Understanding The Role Of Selenium In Immune Health – Platelet serotonin (5-HT) concentration, platelet monoamine oxidase B (MAO-B) activity and HTR2A, HTR2C and MAOB gene polymorphisms in asthma
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Understanding The Role Of Selenium In Immune Health
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A Comprehensive Review On Selenium And Its Effects On Human Health And Distribution In Middle Eastern Countries
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Fan Fan Zhang Ciprofiles Xylit Preprints, 3, *
Introducing Immune Support (with Quercetin, Bromelain, Zinc And Seleni
Hubei Key Laboratory of Biological Targeted Therapy, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
Hubei Engineering Research Center for Immunological Diagnosis and Therapy of Cardiovascular Diseases, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, China
Submission received: 2023 February 23 / Revised: 2023 April 19 / Adopted: 2023 April 27 / Published: 2023 May 8
Selenium is an essential trace element for health. Obtained from food and absorbed in the liver, selenium performs various physiological functions in the body in the form of selenoproteins, which are best known for their redox activity and anti-inflammatory properties. Selenium promotes the activation of immune cells and is important for the activation of the immune system. Selenium is also needed for brain function. Selenium supplementation can regulate lipid metabolism, cell apoptosis, and autophagy and have significant palliative effects on many cardiovascular diseases. However, the effect of increased selenium on cancer risk remains unclear. Elevated serum selenium increases the risk of type 2 diabetes, and the relationship is both complex and simple. Selenium supplementation is of some benefit; However, existing research does not fully explain the effects of selenium on various diseases. Furthermore, more interventional studies are needed to test the beneficial or harmful effects of selenium supplementation in various diseases.
How Do Zinc & Selenium Help Your Immune System?
Micronutrients play an important role in maintaining basic physiological functions [1]. Selenium (Se) is a trace element, which in 1817 discovered by the Swedish chemist Jans Jacob Berzelius. In fact, selenium is naturally occurring toxic [2]; However, this view changed after the unexpected discovery by Schwarz and Foltz in 1957 that selenium prevented liver necrosis in rats [3]. Since then, the perception of selenium as a health threat has changed. In fact, selenium is beginning to be recognized as a beneficial element for health. Selenium obtained from the diet plays its physiological role because many proteins are incorporated into components of the amino acid selenocysteine (Sec) [4]. Importantly, selenium provides selenoprotein molecules with numerous redox properties that support redox homeostasis [5, 6].
The amount of selenium in the human body is about 3-20 mg. As an important trace mineral, selenium is mainly obtained from foods such as grains, meat, fish and eggs [7]. In general, the concentration of selenium varies between different foods and foods of animal origin > vegetables > whole grains > fruits. Cereals are the main source of selenium; However, their selenium content is relatively low, ranging from 0.01 to 0.55 μg/g. Selenium levels in animal foods range from 0.08 to 0.7 μg/g, and less than 0.1 μg/g in vegetables and fruits. Brazil nuts are the richest source of dietary selenium, with a selenium content of up to 512 g/g [8]. The main source of selenium in plants is soil. A total soil selenium content of less than 0.1 mg/kg is considered selenium deficient, 0.2–0.3 mg/kg is generally considered selenium deficient, and more than 0.4 mg/kg is selenium enriched [ 9 ]. The plant bioavailability of different forms of selenium varies in soil and is selenate > organic selenium > selenite > selenium > selenide. In addition, soil pH, redox conditions, microbial activity and organic matter also affect Se uptake by plants, although these factors will not be described in detail here. The World Health Organization (WHO) recommends an intake of 55 µg of selenium per day for adults, with an upper limit of 400 µg per day. Moderate intake of selenium and maintaining a balanced diet are very important.
The form of selenium in food affects its absorption in the human body. Dietary selenium is usually available as organic selenium compounds, selenate and selenite, with a bioavailability of 70-95% [10, 11]. Selenoamino acids are often more bioavailable than inorganic selenium [12], and selenium is more bioavailable in plant foods than in animal foods [11]. Selenomethionine (SeMet), the main dietary form of selenium, cannot be synthesized by higher organisms. Semet synthesis depends on plants and fungi [13]. About 90% of the selenium in plants is semet. Bioavailability reaches 95-98% [14, 15]. Selenocysteine (Sec) is another organic selenium compound that comes mainly from animal foods. Inorganic selenium accumulates in plants mainly through sulfur assimilation, but it is also present in water. Selenites and selenites that are ingested by humans are eventually converted to semet.
Selenium is obtained from food and the human body contains natural organic forms of selenocysteine and selenoprotein. They accumulate in various organs and tissues: 30% in liver, 30% in muscle, 15% in kidney, 10% in plasma and 15% in other organs [16]. Selenium concentration in the liver reflects the level of intestinal absorption. Selenoprotein P (SELENOP) is synthesized in the liver, which enters the blood and provides selenium to other tissues and organs [17, 18, 19]. The biological effects of selenium are mainly determined by selenoproteins [20]. Almost all selenoproteins contain a single Sec residue in their enzyme active sites [21], which are essential for their activity. Sec, the 21st naturally occurring, genetically encoded amino acid, is a cysteine (Cys) sulfur-to-selenium substitution variant [22]. Selenium and sulfur belong to the same group. Therefore, Sec and Cys have similar chemical properties and participate in similar chemical reactions [23]. However, compared to Cys, Sec exhibits higher nucleophilicity [24], sensitivity to oxidation and acidity, which is mainly reflected in its lower pKa (5.2) [25, 26]. Therefore, most side-chain selenols are deprotonated at biological pH, with Sec being reactively superior to Cys [ 27 , 28 ].
Essential Nutrients For Your Immune System
In humans, Sec is the only naturally occurring amino acid lacking a cognate aminoacyl-tRNA synthetase. Thus, Sec requires a specific biosynthetic pathway [29] (Figure 1). First, seryl-tRNA synthetase (SerRS), catalyzed by selenocysteine-specific tRNA (tRNA)
Sec can bind to insertion sequence-binding protein 2 (SBP2), which specifically recognizes the stop codon UGA [ 32 , 33 ]. This process requires a Sec insertion sequence (SECIS) element located in the 3′ untranslated region of the mRNA to decode the UGA codon to Sec [ 34 , 35 ]. Finally, through the interaction of SECIS and SBP2, Sec enters the ribosome and is cotranslationally incorporated into nascent polypeptide chains [ 20 ].
A total of 25 selenoprotein genes have been described in humans, and most of these genes encode redox enzymes [36, 37]. Selenoproteins are distributed in different organs and tissues and have different surface specificities and functions (Table 1). The glutathione peroxidase (GPX) and thioredoxin reductase (TxnRd) families are involved in the maintenance of cellular antioxidant defense systems and intracellular redox states to maintain cell viability [ 38 , 39 ] (see below). These families often operate in parallel in humans. Three iodothyronine deiodinases (Dio1, 2, 3) are selenoproteins with expression patterns associated with development, cellularity, and pathology. Dio1 and Dio2 are involved in the production of active thyroid hormone T3 [40], while Dio3 contributes to the production of inactive rT3 and T2. Human selenopus is a monomeric glycoprotein containing 10 selenocysteine residues, an important feature that distinguishes it from other selenoproteins. Thus, SELENOP, a selenium transport protein, accounts for about 40% of the total selenium concentration in human plasma and can bind to specific receptors in cell membranes to transport selenium to other cells, such as low-density lipoprotein receptor-related protein 8 (LRP8) and megalin receptors on the kidney. epithelial cells of proximal tubules [17, 41]. SELENOP also has redox properties and is associated with the protection of endothelial function. SELENOP binds to heparin and is associated with insulin resistance. Selenoprotein S is associated with inflammation