Obesity and Male Reproduction: Do Sirtuins Play a Role?

Obesity is a major current public health problem of global significance. A progressive sperm quality decline, and a decline in male fertility, have been reported in recent decades. Several studies have reported a strict relationship between obesity and male reproductive dysfunction. Among the many mechanisms by which obesity impairs male gonadal function, sirtuins (SIRTs) have an emerging role. SIRTs are highly conserved nicotinamide adenine dinucleotide (NAD+)-dependent deacetylases that play a role in gene regulation, metabolism, aging, and cancer. SIRTs regulate the energy balance, the lipid balance, glucose metabolism, and adipogenesis, but current evidence also indicates a role for SIRTs in male reproduction. However, the majority of the studies have been conducted in animal models and very few have been conducted with humans. This review shows that SIRTs play an important role among the molecular mechanisms by which obesity interferes with male fertility. This highlights the need to deepen this relationship. It will be of particular interest to evaluate whether synthetic and/or natural compounds capable of modifying the activity of SIRTs may also be useful for the treatment of obesity and its effects on gonadal function. Although few studies have explored the role of SIRT activators in obesity-induced male infertility, some molecules, such as resveratrol, appear to be effective in modulating SIRT activity, as well as counteracting the negative effects of obesity on male fertility. The search for strategies to improve male reproductive function in overweight/obese patients is a challenge and understanding the role of SIRTs and their activators may open new interesting scenarios in the coming years.

Antioxidant Paradox in Male Infertility: ‘A Blind Eye’ on Inflammation

The pathophysiology of male infertility involves various interlinked endogenous pathways. About 50% of the cases of infertility in men are idiopathic, and oxidative stress (OS) reportedly serves as a central mechanism in impairing male fertility parameters. The endogenous antioxidant system operates to conserve the seminal redox homeostasis required for normal male reproduction. OS strikes when a generation of seminal reactive oxygen species (ROS) overwhelms endogenous antioxidant capacity. Thus, antioxidant treatment finds remarkable relevance in the case of idiopathic male infertility or subfertility. However, due to lack of proper detection of OS in male infertility, use of antioxidant(s) in some cases may be arbitrary or lead to overuse and induction of ‘reductive stress’. Moreover, inflammation is closely linked to OS and may establish a vicious loop that is capable of disruption to male reproductive tissues. The result is exaggeration of cellular damage and disruption of male reproductive tissues. Therefore, limitations of antioxidant therapy in treating male infertility are the failure in the selection of specific treatments targeting inflammation and OS simultaneously, two of the core mechanisms of male infertility. The present review aims to elucidate the antioxidant paradox in male infertility treatment, from the viewpoints of both induction of reductive stress as well as overlooking the inflammatory consequences.

The cytoplasmic incompatibility Cif proteins from prophage WO modify sperm genome integrity

Inherited microorganisms can selfishly manipulate host reproduction to drive through populations. In Drosophila melanogaster, germline expression of the native prophage WO proteins CifA and CifB cause cytoplasmic incompatibility (CI) in which sperms fertilize uninfected embryos that suffer catastrophic mitotic defects and lethality; however in infected females, CifA rescues the embryonic lethality and thus imparts a fitness advantage to Wolbachia. Despite widespread relevance to sex determination, evolution, and vector control, the mechanisms underlying when and how CI impairs male reproduction remain unknown and a topic of debate. Here we use cytochemical, microscopic, and transgenic assays in D. melanogaster to demonstrate that CifA and CifB proteins of wMel localize to nuclear DNA throughout the process of spermatogenesis. Cif proteins cause abnormal histone retention in elongating spermatids and protamine deficiency in mature sperms of CI-causing males. Protamine-deficient sperms travel to the female reproductive tract together with Cif proteins. In female ovaries, CifA localizes to germ cell nuclei and overlaps with Wolbachia in the nurse cell cytoplasm and the oocyte, however Cifs are not present in late-stage oocytes and the embryo. Moreover, CI and rescue are contingent upon a newly annotated CifA bipartite nuclear localization sequence. Our results reveal a previously unrecognized phenomena in which prophage proteins invade animal gametic nuclei and modify the histone-protamine transition of spermatogenesis.

Amelioration of ethanol reprotoxicity by aqueous Spinacia oleracea extract in male rabbits Oryctolagus cuniculus

Spinacia oleracea “Spinach” is a plant rich in antioxidants; it leads to improved male reproduction. For this reason, the objective of this study is to evaluate the effect of the aqueous extract of this plant on the fertility of adult male rabbits after their administration with ethanol. The rabbits were divided into four groups: control group, group treated with 150 mg / kg / day of aqueous Spinacia oleracea extract (Ep), group treated with 40% ethanol (EtOH), and group treated with 150 mg / kg / day of aqueous Spinacia oleracea extract + 40% ethanol (Ep + EtOH), for a period of five successive weeks. Treatment was administered orally. After sacrificing the rabbits, the reproductive organs were removed and weighed. Certain sperm parameters (concentration, mobility, speed, and vitality), the testosterone level and the weight of the testes and epididymis were assessed. The results obtained showed a decrease in the concentration, mobility, speed and vitality of sperm, accompanied by a decrease in testosterone levels, and in the weight of the testes and epididymis in the group treated with ethanol, on the other hand, treatment with aqueous Spinacia oleracea extract revealed an increase in these parameters. In conclusion, treatment with aqueous Spinacia oleracea extract can repair the damage caused by ethanol.

Normal Reproductive function in male mice lacking pituitary kisspeptin receptor.

The anterior pituitary secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) regulate gonadal development, gametogenesis and the secretion of the gonadal steroid hormones. The gonadotroph is primarily regulated by hypothalamic secretion of gonadotropin-releasing hormone (GnRH) from neurons of the rostral hypothalamus and is mediated by GnRH receptor signaling. Kisspeptin (KISS1)/kisspeptin receptor (KISS1R) signaling in GnRH neurons plays an essential role in reproductive function. As the kisspeptin receptor is present in the pituitary, kisspeptin signaling via the Kiss1r may regulate reproductive function at the level of pituitary. Using Cre/Lox technology, we deleted the Kiss1r gene in pituitary gonadotropes (PKiRKO). PKiRKO male and females have normal genital development, puberty onset, and fertility. Females have normal LH, FSH and estradiol while males had significantly increased basal serum FSH levels with no differences in basal serum LH, or testosterone levels. Overall, these findings indicate that the pituitary KISS1R does not play a role in male reproduction.

TXNRD3 supports male fertility via the redox control of spermatogenesis

Thioredoxin/glutathione reductase (TGR, TXNRD3) is a thiol oxidoreductase of unknown function composed of thioredoxin reductase and glutaredoxin domains. This NADPH-dependent enzyme evolved by gene duplication within the Txnrd family, is expressed in the testes and can reduce both thioredoxin and glutathione in vitro. To characterize the function of TXNRD3 in vivo, we generated a strain of mice with the deletion of Txnrd3 gene. We show that Txnrd3 knockout mice are viable and without discernable gross phenotypes, but TXNRD3 deficiency leads to fertility impairment in male mice. Txnrd3 knockout animals exhibit a lower fertilization rate in vitro, a sperm movement phenotype and an altered redox status of thiols. Proteomic analyses revealed a broad range of substrates reduced by TXNRD3 during sperm maturation, presumably as a part of quality control. The results show that TXNRD3 plays a critical role in male reproduction via the thiol redox control of spermatogenesis.

PA1 Participates in the Maintenance of Blood-Testis Barrier Integrity via Cooperation with JUN in the Sertoli Cells of Mice.

BackgroundThe blood-testis barrier (BTB) is essential to the microenvironment of spermatogenesis, and Sertoli cells provide the cellular basis for BTB construction. Numerous nuclear transcription factors have been identified to be vital for the proper functioning of Sertoli cells. PA1 has been reported to play important roles during diverse biological processes, yet its potential function in male reproduction is still unknown. ResultsHere, we show that PA1 was highly expressed in human and mouse testis and predominantly localized in the nuclei of Sertoli cells. Sertoli cell-specific Pa1 knockout resulted in an azoospermia-like phenotype in mice. The knockout of this gene led to multiple defects in spermatogenesis, such as the disorganization of the cytoskeleton during basal and apical ectoplasmic specialization and the disruption of the BTB. Further transcriptomic analysis, together with Cut-Tag results of PA1 in Sertoli cells, revealed that PA1 could affect the expression of a subset of genes that are essential for the normal function of Sertoli cells, including those genes associated with actin organization and cellular junctions such as Connexin43 (Cx43). We further demonstrated that the expression of Cx43 depended on the interaction between JUN, one of the AP-1 complex transcription factors, and PA1. ConclusionOverall, our findings reveal that PA1 is essential for the maintenance of BTB integrity in Sertoli cells and regulates BTB construction-related gene expression via transcription factors. Thus, this newly discovered mechanism in Sertoli cells provides a potential diagnostic or even therapeutic target for some individuals with azoospermia.

Historical Roles of Selenium and Selenoproteins in Health and Development: The Good, the Bad and the Ugly

Selenium is a fascinating element that has a long history, most of which documents it as a deleterious element to health. In more recent years, selenium has been found to be an essential element in the diet of humans, all other mammals, and many other life forms. It has many health benefits that include, for example, roles in preventing heart disease and certain forms of cancer, slowing AIDS progression in HIV patients, supporting male reproduction, inhibiting viral expression, and boosting the immune system, and it also plays essential roles in mammalian development. Elucidating the molecular biology of selenium over the past 40 years generated an entirely new field of science which encompassed the many novel features of selenium. These features were (1) how this element makes its way into protein as the 21st amino acid in the genetic code, selenocysteine (Sec); (2) the vast amount of machinery dedicated to synthesizing Sec uniquely on its tRNA; (3) the incorporation of Sec into protein; and (4) the roles of the resulting Sec-containing proteins (selenoproteins) in health and development. One of the research areas receiving the most attention regarding selenium in health has been its role in cancer prevention, but further research has also exposed the role of this element as a facilitator of various maladies, including cancer.