Hemodialysis with regenerated cellulosic membranes does not reduce plasma selenium levels in chronic uremic patients

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.

Trace elements in hemodialysis patients: a systematic review and meta-analysis

BACKGROUND

Hemodialysis patients are at risk for deficiency of essential trace elements and excess of toxic trace elements, both of which can affect health. We conducted a systematic review to summarize existing literature on trace element status in hemodialysis patients.

METHODS

All studies which reported relevant data for chronic hemodialysis patients and a healthy control population were eligible, regardless of language or publication status. We included studies which measured at least one of the following elements in whole blood, serum, or plasma: antimony, arsenic, boron, cadmium, chromium, cobalt, copper, fluorine, iodine, lead, manganese, mercury, molybdenum, nickel, selenium, tellurium, thallium, vanadium, and zinc. We calculated differences between hemodialysis patients and controls using the differences in mean trace element level, divided by the pooled standard deviation.

RESULTS

We identified 128 eligible studies. Available data suggested that levels of cadmium, chromium, copper, lead, and vanadium were higher and that levels of selenium, zinc and manganese were lower in hemodialysis patients, compared with controls. Pooled standard mean differences exceeded 0.8 standard deviation units (a large difference) higher than controls for cadmium, chromium, vanadium, and lower than controls for selenium, zinc, and manganese. No studies reported data on antimony, iodine, tellurium, and thallium concentrations.

CONCLUSION

Average blood levels of biologically important trace elements were substantially different in hemodialysis patients, compared with healthy controls. Since both deficiency and excess of trace elements are potentially harmful yet amenable to therapy, the hypothesis that trace element status influences the risk of adverse clinical outcomes is worthy of investigation.

Selenium status indices, laboratory data, and selected biochemical parameters in end-stage renal disease patients

We investigated the relations between selenium status (SeS) parameters, indexes of nutrition, erythropoiesis, and uremic toxemia, serum electrolytes, and other biochemical markers in end-stage renal disease (ESRD) patients, as no multivariate statistical analysis concerning all of these parameters was performed so far. SeS was evaluated by plasma Se concentration (plSe) and glutathione peroxidase (plGSHPx) activity in 69 uremic patients treated with hemodialysis (HD) and 40 healthy controls. The hierarchical multivariate partial least squares model (PLS2) was employed to establish data structure and correlations between parameters investigated. plSe and plGSHPx activity were significantly lower in patients when compared with controls (p=0.000). plSe was positively associated with indexes of erythropoiesis and nutritional status, as well as serum electrolytes and parameters of uremic toxemia. plGSHPx was inversely dependent on the pair of parameters: intact parathyroid hormone (iPTH) and aluminum plasma concentration (Al). We conclude that (1) ESRD strongly decreases selenium status and (2) the PLS2 approach revealed the existence of significant interactions among plSe, plGSHPx, and selected biochemical parameters or groups of such parameters; some of these associations need further studies to be clarified.

Selenium in global food systems

Food systems need to produce enough of the essential trace element Se to provide regular adult intakes of at least 40 μg/d to support the maximal expression of the Se enzymes, and perhaps as much as 300 μg/d to reduce risks of cancer. Deprivation of Se is associated with impairments in antioxidant protection, redox regulation and energy production as consequences of suboptimal expression of one or more of the Se-containing enzymes. These impairments may not cause deficiency signs in the classical sense, but instead contribute to health problems caused by physiological and environmental oxidative stresses and infections. At the same time, supranutritional intakes of Se, i.e. intakes greater than those required for selenocysteine enzyme expression, appear to reduce cancer risk. The lower, nutritional, level is greater than the typical intakes of many people in several parts of the world, and few populations have intakes approaching the latter, supranutritional, level. Accordingly, low Se status is likely to contribute to morbidity and mortality due to infectious as well as chronic diseases, and increasing Se intakes in all parts of the world can be expected to reduce cancer rates.

The effect of different dialysis membranes on oxidative stress and selenium status

BACKGROUND

Oxidative stress is an important risk factor for the development and progression of several complications in hemodialysis patients. The aim of this study was to evaluate the effects of two different dialysis membranes on oxidative stress and selenium status.

METHODS

Forty long-term dialysis patients and 20 age-matched healthy controls were enrolled into our study. Serum malondialdehyde (MDA) and selenium (Se) concentrations, and glutathione peroxidase (GSH-Px) activities were determined before and after hemodialysis (HD) using a hemophan (H) or a polysulfone (PS) membrane.

RESULTS

MDA levels in the HD patients were significantly higher than those in the control group (p < 0.001). GSH-Px activity and selenium concentrations were significantly lower in HD patients compared to the control group (p < 0.001). MDA levels were significantly increased (p < 0.05); GSH-Px activity and selenium concentrations were significantly reduced (p < 0.001) in the PS membrane group compared to H membrane group after HD.

CONCLUSIONS

Comparing with H membrane, PS membrane caused more oxidative stress and lower levels of Se in HD patients.

Sequential changes in plasma selenium concentration after cadaveric renal transplantation

Background

Previous investigations have shown that plasma selenium concentrations are significantly lower in patients with established chronic graft nephropathy (CGN) than in healthy transplant controls. The aims of this study were to determine when in the transplant process low selenium concentrations become apparent and to explore the relationship between selenium levels and risk factors for CGN.

Methods

Plasma selenium concentrations were measured in 40 patients (20 receiving cyclosporin, 20 receiving tacrolimus) undergoing transplantation. Samples were obtained immediately before transplantation and at 3, 6 and 12 months after transplantation.

Results

A low plasma selenium concentration was found in 30 patients at the time of transplantation but this had normalized in the majority of patients by 3 months. Plasma selenium concentrations at 3, 6 and 12 months were significantly higher than baseline values for both treatment arms, but were significantly lower at 3 months in patients who experienced either clinical acute rejection (CAR) or cytomegalovirus (CMV) infection during the preceding months.

Conclusion

Low plasma selenium concentrations are common at the time of transplantation but appear to normalize thereafter. The identification of low selenium levels in patients who experience CAR or CMV (two important risk factors for clinically apparent CGN) suggests that the relationship between selenium and CGN warrants further investigation.

Selenate-supplemented nutritional formula increases plasma selenium in hemodialysis patients

OBJECTIVE

The purpose of this study was to determine the short-term effect of feeding selenium-supplemented formulas on the selenium status of end-stage renal disease patients on hemodialysis.

DESIGN AND SETTING

The prospective, randomized, single-blind study of parallel design was conducted at three hemodialysis clinics.

PATIENTS

A total of 79 hemodialysis patients were randomly assigned into one of three groups.

INTERVENTION

Liquid nutritional formula supplemented with either selenite (28 microg Se/8 oz, n = 26), selenate (28 microg Se/8 oz, n = 26), or nonfortified (7 microg Se/8 oz, n = 27) was fed to hemodialysis patients as their sole source of nutrition for 14 days.

MAIN OUTCOME MEASURE

Plasma and red blood cell (RBC) selenium and glutathione peroxidase (GPX) activities were measured in predialysis blood both before (day 1) and after (day 8) a 7-day baseline period, and after subjects received the formula as the sole source of nutrition (approximately 35 kcal/kg/d) for 14 days (day 22).

RESULTS

Selenium intake (Mean +/- SEM, microg/d) was 134 +/- 9, 140 +/- 9, and 35 +/- 2 for patients receiving selenite-, selenate-, or non-supplemented formula, respectively. On day 22, plasma selenium (micromol/L) was greater (P <.032) in the selenate-supplemented group (1.5 +/- 0.1) compared with the nonsupplemented group (1.2 +/- 0.1), but not compared with the selenite-supplemented group (1.4 +/- 0.1). Plasma GPX activity was 44% to 60% that of healthy controls and not different among groups. RBC selenium and GPX activities were within the normal range and were not different among groups.

CONCLUSION

The results of this study indicate that a liquid formula supplemented with selenium as selenate is successful at maintaining selenium concentrations within normal range, as well as significantly increasing plasma selenium levels compared with nonsupplementation.

Thyroid function and plasma selenium in chronic uremic patients on hemodialysis treatment

It has been shown recently that Selenium (Se), an essential trace element for humans, is involved in the regulation of thyroid function, since the enzyme that catalyzes the liver conversion of the thyroid hormone T4 to the more active form T3 is a selenoenzyme. In chronic uremic patients, low blood Se levels as well as thyroid function abnormalities are often found. The present study was carried out to verify whether any correlation exists between Se levels and thyroid function, and to evaluate possible changes in hormonal pattern during Se supplementation in 10 chronic uremic patients on hemodialysis (HD) treatment. Se was supplemented orally as sodium selenite over six consecutive months. Basic plasma Se levels were significantly lower in patients than in normal controls. Right from the start of Se supplementation, plasma Se concentration promptly normalized and leveled off in the normal range throughout the study. Significant increase of FT3 and reduction of TSH levels were detected during Se supplementation. In Se-supplemented patients, a significant direct correlation was also found between reverse T3 (rT3) and TSH, and a significant inverse correlation was found between Se and TSH. Our results suggest that Se deficiency in chronic uremic patients represents a factor influencing the thyroid function and that the Se status should be determined in the evaluation of thyroid metabolism in these patients.

Selenium in uremia

The importance of selenium as an essential trace element for man has been increasingly recognized during the last several years. Selenium deficiency has been associated with cases of congestive cardiomyopathy, skeletal myopathy, anemia, enhanced cancer risk, elevated incidence of cardiovascular disease, immune system alterations, hair and nail changes, and abnormalities in thyroid hormone metabolism. These symptoms are frequently present in chronic uremic patients. Nevertheless, the prevalence and significance of selenium deficiency in the uremic syndrome is still not clearly defined. This article reviews the selenium status in chronic uremic patients, the supposed pathogenetic mechanisms of selenium disturbance in uremia, and the possible role of selenium deficiency on some uremic abnormalities.