Abstract:a b s t r a c tSpecific Se-metabolites have been recognized to be the main elements responsible for beneficial effects of Se-enriched diet, and Se-methylselenocysteine (SeMCys) is thought to be among the most effective ones. Here we show that an engineered Saccharomyces cerevisiae strain, expressing a codon optimized heterologous selenocysteine methyltransferase and endowed with high intracellular levels of S-adenosyl-methionine, was able to accumulate SeMCys at levels higher than commercial selenized yeasts. … Show more
“…Although the majority of seleno proteins are antioxidant in nature, some seleno metabolites are known to induce oxidative stress [81][82][83]. A redox imbalance of extracellular levels of reduced to oxidised glutathione in selenised yeast has been hypothesised as being responsible for Se toxicities [84]. Morgan et al have shown that dosing the nematode Caenorhabditis elegans to a level of Se beyond the beneficial antioxidant level causes reactive oxygen species formation and Se induced motility problems that can be reversed by reduced glutathione [85].…”
There is marked controversy on the beneficial levels of selenium (Se) to be used as a dietary supplement. The form of supplemented Se and the baseline plasma or serum Se status among supplemented populations are generally considered as crucial factors in this controversy. However, responses to supplemented Se can further vary with other factors, including health status, lifestyle, demographics and genetics. In the present study, the putative supplementation benefits of Se as 200 µg/day selenised yeast for six months were evaluated among a stratified male population from Auckland, New Zealand. Our study considered changes in surrogate biomarkers for cancer including antioxidant selenoenzymes glutathione peroxidase (GPx) and thioredoxin reductase activity (TR) levels, basal and peroxide-induced DNA damage levels. A total of 569 subjects self-reporting a European ancestry signed in for the study and provided answers to a basic demographic, health and lifestyle questionnaire. The effects of Se supplementation on biomarkers showed significant variability based on age, BMI, health status and seleno-genotypes of SELS rs4965373, GPx1 rs1050450, and SEPP1 rs3877899. The data indicate that the benefits of supplementary Se vary significantly across a population, based on demographics, lifestyle, health conditions and seleno-genotypes. As a contrast to "one-size-fits-all" nutritional interventions, these observations collectively inform rational targeting and personalisation of future Se-based dietary supplementation in regards to cancer chemoprevention strategies. This work also represents a way forward in critically understanding Se requirements in populations.
“…Although the majority of seleno proteins are antioxidant in nature, some seleno metabolites are known to induce oxidative stress [81][82][83]. A redox imbalance of extracellular levels of reduced to oxidised glutathione in selenised yeast has been hypothesised as being responsible for Se toxicities [84]. Morgan et al have shown that dosing the nematode Caenorhabditis elegans to a level of Se beyond the beneficial antioxidant level causes reactive oxygen species formation and Se induced motility problems that can be reversed by reduced glutathione [85].…”
There is marked controversy on the beneficial levels of selenium (Se) to be used as a dietary supplement. The form of supplemented Se and the baseline plasma or serum Se status among supplemented populations are generally considered as crucial factors in this controversy. However, responses to supplemented Se can further vary with other factors, including health status, lifestyle, demographics and genetics. In the present study, the putative supplementation benefits of Se as 200 µg/day selenised yeast for six months were evaluated among a stratified male population from Auckland, New Zealand. Our study considered changes in surrogate biomarkers for cancer including antioxidant selenoenzymes glutathione peroxidase (GPx) and thioredoxin reductase activity (TR) levels, basal and peroxide-induced DNA damage levels. A total of 569 subjects self-reporting a European ancestry signed in for the study and provided answers to a basic demographic, health and lifestyle questionnaire. The effects of Se supplementation on biomarkers showed significant variability based on age, BMI, health status and seleno-genotypes of SELS rs4965373, GPx1 rs1050450, and SEPP1 rs3877899. The data indicate that the benefits of supplementary Se vary significantly across a population, based on demographics, lifestyle, health conditions and seleno-genotypes. As a contrast to "one-size-fits-all" nutritional interventions, these observations collectively inform rational targeting and personalisation of future Se-based dietary supplementation in regards to cancer chemoprevention strategies. This work also represents a way forward in critically understanding Se requirements in populations.
“…It should be stressed that binding of selenium by yeasts decreases with high contents of sulfur and heavy metals in the culture media. Furthermore, the presence of glucose may cause a reduction of selenium occurring in the form of SeO 3 2 − ions, which results in the formation of red elemental selenium (Mapelli et al 2011). …”
Section: Intracellular Accumulation Of Seleniummentioning
confidence: 99%
“…Fig. 1Pathway of reduction of selenium in yeast cells (Hoefig et al 2011; Kitajima and Chiba 2013; Mapelli et al 2011). a Sulfurylase ATP; b kinase APSe; c reductase PAPSe; d sulphate reductase…”
Section: Metabolism Of Selenium By Yeast Cellsmentioning
This paper examines the process of selenium bioaccumulation and selenium metabolism in yeast cells. Yeast cells can bind elements in ionic from the environment and permanently integrate them into their cellular structure. Up to now, Saccharomyces cerevisiae, Candida utilis, and Yarrowia lipolytica yeasts have been used primarily in biotechnological studies to evaluate binding of minerals. Yeast cells are able to bind selenium in the form of both organic and inorganic compounds. The process of bioaccumulation of selenium by microorganisms occurs through two mechanisms: extracellular binding by ligands of membrane assembly and intracellular accumulation associated with the transport of ions across the cytoplasmic membrane into the cell interior. During intracellular metabolism of selenium, oxidation, reduction, methylation, and selenoprotein synthesis processes are involved, as exemplified by detoxification processes that allow yeasts to survive under culture conditions involving the elevated selenium concentrations which were observed. Selenium yeasts represent probably the best absorbed form of this element. In turn, in terms of wide application, the inclusion of yeast with accumulated selenium may aid in lessening selenium deficiency in a diet.
“…However, within peptides from the same protein, SeMet/Met ratios will vary depending on the differential exposure to oxidative or enzymatic degradation of SeMet side chain and its position in the protein (buried or exposed), and also to the change in the production rate of each protein after Se addition to growth media [50]. Differences in protein content might also be ascribed to diverse manufacturing methods or bioprocessing to which specific yeast is subjected during fermentation, recovery and drying operations [52][53][54]. For example, Tdh3 was identified in two products but at opposing abundance levels.…”
Section: Determination Of Inter-batch and Inter-product Protein Contementioning
The trace mineral selenium (Se) is an essential element for human and animal nutrition. The addition of Se to the diet through dietary supplements or fortified food/feed is increasingly common owing to the often sub-optimal content of standard diets of many countries. Se supplements commercially available include the inorganic mineral salts such as sodium selenite or selenate, and organic forms such as Se-enriched yeast. Today, Se yeast is produced by several manufacturers and has become the most widely used source of Se for human supplementation and is also widely employed in animal nutrition where approval in all species has been granted by regulatory bodies such as the European Food Safety Authority (EFSA). Characterisation and comparison of Se-enriched yeast products has traditionally been made by quantifying total selenomethionine (SeMet) content. A disadvantage of this approach, however, is that it does not consider the effects of Se deposition on subsequent digestive availability. In this study, an assessment was made of the water-soluble extracts of commercially available Se-enriched yeast samples for free, peptide-bound and total water-soluble SeMet. Using LC-MS/MS, a total of 62 Se-containing proteins were identified across four Se yeast products, displaying quantitative/ qualitative changes in abundance relative to the certified reference material, SELM-1 (P value <0.05; fold change ≥2). Overall, the study indicates that significant differences exist between Se yeast products in terms of SeMet content, Secontaining protein abundance and associated metabolic pathways.
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