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PubMed2007

Selenium and intractable epilepsy: is there any correlation?

Oxidative stress and generation of reactive oxygen species are strongly implicated in a number of neuronal and neuromuscular disorders, including epilepsy. The functions of selenium as an antioxidant trace element are believed to be carried out by selenoproteins that possess antioxidant activities and the ability to promote neuronal cell survival. Because of this protective role of selenium against oxidative damage, a case-control study was designed to compare its serum level between intractable epileptic patients and normal subjects. Eighty patients who met the criteria of intractable epilepsy were compared with a normal control group of the same age, socioeconomic level, and place of living. Serum selenium level was measured with an atomic absorption spectrophotometer. The mean (+/- S.D.) of serum selenium were 68.88 (+/-17.58) ng/mL and 85.93 (+/-13.93) ng/mL in the patient and control groups respectively. Independent sample t test with P < 0.05 indicated a significant lower mean of serum selenium in the patient group compared with that of the normal control group. However, there was no association between serum selenium and some suggested predictive factors of intractable seizures, including age at the onset of seizures, neonatal seizure, neurologic impairment, and etiology of epilepsy. Measurement of serum selenium in patients with intractable epilepsy should be considered.

Adolescent↗
PubMed1995

Plasma levels of the antioxidant selenium and risk of myocardial infarction among U.S. physicians.

The well-known antioxidant properties of selenium have been linked to a lower incidence of cardiovascular disease in humans, but the findings remain controversial. To explore whether the plasma selenium level predicts risk of myocardial infarction (MI), we analyzed prospectively collected plasma samples in a nested case-control study among participants in the Physicians' Health Study, a randomized trial of aspirin and beta-carotene. Blood specimens were collected between August 1982 and December 1984 and stored at -80 degrees C. All infarcts were documented by medical records. This study is based on 251 subjects who had infarctions and an equal number of healthy controls, matched by age, smoking status, and time from randomization. The mean +/- SD levels of plasma selenium were 114.4 +/- 15.1 ng/g in the cases with MI, and 113.2 +/- 15.7 ng/g in controls (paired t = 0.94, p = 0.35). Conditional logistic regression analysis by quintile of plasma selenium levels showed no suggestion of any protective effect of selenium; subjects in the highest quintile had a relative risk of 1.27 (95% confidence interval 0.71 to 2.29) when compared with the bottom quintile, and 1.53 (95% confidence interval 0.61 to 3.84) after adjustment for other cardiovascular risk factors. These data provide no evidence for an association between increased plasma selenium and reduced risk of MI at the current levels of selenium intake within the U.S.

Adult↗
PubMed1997

Differential induction of growth arrest inducible genes by selenium compounds.

The effects of two types of selenium compounds on the expression levels of growth arrest and DNA damage-inducible (gadd) genes and on selected cell death genes were examined in mouse mammary MOD cells to test the hypothesis that the diversity of selenium-induced cellular responses to these compounds could be distinguished by unique gene expression patterns. Whereas the expression patterns of known cell death-related genes (bcl-2 and bax) were not informative with respect to the cellular response patterns upon exposure to selenium compounds, time-dependent and selenium species-specific induction patterns were observed for gadd34, gadd45 and gadd153 genes. It was also observed that the MOD cells expressed a truncated p53 transcript but no detectable immunoreactive P53 protein, indicating a null p53 phenotype. The fact that selenium compounds induced growth arrest and death of these cells and that these compounds induced specific patterns of expression of gadd genes indicates that these genes may mediate some selenium-induced cellular responses. The findings further imply that selenium compounds may be effective chemopreventive agents for human breast carcinogenesis, in which p53 mutations are frequent.

Animals↗
PubMed1982

Serum selenium levels in liver diseases.

A possible pathogenetic role of selenium deficiency in alcoholic cirrhosis of the liver has previously been discussed. In the present study serum selenium was analyzed in 5 groups of liver diseases. The method used for selenium determination was electrothermal atomic absorption, after thermal stabilization of selenium compounds by addition of nickel nitrate. The selenium level of a reference group of healthy Norwegian adults (n = 40) was 1.53 +/- 0.25 mumol/l. The serum concentrations of selenium in patients suffering from alcoholic cirrhosis, chronic active hepatitis and chronic persistent hepatitis were lowered to 40-80 per cent of those of the reference group. In alcoholic cirrhosis and chronic active hepatitis the decreased serum selenium concentrations were significantly correlated to decreased levels of albumin and prealbumin.

Hepatitis, Chronic↗
PubMed1988

Human glutathione peroxidase activity in cases of high selenium exposures.

Four communities with water supplies having selenium concentrations of less than 3.1, 1.7, 189, and 496 micrograms/liter were selected for study. Samples of blood, urine, and tap water were obtained from participants in each community and analyzed for selenium content. Blood samples were also analyzed for glutathione peroxidase activity. Results showed an increase in selenium concentration in the urine as the water selenium increased. Selenium concentrations in blood did not reflect the increased selenium exposure. Glutathione peroxidase activity in whole blood decreased in highly exposed participants compared to those with low exposure. We conclude that glutathione peroxidase activity in cases of possible environmental toxic exposures will not show the increased activity seen in supplementation of selenium to deficient subjects.

Adolescent↗
PubMed1989

Selenium deficiency in low birth weight neonates: an unrecognized problem.

To determine whether selenium deficiency is common among low birth weight infants in our neonatal intensive care unit, we surveyed blood samples from healthy full-term and preterm infants born in our hospital over a 3-month period. Selenium was measured by electrothermal atomic absorption spectrometry. Glutathione peroxidase was measured in plasma by an automated method. Baseline (less than 72 hours postnatal) selenium concentration and glutathione peroxidase activity were significantly lower in low birth weight infants than in full-term babies. Sequential selenium analyses were obtained in 16 sick low birth weight neonates who remained in the intensive care nursery for up to 6 weeks because of lung disease. All were fed parenterally without supplemental selenium, with or without oral intake, for periods varying from 3 to 60 days. All had a marked decrease from baseline selenium levels, and values below the detection limit of our assay were found in seven infants. Selenium deficiency is much more common in small infants than is generally realized, but the clinical significance in neonates is poorly understood.

Bronchopulmonary Dysplasia↗
PubMed2003

Natural variation of copper, zinc, cadmium and selenium concentrations in Bembicium nanum and their potential use as a biomonitor of trace metals.

Copper, zinc, cadmium and selenium were measured in the gastropod mollusc Bembicium nanum at two uncontaminated locations, Jervis Bay and Rosedale, NSW, to determine natural variability of metals associated with gender, mass, shore position and temporal variability. Trace metals were also measured in B. nanum at three industrialised locations to determine the accumulation of trace metals in contaminated environments.Copper, zinc, cadmium and selenium concentrations were not significantly different between male and female B. nanum. No significant relationships were found between zinc, cadmium and selenium concentrations and mass. There was a significant relationship between copper concentration and mass but only 19% of the variation was explained by mass. Generally inherent variability within samples had a greater influence than gender or variations in mass on trace metal concentrations. No trend was found in cadmium and selenium concentrations with variation in shoreline position. Copper and zinc concentrations increased further away from the low tide mark, with a decrease in metal concentrations at the furthest site from the water. Variability in metal concentrations is attributable to variations in food source, food availability and different immersion times.Copper, zinc, cadmium and selenium concentrations varied over a 12-month period. Copper, cadmium and selenium were taken up and lost over time, as metal body burden followed the same trend as metal concentrations. Zinc concentrations were influenced by mass. Copper and cadmium concentrations fluctuated throughout the 12-month period but with no clear seasonal trends. Selenium concentrations peaked in spring (October), with concentrations remaining uniform over the other months. These differences in mean concentrations between months were most likely due to inherent trace metal variability associated with differences in food availability and changes in metabolic rates associated with changes in temperature during the study period. Measurement of trace metals in B. nanum at contaminated sites showed that B. nanum accumulates metals in response to contamination.B. nanum meets most of the requirements to be a biomonitor of trace metal contamination as they are abundant, sedentary, easy to identify, provide sufficient tissue for analysis, tolerate high concentrations of pollutants and they accumulate trace metals in response to contamination. However, as trace metal concentration can vary with mass, shoreline position and temporally, care must be taken to collect individual organisms with similar mass from similar shoreline positions and times.

Animals↗
PubMed1998

Serum selenium levels as indicators of body status in cancer patients and their relationship with other nutritional and biochemical markers.

A cross-sectional study of serum selenium levels in patients (n = 59) with different types of cancer from southeastern Spain was carried out using hydride generation atomic absorption spectrometry. The subjects were divided into four groups according to the cancer location (respiratory, digestive, haematological and gynaecological groups). Serum selenium levels in all patients (54.41 +/- 24.80 mg/l) were significantly lower (P < 0.001) than those determined in control groups [healthy subjects from the same area (n = 130) and institutionalized elderly people (n = 93)]. Mean serum selenium concentrations were not significantly different among the four groups considered (P > 0.05). Linear regression analyses performed on serum selenium levels and biochemical markers (total cholesterol, triglycerides, transaminases, uric acid and urea) did not establish any statistically significant correlation (P > 0.05). No significant relationships between serum selenium concentrations and sex or age of patients was observed (P > 0.05). Given the marked overlap between the two ranges of the populations (the means are within approx. 1/2 S.D.) the predictive values of serum selenium are low. Thus, there is indeed a statistical significance between the means, but selenium cannot be used to determine whether or not a patient has cancer disease.

Adult↗
PubMed1999

Serum and urine selenium concentrations as indicators of body status in patients with diabetes mellitus.

Serum and urine selenium levels were determined in patients with diabetes by hydride generation atomic absorption spectrometry. Mean serum selenium concentrations measured in patients with diabetes mellitus (64.9 +/- 22.8 micrograms/l) were significantly lower than those determined in the control group (74.9 +/- 27.3 micrograms/l) (P < 0.05). Mean serum selenium concentrations were not significantly different between the two groups of diabetic patients considered (P > 0.05). Mean urine selenium concentration in diabetic patients (18.8 +/- 10.7 micrograms/l) were not significantly different from those measured in the control group (20.2 +/- 10.1 micrograms/l) (P < 0.05). No significant differences in serum and urine selenium levels were found if related to sex of patients (P > 0.05). Application of linear regression analysis to serum and urine selenium levels and patients' age showed a non-statistically significant correlation (P > 0.05). Given the marked overlap between the two ranges of the populations, the predictive values of serum selenium in diabetic patients are low.

Adolescent↗
PubMed2000

The importance of selenium to human health.

The essential trace mineral, selenium, is of fundamental importance to human health. As a constituent of selenoproteins, selenium has structural and enzymic roles, in the latter context being best-known as an antioxidant and catalyst for the production of active thyroid hormone. Selenium is needed for the proper functioning of the immune system, and appears to be a key nutrient in counteracting the development of virulence and inhibiting HIV progression to AIDS. It is required for sperm motility and may reduce the risk of miscarriage. Deficiency has been linked to adverse mood states. Findings have been equivocal in linking selenium to cardiovascular disease risk although other conditions involving oxidative stress and inflammation have shown benefits of a higher selenium status. An elevated selenium intake may be associated with reduced cancer risk. Large clinical trials are now planned to confirm or refute this hypothesis. In the context of these health effects, low or diminishing selenium status in some parts of the world, notably in some European countries, is giving cause for concern.

Acquired Immunodeficiency Syndrome↗
PubMed2004

Aquatic selenium pollution is a global environmental safety issue.

Selenium pollution is a worldwide phenomenon and is associated with a broad spectrum of human activities, ranging from the most basic agricultural practices to the most high-tech industrial processes. Consequently, selenium contamination of aquatic habitats can take place in urban, suburban, and rural settings alike--from mountains to plains, from deserts to rainforests, and from the Arctic to the tropics. Human activities that increase waterborne concentrations of selenium are on the rise and the threat of widespread impacts to aquatic life is greater than ever before. Important sources of selenium contamination in aquatic habitats are often overlooked by environmental biologists and ecological risk assessors due to preoccupation with other, higher priority pollutants, yet selenium may pose the most serious long-term risk to aquatic habitats and fishery resources. Failure to include selenium in the list of constituents measured in contaminant screening/monitoring programs is a major mistake, both from the hazard assessment aspect and from the pollution control aspect. Once selenium contamination begins, a cascade of bioaccumulation events is set into motion which makes meaningful intervention nearly impossible. However, this cascade of events need not happen if adequate foresight and planning are exercised. Early evaluation and action are key. Prudent risk management based on environmentally sound hazard assessment and water quality goals can prevent biological impacts.

Agriculture↗
PubMed2000

Selenium determination in human plasma lipoprotein fractions by mass spectrometry analysis.

Previous observations have suggested that lipoproteins may be involved in the transport of selenium in humans. To further investigate this question, selenium was measured in lipoprotein fractions isolated from plasma of healthy adults. A gas chromatographic-mass spectrometric method using the isotopic dilution technique was developed to ensure a reliable measurement of low amounts of selenium. About 3% of total plasma selenium was bound to lipoproteins, mainly to the LDL fraction. After solvent fractionation of LDL and HDL, the major part of the selenium was recovered in the protein extract, suggesting that it may be incorporated in apolipoproteins. The exact form of Se is not yet clearly established. Considering the different Se compounds found in proteins, it is postulated to be selenomethionine, and/or participating in a selenium-sulphur bond. This could explain why the amount of selenium bound to apolipoprotein B in LDL was about twice that which could be expected from a random substitution of selenomethionine for methionine.

Adult↗
PubMed2002

Rationale for a tissue-based selenium criterion for aquatic life.

This paper proposes a national tissue-based criterion for the protection of aquatic life in the United States based on the growing body of selenium literature, but may be of international importance due to the raising global awareness of selenium contamination. A recent peer consultation workshop was undertaken by the US Environmental Protection Agency to address the technical issues underlying the freshwater aquatic life chronic criterion for selenium. The workshop participants discussed concerns associated with three possibilities for a new criterion: a water-based criterion, a tissue-based criterion, and a sediment-based criterion. Since the current national water quality criterion was established in 1987, several publications have reported adverse effects in fish from dietary selenium exposure with waterborne concentrations below the current criterion of 5 microg/l. Based on this literature, a water-based criterion seems unsuitable because of the propensity for selenium to bioaccumulate through the food chain to toxic dietary concentrations. There is little information to support a sediment-based criterion. A tissue-based criterion accounts for selenium's biogeochemical pathways because it integrates the route, duration, and magnitude of exposure, chemical form, metabolic transformations, and modifying biotic and abiotic factors. The convergence of laboratory and field data shows 4 microg/g to be a conservative value for a national tissue-based criterion for selenium.

Animals↗
PubMed2002

Development of aquatic life criteria for selenium: a regulatory perspective on critical issues and research needs.

The US is currently in the process of revising its freshwater, chronic aquatic life criterion for selenium. The fundamental issues being addressed include which environmental compartment(s) support the most reliable expression of the criterion, which form(s) of selenium should be measured in the medium (media) of choice, and which site-specific water quality (or other factors) should be linked to the expression of the criterion. Literature reviews and a recent workshop were conducted to assess the state of the science on various issues related to water-, tissue- and sediment-based criteria for selenium. Evaluation of many of these issues is ongoing. In terms of water column criteria issues, data limitations will likely restrict the expression of a criterion to operationally defined forms (e.g. total recoverable, dissolved). The specific identity of organoselenium in natural systems is lacking and may not be appropriately represented by free seleno-amino acids (e.g. selenomethionine). The available data do not appear to support quantitative relationships between chronic toxicity and water quality characteristics. In terms of a tissue-based criterion, reproductive tissue (ovary, egg) has been recommended as the tissue of choice, but practical concerns and data availability require consideration of other tissues (e.g. whole-body). Organoselenium (bound to peptides or proteins) is thought to be the form of greatest toxicological importance in fish, however, direct measurements of organoselenium compounds in tissues are very limited. Route of exposure (food vs. water uptake) may prove important for establishing diagnostic tissue residues for selenium based on laboratory data. Data on toxicological aspects of selenium in sediments appear sparse, particularly in relation to different sedimentary forms. Reliable assessments of bioaccumulation will likely be critical for making site-specific modifications to chronic selenium criteria, however, many technical issues for assessing bioaccumulation remain. The need for improved analytical methods for directly speciating organoselenium in various environmental media underpins many of the current data gaps. Improving analytical methodologies to enable affordable and reliable measurement of organoselenium compounds holds significant promise for advancing selenium ecotoxicological research.

Animals↗
PubMed1996

Serum and tissue selenium contents related to renal disease and colon cancer as determined by electrothermal atomic absorption spectrometry.

Microwave digestion with nitric acid and hydrogen peroxide was applied to the determination of selenium in biological tissues by Electrothermal Atomic Absorption Spectrometry (ETAAS). Validation of this method is presented in terms of adequate recovery of selenium from standard reference materials and the method is applied to carcinogen human colon tissue. Ultramicrofiltration was used to study selenium protein binding and its fractionation and speciation in blood serum. These studies showed that 95% of the total selenium in serum seems to be bonded to high-molecular-weight proteins. Experiments with renal failure patients showed lower selenium levels than in the health population (0.57 +/- 0.23 mM versus 0.81 +/- 0.11 mM). A wider distribution pattern of total serum selenium concentration (from 0.1 to 1 mM) was clearly observed in renal failure patients. However, the ultramicrofiltrable selenium fraction was always constant, even in the presence of desferrioxamine (DFO).

Adult↗
PubMed1996

Correlation of mercury and selenium in the human kidney.

The total mercury (Hg) and selenium (Se) concentrations were determined in kidney cortex samples of 195 deceased, non-occupationally burdened individuals. Mercury was determined by means of Cold-vapour Atomic Absorption Spectrometry (CV-AAS) and selenium by Graphite-Furnace Atomic Absorption Spectrometry (GF-AAS). The molar Se/Hg ratio is high (up to (a) 300) in cases with relatively low mercury concentrations [Hg]. The ratio decreases with increasing [Hg]. At [Hg] of 700-1000 ng/g it reaches unity, where it remains constant even at larger [Hg]. Since in vitro mercury and selenium form relatively stable adducts, our results suggest the formation of a 1:1 Hg-Se compound that may explain mercury detoxification by selenium. This effect also results in the trapping of available selenium by mercury, too. Decreasing the reserve of free (i.e. not Hg-bound) selenium. The effect of this decrease of free selenium is under further investigation.

Adolescent↗
PubMed1998

Trace elements and cardioprotection: increasing endogenous glutathione peroxidase activity by oral selenium supplementation in rats limits reperfusion-induced arrhythmias.

Oxyradicals have been implicated as a possible cause of reperfusion-arrhythmias (RA). However, the use of diverse exogenous oxyradical scavengers designed to reduce RA has given contradictory results. The aim of the present study was to determine whether enhancing the activity of the main endogenous enzyme involved in peroxide elimination in cardiac cells, namely glutathione peroxidase, may limit RA in isolated heart preparations by increasing their antioxidant status. For this purpose, a group of 15 male Wistar rats received a selenium enriched diet for ten weeks (1.5 mg Se/kg diet). Control animals (n = 15) received a standard diet containing 0.05 mg Se/kg diet. The incidence of early ventricular arrhythmias was investigated during the reperfusion period following 10 min regional ischemia induced ex-vivo by left coronary artery ligation. Our results show that selenium-supplementation significantly increased the global selenium status of the animals. In the isolated heart preparations, the selenium supplementation induced a significant reduction of the severity of RA as assessed by the arrhythmia score and the limitation of the incidence of both ventricular tachycardia (control: 91% vs selenium: 36%, p < 0.05) and irreversible ventricular fibrillation (control: 45% vs selenium: 0%, p < 0.05). These effects were associated with a significant increase in cardiac mitochondrial and cytosolic glutathione peroxidase activities in both the left and the right ventricles. These results illustrate the potential protective effect of selenium against ischemia-reperfusion injury and suggest that peroxides might play a key role in the genesis of some aspects of the reperfusion syndrome.

Administration, Oral↗
PubMed1999

Recent developments in selenium metabolism and chemical speciation: a review.

The biological roles of selenium and its mode of action have only recently begun to be revealed. To date, the major functions of selenium can be attributed to its antioxidative properties and its role in the regulation of thyroid hormone metabolism, cell growth and eicosanoid biosynthesis. The unusual feature of selenoprotein synthesis is that selenocysteine insertion is specified by the stop UGA codon. A number of selenocysteine-specific gene products and a stem-loop structure in the 3' untranslated region are required for selenocysteine biosynthesis and the decoding of UGA codons in the open reading frame of the mRNA. The major biological functions of selenium are achieved through its redox activity when present as selenocysteine at the active sites of selenoproteins and these proteins are selenium-dependent since replacement with the sulphur analogue cysteine causes loss of enzyme activity. Both organic and inorganic forms of selenium may be utilised by the body, with the selenoamino acids showing greatest bioavailability. Knowledge of the biochemistry of the element coupled with appropriate techniques for the study of the distribution of selenium species in health and disease could help to identify sensitive markers of selenium status.

Animals↗