351
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Tiwary AK, Panter KE, Stegelmeier BL, James LF, Hall JO. Evaluation of the respiratory elimination kinetics of selenium after oral administration in sheep. Am J Vet Res 2006; 66:2142-8. [PMID: 16379660 DOI: 10.2460/ajvr.2005.66.2142] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To evaluate the respiratory excretion and elimination kinetics of organic and inorganic selenium after oral administration in sheep. ANIMALS 38 crossbred sheep. PROCEDURES Selenium was administered PO to sheep as a single dose of 0, 1, 2, 3, or 4 mg/kg as sodium selenite or selenomethionine. Expired air was collected and analyzed from all sheep at 4, 8, and 16 hours after administration. RESULTS Clinical signs consistent with selenium intoxication were seen in treatment groups given sodium selenite but not in treatment groups given the equivalent amount of selenium as selenomethionine. However, a distinct garlic-like odor was evident in the breath of all sheep receiving 2 to 4 mg of selenium/kg. The intensity of odor in the breath did not correlate with clinical signs in affected animals receiving sodium selenite treatment. CONCLUSIONS AND CLINICAL RELEVANCE The concentration of selenium in expired air was greater in sheep receiving selenium as selenomethionine than sodium selenite. The concentration of selenium in expired air from sheep receiving high doses of selenium (3 and 4 mg of selenium/kg) was larger and selenium was expired for a longer duration than the concentration of selenium in expired air from sheep receiving low doses of selenium (1 and 2 mg of selenium/kg).
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Affiliation(s)
- Asheesh K Tiwary
- Utah Veterinary Diagnostic Laboratory, 950 E 1400 N, Logan, UT 84341, USA
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352
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Cabañero AI, Madrid Y, Cámara C. Selenium long-term administration and its effect on mercury toxicity. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2006; 54:4461-8. [PMID: 16756381 DOI: 10.1021/jf0603230] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
An in vivo experiment was conducted to assess selenium bioaccumulation and bioaccessibility through the food chain and its effect on Hg toxicity. For this purpose 72 chickens were fed under different controlled conditions. Chickens were exposed to a common basal diet or a diet supplemented with Hg(II), MeHg, and Se(IV). Enzymatic digestion (feed, chicken muscle, liver, and kidney) as well as simulated human gastric and intestinal digestion (chicken muscle) led to the identification of selenomethionine (SeMet) in all the samples analyzed. Therefore, although chickens have no efficient mechanism for SeMet synthesis they can be considered as a source of SeMet due to its diet and the plant-animal food chain. The kidneys were the target organ for both total Se and SeMet in chickens (1604 +/- 136 and 128 +/- 6 microg kg(-1), respectively), but the greatest body store, among the tissues studied, was the muscle in both cases (84-96% of total Se). Long-term administration of inorganic and organic mercury did not alter SeMet distribution significantly. The antagonistic effect of Se on Hg toxicity by favoring MeHg demethylation is discussed.
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Affiliation(s)
- Ana I Cabañero
- Departamento de Química Analítica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain
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353
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Opinion of the Panel on additives and products or substances used in animal feed (FEEDAP) on the safety and efficacy of the product Sel‐Plex 2000 as a feed additive according to Regulation (EC) No 1831/2003. EFSA J 2006. [DOI: 10.2903/j.efsa.2006.348] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
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354
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Lee JH, Chung KY, Bang D, Lee KH. Searching for aging-related proteins in human dermal microvascular endothelial cells treated with anti-aging agents. Proteomics 2006; 6:1351-61. [PMID: 16404724 DOI: 10.1002/pmic.200500287] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Endothelial cells constitute an interface between blood and tissue and act as a medium for active interaction between plasma and the intracellular environment for homeostasis. Aging of endothelial cells plays a significant role in the pathophysiology of age-related vascular diseases; however, precise mechanisms for senescence have not been elucidated. Proteomics allows identification of protein structures, functions, and characteristics, and can be applied to the study of aging processes. Using cultured human dermal microvascular endothelial cells and two-dimensional proteomic mapping, we studied the effects of kinetin, epigallocatechin-3-gallate, all-trans-retinoic acid, and selenium on their senescence and searched for the aging-related proteins. The treatments resulted in 68 qualitative changes and 172 quantitative changes, and we were able to identify 46 spots among them. All of the agents indicated above induced changes in the expression of moesin, rho guanosine-5'-diphosphate-dissociation inhibitor, and actin, confirmed by immunoblotting and confocal laser microscopy. As these proteins were associated with cell cycle and cytoskeleton, immunoblotting of the proteins related to cell cycle was performed. Although practical significance remains to be confirmed by in vivo research, this fundamental discovery may provide a basis for understanding the mechanism of aging and age-related diseases.
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Affiliation(s)
- Ju Hee Lee
- Department of Dermatology, Cutaneous Biology Research Institute, Yonsei University College of Medicine, Seodaemoon-Gu, Seoul, Korea
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355
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Abstract
Thyroid hormone synthesis, metabolism and action require adequate availability of the essential trace elements iodine and selenium, which affect homeostasis of thyroid hormone-dependent metabolic pathways. The three selenocysteine-containing iodothyronine deiodinases constitute a novel gene family. Selenium is retained and deiodinase expression is maintained at almost normal levels in the thyroid gland, the brain and several other endocrine tissues during selenium deficiency, thus guaranteeing adequate local and systemic levels of the active thyroid hormone T(3). Due to their low tissue concentrations and their mRNA SECIS elements deiodinases rank high in the cellular and tissue-specific hierarchy of selenium distribution among various selenoproteins. While systemic selenium status and expression of abundant selenoproteins (glutathione peroxidase or selenoprotein P) is already impaired in patients with cancer, disturbed gastrointestinal resorption, unbalanced nutrition or patients requiring intensive care treatment, selenium-dependent deiodinase function might still be adequate. However, disease-associated alterations in proinflammatory cytokines, growth factors, hormones and pharmaceuticals modulate deiodinase isoenzyme expression independent from altered selenium status and might thus pretend causal relationships between systemic selenium status and altered thyroid hormone metabolism. Limited or inadequate supply of both trace elements, iodine and selenium, leads to complex rearrangements of thyroid hormone metabolism enabling adaptation to unfavorable conditions.
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Affiliation(s)
- Josef Köhrle
- Institut für Experimentelle Endokrinologie und Endokrinologisches Forschungs-Centrum der Charité EnForCé, Charité Universitätsmedizin Berlin, Berlin, Germany.
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356
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Safaya R, Chai H, Kougias P, Lin P, Lumsden A, Yao Q, Chen C. Effect of lysophosphatidylcholine on vasomotor functions of porcine coronary arteries. J Surg Res 2005; 126:182-8. [PMID: 15919417 DOI: 10.1016/j.jss.2005.01.015] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2004] [Revised: 01/22/2005] [Accepted: 01/24/2005] [Indexed: 10/25/2022]
Abstract
BACKGROUND Lysophosphatidylcholine (LPC) is a product of phosphatidylcholine hydrolysis by phospholipase A(2) and a mediator of the lipid-induced atherosclerotic changes. In this study, we determined the effects of LPC on vasomotor functions, oxidative stress, and endothelial nitric oxide synthase (eNOS) expression in porcine coronary arteries. METHODS Porcine coronary arteries were cut into 5-mm rings and were treated with LPC or antioxidant selenomethionine (SeMet). For the vasomotor studies, we used a myograph tension system. Levels of superoxide anion (O(2)(-)) were detected by the lucigenin-enhanced chemiluminescence method. The eNOS protein level was studied by immunohistochemistry with avidin-biotin complex immunoperoxidase procedure. RESULTS Endothelium-dependent relaxation in response to bradykinin was reduced by 36% and 81% for the rings treated with 12.5 and 25 mum of LPC, respectively, as compared with controls (P < 0.05). Endothelium-independent relaxation in response to sodium nitroprusside also was reduced by 63% after treatment with 25 mum LPC (P < 0.05). The O(2)(-) level was increased in the porcine arteries treated with 25 mum of LPC by 41% as compared with controls (P < 0.05). The antioxidant SeMet reversed the effects of LPC on vascular relaxation and O(2)(-) production. Immunoreactivity of eNOS in LPC-treated vessel rings also was reduced substantially. CONCLUSIONS LPC impairs endothelium-dependent and endothelium-independent vasorelaxation. This effect is associated with increased superoxide radical production and decreased eNOS activity and is practically reversed with the use of the antioxidant SeMet.
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Affiliation(s)
- Rakesh Safaya
- Molecular Surgeon Research Center, Division of Vascular Surgery and Endovascular Therapy, Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston, Texas, USA
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357
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Bou R, Guardiola F, Barroeta AC, Codony R. Effect of dietary fat sources and zinc and selenium supplements on the composition and consumer acceptability of chicken meat. Poult Sci 2005; 84:1129-40. [PMID: 16050130 DOI: 10.1093/ps/84.7.1129] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
A factorial design was used to study the effect of changes in broiler feed on the composition and consumer acceptability of chicken meat. One week before slaughter, 1.25% dietary fish oil was removed from the feed and replaced by other fat sources (animal fat or linseed oil) or we continued with fish oil, and diets were supplemented with Zn (0, 300, or 600 mg/kg), and Se (0 or 1.2 mg/kg as sodium selenite or 0.2 mg/kg as Se-enriched yeast). The changes in dietary fat led to distinct fatty acid compositions of mixed raw dark and white chicken meat with skin. The fish oil diet produced meat with the highest eicosapentanoic acid (EPA) and docosahexanoic acid (DHA) content, whereas the linseed oil diet led to meat with the highest content in total n-3 polyunsaturated acids (PUFA), especially linolenic acid. However, meat from animals on the animal fat diet was still rich in very long-chain n-3 PUFA. Se content was affected by Se and Zn supplements. Se content increased with Zn supplementation. However, only Se from the organic source led to a significant increase in this mineral in meat compared with the control. Consumer acceptability scores and TBA values of cooked dark chicken meat after 74 d or after 18 mo of frozen storage were not affected by any of the dietary factors studied.
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Affiliation(s)
- R Bou
- Nutrition and Food Science Department-CeRTA, Faculty of Pharmacy, University of Barcelona, Avinguda Joan XXIII s/n, E-08028 Barcelona, Spain
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358
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Mihaliková K, Gresáková L, Boldizárová K, Faix S, Leng L, Kisidayová S. The effects of organic selenium supplementation on the rumen ciliate population in sheep. Folia Microbiol (Praha) 2005; 50:353-6. [PMID: 16408856 DOI: 10.1007/bf02931418] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
The effect of selenium supplementation on the rumen protozoan population of sheep was demonstrated. Both the total and generic counts of rumen ciliates in sheep fed a diet with basal Se content (70 microg/kg dry matter) were compared to those of animals given feed supplemented with inorganic (disodium selenite) or organic Se (selenized yeast) (310 microg/kg dry matter). The genera of Entodinium, Isotricha, Dasytricha, Ophryoscolex, Diploplastron and Polyplastron occurred in all sheep except for the control, in which Ophryoscolex was not observed. The population of Ophryoscolex caudatus f. tricoronatus was significantly higher in sheep supplemented with organic Se than in animals given inorganic Se (by 160 %). Supplementation of feed with selenized yeast induced significant growth in the Diploplastron population (by 63 %) while no change occurred in sheep given selenite. The populations of Dasytricha ruminantium and Polyplastron multivesiculatum were higher than control in both Se-supplemented groups. The ciliate population of Entodinium spp. was not influenced by Se supplements. Our results suggest a protective effect of Se feed supplementation on the development of some rumen ciliate species in young ruminants.
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Affiliation(s)
- K Mihaliková
- Institute of Animal Physiology, Slovak Academy of Science, 040 01 Kosice, Slovakia.
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359
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Bryszewska MA, Ambroziak W, Rudzinski J, Lewis DJ. Characterisation of selenium compounds in rye seedling biomass using 75Se-labelling/SDS-PAGE separation/γ-scintillation counting, and HPLC-ICP-MS analysis of a range of enzymatic digests. Anal Bioanal Chem 2005; 382:1279-87. [PMID: 15977033 DOI: 10.1007/s00216-005-3272-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2005] [Revised: 04/01/2005] [Accepted: 04/13/2005] [Indexed: 10/25/2022]
Abstract
In the present study, selenium-enriched plant biomass was investigated to evaluate the ability of rye seedlings to take up, and assimilate, inorganic selenium. Two different analytical approaches were used. Electrophoretic separation (SDS-PAGE) of proteins extracted from 75Se-labelled biomass was used to investigate the biotransformation of selenite into organic forms of the element. Ion-pair chromatography coupled with ICP-MS detection was chosen for the analysis of selenium species, enzymatically extracted from the plant biomass. The results of three enzymatic hydrolysis procedures and three sequential enzymatic extractions procedures are compared. The most effective single extraction was proteolysis (using protease type XIV), giving an overall extraction efficiency of 48%. However, for combinations of enzymes, the most effective was cellulase (Trichoderma viride) followed by sequential extraction of the solid pellet using protease type XIV, giving an extraction efficiency of 70%. The complementary data from the electrophoretic fractionation of proteins, and the HPLC separation of Se-species in the proteolytic digests, reveal the existence of large number of selenium-containing compounds in the rye seedling plant biomass. The results showed the complete biotransformation of inorganic selenium into organic forms during germination of the rye seedlings. HPLC-ICP-MS analysis of extracts from the plant biomass did not show the presence of selenate or selenite. At the time of this study, the lack of suitable organic-MS facilities meant that it was not possible to characterise them fully. However, the data does show that a combination of different enzymes, rather than just the commonly-used protease, should be considered when developing an extraction strategy for selenium in different food types to those already reported in the literature.
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Affiliation(s)
- Malgorzata A Bryszewska
- Institute of General Food Chemistry, Technical University of Łódź, Stefanowskiego 4/10, 90-924, Łódź, Poland.
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360
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Hamdaoui MH, Chahed A, Ellouze-Chabchoub S, Marouani N, Ben Abid Z, Hédhili A. Effect of green tea decoction on long-term iron, zinc and selenium status of rats. ANNALS OF NUTRITION AND METABOLISM 2005; 49:118-24. [PMID: 15802907 DOI: 10.1159/000084745] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2003] [Accepted: 07/14/2004] [Indexed: 11/19/2022]
Abstract
AIMS The objective was to examine the effect of green tea decoction given at two different concentrations on the long-term (6 weeks) iron, zinc and selenium status of rats. METHODS During the experimental period, the rats were given ad libitum a basic diet + ultra pure water (control group), a basic diet + green tea decoction prepared from 50 g/l (tea 50 group), or a basic diet + green tea decoction prepared from 100 g/l (tea 100 group). The zinc and iron status was evaluated by determining their concentrations in the serum, blood precipitate, liver, spleen, femur, heart and kidney. Selenium status was evaluated by the serum selenium concentration and whole blood glutathione peroxidase activity. RESULTS Green tea decoction significantly reduced serum iron by 26% in the tea groups (p < 0.01). The blood precipitate of iron was significantly decreased by 25 and 41% in the tea 50 and tea 100 groups (p < 0.01), respectively. The reserve of iron stored in the liver, spleen and femur was significantly reduced in the tea 100 group by 32% (p < 0.02), 20% (p < 0.04) and 35% (p < 0.005), respectively. Moreover, the two concentrations of green tea significantly decreased the reserve of iron stored in the kidney (p < 0.005) and heart (p < 0.02). In contrast with its effects on iron status, green tea decoction significantly increased the serum zinc in the tea 100 group by 24% (p < 0.001). It also increased the blood precipitate of zinc by 50 (p < 0.01) and 75% (p < 0.0001) in tea 50 and tea 100 groups, respectively. In the kidney, heart and femur, zinc significantly increased in the tea groups dependent on the tea dose. Similarly, the high concentration of green tea decoction significantly increased the serum selenium concentration by 16% (p < 0.004). In addition, both concentrations of green tea decoction significantly increased the whole blood glutathione peroxidase activity by 102 and 130% (p < 0.01). CONCLUSION Green tea decoction reduced the iron status and improved the zinc and selenium status of rats. These effects may constitute another beneficial effect of the green tea decoction which could play an important role in the antioxidant processes.
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Affiliation(s)
- Mohamed Hédi Hamdaoui
- Unité de Recherche sur l'Anémie Nutritionnelle et la Biodisponibilité des Oligoéléments, Ecole Supérieure des Sciences et Techniques de la Santé de Tunis, Tunisie.
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361
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Połatajko A, Banaś B, Encinar JR, Szpunar J. Investigation of the recovery of selenomethionine from selenized yeast by two-dimensional LC–ICP MS. Anal Bioanal Chem 2005; 381:844-9. [PMID: 15662510 DOI: 10.1007/s00216-004-2996-0] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2004] [Revised: 11/16/2004] [Accepted: 11/30/2004] [Indexed: 11/29/2022]
Abstract
Determination of selenomethionine in selenized yeast by HPLC-ICP MS has been revisited with the focus on recovery of this amino acid during the proteolytic digestion and chromatography steps. Recovery of the extracted selenium from an anion-exchange column was 100% but selenomethionine quantified by the method of standard additions accounted only for 67% of the selenium injected. Analysis (by size-exclusion LC-ICP MS) of the eluate collected before and after the selenomethionine peak showed the presence of oxidized selenomethionine (ca. 3%) and selenomethionine likely to be unspecifically associated with the biological matrix continuum (ca. 11%). This finding was validated by two-dimensional LC-ICP MS using a different elution order, i.e. size-exclusion anion-exchange. The approach developed enabled demonstration that more than 80% of selenium in the selenized yeast is actually present in the form of selenomethionine and suggests that many results reported elsewhere for the concentration of this vital amino acid in selenized yeast may be negatively biased. The research also provided insight into speciation of selenium in the solid residue after proteolytic extraction but the additional amount of selenomethionine recovered was negligible (<1.5%).
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Affiliation(s)
- Aleksandra Połatajko
- Equipe de Chimie Analytique Bio-inorganique, CNRS UMR 5034, Hélioparc, 2, av. Pr. Angot, 64053 Pau, France
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362
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Lippman SM, Goodman PJ, Klein EA, Parnes HL, Thompson IM, Kristal AR, Santella RM, Probstfield JL, Moinpour CM, Albanes D, Taylor PR, Minasian LM, Hoque A, Thomas SM, Crowley JJ, Gaziano JM, Stanford JL, Cook ED, Fleshner NE, Lieber MM, Walther PJ, Khuri FR, Karp DD, Schwartz GG, Ford LG, Coltman CA. Designing the Selenium and Vitamin E Cancer Prevention Trial (SELECT). ACTA ACUST UNITED AC 2005; 97:94-102. [PMID: 15657339 DOI: 10.1093/jnci/dji009] [Citation(s) in RCA: 212] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Prostate cancer continues to be a major health threat, especially among African American men. The Selenium and Vitamin E Cancer Prevention Trial (SELECT), which opened on July 25, 2001, was planned to study possible agents for the prevention of prostate cancer in a population of 32,400 men in the United States, including Puerto Rico, and Canada. SELECT is a phase III randomized, placebo-controlled trial of selenium (200 microg/day from L-selenomethionine) and/or vitamin E (400 IU/day of all rac alpha-tocopheryl acetate) supplementation for a minimum of 7 years (maximum of 12 years) in non-African American men at least 55 years of age and African American men at least 50 years of age. SELECT is a large, simple trial that conforms as closely as possible with community standards of care. This commentary discusses the design problems the SELECT investigators had to resolve in developing the trial, including the role of prostate cancer screening, the best forms and doses of the study agents, and estimation of the event (prostate cancer) rate of men on the placebo arm.
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Affiliation(s)
- Scott M Lippman
- The University of Texas M.D. Anderson Cancer Center, Houston, TX 77030-4009, USA.
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363
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Margaritis I, Rousseau AS, Hininger I, Palazzetti S, Arnaud J, Roussel AM. Increase in selenium requirements with physical activity loads in well-trained athletes is not linear. Biofactors 2005; 23:45-55. [PMID: 15817998 DOI: 10.1002/biof.5520230106] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Selenium requirements in athletes are supposed to be increased with energy expenditure (EE) to preserve selenium status and an optimal antioxidant balance. The question of whether selenium intakes are related to EE and whether plasma selenium status induces up-regulation in erythrocyte endogenous antioxidant defense and decreases plasma oxidative damage markers in athletes was addressed. 118 well-trained athletes completed 7 d food and activities records in a cross-sectional study. Blood was sampled on day 8. Among the athletes, 23% of the males and 66% of the females had selenium intakes below two-third of the French RDA. Plasma selenium concentrations in most of less trained athletes were lower than the postulated concentration to be required to maximize erythrocyte GSH-Px activity. Athletes with the highest daily EE had the highest selenium intakes, percentage of vegetal protein intakes and plasma selenium concentrations. Only 2.6% of the athletes exhibited low plasma selenium concentrations (< 0.75 micromol/l). The relation between plasma selenium and EE was polynomial (r = 0.50; P < 0.005). Erythrocyte GSH-Px activity in athletes was not linked to selenium status. Selenium requirements are increased in athletes without being linearly related to EE.
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Affiliation(s)
- Irène Margaritis
- Laboratoire Physiologie des Adaptations, Performance Motrice et Santé, Faculté des Sciences du Sport, Université de Nice-Sophia-Antipolis, Nice, France.
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364
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McSheehy S, Yang L, Sturgeon R, Mester Z. Determination of Methionine and Selenomethionine in Selenium-Enriched Yeast by Species-Specific Isotope Dilution with Liquid Chromatography−Mass Spectrometry and Inductively Coupled Plasma Mass Spectrometry Detection. Anal Chem 2005; 77:344-9. [PMID: 15623314 DOI: 10.1021/ac048637e] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Selenomethionine (SeMet) and methionine (Met), liberated by acid hydrolysis of selenium-enriched yeast, were quantified by liquid chromatography-mass spectrometry (LC/MS) using standard additions calibrations as well as isotope dilution (ID) based on species-specific (13)C-enriched spikes. LC inductively coupled plasma mass spectrometry (ICPMS) was also employed for the quantification of SeMet, and (74)Se-enriched SeMet was used for ID calibration. The results were evaluated to ascertain the feasibility of using these methods in a campaign to certify selenized yeast. Good agreement was found between the methods, which, when averaged, gave concentrations of 5482.2 +/- 101 and 3256.9 +/- 217.4 microg/g for Met and SeMet, respectively. This corresponds to a 1.68:1 Met-to-SeMet ratio in the yeast. Quantification by ID LC/MS and LC ICPMS yields the most precise sets of results with relative standard deviations in the range 0.5-1.3% (n = 6). A total selenium concentration of 2064.6 +/- 45.4 microg/g was obtained for this yeast material. The extraction efficiency and a mass balance budget were determined. Acid hydrolysis liberated 81.0% of the total selenium present. SeMet comprised 79.0% of the extracted selenium and 63.9% of the total selenium present in the yeast.
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Affiliation(s)
- Shona McSheehy
- Institute for National Measurement Standards, National Research Council of Canada, Ottawa, Ontario, Canada K1A 0R9
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365
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Ryser AL, Strawn DG, Marcus MA, Johnson-Maynard JL, Gunter ME, Möller G. Micro-spectroscopic investigation of selenium-bearing minerals from the Western US Phosphate Resource Area. GEOCHEMICAL TRANSACTIONS 2005; 6:1. [PMID: 35412760 PMCID: PMC1475786 DOI: 10.1186/1467-4866-6-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2004] [Accepted: 12/08/2004] [Indexed: 05/08/2023]
Abstract
Mining activities in the US Western Phosphate Resource Area (WPRA) have released Se into the environment. Selenium has several different oxidation states and species, each having varying degrees of solubility, reactivity, and bioavailability. In this study we are investigating the speciation of Se in mine-waste rocks. Selenium speciation was determined using bulk and micro-x-ray absorption spectroscopy (XAS), as well as micro-x-ray fluorescence mapping. Rocks used for bulk-XAS were ground into fine powders. Shale used for micro-XAS was broken along depositional planes to expose unweathered surfaces. The near edge region of the XAS spectra (XANES) for the bulk rock samples revealed multiple oxidation states, with peaks indicative of Se(-II), Se(IV), and Se(+VI) species. Micro-XANES analysis of the shale indicated that three unique Se-bearing species were present. Using the XANES data together with ab initio fitting of the extended x-ray absorption fine structure region of the micro-XAS data (micro-EXAFS) the three Se-bearing species were identified as dzharkenite, a di-selenide carbon compound, and Se-substituted pyrite. Results from this research will allow for a better understanding of the biogeochemical cycling of Se in the WPRA.
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Affiliation(s)
- Amy L Ryser
- University of Idaho, Moscow, Idaho 83844-2339
| | | | - Matthew A Marcus
- Lawrence Berkeley National Laboratory, Berkeley, California 94720
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366
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Frank DH, Roe DJ, Chow HHS, Guillen JM, Choquette K, Gracie D, Francis J, Fish A, Alberts DS. Selective modulation of the therapeutic efficacy of anticancer drugs by selenium containing compounds against human tumor xenografts. Clin Cancer Res 2004; 13:299-303. [PMID: 14973093 DOI: 10.1158/1055-9965.epi-03-0163] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE Studies were carried out in athymic nude mice bearing human squamous cell carcinoma of the head and neck (FaDu and A253) and colon carcinoma (HCT-8 and HT-29) xenografts to evaluate the potential role of selenium-containing compounds as selective modulators of the toxicity and antitumor activity of selected anticancer drugs with particular emphasis on irinotecan, a topoisomerase I poison. EXPERIMENTAL DESIGN Antitumor activity and toxicity were evaluated using nontoxic doses (0.2 mg/mouse/day) and schedule (14-28 days) of the selenium-containing compounds, 5-methylselenocysteine and seleno-L-methionine, administered orally to nude mice daily for 7 days before i.v. administration of anticancer drugs, with continued selenium treatment for 7-21 days, depending on anticancer drugs under evaluation. Several doses of anticancer drugs were used, including the maximum tolerated dose (MTD) and toxic doses. Although many chemotherapeutic agents were evaluated for toxicity protection by selenium, data on antitumor activity were primarily obtained using the MTD, 2 x MTD, and 3 x MTD of weekly x4 schedule of irinotecan. RESULTS Selenium was highly protective against toxicity induced by a variety of chemotherapeutic agents. Furthermore, selenium increased significantly the cure rate of xenografts bearing human tumors that are sensitive (HCT-8 and FaDu) and resistant (HT-29 and A253) to irinotecan. The high cure rate (100%) was achieved in nude mice bearing HCT-8 and FaDu xenografts treated with the MTD of irinotecan (100 mg/kg/week x 4) when combined with selenium. Administration of higher doses of irinotecan (200 and 300 mg/kg/week x 4) was required to achieve high cure rate for HT-29 and A253 xenografts. Administration of these higher doses was possible due to selective protection of normal tissues by selenium. Thus, the use of selenium as selective modulator of the therapeutic efficacy of anticancer drugs is new and novel. CONCLUSIONS We demonstrated that selenium is a highly effective modulator of the therapeutic efficacy and selectivity of anticancer drugs in nude mice bearing human tumor xenografts of colon carcinoma and squamous cell carcinoma of the head and neck. The observed in vivo synergic interaction is highly dependent on the schedule of selenium.
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Affiliation(s)
- Denise H Frank
- Arizona Cancer Center, and Section of Hematology and Oncology, Department of Medicine, College of Medicine, University of Arizona, Tucson, Arizona 85724, USA.
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367
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Abstract
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.
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Affiliation(s)
- Margaret P Rayman
- Centre for Nutrition and Food Safety, School of Biomedical and Molecular Sciences, University of Surrey, UK.
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368
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369
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Cabañero AI, Madrid Y, Cámara C. Enzymatic probe sonication extraction of Se in animal-based food samples: a new perspective on sample preparation for total and Se speciation analysis. Anal Bioanal Chem 2004; 381:373-9. [PMID: 15372134 DOI: 10.1007/s00216-004-2798-4] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2004] [Revised: 07/29/2004] [Accepted: 07/30/2004] [Indexed: 11/25/2022]
Abstract
This paper describes a fast, simple and novel extraction method for total selenium and selenium species determination in food samples. Parameters influencing extraction, such as sonication time, extracting media, temperature, sample mass, ultrasound amplitude and sample/enzyme mass ratio were investigated. The enzymatic hydrolysis proposed, enhanced by probe sonication, allowed the quantitative extraction of selenium in chicken muscle, liver, kidney and feed (97, 93, 95 and 102%, respectively) in 2 min, maintaining the original Se-species integrity. Total Se content of the samples was determined using inductively coupled plasma mass spectrometry. Se-species were identified and quantified using high-performance liquid chromatography in conjunction with inductively coupled plasma mass spectrometry. Chromatographic analyses were carried out under two chromatographic conditions and led to the identification of SeMet in all samples. The accuracy of the proposed method was assessed using certified reference materials as well as microwave digestion. Potential advantages of the proposed method over traditional hydrolysis are speed, simplicity and safety of the procedure.
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Affiliation(s)
- Ana I Cabañero
- Departamento de Química Analítica, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria s/n, 28040, Madrid, Spain
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370
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Ramos A, Lane AN, Hollingworth D, Fan TWM. Secondary structure and stability of the selenocysteine insertion sequences (SECIS) for human thioredoxin reductase and glutathione peroxidase. Nucleic Acids Res 2004; 32:1746-55. [PMID: 15026534 PMCID: PMC390329 DOI: 10.1093/nar/gkh331] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
We have used high resolution NMR and thermodynamics to characterize the secondary structure and stability of the selenocysteine insertion sequences (SECIS) of human glutathione peroxidase (58 nt) and thioredoxin reductase (51 nt). These sequences are members of the two classes of SECIS recently identified with two distinct structures capable of directing selenocysteine incorporation into proteins in eukaryotes. UV melting experiments showed a single cooperative and reversible transition for each RNA, which indicates the presence of stable secondary structures. Despite their large size, the RNAs gave well resolved NMR spectra for the exchangeable protons. Using NOESY, the imino protons as well as the cytosine amino protons of all of the Watson-Crick base pairs were assigned. In addition, a number of non-canonical base pairs including the wobble G.U pairs were identified. The interbase-pair NOEs allowed definition of the hydrogen-bonded structure of the oligonucleotides, providing an experimental model of the secondary structure of these elements. The derived secondary structures are consistent with several features of the predicted models, but with some important differences, especially regarding the conserved sequence motifs.
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Affiliation(s)
- Andres Ramos
- Division of Molecular Structure, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, UK
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371
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Mackowiak C, Amacher M, Hall J, Herring J. Chapter 19 Uptake of selenium and other contaminant elements into plants and implications for grazing animals in Southeast Idaho. LIFE CYCLE OF THE PHOSPHORIA FORMATION - FROM DEPOSITION TO THE POST-MINING ENVIRONMENT 2004. [DOI: 10.1016/s1874-2734(04)80021-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
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372
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373
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Badawi H, Förner W, Seddigi Z. MP2 C–N barrier and vibrational spectra and assignments for CH2CH–NCX (X=O, S and Se). ACTA ACUST UNITED AC 2003. [DOI: 10.1016/s0166-1280(03)00235-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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374
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Das A, Desai D, Pittman B, Amin S, El-Bayoumy K. Comparison of the Chemopreventive Efficacies of 1,4-phenylenebis(methylene)selenocyanate and Selenium-Enriched Yeast on 4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone Induced Lung Tumorigenesis in A/J Mouse. Nutr Cancer 2003; 46:179-85. [PMID: 14690794 DOI: 10.1207/s15327914nc4602_11] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
Epidemiological studies, clinical intervention trials (including the trial with selenium-enriched yeast by Clark et al. JAMA 276, 1957, 1996) and assays in laboratory animals provide evidence for a protective role of selenium against the development of several cancers, including lung cancer. We have demonstrated that selenium in the form of 1,4-phenylenebis(methylene)selenocyanate (p-XSC) is a promising chemopreventive agent in the A/J mouse lung tumor model induced with the carcinogenic tobacco-specific nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK); under identical conditions, selenomethionine (SM), a component of selenium-enriched yeast, had no effect. The lack of an effect of SM suggests that other forms of selenium, or selenium-enriched yeast as a whole, are essential for lung cancer prevention; moreover, various species may respond differently to a given form of selenium. Therefore, in this study, we compared the chemopreventive efficacies of p-XSC with selenium-enriched yeast. Groups of 5-wk-old mice were fed either control diet or experimental diet containing p-XSC (5 or 10 ppm as selenium, equivalent to 20% and 40% maximum tolerated dose [MTD], respectively) or selenium-enriched yeast (5 or 10 ppm). Beginning at Wk 7, each mouse received NNK (3 mmol) in 0.1 ml cottonseed oil by intragastric intubation, once weekly for 8 wk. Twenty-six weeks after the first NNK administration, mice were killed and tumors in lung and forestomach were counted. p-XSC at 5 and 10 ppm doses significantly reduced lung tumor induction by NNK from 10.4 -/+ 6.0 (multiplicity) to 2.7 -/+ 1.5 (P < 0.001) and 1.8 -/+ 2.0 (P < 0.0001) respectively, whereas selenium-enriched yeast had no effect. p-XSC at 10 ppm also significantly reduced the incidence level from 96% to 68% (P < 0.01). The amounts of selenium that reach the target organ (lung) after dietary administration of p-XSC (326 -/+ 69 ng Se/g lung tissue) were significantly higher than that from selenium-enriched yeast (34 -/+ 8.5 ng Se/g lung tissue). However, the levels of selenium in plasma from selenium-enriched yeast (620 -/+ 54 ng Se/g plasma) were twofold higher than those from p-XSC (355 -/+ 85 ng Se/g plasma). In biochemical studies, p-XSC was shown to significantly inhibit formation of O6-methylguanine (O6-MG) and 7-methylguanine (7-MG) in the lungs and livers of mice treated with NNK. The lack of effect of selenium-enriched yeast on these lesions agrees with the results of the bioassay. Collectively, the results of this study clearly indicate that as a chemopreventive agent, p-XSC is superior to selenium-enriched yeast under the conditions of the present protocol. The inhibition of DNA methylation and the significantly higher retention of selenium from p-XSC as compared with selenium-enriched yeast in the target organ may in part account for the inhibition of lung tumorigenesis.
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Affiliation(s)
- Arunangshu Das
- Institute for Cancer Prevention (formerly American Health Foundation), 1 Dana Road, Valhalla, NY 10595, USA
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375
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Pinnell SR. Cutaneous photodamage, oxidative stress, and topical antioxidant protection. J Am Acad Dermatol 2003; 48:1-19; quiz 20-2. [PMID: 12522365 DOI: 10.1067/mjd.2003.16] [Citation(s) in RCA: 281] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
UNLABELLED New methods to protect skin from photodamage from sun exposure are necessary if we are to conquer skin cancer and photoaging. Sunscreens are useful, but their protection is not ideal because of inadequate use, incomplete spectral protection, and toxicity. Skin naturally uses antioxidants (AOs) to protect itself from photodamage. This scientific review summarizes what is known about how photodamage occurs; why sunscreens--the current gold standard of photoprotection--are inadequate; and how topical AOs help protect against skin cancer and photoaging changes. This review is intended to be a reference source, including pertinent comprehensive reviews whenever available. Although not all AOs are included, an attempt has been made to select those AOs for which sufficient information is available to document their potential topical uses and benefits. Reviewed are the following physiologic and plant AOs: vitamin C, vitamin E, selenium, zinc, silymarin, soy isoflavones, and tea polyphenols. Their topical use may favorably supplement sunscreen protection and provide additional anticarcinogenic protection. (J Am Acad Dermatol 2003;48:1-19.) LEARNING OBJECTIVE At the completion of this learning activity, participants should have an understanding of current information about how the sun damages skin to produce skin cancer and photoaging changes, how the skin naturally protects itself from the sun, the shortcomings of sunscreens, and the added advantages of topical AOs for photoprotection.
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Affiliation(s)
- Sheldon R Pinnell
- Duke University Medical Center, Department of Medicine, Division of Dermatology, Durham, North Carolina 27707, USA.
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376
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Schrauzer GN. The nutritional significance, metabolism and toxicology of selenomethionine. ADVANCES IN FOOD AND NUTRITION RESEARCH 2003; 47:73-112. [PMID: 14639782 DOI: 10.1016/s1043-4526(03)47002-2] [Citation(s) in RCA: 194] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
SeMet is a naturally occurring toxic amino acid but at the same time represents the major nutritional source of selenium for higher animals and humans. The ability of SeMet to be incorporated into the body proteins in place of Met furthermore provides a means of reversible Se storage in organs and tissues. This property is not shared by any other naturally occurring selenoamino acid and thus could be associated with a specific physiological function of SeMet. Since higher animals cannot synthesize SeMet, yet from it all needed forms of Se are produced, SeMet meets the criteria of an essential amino acid. Accordingly, SeMet, or enriched food sources thereof, are appropriate forms of Se for human nutritional Se supplementation. However, while SeMet or Se yeast are already widely used in over-the-counter nutritional supplements, infant formulas and parenteral feeding mixtures still contain Se in the form of sodium selenate or sodium selenite, even though these are not the normal nutritional forms of Se. In animal nutrition, these inorganic selenium salts are increasingly replaced by food sources of SeMet such as Se yeast. Synthetic SeMet could also be employed as a feed additive, but its regulatory status is as yet undetermined. The optimal nutritional levels of SeMet for different animal species still need to be determined. The expectation is that lower additions to feedstock of equivalent levels of SeMet will suffice to achieve adequacy than currently approved maximum levels of Se in the form of inorganic Se salts.
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Affiliation(s)
- Gerhard Norbert Schrauzer
- Biological Trace Element Research Institute, 2400 Boswell Rd., Suite 200, Chula Vista, CA 91914, USA
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377
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Chasteen TG, Bentley R. Biomethylation of selenium and tellurium: microorganisms and plants. Chem Rev 2003; 103:1-25. [PMID: 12517179 DOI: 10.1021/cr010210+] [Citation(s) in RCA: 263] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Thomas G Chasteen
- Department of Chemistry, Sam Houston State University, Huntsville, Texas 77341, USA.
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378
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Cases J, Wysocka IA, Caporiccio B, Jouy N, Besançon P, Szpunar J, Rouanet JM. Assessment of selenium bioavailability from high-selenium spirulina subfractions in selenium-deficient rats. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2002; 50:3867-3873. [PMID: 12059173 DOI: 10.1021/jf011646t] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
It was previously found that the bioavailability of Se from Se-rich spirulina (SeSp) was lower than that from selenite or selenomethionine when fed to Se-deficient rats. The present study examined the bioavailability of Se from SeSp subfractions: a pellet (P) issuing from the centrifugation of a suspension of broken SeSp and a retentate (R) resulting from ultrafiltration of the supernatant through a 30 kDa exclusion membrane. Animals were fed a torula yeast based diet with no Se (deficients) or supplemented with 75 microg of Se/kg of diet as sodium selenite (controls) for 42 days. Se-deficient rats were then repleted for 56 days with Se (75 microg/kg of diet) supplied as sodium selenite, SeSp, P, or R. During this period, controls continued to receive sodium selenite. Speciation of Se in subfractions showed that the majority was present in the form of high molecular weight compounds; free selenomethionine was only a minor constituent. Gross absorption of Se from sodium selenite, P, and R was not different and was higher than from SeSp. Only retentate allowed full replenishment of Se concentration in liver and kidney (as did sodium selenite) and glutathione peroxidase (GSHPx) activity in liver, kidney, plasma, and erythrocytes. The bioavailabilities of Se in retentate, as assessed by slope ratio analysis using selenite as a reference Se, were 89 and 112% in the tissue Se content and 106-133% in the GSHPx activities. SeSp and P exhibited a gross bioavailability of <100%. These results indicate that Se in retentate is highly bioavailable and represents an interesting source of Se for food supplementation.
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Affiliation(s)
- Julien Cases
- Unité Nutrition, Laboratoire Génie Biologique et Sciences des Aliments, Université Montpellier II, Place Eugène Bataillon, 34095, France
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379
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Abstract
There are several selenocompounds in tissues of plants and animals. Selenate is the major inorganic selenocompound found in both animal and plant tissues. Selenocysteine is the predominant selenoamino acid in tissues when inorganic selenium is given to animals. Selenomethionine is the major selenocompound found initially in animals given this selenoamino acid, but is converted with time afterwards to selenocysteine. Selenomethionine is the major selenocompound in cereal grains, grassland legumes and soybeans. Selenomethionine can also be the major selenocompound in selenium enriched yeast, but the amount can vary markedly depending upon the growth conditions. Se-methylselenocysteine is the major selenocompound in selenium enriched plants such as garlic, onions, broccoli florets and sprouts, and wild leeks.
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Affiliation(s)
- P D Whanger
- Department of Environmental and Molecular Toxicology, Oregon State University, Corvallis 97331, USA.
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380
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Gromer S, Gross JH. Methylseleninate is a substrate rather than an inhibitor of mammalian thioredoxin reductase. Implications for the antitumor effects of selenium. J Biol Chem 2002; 277:9701-6. [PMID: 11782468 DOI: 10.1074/jbc.m109234200] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Biochemical and clinical evidence indicates that monomethylated selenium compounds are crucial for the tumor preventive effects of the trace element selenium and that methylselenol (CH(3)SeH) is a key metabolite. As suggested by Ganther (Ganther, H. E. (1999) Carcinogenesis 20, 1657-1666), methylselenol and its precursor methylseleninate might exert their effects by inhibition of the selenoenzyme thioredoxin reductase via the irreversible formation of a diselenide bridge. Here we report that methylseleninate does not act as an inhibitor of mammalian thioredoxin reductase but is in fact an excellent substrate (K(m) of 18 microm, k(cat) of 23 s(-1)), which is reduced by the enzyme according to the equation 2 NADPH + 2 H(+) + CH(3)SeO(2)H --> 2 NADP(+) + 2 H(2)O + CH(3)SeH. The selenium-containing product of this reaction was identified by mass spectrometry. Nascent methylselenol was found to efficiently reduce both H(2)O(2) and glutathione disulfide. The implications of these findings for the antitumor activity of selenium are discussed. Methylseleninate was a poor substrate not only for human glutathione reductase but also for the non-selenium thioredoxin reductases enzymes from Drosophila melanogaster and Plasmodium falciparum. This suggests that the catalytic selenocysteine residue of mammalian thioredoxin reductase is essential for methylseleninate reduction.
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Affiliation(s)
- Stephan Gromer
- Biochemistry Center, Heidelberg University, Im Neuenheimer Feld 328, D-69120 Heidelberg, Germany.
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381
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Arteel GE, Sies H. The biochemistry of selenium and the glutathione system. ENVIRONMENTAL TOXICOLOGY AND PHARMACOLOGY 2001; 10:153-158. [PMID: 21782571 DOI: 10.1016/s1382-6689(01)00078-3] [Citation(s) in RCA: 194] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
In the context of defense against pro-oxidants, selenium and the glutathione (GSH) system play key functions. Major roles of GSH include direct interception of pro-oxidants, as well as a reduction of other antioxidants from their oxidized forms. Furthermore, GSH has ancillary functions, such as metabolism, cell signaling, and protein interactions, that can also mediate defense against oxidants. Protection by selenium in the mammalian cell is mediated by selenol-aminoacids, either as selenocysteine or selenomethionine. The active site of the potent glutathione peroxidases (GPx) contains selenocysteine residues. Furthermore, other selenoproteins (e.g. selenoprotein P and thioredoxin reductase) also have been shown to possess antioxidant properties. Synthetic organoselenium compounds (e.g. ebselen) have also shown promise as pharmacologic antioxidants in in vivo models of tissue damage due to oxidative stress. The specific function of selenoproteins and organoselenium compounds in defense against peroxynitrite, by reduction of this potent oxidizing and nitrating species to nitrite, is also discussed.
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Affiliation(s)
- G E Arteel
- Laboratory of Hepatobiology and Toxicology, Department of Pharmacology, CB #7365 Mary Ellen Jones Building, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7365, USA
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382
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Abstract
Selenium supplements contain selenium in different chemical forms. In the majority of supplements, the selenium is present as selenomethionine. However, in multivitamin preparations, infant formulas, protein mixes, weight-loss products and animal feed, sodium selenite and sodium selenate are predominantly used. In some products, selenium is present in protein- or amino acid chelated forms; in still others, the form of selenium is not disclosed. Current evidence favors selenomethionine over the other forms of selenium. Extradietary supplementation of selenium at the dosage of 200 micrograms per day is generally considered safe and adequate for an adult of average weight subsisting on the typical American diet.
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Affiliation(s)
- G N Schrauzer
- Department of Chemistry and Biochemistry, University of California San Diego and Biological Trace Element Research Institute, 92121, USA
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