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1.
Multiple nutritional factors and thyroid disease, with particular reference to autoimmune thyroid disease.
Rayman, MP
The Proceedings of the Nutrition Society. 2019;(1):34-44
Abstract
Hashimoto's thyroiditis (HT) and Graves' disease (GD) are examples of autoimmune thyroid disease (AITD), the commonest autoimmune condition. Antibodies to thyroid peroxidase (TPO), the enzyme that catalyses thyroid-hormone production and antibodies to the receptor for the thyroid-stimulating hormone, are characteristic of HT and GD, respectively. It is presently accepted that genetic susceptibility, environmental factors, including nutritional factors and immune disorders contribute to the development of AITD. Aiming to investigate the effect of iodine, iron and selenium in the risk, pathogenesis and treatment of thyroid disease, PubMed and the Cochrane Library were searched for relevant publications to provide a narrative review. Iodine: chronic exposure to excess iodine intake induces autoimmune thyroiditis, partly because highly-iodinated thyroglobulin (Tg) is more immunogenic. The recent introduction of universal salt iodisation can have a similar, although transient, effect. Iron: iron deficiency impairs thyroid metabolism. TPO is a haem enzyme that becomes active only after binding haem. AITD patients are frequently iron-deficient since autoimmune gastritis, which reduces iron absorption and coeliac disease which causes iron loss, are frequent co-morbidities. In two-thirds of women with persistent symptoms of hypothyroidism despite appropriate levothyroxine therapy, restoration of serum ferritin above 100 µg/l ameliorated symptoms. Selenium: selenoproteins are essential to thyroid action. In particular, the glutathione peroxidases remove excessive hydrogen peroxide produced there for the iodination of Tg to form thyroid hormones. There is evidence from observational studies and randomised controlled trials that selenium, probably as selenoproteins, can reduce TPO-antibody concentration, hypothyroidism and postpartum thyroiditis. Appropriate status of iodine, iron and selenium is crucial to thyroid health.
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2.
Selenium and selenoproteins: from endothelial cytoprotection to clinical outcomes.
Lopes Junior, E, Leite, HP, Konstantyner, T
Translational research : the journal of laboratory and clinical medicine. 2019;:85-104
Abstract
The role of the vascular endothelium in inflammation was demonstrated experimentally through biomarkers of endothelial dysfunction and cytoprotection. Selenium is a trace element essential for cell protection against oxidative lesions triggered by reactive oxygen species or inflammatory responses. Preclinical studies have demonstrated a relationship between adhesion molecules as biomarkers of endothelial dysfunction and selenoproteins as biomarkers of selenium status under conditions that mimic different diseases. Most studies in humans indicate an association between selenium deficiency and increased risk of morbidity and mortality, yet the pathophysiology of selenium in endothelial activation remains unknown. Here, we summarize selenium-dependent endothelial function evaluation techniques and focus on the role of selenium in endothelial cytoprotection according to current scientific knowledge. Most studies on the role of selenium in endothelial processes show selenium-dependent endothelial functions and explain how cells and tissues adapt to inflammatory insults. Taken together, these studies show an increase in adhesion molecules and a decrease in the expression of selenoproteins following a decreased exposure to selenium. Few clinical trials have enough methodological quality to be included in meta-analysis on the benefits of selenium supplementation. Furthermore, the methodology adopted in many studies does not consider the relevant findings on the pathophysiology of endothelial dysfunction. Preclinical studies should be more frequently integrated into clinical studies to provide clearer views on the role of selenium status in endothelial cytoprotection.
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3.
Selenium Status in Elderly People: Longevity and Age-Related Diseases.
Robberecht, H, De Bruyne, T, Davioud-Charvet, E, Mackrill, J, Hermans, N
Current pharmaceutical design. 2019;(15):1694-1706
Abstract
BACKGROUND Selenium (Se) is a trace element active in selenoproteins, which can regulate oxidative stress. It is generally perceived as an import factor for maintaining health in the elderly. METHODS The goal of this review is to discuss selenium concentration in biological samples, primarily serum or plasma, as a function of age and its relation with longevity. The elemental level in various age-related diseases is reviewed. CONCLUSION Highest selenium values were observed in healthy adults, while in an elderly population significantly lower concentrations were reported. Variables responsible for contradictory findings are mentioned. Risk and benefits of Se-supplementation still remain under debate.
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4.
Selenium, Selenoproteins and Viral Infection.
Guillin, OM, Vindry, C, Ohlmann, T, Chavatte, L
Nutrients. 2019;(9)
Abstract
Reactive oxygen species (ROS) are frequently produced during viral infections. Generation of these ROS can be both beneficial and detrimental for many cellular functions. When overwhelming the antioxidant defense system, the excess of ROS induces oxidative stress. Viral infections lead to diseases characterized by a broad spectrum of clinical symptoms, with oxidative stress being one of their hallmarks. In many cases, ROS can, in turn, enhance viral replication leading to an amplification loop. Another important parameter for viral replication and pathogenicity is the nutritional status of the host. Viral infection simultaneously increases the demand for micronutrients and causes their loss, which leads to a deficiency that can be compensated by micronutrient supplementation. Among the nutrients implicated in viral infection, selenium (Se) has an important role in antioxidant defense, redox signaling and redox homeostasis. Most of biological activities of selenium is performed through its incorporation as a rare amino acid selenocysteine in the essential family of selenoproteins. Selenium deficiency, which is the main regulator of selenoprotein expression, has been associated with the pathogenicity of several viruses. In addition, several selenoprotein members, including glutathione peroxidases (GPX), thioredoxin reductases (TXNRD) seemed important in different models of viral replication. Finally, the formal identification of viral selenoproteins in the genome of molluscum contagiosum and fowlpox viruses demonstrated the importance of selenoproteins in viral cycle.
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5.
A meta-analysis of randomized controlled trials: Efficacy of selenium treatment for sepsis.
Li, S, Tang, T, Guo, P, Zou, Q, Ao, X, Hu, L, Tan, L
Medicine. 2019;(9):e14733
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Abstract
BACKGROUND To understand the clinical outcomes of selenium therapy in patients with sepsis syndrome, we conducted a meta-analysis of randomized controlled trials (RCT). METHODS A total of 13 RCTs comparing selenium and placebo for patients with sepsis were reviewed systematically. RESULTS However, we could not detect the association of selenium treatment with a decreased mortality at different time course (relative risk [RR] [95% confidence interval, CI]: 0.94 [0.82-1.06] at day 28; 0.73 [0.36-1.47] at day 90; 1.16 [0.78-1.71] at 6 months; respectively). Selenium supplementation did not show favorable efficacy in the incidence of renal failure, secondary infection or duration of mechanical ventilation (RR [95% CI]: 0.65 [0.41-1.03]; 0.96 [0.87-1.06]; standard mean difference [SMD] [95% CI]: 0.17 [-0.30-0.63]; respectively). Interestingly, we found that selenium therapy was benefit for sepsis patients with reduced duration of vasopressor therapy, staying time in intensive care unit and hospital, and incidence of ventilator-associated pneumonia (SMD [95% CI]: -0.75 [-1.37 to -0.13]; -0.15 [CI: -0.25 to -0.04]; -1.22 [-2.44 to -0.01]; RR [95% CI]: 0.61 [0.42-0.89]; respectively). CONCLUSION Based on our findings, intravenous selenium supplementation could not be suggested for routine use.
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An Overview of Hazardous Impacts of Soil Salinity in Crops, Tolerance Mechanisms, and Amelioration through Selenium Supplementation.
Kamran, M, Parveen, A, Ahmar, S, Malik, Z, Hussain, S, Chattha, MS, Saleem, MH, Adil, M, Heidari, P, Chen, JT
International journal of molecular sciences. 2019;(1)
Abstract
Soil salinization is one of the major environmental stressors hampering the growth and yield of crops all over the world. A wide spectrum of physiological and biochemical alterations of plants are induced by salinity, which causes lowered water potential in the soil solution, ionic disequilibrium, specific ion effects, and a higher accumulation of reactive oxygen species (ROS). For many years, numerous investigations have been made into salinity stresses and attempts to minimize the losses of plant productivity, including the effects of phytohormones, osmoprotectants, antioxidants, polyamines, and trace elements. One of the protectants, selenium (Se), has been found to be effective in improving growth and inducing tolerance against excessive soil salinity. However, the in-depth mechanisms of Se-induced salinity tolerance are still unclear. This review refines the knowledge involved in Se-mediated improvements of plant growth when subjected to salinity and suggests future perspectives as well as several research limitations in this field.
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The Link Between Selenium, Oxidative Stress and Pregnancy Induced Hypertensive Disorders.
Bizerea, TO, Dezsi, SG, Marginean, O, Stroescu, R, Rogobete, A, Bizerea-Spiridon, O, Ilie, C
Clinical laboratory. 2018;(10):1593-1610
Abstract
BACKGROUND The first line of defence against oxidative stress (OS) are the endogenous antioxidants, such as the Se containing compounds. During pregnancy, OS is caused by the intense growth activity of the fetus; therefore, the placenta is a key place for the activity of many seleno-compounds such as glutathione-peroxidase and thioredoxinreductase. METHODS This review aims to establish the link between the type of selenium compounds, their concentration, their metabolic pathways, and their role in both physiologic and pathologic processes during pregnancy. RESULTS A review of current literature establishes that Se containing compounds have a strong antioxidant effect. The limits that define deviations from the normal concentration range of selenium are very close. Both selenium deficiency and excess have an effect on human health. It is well known that oxidative stress, namely the increase in the concentration of reactive species of oxygen and nitrogen (ROS and RNS) and the disruption of cellular redox homeostasis, are responsible for a number of inflammatory, degenerative, autoimmune, and neoplastic diseases. Selenium deficiency in the pregnant woman's body is considered a risk factor for immune deficiency, PIH, spontaneous abortions, and premature birth. In regard to the fetus, while there seems to be a certain protection against selenium-induced toxicity, studies have shown that selenium defficiency leads to IUGR and SGA newborns. Also, combined deficiency of selenium and iodine has been linked to endemic cretinism in newborns. CONCLUSIONS The antioxidant role that selenium performs through selenoproteins is major. Selenium-containing proteins, especially glutathione peroxidase, as antioxidant enzymes, are involved in regulating the ROS and RNS levels and redox balancing in almost all tissues. Among the multiple benefits of selenium in optimal concentrations in the body are stimulation and support of female fertility, as well as good development of the fetus. Hypertensive pathologies that occur in one of ten pregnant women, especially during the second part of the gestation period, are largely due to selenium deficiency.
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[Recent research progress of selenium polysaccharides from medicinal plants].
Liang, H, Huang, J, Wang, L, Chen, J, Tian, ML
Zhongguo Zhong yao za zhi = Zhongguo zhongyao zazhi = China journal of Chinese materia medica. 2018;(15):3080-3092
Abstract
Selenium polysaccharides (Se polysaccharides) are a kind of organic selenium compounds which obtain the activities from Se and polysaccharides. Comparing to Se or polysaccharides, Se polysaccharides exhibit improved biological activities and are more prone to be absorbed by human bodies, therefore, they have been widely used in medical applications, such as immunomodulation, anti-tumor, anti-oxidation, anti-aging. Due to their unique pharmacological activities, Se polysaccharides from medicinal plants have gradually become a research hotspot. However, only a few of Se polysaccharides have been separated and purified in recent years. The structure of polysaccharides is also very complex, therefore, determination of the chemical structure and mechanism of bioactivity of Se polysaccharide in vivo remain to be further studied. This article systematically introduced the main source and biological activities of Se polysaccharides from medicinal plants. The purpose of this review is to provide a basis for the further research of Se polysaccharides.
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9.
Selenoproteins in human body: focus on thyroid pathophysiology.
Valea, A, Georgescu, CE
Hormones (Athens, Greece). 2018;(2):183-196
Abstract
Selenium (Se) has a multilevel, complex and dynamic effect on the human body as a major component of selenocysteine, incorporated into selenoproteins, which include the selenocysteine-containing enzymes iodothyronine deiodinases. At the thyroid level, these proteins play an essential role in antioxidant protection and hormone metabolism. This is a narrative review based on PubMed/Medline database research regarding thyroid physiology and conditions with Se and Se-protein interferences. In humans, Se-dependent enzyme functions are best expressed through optimal Se intake, although there is gap in our knowledge concerning the precise mechanisms underlying the interrelation. There is a good level of evidence linking low serum Se to autoimmune thyroid diseases and, to a lesser extent, differentiated thyroid cancer. However, when it comes to routine supplementation, the results are heterogeneous, except in the case of mild Graves' orbitopathy. Autoimmune hypothyroidism is associated with a state of higher oxidative stress, but not all studies found an improvement of thyroid function after Se was introduced as antioxidant support. Meanwhile, no routine supplementation is recommended. Low Se intake is correlated with an increased risk of developing antithyroid antibodies, its supplementation decreasing their titres; there is also a potential reduction in levothyroxine replacement dose required for hypothyroidism and/or the possibility that it prevents progression of subclinical hypothyroidism, although not all studies agree. In thyroid-associated orbitopathy, euthyroidism is more rapidly achieved if the micronutrient is added to traditional drugs, while controls appear to benefit from the microelement only if they are deficient; thus, a basal assay of Se appears advisable to better select patients who need substitution. Clearly, further Se status biomarkers are required. Future introduction of individual supplementation algorithms based on baseline micronutrient levels, underlying or at-risk clinical conditions, and perhaps selenoprotein gene polymorphisms is envisaged.
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10.
Selenium in the prevention and subsidiary therapy of cancer of soft tissues.
Raganová, A, Gažová, A, Tomo, I, Kristová, V
Ceska a Slovenska farmacie : casopis Ceske farmaceuticke spolecnosti a Slovenske farmaceuticke spolecnosti. 2018;(2):66-70
Abstract
Selenium as an antioxidant has attracted attention because of its anticancer activity. This review presents a view on selenium and its compounds exerting influence against cancer in the soft tissues. The results reveal a significant strong association between a low selenium level in blood and a cancer risk. Seleno-supplementation is important in the prevention of metastatic cancer. These results help to elucidate the anticancer effect of selenium providing further evidence to exploit novel anticancer agents targeting selenium-containing organic compounds. Key words: selenium • cancer prevention • cancer treatment • soft tissues.