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Nutrients Sep 2018Selenium is an essential micronutrient that plays a crucial role in development and a wide variety of physiological processes including effect immune responses. The... (Review)
Review
Selenium is an essential micronutrient that plays a crucial role in development and a wide variety of physiological processes including effect immune responses. The immune system relies on adequate dietary selenium intake and this nutrient exerts its biological effects mostly through its incorporation into selenoproteins. The selenoproteome contains 25 members in humans that exhibit a wide variety of functions. The development of high-throughput omic approaches and novel bioinformatics tools has led to new insights regarding the effects of selenium and selenoproteins in human immuno-biology. Equally important are the innovative experimental systems that have emerged to interrogate molecular mechanisms underlying those effects. This review presents a summary of the current understanding of the role of selenium and selenoproteins in regulating immune cell functions and how dysregulation of these processes may lead to inflammation or immune-related diseases.
Topics: Adaptive Immunity; Animals; Host-Pathogen Interactions; Humans; Immune System; Immune System Diseases; Immunity, Innate; Inflammation; Leukocytes; Neoplasms; Selenium; Selenoproteins; Tumor Escape
PubMed: 30200430
DOI: 10.3390/nu10091203 -
Inflammopharmacology Jun 2020Selenium is an essential immunonutrient which holds the human's metabolic activity with its chemical bonds. The organic forms of selenium naturally present in human body... (Review)
Review
Selenium is an essential immunonutrient which holds the human's metabolic activity with its chemical bonds. The organic forms of selenium naturally present in human body are selenocysteine and selenoproteins. These forms have a unique way of synthesis and translational coding. Selenoproteins act as antioxidant warriors for thyroid regulation, male-fertility enhancement, and anti-inflammatory actions. They also participate indirectly in the mechanism of wound healing as oxidative stress reducers. Glutathione peroxidase (GPX) is the major selenoprotein present in the human body, which assists in the control of excessive production of free radical at the site of inflammation. Other than GPX, other selenoproteins include selenoprotein-S that regulates the inflammatory cytokines and selenoprotein-P that serves as an inducer of homeostasis. Previously, reports were mainly focused on the cellular and molecular mechanism of wound healing with reference to various animal models and cell lines. In this review, the role of selenium and its possible routes in translational decoding of selenocysteine, synthesis of selenoproteins, systemic action of selenoproteins and their indirect assimilation in the process of wound healing are explained in detail. Some of the selenium containing compounds which can acts as cancer preventive and therapeutics are also discussed. These compounds directly or indirectly exhibit antioxidant properties which can sustain the intracellular redox status and these activities protect the healthy cells from reactive oxygen species induced oxidative damage. Although the review covers the importance of selenium/selenoproteins in wound healing process, still some unresolved mystery persists which may be resolved in near future.
Topics: Animals; Antioxidants; Humans; Inflammation; Oxidation-Reduction; Reactive Oxygen Species; Selenium; Selenoproteins
PubMed: 32144521
DOI: 10.1007/s10787-020-00690-x -
Current Protein & Peptide Science 2014Selenium (Se) is an essential trace element for humans, plants and microorganisms. Inorganic selenium is present in nature in four oxidation states: selenate, selenite,... (Review)
Review
Selenium (Se) is an essential trace element for humans, plants and microorganisms. Inorganic selenium is present in nature in four oxidation states: selenate, selenite, elemental Se and selenide in decreasing order of redox status. These forms are converted by all biological systems into more bioavailable organic forms, mainly as the two seleno-amino acids selenocysteine and selenomethionine. Humans, plants and microorganisms are able to fix twhese amino acids into proteins originating Se-containing proteins by a simple replacement of methionine with selenomethionine, or "true" selenoproteins if the insertion of selenocysteine is genetically encoded by a specific UGA codon. Selenocysteine is usually present in the active site of enzymes, being essential for their catalytic activity. This review will focus on the strategies adopted by the different biological systems for selenium incorporation into proteins and on the importance of this element for the physiological functions of living organisms. The most known selenoproteins of humans and microorganisms will be listed highlighting the importance of this element and the problems connected with its deficiency.
Topics: Animals; Bacteria; Bacterial Proteins; Humans; Plant Proteins; Plants; Proteome; Selenium; Selenoproteins
PubMed: 24910086
DOI: 10.2174/1389203715666140608151134 -
Nutrients Sep 2021Selenium (Se) is a micronutrient essential for life. Dietary intake of Se within the physiological range is critical for human health and reproductive functions.... (Review)
Review
Selenium (Se) is a micronutrient essential for life. Dietary intake of Se within the physiological range is critical for human health and reproductive functions. Selenium levels outside the recommended range have been implicated in infertility and variety of other human diseases. However, presently it is not clear how different dietary Se sources are processed in our bodies, and in which form or how much dietary Se is optimum to maintain metabolic homeostasis and boost reproductive health. This uncertainty leads to imprecision in published dietary guidelines and advice for human daily intake of Se and in some cases generating controversies and even adverse outcomes including mortality. The chief aim for this review is to describe the sources of organic and inorganic Se, the metabolic pathways of selenoproteins synthesis, and the critical role of selenprotenis in the thyroid gland homeostasis and reproductive/fertility functions. Controversies on the use of Se in clinical practice and future directions to address these challenges are also described and discussed herein.
Topics: Diet; Female; Fertility; Homeostasis; Humans; Male; Reproduction; Selenium; Selenoproteins; Thyroid Gland
PubMed: 34579133
DOI: 10.3390/nu13093256 -
International Journal of Cancer Apr 2022Evidence on the association between selenium and cancer risk is inconclusive. We conducted a Mendelian randomization study to examine the associations of selenium levels...
Evidence on the association between selenium and cancer risk is inconclusive. We conducted a Mendelian randomization study to examine the associations of selenium levels with 22 site-specific cancers and any cancer. Single nucleotide polymorphisms (SNPs) strongly associated with toenail and blood (TAB) and blood selenium levels in mild linkage disequilibrium (r < .3) were used as instrumental variables. Genetic associations of selenium-associated SNPs with cancer were obtained from the UK Biobank including a total of 59 647 cancer cases and 307 914 controls. Associations with P < .1 in UK Biobank were tested for replication in the FinnGen consortium comprising more than 180 000 individuals. The inverse-variance weighted method accounting for linkage disequilibrium was used to estimate the associations. Genetically predicted TAB selenium levels were not associated with the risk of the 22 site-specific cancers or any cancer (all 22 site-specific cancers). Similarly, we observed no strong association for genetically predicted blood selenium levels. However, genetically predicted blood selenium levels showed suggestive associations with risk of kidney cancer (odds ratio [OR] per one-unit increase in log-transformed levels: 0.83; 95% confidence interval [CI]: 0.67-1.03) and multiple myeloma (OR: 1.40; 95% CI: 1.02-1.93). The same direction of association for kidney cancer but not for multiple myeloma was observed in FinnGen. In the metaanalysis of UK Biobank and FinnGen, the OR of kidney cancer was 0.83 (95% CI: 0.69-1.00). Our study suggests that high selenium status may not prevent cancer development. The associations for kidney cancer and multiple myeloma need to be verified in well-powered studies.
Topics: Humans; Kidney Neoplasms; Mendelian Randomization Analysis; Multiple Myeloma; Nails; Polymorphism, Single Nucleotide; Selenium
PubMed: 34910310
DOI: 10.1002/ijc.33902 -
Hormones (Athens, Greece) Mar 2020Both selenium (Se) deficiency and excess are found in natural locations throughout the world, though Se excess can also be caused by supplementation with Se. Both have... (Review)
Review
Both selenium (Se) deficiency and excess are found in natural locations throughout the world, though Se excess can also be caused by supplementation with Se. Both have been associated with adverse health effects that have often been characterized by a U-shaped relationship. Some health effects, such as increased mortality, are associated with both low and high Se status. Certain people and populations are better able to tolerate low or high Se intake than others; there are a number of possible explanations for this fact. Firstly, it may relate to the presence of polymorphisms (SNPs) in genes that improve the ability to deal with a low or high Se intake. Secondly, high Se status, with apparent absence of toxicity and even beneficial effects, can be found in populations exposed to toxic elements that are known to interact with Se, forming complexes in some cases. Thirdly, beneficial and harmful effects of Se depend on Se dose and form (speciation); for instance, at a high dose, selenomethionine (SeMet) has toxic effects that are mediated by metabolism to selenols/selenolates that can redox-cycle, generate superoxide radicals and react with thiols/diselenides to produce selenyl sulphides/disulphides. Finally, it is possible that exposure to a high Se intake from birth or from a very young age may alter the composition of the gut microbiota in such a way that excess Se is more readily excreted, thus reducing its toxicity.
Topics: Health; Humans; Mercury; Mortality; Nutritional Status; Polymorphism, Single Nucleotide; Selenium; Selenomethionine; Selenoproteins
PubMed: 31388899
DOI: 10.1007/s42000-019-00125-5 -
European Journal of Cancer (Oxford,... Sep 2021Selenium is an essential trace element for regulating immune functions through redox-regulating activity of selenoproteins (e.g. glutathione peroxidase), protecting... (Review)
Review
Selenium is an essential trace element for regulating immune functions through redox-regulating activity of selenoproteins (e.g. glutathione peroxidase), protecting immune cells from oxidative stress. However, in cancer, selenium has biological bimodal action depending on the concentration. At nutritional low doses, selenium, depending on its form, may act as an antioxidant, protecting against oxidative stress, supporting cell survival and growth, thus, plays a chemo-preventive role; while, at supra-nutritional higher pharmacological doses, selenium acts as pro-oxidant inducing redox signalling and cell death. To date, many studies have been conducted on the benefits of selenium intake in reducing the risk of cancer incidence at the nutritional level, indicating that likely selenium functions as an immunostimulator, i.e. reversing the immunosuppression in tumour microenvironment towards antitumour immunity by activating immune cells (e.g. M macrophages and CD8 T-lymphocytes) and releasing pro-inflammatory cytokines such as interferon-gamma; whereas, fewer studies have explored the effects of supra-nutritional or pharmacological doses of selenium in cancer immunity. This review, thus, systematically analyses the current knowledge about how selenium stimulates the immune system against cancer and lay the groundwork for future research. Such knowledge can be promising to design combinatorial therapies with Selenium-based compounds and other modalities like immunotherapy to lower the adverse effects and increase the efficacy of treatments.
Topics: Humans; Immune System; Neoplasms; Selenium; Tumor Microenvironment
PubMed: 34392068
DOI: 10.1016/j.ejca.2021.07.013 -
Molecules (Basel, Switzerland) Mar 2013Selenium (Se³⁴₇₉) is a metalloid which is close to sulfur (S) in terms of properties. The Se concentration in soil varies with type, texture and organic matter... (Review)
Review
Selenium (Se³⁴₇₉) is a metalloid which is close to sulfur (S) in terms of properties. The Se concentration in soil varies with type, texture and organic matter content of the soil and with rainfall. Its assimilation by plants is influenced by the physico-chemical properties of the soil (redox status, pH and microbial activity). The presence of Se in the atmosphere is linked to natural and anthropogenic activities. Selenoproteins, in which selenium is present as selenocysteine, present an important role in many body functions, such as antioxidant defense and the formation of thyroid hormones. Some selenoprotein metabolites play a role in cancer prevention. In the immune system, selenium stimulates antibody formation and activity of helper T cells, cytotoxic T cells and Natural Killer (NK) cells. The mechanisms of intestinal absorption of selenium differ depending on the chemical form of the element. Selenium is mainly absorbed in the duodenum and caecum by active transport through a sodium pump. The recommended daily intake of selenium varies from 60 μg/day for women, to 70 μg/day for men. In growing ruminants the requirements are estimated at 100 μg/kg dry matter and 200 μg/Kg for pregnant or lactating females. A deficiency can cause reproductive disorders in humans and animals.
Topics: Animals; Environment; Humans; Nutritional Requirements; Selenium; Selenocysteine; Selenoproteins
PubMed: 23486107
DOI: 10.3390/molecules18033292 -
Cell Metabolism Mar 2022Although the neurogenesis-enhancing effects of exercise have been extensively studied, the molecular mechanisms underlying this response remain unclear. Here, we propose...
Although the neurogenesis-enhancing effects of exercise have been extensively studied, the molecular mechanisms underlying this response remain unclear. Here, we propose that this is mediated by the exercise-induced systemic release of the antioxidant selenium transport protein, selenoprotein P (SEPP1). Using knockout mouse models, we confirmed that SEPP1 and its receptor low-density lipoprotein receptor-related protein 8 (LRP8) are required for the exercise-induced increase in adult hippocampal neurogenesis. In vivo selenium infusion increased hippocampal neural precursor cell (NPC) proliferation and adult neurogenesis. Mimicking the effect of exercise through dietary selenium supplementation restored neurogenesis and reversed the cognitive decline associated with aging and hippocampal injury, suggesting potential therapeutic relevance. These results provide a molecular mechanism linking exercise-induced changes in the systemic environment to the activation of quiescent hippocampal NPCs and their subsequent recruitment into the neurogenic trajectory.
Topics: Aging; Animals; Cell Proliferation; Hippocampus; Mice; Neural Stem Cells; Neurogenesis; Selenium
PubMed: 35120590
DOI: 10.1016/j.cmet.2022.01.005 -
Advances in Clinical and Experimental... Feb 2018Selenium is a trace element which fulfils important functions in the organism. Its deficit may cause acute disorders, but an overdose can also lead to severe... (Review)
Review
Selenium is a trace element which fulfils important functions in the organism. Its deficit may cause acute disorders, but an overdose can also lead to severe consequences. The functions of selenium in the organism are mainly connected with its antioxidant properties, as it is an essential part of important antioxidant enzymes. Disturbances of oxidant balance have been found to be involved in the activity of numerous harmful factors as well as in the pathogenesis of diverse illnesses. Selenium administration has proved to be effective against the toxicity of many agents and the side effects of drugs. However, the narrow range between therapeutic and toxic doses of selenium, as well as the dependence of its effect on the applied form, dose and method of treatment, makes the choice of the most effective supplement a very complex issue. Divergent forms of selenium are still being studied, including both inorganic and organic compounds as well as Se-enriched natural products. The newest research has also involved selenium nanoparticles. The aim of this review is to present the great potential of selenium for protecting the organism against a wide variety of environmental pollutants, drugs and physical factors.
Topics: Antioxidants; Dietary Supplements; Humans; Oxidative Stress; Selenium; Trace Elements
PubMed: 29521069
DOI: 10.17219/acem/67222