Modulation of testicular and whole blood trace element concentrations in conjunction with testosterone release following kisspeptin administration in male rabbits (Oryctolagus cuniculus)

Differences between some biochemical components in seminal plasma of first and second ejaculations in dual-purpose Simmental (Fleckvieh) bulls and their relationships with semen quality parameters

This study aimed to evaluate differences in seminal plasma zinc (Zn), copper (Cu), iron (Fe), catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx) levels in the first and second ejaculations and their relationships with semen quality parameters in Fleckvieh bulls. Repetitive ejaculates were separately collected, analyzed, and frozen from the sires. Progressive motility of frozen-thawed semen (PMFT) was considered the main factor for more data classification into three following groups: <40.00%, 40.00 - 50.00%, and >50.00%. Seminal plasma trace elements and enzymes were determined using atomic absorption spectrometry and ELISA, respectively. The results revealed significant differences between the first and second ejaculations. Semen concentration, SOD, GPx, and Fe were different in ejaculations. Although PMFT groups in different ejaculations did not show significant differences, there was significant alteration between different PMFT groups and first and second ejaculations. All frozen-thawed semen CASA parameters (except lateral head displacement) were associated with fresh motility parameters and before and after thawing sperm viability. Also, a correlation between seminal Zn concentration with fresh semen gross and progressive motility, average path velocity, and beat cross frequency, Cu with SOD and Fe and semen concentration was observed. CAT was associated with fresh and frozen-thawed sperm motility parameters except for lateral head displacement and angular displacement. Although our findings showed differences between the first and second ejaculations in some parameters, PMFT, which is the most important indicator for estimating bull fertility, was not different between them.

Kisspeptin and its Effect on Mammalian Spermatogensis

BACKGROUND

Kisspeptin and its receptor, GPR54, are regarded as key regulators of and catalysts for male puberty onset, and also fundamental gatekeepers of spermatogenesis in mammals. Consequently, the loss function of kisspeptin or GPR54 leads to a symptom of Hypogonadotropic Hypogonadism (HH) in human and HH accompanied by lower gonadotrophic hormone levels, smaller testes, impaired spermatogenesis and abnormal sexual maturation in mice. Besides its well-recognized functions in hypothalamus before and during puberty, accumulating data strongly support kisspeptin production in testis, and participation in somatic and germ cell development and sperm functions as well. This review aims to summarize recent findings regarding kisspeptin activity in the testes and sperm function.

METHODS

We undertook a keyword search of peer-reviewed research literature including data from in vivo and in vitro studies in humans and genetically modified animal models to identify the roles of kisspeptins in male reproduction.

RESULTS

A plethora of studies detail the role of kisspeptins and GPR54 in mammalian spermatogenesis in vivo and in vitro. This review identified recent findings regarding the kisspeptin system in male gonads, and regulation of kisspeptin in testicular physiology and male reproductive defects and disorders.

CONCLUSION

The findings of this review confirm the importance role of kisspeptins in male fertility. Understanding their biphasic roles in testis may help to consider kisspeptins as potential pharmacological targets for treating human infertility.

A potential role for zinc transporter 7 in testosterone synthesis in mouse Leydig tumor cells

Previous studies have demonstrated that zinc (Zn) is an essential trace element which is involved in male reproduction. The zinc transporter (ZnT) family, SLC30a, is involved in the maintenance of Zn homeostasis and in mediating intracellular signaling events; however, relatively little is known regarding the effect of ZnTs on testosterone synthesis. Thus, in the present study, we aimed to determine the effect of Zn transporter 7 (ZnT7) on testosterone synthesis in male CD-1 mice and mouse Leydig cells. The findings of the present study revealed that the concentrations of Zn in the testes and Leydig cells were significantly lower in mice fed a Zn-deficient diet compared with the control mice fed a Zn-adequate diet. In addition, ZnT7 was principally expressed and colocalized with steroidogenic acute regulatory protein (StAR) in the Leydig cells of male CD-1 mice. ZnT7 expression was downregulated in the mice fed a Zn-deficient diet, which led to decreases in the expression of the enzymes involved in testosterone synthesis namely cholesterol side‑chain cleavage enzyme (P450scc) and 3β-hydroxysteroid dehydrogenase/D5-D4 isomerase (3β-HSD) as well as decreased serum testosterone levels. These results suggested that Znt7 may be involved in testosterone synthesis in the mouse testes. To examine this hypothesis, we used the mouse Leydig tumor cell line (MLTC-1 cell line) in which the ZnT7 gene had been silenced, in order to gauge the impact of changes in ZnT7 expression on testosterone secretion and the enzymes involved in testosterone synthesis. The results demonstrated that ZnT7 gene silencing downregulated the expression of StAR, P450scc and 3β-HSD as well as progesterone concentrations in the human chorionic gonadotrophin (hCG)-stimulated MLTC-1 cells. Taken together, these findings reveal that ZnT7 may play an important role in the regulation of testosterone synthesis by modulating steroidogenic enzymes, and may represent a therapeutic target in testosterone deficiency.