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PubMed1989

Biochemical studies of a selenium-deficient population in China: measurement of selenium, glutathione peroxidase and other oxidant defense indices in blood.

Selenium deficiency is necessary for the development of the cardiomyopathy known as Keshan disease. Healthy boys and men (19-22 per group) from a low selenium area (Dechang County) and from an area where sodium selenite was added to salt (Mianning County) were studied. Keshan disease was endemic in Dechang but occurred rarely in Mianning. After an initial blood sampling, each subject received daily selenium supplements (100 micrograms selenium for boys and 200 micrograms for men) as sodium selenate for 14 d. Blood was sampled again at 7 and 14 d. Boys from Dechang had blood selenium levels similar to levels reported for patients with Keshan disease. Plasma glutathione peroxidase activity in boys and men from Dechang was 33 and 43%, respectively, of values from the corresponding groups in Mianning. Comparison of plasma selenium concentrations in boys and men from Dechang gave values of 33 and 38%, respectively, of the corresponding groups in Mianning. Selenium status did not affect red blood cell superoxide dismutase or catalase activities. Plasma vitamin E concentration was below the normal range in all groups but was unaffected by selenium status. Measurements of plasma malondialdehyde revealed no difference between subjects from Dechang and subjects from Mianning. Selenium supplementation raised plasma glutathione peroxidase activity and plasma selenium concentration in all groups. Groups with higher plasma selenium concentration had relatively smaller increases in glutathione peroxidase activity than in selenium concentration. These results characterize the selenium deficiency in subjects at risk for developing Keshan disease. The results obtained with supplementation of selenium indicate the presence of additional plasma forms of selenium besides glutathione peroxidase.

Adolescent↗

PubMed2004

Selenium in pregnancy: is selenium an active defective ion against environmental chemical stress?

Transportation of selenium from mother to fetus and its possible effects on mother's zinc, copper, cadmium, and mercury levels were studied together during the first trimester and at term in 216 mothers. Mothers came from three geographical places with different selenium intakes. The role of selenium as a biomarker for the vital function was estimated by studying the associations between tissue or blood selenium content and placental cytochrome P450 enzyme activities and the newborn's birth weight. Regardless of the selenium intake of the mothers, higher concentrations were found in the cord blood than in mother's blood reflecting active transportation of selenium to the fetus. Active smoking was associated with higher placental selenium concentrations like it is associated with higher placental zinc concentrations. When the cadmium concentrations were high in placenta, as in smokers, the transfer of selenium from blood to placenta was increased, decreasing the selenium levels in blood. On the other hand, the high selenium concentrations in blood were connected to lower cadmium concentrations in placenta also in nonsmokers. Selenium had correlations with copper and zinc. ECOD activity in placental tissue, mercury in mothers' hair, mothers' age, and selenium concentrations in cord blood and placental selenium all seem to have connections with xenobiotic-metabolizing enzymes linked effects among mothers. These data suggest that selenium has an active role in the mother's defense systems against the toxicity of environmental pollutants and the constituents of cigarette smoke.

Adult↗

PubMed2000

Preparation of selenium yeasts I. Preparation of selenium-enriched Saccharomyces cerevisiae.

Selenium (Se) is an essential micronutrient for human and animal organisms. Organic selenium complexes and selenium-containing amino acids are considered the most bioavailable. Under appropriate conditions yeasts are capable of accumulating large amounts of trace elements, such as selenium, and incorporating them into organic compounds. It has been found that introduction of water-soluble selenium salt as a component of the culture medium for yeasts produced by conventional batch processing results in a substantial amount of selenium being absorbed by the yeast. Using a culture medium supplemented with 30 microg/mL sodium-selenite added during the exponential growth phase results in selenium-accumulation in the range of 1200-1400 microg/g dried baker's yeast (Saccharomyces cerevisiae) measured by ICP-AES method. In our previous studies it was shown that higher amounts of sodium-selenite in the culture medium have a strong inhibitory effect on the growth of this yeast. As a consequence of variations in cultivation conditions we obtained selenium yeast with different inorganic selenium content. The most important parameters influencing incorporated forms of selenium are pH value and dissolved oxygen level in the culture medium, and depending on these the selenium consumption rate of the yeast. A 0.40-0.50 mg/g h-1 specific selenium consumption rate was found to be appropriate to obtain selenium-enriched bakers' yeast of a high quality. Under suitable conditions the undesirable inorganic selenium content of the yeast could be suppressed to as low as 5-6% at the expense, however, of approximately a 20% decrease in the final biomass.

Culture Media↗

PubMed1998

Distribution of selenium between plasma fractions in guinea pigs and humans with various intakes of dietary selenium.

The distribution of selenium between the plasma fractions was investigated in guinea pigs fed various levels (basal, 0.5, 1.0, 2.0, 4.0, 6.0 and 8.0 mg Se/kg) of dietary selenomethionine (Semet) and in humans living in different areas of China with different selenium status. There was a corresponding increase of selenium concentration in liver, kidney, brain, testis, spleen, heart and muscle with each increase of dietary selenium, but there were no increases of glutathione peroxidase (GPX) activity in liver, brain, testis, heart or muscle in pigs fed any of the selenium levels as compared to controls fed a basal commercial diet. On a percentage distribution basis, the selenium in selenoprotein P decreased and that in the albumin fraction increased with increased dietary intakes of selenium as Semet. The ratios of selenium to albumin in either the plasma or the albumin fractions increased with each increase in dietary selenium. The greatest percentage of selenium was in the albumin fraction of Chinese living in the high selenium areas whereas the greatest amount was in the selenoprotein P fraction in subjects living in deficient and adequate areas of China. Increases in the ratios of selenium to albumin in either the plasma or the albumin fraction also occurred with increases of selenium intake of these subjects. The results indicate that the distribution of selenium in plasma fractions reflect the levels of dietary intakes of Semet.

Adult↗

PubMed2004

Assessment of requirements for selenium and adequacy of selenium status: a review.

OBJECTIVE: The intent of this review is to evaluate the scientific evidence for the assessment of adequacy of selenium status and of the requirements for selenium. From this evidence, attempts have been made to define levels of plasma selenium and dietary selenium intake, which could be used for the assessment of deficiency or adequacy of selenium status. METHOD: The first section briefly reviews the methods for assessment of selenium status. The second section outlines the requirements for selenium based on a number of criteria, and how these have been translated into recommended intakes of selenium. In the final section, levels of plasma selenium and dietary intake based on different criteria of adequacy have been proposed. RESULTS AND CONCLUSION: The minimum requirement for selenium is that which prevents the deficiency disease, Keshan disease. The recommended intakes of selenium have been calculated from the requirement for optimum plasma glutathione peroxidase (GPx) activity that must, because of the hierarchy of selenoproteins, also take account of the amounts needed for normal levels of other biologically necessary selenium compounds. Whether optimal health depends upon maximization of GPx or other selenoproteins, however, has yet to be resolved, and the consequences of less-than-maximal GPx activities or mRNA levels need investigation. Intakes, higher than recommended intakes, and plasma selenium concentrations that might be protective for cancer or result in other additional health benefits have been proposed. There is an urgent need for more large-scale trials to assess any such beneficial effects and to provide further data on which to base more reliable estimates for intakes and plasma selenium levels that are protective.

Glutathione Peroxidase↗

PubMed2001

The lowering effect of high copper intake on selenium retention in weanling rats depends on the selenium concentration of the diet.

The question addressed was whether the influence of dietary copper concentration on selenium metabolism depends on the amount of selenium in the diet. Weanling, male rats were fed purified diets containing either 1 (low), 4 (normal) or 42 (high) mg Cu/kg diet and either 0.03 (low), 0.05 (normal) or 1.0 (high) mg Se/kg diet in a 3(2) factorial design. Extra copper was added to the diets in the form of CuSO(4) x 5H(2)O and selenium as Na(2)SeO(3) x 5H(2)O. In rats fed either the low or normal amounts of selenium, higher intakes of copper decreased the apparent intestinal selenium absorption and increased urinary selenium excretion. The effects of copper on selenium absorption, excretion and retention were not seen in rats fed the high-selenium diets. An increase in dietary copper concentrations elevated selenium concentrations in the liver and kidneys, but slightly lowered those in the spleen of rats that were fed the diets with the normal level of selenium. In rats that were fed the diets with either low or high selenium concentration, copper intake had no effect on organ selenium concentrations. Glutathione peroxidase activity in erythrocytes was raised by feeding the diets which contained either normal or high copper content instead of those that were low in copper. It is concluded that the amount of selenium in the diet determines whether or not an increase in dietary copper concentration affects selenium metabolism.

Animals↗

PubMed1993

Selenium status of lactating women is affected by the form of selenium consumed.

The impact of providing selenomethionine (2.7 mumol Se) or selenium-enriched yeast (2.9 mumol Se) on the selenium status of lactating and nonlactating women with customary intakes of approximately 1.3 mumol Se/d was studied. Plasma selenium declined in unsupplemented lactating women but not in nonlactating women. Selenomethionine increased plasma selenium in both lactating and nonlactating women whereas selenium-enriched yeast increased plasma selenium only in nonlactating women. Erythrocyte selenium concentration was not significantly modified by lactation. Plasma glutathione peroxidase (GPx) activity decreased with duration of lactation in unsupplemented women and selenomethionine or selenium-enriched yeast supplementation prevented the decline. Milk selenium declined markedly for 20 wk after parturition in unsupplemented women. Selenomethionine significantly increased milk selenium concentrations whereas selenium-enriched yeast prevented a decline. These results clearly show that the source of selenium provided to lactating women can significantly influence selected indexes of selenium status, including milk selenium concentration.

Adolescent↗

PubMed2002

Serum selenium and risk of large size colorectal adenomas in a geographical area with a low selenium status.

OBJECTIVE: Selenium is a fundamental nutrient to human health that might have anticarcinogenic effects. Previous studies have assessed the possible relationship of selenium status to colorectal adenomas with controversial results. We primarily aimed to assess the relationship of serum selenium status with the presence of large size colorectal adenomas in subjects living in a poor selenium region. The serum selenium status in colorectal cancer was also evaluated. METHODS: Serum selenium levels were measured in 28 patients with large size sporadic adenomatous polyps, 24 patients with colorectal adenocarcinomas, and 35 age-matched healthy individuals. A logistic regression analysis was performed to assess the relationship of serum selenium to colorectal adenomatous polyps after adjusting for confounding variables (age, sex, smoking habit, and alcohol drinking). RESULTS: Among subjects aged < or = 60 yr, mean serum selenium levels were significantly lower in both patient groups (adenoma, 57.9 +/- 4.3 microg/L; cancer, 43.7 +/- 6.6 microg/L) than in healthy controls (88.9 +/- 8 microg/L) (p = 0.0001). There were no difference among subjects > 60 yr old. A significant inverse association between selenium status and the diagnosis of large size adenomatous polyps after adjusting for confounding variables was found (adjusted p = 0.029). Subjects with higher selenium status (> or = 75th percentile value of 82.11 microg/L) had a lower probability (OR = 0.17, 95% CI = 0.03-0.84) to be in the adenoma group than subjects with lower selenium status (< 82.11 microg/L). This association was more marked in subjects aged < or = 60 yr (adjusted p value = 0.04, OR = 0.08, 95% CI = 0.007-0.91), and was not significant in older subjects. CONCLUSIONS: Results suggest that high selenium status may decrease the risk of large size adenomas in a low selenium region, and that this preventive effect seems to be exclusive to subjects < or = 60 yr. These results will need to be confirmed in additional epidemiological studies before recommending selenium supplementation in patients with colon adenomas.

Adenoma↗

PubMed1980

Relationship of dietary selenium to selenium in plasma and milk from dairy cows.

In a 13-wk trial Holstein cows in mid-lactation were fed four diets containing natural selenium alone or supplemented with .1, .2, or .5 mg of inorganic selenium per kilogram of diet. Dietary selenium concentration averaged .334, .385, .456, and .772 mg/kg. Selenium plasma in wk 7 averaged .112 mu/ml with no differences among treatments; milk selenium ranged from .040 to .046 mu/ml and was higher in the two higher selenium diets. In wk 13 selenium in plasma and milk averaged .119 and .054 with no treatment differences. The 7 and 13 wk concentrations were higher than pretrial .084 and .033 mu/ml for plasma and milk during which time dietary selenium concentration was .254 mg/kg. Selenium concentration increased linearly from about .08 to .120 mu/ml of plasma and about .030 to .055 mu/ml of milk as intake of selenium increased from about 2 to 6 mg/day. Increase in selenium intake from 6 to 12 mg/day resulted in little change in plasma and milk selenium. Moderate concentrations of dietary selenium (.3 to .7 mg/kg) do not result in toxic amounts of selenium in milk.

Animals↗

PubMed1983

Blood selenium and glutathione peroxidase levels and dietary selenium of free-living and institutionalized elderly subjects.

The purpose of this study was to evaluate the selenium status of healthy free-living and institutionalized elderly people. For the 36 free-living elderly dietary selenium intake averaged 94 +/- 44 micrograms Se/day and a positive correlation coefficient was found between dietary selenium and dietary calories (r = 0.46; P less than 0.05), dietary protein (r = 0.60; P less than 0.01), and dietary fat (r = 0.43; P less than 0.05). Diet histories from the institutionalized subjects revealed a strong correlation coefficient between selenium and carbohydrate (r = 0.51; P less than 0.005) and selenium and calories (r = 0.44; P less than 0.05). Mean erythrocyte and plasma selenium levels for the free-living subjects were 0.20 +/- 0.06 micrograms/ml and 0.10 +/- 0.03 micrograms/ml, respectively, while mean erythrocyte glutathione peroxidase (GSH-Px) activity was 27.5 +/- 5.0 units/g protein. For the free-living subjects positive correlation was found between dietary selenium and erythrocyte selenium levels (r = 0.38; P less than 0.05) but no correlation existed between dietary selenium and plasma selenium (r = 0.13; P greater than 0.05) and RBC GSH-Px (r = -0.15; P greater than 0.05). The dietary selenium levels and blood selenium and GSH-Px levels were above the levels found in populations proposed to be at risk for selenium deficiency. Thus, these elderly appear to have adequate selenium status.

Aged↗

PubMedDate not supplied

Comparison of whole blood selenium values and erythrocyte glutathione peroxidase activities of normal individuals on supplementation with selenate, selenite, L-selenomethionine, and high selenium yeast.

The selenium levels and the glutathione peroxidase activity GSH-PX of whole blood and of erythrocytes, respectively, were determined in 139 normal Danes and related to sex and smoking habits. No differences were found in relation to sex apart from a higher GSH-PX activity of females when assayed with tertiary butyl hydroperoxide. Smokers showed significantly lower selenium values than non-smokers (p less than 0.05), but the two groups had identical GSH-PX activities. Individuals from the above-mentioned group were divided into four groups, receiving daily oral doses of 200 micrograms of selenium in the form of selenite, selenate, L-selenomethionine, and selenium as contained in yeast. Whole blood selenium values and the erythrocyte glutathione peroxidase activities were determined during three months of supplementation followed by a withdrawal period of four months. Both the inorganic selenium compounds and the organic derivatives gave rise to steady state levels of GSH-PX after one month of supplementation. However, the selenium levels in the groups receiving organic selenium showed a steady rise during the whole period, whereas those supplemented with inorganic selenium leveled off after a period of one to three months. The data for smokers and nonsmokers revealed identical results when organic selenium was supplemented. However, selenite gave rise to significantly higher selenium levels and GSH-PX activities in smokers than in non-smokers. Less significant (p less than 0.08) elevations of both parameters were also observed among the smokers in the selenate group. By taking both the selenium level and the GSH-PX activity into consideration, organic selenium (i.e., L-(+) selenomethionine) was judged to be more bioavailable than selenite and selenate.

Adult↗

PubMedDate not supplied

Serum selenium levels in diabetic children. A followup study during selenium-enriched agricultural fertilization in Finland.

The effect of increased selenium uptake on serum selenium in diabetic children was investigated during the first 9 yr of the Finnish nationwide selenium fertilization program, which started in 1984. Serum selenium concentrations were followed in 237 diabetic children (mean age 8.1 yr) and 214 controls from 1984 to 1992. The control group consisted of 107 siblings of the diabetics and of 107 other healthy children of corresponding age groups. Selenium was determined by direct electrothermal atomic absorption spectrophotometry. The effect of the increased uptake was seen in both diabetic and in control persons. Before the autumn of 1985, diabetic patients had significantly higher serum selenium levels than their siblings or the other healthy controls. Toward the end of year 1987, this difference had disappeared. After that, serum selenium levels continued to increase until the year 1990. In 1990 the mean selenium serum level of diabetic patients was 1.36 mumol/L and that of controls 1.33 mumol/L. The duration of diabetes did not have any effect on selenium serum levels. Slightly higher serum selenium in new diabetic patients before the start of therapy was explained by the dehydration state. The patients who were younger than 3 yr had slightly lower selenium serum levels when compared with older age groups. This difference was observed, however, only during the first 3 yr of the study. After that, when the selenium intake increased in general, no age-dependent differences were found anymore. There were no significant differences in serum selenium levels between males and females in either diabetic patients or in controls.

Adult↗

PubMed2006

Comparative on causes and accumulation of selenium in the tree-rings ambient high-selenium coal combustion area from Yutangba, Hubei, China.

Toxic trace elements emitted during coal combustion are the main sources of air pollution. They are released into the atmosphere mainly in the forms of fine ash, smoke and flue, and thus adversely affect plant, animal and human health. Selenium is one of toxic and the most volatile in coal. Large amount of atmospheric emission of selenium, as well as selenium present and scrubber stockpiles in ash may create serious environmental problems. In the paper, on the basis of investigating the abundance and distribution of selenium in plant-rings during recent 20 years, the bioaccumulation of selenium is explained that selenium in plant, which were collected from the village of selenium-rich coal combustion, is much higher than that in plants collected away from the village of selenium-rich coal combustion. The main origins of selenium are selenium-rich coal combustion and high-selenium rock weathered. The selenium recycle by food chain and selenium will accumulate and redistribute in environments.

China↗

PubMed1984

Hematologic data of selenium-deficient and selenium-supplemented rats.

Effect of dietary selenium as sodium selenite on in vivo hematological parameters of Sprague-Dawley rats was examined over a 7-month period. Dietary selenium did not alter total hemoglobin, hematocrits, erythrocyte counts, or the osmotic fragility pattern of rat blood. Selenium-excessive (1.0 ppm) rats showed slightly lower but not significantly lower methemoglobin levels than selenium-adequate (0.1 ppm) or selenium-deficient rats. Platelet counts tended to be higher in selenium-excessive rats and lower in selenium-deficient rats than in selenium-adequate rats, but the differences were not statistically significant. No clear trends were observed regarding the effect of dietary selenium on total leukocyte and differential leukocyte counts. After 7 months of dietary treatment blood glutathione peroxidase activity in selenium-deficient rats and in selenium-excessive rats was 16.8% and 142.2% of the activity in selenium-adequate rats. The results indicate that long-term selenium deficiency in rats produces no abnormal hematological parameters or any compensated hemolytic anemia in vivo.

Animals↗

PubMed1996

Selenium administration to a ten-year-old patient receiving long-term total parenteral nutrition (TPN)--changes in selenium concentration in the blood and hair.

Muscle pain in the lower limbs occurred in a child with short bowel syndrome who has been receiving longterm total parenteral nutrition (TPN). Biochemical parameters revealed that the plasma and erythrocyte selenium concentrations were below the normal range for children and intravenous injection of selenium prepared from selenious acid was started at a dose of 100 micrograms per day. Muscle pain in the lower limbs disappeared one month afterwards. At this point in time, the elevation of the plasma selenium concentration was noted but the erythrocyte selenium concentration remained low. When administration was suspended due to catheter-induced fever five months later, the whole blood selenium concentration decreased again and the symptoms recurred. Accordingly, the dose of selenium was increased to 200 micrograms/day. Subsequently, the blood selenium concentration recovered to the normal range for children. After the dose increase to 200 micrograms/day, concentrations in hair samples collected at every centimeter distance from the root end were determined. The selenium concentration at the root end was found to be higher than the normal range for children, indicating that this was an excessive dose case. Although the dose was decreased from 200 micrograms/day to 120 micrograms/day, the plasma and erythrocyte selenium levels did not go down. Furthermore, the selenium level in the hair reached a plateau, and no recurrence of symptoms was observed. The above results indicate the usefulness of monitoring the selenium concentration in hair in addition to determining the blood selenium level and GSH-Px activity in administering selenium to children undergoing TPN.

Adolescent↗

PubMed2002

Brain selenium accumulation in rat pups of selenium supplemented mothers.

Selenium is essential for normal mammalian development. Being a component of antioxidant enzyme, glutathione peroxidase, it plays a major role in protecting the cells from free radical damage. The level of glutathione peroxidase was directly related to the amount of selenium present in various tissues and organs. A decrease in selenium leads to various pathological changes in humans as well as in various laboratory animals. The aim of the present study was to understand whether there is an increase in the level of selenium in different brain regions of rat pups whose mothers were supplemented with selenium, either 2 or 4 mg/l of their drinking water throughout the period of their pregnancy. There was a significant increase in the level of selenium in the cerebellum, cortex and hypothalamic and hippocampal tissues of selenium supplemented mothers as compared with those of non-supplemented mothers. The brain stem of these animals did not show any significant difference in the level of selenium. Furthermore, the differences in the level of selenium between the rat pups of 2 mg/l selenium supplemented mothers and 4 mg/l selenium supplemented mothers were not statistically significant. These studies suggest that supplementation of selenium to mothers during the period of their pregnancy can selectively increase the level of this trace element in different brain regions. Further studies are necessary to understand the significance of selective accumulation of selenium in specific brain regions on brain development and function.

Animals↗

PubMed1993

Bioavailability of selenium from selenium-enriched garlic.

We previously reported that garlic grown in a selenium-fertilized medium (selenium-enriched garlic) is superior to regular garlic in mammary cancer prevention in an animal model (Nutr Cancer 17, 279-286, 1992). The present study was designed to evaluate the nutritional bioavailability of selenium from this garlic with use of two liver selenoenzymes as biomarkers: glutathione peroxidase and type I 5'-deiodinase. Rats were fed a selenium-deficient diet (0.01 ppm Se) from weaning for four weeks to deplete both enzymes. They were then supplemented with nutritional levels of selenium (0.1-0.5 ppm) in the form of sodium selenite (positive control) or selenium-enriched garlic. Our results showed that selenium-enriched garlic was just as effective as selenite in restoring the activity of both selenoenzymes. This was demonstrated in a time course repletion experiment as well as in a dose-response experiment. Thus the selenium in selenium-enriched garlic has potent nutritional and anticancer efficacy. The type I 5'-deiodinase enzyme catalyzes the conversion of thyroxine (T4) to 3,5,3'-triiodothyronine (T3) and is responsible for most of the circulating T3. Because cancer chemoprevention by selenium usually requires pharmacological levels of selenium, we also examined the possible modulation of type I 5'-deiodinase by long-term feeding of selenium-enriched garlic at 3 ppm Se in the diet. The observation that a high intake of selenium-enriched garlic did not affect 5'-deiodinase activity suggests that its anticarcinogenic effect is unlikely to be mediated by an imbalance in the blood T4-to-T3 ratio.

Animals↗

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↗