Chronic intermittent hypoxia stimulates testosterone production in rat Leydig cells

Chronic intermittent hypoxia-induced hypertension: the impact of sex hormones

Obstructive sleep apnea, a common form of sleep-disordered breathing, is characterized by intermittent cessations of breathing that reduce blood oxygen levels and contribute to the development of hypertension. Hypertension is a major complication of obstructive sleep apnea that elevates the risk of end-organ damage. Premenopausal women have a lower prevalence of obstructive sleep apnea and cardiovascular disease than men and postmenopausal women, suggesting that sex hormones play a role in the pathophysiology of sleep apnea-related hypertension. The lack of protection in men and postmenopausal women implicates estrogen and progesterone as protective agents but testosterone as a permissive agent in sleep apnea-induced hypertension. A better understanding of how sex hormones contribute to the pathophysiology of sleep apnea-induced hypertension is important for future research and possible hormone-based interventions. The effect of sex on the pathophysiology of sleep apnea and associated intermittent hypoxia-induced hypertension is of important consideration in the screening, diagnosis, and treatment of the disease and its cardiovascular complications. This review summarizes our current understanding of the impact of sex hormones on blood pressure regulation in sleep apnea with a focus on sex differences.

Consequences of Exposure to Hypobaric Hypoxia Associated with High Altitude on Spermatogenesis and Seminal Parameters: A Literature Review

Preclinical research has provided compelling evidence indicating that exposure to hypobaric hypoxia (HH) results in a deterioration of spermatogenesis. This adverse effect extends to the underlying molecular mechanisms, progressively leading to impairments in the seminiferous epithelium and germ cells and alterations in semen parameters. Indeed, several studies have demonstrated that animals exposed to HH, whether in natural high-altitude environments or under simulated hypoxic conditions, exhibit damage to the self-renewal and differentiation of spermatogenesis, an increase in germline cell apoptosis, and structural alterations in the seminiferous tubules. One of the primary mechanisms associated with the inhibition of differentiation and an increase in apoptosis among germ cells is an elevated level of oxidative stress, which has been closely associated with HH exposure. Human studies have shown that individuals exposed to HH, such as mountaineers and alpinists, exhibit decreased sperm count, reduced motility, diminished viability, and increased sperm with abnormal morphology in their semen. This evidence strongly suggests that exposure to HH may be considered a significant risk factor that could elevate the prevalence of male infertility. This literature review aims to provide a comprehensive description and propose potential mechanisms that could elucidate the infertility processes induced by HH. By doing so, it contributes to expanding our understanding of the challenges posed by extreme environments on human physiology, opening new avenues for research in this field.

Special Staining and Protein Expression of VEGF/EGFR and P53/NF-κB in Cryptorchid Tissue of Erhualian Pigs

Erhualian pigs exhibit one of the highest reproductive rates globally, and cryptorchidism is a crucial factor affecting reproductive abilities of boars. This investigation focused on cryptorchid tissues from Erhualian pigs, where the histological structure of cryptorchidism was observed using specialized staining. In addition, protein expression of P53/NF-κB in cryptorchid tissues was assessed using Western blot and immunohistochemistry. In comparison to normal Erhualian testes, Masson's trichrome staining indicated a reduction in collagen fibers in the connective tissue and around the basal membrane of the seminiferous tubules in cryptorchid testes. Moreover, collagen fiber distribution was observed to be disordered. Verhoeff Van Gieson (EVG) and argyrophilic staining demonstrated brownish-black granular nucleoli organized regions in mesenchymal cells and germ cells. When compared to normal testicles, the convoluted seminiferous tubules of cryptorchids exhibited a significantly reduced number and diameter (p < 0.01). Notably, VEGF/EGFR and P53/NF-κB expression in cryptorchidism significantly differed from that in normal testes. In particular, the expression of VEGF and P53 in cryptorchid tissues was significantly higher than that in normal testes tissues, whereas the expression of EGFR in cryptorchid tissues was significantly lower than that in normal testes tissues (all p < 0.01). NF-κB expressed no difference in both conditions. The expressions of VEGF and NF-κB were observed in the cytoplasm of testicular Leydig cells and spermatogenic cells, but they were weak in the nucleus. EGFR and P53 were more positively expressed in the cytoplasm of these cells, with no positive expression in the nucleus. Conclusion: There were changes in the tissue morphology and structure of the cryptorchid testis, coupled with abnormally high expression of VEGF and P53 proteins in Erhualian pigs. We speculate that this may be an important limiting factor to fecundity during cryptorchidism.

Gestational intermittent hypoxia increases FosB-immunoreactive perikaryas in the paraventricular nucleus of the hypothalamus of adult male (but not female) rats

Sleep-disordered breathing is a respiratory disorder commonly experienced by pregnant women. The recurrent hypoxaemic events associated with sleep-disordered breathing have deleterious consequences for the mother and fetus. Adult male (but not female) rats born to dams subjected to gestational intermittent hypoxia (GIH) have a higher resting blood pressure than control animals and show behavioural/neurodevelopmental disorders. The origin of this persistent, sex-specific effect of GIH in offspring is unknown, but disruption of the neuroendocrine stress pathways is a key mechanism by which gestational stress increases disease risk in progeny. Using FosB immunolabelling as a chronic marker of neuronal activation, we determined whether GIH augments basal expression of FosB in the perikaryas of cells in the paraventricular nucleus of the hypothalamus (PVN), a key structure in the regulation of the stress response and blood pressure. From gestational day 10, female rats were subjected to GIH for 8 h/day (light phase) until the day before delivery (gestational day 21); GIH consisted of 2 min hypoxic bouts (10.5% O2 ) alternating with normoxia. Control rats were exposed to intermittent normoxia over the same period (GNX). At adulthood (10-15 weeks), the brains of male and female rats were harvested for FosB immunohistochemistry. In males, GIH augmented PVN FosB labelling density by 30%. Conversely, PVN FosB density in GIH females was 28% lower than that of GNX females. We conclude that GIH has persistent and sex-specific impacts on the development of stress pathways, thereby offering a plausible mechanism by which GIH can disturb neural development and blood pressure homeostasis in adulthood. NEW FINDINGS: What is the central question of this study? In pregnant women, sleep apnoea increases the risk of disease for the offspring at various life stages. Given that gestational stress disrupts the programming of the stress pathways, we determined whether exposing female rats to gestational intermittent hypoxia (GIH) activates hypothalamic neurons regulating the stress response in adult rats. What is the main finding and its importance? Using FosB immunolabelling as a marker of marker of neuronal activation, we showed that GIH augmented basal activation of the paraventricular nucleus of the hypothalamus in males, but not females. Disruption of the stress pathways is a new hypothesis to explain the persistent and sex-specific impacts of GIH on offspring health.

Effect of High-Fructose Diet-Induced Metabolic Syndrome on the Pituitary-Gonadal Axis in Male Rats

Plasma testosterone levels have been found to decrease in older insulin-resistant male patients. Both lower total testosterone levels and a higher incidence of metabolic syndrome have also been reported. The aim of this study was to investigate the effects of high-fructose diet-induced diabetes on both the testosterone release by Leydig cells and the activity of the hypothalamus-pituitary-gonadal (HPG) axis in male rats. Male rats were fed with either standard chow (control group) or a high-fructose diet (fructose-fed group) for 21 weeks. Hyperglycemia, hyperinsulinemia, and hypertension were observed in the fructose-fed group. Moreover, plasma testosterone and LH levels decreased in the fructose-fed group compared to the control group. Sperm motility was also reduced by 15% in the fructose-fed rats. In contrast, the basal release of testosterone from rat Leydig cells was not altered by fructose feeding. Moreover, in vitro studies showed that the testosterone release, in response to different stimulants, including forskolin (an adenylyl cyclase activator, 10^-5 M), 8-Br-cAMP (a permeable analog of cAMP, 10^-5 M), A23187 (a calcium ionophore, 10^-5 M), or 25-hydroxy-cholesterol (water-soluble cholesterol, 10^-5 M), did not significantly differ between the fructose-fed and control groups. Interestingly, the release of testosterone in response to human chorionic gonadotropin (hCG, 0.05 IU/mL) was enhanced by eightfold in the control group, but elevenfold in the fructose-fed group. LH receptor expression in rat Leydig cells was also increased. Moreover, LH secretion from the anterior pituitary was altered in the fructose diet-fed group. These results suggest that fructose diet-fed rats have lower plasma testosterone levels, which can lead to a higher sensitivity of hCG in Leydig cells.

Hypobaric hypoxia exposure alters transcriptome in mouse testis and impairs spermatogenesis in offspring

Male fertility relies on continual and robust spermatogenesis. Environmental hypoxia adversely affects reproductive health in humans and animal studies provide compelling evidences that hypoxia impairs spermatogenesis in directly exposed individuals. However, a detail examination of hypoxia induced changes in testicular gene expression is still lacking and spermatogenesis in offspring of hypoxia exposed animals of awaits investigation. In this study, a hypobaric hypoxic chamber was used to simulate hypoxic conditions in mice and effects of hypoxia on spermatogenesis, fertility and testicular gene expression were evaluated. The results showed that hypoxia exposure reduced the number of undifferentiated spermatogonia but did not change the regenerative capacity of spermatogonial stem cells (SSCs) after transplantation. Hypoxia significantly increased the percent of abnormal sperm and these defects were recovered 2 months after returning to the normoxia. Transcriptome analysis of testicular tissues from control and hypoxia treated animals revealed that 766 genes were up-regulated and 965 genes were down-regulated. Surprisingly, expressions of genes that regulate epigenetic modifications were altered, indicating hypoxia-induced damage to spermatogenesis may be intergenerational. Indeed, animals that were sired by hypoxia exposed males exhibited impaired spermatogenesis. Together, these findings suggest that hypoxia exposure alters testicular gene expression and causes long-lasting damage to spermatogenesis.

Effects of Environmental and Pathological Hypoxia on Male Fertility

Male infertility is a widespread health problem affecting approximately 6%-8% of the male population, and hypoxia may be a causative factor. In mammals, two types of hypoxia are known, including environmental and pathological hypoxia. Studies looking at the effects of hypoxia on male infertility have linked both types of hypoxia to poor sperm quality and pregnancy outcomes. Hypoxia damages testicular seminiferous tubule directly, leading to the disorder of seminiferous epithelium and shedding of spermatogenic cells. Hypoxia can also disrupt the balance between oxidative phosphorylation and glycolysis of spermatogenic cells, resulting in impaired self-renewal and differentiation of spermatogonia, and failure of meiosis. In addition, hypoxia disrupts the secretion of reproductive hormones, causing spermatogenic arrest and erectile dysfunction. The possible mechanisms involved in hypoxia on male reproductive toxicity mainly include excessive ROS mediated oxidative stress, HIF-1α mediated germ cell apoptosis and proliferation inhibition, systematic inflammation and epigenetic changes. In this review, we discuss the correlations between hypoxia and male infertility based on epidemiological, clinical and animal studies and enumerate the hypoxic factors causing male infertility in detail. Demonstration of the causal association between hypoxia and male infertility will provide more options for the treatment of male infertility.

Obstructive Sleep Apnea Is Associated With Low Testosterone Levels in Severely Obese Men

Background

Disrupted sleep affects cardio-metabolic and reproductive health. Obstructive sleep apnea syndrome represents a major complication of obesity and has been associated with gonadal axis activity changes and lower serum testosterone concentration in men. However, there is no consistent opinion on the effect of obstructive sleep apnea on testosterone levels in men.

Objective

The aim of this study was to determine the influence of obstructive sleep apnea on total and free testosterone levels in severely obese men.

Materials and methods

The study included 104 severely obese (Body Mass Index (BMI) ≥ 35 kg/m2) men, aged 20 to 60, who underwent anthropometric, blood pressure, fasting plasma glucose, lipid profile, and sex hormone measurements. All participants were subjected to polysomnography. According to apnea-hypopnea index (AHI) patients were divided into 3 groups: <15 (n = 20), 15 - 29.9 (n = 17) and ≥ 30 (n = 67).

Results

There was a significant difference between AHI groups in age (29.1 ± 7.2, 43.2 ± 13.2, 45.2 ± 10.2 years; p < 0.001), BMI (42.8 ± 5.9, 43.2 ± 5.9, 47.1 ± 7.8 kg/m2; p = 0.023), the prevalence of metabolic syndrome (MetS) (55%, 82.4%, 83.6%, p = 0.017), continuous metabolic syndrome score (siMS) (4.01 ± 1.21, 3.42 ± 0.80, 3.94 ± 1.81, 4.20 ± 1.07; p = 0.038), total testosterone (TT) (16.6 ± 6.1, 15.2 ± 5.3, 11.3 ± 4.44 nmol/l; p < 0.001) and free testosterone (FT) levels (440.4 ± 160.8, 389.6 ± 162.5, 294.5 ± 107.0 pmol/l; p < 0.001). TT level was in a significant negative correlation with AHI, oxygen desaturation index (ODI), BMI, MetS and siMS. Also, FT was in a significant negative correlation with AHI, ODI, BMI, age, MetS and siMS. The multiple regression analysis revealed that both AHI and ODI were in significant correlation with TT and FT after adjustment for age, BMI, siMS score and MetS components.

Conclusion

Obstructive sleep apnea is associated with low TT and FT levels in severely obese men.