Effects of long-term selenium yeast supplementation on selenium status studied in the rat

To investigate the selenium status during long-term dietary supply of selenium yeast, 30-day-old male rats were fed for 379 days a methionine-adequate low-selenium diet supplemented with 0.2 mg Se/kg (selenium-adequate diet) or 1.5 mg Se/kg (high-selenium diet) in the form of selenium yeast that contained 60% of the element as l-selenomethionine. Their selenium load was determined at several intervals by neutron activation analysis of the selenium concentrations in the main selenium body pools, skeletal muscle and liver. After 64 days the tissue selenium concentrations plateaued in both groups and then stayed at that level. Compared with the selenium-adequate group, elevated tissue selenium concentrations were found in the high-selenium group, but the increase by a factor of 3.5 in the muscle and by a factor of 2.3 in the liver was smaller than the 7.5-fold increase in the selenium intake. In the selenium-adequate group about 50% of the muscle selenium and 30% of the liver selenium and in the high-selenium group about 85% of the muscle selenium and 70% of the liver selenium were estimated to be present in non-selenoprotein forms. During selenium depletion the liver glutathione peroxidase activity in the high-selenium group remained unaffected for 4 weeks and then decreased more slowly than that in the selenium-adequate group. From these results it can be concluded that selenium incorporated from the selenium yeast diet into non-selenoprotein forms can serve as an endogenous selenium source to maintain selenoprotein levels in periods of insufficient selenium supply.     

Iron depletion without anemia is not associated with impaired selenium status in college-aged women

Iron-deficiency anemia has been shown to alter body mineral concentrations and activities of iron- and non-iron-containing enzymes, especially those with antioxidant functions. These effects, however, have been less studied in nonanemic iron-depleted individuals. Thus, this study assessed indices of selenium status in 12 college-aged females with adequate iron stores and 15 college-aged females with low iron stores before and after iron therapy. Blood samples were drawn at baseline for both groups and following iron supplementation in the low-iron-stores group. Hematocrit, hemoglobin, and serum ferritin concentrations of the low-iron-stores group were significantly lower than those of the control group. The serum transferrin receptor-to-serum ferritin ratio in the low-iron-stores group was significantly greater than that of the control group. Serum selenium and glutathione peroxidase concentrations of the low-iron-stores group were not significantly different from those of the controls. Iron supplementation significantly increased hemoglobin, hematocrit, and serum ferritin concentrations and significantly decreased the serum transferrin receptor concentration and serum transferrin receptor:serum ferritin ratio in the low-iron-stores group posttreatment compared to pretreatment. Serum selenium and glutathione peroxidase concentrations did not differ significantly from pretreatment to posttreatment in the low-iron-stores group. Results of this study indicate that low iron stores without anemia are not associated with impaired selenium status in college-aged females.     

Effect of selenium and protein deficiency on selenium and glutathione peroxidase in rats

Twenty-four weanling male Wistar rats were divided into four groups fed diets containing adequate or deficient levels of selenium (0.5 ppm [+ Se] or <0.02 ppm [−Se] and protein (15% [+Pro] or 5% [−Pro]), but adequate levels of all other nutrients for 4 wk to determine the effects of Se deficiency and protein deficiency on tissue Se and glutathione peroxidase (GSHPx) activity in rats. Plasma, heart, liver, and kidney Se and GSHPx were significantly lower in Se-deficient groups in relation to Se-sufficient groups. In Se-deficient groups, Se and GSHPx were significantly higher in −Se−Pro rats in heart, liver, and kidney. Data analysis showed that there were significant interaction effects between dietary Se and protein on Se and GSHPx of rats. It is assumed that under the condition of Se deficiency. a low level of protein may decrease Se and GSHPx utilization, increase GSHPx synthesis, and result in Se redistribution. This could account for high levels of Se and GSHPx in the −Se−Pro rats compared to −Se+Pro rats.     

Effect of supplementation with selenium on whole blood glutathione peroxidase activities and on plasma and tissue selenium concentrations in lambs

In recent years the selenium (Se) intake of the human population of the UK has shown a marked decline from 60 μg/d in 1978 to around 30 μg/d in 1990 owing largely to a significant reduction in the importation of North American wheat for bread-making fluor. Other countries (Finland, for example) in similar situations have instituted fertilization programs in order to raise cereal Se concentrations and thus boost dietary intakes. An alternative approach would be to increase the Se concentration of carcass meat by supplementation of meat animals for a limited period prior to slaughter. A trial was set up with store lambs to evaluate this approach. Sixteen Scottish Blackface lambs were stratified according to live weight and then randomly allocated to one of four treatments: unsupplemented, or 3.5, 7, or 10.5 mg. Se/head/wk. After 14 wk, the lambs were sacrificed and samples of shoulder and thigh muscle, liver, and kidney were obtained for analysis. All three treatments effected an increase in whole blood glutathione peroxidase (GSH-Px) and plasma Se concentrations over controls. Shoulder, thigh, and liver Se exhibited a dose-response relationship to treatment, but kidney Se concentrations were unaffected by treatment. Muscle and some organ meat Se concentrations can therefore be increased by supplementation and could contribute to increased human dietary intakes of the element.     

Characterization of selenium status of inhabitants in the region Ústi nad orlici,czech republic by inaa of blood serum and hair and fluorimetric analysis of urine

Selenium is an essential trace element and its isufficient status may cause serious health complications for both individuals and the whole populations. To investigate the selenium status of the subpop-ulation in northeastern Bohemia represented by the region ústí nad Orlicí, 253 serum, 469 urine, and 31 hair samples from 470 randomly selected volunteers between 6 and 65 yr of age have been analyzed for selenium concentration. Serum and hair Se were detected by instrumental neutron activation analysis (means: 55 ±11 Μg Se/L sera, 0.268 ±0.040 Μg Se/g hair). Urine Se was measured by fluorimetry (12 ±5 Μg Se/L urine) with coanalyses of Lyphocheck urine, SRM Urine 2670, and Seronorm urine for quality control of the method. Results proved significant age-dependent differences, but gender differences were not significant. The frequency plot of serum Se proved maximal frequencies in adults between 55 and 70 Μg Se/L and in children in the range 45–55 Μg Se/L. The same plots of urine Se for both age groups showed maximal frequency in the limits 8–15 Μg Se/L. All indices used (Se in serum, urine, and hair) confirmed mild to severe selenium deficiency in the population of the region.     

Effects of low selenium diets on antioxidant status and MPTP toxicity in mice

To investigate the role of chronic oxidative stress in MPTP neurotoxicity, C57BL mice were maintained 6–8 weeks on diets deficient in nutrients essential to cellular antioxidant defenses, selenium (Se) and alpha-tocopherol (vit E), and the effects on tissue antioxidant status and MPTP toxicity were evaluated relative to controls on supplemented diets. Activities of the major antioxidant enzymes, glutathione peroxidase (GPx), catalase, and superoxide dismutase, and levels of malondialdehyde as a marker for oxidative stress, were measured in brain, lung, liver and blood. Caudate depletion of dopamine and its metabolites served as a measure of MPTP neurotoxicity. For mice on the Se deficient diet, levels of the selenoenzyme GPx decreased from 50% in brain to 90% in blood. No compensatory changes in the activities of the other antioxidant enzymes were observed and addition of vit E to the diet did not alter antioxidant enzyme activities or malondialdehyde levels. In animals not treated with MPTP, the Se deficient diet significantly increased malondialdehyde only in liver. No protective effect of the antioxidant supplements against caudate depletion of dopamine and its metabolites was observed. However, malondialdehyde levels were increased in the brains of MPTP treated mice on the low Se diets, suggesting the possibility of secondary oxidative damage to tissues accompanying the destruction of substantia nigra neurons by MPTP.     

Effects of excess selenomethionine on selenium status indicators in pregnant long-tailed macaques (Macaca fascicularis)

Forty pregnant long-tailed macaques were treated daily for 30 d with 0, 25, 150 or 300 μg selenium as L-selenomethionine/kg body weight. Erythrocyte and plasma selenium and glutathione peroxidase specific activities, hair and fecal selenium, and urinary selenium excretion were increased by and were linearly related to L-selenomethionine dose. Hair selenium was most sensitive to L-selenomethionine dose, with an 84-fold increase in the 300 μg selenium/(kg-d) group relative to controls (r=0.917). Daily urinary selenium excretion (80-fold,r=0.958), plasma selenium (22-fold,r=0.885), erythrocyte selenium (24-fold,r=0.920), and fecal selenium (18-fold,r=0.911) also responded strongly to L-selenomethionine. Erythrocyte and plasma glutathione peroxidase specific activities increased 154% and 69% over controls, respectively. Toxicity was associated with erythrocyte selenium >2.3 μg/mL, plasma selenium >2.8 μg/mL, and hair selenium >27 μg/g. Plasma, erythrocyte, and hair selenium concentrations may be useful for monitoring and preventing the toxicity of L-selenomethionine administered to humans in cancer chemoprevention trials.     

Serum selenium and selenoprotein P status in adult Danes – 8-year followup

Selenium is an essential micronutrient important to human health. The main objective of this study is to describe serum selenium and selenoprotein P status in two samples of the Danish population. In addition, the influence of various factors potentially associated with selenium status was investigated.Blood samples from a total of 817 randomly selected subjects from two cities in Denmark were analyzed. Half of the samples were collected in 1997–1998 and the other half in 2004–2005. Samples from women aged 18–22, 40–45 and 60–65 years, and men aged 60–65 years were selected for this study. All subjects had filled in a food frequency questionnaire (FFQ) and a questionnaire with information about smoking habits, alcohol consumption and exercise habits.Mean serum selenium level was 98.7±19.8 μg/L and median selenoprotein P level was 2.72 (2.18–3.49) mg/L. Serum selenium and selenoprotein P increased with age, and selenoprotein P was higher in men than in women. Serum selenium levels decreased by 5% on average from 1997–98 to 2004–05 (P<0.001), whereas selenoprotein P level increased (P<0.001). The intake of fish correlated weakly with serum selenium level (r=0.14, P<0.001) but not with selenoprotein P level. Smoking status, alcohol intake, exercise habits, BMI and medicine use did not influence selenium status.It is concluded that selenium status in this Danish population is at an acceptable level. No major groups with regard to age, sex or lifestyle factors could be identified as being in risk for selenium deficiency.     

The effect of nationwide selenium enrichment of fertilizers on selenium status of healthy finnish medical students living in south western Finland

In Finland commercial fertilizers have been enriched with sodium selenate since July 1, 1984 in order to compensate for the poor selenium content of the soil. Fertilizers that are used for the production of hay and fodder were supplemented with 6 mg/kg of selenium, whereas fertilizers used for the production of cereals were supplemented with a higher dose, 16 mg/kg fertilizer. The effects of selenium fertilization were first seen in dairy products in June 1985, and from the beginning of August 1985, the effect was evident also in wheat flour, beef, and bovine liver. In this study the selenium status of 108 healthy young adults has been systematically documented since November 1985, at which time the mean selenium serum level (S-Se) was 1.05 umol/L. A steady increase was observed until November 1989, when the maximum level, with a mean of S-Se 1.6 umol/L was reached. After that, a slight decrease has occurred. The mean serum selenium level in autumn 1991 in a new group of 35 students was 1.58 umol/L. This decrease can be explained by the high amount of imported cereals in 1988 and 1989, which was reflected also in the serum selenium levels. The glutathione peroxidase activity in erythrocytes in 1989–1990 was at the same level as in 1985 and 1986.     

Effects of selenium status and supplementary seleno-chemical sources on mouse T-cell mitogenesis

Although selenium is thought to be essential for various immune responses, the excess supplementation may have an adverse effect on certain immunological functions. The present study was designed to determine the effective chemical forms of selenium and their optimal levels on T-cell mitogenesis with splenic cells from mice given a selenium-deficient diet for 8 weeks to avoid effects of cellular selenium sources. Although selenium in tissues, except for spleen and thymus, was almost depleted by feeding selenium-deficient diet, the lymphoid organs still contained low levels of selenium. Both activities of cellular glutathione peroxidase (cGPx) and thioredoxin reductase (TR) in liver and splenic cells showed a tendency to decrease by selenium deficiency. However, splenic cells were tolerant against decrease of the selenoenzyme activities, and TR was also more tolerant than cGPx. T-cell proliferation of the selenium-insufficient splenic cells induced by concanavalin A was increased by addition of Na₂SeO₃, Na₂SeO₄, Na₂Se, seleno-dl-cystine, seleno-l-methionine and selenocystamine. Their promoting action was observed at levels lower than 0.1 μmol/L and was completely suppressed at the highest concentration (1 μmol/L), except for selenocystamine. Na₂SeO₃ was one of the efficient selenocompounds for the mitogenesis, which was concomitant with the significant induction of cGPx and TR. However, recovery of cGPx activity in the selenium-insufficient cells by supplementary Na₂SeO₃ was only partial, while TR activity was readily recovered from selenium deficiency. These results therefore indicate that only low levels of selenium is essential for T-cell mitogenesis even in selenium-insufficient splenic cells, and TR, which is readily recovered by Na₂SeO₃, may be the critical enzyme.     

Influence of selenium deficiency on the acute cardiotoxicity of adriamycin in rats

The influence of selenium (Se) deficiency on the acute cardiotoxicity induced by the anticancer drug adriamycin (ADR) has been studied in rats by electrocardiography. Two categories were formed by feeding groups of rats a Se-supplemented and a Se-deficient diet. The supplemented animals were taken as normals. The two categories were treated with iv injections of saline solution containing ADR at doses of 0, 7.5, and 15 mg/kg body wt. The cardiac Se concentration and glutathione peroxidase (GSH-Px) activity in the Se-deficient groups were <2% lower than in the normals. The normal groups showed significant widening of the SaT and QaT durations when given 15 mg/kg ADR. The Se-deficient groups exhibited a dose-dependent widening of the SaT and QaT duration at 7.5 and 15 mg/kg and narrowing of the PQ duration at 15 mg/kg ADR. No heart rate or QRS duration changes were detected in both categories. Our results suggest that an imbalance of the antioxidant system is associated with Se deficiency and that Se plays a role in preventing the cardiac functional disorder attributable to oxygen free radical formation induced by ADR.     

Levels of selenium in plasma and glutathione peroxidase in erythrocytes and the risk of breast cancer

Plasma selenium and glutathione peroxidase in erythrocytes were analyzed in a case-control study encompassing 441 cases with breast cancer and 191 controls with benign breast disease. No difference in mean serum selenium level between cases and controls on supplementary selenium intake was seen. If only individuals without supplementary intake, 278 cases and 135 controls, were considered a preventive effect was found increasing with selenium level. This finding was significant among women 50 years old or more with Mantel-Haenszel odds ratio=0.16 for individuals with serum selenium >1.21 μmol/L. Also for subjects with serum selenium in the range 1.00–1.21 μmol/L a significant preventive effect was seen with odds ratio=0.38. For women under 50 years of age a nonsignificant preventive effect was seen. Glutathione peroxidase in erythrocytes did not correlate well with serum selenium and was not a marker for the risk of breast cancer.     

Selenium status of healthy immigrant parisian preschool children

Plasma selenium (Se) concentration and erythrocyte glutathione peroxidase activity (GPx) were assessed in a population of healthy preschool children two to five years old, residing in the city of Paris. In the 118 subjects, mean (±SD) plasma Se concentration was 62.10 ±13.96 μg/L, and mean GPx activity was 23.58±8.52 U/g Hb. Mean plasma Se of male children was significantly (p=0.001) higher (12%) than levels of girls. Plasma selenium levels were not correlated with erythrocyte GPx activity. Children from Mediterranean origin had a slightly lower erythrocyte GPx activity (p<0.05) than children from other regions. Mean plasma Se concentration of this group corresponded to the lower limit of intervals, which characterizes geographical regions of intermediate selenium concentrations.     

Glutathione peroxidase activity,selenium, and lipid peroxide concentrations in blood from a healthy Polish population

Selenium (Se) concentrations in whole blood and plasma of 19 nonpregnant women. 14 mothers at delivery, 14 neonates, and 13 infants, aged 2–12 mo, were evaluated. The activity of glutathione peroxidase (GSH-Px) in erythrocytes and plasma and the level of lipid peroxides in plasma were also analyzed. Selenium concentrations in whole blood and plasma in mothers at delivery were significantly lower compared to nonpregnant women. Selenium concentrations in cord blood components were lower compared to mothers, but the differences were not significant. The concentration of the element decreased in the first few months of life. Glutathione peroxidase activity in erythrocytes differed only slightly in the examined groups. In plasma, however, the enzyme activity was significantly lower in pregnant compared to nonpregnant women and in neonates compared to their mothers. Lipid peroxide concentrations in plasma differed only slightly in the examined groups. The results obtained are discussed in terms of the observations of other investigators.     

Effects of dietary selenium supplementation on tissue selenium distribution and glutathione peroxidase activity in Chinese Ring Necked Pheasants

The objective of this study was to determine the concentration of total selenium (Se) and the proportions of total Se comprised as selenomethionine (SeMet) and selenocysteine (SeCys) in the postmortem tissues of female pheasants (Phasianus Colchicus Torquator) offered diets that contained graded additions of selenised-enriched yeast (SY) or a single comparative dose of sodium selenite (SS). Thiobarbituric acid reactive substances (TBARS) and tissue glutathione peroxidase (GSH-Px) activity of breast (Pectoralis Major) were assessed at 0 and 5 days postmortem. A total of 216 female pheasant chicks were enrolled into the study. Twenty-four birds were euthanased at the start of the study, and samples of blood, breast muscle, leg muscle (M. Peroneus Longus and M. Gastrocnemius), heart, liver, kidney and gizzard were collected for determination of total Se. Remaining birds were blocked by live weight and randomly allocated to one of four dietary treatments (n = 48 birds/treatment) that either differed in Se source (SY v. SS) or dose (control (0.17 mg total Se/kg), SY-L and SS-L (0.3 mg/kg total Se as SY and SS, respectively) and SY-H (0.45 mg total Se/kg)). Following 42 and 91 days of treatment, 24 birds per treatment were euthanased, and samples of blood, breast muscle, leg muscle, heart, liver, kidney and gizzard were retained for determination of total Se and the proportion of total Se comprised as SeMet or SeCys. Whole blood GSH-Px activity was determined at each time point. Tissue GSH-Px activity and TBARS were determined in breast tissue at the end of the study. There were increases in both blood and tissues to the graded addition of SY to the diet (P < 0.001), but the same responses were not apparent with the blood and tissues of selenite-supplemented birds receiving a comparable dose (SY-L v. SS-L). Although there were differences between tissue types in the distribution of SeMet and SeCys, there were few differences between treatments. There were effects of treatment on erythrocyte GSH-Px activity (P = 0.012) with values being higher in treatments SY-H and SS-L when compared with the negative control and treatment SY-L. There were no effects of treatment on tissue GSH-Px activity, which is reflected in the overall lack of any treatment effects on TBARS.     

Bioavailability of selenium accumulated by selenite-reducing bacteria

The bioavailability of selenium (Se) was determined in bacterial strains that reduce selenite to red elemental Se (Se^o). A laboratory strain ofBacillus subtilis and a bacterial rod isolated from soil in the vicinity of the Kesterson Reservoir, San Joaquin Valley, CA, (Microbacterium arborescens) were cultured in the presence of 1 mM sodium selenite (Na₂SeO₃). After harvest, the washed, lyophilizedB. subtilis andM. arborescens samples contained 2.62 and 4.23% total Se, respectively, which was shown to consist, within error, entirely of Se^o. These preparations were fed to chicks as supplements to a low-Se, vitamin E-free diet. Three experiments showed that the Se in both bacteria had bioavailabilities of approx 2% that of selenite. A fourth experiment revealed that gray Se^o had a bioavailability of 2% of selenite, but that the bioavailability of red Se^o depended on the way it was prepared (by reduction of selenite). When glutathione was the reductant, bioavailability resembled that of gray Se^o and bacterial Se; when ascorbate was the reductant, bioavailability was twice that level (3–4%). These findings suggest that aerobic bacteria such asB. subtilis andM. arborescens may be useful for the bioremediation of Se-contaminated sites, i.e., by converting selenite to a form of Se with very low bioavailability.     

Selenium depletion in patients on home parenteral nutrition

Severe selenium (Se) depletion was found in nine patients receiving long-term home parenteral nutrition because of short bowel syndrome. Plasma Se ranged from 0–0.51 (median 0.21 μmol/L) and erythrocyte Se ranged from 0.7–2.6 (median 1.8 μmol/gHgb), which was significantly lower than in the controls. Glutathione peroxidase (GSHPx) in plasma and erythrocytes was also decreased. After bolus injections with 200 μg Se/d in the form of sodium selenite for 4 mo, followed by 100 μg/d for 8 mo, plasma Se increased to values slightly but significantly higher than in the controls. Erythrocyte Se reached normal levels in most of the patients after 4 mo substitution, but it remained lower than in the controls. Following Se supplementation, plasma and erythrocyte GSHPx did not differ between patients and controls. These data suggest that all patients receiving long-term parenteral nutrition because of short bowel syndrome should receive at least 100 μg sodium selenite/d when given as bolus injections to avoid Se depletion.     

Effects of nationwide addition of selenium to fertilizers on foods,and animal and human health in Finland: From deficiency to optimal selenium status of the population

Despite different geological features the Nordic countries are generally selenium-poor areas. In each country various factors such as food importation and life-style determine the selenium (Se) intake. Due to an extremely low Se intake in the 1970s in Finland, 0.025 mg/day, an official decision was made in 1984 to supplement multinutrient fertilizers with Se in the chemical form of sodium selenate. Almost all fertilizers used in Finland since 1985 have contained Se. Currently all crop fertilizers contain 15 mg Se/kg. Finland is still the only country to take this country-wide measure.In a national monitoring programme, sampling of cereals, basic foodstuffs, feeds, fertilizers, soils, and human tissues has been carried out annually since 1985 by four governmental research organizations. Sampling of foods has been done four times per year and human blood has been obtained annually from the same (n = 60) adults. The accuracy of analyses has been verified by annual interlaboratory quality control. During this programme the selenium concentration of spring cereals has increased on average 15-fold compared with the level before the Se fertilization. The mean increase in the Se concentration in beef, pork and milk was 6-, 2- and 3-fold. In terms of Se, organically grown foods of plant origin are generally comparable to products produced before the Se supplementation of fertilizers. Milk from organically fed cows is 50% lower in Se than the usual milk. The average dietary human intake increased from 0.04 mg Se/day/10 MJ in 1985 to a present plateau of 0.08 mg Se/day/10 MJ, which is well above the current nutrition recommendations. Foods of animal origin contribute over 70% of the total daily Se intake. The mean human plasma Se concentration increased from 0.89 μmol/L to a general level of 1.40 μmol/L that can be considered to be an optimal status. The absence of Se deficiency diseases and a reference population have made conclusions on the impact on human health difficult. However, the rates of cardiovascular diseases and cancers have remained similar during the pre- and post-supplementation indicating medical and life-style factors to be much stronger determinants than Se. The nationwide supplementation of fertilizers with sodium selenate is shown to be effective and safe in increasing the Se intake of the whole population. Also, the health of animals has improved.     

Selenium status is decreased in patients with intrinsic asthma

Lowered selenium (Se) status has been observed in asthma patients. An increased production of reactive oxygen species (ROS) owing to inflammatory condition has also been found in these patients and thus antioxidant properties of Se via glutathione peroxidase (GPx) activity are of great importance. Concentrations of Se in plasma and erythrocytes as well as eryth-rocyte GPx activity in 22 intrinsic asthma patients (five patients; all women were aspirin-sensitive) were compared with those of 33 control subjects. Se concentrations in both plasma and erythrocytes and GPx activity were decreased in intrinsic asthma patients. There were no significant differences in investigated parameters of Se status between aspirin-tolerant and aspirin-intolerant patients within intrinsic asthma group. Significantly high positive correlation between plasma and erythrocyte Se concentrations was found when regarding all subjects as a whole. Se supplementation might be beneficial to patients with intrinsic asthma, which may be at risk of Se deficiency.