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 73 records · Page 4Linked to original sources
PubMedDate not supplied

Selenium administration does not cause thyroid insufficiency in subjects with mild iodine deficiency and sufficient selenium intake.

Selenium is a trace element essential for the activity of type I 5'-deiodinase which converts thyroxine (T4) to 3,5,3'-triiodothyronine (T3). In iodine deficient hypothyroid children at low selenium dietary intake the supplementation of selenium induced a significant decrement of serum FT4 and T4 concentrations and an increase of serum TSH concentrations. Since in western countries selenium tablets begin to be largely consumed as a diet integrator, we have administered 100 micrograms/day of selenium as selenium methionine to 8 euthyroid female subjects with a positive iodine-perchlorate discharge test who had a previous episode of subacute or postpartum thyroiditis. We have studied subjects with positive iodine-perchlorate discharge test since the test indicates the existence of a subtle defect of thyroid hormone synthesis and therefore these subjects are prone to develop thyroid dysfunction. In contrast to previous findings in hypothyroid children at low iodine and selenium dietary intake, the supplementation of selenium did not decompensate thyroid hormone synthesis of euthyroid subjects with reduced thyroid iodine organification. The lack of any effect of selenium on thyroid hormone synthesis even in subjects with subtle thyroid hormone synthesis defect may be due to the fact that these subjects had a sufficient selenium dietary intake before selenium supplementation and an only marginally reduced dietary iodine intake.

Adult↗
PubMed1991

Effects of selenium supplementation on blood and urine selenium levels and liver function in patients with primary biliary cirrhosis.

To study the mechanism of the reduced serum selenium concentration in patients with liver damage we administered 200 micrograms (2.53 mumol) selenium daily as selenium-rich yeast to 8 patients with primary biliary cirrhosis and 8 healthy controls over 16 weeks. Initially selenium concentrations in serum were 24% lower (P less than 0.001) in patients than controls. During supplementation serum selenium levels increased in both groups but the difference between them persisted. Throughout the study whole blood selenium levels and glutathione peroxidase activities were also somewhat lower (P = NS) in patients than controls. Selenium supplementation had no effect on whole blood glutathione peroxidase activities in either group. The basal 24 h urinary excretion of selenium was similar in both groups but was increased more by supplementation in patients than controls. Selenium administration did not influence the liver function of the patients. We conclude that impaired hepatic production of selenium-containing serum compounds is the most likely explanation for the reduced serum selenium concentration in patients with primary biliary cirrhosis.

Adult↗
PubMed1991

Selenium status of preterm infants fed human milk, preterm formula, or selenium-supplemented preterm formula.

The selenium status of 46 orally fed vitamin E-sufficient preterm infants (birth weight less than 1700 gm) was studied longitudinally for 3 weeks to determine the efficacy of selenium supplementation. Infants were fed either human milk (n = 21; 24 ng selenium/ml), preterm formula (n = 13; 7.8 ng selenium/ml), or preterm formula supplemented with sodium selenite (n = 12; 34.8 ng selenium/ml). Plasma and erythrocyte selenium and glutathione peroxidase activity and urinary and dietary selenium content were evaluated on study day 1 (day enteral feeds reached 100 kcal/kg/day) and weekly for 3 weeks. Throughout the study, selenium intakes of infants fed preterm formula plus sodium selenite were greater than those of infants fed human milk, which were greater than those of infants fed preterm formula (p less than 0.001). After 3 weeks no differences were observed among groups for plasma or erythrocyte selenium or glutathione peroxidase. Plasma selenium and glutathione peroxidase values within all groups were low compared with those reported for term infants fed human milk. Whereas urinary selenium levels of infants fed preterm formula plus sodium selenite were greater than those of infants fed preterm formula at weeks 1 and 2 (p less than 0.01), infants fed human milk and preterm formula had lower levels at week 3 than on study day 1 (p less than 0.05). We conclude that blood selenium measurements typically used to monitor selenium status do not reflect dietary selenium intakes of orally fed preterm infants.

Enteral Nutrition↗
PubMed1995

Efficacy of cancer prevention by high-selenium garlic is primarily dependent on the action of selenium.

We reported previously that garlic cultivated with selenite fertilization showed powerful chemopreventive activity in the rat dimethylbenz[a]anthracene (DMBA)-induced mammary tumor model (Carcinogenesis 15, 573-576, 1994). In order to ascertain that the efficacy of the high-selenium garlic in cancer protection is primarily dependent on the action of selenium we compared the effects of two batches of garlic powder with marked differences in their level of selenium enrichment, 112 or 1355 p.p.m. Se dry weight. Both products were added to the diet to achieve the same final concentration of 2 p.p.m. Se. The supplementation protocol was designed to evaluate the efficacy during either the initiation phase or post-initiation phase of DMBA mammary carcinogenesis. Significant tumor reduction was observed with either treatment protocol. Furthermore, the magnitude tumor suppression, as well as the extent of DMBA-DNA adduct inhibition, were very similar with the two batches of garlic, even though the amounts of garlic in the diet varied considerably between them (1.8% for the 112 p.p.m. Se garlic versus 0.15% for the 1355 p.p.m. Se garlic). This suggests that the anti-cancer activity of the high-selenium garlic was likely to be accounted for by the effect of selenium, rather than the effect of garlic per se. A continuous feeding of the high-selenium garlic produced a modest increase in total selenium in various tissues. In general the profile of selenium accumulation was comparable in rats ingesting either the 112 or the 1355 p.p.m. Se garlic. Thus, based on the results of several biological responses, it appears that the ability of the high-selenium garlic to protect against tumorigenesis is primarily dependent on increased intake of selenium provided by the vegetable. Future research will be focused on the chemical form of selenium in the garlic.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1995

Altered selenium-binding protein levels associated with selenium resistance.

Our previous studies have sought to elucidate the mechanism by which selenium inhibits cell growth since the mechanisms involved may be relevant to the chemopreventive properties of selenium. In a previous report, we described the isolation of a selenium-resistant cell line, B19, from a selenium-sensitive parental cell line, C57. In this report we identify biochemical changes that may be responsible for conferring selenium resistance. Altered selenium uptake and intracellular glutathione concentrations were eliminated as possible modes of resistance since these two parameters were similar between the two cell lines. However, when the selenium-containing protein complements of the two cell lines were compared by labelling with [75Se]selenite, both increases and decreases in a number of selenium-labelling proteins were found in the B19 cells. The most striking differences were the presence of two 72 kDa selenium-labelling proteins in B19 cells which could not be detected in C57 cells. The levels of a number of mRNAs encoding antioxidant or detoxification enzymes were also compared between the two cell lines but only minor changes were found. This work suggests that further analysis of the 72 kDa selenium-labelling proteins may reveal insights into the mechanisms of growth inhibition by selenium.

Animals↗
PubMed1994

Selenium status and the effect of organic and inorganic selenium supplementation in a group of elderly people in Denmark.

The selenium status of 57 elderly people (> or = 65 years) has been investigated on the basis of selenium concentration in serum, whole blood and erythrocytes and on the basis of the activity of the selenium-dependent enzyme glutathione peroxidase (GSH-px) in erythrocytes and plasma. Thirty-six elderly subjects participated in a 4-month trial of supplementation: 12 subjects were supplemented with 125 micrograms organic selenium, 12 subjects were supplemented with 125 micrograms inorganic selenium and 12 subjects participated as controls. The results showed that the selenium status of the elderly people was not significantly lower than that of younger people (p > 0.05). The effect of organic and inorganic selenium on the activity of GSH-px in plasma and erythrocytes showed a nearly identical increase (25-35%) during the period of supplementation. The effect of inorganic selenium supplementation caused a 30% increase in selenium concentration in plasma and erythrocytes which stabilized after 4 weeks. The effect of organic selenium supplementation on selenium concentration in plasma and erythrocytes showed an increase of up to 100% and 120% during the period of supplementation.

Age Factors↗
PubMed1981

Transfer of selenium from blood to milk in goats and noninterference of copper with selenium metabolism.

The mechanism of selenium secretion by the mammary gland and effects of dietary copper and selenium metabolism on selenium in milk were investigated. Radioactive sodium selective selenite was injected into the jugular vein of lactating goats fed concentrates containing 15 or 115 ppm copper. Blood and milk samples were collected hourly for 8 h and daily for 1 wk. Whole blood, plasma, whole milk, and casein, whey, and cream fractions of milk were counted for selenium-75. No significant differences due to dietary copper were seen. The selenium-75 was primarily associated with the casein in milk. The association of selenium with the whey fraction was greater for early periods than later and varied between animals. The specific activity based on protein content was greater in casein than in whey. Peak selenium-75 in whole milk occurred 2 h after the peak in plasma. On day 7 following selenium-75 dosing, kidney had the highest specific activity, and liver was slightly higher than mammary tissue. All subcellular organelle fractions of liver, kidney, and mammary tissue by homogenization and differential centrifugation contained significant selenium-75. Selenium normally is secreted from the mammary secretory cell in combination with protein through the secretory vesicles, metabolism of selenite prior to milk secretion is important, and copper does not interfere with normal metabolism of selenium.

Animals↗
PubMed1990

The form of selenium determines the response to supplementation in a selenium replete population.

In an ongoing study of selenium bioavailability, effects of supplementation with organic and inorganic forms of selenium were investigated in healthy, Norwegian women, aged 23-50 years. In phase I of the study, 58 women received 200 micrograms selenium per day either as selenite or selenium-rich pea flour for 3 months. The selenium tablets were taken together with placebo or ascorbic acid in a double blind design. Initial blood and serum selenium concentrations were 153 +/- 15 micrograms/l and 117 +/- 12 micrograms/l, respectively. These are average values for Norwegians. Indications of increased blood levels were seen in all groups, but the rise reached significance only for the subgroup receiving selenite and ascorbic acid, 14 micrograms/l, P less than 0.05. On the other hand, selenium analysis of 72-h urine samples confirmed that at an average 50 per cent of the selenium supplements had been absorbed. In phase II of the study, 28 of the participants continued for another 5 weeks, still on 200 micrograms Se per day, but this time consuming commercially available preparations. Of four preparations that were tested, two consisted of yeast Se. Only one of these produced a significant rise in blood and serum selenium levels, 60 and 55 micrograms/l respectively. Blood glutathione peroxidase values were not affected by any supplementation. The study demonstrates that different forms of organic selenium elicit widely different responses when administered to a relatively selenium-replete population, and that the explanation for this must be sought at the metabolic level.

Adult↗
PubMed1988

Effect of selenium supplementation to fertilizers on the selenium status of the population in different parts of Finland.

Concentrations of selenium in the soil are very low in most regions in Finland, which explains the low selenium contents of agricultural plants and the low dietary intake of selenium. The poor selenium status of the population in Finland has been considered a possible risk to public health. In 1984, it was decided to increase the selenium intake by adding selenate to common agricultural fertilizers. In this study, the selenium concentrations of whole blood and plasma, as well as erythrocyte glutathione peroxidase activities, were measured in blood samples from four different localities in Finland, in 1984 and 1986, before and during the agricultural selenium supplementation. A low blood level of selenium in the inhabitants of central Finland was demonstrated in 1984. The selenium level of people from the south-west archipelago was a little higher, and that from the northern part of Finland considerably higher than the level in the rest of the country. By 1986, differences between these localities had almost disappeared, and most levels had increased. Plasma selenium concentrations were lower than those in whole blood samples; the concentrations showed a significant correlation. The glutathione peroxidase activities were at the same level in all four localities in 1984. By 1986, they had all increased to a slightly higher level. A weak correlation was found between erythrocyte glutathione peroxidase activity and blood selenium level.

Adult↗
PubMed1984

Differences in the effects of selenite and biological selenium on the chemical form and distribution of mercury after the simultaneous administration of HgCl2 and selenium to rats.

The interaction was compared between inorganic (HgCl2) mercury and selenite (Na2SeO3) vs. the interaction between inorganic mercury and biological selenium (a freeze-dried preparation of liver from rats treated with selenite). Organ concentrations of selenium were always significantly lower after biological selenium than after selenite. Biological selenium affected the organ distribution of inorganic mercury differently than selenite. Furthermore, the speciation of mercury was affected by this form of selenium. A mercury-selenide compound (presumably HgSe) accounted for a greater proportion of total mercury in tissues after selenite than after a dose of biological selenium. Administration of selenomethionine had a similar effect on the speciation of mercury to that seen after biological selenium. As the forms of selenium in selenomethionine or selenium deposited in the liver are most likely nearer than selenite to selenium present in food, our results suggest that, as far as the reaction of mercury with selenide is concerned, experiments with selenite overestimate the protective effect of dietary selenium against inorganic mercury and possibly against methylmercury.

Animals↗
PubMedDate not supplied

Effect of selenium supplementation on platelet selenium, glutathione peroxidase, and aggregation.

The selenium content of platelets is extremely high. About half of this selenium originates from irreversible incorporation by bone marrow precursor cells, which satisfy their need for selenium even under conditions of marked selenium deficiency. In order to study the effect of increased dietary selenium supply on the concentration of selenium, glutathione peroxidase (GSH-Px-) activity, and aggregability of platelets, normal healthy subjects were supplemented with 300 micrograms of selenium as Se-rich yeast/d for 3 mo. No significant effect of Se supplementation on platelet Se and GSH-Px were observed, whereas erythrocytes accumulated Se without reaching saturation. Although platelet aggregability was variable during the period of observation, this was traced back to factors other than selenium, including environmental temperature. This study demonstrates that the selenium concentration of platelets is subject to tight physiological control also at high dietary selenium intakes.

Adult↗
PubMed1983

Selenium-dependent and non-selenium-dependent glutathione peroxidases in human tissue extracts.

A method for the assessment of both selenium-dependent and non-selenium-dependent glutathione peroxidases on crude tissue extracts in human is described. The enzyme activity is measured by the coupled assay system in which oxidation of reduced glutathione (GSH) is coupled to NADPH oxidation catalyzed by glutathione reductase. Total glutathione peroxidase activity is measured with cumene hydroperoxide as substrate. Selenium-dependent glutathione peroxidase is measured with tert-butyl hydroperoxide. This substrate is preferable to H2O2 which gives too high blank values compared to the assay values. The difference between total glutathione peroxidase and selenium-dependent glutathione peroxidase activities represents the non-selenium-dependent glutathione peroxidase activity. Studies of substrate specificity of the two glutathione peroxidases separated by gel filtration as well as linearity and recovery studies are presented. For a given tissue, the relative amounts of the two glutathione peroxidases given by our assay are identical to those estimated by quantifying the elution peaks after gel filtration. Based on the percentages of the two glutathione peroxidases, human tissues can be classified in four groups: (1) the non-selenium-dependent glutathione peroxidase is predominant in liver, in renal cortex and skeletal muscle; (2) non-selenium-dependent and selenium-dependent glutathione peroxidases are in equal amounts in renal medulla; (3) the selenium-dependent glutathione peroxidase is predominant in adrenal glands and platelets; (4) the selenium-dependent glutathione peroxidase represents 100% of the glutathione peroxidase activity in the other organs. The heart and the brain are of special interest in this group because of the physiological role and the regulation of the selenoenzyme.

Chromatography, Gel↗
PubMed1995

Effect of nationwide selenium supplementation in Finland on selenium status in children with juvenile rheumatoid arthritis. A ten-year follow-up study.

A study was performed on the effect of increased selenium intake on the serum selenium level of 212 children with juvenile rheumatoid arthritis (JRA) and of 214 controls in a follow-up study during the Finnish nationwide selenium fertilization programme, which was started in 1984. The mean serum level of selenium increased from 0.90 mumol l-1 in 1985 to 1.56 mumol l-1 in 1990 in the children with JRA. The corresponding selenium levels in the controls were 0.87 mumol l-1 in 1985 and 1.33 mumol l-1 in 1990. Boys had slightly higher selenium levels in all the age groups among the patients and the controls. During the entire 10-year observation period, the patients with JRA had slightly higher mean levels of selenium than the controls. The age of the children did not have any significant effect on the selenium level in either group. The present study shows that the main factor affecting the serum level of selenium was the dietary intake of selenium both in patients and in healthy controls.

Adolescent↗
PubMed1980

A biological assay for determination of availability of selenium for restoring blood plasma gluthathione peroxidase activity in selenium-depleted chicks.

This study was undertaken to develop an assay for the determination of biological availability of selenium. In a preliminary experiment, commercial male, White Leghorn chicks had significantly reduced glutathione peroxidase activity in blood plasma after 7 days of depletion on a selenium-deficient (0.04 ppm of Se) diet. Selenium-depleted chicks fed graded levels of selenium (0.02--0.10 ppm in steps of 0.02 ppm) for 9 days had glutathione peroxidase activity in blood plasma which was linearly, highly correlated with dietary selenium content. In three subsequent experiments, chicks were fed a selenium-deficient diet for 7 days and were then distributed into groups of five chicks each. The standard diets, which contained 0.02, 0.04, 0.06, 0.08 and 0.10 ppm of selenium added as NaHSeO3, and the test diets, which contained three levels of each test substance and provided selenium supplements within the standard range, were each fed to three groups of chicks for 9 days. The dose parameter was selenium, in the standard groups added as NaHSeO3 and in the test groups provided by the selenium present in the test substance. The response parameter was blood plasma glutathione peroxidase activity. Statistical analyses of the results utilizing four fish meals as test substances revealed that the assay complied with the requirements for statistical and fundamental validity.

Animals↗
PubMed1984

Effects of a low selenium status on the distribution and retention of selenium in the rat.

In the tissues of rats fed a selenium-deficient diet the changes in the selenium content and the retention of the element after administration of a small amount of selenium to the depleted animals were determined. In the liver and in the erythrocytes, which are the main glutathione peroxidase pools, the decrease in the selenium content was great and the retention in the depleted rats only slightly increased in comparison with the control animals fed sufficient amounts of the element. In the testes and in the adrenals the decreases in the selenium content were the smallest, and here retention was about 15 times greater than in the control animals. Also in other tissues, such as the thymus, spleen, bone and kidney, retention was considerably increased in the depleted rats. The results indicate that regulation mechanisms exist, which in nutritional selenium deficiency cause reduced excretion of the element and priority of supply to certain tissues. This, in turn, leads to a redistribution of selenium in the organism and, as the glutathione peroxidase decreases to a greater extent than the selenium, also to a redistribution of the element among its different binding forms. As the selenium content is most probably kept up in particular in sites in which the element is most needed, the findings suggest important functions of selenium in these tissues.

Adrenal Glands↗
PubMed1985

Selenium supplementation in X-linked muscular dystrophy. Effects on erythrocyte and serum selenium and on erythrocyte glutathione peroxidase activity.

The selenium concentrations in serum and erythrocytes and the erythrocyte glutathione peroxidase activity were determined in 15 boys with the Duchenne type and in 5 boys with the Becker type of X-linked muscular dystrophy before and during long-term selenium and alpha-tocopherol supplementation and compared with values in unsupplemented controls. The purpose of the treatment was to improve the muscular strength. Twelve of the 20 patients had pretreatment levels of selenium in serum that were within the 95% confidence limit of the unsupplemented control children. The values in 2 patients, both with the Duchenne type of muscular dystrophy, fell below this level. Selenium supplementation in a daily dose of 6 micrograms/kg/day for 6 months caused a substantial rise in both serum and erythrocyte selenium, suggesting suboptimal pretreatment body contents of selenium. The greatest increases in both serum and erythrocyte selenium were observed in subjects with initially low selenium levels. Only in 4 of the 20 patients did the selenium supplementation result in a significant rise in erythrocyte glutathione peroxidase activity. As no sure improvement was noted in muscular strength during this treatment period, the Se dose was increased to 20 micrograms/kg/day. This resulted in a further rise in both serum and erythrocyte selenium, but not in erythrocyte glutathione peroxidase activity.

Adolescent↗
PubMed1992

Glutathione redox cycle enzymes and selenium in severe rheumatoid arthritis: lack of antioxidative response to selenium supplementation in polymorphonuclear leucocytes.

The antioxidant capacity of the glutathione redox cycle and the concentrations of selenium in serum, red blood cells or whole blood, and polymorphonuclear leucocytes was evaluated in nine patients with severe rheumatoid arthritis (RA) and eight healthy controls receiving daily supplementation with 250 micrograms selenomethionine for six months. Serum and whole blood concentrations of selenium and the activity of the selenium dependent enzyme glutathione peroxidase (GSH-Px) were low in the serum, red blood cells, and polymorphonuclear leucocytes of patients with RA before selenium supplementation. During supplementation serum and whole blood concentrations of selenium and the activity of GSH-Px in serum and red blood cells of patients with RA and serum GSH-Px in controls increased. Selenium and GSH-Px in polymorphonuclear leucocytes were unaffected in patients with RA in contrast with the controls where both were augmented. Glutathione reductase activity in the red blood cells and polymorphonuclear leucocytes of patients with RA was low but increased during selenium supplementation. Whole blood concentrations of glutathione were slightly lower in patients with RA than controls and no difference in the content in polymorphonuclear leucocytes was found between the groups. The activity in red blood cells of glucose-6-phosphate dehydrogenase was high in patients with RA, indicating sufficient function of the hexose monophosphate pathway. The reduced antioxidant activity of the glutathione redox cycle in patients with severe RA was mainly due to the low availability of selenium. This was further supported by the response to selenium supplementation in serum and red blood cells. In the polymorphonuclear leucocytes, however, no biochemical effects of selenium supplementation were seen. This lack of antioxidative response could play a pathogenetic part in inflammation in patients with RA.

Adult↗
PubMed1990

Dietary selenium intakes and plasma selenium concentrations of formula-fed and cow's milk-fed infants.

The plasma selenium concentrations of 57 infants 8 to 12 months of age were assessed using flameless atomic absorption spectrophotometry. The infants ingested either cow's milk or whey-predominant milk-based infant formula as their primary beverage as part of a mixed diet for at least 3 months. The calculated mean +/- standard deviation (SD) daily dietary selenium intake of 26 infants fed cow's milk (34 +/- 13 micrograms), assessed by a 3-day diet record and/or a 24-hour diet recall, was significantly (p less than or equal to .001) greater than that of 31 formula-fed infants (22 +/- 11 micrograms). The mean +/- SD plasma selenium concentration of infants fed cow's milk (39 +/- 11 micrograms/L) was also significantly (p less than or equal to .05) greater than that of infants fed formula (31 +/- 12 micrograms/L). Both groups of infants ingested similar amounts of total energy; however, the infants fed cow's milk received more total protein and selenium and a greater percentage of protein and selenium from their primary beverage than did the infants receiving formula. Both groups of infants were consuming a mixed diet with similar sources of selenium. To examine the selenium status of infants as well as other individuals better, further analysis of foods is clearly needed to provide more information on dietary selenium sources. The influence of variables such as body size and ethnicity, intake, sources and forms of dietary protein, and dietary forms of selenium on plasma selenium concentrations must also be investigated.

Animals↗