Conjugated diene fatty acids in patients with chronic renal failure: evidence of increased lipid peroxidation?

Pathogenesis of Congenital Malformations: Possible Role of Oxidative Stress

OBJECTIVE

Congenital anomalies are important causes of morbidity and mortality in children. Oxidative stress (OS) is involved in the physiopathology of pregnancy-related congenital malformations. This review summarizes the role of OS in the pathogenesis of congenital malformations; in particular, its purpose is to describe how OS influences the development of heart congenital malformations, oesophageal atresia, biliary atresia, diaphragmatic hernia, and autosomal dominant polycystic kidney disease.

STUDY DESIGN

Systematic review of previous studies about the role of OS in pregnancy and its possible effects in developing of congenital malformations. One electronic database (PubMed) was searched and reference lists were checked.

RESULTS

An imbalance between the production of reactive oxygen species (ROS) and antioxidant defense can occur early in pregnancy and continue in the postnatal life, producing OS. It may destroy the signaling pathways needed for a correct embryogenesis leading to birth defects. In fact, cell functions, especially during embryogenesis, needs specific signaling pathways to regulate the development. These pathways are sensitive to both endogenous and exogenous factors; therefore, they can produce structural alterations of the developing fetus.

CONCLUSION

Because OS plays a significant role in pathogenesis of congenital malformations, studies should be developed in order to better define their OS mechanisms and the beneficial effects of supplemental therapeutic strategies.

KEY POINTS

· Oxidative stress is involved in the pathogenesis of congenital malformations.. · Heart malformations, oesophageal atresia, biliary atresia, diaphragmatic hernia, and autosomal dominant polycystic kidney are analyzed.. · A knowledge of pathomechanism of OS-related congenital malformations could be useful to prevent them..

Zinc mitigates renal ischemia-reperfusion injury in rats by modulating oxidative stress, endoplasmic reticulum stress, and autophagy

Oxidative stress is a major factor involved in the pathogenesis of renal ischemia/reperfusion (I/R). Exogenous zinc (Zn) was suggested as a potent antioxidant; however, the mechanism by which it strengthens the organ resistance against the effects of reactive oxygen species (ROS) is not yet investigated. The present study aims to determine whether acute zinc chloride (ZnCl₂ ) administration could attenuate endoplasmic reticulum (ER) stress, autophagy, and inflammation after renal I/R. Rats were subjected to either sham operation (Sham group, n = 6), or 1 hr of bilateral ischemia followed by 2 hr of reperfusion (I/R groups, n = 6), or they received ZnCl₂ orally 24 hr and 30 min before ischemia (ZnCl₂ group, n = 6). Rats were subjected to 1 hr of bilateral renal ischemia followed by 2 hr of reperfusion (I/R group, n = 6). Our results showed that ZnCl₂ enhances renal function and reduces cytolysis (p < 0,05). In addition, it increased significantly the activities of antioxidant enzymes (SOD, CAT, and GPX) and the level of GSH in comparison to I/R (p < 0,05). Interestingly, ZnCl₂ treatment resulted in significant decreased ER stress, as reflected by GRP78, ATF-6,p-eIF-2α, XPB-1, and CHOP downregulaion. Rats undergoing ZnCl₂ treatment demonstrated a low expression of autophagy parameters (Beclin-1 and LAMP-2), which was correlated with low induction of apoptosis (caspase-9, caspase-3, and p-JNK), and reduction of inflammation (IL-1ß, IL-6, and MCP-1) (p < 0,05). In conclusion, we demonstrated the potential effect of Zn supplementation to modulate ER pathway and autophagic process after I/R.

Hemodiafiltration improves plasma 25-hepcidin levels: a prospective, randomized, blinded, cross-over study comparing hemodialysis and hemodiafiltration

Background/Aims

Data from studies comparing the effect of hemodiafiltration (HDF) and conventional hemodialysis (HD) on clinically important outcomes are insufficient to support superiority of HDF. None of these studies has been participant-blinded.

Methods

We performed a prospective, randomized, and patient-blinded cross-over study. Twenty patients on chronic HD received either HD for 2 months followed by post-dilution HDF for 2 months or in opposite order. A range of clinical parameters, as well as markers of inflammation, oxidative stress and iron metabolism was measured.

Results

The two treatments were similar with respect to dialysis-related complications, quality of life, and the biomarkers of oxidative stress and inflammation. Compared to HD, 25-hepcidin and β₂-microglobulin were 38 and 32%, respectively, lower after 60 days of HDF (p < 0.001 and p < 0.01, respectively). The consumption of ESA (erythropoietin-stimulating agent) and LMWH (low-molecular-weight heparin) was significantly higher with HDF.

Conclusion

In short term, HDF is not superior to HD regarding dialysis-related complications. The higher ESA consumption observed with HDF can be explained by blood clotting in tubing and dialyzers, as more anticoagulation was needed with post-dilution HDF. In a longer perspective, lowering serum hepcidin levels may improve pathological iron homeostasis.

Caffeic acid phenethyl ester suppresses oxidative stress in Escherichia coli-induced pyelonephritis in rats

Although oxidative damage is known to be involved in inflammatory-mediated tissue destruction, modulation of oxygen free radical production represents a new approach to the treatment of inflammatory diseases. Caffeic acid phenethyl ester (CAPE), an active component of propolis from honeybee hives, has antioxidant, anti-inflammatory and antibacterial properties. For that reason, we aimed to investigate the efficiency of CAPE administration in preventing oxidative damage in pyelonephritis (PYN) caused by Escherichia coli. In this study, 35 Wistar rats were grouped as follows: control, PYN 24 h, PYN 48 h, PYN 72 h, CAPE 24 h, CAPE 48 h and CAPE 72 h. E. coli (1 x 10(9) c.f.u.) were inoculated into the rats in both PYN and CAPE groups via urethral catheterization. Ten microM/kg-body weight CAPE was injected to the rats in all CAPE groups 24 h before E. coli infection, and injections were repeated at 24-h intervals. Rats were sacrificed 24 h, 48 h and 72 h after infection in both PYN and CAPE groups. Malondialdehyde (MDA) and nitric oxide (NO) levels were significantly increased in kidneys of PYN groups. The activities of the antioxidant enzymes, catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and xanthine oxidase (XO) were also elevated by E. coli. However, CAPE administration reduced MDA and NO levels, as well as XO activity, although it increased SOD and GSH-Px activities. Histopathological examination showed that CAPE reduced the inflammation grade induced by E. coli. In conclusion, CAPE administrations decrease the oxidative damage occurring in PYN and therefore could be used for medical management of bacterial nephropathy.

Changes in Conjugated Linoleic Acid and Palmitoleic Acid Are Correlated to Retinol Levels in Chronic Renal Failure in Both Hemodialysis and Conservative Treatment Patients

An increase in conjugated linoleic acid (CLA), a natural fatty acid present in our diet, which possesses anticarcinogenic and antiatherogenic activities in experimental models, has been found in both the plasma and adipose tissue of end-stage chronic renal failure (ESCRF) patients. Increased levels of retinol have also been found in those patients, due to a reduced excretion of the retinol-binding protein. Since retinol is known to influence lipid metabolism, we evaluated whether changes in retinol, CLA, and other fatty acids are correlated in the plasma of CRF patients. We measured CLA, retinol, and unsaturated fatty acids in the plasma of the following groups: (A) 35 ESCRF patients; (B) 20 hemodialysis (HD) patients; (C) 20 healthy controls. Subjects with total cholesterol and/or triglycerides higher than 250 mg/dL were excluded. We found a significant increase in CLA, retinol, palmitoleic (16:1), and oleic (18:1) acids in ESCRF patients. In HD patients we found a similar pattern, however, CLA increase was not significant. No changes were observed in the other fatty acids measured. In the groups of ESCRF and HD patients, a positive correlation between the levels of plasma retinol and CLA, and between retinol and 16:1 was found. These correlations were not detected in controls. The abnormal levels of plasma retinol in CRF patients might partly explain the changes in CLA and 16:1. The influence of retinol levels on these fatty acids might be due to an induction of delta 9 desaturase. In fact, 16:1 is known to be produced, partly, by delta 9 desaturation of palmitic acid. Moreover, the formation of CLA from delta 9 desaturation of vaccenic acid-a trans-monounsaturated fatty acid present in our diet-has recently been demonstrated in humans. Nevertheless, our data do not represent direct evidence supporting an increased delta 9 desaturase activity in CRF patients. Another possible explanation might be a variation in the exogenous intake.

Lipid peroxidation and antioxidant enzymes in children with chronic renal failure

Increased lipid peroxidation (LP) has been observed in dialysis patients and in predialysis adults with advanced chronic renal failure (CRF). The aim of this study was to investigate whether predialysis CRF children have increased LP in plasma and red blood cells (RBC) and to evaluate the activity of the antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px)] in RBC. Concentrations of selenium (Se), copper (Cu), and zinc (Zn)-cofactors of these enzymes-were determined both in erythrocytes and in plasma. LP was monitored by plasma and erythrocyte malonyldialdehyde (MDA) and by plasma organic hydroperoxide (OHP) concentrations. Forty-six predialysis children, aged 5-18 years, divided into two groups according to their serum creatinine levels [group I ( n=14, mean serum creatinine 421.61+/-141.08 micromol/l), group II ( n=32, mean serum creatinine 174.94+/-45.50 micromol/l)] and 27 age-matched healthy subjects were enrolled in the study. Significantly higher concentrations of plasma and erythrocyte MDA and plasma OHP, significantly lower activities of GSH-Px and CAT, and significantly lower concentrations of erythrocyte Se, Cu, and Zn and plasma Se and Cu were found in both groups of renal patients compared with controls. The SOD activity was reduced in both groups of CRF children. In group I the activity of SOD and GSH-Px was significantly lower than in group II. In summary, there is increased LP in plasma and RBC in children with predialysis CRF, even those patients with moderate renal insufficiency. The activity of the enzymatic antioxidant defense system is reduced in the RBC of predialysis patients. The antioxidant capacity is related to the severity of renal failure.

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 stress in haemodialysis--intradialytic changes

Oxidative stress is likely to be involved in the development of complications due to haemodialysis. Though there is evidence for production of oxygen free radicals during haemodialysis, reports on net oxidative imbalance due to a single dialysis session are conflicting. Hence, a time-course analysis of changes in lipid peroxides (LPO) along with antioxidant enzymes and vitamins was carried out. Hourly changes in LPO and antioxidants were studied during a first-use cuprophan membrane and acetate dialysis in 20 patients on regular haemodialysis treatment. Data were corrected for haemoconcentration and standardised to measure the rate of change before statistical evaluation using analysis of variance for repeated measures. The results of the study showed a net oxidative stress due to a single dialysis session in the form of increased plasma and erythrocyte lipid peroxidation, decrease in plasma vitamin E, slight increase in plasma superoxide dismutase and erythrocyte glutathione peroxidase and no change in plasma glutathione peroxidase. erythrocyte superoxide dismutase and plasma vitamin A levels. The oxygen radical production was found to be maximum in the first hour of dialysis.

Caffeic acid phenethyl ester changes the indices of oxidative stress in serum of rats with renal ischaemia-reperfusion injury

Oxygen-derived free radicals have been implicated in the pathogenesis of renal injury after ischaemia-reperfusion. Caffeic acid phenethyl ester (CAPE), an active component of propolis extract, exhibits antioxidant properties. To investigate whether treatment with either CAPE or alpha-tocopherol modifies the levels of the endogenous indices of oxidant stress, we examined their effects on an in vivo model of renal ischaemia-reperfusion injury in rats. CAPE at 10 micromol kg(-1) or alpha-tocopherol at 10 mg kg(-1) was administered intraperitoneally before reperfusion. Acute administration of both CAPE and alpha-tocopherol altered the indices of oxidative stress differently in renal ischaemia-reperfusion injury.

Vitamin E, lipid profile, and peroxidation in hemodialysis patients

BACKGROUND

Hypertriglyceridemia, lipid peroxidation, and abnormalities of the plasma fatty acid (PUFA) profile may be important risk factors for the atherosclerotic cardiovascular disease in hemodialysis (HD) patients.

METHODS

We investigated how these factors are affected by vitamin E supplementation carried out by oral administration (clinical study 1) and dialysis with vitamin E-modified dialyzers (clinical study 2).

RESULTS

In the HD patients, conditions of relative vitamin E deficiency were observed [lowered vitamin E/triglyceride (TG) ratio] in the presence of high levels of thiobarbituric acid reactants (TBARs) and decreased levels of the polyunsaturated fraction of PUFAs paired with an increased amount of monounsaturated ones (MUFA). In both studies, vitamin E supplementation significantly increased the levels of vitamin E in the plasma without affecting TG levels and provided a partial correction of TBAR levels. Of note was the relative increase in the PUFA fraction, which gave solid proof of an anti(per)oxidant effect of vitamin E supplementation in HD patients. Vitamin E supplementation was also observed to increase plasma levels of reduced glutathione and NOx (NO2 + NO3).

CONCLUSION

The results suggest that vitamin E supplementation may be an effective accessory therapy to combat oxidative stress-lowering lipid peroxidation in HD patients.

Changes in conjugated linoleic acid and its metabolites in patients with chronic renal failure

BACKGROUND

Conjugated linoleic acid (CLA) is a mixture of isomers of linoleic acid with conjugated double bonds that constitutes the most abundant fatty acid with conjugated dienes (CDs) in humans. CLA, erroneously considered in the past as a product of lipoperoxidation, has a dietary origin and has shown to possess anticarcinogenic and anti-atherogenic activity, mainly in animal studies. CLA can be metabolized to conjugated linolenic acid (CD18:3) and to conjugated eicosatrienoic acid (CD20:3) and these metabolites may be implicated in CLA activity. Because of the presence of dyslipidemia and the high incidence of cardiovascular and neoplastic diseases in uremic patients, we evaluated CLA and its metabolites in these patients in order to evaluate their metabolism and site distribution.

METHODS

We measured CLA, CD18:3, CD20:3, CD fatty acid hydroperoxides (lipoperoxidation products), and linoleic acid in the plasma, adipose tissue, and red blood cell (RBC) membranes by using high-pressure liquid chromatography in the following groups: (1) 23 chronic renal failure (CRF) patients with creatine clearance (CCr)> 10 mL/min (26.2 +/- 16.7); (2) 21 end-stage CRF patients in conservative treatment with CCr <10 mL/min (6.8 +/- 1.8); (3) 30 hemodialysis (HD) patients; and (4) 30 healthy controls.

RESULTS

The incorporation of CLA, CD18:3, and CD20:3 in RBC membranes was significantly reduced in group 1 and was even more reduced in groups 2 and 3. CLA significantly increased both in the plasma and adipose tissue of end-stage CRF patients only. CD18:3 and CD20:3 did not change in the plasma and adipose tissue of any group. No significant changes in linoleic acid and CD fatty acid hydroperoxides were found.

CONCLUSIONS

The alterations of CD in CRF patients are not due to lipoperoxidation. The increased levels of CLA in plasma and adipose tissue of end-stage CRF patients may be due either to a reduced metabolization of CLA to CD18:3 and CD20:3, or to an altered site distribution with reduced incorporation in cellular membranes and accumulation in the plasma and adipose tissue. The clinical significance of these changes remains to be investigated.

Increased intracellular reactive oxygen species in patients with end-stage renal failure: effect of hemodialysis

BACKGROUND

Reactive oxygen species (ROS) have been implicated in various forms of cellular injury. ROS may cause cell damage and are involved in the pathophysiology of several diseases, including atherosclerosis and chronic inflammation.

METHODS

Disturbances of intracellular ROS levels were investigated in 28 patients with end-stage renal failure. The intracellular ROS levels were measured in lymphocytes before and after hemodialysis using biocompatible membranes and were compared with those from 11 patients with end-stage renal failure, not yet on renal replacement therapy, and 27 healthy control subjects. ROS levels were measured spectrophotometrically using the intracellular dye dichlorofluorescin diacetate.

RESULTS

The spontaneous production of ROS was significantly higher in lymphocytes from patients with end-stage renal failure compared with healthy control subjects (P < 0.01). The addition of 100 nmol/L phorbol-myristate-acetate (PMA) produced a significant increase of ROS, both in lymphocytes from patients with end-stage renal failure and healthy control subjects. The PMA-induced ROS increase was significantly higher in lymphocytes from patients with end-stage renal failure compared with healthy control subjects (P < 0.01). In patients with end-stage renal failure, not yet on renal replacement therapy, the PMA-induced ROS was also significantly higher compared with healthy control subjects. The PMA-induced ROS increases were significantly inhibited by catalase, but not by superoxide dismutase or the superoxide dismutase mimetic, tempol. PMA-induced ROS was significantly reduced by tyrphostin A51 in lymphocytes from patients with end-stage renal failure and from healthy control subjects (each P < 0.01), indicating the involvement of a tyrosine kinase-dependent pathway. In patients with end-stage renal failure, the spontaneous and the PMA-induced production of ROS was not significantly different before and after hemodialysis.

CONCLUSIONS

Regular hemodialysis sessions using biocompatible membranes have no effect on the elevated intracellular ROS in patients with end-stage renal failure.

Peroxidação lipídica em pacientes com insuficiência renal crônica

Trabalhos demonstram desequilíbrio entre atividade oxidante/antioxidante e um aumento nos níveis de radicais livres em pacientes com insuficiência renal crônica. Várias pesquisas mostram uma maior peroxidação lipídica em eritrócitos e outras células do sangue com implicações importantes na morbidade destes pacientes, principalmente por doenças cardiovasculares. Os níveis de antioxidantes enzimáticos como a glutationa peroxidase, superóxido dismutase e catalase estão reduzidos, bem como os dos elementos traço (Selênio, Zinco). A diminuição das defesas antioxidantes permite o aumento da formação de espécies reativas de oxigênio, o que caracteriza a condição de estresse oxidativo. Em decorrência disto, ocorrem lesões oxidativas que podem alterar a fluidez da membrana dos eritrócitos, contribuindo para a hemólise e piora da anemia, além de causar a oxidação das lipoproteínas de baixa densidade do colesterol, a qual tem um papel importante na patogênese da aterosclerose, que ocorre freqüentemente nos pacientes com insuficiência renal crônica. O objetivo deste trabalho é discutir a relação da peroxidação lipídica e da diminuição das defesas antioxidantes do organismo como fatores importantes na patogênese da insuficiência renal crônica e suas complicações.

Higher levels of antioxidant defenses in enalapril-treated versus non-enalapril-treated hemodialysis patients

We previously reported chronic treatment with angiotensin-converting enzyme inhibitors (ACEis) increases antioxidant defenses in mice. In the present study, however, we examined various antioxidant defenses in chronic hemodialysis (HD) patients either treated with enalapril (10 mg/d) for at least 6 months (+ACEi; n = 11) or untreated (-ACEi; n = 11). The relationship between antioxidant status and HD was investigated by determining oxidative stress markers and antioxidant defenses in a group of chronic HD patients (n = 33) and a group of age-matched controls (n = 29). The effect of a single HD session on those parameters was also evaluated. Before an HD session (pre-HD), HD patients had significantly lower levels of red blood cell (RBC) glutathione (GSH), selenium-dependent glutathione peroxidase activity (RBC-Se-GPx), plasma ubiquinol-10, and alpha-tocopherol than controls. In a randomly selected group of patients (n = 19), a single HD session caused an additional decrease in RBC-GSH and plasma ubiquinol-10 levels. Plasma thiobarbituric acid reactive substance (TBARS) levels were significantly greater in pre-HD patients than controls. Post-HD plasma TBARS levels were similar to control values. The cohort of +ACEi HD patients had greater pre-HD RBC-GSH content, RBC-Se-GPx activity, and plasma beta-carotene concentrations than -ACEi patients (RBC-GSH: +ACEi, 3.1 +/- 0.9 micromol/mL packed RBCs [PRBCs]; -ACEi, 1.2 +/- 0.3 micromol/mL PRBCs [P < 0.05 v +ACEi]; RBC-Se-GPx: +ACEi, 5.8 +/- 0.7 U/mL PRBCs; -ACEi, 4.3 +/- 0.2 U/mL PRBCs [P < 0.05 v +ACEi]; plasma beta-carotene: +ACEi, 0.54 +/- 0.16 micromol/L plasma; -ACEi, 0.19 +/- 0.05 micromol/L plasma [P < 0.05 v +ACEi]). Results show profound alterations in the circulating antioxidant systems of chronic HD patients and that additional oxidative stress occurs during the HD procedure. In addition, in +ACEi HD patients, the levels of several antioxidant defenses are greater than in those in -ACEi HD patients.

Nitric oxide production is reduced in patients with chronic renal failure

In patients with chronic renal failure (CRF), atherosclerosis is a major cause of cardiovascular morbidity and mortality. Generally, atherosclerosis has been associated with a reduced bioavailability of nitric oxide (NO). Experimental studies have indicated the presence of enhanced NO degradation by reactive oxygen species as well as decreased NO production as possible causes for this reduced NO bioavailability. So far, the question whether or not NO production is impaired in patients with CRF has never been investigated. Therefore, we measured whole body NO production in 7 patients with CRF, and in 7 matched healthy subjects. To assess the relative importance of a dysfunction of NO synthase (NOS), we compared the NO production of these patients to that of 2 other groups known to have endothelial dysfunction, ie, 7 patients with familial hypercholesterolemia (FH) who did not yet have signs of clinical cardiovascular disease (all nonsmokers), and 5 cigarette smokers. These groups were also compared with 7 nonsmoking, age-matched healthy subjects. Whole body NO production, determined as in vivo arginine-to-citrulline conversion, was assessed by giving an intravenous infusion of [15N2]-arginine as a substrate for NOS and measuring isotopic plasma enrichment of [15N]-citrulline by LC-MS. NO production in the CRF patients (0.13+/-0.02 micromol. kg-1. h-1) was significantly lower (P<0.05) than in the corresponding control group (0.23+/-0.09 micromol. kg-1. h-1). NO production also tended to be lower in the FH patients (0.16+/-0.04 micromol. kg-1. h-1), but the difference with the corresponding control group did not reach significance (0.22+/-0.06 micromol. kg-1. h-1). In the group of smokers, NO production was similar to that in nonsmokers (0. 22+/-0.09 micromol. kg-1. h-1). In conclusion, it is demonstrated for the first time that basal whole body NO production is reduced in patients with CRF. This finding implies that therapeutic interventions to endothelial dysfunction in these patients should be primarily directed toward improvement of NO production. The finding of only a tendency toward reduction of NO production in patients with FH and the absence of a reduction in cigarette smokers suggests that other mechanisms such as enhanced NO degradation may be involved in the decrease of NO bioavailability in these groups.

Antioxidant effects of a supplemented very low protein diet in chronic renal failure

Increased peroxidation of lipids in red blood cells (RBC) in patients with advanced chronic renal failure (CRF) reflects increased generation of reactive oxygen species (ROS), which may contribute to the metabolic damage induced by CRF and to its progression. We have evaluated parameters indicative of lipoperoxidation (LPO) of RBC at baseline in patients with CRF compared to controls, and the effects of a very low protein diet supplemented with amino and keto acids and vitamins A, C, E (VLPD) over a 6-month period. The presence of peroxidation damage in CRF patients before the administration VLPD was demonstrated by elevated levels of free malondialdehyde (MDA) (p < .0003) and decreased levels of polyunsaturated fatty acids (PUFA), particularly C20:4 (p < .001), C22:4 (p < .0001) and C22:5 (p < .0001) when compared to controls. Similarly, RBC vitamin E content was significantly decreased (p < .0001) while enzymatic activities were unalterated. VLPD reduced erythrocyte LPO as suggested by (a) decreased levels of free and total RBC MDA (p < .003 and p < .03, respectively), (b) increased levels of PUFA, particularly C22:4 and C22:5 (p < .003 and p < .03, respectively), and (c) increased levels of vitamins A and E (p < .001 and p < .04, respectively) as compared to prediet results. Antioxidant enzyme activities were not modified. These results suggest that VLPD has a protective role against LPO of erythrocytes in patients with CRF.

Protein oxidation in hemodialysis and kidney transplantation

Oxidative damage of plasma proteins determined with the markers carbonyl group (CG) content and thiobarbituric acid-reactive substances (TBARS) was studied in 13 hemodialyzed and eight kidney-transplanted patients. The level of CGs was 38% higher in hemodialysis (HD) patients (1.49 +/- 0.05 nmol/mg protein) than in the healthy subjects (1.08 +/- 0.03 nmol/mg protein); the TBARS level was also higher in HD patients than in the control group (2.64 +/- 0.15 v 1.81 +/- 0.09 nmol/mL, P < .001). These data confirm that in end-stage renal failure, an increased oxidative stress is present and is able to induce protein damage. After transplantation, the CG content in protein was reduced (1.34 +/- 0.08 nmol/mg protein), but it was not significantly different from the level in the HD group. The failure to return to the normal range suggests that an impaired redox status is maintained, resulting in a sustained elevation of CG. Conversely, the level of TBARS in transplanted patients (1.99 +/- 0.22 nmol/mL) was not significantly different from that in the control group (1.81 +/- 0.09), suggesting that lipoperoxidation may be inhibited. These results may be explained by the different turnover rates of the molecules and by the distinct origin of the two markers, resulting from the damage of proteins or lipids. Thus, lipoperoxidation would produce rapidly removable molecules, whereas protein oxidation damage would tend to accumulate. However, the significant correlation found between CGs and TBARS indicates that a common cause (oxidative stress) binds the two markers of damage.