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Selenium is an essential trace element important for human health. A balanced intake is, however, crucial to maximize the health benefits of selenium. At physiological concentrations, selenium mediates antioxidant, anti‐inflammatory, and pro‐survival actions. However, supra‐nutritional selenium intake was associated with increased diabetes risk leading potentially to endothelial dysfunction, the initiating step in atherosclerosis. High selenium causes apoptosis in cancer cells via endoplasmic reticulum (ER) stress, a mechanism also implicated in endothelial dysfunction. Nonetheless, whether ER stress drives selenium‐induced endothelial dysfunction, remains unknown. Here, we investigated the effects of increasing concentrations of selenium on endothelial cells. High selenite reduced nitric oxide bioavailability and impaired angiogenesis. High selenite also induced ER stress, increased reactive oxygen species (ROS) production, and apoptosis. Pretreatment with the chemical chaperone, 4‐phenylbutyrate, prevented the toxic effects of selenium. Our findings support a model where high selenite leads to endothelial dysfunction through activation of ER stress and increased ROS production. These results highlight the importance of tailoring selenium supplementation to achieve maximal health benefits and suggest that prophylactic use of selenium supplements as antioxidants may entail risk. [ABSTRACT FROM AUTHOR]

Clinical trials have suggested a protective effect of selenium supplementation on the risk of esophageal cancer, which may be mediated through the antioxidant activity of selenoenzymes. We investigated whether serum selenium concentrations, selenoenzyme activity, oxidative stress and genetic variation in selenoenzymes were associated with the risk of neoplastic progression to esophageal adenocarcinoma (EA) and two intermediate endpoints, aneuploidy and tetraploidy. In this prospective cohort study, during an average follow-up of 7.3 years, 47 EA cases, 41 aneuploidy cases and 51 tetraploidy cases accrued among 361 participants from the Seattle Barrett's Esophagus Research Study who were free of EA at the time of blood draw and had at least one follow-up visit. Development to EA was assessed histologically and aneuploidy and tetraploidy by DNA content flow cytometry. Serum selenium concentrations were measured using atomic absorption spectrometry, activity of glutathione peroxidase (GPX) 1 and GPX3 by substrate-specific coupled test procedures, selenoprotein P (SEPP1) concentrations and protein carbonyl content by ELISA method and malondialdehyde concentrations by HPLC. Genetic variants in GPX1-4 and SEPP1 were genotyped. Serum selenium was not associated with the risk of neoplastic progression to EA, aneuploidy or tetraploidy (P for trend = 0.25 to 0.85). SEPP1 concentrations were positively associated with the risk of EA [hazard ratio (HR) = 3.95, 95% confidence intervals (CI) = 1.42-10.97 comparing the third tertile with the first] and with aneuploidy (HR = 6.53, 95% CI = 1.31-32.58), but not selenoenzyme activity or oxidative stress markers. No genetic variants, overall, were associated with the risk of neoplastic progression to EA (global p = 0.12-0.69). Our results do not support a protective effect of selenium on risk of neoplastic progression to EA. Our study is the first to report positive associations of plasma SEPP1 concentrations with the risk of EA and aneuploidy, which warrants further investigation. [ABSTRACT FROM AUTHOR]

Objective: We assessed the impact of selenium, a trace element with antioxidant properties on a simple measure of oxidative stress in pregnant women. Study design: A novel assay of prooxidant-antioxidant balance (PAB) was applied in a double-blind, placebo-controlled study of selenium supplementation in pregnancy. We measured the prooxidant burden and the antioxidant capacity simultaneously in one assay, thereby calculating a redox index. A total of 166 primigravid pregnant women in the first trimester of pregnancy, were randomized to receive 100 μg of selenium (n=83) or placebo (n=83) per day until delivery. PAB values and serum selenium concentrations were measured at baseline and at the end of study. Results: Pretreatment demographic data and biochemical indices including serum selenium concentrations did not differ significantly between the groups. The drop-out rates for the groups were 22/83 and 19/83 for the selenium and placebo groups, respectively. Supplementation with selenium was associated with a significant increase in mean serum selenium concentration (P<0.001) but without significant change in mean PAB value. In contrast, mean serum selenium concentration remained unchanged and mean PAB values increased significantly (P<0.05 in the control group). Conclusion: Our findings suggest that selenium supplementation may reduce oxidative stress associated with pregnancy. [ABSTRACT FROM AUTHOR]

Abstract The essential trace element, selenium (Se), is crucial to the brain but it may be potentially neurotoxic, depending on dosage and speciation; Se has been discussed for decades in relation to Alzheimer's disease (AD). Selenoprotein P (SELENOP) is a secreted heparin-binding glycoprotein which serves as the main Se transport protein in mammals. In vivo studies showed that this protein might have additional functions such as a contribution to redox regulation. The current review focuses on recent research on the possible role of SELENOP in AD pathology, based on model and human studies. The review also briefly summarizes results of epidemiological studies on Se supplementation in relation to brain diseases, including PREADViSE, EVA, and AIBL. Although mainly positive effects of Se are assessed in this review, possible detrimental effects of Se supplementation or exposure, including potential neurotoxicity, are also mentioned. In relation to AD, various roles of SELENOP are discussed, i.e. as the means of Se delivery to neurons, as an antioxidant, in cytoskeleton assembly, in interaction with redox-active metals (copper, iron, and mercury) and with misfolded proteins (amyloid- beta and hyperphosphorylated tau-protein). Graphical abstract fx1 Highlights • Se is crucial to the brain; its deprivation causes irreversible damage to neuronal tissue. • SELENOP delivers Se to the brain by binding to a surface receptor, ApoER2. • SELENOP is strongly linked to hallmarks of AD (A β plaques and neurofibrillary tangles). • Studies indicate a beneficial effect of Se and SELENOP in cognition and AD pathology. • SELENOP binds redox-active metals in the brain, providing neuroprotection. [ABSTRACT FROM AUTHOR]