 g/dL after 12 months (p<0.001) on VECMs. Conversely, the rHuEpo dosage decreased from 7,762 ± 5,865 IU/week at baseline to 6,390 ± 5,679 IU/week after 12 months (p<0.001). The proportion of patients who were at target Hb levels (European Best Practice Guidelines) increased from 49.4% at baseline to 80% after 12 months (p<0.001).

Conclusions

Dialysis with VECM in stable chronic HD patients was associated with significantly improved Hb levels and lower rHuEpo requirements. These results suggest that the antioxidant properties of VECMs may impact favorably on anemia management in chronic HD patients. Possible mechanisms include enhanced membrane biocompatibility, reduced oxidative stress and inflammation with VECMs, resulting in improved red blood cell survival and/or rHuEpo responsiveness. This therapy may potentially contribute to more effective anemia management in hemodialysis patients, and merits further rigorous study.

Systemic Redox Imbalance in Chronic Kidney Disease: A Systematic Review

Patients with chronic kidney disease (CKD) experience imbalance between oxygen reactive species (ROS) production and antioxidant defenses leading to cell and tissue damage. However, it remains unclear at which stage of renal insufficiency the redox imbalance becomes more profound. The aim of this systematic review was to provide an update on recent advances in our understanding of how the redox status changes in the progression of renal disease from predialysis stages 1 to 4 to end stage 5 and whether the various treatments and dialysis modalities influence the redox balance. A systematic review was conducted searching PubMed and Scopus by using the Cochrane and PRISMA guidelines. In total, thirty-nine studies met the inclusion criteria and were reviewed. Even from an early stage, imbalance in redox status is evident and as the kidney function worsens it becomes more profound. Hemodialysis therapy per se seems to negatively influence the redox status by the elevation of lipid peroxidation markers, protein carbonylation, and impairing erythrocyte antioxidant defense. However, other dialysis modalities do not so far appear to confer advantages. Supplementation with antioxidants might assist and should be considered as an early intervention to halt premature atherogenesis development at an early stage of CKD.

Vitamin E-coated filter decreases levels of free 4-hydroxyl-2-nonenal during haemodialysis sessions

Uraemic subjects undergoing chronic haemodialysis show increased oxidative stress. The use of non-biocompatible filters and reduced antioxidative defences are important sources of reactive oxygen species (ROS) release. The highly oxidative environment accelerates the onset and progression of tissue damage and atherosclerotic cardiovascular disease. The aldehyde 4-hydroxyl-2-nonenal (HNE) is probably the best marker of oxidative stress. In this study, the concentration of plasma HNE was evaluated in eight uremic subjects during two sessions of haemodialysis: the first using a standard biocompatible filter and the second using a filter coated with vitamin E. Baseline plasma levels of HNE were elevated, and dropped during haemodialysis. At the end of the session, however, low levels were maintained only when the vitamin E-modified filter was used. By contrast, a marked increase in HNE was recorded at the end of the session in all subjects who underwent haemodialysis with the conventional filter. This study provides evidence that the vitamin E-coated filter plays a role in counteracting oxidative stress. The chronic use of vitamin E-modified filters in haemodialysed subjects might help to counterbalance oxidative attack and, consequently, contribute to preventing cardiovascular disease.

Alpha-tocopherol supplementation decreases electronegative low-density lipoprotein concentration [LDL(-)] in haemodialysis patients

BACKGROUND

Oxidative stress is a significant contributor to cardiovascular diseases (CVD) in haemodialysis (HD) patients, predisposing to the generation of oxidized low-density lipoprotein (oxLDL) or electronegatively charged LDL subfraction. Antioxidant therapy such as alpha-tocopherol acts as a scavenger of lipid peroxyl radicals attenuating the oxidative stress, which decreases the formation of oxLDL. The present study was designed to investigate the influence of the alpha-tocopherol supplementation on the concentration of electronegative low-density lipoprotein [LDL(-)], a minimally oxidized LDL, which we have previously described to be high in HD patients.

METHODS

Blood samples were collected before and after 120 days of supplementation by alpha-tocopherol (400 UI/day) in 19 stable HD patients (50 +/- 7.8 years; 9 males). The concentrations of LDL(-) in blood plasma [using an anti-LDL- human monoclonal antibody (mAb)] and the anti-LDL(-) IgG auto-antibodies were determined by ELISA. Calculation of body mass index (BMI) and measurements of waist circumference (WC), triceps skin folds (TSF) and arm muscle area (AMA) were performed.

RESULTS

The plasma alpha-tocopherol levels increased from 7.9 microM (0.32-18.4) to 14.2 microM (1.22-23.8) after the supplementation (P = 0.02). The mean concentration of LDL(-) was reduced from 570.9 microg/mL (225.6-1241.0) to 169.1 microg/mL (63.6-621.1) (P < 0.001). The anti-LDL(-) IgG auto-antibodies did not change significantly after the supplementation. The alpha-tocopherol supplementation also reduced the total cholesterol and LDL-C levels in these patients, from 176 +/- 42.3 mg/dL to 120 +/- 35.7 mg/dL (P < 0.05) and 115.5 +/- 21.4 mg/dL to 98.5 +/- 23.01 mg/dL (P < 0.001), respectively.

CONCLUSION

The oral administration of alpha-tocopherol in HD patients resulted in a significant decrease in the LDL(-), total cholesterol and LDL-C levels. This effect may favour a reduction in cardiovascular risk in these patients, but a larger study is required to confirm an effect in this clinical setting.

Membranes for dialysis: can we do without them?

Over the past five decades, membranes used for the treatment of chronic kidney disease have continuously evolved. In the course of this evolution, the use of classical non-modified cellulose membranes has declined in favor of cellulose-based membranes in which the basic structure has been modified to improve the biocompatibility profile of the material as well as membranes based on synthetic polymers. In addition to providing improved biocompatibility, manufacturing methods have been innovatively adapted to produce membranes with optimized pore size and pore size distribution. This has led to the more effective removal of molecules involved in the development of complications associated with dialysis treatment. More recently, the approach has been move membranes beyond being just selective barriers with a high performance and to incorporate biological function. Despite these advances, membranes in current clinical use represent a compromise: while efficient in their removal of water soluble compounds, they are non selective, retain some bioreactivity and differ in their ability to adsorb endotoxins or bacterial fragments that may be present in the dialysis fluid. In this paper, an overview of the membranes used in current clinical practice and their limitations are discussed, together with approaches to solute transport in which no membranes are used.

Vitamin E in renal therapeutic regiments

Administration of vitamin E in children with immunoglobulin A (IgA) nephropathy, focal segmental glomerulosclerosis (FSGS) and type I diabetes demonstrated potential towards ameliorating progression. Oral vitamin E therapy reduced endothelial dysfunction, lipid peroxidation and oxidative stress in patients with chronic kidney failure (CKF). Moreover, the use of vitamin E-bonded hemodialyzers reduced atherosclerotic changes, erythropoietin dosage and muscular cramps in patients on hemodialysis (HD). However, several controlled clinical trials failed to document beneficial effects on the study subjects' cardiovascular and renal outcomes. A recent report of increased all-cause mortality in adult patients receiving high dose vitamin E therapy has caused considerable concern and debate. These issues regarding the efficacy and safety of vitamin E in renal therapeutic regimens will be reviewed in this article.

A systematic review of the effect of the Excebrane dialyser on biomarkers of lipid peroxidation

BACKGROUND

Oxidative stress is prevalent in dialysis patients and has been implicated in the pathogenesis of cardiovascular disease and anaemia. We conducted a systematic review and meta-analysis to examine the effect of Excebrane, a vitamin E-coated cellulose-based dialyser, on circulating biomarkers of lipid peroxidation, as surrogate markers of oxidative stress.

METHODS

The primary sources used to identify candidate studies included PubMed, the Cochrane Central Register of Controlled Trials, a bibliography provided by the dialyser manufacturer, and a manual search of abstracts from proceedings of scientific meetings and review articles. Studies were selected for analysis if their design included a comparator group (primarily within patient comparison, i.e. pre- and post-study evaluations). For the meta-analysis, we computed the overall change of the outcome from baseline using a random-effects model. A supplemental analysis was performed in which the absolute levels of these biomarkers of lipid peroxidation were converted to a common unit by calculating standardized effect sizes.

RESULTS

Fourteen peer-reviewed articles met the criteria. The studies consisted of 11 single arm, one randomized crossover and two randomized controlled trials, with a total of 37 to 158 evaluable patients, according to the outcome of interest analysed. Due to the paucity of randomized trials, the meta-analysis was limited to the Excebrane arm of each study. When the studies were combined according to similar measurement units, the overall mean decrease in malondialdehyde (MDA) level was -0.3 mM (95% CI, -0.5 to -0.1 mM; seven studies) and -0.8 nmol/mg low-density lipoprotein (LDL) (95% CI, -1.3 to -0.4 nmol/mg LDL; three studies), respectively. The summary estimate revealed a non-significant decrease in pre-dialysis thiobarbituric acid reactive substances (TBARS) level of 0.4 microM (95% CI, -1.2 to 0.4 microM; three studies). When the MDA and TBARS studies were combined using the standardized effect size, the mean decrease in these biomarkers of lipid peroxidation was statistically significant at -1.7 units (95% CI, -2.7, -0.7 units; 13 studies). A meta-analysis on the effect of Excebrane on pre-dialysis levels of oxidized-LDL could not be performed due to study heterogeneity.

CONCLUSION

The conversion of dialysis patients to a vitamin E-coated dialyser is associated with an improvement in circulating biomarkers of lipid peroxidation, which is of potential clinical benefit.

Hemodialysis reduces inhibitory effect of plasma ultrafiltrate on LDL oxidation and subsequent endothelial reactions

Oxidative modification of low-density lipoprotein (LDL) and its deleterious effect on endothelium is implicated in the pathogenesis of atherosclerosis. Endothelium responds to such an insult by upregulating the synthesis of heme oxygenase-1 (HO-1) and ferritin. Endothelial cell damage and dysfunction have been observed in patients with chronic kidney disease (CKD) on maintenance hemodialysis (HD). We studied the effect of low-molecular-weight components of uremic plasma on LDL oxidation and LDL-oxidation-provoked endothelial cell reactions, such as the induction of cytotoxicity and the upregulation of cell-protective HO-1 and ferritin. Plasma ultrafiltrate (molecular weight<5000 Da) from CKD patients on HD or when treated conservatively exhibited a pronounced inhibition on heme-mediated oxidative modification of LDL. Endothelial cell cytotoxicity provoked by LDL oxidation was also attenuated by plasma ultrafiltrate from CKD patients. During HD treatment, a dramatic drop occurred in the retardation of oxidative reactions, and a loss of endothelial cytoprotection exerted by plasma ultrafiltrate was noted. The upregulation of HO-1 and ferritin in response to oxidative stress of LDL was blunted by uremic plasma ultrafiltrate that was released by the end of HD. The decreased antioxidant capacity of ultrafiltrate after HD occurred as a consequence of the intradialytic removal of L-ascorbic acid, uric acid, bilirubin, 3-indoxyl sulfate, indoxyl-beta-D-glucuronide, p-cresol, and phenol. Intradialytic removal of L-ascorbic acid, uric acid, bilirubin, 3-indoxyl sulfate, indoxyl-beta-D-glucuronide, p-cresol, and phenol increases the risk of LDL oxidation and subsequent endothelial cell damage, which underlines the importance of activation of cytoprotective HO-1 and ferritin in endothelium.

Pharmacologic adjuvants to epoetin in the treatment of anemia in patients on hemodialysis

Anemia is a common complication of chronic kidney disease, particularly in patients who are on dialysis. The use of recombinant human erythropoietin has led to the eradication of severe anemia in the dialysis population. Correction of anemia in these patients has been associated with better quality of life and clinical outcomes. Some hemodialysis patients have anemia that either is relatively refractory to epoetin therapy or requires very high doses of epoetin (i.e., hyporesponsiveness), despite having adequate iron stores, and are thus unable to achieve or maintain target hemoglobin levels. Several pharmacologic agents have been studied for effects on improving response to epoetin, either to counter hyporesponsiveness or simply to reduce epoetin use for purely economic reasons. This review examines the available literature regarding the efficacy of these potential pharmacologic adjuvants to epoetin in the treatment of anemia in patients on maintenance hemodialysis, with special emphasis on androgens, vitamin C (ascorbic acid), and L-carnitine. A review of published guidelines and recommendations for use of these agents in hemodialysis patients is provided.