17α-estradiol does not adversely affect sperm parameters or fertility in male mice: implications for reproduction-longevity trade-offs

17α-estradiol (17α-E2) is referred to as a nonfeminizing estrogen that was recently found to extend healthspan and lifespan in male, but not female, mice. Despite an abundance of data indicating that 17α-E2 attenuates several hallmarks of aging in male rodents, very little is known with regard to its effects on feminization and fertility. In these studies, we evaluated the effects of 17α-E2 on several markers of male reproductive health in two independent cohorts of mice. In alignment with our previous reports, chronic 17α-E2 treatment prevented gains in body mass, but did not adversely affect testes mass or seminiferous tubule morphology. We subsequently determined that chronic 17α-E2 treatment also did not alter plasma 17β-estradiol or estrone concentrations, while mildly increasing plasma testosterone levels. We also determined that chronic 17α-E2 treatment did not alter plasma follicle-stimulating hormone or luteinizing hormone concentrations, which suggests 17α-E2 treatment does not alter gonadotropin-releasing hormone neuronal function. Sperm quantity, morphology, membrane integrity, and various motility measures were also unaffected by chronic 17α-E2 treatment in our studies. Lastly, two different approaches were used to evaluate male fertility in these studies. We found that chronic 17α-E2 treatment did not diminish the ability of male mice to impregnate female mice, or to generate successfully implanted embryos in the uterus. We conclude that chronic treatment with 17α-E2 at the dose most commonly employed in aging research does not adversely affect reproductive fitness in male mice, which suggests 17α-E2 does not extend lifespan or curtail disease parameters through tradeoff effects with reproduction.

Dietary myricetin assuages atrazine-mediated hypothalamic-pituitary-testicular axis dysfunction in rats

Atrazine (ATZ) exposure is associated with reproductive dysfunction in both animals and humans. Myricetin, a flavonoid compound, is well documented for its numerous pharmacological activities. However, the impact of myricetin on the atrazine-mediated dysfunctional hypothalamic-pituitary-testicular axis is not known. This study investigated the role of myricetin on the atrazine-induced alterations in the male reproductive axis in rats orally gavaged with ATZ alone (50 mg/kg) or co-treated with ATZ + myricetin (MYR) at 5, 10, and 20 mg/kg for 30 consecutive days. Myricetin assuaged ATZ-induced reductions in intra-testicular testosterone, serum follicle-stimulating hormone, luteinizing hormone, and testosterone, coupled with decreases in alkaline phosphatase, acid phosphatase, lactate dehydrogenase, and glucose-6-phosphate dehydrogenase activities. Also, MYR treatment improved epididymal sperm count and motility and decreased sperm defects in ATZ-treated rats. Testicular sperm number, daily sperm production, and sperm viability remained unchanged in all treatment groups. Administration of MYR abated ATZ-mediated depletion in antioxidant status, an increase in myeloperoxidase activity, nitric oxide, hydrogen peroxide, malondialdehyde levels, and reactive oxygen and nitrogen species, as well as the histological lesions in the hypothalamus, epididymis, and testes of treated animals. All in all, MYR mitigated atrazine-mediated functional changes in the reproductive axis via anti-inflammatory and antioxidant mechanisms in atrazine-exposed rats. Dietary intake of MYR could be a worthy chemoprotective approach against reproductive dysfunction related to ATZ exposure.

Female Athlete Triad and Male Athlete Triad Syndrome Induced by Low Energy Availability: An Animal Model

Energy availability (EA) is defined the difference in energy intake and exercise energy expenditure. Reduction of EA (i.e. Low energy availability, LEA) often causes abnormalities of reproduction system and drastic bone loss in some female athletes, the phenomenon is called as female athlete triad. More than ever before, it is considered a serious problem, the reason of these are (1) the syndrome occurred in female athletes but also male athletes, (2) LEA is leads to dysfunction of various organs other than reproductive system (Relative energy deficiency in sport, RED-S). On the other hand, we have focused on this syndrome and have proposed novel insights into the physiological effects of LEA on bone and solutions through nutritional treatment by recreating it in animal models. In this review, we will summarize the epidemiological and physiological perspectives of these diseases from historical background to recent findings, and introduce the usefulness of using animal models to explore mechanisms and treatments.

Kisspeptin neuron electrophysiology: Intrinsic properties, hormonal modulation, and regulation of homeostatic circuits

The obligatory role of kisspeptin (KISS1) and its receptor (KISS1R) in regulating the hypothalamic-pituitary-gonadal axis, puberty and fertility was uncovered in 2003. In the few years that followed, an impressive body of work undertaken in many species established that neurons producing kisspeptin orchestrate gonadotropin-releasing hormone (GnRH) neuron activity and subsequent GnRH and gonadotropin hormone secretory patterns, through kisspeptin-KISS1R signaling, and mediate many aspects of gonadal steroid hormone feedback regulation of GnRH neurons. Here, we review knowledge accrued over the past decade, mainly in genetically modified mouse models, of the electrophysiological properties of kisspeptin neurons and their regulation by hormonal feedback. We also discuss recent progress in our understanding of the role of these cells within neuronal circuits that control GnRH neuron activity and GnRH secretion, energy balance and, potentially, other homeostatic and reproductive functions.