Effect of hemodialysis on the antioxidative properties of serum

Albumin redox state of maintenance haemodialysis patients is positively altered after treatment

BACKGROUND AND AIM

Maintenance haemodialysis patients have increased morbidity and mortality which is mainly driven by an elevated inflammation level due to the uraemic milieu. A major part of this increased inflammation level is the degree of oxidative stress which can be assessed by albumin redox state (ARS). Aim of this study was to evaluate how the ARS is affected by a haemodialysis treatment and different dialyzer properties.

METHODS

ARS was determined before and after haemodialysis treatment by fractionating it into reduced human mercaptalbumin (HMA), reversibly oxidized human non-mercaptalbumin 1 (HNA-1), and irreversibly oxidized human non-mercaptalbumin 2 (HNA-2) by high-performance liquid chromatography. In healthy individuals, albumin circulates in the following proportions: HMA 70-80%, HNA-1 20-30% and HNA-2 2-5%. High flux (FX 100 [Fresenius Medical Care], BG 1.8 [Toray], Xevonta Hi 18 [B. Braun], CTA-2000 [Kawasumi]) and low flux FX10 [Fresenius Medical Care] dialyzers were used.

RESULTS

58 patients (59% male, median age 68 years, median time on haemodialysis 32 month) were included in the study. Before haemodialysis treatment, HMA (median 55.9%, IQR 50.1-61.2%) was substantially lower than in healthy individuals. Accordingly, oxidized albumin fractions were above the level of healthy individuals (median HNA-1 38.5%, IQR 33.3-43.2%; median HNA-2 5.8%, IQR 5.1-6.7%). Before haemodialysis treatment HMA was significantly higher in patients usually treated with high flux membranes (p < 0.01). After haemodialysis treatment there was a significant increase of HMA and a decrease of HNA-1 and HNA-2 (p < 0.01). These effects were more pronounced in patients treated with high flux dialyzers (p < 0.01). There were no differences of ARS alteration with regard to the dialyzer´s sterilization mode or the presence of diabetes.

CONCLUSION

The study confirms that the ARS is positively altered by haemodialysis and shows for the first time that this effect depends on dialyzer properties.

Effect of Diet and Supplementation on Serum Vitamin C Concentration and Antioxidant Activity in Dialysis Patients

Loss of vitamin C, especially in conjunction with an inadequate supply, can lead to decreased plasma concentrations of vitamin C. This in turn can lead to overt or subclinical deficiency. The present study aimed to evaluate the effects of diet and supplementation on vitamin C concentrations and serum antioxidant activity (FRAP) in hemodialysis (HD) patients. Sixty-eight HD patients participated in the study. In all of them, the diet was initially determined, and they were divided into five groups according to the diet and supplementation used. Group 1 received an unchanged diet, considered by them to be optimal; in group 2, the standard diet used in HD patients was introduced; in group 3, a standard diet enriched with natural antioxidants was employed; in group 4, a standard diet as in group 2 was used, but enriched with supplements (vitamin C, vitamin E, Se, and Zn). In contrast, group 5 consisted of HD patients with coexisting diabetes. Vitamin C serum levels were determined by high-performance liquid chromatography HPLC and antioxidant activity by The Ferric Reducing Ability of Plasma FRAP. The study shows that a well-chosen diet can slow the build-up of malnutrition and increase antioxidant activity as measured by the FRAP method in the blood of hemodialysis patients. Vitamin C supplementation can improve antioxidant status in hemodialysis patients. * The results presented in this paper complement our study, which assessed the effect of diet on the activity of erythrocyte antioxidant enzymes: Catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px), but also on the concentrations of non-enzymatic antioxidants (tocopherols, carotenoids, and vitamin C) in hemodialysis patients. In the study, plasma malondialdehyde (MDA) concentrations were assessed as an indicator of oxidative damage.

Prooxidant-antioxidant balance, hsTnI and hsCRP: mortality prediction in haemodialysis patients, two-year follow-up

Oxidative stress and inflammation are highly intertwined pathophysiological processes. We analyzed the markers of these processes and high-sensitive troponin I (hsTnI) for mortality prediction in patients on haemodialysis. This study enrolled a total of 62 patients on regular haemodialysis. The patients were monitored for two years, and the observed outcomes were all-cause and cardiovascular mortality. Blood samples were taken before one dialysis session for analysis of the baseline concentrations of prooxidant–antioxidant balance (PAB), total antioxidant status (TAS), total oxidative status (TOS), hsTnI, hsCRP and resistin. The overall all-cause mortality was 37.1% and CVD mortality 16.1%. By univariate and multivariate logistic regression, our findings suggest that good predictors of all-cause mortality include hsCRP and PAB (p < .05) and of CVD mortality hsCRP (p < .05) and hsTnI (p < .001). To evaluate the relationship between the combined parameter measurements and all-cause/CVD mortality risk, patients were divided into three groups according to their PAB, hsCRP and hsTnI concentrations. The cutoffs for hsCRP and hsTnI and the median for PAB were used. Kaplan–Meier survival curves pointed out that the highest mortality risk of all-cause mortality was in the group with hsCRP levels above the cutoff and PAB levels above the median (p < .001). The highest risk of CVD mortality was found in the group with hsCRP and hsTnI levels above the cutoff levels (p = .001). Our data suggest that hsCRP and PAB are very good predictors of all-cause mortality. For CVD complications and mortality prediction in HD patients, the most sensitive parameters appear to be hsTnI and hsCRP.

Rapamycin alleviates oxidative stress-induced damage in rat erythrocytes

An imbalanced cellular redox system promotes the production of reactive oxygen species (ROS) that may lead to oxidative stress-mediated cell death. Erythrocytes are the best-studied model of antioxidant defense mechanism. The present study was undertaken to investigate the effect of the immunosuppressant drug rapamycin, an inducer of autophagy, on redox balance of erythrocytes and blood plasma of oxidatively challenged rats. Male Wistar rats were oxidatively challenged with HgCl2 (5 mg/kg body mass (b.m.)). A significant (p < 0.05) induction in ROS production, plasma membrane redox system (PMRS), intracellular Ca2+ influx, lipid peroxidation (LPO), osmotic fragility, plasma protein carbonyl (PCO) content, and plasma advanced oxidation protein products (AOPP) and simultaneously significant reduction in glutathione (GSH) level and ferric reducing ability of plasma (FRAP) were observed in rats exposed to HgCl2. Furthermore, rapamycin (0.5 mg/kg b.m.) provided significant protection against HgCl2-induced alterations in rat erythrocytes and plasma by reducing ROS production, PMRS activity, intracellular Ca2+ influx, LPO, osmotic fragility, PCO content, and AOPP and also restored the level of antioxidant GSH and FRAP. Our observations provide evidence that rapamycin improves redox status and attenuates oxidative stress in oxidatively challenged rats. Our data also demonstrate that rapamycin is a comparatively safe immunosuppressant drug.

Proteomic Investigations into Hemodialysis Therapy

The retention of a number of solutes that may cause adverse biochemical/biological effects, called uremic toxins, characterizes uremic syndrome. Uremia therapy is based on renal replacement therapy, hemodialysis being the most commonly used modality. The membrane contained in the hemodialyzer represents the ultimate determinant of the success and quality of hemodialysis therapy. Membrane's performance can be evaluated in terms of removal efficiency for unwanted solutes and excess fluid, and minimization of negative interactions between the membrane material and blood components that define the membrane's bio(in)compatibility. Given the high concentration of plasma proteins and the complexity of structural functional relationships of this class of molecules, the performance of a membrane is highly influenced by its interaction with the plasma protein repertoire. Proteomic investigations have been increasingly applied to describe the protein uremic milieu, to compare the blood purification efficiency of different dialyzer membranes or different extracorporeal techniques, and to evaluate the adsorption of plasma proteins onto hemodialysis membranes. In this article, we aim to highlight investigations in the hemodialysis setting making use of recent developments in proteomic technologies. Examples are presented of why proteomics may be helpful to nephrology and may possibly affect future directions in renal research.

Plasma protein thiolation index (PTI) as a biomarker of thiol-specific oxidative stress in haemodialyzed patients

The role of oxidative stress in patients with end stage renal disease (ESRD), which occurs at significantly higher levels than in the general population, is often underestimated in clinical practice. Emerging evidence highlights the strong correlation of oxidative stress with chronic inflammation and cardiovascular disease, which are highly prevalent in most patients on maintenance haemodialysis (HD) and are a major risk factor for mortality in this population. In this study, total plasma thiols and plasma S-thiolated proteins were measured in patients with ESRD, before and after a regular HD session, and compared to age-matched healthy subjects. We found a significant decrease in the level of total plasma thiols and, conversely, a significant increase in the level of S-thiolated proteins in these patients. In most patients, post-HD plasma level of total thiols did not differ from the one in healthy subjects, whereas plasma level of S-thiolated proteins was lower in HD patients than in age-matched healthy controls. This suggests that a single HD session restores plasma thiol redox status and re-establishes the antioxidant capacity of plasma thiols. Additionally, we determined protein thiolation index (PTI), i.e., the molar ratio between the sum of all low molecular mass thiols bound to S-thiolated plasma proteins and protein free cysteinyl residues. Patients with ESRD had a significantly higher PTI compared to age-matched healthy subjects and HD was associated with a decrease in PTI to normal, or lower than normal, levels. Although this study is limited in size, our results suggest that PTI is a useful indicator of thiol-specific oxidative stress in patients with ESRD on maintenance HD. This study also emphasizes that PTI determination is a cheap and simple tool suitable for large-scale clinical studies that could be used for routine screening of thiol-specific oxidative stress.

Effects of uremic solutes on reactive oxygen species in vitro model systems as a possibility of support the renal function management

BACKGROUND

In view of the prevalence of oxidative stress in chronic kidney disease (CKD) patients, the loss of low-molecular-weight biomolecules by hemodialysis and the antioxidant potential of some uremic solutes that accumulate in CKD, we used in vitro model systems to test the antioxidant potential of the following uremic solutes: uric acid, hippuric acid, p-cresol, phenol, methylguanidine, L-arginine, L-tyrosine, creatinine and urea.

METHODS

The in vitro antioxidant efficiencies of the uremic solutes, isolated or in mixtures, were tested with the following assays: i) ABTS radical cation decolorization assay; ii) hypochlorous acid (HOCl/OCl(-)) scavenging activity; iii) superoxide anion radical (O2(•-)) scavenging activity; iv) crocin bleaching assay (capture of peroxyl radical, ROO(•)); v) hydrogen peroxide (H2O2) scavenging activity.

RESULTS

Four of the tested uremic solutes (p-cresol, phenol, L-tyrosine, uric acid) were effective antioxidants and their IC50 were found in three model systems: ABTS(•+), HOCl/OCl(-) and crocin bleaching assay. In the 4-solutes mixtures, each one of the solute captured 12.5% for the IC50 of the mixture to ABTS(•+) or HOCl/OCl(-), exhibiting a virtually exact additive effect. In the 2-solutes mixtures, for ROO(•) capture, it was observed the need of more mass of uremic solutes to reach an IC50 value that was higher than the projected IC50, obtained from the IC50 of single solutes (25% of each, in the binary mixtures) in the same assay. In model systems for O2(•-) and H2O2, none of the uremic solutes showed scavenging activity.

CONCLUSIONS

The use of the IC50 as an analytical tool to prepare and analyze mixtures allows the determination of their scavenging capacities and may be useful for the assessment of the antioxidant status of biological samples under conditions of altered levels of the endogenous antioxidant network and/or in the employment and monitoring of exogenous antioxidant therapy.

A central role for intermolecular dityrosine cross-linking of fibrinogen in high molecular weight advanced oxidation protein product (AOPP) formation

BACKGROUND

Advanced oxidation protein products (AOPPs) are dityrosine cross-linked and carbonyl-containing protein products formed by the reaction of plasma proteins with chlorinated oxidants, such as hypochlorous acid (HOCl). Most studies consider human serum albumin (HSA) as the main protein responsible for AOPP formation, although the molecular composition of AOPPs has not yet been elucidated. Here, we investigated the relative contribution of HSA and fibrinogen to generation of AOPPs.

METHODS

AOPP formation was explored by SDS-PAGE, under both reducing and non-reducing conditions, as well as by analytical gel filtration HPLC coupled to fluorescence detection to determine dityrosine and pentosidine formation.

RESULTS

Following exposure to different concentrations of HOCl, HSA resulted to be carbonylated but did not form dityrosine cross-linked high molecular weight aggregates. Differently, incubation of fibrinogen or HSA/fibrinogen mixtures with HOCl at concentrations higher than 150 μM induced the formation of pentosidine and high molecular weight (HMW)-AOPPs (>200 k Da), resulting from intermolecular dityrosine cross-linking. Dityrosine fluorescence increased in parallel with increasing HMW-AOPP formation and increasing fibrinogen concentration in HSA/fibrinogen mixtures exposed to HOCl. This conclusion is corroborated by experiments where dityrosine fluorescence was measured in HOCl-treated human plasma samples containing physiological or supra-physiological fibrinogen concentrations or selectively depleted of fibrinogen, which highlighted that fibrinogen is responsible for the highest fluorescence from dityrosine.

CONCLUSIONS

A central role for intermolecular dityrosine cross-linking of fibrinogen in HMW-AOPP formation is shown.

GENERAL SIGNIFICANCE

These results highlight that oxidized fibrinogen, instead of HSA, is the key protein for intermolecular dityrosine formation in human plasma.

Asymmetric dimethylarginine: a novel cardiovascular risk factor in end-stage renal disease

OBJECTIVE

This cross-sectional study explored the association between carotid intima-media thickness (CIMT) and the oxidative stress markers asymmetric dimethylarginine (ADMA) and homo cysteine in patients with end-stage renal disease who were on haemodialysis.

METHODS

A total of 30 patients undergoing chronic haemodialysis treatment were recruited to this study. Homocysteine and ADMA levels were determined using a fluorescence polarization immunoassay and an enzyme-linked immunosorbent assay, respectively. CIMT was measured as a marker of atherosclerosis using high-resolution ultrasonography and was performed after haemodialysis.

RESULTS

Significant positive correlations were found between CIMT and ADMA, and CIMT and duration of haemodialysis. Linear regression analysis showed that ADMA level and age were significant independent determinants of CIMT, whereas homo cysteine was not.

CONCLUSIONS

The relationship demonstrated between plasma ADMA and carotid artery thickening suggests that ADMA may be a novel marker of atherosclerosis in patients on haemodialysis.

Oxidative Stress Markers in Hemodialysis and Peritoneal Dialysis Patients, Including Coenzyme Q10 and Ischemia-Modified Albumin

Objectives

Oxidative stress results from an imbalance between the production of free radicals and antioxidant activity. There is wide agreement that patients undergoing regular dialysis treatment experience increased oxidative stress. The aim of this study was to investigate serum total antioxidant status (TAS), total oxidant status (TOS), ischemia-modified albumin (IMA), and coenzyme Q10 (CoQ10) levels in hemodialysis (HD) and continuous ambulatory peritoneal dialysis (CAPD) patients, compared with controls.

Methods

This study was performed on 41 (21 men, 20 women) CAPD patients, 38 (20 men,18 women) HD patients, and 43 (23 men, 20 women) healthy control subjects. CoQ10 levels were standardized using blood lipids.

Results

Serum TAS levels and CoQ10/total cholesterol values of the HD and CAPD patients were significantly lower, whereas serum IMA and TOS levels were significantly higher, than those of controls. Furthermore, CoQ10/LDL, CoQ10/triglycerides, and CoQ10/total cholesterol + triglycerides values of the CAPD patients were significantly lower than those of controls. No differences were found between serum IMA, TAS, TOS, CoQ10 levels, and adjusted CoQ10 values of the CAPD and HD patients.

Conclusions

Our results suggest that oxidative stress is increased in HD and CAPD patients compared with controls, as proven by decreased TAS and adjusted CoQ10 levels and increased TOS and IMA levels. Therefore, an antioxidant supplementation to these patients may be suggested.

Adsorption and carbonylation of plasma proteins by dialyser membrane material: in vitro and in vivo proteomics investigations

BACKGROUND

Protein carbonylation is an irreversible and not reparable reaction which is caused by the introduction into proteins of carbonyl derivatives such as ketones and aldehydes, generated from direct oxidation processes or from secondary protein reaction with reactive carbonyl compounds. Several studies have demonstrated significantly increased levels of reactive carbonyl compounds, a general increase in plasma protein carbonyls and carbonyl formation on major plasma proteins in blood from uremic patients, particularly those undergoing chronic haemodialysis.

MATERIALS AND METHODS

In the present preliminary study, we first assessed by an in vitro filtration apparatus the possible effects of different materials used for haemodialysis membranes on protein retention and carbonylation. We employed hollow fiber minidialyzers of identical structural characteristics composed of either polymethylmethacrylate, ethylenevinyl alcohol, or cellulose diacetate materials. Protein Western Blot and SDS-PAGE coupled to mass spectrometry analysis were applied to highlight the carbonylated protein-binding characteristics of the different materials. We also investigated in vivo protein carbonylation and carboxy methyl lisine-modification in plasma obtained before and after a haemodialysis session.

RESULTS

Our data underline a different capability on protein adsorption associated with the different properties of the filter materials, highlighting the central buffering and protective role of serum albumin. In particular, polymethylmethacrylate and cellulose diacetate showed, in vitro, the highest capacity of binding plasma proteins on the surface of the hollow fiber minidialyzers.

CONCLUSIONS

The present study suggests that biomaterials used for fabrication of haemodialysis membrane may affect the carbonyl balance in chronic uremic patients.

Acute effects of hemodialysis on oxidative stress parameters in chronic uremic patients: comparison of two dialysis membranes

Uremic state and hemobioincompatibility are implicated in subclinical inflammation and oxidative stress and progression of atherosclerosis in the hemodialysis (HD) population. To what extent different dialysis membranes contribute to oxidative stress induced by a dialysis procedure per se is still a subject of debate. Fifteen HD patients and 15 healthy controls were enrolled in this study. Patients received two index HD sessions with a cuprophane and polysulfone membrane two weeks apart. Blood samples were collected at baseline and then before and after HD sessions. We determined serum thiobarbituric acid, protein carbonyl, and serum nitrite/nitrate levels as markers of oxidative damage. We also measured erythrocyte glutathione level, catalase, superoxide dismutase and glutathione peroxidase activity, and serum vitamin C and E levels as antioxidant markers. At baseline, HD patients, in comparison with normal controls, had a trend towards increased oxidant state and depletion of antioxidants. Cuprophane dialysis induced a higher increase in production of oxidants, along with a lower compensatory increase of antioxidants when compared with polysulfone dialysis. In conclusion, a single HD session, even when conducted with a biocompatible membrane, appears to play an important role in the imbalance between ROS production and antioxidant defense, but to a milder extent than cuprophane dialysis.

The effect of hemodialysis on accelerated atherosclerosis in diabetic patients: correlation of carotid artery intima-media thickness with oxidative stress

OBJECTIVE

Both diabetes and hemodialysis (HD) are associated with increased oxidative stress. The aim of this study was to clarify the effect of maintenance HD on oxidative stress parameters in diabetic patients and to explore any relation between carotid artery intima-media thickness (CIMT) and oxidative stress markers.

METHODS

Twenty Type 2 diabetic patients undergoing chronic maintenance HD, 20 type 2 diabetic patients with normal renal function, and 20 age- and sex-matched healthy subjects were included. Serum thiobarbituric acid reactive substances (TBARS), protein carbonyl content (PCO), and nitrite/nitrate levels were determined as oxidative stress markers. Serum vitamin E, plasma sulfhydryl (P-SH), erythrocyte glutathione (GSH) levels, and superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities were measured as antioxidants. CIMT was assessed by carotid artery ultrasonography.

RESULTS

Both diabetic patient groups had enhanced oxidative stress indicated by higher levels of TBARS, PCO, and nitrate/nitrite and lower activities of SOD, CAT, and GPx compared to controls. Diabetic patients undergoing HD had significantly higher CIMT (P=.001) and higher levels of nitrite/nitrate (P=.05), PCO (P=.03), and GSH (P=.04) but significantly lower levels of P-SH (P<.001), serum vitamin E (P=.04), SOD (P=.02), CAT (P=.001), and GPx (P=.006) compared to diabetic patients with normal renal functions. There were significant negative correlations between CIMT and SOD (r=-0.50, P<.001), CAT (r=-0.41, P=.003), and P-SH levels (r=-0.51, P<.001) and significant positive correlation between CIMT and nitrite/nitrate levels (r=0.41, P=.003) and TBARS (r=0.35, P=.02). Linear regression analysis showed TBARS was significantly and positively correlated with CIMT (P=.04), while SOD and P-SH were significantly and negatively correlated with CIMT (P=.05 and P=.02, respectively).

CONCLUSIONS

Hemodialysis exacerbates oxidative stress and disturbances in antioxidant enzymes in diabetic patients. Serum nitrite/nitrate and TBARS can be used as positive determinants, while erythrocyte SOD, CAT activities, and P-SH level can be used as negative determinants of atherosclerosis assessed by CIMT in diabetic patients.

Plasma-advanced oxidation protein products are potent high-density lipoprotein receptor antagonists in vivo

Advanced oxidation protein products (AOPPs) are carried by oxidized plasma proteins, especially albumin and accumulate in subjects with renal disease and coronary artery disease. AOPPs represent an excellent novel marker of oxidative stress and their roles in the development of cardiovascular disease might be of great importance. Here, we show that in vitro-generated AOPP-albumin binds with high affinity to the high-density lipoprotein (HDL) receptor scavenger receptor class B type I (SR-BI). Already an equimolar concentration of AOPP-albumin to HDL blocked HDL association to SR-BI and effectively inhibited SR-BI-mediated cholesterol ester (CE) uptake. Interestingly, albumin extensively modified by advanced glycation end products (AGE-albumin), which is an established SR-BI ligand known to accumulate in renal disease, only weakly interfered with HDL binding to SR-BI. Furthermore, AOPP-albumin administration increased the plasma half-life of [3H]CE-HDL in control mice 1.6-fold (P=0.01) and 8-fold (P=0.0003) in mice infected with adenoviral vectors encoding human SR-BI. Moreover, albumin isolated from hemodialysis patients, but not albumin isolated from healthy controls, markedly inhibited SR-BI-mediated HDL-CE transfer in vitro dependent on the AOPP content of albumin. These results indicate that AOPP-albumin effectively blocks SR-BI in vitro and in vivo. Thus, depressed plasma clearance of HDL-cholesterol may contribute to the abnormal composition of HDL and the high cardiovascular risk observed in patients with chronic renal failure.

Oxidative damage of albumin in advanced liver disease

Albumin has a number of biological functions and the serum albumin level is related to prognosis in advanced liver disease. Oxidative stress is believed to play an important role in the pathogenesis of liver failure. The aim of the present study was to characterize oxidative modification of albumin in patients with various degrees of liver failure and to investigate implications for its binding function. Patients with liver cirrhosis (n=10), acute-on-chronic liver failure (n=8) and healthy controls (n=15) were included in the study. Three fractions of albumin were separated by HPLC according to the redox state of cysteine-34 and detected by fluorescence as well as UV absorption. Carbonyl groups were measured as a marker of oxidative modification in plasma proteins and, by western blotting, on albumin. Progressive oxidative modification of albumin was found with increasing severity of liver failure indicated by an increased content of carbonyl groups and oxidation of cysteine-34. Fluorescence properties of albumin were altered by oxidation and, in patients with acute-on-chronic liver failure, by high plasma levels of bilirubin. This alteration of albumin fluorescence by bilirubin provides evidence for a preferred binding of bilirubin to the fully reduced form of albumin.

Single bouts of exercise affect albumin redox state and carbonyl groups on plasma protein of trained men in a workload-dependent manner

The purpose of this study was to investigate the effect of single bouts of exercise at three different intensities on the redox state of human serum albumin (HSA) and on carbonyl groups on protein (CP) concentrations in plasma. Trained men [n = 44, maximal oxygen consumption (Vo(2max)): 55 +/- 5 ml.kg(-1).min(-1), nonsmokers, 34 +/- 5 years of age] from a homogenous population, volunteers from a police special forces unit, were randomly assigned to perform on a cycle ergometer either at 70% (n = 14), 75% (n = 14), or 80% (n = 16) of Vo(2max) for 40 min. Blood was collected before exercise, immediately after the exercise test (IE), and 30 min after each test (30M) and 30 h after each test (30H). The reduced fraction of HSA, human mercaptalbumin (HMA), decreased at all three exercise intensities IE and 30M, returning to preexercise values by 30H (P < 0.05). HMA was primarily oxidized to its reversible fraction human nonmercaptalbumin 1 (HNA1). CP concentrations increased at 75% of Vo(2max) IE and 30M with a tendency (P < 0.1) and at 80% Vo(2max) IE and 30M significantly, returning to preexercise concentrations by 30H (P < 0.01). These results indicate that the HSA redox system in plasma is activated after a single bout of cycle ergometer exercise at 70% Vo(2max) and 40 min duration. The extent of the HSA modification increased with exercise intensity. Oxidative protein damage, as indicated by CP, was only significantly increased at 80% Vo(2max) intensity in this homogenous cohort of trained men.

Several indicators of oxidative stress, immunity, and illness improved in trained men consuming an encapsulated juice powder concentrate for 28 weeks

Phytonutrients from plant foods provide numerous antioxidants. We hypothesized that supplementation for 28 wk with a commercially available encapsulated juice powder concentrate (JPC) could influence indicators of oxidative stress, immunity, and illness. Trained men (n = 41; 34 +/- 5 y; maximum oxygen uptake = 55 +/- 7 mL x kg(-1) x min(-1)) from a homogenous police Special Forces unit were randomly assigned in a double blind manner to either JPC (n = 21) or placebo (n = 20). We used multiple 7-d food records to assess dietary intake and found inadequate mean daily fruit and vegetable consumption (3.2 +/- 1.2 servings). The group physician documented all duty days lost due to illness. We collected plasma at baseline and study wk 4, 8, 16, and 28 for analysis of carbonyl groups on protein (CP) and TNFalpha. Over the 28-wk investigation, CP was lower in the JPC group, with both a treatment and a time x treatment interaction (P < 0.05). Concentrations of both CP and TNFalpha at 16 and 28 wk were lower in the JPC than in the placebo group (P < 0.001). TNFalpha increased during the first 8 wk followed by a decrease in both groups for the following 20 wk (P < 0.001). Over the final 20 wk of the study, the placebo group tended to have more days of illness than the JPC group (P = 0.068). These data suggest beneficial JPC effects with regard to reduction of duty days lost due to illness and reduction of CP and TNFalpha concentrations in this group of trained men over 28 wk.

The impact of preoperative micronutrient supplementation in lung surgery. A prospective randomized trial of oral supplementation of combined alpha-ketoglutaric acid and 5-hydroxymethylfurfural

OBJECTIVE

Preoperative micronutrient supplementation in fast-track surgery programs have shown to reduce complications, shorten recovery, and thereby lower costs. In a prospective randomized study, the metabolic effects of a combination of alpha-ketoglutaric acid (alpha-KG) and 5-hydroxymethylfurfural (5-HMF) were evaluated concerning their impact on improvement of exercise capacity and reduction of oxidative stress in lung surgery.

METHODS

Thirty-two consecutive patients admitted for lung resection due to NSCLC were randomized to the study protocol. All patients received preoperative nutritional guidelines according to general recommendations. In 16 (study group), a supplementation of 7.2g alpha-KG and 720 mg 5-HMF/day (SANOPAL) was administered from days 1 to 10. Spiroergometric evaluation was carried out at baseline and day 10 after micronutrient supplementation. Blood samples for the determination of oxidative stress, i.e. carbonyl proteins (CPs) and isoprostanes (IPs) were taken on at baseline, in the operating room just before resection treatment, and 25 min after single lung ventilation (SLV).

RESULTS

Spiroergometric re-evaluation showed a significant increase of VO2max (p=0.0108) and Watt's (p=0.011) in favor of the study group. Determination of oxidative stress showed a significant reduction of CPs before (p=0.048) and after SLV (p=0.0001) for the study group compared to the control group. The same is true for IPs before (p=0.003) and after SLV (p=0.02). Hospitalization and intensive care unit (ICU) of the study group showed a significant reduction compared to the control group (p=0.03 and p=0.02, respectively).

CONCLUSIONS

Simple oral supplementation using a combination of alpha-KG and 5-HMF of preoperative micronutrition may therefore be one further step in a multimodality approach of fast-track surgery programs also in lung surgery.

Erythrocyte transmembrane electron transfer in haemodialysis patients

BACKGROUND AND AIMS

Patients with chronic renal failure, especially those treated with haemodialysis, have an increased risk of developing atherosclerotic vascular disease probably as a result of enhanced oxidative stress. The human cell membrane possesses electron transfer systems which protect against extracellular pro-oxidant challenge. We evaluated (1) the erythrocyte velocity of ferricyanide reduction (RBC vfcy) in 25 uraemic patients (aged 25-71 years; 14 males), (2) the changes induced by a single haemodialysis session and (3) biomarkers of oxidative stress.

METHODS AND RESULTS

Before and after a mid-week dialysis session, we measured RBC vfcy, erythrocyte glutathione (RBC GSH), plasma and red cell membrane malondialdehyde (P and RBC MDA), plasma sulphydryl groups (P SH), plasma vitamin C levels and haemolysis percentage. Pre-dialysis RBC GSH (0.68+/-0.13 vs 0.80+/-0.13 mg/mL, p<0.01), P SH (266+/-74 vs 406+/-78 micromol/L, p<0.01) and plasma vitamin C (7.0+/-5.1 vs 21.5+/-8.5mg/L, p<0.001) were lower than in 25 age-sex-matched healthy controls; P MDA (1.57+/-0.52 vs 0.54+/-0.29 nmol/mL, p<0.001), RBC MDA (0.42+/-0.13 vs 0.34+/-0.16 nmol/mL, p<0.05) and haemolysis (1.2+/-0.3 vs 0.7+/-0.3%, p<0.001) were increased. Baseline RBC vfcy did not differ from normals (13.1+/-5.2 vs 12.9+/-3.2 mmol/mL/h). Following dialysis, RBC vfcy (to 8.9+/-4.5 mmol/mL/h, p<0.001) decreased, as well as P MDA, RBC MDA and plasma vitamin C (to 2.5+/-1.4 mg/L, p<0.001), whereas P SH groups increased (to 413+/-99 micromol/L, p<0.001); haemolysis percentage remained high. RBC vfcy values were correlated to RBC GSH and vitamin C levels.

CONCLUSIONS

Uraemic patients showed signs of oxidative stress. Pre-dialysis RBC vfcy is maintained in the normal range on account of a reduced intracellular content of GSH and in spite of low plasma ascorbate. A single haemodialysis treatment reduced biomarkers of protein and lipid oxidation but markedly impaired transmembrane electron transfer, which could be explained by acute depletion of electron donors.

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.

Protein oxidation in Type 2 diabetic patients on hemodialysis

BACKGROUND

Oxidative stress is considered to be a unifying link between diabetes mellitus (DM) and its complications, including nephropathy. There have been many reports on increased production of oxidants and decreased level of antioxidants in diabetic patients. The dialysis procedure contributes to oxidative stress. An increase in oxidative stress may contribute to the development of oxidative protein damage in diabetic patients. Our aim was to reveal the effects of diabetes and hemodialysis (HD) on oxidative modifications of plasma proteins.

METHODS

We measured reactive carbonyl derivates (PCO), protein thiol (P-SH), and reduced glutathione (GSH) levels in Type 2 diabetic (DM) and diabetic hemodialysed patients (DHD) and in healthy control participants.

RESULTS

Protein carbonyl (PCO) content increased significantly in all patient groups relative to the controls. The dialysis procedure caused an additional increase in PCO levels in DHD patients before and after dialysis compared with the level in DM patients. There was a significant decrease in P-SH levels in DHD patients compared with the level in healthy participants and DM patients. There was no significant difference in the whole blood GSH levels between the DM patients and control participants. It was significantly higher in DHD patients in comparison to the DM patients.

CONCLUSIONS

We conclude that PCO level increases in DM patients, and this increase is more profound in DHD patients, indicating that both diabetes and dialysis contribute to increased protein oxidation. The low P-SH level in DHD patients, but not in DM patients, suggests that dialysis is responsible for this decrease. We propose plasma PCO derivate as a novel specific marker for oxidative protein damage.

Comparison of oxidative damage in Malaysian end-stage renal disease patients with or without non-insulin-dependent diabetes mellitus

BACKGROUND

Comparisons of oxidative indices and total antioxidant status between end-stage renal disease (ESRD) patients with or without diabetes is scant, especially in the Asian population.

METHOD

The assays were carried out according to known established protocols.

RESULT

The present study showed that ESRD patients with or without non-insulin-dependent diabetes mellitus (NIDDM) did not have any significant differences in antioxidant enzyme activities, advanced glycated end products (AGE), advanced oxidized protein products (AOPP) and ferric reducing ability of plasma (FRAP), indicating that hyperglycemia does not exacerbate oxidative damage in ESRD. The regulation of catalase and glutathione peroxidase is also altered in ESRD. Elevated FRAP was observed in both ESRD groups (with and without NIDDM). The dialysis process did not alter the antioxidant enzyme activities but decreased AGEs and FRAP and increased AOPP levels.

CONCLUSION

Oxidative stress is present in ESRD but this is not significantly exacerbated by hyperglycemia. The contribution of components in the pathology of renal failure towards oxidative stress exceeds that of hyperglycemia.

Analytical aspects of oxidatively modified substances in sports and exercises

Despite the health-promoting effects of physical activity, exercise enhances the formation of free radicals and other reactive species in animals and humans. Numerous techniques have been established to investigate the diverse modifications of biomolecules by oxidative stress. These analytical procedures include different methods, ranging from simple photometric assays to a combination of chromatographic methods with mass spectrometry. We summarize briefly those analytical techniques of oxidative damage to biomolecules that have been applied to the investigation of oxidative stress during exercise.