Article

Selenium in the Environment, Metabolism and Involvement in Body Functions

ULg-FMV, Nutrition Unit, Department of Animal Production, Boulevard de Colonster 20, Bât. B43 4000, Liège, Belgium. .
Molecules (Impact Factor: 2.42). 03/2013; 18(3):3292-311. DOI: 10.3390/molecules18033292
Source: PubMed

ABSTRACT

Selenium (Se34 79) 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.

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Available from: I. Dufrasne, Feb 05, 2015
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    • "In addition to being released into the environment by the natural weathering of rocks, selenium is released in larger quantities from metal ore during metal extraction, from coal and petroleum during burning, and from phosphate containing rocks that are used to manufacture agricultural fertilizer (Lakin, 1972). High soil concentrations of selenium have been found in areas contaminated with runoff from heavily used agricultural areas, industrial waste sites, and mining waste dumps (Mehdi et al., 2013). Selenium contamination from agricultural runoff is widespread across the western United States, affecting approximately 1.5 million acres across 8 states (Brown, Jr. et al., 1999). "
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    ABSTRACT: A plethora of toxic compounds – including pesticides, heavy metals, and metalloids – have been detected in honey bees (Apis mellifera) and their colonies. One such compound is selenium, which bees are exposed to by consuming nectar and pollen from flowers grown in contaminated areas. Though selenium is lethal at high concentrations, sublethal exposure may also impair honey bees’ ability to function normally. Examining the effect of selenium exposure on learning and memory provides a sensitive assay with which to identify sublethal effects on honey bee health and behavior. To determine whether sublethal selenium exposure causes learning and memory deficits, we used proboscis extension reflex conditioning coupled with recall tests 30 min and 24 h post-conditioning. We exposed forager honey bees to a single sublethal dose of selenium, and 3 h later we used an olfactory conditioning assay to train the bees to discriminate between one odor associated with sucrose-reinforcement and a second unreinforced odor. Following conditioning we tested short- and long-term recall of the task. Acute exposure to as little as 1.8 ng of an inorganic form of selenium (sodium selenate) before conditioning caused a reduction in behavioral performance during conditioning. And, exposure to 18 ng of either an inorganic form (sodium selenate) or an organic form (methylseleno-l-cysteine) of selenium caused a reduction in the bees' performance during the long-term recall test. These concentrations of selenium are lower than those found in the nectar of plants grown in selenium-contaminated soil, indicating that even low-grade selenium toxicity produces significant learning and memory impairments. This may reduce foragers’ ability to effectively gather resources for the colony or nurse bees’ ability to care for and maintain a healthy colony.
    Full-text · Article · May 2016 · Ecotoxicology and Environmental Safety
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    • "Thus, Se belongs to the elements with wide spectra of beneficial health effects, such as providing a decrease in the incidence of cancer, prophylaxis of cardiovascular diseases, therapy of particular muscle disorders , and delay of the onset of AIDS in HIV-positive patients (Hatfield 2001; Hatfield et al. 2014). Se belongs to the ubiquitous soil elements, but soil physicochemical parameters, the ability of the plant species to accumulate Se, and particular environmental conditions can affect its contents in crop production (Mehdi et al. 2013. The Se content of various diets differs significantly depending on the food items, and to a greater extent on the geographical origin and respective soil Se content (Kieliszek & Błażejak 2013). "
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    ABSTRACT: A model small-scale field experiment was set up to investigate selenium (Se) uptake by four different varieties of broccoli plants, as well as the effect of Se foliar application on the uptake of essential elements for plants calcium (Ca), copper (Cu), iron (Fe), potassium (K), magnesium (Mg), manganese (Mn), phosphorus (P), sulfur (S), and zinc (Zn). Foliar application of sodium selenate (Na2SeO4) was carried out at two rates (25 and 50 g Se/ha), and an untreated control variant was included. Analyses of individual parts of broccoli were performed, whereby it was found that Se in the plant accumulates mainly in the flower heads and slightly less in the leaves, stems, and roots, regardless of the Se rate and broccoli variety. In most cases, there was a statistically significant increase of Se content in all parts of the plant, while there was no confirmed systematic influence of the addition of Se on the changing intake of other monitored elements. Selenization of broccoli leads to an effective increase in the Se content at a rate of 25 g/ha, whereas the higher rate did not result in a substantial increase of Se content compared to the lower rate in all varieties. Therefore, the rate of 25 g/ha can be recommended as effective to produce broccoli with an increased Se content suitable for consumption. Moreover, Se application resulted in an adequate increase of the main organic compounds of Se, such as selenocystine (SeCys2), selenomethionine (SeMet), and Se-methylselenocysteine (Se-MeSeCys).
    Full-text · Article · Sep 2015 · Food Additives & Contaminants: Part A
    • "Selenium influence in several aspects of human health, including the induction of adequate immune response. Through incorporation in selenoproteins, selenium is involved in regulating important cellular processes in practically all tissues and cell types, including those involved in innate and adaptive immune responses such as in the spleen, liver, and lymph nodes (Hoffmann; Berry, 2008; Mehdi et al. 2013). Dietary Se and selenoproteins are also involved in immunoregulation, which is crucial for preventing excessive responses that may lead to autoimmunity or chronic inflammation (Huang et al. 2012). "
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    ABSTRACT: The HIV infection is characterized by both quantitative and functional progressive decrease of host's immunity, particularly related to the CD4+ T-cell depletion. The introduction of antiretroviral therapy increased the life expectancy of HIV/AIDS patients due to the increase in CD4+ T-cells, the inhibition of HIV replication, and the risk reduction of opportunistic infections. Despite the treatment efficacy, the patients are susceptible to side effects such as metabolic changes, which contribute to micronutrients deficiency and, consequently, promote a negative impact on immune function. In AIDS pathogenesis, a selenium deficient state may influence in the progression of HIV infection, since selenium plays an important role in the immune system. Recent studies have demonstrated that selenium supplementation in HIV-infected patients improves their pathophysiology. The relation between immune functions and selenoproteins as well as selenium metabolites highlights the selenometabolomics. This review describes the status of selenium and their metabolites in the HIV infection in the antiretroviral therapy context.
    No preview · Chapter · Aug 2015
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