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PubMed1983

Selenium status of a rural (predominantly Amish) community living in a low-selenium area.

Selenium intake and blood selenium and selenium-dependent glutathione peroxidase concentrations were assessed in a rural, 71% Amish, sample of residents in a region with low availability of soil selenium and in urban (Columbus, OH) residents. Subjects were interviewed (24-h dietary recalls) on three separate occasions over an 18-month period, and blood and food samples were taken for analysis (maximum subject observations = 452). Mean selenium intake of the entire population was 82.8 +/- 4.4 micrograms/day. Rural and urban residents at 82.0 +/- 4.9 and 83.6 +/- 4.4 micrograms/day, respectively, did not differ significantly in intake. A breakdown by gender within location demonstrated that rural males consumed the most selenium (104.7 +/- 6.1 micrograms/day) and rural females the least (59.3 +/- 6.3 micrograms/day). Rural subject groups had significantly lower mean whole blood, plasma, and erythrocyte selenium levels (12.5 to 14.5%) as well as blood selenium-dependent glutathione peroxidase concentrations (5.6 to 10.8%) than urban groups. Subjects in both cohorts were in adequate selenium status as judged by blood parameters, even though about one-fourth of the dietary observations were below the safe and adequate range of selenium intake established by the Food and Nutrition Board. The rural diet was 18.3% lower in selenium density than the urban diet. High selenium grain products (greater than 0.2 micrograms/g) were the most important dietary selenium source in both groups, providing 29.3 to 41.6% of total intake.

Adolescent↗
PubMed1990

Selenium intake, age, gender, and smoking in relation to indices of selenium status of adults residing in a seleniferous area.

Duplicate meals, serum, whole blood, and toenails were collected every 3 mo for 1 y from a group of 44 free-living adults residing in high-selenium areas of South Dakota and Wyoming to assess the relation of selenium intake to indices of selenium status. The average selenium values for the group were as follows: dietary intake, 174 +/- 91 micrograms/d (mean +/- SD), 2.33 +/- 1.08 micrograms/kg body wt; serum, 2.10 +/- 0.38 mumol/L; whole blood, 3.22 +/- 0.79 mumol/L; and toenails, 15.2 +/- 3.0 nmol/g. Selenium intake (micrograms/kg body wt) was strongly correlated (all values, P less than 0.01) with selenium concentration of serum (r = 0.63), whole blood (r = 0.62), and toenails (r = 0.59). Men and women had similar mean values of serum, whole blood, and toenail selenium despite higher selenium intakes in men. Smokers had lower tissue selenium concentrations than did nonsmokers due, at least in part, to lower selenium intake. Age was not associated with tissue selenium content. Of the variables examined selenium intake was clearly the strongest predictor of tissue selenium concentration.

Adult↗
PubMedDate not supplied

The effect of selenium supplementation on selenium status of patients receiving chronic total parenteral nutrition.

Patients receiving long-term total parenteral nutrition (TPN) are at risk for selenium deficiency. The purpose of this study was to determine the effect of parenteral selenium as selenious acid on the selenium status of seven long-term TPN patients. Patients received a dosage of zero, 80, or 160 micrograms Se/day for 1 month each. The measures of selenium status used were selenium levels in plasma and glutathione-peroxidase activities in erythrocytes and platelets. Urinary selenium excretion was measured. Control subjects were selected to match the sex, age, and weight of the patients. With increasing levels of parenteral selenium, there was increasing plasma selenium concentration as well as erythrocyte and platelet glutathione-peroxidase activity. There was no statistical difference between the patients during the time they received the 160 micrograms parenteral selenium treatment and the control subjects for platelet glutathione-peroxidase activity. At the 160 micrograms Se/day level, patient plasma selenium concentrations increased from 28% to 58% of the control levels. Four patients were studied after they returned to the 80 micrograms parenteral selenium/day from the 160-micrograms Se/day treatment. With decreasing parenteral selenium, three patients had decreasing platelet glutathione-peroxidase activity, while plasma selenium concentration decreased in two patients. These data suggest that some patients receiving long-term parenteral nutrition should receive parenteral selenium.

Adult↗
PubMed1990

Elevation of rat liver mRNA for selenium-dependent glutathione peroxidase by selenium deficiency.

Selenium-dependent glutathione peroxidase (Se-GSH-Px, GSH-H2O2 oxidoreductase EC 1.11.1.9) is the best characterized selenoprotein in higher animals, but the mechanism whereby selenium becomes incorporated into the enzyme protein remains under investigation. To elucidate the mechanism of insertion of selenium into Ge-GSH-Px further, we have systematically analyzed and compared the results of Western blot, in vitro translation immunoprecipitation, and Northern blot experiments conducted with liver proteins and RNAs obtained from rats fed on selenium-deficient and selenium-supplemented diets. The anti-serum employed in this study was raised against an electrophoretically pure Se-GSH-Px preparation obtained from rat livers by a simplified purification procedure involving separation by high performance liquid chromatography on a hydrophobic interaction column. Different forms of Se-GSH-Px, including apo-protein, cross-reacted with this antiserum and Western blot analysis found no Se-GSH-Px protein present in livers from rats fed on selenium-deficient diets. By contrast, a distinct protein band corresponding to purified Se-GSH-Px was detected in livers from selenium-supplemented animals, a result consistent with the finding that the Se-GSH-Px activity was reduced to undetectable levels in livers of selenium-deficient rats. The in vitro translation experiments, however, indicated not only that mRNA for Se-GSH-Px was present during selenium deficiency but also that its translation products contained 2-3-fold as much immunoprecipitable protein as the products of poly(A) RNA from livers of selenium-supplemented rats. This result suggests that the Se-GSH-Px mRNA may be increased in the selenium-deficient state. Elevated levels of Se-GSH-Px mRNA were directly demonstrated in Northern blot experiments employing cDNA clone pGPX1211 as a probe. A similar increase in Se-GSH-Px mRNA was observed in such other tissues as kidney, testis, brain, and lung tissue, in selenium-deficient states. The present data support the co-translational mechanism for the incorporation of selenium into Se-GSH-Px in rat liver.

Animals↗
PubMed1993

Plasma and liver selenium levels in the rat during supplementation with 0.5, 2, 6, and 15 ppm selenium in drinking water.

Plasma and liver selenium of Wistar rats were determined after 1, 3, and 6 mo supplementation with 0.5, 2, 6, or 15 ppm selenium as sodium selenite in drinking water. Plasma selenium was not different from control values at additional intake of 0.5 ppm but increased above usual levels at higher intakes. A highly significant correlation was observed between the total quantity of selenium ingested and plasma selenium after 1 mo treatment (r = 0.99, p < 0.01), but was less pronounced after 3 and 6 mo (0.94, p < 0.05, and 0.78, p < 0.05, respectively). The decrease in plasma selenium with time of treatment was more pronounced at higher intakes. There was also a highly significant correlation between total selenium intake and liver selenium concentration (r = 0.99, p < 0.01) after 1 mo of treatment, but this time liver selenium did not change with time, and the correlation remained highly significant throughout the investigation. Liver selenium therefore appears as a more sensitive and more representative measure of selenium intake than plasma selenium. Most supplements did not affect body weight and survival of animals, except when the diet was supplemented with 15 ppm for 6 mo; however, alterations in biochemical parameters concerning lipid status and hepatic function were observed at levels above 2.0 ppm.

Animals↗
PubMed1988

Effect of dietary sodium nitroprusside as a source of cyanide on the selenium status of chicks given diets of varying selenium concentration.

1. The interaction between dietary cyanide, given in the form of sodium nitroprusside (SNP), and selenium has been studied in two experiments with growing chicks from 14 to 38 d of age. 2. In experiment 1, dietary selenium at 10 mg Se/kg reduced growth, food intake and efficiency of utilisation, and increased relative liver size and selenium content. All of these effects were eliminated by the addition of 0.1 g SNP/kg except for liver selenium content, which progressively declined towards control values as SNP was increased to 0.4 g/kg in increments of 0.1 g/kg. At 0.3 g SNP/kg, cyanide toxicity, as judged by decreased growth, reached significance. 3. In experiment 2, similar effects were observed with selenium at 10 mg Se/kg and SNP at 0.3 g/kg, but selenium deficiency was not evident from growth indicators when selenium supplementation of the diet was omitted completely, nor did these indicators suggest that deficiency was induced by cyanide. 4. In both experiments, plasma and liver glutathione peroxidase activity reflected the dietary selenium content. There was an interaction with dietary SNP content. With selenium intake at a toxic level, SNP increased enzyme activity, further evidence of alleviation of selenium toxicity, but when selenium intake was low and normal, SNP decreased activity in liver, an indication that cyanide could induce deficiency. 5. A possible mechanism for alleviation of selenium toxicity is proposed.

Animals↗
PubMed1985

Effect of selenium supplementation on selenium balance in the dependent elderly.

Although trace minerals are necessary constituents of enzymes, dietary requirements of these nutrients for the elderly are unknown. This study measured selenium balance in six dependent elderly men before and after five weeks daily administration of 200 micrograms organically-bound selenium; dietary selenium intake averaged 62.1 +/- 7 micrograms/day during both study periods. Selenium status was assessed not only chemically but also biologically as red cell and platelet glutathione peroxidase activities. Plasma selenium averaged 8.8 +/- 0.8 micrograms% (normal: 10 +/- 2 micrograms %) when intake derived from dietary sources alone and increased during medicinal supplementation to an average of 12.8 +/- 1.9 micrograms %. The rise in plasma selenium was not associated with an increase in red cell or platelet glutathione peroxidase activity. The effect of selenium supplementation on in vivo platelet aggregability was studied by measuring plasma levels of beta-thromboglobulin and platelet factor 4, two proteins secreted concomitant with aggregation. beta-thromboglobulin diminished 7.5 +/- 11.0 ng/ml and platelet factor 7.6 +/- 11.0 ng/ml during selenium supplementation despite no change in platelet glutathione peroxidase activity. These data support the concept that selenium nutritional status should be assessed not only by blood selenium content but also by selenium-dependent enzyme activity or selenium-dependent biologic effect.

Aged↗
PubMed1995

Selenium status of New Zealand infants fed either a selenium supplemented or a standard formula.

OBJECTIVE: New Zealand soils are deficient in the essential micronutrient, selenium. New Zealand infants have low selenium levels at birth and experience a further decline if fed cows milk based formula. This study examined the selenium status of infants fed with a new commercially available selenium supplemented formula. METHODOLOGY: Forty-four newborn infants, whose mothers wished to formula feed, were randomized in an open controlled trial to be fed a commercially available selenium supplemented cows milk formula (containing 17 micrograms Se/L) or an unsupplemented formula (containing 4.6 micrograms Se/L). Cord, 1 and 3 month blood samples were obtained for selenium status (plasma and red cell selenium and glutathione peroxidase) and thyroid function. RESULTS: Mean plasma selenium and glutathione peroxidase values were significantly higher in supplemented than unsupplemented infants at 1 month (unpaired t-tests; P < 0.0001 and P = 0.001 respectively) and 3 months (P < 0.0001 and P = 0.0005). Analysis within treatment groups between time points (paired t-tests) showed that selenium supplementation prevented the fall in plasma selenium from birth to 1 month seen in unsupplemented infants and was associated with a rise in levels between 1 and 3 months (P = 0.002). CONCLUSIONS: Supplementing cows milk formula with selenium to replicate the levels found in breast milk is nutritionally sound. Feeding from a few days of age with a formula containing 17 micrograms Se/L in infants with low selenium status at birth is sufficient to cause a rise to 80% of adult levels at 3 months of age.

Analysis of Variance↗
PubMed1975

Distribution of selenium in egg white and yolk after feeding natural and synthetic selenium compounds.

Practical diets containing various selenium levels, with and without selenite supplementation, were fed to hens. Eggs were then collected over a 14-day period to determine how quickly changes in dietary selenium affected egg white and yolk selenium. Changes in egg white selenium content were rapid and essentially completed seven days after changing the selenium content of a practical diet. Changes in egg yolk were not yet completed by 14 days. When selenium from practical feedstuffs was fed, the selenium content of dried egg white was about equal to or greater than the selenium content of dried egg yolk. When selenite was fed, the selenium content of dried yolk was higher. Feeding selenomethionine resulted in more selenium in egg white than in egg yolk. Feeding selenocystine resulted in more selenium in egg yolk than egg white, a pattern similar to that from feeding selenite. The data suggest that selenocystine is not incorporated into protein but is metabolized to an inorganic selenium compound.

Animal Feed↗
PubMed1978

[Distribution pattern, statistical analysis and correlation of selenium levels in swine selenium-indicating organs].

There is a potential risk of excessive selenium levels in organs of swine, resulting in toxicity and residues in pork, or selenium deficit. Therefore, random selenium mean values in "selenium-indicating" organs of pigs selected from suspicious populations were compared with mean and limiting values (reference or normal values) recorded from animals with intact metabolism. Prerequisites required for such comparative assessment included the availability of estimated variance values and knowledge of the presence of abscence of agreement between normal distribution and empirical frequency distribution for the population concerned. Knowledge must be available also on the informative value of measured selenium data in blood plasma and their relevance to the general selenium situation in the organism and muscle at large. These were some of the problems studied by determining selenium levels in the liver, kidneys, blood plasma, and M. longissimus dorsi. Organic selenium concentrations were found to be distributed with right axis deviation but almost normal. The parameters established were typical of the majority of data known from literature. Those date, however, are quite variable, so that the need for independently prepared reference values cannot be abandoned. Correlation analysis showed reciprocal relationships between selenium levels in blooc plasma, liver, and muscles but much less correlation between these, on the one hand, and selenium in kidneys, on the other. The correlations between blood plasma and muscle selenium were close enough to take blood plasma values recorded from the living animal as reference from which to draw conclusions as to the muscular selenium state.

Animals↗
PubMed1977

Sulphur-selenium studies in sheep. I. The effects of varying dietary sulphate and selenomethionine on sulphur, nitrogen and selenium metabolism in sheep.

Sulphur, selenium and nitrogen metabolism were studied in Merino wethers fed for 35-day periods on semipurified diets in which the sulphur content was increased to either 0-07 or 0-20% by the addition of sodium sulphate. At both levels of sulphur, additions of selenium as DL-selenomethionine increased the basal level of selenium (0-02 microgram/g) to 0-06, 0-09 and 0-67 microgram/g. Both levels of dietary sulphur supported positive sulphur balances but a reduction in sulphur intake per se resulted in a significant depression in dry matter digestibility (P less than 0-05), apparent nitrogen digestibility (P less than 0-05), nitrogen balance (P less than 0-01), sulphur balance (P less than 0-05) and plasma sulphate-sulphur (P less than 0-05) and wool (P less than 0-01) selenium levels. Selenium balance was not affected by differences in sulphate-sulphur intake. Selenium balances (P less than 0-001), plus the selenium levels in plasma (P less than 0-001), and wool (P less than 0-001) were significantly different at the different levels of selenium supplementation. A positive selenium balance was achieved when the selenium intake was approximately 37 microgram/day, regardless of sulphur treatment. The validity of using plasma and/or wool selenium levels as indices of the selenium status of sheep is questioned.

Animals↗
PubMed1988

Dose-dependent distribution of injected selenium in rat blood. Effect of previous selenium intake in drinking water.

The effect of an administered dose of 75Se-selenite and a previously increased selenium intake in drinking water (0.1 mg/l) on the distribution of injected selenium in rat blood was studied. In a dose range of 0.01-1.6 mg Se/kg body weight the ratio of injected selenium in blood plasma and in blood cells decreased from 3.20 in rats with increased selenium intake and 4.60 in rats without this intake, to 0.13 and 0.10, respectively. After injection of high selenite doses, 85-88% of the selenium present in the blood was localized in blood cells irrespective of increased selenium intake by drinking water. Possible relationship between accumulation of selenium in blood cells and its toxic effect in the organism is discussed. Previously increased intake of selenium had no effect on the levels of selenium in blood cells but affected significantly its plasma levels. The results indicate that the previously increased selenium intake in drinking water increases the capacity of the plasma for selenium injected in the form of selenite.

Animals↗
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↗