Dehydroascorbic acid and oxidative stress in haemodialysis patients.

BACKGROUND: The amount of dehydroascorbic acid contained within total ascorbic acid (oxidized as well as non-oxidized forms) in plasma, hereafter referred to as the dehydroascorbic acid fraction, may be a measure of oxidative stress during haemodialysis. In the present study, we determined this fraction in chronic haemodialysis patients. METHODS: Using high performance liquid chromatography, dehydroascorbic acid and total ascorbic acid levels were measured in 80 maintenance haemodialysis patients for a period of > 2 years as well as in 49 controls, to examine a possible association of these compounds with clinical parameters and/or drugs taken by the patients. RESULTS: Dialysis patients who had an increased plasma urate level (P < 0.05) and had been taking allopurinol (P < 0.05) or NSAID (non-steroid anti-inflammatory drugs) (P < 0.01), and dialysis patients who were younger (< or = 55 years), as compared with older dialysis patients (P < 0.01), were found to have a lower dehydroascorbic acid fraction by multivariate analysis. Mean plasma dehydroascorbic acid levels and dehydroascorbic acid fractions were significantly lower in the younger haemodialysis patients (4.8 +/- 0.7 micromol/l and 28.4 +/- 3.9%) than in healthy younger controls (13.3 +/- 1.1 micromol/l and 41.1 +/- 1.8%) (P < 0.0001 and P < 0.01, respectively). Moreover, a correlation was found between plasma dehydroascorbic acid fraction and plasma lipid peroxide (r = 0.66, P < 0.01) in patients who had not been taking allopurinol and/or NSAID. CONCLUSION: We found that dehydroascorbic acid fraction was related to patients' age, plasma urate level and to taking allopurinol or NSAID. Dehydroascorbic acid fraction may be another indirect index of oxidative stress.     

Protective effects of high-density lipoprotein against oxidative stress are impaired in haemodialysis patients.

INTRODUCTION: Cardiovascular diseases represent the major cause of mortality in haemodialysis (HD) patients. Oxidized low-density lipoprotein (Ox-LDL) is a major cardiovascular risk factor, implicated in atherosclerotic plaque formation. It has been suggested that high-density lipoprotein (HD) has the capacity to reduce the oxidative modifications of LDL. The aim of this study is to analyse the protective effects of HDL in HD patients. METHODS: In vitro copper-induced LDL oxidation was evaluated in 12 patients with chronic renal failure (mean age 61.0+/-12.8 years) and compared to 25 healthy subjects (mean age 57.3+/-19.2 years). LDL were incubated in oxygen-saturated PBS, LDL oxidation was initiated by Cu (II) in the presence and absence of HDL and assessed by measuring the absorbance (abs) increase at 234 nm due to conjugated diene formation. Duration of lag time, maximum velocity (V(max.)) of lipid peroxidation, oxidation slope and half-time of maximum diene formation (T (1/2)) were obtained by kinetic modelling analysis. RESULTS: HDL (1.06+/-0.31 vs 1.23+/-0.39 mmol/l) and Apo AI (1. 17+/-0.39 vs 1.49+/-0.20 g/l) levels were decreased in HD patients. In the absence of HDL, LDL obtained from HD patients showed an enhanced susceptibility to oxidation in vitro as demonstrated by the significant decrease in lag time (54.5+/-22.2 vs 79.4+/-37.8 min) and a significant increase in V(max.) (0.026+/-0.006 vs 0.017+/-0. 005 abs/min). In all cases, HDL (from 0.1 to 2 microM) prevented LDL oxidation in vitro; however, this effect was significantly reduced in HD patients: increase in lag time 54.2% vs 150.4% in HD vs controls; increase in T (1/2) 52.2% vs 124.6% in HD vs controls; decrease in V(max). 13.5% vs 38.5% in HD vs controls. CONCLUSIONS: These results suggest that qualitative abnormalities such as an impairment of HDL-associated enzymes are associated with a decrease of HDL levels during HD. Hence, in addition to the known impairment of reverse cholesterol transport, the reduction of HDL protective capacity against oxidative stress could be involved in the development of HD-induced atherosclerosis.     

Enhanced oxidative stress in haemodialysis patients receiving intravenous iron therapy.

BACKGROUND: Iron balance is critical for adequate erythropoiesis and there remains much debate concerning the optimal timing and dosage of iron therapy for haemodialysis patients receiving recombinant human erythropoietin therapy. METHODS: In this study, we examined the influence of baseline ferritin level and intravenous infusion of 100 mg ferric saccharate on the oxidative status of the patients on maintenance haemodialysis. The levels of antioxidant enzymes and lipid peroxides were determined in erythrocytes and plasma of 50 uraemic patients on haemodialysis. These patients were divided into groups 1, 2, and 3, based on their baseline serum ferritin levels of <300, 301-600, and >601 microg/l, respectively. RESULTS: We found that the mean superoxide dismutase (SOD) activities in the erythrocytes were similar in the three groups of patients and did not differ from those of the age-matched controls. On the other hand, all the haemodialysis patients showed significantly higher plasma SOD activity as compared to controls. After intravenous iron infusion, group 3 patients showed the largest decrease in plasma SOD activity. The plasma glutathione peroxidase (GSHPx) activities of the patients in all three groups and the erythrocyte GSHPx activities of the patients in the groups 2 and 3 were lower than those of the healthy controls. In all three groups of patients, no difference in GSHPx activity was found before and after intravenous iron infusion. On the other hand, we found that the average baseline levels of plasma lipid peroxides of all three groups of patients were significantly higher than that of the controls. The patients in group 3 with the highest serum ferritin levels showed the highest levels of plasma lipid peroxides. More importantly, we found that after iron infusion, the patients in all three groups, particularly those in group 3, showed significantly elevated levels of plasma lipid peroxides. CONCLUSION: We demonstrated that increased oxidative stress in the blood circulation of the uraemic patients on haemodialysis is exacerbated by the elevated baseline serum ferritin levels and intravenous iron infusion. The resultant oxidative damage may contribute to the increased incidence of atherosclerosis in the patients with end-stage renal disease on long-term haemodialysis.     

Cardiac troponin T and malondialdehyde modified plasma lipids in haemodialysis patients.

BACKGROUND: In patients with end-stage renal disease (ESRD), treated with haemodialysis, a high overall mortality is observed. A previous study showed that cardiac troponin T (cTnT) is a strong independent predictor of outcome in this population. In this study we investigated possible causes of cTnT increase and its relationship with a marker of oxidative stress. METHODS: In a group of 71 haemodialysis patients (36 male, 35 female, mean age 68.7+/-1.5 years) we determined cTnT and compared its presence with several biochemical parameters and with malondialdehyde (MDA), which is an indicator of oxidative stress. None of the patients suffered an acute coronary event during the observation period. Three measurements of cTnT and MDA were performed with a 2-week interval. Forty-nine patients underwent a transthoracic echocardiography. RESULTS: Twenty-nine patients (or 40.8%) had a positive cTnT determination (defined as cTnT >/=0.10 ng/ml). cTnT positive patients had significantly higher levels of MDA (P=0.0125), C-reactive protein (CRP) (P=0.04) and pre-dialysis urea (P=0.04). Regression analysis showed that both pre-dialysis urea and MDA independently influenced cTnT. No correlation was found with age, dialysis adequacy, post-dialysis urea, total cholesterol, white blood cell count, fibrinogen or any of the echocardiographical parameters. Presence of heart failure, diabetes or use of medication could not discriminate between cTnT positive and cTnT negative patients. MDA levels correlated positively with time on haemodialysis (P=0.0021). Echocardiography showed left ventricular hypertrophy in 88% of the examined patients and impaired wall motion in 35%. Patients with clinical signs of heart failure had a lower ejection fraction and worse wall motion score index. No correlation existed between echocardiographic findings and cTnT or MDA. Survival was independently predicted by cTnT (P=0.0025), MDA (P=0.0007), CRP (P=0.006) and age (P=0.0143). Patients with both cTnT and CRP increase had a survival of <50% at 1 year, compared with 90% in patients with both cTnT and CRP within the normal range and 80% when either CRP or cTnT was increased (chi(2)=12.127; P=0.0023). CONCLUSIONS: This study confirms that the presence of cTnT predicts prognosis in ESRD. The presence of cTnT is linked to oxidative stress, inflammation and uraemia. The absence of specific findings on EKG and echocardiography points towards subclinical myocardial damage caused by endothelial disturbances.     

Long-term use of vitamin E-coated polysulfone membrane reduces oxidative stress markers in haemodialysis patients.

BACKGROUND: Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide synthase and an independent predictor of overall mortality and cardiovascular outcome in haemodialysis (HD) patients. In the present study, we compared the effects of a vitamin E-coated polysulfone membrane (PSE) and a non-vitamin E-coated polysulfone membrane (PS) on oxidative stress markers such as ADMA. METHODS: Thirty-one HD patients were enrolled to this investigation. They were allocated into two groups: in the PSE group (n = 16), PSE was used for 6 months, followed by PS for an additional 12 months; in the PS group (n = 15), PS was used for the entire observation period. Plasma ADMA, oxidized low density lipoprotein (Ox-LDL) and malondialdehyde LDL (MDA-LDL) levels were measured at baseline, 3, 6, 12 and 18 months. Plasma ADMA in peritoneal dialysis (PD) patients and in healthy individuals was also measured. RESULTS: Predialysis concentrations of ADMA (0.72+/- 0.13 nmol/ml) were significantly higher in the HD group than in both PD patients (0.63+/-0.10 nmol/ml, P<0.01) and healthy individuals (0.44+/-0.01 nmol/ml, P<0.0001). Treatment with PSE for 6 months significantly reduced predialysis levels of ADMA (0.54+/-0.09 nmol/ml) compared with baseline (0.74+/-0.12 nmol/ml; P<0.01). Predialysis levels of Ox-LDL and MDA-LDL after 6 months therapy with PSE were also significantly lower than baseline values. Treatment with PS subsequent to treatment with PSE again increased ADMA, Ox-LDL and MDA-LDL back to baseline levels. In the PS group, ADMA, Ox-LDL and MDA-LDL levels remained unchanged during the entire treatment period of 18 months. CONCLUSIONS: We confirmed that use of PSE reduced ADMA that had accumulated in HD patients. This finding indicates that PSE exerts anti-oxidant activity. A randomized controlled study will be required to determine whether PSE prevents cardiovascular diseases and other dialysis-related complications by reducing oxidative stress.     

Carotid artery intima-media thickness correlates with oxidative stress in chronic haemodialysis patients with accelerated atherosclerosis.

BACKGROUND: Accelerated atherosclerosis is the major cause of mortality in patients on chronic haemodialysis (HD). Increased oxidative stress might be the major factor leading to high cardiovascular mortality rate in HD patients. The aim of our study was to clarify effects of uraemia and dialysis on oxidative stress parameters and explore the relation between oxidative stress markers and carotid artery intima-media thickness (CIMT) as an indicator of atherosclerosis. METHODS: Twenty chronic HD patients, 20 predialytic uraemic patients and 20 healthy subjects were included in the study. Serum thiobarbituric acid reactive substances (TBARS), protein carbonyl content (PCO) and nitrite/nitrate levels were determined as oxidative stress markers. Serum vitamin E, plasma sulfhydryl (P-SH), erythrocyte glutathione (GSH), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) activities were measured as antioxidants. CIMT was assessed by carotid artery ultrasonography. RESULTS: Both chronic HD and predialytic uraemic patients had enhanced oxidative stress indicated by higher levels of nitrite/nitrate, TBARS and PCO, and lower levels of P-SH, SOD, CAT and GPx compared to controls. HD patients had significantly higher CIMT and nitrite/nitrate while significantly lower P-SH,vitamin E, SOD, CAT and GPx compared to predialytic uraemic patients. There was a significant positive correlation between CIMT and TBARS (r = 0.38, P = 0.003) and nitrite/nitrate levels (r = 0.41, P = 0.001), while there was a significant negative correlation between CIMT and SOD (r = -0.35, P = 0.01), CAT (r = -0.65, P < 0.001) and P-SH levels (r = -0.50, P < 0.001). A linear regression analysis showed that TBARS were still significantly and positively correlated with CIMT (P = 0.001), while CAT and P-SH were significantly and negatively correlated with CIMT (P = 0.002 and P = 0.048, respectively). CONCLUSIONS: HD exacerbates oxidative stress and disturbances in antioxidant enzymes in uraemic patients. We propose that serum TBARS and nitrite/nitrate can be used as positive determinants, while erythrocyte SOD, CAT and P-SH may be used as negative determinants of atherosclerosis assessed by CIMT in uraemic and HD patients.     

Markers of oxidative stress in the skeletal muscle of patients on haemodialysis.

BACKGROUND: Increased oxidative stress may play a role in morbidity and mortality of patients with renal failure. Most studies have examined serum markers of oxidation, but it is unclear whether oxidative stress is involved in skeletal muscle atrophy. METHODS: This study examined markers of oxidative stress in the skeletal muscle of 10 haemodialysed patients and 10 control subjects. Biopsies from the quadriceps femoris were analysed for reduced and oxidized glutathione, protein thiols, malonaldehyde and heat shock proteins (HSP27, HSP60 and HSP70), superoxide dismutase and catalase activities. A novel microdialysis procedure was used to examine hydroxyl radical activity in the interstitial fluid of the tibialis anterior. RESULTS: Patients had muscle atrophy with a reduced diameter of both type I and II fibres (by 15 and 20%, respectively). Muscle microdialysates contained 2,3- and 2,5-dihydroxybenzoates formed from salicylate indicating hydroxyl radical activity, with no differences between patients and control subjects. Muscle protein thiol and oxidized glutathione contents were unchanged in patients, but malonaldehyde content was reduced. In contrast, total muscle glutathione and heat shock protein contents were increased. Muscle superoxide dismutase activity was unchanged, but catalase activity was reduced in patients. CONCLUSIONS: The muscle of patients undergoing haemodialysis undergoes some adaptive responses in total glutathione content, heat shock protein content and catalase activity that are potentially related to chronic oxidative stress. However, there is no evidence of gross oxidation, nor any clear relationship between oxidative stress and muscle fibre atrophy, arguing against a direct role of oxidants in the degenerative processes.     

Methaemoglobinaemia and haemolysis associated with hydrogen peroxide in a paediatric haemodialysis centre: a warning note.

BACKGROUND: Haemodialysis exposes patients to contaminants in the dialysate. The AAMI standards deal only with two disinfectants, chlorine and chloramine. We report an event of methaemoglobinaemia and haemolysis related to an unsuspected disinfection agent. METHODS: Nine children aged 3-17 years undergoing dialysis after reconstruction of our paediatric dialysis unit developed methaemoglobinaemia of 3.1-11%, with a mean reduction in haemoglobin levels of 11.9 +/- 5.9% (P < 0.001). Air bubbles were noted in the bloodlines. The water treatment system (WTS) of the dialysis unit is disinfected when necessary by adding concentrated hydrogen peroxide (HP) to the storage tank and circulating it through the re-circulation loop with draining and subsequent flushings. Total chlorine analysis of the water is performed by DPD-iodide colorimetric method. RESULTS: Dialysis water testing yielded a high chloramine concentration in the storage tank and points- of-use stations (3.08 and 2.06 p.p.m., respectively). However, this finding was not true for the tap water, and it also failed to explain the air bubbles in the dialysis tubing. The concentration of free chlorine was within the recommended range. Further investigation revealed that the WTS was disinfected by the service company during remodelling of the unit, without notification of the hospital staff. Since the DPD-iodide test is not specific, and in effect detects not only total chlorine, but all oxidants capable of oxidizing iodide, we assumed the culprit was residual HP that was inadequately flushed from the water system. CONCLUSIONS: HP used for disinfection of the WTS can pose a serious dialysis risk if not flushed out properly. Total chlorine analysis should be performed before every dialysis session, and positive results should prompt further work-up for other oxidants. The clinical staff must always be involved in decisions regarding any intervention in the dialysis water system.     

Oxidative stress and ferritin levels in haemodialysis patients.

BACKGROUND: Increased oxidative stress (OS) and inflammation are associated with atherosclerotic coronary artery disease in haemodialysis (HD) patients. Ferritin may have other effects in addition to its role in storing intracellular iron. This study was performed to determine any relationships between markers of OS, nutrition and inflammation in HD patients with normal and high ferritin levels. METHODS: Our cohort comprised 34 maintenance dialysis patients on erythropoietin therapy and 22 healthy controls. HD patients were divided into two groups: 17 with normal (<800 ng/ml) and 17 with high (>800 ng/ml) ferritin levels, and we measured lipid profile, albumin, highly sensitive C-reactive protein (hsCRP), anti-oxidant enzymes [whole blood glutathione peroxidase (Gpx), serum superoxide dismutase (SOD), paraoxonase, arylestherase (AE) and total anti-oxidant status (TAOC)], anti-oxidants (vitamin C) and lipid peroxidation products [red blood cell malondialdehyde (RBC MDA)]. RESULTS: Compared with controls, the HD patients had higher serum urea, blood pressure, triglyceride, hsCRP, RBC MDA, SOD and TAOC values and lower albumin, low-density lipoprotein cholesterol, apolipoprotein AI, paraoxonase, AE and whole blood Gpx activities. Serum vitamin C, uric acid, apolipoprotein B, total- and high-density lipoprotein cholesterol, apolipoprotein B MDA, and lymphocyte levels in the HD patients with normal and high ferritin levels were similar. The OS markers of HD patients did not differ, whether or not they received intravenous iron supplementation or had transferrin saturations < 50% or > or = 50%. CONCLUSION: HD patients are in a higher oxidative state, which results in the reduction of total anti-oxidant capacity and also have an increased inflammation status. We could not find a relationship between ferritin level and OS markers in HD patients receiving erythropoietin.     

Treatment with different doses of folic acid in haemodialysis patients: effects on folate distribution and aminothiol concentrations.

BACKGROUND: Hyperhomocysteinaemia is highly prevalent among haemodialysis patients and may contribute to their increased cardiovascular risk. Treatment with pharmacological doses of folic acid lowers the plasma homocysteine concentration in these patients. The purpose of the present study was to expand the knowledge about such treatment by testing the effects of stepwise increases in the dose of folic acid on the concentrations of plasma and red blood cell folate as well as the total plasma concentrations of homocysteine (tHcy), cysteine (tCys), and glutathione (tGSH) in patients on chronic hemodialysis. METHODS: Fourteen stable haemodialysis patients completed the study which consisted of four consecutive periods, each of 6 weeks duration: (i) no treatment with folic acid (control period); (ii) 5 mg of folic acid three times per week (15 mg/week); (iii) 5 mg of folic acid daily (35 mg/week); (iv) 10 mg of folic acid daily (70 mg/week). RESULTS: Neither plasma or red cell folate nor plasma aminothiol concentrations changed significantly during the control period. The mean red cell folate concentration doubled during the administration of folic acid at the dose of 15 mg/week but at higher doses the further rise was only marginal. The mean folate concentration in plasma increased steeply especially at the higher doses of folic acid. During treatment with 15 mg/week of folic acid, tHcy fell by a mean of 36%, tGSH increased by a mean of 34%, but tCys was unaffected. Increases in the dose of folic acid did not augment these responses. CONCLUSIONS: The maximal effect on tHcy seemed to be obtained already at the lowest given dose of folic acid (15 mg/week). At that dose, the red blood cells approached folate saturation, which may reflect the situation in other cells that participate in homocysteine metabolism and explain why further increases in the dose of folic acid are not effective from a tHcy-lowering point of view.     

Autoantibodies against N-homocysteinylated proteins in patients on long-term haemodialysis

Background. Autoantibodies against N-homocysteinylated (N-Hcy)proteins at high titres have been demonstrated in patients withpremature coronary artery disease (CAD) and stroke. Since recently,elevated N-Hcy-proteins levels have been reported in haemodialysispatients, we sought to investigate whether anti-N-Hcy-proteinantibodies occur in such subjects and if they are associatedwith cardiovascular risk. Methods. We studied 43 patients, aged 27–89 (mean 58.8)years, dialysed for, on average, 50 months and 31 age- and sex-matchedhealthy controls. IgG antibodies against N-Hcy-albumin and -haemoglobinwere determined using an in-house enzyme-linked immunosorbentassay. Results. Haemodialysis patients had higher plasma tHcy (23.18± 1.37 vs 13.51 ± 0.64; P < 0.0001), serumfolate (29.7 ± 6.9 vs 9.9 ± 3.8 nmol/l; P <0.0001) and anti-N-Hcy-albumin and -haemoglobin antibodies (absorbancyat 490 nm: 0.39 ± 0.22 vs 0.34 ± 0.12; P = 0.03and 0.60 ± 0.31 vs 0.42 ± 0.09; P < 0.0001,respectively) than controls. Levels of anti-N-Hcy-albumin antibodies,but not those against haemoglobin, correlated negatively withthe duration of haemodialysis (r = –0.39; P = 0.01). Thiscorrelation disappeared after a 6-month follow-up. Haemodialysispatients treated with folic acid on a long-term basis had similarlevels of anti-N-Hcy-albumin and -haemoglobin antibodies comparedwith the minority which denied taking this vitamin (absorbancyA490: 0.35 ± 0.22 vs 0.38 ± 0.05; P = 0.5 and0.63 ± 0.30 vs 0.51 ± 0.11; P = 0.4, respectively). Conclusions. Our study shows that an autoimmune response toanti-N-Hcy-proteins occurs in patients on maintenance haemodialysisand is more pronounced than in healthy subjects.     

A registry of haemodialysis patients and the progress of haemodialysis services in Lithuania.

Background. Until 1990, haemodialysis (HD) in Lithuania wasunderdeveloped, but after independence, development of HD started.Until 1996, no precise data about HD patients in Lithuania wereavailable. In order to create a registry of HD, we started tocollect data about dialysis services and HD patients in 1996.Every collection of data was followed by distribution and discussionof the results within the nephrological community. This studydescribes the changes of Lithuanian HD between 1996–2002. Methods. Between 1996 till 2002 all HD centres in Lithuaniawere annually visited and data were collected about all HD patients(response rate of 100%). The evaluation of the results duringour observational study was made according to the European BestPractice Guidelines. During annual conferences for nephrologists,the guidelines and data of our HD registry were presented. Results. There was an increase in the number of HD stations(from 25 p.m.p. to 75 p.m.p., P<0.001), in HD patients (from60 p.m.p. to 237 p.m.p., P<0.001) and in the incidence ofnew HD patients (from 54.3 p.m.p. to 103 p.m.p., P<0.01).The mean age of HD patients increased from 47.2±16.1years in 1996 to 56.0±14.9 in 2002 (P<0.001). Themain underlying cause of ESRD was chronic glomerulonephritis,but its rate decreased from 54.5% in 1996 to 27.5% in 2002 (P<0.001).The percentage of diabetics increased from 7.1% to 16.4%, P<0.05,and in hypertensive nephropathy from 3.1% to 10.9%, P<0.05.We observed improvement of the quality of HD in Lithuania duringthese 5 years. The percentage of patients on bicarbonate HDincreased from 7.1% in 1996 to 100% in 2002 (P<0.001). Thepercentage of patients receiving more than 12 h HD/week increasedfrom 30.8% in 1996 to 53.5% in 2002 (P<0.001). The mean Kt/Vin 1999 was 0.81±0.53, but it increased in 2002 to 1.22±0.27,P<0.001. In 2002, 84.6% of all HD patients were examinedfor HB_sAg, 82.3% for anti–HCV, 31.2% for anti-HB_s and57.1% for anti-HB_c. The percentage of patients receiving phosphatebinders increased from 65.2% in 1996 to 84.4% in 1997 and 90.5%in 2002. Serum parathyroid hormone (PTH) levels were measuredin 27.3% of HD patients in 1999 but in 85.2% of patients in2002. The mean haemoglobin (Hb) concentration increased from92±15.4 g/l to 105±14.7 g/l; the percentage ofpatients with Hb>100 g/l increased from 27.5% to 64% in 2001.The percentage of HD patients receiving epoetin was 94.6% in2001 as compared with 78% in 1997. There was a marked increasein the use of intravenous iron (from 7.5% patients in 1997 to70.8% in 2000). The mean weekly dose of Epo was lower in HDpatients receiving intravenous iron than in patients receivingoral iron. Conclusions. Over the period of 1996–2002 the HD servicessignificantly expanded in Lithuania. The introduction of EuropeanBest Practice Guidelines and the establishment of a HD registrywith feedback of the results stimulated the significant progressin the quality of HD and in the management of the patients.     

Blood oxidative stress and lipoprotein oxidizability in haemodialysis patients: effect of the use of a vitamin E-coated dialysis membrane.

BACKGROUND: Oxidative stress has been shown in haemodialysis patients in relation with an increased production of free radicals due to membrane-induced complement and leukocyte activation. In order to minimize membrane bioincompatibility and thereby oxidative stress, more compatible filters have been perfected. Among them, a high-flux vitamin E-coated membrane (CL-EE) has been proposed recently. In vivo, little data is available on the consequences of the use of vitamin E-coated membranes. In the present study, the effects of a 3-month use of CL-EE dialysis membranes compared to conventional membranes have been evaluated in 12 haemodialysis patients on the blood oxidative stress status before and after the dialysis session. METHODS: We determined the lipid peroxidation status (plasma thiobarbituric acid-reactive substances) and antioxidant defence (erythrocyte Cu,Zn-superoxide dismutase and plasma and erythrocyte glutathione peroxidase activities, plasma vitamin E, beta-carotene, vitamin A and total antioxidant status). Also, we simultaneously determined the antioxidant content and the copper oxidizability of isolated low density- and high density-lipoproteins (LDLs and HDLs). RESULTS: The main consequence observed under these conditions was a marked enrichment of plasma with vitamin E, which was also significantly and selectively noted in HDLs (no changes in LDL vitamin E content), perhaps related to a specific storage capacity for vitamin E in HDLs of haemodialysis patients. The beta-carotene content of plasma, LDLs and HDLs was also higher after use of vitamin E-coated membranes than after use of high-flux biocompatible membranes. HDL copper oxidizability was reduced (as shown by an increased lag time) before dialysis after use of CL-EE membranes compared to conventional membranes, whereas LDL oxidizability remained unchanged. CONCLUSION: A 3-month use of vitamin E-coated membranes resulted in a significant increase in plasma and HDL vitamin E content, associated with a lower oxidizability of HDLs, which could be beneficial for haemodialysis patients.     

Insomnia in maintenance haemodialysis patients.

BACKGROUND: Studies in the last 15 years have shown a high prevalence of sleep disorders in maintenance haemodialysis (HD) patients. METHODS: To investigate whether the new technical and therapeutic advances of the last decade have had a positive impact on sleep disturbances in HD patients: 694 patients (384 males, 310 females) were surveyed using a specific questionnaire; their clinical, lifestyle and dialysis data were also recorded. RESULTS: Forty-five per cent of patients (n=311; 156 males, 155 females) complained of insomnia, defined either by delayed sleep onset and/or night-time waking, and were included in the insomnia group; the remainder were used as controls (control group). There was a significantly higher risk of insomnia in patients with >12 months on dialysis, in patients dialysed in the morning (P<0.003), and in patients with higher parathyroid hormone (PTH) levels (P<0.05). Body mass index, body weight gain and blood pressure did not differ between the groups, and neither did the dialysis parameters. Creatinine and urea plasma levels were higher in the control group vs the insomnia group (P<0.001), but there was no difference in haemoglobin concentrations or use of erythropoietin, calcitriol and antihypertensive drugs. Cigarette smoking, caffeine or alcohol intake were comparable in the two groups. The most frequently recorded sleep disorders were night-time waking (92%), trouble falling asleep (67%) and early morning waking (62%). Restless leg symptoms were described in 52% of patients with insomnia. CONCLUSIONS: The prevalence of insomnia in HD patients is still very high; elderly patients, and those with longer time on dialysis and high levels of PTH are at major risk of insomnia, whereas type of dialysis, haemoglobin levels and behavioural factors do not seem to play a critical role in determining this sleep disorder.     

Curcumin protects against gallic acid-induced oxidative stress,suppression of glutathione antioxidant defenses,hepatic and renal damage in rats

Curcumin (Cur) and gallic acid (Gal) are major food additives. Cur has well-known antioxidant properties, whereas Gal has both antioxidant and pro-oxidant effects. The present study investigated the effects of oral administration of Gal with or without Cur on antioxidant enzymes activities, glutathione (GSH) and the enzymes in its metabolism in rat liver in vivo and markers of tissue damage in the serum. Results showed that the increase in serum creatinine level, alkaline phosphatase and lactate dehydrogenase activities by Gal treatment were inhibited by combined administration of Gal and Cur. The decrease in GSH-peroxidase, GSH-S-transferase, superoxide dismutase and GSH-reductase activities by Gal treatment were inhibited when both Gal and Cur were administered together. The malondialdehyde concentration and catalase activity were significantly increased following administration of Gal but not when the administration of Gal was combined with Cur. Finally, the increase in GSH level was seen following administration of Cur alone or in combination with Gal but not with Gal alone. These results suggest that Gal might induce oxidative stress in the rat liver and affect renal function that can be inhibited by the combined administration of Gal and Cur.     

Citrate anticoagulation abolishes degranulation of polymorphonuclear cells and platelets and reduces oxidative stress during haemodialysis.

BACKGROUND: During haemodialysis (HD), polymorphonuclear cells (PMNs) and platelets are activated and release various granule products, including myeloperoxidase (MPO) and platelet factor 4 (PF4). MPO triggers the generation of reactive oxygen species, leading to irreversible protein, carbohydrate and lipid modification. PF4 probably also contributes to oxidative stress. As previously shown, HD-induced PMN degranulation is almost completely abolished during citrate anticoagulation, most probably due to its calcium chelation ability. METHODS: In the present study, apart from HD-induced PMN and platelet degranulation, oxidative stress was analysed during three modes of anticoagulation. Heparin, dalteparin and citrate (HDhep, HDdal and HDcit) were compared in a randomized, crossover fashion in eight chronic HD patients. Multiple blood samples were taken during the third HD session of each modality, from both the afferent and efferent line. Besides the degranulation markers MPO and PF4, various markers of oxidative stress were measured, including oxidized low-density lipoprotein (ox-LDL), malondialdehyde (MDA) and carboxymethyllysine (CML). RESULTS: During HDhep and HDdal, marked degranulation was observed shortly after the start of HD. In contrast, during HDcit, PF4 and MPO levels remained unaltered, suggesting no release at all. After 1 week of HDcit, ox-LDL levels were markedly reduced [median 26% (3-65%), P=0.01], if compared with HDhep and HDdal. As regards MDA and CML, no differences were found. CONCLUSIONS: This study shows first, that HD-induced PMN and platelet degranulation are early, most probably calcium-dependent processes and, secondly, that the formation of ox-LDL is clearly dependent on the type of anticoagulant applied.     

Oxidative stress and haemodialysis: role of inflammation and duration of dialysis treatment.

BACKGROUND: Oxidative stress has long been demonstrated in haemodialysis patients. However, the factors influencing their oxidative status have not been characterized extensively in these patients. Therefore, the present study was designed to investigate the influence of a large number of factors known to be associated with oxidative stress. METHODS: In the present cross-sectional study, we determined the plasma levels of lipid and protein oxidation markers in 31 non-smoking haemodialysis patients and 18 non-smoking healthy subjects, together with various components of the antioxidant system at the plasma and erythrocyte level. RESULTS: No influence of age, diabetes or iron overload on oxidative markers and plasma and erythrocyte antioxidant systems was detected in these haemodialysis patients. The lack of an association between iron overload and oxidative status may be related to the lower level of plasma ascorbate in haemodialysis patients, since ascorbate favours the generation of free iron from ferritin-bound iron. Interestingly, plasma C reactive protein (CRP) levels measured by highly sensitive CRP assay were correlated positively with plasma levels of thiobarbituric acid reactive substances (r=0.38, P<0.04) and negatively with plasma alpha-tocopherol levels (r=-0.46, P<0.01). Moreover, significant inverse correlations were observed between duration of dialysis treatment and plasma levels of alpha-tocopherol (r=-0.49, P<0.02) and ubiquinol (r=-0.40, P<0.05). CONCLUSIONS: Our results suggest that inflammatory status and duration of dialysis treatment are the most important factors relating to oxidative stress in haemodialysis patients.