Role of Selenium and Selenoproteins in Male Reproductive Function: A Review of Past and Present Evidences

Abstract

Selenium (Se) is an important trace mineral having many essential roles at the cellular and organismal levels in animal and human health. The biological effects of Se are mainly carried out by selenoproteins (encoded by 25 genes in humans and 24 in mice). As an essential component of selenoproteins, Se performs structural and enzymic roles; in the latter context it is well known for its catalytic and antioxidative functions. Studies involving different animal models have added great value to our understanding regarding the potential implications of Se and selenoproteins in mammalian fertility and reproduction. In this review, we highlight the implications of selenoproteins in male fertility and reproduction followed by the characteristic biological functions of Se and selenoproteins associated with overall male reproductive function. It is evident from observations of past studies (both animal and human) that Se is essentially required for spermatogenesis and male fertility, presumably because of its vital role in modulation of antioxidant defense mechanisms and other essential biological pathways and redox sensitive transcription factors. However, bearing in mind the evidences from mainstream literature, it is also advisable to perform more studies focusing on the elucidation of additional roles played by the peculiar and canonical selenoproteins i.e., glutathione peroxidase 4 (GPX4) and selenoprotein P (SELENOP) in the male reproductive functions. Nevertheless, search for the elucidation of additional putative mechanisms potentially modulated by other biologically relevant selenoproteins should also be included in the scope of future studies. However, as for the implication of Se in fertility and reproduction in men, though a few clinical trials explore the effects of Se supplementation on male fertility, due to inconsistencies in the recruitment of subjects and heterogeneity of designs, the comparison of such studies is still complicated and less clear. Therefore, further research focused on the roles of Se and selenoproteins is awaited for validating the evidences at hand and outlining any therapeutic schemes intended for improving male fertility. As such, new dimensions could be added to the subject of male fertility and Se supplementation.

Dietary Selenium Supplementation Ameliorates Female Reproductive Efficiency in Aging Mice

“…During last few years, antioxidants such as N-acetyl-l-cysteine (NAC) [6], resveratrol [4], and melatonin (MT) [8] have been demonstrated to ameliorate the ovarian redox status and oocyte and embryo quality, thereby delaying the age-related decline in fertility in mouse models of reproductive aging. Selenium (Se) is known as an essential trace mineral (micronutrient) and performs several important functions at the level of the cell and the organism in animal and human health [9][10][11]. Although the cellular biochemistry of Se and its regulation in body are complex processes [12][13][14], it is well-established that the canonical biological roles of Se are mainly performed by selenoproteins which are encoded by 25 genes in humans and 24 in mice [9,15].…”

“…Although, not all the selenoproteins have been functionally characterized, the majority of them perform oxidoreductase functions [15]. Due to their diverse properties, selenoproteins have been demonstrated to serve a number of physiological processes, including male [10] and female [9] reproduction.…”

“…Selenium is generally utilized in the form organic and inorganic species [10,[17][18][19]. Selenomethionine (SeMet) is the most common organic form (mainly Se-yeast) of Se present in a wide range of human and animal diets, whereas inorganic chemical forms such as, sodium selenite are usually used for supplementing animal feed [18][19][20].…”

“…Selenomethionine (SeMet) is the most common organic form (mainly Se-yeast) of Se present in a wide range of human and animal diets, whereas inorganic chemical forms such as, sodium selenite are usually used for supplementing animal feed [18][19][20]. It has been argued that the potential beneficial and/or adverse effects of Se are mainly dependent on the form being utilized; however, the total intake of Se has also been considered as an important factor in this regard [10,19]. The bioavailability of organic Se species such as, SeMet is usually higher compared to the inorganic selenite and selenate species [13,17].…”

“…The response curve of Se is U-shaped with a constringe window between deficient and excessive intakes [11]. Both Se deficiency and excess levels have been shown to influence the redox status and lead to severe adverse health consequences in animals and humans [10,21]. Interestingly, recently it has been demonstrated that plasma Se concentrations tend to decline in certain healthy human populations comprised of older subjects [22].…”