Evaluation of oxidant stress in dialysis patients

Oxidative Stress Markers in Chronic Kidney Disease with Emphasis on Diabetic Nephropathy

Diabetes prevalence is increasing worldwide, especially through the increase of type 2 diabetes. Diabetic nephropathy occurs in up to 40% of diabetic patients and is the leading cause of end-stage renal disease. Various factors affect the development and progression of diabetic nephropathy. Hyperglycaemia increases free radical production, resulting in oxidative stress, which plays an important role in the pathogenesis of diabetic nephropathy. Free radicals have a short half-life and are difficult to measure. In contrast, oxidation products, including lipid peroxidation, protein oxidation, and nucleic acid oxidation, have longer lifetimes and are used to evaluate oxidative stress. In recent years, different oxidative stress biomarkers associated with diabetic nephropathy have been found. This review summarises current evidence of oxidative stress biomarkers in patients with diabetic nephropathy. Although some of them are promising, they cannot replace currently used clinical biomarkers (eGFR, proteinuria) in the development and progression of diabetic nephropathy.

Oxidized Low-density Lipoprotein and the Incidence of Age-related Macular Degeneration

PURPOSE

To examine the relationship between serum oxidized low-density lipoprotein (ox-LDL) cholesterol and the incidence of age-related macular degeneration (AMD) over a 25-year period in a sample of persons from the population-based Beaver Dam Eye Study (BDES).

DESIGN

Observational prospective cohort study.

PARTICIPANTS

A total of 4972 people from the BDES (aged 43-84 years and living in Beaver Dam, Wisconsin in 1988) seen during at least 1 of 6 examination phases at approximately 5-year intervals between 1988 and 2016.

METHODS

A 50% random sample of participants (N = 2468) was selected for ox-LDL measurements. Stored frozen specimens from every examination phase were processed using an enzyme-linked immunosorbent assay from a single batch. All available intervals were included for a person, resulting in 6586 person-visits.

MAIN OUTCOME MEASURES

Age-related macular degeneration was assessed using the Wisconsin Age-related Maculopathy Grading System, and severity was defined using a 5-step severity scale. The severity of the worse eye at each examination was used for analyses. A multi-state Markov (MSM) model was fit to simultaneously assess the ox-LDL relationship to all AMD transitions, including incidence of any AMD, incidence of late AMD, and worsening and improvement of AMD over the 25 years of the study.

RESULTS

The mean (standard deviation) level of ox-LDL was 75.3 (23.1) U/L at the baseline examination. When adjusting for age, sex, ARMS2 and CFH risk alleles, and examination phase, the ox-LDL at the beginning of a period was not statistically significantly associated with the incidence of any AMD (hazard ratio per 10 U/L ox-LDL was 1.03, 95% confidence interval 0.98,1.09). Furthermore, ox-LDL was not associated with worsening anywhere along the AMD severity scale, nor with incidence of late AMD. The lack of relationships of ox-LDL to the incidence of any AMD or worsening of AMD remained after adjustment for history of statin use, smoking status, body mass index, and history of cardiovascular disease (data not shown).

CONCLUSIONS

Our findings do not provide evidence for statistically significant relationships between ox-LDL and AMD disease development or worsening of AMD.

Analysis and Chemistry of Novel Protein Oxidation Markers in Vivo

Proteins continually undergo spontaneous oxidation reactions, which lead to changes in structure and function. The quantitative assessment of protein oxidation adducts provides information on the level of exposure to reactive precursor compounds with a high oxidizing potential and reactive oxygen species (ROS). In the present work, we introduce N⁶-(2-hydroxyethyl)lysine as a novel marker based on the ratio of glycolaldehyde and its oxidized form glyoxal. The high analytical potential was proven with a first set of patients undergoing hemodialysis versus healthy controls, in comparison with well-established parameters for oxidative stress. In vitro experiments with N¹- t-BOC-lysine and N¹- t-BOC-arginine enlightened the mechanistic relationship of glycolaldehyde and glyoxal. Oxidation was strongly dependent on the catalytic action of the ε-amino moiety of lysine. Investigations on the formation of N⁶-carboxymethyl lysine revealed glycolaldehyde-imine as the more reactive precursor, even though an additional oxidative step is required. As a result, a novel and very effective alternative mechanism was unraveled.

Oxidative Stress Biomarkers: Establishment of Reference Values for Isoprostanes, AOPP, and NPBI in Cord Blood

Oxidative stress (OS) is a common pathogenic factor involved in the onset of several diseases in humans, from immunologic disorders to malignancy, being a serious public health problem. In perinatal period, OS has been associated with adverse outcome of pregnancy and neonatal diseases. Dangerous effects of OS are mediated by increased production of free radicals (FRs) following various mechanisms, such as hypoxia, ischemia reperfusion, hyperoxia, inflammation, mitochondrial dysfunction, Fenton chemistry, and prostaglandin metabolism. FRs have short half-life, and their measurement in vivo is faced with many challenges. However, oxyradical derivatives are stable and thus may be measured and monitored repeatedly. The quantification of OS is based on the measurement of specific biomarkers in biologic fluids and tissues, which reflect induced oxidative damage to lipids, proteins, and DNA. Prostanoids, non–protein-bound iron (NPBI), and advanced oxidation protein products (AOPP) are actually considered truly specific and reliable for neonatal injury. Defining reference values for these biomarkers is necessary to investigate their role in neonatal diseases or also to evaluate the success of treatments. In this work, we wanted to define laboratory reference values for biomarkers of OS in a healthy population of term newborns.

Serum Gamma-Glutamyltransferase Levels Predict Clinical Outcomes in Hemodialysis Patients

BACKGROUND

Gamma-glutamyltransferase (GGT) is a biomarker of liver injury. GGT has also been reported to be a marker of oxidative stress and a predictor of mortality in the general population. Hemodialysis (HD) patients suffer from oxidative stress. The aim of our study was to investigate the relationship between serum GGT levels and clinical outcomes in HD patients.

METHODS

A total of 1,634 HD patients were enrolled from the Clinical Research Center registry for end-stage renal disease, a prospective cohort in Korea. Patients were categorized into three groups by tertiles of serum GGT levels. The primary outcome was all-cause, cardiovascular, or infection-related mortality and hospitalization.

RESULTS

During the median follow-up period of 30 months, the highest tertile of serum GGT levels had a significantly higher risk for all-cause mortality (hazard ratio (HR) 2.39, 95% confidence interval (CI), 1.55-3.69, P<0.001), cardiovascular mortality (HR 2.14, 95% CI, 1.07-4.26, P = 0.031) and infection-related mortality (HR 3.07, 95% CI, 1.30-7.25, P = 0.011) using tertile 1 as the reference group after adjusting for clinical variables including liver diseases. The highest tertile also had a significantly higher risk for first hospitalization (HR 1.22, 95% CI, 1.00-1.48, P = 0.048) and cardiovascular hospitalization (HR 1.42, 95% CI, 1.06-1.92, P = 0.028).

CONCLUSIONS

Our data demonstrate that high serum GGT levels were an independent risk factor for all-cause, cardiovascular, and infection-related mortality, as well as cardiovascular hospitalization in HD patients. These findings suggest that serum GGT levels might be a useful biomarker to predict clinical outcomes in HD patients.

Serum Gamma-Glutamyltransferase Levels Predict Mortality in Patients With Peritoneal Dialysis

Serum gamma-glutamyltransferase (GGT) level has been considered marker of oxidative stress as well as liver function. Serum GGT level has been reported to be associated with the mortality in hemodialysis patients. However, it is not well established whether serum GGT level is associated with all-cause mortality in peritoneal dialysis (PD) patients. The aim of this study was to determine the association between serum GGT levels and all-cause mortality in PD patients.PD patients were included from the Clinical Research Center registry for end-stage renal disease cohort, a multicenter prospective observational cohort study in Korea. Patients were categorized into 3 groups by tertile of serum GGT levels as follows: tertile 1, GGT < 16 IU/L; tertile 2, GGT = 16 to 27 IU/L; and tertile 3, GGT > 27 IU/L. Primary outcome was all-cause mortality.A total of 820 PD patients were included. The median follow-up period was 34 months. Kaplan-Meier analysis showed that the all-cause mortality rate was significantly different according to tertiles of GGT (P = 0.001, log-rank). The multivariate Cox regression analysis showed that higher tertiles significantly associated with higher risk for all-cause mortality (tertile 2: hazard ratio [HR] 2.08, 95% confidence interval [CI], 1.17-3.72, P = 0.013; tertile 3: HR 1.83, 95% CI, 1.04-3.22, P = 0.035) in using tertile 1 as the reference group after adjusting for clinical variables.Our study demonstrated that high serum GGT levels were an independent risk factor for all-cause mortality in PD patients. Our findings suggest that serum GGT levels might be a useful biomarker to predict all-cause mortality in PD patients.

Markers of inflammation, oxidative stress, and endothelial dysfunction and the 20-year cumulative incidence of early age-related macular degeneration: the Beaver Dam Eye Study

IMPORTANCE Modifying levels of factors associated with age-related macular degeneration (AMD) may decrease the risk for visual impairment in older persons. OBJECTIVE To examine the relationships of markers of inflammation, oxidative stress, and endothelial dysfunction to the 20-year cumulative incidence of early AMD. DESIGN, SETTING, AND PARTICIPANTS This longitudinal population-based cohort study involved a random sample of 975 persons in the Beaver Dam Eye Study without signs of AMD who participated in the baseline examination in 1988-1990 and up to 4 follow-up examinations in 1993-1995, 1998-2000, 2003-2005, and 2008-2010. EXPOSURES Serum markers of inflammation (high-sensitivity C-reactive protein, tumor necrosis factor-α receptor 2, interleukin-6, and white blood cell count), oxidative stress (8-isoprostane and total carbonyl content), and endothelial dysfunction (soluble vascular cell adhesion molecule-1 and soluble intercellular adhesion molecule-1) were measured. Interactions with complement factor H (rs1061170), age-related maculopathy susceptibility 2 (rs10490924), complement component 3 (rs2230199), and complement component 2/complement factor B (rs4151667) were examined using multiplicative models. Age-related macular degeneration was assessed from fundus photographs. MAIN OUTCOMES AND MEASURES Early AMD defined by the presence of any size drusen and the presence of pigmentary abnormalities or by the presence of large-sized drusen (≥125-μm diameter) in the absence of late AMD. RESULTS The 20-year cumulative incidence of early AMD was 23.0%. Adjusting for age, sex, and other risk factors, high-sensitivity C-reactive protein (odds ratio comparing fourth with first quartile, 2.18; P = .005), tumor necrosis factor-α receptor 2 (odds ratio, 1.78; P = .04), and interleukin-6 (odds ratio, 1.78; P = .03) were associated with the incidence of early AMD. Increased incidence of early AMD was associated with soluble vascular cell adhesion molecule-1 (odds ratio per SD on the logarithmic scale, 1.21; P = .04). CONCLUSIONS AND RELEVANCE We found modest evidence of relationships of serum high-sensitivity C-reactive protein, tumor necrosis factor-α receptor 2, interleukin-6, and soluble vascular cell adhesion molecule-1 to the 20-year cumulative incidence of early AMD independent of age, smoking status, and other factors. It is not known whether these associations represent a cause and effect relationship or whether other unknown confounders accounted for the findings. Even if inflammatory processes are a cause of early AMD, it is not known whether interventions that reduce systemic inflammatory processes will reduce the incidence of early AMD.

Paricalcitol reduces oxidative stress and inflammation in hemodialysis patients

BACKGROUND

Treatment with selective vitamin D receptor activators such as paricalcitol have been shown to exert an anti-inflammatory effect in patients on hemodialysis, in addition to their action on mineral metabolism and independently of parathyroid hormone (PTH) levels. The objective of this study was to evaluate the additional antioxidant capacity of paricalcitol in a clinical setting.

METHODS

The study included 19 patients with renal disease on hemodialysis, of whom peripheral blood was obtained for analysis at baseline and three months after starting intravenous paricalcitol treatment. The following oxidizing and inflammatory markers were quantified: malondialdehyde (MDA), nitrites and carbonyl groups, indoleamine 2,3-dioxygenase (IDO), tumor necrosis factor alfa (TNF-α), interleukin-6 (IL-6), interleukin-18 (IL-18) and C-reactive protein (CRP). Of the antioxidants and anti-inflammatory markers, superoxide dismutase (SOD), catalase, reduced glutathione (GSH), thioredoxin, and interleukin-10 (IL-10) levels were obtained.

RESULTS

Baseline levels of oxidation markers MDA, nitric oxide and protein carbonyl groups significantly decreased after three months on paricalcitol treatment, while levels of GSH, thioredoxin, catalase and SOD activity significantly increased. After paricalcitol treatment, levels of the inflammatory markers CRP, TNF-α, IL-6 and IL-18 were significantly reduced in serum and the level of anti-inflammatory cytokine IL-10 was increased.

CONCLUSIONS

In renal patients undergoing hemodialysis, paricalcitol treatment significantly reduces oxidative stress and inflammation, two well known factors leading to cardiovascular damage.

Hemodialysis alters lipid profiles, total antioxidant capacity, and vitamins A, E, and C concentrations in humans

Although hemodialysis (HD) is essential for end-stage renal disease patients, at the same time it causes oxidative stress and long-term pro-atherosclerotic effects. This study aimed to determine lipid profile as well as the total antioxidant capacity (TAC) and vitamins A, E, and C in HD patients. The study enrolled 31 patients (50.3 ± 14.9 years old) undergoing maintenance 4-hour HD three times per week with a polysulfone membrane dialyzer for a mean of 76.1 months (range, 7-120 months) and 31 healthy individuals (47.8 ± 13.9 years old). Lipid profiles were determined spectrophotometrically using commercially available kits. Total antioxidant capacity was determined by ferric reducing/antioxidant power assay, levels of vitamins A and E were assayed using high-pressure liquid chromatography, and the level of vitamin C was measured by a photometric method. Our results showed that before HD, the levels of TAC and vitamin A were significantly higher than in normal subjects, whereas the levels of high-density lipoprotein (HDL) and vitamin C were lower than in control subjects (P < .001). There was no significant difference between normal subjects and patients before dialysis regarding low-density lipoprotein (LDL) and vitamin E levels (P > .05). After HD, the levels of HDL-cholesterol, vitamins E and C, and TAC decreased significantly (P < .001), but the decreased level of vitamin A still remained higher than controls (P < .05), whereas the levels of LDL were significantly higher than controls (P < .001). In conclusion, alterations in the lipoprotein profiles and antioxidant markers following HD suggest an increased risk of atherosclerosis in these patients.

Dialysis modality-dependent changes in serum metabolites: accumulation of inosine and hypoxanthine in patients on haemodialysis

BACKGROUND

The body metabolism of patients with end-stage renal disease may be altered in response to long-term dialysis treatment. Moreover, the pattern of serum metabolites could change depending on the type of dialysis modality used. However, dialysis modality-dependent changes in serum metabolites are poorly understood. Our aim was to profile comprehensively serum metabolites by exploiting a novel method of (1)H-NMR-based metabonomics and identify the differences in metabolite patterns in subjects receiving haemodialysis (HD) and peritoneal dialysis (PD).

METHODS

Anuric and non-diabetic HD patients were matched to PD patients for age, sex and dialysis duration. Accurate concentrations of serum metabolites were determined using the target-profiling procedure, and differences in the levels of metabolites were compared using multivariate analysis.

RESULTS

Principal Components Analysis score plots showed that the metabolic patterns could be discriminated by dialysis modalities. Hypoxanthine and inosine were present only with HD, whereas serum xanthine oxidase activity and uric acid levels were not different. In contrast, PD was associated with higher levels of lactate, glucose, maltose, pyruvate, succinate, alanine, and glutamate linked to glucose metabolism and the tri-carboxylic acid cycle. Maltose appeared only in patients using icodextrin solution for PD. Known uraemic retention solutes such as urea, creatinine, myo-inositol and trimethylamine-N-oxide were increased in both dialysis groups.

CONCLUSIONS

Metabonomics shows apparent differences in the profiles of serum metabolites between HD and PD, which were influenced by dialysis-related processes. Inosine and hypoxanthine are present only in HD patients, which is likely to represent more hypoxic and oxidative stress.

Effects of Hemodialysis, Dialyser Type and Iron Infusion on Oxidative Stress in Uremic Patients

Uremic patients undergoing hemodialysis (HD) are considered to face an elevated risk for atherosclerosis and cancer. This has been attributed in part to an increased oxidative stress. In this pilot study, oxidative cell damage in blood of HD-patients was compared to those of controls: total DNA damage (basic and specific oxidative DNA damage), modulation of glutathione levels (total and oxidized glutathione) and of lipid peroxidation were monitored via the Comet assay (with and without FPG), a kinetic photometric assay and HPLC quantification of plasma malondialdehyde (MDA), respectively. In some samples, leukocytes were analysed for malondialdehyde-deoxyguanosine-adducts (M1dG) with an immunoslot blot technique. HD-patients (n=21) showed a significant increase of total DNA damage (p<10(-12)), compared to controls (n=12). In a subset of patients and controls, GSSG levels and M1dG, however, only increased slightly, while tGSH and MDA levels did not differ. The influence of different low flux HD-membranes was tested in a pilot study with nine patients consecutively dialysed on three membrane types for four weeks each. In addition to the individual disposition of the patient, the dialyser membrane had a significant impact on oxidative stress. Total DNA damage was found to be almost identical for polysulfone and vitamin E coated cellulosic membranes, whereas a slight, but significant increase was observed with cellulose-diacetate (p<0.001). In patients receiving iron infusion during HD, MDA-formation (n=11) and total DNA damage (n=10) were additionally increased (p<0.005). Our results show an increased oxidative damage in HD-patients, compared to healthy volunteers. Significant influences were found for the dialyser membrane type and iron infusion.

Antioxidant Status of Patients on Peritoneal Dialysis: Associations with Inflammation and Glycoxidative Stress

Background

Patients on peritoneal dialysis (PD) frequently exhibit oxidant–antioxidant imbalance, advanced glycation end-product overload, and subclinical inflammation but the interrelations between these pathophysiological changes have not been fully elucidated.

Subjects and Methods

To study possible associations, a cross-sectional study of antioxidant status, glycoxidative stress, and inflammation, using HPLC and ELISA methods, was undertaken in 37 PD patients and age- and sex-matched healthy controls.

Results

Plasma ascorbate concentrations were low in patients not taking at least low-dose vitamin C supplements. In patients taking vitamin C supplements, there was a positive relation between ascorbate and pentosidine concentrations. Vitamin E and carotenoid concentrations were comparable between patients and controls, while lycopene and lutein/zeaxanthin concentrations were lower. Interleukin-6, C-reactive protein (CRP), and pentosidine concentrations were elevated in PD patients. β–Cryptoxanthin, lycopene, and lutein/zeaxanthin concentrations were inversely related to interleukin-6 concentrations. β–Cryptoxanthin concentrations were also inversely related to CRP concentrations. Pentosidine showed a low dialysate-to-plasma ratio, indicating low peritoneal clearance. Pentosidine concentrations increased with duration of PD therapy, while α– and β–carotene concentrations decreased. Malondialdehyde concentrations were elevated compared to controls but remained within the normal range. Retinol concentrations decreased with PD therapy and were inversely related to interleukin-6 and CRP concentrations.

Conclusions

Low-dose vitamin C supplements and a carotenoid-rich diet should be recommended for PD patients to maintain normal antioxidant status and efficiently counteract the chronic inflammatory response, rather than high doses of vitamin C, which could play a role as a precursor of pentosidine.

Growth of β2-microglobulin-related amyloid fibrils by non-esterified fatty acids at a neutral pH

Aβ2M (β2-microglobulin-related) amyloidosis is a frequent and serious complication in patients on long-term dialysis. Partial unfolding of β2-m (β2-microglobulin) may be essential to its assembly into Aβ2M amyloid fibrils in vivo. Although SDS around the critical micelle concentration induces partial unfolding of β2-m to an α-helix-containing aggregation-prone amyloidogenic conformer and subsequent amyloid fibril formation in vitro, the biological molecules with similar activity under near-physiological conditions are still unknown. The effect of various NEFAs (non-esterified fatty acids), which are representative anionic amphipathic compounds in the circulation, on the growth of Aβ2M amyloid fibrils at a neutral pH was examined using fluorescence spectroscopy with thioflavin T, CD spectroscopy, and electron microscopy. Physiologically relevant concentrations of laurate, myristate, oleate, linoleate, and mixtures of palmitate, stearate, oleate and linoleate, induced the growth of fibrils at a neutral pH by partially unfolding the compact structure of β2-m to an aggregation-prone amyloidogenic conformer. In the presence of human serum albumin, these NEFAs also induced the growth of fibrils when their concentrations exceeded the binding capacity of albumin, indicating that the unbound NEFAs rather than albumin-bound NEFAs induce the fibril growth reaction in vitro. These results suggest the involvement of NEFAs in the development of Aβ2M amyloidosis, and in the pathogenesis of Aβ2M amyloidosis.

Nutritional and anti-inflammatory interventions in chronic heart failure

Currently, there are 5 million individuals with chronic heart failure (CHF) in the United States who have poor clinical outcomes, including high death rates. Observational studies have indicated a reverse epidemiology of traditional cardiovascular risk factors in CHF; in contrast to trends seen in the general population, obesity and hypercholesterolemia are associated with improved survival. The temporal discordance between the overnutrition (long-term killer) and undernutrition (short-term killer) not only can explain some of the observed paradoxes but also may indicate that malnutrition, inflammation, and oxidative stress may play a role that results in protein-energy wasting contributing to poor survival in CHF. Diminished appetite or anorexia and nutritional deficiencies may be both a cause and a consequence of this so-called malnutrition-inflammation-cachexia (MIC) or wasting syndrome in CHF. Neurohumoral activation, insulin resistance, cytokine activation, and survival selection-resultant genetic polymorphisms also may contribute to the prominent inflammatory and oxidative characteristics of this population. In patients with CHF and wasting, nutritional strategies including amino acid supplementation may represent a promising therapeutic approach, especially if the provision of additional amino acids, protein, and energy includes nutrients with anti-inflammatory and antioxidant properties. Regardless of the etiology of anorexia, appetite-stimulating agents, especially those with anti-inflammatory properties such as megesterol acetate or pentoxyphylline, may be appropriate adjuncts to dietary supplementation. Understanding the factors that modulate MIC and body wasting and their associations with clinical outcomes in CHF may lead to the development of nutritional strategies that alter the pathophysiology of CHF and improve outcomes.

Ascorbic acid and α-tocopherol protect anticancer drug cisplatin induced nephrotoxicity in mice: a comparative study

BACKGROUND

Oxidative stress, resulting from an imbalance between prooxidant and antioxidant systems in favor of the former, largely contributes to immune system deregulation and complications observed in end-stage renal disease (ESRD) and patients treated with hemodialysis. Reactive oxygen species and free radicals are involved in the nephrotoxicity induced by a synthetic anticancer drug cisplatin.

METHODS

A comparative study on the nephroprotective effects of antioxidant vitamins (250 and 500 mg/kg, p.o.), vitamin C (ascorbic acid) and vitamin E (alpha-tocopherol), was evaluated using cisplatin (10 mg/kg body wt, i.p.) induced oxidative renal damage in mice. Urea and creatinine in serum were estimated for the renal function. Antioxidant status was estimated in kidney homogenate.

RESULTS

We found that both vitamins at 500 mg/kg significantly (P<0.01) protected the nephrotoxicity induced by cisplatin. The cisplatin induced increase of urea and creatinine concentrations were reduced in the vitamins plus cisplatin (250 and 500 mg/kg, p.o.)-treated groups. However the cisplatin induced decline of renal antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) activities were increased only in the 500 mg/kg vitamins treated groups. Both vitamins at 250 and 500 mg/kg could increase the concentration of reduced glutathione (GSH) and protected the increase of cisplatin induced lipid peroxidation.

CONCLUSIONS

Higher doses of vitamins are effective to protect oxidative renal damage and vitamin C is the better nephroprotective agent than vitamin E. The protection is mediated partially by preventing the decline of renal antioxidant status.

The kidney disease wasting: Inflammation, oxidative stress, and diet-gene interaction

The 350,000 maintenance hemodialysis (MHD) patients in the United States have an unacceptably high mortality rate of >20%/year. Almost half of all deaths are assumed to be cardiovascular. Markers of kidney disease wasting (KDW) such as hypoalbuminemia, anorexia, body weight and fat loss, rather than traditional cardiovascular risk factors, appear to be the strongest predictors of early death in these patients. The KDW is closely related to oxidative stress (SOX). Such SOX markers as serum myeloperoxidase are associated with pro-inflammatory cytokines and poor survival in MHD patients. Identifying the conditions that modulate the KDW/SOX-axis may be the key to improving outcomes in MHD patients. Dysfunctional lipoproteins such as a higher ratio of the high-density lipoprotein inflammatory index (HII) may engender or aggravate the KDW, whereas functionally intact or larger lipoprotein pools, as in hypercholesterolemia and obesity, may mitigate the KDW in MHD patients. Hence, a reverse epidemiology or "bad-gone-good" phenomenon may be observed. Diet and gene and their complex interaction may lead to higher proportions of pro-inflammatory or oxidative lipoproteins such as HII, resulting in the aggravation of the SOX and inflammatory processes, endothelial dysfunction, and subsequent atherosclerotic cardiovascular disease and death in MHD patients. Understanding the factors that modulate the KDW/SOX complex and their associations with genetic polymorphism, nutrition, and outcomes in MHD patients may lead to developing more effective strategies to improve outcomes in this and the 20 to 30 million Americans with chronic disease states such as individuals with chronic heart failure, advanced age, malignancies, AIDS, or cachexia.

Beneficial in vitro effect of N-acetyl-cysteine on oxidative stress and apoptosis

Chronic renal failure (CRF) is usually accompanied by abnormalities of both humoral and cellular immune response. The aim of the study was to investigate the influence of N-acetyl-cysteine (NAC) on intracellular oxidative stress and apoptosis rate of T lymphocytes in children with CRF. Twenty-two children (aged 4-16, mean 7.4) with CRF treated with dialysis were enrolled in the study. Intracellular reactive oxygen species (ROS) production was quantified by mean rhodamine 123 (RHO) fluorescence intensity with flow cytometry. Annexin V FITC was used for identifying apoptotic cells. Mean fluorescence intensity (MFI), which reflected intracellular oxidative stress in T lymphocytes, was increased in patients with CRF compared with the controls (CD3+: 31.58+/-11.58 vs 22.55+/-4.97, p = 0.043; CD3+CD4+: 32.50+/-8.59 vs 27.75+/-12.76, NS; CD3+CD8+: 32.10+/-11.85 vs 20.77+/- 4.89, p =0.012). Apoptotic T lymphocytes occurred more frequently in patients with CRF treated with hemodialysis (HD) (11.36+/-6.96%) than in the controls (6.14%+/-3.36%; p = 0.025). After 24 h incubation with NAC MFI and apoptosis rate decreased significantly in all subpopulations of lymphocytes. NAC, as a strong antioxidant, has a favorable effect on intracellular oxidative stress and apoptosis rate of T lymphocytes in patients with CRF. A decreased apoptosis rate may have positive effect on functional abnormalities of T cells already found in patients with CRF.

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.

RENAL RESEARCH INSTITUTE SYMPOSIUM: Efforts to Determine the Role of Oxidant Stress in Dialysis Outcomes

The role of elevated markers of oxidant stress needs to be established in longitudinal studies. Oxidant stress markers such as malonaldehyde (MDA), isoprostanes, and breath hydrocarbons warrant rigorous application to outcomes, if they are to be used as clinical parameters. For example, investigations of C-reactive protein (CRP), parathyroid hormone (PTH), and several other clinical indicators have shown that these markers can be used to predict outcomes such as morbidity and mortality. Long-term followup is needed for intervention studies with antioxidants, since effects with short-term studies may be focused on critically-ill individuals where intervention would not be expected to be effective. Oxidant stress studies in this population especially need a long-term approach to test the hypothesis that antioxidant intervention is beneficial.

Current studies on oxidant stress in dialysis

Breath ethane measurements in hemodialysis indicate that a portion of these patients suffer increased oxidant stress, consistent with findings using other methods for oxidant stress determination. Loosely-bound iron definitely appears in the bloodstream when substantial doses of IV iron are administered, since transferrin is fully saturated, but our investigations generally do not show short-term oxidant stress from this treatment. If small doses of IV iron are utilized, transferrin saturation can be avoided, and risk is minimized. The vitamin C status of hemodialysis patients is usually lower than the general population, and the impact of this deficiency must be assessed in controlled investigations. Various interventions, including the vitamin E-bonded dialyzer and dietary antioxidant supplements, may ameliorate a portion of the oxidant stress in hemodialysis patients.

Oxidative stress in end-stage renal disease: an emerging threat to patient outcome

INTRODUCTION

Patients affected by end-stage renal disease (ESRD) experience an excess of morbidity and mortality due to cardiovascular disease (CVD), which cannot be fully explained by the classical CVD risk factors. Among emerging CVD risk factors, oxidative stress is currently being given emphasis.

METHODS

We achieved a consensus on key points relating to oxidative stress in ESRD patients.

RESULTS

ESRD patients are subjected to enhanced oxidative stress, as a result of reduced anti-oxidant systems (vitamin C and selenium deficiency, reduced intracellular levels of vitamin E, reduced activity of the glutathione system) and increased pro-oxidant activity (advanced age, high frequency of diabetes, chronic inflammatory state, uraemic syndrome, bio-incompatibility of dialysis membranes and solutions). Oxidative stress and inflammation are deeply inter-related, as different oxidant free radicals are generated by phagocytic cells in response to inflammatory stimuli: both are related to endothelial dysfunction, as the endothelium is a source and a target of oxidants and participates in the inflammatory response. There is growing evidence, from experimental and clinical studies, that oxidative stress may be implicated in the pathogenesis of atherosclerosis and other complications of ESRD, namely dialysis-related amyloidosis, malnutrition and anaemia. Given that free radicals have very short half-lives (seconds), the clinical assessment of oxidative stress is based on the measurement of different stable oxidized compounds (such as lipid peroxidation products, advanced glycation and oxidation lipid and protein products, nucleic acid oxidation derivatives) or antibodies directed against oxidized epitopes (such as anti-oxidized low-density lipoprotein antibodies). At the same time, both enzymatic anti-oxidants (superoxide dismutase, catalase, glutathione peroxidase) and non-enzymatic anti-oxidants (glutathione, vitamin C, vitamin E, negative inflammatory proteins) can be evaluated. However, many laboratory methods assessing various oxidative stress components still have to be standardized. Moreover, it is still uncertain whether it is better measuring plasma and/or intracellular concentrations or activities of these components. The possibility of improving patient outcome by therapeutic interventions aimed at reducing oxidative stress, e.g. by vitamin C or vitamin E supplementation, currently is to the fore, but results so far have remained inconclusive.

CONCLUSIONS

It is important to consider oxidative stress as a potentially important source of patient morbidity and mortality, although this knowledge is not yet immediately applicable in the clinical arena. Further well-designed, randomized controlled clinical trials with anti-oxidants (e.g. vitamin E, vitamin C, N-acetyl cysteine, L-arginine) are required to establish evidence-based recommendations for clinical practice.

A new approach to classifying malnutrition in the hemodialysis patient

BACKGROUND

Novel classification nomenclature defining the type of malnutrition by the root cause of the hypoalbuminenia has been developing in the literature since 1999. As the classification of malnutrition became more definite in the literature, the need to assess the type of malnutrition, thereby the root cause(s) and initiate appropriate intervention(s), has become apparent.

METHODS

In September 1999, San Diego Dialysis began a continuous quality improvement (CQI) project to assess the root causes of hypoalbuminemia for patients with serum albumin level <3.5 g/dL. An extensive review of the literature was conducted on the subject of malnutrition, inflammation, and the acute-phase reaction.

FINDINGS

Two major groups of patients emerged: those consuming adequate protein and calories, yet presenting with hypoalbuminemia, and those suffering from a protein calorie deficit. Observation of the second group showed that although the monthly percentage of patients with hypoalbuminemia remained fairly constant, the names on the list changed from month to month.

CONCLUSIONS

The CQI team developed a protocol and a unique nomenclature to classify the types of malnutrition, type I, type IIa, type IIb, or mixed, by adapting the definitions in the literature through clinical practice. Interventions were developed to address each classification of malnutrition.