Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Selenium”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,099 records · Page 61Linked to original sources

[Selenium methylation and toxicity mechanism of selenocystine].

Selenium is an essential trace element and a toxicant for animals. Selenocystine, a selenium-containing amino acid, is one of the chemical forms in which selenium exists in food. This review summarized recent studies on the toxicity mechanism of selenocystine in experimental animals. Hepatotoxicity is caused by repeated oral administration of selenocystine. Selenocystine is metabolized by reduced glutathione and/or glutathione reductase to hydrogen selenide via selenocysteine-glutathione selenenyl sulfide. The hydrogen selenide is a key intermediate in the selenium methylation metabolism of inorganic and organic selenium compounds. Accumulation of the hydrogen selenide resulting from inhibition of the selenium methylation metabolism, detoxification metabolic pathway of selenium, is found in animals following repeated administration of a toxic dose of selenocystine. The excess of the hydrogen selenide produced by inhibition of the selenium methylation metabolism contributes to the hepatotoxicity caused by selenocystine.

Animals↗

Antimutagenic activity of selenium-enriched green tea toward the heterocyclic amine 2-amino-3-methylimidazo[4,5-f]quinoline.

Both selenium and green tea have been reported to exhibit antigenotoxic and cancer chemopreventive properties. We compared the antimutagenic activities of regular green tea and selenium-enriched green tea obtained from Hubei Province, China, toward the heterocyclic amine, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) in the Salmonella assay. Selenium-enriched green tea obtained by foliar application of selenite exhibited concentration-dependent inhibition of IQ-induced mutagenesis in the presence of rat liver S9 and was significantly more effective than regular green tea tested under the same conditions. Analytical studies revealed no major differences in the polyphenol or caffeine content between regular green tea and selenium-enriched green tea, but the latter tea contained approximately 60-fold higher concentrations of selenium compared with regular green tea. The only soluble form of selenium was identified as selenite. The antimutagenic effects of certain individual tea constituents, such as epicatechin gallate and catechin, were enhanced by the addition of selenite to the Salmonella assay. Sodium selenite, sodium selenate, seleno-DL-cysteine, seleno-L-methionine, and L-Se-methylselenocysteine were not antimutagenic toward IQ when tested alone, but augmented significantly the inhibitory potency of green tea. The results suggested an enhancing ("coantimutagenic") effect of selenium in combination with green tea in vitro, but in vivo studies are needed to assess whether there is a synergistic effect of tea and selenium to protect against heterocyclic amine-induced mutagenesis and carcinogenesis.

Animals↗

Metabolites of sodium selenite and methylated selenium compounds administered at cancer chemoprevention levels in the rat.

1. The metabolism of orally-administered sodium selenite and five methylated selenium compounds was investigated in the female rat at dosages equivalent to those used in other studies for prevention of mammary cancer. Dimethyl selenide (DMSe) exhaled within 24 h following dosing was measured, along with inorganic and monomethylated (MMSe) forms of selenium plus trimethylselenonium ion (TMSe+) in urine. 2. MMSe was the dominant metabolite of selenite given at low levels (0.1 ppm in the diet), but excretion of DMSe and TMSe+ increased sharply when selenite dosage was increased to the chemopreventive range of 3 ppm dietary Se. When similar chemopreventive levels of mono-, di-, or trimethylated compounds were administered, the total quantity of methylated metabolites was greater than for selenite and the metabolite profile reflected the expected point of entry into the intermediary metabolism pathway; the major metabolites were MMSe from Se-methylselenocysteine, DMSe from selenobetaine methyl ester, and TMSe+ from selenobetaine. However, the profile of metabolites provided clear evidence that the methylated selenium compounds underwent demethylation, as shown by the excretion of inorganic and MMSe. Selenium administered as dimethyl selenoxide was almost completely excreted and about 90% of the dose was recovered as DMSe, indicating that reduction was the major pathway. For TMSe+, about 10% of the dose was excreted as DMSe and 84% as TMSe+. 3. A low, non-toxic level of sodium arsenite (5 ppm As in the diet) that is known to modify differentially the anticarcinogenic activity of selenite and methylated selenium compounds did not modify the excretion of the methylated selenium metabolites. 4. It is concluded that high anticarcinogenic activity is associated with extensive excretion of methylated Se excretory metabolites, but high output of such metabolites per se does not necessarily lead to anticarcinogenic activity. The whole animal has extensive capabilities for interconverting forms of selenium, and retains significant amounts in tissues, complicating the interpretation of Se metabolism and anticarcinogenic action. Further research is needed on the forms of selenium present in tissues.

Animals↗

[Effect of selenium dioxide on proliferation, apoptosis, and elomerase activity of human lung cancer cell line in vitro].

BACKGROUND & OBJECTIVE: It was reported that selenium could induce apoptosis of cancer cells; moreover, apoptosis of cancer cells and telomerase activity were closely related to the development of cancer. This study was designed to investigate the effect of selenium dioxide on human pulmonary adenocarcinoma GLC-82 cell to reveal its probable mechanism and the relationship between apoptosis and telomerase activity. METHODS: Methyl thiazolyl tetrazolium(MTT) method was used to determine the growth inhibition rates of lung cancer GLC-82 cells by various concentrations of selenium dioxide at different time. TRAP-PCR-ELISA assay was used to examine the changes of GLC-82 cells treated with selenium dioxide. The cell apoptotic rate was measured by flow cytometry (FCM). DNA ladder was showed by DNA agarose gel electrophoresis. The morphological changes of the cancer cells were examined under light and electron microscope. RESULTS: After being treated with 3, 10, 30 micromol/L selenium dioxide, the proliferation and telomerase activity of GLC-82 cells were markedly inhibited. The growth inhibition rates in GLC-82 cells for 24 hours were 0.7%, 12.8%, and 31.8%; for 72 hours were 15.1%, 51.2%, and 61.1%, respectively. Telomerase activity of GLC-82 cells for 24 hours were 1.173+/-0.029,1.127+/-0.067, and 1.050+/-0.098(P< 0.05); for 48 hours were 1.150+/-0.026, 1.047+/-0.060, and 0.950+/-0.036(P< 0.05), respectively (control group: 1.227+/-0.032 and 1.167+/-0.023, respectively). An apoptosis peak appeared before diploid peak in FCM. Agarose gel electrophoresis showed overt ladder-shape band of cell apoptosis. GLC-82 cells treated by selenium dioxide showed morphological characteristics of apoptotic cells. CONCLUSION: Selenium dioxide could significantly inhibit the growth of lung cancer GLC-82 cells through inducing apoptosis and inhibiting the telomerase activity. Selenium dioxide has strong growth inhibitory effect in a dose-and time-dependent manner.

Apoptosis↗

Circulating levels of selenium and zinc in relation to nutritional status in patients with head and neck cancer.

There is evidence that selenium and zinc are involved in malignant neoplasia. The exact role of these trace elements, however, is not completely understood. For this reason, we studied circulating levels of selenium and zinc in relation to food intake and nutritional status in 14 patients with head and neck cancer. Six patients without cancer served as controls. The patients with cancer were in different stages of disease. They were untreated or in an initial phase of oncologic treatment. Five of these patients were severely cachectic according to weight loss and nutritional status, which included body mass index, anthropometric values, and serum albumin level. These patients also demonstrated decreased circulating levels of selenium and zinc. Plasma glutathione peroxidase (selenium-dependent enzyme) activity, however, was not significantly different when the cachectic patients with cancer were compared with controls. We found that the plasma selenium level was positively correlated to both short-term and long-term selenium intake when all 20 patients were accounted for. However, no significant correlation could be shown between plasma selenium and serum albumin levels. Although only one patient demonstrated a plasma value below the reference value, serum zinc was positively correlated to the serum albumin level. We conclude that plasma selenium concentrations are essentially related to food intake but not necessarily to weight loss. Low circulating levels of zinc are, rather, associated with the catabolic state of the patient with cancer.

Adult↗

Selenium speciation in animal tissues after enzymatic digestion by high-performance liquid chromatography coupled to inductively coupled plasma mass spectrometry.

A procedure is described for the enzymatic digestion of tuna and mussel samples that allows the determination of selenium species by high-performance liquid chromatography in conjunction with inductively coupled plasma mass spectrometry. The species were extracted by two-step enzymatic hydrolysis with a non-specific protease (subtilisin). The selenium species were separated on a Spherisorb 5 ODS/AMINO column using two different chromatographic conditions, namely phosphate buffers at pH 2.8 and pH 6.0 as mobile phases. The method determines organic (trimethylselenonium, selenocystine, selenomethionine and selenoethionine) and inorganic selenium species (selenite and selenate), but only organic selenium species were found in the samples. The sum of identified selenium species in the sample was about 30% of the total selenium present in the enzymatic extract despite the fact that recoveries of total hydrolysed selenium were 93-102%. Trimethylselenonium ion and selenomethionine were found in both tuna and mussel samples and an unknown selenium species was also found in tuna samples.

Animals↗

The effect of a selenium supplementation on the outcome of patients with severe systemic inflammation, burn and trauma.

Patients with systemic inflammatory response syndrome (SIRS) and sepsis exhibit decreased plasma selenium and glutathione peroxidase activity. This has been shown in several clinical studies. Moreover, the degree of selenium deficiency correlates with the severity of the disease and the incidence of mortality. Patients with SIRS and sepsis are exposed to severe oxidative stress. Selenoenzymes play a major role in protecting cells against peroxidation, especially lipid peroxidation and are involved in the regulation of inflammatory processes. Therefore, selenium substitution in those patients might be effective in the prevention of multiorgan failure. The results of randomised clinical trials investigating selenium substitution in critical ill patients with inflammation are reviewed. In two independently performed randomised, prospective clinical trials, including patients with systemic inflammatory response syndrome or sepsis, the supplementation of selenium revealed a significant reduction in multiorgan failure and, especially, a lower incidence of acute renal failure and respiratory distress syndrome. One of those trials also could demonstrate a significant reduction of mortality in the most severely ill patients. Two other studies, where selenium together with other trace elements or a mixture of antioxidants were used in the treatment of patients with severe burn injuries or trauma showed a significant reduction in the secondary infection rate, including sepsis. Thus, selenium supplementation seems to improve the outcome of patients with SIRS, sepsis and severe injury, however, pivotal prospective clinical trials with sufficient statistical power are now necessary to finally prove the efficacy of a selenium supplementation in these diseases.

Adult↗

Evidence for a strong selenium-aromatic interaction derived from crystallographic data and ab initio quantum chemical calculations.

Increasing attention is being paid to the role of selenium, both as an essential component required for the activity of many enzymes and in the context of selenium-based pharmaceutical agents. A wide range of therapeutics that include selenium are on the market and under development, such as antihypertensive, anticancerogenic, antiviral, and immunosuppressive agents. Computer-aided drug design (CADD) has proven to be an important tool for the development of new drugs. Many CADD techniques, including docking, molecular dynamics simulation, and other receptor-based approaches, require an accurate understanding of the nature of the intermolecular forces that act to stabilize protein-ligand complexes; moreover, a quantitative assessment of these interactions furthers our efforts to rationalize the drug design process. In this paper, we consider one class of interaction involving selenium, that between Se and aromatic rings. Prior work has shown that interactions between divalent sulfur and aromatic rings are observed much more frequently than would be expected on the basis of chance, both in protein structures and the crystal structures of organic compounds that include these moieties. Recent studies on the optimization of inhibitor-protein binding also suggest that sulfur-aromatic interactions are important in stabilizing these complexes and may be crucial focal point for CADD. Given that selenium and sulfur have similar chemistry, and that selenium is significantly more polarizable, we propose that Se-aromatic interactions may also play an important stabilizing role in the structure of folded proteins and in drug-protein complexes. We have tested this hypothesis against data from the Cambridge Crystallographic Database and ab initio quantum chemical calculations. We have found evidence that selenium does interact strongly with aromatic rings and may play a role analogous to sulfur in stabilizing protein folds. In addition, selenium should be considered along with sulfur in rational drug design strategies that seek to improve binding to target protein sites that include aromatic rings.

Crystallography, X-Ray↗

Serum selenium and risk of prostate cancer in U.S. blacks and whites.

Prostate cancer is the fourth most common cancer in men worldwide and the most common cancer in men in the United States, with reported incidence rates for U.S. blacks being the highest in the world. The etiology of prostate cancer and an explanation for the racial disparity in incidence in the United States remain elusive. Epidemiologic studies suggest that selenium, an essential trace element, may protect against the disease. To further explore this hypothesis, we measured serum selenium in 212 cases and 233 controls participating in a multicenter, population-based case-control study that included comparable numbers of U.S. black and white men aged 40-79 years. Serum selenium was inversely associated with risk of prostate cancer (comparing highest to lowest quartiles, OR = 0.71, 95% CI 0.39-1.28; p for trend = 0.11), with similar patterns seen in both blacks and whites. Cubic regression spline analysis of continuous serum selenium indicated a reduced risk of prostate cancer above concentrations of 0.135 microg/ml (median among controls) compared to a reference value set at the median of the lowest selenium quartile. Because both the selenoenzyme GPX and vitamin E can function as antioxidants, we also explored their joint effect. Consistent with other studies, the inverse association with selenium was strongest among men with low serum alpha-tocopherol concentrations. In conclusion, our results suggest a moderately reduced risk of prostate cancer at higher serum selenium concentrations, a finding that can now be extended to include U.S. blacks. Since selenium exposure varies widely throughout the world, further research on optimal concentrations for cancer prevention is justified.

Adult↗

Antigenotoxic properties of selenium compounds on potassium dichromate and hydrogen peroxide.

Selenium is an environmental metal that occurs ubiquitously and is produced throughout the world for various industrial activities. Selenium has been reported to have anticarcinogenic and preventive effects in clinical and epidemiological studies. Selenium supplements can inhibit chemically-induced tumours. From the viewpoint of genotoxicity, selenium has not been adequately studied and an IARC review concluded that there were not sufficient data to consider it a carcinogen for man. In contrast, hexavalent chromium is classified as a known respiratory carcinogen producing DNA damage through free oxygen radicals. In the present study, a collaborative study has been carried out to evaluate the genotoxicity of selenium compounds and their possible interactions with potassium dichromate and hydrogen peroxide. Thus, in laboratory 1 (U.K.), the genotoxic effects of three selenium compounds were examined. Sodium selenate, sodium selenite, and selenous acid were investigated in the Ames test using strain TA102 and in the Comet assay using human lymphocytes, and also investigated for their interaction with potassium dichromate. In the Ames test, it was shown that potassium dichromate produced a highly mutagenic response, whilst the three selenium compounds did not. In combination, sodium selenate reduced the genotoxicity of potassium dichromate, but sodium selenite and selenous acid had no effect. In the Comet assay, potassium dichromate induced DNA damage, but so did the selenium compounds. In combination with potassium dichromate, however, only sodium selenate reduced its effect, whereas sodium selenite and selenous acid exacerbated DNA damage. In laboratory 2 (Spain), in the TK6 lymphoblastoid cell line, the Comet assay showed that sodium selenite was non-genotoxic, while potassium dichromate and hydrogen peroxide induced DNA damage. It was also shown that sodium selenite did not decrease the genotoxicity of potassium dichromate or hydrogen peroxide when administered as a pre-treatment or at the same time, or when potassium dichromate and sodium selenite treatments were for different time periods. Thus, only sodium selenate has shown antigenotoxic properties against potassium dichromate in the Ames test and in human lymphocytes in the Comet assay.

Comet Assay↗

Separation of selenium-containing proteins in human and mouse plasma using tandem high-performance liquid chromatography columns coupled with inductively coupled plasma-mass spectrometry.

An analytical method that uses two different high-performance liquid chromatography (HPLC) columns in tandem has been developed that separates three major selenium-containing proteins (albumin, glutathione peroxidase, and selenoprotein P) found in human blood plasma. The first column was a heparin affinity column and the second was a gel filtration column whose outlet was directly connected to an inductively coupled plasma-mass spectrometer. The method successfully separated plasma selenium into the three selenium-containing proteins and revealed the preferential retention of selenium in the form of selenoprotein P in a selenium-deficient human and in selenium-deficient mice. Our results also confirm the results of previous studies that showed a preference for supplemented selenium to be taken up as selenoprotein P in rats. Advantages of the tandem column method are that it allows rapid and convenient analyses of the distribution of plasma selenium, and that it is suitable for stable isotope tracer studies and metal interaction studies.

Adult↗

Dietary selenium reduces the formation of aberrant crypts in rats administered 3,2'-dimethyl-4-aminobiphenyl.

Human epidemiologic studies suggest that low selenium status is associated with increased cancer risk and that selenium supplementation is associated with reduction in the incidence of several cancers, including colorectal cancer. Aromatic and heterocyclic amine carcinogens are thought to be important in the etiology of human colorectal cancer, but no information is available on the effects of selenium on aromatic amine-induced colon cancer. In order to investigate this effect, aberrant crypt foci (ACF), the putative preneoplastic lesions of colon cancer in humans and rodents, were used as a biomarker to test the hypothesis that selenium supplementation can reduce aromatic amine-induced colon carcinogenesis. Male weanling F344 inbred rats were fed a basal torula yeast selenium-deficient diet supplemented with 0, 0.1, or 2. 0 mg selenium/kg diet as selenite, selenate, or selenomethionine (SeMet). Animals were fed the diets for 4 weeks and then administered 1 sc injection/week for 2 weeks of 3, 2'-dimethyl-4-aminobiphenyl (DMABP; 100 mg/kg) or vehicle (peanut oil). At 12 weeks, the rats were euthanized and the colon and rectum were removed, opened longitudinally, and fixed in 70% ethanol. Glutathione peroxidase activities in erythrocytes and liver cytosol and selenium concentrations in the colon/rectum and kidney increased significantly (p < 0.05) and in a dose-dependent manner with each of the three selenium diets. No ACF were identified in vehicle-treated rats. In DMABP-treated rats, ACF frequencies decreased significantly (p < 0.05) in groups supplemented with 0.1 or 2.0 mg selenium/kg diet as selenite and selenate but not SeMet. There were no significant differences in ACF and aberrant crypts between rats fed 0.1 vs 2.0 mg selenium/kg diet. These results suggest that dietary selenium, depending on chemical form, can reduce aromatic amine-induced colon carcinogenesis.

Aminobiphenyl Compounds↗

Inhibition of chemical carcinogenesis and tumorigenesis by selenium.

Selenium is effective in inhibiting the incidence and total number of tumors resulting from treatment with various chemical carcinogens. This inhibition occurs both at the initiation and promotion phases of chemical carcinogenesis. At least part of the inhibition of the initiation stage is associated with changes in the metabolism of the parent carcinogen. Studies with 7,12-dimethylbenz(a)anthracene suggest that selenium specifically blocks the enzyme(s) responsible for the formation of anti-dihydrodiol epoxide adducts to DNA. Selenium is also effective in reducing the in vitro and in vivo growth of numerous neoplastic cells. However, differences in the sensitivity to selenium are evident in the various tumor cell lines that have been examined. Continuous selenium intake appears to be necessary to maximal inhibition in both models of carcinogenesis. Evidence suggests that selenodiglutathione or some other intermediate in selenium metabolism is responsible for the anticarcinogenic and antitumorigenic properties of this trace element. The mechanism by which selenium produces these effects is unknown, but it may relate to alterations in either RNA transcription or translation. These and other data strongly suggest that selenium is a naturally occurring anticarcinogenic and antitumorigenic agent.

9,10-Dimethyl-1,2-benzanthracene↗

Selenium in wetlands and waterfowl foods at Kesterson Reservoir, California, 1984.

Kesterson Reservoir (Kesterson) received subsurface agricultural drainwater containing high levels of salts and selenium from farmland in the San Joaquin Valley of California. The accumulation of selenium in wetlands and waterfowl foods at Kesterson was investigated during May, August, and December of 1984. High concentrations of selenium vegetation, and aquatic insects. Mean selenium concentrations in aquatic plants and insects ranged from 1.5 to 170 micrograms/g dry weight and were about 11 to 290 times those found at a nearby reference site. Concentrations in some waterfowl food plants and insects at Kesterson were up to 64 times those reported to be a health hazard to birds. Selenium concentrations were more seasonally variable in aquatic plants than in aquatic insects. Few differences in selenium accumulation were found among ponds. Deposition of selenium in plant parts was not uniform; rhizomes contained higher concentrations than seeds and leaves were intermediate. Most biota bioaccumulated maximum selenium concentrations that were 1,000 to nearly 5,000 times the concentration in the water.

Animals↗

Selenium content of goat milk and its distribution in protein fractions.

This study reports on selenium distribution in goat milk. Skim milk was found to contain the major part (94%) of total milk selenium. The selenium distribution over casein and whey protein fractions depends on the separation method used, but irrespective of these methods, skim milk selenium is mainly associated with the casein fraction (greater than 69%). Approximately 9%, 7% and 24% of selenium is removed by dialysis (molecular cutoff 10-12 kDa) from skim milk, casein and whey respectively, indicating a major association of selenium with milk proteins. This observation is confirmed by selenium analysis of individual caseins and whey proteins isolated through ion-exchange chromatography and gel filtration. Selenium concentrations of the different isolated milk proteins show considerable variation (caseins: 294-550 ng Se/g; whey proteins: 217-457 ng Se/g).

Animals↗

Selenium content of mushrooms.

The selenium contents of 83 species of wild mushrooms were determined by oxygen combustion of the sample, followed by conversion of selenite to bromopiazselenol and final estimation by electron capture gas-liquid chromatography. Selenium concentration were found to range from 0.012-20.0 mg/kg dry weight. Selenium content was species-dependent. High concentrations were found in Agaricaceae and in certain Boletaceae of the genus Tubiporus, whereas in Russulaceae, Amanitaceae and Cantharellaceae selenium-rich species were absent or rare. Ascomycetes and all mushrooms growing on wood had a very low selenium content. The highest selenium concentrations (up to 20 ppm) were found in Boletus (Tubiporus) edulis, a most popular edible mushroom. Analyses of various parts of carpophores of B. edulis, Suillus luteus and Amanita muscaria indicate that in all three species the stalk contains less selenium than the fleshy part of the cap. In Boletus and Suillus the highest selenium content was found in the tubes.

Basidiomycota↗

Depressed selenium and vitamin E levels in an alcoholic population. Possible relationship to hepatic injury through increased lipid peroxidation.

Serum selenium and vitamin E levels have been measured in subjects with established alcoholic liver disease, in alcoholics within the community, and in appropriate controls. Both serum selenium and vitamin E levels were shown to be significantly depressed (P less than 0.01) in the alcoholic study groups and serum selenium was more markedly depressed in subjects with established liver disease (controls, serum selenium 108 +/- 13 micrograms/liter, vitamin E 27.6 +/- 7.2 mumol/liter; community alcoholics, serum selenium 94 +/- 19 micrograms/liter, vitamin E 15.3 +/- 3.4 mumol/liter; alcoholic liver disease, serum selenium 78 +/- 15 micrograms/liter, vitamin E 14.7 +/- 5.6 mumol/liter). Depressed serum selenium levels correlated closely with poor nutritional status (r = 0.91). There were no changes in serum glutathione peroxidase activity. Liver disease activity, as judged by transaminase (AST), was more markedly abnormal in subjects with combined vitamin E and selenium deficiency compared to those with normal levels or isolated deficiencies (no deficiency, AST 48 +/- 19 units, combined deficiency, AST 75 +/- 21 units, P less than 0.03). Serum lipid peroxides were elevated in those with combined deficiency and the values correlated significantly with serum transaminases (r = 0.40, P = 0.03).

Adult↗

Physiological and nutritional importance of selenium.

The essential trace element selenium has recently attracted attention because of its potentialities in the maintenance of human health. Selenium forms part of the active site of the peroxide-destroying enzyme glutathione peroxidase, and it also has other functions, for example in biotransformation, detoxification and the immune response. Functional and clinical consequences of selenium deficiency states have been described, and the selenium requirement, which is influenced by the usual selenium exposure, has been discussed. Wide variations have been found in selenium status in different parts of the world, and populations or groups of patients exposed to marginal deficiency are more numerous than was previously thought. Current research activities in the field of human medicine and nutrition are devoted to the possibilities of using selenium for the prevention or treatment of degenerative or free radical diseases such as neurological disorders, inflammatory diseases or cancer. Pharmacological selenium doses are also recommended as an adjuvant in some treatments.

Cardiovascular Diseases↗