Selenium Consumption Research Articles

Effects of Long-Term Selenium Supplementation on the Incidence of Type 2 Diabetes

Findings from animal models suggest that selenium supplementation improves glucose metabolism. To examine the effect of long-term selenium supplementation on the incidence of type 2 diabetes. Secondary analysis of a randomized, double-blind, placebo-controlled trial. Areas of low selenium consumption of the eastern United States. 1202 persons seen in dermatology clinics who did not have type 2 diabetes at baseline. Oral administration of selenium, 200 microg/d, or placebo. Incidence of type 2 diabetes. During an average follow-up of 7.7 years (SD, 2.7), type 2 diabetes developed in 58 selenium recipients and 39 placebo recipients (incidence, 12.6 cases per 1000 person-years vs. 8.4 cases per 1000 person-years, respectively; hazard ratio, 1.55 [95% CI, 1.03 to 2.33]). The lack of benefit of selenium supplementation on the incidence of type 2 diabetes persisted in analyses stratified by age, sex, body mass index, and smoking status. An exposure-response gradient was found across tertiles of baseline plasma selenium level, with a statistically significantly increased risk for type 2 diabetes in the highest tertile of baseline plasma selenium level (hazard ratio, 2.70 [CI, 1.30 to 5.61]). Diabetes was a secondary outcome in the parent trial. Diagnoses of diabetes were self-reported but were validated in most participants. The sample was mostly older and white. Selenium supplementation does not seem to prevent type 2 diabetes, and it may increase risk for the disease. Click here for related information on selenium.

Dietary Selenium Intake and Genetic Polymorphisms of the GSTP1 and p53 Genes on the Risk of Esophageal Squamous Cell Carcinoma

Few studies have assessed potential effect modifications by polymorphisms of susceptibility genes on the association between selenium intake and esophageal squamous cell carcinoma (ESCC). We studied the joint effects of dietary selenium and the GSTP1 and p53 polymorphisms on ESCC risk in a population-based case-control study with 218 ESCC cases and 415 controls in Taixing City, China. Dietary selenium intake was estimated from a food frequency questionnaire with 97 food items. GSTP1 and p53 polymorphisms were detected by RFLP-PCR assays. Logistic regression analyses were done to estimate odds ratios (OR) and 95% confidence intervals (95% CI). Reduced ESCC risk was observed among individuals in the highest quartile of dietary selenium intake (adjusted OR, 0.31; 95% CI, 0.13-0.70) with a dose-dependent gradient (P(trend) = 0.01). The p53 Pro/Pro genotype was associated with increased risk of ESCC compared with the Arg/Arg genotype (adjusted OR, 2.02; 95% CI, 1.19-3.42). When combined with selenium consumption, an obvious increased risk was observed among individuals with the p53 Pro/Pro or GSTP1 Ile/Ile genotype with adjusted ORs of 3.19 (95% CI, 1.74-5.84) and 1.90 (95% CI, 1.03-3.51), respectively. Among smokers and alcohol drinkers, elevation of ESCC risk was more prominent among p53 Pro/Pro individuals who consumed a low level of dietary selenium (adjusted OR, 3.59; 95% CI, 1.49-8.66 for smokers and 6.19; 95% CI, 1.83-20.9 for drinkers). Our study suggests that the effect of dietary selenium on the risk of ESCC may be modulated by tobacco smoking, alcohol drinking, and p53 Pro/Pro and GSTP1 Ile/Ile genotypes.

Estimation of Selenium Consumption during Selenization of Cu-In Metallic Layer in a Quazi-Closed System

Selenium vapour distribution and consumption during selenization process of Cu-In metallic layers provided in a quasi-closed system with inert gas environment at atmospheric pressure were studied. A model taking into account the four most important mechanisms of Se consumption, namely the creation and maintenance of Se vapour over-pressure, the out-diffusion through open boundaries of quasi-closed system, the drift transport by constant nitrogen flux and chemical reactions with Cu-In metallic layers, is developed to estimate the total amount of selenium required for selenization process. The diffusion mechanism was found to be dominating the selenium consumption for the used reactor design. Calculated values find a good agreement with experimental results from weighing of the Se source material before and after selenization.

Quantitative determination of selenium metabolites in human urine by LC-DRC-ICP-MS

Two selenium metabolites, Se-methylseleno-N-acetylgalactosamine (SeGal-N-Ac) and Se-methylselenogalactosamine (SeGal-NH2), were quantified in human urine by LC-DRC-ICP-MS. Urine samples were analysed after 1 + 1 dilution in a reversed phase chromatographic system using an eluent consisting of 200 mM ammonium acetate and 5% methanol with a pH of 9.25 and quantified by standard addition. Samples were collected from 8 volunteers before and after 5 days ingestion of 100 μg Se day−1 in form of selenized yeast. The average concentration of (SeGal-NH2) before and after selenium intake was 1.4 and 1.9 μg Se L−1, respectively, while the average concentration of Se-Gal-N-Ac increased from 2.6 to 11.6 μg Se L−1 before and after selenium consumption. Detection limits calculated on basis of three times the standard deviation on peak areas of 2 μg Se L−1 solutions were 0.1 μg Se L−1 for SeGal-NH2 and 0.2 μg Se L−1 for SeGal-N-Ac based on peak areas and monitoring 80Se. The precision expressed as the relative standard deviation (n = 6) at the 2 μg Se L−1 level was 3.1 and 1.7% for SeGal-NH2 and SeGal-N-Ac, respectively, while the corresponding values were 1.0 and 0.7% at the 10 μg Se L−1 level. Linearity in urine matrix was examined in the range 0.5–100 μg Se L−1 and correlation coefficients better than 0.999 were obtained. As the cationic compound SeGal-NH3+ may be confounded with the trimethylselenonium ion (TMSe+), urine samples were also analysed in a cation exchange chromatographic system in which SeGal-NH3+ was separated from the trimethylselenonium ion. None of the samples contained TMSe+ in detectable amounts. Three sample introduction systems were compared—a microconcentric nebuliser in combination with a cyclonic spray chamber (MCN), a direct injection nebuliser (DIN) and an ultrasonic nebuliser (USN). The MCN was most suitable for this purpose.

Influence of the selenium flux on the growth of Cu(In,Ga)Se 2 thin films

In order to control the selenium to metal flux ratio (SMR) during the co-evaporation process for the fabrication of Cu(In,Ga)Se 2 (CIGS) thin films, we establish a new method for the determination of the fluxes. CIGS absorber layers prepared at varying SMRs exhibit either metal rich (at SMR⩽1.5) or Na-rich (SMR=4.5) segregations, which limit the performance of the cells, and thereby define a minimum SMR needed to obtain good quality material. This minimum SMR and, therefore, the overall selenium consumption are lower when using fast processes. A systematic study on the texture of absorber layers prepared by three stage processes shows that increasing the selenium flux leads towards a (2 2 0/2 0 4) orientation, while either a high Na supply (NaF precursor) or a lack of Na (Na-barrier layer) promotes the (1 1 2) orientation.

Selenium speciation in urine by ion-pairing chromatography with perfluorinated carboxylic acids and ICP-MS detection

Five aqueous standards, selenomethionine (SeMet), methylselenomethionine (MeSeMet), methylselenocysteine (MeSeCys), selenogammaaminobutyric acid (SeGaba) and the trimethylselenonium ion (TMSe), were separated in ion-pairing chromatographic systems based on perfluorinated carboxylic acids in methanol. Two different perfluorinated carboxylic acids, heptafluorobutanoic acid (HFBA) and nonafluoropentanoic acid (NFPA), were used as ion-pairing agents in the separation. The selectivities of the ion-pairing agents were different. The separation was performed on a microbore column, which was connected to the ICP-MS via a laboratory-made direct injection nebuliser. This nebulisation system allowed methanol concentrations of 50% in the eluent when a flow rate of 50 µl min−1 was used. The detection limits in urine were between 0.8 and 1.7 µg l−1 corresponding to absolute detection limits of between 2.3 and 5.1 pg. Urine samples from different individuals before and during supplementation with selenomethionine were analysed. Several species were separated in the different urine samples. A major component eluting at the beginning of the chromatogram was predominant in many samples, especially after selenium consumption. This species was not identified and solid phase extraction experiments suggested that it was neutral. When different urine samples were spiked with the available standards, co-elution of species with TMSe, MeSeMet or SeMet was observed in some samples. None of these species were major compounds in urine samples—even after massive consumption of selenium-containing supplements. The selenium species in the urine samples showed a limited stability, as they changed during storage at +4 °C as well as −18 °C.

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

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

Selected measures of selenium status in full-term and preterm neonates, their mothers and nonpregnant women

The purpose of this study was to determine selenium status in five subject groups: 13 premature neonates (30–35 wk gestation) and their mothers (17–40 y), 15 full-term neonates (38–43 wk gestation) and their mothers (17–39 y), and 15 women aged 17 to 40 years who were not pregnant. Macronutrient and selenium consumption was estimated from the women's recall of a typical day's diet. The concentration of selenium in plasma, and the specific activity of glutathione peroxidase in red blood cells and in platelet-rich plasma (PRP), were measured in blood samples from control subjects and in maternal and umbilical-cord blood samples taken at delivery. Selenium intake, plasma selenium, and red blood cell glutathione-peroxidase activity were not different among the 3 adult groups. Full-term neonates had more selenium in plasma than the premature neonates, possibly because of accumulation of this element during gestation. PRP glutathione-peroxidase activity was significantly less in the full-term mothers than in the control subjects. Also, the full-term neonates had less PRP glutathione-peroxidase activity than the premature neonates. These biochemical differences seem to reflect physiological changes associated with pregnancy and gestational age.

Selenium and mercury in foodstuff from a locality with elevated intake of methylmercury.

Measurements were made on mercury and selenium concentrations in foodstuffs, mainly in fish, obtained on the Takarajima Island of the Tokara Islands and the surrounding sea. The selenium consumption was evaluated in comparison with mercurial consumption.