Lipoperoxidation in plasma and red blood cells of patients undergoing haemodialysis: vitamins A, E, and iron status

Associations of circulating vitamins with 10-year retinal neurodegeneration: the Alienor Study

OBJECTIVE

To investigate the associations between circulating vitamins A, D, E, B6, B9, B12 and longitudinal changes in retinal nerve fiber layer (RNFL) thickness.

METHODS

The Alienor study, a prospective population-based cohort (Bordeaux, France), includes 963 individuals aged 73 years or older at baseline. The present study included 646 participants with complete RNFL measurement and vitamins. Study period is from 2009 to 2020. Peripapillary RNFL thickness was measured using spectral domain optical coherence tomography (SD-OCT). Plasma vitamins A, D and E and, serum vitamins B6, B9 and B12 were measured from blood sample. We performed linear mixed models, adjusted for age, gender, axial length, family history of glaucoma, and alcohol consumption to evaluated associations between vitamins and RNFL thickness changes over time.

RESULTS

Individuals having higher concentrations of vitamin E, D and B9 had a slower RNFL thinning during the 10-years of follow-up. Indeed, a 1-standard deviation (SD) increase of vitamin E (10.8 μmol/L), D (17.6 nmol/L) and B9 (11 μmol/L) were associated with slower RNFL thinning by 0.14 μm/year (95% confidence interval (CI), 0.03-0.25, p = 0.01), 0.14 μm/year (95% CI, 0.02-0.27, p = 0.02) and 0.11 μm/year (95% CI: 0.007-0.21, p = 0.04), respectively. No significant associations were observed for vitamins A, B6 and B12 with RNFL thinning.

CONCLUSIONS

Higher levels of vitamins E, D and B9 were associated with a slower RNFL thickness on SD-OCT over time, suggesting that those vitamins may contribute to the neuroprotection of the retina.

Oxidants and Antioxidants in the Redox Biochemistry of Human Red Blood Cells

Red blood cells (RBCs) are exposed to both external and internal sources of oxidants that challenge their integrity and compromise their physiological function and supply of oxygen to tissues. Autoxidation of oxyhemoglobin is the main source of endogenous RBC oxidant production, yielding superoxide radical and then hydrogen peroxide. In addition, potent oxidants from other blood cells and the surrounding endothelium can reach the RBCs. Abundant and efficient enzymatic systems and low molecular weight antioxidants prevent most of the damage to the RBCs and also position the RBCs as a sink of vascular oxidants that allow the body to maintain a healthy circulatory system. Among the antioxidant enzymes, the thiol-dependent peroxidase peroxiredoxin 2, highly abundant in RBCs, is essential to keep the redox balance. A great part of the RBC antioxidant activity is supported by an active glucose metabolism that provides reducing power in the form of NADPH via the pentose phosphate pathway. There are several RBC defects and situations that generate oxidative stress conditions where the defense mechanisms are overwhelmed, and these include glucose-6-phosphate dehydrogenase deficiencies (favism), hemoglobinopathies like sickle cell disease and thalassemia, as well as packed RBCs for transfusion that suffer from storage lesions. These oxidative stress-associated pathologies of the RBCs underline the relevance of redox balance in these anucleated cells that lack a mechanism of DNA-inducible antioxidant response and rely on a complex and robust network of antioxidant systems.

Effects of hemodialysis on blood fatty acids

Omega‐3 (n‐3) fatty acids have beneficial cardiovascular effects, perhaps also in chronic kidney disease (CKD) patients. A low omega‐3 index is an independent cardiovascular risk factor in end‐stage renal disease (ESRD) dialysis patients. However, the plasma measurements invariably ignore circulating blood cells, including the preponderant erythrocytes (RBCs). We measured fatty acids (HPLC‐MS lipidomics) in all components of the circulating blood, since RBC n‐3 fatty acid status has been linked to cardiovascular disease and mortality. We studied 15 healthy persons and 15 CKD patients undergoing regular hemodialysis treatments. While total fatty acid levels differed significantly in RBCs from healthy controls and CKD patients, the hemodialysis treatment had no effect on plasma or RBC fatty acid levels. No changes occurred in the percentage of eicosapentaenoic acid (C20:5 n‐3, EPA) and docosahexaenoic acid (C22:6 n‐3; DHA) (omega‐3 quotient) in RBC membrane fatty acids. Nonetheless, hemodialysis treatments increased plasma levels of various total fatty acids, namely C12:0, C14:0, C16:0, C20:2 n‐6, C20:4 n‐6, and C22:6 n‐3 (DHA), while plasma levels of free fatty acids were unchanged. These data suggest that despite significant changes in fatty acids signatures between healthy persons and CKD patients, hemodialysis does not alter RBC n‐3 fatty acid status, including the omega‐3 quotient. The dialysis treatment per se does not appear to be responsible for a lower omega‐3 index in CKD patients.

Linking chronic kidney disease and Parkinson's disease: a literature review

Chronic kidney disease (CKD) has been typically implicated in cardiovascular risk, considering the function the kidney has related to blood pressure, vitamin D, red blood cell metabolism, and electrolyte and acid-base regulation. However, neurological consequences are also attributed to this disease. Among these, recent large epidemiological studies have demonstrated an increased risk for Parkinson's disease (PD) in patients with CKD. Multiple studies have evaluated individually the association of blood pressure, vitamin D, and red blood cell dysmetabolism with PD, however, no study has reviewed the potential mechanisms related to these components in context of CKD and PD. In this review, we explored the association of CKD and PD and linked the components of the former to propose potential pathways explaining a future increased risk for PD, where renin-angiotensin system, oxidative stress, and inflammation have a main role. Potential preventive and therapeutic interventions based on these associations are also explored. More preclinical studies are needed to confirm the potential link of CKD conditions and future PD risk, whereas more interventional studies targeting this association are warranted to confirm their potential benefit in PD.

Oxidative Stress in the Pathophysiology of Kidney Disease: Implications for Noninvasive Monitoring and Identification of Biomarkers

Kidney disease represents a serious global health problem. One of the main concerns is its late diagnosis, only feasible in a progressed disease state. The lack of a clinical manifestation in the early stages and the fact that the commonly measured parameters of renal function are markedly reduced only during advanced stages of the disease are the main cause. Changes at the molecular level of the kidney tissue occur even before nitrogenous substances, such as creatinine and urea, start to accumulate in the blood. Renal proximal tubules contain a large number of mitochondria and are critical for the energy-demanding process of reabsorption of water and solutes. Mitochondria are the largest producers of oxygen radicals, which, in turn, increase the susceptibility of kidneys to oxidative stress-induced damage. Free radicals and prooxidants produced during acute or chronic kidney injury may further aggravate the course of the disease and play a role in the pathogenesis of subsequent complications. Prevention might be the solution in CKD, but patients are often reluctant to undergo preventive examinations. Noninvasive markers and the possibility to obtain samples at home might help to increase compliance. This review will provide an overview of the possible uses of markers of oxidative status in noninvasive biofluids in patients with renal disease.

Review on nutritional composition of orange-fleshed sweet potato and its role in management of vitamin A deficiency

A wide variety of the roots and tubers plays a major role in human diet, animal feed, and industrial raw materials. Sweet potatoes (SPs) play an immense role in human diet and considered as second staple food in developed and underdeveloped countries. Moreover, SP production and management need low inputs compared to the other staple crops. The color of SP flesh varied from white, yellow, purple, and orange. Scientific studies reported the diversity in SP flesh color and connection with nutritional and sensory acceptability. Among all, orange-fleshed sweet potato (OFSP) has been attracting food technologists and nutritionists due to its high content of carotenoids and pleasant sensory characteristics with color. Researchers reported the encouraging health effects of OFSP intervention into the staple food currently practicing in countries such as Uganda, Mozambique, Kenya, and Nigeria. Scientific reviews on the OFSP nutritional composition and role in vitamin A management (VAM) are hardly available in the published literature. So, this review is conducted to address the detailed nutritional composition (proximate, mineral, carotenoids, vitamins, phenolic acids, and antioxidant properties), role in vitamin A deficiency (VAD) management, and different food products that can be made from OFSP.

Oxidative Stress in Animal Models of Acute and Chronic Renal Failure

Introduction

Kidney disease is a worldwide health and economic burden, with rising prevalence. The search for biomarkers for earlier and more effective disease screening and monitoring is needed. Oxidative stress has been linked to both, acute kidney injury (AKI) and chronic kidney disease (CKD). The aim of our study was to investigate whether the concentrations of systemic markers of oxidative stress and antioxidant status are affected by AKI and CKD, and to identify potential biomarkers.

Methods

In adult male Wistar rats, AKI was induced by bilateral nephrectomy, and CKD was induced by 5/6 nephrectomy. Blood was collected 48 hours after surgery in AKI and 6 months after surgery in CKD. Advanced oxidation protein products (AOPP), thiobarbituric acid reactive substances (TBARS), advanced glycation end products (AGEs), fructosamine, total antioxidant capacity (TAC), and ferric reducing antioxidant power (FRAP) were measured.

Results

Impaired renal function was confirmed by high concentrations of plasma creatinine and urea in AKI and CKD animals. AOPP and fructosamine were higher by 100% and 54% in AKI, respectively, and by 100% and 199% in CKD, respectively, when compared to corresponding control groups. Similarly, there was approximately a twofold increase in AGEs (by 92%) and TAC (by 102%) during AKI. In CKD, concentrations of FRAP, as an antioxidative status marker, were doubled (by 107%) when compared to the control group, but concentration of TAC, another marker of antioxidative status, did not differ between the groups.

Conclusions

AKI and CKD led to increased systemic oxidative stress. AOPP and fructosamine could be considered potential biomarkers for both, acute and chronic kidney damage. On the other hand, AGEs, TAC, and FRAP seem to be disease specific, which could help to differentiate between acute and chronic kidney injuries. However, this needs further validation in clinical studies.

Blood Fatty Acid Status and Clinical Outcomes in Dialysis Patients: A Systematic Review

Blood fatty acids (FAs) are derived from endogenous and dietary routes. Metabolic abnormalities from kidney dysfunction, as well as cross-cultural dietary habits, may alter the FA profile of dialysis patients (DP), leading to detrimental clinical outcomes. Therefore, we aimed to (i) summarize FA status of DP from different countries, (ii) compare blood FA composition between healthy controls and DP, and (iii) evaluate FA profile and clinical endpoints in DP. Fifty-three articles from 1980 onwards, reporting FA profile in hemodialysis and peritoneal DP, were identified from PubMed, Embase, and the Cochrane library. Studies on pediatric, predialysis chronic kidney disease, acute kidney injury, and transplant patients were excluded. Moderate to high levels of n-3 polyunsaturated fatty acids (PUFA) were reported in Japan, Korea, Denmark, and Sweden. Compared to healthy adults, DP had lower proportions of n-3 and n-6 PUFA, but higher proportion of monounsaturated fatty acids. Two studies reported inverse associations between n-3 PUFAs and risks of sudden cardiac death, while one reported eicosapentaenoic acid + docosahexaenoic acid)/arachidonic acid ratio was inversely associated with cardiovascular events. The relationship between all-cause mortality and blood FA composition in DP remained inconclusive. The current evidence highlights a critical role for essential FA in nutritional management of DP.

Oxidative stress, eryptosis and anemia: a pivotal mechanistic nexus in systemic diseases

The average lifespan of circulating erythrocytes usually exceeds hundred days. Prior to that, however, erythrocytes may be exposed to oxidative stress in the circulation which could cause injury and trigger their suicidal death or eryptosis. Oxidative stress activates Ca²⁺ -permeable nonselective cation channels in the cell membrane, thus, stimulating Ca²⁺ entry and subsequent cell membrane scrambling resulting in phosphatidylserine exposure and activation of Ca²⁺ -sensitive K⁺ channels leading to K⁺ exit, hyperpolarization, Cl^- exit, and ultimately cell shrinkage due to loss of KCl and osmotically driven water. While the mechanistic link between oxidative stress and anemia remains ill-defined, several diseases such as diabetes, hepatic failure, malignancy, chronic kidney disease and inflammation have been identified to display both increased oxidative stress as well as eryptosis. Recent compelling evidence suggests that oxidative stress is an important perpetrator in accelerating erythrocyte loss in different systemic conditions and an underlying mechanism for anemia associated with these pathological states. In the present review, we discuss the role of oxidative stress in reducing erythrocyte survival and provide novel insights into the possible use of antioxidants as putative antieryptotic and antianemic agents in a variety of systemic diseases.

Oxidative Stress in Kidney Diseases: The Cause or the Consequence?

Exaggerated oxidative stress (OS) is usually considered as a disturbance in regular function of an organism. The excessive levels of OS mediators may lead to major damage within the organism’s cells and tissues. Therefore, the OS-associated biomarkers may be considered as new diagnostic tools of various diseases. In nephrology, researchers are looking for alternative methods replacing the renal biopsy in patients with suspicion of chronic kidney disease (CKD). Currently, CKD is a frequent health problem in world population, which can lead to progressive loss of kidney function and eventually to end-stage renal disease. The course of CKD depends on the primary disease. It is assumed that one of the factors influencing the course of CKD might be OS. In the current work, we review whether monitoring the OS-associated biomarkers in nephrology patients can support the decision-making process regarding diagnosis, prognostication and treatment initiation.

Perspectives in Pediatric Pathology, Chapter 22. Testicular Involvement in Systemic Diseases

Normal testicular physiology requires appropriate function of endocrine glands and other tissues. Testicular lesions have been described in disorders involving the hypothalamus-hypophysis, thyroid glands, adrenal glands, pancreas, liver, kidney, and gastrointestinal tract. Testicular abnormalities can also associate with chronic anemia, obesity, and neoplasia. Although many of the disorders that affect the above-mentioned glands and tissues are congenital, acquired lesions may result in hypogonadism in children and adolescents.

Evaluation of oxidative stress and thyroid hormone status in hemodialysis patients in Gorgan

AIMS

The aim of this study focused on serum malondialdehyde (MDA) levels and erythrocyte superoxide dismutase (SOD) and catalase (CAT) activities in hemodialysis patients and compared with control groups.

MATERIALS AND METHODS

Forty-five hemodialyzed patients and 45 control groups recruited in this study. Serum creatinine and urea, thyroid hormones (THs) levels and erythrocyte antioxidant enzyme activities were determined.

RESULTS

Hemodialysis (HD) patients showed higher levels of MDA than control groups (P < 0.01), but the levels of thyroxin (T3), free triiodothyronine (fT3), and free thyroxin (fT4), SOD and CAT were low in HD patients (P < 0.01). Serum T3, fT3, and fT4 levels were significantly negative correlated with MDA (P < 0.01).

CONCLUSION

It is concluded that serum lipid peroxidation is markedly increased in HD patients. This means that elevated reactive oxygen species may interact with the lipid molecules in HD patients. HD may cause significant changes in TH levels. Thyroid-stimulating hormone level in HD patients is slightly similar to that of control groups. This suggests that thyroid is able to resynthesize for hormonal urinary losses.

Red blood cell abnormalities and the pathogenesis of anemia in end-stage renal disease

Anemia is the most common hematologic complication in end-stage renal disease (ESRD). It is ascribed to decreased erythropoietin production, shortened red blood cell (RBC) lifespan, and inflammation. Uremic toxins severely affect RBC lifespan; however, the implicated molecular pathways are poorly understood. Moreover, current management of anemia in ESRD is controversial due to the "anemia paradox" phenomenon, which underlines the need for a more individualized approach to therapy. RBCs imprint the adverse effects of uremic, inflammatory, and oxidative stresses in a context of structural and functional deterioration that is associated with RBC removal signaling and morbidity risk. RBCs circulate in hostile plasma by raising elegant homeostatic defenses. Variability in primary defect, co-morbidity, and therapeutic approaches add complexity to the pathophysiological background of the anemic ESRD patient. Several blood components have been suggested as biomarkers of anemia-related morbidity and mortality risk in ESRD. However, a holistic view of blood cell and plasma modifications through integrated omics approaches and high-throughput studies might assist the development of new diagnostic tests and therapies that will target the underlying pathophysiologic processes of ESRD anemia.

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.

Effect of reuse of polysulfone membrane on oxidative stress during hemodialysis

Patients with chronic renal failure, especially those on long-term hemodialysis (HD), have a high incidence of premature cardiovascular disease. Oxidative stress, which occurs when there is an excessive free radical production or low antioxidant level, has recently been implicated as a causative factor in atherogenesis. Hourly changes in malondialdehyde (MDA) and antioxidant enzymes, vitamins, lipid profile and ferric reducing ability of plasma (FRAP) were studied with the first use and immediate subsequent reuse of polysulfone dialysis membrane in 27 patients on regular HD treatment. Data were corrected for hemoconcentration and standardized to measure the rate of change. Increase in MDA and erythrocyte catalase along with decrease in plasma vitamin E and FRAP levels and no change in glutathione peroxidase levels were observed as a result of both fresh and reuse dialysis. These findings indicate a net oxidative stress in both fresh as well as dialyzer reuse sessions. There was no significant change in oxidative stress in both fresh and reuse sessions. The oxidative stress with reuse dialysis was less when compared to first use dialysis, but the difference was not statistically significant.

Glutathione S-transferase A1, M1, P1 and T1 null or low-activity genotypes are associated with enhanced oxidative damage among haemodialysis patients

BACKGROUND

Increased oxidative stress is a hallmark of end-stage renal disease (ESRD). Glutathione S-transferases (GST) are involved in the detoxification of xenobiotics and protection of oxidative damage. We hypothesized that genetic polymorphism in antioxidant enzymes GSTA1, GSTM1, GSTP1 and GSTT1 is more frequent in ESRD and modulates the degree of oxidative stress in these patients.

METHODS

GSTA1, GSTM1, GSTP1 and GSTT1 genotypes were determined in 199 ESRD patients and 199 age- and gender-matched controls. Markers of protein and lipid oxidative damage [thiol groups, carbonyl groups, advanced oxidative protein products, nitrotyrosine, malondialdehyde (MDA) and MDA adducts], together with total oxidant status and pro-oxidant-antioxidant balance were determined.

RESULTS

Individual GST polymorphisms influence vulnerability to both protein and lipid oxidation, with GSTM1-null gene variant having the most pronounced effect. Furthermore, a strong combined effect of null/low-activity GSTM1, GSTT1, GSTA1 and GSTP1 genotypes in terms of susceptibility towards oxidative and carbonyl stress was found in ESRD patients. When patients were stratified according to GSTM1 and GSTT1, the highest oxidant damage was noted in those with the GSTM1-null/GSTT1-null genotype. The observed effect was even stronger in patients with the third low-activity GSTP1 or GSTA1 genotype. Finally, the level of oxidative and carbonyl stress was most pronounced in the subgroup of patients with all four null or low-activity GSTM1, GSTT1, GSTP1 and GSTA1 genotypes.

CONCLUSIONS

According to the GST genotype, ESRD patients may be stratified in terms of the level of oxidative and carbonyl stress that might influence cardiovascular prognosis, but could also improve efforts towards individualization of antioxidant treatment.

HDL proteome in hemodialysis patients: a quantitative nanoflow liquid chromatography-tandem mass spectrometry approach

Aside from a decrease in the high-density lipoprotein (HDL) cholesterol levels, qualitative abnormalities of HDL can contribute to an increase in cardiovascular (CV) risk in end-stage renal disease (ESRD) patients undergoing chronic hemodialysis (HD). Dysfunctional HDL leads to an alteration of reverse cholesterol transport and the antioxidant and anti-inflammatory properties of HDL. In this study, a quantitative proteomics approach, based on iTRAQ labeling and nanoflow liquid chromatography mass spectrometry analysis, was used to generate detailed data on HDL-associated proteins. The HDL composition was compared between seven chronic HD patients and a pool of seven healthy controls. To confirm the proteomics results, specific biochemical assays were then performed in triplicate in the 14 samples as well as 46 sex-matched independent chronic HD patients and healthy volunteers. Of the 122 proteins identified in the HDL fraction, 40 were differentially expressed between the healthy volunteers and the HD patients. These proteins are involved in many HDL functions, including lipid metabolism, the acute inflammatory response, complement activation, the regulation of lipoprotein oxidation, and metal cation homeostasis. Among the identified proteins, apolipoprotein C-II and apolipoprotein C-III were significantly increased in the HDL fraction of HD patients whereas serotransferrin was decreased. In this study, we identified new markers of potential relevance to the pathways linked to HDL dysfunction in HD. Proteomic analysis of the HDL fraction provides an efficient method to identify new and uncharacterized candidate biomarkers of CV risk in HD patients.

Microvascular reactivity in lean, overweight, and obese hypertensive adolescents

The microvascular responses to endothelium-dependent vasodilators (e.g., acetylcholine), endothelium-independent vasodilators (e.g., sodium nitroprusside), and to local heating were studied (for the first time) in adolescents with essential hypertension, grouped according to their body mass index. The forearm microvascular reactivities of thirty-three hypertensive adolescents (ten lean, 13 overweight, and ten obese) and 19 healthy controls were assessed by means of laser Doppler flowmetry. Blood levels of enzymatic and nonenzymatic antioxidants and malondialdehyde were determined. The perfusion increments in response to acetylcholine iontophoresis were not significantly attenuated in the patient groups as compared with the controls. Sodium nitroprusside (SNP) iontophoresis resulted in significantly smaller perfusion increments in the lean and obese hypertensives than in the controls (both p < 0.05). Similar responses to local heating (44°C) performed after either acetylcholine or SNP iontophoresis were observed at the respective measurement sites. As compared with the controls, we found elevated ratios of the whole blood oxidized and reduced glutathione in all the patient groups (all p < 0.001), increased erythrocyte catalase activities in the overweight hypertensives (p < 0.05), and decreased ratios of the plasma alpha-tocopherol and triglycerides in the obese hypertensive group (p < 0.05).

CONCLUSION

The endothelium-dependent microvascular reactivity was not significantly attenuated in the hypertensive adolescents in contrast with the impaired endothelium-independent vasorelaxation in the lean and obese hypertensives.

Cardiovascular Biomarkers in Chronic Kidney Disease

Cardiovascular morbidity and mortality are markedly increased in chronic renal failure patients. Although it cannot be regarded as a cardiovascular disease risk equivalent, kidney dysfunction is considered an independent predictor of increased cardiovascular risk that increases with deteriorating kidney function. The association is a very complex one, and the term cardiorenal syndrome is now widely used. Cardiovascular disease in chronic kidney disease patients usually manifests as ischemic heart disease (in the form of angina, acute coronary syndrome or sudden cardiac death), cerebrovascular disease, peripheral vascular disease, and congestive heart failure. Vascular disease includes atherosclerosis and vascular calcifications, and cardiomyopathy comprises left ventricular hypertrophy, cardiac fibrosis and left ventricular systolic and diastolic dysfunction. In addition to the well-established traditional risk factors such as hypertension, hyperlipidemia, insulin resistance and diabetes mellitus, the association is supported by synergistic action of non-traditional risk factors such as excessive calcium-phosphorus load, hyperparathyroidism, anemia, hemodynamic overload, malnutrition, inflammation, hyperhomocysteinemia, altered nitric oxide synthase and increased oxidative stress. This paper summarizes the current understanding of the significance of specific uremic retention solutes, natriuretic peptides, biochemical markers of disorders in calcium-phosphorus homeostasis, systemic inflammation, oxidative stress, and dyslipidemia.

Oxidative stress in renal dysfunction: mechanisms, clinical sequelae and therapeutic options

Oxidative stress has been increasingly linked to the high incidence of cardiovascular events in patients with chronic kidney disease (CKD), especially as traditional cardiovascular risk factors seem to not be able to account for the huge cardiovascular morbidity and mortality in this population group. Oxidative stress is increased in patients with renal impairment as a result of increased oxidant activity and reduced antioxidant capacity, and this is increased in a graded manner with increasing renal dysfunction. Inflammation, which is also present in CKD, further amplifies the oxidant generation process. The two clinical sequelae of oxidative stress are endothelial dysfunction and left ventricular hypertrophy, which have adverse cardiovascular consequences. With our new understanding of oxidative stress, it is now important to assess treatment options that reduce it in the hope that they reverse endothelial dysfunction and left ventricular hypertrophy and the clinical sequelae of these abnormalities.

The Influence of Extracorporeal Circulation on the Susceptibility of Erythrocytes to Oxidative Stress

Extracorporeal circulation (ECC), a necessary and integral part of cardiac surgery, can itself induce deleterious effects in patients. The pathogenesis of diffuse damage of several tissues is multifactorial. It is believed that circulation of blood extracorporeally through plastic tubes causes a whole body inflammatory response and a severe shear stress to blood cells. The aim of this study was to evaluate the level of oxidative stress and its deleterious effect on red blood cell (RBC) before (pre-ECC), immediately after (per-ECC) and 24 h after an ECC (24 h post-ECC). Several indicators of extracellular oxidative status were evaluated. The ascorbyl free radical (AFR) was directly measured in plasma using electron spin resonance (ESR) spectroscopy and expressed with respect to vitamin C levels in order to obtain a direct index of oxidative stress. Allophycocyanin assay was also used to investigate the plasma antioxidant status (PAS). Indirect parameters of antioxidant capacities of plasma such as vitamin E, thiol and uric acid levels were also quantified. RBC alterations were evaluated through potassium efflux and carbonyl levels after action of AAPH, a compound generating carbon centered free radicals. No changes in plasma uric acid and thiols levels were observed after ECC. However, vitamin E levels and PAS were decreased in per-ECC and 24h post-ECC samples. Vitamin C levels were significantly lower in 24 h post-ECC and the AFR/ vitamin C ratio was increased. Differences in results had been noted when measurements took account of hemodilution. Increases of uric acid and thiols levels were observed after ECC. Vitamin E levels were not modified. However after hemodilution correction a significant decrease of vitamin C level was noted in 24 h post-ECC samples as compared to per-ECC sample. Whatever the way of measurement, vitamin C levels decreased suggesting the occurrence of ECC induced-oxidative stress. Concerning RBC, in the absence of AAPH, extracellular potassium remained unchanged between pre-, per- and 24 h post-ECC. AAPH induced a significant increase in extracellular potassium and carbonyls levels of RBC membranes, which was not modified by ECC. These results suggest the absence of alterations of RBC membrane during ECC despite the occurrence of disturbances in PAS. Such protection is of particular importance in a cell engaged in the transport of oxygen and suggests that RBC are equipped with mechanisms affording a protection against free radicals.

GST M1 polymorphism associates with DNA oxidative damage and mortality among hemodialysis patients

Leukocyte 8-hydroxy-2'-deoxyguanosine (8-OHdG) is a surrogate marker of oxidant-induced DNA damage in patients undergoing maintenance hemodialysis (MHD). Glutathione S-transferase M1 (GST M1) is a member of the GST family of proteins, which protect cellular DNA against oxidative damage. This study tested the association of a common GST M1 gene polymorphism [GST M1(-)], known to produce a dysfunctional enzyme, with levels of 8-OHdG in peripheral blood leukocytes and all-cause mortality among MHD patients. Among 488 MHD patients and 372 gender-matched healthy subjects, the frequency of the GST M1(-) genotype was 63.1 and 60.2%, respectively. The GST M1(-) genotype was associated with significantly higher levels of leukocyte 8-OHdG compared with the GST M1(+) genotype, even after adjustment for potential confounders (P < 0.001). Moreover, GST M1(-) patients who also had a common polymorphism in the DNA repair enzyme 8-oxoguanine DNA glycosylase 1 or who underwent dialysis with a bioincompatible cellulose membrane had the highest median levels of leukocyte 8-OHdG. Multivariate Cox regression revealed that among MHD patients, GST M1(-) genotype approximately doubled the risk for all-cause mortality (hazard ratio 2.24; 95% confidence interval 1.30 to 4.51) during the mean follow-up of 34 mo. In conclusion, patients without GST M1 activity are more vulnerable to oxidative stress and are at greater risk for death compared with those who possess GST M1 activity.

Lipoperoxidation and hemodialysis

It has been suggested that hemodialysis patients may be under increased oxidative stress and may therefore benefit from the long-term use of antioxidants (particularly for the reduction of the risk of heart disease). The aim of this study was, first, to evaluate the effect of hemodialysis by itself on lipid and lipoprotein oxidation profiles and, second, to analyze the effect of vitamin C supplementation in patients with end-stage renal disease starting hemodialysis. Forty-one patients with end-stage renal disease were enrolled and randomized to receive 1000 mg/d vitamin C or matching placebo before starting hemodialysis. We measured lipid profile and the susceptibility of low-density lipoprotein (LDL) and high-density lipoprotein (HDL) to oxidation using copper ions at the moment of inclusion and after 1 year. All lipoperoxidation parameters were included. Hemodialysis by itself improved the lipid profile, lowering total cholesterol (176.4 +/- 48.4 to 154.2 +/- 28.8 mg/dL, P < .01), LDL cholesterol (94.1 +/- 39.6 to 76.1 +/- 26.6 mg/dL LDL, P < .03), and phospholipids levels (196.5 +/- 36.7 to 182.9 +/- 36.1 mg/dL, P < .05) in all patients on maintenance hemodialysis. The HDL cholesterol was also decreased (49.4 +/- 19.8 to 43.4 +/- 24.1 mg/dL HDL, P < .03). No significant differences were detected between patients receiving vitamin C and those receiving placebo. Thiobarbituric acid reactive substances (TBARS) and lipoperoxides increased in patients after a year of hemodialysis, but the difference was lower in those administered vitamin C for a year-TBARS LDL (in nanograms per gram LDL): 0.25 +/- 0.20 to 0.38 +/- 0.2 in vitamin C-treated subjects and 0.28 +/- 0.17 to 0.46 +/- 0.21 in those treated with placebo (P < .007); TBARS HDL (in nanograms per gram HDL): 0.22 +/- 0.12 to 0.34 +/- 0.30 in patients receiving vitamin C and 0.20 +/- 0.18 to 0.28 +/- 0.19 in those receiving placebo (P = .071). Hemodialysis by itself seems to improve the lipid profile in patients with a previous prooxidative state such as uremia. Although our results failed to demonstrate significant differences between vitamin C-treated and untreated patients, and despite the small number of patients, the trend toward a decrease in oxidation products due to vitamin C supplementation may be beneficial for oxidation parameters. This area remains controversial and under active investigation. Further research is necessary before a firm conclusion can be reached.

Infrared spectroscopy: a reagent-free method to distinguish Alzheimer's disease patients from normal-aging subjects

The physiopathogenesis of Alzheimer's disease (AD) is related to various biochemical mechanisms that may be reflected by changes in plasma components. In the current study, Fourier transform-infrared (FT-IR) spectroscopy was used to identify these biochemical variations by monitoring spectral differences in the plasma of 40 AD patients compared with those of 112 control subjects. A hierarchical classification in the whole mid-infrared region allowed a clear separation between AD and controls (C) that was optimized by using a restricted spectral range (1480-1428 cm(-1)). Spectral changes confirmed vibration differences between AD and C mostly related to modified lipid and nucleic acid structures involved in oxidative stress-dependent processes of AD. Moreover, the analysis of samples in the 1480-910-cm(-1) region allowed the distinction between C and AD with an accuracy of 98.4% and showed 2 subgroups C(1) and C(2) within the C group. Interestingly, the C(1) subgroup was located closer to the AD group than the C(2) subgroup, which suggests biochemical differences within the nondemented subjects. Biochemical studies revealed a significant increase in a specific marker of oxidative stress, F8-isoprostanes (8-epi-PGF2alpha) levels, in the plasma of AD patients as compared with total controls and subgroup C(2) but not subgroup C(1). Thus, these results suggest that use of FT-IR spectroscopy could be valuable to distinguish AD patients from normal-aging subjects.

Effects of hemodialysis on testicular volume and oxidative stress in humans

PURPOSE

Male infertility is a serious problem in patients on hemodialysis. Our understanding is that end stage renal disease or hemodialysis causes poor semen quality but the mechanism leading to impaired spermatogenesis is largely unknown.

MATERIALS AND METHODS

Testicular volume in 120 patients on maintenance hemodialysis was compared with that in age matched healthy controls. Volume was correlated with clinical findings. In 10 testicular biopsy specimens from patients on hemodialysis who visited our infertility clinic Western blotting was performed to examine the generation of 4-HNE modified proteins, which are markers of oxidative stress, and the expression of proliferating cell nuclear antigen. Interstitial fibrosis was determined by Masson's trichrome staining.

RESULTS

Mean bilateral testicular volume in patients on hemodialysis was significantly smaller than that in healthy controls (31.7 vs 36.4 ml, p <0.01) in a hemodialysis duration dependent manner (r = -0.32, p <0.01). The increase in serum ferritin correlated inversely with testicular volume (r = -0.25, p <0.01). The generation of 4-HNE modified proteins was significantly increased 3.1-fold in patients on hemodialysis, following the 60% decreased expression of proliferating cell nuclear antigen. Quantitative analysis of Masson's trichrome staining revealed increased interstitial fibrosis in patients on hemodialysis compared with that in controls (41.5% vs 14.8%, p <0.01). Serum ferritin, proliferating cell nuclear antigen expression and interstitial fibrosis correlated with the generation of 4-HNE modified proteins (p <0.05).

CONCLUSIONS

Testicular volume, which is a parameter of spermatogenesis, is impaired in patients on hemodialysis and oxidative stress is considered to be involved in the process. Serum ferritin is a useful parameter for predicting oxidative stress in the testis.

Compositional and oxidative analysis in the saliva and serum of predialysis chronic kidney disease patients and end-stage renal failure patients on peritoneal dialysis

Chronic renal failure (CRF) is often treated with peritoneal dialysis, although increased oxidative stress has been reported in such patients. The purpose of the current study was to analyze and compare oxidative stress and other compositional parameters in the saliva, serum and peritoneal dialytic fluid (PDF) of patients with chronic kidney disease (CKD), including predialysis CKD patients and end-stage renal disease (ESRD) patients treated with peritoneal dialysis. Twenty-three consenting patients participated in the current study. Saliva and serum samples collected from both groups and PDF from the dialysis patients were all examined for uric acid (UA), total antioxidant status, total protein and total albumin. The antioxidant enzyme peroxidase was examined both in saliva and serum, while the antioxidant enzyme superoxide dismutase (SOD) was examined solely in saliva. Various electrolytes were examined. Discrepancies were found between saliva and serum antioxidant status following peritoneal dialysis in ESRD patients. Oxidative stress was enhanced in the saliva but reduced in the serum. Significant changes in both oxidative-related and non-related parameters were demonstrated in saliva, serum and PDF. Salivary lactate dehydrogenase was substantially lower in the dialysis patients (by 92%, P = 0.02), as was the salivary UA concentration (by 22%, P = 0.05) and serum UA concentration (by 20%, P = 0.03). In contrast, salivary peroxidase and SOD were higher by 15% and 35%, respectively (P = 0.01), in these patients. We suggest monitoring salivary UA for assessing the baseline oral oxidative status of CRF and dialyzed patients.

Slow intravenous iron administration does not aggravate oxidative stress and inflammatory biomarkers during hemodialysis: a comparative study between iron sucrose and iron dextran

BACKGROUND/AIMS

Fast intravenous (i.v.) iron administration during hemodialysis (HD) is associated with the augmentation of oxidative stress and the increase in inflammatory biomarkers, which are also induced by the hemodialysis procedure itself. The aim of this study was to investigate if slow i.v. iron administration would aggravate the status of oxidative stress and inflammatory biomarkers during a hemodialysis session.

METHODS

Twenty dialysis patients 30-92 years of age that were iron replete and had values for hemoglobin, transferrin saturation and serum ferritin among recommended goals were evaluated in three separate hemodialysis sessions. In the first session patients did not receive any iron treatment, whereas during the second and the third session patients received slow (60 min) i.v. infusions of 100 mg of iron sucrose and 100 mg of iron dextran, respectively. Blood samples were drawn before the hemodialysis session, 15 min after the end of iron administration and at the end of the hemodialysis session in all occasions, for the measurement of markers of oxidant stress (oxidized LDL and ischemia-modified albumin) and inflammation (high-sensitivity C-reactive protein, interleukin-6 and tumor necrosis factor-alpha).

RESULTS

Oxidized LDL was not significantly altered during hemodialysis and this pattern was similar between the three occasions studied. In contrast, ischemia-modified albumin was significantly increased and this effect was also not different between the net hemodialysis and the occasions of iron administration. High-sensitivity CRP, IL-6 and TNF-alpha were all significantly elevated during hemodialysis and again both types of iron administration did not produce significant changes in this pattern.

CONCLUSION

We did not find an increase in the markers of oxidation/inflammation studied, after slow i.v. iron administration during hemodialysis session.

Iron-induced oxidative stress in haemodialysis patients: a pilot study on the impact of diabetes

BACKGROUND

Administration of intravenous iron preparations in haemodialysis patients may lead to the appearance of non-transferrin bound iron which can catalyse oxidative damage. We investigated this hypothesis by monitoring the oxidative stress of haemodialysis patients and the impact of iron and diabetes mellitus herein.

MATERIALS AND METHODS

Baseline values of serum iron and related proteins, transferrin glycation, non-transferrin bound iron, antioxidant capacity and lipid peroxidation (malondialdehyde) of 11 haemodialysis patients (six non-diabetic and five type 2 diabetes) were compared to those of non-haemodialysis control subjects (non-diabetic and type 2 diabetes). Changes in these parameters were monitored during haemodialysis before and after iron administration.

RESULTS

Baseline values of malondialdehyde correlated with ferritin concentration (r = 0.664, P = 0.036) and were elevated to the same extent in non-diabetic and diabetic haemodialysis patients (median of 1.09 compared to 0.60 mumol/l in control persons, P < 0.02). After iron infusion, transferrin saturation increased more markedly in non-diabetic subjects from 28% to 185% vs. from 33% to 101% in diabetic patients (P = 0.008). This increase was accompanied by the appearance of non-transferrin bound iron (5.91 +/- 1.33 micromol/l), a loss in plasma iron-binding antioxidant capacity and a further increase in malondialdehyde which was more pronounced in diabetic patients (from 0.93 +/- 0.30 micromol/l to 2.21 +/- 0.69 micromol/l vs. from 1.21 +/- 0.42 micromol/l to 1.86 +/- 0.56 micromol/l in the non-diabetic subjects, P = 0.046).

CONCLUSIONS

In haemodialysis patients, higher lipid peroxidation is determined by higher body iron stores. The increase induced by iron infusion is accompanied by a loss in iron-binding antioxidant capacity and is more pronounced in diabetes mellitus.

Oxidative stress and δ-ALA-D activity in chronic renal failure patients

In this paper, we studied the influence of uremia and hemodialysis on oxidative parameters and delta-aminolevulinic acid dehydratase (delta-ALA-D) activity in control subjects, patients with chronic renal failure (CRF) on hemodialysis treatment (HD) and in patients not undergoing hemodialysis (ND). An increased lipid peroxidation was observed in the serum of HD and ND patients, as measured by the MDA serum levels. However, the level of MDA from erythrocytes was only elevated in HD patients. Blood catalase activity was increased in HD and ND groups. This study also showed a decreased activity of blood delta-aminolevulinic acid dehydratase (delta-ALA-D) in both groups of patients. This study demonstrated a positive correlation between ALA-D activity and hemoglobin, suggesting that inhibition of this enzyme might enhance anemia in CRF. A negative correlation was found between the alteration in delta-ALA-D activity and oxidative stress, which may indicate that the inhibition of ALA-D can be used as an index of oxidative stress.

Effects of diabetes mellitus, chronic renal failure and hemodialysis on serum and salivary antioxidant status

AIM

To analyze various oxidative stress parameters in the saliva and serum of patients with chronic renal failure (CRF) and/or diabetes mellitus (DM), and to compare them in dialytic vs. pre-dialytic patients.

METHOD

50 consenting patients were divided into five subgroups of patients: severe CRF (dialytic) without DM, severe CRF (dialytic) with DM, mild CRF (pre-dialytic) without DM, mild CRF (pre-dialytic) with DM, and with DM but without CRF (controls). Uric acid (UA), peroxidase and total antioxidant status (TAS) were studied in both saliva and serum; superoxide dismutase (SOD) was evaluated only in saliva. Both saliva collection and serum harvesting were done simultaneously.

RESULTS

In severe-CRF patients without DM, median TAS, UA and SOD levels decreased following dialysis (54, 85, 48%, respectively), and peroxidase levels increased slightly (9%). In severe-CRF patients with DM, median TAS and SOD levels increased following dialysis (33 and 54%, respectively) while median UA and peroxidase levels decreased (68 and 10%, respectively).

CONCLUSIONS

DM, CRF and hemodialysis were found to increase the oxidative stress burden in both serum and saliva. Therefore, antioxidant assessment may be used to monitor baseline oxidative status in these situations though larger randomized studies are in order.

Oxidative stress in hepatitis C infected end-stage renal disease subjects

BACKGROUND

Both uremia and hepatitis C infection is associated with increased oxidative stress. In the present study, we aimed to find out whether hepatitis C infection has any impact on oxidative stress in hemodialysis subjects.

METHODS

Sixteen hepatitis C (+) hemodialysis subjects, 24 hepatitis C negative hemodialysis subjects and 24 healthy subjects were included. Total antioxidant capacity, total peroxide level and oxidative stress index were determined in all subjects.

RESULTS

Total antioxidant capacity was significantly higher in controls than hemodialysis subjects with or without hepatitis C infection (all p < 0.05/3), while total peroxide level and oxidative stress index were significantly lower (all p < 0.05/3). Hepatitis C (-) hemodialysis subjects had higher total antioxidant capacity compared to hepatitis C (+) hemodialysis subjects (all p < 0.05/3). Total peroxide level and oxidative stress index was comparable between hemodialysis subjects with or without hepatitis C infection (p > 0.05/3).

CONCLUSION

Oxidative stress is increased in both hepatitis C (+) and hepatitis C (-) hemodialysis subjects. However, hepatitis C infection seems to not cause any additional increase in oxidative stress in hemodialysis subjects and it may be partly due to protective effect of dialysis treatment on hepatitis C infection.

The determinants of endothelial dysfunction in CKD: oxidative stress and asymmetric dimethylarginine

BACKGROUND

Oxidative stress is related to endothelial dysfunction (ED) and cardiovascular outcomes in patients with chronic kidney disease. Increased asymmetric dimethylarginine (ADMA) levels are among the main causes of ED. We aim to investigate any association between ED and ADMA levels, as well as levels of oxidative stress markers, in patients with chronic kidney disease.

METHODS

One hundred fifty-nine patients without diabetes with chronic kidney disease were studied. Staging was performed according to glomerular filtration rate, determined as stages 1 to 5 according to the Kidney Disease Outcomes Quality Initiative (n = 30, 33, 28, 32, and 36, respectively). The control group consisted of 30 healthy subjects. Oxidative stress markers (plasma malondialdehyde [MDA], erythrocyte superoxide dismutase [SOD], glutathione peroxidase [GSH-Px]), trace elements (erythrocyte zinc [EZn], erythrocyte copper [ECu]), plasma selenium (Se), and serum ADMA were studied. Brachial artery endothelium-dependent vasodilatation (FMD) was calculated for all.

RESULTS

FMD, SOD, GSH-Px, EZn, ECu, and Se values were lower, whereas MDA and ADMA levels were higher in patients than controls. Glomerular filtration rate correlated negatively with MDA and ADMA levels and positively with FMD, SOD, and GSH-Px values. These parameters were significantly different among patients with stages 2, 3, 4, and 5 (hemodialysis group; P < 0.001 for all). Regression analysis showed that ADMA (beta = -0.228; P < 0.01), SOD (beta = 0.405; P < 0.001), and oxidized low-density lipoprotein levels (beta = -0.428; P < 0.001) were related independently to FMD, whereas glomerular filtration rate was not involved in the model.

CONCLUSION

The present results imply that FMD, oxidative stress, and ADMA levels all are associated with stage of chronic kidney disease. Additionally, levels of oxidative stress markers and ADMA independently determine endothelial function.

Vitamin A and zinc status in patients on maintenance haemodialysis

BACKGROUND

The objective of this study was to assess the vitamin A and zinc serum levels in patients undergoing haemodialysis (HD) in the city of Recife, in the north-eastern region of Brazil.

METHODS

The study comprised 55 patients and 28 healthy controls. The retinol and zinc serum concentrations were analysed by using high-performance liquid chromatography (HPLC) and atomic absorption spectrophotometry, respectively.

RESULTS

The mean retinol serum concentration in patients (2.50 +/- 0.86 micromol/L) was significantly greater (P < 0.001) than that found in controls (1.26 +/- 0.86 micromol/L). The retinol serum levels in the patients were as follows: 47.3% of the patients had elevated levels (>/= 2.24 and < 3.50 micromol/L); 16.4% of the patients had serum levels >/= 3.50 micromol/L, which indicated hypervitaminosis; and 9.1% of the patients had serum levels below the normal range (<1.05 micromol/L), a rate that among the controls was 42.9% (P < 0.01). In regard to zinc, the serum levels found in the patients (10.59 +/- 3.12 micromol/L) were similar to those found in the controls (11.43 +/- 2.82 micromol/L) (P > 0.05). Although 49.1% of the patients and 35.7% of the controls were classified as deficient in zinc, this difference was not statistically significant (P > 0.05).

RESULTS

The results identified a high prevalence of zinc deficiency in the groups studied, and point to a trend towards more elevated retinol serum levels in patients undergoing dialysis as compared with those in healthy controls.

Erythrocyte susceptibility to oxidative stress in chronic renal failure patients under different substitutive treatments

An increased oxidative stress is now considered one of the major risk factors in chronic renal failure (CRF) patients that may be exacerbated by dialysis. It has been postulated that this increased oxidative stress might cause an augmented red blood cell (RBC) membrane lipid peroxidation with the consequent alteration in membrane deformability. The aim of this study was to evaluate RBC susceptibility to an in vitro induced oxidative stress and RBC antioxidant potential in different groups of CRF patients undergoing different substitutive treatment modalities. Fifteen end-stage CRF patients were evaluated in conservative treatment, 23 hemodialysis (HD) patients, 15 continuous ambulatory peritoneal dialysis (CAPD) patients, 15 kidney transplanted patients, and 16 controls. Their RBCs were incubated with the oxidative stress-inducing agent tert-butylhydroperoxide both in the presence and in the absence of the catalase inhibitor sodium azide, and the level of malondialdehyde (MDA) (a product of lipid peroxidation), was measured at 0, 5, 10, 15, and 30 min of incubation. In addition, the RBC content of reduced glutathione (GSH) was measured by HPLC. As opposed to the controls, RBCs from end-stage CRF patients exhibited an increased sensitivity to oxidative stress induced in vitro, both in the absence and presence of a catalase inhibitor, as demonstrated by a significantly higher level of MDA production at all the incubation times (P < 0.05). Different substitutive treatments had different impacts on this phenomenon; CAPD and kidney transplantation were able to normalize this alteration while HD was not. GSH appeared to be related to the increase in RBC susceptibility to oxidative stress; its content being significantly elevated in end-stage CRF and HD patients as compared with CAPD and transplanted patients and controls (P < 0.05). No significant changes were observed in the RBC glutathione content during the HD session. The increase of GSH in RBCs of end-stage CRF and HD patients seems to indicate the existence of an adaptive mechanism under increased oxidative stress occurring in vivo. Unlike HD, the beneficial effect of CAPD on the anemia of dialysis patients might partly be due to a condition of lower oxidative stress that might in addition counterbalance the cardiovascular negative effects of dislipidemia of CAPD patients.

High iron storage levels are associated with increased DNA oxidative injury in patients on regular hemodialysis

BACKGROUND

Accumulating evidence suggests that oxidative stress is enhanced in patients on regular hemodialysis (HD). Iron supplementation is essential for the treatment of renal anemia, but there is a possibility that it could enhance oxidative stress by inducing the Fenton reaction. Here, we report our investigation of the relation between iron storage and DNA oxidative injury in HD patients.

METHODS

The study subjects were 48 patients on regular HD (age, 62.7 +/- 12.1 years; HD duration, 67.2 +/- 62.5 months; non-diabetic/diabetic; 22:26). Patients who were positive for hepatitis C virus antibody (HCV Ab), or hepatitis B surface antigen (HBsAg), and those with inflammatory or malignant diseases were excluded. The serum 8-hydroxy-2'-deoxyguanosine (8-OHdG) level, a marker of DNA oxidative injury, was measured before the first HD session of the week in all patients, and factors associated with high serum 8-OHdG were investigated. In 9 patients with a serum ferritin level of more than 1000 ng/ml at study entry, serum 8-OHdG levels were followed up for 6 months in the absence of iron supplementation.

RESULTS

Multivariate analysis showed that the serum ferritin level was a significant and independent determinant of serum 8-OHdG, and serum ferritin correlated significantly with the total dose of iron supplementation during the 6-month period of the study. In the nine patients, without iron supplementation, serum 8-OHdG levels, as well as serum ferritin, decreased significantly during follow-up.

CONCLUSIONS

Our results suggest that increased iron storage may induce DNA oxidative injury in patients on regular HD, and that the serum ferritin level is a surrogate marker for this pathological condition.

Influence de l'hémodialyse sur les concentrations de malonedialdéhyde total et libre, mesurées par une nouvelle technique HPLC spécifique

Accurate evaluation of oxidative stress is needed for patients on chronic hemodialysis (HD), as cardiovascular risk level seems related to it. Oxidative stress is often evaluated by measuring an end product of lipoperoxidation named malondialdehyde (MDA). However, the most common technique for measuring MDA, the Thio Barbituric Acid Reactive Substances method (TBARS), is known to be sensitive but poorly specific. We measured true total and free plasma MDA in fifty-four unselected patients on long-term HD, before and after HD sessions, by a new, highly specific HPLC method. Total and free MDA were higher before than after dialysis. Essentially, free MDA was decreased by HD but its fractional decrease was lower than that of urea or creatinine. This confirms that, in fact, free MDA is more or less bound to low molecular weight compounds and/or suggests that MDA may be produced mainly during HD sessions. We propose this new tool to further explore the relationship between oxidative stress, HD and true MDA.

Tyrosine nitration in plasma proteins from patients undergoing hemodialysis

BACKGROUND

A growing body of evidence suggesting that oxidative stress might be one of the most important complications occurring during hemodialysis (HD) has accumulated. However, although the role of reactive oxygen species has been investigated extensively, little is known about the involvement of reactive nitrogen species. In the present investigation, levels of protein modifications in the form of tyrosine nitration in patients undergoing long-term HD therapy were evaluated.

METHODS

Tyrosine nitration of plasma proteins was detected by means of Western blotting using a specific nitrotyrosine-recognizing monoclonal antibody, and band intensity was evaluated by using image analysis software. Immunoprecipitation of plasma proteins by antinitrotyrosine-agarose--conjugated antibodies, followed by Western blotting, was used in an attempt to identify the nitrated proteins.

RESULTS

Although several proteins with nitrated tyrosine residues were observed in plasma of healthy individuals, increased nitration levels were observed in some specific proteins in all patients tested (n = 25) compared with controls (n = 6). At least 6 apparent bands appeared to be more nitrated than their counterparts in plasma from controls. Ceruloplasmin was identified as 1 of the proteins with significantly increased nitration in patients.

CONCLUSION

Results of the present investigation show that specific plasma proteins of HD patients are post-translationally modified by nitration of their tyrosine residues. The nature of these proteins, as well as the exact molecular mechanisms and consequences of these modifications, warrant additional investigation.

Oxidative and antioxidative status in pregnant women with either gestational or type 1 diabetes

OBJECTIVES

To evaluate oxidative and antioxidative status in pregnant diabetic women between 26 and 32 weeks of gestation.

DESIGN AND METHODS

Free and total malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPX), and vitamins A and E were determined in plasma and erythrocytes of 54 pregnant women. Among these, 27 were diabetics with either gestational diabetes mellitus (GDM), sub-group I, or previous insulin-dependent diabetes mellitus (type 1 diabetes), sub-group II. The other 27 patients were controls. Fasting plasma glucose and HbA(1c) levels were determined in all women.

RESULTS

HbA(1c) levels, plasma-, and erythrocyte-free MDA levels were significantly higher in all diabetic women and in both sub-groups than in controls. Plasma vitamin E and erythrocyte vitamin A levels were significantly lower in all diabetic women than in controls. Moreover, GPX and SOD activities were significantly reduced in all diabetic women, GPX in both sub-groups and SOD only in type 1 diabetes.

CONCLUSIONS

The increased oxidative stress we demonstrated in pregnant women with previous type 1 diabetes or with GDM should be monitored by strictly controlling blood glucose during pregnancy with stringent recommendations and perhaps antioxidant supplementation.

Oxidative stress in patients with chronic renal failure: effects of hemodialysis

OBJECTIVE

To investigate blood oxidative status of patients with chronic renal failure (CRF) and possible effects of hemodialysis on the development of oxidative stress in blood.

MATERIALS AND METHODS

The levels of malondialdehyde (MDA) and oxidation resistance (OR) values were measured in blood plasma, erythrocyte hemolysate and erythrocyte membrane fractions of 33 patients with CRF and of 12 healthy controls. Of the 33 patients, 17 subjects were under hemodialysis treatment.

RESULTS

MDA levels were found to be increased in all blood fractions of the patients. OR values were unchanged in erythrocyte hemolysates but decreased in plasma and erythrocyte membrane fractions of the CRF patients. Moreover, erythrocyte MDA levels were determined to be higher in hemodialyzed patients compared with both controls and non-hemodialyzed patients. OR values were lower in all blood fractions of the hemodialyzed patients relative to controls and non-hemodialyzed patients.

CONCLUSION

Results suggest that there is a significant oxidative stress (expressed as peroxidation) in blood samples from patients with CRF, which is further exacerbated by hemodialysis.

The Effects of Exercise on Markers of Lipid Peroxidation in Renal Dialysis Patients Compared with Control Subjects

PURPOSE

The purpose of this study was to compare the susceptibility to exercise-induced lipid peroxidation of patients on chronic maintenance dialysis (CMD) and non-CMD control subjects.

DESIGN

Cross-sectional comparison of exercise-induced changes in breath ethane and pentane flux between patients on CMD (group A) and an age-, gender-, medical diagnosis-, smoking-, and ethanol consumption-matched comparison group (group B). Breath ethane and pentane were measured at rest before exercise, during cardiopulmonary exercise stress testing (CPX) at lactic acidosis threshold (Vo2lat), and 5 minutes after CPX.

RESULTS

Group comparisons of clinical characteristics reveal that the groups were similar in terms of age, ethnicity, comorbid diagnoses, prevalence of medication use, BMI, measurements of aerobic exercise capacity, cigarette smoking and ethanol consumption behaviors. All subjects successfully completed the CPX protocol achieving Vo2lat. There were significant differences in breath ethane flux between group A and B subjects, with greater pre-exercise, Vo2lat, and postexercise ethane levels in group A compared with group B subjects, and significant group differences, with lower breath ethane/pentane flux ratios at rest, Vo2lat, and recovery with lower ratios in group B than group A subjects.

DISCUSSION/CONCLUSIONS

This study shows that patients on CMD have greater lipid peroxidation compared with control subjects at rest and during and after physical exercise. In addition, compared with control subjects, patients on CMD preferentially peroxidize n-3 polyunsaturated fatty acids at rest and during physical exercise and recovery. The lipid peroxidation profile may result in an unfavorable endoperoxide shift and should be evaluated further, along with modalities to reduce oxidative stress among patients on CMD.

Association between antioxidant nutritional indicators and the incidence of dementia: results from the PAQUID prospective cohort study

OBJECTIVE

To analyse the relation between antioxidant vitamins A, E, and malondialdehyde (MDA) lipoperoxidation product plasma concentrations with incident dementia.

DESIGN

: A nested case-control within the PAQUID (Personnes Agées QUID) cohort.

SETTING

The PAQUID population-based prospective cohort in southwestern France.

SUBJECTS

Among 626 subjects with blood collection at baseline, 46 developed a dementia during the follow-up and were considered to be cases. Each case was matched (on age and sex) to three controls.

RESULTS

Plasma vitamin E concentrations were lower among cases (mean value at 22.62 micromol/l (s.d.: 7.38) vs 24.99 (s.d.: 6.73 among controls). The same trend was observed for vitamin A concentrations, but the difference was not significant. On the contrary, MDA concentrations tended to be higher (mean value 1.35 micromol/l (s.d.: 0.53) vs 1.23 (s.d.: 0.44)) among cases. In logistic regression models, plasma values were split into tertiles. Adjusted for confounders, the risk of dementia was significantly increased in the lowest vitamin E tertile (< or =21.0 micromol/l) (OR=3.12, P=0.033) compared to the highest one (> or =25.5 micromol/l). The risk of Alzheimer's disease was also increased, with borderline significance (OR=3.06, P=0.053). Risks associated with vitamin A were nonsignificant. Similarly, there was a trend to an increased risk of dementia in the highest tertile of MDA (OR=1.67, P=0.31).

CONCLUSIONS

These results suggest that subjects with low plasma vitamin E concentrations are at a higher risk of developing a dementia in subsequent years.

8-iso-prostaglandin F2alpha as a useful clinical biomarker of oxidative stress in ESRD patients

BACKGROUND/AIMS

Chronic renal failure is associated with elevated indices of oxidative stress. We tested the hypothesis that the in vivo formation of the F(2)-isoprostane (8-iso-prostaglandin PGF(2alpha)), a bioactive product of arachidonic acid peroxidation, is enhanced in end-stage renal disease (ESRD) patients receiving hemodialysis (HD) and continuous ambulatory peritoneal dialysis (CAPD).

METHODS

Plasma samples were obtained from 35 HD patients, 30 CAPD patients and 30 age- and sex-matched healthy subjects for measurement of immunoreactive 8-iso-PGF(2alpha).

RESULTS

Plasma 8-iso-PGF(2alpha) levels were significantly higher (p < 0.001) in HD and CAPD patients (346.3 +/- 132.4 pg/ml; range 49.8-870) than in age-matched control subjects (150.9 +/- 61.6 pg/ml; range 33.5-235). In addition, we also found that 8-iso-PGF(2alpha) concentration was significantly (p = 0.007) higher in HD patients (389.8 +/- 148.3 pg/ml) than in CAPD patients (254.3 +/- 76.6 pg/ml). Plasma 8-iso-PGF(2alpha) concentration was linearly correlated with serum haptoglobin, C-reactive protein (CRP) and plasma MDA (r = 0.58, p = 0.003; r = 0.29, p < 0.05 and r = 0.38, p < 0.05 respectively). On the other hand, plasma 8-iso-PGF(2alpha) levels were inversely associated with serum albumin and total cholesterol (r = -0.31 and r = -0.28, respectively; p < 0.05).

CONCLUSIONS

We conclude that ESRD on both HD and CAPD is associated with increased formation of F(2)-isoprostanes, a correlate of enhanced lipid peroxidation. We also found that plasma 8-iso-PGF(2alpha) was casually related to some acute phase reactant proteins such as serum CRP, albumin and haptoglobin. This may provide an important biochemical link between lipid peroxidation, inflammation and accelerated atherosclerosis in the uremic milieu.

Intravenous iron: the iatrogenic kick to lose control over oxygen?

Effective erythropoiesis requires both erythropoietin and iron. Regular, intravenous iron supplements represent a standard adjuvant therapy for the treatment of anemia of chronic kidney disease. In this paper, the authors speculate upon potential deleterious effects of intravenous iron on cellular physiology in the setting of the increased oxidant burden of hemodialysis patients.

Vitamin E-bonded hemodialyzer improves atherosclerosis associated with a rheological improvement of circulating red blood cells

BACKGROUND

Vitamin E-bonded hemodialyzer is known to improve oxidative stress in patients with hemodialysis. However, there is little information available as to whether or not this membrane clinically improves atherosclerosis. Furthermore, it remains unknown whether there is any effect of the membrane on rheology of circulating red blood cells.

METHOD

We conducted a randomized, open-labeled, prospective control study (N = 34) for 1 year to investigate the effect of vitamin E-bonded cellulose membrane dialyzer (EE) (N = 17) on carotid atherosclerotic changes [intima-media thickness (IMT) of carotid arteries] and the viscosity, percentage of dysmorphism (%DMR) of red blood cells (RBCs) and their distribution width-standard deviation (RDW-SD), in comparison with cellulose membrane (SU) (N = 17) identical to EE without vitamin E-bonded membrane. Erythropoietin (EPO) dose used for the treatment of uremic anemia was also calculated.

RESULTS

The IMT significantly decreased in the EE group, while in the SU group the IMT significantly increased. The viscosity of RBCs in hemodialysis patients (4.70 +/- 0.45 cP) was greater than that in healthy individuals (3.73 +/- 0.15 cP). EE significantly improved the viscosity (from 4.84 +/- 0.41 cP to 4.51 +/- 0.54 cP, P < 0.01), %DMR (from 2.29 +/- 2.17% to 1.90 +/- 1.49%, P < 0.01), and RDW-SD (from 54.4 +/- 7.6 fL to 49.3 +/- 5.9 fL, P < 0.01). On the contrary, these parameters all worsened in the SU group. EPO dose needed for the treatment of anemia was significantly (P < 0.05) reduced from 5383 +/- 2655 U/week to 4235 +/- 3103 U/week in the EE group. During these period, mean blood pressure, Kt/V urea, and serum beta2-microglobulin were not changed between the two groups.

CONCLUSION

These findings suggest that vitamin E-bonded hemodialyzer is very useful for improving atherosclerosis from a clinical point of view. As one of the underlying mechanisms, as well as antioxidant effects, we want to address an important role of the improvement of rheology of circulating RBCs, which may also help to reduce the requirement of EPO dose in the treatment of anemia of ESRD patients.