Selenium: an element for life
TL;DR: The evidence is at present conflicting as to whether Se supplementation is of benefit in patients with HT, though there are indications that it is advantageous in cases of mild/moderate Graves’ Orbitopathy and the role of Se in type 2 diabetes mellitus is ambiguous.
Abstract: This review aims to illustrate the importance of selenium (Se) for maintenance of overall health, especially for the thyroid, immunity, and homeostasis. Furthermore, it outlines the role of Se in reproduction and in virology and discusses the effects of Se supplementation in critical illness. The multifaceted aspects of this essential nutrient have attracted worldwide clinical and research interest in the last few decades. Se exerts its activity in the form of the aminoacid selenocysteine incorporated in selenoproteins. The impact of Se administration should be considered in relation to its apparent U shaped effects, i.e., exhibiting major advantages in Se-deficient individuals but specific health risks in those with Se excess. Addition of selenium to the administration of levothyroxine may be useful in patients with low Se intake and with mild-form or early-stage Hashimoto’s thyroiditis (HT). Serum Se concentration (possibly also at tissue level) decreases in inflammatory conditions and may vary with the severity and duration of the inflammatory process. In such cases, the effect of Se supplementation seems to be useful and rational. Meanwhile, Se’s ability to improve the activity of T cells and the cytotoxicity of natural killer cells could render it effective in viral disease. However, the evidence, and this should be stressed, is at present conflicting as to whether Se supplementation is of benefit in patients with HT, though there are indications that it is advantageous in cases of mild/moderate Graves’ Orbitopathy. The role of Se in type 2 diabetes mellitus (T2DM) is ambiguous, driven by both Se intake and serum levels. The evidence that insulin and glycaemia influence the transport and activity of Se, via regulatory activity on selenoproteins, and that high serum Se may have a diabetogenic effect suggests a ‘Janus-effect’ of Se in T2DM. Though the evidence is not as yet clear-cut, the organic form (selenomethionine), due to its pharmacokinetics, is likely to be more advantageous in long-term prevention, and supplementation efforts, while the inorganic form (sodium selenite) has proven effective in an acute, e.g., sepsis, clinical setting. Recent data indicate that functional selenoprotein single-nucleotide polymorphisms (SNPs) may interfere with Se utilization and effectiveness.
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01 Jan 2016
TL;DR: Aspirin has been widely used to prevent myocardial infarction and ischemic stroke, but some studies have suggested it increases risk of hemorrhagic stroke as mentioned in this paper, which is not the case here.
Abstract: Context.— Aspirin has been widely used to prevent myocardial infarction and ischemic stroke but some studies have suggested it increases risk of hemorrhagic stroke. Objective.— To estimate the risk of hemorrhagic stroke associated with aspirin treatment. Data Sources.— Studies were retrieved using MEDLINE (search terms, aspirin, cerebrovascular disorders, and stroke), bibliographies of the articles retrieved, and the authors’ reference files. Study Selection.— All trials published in English-language journals before July 1997 in which participants were randomized to aspirin or a control treatment for at least 1 month and in which the incidence of stroke subtype was reported. Data Extraction.— Information on country of origin, sample size, duration, study design, aspirin dosage, participant characteristics, and outcomes was abstracted independently by 2 authors who used a standardized protocol. Data Synthesis.— Data from 16 trials with 55 462 participants and 108 hemorrhagic stroke cases were analyzed. The mean dosage of aspirin was 273 mg/d and mean duration of treatment was 37 months. Aspirin use was associated with an absolute risk reduction in myocardial infarction of 137 events per 10 000 persons (95% confidence interval [CI], 107-167;P,.001) and in ischemic stroke, a reduction of 39 events per 10 000 persons (95% CI, 17-61; P,.001). However, aspirin treatment was also associated with an absolute risk increase in hemorrhagic stroke of 12 events per 10 000 persons (95% CI, 5-20; P,.001). This risk did not differ by participant or study design characteristics. Conclusions.— These results indicate that aspirin therapy increases the risk of hemorrhagic stroke. However, the overall benefit of aspirin use on myocardial infarction and ischemic stroke may outweigh its adverse effects on risk of hemorrhagic stroke in most populations.
1,450 citations
TL;DR: In this article, a meta-analysis of randomized controlled trials (RCTs) was conducted to understand the clinical outcomes of selenium therapy in patients with sepsis syndrome.
771 citations
TL;DR: There are still several challenges, particularly in achieving stringent discharge limits, the long-term stability of biogenic selenium and predicting the fate of bioreduced Selenium in the environment and biotechnological advances made in the treatment ofselenium contaminated wastewaters.
321 citations
TL;DR: The effect of antioxidants in cancer treatment, the effect of combined treatment of antioxidants with traditional cancer therapies, and the side effects of excessive antioxidant intake are examined.
294 citations
Cites background from "Selenium: an element for life"
...Therefore, maintaining a moderate level of Se is beneficial to human health [84,85]....
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TL;DR: It is essential to supplement the deficiency of this micronutrient with selenium-enriched food or yeast cell biomass in the diet, as this element has the highest activity as a free radical scavenger and anti-cancer agent.
Abstract: Selenium is a micronutrient that is essential for the proper functioning of all organisms. Studies on the functions of selenium are rapidly developing. This element is a cofactor of many enzymes, for example, glutathione peroxidase or thioredoxin reductase. Insufficient supplementation of this element results in the increased risk of developing many chronic degenerative diseases. Selenium is important for the protection against oxidative stress, demonstrating the highest activity as a free radical scavenger and anti-cancer agent. In food, it is present in organic forms, as exemplified by selenomethionine and selenocysteine. In dietary supplementation, the inorganic forms of selenium (selenite and selenate) are used. Organic compounds are more easily absorbed by human organisms in comparison with inorganic compounds. Currently, selenium is considered an essential trace element of fundamental importance for human health. Extreme selenium deficiencies are widespread among people all over the world. Therefore, it is essential to supplement the deficiency of this micronutrient with selenium-enriched food or yeast cell biomass in the diet.
264 citations
Cites background from "Selenium: an element for life"
...Increased accumulation of this element led to dystrophy of cardiac muscle or acute hepatic necrosis [4]....
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TL;DR: The crucial factor that needs to be emphasised with regard to the health effects of selenium is the inextricable U-shaped link with status; whereas additional seenium intake may benefit people with low status, those with adequate-to-high status might be affected adversely and should not take selenum supplements.
2,297 citations
University of Texas MD Anderson Cancer Center1, Case Western Reserve University2, Cleveland Clinic3, University of Colorado Denver4, University of Texas Health Science Center at San Antonio5, National Institutes of Health6, University of California, San Diego7, University of Western Ontario8, Duke University9, Mayo Clinic10, University of Washington11, University of California, Los Angeles12, Columbia University13, University of British Columbia14, University of California, Irvine15, University of Michigan16
TL;DR: Selenium or vitamin E, alone or in combination at the doses and formulations used, did not prevent prostate cancer in this population of relatively healthy men.
Abstract: Context Secondary analyses of 2 randomized controlled trials and supportive epidemiologic and preclinical data indicated the potential of selenium and vitamin E for preventing prostate cancer. Objective To determine whether selenium, vitamin E, or both could prevent prostate cancer and other diseases with little or no toxicity in relatively healthy men. Design, Setting, and Participants A randomized, placebo-controlled trial (Selenium and Vitamin E Cancer Prevention Trial [SELECT]) of 35 533 men from 427 participating sites in the United States, Canada, and Puerto Rico randomly assigned to 4 groups (selenium, vitamin E, selenium + vitamin E, and placebo) in a double-blind fashion between August 22, 2001, and June 24, 2004. Baseline eligibility included age 50 years or older (African American men) or 55 years or older (all other men), a serum prostate-specific antigen level of 4 ng/mL or less, and a digital rectal examination not suspicious for prostate cancer. Interventions Oral selenium (200 μg/d from L-selenomethionine) and matched vitamin E placebo, vitamin E (400 IU/d of all rac-α-tocopheryl acetate) and matched selenium placebo, selenium + vitamin E, or placebo + placebo for a planned follow-up of minimum of 7 years and a maximum of 12 years. Main Outcome Measures Prostate cancer and prespecified secondary outcomes, including lung, colorectal, and overall primary cancer. Results As of October 23, 2008, median overall follow-up was 5.46 years (range, 4.17-7.33 years). Hazard ratios (99% confidence intervals [CIs]) for prostate cancer were 1.13 (99% CI, 0.95-1.35; n = 473) for vitamin E, 1.04 (99% CI, 0.87-1.24; n = 432) for selenium, and 1.05 (99% CI, 0.88-1.25; n = 437) for selenium + vitamin E vs 1.00 (n = 416) for placebo. There were no significant differences (all P>.15) in any other prespecified cancer end points. There were statistically nonsignificant increased risks of prostate cancer in the vitamin E group (P = .06) and type 2 diabetes mellitus in the selenium group (relative risk, 1.07; 99% CI, 0.94-1.22; P = .16) but not in the selenium + vitamin E group. Conclusion Selenium or vitamin E, alone or in combination at the doses and formulations used, did not prevent prostate cancer in this population of relatively healthy men. Trial Registration clinicaltrials.gov identifier: NCT00006392Published online December 9, 2008 (doi:10.1001/jama.2008.864).
1,942 citations
"Selenium: an element for life" refers background in this paper
...5 years, showed no statistically significant increased risk of diabetes for both Se alone or Se ? vitamin E arms [126]....
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1,676 citations
"Selenium: an element for life" refers background in this paper
...However, the essentiality of the trace element was not discovered until 140 years later [4]....
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TL;DR: The goal of this review is to place the exciting advances that have occurred in understanding of the molecular biology of the types 1, 2, and 3 (D1, D2, and D3, respectively) iodothyronine deiodinases into a biochemical and physiological context.
Abstract: The goal of this review is to place the exciting advances that have occurred in our understanding of the molecular biology of the types 1, 2, and 3 (D1, D2, and D3, respectively) iodothyronine deiodinases into a biochemical and physiological context. We review new data regarding the mechanism of selenoprotein synthesis, the molecular and cellular biological properties of the individual deiodinases, including gene structure, mRNA and protein characteristics, tissue distribution, subcellular localization and topology, enzymatic properties, structure-activity relationships, and regulation of synthesis, inactivation, and degradation. These provide the background for a discussion of their role in thyroid physiology in humans and other vertebrates, including evidence that D2 plays a significant role in human plasma T3 production. We discuss the pathological role of D3 overexpression causing “consumptive hypothyroidism” as well as our current understanding of the pathophysiology of iodothyronine deiodination during illness and amiodarone therapy. Finally, we review the new insights from analysis of mice with targeted disruption of the Dio2 gene and overexpression of D2 in the myocardium. (Endocrine Reviews 23: 38–89, 2002)
1,670 citations
1,133 citations