Effects of methionine loading on plasma and erythrocyte sulphur amino acids and sulph-hydryls before and after co-factor supplementation in haemodialysis patients.

BACKGROUND: Hyperhomocysteinaemia, which is potentially atherogenic, is common in chronic haemodialysis (HD) patients but the reason for this is not yet known. The methionine (Met) loading test (MLT) is used to test the capacity of homocysteine (Hcy) disposal by the trans-sulphuration pathway and thus may provide information on the metabolism of sulphur amino acids. The availability of vitamin B(6) and folic acid, as co-factors for Hcy metabolism may affect the response to MLT. In the present study, we compared the effect of Met loading on plasma and erythrocyte (RBC) sulphur amino acids and sulph-hydryls before and after co-factor supplementation in healthy subjects and HD patients. METHODS: In 10 HD patients and 10 healthy subjects the effect of Met loading, 0.1 g/kg BW, on plasma and RBC methionine metabolites was studied over 7 h, before and after 4 weeks supplementation with high daily doses of vitamin B(6) (200 mg) and folic acid (15 mg). RESULTS: MLT before vitamin supplementation in HD patients, compared to the healthy subjects, caused significantly greater increases in plasma Hcy levels (43+/-12 vs 15+/-5 micromol/l), cysteinesulphinic acid (CSA) (1.34 vs 0.36 micromol/l) and gamma-glutamylcysteine (0.98+/-0.83 vs -01+/-0.42 micromol/l) and no decline in plasma cysteine (Cys) (0.5+/-33.9 vs -31+/-26 micromol/l), but no significant differences in plasma taurine, cysteinylglycine, and glutathione concentrations. In RBCs there was a small increase in Hcy levels and a more marked increase in Tau levels, with no difference between the healthy subjects and HD patients. Vitamin supplementation in pharmacological doses failed to correct the abnormal responses to MLT in the HD patients. CONCLUSIONS: Oral methionine loading in HD patients leads to higher accumulation of Hcy and other Met metabolites in plasma and RBCs than in healthy subjects, indicating impaired metabolism of sulphur amino acids via the trans-sulphuration pathway. Supplementation with high doses of vitamin B(6) and folic acid does not correct this impairment, suggesting that it most probably is not due to lack of these co-factors.     

Effects of vitamin E-coated dialyzer on oxidative stress and inflammation status in hemodialysis patients: a systematic review and meta-analysis

Background: Vitamin E-coated dialyzer may have an effect on oxidative stress and inflammation status in hemodialysis (HD) patients. Therefore, we performed a systematic review to assess the anti-oxidation and anti-inflammatory effects of vitamin E-coated dialyzer in HD patients. Methods: The randomized controlled trials (RCTs) and quasi-RCTs of vitamin E-coated dialyzer versus conventional dialyzer for HD patients were searched from multiple databases. We screened relevant studies according to predefined inclusion criteria and performed meta-analyses using RevMan 5.1 software. Results: Meta-analysis showed vitamin E-coated dialyzer therapy could significantly decrease the serum thiobarbituric acid reacting substances (TBARS) (SMD, ?0.95; 95% CI, ?1.28 to ?0.61; p?p?=?0.005), interleukin-6 (IL-6) (SMD, ?0.65; 95% CI, ?0.97 to ?0.32; p?p?=?0.03) compared with that of the control group. However, vitamin E-coated dialyzer did not result in increasing the total antioxidant status (TAS) (SMD, 0.23; 95% CI, ?0.16 to 0.61; p?=?0.25) and the fractional clearance of urea index (Kt/v) levels (MD, ?0.07; 95% CI, ?0.14 to 0.00; p?=?0.06), in addition, there was no significant difference in plasma superoxide dismutase (SOD) level compared with that of the conventional dialyzer &; oral vitamin E group (SMD, 0.28; 95% CI, ?0.20 to 0.75; p?=?0.26). Conclusions: Vitamin E-coated dialyzer can reduce the oxidative stress and inflammation status reflected by the decreasing of serum TBARS, oxLDL, CRP, and IL-6 levels, and this new dialyzer does not affect the dialysis adequacy.     

Effects of a vitamin E-bonded membrane and of glutathione on anemia and erythropoietin requirements in hemodialysis patients

BACKGROUND: The oxidative damage of RBC membranes in hemodialysis (HD) patients increases red blood cell (RBC) susceptibility to hemolysis and impairs cell survival. Reduction of the oxidative stress might lead to better control of anemia and reduction of the erythropoietin (rhEPO) dose. METHODS: We studied 38 stable HD patients, given a mean dose of rhEPO of 104+/-65 U/kg BW/week, at baseline and during antioxidant treatment with either a full or a 50% dose of EPO. Antioxidant treatment involved the combined use of glutathione, GSH (1200 mg i.v. at the end of each dialysis session) and a vitamin E-bonded HD membrane, CL-E. RBC and reticulocyte counts were done monthly. RBC survival (51Cr T/2) was assayed in 18 patients before and after the end of the study. Oxidative status was determined in 10 patients by measuring plasma concentrations of malondyhaldeide-4-hydroxynonenal (MDA-4HNE), reactive oxygen molecular species (ROMs), and oxydized-LDL (oxLDL) as indices of oxidative stress, alpha-tocopherol and total thiols as single antioxidants, and TAS as a marker of total antioxidant plasma activity. RESULTS: Antioxidant treatment significantly reduced the high basal plasma concentrations of MDA4HNE and oxLDL, and significantly increased those of alpha-tocopherol, whereas TAS and thiols were unmodified. These changes lasted after the reduction of EPO. Anemia significantly improved with treatment, due to a significant increase in RBC survival. A close direct linear relationship was detected between plasma levels of vitamin E and hemoglobin. CONCLUSIONS: Adequate control of oxidative stress achieves better control of anemia in HD patients. Since several antioxidant systems are impaired in uremia, the combined use of the CL-E membrane and GSH seems to be the best antioxidant therapy so far, with significant saving of the rhEPO dose.     

Effects of vitamin C infusion and vitamin E-coated membrane on hemodialysis-induced oxidative stress

Chronic hemodialysis (HD) patients manifest anemia and atherosclerosis with associated oxidative stress. We explored whether intravenous infusion of vitamin C (VC) and/or use of vitamin E (VE)-coated dialysis membrane could palliate HD-evoked oxidative stress. Eighty patients undergoing chronic HD were enrolled and randomly assigned into four groups: HD with intravenous VC (n=20), HD with VE-coated dialyzer (n=20), HD with both (n=20), and HD with neither (n=20). We evaluated oxidative stress in blood and plasma, erythrocyte methemoglobin/ferricyanide reductase (red blood cells (RBC)-MFR) activity, plasma methemoglobin, and pro-inflammatory cytokines in these patients. All patients showed marked increases (14-fold) in blood reactive oxygen species (ROS) after HD. The types of ROS were mostly hydrogen peroxide, and in lesser amounts, O2*- and HOCl. HD resulted in decreased plasma VC, total antioxidant status, and RBC-MFR activity and increased plasma and erythrocyte levels of phosphatidylcholine hydroperoxide (PCOOH) and methemoglobin. Intravenous VC significantly palliated HD-induced oxidative stress, plasma and RBC levels of PCOOH, and plasma methemoglobin levels and preserved RBC-MFR activity. The VE-coated dialyzer effectively prevented RBCs from oxidative stress, although it showed a partial effect on the reduction of total ROS activity in whole blood. In conclusion, intravenous VC plus a VE-coated dialyzer is effective in palliating HD-evoked oxidative stress, as indicated by hemolysis and lipid peroxidation, and by overexpression of proinflammation cytokines in HD patients. Using VE-coated dialyzer per se is, however, effective in reducing lipid peroxidation and oxidative damage to RBCs.     

Electrolyzed-reduced water reduced hemodialysis-induced erythrocyte impairment in end-stage renal disease patients

Chronic hemodialysis (HD) patients increase erythrocyte susceptibility to hemolysis and impair cell survival. We explored whether electrolyte-reduced water (ERW) could palliate HD-evoked erythrocyte impairment and anemia. Forty-three patients undergoing chronic HD were enrolled and received ERW administration for 6 month. We evaluated oxidative stress in blood and plasma, erythrocyte methemoglobin (metHb)/ferricyanide reductase activity, plasma metHb, and proinflammatory cytokines in the chronic HD patients without treatment (n=15) or with vitamin C (VC)- (n=15), vitamin E (VE)-coated dialyzer (n=15), or ERW treatment (n=15) during an HD course. The patients showed marked increases (15-fold) in blood reactive oxygen species, mostly H(2)O(2), after HD without any treatment. HD resulted in decreased plasma VC, total antioxidant status, and erythrocyte metHb/ferricyanide reductase activity and increased erythrocyte levels of phosphatidylcholine hydroperoxide (PCOOH) and plasma metHb. Antioxidants treatment significantly palliated single HD course-induced oxidative stress, plasma and RBC PCOOH, and plasma metHb levels, and preserved erythrocyte metHb /ferricyanide reductase activity in an order VC>ERW>VE-coated dialyzer. However, ERW had no side effects of oxalate accumulation easily induced by VC. Six-month ERW treatment increased hematocrit and attenuated proinflammatory cytokines profile in the HD patients. In conclusion, ERW treatment administration is effective in palliating HD-evoked oxidative stress, as indicated by lipid peroxidation, hemolysis, and overexpression of proinflammatory cytokines in HD patients.     

Haemolysis in haemodialysis patients: evidence for impaired defence mechanisms against oxidative stress.

BACKGROUND: Uraemic patients have a decreased ability to withstand oxidative stress. It is postulated that their antioxidant capacity is reduced, yet the mechanism remains unclear. Recently 33 haemodialysis (HD) patients were exposed to chloramine contamination in the water supply. This led to haemolysis in 24 patients, while nine were unaffected. In the former group haemoglobin decreased from 11.7+/-1.1 to 8.5+/- 1.4 g/dl (P<0.0001) and returned to 11.4+/-0.9 g/dl (P<0.0001) following recovery. During haemolysis, haptoglobin was 38.4+/-10.6 vs 138.1+/-8.3 ng/dl (P<0.0001) following recovery. METHODS: To explore the factors affecting the severity of haemolysis we studied extracellular and intracellular anti-oxidant defence mechanisms 3 months after recovery. In 29 patients and 20 controls we determined plasma glutathione (GSH), and the erythrocyte enzymes glutathione peroxidase (GSH-Px), glutathione reductase (GSH-Rx), and superoxide dismutase (SOD). Serum malondialdehyde (MDA) was measured as a marker of oxidative stress. RESULTS: Plasma GSH was lower in patients as compared to controls (5.49+/-0.26 vs 7.4+/-0.5 micromol/l, P<0.005). There was an inverse correlation between GSH and the degree of haemolysis (r=-0.42, P<0.02). Patients had higher GSH-Rx (4.64+/-0.15 vs 3.97+/-0.12 U/gHb, P<0.02), lower GSH-Px (29. 7+/-1.85 vs 35.5+/-1.62 U/gHb, P<0.001), and similar SOD (0.63+/-0. 02 vs 0.51+/-0.02 U/mgHb) as compared to controls. There was no correlation between the enzyme levels and the degree of haemolysis. MDA was higher in patients (2.37+/-0.07 vs 0.97+/-0.1 nmol/ml, P<0. 0001). There was a correlation between MDA and the years patients were on HD (r=0.43, P<0.02). CONCLUSIONS: These data indicate that HD patients have an impaired anti-oxidant response, which may be attributed in part, to plasma GSH deficiency. Patients with the lowest plasma GSH levels are more susceptible to oxidative stress and consequent haemolysis.     

Oxidative status and prevalent cardiovascular disease in patients with chronic renal failure treated by hemodialysis

BACKGROUND: Hemodialysis (HD) patients are exposed to oxidative stress which contributes to cardiovascular disease (CVD). The purpose of this study was to investigate the oxidative and antioxidative status in HD patients with (CVD+, n = 38) and without (CVD-, n = 67) prevalent CVD. PATIENTS AND METHODS: A total of 105 HD patients and 21 healthy controls were assessed for lipid peroxidation indices (plasma malondialdehyde (MDA)), oxidizability of apolipoprotein B-containing lipoproteins (apo B-deltaMDA) and red blood cells (RBC-MDA) together with various components of the antioxidant system in plasma (paraoxonase/arylesterase activities, total carotenoids, vitamins C and E) and RBC (superoxide dismutase and glutathione peroxidase activities). RESULTS: Plasma MDA and RBC-MDA were significantly higher, vitamin C and total carotenoid levels were significantly lower in both CVD+ and CVD- HD groups than in the control group. Plasma MDA levels were significantly higher and serum paraoxonase activity, uric acid and albumin levels were significantly lower in patients with CVD+ HD patients compared to those of the CVD- patients. CONCLUSION: This study suggests that the elevated level of plasma MDA and the lower activity of paraoxonase could contribute to the increased incidence of cardiovascular disease in hemodialysis patients.     

N-acetylcysteine reduces malondialdehyde levels in chronic hemodialysis patients--a pilot study

BACKGROUND: Oxidative stress has been implicated in the development of endothelial damage in hemodialysis (HD). We have assessed the effects of N-acetylcysteine (NAC), a compound with antioxidant effects, on malondialdehyde (MDA), a marker of oxidative stress on lipid peroxidation. METHODS: A clinical trial was conducted in which 24 chronic HD patients were divided into 2 groups according to gender, age, time on HD and cause of renal failure. The NAC group (n = 12) received 600 mg of NAC twice a day for 30 days. The remaining patients constituted the control group (n = 12). MDA levels were measured pre- and post-dialysis at the beginning of the study (baseline) and on day 30 (30 days). RESULTS: Baseline pre- and post-dialysis MDA levels were not different between both groups and were above normal values. A significant decrease was found in the NAC group when either pre- or post-dialysis MDA levels were compared to the corresponding control group levels on day 30 (pre-dialysis NAC vs control group 3.01 +/- 0.6 vs 4.5 +/- 0.73 micromol/l, p < 0.0001, post-dialysis NAC vs control group 2.76 +/- 0.5 vs 4.39 +/- 0.7 micromol/l, p < 0.0001). Only in the NAC group were pre-dialysis MDA 30-day levels different from pre-dialysis baseline levels (3.01 +/- 0.6 vs 5.07 +/- 1.6 micromol/l, p < 0.002). Post-dialysis MDA 30-day concentrations were significantly lower than post-dialysis MDA baseline levels (2.76 +/- 0.5 vs 4.32 +/- 0.7 micromol/l, p < 0.002) and pre-dialysis MDA 30-day measurements (2.76 +/- 0.5 vs 3.01 +/- 0.6 micromol/l, p < 0.011). CONCLUSIONS: MDA levels are elevated in chronic HD patients and are not significantly reduced by HD. NAC significantly reduces malondialdehyde levels in chronic HD patients.     

Is the bioreactivity of vitamin-E-modified dialyzer an expression of increased plasmatic vitamin E concentration?

The present study was designed to test the biocompatibility of a new vitamin E-modified multilayer membrane compared with highly biocompatible polysulphone dialyzer and acrylonitrile dialyzer. Thirty patients (mean age 53.2 +/- 15.3 SD years; dialytic age 36 +/- 5.6 months) were selected for the study. The study was divided into three periods of 6 months (phases A, B and C). In the first phase (from Jan. 1999 to June 1999) patients undergoing maintenance bicarbonate dialysis were randomly divided into three filter groups composed, respectively, of 10 patients: acrylonitrile group, polysulphone group and vitamin E-coated dialyzer group. In the phase B (from July 1999 to Dec. 1999) and in the phase C (from Jan. 2000 to June 2000), all three groups changed their own dialysis membranes. Vitamin E-coated dialyzer causes significant decreases in beta(2)-microglobulin, ferritin and immunoglobulin G, a normalization of complement C3 and an increase of plasmatic vitamin E compared to other filters. In the VE group homocysteine decreases but not in a significant manner. In addition, this dialyzer seems not to influence lipid pattern and protein-energy malnutrition parameters. These results clearly show a positive effect of this new filter in influencing different biochemical parameters, perhaps saving vitamin E and reducing polymorphonuclear cell activation.     

Low dialysance of asymmetric dimethylarginine (ADMA)--in vivo and in vitro evidence of significant protein binding

BACKGROUND: Increased blood levels of the endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA) predict cardiovascular mortality in patients with end-stage renal disease. Despite its low molecular weight, available information on the impact of hemodialysis (HD) on ADMA plasma levels is controversial. METHODS: We assessed plasma concentrations, dialyzer clearance and total amount of ADMA removed in 30 patients with end-stage renal disease during regular HD. In addition, plasma ADMA levels were assessed in 10 patients with acute renal failure treated with extended HD. RESULTS: Regular HD decreased plasma creatinine (from 774 +/- 42 to 312 +/- 17 micromol/l) and urea (from 24.5 +/- 1.5 to 8.4 +/- 0.5 mmol/l) concentrations significantly (both p < 0.001), whereas plasma ADMA remained unchanged (4.35 +/- 0.19 vs. 4.76 +/- 0.24 micromol/l). ADMA clearance was 92 +/- 6 ml/min, and the total amount removed in the spent dialysate was 37 +/- 4 micromol. The clearances of creatinine (161 +/- 3 ml/min) and of urea (173 +/- 3 ml/min) were significantly higher. Furthermore, even during extended HD, plasma ADMA concentrations did not decrease significantly (1.73 +/- 0.22 vs. 1.63 +/- 0.18 micromol/l). CONCLUSION: In conclusion, dialysance of ADMA is markedly lower than expected from its molecular weight because of significant protein binding of the substance. Since markedly increased ADMA blood concentrations have been linked to cardiovascular complications due to atherosclerosis in patients with ESRD, new strategies should be evaluated to remove this putative uremic toxin.     

Effects of vitamin E-coated dialysis membranes on anemia,nutrition and dyslipidemia status in hemodialysis patients: a meta-analysis

Abstract

Background: This was controversial whether vitamin E-coated dialyzer therapy was beneficial for the complications associated with hemodialysis. Therefore, we performed this systematic review to evaluate the effects of vitamin E-coated dialyzer. Methods: Related trials were searched from multiple electronic databases. We conducted meta-analysis to assess changes in the predefined outcomes using RevMan 5.3 software. Results: Meta-analysis showed vitamin E-coated dialyzer therapy could decrease erythropoietin (EPO) resistance index (SMD, ?0.24; 95% CI, ?0.47 to ?0.01; p?=?0.04). However, pooled-analysis showed vitamin E-coated dialyzer therapy could not decrease weekly EPO dose (SMD, ?0.11; 95% CI, ?0.32 to 0.09; p?=?0.28) and intima–media thickness (IMT) of the carotid artery (MD, ?0.09; 95% CI, ?0.2 to 0.01; p?=?0.09), and vitamin E-coated dialyzer therapy did not improve the serum hemoglobin (MD, ?0.03; 95% CI, ?0.18 to 0.13; p?=?0.74), albumin levels (SMD, ?0.64; 95% CI, ?1.62 to 0.34; p?=?0.2), in addition, there was no significant difference in serum cholesterol (SMD, ?0.07; 95% CI, ?0.45 to 0.31; p?=?0.71), triglycerides (MD, ?2.77; 95% CI, ?32.42 to 26.87; p?=?0.85), high density lipoprotein (HDL) (SMD, 0.24; 95% CI, ?0.14 to 0.62; p?=?0.22) and low density lipoprotein (LDL) (SMD, 0.00; 95% CI, ?0.38 to 0.37; p?=?0.98) levels. Conclusions: Vitamin E-coated dialyzer may reduce the EPO resistance, but there is no conclusive evidence that vitamin E-coated dialyzer can improve the renal anemia, malnutrition, dyslipidemia and atherosclerosis status in hemodialysis (HD) patients. However, high-quality trials with hard clinical endpoints are required to fully elucidate the clinical value of vitamin E-coated dialyzer therapy.     

Effect of vitamin E therapy on oxidative stress and erythrocyte osmotic fragility in patients on peritoneal dialysis and hemodialysis

BACKGROUND: Several medications have been tested with the aim of decreasing oxidative stress and erythrocyte osmotic fragility in patients on dialysis. The aim of the present study was to assess the influence of vitamin E therapy on oxidative stress and erythrocyte osmotic fragility in patients on hemodialysis (HD) and peritoneal dialysis (PD). METHODS: This was a placebo-controlled study. The study was performed on 34 HD patients, 13 PD patients and 22 healthy volunteers with a mean age of 45.57 +/- 8.54 years. HD patients were divided into 2 groups: treatment (n=19) and control (n=15). Vitamin E was administered, 300 mg/day, to the HD treatment group and PD patients for 20 weeks. Lipid peroxidation, antioxidant condition and erythrocyte osmotic fragility (EOF) were examined before and after treatment. RESULTS: Before the treatment, the levels of EOF (p<0.001) and malondialdehyde (MDA) (p<0.001) were significantly lower, and erythrocyte superoxide dismutase (SOD) (p=0.001) and vitamin E levels (p<0.001) were significantly higher in the healthy group than PD and HD groups. Serum vitamin E increased from 0.93 +/- 0.16 to 1.09 +/- 0.14 mg/dL (p=0.001), EOF decreased from 0.49% +/- 0.03% to 0.42% +/- 0.04% NaCl (p<0.001), and plasma MDA values decreased from 2.77 +/- 0.87 to 2.20 +/- 0.767 nmol/mL (p=0.018) in the HD treatment group after vitamin E treatment. Levels of EOF decreased from 0.51% +/- 0.09% to 0.43% +/- 0.03% NaCl in the PD treatment group after vitamin E treatment (p=0.021). CONCLUSION: Vitamin E therapy is effective in decreasing the levels of EOF in patients on HD and PD, and it is also effective in decreasing lipid peroxidation in patients on HD.     

Plasma protein thiol oxidation and carbonyl formation in chronic renal failure

BACKGROUND: Myeloperoxidase-catalyzed oxidative pathways have recently been identified as an important cause of oxidant stress in uremia and hemodialysis (HD), and can lead to plasma protein oxidation. We have examined patterns of plasma protein oxidation in vitro in response to hydrogen peroxide (H2O2) and hypochlorous acid (HOCl). We measured thiol oxidation, amine oxidation, and carbonyl concentrations in patients on chronic maintenance HD compared with patients with chronic renal failure (CRF) and normal volunteers. We have also examined the effect of the dialysis procedure on plasma protein oxidation using biocompatible and bioincompatible membranes. METHODS: Plasma proteins were assayed for the level of free thiol groups using spectrophotometry, protein-associated carbonyl groups by enzyme-linked immunosorbent assay, and oxidation of free amine groups using a fluorescent spectrophotometer. RESULTS: In vitro experiments demonstrate HOCl oxidation of thiol groups and increased carbonyl formation. In vivo, there are significant differences in plasma-free thiol groups between normal volunteers (279 +/- 12 micromol/L), CRF patients (202 +/- 20 micromol/L, P = 0.005) and HD patients (178 +/- 18 micromol/L, P = 0.0001). There are also significant differences in plasma protein carbonyl groups between normal volunteers (0.76 +/- 0.51 micromol/L), CRF patients (13.73 +/- 4.45 micromol/L, P = 0.015), and HD patients (16.95 +/- 2.62 micromol/L, P = 0.0001). There are no significant differences in amine group oxidation. HD with both biocompatible and bioincompatible membranes restored plasma protein thiol groups to normal levels, while minimally affecting plasma protein carbonyl expression. CONCLUSIONS: First, both CRF and HD patients have increased plasma protein oxidation manifested by oxidation of thiol groups and formation of carbonyl groups. Second, HD with biocompatible and bioincompatible membranes restored plasma protein thiol groups to normal levels. Third, these experiments suggest that there is a dialyzable low molecular weight toxin found in uremia that is responsible for plasma protein oxidation.     

Effects of high-dose folic acid and pyridoxine on plasma and erythrocyte sulfur amino acids in hemodialysis patients.

In this investigation, sulfur amino acids (sAA) and sulfhydryls were determined in the plasma and erythrocytes (RBC) of 10 uremic patients on regular hemodialysis (HD) treatment and 10 healthy subjects, before and after supplementation with 15 mg/d of folic acid and 200 mg/d of pyridoxine for 4 wk. The basal total plasma concentrations of homocysteine (Hcy), cysteine (Cys), cysteinylglycine (Cys-Gly), gamma-glutamylcysteine (gamma-Glu-Cys), glutathione (GSH), and free cysteinesulfinic acid (CSA) were significantly higher in HD patients when compared to healthy subjects, whereas methionine (Met) and taurine (Tau) concentrations were the same in the two groups. HD patients showed significantly higher RBC levels of Hcy and Cys-Gly, whereas the RBC concentrations of Met, Cys, Tau, and GSH were not different from those in the healthy subjects. The plasma concentrations of sAA and sulfhydryls differed compared with RBC levels in the healthy subjects and HD patients. In both groups, supplementation with high doses of folic acid and pyridoxine reduced the plasma Hcy concentration. In addition, increased plasma concentrations of Cys-Gly and GSH were found in the HD patients and of CSA in the healthy subjects. After vitamin supplementation, the RBC concentrations of Hcy, Cys, and GSH increased and that of Tau decreased in healthy subjects. The only significant finding in RBC of HD patients was an increase in GSH levels after supplementation. This study shows several RBC and plasma sAA and sulfhydryl abnormalities in HD patients, which confirms earlier findings that RBC and plasma pools play independent roles in interorgan amino acid transport and metabolism. Moreover, high-dose supplementation with folic acid and pyridoxine significantly reduced Hcy levels, but did not restore the sAA and sulfhydryl abnormalities to normal levels. The increase that was observed in GSH after vitamin supplementation may have a beneficial effect in improving blood antioxidant status in uremic patients. Finally, the findings of elevated plasma Cys levels correlating to the elevated plasma Hcy levels in the presence of elevated plasma CSA levels, both before and after vitamin supplementation, led to the hypothesis that a block in decarboxylation of CSA is linked to hyperhomocysteinemia in end-stage renal failure.     

Smoking is associated with alterations of blood thiol-group related antioxidants in patients on hemodialysis

Cardiovascular disease is the major complication and cause of mortality in the dialysis population, accounting for about 40% of deaths. Oxidative stress has been strongly implicated in the pathogenesis of these events. As patients in end-stage renal disease (ESRD) are in a state of elevated free radical activity, the aim of the present study was to investigate the negative impact of smoking in 45 male hemodialysis (HD) patients. These patients, who were 40-85 years of age (mean age 60.9 +/- 13.3 years), had been on hemodialysis for at least 12 months before participating in this study. Fasting blood sampling for serum lipid, albumin, urate, lipid peroxides total blood glutathione (tGSH), non-GSH free sulfhydryl compounds (non-GSH fSH), plasma glutathione peroxidase (pGSHPx), erythrocytes glutathione peroxidase (rGSHPx), plasma glutathione S-transferase (pGST) and erythrocytes glutathione S-transferase (rGST) were determined. Our study showed that the plasma malonyldialdehyde (MDA) concentration was significantly higher in HD patients who smoked than in those who were non- smokers (1.99 +/- 0.53 vs. 1.55 +/- 0.46 nmol/ml, p = 0.008). No association was found between levels of MDA in smokers and BMI, serum cholesterol and triglycerides and smoking index. We also found that the circulating plasma levels of tGSH and non-GSH fSH was lower in the HD patients who smoked (tGSH 164.9 +/- 41.5 vs. 203.4 +/- 45.3 microg/ml; fSH 271.1 +/- 55.8 vs. 308.8 +/- 46.7 microg/ml; p < 0.05 and p < 0.001, respectively). There were no significant differences in the plasma levels of uric acid, pGSHPx, rGSHPx, pGST, rGST, albumin, and age between the 2 groups. Partial correlation analysis of the plasma levels of the measured antioxidants and the smoking index revealed a negative correlation between the plasma levels of tGSH and smoking index (r = -0.62, p < 0.003). Similarly, the plasma levels of tGSH was found negatively correlated with the levels of plasma MDA (r = -0.32, p < 0.05) of the HD patients. In conclusion, our data suggest that cigarette smoking has a negative impact on plasma-circulating products of lipid peroxidation in HD patients. The lower blood levels of the tGSH and non-GSH fSH in HD patients who smoked suggests that these patients may be more susceptible to oxidative damage caused by smoking.     

Influence of oral vitamin E therapy on micro-inflammation and cardiovascular disease markers in chronic hemodialysis patients

BACKGROUND: The aim of this study was to evaluate the influence of oral vitamin E therapy on serum concentrations of several markers of micro-inflammation and cardiovascular disease in chronic hemodialysis (HD) patients. METHODS: 29 HD patients were randomized into two groups: 15 patients were treated orally with 400 mg of vitamin E daily for a period of five weeks, and 14 patients received no antioxidant supplementation. Before and after vitamin E therapy, serum concentrations of vitamin E (high-performance liquid chromatography), pregnancy-associated plasma protein-A (immunochemical--TRACE assay), C-reactive protein (nephelometry), intercellular adhesion molecule-1 (ELISA), and E-selectin (ELISA) were measured. HD patients were compared with 16 healthy controls. RESULTS: Baseline serum concentrations of PAPP-A and CRP were significantly higher in HD patients than in healthy controls (PAPP-A: 26.23+/-11.94 vs. 11.41+/-1.94 mIU/L, p<0.001; CRP: 5.20+/-3.50 vs. 3.40+/-3.80 mg/L, p<0.05). After five weeks of oral vitamin E intake, serum PAPP-A, CRP, ICAM-1, and E-selectin concentrations remained unchanged in both groups of HD patients. CONCLUSION: Chronic micro-inflammation in HD patients is documented by the elevation of CRP and PAPP-A. A daily oral dose of 400 mg of vitamin E does not seem to be able to reduce enhanced oxidative stress and micro-inflammation in chronic HD patients.     

Oxidative stress is reduced by the long-term use of vitamin E-coated dialysis filters

BACKGROUND: Oxidative stress during hemodialysis is thought to promote the progression of vascular complications in hemodialysis patients. The protective role of vitamin E as a lipophilic antioxidant against oxidative stress has been widely investigated. Here we investigated the effects of a vitamin E-coated regenerated cellulose hollow fiber dialyzer (CL-EE) on oxidative stress compared with a polysulfone hollow fiber (CL-PS). METHODS: For at least three months before beginning the protocol, 10 nondiabetic (NDM) patients (70.0 +/- 7.5 years; 6 males and 4 females) and 8 diabetic (DM) patients (65.0 +/- 7.4 years; 4 males, 4 females) were dialyzed with CL-PS. After that, we treated all of the patients with CL-EE for six months. Malondialdehyde (MDA), advanced glycation end products (AGEs), and 8-hydroxydeoxyguanosine (8-OHdG) were monitored as biomarkers for oxidative stress at the start and then at one, three, and six months into treatment with CL-EE. RESULTS: Serum MDA, AGE, and 8-OHdG levels increased after the hemodialysis with CL-PS. The increase of the biomarkers was completely prevented by a single use of CL-EE. Long-term hemodialysis with CL-EE for six months significantly reduced the basal levels of the oxidant markers at one month for AGE and at six months for 8-OHdG in both DM and NDM patients. Serum MDA was reduced in only DM patients at three months. The improvement of the oxidative stress with CL-EE was more prominent in the DM patients. CONCLUSIONS: Long-term treatment with CL-EE efficiently improves the oxidative stress associated with hemodialysis and potentially reduces dialysis complications due to oxidative stress.     

Vitamin E attenuates oxidative stress induced by intravenous iron in patients on hemodialysis

Intravenous iron application to anemic patients on hemodialysis leads to an "oversaturation" of transferrin. As a result, non-transferrin-bound, redox-active iron might induce lipid peroxidation. To test the hypothesis that vitamin E attenuates lipid peroxidation in patients receiving 100 mg of iron(III) hydroxide sucrose complex intravenously during a hemodialysis session, 22 patients were investigated in a randomized cross-over design, either with or without a single oral dose of 1200 IU of all-rac-alpha-tocopheryl acetate taken 6 h before the hemodialysis session. Blood was drawn before and 30, 60, 90, 135, and 180 min after the start of the iron infusion, and areas under the curve (AUC0-180 min) of ratios of plasma malondialdehyde (MDA) to cholesterol and plasma total peroxides to cholesterol (two markers of lipid peroxidation) were determined as the outcome variables. At baseline of the session without vitamin E supplementation, plasma alpha-tocopherol concentrations (27.6 +/- 1.8 micromol/L) and ratios of alpha-tocopherol to cholesterol (5.88 +/- 1.09 mmol/mol) were normal, plasma MDA concentrations were above normal (1.20 +/- 0.28 micromol/ L), and bleomycin-detectable iron (BDI), indicating the presence of redox-active iron, was not detectable. Upon iron infusion, BDI and MDA concentrations increased significantly (P < 0.001). BDI concentrations explained the increase over baseline in MDA concentrations (MDA = 1.29 +/- 0.075 x BDI). Vitamin E supplementation, leading to a 68% increase in plasma alpha-tocopherol concentrations, significantly reduced the AUC0-180 min of MDA to cholesterol (P = 0.004) and peroxides to cholesterol (P = 0.002). These data demonstrate that a single oral dose of vitamin E attenuates lipid peroxidation in patients on hemodialysis receiving intravenous iron. Given that intravenous iron is applied repeatedly to patients on hemodialysis, this therapeutic approach may protect against oxidative stress-related degenerative disease in the long term.     

Convective and diffusive losses of vitamin C during haemodiafiltration session: a contributive factor to oxidative stress in haemodialysis patients.

BACKGROUND: Enhanced oxidative stress in haemodialysis (HD) patients may be considered as a risk factor for accelerated atherosclerosis. Reduced antioxidant defences include impairment in enzyme activities and decreased plasma levels of hydrophilic vitamin C (vit C), and cellular levels of lipophilic vitamin E (vit E). METHODS: We investigated plasma levels of vit C in 19 patients undergoing regular haemodiafiltration (HDF) (mean age 62+/-7 years) and in 1846 healthy elderly subjects (HS) (mean age 69+/-5 years). The contribution of convection and diffusion was determined using paired filtration dialysis (PFD), a modified HDF technique which physically separates convective from diffusive fluxes. Blood samples were collected before and after the HDF session; in addition at 60 min of HDF, samples were drawn from arterial lines (AL) and venous lines (VL), dialysate (D) and ultrafiltrate (UF). Blood levels of total vit C were determined using an HPLC fluorescence method. Markers of oxidative stress were also assessed in both populations as follows: levels of malondialdehyde (MDA) were determined by fluorometric assay, measurements of advanced oxidation protein products (AOPP) and glutathione peroxidase (GSH-Px) activity were performed by spectrophotometric assay, and plasma vit E content was obtained by an HPLC procedure. RESULTS: A significant reduction in plasma vit C level was observed in HDF patients when compared with HS (1.6+/-1.4 microg/ml in HDF vs 6.6+/-3.7 microg/ml in HS; P<0.01). The HDF session was associated with a dramatic reduction in vit C levels (1.87+/-1.57 microg/ml before HDF and 0.98+/-0.68 microg/ml after HDF); at 60 min of HDF, concentrations were as follows: AL=1.35+/-1.27 microg/ml; VL=0.37+/-0.31 microg/ml, D=0.40+/-0.34 microg/ml, UF=1.24+/-1.18 microg/ml; corresponding to a diffusive flux of 271 microg/min and a convective flux of 126 microg/min. Total loss of vit C could be assessed at 66 mg/session (8--230 mg/session). According to this loss of vit C, presence of an oxidative stress was demonstrated in HD population as shown by a significant increase in MDA (1.66+/-0.27 microM in HD vs 0.89+/-0.25 microM in HS; P<0.01) and AOPP (77.5+/-29.3 microM in HD vs 23.5+/-13.2 microM in HS; P<0.01) levels, and a decrease in GSH-Px activity (259.2+/-106.3 U/l in HD vs 661.2+/-92.2 U/l in HS; P<0.01). No change in plasma vit E between both populations (30.7+/-9.1 microM in HD vs 35.3+/-7.34 microM in HS) was observed. CONCLUSIONS: These results suggest that HDF with highly permeable membranes is associated with a significant loss of vit C. Diffusive transport is responsible for two-thirds whereas convective phenomenon accounts for only one-third of this loss.