Oxidative stress and haemodialysis: role of inflammation and duration of dialysis treatment

BACKGROUND

Oxidative stress has long been demonstrated in haemodialysis patients. However, the factors influencing their oxidative status have not been characterized extensively in these patients. Therefore, the present study was designed to investigate the influence of a large number of factors known to be associated with oxidative stress.

METHODS

In the present cross-sectional study, we determined the plasma levels of lipid and protein oxidation markers in 31 non-smoking haemodialysis patients and 18 non-smoking healthy subjects, together with various components of the antioxidant system at the plasma and erythrocyte level.

RESULTS

No influence of age, diabetes or iron overload on oxidative markers and plasma and erythrocyte antioxidant systems was detected in these haemodialysis patients. The lack of an association between iron overload and oxidative status may be related to the lower level of plasma ascorbate in haemodialysis patients, since ascorbate favours the generation of free iron from ferritin-bound iron. Interestingly, plasma C reactive protein (CRP) levels measured by highly sensitive CRP assay were correlated positively with plasma levels of thiobarbituric acid reactive substances (r=0.38, P<0.04) and negatively with plasma alpha-tocopherol levels (r=-0.46, P<0.01). Moreover, significant inverse correlations were observed between duration of dialysis treatment and plasma levels of alpha-tocopherol (r=-0.49, P<0.02) and ubiquinol (r=-0.40, P<0.05).

CONCLUSIONS

Our results suggest that inflammatory status and duration of dialysis treatment are the most important factors relating to oxidative stress in haemodialysis patients.

Critical evaluation of plasma and LDL oxidant-trapping potential in hemodialysis patients

BACKGROUND

We investigated whether the total peroxyl radical-trapping antioxidant potential (TRAP) assay, which has recently been proposed as a gauge of oxidative stress, could serve to evaluate plasma and low density lipoprotein (LDL) antioxidant state in hemodialysis (HD) patients.

METHODS

TRAP was determined by the lag time of the chemiluminescence reaction induced by azo-initiator-catalyzed linoleic acid peroxidation in the plasma and corresponding LDL preparations of 23 HD patients and 22 healthy subjects. Antioxidant systems, including glutathione peroxidase (GSH-Px), ascorbate, vitamin E, and uric acid, oxidative stress markers including malondialdehyde (MDA), carbonyls, and advanced oxidation protein products (AOPP), and lipids, including cholesterol and triglycerides, were also determined in the plasma.

RESULTS

Both plasma and LDL-TRAP were significantly increased in HD patients despite decreased GSH-Px and ascorbate and increased MDA, carbonyl, and AOPP plasma levels. Plasma TRAP values were closely related to both uric acid and AOPP levels, and LDL-TRAP values were related to triglycerides and AOPP levels. In vitro studies showed that: (a) plasma TRAP of control plasma increased regularly with supplementation of uric acid, although not reaching that of HD plasma with similar uric acid levels; (b) the addition of human serum albumin-AOPP also regularly increased control plasma TRAP, but was close to that of HD plasma with similar AOPP levels; and (c) LDL-TRAP was increased following LDL enrichment with triglycerides.

CONCLUSION

Our study demonstrates that TRAP is not a relevant parameter for evaluating plasma or LDL antioxidant capacity in HD patients, due to the high plasma levels of uric acid, triglycerides and AOPP, which by themselves do not exert efficient antioxidant activity in vivo, but in vitro are able to scavenge the peroxyl radicals involved in the TRAP assay.

Pharmacokinetics of oxiracetam in patients with renal impairment after a 800 mg single oral dose

The pharmacokinetics of oxiracetam in patients with renal impairment were investigated after administration of a 800 mg single oral dose of oxiracetam. The renal insufficiency was estimated on the basis of the creatinine clearance (CLcr) which ranged from 9 to 95 ml/min among the 20 patients. In plasma, the terminal elimination half-life (T1/2) ranged from 10.6 to 68.1 h, the highest T1/2 corresponding to the patients with a high degree of renal impairment. In urine, the amounts of oxiracetam excreted during the 48 h postdosing represented 8.3 to 82.6% of the dose. They were lower in patients with a high degree of renal impairment. The correlations between the total clearance of oxiracetam, the renal clearance, the terminal apparent elimination rate constant in plasma, and CLcr were estimated by linear regression analysis. The correlation coefficients were 0.916, 0.985 and 0.803 respectively. The apparent volume of distribution of the central compartment V(1) and the total volume of distribution at the steady-state V(SS) were not dependent on the degree of renal impairment. The mean values +/- SD were 25.9 +/- 13.0 litres and 48.3 +/- 21.5 litres respectively. Oxiracetam concentrations in plasma of patients were estimated for repeated administration of 800 mg of oxiracetam.(ABSTRACT TRUNCATED AT 250 WORDS)

[Destructive spondylarthropathy with amyloid deposits in 3 patients on chronic hemodialysis]

Destructive spondyloarthropathy is a recently described complication of chronic hemodialysis. Three patients presenting spondyloarthropathy with destructive discovertebral lesions of the cervical or lumbar sections of the spine underwent surgery due to neurologic complications: persistent radiculalgia (two cases), regressive tetraparesis (one case). Discal lesions were associated with dislocation of the posterior intervertebral articulations and slipping of vertebrae. These patients had been receiving chronic hemodialysis for more than ten years; two presented hyperparathyroidism and blood aluminum was markedly increased in all cases. Two patients had undergone surgery for bilateral carpal tunnel syndrome. Anatomopathological examination of surgical specimens demonstrated the presence of amyloid deposits in the intervertebral disc. This suggests that amyloidosis, which is frequently seen with carpal tunnel syndrome in patients receiving prolonged hemodialysis, also plays a role in the development of spondyloarthropathy.

Possible link between changes in plasma 24,25-dihydroxyvitamin D and healing of bone resorption in dialysis osteodystrophy

Histomorphometric studies of bone biopsies were performed on 12 hemodialyzed patients before and after six months of treatment with 25-(OH) and 1 alpha-(OH) vitamin D3. Patients could be classified into three groups according to bone resorption: Group I with normal bone resorption; Group II with elevated initial bone resorption unresponsive to vitamin D treatment; group III with elevated initial bone resorption sensitive to vitamin D treatment. None of the patients had histological signs of osteomalacia. In Group I, plasma concentrations of 24,25-(OH)2D and the ratio of 24,25-(OH)2D to 25-(OH) D remained in the normal range throughout the study; in Group II these parameters were subnormal initially and did not increase above normal except in one case; in Group III, plasma concentrations of 24,25-(OH)2D were high before or at the beginning of vitamin D administration and normal at the time of the second biopsy and wide variations were observed in the ratio of 24,25-(OH)2D to 25-(OH)D. No difference was found between these last two groups with regard to the cumulative dose of vitamin D derivatives administered or the changes in plasma PTH, CT, calcium and phosphate. These observations suggest a specific regulation of plasma 24,25-(OH)2D concentrations in hemodialyzed patients and a possible link (independent of circulating PTH, CT, or phosphate) between this regulation and healing of bone resorption. However, no correlation was found between plasma 24,25-(OH)2D and either one of the simultaneously measured biochemical or histological parameters.

[Primary hyperparathyroidism. Current aspects of its diagnosis apropos of a case with digestive and neuropsychiatric manifestations]

On the basis of a dramatic hypercalcemia revealed by digestive and neuropsychic symptoms and related to a primary hyperparathyroidism, the authors recall all the clinical circumstances which should lead to determination of plasma calcium as well as the clinical and biological particularities which, in front of a hypercalcemia, suggest a primary hyperparathyroidism. The stress the usefulness and the limits of the dosage of plasma immunoreactive parathyroid hormone as well as the difficulties to differentiale primary from paraneoplasic hyperparathyroidism. The recent pathophysiological concepts of malignant hypercalcemia reviewed.