Erythrocyte glutathione transferase: a potential new biomarker in chronic kidney diseases which correlates with plasma homocysteine.

The erythrocyte glutathione S-transferase (e-GST) is a member of a superfamily of inducible enzymes involved in cell detoxification that shows an increased expression in chronic kidney disease (CKD) patients. We propose a new automated analysis procedure for e-GST activity that has been validated in 72 CKD patients and 62 maintenance hemodialysis patients (MHD). Regression analysis was carried out to assess association between e-GST activity data, main clinical variables, and plasma homocysteine (Hcy), a modified sulfur amino acid known as potential risk factor for cardiovascular disease that is increased above normal levels in more than 90% of the uremic patients. An increased e-GST activity was confirmed in MHD patients (N=62; 10.2±0.4 U/gHb) compared with healthy subjects (N=80; 5.8±0.4 U/gHb), and as an original finding, a significant increase of e-GST activity was observed in pre-dialysis CKD patients with a positive correlation with disease severity weighted according to the four stages of "Kidney Disease Outcomes Quality Initiative" classification (7.4±0.5, 8±1, 9.5±0.6, 12±1 U/gHb, respectively). No correlation was found between e-GST activity and hemoglobin, transferrin, blood iron and the markers of systemic inflammation and renal function such as alpha-1 acid glycoprotein and high-sensitive C-Reactive Protein, beta-2 microglobulin and the index of malnutrition-inflammation PINI, while a significant correlation was observed for the first time between plasma Hcy and e-GST activity (r2=0.64, P<0.0001) in MHD patients. Hcy, however, was not identified as an inhibitor of e-GST enzyme. The results in this study suggest the potential for automated e-GST analysis as a valuable tool to further explore phase II-related uremic toxicity in CKD and MHD patients.

Vitamin E-related inhibition of monocyte 5-lipoxygenase and cardiovascular outcome in maintenance hemodialysis patients.

A daily supplement of vitamin E is recommended for the secondary prevention of cardiovascular events in end-stage renal disease patients on maintenance hemodialysis. Vitamin E has been entrusted with therapeutic properties against cardiovascular disease for more than 60 years. Several epidemiological studies and intervention trials have been performed with vitamin E, and some of them showed that it prevents atherosclerosis. For a long time, vitamin E was assumed to act by decreasing the oxidation of low-density lipoproteins, a key step in atherosclerosis initiation. However, at the cellular level vitamin E interferes with smooth muscle cell proliferation, platelet aggregation, monocyte adhesion, and oxidized low-density lipoproteins uptake and cytokine production, all reactions implied in the progression of atherosclerosis. Recent research points out that these effects may be not only the result of the antioxidant activity of vitamin E but also of its distinct molecular actions. These biological properties of vitamin E may allow to design better strategies for primary and secondary prevention of cardiovascular disease, with a potential exploitation of vitamin E supplements in primary and secondary prevention of major adverse cardiovascular events in all uremic patients. In this review, we also outline relevant patents on vitamin E and lipoxygenase inhibitors.

Chronic treatment with statins increases the availability of selenium in the antioxidant defence systems of hemodialysis patients.

PROJECT: Oxidative stress (OS) is enhanced in hemodialysis (HD) patients. Lipid peroxidation and oxidative damage to glycids, proteins and nucleic acids are the main consequences of OS and are associated with increased cardiovascular risk. Vitamin E and glutathione peroxidase (GSH-Px) represent the main antioxidant systems in human cells. Selenium (Se), bound to the active sites of GSH-Pxs, plays a critical role in this antioxidant defence system. Statins are widely used and extensively investigated in the prevention of cardiovascular disease, notably in high-risk subjects. Several studies show antioxidant effects of statins not related to their lipid-lowering action. Our study aimed to compare serum Se concentration in ESRD patients on maintenance HD and in homogeneous healthy subjects and to investigate whether chronic treatment with statins may interfere with serum Se concentration in HD patients. PROCEDURE: A total of 103 HD patients and 69 healthy subjects were enrolled; HD patients were divided into patients who were not treated with statins (group A) and patients who assumed statins since 6 months at least (group B). Serum Se was determined by atomic absorption spectrometry. RESULTS: Serum Se was significantly lower in HD patients of group A compared with healthy subjects (81.65+/-19.66 Vs. 96.47+/-15.62 mcg/L, p<0.0040). However, in HD patients who assumed statins serum, Se was significantly higher than in HD patients who did not (111.83+/-18.82 vs. 81.65+/-19.66 mcg/L, p<0.0001). CONCLUSIONS: Our results suggest that in HD patients chronic treatment with statins is related to higher-serum Se concentration.

Acid-base balance and oxygen tension during dialysis in uremic patients with chronic obstructive pulmonary disease.

Recent reports on the effects of dialysis on acid-base balance and metabolic acidosis correction in end-stage renal disease (ESRD) patients with chronic obstructive pulmonary disease (COPD) are lacking. Here, we compared acid-base balance and blood gasses among 14 patients with established COPD (group A) and eight patients with normal respiratory function (group B). The two groups were homogeneous for age, time on dialysis, and male/female ratio. At the beginning of dialysis, acid-base balance and blood gasses were comparable between patients of groups A and B. A significant difference between groups was observed only in pCO(2) at 20 min, together with a delay in pH increase. Effective correction of acidosis was reported at the end of dialysis and is not significantly affected by COPD. Nevertheless, weight loss must be carefully monitored in these patients in order to prevent hyperhydration and worsening of respiratory function.

5-Lipoxygenase-mediated mitochondrial damage and apoptosis of mononuclear cells in ESRD patients.

BACKGROUND: 5-Lipoxygenase activity is enhanced in peripheral blood mononuclear cells (PBMC) from end-stage renal disease (ESRD) patients on maintenance hemodialysis (HD), leading to lipoperoxidation and reactive oxygen species formation. These effects are prevented by vitamin E, which inhibits 5-lipoxygenase activity. The present study was designed to test the possibility that 5-lipoxygenase activation might cause mitochondrial damage and cytochrome c release, ultimately leading PBMC to apoptosis. METHODS: Apoptosis, mitochondrial uncoupling, and cytochrome c release were investigated in PBMC from 16 healthy volunteers and 16 ESRD patients on maintenance HD with cuprammonium rayon (CL-S) membranes in a two-step crossover study: after a four-week treatment with vitamin E-coated cuprammonium rayon (CL-E) membranes, and again after a four-week treatment with oral vitamin E. RESULTS: Compared to healthy controls, PBMC from ESRD patients showed an approximately threefold increase in mitochondrial uncoupling and cytochrome c release (within 4 and 8 hours, respectively), followed by an approximately threefold increase in apoptotic body formation (within 48 hours). Regardless of the administration route, vitamin E reduced mitochondrial uncoupling, cytochrome c release and apoptosis of mononuclear cells, as did the 5-lipoxygenase inhibitor eicosatetraynoic acid. Conversely, the cyclooxygenase inhibitor indomethacin was ineffective. CONCLUSIONS: Reported data suggest that the 5-lipoxygenase branch of the arachidonate cascade is only responsible for mitochondrial disruption and apoptosis of PBMC of ESRD patients, and that vitamin E may be helpful in the control of oxidative stress-related disease in these subjects, independent of the administration route.

Arachidonate cascade, apoptosis, and vitamin E in peripheral blood mononuclear cells from hemodialysis patients.

BACKGROUND: Lipid peroxidation and oxidative stress are enhanced in peripheral blood mononuclear cells (PBMCs) from hemodialysis (HD) patients because of upregulation of the 5-lipoxygenase pathway of the arachidonate cascade. 5-Lipoxygenase activity is specifically inhibited by vitamin E both in vitro and in vivo regardless of its administration route. METHODS: The effect of arachidonate cascade enzymes and vitamin E on oxidative stress and apoptosis was investigated in PBMCs from 16 maintenance HD patients treated for at least 6 months with cuprammonium rayon membranes in a two-step crossover study: after a 4-week treatment with vitamin E-coated cuprammonium rayon membranes and again after a 4-week treatment with oral vitamin E. Control PBMCs were obtained from 16 healthy volunteers. RESULTS: Membrane lipoperoxidation, cellular luminescence, membrane fluidity, and leukotriene B(4) content were significantly greater in PBMCs from HD patients; lipoxygenase was upregulated, but prostaglandin H synthase (PHS) was not affected. Regardless of administration route, vitamin E partially controlled lipid peroxidation and oxidative stress through direct inhibition of 5-lipoxygenase. Cultured PBMCs from HD patients showed a significant increase in apoptotic cells compared with controls. Vitamin E markedly reduced cell luminescence, membrane fluidity, and apoptosis, whereas the PHS inhibitor indomethacin was ineffective. Similar results were obtained with control PBMCs induced to apoptosis by hydrogen peroxide. CONCLUSION: Reported data suggest that the 5-lipoxygenase branch of the arachidonate cascade is only responsible for membrane peroxidation, oxidative stress, and apoptosis of PBMCs of HD patients, and administration of vitamin E may be helpful in the control of oxidative stress-related disease in these subjects.

Severe dietary protein restriction in overt diabetic nephropathy: benefits or risks?

OBJECTIVE: To evaluate whether restricting protein intake may delay the progression of chronic renal failure caused by overt diabetic nephropathy and also whether this increases the risk of malnutrition. DESIGN: Prospective clinical trial. SETTING: Nephrology outpatients. PATIENTS: Sixty-nine patients (32 affected by type 1 and 37 by type 2 diabetes, all treated with insulin) affected by both overt diabetic nephropathy and hypertension. INTERVENTION: The study was started once hypertension and glycemia had been under control for at least 3 months. Two groups of patients, matched for similar mean glomerular filtration rate value and nutritional status, were studied: a low-protein diet (0.6 g/kg/d) was randomly prescribed to 35 patients, whereas in the other 34 patients a free diet intake was maintained for 12 months. MAIN OUTCOME MEASURE: Renal function and nutritional status. RESULTS: The protein intake was significantly different in the 2 groups of patients, whereas the average decline of glomerular filtration rate during the follow-up was comparable. In the low-protein diet group, serum prealbumin concentration significantly decreased after 9 months, whereas serum albumin decreased at the end of the study. CONCLUSION: Severe dietary protein restriction does not seem to delay the progression of renal disease in patients with overt diabetic nephropathy, whereas it may induce malnutrition.