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

Protective Effects of Different Selenium Green Tea Polysaccharides on the Development of Type 2 Diabetes in Mice

Selenium polysaccharides have attracted significant interest due to their superior function to that of individual polysaccharides. However, limited research has compared the protective effects of different selenium polysaccharides from different selenization methods on diabetes. This work aims to compare the preventive effects of natural selenium-enriched green tea polysaccharides (NSe-TPS), synthetic selenized green tea polysaccharides (PCSe-TPS), and a mixture of sodium selenite and green tea polysaccharides (ordinary tea polysaccharides (Ord-TPS)+Se) on the development of diabetes. While establishing a diabetes model induced by a high-sugar, high-fat diet combined with streptozotocin, different selenium polysaccharides were administered daily by gavage for nine weeks. Our findings indicate that PCSe-TPS exhibited superior preventive effects on developing type 2 diabetes compared to NSe-TPS and Ord-TPS+Se. PCSe-TPS effectively regulated glucose metabolism and insulin resistance by activating the PI3K/Akt pathway, thereby preventing elevated blood glucose levels. Additionally, PCSe-TPS mitigated oxidative damage and inflammatory responses in liver tissues. Notably, PCSe-TPS intervention reversed the decline in bacterial species richness and the abundance of unclassified_Oscillospiraceae during the development of diabetes in mice. These results provide valuable insights into the protective effects of PCSe-TPS against diabetes development, highlighting its advantages over NSe-TPS and Ord-TPS+Se.

Selenium Speciation Analysis Reveals Improved Antioxidant Status in Finisher Pigs Fed L-Selenomethionine, Alone or Combined with Sodium Selenite, and Vitamin E

Conditions associated with selenium (Se) and/or vitamin E (VitE) deficiency are still being reported in high-yielding pigs fed the recommended amounts. Here, the dietary effects of Se source (sodium selenite, NaSe, 0.40 or 0.65 mg Se/kg; L-selenomethionine, SeMet, 0.19 or 0.44 mg Se/kg; a NaSe-SeMet mixture, SeMix, 0.44-0.46 mg Se/kg) and VitE concentration (27, 50-53 or 101 mg/kg) on the antioxidant status of finisher pigs were compared with those in pigs fed non-Se-supplemented diets (0.08-0.09 mg Se/kg). Compared to NaSe-enriched diets, SeMet-supplemented diets resulted in significantly (p < 0.0018) higher plasma concentrations of total Se (14-27%) and selenospecies (GPx3, SelP, SeAlb; 7-83%), significantly increased the total Se accumulation in skeletal muscles, myocardium, liver and brain (10-650%), and enhanced the VitE levels in plasma (15-74%) and tissues (8-33%) by the end of the 80-day trial, proving better Se distribution and retention in pigs fed organic Se. Injecting lipopolysaccharide (LPS) intravenously half-way into the trial provoked a pyrogenic response in the pigs followed by a rapid increase of inorganic Se after 5-12 h, a drastic drop of SeMet levels between 12 and 24 h that recovered by 48 h, and a small increase of SeCys by 24-48 h, together with a gradual rise of GPx3, SelP and SeAlb in plasma up to 48 h. These changes in Se speciation in plasma were particularly significant (0.0024 > p > 0.00007) in pigs receiving SeMet- (0.44 mg Se/kg, above EU-legislated limits) or SeMix-supplemented (SeMet and NaSe both at 0.2 mg Se/kg, within EU-legislated limits) diets, which demonstrates Se metabolism upregulation to counteract the LPS-induced oxidative stress and a strengthened antioxidant capacity in these pigs. Overall, a Se source combination (without exceeding EU-legislated limits) and sufficient VitE supplementation (≥ 50 mg/kg) improved the pigs' antioxidant status, while doubling the allowed dietary organic Se increased the Se in tissues up to sixfold without compromising the animal's health due to toxicity. This study renders valuable results for revising the current dietary SeMet limits in swine rations.

Long-Term Selenium-Yeast Supplementation Does Not Affect Bone Turnover Markers: A Randomized Placebo-Controlled Trial

Higher selenium status has been associated with lower bone turnover markers (BTM) in epidemiological studies. However, the long-term impact of selenium supplementation on BTMs has not been studied. We investigated the effects of selenium supplementation on BTMs including osteocalcin (OC), procollagen type I N-terminal propeptide (PINP), collagen type I cross-linked C-telopeptide (CTX), and bone alkaline phosphatase (BALP) in the short (6 months) and long term (5 years). A total of 481 Danish men and women (60-74 years) were randomized to receive placebo-yeast versus 100, 200, or 300 μg selenium as selenium-enriched yeast daily for 5 years. Plasma selenium concentration was measured using inductively coupled plasma mass spectrometry, and BTMs were measured in nonfasted samples at baseline, 6 months, and 5 years. Data were analyzed by ANCOVA to investigate the shape of the dose-response relationships. Covariates included age, body mass index, baseline selenium status, baseline BTM, smoking, alcohol, supplement use, and medication. Plasma selenium concentration (mean 86.5 μg/d at baseline) increased significantly with increasing selenium supplementation to 152.6, 209.1, and 253.7 μg/L after 6 months and remained elevated at 5 years (158.4, 222.4, and 275.9 μg/L for 100, 200, and 300 μg supplemental selenium/d, respectively (p < 0.001)). There was no change in plasma selenium concentration in the placebo-treated group. There was no significant effect of selenium supplementation on OC (6 months p = 0.37; 5 years p = 0.63), PINP (6 months p = 0.37; 5 years p = 0.79), CTX (6 months p = 0.91; 5 years p = 0.58) or BALP (6 months p = 0.17; 5 years p = 0.53). The relatively replete baseline selenium status in the study participants may explain this lack of effect. Testing in more deficient populations may provide further insights into the impact of selenium supplementation on bone health. © 2022 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Selenium as a Bioactive Micronutrient in the Human Diet and Its Cancer Chemopreventive Activity

This review answers the question of why selenium is such an important trace element in the human diet. Daily dietary intake of selenium and its content in various food products is discussed in this paper, as well as the effects of its deficiency and excess in the body. Moreover, the biological activity of selenium, which it performs mainly through selenoproteins, is discussed. These specific proteins are responsible for thyroid hormone management, fertility, the aging process, and immunity, but their key role is to maintain a redox balance in cells. Furthermore, taking into account world news and the current SARS-CoV-2 virus pandemic, the impact of selenium on the course of COVID-19 is also discussed. Another worldwide problem is the number of new cancer cases and cancer-related mortality. Thus, the last part of the article discusses the impact of selenium on cancer risk based on clinical trials (including NPC and SELECT), systematic reviews, and meta-analyses. Additionally, this review discusses the possible mechanisms of selenium action that prevent cancer development.

Selenium status is independently related to bone mineral density, FRAX score, and bone fracture history: NHANES, 2013 to 2014

Selenium is an essential trace mineral element for humans. Although previous in vitro and animal studies have reported the vital role of selenium in bone, the results of the relationship between the selenium status and bone health were inconsistent in epidemiological studies. The risk of selenium deficiency is negligible for U.S. general population, however, the relationship between selenium status and bone health has never been surveyed in a nationally representative sample. In this study, we analyzed the data of 2983 adults (aged ≥40 years) in the National Health and Nutrition Examination Survey (NHANES) 2013-2014 to investigate the association among three markers of the selenium status (measured from whole blood, serum, and dietary intake), total spine and femur bone mineral density (BMD), and FRAX scores, and history of bone fractures. We found a one-unit increase in the ln-whole-blood selenium level was correlated with an increase in the total femur BMD of 0.064 g/cm² (S.E. = 0.025; P = 0.022) in all participants and 0.086 g/cm² (S.E. = 0.031; P = 0.013) in menopausal women. Additionally, a one-unit increase in the ln-selenium intake amount was associated with an increase in the total femur BMD of 0.014 g/cm² (S.E. = 0.007; P = 0.043) in all participants. We also found that the dietary and whole-blood selenium statuses were negatively associated with the FRAX score, while levels of all the three selenium biomarkers were negatively associated with a history of bone fractures. In conclusion, increased selenium status is correlated with an increased total femur BMD, decreased FRAX scores, and a reduced incidence of previous bone fractures in the U.S. representative survey of adults. Further study is warranted to clarify the causal inference.

Selenium Kinetics in Humans Change Following 2 Years of Supplementation With Selenomethionine

BACKGROUND

Selenium (Se) is a nutritionally essential trace element and health may be improved by increased Se intake. Previous kinetic studies have shown differences in metabolism of organic vs. inorganic forms of Se [e.g., higher absorption of selenomethionine (SeMet) than selenite (Sel), and more recycling of Se from SeMet than Sel]. However, the effects on Se metabolism after prolonged Se supplementation are not known.

OBJECTIVE

To determine how the metabolism and transport of Se changes in the whole-body in response to Se-supplementation by measuring Se kinetics before and after 2 years of Se supplementation with SeMet.

METHODS

We compared Se kinetics in humans [n = 31, aged 40 ± 3 y (mean ± SEM)] studied twice after oral tracer administration; initially (PK1), then after supplementation for 2 y with 200 µg/d of Se as selenomethionine (SeMet) (PK2). On each occasion, we administered two stable isotope tracers of Se orally: SeMet, the predominant food form, and selenite (Na₂⁷⁶SeO_3, or Sel), an inorganic form. Plasma and RBC were sampled for 4 mo; urine and feces were collected for the initial 12 d of each period. Samples were analyzed for tracers and total Se by isotope dilution GC-MS. Data were analyzed using a compartmental model, we published previously, to estimate fractional transfer between pools and pool masses in PK2.

RESULTS

We report that fractional absorption of SeMet or Sel do not change with SeMet supplementation and the amount of Se absorbed increased. The amount of Se excreted in urine increases but does not account for all the Se absorbed. As a result, there is a net incorporation of SeMet into various body pools. Nine of the 11 plasma pools doubled in PK2; two did not change. Differences in metabolism were observed for SeMet and Sel; RBC uptake increased 247% for SeMet, urinary excretion increased from two plasma pools for Sel and from two different pools for SeMet, and recycling to liver/tissues increased from one plasma pool for Sel and from two others for SeMet. One plasma pool increased more in males than females in PK2.

CONCLUSIONS

Of 11 Se pools identified kinetically in human plasma, two did not increase in size after SeMet supplementation. These pools may be regulated and important during low Se intake.

An in Vitro System for Evaluation of Oxidative Stress and the Effects of Antioxidants

Oxidative stress is defined as an imbalance between prooxidants and antioxidants. There is a need for a simple in vitro method for evaluation of the effects of oxidative stress and the effects of antioxidants. In the present study, we used primary cultures of human lymphocytes exposed to either paraquat (PQ) or mitomycin C., two prooxidants generating two different types of free-radicals formed either by P450-reductase or by DT-diaphorase, respectively. The toxicity was measured by estimation of DT-diaphorase and glutathione peroxidase (GSH-Px) activity, and by estimation of the level of malondialdehyde (MDA) as a function of time and increasing doses of the two prooxidants. The enzyme activities were related to both total DNA content and total protein content of cellular homogenate. All estimations were made by exposing human lymphocytes to increasing concentrations (up to 100μM) of the two prooxidants. However, since cellular death occurred at concentrations above 60μM, only data for exposure to concentrations below 70μM are presented. When the enzyme activities were expressed per cellular unit (i.e. per gram DNA) 30μM mitomycin C induced a 30% increase in DT-diaphorase activity. Similarly, a dose-dependent increase (maximum 100% increase) in DT-diaphorase activity was found after exposure to PQ (up to 60μM). Similar data were obtained when data were related to the total protein. Only a minor increase (11%) in GSH-Px activity was induced by 50μM mitomycin C., whereas 20-70μM PQ induced a 41% increase in GSH-Px activity. Both prooxidants induced more than a doubling in the cellular MDA concentration. These findings demonstrate that both DT-diaphorase and GSH-Px are up-regulated during oxidative stress. However, sensitivity to prooxidant-induced stress seems to depend to some extent on the chemistry of the free-radicals generated. Thus, the single-electron pyridium cations generated by PQ seem to be more toxic than the single-electron semi-quinones generated by mitomycin C. The same cellular system was used to evaluate the effects of antioxidants. Quercetin, a naturally occuring flavone, and selenium (sodium selenite), which is an essential part of glutathione peroxidase, were selected. PQ-induced stress and exposure to 5μg/ml quercetin for 4 hours decreased the MDA level in the medium by 11% and in the cells by 33%. PQ-induced stress and exposure to 160μg/l selenium for 18 hours reduced MDA levels similarly, by 19% in the medium and 14% in the cells. Both antioxidants induced a 50% reduction in GSH-Px activity.

Challenges and perspectives of selenium supplementation in Graves' disease and orbitopathy

PURPOSE

This review focuses on the results of prospective randomized clinical trials and the conclusions from respective meta-analyses in order to summarize experiences with adjuvant selenium (Se) supplementation in Graves' hyperthyroidism and orbitopathy, while identifying ambiguous findings and highlighting important open research issues.

METHODS

We searched the PubMed and the Cochrane Central Register of Controlled Trials (CENTRAL) through May 31, 2019, for relevant studies.

RESULTS

The available evidence concerning routine use of Se in the treatment of Graves' hyperthyroidism remains ambiguous. Results of meta-analyses, including ten RCTs, suggest that adjuvant Se supplementation can enhance the restoration of biochemical euthyroidism. Unfortunately, these results must be judged cautiously owing to several important limitations. Moreover, an in-depth analysis of relevant long-term clinical measures of therapeutic success (such as remission rate after antithyroid drug treatment), besides surrogate markers (for example, hormone or autoantibody concentrations), is generally missing. Based on a single study, Se supplementation is recommended in patients with mild orbitopathy of short duration because it may decrease inflammation and eye-specific symptoms while also achieving a marked improvement in disease-specific quality of life. The effects of Se supplementation on moderate-to-severe orbitopathy remain as yet unknown.

CONCLUSIONS

Additional randomized clinical trials with clinically relevant endpoints are urgently needed to further aid in clinical decision-making, including better stratification of Graves' disease patients, who are most likely to benefit from Se supplementation.

Assessing the Efficacy of Dietary Selenomethionine Supplementation in the Setting of Cardiac Ischemia/Reperfusion Injury

Oxidative stress is a major hallmark of cardiac ischemia/reperfusion (I/R) injury. This partly arises from the presence of activated phagocytes releasing myeloperoxidase (MPO) and its production of hypochlorous acid (HOCl). The dietary supplement selenomethionine (SeMet) has been shown to bolster endogenous antioxidant processes as well as readily react with MPO-derived oxidants. The aim of this study was to assess whether supplementation with SeMet could modulate the extent of cellular damage observed in an in vitro cardiac myocyte model exposed to (patho)-physiological levels of HOCl and an in vivo rat model of cardiac I/R injury. Exposure of the H9c2 cardiac myoblast cell line to HOCl resulted in a dose-dependent increase in necrotic cell death, which could be prevented by SeMet supplementation and was attributed to SeMet preventing the HOCl-induced loss of mitochondrial inner trans-membrane potential, and the associated cytosolic calcium accumulation. This protection was credited primarily to the direct oxidant scavenging ability of SeMet, with a minor contribution arising from the ability of SeMet to bolster cardiac myoblast glutathione peroxidase (GPx) activity. In vivo, a significant increase in selenium levels in the plasma and heart tissue were seen in male Wistar rats fed a diet supplemented with 2 mg kg⁻¹ SeMet compared to controls. However, SeMet-supplementation demonstrated only limited improvement in heart function and did not result in better heart remodelling following I/R injury. These data indicate that SeMet supplementation is of potential benefit within pathological settings where excessive HOCl is known to be generated but has limited efficacy as a therapeutic agent for the treatment of heart attack.

A 2018 European Thyroid Association Survey on the Use of Selenium Supplementation in Graves' Hyperthyroidism and Graves' Orbitopathy

OBJECTIVE

Selenium (Se) supplementation has been suggested in the treatment of Graves' disease (GD). We sought to investigate Se prescription patterns for GD across European countries.

METHODS

Members of the European Thyroid Association were invited to participate in an online survey investigating the use of Se in GD either without or with orbitopathy (GO). Of 872 invited members, 244 (28%) completed the survey. After exclusion of basic scientists and non-European members, 197 responses were retrieved out of clinical trials (nearly half of clinician members), of whom 61 do not use Se. Thus, 136 respondents remained for further analyses.

RESULTS

Among the 136 analyzed respondents, most (64.7%) were not aware of the Se status in their populations, did not assess Se levels (78.7%), nor considered iodine status (74.3%). In GD without GO, 38.2% recommend Se supplementation ("sometimes" [27.2%], "frequently" [5.9%] or "always" [5.1%]). When GO occurs, 94.1% recommend Se supplementation ("sometimes" [39%], "frequently" [30.1%] or "always" [25%]). Of these, 60.1% recommend Se as an alternative to watchful waiting in patients with mild ocular involvement and 44.9% as an adjuvant to the established treatment modalities in patients with moderate to severe ocular involvement.

CONCLUSIONS

In Graves' hyperthyroidism without GO, 38.2% of ETA (European Thyroid Association) members recommend Se supplementation. Conversely, Se is recommended by the majority of respondents in GO, both in patients with mild and moderate to severe ocular involvement. This clinical practice is partially in disagreement with current European treatment guidelines that recommend Se as a 6-month treatment in mild GO only.

SEXUAL DIMORPHISM IN SELENIUM METABOLISM AND SELENOPROTEINS

Sexual dimorphism, the condition in which males and females in a species differ beyond the morphology of sex organs, delineates critical aspects of the biology of higher eukaryotes, including selenium metabolism. While sex differences in selenium biology have been described by several laboratories, delineation of the effects of sex in selenium function and regulation of selenoprotein expression is still in its infancy. This review encompasses the available information on sex-dependent parameters of selenium metabolism, as well as the effects of selenium on sex hormones. Gaps in the current knowledge of selenium and sex are identified and discussed.

Selenium Homeostasis and Clustering of Cardiovascular Risk Factors: A Systematic Review

Selenium is a trace element required for a range of cellular functions. It is widely used for the biosynthesis of the unique amino acid selenocysteine [Sec], which is a structural element of selenoproteins. This systematic review focused on the possible relation between selenium and metabolic risk factors. The literature was searched via PubMed, Scopus, ISI Web of Science, and Google Scholar. Searches were not restricted by time or language. Relevant studies were selected in three phases. After an initial quality assessment, two reviewers extracted all the relevant data, whereas the third reviewer checked their extracted data. All evidence came from experimental and laboratory studies. Selenoprotein P is the best indicator for selenium nutritional levels. In addition, high levels of selenium may increase the risk of metabolic syndrome while the lack of sufficient selenium may also promote metabolic syndrome. selenium supplementation in subjects with sufficient serum selenium levels has a contrary effect on blood pressure, LDL, and total cholesterol. According to the bioavailability of different types of selenium supplementation such as selenomethionine, selenite and selenium-yeast, it seems that the best nutritional type of selenium is selenium-yeast. Regarding obtained results of longitudinal studies and randomized controlled trials, selenium supplementation should not be recommended for primary or secondary cardio-metabolic risk prevention in populations with adequate selenium status.

Biomarkers of selenium status

The essential trace element, selenium (Se), has multiple biological activities, which depend on the level of Se intake. Relatively low Se intakes determine the expression of selenoenzymes in which it serves as an essential constituent. Higher intakes have been shown to have anti-tumorigenic potential; and very high Se intakes can produce adverse effects. This hierarchy of biological activities calls for biomarkers informative at different levels of Se exposure. Some Se-biomarkers, such as the selenoproteins and particularly GPX3 and SEPP1, provide information about function directly and are of value in identifying nutritional Se deficiency and tracking responses of deficient individuals to Se-treatment. They are useful under conditions of Se intake within the range of regulated selenoprotein expression, e.g., for humans <55 μg/day and for animals <20 μg/kg diet. Other Se-biomarkers provide information indirectly through inferences based on Se levels of foods, tissues, urine or feces. They can indicate the likelihood of deficiency or adverse effects, but they do not provide direct evidence of either condition. Their value is in providing information about Se status over a wide range of Se intake, particularly from food forms. There is need for additional Se biomarkers particularly for assessing Se status in non-deficient individuals for whom the prospects of cancer risk reduction and adverse effects risk are the primary health considerations. This would include determining whether supranutritional intakes of Se may be required for maximal selenoprotein expression in immune surveillance cells. It would also include developing methods to determine low molecular weight Se-metabolites, i.e., selenoamino acids and methylated Se-metabolites, which to date have not been detectable in biological specimens. Recent analytical advances using tandem liquid chromatography-mass spectrometry suggest prospects for detecting these metabolites.

The advantages of deep ocean water for the development of functional fermentation food

Deep ocean water (DOW) is obtained from 600 m below the sea surface. In recent years, DOW has been applied in the development of fermentation biotechnologies and functional foods. DOW is rich in trace minerals, comprises multiple physiological and health functions, and is able to promote microbe growth; therefore, the application of DOW directly benefits the development of the fermentation industry and functional foods. This study integrated the current health functions and applications of DOW with the latest results from studies related to fermentation biotechnology. Subsequently, the influence of applying DOW in fermented functional food development and the effects in health function improvements were summarized. According to the previous studies, the main reasons for the increased effect of fermented functional foods through the application of DOW are increased generation of functional metabolite contents in the microbes, intrinsic health functions of DOW, and the microbial use of mechanisms of converting the absorbed inorganic ions into highly bioavailable organic ions for the human body. These combined advantages not only enhance the health functions of fermentation products but also provide fermentation products with the intrinsic health functions of DOW.

The effect on selenium concentrations of a randomized intervention with fish and mussels in a population with relatively low habitual dietary selenium intake

Selenium status of the Danish population is below that assumed optimal for the suggested protective effects against chronic diseases, including certain cancers. Fish and shellfish are important dietary sources of selenium in Denmark. We investigated the effect of increased fish and mussel intake on selenium blood concentrations in a population with relatively low habitual dietary selenium intake. We randomly assigned 102 healthy men and women (all non-smokers) aged 48–76 years to an intervention group (n = 51) or a control group (n = 51). Intervention participants received 1000 g fish and mussels/week for 26 weeks (~50 μg selenium/day). Controls received no intervention. Non-fasting blood samples were taken and whole blood selenium was determined using inductively coupled plasma-mass spectrometry (ICP-MS), and plasma selenoprotein P (SelP) was determined by high performance liquid chromatography coupled to ICP-MS. All available observations were included in linear multiple regression analysis to evaluate the effect of the intervention. The difference in mean change for intervention compared with control persons was 14.9 ng/mL (95% CI: 10.2, 19.7) for whole blood selenium, and 7.0 ng/mL (95% CI: 3.1, 10.9) for plasma SelP (Weeks 0–26). Selenium concentrations were significantly increased after 26 weeks of intervention, albeit to a lower degree than expected.

Long-term selenium supplementation of humans: selenium status and relationships between selenium concentrations in skeletal muscle and indicator materials

Supplementation with elevated doses of l-selenomethionine (SeM) or selenium-enriched yeast that contains SeM as the main selenium species is frequently used as a protective or therapeutic measure. Information on the effects of long-term selenium supplementation on the body selenium status is, however, rather scarce. We therefore investigated fifteen male test persons who had taken selenium yeast and/or SeM supplements in medium doses of 62.5-125 microg Se/day or high doses of 200-262.5 microg Se/day for periods ranging from 1 year to 24 years. Seven non-supplemented men served as controls. As skeletal muscle is the main selenium pool, thigh muscle biopsy samples were taken. The selenium concentrations in these biopsies and in samples of the indicator materials blood, blood plasma, blood cells, head hair and toenails were determined by neutron activation analysis. Compared with the controls, the muscle selenium level was raised with additional selenium supplementation, but the relative increase in the mean muscle selenium concentration (by factors of about 1.6 and 2 for the medium and high doses, respectively) was lower than that in the selenium intake. Highly significant correlations found between the selenium concentrations in muscle and whole blood (R=0.90), red blood cells (R=0.91), blood plasma (R=0.87), head hair (R=0.89) and toenails (R=0.85) show that in humans supplemented in this way the selenium status can be assessed in a relatively easy way by analysis of the selenium retention in these indicator materials.

Effect of selenium supplementation and source on the selenium status of horses

This study was conducted to determine the effect of Se supplementation and source on the Se status of horses. Eighteen 18-mo-old nonexercised horses were randomly assigned within sex to 1 of 3 treatments: 1) control (CTRL, no supplemental Se, 0.15 mg of Se/kg of total diet DM); 2) inorganic Se (INORG, CTRL + 0.45 mg of Se/kg of total diet DM from NaSeO3); or organic Se [ORG, CTRL + 0.45 mg of Se/kg of total diet DM from zinc-L-selenomethionine (Availa Se, Zinpro, Corp., Eden Prairie, MN)]. Horses were acclimated to the CTRL diet (7.1 kg of DM alfalfa hay and 1.2 kg of DM concentrate per horse daily) for 28 d. After the acclimation period, the appropriate treatment was top-dressed on the individually fed concentrate for 56 d. Jugular venous blood samples were collected on d 0, 28, and 56. Middle gluteal muscle biopsies were collected on d 0 and 56. Muscle and plasma were analyzed for Se concentrations. Glutathione peroxidase activity was measured in muscle (M GPx-1), plasma (P GPx-3), and red blood cells (RBC GPx-1). Data were analyzed as a repeated measures design. Mean plasma Se concentration on d 28 and 56 was greater (P < 0.05) for Se-supplemented horses compared with CTRL horses, and tended (P < 0.1) to be greater in ORG vs. INORG on d 28. Mean muscle Se concentration and P GPx-3 activities increased (P < 0.05) from d 0 to 56 but were not affected by treatment. Mean RBC GPx-1 activity tended to be greater (P < 0.1) in ORG than INORG or CTRL horses on d 28, and tended to be greater (P < 0.1) for INORG compared with ORG horses on d 56. Mean RBC GPx-1 activity of INORG and ORG horses was not different from that of CTRL on d 56. Mean M GPx-1 activity decreased (P < 0.01) from d 0 to 56. In conclusion, zinc-L-selenomethionine was more effective than NaSeO3 at increasing plasma Se concentration from d 0 to 28; however, both supplemental Se sources had a similar effect by d 56. No difference in Se status due to Se supplementation or source could be detected over a 56-d supplementation period by monitoring middle gluteal muscle Se, M GPx-1, or P GPx-3. Results for RBC GPx-1 also were inconclusive relative to the effect of Se supplementation and source.

Current mass spectrometry strategies for selenium speciation in dietary sources of high-selenium

This document reviews the most relevant mass spectrometry approaches to selenium (Se) speciation in high-Se food supplements in terms of qualitative and quantitative Se speciation and Se-containing species identification, with special reference to high-Se yeast, garlic, onions and Brazil nuts. Important topics such as complexity of Se speciation in these materials and the importance of combining Se-specific detection and molecule-specific determination of the particular species of this element in parallel with chromatography, to understand their nutritional role and cancer preventive properties are critically discussed throughout. The versatility and potential of mass spectrometric detection in this field are clearly demonstrated. Although great advances have been achieved, further developments are required, especially if "speciated"certified reference materials (CRMs) are to be produced for validation of measurements of target Se-containing species in Se-food supplements.

The use of high-selenium yeast to raise selenium status: how does it measure up?

Selenium-enriched yeast (Se-yeast) is a common form of Se used to supplement the dietary intake of this important trace mineral. However, its availability within the European Union is under threat, owing to concerns expressed by the European Community (EC) Scientific Committee on Food that Se-yeast supplements are poorly characterised and could potentially cause the build up of Se in tissues to toxic levels. The present review examines the validity of these concerns. Diagrams of the biosynthesis and metabolism of Se compounds show which species can be expected to occur in Se-yeast preparations. Se-yeast manufacture is described together with quality-control measures applied by reputable manufacturers. The way in which speciation of Se-yeast is achieved is explained and results on amounts of Se species in various commercial products are tabulated. In all cases described, selenomethionine is the largest single species, accounting for 54-74 % of total Se. Se-yeast is capable of increasing the activity of the selenoenzymes and its bioavailability has been found to be higher than that of inorganic Se sources in all but one study. Intervention studies with Se-yeast have shown the benefit of this form in cancer prevention, on the immune response and on HIV infection. Of about one dozen supplementation studies, none has shown evidence of toxicity even up to an intake level of 800 microg Se/d over a period of years. It is concluded that Se-yeast from reputable manufacturers is adequately characterised, of reproducible quality, and that there is no evidence of toxicity even at levels far above the EC tolerable upper intake level of 300 microg/d.

Environmental induction models for the investigation of activity: changes in glutathione peroxidase, a crucial factor of the antioxidant defence

Glutathione peroxidase enzyme superfamily plays significant role in the elimination of reactive oxygen free radicals in the animals. Many characteristics of these proteins have been revealed already, but their regulation is still not known. Several data suggest that some environmental factors have certain regulatory effect, while others propose strict genetic regulation. In this report we present four different environmental induction models in which New Zealand white rabbits were used as experimental animals. In three models, free radical load of different origin, lipidperoxide load, application of a glutathione depletor or a prooxidant agent, was introduced. Beside these negative models a positive model was also constructed in which additive selenium was supplied. Glutathione peroxidase activity was measured in blood serum, erythrocyte haemolysate and liver. Reduced glutathione, and malondialdehyde concentration in the liver were also determined. According to the results, the established models are capable for analysing the enzyme activity x environmental interactions.

The major selenium-containing protein in human peripheral granulocytes

Previously, a selenium-containing protein with subunit molecular weight of 15 kDa was found in peripheral human granulocytes. In continuation of this work, the present communication accounts for purification, identification, and characterization of this major selenium-containing protein. The protein was purified on a heparin-Sepharose column followed by Sephacryl S-200 column chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis visualized two bands with subunit molecular weights around 15 kDa. o-Phthaldialdehyde precolumn derivatization and reverse-phase high-performance liquid chromatography showed that the protein contains selenocysteine or selenocystine residues. High-performance gel filtration and isoelectric focusing revealed that the protein had an apparent molecular weight of 32 kDa and a pI value of 7.9. The addition of the protein synthesis inhibitor puromycin to the cell culture medium decreased the 15-kDa protein synthesis. These data suggest that the major selenium-containing protein in peripheral human granulocytes might be a protein with two subunits around 15 kDa. Enzyme studies showed that the protein had peroxidase activity assayed with H2O2 as a substrate and O-dianisidine as a hydrogen donor. This enzymatic activity competed with glutathione peroxidase on the consumption of H2O2, leading to an "inhibiton" of glutathione peroxidase (GSH-Px) activity. Sodium azide could eliminate the inhibition of the protein to GSH-Px. All of the above results implicated that the protein might be a H2O2-dependent selenium containing peroxidase different from GSH-Px. Therefore, the biological function of the protein could be related to eliminating H2O2 generated in the respiratory burst reaction of granulocytes, thus protecting these cells from oxidative damage during phagocytosis.

Thioredoxin reductase is one of the selenoproteins in both promyelocytic and granulocytic HL-60 cells

Human leukemia promyelocytic HL-60 cells differentiate into granulocytes when cultured with 1.25% dimethyl sulfoxide for 3 d. The radioactive Na2 75SeO3 incorporation and the amount of total proteins were interrelated in both promyelocytic and granulocytic HL-60. Promyelocytic cells had four times higher 75Se incorporation and 34% more protein synthesis than the granulocytic cells on the fifth culturing day. The enzyme activities of glutathione peroxidase (GSH-Px, E.C. 1.11.1.9) and thioredoxin reductase (TrxR, E.C. 1.6.4.5) in both types of cells increased significantly and approached steady stage on the third day. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (PAGE) analysis and autoradiography of the proteins from the cells revealed three proteins with molecular weights of 57, 28, and 21 kDa, respectively. These three 75Se-labeled proteins were present in both types of cells. The proteins from HL-60 cells were separated by DEAE-Sepharose and 2'5'-ADP-Sepharose columns. The purified 57-kDa protein had TrxR activity of 0.744 micromol 5'-thionitrobenzoic acid (TNB) formed/min/mg protein and two isoelectric points at pH 5.9 and 6.0. These results suggest that TrxR is one of the selenoproteins in both promyelocytic and granulocytic HL-60 cells.

The effects of oxidative stress in in vitro cultured astroglial cells

It has been suggested that glial cells in the central nervous system might function as a buffer and protect neurons and synapses. Associated with such a function, glial cells might be affected in degenerative diseases, for example, Alzheimer's disease and Parkinson's disease, due to generation of free-radicals. Free-radicals might be generated during the metabolic transformation of xenobiotics. The purpose of the present study was to determine whether a xenobiotic (in this case, paraquat), is metabolised in glial cells during the generation of free-radicals. Furthermore, this study determined whether free-radicals can induce DNA fragmentation and whether this fragmentation can be repaired. The data produced indicated that astroglial cells contain P450-reductase which transforms paraquat into a pyridium free-radical. In turn, this causes a dose-dependent DNA fragmentation, as determined by using single-cell gel electrophoresis. The dose-dependent effect was valid up to 80μM paraquat. The oxidative stress induced in the astroglial cells was also associated with a maximum 15% increase in the anti-oxidative enzyme, glutathione peroxidase. After exposure to 40μM paraquat, followed by growth of the cells in a paraquat-free medium, DNA repair was shown to be rather slow, and was only obvious two hours after exposure to paraquat. This might be related the shuttle in which paraquat/P450-reductase is implicated, which causes a protracted generation of free-radicals. The data are discussed in relation to the available literature.

Different selenium-containing proteins in the extracellular and intracellular media of leucocytes cultivated in vitro

The purpose of this communication is to elucidate if selenium plays a role in the function of granulocytes and lymphocytes. Thus, the incorporation of selenium in proteins from granulocytes and lymphocytes cultured with 1 microCi/mL radioactive Na2(75)SeO3 was studied. The protein peaks containing 75Se from two columns of Heparin Sepharose CL-6B and Sephacryl S-200 HR were separated further by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. The results showed that the incorporation of 75Se into granulocytes was about six times higher than that of lymphocytes during a 96-h cultivation, however, the GSH-Px activity in granulocytes did not change significantly. On the other hand, the GSH-Px activity of lymphocytes rose significantly after three days cultivation. These data indicated that the main chemical form of selenium in granulocytes was not GSH-Px. Results from SDS-PAGE revealed a strongly 75Se-labeled protein band with subunit molecular weight of 15 kDa in the supernatant of granulocyte homogenate. However, the main chemical forms of selenium in the culture media of granulocytes and lymphocytes were found to be selenoprotein P. The different forms of selenium-containing proteins in the intracellular and extracellular media of granulocytes indicated the different functions of these proteins.

Uptake of various trace elements during germination of wheat, buckwheat and quinoa

The practice of sprouting is widely used to improve the nutritional value of grain seeds. Several nutritive factors such as vitamin concentrations and bioavailability of trace elements and minerals increase during germination. The objective of this work was to study the enrichment of various essential trace elements during germination of wheat (Triticum aestivum), buckwheat (Fagopyrum esculentum), and quinoa (Chenopodium quinoa) seeds in order to improve their nutritional role as a source of bioavailable trace elements. Seeds were sprouted either in distilled- or tap-water and in five different electrolyte solutions to investigate the concentration-dependent uptake. The time-dependence was investigated by analyzing aliquots of the sprouts after certain germination periods. Samples were analyzed after freeze drying for their Li, V, Cr, Fe, Mn, Co, Cu, Zn, Sr, Mo, As and Se concentrations with inductively-coupled plasma mass-spectrometry (ICP-MS). As a control for possible changes in the biochemical metabolism of the sprouts, the biosynthesis of vitamin C was also determined by using reversed-phase ion-pair HPLC. It was shown that quinoa was the most resistant to the applied electrolyte solutions and had the highest uptake rates for almost all elements, followed by buckwheat and wheat. Greatest increases were observed for Co, Sr, and Li. No significant changes in vitamin C biosynthesis were observed between sprouts grown in different electrolyte solutions. The time-dependent uptake for most elements was characterized by a significant absorption during soaking of the seeds, followed by a lag phase during the first day of germination and an increased uptake during the second and third day. Se and As showed distinctly different uptake behaviors.

Fluctuations in Fe, Cu, Zn, Br, As, Se, and Rb concentrations in C57L/J mice bearing BW7756 murine hepatoma using radioisotope-induced X-ray fluorescence

The effects of selenite or selenate supplementation on the concentration and distribution of Fe, Cu, Zn, As, Br, and Rb are investigated using the radioisotope-induced X-ray fluorescence, RIXRF. These effects are studied in the animals bearing BW7756 murine hepatoma and healthy animals for both of the oxidation states. Selenite and selenate induce different effects on the distribution of selenium, zinc, copper, bromine, and rubidium. The differences may be attributed to the differences in the inter element interaction after absorption into the bloodstream as well as to the mode of their intestinal absorption. Simultaneous supplementation of copper with selenite or selenate at the described levels has a profound influence on the concentration levels of other elements in the normal as well as in the diseased mice. The administration of selenium (0.67 micrograms/g body wt sodium selenite or sodium selenate, daily) and selenium and copper (0.67 and 1.35 micrograms/g body wt, respectively) has no effect on the incidence rate of hepatoma development.

Serum selenium concentration and risk of ischaemic heart disease in a prospective cohort study of 3000 males

Whether an association, causative or not, exists between the level of serum selenium and the risk of ischaemic heart disease (IHD) remains unsettled. We investigated the issue in a cohort of 3387 males aged 53-74 years (mean 63). Based on information about health status, life-style and socioeconomic factors given in a prefilled comprehensive questionnaire, the men were interviewed and the information validated. Following the interview, they underwent a clinical examination and had a venous blood sample drawn for the determination of a number of biochemical characteristics. Three hundred and forty-six men were excluded due to prevalent cardiovascular disease, including stroke. During the next three years (1986-1989) 107 men (approximately 3%) suffered an IHD event; 25 events were fatal. Compared to others, men with serum selenium levels less than or equal to 1 mumol/l, approximately the lowest tertile, had a 70% increased risk of IHD, relative risk (RR) with 95% confidence limits was 1.70 (1.14-2.53). After multivariate adjustment for cholesterol, social class, smoking and age, RR was 1.55 (1.00-2.39). Serum selenium level was significantly (P less than 0.05), but not strongly, correlated with a number of IHD risk factors: serum cotinine, tobacco smoking, social class, alcohol consumption, total cholesterol, hypertension, age and physical inactivity. Body mass index, HDL-cholesterol and triglycerides were not significantly associated with serum selenium. We conclude that middle-aged and elderly Danish men with serum selenium less than or equal to 1 mumol/l had a significantly increased risk of ischaemic heart disease. This association was not explained by the interrelationship of serum selenium and major cardiovascular risk factors.

[75Se]selenite and [75Se]selenate fluctuations during the development of murine hepatoma

The distribution of selenate and selenite selenium in C57L/J mice during the progression of BW7756 murine hepatoma was investigated using intra-ocular injection with the oxyanions labeled with 75Se radioisotope. Comparison is made with the normal distribution of selenium studied by the RIXRF method. The trace elemental profiles, TEP, for the two oxidation states are compared in healthy and disease states. It has been found that the presence of tumor significantly changes the level of tracer in various uninvolved organs. These changes are prominent in the early growth phase of the tumor. The two oxidation states show differences in the TEP for kidney, spleen, stomach and testes.

Time-dependent distribution of selenate and selenite selenium in male C57L/J mice

The distribution and retention of selenate and selenite in C57L/J mice was investigated using 75Se radioisotope. The comparison is made with the normal distribution of the element determined by using radioisotope-induced x-ray fluorescence, RIXRF methods. The distribution of the two oxidation states measured as activity of 75Se was almost identical but differed from the normal trace elemental profile, TEP. The excretion rates of the two selenium species in the initial phase are different with more selenate being excreted than selenite in the first 2 days. It was found that the wholebody excretion rates followed a pure first-order pattern this was not true for the individual organs of the animals.

Biochemical and clinical effects of an antioxidative supplementation of geriatric patients. A double blind study

Ninety seven geriatric patients from two Danish homes for old people accepted to participate in a blinded experiment designed to counteract ageing phenomena. The subjects were split into two groups, i.e., the verum and the placebo group. The verum group received daily for one year an antioxidative cocktail consisting of: 300 micrograms selenium as L-selenomethionine, 45 mg zinc, 270 mg vitamin C, 2.7 mg vitamin A, 6 mg vitamin B-6, and 465 mg vitamin E (d-alfatocopherol). Furthermore, in order to enhance exchange in polyenoic acids, each subject received daily 250 mg gamma-linolenic acid. The placebo groups received similar looking pills and capsules without the active components. During one year in the verum group, the whole blood selenium, the hydrogen-dependent glutathione peroxidase (GSH-Px) of erythrocytes, and the vitamin E level in serum was found increased compared to the pretreatment values and to the placebo group. No change could be traced in the t-butylhydroperoxide dependent GSH-Px, an enzyme that also assays the glutathione-s-transferase. During the same period of time, the fasting levels of serum fatty acids and the content of lipofuscin in erythrocytes were estimated. Compared to the pretreatment values, the lipofuscin level declined significantly and the level of w-3 penta- and hexaenoic acids increased in the verum, but not in the placebo group. During the study period, slight, but significant improvements in psychological scores could be traced. Furthermore, the assays of bloodflow in different areas of the brain surface (i.e., the ISI values) revealed a general trend to improvement in all areas, when the ISI values were compared during treatment with the pretreatment values and the values in the placebo group.