Selenium. Role of the Essential Metalloid in Health

Abstract

Selenium is an essential micronutrient in mammals, but is also recognized as toxic in excess. It is a non-metal with properties that are intermediate between the chalcogen elements sulfur and tellurium. Selenium exerts its biological functions through selenoproteins. Selenoproteins contain selenium in the form of the 21st amino acid, selenocysteine (Sec), which is an analog of cysteine with the sulfur-containing side chain replaced by a Se-containing side chain. Sec is encoded by the codon UGA, which is one of three termination codons for mRNA translation in non-selenoprotein genes. Recognition of the UGA codon as a Sec insertion site instead of stop requires a Sec insertion sequence (SECIS) element in selenoprotein mRNAs and a unique selenocysteyl-tRNA, both of which are recognized by specialized protein factors. Unlike the 20 standard amino acids, Sec is biosynthesized from serine on its tRNA. Twenty-five selenoproteins are encoded in the human genome. Most of the selenoprotein genes were discovered by bioinformatics approaches, searching for SECIS elements downstream of in-frame UGA codons. Sec has been described as having stronger nucleophilic and electrophilic properties than cysteine, and Sec is present in the catalytic site of all selenoenzymes. Most selenoproteins, whose functions are known, are involved in redox systems and signaling pathways. However, several selenoproteins are not well characterized in terms of their function. The selenium field has grown dramatically in the last few decades, and research on selenium biology is providing extensive new information regarding its importance for human health.

Early-life nutritional effects on the female reproductive system

“…It is an antioxidant found in trace amounts in many foods including nuts, cereals, fish, and eggs and is often associated with redox reactions and signalling pathways (Kurokawa & Berry 2013), and recently has been suggested to play a role in corpus luteum and/or placental function in pregnant cows (Kamada et al 2014). Although essential in trace amounts, high levels of selenium result in toxicity (Gore et al 2010).…”

Placental Metal Concentrations in Relation to Maternal and Infant Toenails in a U.S. Cohort

“…Manganese (Mn) is an essential nutrient that acts as a neurodevelopmental toxicant at supraoptimal concentrations (11). Selenium (Se) is an essential micronutrient in mammals that has a narrow window of sufficiency (12), and can be toxic in extreme excess (13). Zinc is also an essential nutrient, which plays key roles in embryogenesis, fetal growth and development and mammary gland function for milk synthesis and secretion (14).…”

Selenomethionine Ameliorates Neuropathology in the Olfactory Bulb of a Triple Transgenic Mouse Model of Alzheimer’s Disease

“…Selenium (Se) is a vital non-metallic trace element that is rich in the brain and possesses beneficial biochemical and pharmacological properties (including antioxidation, anticancer, and anti-inflammatory) [16]. It has been shown in our previous study that selenomethionine (Se-Met), a major form of Se in organisms, effectively increase oxidation resistance as well as reduce the production and deposition of Aβ and tau hyperphosphorylation in the cortex and hippocampus of a triple transgenic mouse model of AD (3× Tg-AD), thereby suggesting a promising therapeutic option for AD [17].…”