Effects of erythropoietin and vitamin E-modified membrane on plasma oxidative stress markers and anemia of hemodialyzed patients

Induction of Vesicular Trafficking and JNK-Mediated Apoptotic Signaling in Mononuclear Leukocytes Marks the Immuno-Proteostasis Response to Uremic Proteins

INTRODUCTION

Uremic retention solutes have been alleged to induce the apoptotic program of different cell types, including peripheral blood mononuclear leukocytes (PBL), which may contribute to uremic leukopenia and immune dysfunction.

METHODS

The molecular effects of these solutes were investigated in uremic PBL (u-PBL) and mononuclear cell lines (THP-1 and K562) exposed to the high molecular weight fraction of uremic plasma (u-HMW) prepared by in vitro ultrafiltration with 50 kDa cut-off microconcentrators.

RESULTS

u-PBL show reduced cell viability and increased apoptotic death compared to healthy control PBL (c-PBL). u-HMW induce apoptosis both in u-PBL and c-PBL, as well as in mononuclear cell lines, also stimulating cellular H2O2 formation and secretion, IRE1-α-mediated endoplasmic reticulum stress signaling, and JNK/cJun pathway activation. Also, u-HMW induce autophagy in THP-1 monocytes. u-PBL were characterized by the presence in their cellular proteome of the main proteins and carbonylation targets of u-HMW, namely albumin, transferrin, and fibrinogen, and by the increased expression of receptor for advanced glycation end-products, a scavenger receptor with promiscuous ligand binding properties involved in leukocyte activation and endocytosis.

CONCLUSIONS

Large uremic solutes induce abnormal endocytosis and terminal alteration of cellular proteostasis mechanisms in PBL, including UPR/ER stress response and autophagy, ultimately activating the JNK-mediated apoptotic signaling of these cells. These findings describe the suicidal role of immune cells in facing systemic proteostasis alterations of kidney disease patients, a process that we define as the immuno-proteostasis response of uremia.

Vitamin E (Alpha-Tocopherol) Metabolism and Nutrition in Chronic Kidney Disease

Vitamin E (alpha-tocopherol) is an essential micronutrient and fat-soluble antioxidant with proposed role in protecting tissues from uncontrolled lipid peroxidation. This vitamin has also important protein function and gene modulation effects. The metabolism of vitamin E depends on hepatic binding proteins that selectively retain food alpha-tocopherol for incorporation into nascent VLDL and tissue distribution together with esterified cholesterol and triglycerides. Chronic kidney disease (CKD) is a condition of oxidative stress and increased lipid peroxidation, that are associated with alterations of alpha-tocopherol metabolism and function. Specific changes have been reported for the levels of its enzymatic metabolites, including both short-chain and long-chain metabolites, the latter being endowed with regulatory functions on enzymatic and gene expression processes important for the metabolism of lipids and xenobiotics detoxification, as well as for the control of immune and inflammatory processes. Vitamin E therapy has been investigated in CKD using both oral vitamin E protocols and vitamin E-coated hemodialyzers, showing promising results in the secondary prevention of cardiovascular disease, as well as of immune and hematological complications. These therapeutic approaches are reviewed in the present article, together with a narrative excursus on the main findings indicating CKD as a condition of relative deficiency and impaired metabolism of vitamin E.

Erythropoietin therapy improves endothelial function in patients with non-dialysis chronic kidney disease and anemia (EARNEST-CKD): A clinical study

BACKGROUND

This study investigated whether administering erythropoiesis-stimulating agents (ESAs) improves endothelial function in patients with non-dialysis chronic kidney disease (CKD) and anemia.

METHODS

This single-center, prospective, single-arm comparison study enrolled patients with non-dialysis CKD (stages 4-5) and hemoglobin levels <10 g/dL. ESA administration followed the Kidney Disease: Improving Global Outcomes guideline. The primary endpoint was the change in flow-mediated dilatation after ESA administration in individual patients. The secondary endpoints were changes in 6-minute walk test results, blood pressure, New York Heart Association class, and echocardiographic parameters. The echocardiographic parameters examined included chamber quantification, Doppler parameters, and systolic and diastolic function parameters.

RESULTS

Initially, 13 patients were screened, but 2 discontinued due to either heart failure or voluntary withdrawal. The mean flow-mediated dilatation values significantly increased by 10.59% (from 1.36% ± 1.91% to 11.95% ± 8.11%, P = .001). Echocardiographic findings showed that the left ventricular mass index decreased by 11.9 g/m2 (from 105.8 ± 16.3 to 93.9 ± 19.5 g/m2, P  =  .006), and the left atrial volume index decreased by 10.8 mL/m2 (from 50.1 ± 11.3 to 39.3 ± 11.3 mL/m2, P = .004) after 12 weeks of ESA administration. There were no significant differences between pre- and post-ESA treatment 6-minute walk test results. No significant side effects were observed during the study period.

CONCLUSIONS

This is the first clinical study to demonstrate that an ESA improves endothelial dysfunction, left ventricular hypertrophy, and left atrial volume in patients with non-dialysis CKD. Thus, ESAs may be considered as adjunctive therapy for reducing cardiovascular risk in these patients.

Antioxidant Supplementation in Renal Replacement Therapy Patients: Is There Evidence?

The disruption of balance between production of reactive oxygen species and antioxidant systems in favor of the oxidants is termed oxidative stress (OS). To counteract the damaging effects of prooxidant free radicals, all aerobic organisms have antioxidant defense mechanisms that are aimed at neutralizing the circulating oxidants and repair the resulting injuries. Antioxidants are either endogenous (the natural defense mechanisms produced by the human body) or exogenous, found in supplements and foods. OS is present at the early stages of chronic kidney disease, augments progressively with renal function deterioration, and is further exacerbated by renal replacement therapy. End-stage renal disease patients, on hemodialysis (HD) or peritoneal dialysis (PD), suffer from accelerated OS, which has been associated with increased risk for mortality and cardiovascular disease. During HD sessions, the bioincompatibility of dialyzers and dialysate trigger activation of white blood cells and formation of free radicals, while a significant loss of antioxidants is also present. In PD, the bioincompatibility of solutions, including high osmolality, elevated lactate levels, low pH, and accumulation of advanced glycation end-products trigger formation of prooxidants, while there is significant loss of vitamins in the ultrafiltrate. A number of exogenous antioxidants have been suggested to ameliorate OS in dialysis patients. Vitamins B, C, D, and E, coenzyme Q10, L-carnitine, a-lipoic acid, curcumin, green tea, flavonoids, polyphenols, omega-3 polyunsaturated fatty acids, statins, trace elements, and N-acetylcysteine have been studied as exogenous antioxidant supplements in both PD and HD 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.

Vitamin E: Emerging aspects and new directions

The discovery of vitamin E will have its 100th anniversary in 2022, but we still have more questions than answers regarding the biological functions and the essentiality of vitamin E for human health. Discovered as a factor essential for rat fertility and soon after characterized for its properties of fat-soluble antioxidant, vitamin E was identified to have signaling and gene regulation effects in the 1980s. In the same years the cytochrome P-450 dependent metabolism of vitamin E was characterized and a first series of studies on short-chain carboxyethyl metabolites in the 1990s paved the way to the hypothesis of a biological role for this metabolism alternative to vitamin E catabolism. In the last decade other physiological metabolites of vitamin E have been identified, such as α-tocopheryl phosphate and the long-chain metabolites formed by the ω-hydroxylase activity of cytochrome P-450. Recent findings are consistent with gene regulation and homeostatic roles of these metabolites in different experimental models, such as inflammatory, neuronal and hepatic cells, and in vivo in animal models of acute inflammation. Molecular mechanisms underlying these responses are under investigation in several laboratories and side-glances to research on other fat soluble vitamins may help to move faster in this direction. Other emerging aspects presented in this review paper include novel insights on the mechanisms of reduction of the cardiovascular risk, immunomodulation and antiallergic effects, neuroprotection properties in models of glutamate excitotoxicity and spino-cerebellar damage, hepatoprotection and prevention of liver toxicity by different causes and even therapeutic applications in non-alcoholic steatohepatitis. We here discuss these topics with the aim of stimulating the interest of the scientific community and further research activities that may help to celebrate this anniversary of vitamin E with an in-depth knowledge of its action as vitamin.

"Effects of recombinant human erythropoietin high mimicking abuse doses on oxidative stress processes in rats"

Although many studies highlight how long-term moderate dose of Recombinant Human Erythropoietin (rHuEPO) treatments result in beneficial and antioxidants effects, few studies take into account the effects that short-term high doses of rHuEPO (mimicking abuse conditions) might have on the oxidative stress processes. Thus, the aim of this study was to investigate the in vivo antioxidant activity of rHuEPO, administered for a short time and at high doses to mimic its sports abuse as doping. Male Wistar healthy rats (n=36) were recruited for the study and were treated with three different concentrations of rHuEPO: 7.5, 15, 30μg/kg. Plasma concentrations of erythropoietin, 8-epi Prostaglandin F2α, plasma and urinary concentrations of NOx were evaluated with specific assay kit, while hematocrit levels were analyzed with an automated cell counter. Antioxidant activity of rHuEPO was assessed analyzing the possible variation of the plasma scavenger capacity against hydroxylic and peroxylic radicals by TOSC (Total Oxyradical Scavenging Capacity) assay. Statistical analyses showed higher hematocrit values, confirmed by a statistically significant increase of plasmatic EPO concentration. An increase in plasma scavenging capacity against peroxyl and hydroxyl radicals, in 8-isoprostane plasmatic concentrations and in plasmatic and urinary levels of NOX were also found in all the treated animals, though not always statistically significant. Our results confirm the literature data regarding the antioxidant action of erythropoietin administered at low doses and for short times, whereas they showed an opposite incremental oxidative stress action when erythropoietin is administered at high doses.

Vitamin E supplementation fails to impact measures of oxidative stress or the anaemia of feline chronic kidney disease: a randomised, double-blinded placebo control study

This study was designed to test the hypothesis that supplementation with vitamin E, an antioxidant, in cats with chronic kidney disease (CKD), would reduce oxidative stress and its impact on RBC membrane fragility, resulting in these cats maintaining a greater packed cell volume (PCV) compared with CKD cats not receiving supplementation.

Thirty‐six cats with CKD were randomly assigned to receive either daily vitamin E or a placebo for 3 months in a double‐blinded study design.

History and physical examination, blood pressure, complete blood count (CBC), PCV, biochemical profile and urinalysis (UA) were determined. Parameters of oxidative stress and osmotic fragility were measured. Cats were administered vitamin E or placebo once daily for 3 months. Cats were then reassessed and the diagnostics were repeated.

Twenty‐four cats completed the study, 11 in the vitamin E group and 13 in the placebo group. There were no significant differences between the two groups at the start, or upon completion of the study with regard to biochemical parameters, oxidative stress, erythrocyte osmotic fragility or PCV. None of these parameters changed significantly in either group over the treatment period.

Daily supplementation with 30 IU of vitamin E did not affect the measures of oxidative stress or the anaemia seen in cats with CKD.

Vitamin E therapy beyond cancer: Tocopherol versus tocotrienol

The discovery of vitamin E (α-tocopherol) began in 1922 as a vital component required in reproduction. Today, there are eight naturally occurring vitamin E isoforms, namely α-, β-, γ- and δ-tocopherol and α-, β-, γ- and δ-tocotrienol. Vitamin E is potent antioxidants, capable of neutralizing free radicals directly by donating hydrogen from its chromanol ring. α-Tocopherol is regarded the dominant form in vitamin E as the α-tocopherol transfer protein in the liver binds mainly α-tocopherol, thus preventing its degradation. That contributed to the oversight of tocotrienols and resulted in less than 3% of all vitamin E publications studying tocotrienols. Nevertheless, tocotrienols have been shown to possess superior antioxidant and anti-inflammatory properties over α-tocopherol. In particular, inhibition of 3-hydroxy-3-methylglutaryl-coenzyme A reductase to lower cholesterol, attenuating inflammation via downregulation of transcription factor NF-κB activation, and potent radioprotectant against radiation damage are some properties unique to tocotrienols, not tocopherols. Aside from cancer, vitamin E has also been shown protective in bone, cardiovascular, eye, nephrological and neurological diseases. In light of the different pharmacological properties of tocopherols and tocotrienols, it becomes critical to specify which vitamin E isoform(s) are being studied in any future vitamin E publications. This review provides an update on vitamin E therapeutic potentials, protective effects and modes of action beyond cancer, with comparison of tocopherols against tocotrienols. With the concerted efforts in synthesizing novel vitamin E analogs and clinical pharmacology of vitamin E, it is likely that certain vitamin E isoform(s) will be therapeutic agents against human diseases besides cancer.

Influence of Hemodialysis on Lipid Peroxidation, Enzymatic and Non-Enzymatic Antioxidant Capacity in Chronic Renal Failure Patients

BACKGROUND

Free radical induced damages are thought to be involved in chronic kidney disease (CKD), especially in patients who are on hemodialysis (HD) for prolonged periods. Hemodialysis can influence multiple biochemical factors, several of which are useful, although the rest can be harmful and increase the severity of disease.

OBJECTIVES

The purpose of this study was to evaluate the effect of the HD membrane polysulfone on oxidative stress markers, by measuring the level of lipid peroxidation and total antioxidant activity (TAC), in the blood of HD patients.

PATIENTS AND METHODS

This study was carried out on 31 HD patients and 31 healthy persons, matched for age and sex, as control group. Blood samples were drawn before and after HD from arteriovenous fistulas, and once from the controls. Superoxide dismutase (SOD), catalase (CAT) and thiobarbituric acid-reactive substance (TBARS) in blood hemolyzate, Glutathione peroxidase (GpX) of whole blood and TAC of plasma were measured, respectively. Then, we investigated the association between TAC of plasma, measured by ferric reducing antioxidant power (FRAP), and lipid peroxidation level with its related parameters, in HD patients.

RESULTS

The SOD, GpX and CAT were decreased after HD (P < 0.05). Also, FRAP was shown to decrease after HD (P < 0.05). However, erythrocyte TBARS levels (μmol/gr of Hb) were increased after HD, in comparison with controls, and before HD (P < 0.05). There was a significant negative correlation between TBARS and antioxidant indices, such as SOD (r = -0.67, P = 0.001), GpX (r = -0.76, P = 0.001), CAT (r = -0.63, P = 0.001) and FRAP (r = -0.84, P = 0.001). The FRAP was significantly and directly correlated with uric acid (r = +0.62, P = 0.001), SOD (r = +0.72, P = 0.001), GpX (r = +0.87, P = 0.001) and CAT (r = +0.84, P = 0.001).

CONCLUSIONS

The results of our study proposed that there is a loss or inactivation of antioxidant factors, coupled with increased lipid peroxidation during the procedure of HD, possibly through the dialyzer membrane, with probable consequences on the severity of illness.

Pharmacokinetic and pharmacodynamic considerations on the erythropoietin effect and adverse events of darbepoetin

INTRODUCTION

In the TREAT and RED-HF trials, patients who received a high darbepoetin dose had an increased risk of adverse events. To find an explanation, the published literature was analyzed on the pharmacokinetics and pharmacodynamics of darbepoetin.

AREAS COVERED

Based on the sigmoid Emax model, the concentration producing 50% of the maximum erythropoietin effect is reported as CE50 = 0.41 ng/ml and the Hill coefficient as H = 3.0 for darbepoetin. Accordingly, a pharmacodynamics-based threshold concentration can be estimated with CE05 = 0.153 ng/ml producing 5% of Emax and a ceiling concentration with CE95 = 1.098 ng/ml producing 95% of Emax, respectively.

EXPERT OPINION

Darbepoetin trough levels should not be less than the threshold concentration but peak levels above the ceiling concentration could be associated with an increased risk of adverse events. The time span associated with the concentration fluctuation between the ceiling and the threshold concentration is estimated with 236 h (= 2.84 times elimination half-life of 83 h) and shorter than the 336 h when dosing every other week. According to such time-dependent pharmacodynamics, a weekly dosing regimen might be more effective and associated with less adverse events than higher doses every other week in patients with suboptimal response to a normal darbepoetin dose.

Impact of inflammation on anti-oxidative effects of vitamin E-coated membrane dialyzer in patients on chronic hemodialysis

Hemodialysis (HD) with the use of vitamin E-coated membrane (VEM) dialyzers is shown to exert anti-inflammatory and antioxidative effects in patients with end-stage renal disease on HD. However, the association of baseline inflammatory status with the antioxidative effects of VEM has not been investigated thus far. Thirty-five stable end-stage renal disease patients treated with VEM for 6 months were enrolled in the present prospective, observational cohort study. For the previous 3 months minimum, 17 (48%) patients were dialyzed with a cellulose, eight (23%) patients with a hemophane, and 10 (29%) patients with a polysulfone 1.2 to 1.5 m(2) hollow fiber dialyzer. The effects of treatment on oxidized low-density lipoprotein (oxLDL) were stratified according to half percentiles of baseline serum logC-reactive protein and interleukin-6, and the association between treatment goal, arbitrarily defined as a minimum 30% decrease in baseline oxLDL, was assessed with the use of logistic regression analysis. The higher C-reactive protein and interleukin-6 half percentiles were independently and additively associated with a higher odds ratio for achieving treatment goal. Adjustment for baseline oxLDL, age, sex, HD duration, smoking, and body mass index did not attenuate the odds ratios, whereas the history of diabetes, as primary renal disease, significantly decreased the odds ratio for achieving treatment goal. Increased baseline C-reactive protein and interleukin-6 are independent, additive factors associated with the effect of VEM on oxLDL in HD patients.

A randomized controlled trial evaluating the erythropoiesis stimulating agent sparing potential of a vitamin E-bonded polysulfone dialysis membrane

Background

Vitamin E (VE) bonded polysulfone dialysis membranes have putative erythropoiesis stimulating agent (ESA)-sparing and anti-inflammatory properties based on data from a small number of studies. We sought to investigate this in a large, prospective 12-month randomized controlled trial.

Methods

Two-hundred and sixty prevalent haemodialysis (HD) patients were randomized to dialysis with VE-bonded polysulfone membranes or non-VE-bonded equivalents. All ESA-dosing was performed by means of a computer-based anaemia management decision support system. Monthly data were used to calculate the ESA resistance index (ERI) and blood tests were performed at baseline, 6 and 12 months for measurement of C-reactive protein (CRP) levels.

Results

Of the 260 patients, 123 were randomized to dialysis with the VE-membrane and 12-month data was available for 220 patients. At the study population level, no beneficial effect of the VE membranes on the ERI or CRP levels was observed. Post hoc analyses indicated that there was a significant fall in ERI for patients with the highest baseline ESA resistance dialysed with the VE (9.28 [7.70–12.5] versus 7.70 [5.34–12.7] IU/week/kg/g/dL Hb, P = 0.01) but not the control membranes (9.45 [7.62–12.3] versus 8.14 [4.44–15.6] IU/week/kg/g/dL Hb, P = 0.41); this was not attributable to changes in CRP levels.

Conclusions

Wholesale switching of all chronic HD patients to dialysis with VE-bonded polysulfone membranes appears not to be associated with improvements in ESA-responsiveness or CRP. These membranes may have utility in patients with heightened ESA resistance.

Interventions for erythropoietin-resistant anaemia in dialysis patients

BACKGROUND

People living with end-stage kidney disease (ESKD) often develop anaemia. Erythropoiesis-simulating agents (ESAs) are often given to people living with ESKD to maintain haemoglobin at a level to minimise need for transfusion. However, about 5% to 10% of patients with ESKD exhibit resistance to ESAs, and observational studies have shown that patients requiring high doses of ESA are at increased risk of mortality.

OBJECTIVES

This review aimed to study the effects of interventions for the treatment of ESA-resistant anaemia in people with ESKD.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE and EMBASE for randomised controlled trials (RCT) that involved participants with ESKD on dialysis or who were pre-dialysis patients with chronic kidney disease (stage 5). Date of last search: April 2013.

SELECTION CRITERIA

ESA resistance was defined as failure to achieve or maintain haemoglobin/haematocrit levels within the desired target range despite appropriate ESA doses (erythropoietin ≥ 450 U/kg/wk intravenously or ≥ 300 U/kg/wk subcutaneously; darbepoetin ≥ 1.5 µg/kg/wk) in people who were not nutritionally deficient, or who had haematological or bleeding disorders. Extended inclusion criteria for ESA hyporesponsive state were: erythropoietin dose ≥ 300 U/kg/wk and ≥ 150 U/kg/wk for intravenous administration; or ≥ 200 U/kg/wk and ≥ 100 U/kg/wk for subcutaneous administration; or darbepoetin dose ≥ 1.0 µg/kg/wk).

DATA COLLECTION AND ANALYSIS

Two authors independently assessed study quality and extracted data. Statistical analyses were performed using a random effects model and results expressed as risk ratio (RR) or mean difference (MD) with 95% confidence intervals (CI).

MAIN RESULTS

Titles and abstracts of 521 records were screened, of which we reviewed 99 from the full text. Only two studies matched our inclusion criteria. One study compared intravenous vitamin C versus no study medication for six months in 42 ESKD patients on haemodialysis who required intravenous erythropoietin (dose ≥ 450 U/kg/wk). The other included study compared high-flux dialyser versus low-flux dialyser for six months in 48 haemodialysis patients who required subcutaneous erythropoietin (dose ≥ 200 U/kg/wk). Because interventions differed, data could not be combined for quantitative meta-analysis.

AUTHORS' CONCLUSIONS

There was inadequate evidence identified to inform recommendation of any intervention to ameliorate ESA hyporesponsiveness. Adequately powered RCTs are required to establish the safety and efficacy of interventions to improve responsiveness to ESA therapy.

Randomized controlled open-label trial of vitamin E-bonded polysulfone dialyzer and erythropoiesis-stimulating agent response

BACKGROUND AND OBJECTIVES

A 1-year multicenter prospective randomized controlled study was conducted on the effects of vitamin E-bonded polysulfone dialyzers on erythropoiesis-stimulating agent response in hemodialysis patients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Major inclusion criteria were use of high-flux polysulfone dialyzers with 50-70 ml/min β2-microglobulin clearance over 3 months, transferrin saturation over 20%, same erythropoiesis-stimulating agent for over 3 months, and hemoglobin at 10-12 g/dl. Hemodialysis patients were placed in four interventional groups: two hemoglobin ranges (10.0-10.9 or 11.0-11.9 g/dl) and two dialyzers. Patients were randomly assigned by central registration to a vitamin E-bonded polysulfone dialyzers or polysulfone control group. Primary end point was relative erythropoiesis resistance index at baseline between groups at 12 months. Erythropoiesis resistance index was defined as total weekly erythropoiesis-stimulating agent dose divided by hemoglobin.

RESULTS

There were no statistically significant differences in age or sex. There was no significant difference in relative erythropoiesis resistance index between vitamin E-bonded polysulfone dialyzers and control groups at 12 months (vitamin E-bonded polysulfone dialyzers: 1.1, control: 1.3). The vitamin E-bonded polysulfone dialyzers group showed better relative erythropoiesis resistance index than the control group at 11.0-11.9 g/dl hemoglobin (vitamin E-bonded polysulfone dialyzers: 1.0, control: 1.4 at 12 months, significant difference) but no difference at 10.0-10.9 g/dl hemoglobin.

CONCLUSIONS

The overall relative erythropoiesis resistance index showed no difference between the vitamin E-bonded polysulfone dialyzers and control groups, although the change in relative erythropoiesis resistance index differed according to hemoglobin level.

How the duration period of erythropoietin treatment influences the oxidative status of hemodialysis patients

BACKGROUND

End-stage renal disease is a state of enhanced oxidative stress (OS) and hemodialysis (HD) and renal anemia further augment this disbalance. Anemia correction with erythropoietin (EPO) may improve oxidative status. However, there is no evidence of time dependent effects of EPO therapy on redox status of HD patients.

OBJECTIVE

The aim of this study was to evaluate whether the duration of EPO treatment may affect OS parameters in uremic patients.

PATIENTS AND METHODS

104 HD patients and 29 healthy volunteers were included. Patients were divided into 3 groups according to the duration of EPO treatment. Forth group consisted of HD patients without EPO treatment. Plasma and erythrocyte malondialdehyde (MDA, MDA(rbc)), reactive carbonyl groups (RCG), plasma sulfhydryl (-SH) groups and total antioxidative capacity (TAC) levels were evaluated.

RESULTS

HD patients both with and without EPO treatment, showed a significant increase in all oxidative parameters without significance between EPO treated and -untreated group. The decrease in MDA and MDA(rbc) levels coincided with the duration of EPO treatment. A negative correlation was observed between the duration of EPO treatment and serum MDA (r=-0.309, p=0.003). Increasing periods of EPO treatment were associated with decrease in RCG, without significance between EPO groups. Increase in TAC accompanied increasing durations of EPO treatment, with EPO treatment for more than 24 months causing the most striking changes (p<0.05). There were no significant differences in -SH levels between EPO subgroups.

CONCLUSION

Our results suggest that long term administration of EPO attenuated the lipid peroxidation process and restored the levels of antioxidants.

Erythrocyte glutathione transferase: a new biomarker for hemodialysis adequacy, overcoming the Kt/V(urea) dogma?

Kt/V_urea ratio is commonly used to assess the delivered dose of dialysis in maintenance hemodialysis (MHD) patients. This parameter only reflects the efficacy of dialytic treatments in removing small toxins, but not middle and protein-bound toxins. Erythrocyte glutathione transferase (e-GST), an enzyme devoted to cell depuration against a lot of large and small toxins, is overexpressed in uremic patients. Aim of the present study is to verify whether e-GST may represent a novel biomarker to assess the adequacy of different dialytic techniques complementary to Kt/V_urea parameter. Furthermore, it will be investigated whether e-GST could reflect the ‘average' adequacy of multiple dialytic sessions and not of a single one treatment as it occurs for Kt/V_urea. One hundred and three MHD patients and 82 healthy subjects were tested. Fourty four patients were treated with standard bicarbonate hemodialysis (HD) and 59 patients were on online hemodiafiltration (HDF). In all MHD patients e-GST activity was 60% higher than in healthy controls. In HDF, e-GST activity was lower than in HD subgroup (8.2±0.4 versus 10.0±0.4 U/g_Hb, respectively). Single-pool Kt/V_urea and total weekly Kt/V_urea were higher in HDF than in HD, but no correlation was found between e-GST activity and Kt/V_urea data. e-GST, whose level is stable during the erythrocyte life-span, provides information on the long-term depurative efficacy of dialysis treatments.

Evaluation of the impact of a new synthetic vitamin E-bonded membrane on anemia and rHuEPO requirement in ESRD patients with central venous catheters: a pilot study

In the last years, the number of hemodialysis (HD) patients with erythropoietin (rHuEPO) resistance is increasing. Probably, central venous catheters (CVCs) contribute to this resistance by inducing inflammation and oxidative stress. This study was aimed to compare vitamin E-bonded dialyzer (PSVE) versus polyethersulfone membrane. Sixteen subjects with CVCs were included in a prospective two-arm crossover 12-month study. The primary endpoints were the rHuEPO requirement and the erythropoiesis-stimulating agents (ESA) index, which was defined by the ratio between weekly EPO dosage (IU/kg/week) and Hb levels (g/dl). The mean dosages of rHuEPO to maintain hemoglobin between 10.5 and 12 g/dl were 135 ± 59 and 101 ± 57 IU/kg/week with polysulfone and PSVE, respectively (P = 0.14). The ESA indexes were 12.1 ± 5.2 and 8.7 ± 5.2 (P < 0.0001) with polysulfone and PSVE, respectively. A trend towards consensual changes in protein glycoxidation, antioxidant, and inflammatory markers was observed. In conclusion, the study suggests a role for PSVE in the reduction of ESA index in HD patients with CVCs.

Oxidative stress, renal anemia, and its therapies: is there a link?

In chronic kidney disease, anemia and oxidative stress are common features and both are involved in increasing morbidity and mortality. However, their relationship is still a matter of debate. This article is a review of published data and our experience and is intended to debate the pro and contra arguments concerning renal anemia and its 2 main therapeutic approaches, that are, erythropoietin and intravenous iron supplementation, as additional causes of oxidative stress in end-stage renal disease patients. To date, it seems more likely that renal anemia itself is the main contributor, and intravenous iron further enhances oxidative stress associated with chronic kidney disease. Future randomized prospective trials, with "hard" clinical end-points, are needed to establish the real effect of biochemical pro-oxidative changes on patient's outcome.

Anemia after bariatric surgery: more than just iron deficiency

Bariatric surgery for morbid obesity is rapidly gaining popularity. Restrictive and/or malabsorptive surgical interventions result in dramatic weight loss with significantly decreased obesity-related morbidity and mortality. Anemia, which may affect as many as two-thirds of these patients, is of concern and generally thought to be caused by iron deficiency. Although iron deficiency in this population may be frequent given pouch hypoacidity, defunctionalized small bowel, and red meat intolerance, it may not account for all anemias seen. First, there is increasing evidence that obesity creates a state of chronic inflammation. Both iron deficiency anemia and anemia of chronic inflammation present with low serum iron levels. Most studies reporting anemia after bariatric surgery lack serum ferritin determinations so that the relative contribution of inflammation to anemia cannot be assessed. Second, a significant number of anemias after bariatric surgery remain unexplained and may be attributable to less frequently seen micronutrient deficiencies such as copper, fatsoluble vitamins A and E, or an imbalance in zinc intake. Third, although deficiencies of folate and vitamin B(12) are infrequent, study observation periods may be too short to detect anemia attributable to vitamin B(12) deficiency because vitamin B(12) storage depletion takes many years. This review is intended to increase awareness of the mechanisms of anemia above and beyond iron deficiency in the bariatric patient and provide healthcare providers with tools for a more thoughtful approach to anemia in this patient population.

Cognitive function in chronic kidney disease

Chronic kidney disease (CKD) is a growing public health problem. The incidence of kidney failure is rising in all age groups but particularly in older adults. Individuals in all stages of CKD are at higher risk for development of cognitive impairment and this may be a major determinant in their quality of life. Furthermore, cognitive impairment is associated with an increased risk of death in dialysis patients. Cerebrovascular disease is a strong risk factor for development of cognitive impairment and vascular disease is a more likely cause of cognitive impairment than Alzheimer's disease in patients with CKD. Both traditional and nontraditional vascular risk factors are more common in CKD and dialysis patients may also be at risk for cognitive impairment via nonvascular risk factors and the hemodialysis procedure itself. Unfortunately, because risk factors for cognitive impairment in CKD have not been thoroughly ascertained, evaluation of potential treatments has been limited. Given the high prevalence of cognitive impairment in all stages of CKD, additional studies are needed to evaluate potential risk factors and treatments in this vulnerable population.

Antioxidative effects of erythropoietin

Erythropoietin (EPO) has been shown to exert cytoprotective effects on erythroid progenitor cells as well as various non-erythroid cells. Experimental studies have demonstrated the renoprotective effects of EPO in various acute and chronic renal injury models. These protective effects have been largely attributed to antiapoptotic signalings of EPO. However, injured cells undergoing apoptosis are generally too severely damaged to function properly. Therefore, simply corrupting apoptotic pathway is unlikely to be an effective strategy, because the remaining damaged cells may not function appropriately, or they may eventually undergo necrotic cell death. Recent evidences suggest that EPO also provides cytoprotection by ameliorating oxidative stress, the principal cellular insult. EPO may exert its antioxidative effects directly by exploiting intracellular antioxidative mechanisms such as heme oxygenase-1 and glutathione peroxidase. In addition, EPO may act indirectly by inducing iron depletion and thereby inhibiting iron-dependent oxidative injury. Increasing red blood cells by EPO may also indirectly reduce cellular oxidative stress, as red blood cells are loaded with a substantial amount of antioxidative enzymes. Further investigation regarding the mechanisms of cellular antioxidative responses to EPO would provide a better insight to cytoprotective action of EPO, and would support the development of better cytoprotective drugs in the near future.

Gamma-tocopherol and docosahexaenoic acid decrease inflammation in dialysis patients

OBJECTIVE

Increased cardiovascular risk in hemodialysis patients may be related to augmented oxidative stress and inflammation, for which no proven beneficial therapies are available.

STUDY DESIGN

We examined the effects of gamma tocopherol and docosahexaenoic acid (DHA) administration on inflammation and oxidative stress markers in hemodialysis patients in a randomized, double-blinded, placebo-controlled, clinical trial. Active treatment consisted of capsules containing gamma tocopherol (308 mg) and DHA (800 mg).

SETTING

Outpatient dialysis center.

PATIENTS

Seventy maintenance hemodialysis patients.

MAIN OUTCOME MEASURES

Plasma concentrations of interleukin-6 (IL-6) and protein carbonyl content were determined by enzyme-linked immunosorbant assay. C-reactive protein was measured by nephelometry. The F(2) isoprostanes were measured by gas chromatography-mass spectrometry. Erythrocyte DHA content was measured by gas chromatography.

RESULTS

Sixty-three patients were enrolled, and 57 completed the study. No serious adverse events were attributed to either active treatment or placebo. In the treatment group, but not in the placebo group, there were significant decreases in IL-6 (21.4 +/- 3.5 to 16.8 +/- 3.7 pg/mL), white blood cell (WBC) count (7.4 +/- 0.3 to 6.9 +/- 0.4 10(3)/microL), and neutrophil fraction of WBCs (4.8 +/- 0.3 to 4.4 +/- 0.3 10(3)/microL), at P < .05 for all. There were no significant changes in plasma concentrations of CRP, F(2) isoprostanes, or carbonyls in either group.

CONCLUSION

Thus, gamma tocopherol and DHA are well-tolerated and reduce selected biomarkers of inflammation in hemodialysis patients. Larger randomized, clinical trials will be required to determine if gamma tocopherol and DHA can reduce cardiovascular complications in hemodialysis patients.

Reduction of serum antioxidative capacity during hemodialysis

BACKGROUND

Hemodialysis (HD) is thought to exacerbate oxidative stress (OS). The purpose of this study was to assess patients' oxidative status during and after HD, and to clarify the relation between oxidative status and antioxidant solutes such as uric acid (UA) and ascorbic acid (AsA).

METHODS

Serum diacron-reactive oxygen metabolites (d-ROM), and biological antioxidant potential (BAP), as well as serum concentrations of UA, AsA, urea nitrogen (UN), and creatinine (Cre) were measured in eight HD patients at six time points during and after HD. Inflow and outflow dialyzer blood was evaluated during HD or sham HD (no dialysate flow). Further, BAP was evaluated by adding UA or AsA to post-HD serum.

RESULTS

No changes were found in d-ROM over time, whereas BAP was significantly decreased by HD. No differences were found in d-ROM during HD or sham HD, or between inflow and outflow blood. During HD, significantly lower BAP levels were found in outflow blood than in inflow blood. Serum UA and AsA levels were decreased by HD; however, no increases were observed in BAP levels after the addition of these molecules to post-HD serum.

CONCLUSION

These data indicate that HD reduces serum antioxidative capacity, and the loss of dialyzable molecules may be involved. However, this reduction in capacity does not seem to be caused by the loss of UA or AsA.

Long-term erythropoietin therapy does not affect endothelial markers, coagulation activation and oxidative stress in haemodialyzed patients

INTRODUCTION

Although the general improvement caused by recombinant human erythropoietin (rHuEPO) in the correction of uraemic anaemia cannot be questioned, some data suggest that the changes in the haemostasis, endothelial function and oxidative stress (SOX) are induced. The aim of the present study was to investigate the effect of one-year rHuEPO therapy on the coagulation activation, endothelial injury markers and SOX in haemodialysis (HD) patients.

MATERIALS AND METHODS

Assessment of coagulation activation pathway: tissue factor (TF), its inhibitor (TFPI) and prothrombin fragment 1+2 (F1+2); endothelial injury markers: von Willebrand factor antigen (vWF:Ag) and thrombomodulin (TM); and several parameters related to SOX: total peroxide, Cu/Zn superoxide dismutase (Cu/Zn SOD) and autoantibodies to oxidized LDL (OxLDL-Ab) levels were performed in stable HD patients, treated for 12 months with rHuEPO (n=18; mean dose 113.5+/-41 U/kg/week) or not (with Hg<10 g/dl, n=8 and with Hg>10 g/dl, n=12), none of them on iron therapy.

RESULTS

Patients with Hg<10 g/dl had a significantly lower erythrocytes count, Ht and Hg levels than those with Hg>10 g/dl and those on rHuEPO therapy. Long-term rHuEPO therapy does not affect coagulation pathway and SOX markers. Treatment with this hormone resulted in a tendency to decrease TM and vWF:Ag concentrations, however these changes did not reach a statistical significance.

CONCLUSIONS

These results suggest that one-year rHuEPO therapy seems to exert no additional influence on coagulation activation, endothelial cell damage/activation markers and oxidative stress in patients undergoing regular HD in the absence of concomitant iron supplementation and irrespective from haemoglobin levels.

Long-term erythropoietin therapy does not affect metalloproteinases and their inhibitor levels, oxidative stress and inflammation in hemodialyzed patients

BACKGROUND

Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) play an important role in the atherosclerosis. Recombinant human erythropoietin (EPO) has become widely used to treat anemic hemodialyzed (HD) patients; however, an increased mortality has been reported for HD patients with cardiovascular disease when randomly assigned to normal hematocrit by EPO. Therefore, we conducted a study examining the effect of EPO on MMPs/TIMPs system, oxidative stress and inflammation in these patients.

METHODS

Assessment of MMP-2, MMP-9, TIMP-1 and TIMP-2 were performed in 20 stable HD patients and 15 healthy controls. Additionally, the effects of EPO on malondialdehyde (MDA)--a marker of SOX and C-reactive protein (CRP) levels--as a marker of inflammation were also investigated. Of the 20 patients, 10 were receiving EPO therapy [HD-EPO(+)] for 12 months or more and 10 were not receiving EPO therapy [HD-EPO(-)]. Both groups were not receiving iron supplementation.

RESULTS

All parameters, with the exception of MMP-9, were lower in the healthy subjects compared with the HD subjects, irrespective of EPO administration. There was no difference in MMPs/TIMPs system, MDA and C-reactive levels between HD-EPO(+) and HD-EPO(-) patients.

CONCLUSION

Erythropoietin therapy did not influence MMPs/TIMPs system, inflammation, or SOX in a low-risk HD patient population, in the absence of concomitant iron supplementation and mean Hg levels within target.

Oxidatively-modified and glycated proteins as candidate pro-inflammatory toxins in uremia and dialysis patients

End stage renal disease (ESRD) patients accumulate blood hallmarks of protein glycation and oxidation. It is now well established that these protein damage products may represent a heterogeneous class of uremic toxins with pro-inflammatory and pro-oxidant properties. These toxins could be directly involved in the pathogenesis of the inflammatory syndrome and vascular complications, which are mainly sustained by the uremic state and bioincompatibility of dialysis therapy. A key underlying event in the toxicity of these proteinaceous solutes has been identified in scavenger receptor-dependent recognition and elimination by inflammatory and endothelial cells, which once activated generate further and even more pronounced protein injuries by a self-feeding mechanism based on inflammation and oxidative stress-derived events. This review examines the literature and provides original information on the techniques for investigating proteinaceous pro-inflammatory toxins. We have also evaluated therapeutic - either pharmacological or dialytic - strategies proposed to alleviate the accumulation of these toxins and to constrain the inflammatory and oxidative burden of ESRD.

Reliability of oxidative stress biomarkers in hemodialysis patients: a comparative study

BACKGROUND

Oxidative stress (OS) is considered to play a major role in the development of end-stage renal disease (ESRD) complications. However, conflicting and inconsistent data have been reported on OS in ESRD patients. Our aim was to investigate the reliability of the most popular non-enzymatic plasma OS biomarkers in ESRD.

METHODS

Vitamins A (VitA), E and C (VitC), uric acid, plasma antioxidant and ferric-reducing potential (PAP and PRP), thiols (SH), malondialdehyde (MDA) and lipid hydroperoxides (HPO) were determined before and after dialysis in plasma from 33 ESRD patients on hemodialysis, hemodiafiltration or peritoneal dialysis and 20 control subjects.

RESULTS

In ESRD patients, high PRP and normal PAP values were positively correlated with VitC levels. After dialysis, PRP levels decreased, while unchanged PAP levels correlated positively with high VitA and transiently recovered SH values. All patients showed high levels of both MDA and cholesterol-normalized HPO. However, while the former significantly decreased after dialysis, the latter were unaffected by treatment. Paradoxical correlations of MDA with both VitA and HPO were found.

CONCLUSIONS

Plasma PRP and MDA levels may be dramatically affected by both uremia and dialysis; their use in ESRD patients may therefore lead to OS misevaluation and should be avoided. More reliable results can be obtained using physiologically relevant OS functional tests, such as PAP, and early biomarkers of OS damage, such as SH and HPO.

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.

Telomere Shortening and Haemodialysis

BACKGROUND

Increased oxidative stress is a well described feature of haemodialysis (HD). This is secondary to an increase in the production of reactive oxygen species and impaired antioxidant mechanisms. Telomeres are the specialized ends of eukaryotic chromosomes and consist of tandemly repeated DNA sequences. Telomeres shorten with each cell division and it is well known that telomere length in peripheral blood mononuclear cells (PBMCs) decreases with age. Telomere shortening rate is increased by oxidative stress. In this study we have examined a possible relationship between oxidative stress and telomere shortening in haemodialysis.

METHODS

20 control subjects, 20 non-diabetic and 18 diabetic HD patients were studied. Peripheral blood mononuclear cell telomere length, plasma malondialdehyde plus 4-hydroxyalkenal (MDA+4-HAE) concentration (a marker of oxidative stress) and C-reactive protein (CRP) concentration were measured.

RESULTS

MDA+4-HAE and CRP were significantly higher in the HD patients (CRP, controls 7.5 +/- 1.5, HD patients 16.4 +/- 3.1 mg/l, p < 0.05). There was no difference in mean telomere length between the HD patients and controls (control, 8,283 +/- 179 bp; non-diabetic HD, 7,966 +/- 160 bp; diabetic HD, 8,033 +/- 197 bp) but age adjusted residual telomere length was inversely associated with the length of time on dialysis (r = -0.35, p = 0.03).

CONCLUSION

These results suggest that length of time on dialysis is independently associated with increased telomere shortening in HD patients. We hypothesise that this reflects cumulative DNA exposure to oxidative stress.

Cellulose, modified cellulose and synthetic membranes in the haemodialysis of patients with end-stage renal disease

BACKGROUND

When the kidney fails the blood-borne metabolites of protein breakdown and water cannot be excreted. The principle of haemodialysis is that such substances can be removed when blood is passed over a semipermeable membrane. Natural membrane materials include cellulose or modified cellulose, more recently various synthetic membranes have been developed. Synthetic membranes are regarded as being more "biocompatible" in that they incite less of an immune response than cellulose-based membranes.

OBJECTIVES

To assess the effects of different haemodialysis membrane material in patients with end-stage renal disease (ESRD).

SEARCH STRATEGY

We searched MEDLINE, EMBASE, PreMEDLINE, HealthStar CINAHL, the Cochrane Central Register of Controlled Trials (CENTRAL), Biosis, SIGLE, CRIB, UK National Research Register and reference lists of relevant articles. We contacted biomedical companies, known investigators and handsearched selected journals and conference proceedings. Date of most recent search: June 2004.

SELECTION CRITERIA

All randomised controlled trials (RCTs) or quasi-RCTs comparing different haemodialysis membrane material in patients with ESRD.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed the methodological quality of studies. Data was abstracted onto a standard form by one reviewer and checked by another. Relative Risk (RR) and weighted mean difference (WMD) with 95% confidence intervals (CI)) MAIN RESULTS: Thirty two studies were identified. Pre-dialysis ss(2) microglobulin concentrations were not significantly lower in patients treated with synthetic membranes (WMD -14.67, 95% CI -33.10 to 4.05). When analysed for change in ss(2) microglobulin, a fall was only noted with high-flux membranes. The incidence of amyloid was less in patients who were dialysed for six years with high-flux synthetic membranes (one study, RR 0.03, 95% CI 0.00 to 0.54). There was a significant difference in favour of the synthetic (high-flux) membrane in comparison to cellulose membranes for triglycerides (WMD -0.66; 95% CI -1.18 to -0.14) but not for modified cellulose membranes. Dialysis adequacy measured by Kt/V was marginally higher when cellulose membranes were used (WMD -0.10; 95% CI -0.16 to 0.04), whereas synthetic membranes achieved significantly higher Kt/V values when compared with modified cellulose membranes (WMD 0.20, 95% 0.11 to 0.29) . There were no data on quality of life measures.

AUTHORS' CONCLUSIONS

We found no evidence of benefit when synthetic membranes were compared with cellulose/modified cellulose membranes in terms of reduced mortality no reduction in dialysis-related adverse symptoms. Despite the relatively large number of RCTs undertaken in this area none of the included studies reported any measures of quality of life.

Influence of Epoietinum Therapy on the Oxidative Stress in Haemodialysis Patients

BACKGROUND

The causes of oxidative stress in haemodialysis (HD) patients are still controversial. Beside the uraemic state and dialysis-related factors, adjuvant drug therapies such as epoietinum (rHuEpo) and intravenous iron were involved.

METHODS

Several parameters related to oxidative stress were assessed by spectrophotometry in stable HD patients, treated for at least 2 months with epoietinum (n = 14; mean dose = 97.7 +/- 19.1 U/kg/week) or not (n = 15), none of them on iron therapy, and in 13 controls. Plasma thiobarbituric acid-reactive substances (TBARS) were used as markers of reactive species generation. Erythrocyte and plasma antioxidant systems, reflected by non-protein erythrocyte thiols, and erythrocyte enzyme activities -- superoxide dismutase (SOD), glutathione peroxidase, catalase and plasma total thiols, respectively -- were also investigated.

RESULTS

There were no differences between HD subgroups regarding haemoglobin levels. Plasma TBARS was increased in all HD patients as opposed to controls, irrespective of rHuEpo therapy. In addition, no change in antioxidant status parameters between rHuEpo-treated and -untreated patients was observed. Except for SOD, the other antioxidant indices were higher in all HD patients versus controls.

CONCLUSIONS

These results suggest that (1) chronic HD patients appear to have simultaneously enhanced reactive species generation and antioxidative systems efficiency, and (2) epoietinum therapy did not change their oxidative status, at least in the absence of concomitant iron supplementation and at similar haemoglobin levels.

Association between novel oxidative stress markers and C-reactive protein among adults without clinical coronary heart disease

OBJECTIVE

Increases in the inflammatory marker C-reactive protein (CRP) have been associated with a higher risk of incident coronary heart disease (CHD). The causes of increased CRP, however, are not completely understood. Studies suggest that oxidative stress may have pro-inflammatory effects, but data on the relationship between oxidative stress and CRP in healthy persons is sparse.

METHODS AND RESULTS

We conducted a cross-sectional study of oxidative stress markers and high sensitivity CRP (hsCRP) among 126 adults without CHD. Markers of oxidative stress included the free oxygen radical test (FORT), which reflects levels of organic hydroperoxides, and the redox potential of the reduced glutathione/glutathione disulfide couple, (Eh) GSH/GSSG. In a linear regression model that adjusted for age, sex, body mass index, and other potential hsCRP determinants, the FORT was positively associated with log-transformed hsCRP and explained 14% of log-transformed hsCRP variance (P < 0.001). In contrast, (Eh) GSH/GSSG showed little association with hsCRP.

CONCLUSIONS

Among adults free of CHD, oxidative stress, as measured by the FORT, is significantly associated with higher hsCRP levels, independent of BMI and other CRP determinants. This result suggests that oxidative stress may be a determinant of CRP levels and promote pro-atherosclerotic inflammatory processes at the earliest stages of CHD development.

Cognitive function in dialysis patients

There are few detailed studies of cognitive function in dialysis patients. However, appreciating the prevalence and risk factors for cognitive impairment is important because cognitive impairment may decrease an individual's quality of life, increase resource utilization, and result in suboptimal medical care because of difficulty following caregiver recommendations. Cognitive impairment also is likely to become more of a problem as the dialysis population ages. In this review, we argue that cerebrovascular disease is an important cause of cognitive impairment in dialysis patients and discuss risk factors specific for vascular disease, as well as other factors that may influence cognitive function. We describe the structural brain abnormalities frequently seen in dialysis patients and the specific neurocognitive changes noted in prior studies. We explore potential measures to reduce cognitive impairment in this population. We conclude that additional research is needed in this area.

Erythropoietin Increases Asymmetric Dimethylarginine in Endothelial Cells: Role of Dimethylarginine Dimethylaminohydrolase

Recombinant human erythropoietin therapy frequently causes hypertension in humans and animals with chronic renal failure. Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide (NO) synthase, and its accumulation has been associated with reducing NO bioavailability and increasing superoxide generation. Whether epoetin beta (EPO) or darbepoetin alpha (NESP) can modify the levels of ADMA in endothelial cells was investigated. Endothelial cells from the third passage were incubated for 24 h in the presence of various concentrations of EPO or NESP (0, 0.1, 1, 10, 50, 100, and 200 U/ml). The levels of ADMA, allantoin, nitrate, and nitrite in conditioned media and the activity of dimethylarginine dimethylaminohydrolase (DDAH), the content of thiols and reactive oxygen species in endothelial cells, were determined. When endothelial cells were exposed to EPO or NESP, ADMA concentration in the cell culture medium increased significantly in a dose-dependent manner versus control. This effect was associated with a reduced activity of DDAH, the enzyme that degrades ADMA. Furthermore, EPO- or NESP-induced accumulation of ADMA was accompanied by a significant reduction of NO synthesis and an increase in oxidative stress. Both allantoin, a marker of oxygen free radical generation, and reactive oxygen species increased significantly after EPO or NESP treatment compared with control. The antioxidant pyrrolidine dithiocarbamate preserved DDAH activity and reduced ADMA accumulation in the same way as the co-incubation with anti-EPO neutralizing antibody. EPO and NESP posttranslationally impair DDAH activity via increased oxidative stress, causing ADMA as an important cardiovascular risk factor to accumulate and inhibit NO synthesis.

Antioxidant therapy in uremia: evidence-based medicine?

Because of correlations between cardiovascular disease, inflammation, and renal failure, many investigators are pursuing nontraditional risk factors and therapies in order to reduce cardiovascular morbidity and mortality in the end-stage renal disease (ESRD) population. Despite the disappointing lack of clinical effects with antioxidative therapies seen in large studies of the general population, some studies suggest a diminished cardiovascular risk in individuals with renal failure. This expanding new line of evidence is promising as a method to help alleviate the more than 20-fold increase in risk of cardiovascular events in the ESRD population. Most of the current available studies have evaluated laboratory or physiologic endpoints, such as endothelial function and measures of oxidative burden, and have evaluated relatively small numbers of patients. However, it is currently premature to initiate widespread clinical therapy with antioxidants. Further investigation in this area should be supported to see if reported benefits can be duplicated in more widespread study populations, and to more accurately define the most appropriate choice of therapy, mode of therapy, and dose.

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.

Vitamin E-coated dialyzer and antioxidant defense parameters: Three-month study

Atherosclerotic cardiovascular disease is the most frequent cause of death in patients with end-stage renal disease who have undergone dialysis treatment. Oxidative stress, increased lipid peroxidation, and impaired function of antioxidant systems may contribute to the accelerated development of atherosclerosis in chronic renal failure patients during renal replacement therapy. The aim of this study was to investigate the influence of a vitamin E-coated dialyzer on antioxidant defense parameters in hemodialysis (HD) patients. In 14 HD patients, hemodialysis was performed using a vitamin E-coated dialyzer (Terumo CL-E15NL; Terumo Corporation, Tokyo, Japan) during a 3-month study. In these patients, erythrocyte (ER) antioxidant enzymes, superoxide dismutase (SOD), glutathione peroxidase (GPX), glutathione reductase (GR) and catalase (CAT), plasma total antioxidant capacity (TAC), RBC glutathione (GSH), plasma malondialdehyde (MDA), plasma, and RBC vitamin E were investigated. Each parameter was measured at the beginning of the study, after the 1st, 2nd, and 3rd month of the study, and 10 weeks after the interruption of the use of vitamin E-coated dialyzer. All HD patients were treated by erythropoietin (EPO) and received vitamin C 50 mg/d, pyridoxine 20 mg/d, and folic acid 5 mg/wk during the entire study. The 3-month treatment with the vitamin E-coated dialyzer led to a significant decrease of plasma MDA level (from 2.85 +/- 0.44 to 2.25 +/- 0.37 micromol/L) and to an increase of plasma TAC, RBC, GSH, and the vitamin E levels both in plasma (from 25.9 +/- 2.8 to 33.6 +/- 3.8 micromol/L) and in the RBCs (from 6.7 +/- 0.8 to 7.4 +/- 0.7 micromol/L) by 30% and 10.5%, respectively. Ten-week interruption of the use of the vitamin E-coated dialyzer led to near initial values of MDA (2.90 +/- 0.28 micromol/L), plasma (28.6 +/- 3.5 micromol/L), and RBC (6.9 +/- 0.7 micromol/L) vitamin E and of other investigated parameters. Statistical analysis of results was performed by conventional methods and analysis of variance. The findings of the current study confirm the beneficial effect of the vitamin E-coated dialyzer against oxidative stress in HD patients.

Accumulation of vitamin E metabolites in the blood of renal failure patients

BACKGROUND & AIMS

Carboxyethyl-hydroxychromans (CEHC) are hydrosoluble vitamin E metabolites excreted through the renal filter. In this study we investigated the effect of the kidney damage on the blood levels of CEHC.

METHODS

Plasma levels of alpha-CEHC, gamma-CEHC and their precursors (namely, alpha-tocopherol and gamma-tocopherol) were measured by HPLC with electrochemical detection in chronic (CRF) and end-stage renal failure patients on regular hemodialysis (HD) before and after dialysis. CRF patients (n = 26) were divided into three subgroups with different extent of kidney damage as measured by the intervals of creatinine clearance (CrCl, in ml/min): (a) 2-10, (b) 10-20, and (c) 20-45. HD patients (n = 8) did not show residual renal function. In all the subjects the intake of vitamin E (as alpha-tocopherol) was assessed using a food frequency questionnaire. In the HD group, the plasma concentrations of ascorbic and uric acid (AA and UA, respectively), total thiols, the total antioxidant status (TAS) and reactive carbonyls were also measured.

RESULTS

The progressive deterioration of the kidney function in the different groups of patients produced an exponential increase of both alpha-CEHC and gamma-CEHC in plasma. Compared with healthy controls (alpha-CEHC = 20.1+/-13.4 and gamma-CEHC = 230.6+/-83.0 nmol/l) the levels of CEHC approximately doubled in patients with CrCl < or = 20ml/min (42.4+/-20.2 and 424.5.5+/-174.4; P <0.05 or higher in both) and reached a 3-fold maximum increase in HD patients (77.3+/-45.7 and 636.6+/-219.3). The hemodialysis provided a significant, but only a transient, correction of CEHC accumulation (44.8+/-23.5, 364.2+/-189.9). The HD patients showed lower intake and levels of vitamin E (alpha-tocopherol = 5.1+/-1.0 and gamma-tocopherol =0.32+/-0.11 micromol/mmol cholesterol; P <0.05) compared to healthy controls (5.8+/-0.8 and 0.43+/-0.14), but in the CRF patients tocopherol levels were normal or only slightly decreased even though approximately half of the subject had lowered vitamin E intake. When the entire patient population was considered, the blood concentrations of parental tocopherols and CEHC did not correlate. The HD patients before dialysis showed a marked decrease of TAS/UA, AA and thiols levels, while UA and free carbonyls significantly increased. After dialysis, the depletion of AA and thiols further worsened and also UA and TAS/UA decreased, but free carbonyls slightly increased.

CONCLUSIONS

The results other than to confirm the key importance of the renal route for the excretion of CEHC, demonstrate that CEHC cannot be reliably used to investigate vitamin E biokinetics and transformation without a careful examination of the renal function. CEHC accumulation does not seem to influence the antioxidant status in the plasma of HD patients. Further studies are requested to establish whether such an increase in blood CEHC concentrations might be harmful or could contribute to the biological functions of the vitamin E in uremia and dialysis patients.