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.

Anemia, renal transplantation, and the anemia paradox

Anemia is prevalent in renal transplant recipients (RTRs), as it is in all chronic kidney disease (CKD) populations. Mild anemia occurs in up to 40% of RTRs, and more severe anemia (110 g/L) occurs in about 9% to 22% of patients. As in CKD, impaired graft (renal) function is a major predictor of anemia identified in nearly all studies, suggesting a major role for erythropoietin deficiency. Chronic inflammation, malnutrition, iron deficiency, and medications (angiotensin converting enzyme inhibitors, angiotensin receptor blockers, mycophenolate, azathioprine, and sirolimus) are contributory factors seen in some, but not all, studies. Although pathophysiologic and observational data strongly support a causal association between low hemoglobin levels and cardiovascular outcomes in RTRs, no randomized controlled trial to date has been able to show a clear benefit of anemia treatment on cardiovascular outcomes or mortality in either RTR or other CKD populations. This important paradox has led some investigators to question the causal nature of the association between anemia and heart disease. Resolution of this paradox, at least for patients with stage 2/3 CKD, will depend on the outcome of randomized controlled trials currently in progress. Similar trials sorely are needed in renal transplant populations. In the interim, current opinion favors treating persistent anemia in RTRs to achieve targets similar to those recommended for dialysis and CKD patients.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Effect of hemodialysis on the antioxidative properties of serum

In patients with chronic renal failure undergoing regular hemodialysis (HD), oxidative stress is involved in the development of dialysis-related pathologies. The aim of the study was to measure the effect of HD treatment on the general antioxidative status of serum with special consideration of the specific oxidizability of lipids and proteins. Indicators for the oxidative/antioxidative status of plasma were monitored at the beginning and at the end of a dialysis session on the arterial and venous side of the dialyzer. A decrease in the antioxidant status was accompanied by an increased oxidizability of proteins as well as lipids during HD treatment. During the first passage of the dialyzer, the lag time of lipid oxidation decreased from 114.0+/-19.8 to 81.5+/-18.9 min, the lag time of protein oxidation decreased from 105.0+/-24.6 to 72.9+/-21.3 min and the total antioxidative status decreased from 518+/-24 to 252+/-124 microM trolox equivalents. The carbonyl content of serum proteins was high in patients with end stage renal disease (ESRD) (3.9+/-1.1 vs. 0.9+/-0.1 nmol/mg in controls) but did not change significantly during dialysis procedure. Our data demonstrate that the susceptibility of serum lipids and proteins to oxidative modification is severely increased by HD treatment.

Uremia-related metabolic cardiac risk factors in chronic kidney disease

Growing evidence has been gathered over the last 15 years regarding the role of nontraditional or uremia-related risk factors in the pathogenesis of atherosclerosis in subjects with renal failure. Among those factors, dyslipidemia, inflammation, hyperhomocysteinemia, and oxidant stress have been extensively studied. However, the clinical significance of many of these factors remains controversial in light of reported studies. In this article, the existing evidence regarding the role of uremia-related risk factors in the pathogenesis of atherosclerosis is reviewed, with special emphasis on prevalence, cardiac risk, and management in patients with chronic kidney disease (CKD). Consensus treatment recommendations are provided for risk factors for which there is evidence to support preventive or therapeutic interventions.

Assessment of DNA strand breakage by the alkaline COMET assay in dialysis patients and the role of Vitamin E supplementation

Although the role of reactive oxygen species (ROS) in chronic renal failure (CRF) is not definitely demonstrated, a consistent number of observations has provided evidence for the presence of oxidative stress in uremic patients undergoing maintenance dialysis. In order to investigate this hypothesis further and to understand the role of antioxidant supplementation, peripheral blood lymphocytes were taken from 36 dialysis patients before and after Vitamin E supplementation in a dosage of 600 mg per day (2x300 mg) for 14 weeks and examined in the alkaline Comet assay for DNA strand breakage. The results were also compared with those of 36 controls with comparable age, sex, and smoking habits, and with no history of renal disease. The DNA breakage observed in the lymphocytes of patients before Vitamin E supplementation was significantly higher than in the controls (P<0.001) but a clear protective effect of Vitamin E supplementation were observed after 14 weeks of therapy.

Vitamin E-coated dialyzer reduces oxidative stress in hemodialysis patients

The high incidence of cardiovascular disease in hemodialyzed (HD) patients is well established and oxidative stress has been involved in this phenomenon. The aim of our study was to evaluate if a vitamin E-coated dialyzer could offer protection to HD patients against oxidative stress. Sixteen HD patients were successively assessed for one month (i) on a high biocompatible synthetic dialyzer (AN) and (ii) on a vitamin E-coated dialyzer (VE). Blood samples were taken before and after the dialysis session at the end of each treatment period. HD session conducted with the AN dialyzer was responsible for acute oxidative stress, significantly assessed after HD by a decreased plasma vitamin C level and an increased ascorbyl free radical (AFR)/vitamin C ratio used as an index of oxidative stress. Plasma elastase activity, reflecting neutrophil activation, was also increased; soluble P-selectin, reflecting platelet activation, did not show any variation. The use of the VE dialyzer was associated with a less extended oxidative stress compared with the AN membrane: basal vitamin C level was higher, and after the HD session AFR/vitamin C ratio and elastase activity were not significantly increased. Plasma vitamin E levels were not affected. Our study demonstrates that HD is associated with oxidative stress, which can be partially prevented by the use of a vitamin E-coated dialyzer. Our data suggest that this dialyzer may exert a site-specific scavenging effect on free radical species in synergy with a reduced activation of neutrophils.

Renal vascular changes in renal disease independent of hypertension

INTRODUCTION

Cardiovascular disease is common in patients with renal disease, but little is known about the effect of renal disease and loss of renal function on vascular morphology. Intima proliferation of small renal arteries, which correlates with atherosclerosis in the aorta, is sometimes present in renal disease and has been shown to increase with age and hypertension. We studied the effect of chronic renal disease and renal function, independent of hypertension, on intima proliferation.

METHODS

We retrospectively selected renal biopsies of subjects in whom a glomerular filtration rate (GFR) measurement with [(125)I] iothalamate had been performed. To separate the effects of renal disease and renal function, we selected biopsies from (A) normotensive controls undergoing nephrectomy because of renal carcinomas; (B) normotensive patients with renal disease and GFR > 90 ml/min; (C) normotensive patients with GFR 30-90 ml/min, and (D) hypertensive patients with a GFR < 90 ml/min. The area of the arteriolar lumen, intima, and media were measured.

RESULTS

No significant changes from control subjects were observed in group B. Intima proliferation was observed when renal function declined (intima/total vessel surface ratio was 0.262 +/- 0.071 in group C, 0.192 +/- 0.032 in group A, and 0.205 +/- 0.035 in group B, P < 0.05). The intima proliferation was aggravated in patients with renal insufficiency and hypertension (0.333 +/- 0.121, P < 0.05). Media surface area was not different between groups.

CONCLUSION

Renal disease with preserved GFR does not cause significant intima proliferation of small renal arteries. Loss of renal function is accompanied by intima proliferation, even in the absence of systemic hypertension.