Physiological and nutritional importance of selenium

Tracing the footprints of Arctic pollution: Spatial variations in toxic and essential elements in Svalbard reindeer (Rangifer tarandus platyrhynchus) faeces

The Arctic is an accumulation zone of long-range transported pollution. In addition, local anthropogenic activities further contribute to regional pollution levels. The Svalbard reindeer (Rangifer tarandus platyrhynchus) is a suitable organism for studying and monitoring exposure to anthropogenic pollutants at the base of the terrestrial Arctic food web, and reindeer faeces have been promoted as non-invasive means of biomonitoring contaminant exposure. This study used HR-ICP-MS to analyse levels and composition of 16 elements in Svalbard reindeer faeces (n = 96) and soil (n = 9) from two locations on Svalbard, with the aim to assess whether local anthropogenic pollution influences element bioavailability. One of the sampling areas, the Nordenskiöld coast, is situated on the west coast of Spitsbergen, close to the Arctic Ocean and relatively far from local anthropogenic sources. The other sampling area, Adventdalen, is located further inland and close to Longyearbyen, the largest settlement of the archipelago. There was a significant difference in faecal elemental concentration and composition between the Adventdalen and Nordenskiöld coast reindeer populations. Elements of geogenic origin (e.g., Al, Cu and Fe) were found at higher levels in faeces from Adventdalen. In comparison, levels of Ca, Se and the toxic elements Cd and Pb were higher in faecal samples from the Nordenskiöld coast. The significantly higher levels of faecal Cd and Pb at Nordenskiöld coast may be due to marine input, dietary differences between the populations, or possible anthropogenic influence from the nearby settlement of Barentsburg. There was, however, a decoupling in elemental composition between faecal and soil samples, which may derive from a selective vegetational uptake of elements from the soil. The results suggest that reindeer are exposed to a range of elements and that faeces can be used to monitor the exposure to bioavailable environmental levels of both essential and toxic elements in terrestrial ecosystems.

Improving selenium accumulation in broilers using Escherichia coli Nissle 1917 with surface-displayed selenite reductase SerV01

Selenium levels have a critical impact on livestock and poultry, and selenium nanoparticles (SeNPs) have shown significant efficiency in supplementation. This study identified a high-efficiency selenite reductase, SerV01, in Staphylococcus aureus LZ-01, which can convert Se₂O₃^2- to SeNPs. Subsequently, SerV01 was introduced into the intestines of the broilers using the surface display-engineered E. coli Nissle 1917 (EcN). The results showed that the engineered bacteria (EcN-IS) significantly increased the selenium content by 0.87 mg kg^-1, 0.52 mg kg^-1, and 6.10 mg L^-1 in the liver, breast muscle, and serum, respectively. With SeNPs + EcN-IS treatment, glutathione peroxidase and thioredoxin reductase levels reached 0.7536 ± 0.03176 U μL^-1 protein and 2.463 ± 0.1685 U μL^-1 protein, respectively. With the modified probiotics, the proportion of beneficial intestinal flora increased, with Lactobacillus and Propionibacterium accounting for 75.85% and 0.19%. This technology provides a novel idea to facilitate the exploitation of selenium in broiler diets and improve antioxidant capability.

Interactive effects of freshwater acidification and selenium pollution on biochemical changes and neurotoxicity in Oreochromis mossambicus

Effect of selenium and acidification in freshwater environment was assessed solitary but no reports are available on the impacts of both factors act together. In the present study, effects of combined simultaneous exposure to selenium (Se) and low pH were assessed in Mozambique tilapia, Oreochromis mossambicus. Responses were measured based on antioxidant defenses (enzymatic SOD, CAT, GPx and non-enzymatic GSH), biotransformation enzyme (GST), metallothionein levels (MT), oxidative damage (LPO, CP), Na⁺/K⁺-ATPase (NKA) activity in gills and liver tissues and neurotoxicity (acetylcholinesterase, AChE) response in brain tissue. Fish were exposed to combined treatment at different pH levels (7.5, control (optimum pH for tilapia growth); 5.5, low pH) and Se concentrations (0, 10, and 100 μg L^-1). Toxicity levels of Se were not significantly different under control and low pH indicating that pH did not affect Se toxicity. Levels of GSH and MT were enhanced in Se-exposed fish at both pH. Combined effects of high Se concentration and low pH decreased SOD and CAT activities and increased those of GPx and GST. However, organisms were not able to prevent cellular damage (LPO and CP), indicating a condition of oxidative stress. Furthermore, inhibition of Na⁺/K⁺-ATPase activity was showed. Additionally, neurotoxicity effect was observed by inhibition of cholinesterase activity in organisms exposed to Se at both pH conditions. As a result, the combined stress of selenium and freshwater acidification has a slight impact on antioxidant defense mechanisms while significantly inhibiting cholinesterase and Na+/K + -ATPase activity in fish. The mechanisms of freshwater acidification mediating the toxic effects of trace non-metal element on freshwater fish need to investigate further.

The Association of Circulating Selenium Concentrations with Diabetes Mellitus

PURPOSE

The relationship between circulating selenium and diabetes mellitus (DM) remains inconsistent. Therefore, the relationship between circulating selenium and DM was investigated in the present study.

PATIENTS AND METHODS

All participants (aged ≥18 years) were included from the National Health and Nutrition Examination Survey (NHANES) 1999-2006. Selenium concentrations from the fasting serum samples were determined using inductively coupled mass spectrometry, then grouped into quartiles. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by using multivariate logistic regression analysis and the results were stratified by age and sex.

RESULTS

A total of 2,903 (61.9±13.7 years old) participants (49.3% males) were enrolled, and 580 (19.97%) of them had DM. The mean levels of selenium were 136.4±19.6 µg/L. Patients with DM (138.76±20.02 vs 135.88±19.44, P=0.002) had higher selenium levels compared to those without DM. The OR for DM was 1.12 (95% CI=1.01-1.24; P=0.0270) for each 10 µg/L increment in selenium, and subjects in the highest quartile of selenium levels (>147.00 uµg/L) had 2.82 (95% CI=1.55-5.11; P=0.0007) times higher risk of DM compared to the lowest quartile of selenium levels. Subgroup analysis showed that selenium was independently associated with DM only in female aged <65 years.

CONCLUSION

Circulating selenium levels were positively associated with the odds of DM, but difference in sex and age.

Pharmacokinetics of Selenium in Healthy Piglets After Different Routes of Administration: Application of Pharmacokinetic Data to the Risk Assessment of Selenium

Selenium (Se) is a trace element in the environment. Although it is a necessary trace element for human and animal health, excessive Se can also pollute the environment and show toxic effects on humans and animals. Since the safe dose range of Se is narrow, it is important to study the pharmacokinetics of Se in order to make better use of the biological effects of Se. In the present study, we investigated the pharmacokinetic process of sodium selenate in healthy piglet plasma after either intramuscular injection or oral administrations, and examined dynamic changes of antioxidant system in healthy piglets after Se supplementation. The results showed that the Se reached the peak concentration of (0.2451 ± 0.0123) μg mL^-1 at (0.4237 ± 0.0185) h following intramuscular injection administration and (0.1781 ± 0.0142) μg mL^-1 at (2.1517 ± 0.1806) h following oral administration in the plasma. The average AUC of sodium selenite following intramuscular injection and oral administrations was (31.7260 ± 1.3574) and (75.1460 ± 3.4127) mg L^-1 h^-1, respectively. Total antioxidant capacity (T-AOC), glutathione peroxidase (GPx), and superoxide dismutase (SOD) generally show an upward trend and malondialdehyde (MDA) shows a downward trend, regardless of intramuscular injection or oral sodium selenite. An increased concentration of Se was observed in the serum of healthy piglets after intramuscular injection and oral sodium selenite. Our results indicated that the pharmacokinetic process of sodium selenate in healthy piglet blood conforms to the two-chamber open model. Its pharmacokinetic properties are rapid absorption and slow excretion. Antioxidant systems in healthy piglets vary with Se levels, but there is a significant lag period compared with the latter. Our current findings will provide a more complete understanding of clinical rational Se supplementation and avoid contamination of the environment by overdose.

PVP intercalated metallic WSe2 as NIR photothermal agents for efficient tumor ablation

Transition metal dichalogenides (TMDCs) with unique layered structures hold promising potential as transducers for photothermal therapy. However, the low photothermal conversion efficiency and poor stability in some cases limit their practical applications. Herein, we demonstrate the fabrication of ultrathin homogeneous hybridized TMDC nanosheets and their use for highly efficient photothermal tumor ablation. In particular, the nanosheets were composed of metallic WSe₂ intercalated with polyvinylpyrrolidone (PVP), which was facilely prepared through a solvothermal process from the mixture of selenourea crystals, WCl₆ powder along with PVP polymeric nanogel. Our characterizations revealed that the obtained nanosheets exhibited excellent photothermal conversion efficiency, therapeutic demonstration with improved biocompatibility and physiological stability attributing to the combined merits of metallic phase of WSe₂ and hydrophilic PVP insertion. Both the histological analysis of vital organs and in vitro/in vivo tests confirmed the nanosheets as actively effective and biologically safe in this phototherapeutic technique. Findings from this non-invasive experiment clearly emphasize the explorable therapeutic efficacy of the layered-based hybrid agents in future cancer treatment planning procedures.

Short communication: Effects of different selenium supplements on rumen fermentation and apparent nutrient and selenium digestibility of mid-lactation dairy cows

The aim of this study was to evaluate the dose-dependent effects of a hydroxy-analog of selenomethionine (HMSeBA) on rumen fermentation, apparent nutrient digestibility, and total selenium absorption in mid-lactation dairy cows, and to compare the effects with those of sodium selenite (SS). Fifty mid-lactation dairy cows with similar milk yields, days in milk, and parity were randomly assigned to 1 of 5 treatments according to a randomized complete block design. The cows were fed a basal diet containing 0.06 mg/kg dry matter (DM) of Se (control) or the same basal diet supplemented with SS, yielding 0.3 mg of Se/kg of DM (SS-0.3), or HMSeBA, yielding 0.1, 0.3, or 0.5 mg of Se/kg of DM (SO-0.1, SO-0.3, and SO-0.5, respectively), during the experimental period. The final content of Se in control, SS-0.3, SO-0.1, SO-0.3, and SO-0.5 was 0.06, 0.34, 0.15, 0.33, and 0.52 mg of Se/kg of DM. The experiment lasted for 10 wk, with a pretrial period of 2 wk. Supplementation with HMSeBA altered rumen fermentation by linearly increasing total volatile fatty acids and the molar proportions of propionate and butyrate but decreasing rumen pH, ammonia content, and the ratio of acetate to propionate. Compared with SS, HMSeBA enhanced the molar proportion of propionate in the rumen and the apparent digestibility of crude protein, neutral detergent fiber, acid detergent fiber, and selenium. We demonstrated that HMSeBA promoted rumen fermentation, apparent nutrient digestibility, and selenium absorption, implying that HMSeBA has a greater apparent absorption than SS.

Arsenic, selenium, boron, lead, cadmium, copper, and zinc in naturally contaminated rocks: A review of their sources, modes of enrichment, mechanisms of release, and mitigation strategies

Massive and ambitious underground space development projects are being undertaken by many countries around the world to decongest megacities, improve the urban landscapes, upgrade outdated transportation networks, and expand modern railway and road systems. A number of these projects, however, reported that substantial portions of the excavated debris are oftentimes naturally contaminated with hazardous elements, which are readily released in substantial amounts once exposed to the environment. These contaminated excavation debris/spoils/mucks, loosely referred to as "naturally contaminated rocks", contain various hazardous and toxic inorganic elements like arsenic (As), selenium (Se), boron (B), and heavy metals like lead (Pb), cadmium (Cd), copper (Cu), and zinc (Zn). If left untreated, these naturally contaminated rocks could pose very serious problems not only to the surrounding ecosystem but also to people living around the construction and disposal sites. Several incidents of soil and ground/surface water contamination, for example, have been documented due to the false assumption that excavated materials are non-hazardous because they only contain background levels of environmentally regulated elements. Naturally contaminated rocks are hazardous wastes, but they still remain largely unregulated. In fact, standard leaching tests for their evaluation and classification are not yet established. In this review, we summarized all available studies in the literature about the factors and processes crucial in the enrichment, release, and migration of the most commonly encountered hazardous and toxic elements in naturally contaminated geological materials. Although our focus is on naturally contaminated rocks, analogue systems like contaminated soils, sediments, and other hazardous wastes that have been more widely studied will also be discussed. Classification schemes and leaching tests to properly identify and regulate excavated rocks that may potentially pose environmental problems will be examined. Finally, management and mitigation strategies to limit the negative effects of these hazardous wastes are introduced.

Dietary Antioxidants, Circulating Antioxidant Concentrations, Total Antioxidant Capacity, and Risk of All-Cause Mortality: A Systematic Review and Dose-Response Meta-Analysis of Prospective Observational Studies

The associations of various dietary or circulating antioxidants with the risk of all-cause mortality in the general population have not been established yet. A systematic search was performed in PubMed and Scopus, from their inception up to October 2017. Prospective observational studies reporting risk estimates of all-cause mortality in relation to dietary intake and/or circulating concentrations of antioxidants were included. Random-effects meta-analyses were conducted. Forty-one prospective observational studies (total n = 507,251) involving 73,965 cases of all-cause mortality were included. The RRs of all-cause mortality for the highest compared with the lowest category of circulating antioxidant concentrations were as follows: total carotenes, 0.60 (95% CI: 0.46, 0.74); vitamin C, 0.61 (95% CI: 0.53, 0.69); selenium, 0.62 (95% CI: 0.45, 0.79); β-carotene, 0.63 (95% CI: 0.57, 0.70); α-carotene, 0.68 (95% CI: 0.58, 0.78); total carotenoids, 0.68 (95% CI: 0.56, 0.80); lycopene, 0.75 (95% CI: 0.54, 0.97); and α-tocopherol, 0.84 (95% CI: 0.77, 0.91). The RRs for dietary intakes were: total carotenoids, 0.76 (95% CI: 0.66, 0.85); total antioxidant capacity, 0.77 (95% CI: 0.73, 0.81); selenium, 0.79 (95% CI: 0.73, 0.85); α-carotene, 0.79 (95% CI: 0.63, 0.94); β-carotene, 0.82 (95% CI: 0.77, 0.86); vitamin C, 0.88 (95% CI: 0.83, 0.94); and total carotenes, 0.89 (95% CI: 0.81, 0.97). A nonsignificant inverse association was found for dietary zinc, zeaxanthin, lutein, and vitamin E. The nonlinear dose-response meta-analyses demonstrated a linear inverse association in the analyses of dietary β-carotene and total antioxidant capacity, as well as in the analyses of circulating α-carotene, β-carotene, selenium, vitamin C, and total carotenoids. The association appeared to be U-shaped in the analyses of serum lycopene and dietary vitamin C. The present study indicates that adherence to a diet with high antioxidant properties may reduce the risk of all-cause mortality. Our results confirm current recommendations that promote higher intake of antioxidant-rich foods such as fruit and vegetables.

Bioaccumulation, cytotoxicity and oxidative stress of the acute exposure selenium in Oreochromis mossambicus

Selenium (Se) is an essential trace-element that becomes toxic when present at high concentrations for aquatic organisms. The knowledge about the mechanism of Se toxicity in freshwater ecosystem is still poorly studied. Thus the aim of the present study was to assess the impact of environmentally relevant concentrations of Se toxicity: 5, 10, 25, 50 and 100 µg/L or water only (control) for periods of 96 hour (h) to test for Se accumulation (gill, liver and brain), its effects on enzymatic and non-enzymatic antioxidant defenses (gill and liver), oxidative stress effects on lipid, protein (gill and liver), DNA (liver) and inhibition of AchE (brain) activity were measured in Mozambique tilapia, Oreochromis mossambicus. Our result showed that Se accumulation was observed in the gill, liver and brain tissues of fish exposed to different concentrations and accumulation varied upon different tissues. Enzymatic (SOD, CAT, GPx and GST) and non-enzymatic (GSH and MT) antioxidant enzymes such as superoxide dismutase (SOD), glutathione peroxidase (GPx) and glutathione-s-transferase (GST) were significantly increased after 96 h exposure of higher concentrations Se in the gill and liver tissue with the exception of GST activity was significantly inhibited in liver after 96 h exposure of higher concentrations of Se. In contrast, catalase (CAT) activities were inhibited for both tissues of Se exposure at 96 h. Reduced glutathione (GSH) and Metallothionein (MT) levels were increased in the gill and liver tissues after exposure to Se for 96 h. We also observed that Se affected antioxidant defense, increasing oxidative stress indicator of lipid peroxidation (LPO) and protein carbonyl (PCO) in gill and liver tissues of fish exposed to Se for 96 h at the concentration dependent manner. Increased DNA damage scores observed in liver tissue of fish exposed to Se for concentrations dependent manner, indicating potential of Se on fish. We also observed inhibition of acetylcholine esterase (AchE) activity in brain tissue of fish exposed to Se for higher concentrations. The changes in these parameters can be used as suitable biomarkers for monitoring the toxicity of Se in the aquatic environment.

Induction of oxidative stress and cell apoptosis by selenium: the cure against oral carcinoma

Oral carcinoma (OC) remains one of the most difficult malignancies to cure. selenium (Se) is an essential trace mineral for human and animals, but high concentrations of Se induce apoptosis and oxidative effects. Although cell apoptosis has been evidenced as a critical mechanism mediating the anticancer activity of Se, the underlying molecular mechanisms remain elusive. To explore the role of Se in rat OC, we examined the weather the oxidative stress-mediated apoptotic pathway induced by Se was involved in the development of OC. In this study, we successfully constructed the OC rat model by 4-Nitroquinoline-1-oxide (4-NQO) exposure which reflected from histopathological observations. Se-induced the productions of methane dicarboxylic aldehyde (MDA) and reactive oxygen species (ROS), which was accompanied by the inhibition of superoxide dismutase (SOD) both in vivo and vitro. The anti-apoptotic gene (Bcl-2) was down-regulated and pro-apoptosis members (Bax, Bak, Cyt-c, caspase9 and caspase3) were up-regulated by Se in OC cells. Meanwhile, we also found that Se could strongly inhibited the cell proliferation of OC lines in vitro. These results suggested that excessive Se could effectively cause oxidative stress and induce apoptosis in OC cells, as a result the OC was also inhibited to some extent. Therefore, the information presented in this study is believed to be helpful in supplementing data for further therapy of OC.

Effects of selenium exposure on the hematology, innate immunity, and metabolic rate of yellow-bellied sliders (Trachemys scripta scripta)

Selenium (Se) is a naturally occurring essential element that can be toxic to vertebrates at high concentrations. Despite studies that have documented that wild reptile species can accumulate copious amounts of Se, little is known regarding specific toxicologic effects of Se. In this study, 70 juvenile yellow-bellied sliders (Trachemys scripta scripta) were exposed to one of three seleno-L-methionine (SetMet) treatments (control, n = 24; 15 mg/kg, n = 23; and 30 mg/kg, n = 23) via weekly oral gavage for 5 weeks. At the conclusion of the experiment, kidney, liver, muscle, and blood samples were collected for quantitative Se analysis. Turtles in the SeMet treatment groups accumulated significantly higher amounts of Se in all tissue types relative to controls (all p < 0.001). Turtles in the 30 mg/kg SeMet group also accumulated significantly higher amounts of Se compared to the 15 mg/kg group (all p < 0.001). Although toxicity thresholds for reptiles have not been established, Se concentrations in liver tissue from both SeMet treatment groups exceeded reported avian toxicity thresholds for liver tissue. Neither oxygen consumption nor innate bactericidal capacity were impacted by SeMet exposure. However, turtles in the 30 mg/kg SeMet group exhibited anemia, which has been reported in other vertebrates exposed to Se. Furthermore, juvenile T. s. scripta in the 30 mg/kg SeMet group experienced 17% mortality compared to 0% in the 15 mg/kg treatment and control groups. To our knowledge, this study is the first to report dose-dependent Se-associated anemia and mortality in a chelonian species.

Effects of injectable trace minerals on humoral and cell-mediated immune responses to Bovine viral diarrhea virus, Bovine herpes virus 1 and Bovine respiratory syncytial virus following administration of a modified-live virus vaccine in dairy calves

Our objective was to evaluate the effect of an injectable trace mineral (ITM) supplement containing zinc, manganese, selenium, and copper on the humoral and cell mediated immune (CMI) responses to vaccine antigens in dairy calves receiving a modified-live viral (MLV) vaccine containing BVDV, BHV1, PI3V and BRSV. A total of 30 dairy calves (3.5 months of age) were administered a priming dose of the MLV vaccine containing BHV1, BVDV1 & 2, BRSV, PI3V, and an attenuated-live Mannheimia-Pasteurella bacterin subcutaneously (SQ). Calves were randomly assigned to 1 of 2 groups: (1) administration of ITM SQ (ITM, n=15) or (2) injection of sterile saline SQ (Control; n=15). Three weeks later, calves received a booster of the same vaccine combination SQ, and a second administration of ITM, or sterile saline, according to the treatment group. Blood samples were collected on days 0, 7, 14, 21, 28, 42, 56, and 90 post-vaccination for determination of antibody titer, viral recall antigen-induced IFN-γ production, and viral antigen-induced proliferation by peripheral blood mononuclear cells (PBMC). Administration of ITM concurrently with MLV vaccination resulted in higher antibody titers to BVDV1 on day 28 after priming vaccination compared to the control group (P=0.03). Calves treated with ITM showed an earlier enhancement in PBMC proliferation to BVDV1 following vaccination compared to the control group. Proliferation of PBMC after BVDV stimulation tended to be higher on day 14 after priming vaccination in calves treated with ITM than in the control group (P=0.08). Calves that received ITM showed higher PBMC proliferation to BRSV stimulation on day 7 after priming vaccination compared to the control group (P=0.01). Moreover, calves in the ITM group also had an enhanced production IFN-γ by PBMC after stimulation with BRSV on day 21 after priming vaccination compared to day 0 (P<0.01). In conclusion, administration of ITM concurrently with MLV vaccination in dairy calves resulted in increased antibody titer to BVDV1, and greater PBMC proliferation to BVDV1 and BRSV recall stimulation compared to the control group, suggesting that ITM might represent a promising tool to enhance the humoral and CMI responses to MLV vaccines in cattle.

Levels of sP-selectin and hs-CRP Decrease with Dietary Intervention with Selenium and Coenzyme Q10 Combined: A Secondary Analysis of a Randomized Clinical Trial

Background/Objectives

Inflammation and oxidative stress are central in many disease states. The major anti-oxidative enzymes contain selenium. The selenium intake in Europe is low, and supplementation with selenium and coenzyme Q₁₀, important anti-oxidants, was evaluated in a previous study. The aim of this study was to evaluate response on the inflammatory biomarkers C-reactive protein, and sP-selectin, and their possible impact on cardiovascular mortality.

Subjects/Methods

437 elderly individuals were included in the study. Clinical examination, echocardiography, electrocardiography and blood samples were drawn. The intervention time was 48 months, and median follow-up was 5.2 years. The effects on inflammation/atherosclerosis were evaluated through analyses of CRP and sP-selectin. Evaluations of the effect of the intervention was performed using repeated measures of variance. All mortality was registered, and endpoints of mortality were assessed by Kaplan-Meier plots.

Results

The placebo group showed a CRP level of 4.8 ng/mL at the start, and 5.1 ng/mL at the study end. The active supplementation group showed a CRP level of 4.1 ng/mL at the start, and 2.1 ng/mL at the study end. SP-selectin exhibited a level of 56.6 mg/mL at the start in the placebo group and 72.3 mg/mL at the study end, and in the active group the corresponding figures were 55.9 mg/mL and 58.0 mg/mL. A significantly smaller increase was demonstrated through repeated measurements of the two biomarkers in those on active supplementation. Active supplementation showed an effect on the CRP and sP-selectin levels, irrespective of the biomarker levels. Reduced cardiovascular mortality was demonstrated in both those with high and low levels of CRP and sP-selectin in the active supplementation group.

Conclusion

CRP and sP-selectin showed significant changes reflecting effects on inflammation and atherosclerosis in those given selenium and coenzyme Q₁₀ combined. A reduced cardiovascular mortality could be demonstrated in the active group, irrespective of biomarker level. This result should be regarded as hypothesis-generating, and it is hoped it will stimulate more research in the area.

Short and long term release mechanisms of arsenic, selenium and boron from a tunnel-excavated sedimentary rock under in situ conditions

Sedimentary rocks of marine origin excavated from tunnel construction projects usually contain background levels of hazardous trace elements, but when exposed to the environment, they generate leachates with concentrations of arsenic (As), selenium (Se) and boron (B) exceeding the WHO guideline for drinking water. In this study, the leaching of As, Se and B was evaluated under in situ conditions at various flow patterns, particle size distributions and column thicknesses. The results showed that these trace elements were leached out of the rock via short and long term mechanisms. In the short term, all three elements were rapidly and simultaneously released due to the dissolution of soluble evaporite salts formed from entrapped sea water of the Cretaceous. After their rapid release, however, these trace elements behaved differently as a result of their contrasting adsorption affinities onto minerals like clays and Fe-oxyhydroxides, which were further influenced by the pH, presence of coexisting ions and speciation of the trace elements. Selenium was quickly and easily transported out of the columns because it was mostly present as the very mobile selenate ion (Se[VI]). In comparison, the migration of As and B was hindered by adsorption reactions onto mineral phases of the rock. Boron was initially the least mobile among the three because of its preferential adsorption onto clay minerals that was further enhanced by the slightly alkaline pH and high concentrations of Ca(2+) and Na(+). However, it was gradually re-mobilized in the latter part of the experiments because it was only weakly adsorbed via outer sphere complexation reactions. In the long term, the rock continued to release substantial amounts of As, Se and B via pyrite oxidation and adsorption/desorption reactions, which were regulated by the temperature and rainfall intensity/frequency on site.

The selenium accumulation and its effect on growth, and haematological parameters in red sea bream, Pagrus major, exposed to waterborne selenium

Juvenile Pagrus major (mean length 15.8±1.6cm, and mean weight 90.4±4.7g) were exposed for 4 weeks with waterborne selenium concentration (0, 50, 100, 200, and 400µg/L). The profile of Se accumulation among tissue in P. major is dependent on the exposure periods and Se concentration. After 4 weeks, the highest accumulation of Se was observed in the kidney, and the order of Se accumulation in tissues was kidney≈liver>spleen>intestine>gill>muscle. Se decreased the growth rate, and there was an inverse proportion between growth and Se concentration. The major hematological findings were significant decrease in the RBC count, Ht value, and Hb concentration exposed to ≥100µg/L Se concentrations. Se exposure (≥100µg/L) led to significant increase in the glucose, GOT, and GPT levels, whereas the levels of calcium, magnesium, cholesterol, and total protein did not increase. The results suggest that waterborne Se exposure can induce significant Se accumulation in tissues, inhibition of growth, and hematological alterations.

Mineral contents of seed and seed oils of Capparis species growing wild in Turkey

The mineral contents of seed and seed oils of Capparis species growing wild in Turkey were established by inductively coupled plasma-atomic emission spectrometry. Capparis spinosa var. spinosa (2010) and Capparis ovata var. canescens variety (2009) were determined to be rich in terms of mineral matter as 19,514.60 and 16,995.92 ppm as a total, respectively. C. spinosa var. spinosa collected from Muğla-Milas region (2009) had the highest amount of Ca with 1,010.67 ppm in C. spinosa species and in C. ovata species. C. ovata var. canescens collected from Ankara-Beypazarı (2010) region had the highest amount of Ca with 833.92 ppm Ca amount in C. spinosa var. spinosa, inermis, herbaceae seeds decreased in 2010. C. spinosa var. inermis collected from Antalya-Serik (2010) in C. spinosa species had rich amount of Ca with 123.78 ppm and C. ovata var. palaestina seed oils collected from Mardin-Savur region (2009) had rich amount of Ca with 253.71 ppm in C. ovata species. The oil of C. spinosa var. herbaceae variety collected from Mardin-Midyat region (2010) was determined to have the highest major mineral matter (Ca, K, Mg, Na, and P) with 1,424.37 ppm in C. spinosa species. It was also determined that as a result, caper seed and oils were found to be important sources of nutrients and essential elements.

Characterization of cytosolic glutathione peroxidase and phospholipid-hydroperoxide glutathione peroxidase genes in rainbow trout (Oncorhynchus mykiss) and their modulation by in vitro selenium exposure

Selenium (Se) is an oligonutrient with both essential biological functions and recognized harmful effects. As the selenocysteine (SeCys) amino acid, selenium is integrated in several Se-containing proteins (selenoproteins), many of which are fundamental for cell homeostasis. Nevertheless, selenium may exert toxic effects at levels marginally above those required, mainly through the generation of reactive oxygen species (ROS). The selenium chemical speciation can strongly affect the bioavailability of this metal and its impact on metabolism, dictating the levels that can be beneficial or detrimental towards an organism. Glutathione peroxidase (GPxs) is the largest and the most studied selenoprotein family. Cytosolic glutathione peroxidase (cGPx, GPx1) and phospholipid hydroperoxide glutathione peroxidase (PHGPx, GPx4) are widely distributed throughout tissues, and play a pivotal role in regulating the oxidative status in the cell. In this study we have cloned GPx1 and GPx4 genes in rainbow trout (Oncorhynchus mykiss). The constitutive mRNA expression of these GPx genes was examined in 18 trout tissues and their responsiveness to Se availability was analysed using a rainbow trout liver cell line (RTL). An inorganic (sodium selenite, Na2SeO3) and organic (selenocysteine, Cys-Se-Se-Cys) selenocompound have been used as Se sources. GPx1 activity was also tested to verify the impact of transcript changes on the enzymatic function of these molecules. To understand if the results obtained from the transcript expression analysis were due to Se bioavailability or generation of ROS, the cytoxicity of the two selenocompounds was tested by measuring the impact of Se on cell membrane integrity. Lastly, Se availability was quantified by mass spectrophotometry to determine the amount of Se in the cell culture media, the Se background due to the foetal calf serum supplement and the contribution from the two selenocompounds used in the treatments. Three isoforms of genes for both GPx1 (GPx1a, 1b1 and 1b2) and GPx4 (GPx4a1, a2 and b) have been identified. The discovery of a third gene encoding for GPx1 and GPx4 hints that salmonids may have the biggest selenoproteome amongst all vertebrates. Transcripts of GPx4 genes were more highly expressed in most tissues examined in vivo (except blood, head kidney and spleen), whereas those of the GPx1 genes were more responsive to selenium exposure in vitro, especially to the organic form. Interestingly, GPx1a was the most sensitive to selenium availability in non stressful conditions, whereas GPx1b1 and GPx1b2 were highly induced by exposure to selenium levels that had some toxic effects on the cells. Although the different concentrations tested of the two selenocompounds modulate GPx1 transcript expression to various degrees, no significant change of GPx1 enzymatic activity was detectable. Our results lead us to conclude that trout GPx1 transcripts expression level may represent a sensitive biomarker for selenium intake, helping to evaluate if selenium concentration and chemical speciation impact on cell homeostasis.

Effect of oxygen free radicals and nitric oxide on apoptosis of immune organ induced by selenium deficiency in chickens

Selenium is an essential element with antioxidant roles in immune regulation, but there is little understanding of how Se acts in apoptosis in the immune organs of birds. The aim of study was to evaluate the influence of Se deficiency on oxygen free radicals, NO and apoptosis in immune organ of chickens. 160 1-day-old chickens were randomly assigned to two groups of 80 each and were fed on a low-Se diet (0.032 mg/kg Se) or a control diet (0.282 mg/kg Se), respectively. OFR production in blood was determined on days 30, 45, 60 and 75, respectively. The iNOS-NO system activity in immune organ (thymus, spleen, bursa of fabricius) was identified by NO content and NOS activity assay on days 30, 45, 60 and 75, respectively. Apoptosis was measured by DNA ladder analysis, ultrastructural observations, TdT-mediated dUTP nick end labeling TUNEL assay and flow cytometric analysis of apoptotic DNA. The transcription of factor-associated suicide, caspase-3 mRNA was tested by fluorescence quantitative PCR. The results showed that OFR production, NO and inducible NO synthases (iNOS) activity in the low-Se group were significantly increased (p < 0.05) than in the control group. In addition, apoptosis was observed in chicken immune organ in the low-Se group. The degree and the number of apoptotic cells rose in a time-dependent manner. The expression of Fas and caspase-3 mRNA increased (p < 0.05) than in the control group. It indicated that the oxidative stress and NO played a causative role in the apoptosis of immune tissues induced by selenium deficiency.

[Demand for and clinical practice of complementary selenium therapy in prostate cancer patients]

BACKGROUND

Selenium supplementation is a popular and broadly adopted complementary oncological treatment option. The aim of the study was the evaluation of the necessity and the indication for selenium therapy in prostate cancer patients.

METHODS

295 consecutive patients after radical prostatectomy were evaluated for oncological, basic laboratory and lifestyle characteristics. The selenium level was measured using graphite furnace atom absorption spectroscopy.

RESULTS

The median selenium level was 103.4 (72.9–142.1) μg/l. Correlations were found between a low selenium level and progressed cancer disease, positive lymph node status, chronic nicotine and alcohol abuse, and chronic multiple medications.

CONCLUSION

Based on a documented low selenium level in 96.3% of investigated prostate cancer patients and the known consequences of an insufficient selenium supply, a targeted selenium supplementation is recommended. Selenium therapy should be part of an individual medical nutritional and lifestyle intervention.

Selenium deficiency a factor in endemic goiter persistence in sub-Saharan Africa

BACKGROUND

Goiter is still common in Uganda, despite the present iodized salt coverage of at least 95%. Where there is endemic goiter after adequate iodine supplementation, selenium deficiency could be a factor for the continued occurrence of goiter. The objectives of the present study, therefore, were to determine the serum selenium levels among goitrous patients and nongoitrous controls and to determine the association between goiter and selenium levels among these patients.

METHODS

The investigation was designed as a case control study in which 92 subjects were enrolled, 46 cases and 46 controls of similar age and sex distribution. Subjects were interviewed and examined. Blood samples were taken and selenium concentrations were determined by electrothermal atomic absorption spectrometry.

RESULTS

The overall mean serum selenium levels were 77.25 μg/l (SD 16.78) for the goiter patients and 95.50 μg/l (24.47) for the nongoiter controls. The difference between goitrous and nongoitrous populations was statistically significant (p=0.0001). Selenium levels above 102.8 μg/l had a statistically significant protective effect against goiter with adjusted odds ratio 0.3 (0.13-0.69); p=0.005. Other factors, such as age, main food constituent, and use of iodized salt, had no association with goiter.

CONCLUSIONS

There were significant differences between selenium levels among goitrous patients and nongoitrous controls. High selenium levels seem to have a protective effect against goiter. Selenium supplementation as a preventive strategy is worth further exploration.

Thermodynamics and Dynamic Kinetics of the Oxidation of Selenomethionine to Methionine Selenoxide: A Dft Study

In order to investigate the stability of selenomethionine (SeMet), the oxidation reaction of selenomethionine (SeMet) with an oxygen atom was studied by the density function theory (DFT) method. The structures of reactants, transition state and products were fully optimized at the B3LYP/6-311G** level. Intrinsic reaction coordinate (IRC) calculations were carried out to ensure the validity of the reaction path. The thermodynamic functions, namely entropy, enthalpy, free energy and equilibrium constant, and the reaction rate constant k in Eyring transition state theory, were also calculated. It has been shown that the SeMet oxidation process is favoured at lower temperatures, which might have implications for the storage stability of selenomethionine (SeMet) at lower temperatures.

Protective role of selenium supplementation against cardiac lesions induced by the combination of levomepromazine and risperidone in the rabbit

Neuroleptics are a suspected cause of sudden death in psychiatric patients, especially in those with pre-existing cardiac lesions. As these lesions were previously shown to be associated with selenium (Se) deficiency, the aim of the present study was to evidence the possible protective effect of Se supplementation against cardiac lesions induced by the combination of the neuroleptic drugs levomepromazine and risperidone in the rabbit. Two groups of 6 rabbits were treated with 3 mg/kg of levomepromazine daily intramuscularly combined with 1 mg/kg of risperidone intramuscularly every other week for 3 consecutive months, and one group additionally received a solution of sodium selenite (2 μg/kg/day) intramuscularly during the whole treatment period. Furthermore, one group of six untreated animals was given the Se supplementation and another group of six control animals received saline daily. Blood samples were drawn before and at the end of the treatment period for the measurement of serum Se levels. At the end of the study, all animals were sacrificed and their hearts were removed for the measurement of tissue Se concentrations. In addition, the hearts were prepared for histopathological examination. A variety of cardiac lesions was found in the neuroleptics-treated animals without supplementation and to a lesser extent in the control and Se-supplemented untreated animals. Importantly, only rare cardiac lesions were observed in neuroleptics-Se-treated animals. The most striking differences in Se concentrations were noted in the myocardium: as compared to controls, there was a 43% reduction in neuroleptics-treated, but non-Se-supplemented animals (p < .01), at the end of the treatment period, whereas only a 14% reduction (p < .05) was noted in the neuroleptics-Se-treated animals. These results confirm that neuroleptics induce cardiac lesions associated with Se deficiency. Selenium supplementation markedly decreased the incidence and severity of neuroleptics-induced cardiac lesions and these findings may serve as a basis for further evaluation of the protective role of Se supplementation in neuroleptics-treated patients. However, Se supplementation in normal animals without Se deficiency was also shown to be cardiotoxic.

Role of selenium in heart lesions produced by neuroleptics in the rabbit

Organic and/or functional heart lesions sometimes resulting in sudden death have been described in psychiatric patients treated with neuroleptics. As selenium has been suggested previously to play a role in the development of such lesions, the present study was undertaken to determine whether a correlation could be found between heart lesions induced by neuroleptics and changes in blood selenium as well as myocardial tissue concentrations in the rabbit. Twelve NZW adult rabbits were treated intramuscularly with both levomepromazine (3 mg kg(-1) day(-1)) and risperidone (1 mg kg(-1) once every other week) for 3 months, and compared with 12 saline-treated controls. Blood samples were drawn before and at the end of the study. Tissue samples from the heart, liver and kidneys were obtained at the end of treatment, and the hearts were examined histologically. Heart lesions including disorganization of cardiac fibers, myolysis, interstitial and endocardial fibrosis, and necrosis were noted in treated animals, but not in controls. There was a 20% decrease in selenium blood levels and a 50% decrease in selenium myocardial tissue levels in treated animals compared with controls (P < 0.001). In contrast, no differences in selenium levels in liver and kidneys were found across the experimental groups. These results suggest a possible correlation between selenium depletion and neuroleptics-induced heart lesions.

The bacterial response to the chalcogen metalloids Se and Te

Microbial metabolism of inorganics has been the subject of interest since the 1970s when it was recognized that bacteria are involved in the transformation of metal compounds in the environment. This area of research is generally referred to as bioinorganic chemistry or microbial biogeochemistry. Here, we overview the way the chalcogen metalloids Se and Te interact with bacteria. As a topic of considerable interest for basic and applied research, bacterial processing of tellurium and selenium oxyanions has been reviewed a few times over the past 15 years. Oddly, this is the first time these compounds have been considered together and their similarities and differences highlighted. Another aspect touched on for the first time by this review is the bacterial response in cell-cell or cell-surface aggregates (biofilms) against the metalloid oxyanions. Finally, in this review we have attempted to rationalize the considerable amount of literature available on bacterial resistance to the toxic metalloids tellurite and selenite.

Investigation of lipid peroxide and glutathione redox status of chicken concerning on high dietary selenium intake

This study was designed to investigate the effects of excess (24.5 mg Se/kg feed) inorganic and organic dietary selenium supplementation on 3-week-old broilers. The experiments lasted 4 days. Intensity of lipid peroxidation processes (malondialdehyde, MDA) and the amount (reduced glutathione, GSH) and activity (glutathione peroxidase activity, GSHPx) of gluathione redox system were measured in blood plasma, red blood cell hemolysate and liver. Voluntary feed intake in the selenium-treated groups reduced remarkably. Elevated GSH concentration and GSHPx activity were measured in plasma and liver of both selenium-treated groups compared to the untreated control and the 'pair-fed' controls. The lipid peroxidation processes in the liver showed higher intensity than the control due to both selenium treatment. The applied dose of selenite and selenomethionine does not inhibit, but even improves the activity of glutathione redox system in the liver during the early period of selenium exposure.

Trace elemental analysis of normal, benign hypertrophic and cancerous tissues of the prostate gland using the particle-induced X-ray emission technique

Trace elemental analysis was carried out in the tissue samples of normal, benign hypertrophic and carcinoma prostate using the particle-induced X-ray emission technique. A proton beam of 3 MeV energy was used to excite the samples. The elements Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Se, and Br were identified and their concentrations were estimated. It is observed that in benign tissues the concentrations of Cl, K, Zn, and Se are lower (P<0.05) and those of Cr, Fe, Ni, and Cu are higher (P<0.05 ) than in normal tissues. The concentrations of K, Ca, Zn, Se, and Br are lower (P<0.01) and those of Ti, Cr, Mn, Fe, Ni, and Cu are significantly higher (P<0.0005) in cancerous tissues than in normal tissues. Free radicals generated by elevated levels of Cr, Fe, Ni, and Cu possibly initiate and promote prostate cancer by oxidative DNA damage. The excess Cu levels in cancerous tissues support the fact that Cu promotes cancer through angiogenesis. The higher levels of Fe observed in cancerous tissues might be a consequence of tumor growth through angiogenesis. Significantly higher levels of Ni and Cr observed in carcinoma tissues support the well-established role of Ni and Cr as carcinogens. It is likely that the observed low levels of Zn and Se in cancerous tissues lead to the development of prostate cancer owing to a decrease in antioxidative defense capacity and impaired immune function of cells and also suggest that the inability to retain high levels of Zn and Se may possibly be an important factor in the development and progression of malignant prostate cells. In order to substantiate the observed elevated or deficient levels of trace elements in initiating, promoting, and inhibiting prostate cancer, several cellular and molecular studies are required.

Selenium alters the lipid content and protein profile of rat heart: an FTIR microspectroscopic study

Cardiovascular disease is one of the most important causes of morbidity and mortality in Western countries. In addition, it is well documented that selenium (Se) deficiency has been linked to cardiovascular diseases. This study was undertaken to present the effect of sodium selenite on left and right myocardia, and small veins of normal control rat heart at molecular level by using Fourier transform infrared (FTIR) microspectroscopy. The results mainly reveal that, Se treatment causes an increase in lipid content both in the saturated and unsaturated lipids, and an alteration in protein profile with a decrease in alpha-helix and an increase in beta-sheet structure of the rat heart which might be reflecting a slight subtoxic effect of selenium supplementation on normal rat heart at the dose used in this study.

Determination of Minerals Extracted from Several Commercial Teas (Camellia sinensis) to Hot Water (Infusion)

Mineral contents of some tea and their infusions drunk in Turkey were established by inductively coupled plasma atomic emission spectrometry. The Al, Ca, K, Mg, Mn, P, and S contents were very high in both infusions and tea (i.e., pieces of the tea plant). The As, Cd, Cr, Li, Pb, and Se contents of infusion and tea were found to be very low. The level of K of all samples is higher than those of other minerals. Generally, mineral contents of tea were found to be higher than those of tea infusions. In addition, the health benefits of teas and knowledge of their mineral contents are of great interest and may be useful for further study of enzyme systems and vital biochemical functions.

Cancer chemoprevention: Selenium as a prooxidant, not an antioxidant

Although the average daily dietary selenium (Se) intake in the United States is consistently above the adult RDA of 55 microg Se/day, supranutritional supplements of 200 microg Se/day have been shown to provide chemopreventive benefits against several cancers, particularly prostate cancer. The hypothesis herein contends that selenium compounds with the greatest anticarcinogenic potency are likely to be sodium selenite with Se in the +4 oxidation state and methylseleninic acid. These compounds exert their cancer chemopreventive effects by directly oxidizing critical thiol-containing cellular substrates, and are more effective than the more frequently preferred (used) supplements of selenomethionine and Se-methylselenocysteine that lack oxidation capability. Selenate (+6 Se) the immediate precursor of selenite (+4 Se) can be metabolically reduced, and although less potent than the +4 Se compounds cited above, appears to be a more effective anticarcinogen than organic forms of dietary selenium. Apoptosis, an important, Se-induced anticarcinogenic mechanism, is accomplished by the direct oxidation of vicinal sulfhydryl groups in cysteine clusters within the catalytic domains of cellular enzymes (e.g., protein kinase C), and by the production of CH3Se-, which reacts with O2 to generate superoxide and other reactive oxygen species (ROS). Activated oncogenes "prime" cells for Se-induced prooxidative apoptosis thereby providing the needed margin for "killing" cancer cells while leaving normal, healthy cells unharmed. Selenoethers, such as selenomethionine and Se-methylselenocysteine are not oxidizing agents, and first, must be converted to methylselenol (CH3Se-) that can be directly oxidized to methylseleninic acid. The addition of methioninase, to selenomethionine, or beta-lyase to Se-methylselenocysteine, rapidly produces significant amounts of methylselenol, which may be oxidized to methylseleninic acid or may react with O2 to produce superoxide and ROS, resulting in anticarcinogenic activities comparable to selenite or methylseleninic acid. The relatively large amounts of selenomethionine or Se-methylselenocysteine needed to produce apoptosis in cancer cells compared with selenite or methylseleninic acid are a probable consequence of low tissue levels of the required enzymes. Even though many studies have consistently shown that selenomethionine is an ineffective anticarcinogen at doses corresponding to those currently allowed by the FDA, it has been chosen as the Se intervention agent in the 32,500-man (phase III), NCI-funded SELECT trial, which tests the effectiveness of dietary supplements of dietary supplements of Se and tocopherol, individually or in combination, in the prevention of prostate cancer. In 2013, when the data are in, the value of using Se supplements for cancer chemoprevention is likely to be underestimated.

Mechanisms of selenium inhibition of cell apoptosis induced by oxysterols in rat vascular smooth muscle cells

Our previous study reported that oxysterol cholestane-3beta,5 alpha, 6 beta-triol (Triol) induced vascular smooth muscle cells (VSMCs) apoptosis, which was inhibited by selenium pretreatment. To further investigate the mechanisms of the inhibition, the glutathione peroxidase (GPx) activity, the total antioxidant capacity (T-AOC), the total superoxide dismutase (SOD) activity, and the level of lipid peroxidation (the content of malondialdehyde, MDA) of VSMCs were measured, and fluidity of cell membrane, reactive oxygen species (ROS) level, the reduction of mitochondrial membrane potential (Delta psi(m)), and the intracellular Ca(2+) in single cell were detected using several fluorescence indicators. Meanwhile, the mRNA levels of c-myc, bcl-2, GPx, and thioredoxin reductase (TR) were measured by reverse transcriptase polymerase chain reaction (RT-PCR) analysis. The results showed that the decrease of GPx activity, T-AOC, SOD activity, the fluidity of cell membrane, the Delta psi(m), and the mRNA expression of c-myc, bcl-2, GPx, and TR of VSMCs and the increase of MDA, ROS generation, and intracellular Ca(2+), significantly induced by Triol (10 microM, 24h) were inhibited to a different extent, respectively, when cells were pretreated with sodium selenite (50 nM, 12 or 24h) before exposure to Triol. These effects were time dependent and enhanced with prolongation of the time of pretreatment. In conclusion, the results in the present work showed that the mechanism of selenium inhibition of cell apoptosis induced by oxysterols in rat VSMCs was related with the antioxidation of selenoproteins.

Mineral Composition of Different Parts of Capparis ovata Desf. var. canescens (Coss.) Heywood Growing Wild in Turkey

Major and minor mineral contents of young shoots, flower buds, caperberries (fruit), and seeds of Capparis ovata Desf. var. canescens (Coss.) Heywood, used as a pickling product in Turkey, were determined by inductively coupled plasma atomic emission spectrometry. Twenty-one minerals were assayed in samples. All materials contained high amounts of Ca, K, Mg, Na, P, Pb, and Zn. The highest levels of Ca (598.34-16,947.1 ppm), K (3,093.1-28,163.9 ppm), Na (57.9-444.3 ppm), P (1,690.5-4,153.9 ppm), and Zn (21.1-35.6 ppm) were found in flower buds. The content of K was high in most cases and ranged from 28,163.9 ppm (flower bud) to 3,093.1 ppm (caper seed). Ba, Cd, Cr, Cu, Li, Ni, Pb, and Se contents of caper plant organs were found to be very low. Consequently, caper parts were rich in minerals, and they may be valuable for food uses. The results may also be useful for the evaluation of nutritional information.

Selenium and mortality in the elderly: results from the EVA study

BACKGROUND

Inadequate plasma selenium can adversely affect the maintenance of optimal health; therefore, reported decreases in plasma selenium in an aging population are cause for concern. To further examine this hypothesis, we explored the relationships between plasma selenium and mortality in an elderly population: the EVA (Etude du Vieillissement Artériel) study.

METHODS

The EVA study was a 9-year longitudinal study with 6 periods of follow-up. During the 2-year period from 1991 to 1993 (EVA0), 1389 men and women born between 1922 and 1932 were recruited. The effects of plasma selenium at baseline on mortality were determined by Cox proportional hazards regression analysis, adjusting for the following variables: sociodemographic characteristics, dietary habits, health, and cognitive factors.

RESULTS

During the 9-year follow-up, 101 study participants died. Baseline plasma selenium was higher in individuals who were alive at the end of follow-up [mean (SD), 1.10 (0.20) micromol/L] than in those who died during the follow-up [1.01 (0.20) micromol/L; P <10(-4)]. Mortality rates were significantly higher in individuals with low selenium [increments = 0.2 micromol/L; relative risk (RR) = 1.56 (95% confidence interval, 1.28-1.89)]. After we controlled for various potential confounding factors, this association remained significant [RR = 1.54 (1.25-1.88)]. When the underlying causes of death were considered, we found an association with cancer-related mortality [adjusted RR = 1.79 (1.32-2.44)].

CONCLUSIONS

Even if it is premature to present selenium as a longevity indicator in an elderly population, our results are in accordance those of large, interventional, randomized trials with selenium, which suggest that this essential trace element plays a role in health maintenance in aging individuals.

An imbalance in antioxidant defense affects cellular function: the pathophysiological consequences of a reduction in antioxidant defense in the glutathione peroxidase-1 (Gpx1) knockout mouse

Aerobic cells are subjected to damaging reactive oxygen species (ROS) as a consequence of oxidative metabolism and/or exposure to environmental toxins. Antioxidants limit this damage, yet peroxidative events occur when oxidant stress increases. This arises due to increased radical formation or decreased antioxidative defenses. The two-step enzymatic antioxidant pathway limits damage to important biomolecules by neutralising superoxides to water. However, an imbalance in this pathway (increased first-step antioxidants relative to second-step antioxidants) has been proposed as etiological in numerous pathologies. This review presents evidence that a shift in favor of hydrogen peroxide and/or lipid peroxides has pathophysiological consequences. The involvement of antioxidant genes in the regulation of redox status, and ultimately cellular homeostasis, is explored in murine transgenic and knockout models. The investigations of Sod1 transgenic cell-lines and mice, as well as Gpx1 knockout mice (both models favor H(2)O(2) accumulation), are presented. Although in most instances accumulation of H(2)O(2) affects cellular function and leads to exacerbated pathology, this is not always the case. This review highlights those instances where, for example, increased Sod1 levels are beneficial, and indicates a role for superoxide radicals in pathogenesis. Studies of Gpx1 knockout mice (an important second-step antioxidant) lead us to conclude that Gpx1 functions as the primary protection against acute oxidative stress, particularly in neuropathological situations such as stroke and cold-induced head trauma, where high levels of ROS occur during reperfusion or in response to injury. In summary, these studies clearly highlight the importance of limiting ROS-induced cellular damage by maintaining a balanced enzymatic antioxidant pathway.

Prevention of liquid-diet-induced damages on submandibular glands by selenium supplementation in rats

This study was designed to explore the protective effects of selenium on submandibular glands of rats that were maintained on liquid diet. The animals kept on liquid diet for 10 days following 20 days of solid diet, had severe degeneration on both acinar and ductal cells: pycnotic nuclei, enlarged granular endoplasmic reticulum, swollen mitochondria with separated cristae, reduction of secretory granules and abundant lipid droplets were observed. Body and gland weights of these animals were found to decrease significantly compared to those of control group given solid diet for 30 days. The animals that were fed 20 days with solid diet + 10 days liquid diet and also given selenium 0.4 mg/kg for 30 days, did not have any remarkable sign of degeneration on submandibular glands, and their gland weights significantly increased when compared to the animals fed with liquid diet without selenium supplementation. Submandibular glands of the group that was maintained on solid diet for 30 days and supplemented with selenium in drinking water were found to be normal. They showed consistent gain in both body and gland weights almost equal to that of control group. As a result, we assume that adding selenium in liquid diet can prevent the detrimental effects of liquid diet consumption on submandibular glands.

Selenium deficiency alters the formation of eicosanoids and signal transduction in rat lymphocytes

Previous reports have shown that selenium (Se) nutrition alters the lipoxygenase pathway and mitogenic responses in bovine lymphocytes. In order to further understand how Se may alter lymphocyte function, we examined the effects of Se nutrition on arachidonic acid (AA) metabolism and phospholipase D (PLD) activation. Lymphocytes were isolated from the lymph nodes of rats fed either Se-deficient diet (-Se) or Se-supplemented diet (+Se) for 12 weeks. Our results revealed that calcium ionophore A23187-stimulated lymphocytes derived from -Se rats produced significantly less prostaglandins (PGs) than those obtained from +Se rats. Phospholipase D (PLD) activation by 12-O-tetradecanoylphorbol-13-acetate (TPA) was significantly lower in lymphocytes obtained from -Se rats when compared to cells from +Se rats. Furthermore, the addition of PGE2, PGD2 or PGF2alpha to suspended lymphocytes from -Se rats significantly enhanced PLD activity. The effects of TPA and PGE2 on PLD activation were additive. However, the addition of PGE2 abolished the significant difference in PLD activation between -Se and +Se cells observed in response to TPA alone. Based on these results, we postulate that dietary Se status plays an important role in the regulation of AA metabolism that subsequently affects PLD activation.