Homocysteine and lipid peroxidation in haemodialysis: role of folinic acid and vitamin E

The Role of Oxidative Stress in Kidney Injury

Acute kidney injury and chronic kidney disease are among the most common non-communicable diseases in the developed world, with increasing prevalence. Patients with acute kidney injury are at an increased risk of developing chronic kidney disease. One of kidney injury's most common clinical sequelae is increased cardiovascular morbidity and mortality. In recent years, new insights into the pathophysiology of renal damage have been made. Oxidative stress is the imbalance favoring the increased generation of ROS and/or reduced body's innate antioxidant defense mechanisms and is of pivotal importance, not only in the development and progression of kidney disease but also in understanding the enhanced cardiovascular risk in these patients. This article summarizes and emphasizes the role of oxidative stress in acute kidney injury, various forms of chronic kidney disease, and also in patients on renal replacement therapy (hemodialysis, peritoneal dialysis, and after kidney transplant). Additionally, the role of oxidative stress in the development of drug-related nephrotoxicity and also in the development after exposure to various environmental and occupational pollutants is presented.

Evaluation of the combination effect of rutin and vitamin C supplementation on the oxidative stress and inflammation in hemodialysis patients

Background: Hemodialysis (HD) patients are at risk of malnutrition, cardiovascular complications, and all-cause mortality due to oxidative stress and inflammation. Some studies have demonstrated that rutin attenuates oxidative stress and inflammation in CKD rats, but its effects in HD patients are unknown to date.

Aim: The aim of this study was to evaluate the effect of rutin and vitamin C versus vitamin C alone on oxidative stress and inflammation in HD patients.

Methods: A prospective randomized, open-label, controlled trial enrolled on hundred and five HD patients divided into three groups as follows: patients in group 1 were given a rutin/vitamin C combination (Ruta C group as the combination trade name is known as Ruta C 60 tablets), patients in group 2 were given vitamin C (1 g) (vitamin C group), and group 3 was the control group; the study period was 16 weeks. The following were assessed at baseline and at the end of the study: serum malondialdehyde (MDA), glutathione peroxidase (GPx), high-sensitivity C-reactive protein (hs-CRP), tumor necrosis factor-α (TNF-α), lipid profile levels, and erythrocyte sedimentation rate.

Results: It was found that vitamin C significantly increased serum GPx in group 2 (p = 0.001) compared to a non-significant result in both group 1 and 3; in addition, serum MDA and TNF-α values had decreased significantly in the three groups compared to their baselines; however, a non-significant difference was seen among the studied groups at the end of the study. On the other hand, MDA levels were reduced by 50% in interventional groups compared to 28% in the control group, while the Ruta C group showed an 80% reduction in the level of TNF α compared to the 78% reduction observed in the vitamin C group, and finally, the interventional drugs showed a significant improvement in the lipid profile.

Conclusion: Vitamin C supplementation alone for 16 weeks had a potential effect on the antioxidant’s GPx activity. Moreover, it was reported that both vitamin C alone or the rutin/vitamin C combination (Ruta C) showed a protective role against lipid peroxidation, evidenced by the reduced levels of MDA. Finally, rutin had a favorable synergistic effect with vitamin C in reducing TG and TNF-α levels and increasing HDL-C level.

The effects of vitamin B12 supplementation on metabolic profile of patients with non-alcoholic fatty liver disease: a randomized controlled trial

The present study is the first effort to evaluate the effects of vitamin B12 supplementation on the serum level of liver enzymes, homocysteine, grade of hepatic steatosis, and metabolic profiles in patients with non-alcoholic fatty liver disease (NAFLD). Forty patients with NAFLD were enrolled in a double-blind placebo-controlled trial to receive either one oral tablet of vitamin B12 (1000 µg cyanocobalamin) or a placebo per day for 12 weeks. We investigated serum levels of homocysteine, aminotransferases, fasting blood glucose (FBG), lipids, malondialdehyde (MDA), and homeostasis model assessment of insulin resistance (HOMA-IR). The grade of liver steatosis and fibrosis was measured by real-time 2-dimensional shear wave elastography. Vitamin B12 supplementation significantly decreased serum levels of homocysteine compared to placebo (medians: - 2.1 vs. - 0.003 µmol/l; P = 0.038). Although serum alanine transaminase (ALT) in the vitamin B12 group decreased significantly, this change did not reach a significant level compared to the placebo group (medians: - 7.0 vs. 0.0 IU/l; P > 0.05). Despite the significant within-group decrease in FBG, MDA, and liver steatosis in the vitamin B12 group, between-group comparisons did not reveal any significant difference. Vitamin B12 supplementation might decrease serum levels of homocysteine in patients with NAFLD. The fasting blood glucose and serum levels of MDA were significantly improved in the trial group who received vitamin B12. However, these changes did not reach a significant level compared to the placebo group. In this respect, further studies with larger sample sizes, different doses, and types of vitamin B12 will reveal additional evidence.Trial Registration: At  http://irct.ir/  as IRCT20120718010333N5 on December 25, 2019.

Vitamin E‑coated dialyzer alleviates erythrocyte deformability dysfunction in patients with end‑stage renal disease undergoing hemodialysis

Patients with end-stage renal disease (ESRD) are characterized by augmented oxidative stress (OS) due to the imbalance between the generation of increased concentrations of oxidative molecules and decreased antioxidant capacity. Vitamin E-coated dialyzer membranes (VEMs) have previously been reported to alleviate the imbalance of redox metabolism in patients with ESRD undergoing hemodialysis (HD); however, their effect on the deformability of red blood cells (RBCs) remains unknown. In the present study, 48 patients with ESRD undergoing HD were enrolled and randomly assigned into two groups: HD with VEMs (VEM group; n=24) and HD with polysulfone dialyzer membranes (PM group; n=24), and another 24 healthy volunteers served as the control group. The present study investigated the morphological changes and deformability of RBCs in patients with ESRD and healthy volunteers. The concentration of serum vitamin E, the parameters of antioxidant stress and OS, and the degree of oxidative phosphorylation and clustering of anion exchanger 1 (Band 3) in RBCs were measured. The results obtained suggested that VEM treatment markedly ameliorated the abnormalities of RBC morphology and deformability in patients with ESRD undergoing HD. Mechanistic studies showed that VEM treatment led to a marked improvement in the concentration of serum vitamin E, which was positively associated with the restored antioxidant capacity, and decreased oxidative phosphorylation and clustering of Band 3 in RBCs of patients with ESRD undergoing HD. Taken together, the results of the present study have demonstrated that VEM treatment effectively restored the imbalance of redox metabolism, and improved the oxidative phosphorylation and clustering of Band 3 in RBCs of patients with ESRD undergoing HD via delivering vitamin E, which may alleviate the abnormal morphological and mechanical properties of RBCs. These findings are anticipated to be useful with respect to improving the nursing care and cure rate of patients with ESRD.

Impact of Physical Activity and Natural Bioactive Compounds on Endothelial Dysfunction in Chronic Kidney Disease

Chronic kidney disease (CKD) represents a world-wide public health problem. Inflammation, endothelial dysfunction (ED) and vascular calcifications are clinical features of CKD patients that increase cardiovascular (CV) mortality. CKD-related CV disease pathogenic mechanisms are not only associated with traditional factors such as arterial hypertension and dyslipidemia, but also with ED, oxidative stress and low-grade inflammation. The typical comorbidities of CKD contribute to reduce the performance and the levels of the physical activity in nephropathic patients compared to healthy subjects. Currently, the effective role of physical activity on ED is still debated, but the available few literature data suggest its positive contribution. Another possible adjuvant treatment of ED in CKD patients is represented by natural bioactive compounds (NBCs). Among these, minor polar compounds of extra virgin olive oil (hydroxytyrosol, tyrosol and oleocanthal), polyphenols, and vitamin D seem to exert a beneficial role on ED in CKD patients. The objective of the review is to evaluate the effectiveness of physical exercise protocols and/or NBCs on ED in CKD patients.

Standardized Aronia melanocarpa extract regulates redox status in patients receiving hemodialysis with anemia

The aim of our study was to investigate the effects of one-month consumption of polyphenol-rich standardized Aronia melanocarpa extract (SAE) on redox status in anemic hemodialysis patients. The study included 30 patients (Hb < 110 g/l, hemodialysis or hemodiafiltration > 3 months; > 3 times week). Patients were treated with commercially available SAE in a dose of 30 ml/day, for 30 days. After finishing the treatment blood samples were taken to evaluate the effects of SAE on redox status. Several parameters of anemia and inflammation were also followed. After the completion of the treatment, the levels of superoxide anion radical and nitrites significantly dropped, while the antioxidant capacity improved via elevation of catalase and reduced glutathione. Proven antioxidant effect was followed by beneficial effects on anemia parameters (increased hemoglobin and haptoglobin concentration, decreased ferritin and lactate dehydrogenase concentration), but SAE consumption didn't improve inflammatory status, except for minor decrease in C-reactive protein. The consumption of SAE regulates redox status (reduce the productions of pro-oxidative molecules and increase antioxidant defense) and has beneficial effects on anemia parameters. SAE could be considered as supportive therapy in patients receiving hemodialysis which are prone to oxidative stress caused by both chronic kidney disease and hemodialysis procedure. Additionally, it could potentially be a good choice for supplementation of anemic hemodialysis patients. TRN: NCT04208451 December 23, 2019 "retrospectively registered".

The effects of vitamin E supplementation on malondialdehyde as a biomarker of oxidative stress in haemodialysis patients: a systematic review and meta-analysis

Background

Haemodialysis (HD) patients tend to have higher levels of oxidative stress (OS), associated with increased morbidity and premature mortality, compared to the general population. Levels of malondialdehyde (MDA), a biomarker of OS, are reduced by the antioxidant properties of vitamin E (VE) but outcomes from randomised control trials of VE supplementation on MDA in HD patients have been inconsistent.

Methods

We undertook a systematic review and meta-analysis of adult HD patients from VE supplementation studies with measures of MDA. The following search criteria of MEDLINE and EMBASE were considered from inception to January 2020: ‘dialysis’ AND ‘Vitamin E OR tocopherol’ AND ‘malondialdehyde OR MDA’. Two reviewers independently extracted study data and assessed risk of bias. Mean MDA levels and standard deviation were determined before and after VE supplementation. Standardised mean difference (SMD) and standard error were calculated as the within person difference and units of measure were not consistently recorded across all studies. The SMD were pooled using random effects meta-analysis.

Results

The SMD of MDA levels from 18 comparisons was significantly lower in HD patients following VE supplementation (− 1.55; confidence interval: − 2.17 to − 0.94, P < 0.00001). There were significant levels of heterogeneity between studies (I² value = 91%; P < 0.00001) with evidence of potential publication bias toward smaller studies.

Conclusions

Our findings support the use of VE to reduce the effects of OS in HD patients although high levels of heterogeneity and variation in the methodological approaches used by some studies highlight the need for further investigation.

Cardiovascular disease in dialysis patients

Cardiovascular disease (CVD) is a highly common complication and the first cause of death in patients with end-stage renal disease (ESRD) on haemodialysis (HD). In this population, mortality due to CVD is 20 times higher than in the general population and the majority of maintenance HD patients have CVD. This is likely due to ventricular hypertrophy as well as non-traditional risk factors, such as chronic volume overload, anaemia, inflammation, oxidative stress, chronic kidney disease–mineral bone disorder and other aspects of the ‘uraemic milieu’. Better understanding the impact of these numerous factors on CVD would be an important step for prevention and treatment. In this review we focus non-traditional CVD risk factors in HD 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.

Oxidative stress in hemodialysis: Causative mechanisms, clinical implications, and possible therapeutic interventions

Oxidative stress (OS) is the result of prooxidant molecules overwhelming the antioxidant defense mechanisms. Hemodialysis (HD) constitutes a state of elevated inflammation and OS, due to loss of antioxidants during dialysis and activation of white blood cells triggering production of reactive oxygen species. Dialysis vintage, dialysis methods, and type and condition of vascular access, biocompatibility of dialyzer membrane and dialysate, iron administration, and anemia all can play a role in aggravating OS, which in turn has been associated with increased morbidity and mortality. Oral or intravenous administration of antioxidants may detoxify the oxidative molecules and at least in part repair OS-mediated tissue damage. Lifestyle interventions and optimization of a highly biocompatible HD procedure might ameliorate OS development in dialysis.

Oxidative Stress in Hemodialysis Patients: A Review of the Literature

Hemodialysis (HD) patients are at high risk for all-cause mortality and cardiovascular events. In addition to traditional risk factors, excessive oxidative stress (OS) and chronic inflammation emerge as novel and major contributors to accelerated atherosclerosis and elevated mortality. OS is defined as the imbalance between antioxidant defense mechanisms and oxidant products, the latter overwhelming the former. OS appears in early stages of chronic kidney disease (CKD), advances along with worsening of renal failure, and is further exacerbated by the HD process per se. HD patients manifest excessive OS status due to retention of a plethora of toxins, subsidized under uremia, nutrition lacking antioxidants and turn-over of antioxidants, loss of antioxidants during renal replacement therapy, and leukocyte activation that leads to accumulation of oxidative products. Duration of dialysis therapy, iron infusion, anemia, presence of central venous catheter, and bioincompatible dialyzers are several factors triggering the development of OS. Antioxidant supplementation may take an overall protective role, even at early stages of CKD, to halt the deterioration of kidney function and antagonize systemic inflammation. Unfortunately, clinical studies have not yielded unequivocal positive outcomes when antioxidants have been administered to hemodialysis patients, likely due to their heterogeneous clinical conditions and underlying risk profile.

Intradialytic Oral Protein Supplementation and Nutritional and Inflammation Outcomes in Hemodialysis: A Randomized Controlled Trial

BACKGROUND

Malnutrition is a common finding in hemodialysis patients and can increase oxidative stress and inflammation levels.

STUDY DESIGN

A randomized, controlled, nonblinded, parallel trial.

SETTING & PARTICIPANTS

92 hemodialysis patients from a single center with malnutrition according to subjective global assessment (SGA) score (SGA score > 7).

INTERVENTION

3 treatment groups (23 patients each) received 220mL of fermented vitamin E-fortified whey beverage (15g of whey protein concentrate + 600IU of vitamin E) or 220mL of fermented whey beverage (15g of whey protein concentrate) or vitamin E (600IU) 3 times a week for 8 weeks. The control group (23 patients) received no intervention.

OUTCOME & MEASUREMENTS

Primary outcomes were change in SGA score and malnutrition-inflammation score (MIS) from baseline to the end of the trial.

RESULTS

At the end of the study, 83 patients were analyzed (2, 3, 1, and 3 patients left the study in the vitamin E-fortified whey beverage, whey beverage, vitamin E, and control groups, respectively). Changes in SGA scores were -3.48 (95% CI, -4.90 to -2.00), -3.22 (95% CI, -4.13 to -2.30), -1.70 (95% CI, -3.20 to -0.24), and 1.56 (95% CI, 0.60 to 2.50) for the vitamin E-fortified whey beverage, whey beverage, vitamin E, and control groups, respectively (overall P<0.001; P≤0.001 for each treatment group vs control). Changes in MISs were -3.17 (95% CI, -4.40 to -1.90), -1.83 (95% CI, -2.50 to -1.10), -2.30 (95% CI, -3.50 to -1.10), and 1.48 (95% CI, 0.65 to 2.30) for the vitamin E-fortified whey beverage, whey beverage, vitamin E, and control groups, respectively (overall P<0.001; P<0.001 for each treatment group vs control). Few adverse effects were reported in any group.

LIMITATIONS

Lack of blinding, small sample size, and short duration.

CONCLUSIONS

Whey protein in the form of a new fermented whey beverage and vitamin E supplementation may improve SGA score and MIS in the short term.

Folic acid supplementation at lower doses increases oxidative stress resistance and longevity in Caenorhabditis elegans

Folic acid (FA) is an essential nutrient that the human body needs but cannot be synthesized on its own. Fortified foods and plant food sources such as green leafy vegetables, beans, fruits, and juices are good sources of FA to meet the daily requirements of the body. The aim was to evaluate the effect of dietary FA levels on the longevity of well-known experimental aging model Caenorhabditis elegans. Here, we show for first time that FA extends organism life span and causes a delay in aging. We observed that FA inhibits mechanistic target of rapamycin (mTOR) and insulin/insulin growth factor 1 (IGF-1) signaling pathways to control both oxidative stress levels and life span. The expression levels of stress- and life span-relevant gerontogenes, viz. daf-16, skn-1, and sir. 2.1, and oxidative enzymes, such as glutathione S-transferase 4 (GST-4) and superoxide dismutase 3 (SOD-3), were also found to be highly enhanced to attenuate the intracellular reactive oxygen species (ROS) damage and to delay the aging process. Our study promotes the use of FA to mitigate abiotic stresses and other aging-related ailments.

In vitro antioxidant activity and in vivo antifatigue effect of layered double hydroxide nanoparticles as delivery vehicles for folic acid

Folic acid antioxidants were successfully intercalated into layered double hydroxides (LDH) nanoparticles according to a previous method with minor modification. The resultant folic acid-LDH constructs were then characterized by X-ray powder diffraction and transmission electron microscopy. The in vitro antioxidant activities, cytotoxicity effect, and in vivo antifatigue were examined by a series of assays. The results showed that folic acid-LDH antioxidant system can scavenge 1,1-diphenyl-2-picrylhydrazyl and hydroxyl free radicals and chelate pro-oxidative Cu²⁺. The in vitro cytotoxicity assays indicated that folic acid-LDH antioxidant system had no significant cytotoxic effect or obvious toxicity to normal cells. It also prolonged the forced swimming time of the mice by 32% and 51% compared to folic acid and control groups, respectively. It had an obvious effect on decreasing the blood urea nitrogen and blood lactic acid, while increasing muscle and hepatic glycogen levels. Therefore, folic acid-LDH might be used as a novel antioxidant and antifatigue nutritional supplement.

Oxidative hepatotoxicity effects of monocrotaline and its amelioration by lipoic acid, S-adenosyl methionine and vitamin E

Liver is the major site for several xenobiotics metabolism, and formation of toxic metabolites that may be hepatotoxic, therefore the burden of metabolism and exposure to dangerous chemicals make liver vulnerable to a variety of disorders. Our work aimed to investigate the effects of some antioxidants such as lipoic acid (LA), S-adenosyl methionine (SAM) and vitamin E in a trail to investigate the possibility of using these substances to relieve and protect liver from exposure to monocrotaline (MCT). Twenty-five mature adult rats were classified into five groups (five rats in each group), control group, MCT-induced hepatic damage, LA+MCT, SAM+MCT and vitamin E+MCT group. Homogenates of liver samples were used for measuring the oxidative biomarkers and hepatic antioxidant status. The results showed that administration of vitamin E, SAM and LA caused a significant increase in liver glutathione contents, glutathione reductase, glutathione peroxidase and glutathione-S-transferase activities and a significant decrease in hepatic catalase and superoxide dismutase. We could conclude that administration of natural LA, SAM and vitamin E before and after MCT injection modulate the hepatic oxidative stresses induced by MCT in various extents.

Normal and pathologic concentrations of uremic toxins

An updated review of the existing knowledge regarding uremic toxins facilitates the design of experimental studies. We performed a literature search and found 621 articles about uremic toxicity published after a 2003 review of this topic. Eighty-seven records provided serum or blood measurements of one or more solutes in patients with CKD. These records described 32 previously known uremic toxins and 56 newly reported solutes. The articles most frequently reported concentrations of β2-microglobulin, indoxyl sulfate, homocysteine, uric acid, and parathyroid hormone. We found most solutes (59%) in only one report. Compared with previous results, more recent articles reported higher uremic concentrations of many solutes, including carboxymethyllysine, cystatin C, and parathyroid hormone. However, five solutes had uremic concentrations less than 10% of the originally reported values. Furthermore, the uremic concentrations of four solutes did not exceed their respective normal concentrations, although they had been previously described as uremic retention solutes. In summary, this review extends the classification of uremic retention solutes and their normal and uremic concentrations, and it should aid the design of experiments to study the biologic effects of these solutes in CKD.

Comparative effects of silymarin and vitamin E supplementation on oxidative stress markers, and hemoglobin levels among patients on hemodialysis

BACKGROUND

The incidence of accelerated atherosclerosis among patients on hemodialysis is very high and oxidative stress (OS) is a potentially major contributor to their morbidity and mortality.

OBJECTIVE

To evaluate the effects of Silymarin and/or vitamin E on OS markers and hemoglobin levels in patients on hemodialysis.

METHODS

Eighty patients on hemodialysis were randomized into four groups: Group 1 received silymarin 140 mg 3 times daily; Group 2 received vitamin E 400 IU/day; Group 3 received silymarin 140 mg 3 times daily and vitamin E 400 IU/day; and Group 4 was the control. Samples were obtained at baseline and on day 21 for measurement of malondialdehyde (MDA), red blood cell (RBC) glutathione peroxidase (GPX), and hemoglobin.

RESULTS

Combination of silymarin and vitamin E led to a reduction in the MDA levels (7.84 ± 1.84 vs. 9.20 ± 2.74 nmol/mL; p = 0.008). There was a significant increase in RBC GPX levels in all treatment groups compared with controls after 3 weeks. This was more pronounced in the group receiving combination compared with the group receiving vitamin E or the control group (5.78 ± 3.51, 4.22 ± 1.63, and 3.16 ± 1.89 IU/grHb, respectively; p < 0.001). There was also a significant increase in mean hemoglobin of all treatment groups compared with the control.

CONCLUSIONS

Oral supplementation with silymarin and vitamin E leads to reduction in MDA, increase in RBC GPX, and increase in hemoglobin levels in patients with end-stage renal disease. Studies with larger sample sizes and longer follow-up are required to investigate the effect of silymarin on cardiovascular outcomes and erythropoietin requirement.

Salvianolic acid B inhibits low-density lipoprotein oxidation and neointimal hyperplasia in endothelium-denuded hypercholesterolaemic rabbits

BACKGROUND

Atherosclerosis and restenosis are inflammatory responses involving free radicals and lipid peroxidation and may be prevented/cured by antioxidant-mediated lipid peroxidation inhibition. Salvianolic acid (Sal B), a water-soluble antioxidant obtained from a Chinese medicinal herb, is believed to have multiple preventive and therapeutic effects against human vascular diseases. In this study the in vitro and in vivo inhibitory effects of Sal B on oxidative stress were determined.

RESULTS

In human aortic endothelial cells (HAECs), Sal B reduced oxidative stress, inhibited low-density lipoprotein (LDL) oxidation and reduced oxidised LDL-induced cytotoxicity. Sal B inhibited Cu(2+) -induced LDL oxidation in vitro (with a potency 16.3 times that of probucol) and attenuated HAEC-mediated LDL oxidation as well as reactive oxygen species (ROS) production. In cholesterol-fed New Zealand White rabbits (with probucol as positive control), Sal B intake reduced Cu(2+) -induced LDL oxidation, lipid deposition in the thoracic aorta, intimal thickness of the aortic arch and thoracic aorta and neointimal formation in the abdominal aorta.

CONCLUSION

The data obtained in this study suggest that Sal B protects HAECs from oxidative injury-mediated cell death via inhibition of ROS production. The antioxidant activity of Sal B may help explain its efficacy in the treatment of vascular diseases.

Antioxidant therapy does not ameliorate oxidative stress and inflammation in patients with end-stage renal disease

Oxidative stress and inflammation are common manifestations and major mediators of cardiovascular and many other complications of end-stage renal disease (ESRD). Oxidative stress and inflammation are intimately interrelated as each can cause the other. The present study tested the hypothesis that antioxidant therapy may alleviate oxidative stress and improve inflammation in ESRD patients. We studied 37 hemodialysis patients, of whom 20 were treated daily with a combination of vitamin E, 800 lU; vitamin C, 250 mg; vitamin B6, 100 mg; vitamin B12, 250 microg; and folic acid, 10 mg; whereas 17 patients were given placebo for 8 weeks. Predialysis levels of f-2 isoprostane and protein carbonyl (markers of oxidative stress), C-reactive protein (CRP) and IL6 (markers/ mediators of inflammation) were measured prior to and at 4 and 8 weeks after the onset of therapy. Kt/V, predialysis and postdialysis blood pressure, blood hemoglobin, erythropoietin requirement, plasma ferritin and transferrin saturation, and nutritional indexes were similar among the 2 groups at baseline and remained virtually unchanged throughout the study period. Likewise, plasma f-2 isoprostane, protein carbonyl, CRP, and IL-6 levels remained unchanged and were unaffected by antioxidant administration. In conclusion, the addition of a potent antioxidant cocktail to conventional vitamin supplements had no effect on severity of ESRD-induced oxidative stress, inflammation, hypertension, anemia, or nutritional disorders in hemodialysis patients. Thus, high doses of vitamins beyond the routinely prescribed vitamin supplements do not appear to be indicated in this population.

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

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

Inconsistency of reported uremic toxin concentrations

Discrepancies in reported uremic toxin concentrations were evaluated for 78 retention solutes. For this analysis, 378 publications were screened. Up to eight publications per toxin were retained. The highest and the lowest reported concentrations, as well as the median reported concentration were registered. The ratio between the highest and the lowest (H/L) concentrations and, for some solutes, also the ratio between the highest and the median (H/M) concentrations were calculated. The compounds were arbitrarily subdivided into three groups based on their H/L ratio: group A, H/L < 3 (n = 33); group B, 3 < H/L < 8.5 (n = 20); and group C, H/L > 8.5 (n = 25). Solutes of groups A and B showed a low to intermediate scatter, suggesting a homogeneity of reported data. Group C showed a more substantial scatter. For at least 10 compounds of group C, extremely divergent concentrations were registered (H/M > 5.5) using scatter plot analysis. For all solutes of groups A and B, the highest reported concentration could be used as a reference. For some solutes of group C and for the compounds showing a divergent scatter analysis, however, more refined directives should be followed.

Elimination of lipid peroxide during hemodialysis

BACKGROUND/AIMS

This study is aimed to show the antioxidative effect of hemodialysis (HD) by demonstrating the elimination of toxic lipid peroxides.

METHODS

Blood samples were obtained from patients on regular maintenance HD before and 15, 30, 60, 120 and 240 min after the start of each HD session. Plasma cholesteryl ester hydroperoxide (CE-OOH), phosphatidylcholine hydroperoxide (PC-OOH), and eliminators of lipid peroxides (LOOH) such as apolipoprotein A-I (apoA-I) and lecithin:cholesterol acyltransferase (LCAT) were investigated. The hydroxyl radical scavenging activity was measured for the evaluation of the pro-oxidative side.

RESULTS

CE-OOH and PC-OOH were elevated in patients with chronic kidney disease both on and not on HD, while these values were much higher in HD patients. CE-OOH quickly dropped during the first 30 min of HD, then gradually decreased until 240 min. CE-OOH concentrations were related to those of apoA-I. In contrast, PC-OOH showed an increase 30 min after the start of HD, a change which resembled that of LCAT and was the reverse of the hydroxyl radical scavenging activity.

CONCLUSION

These results demonstrate the antioxidative action through CE-OOH elimination involving apoA-I. The pro- and antioxidative effects of HD on LOOH are not uniform but PC-OOH is mainly influenced prooxidatively.

Folic acid therapy reduces plasma homocysteine levels and improves plasma antioxidant capacity in hemodialysis patients

OBJECTIVE

We evaluated the effects of folic acid on homocysteine levels and oxidative stress in 46 stable patients on hemodialysis.

METHODS

This double-blind, placebo-controlled, randomized trial assessed the effects of 6 mo of 10 mg of folic acid (26 patients) or placebo (20 patients) given three times weekly after each dialysis under nurse supervision on homocysteine levels, total plasma antioxidant capacity, and hydroperoxide plasma levels.

RESULTS

Folic acid treatment normalized plasma homocysteine levels in most patients, significantly increased total plasma antioxidant capacity levels, but had no significant effect on hydroperoxide levels. Placebo treatment had no statistically significant effect on the three parameters.

CONCLUSION

The folic acid therapy protocol effectively lowered plasma homocysteine levels and improved the total plasma antioxidant capacity in hemodialysis patients. Further studies are required to assess the usefulness of folic acid for decreasing cardiovascular mortality in patients with chronic kidney disease.

Analysis of dyslipidemia in patients on chronic hemodialysis in Catalonia

Chronic hemodialysis patients show a high incidence and prevalence of cardiovascular disease of multifactorial etiology and an association between dyslipidemia and accelerated atherosclerosis. We analyzed characteristics of dyslipidemia in 1824 hemodialysis patients (59% men; mean age 65 +/- 15 years) in Catalonia and identified risk factors by logistic regression. Prevalence of dyslipidemia was high (63%). Most frequent lipid alterations were decreased HDL cholesterol (40%), hypertriglyceridemia (31%) and hypercholesterolemia (19%). Total cholesterol/HDL ratio was elevated in 23%. Body mass index (OR 1.08; 95% CI 1.05-1.11), diabetes mellitus (1.4; 1.09-1.79), ischemic heart disease (1.38, 1.08-1.75) and stroke (1.30; 1.0-1.69) were independent factors associated with dyslipidemia. Lengthy time (> 7 years) on dialysis (0.77; 0.59-0.99) and female sex (0.78; 0.64-0.96) were independent protective factors. A significant reduction in the risk of developing dyslipidemia was observed after the age of 50. Lipid-lowering drug use was low (19%), with statins being the most frequent (83%). The percentage of patients reaching target LDL levels according to individual cardiovascular risk (ATPIII) was unsatisfactory, particularly in high risk patients (52%). In light of the high prevalence of dyslipidemia and low adherence to target LDL goals, we conclude that strict control of dyslipidemia should be included in cardiovascular risk prevention strategies for chronic hemodialysis patients.

Oxidative stress, inflammation and cardiovascular mortality in haemodialysis—role of seniority and intravenous ferrotherapy: analysis at 4 years of follow-up

BACKGROUND

Cardiovascular disease is the principal cause of morbidity and mortality in haemodialysis patients. The classic risk factors do not account for all cases of elevated cardiovascular disease in this patient population and it is becoming increasingly clear that other cardiovascular risk factors are implicated. The objective of this study was to analyse whether or not C-reactive protein (CRP) and plasma copper oxidized anti-lipoprotein (oxLDL) antibody titre are risk factors for cardiovascular mortality during 4 years of follow-up.

METHODS

A prospective follow-up study was carried out in 94 stable, chronic haemodialysis patients for 48 months (July 1999-July 2003) (gender: 50 males and 44 females; mean age: 67+/-14 years). Eighty-four per cent of these patients were receiving intravenous erythropoietin and 63% were receiving intravenous ferrotherapy (iron gluconate). Basal markers of inflammation and oxidative stress were determined at the beginning of the study. CRP levels were determined by chemiluminescent enzyme-labelled immunometric assay. The oxLDL antibody titre was measured by enzyme-linked immunosorbent assay using native LDL and oxLDL as antigens.

RESULTS

Fifty deaths occurred during the study, 66% (n = 33) of which were due to cardiovascular disease. Patients presented with basal CRP and oxLDL levels indicative of chronic inflammation and elevated oxidative stress [CRP median: 5.16 mg/l (25-75% percentile: 0.35-88.7 mg/l); oxLDL antibodies median: 153 (optical density at 495 nm x 1000) (25-75% percentile: 112-214)]. A positive correlation was found between CRP and age (r = 0.33, P = 0.003). Study of the risk factors demonstrated that age (P = 0.007), oxLDL antibody titre (P = 0.04) and albumin (P = 0.02) were the only predictors of cardiovascular mortality at 4 years of follow-up in this patient population. The Cox proportional hazards model for cardiovascular mortality showed that of the markers studied, oxLDL antibody titre was an independent risk factor for cardiovascular mortality.

CONCLUSIONS

Oxidative stress (oxLDL antibody titre) is one of the principal risk factors for cardiovascular mortality in this population of haemodialysis patients. Intravenous ferrotherapy, due to its pro-oxidant properties, probably favours oxidative stress. Serum concentration of CRP was not a good predictive factor of cardiovascular mortality during 4 years of follow-up, possibly because of the slight positive correlation that exists between CRP and age.

"New" cardiovascular risk factors in patients with chronic kidney disease: role of folic acid treatment

Cardiovascular disease (CVD) is the principal cause of mortality in patients with chronic renal disease undergoing hemodialysis. In addition to the CVD risk factors, a new hypothesis has recently been aroused related to "new" factors involved in the development of atherosclerosis in the uremic patient; worthwhile mentioning are the homocysteine, inflammation, and oxidative stress, among others. The potential utility of the folic acid in the hyperhomocysteinemia control is well known, although its mechanism of action, either as antioxidant or anti-inflammatory, has not been established. Our results confirm that the patients undergoing dialysis demonstrate hyperhomocysteinemia, an increased inflammatory status, and an increase of the lipid peroxidation markers. The administration of IV folinic acid induces a reduction of homocysteine levels subordinate to the inflammatory status of the patient. Additionally, although no inflammatory effects were shown, the results provide evidence for the antioxidant effect of IV folinic acid administration by reducing the lipid peroxidation marker levels. The statistic analysis demonstrates no correlation among the 3 markers, in spite of its higher levels in these particular patients. Homocysteine does not independently predict mortality in patients taking oral folic acid. Nevertheless, the PCR (an inflammation marker) and the antibody antioxidative-LDL (a lipidic peroxidation marker) show a good prediction of mortality at the 24-month follow-up analysis. The knowledge of these "new" CV risk factors, as well as the factors that influence them, could be useful to prevent the development of atherosclerosis in patients with chronic renal disease.

A role for homocysteine increase in haemolysis of megaloblastic anaemias due to vitamin B12 and folate deficiency: results from an in vitro experience

Megaloblastic anaemias (MA) are frequently associated with haemolysis. The pathogenesis of these finding is not clear, but it is thought to depend on the greater destruction of abnormal and fragile megaloblastic erythrocytes. Vitamin B(12) and folate deficiencies are the commonest cause of MA; these deficiencies may simultaneously induce a significant alteration in homocysteine metabolism leading to hyperhomocysteinemia. Blood cells have enzymes involved in homocysteine metabolism. Considering the possible effects of hyperhomocysteinemia in erythrocyte toxicity (due to oxidative damage and/or to interaction with sulfhydryl residues of structural and enzymatic proteins), the aim of our study was to evaluate (1) the homocysteine blood cells production in patients with MA due to vitamin B(12) and folate deficiency and (2) the possible role and mechanism of hyperhomocysteinemia in MA haemolysis. After incubation at 37 degrees C, blood samples from MA patients showed higher and significant levels of Hcy, LDH, lipid peroxidation parameters (MDA), and ghost protein-bound Hcy than controls. Haemolysis (%) was higher in MA patients than controls and was significantly correlated with Hcy accumulation in the medium, lipid peroxidation indices and ghost protein-bound Hcy. No significant (or significantly lower) alterations through time in considered parameters were observed in the corresponding samples incubated at 4 degrees C or in samples incubated with methionine-free medium (lower Hcy production). Our data, deriving from an in vitro experience, suggest a possible role of Hcy accumulation due to vitamin B(12) and folate deficiencies in haemolysis associated to MA due to vitamin deficiency.

The effect of vitamin E supplementation on antioxidant enzyme activities and lipid peroxidation levels in hemodialysis patients

BACKGROUND

This study has been undertaken to investigate the possible alterations of oxidant/antioxidant status in uremic patients undergoing hemodialysis (HD) and the effects of vitamin E supplementation.

METHODS

Erythrocyte antioxidant enzyme activities [glutathione peroxidase (GSHPx), superoxide dismutase (SOD) and catalase (CAT)] and thiobarbituric acid reactive substance (TBARS) concentrations as a measure of lipid peroxidation in HD patients have been determined and compared with healthy controls. The patient group consisted of 36 uremic patients 21-75 years of age undergoing maintenance HD three times weekly for an average of 41 months. The efficiency of Vitamin E therapy in dialysis patients was also assessed by re-evaluating antioxidant status of the same patients after supplementation of the vitamin E in a dosage of 600 mg/daily for 14 weeks.

RESULTS

A significant decrease in the activities of erythrocyte SOD, CAT and GSHPx and a significant increase in TBARS concentrations were found in patient group compared to control group (p<0.001). A significant correlation between GSHPx activities and duration of HD therapy was also observed (r=-0.46, p<0.01). Vitamin E supplementation caused an increase in GSHPx and SOD activities and a decrease in TBARS concentrations. A slight but not significant increase in CAT activity was also observed by Vitamin E.

CONCLUSIONS

The results suggest the presence of an oxidative activity and the possible preventive role of Vitamin E therapy in uremic patients undergoing HD.

Hyperhomocysteinemia in patients with Behçet’s disease: is it due to inflammation or therapy?

Considerable discrepancies exist in the literature with respect to plasma total homocysteine (tHcy) levels in Behçet's disease (BD). The aim of this study was to evaluate tHcy concentrations in these patients. Thirty-two patients with BD and 20 age- and body mass index-matched healthy volunteers were enrolled. Plasma tHcy concentrations were significantly higher, while vitamin B12 and folate levels were significantly lower in patients with thrombosis and eye involvement than those without. C-reactive protein levels also correlated significantly in a negative manner with vitamin B12 and folate but positively with tHcy. In conclusion, increased use or accelerated catabolism of folate and vitamin B12 due to chronic inflammation and moderately increased tHcy concentrations related with deficiency of these cofactors, and immunosuppressive drug administration might be potential threats of vascular disease in BD.

Review on uremic toxins: classification, concentration, and interindividual variability

BACKGROUND

The choice of the correct concentration of potential uremic toxins for in vitro, ex vivo, and in vivo experiments remains a major area of concern; errors at this level might result in incorrect decisions regarding therpeutic correction of uremia and related clinical complications.

METHODS

An encyclopedic list of uremic retention solutes was composed, containing their mean normal concentration (CN), their highest mean/median uremic concentration (CU), their highest concentration ever reported in uremia (CMAX), and their molecular weight. A literature search of 857 publications on uremic toxicity resulted in the selection of data reported in 55 publications on 90 compounds, published between 1968 and 2002.

RESULTS

For all compounds, CU and/or CMAX exceeded CN. Molecular weight was lower than 500 D for 68 compounds; of the remaining 22 middle molecules, 12 exceeded 12,000 D. CU ranged from 32.0 ng/L (methionine-enkephalin) up to 2.3 g/L (urea). CU in the ng/L range was found especially for the middle molecules (10/22; 45.5%), compared with 2/68 (2.9%) for a molecular weight <500 D (P < 0.002). Twenty-five solutes (27.8%) were protein bound. Most of them had a molecular weight <500 D except for leptin and retinol-binding protein. The ratio CU/CN, an index of the concentration range over which toxicity is exerted, exceeded 15 in the case of 20 compounds. The highest values were registered for several guanidines, protein-bound compounds, and middle molecules, to a large extent compounds with known toxicity. A ratio of CMAX/CU <4, pointing to a Gaussian distribution, was found for the majority of the compounds (74/90; 82%). For some compounds, however, this ratio largely exceeded 4 [e.g., for leptin (6.81) or indole-3-acetic acid (10.37)], pointing to other influencing factors than renal function, such as gender, genetic predisposition, proteolytic breakdown, posttranslation modification, general condition, or nutritional status.

CONCLUSION

Concentrations of retention solutes in uremia vary over a broad range, from nanograms per liter to grams per liter. Low concentrations are found especially for the middle molecules. A substantial number of molecules are protein bound and/or middle molecules, and many of these exert toxicity and are characterized by a high range of toxic over normal concentration (CU/CN ratio). Hence, uremic retention is a complex problem that concerns many more solutes than the current markers of urea and creatinine alone. This list provides a basis for systematic analytic approaches to map the relative importance of the enlisted families of toxins.

Homocysteine, malondialdehyde and endothelial markers in dialysis patients during low-dose folinic acid therapy

OBJECTIVES

Haemodialysis patients have elevated levels of the atherogenic amino acid homocysteine. We wanted to assess the effects of small doses of intravenous folinic acid (the active form of folic acid) on some biochemical risk factors of cardiovascular disease.

DESIGN

Longitudinal and open intervention study.

SETTING

Two dialysis units in the County of Rogaland.

SUBJECTS

All patients on maintenance haemodialysis were invited, and 32 of 35 patients gave their informed consent.

INTERVENTIONS

After each dialysis session, the patients were given 1.0 mg of folinic acid intravenously thrice a week for a period of 3 months. Prior to and during the study, all patients were on maintenance supplementation with small doses of vitamins B1, B2, B3, B5, B6 and B12.

MAIN OUTCOME MEASURES

Changes in the levels of (i) plasma total homocysteine (p-tHcy) and folate, (ii) circulating endothelium related proteins--markers of endothelial activation and (iii) serum malondialdehyde (S-MDA)--a marker of oxidative stress and lipid peroxidation.

RESULTS

The p-tHcy levels were reduced by 37% (P < 0.0001), whilst the serum and erythrocyte folate levels increased by 95 and 104%, respectively (P < 0.0001 for both). The circulating levels of endothelium related cellular adhesion molecules and haemostatic factors remained high and unchanged, except the thrombomodulin (TM) levels increased (P = 0.0004). The high levels of S-MDA were reduced by 26% (P = 0.003).

CONCLUSIONS

Low doses of folinic acid given intravenously to dialysis patients reduced their levels of p-tHcy and S-MDA and thus improved their cardiovascular risk profile. The concurrent increment in TM levels was unexpected and of unknown clinical significance.

Apolipoprotein E deficiency promotes increased oxidative stress and compensatory increases in antioxidants in brain tissue

The epsilon 4 allele of the apolipoprotein E gene (ApoE) is associated with Alzheimer's disease (AD). The extent of oxidative damage in AD brains correlates with the presence of the E4 allele of ApoE, suggesting an association between the ApoE4 genotype and oxygen-mediated damage in AD. We tested this hypothesis by subjecting normal and transgenic mice lacking ApoE to oxidative stress by folate deprivation and/or excess dietary iron. Brain tissue of ApoE-deficient mice displayed increased glutathione and antioxidant levels, consistent with attempts to compensate for the lack of ApoE. Folate deprivation and iron challenge individually increased glutathione and antioxidant levels in both normal and ApoE-deficient brain tissue. However, combined treatment with folate deprivation and dietary iron depleted antioxidant capacity and induced oxidative damage in ApoE-deficient brains despite increased glutathione, indicating an inability to compensate for the lack of ApoE under these conditions. These data support the hypothesis that ApoE deficiency is associated with oxidative damage, and demonstrate a combinatorial influence of genetic predisposition, dietary deficiency, and oxidative stress on oxidative damage relevant to AD.