Effects of Osteocalcin on Synthesis of Testosterone and INSL3 during Adult Leydig Cell Differentiation

In vitro effects of uncarboxylated osteocalcin on buffalo Leydig cell steroidogenesis

Uncarboxylated osteocalcin (UcOCN), a bone derived circulating protein, has been demonstrated to influence steroidogenesis in testicular Leydig cells of murine and human species. However, the role of UcOCN in testosterone biosynthesis remains unexplored in domestic animals. The present study aimed to investigate the impact of UcOCN on the expressions of steroidogenic genes (HSD3β1, HSD3β6, CYP17A1, CYP11A1), testosterone production and GPRC6A receptor localization in buffalo Leydig cells. Leydig cells from the testes of adult Murrah buffalo were isolated, with an average cell count and viability after digestion and Percoll enrichment of 1.43 × 106 cells/g of testes and 78.5%, respectively. Immunophenotyping of Percoll-enriched cell suspension by flow cytometry showed populations of Leydig cells ranging between 69 and 73.9%. Immunostaining confirmed the presence of GPRC6A receptors and CYP11A1 positive Leydig cells. When these cells were cultured and incubated with varying levels of UcOCN (6, 12, 24, and 48 ng/ml) and LH, there was a significant (P < 0.01) increase in testosterone production and up-regulation (P < 0.05) of CYP11A1, CYP17A1, HSD3β1 and HSD3β6 gene expression. In summary, the present study underscored the effects of UcOCN on testosterone biosynthesis, expression of crucial steroidogenic genes and interaction with GPRC6A receptors in buffalo Leydig cells, emphasizing its potential implications in andrology.

Total osteocalcin levels are independently associated with worse testicular function and a higher degree of hypothalamic-pituitary-gonadal axis activation in Klinefelter syndrome

PURPOSE

The role of osteocalcin (OCN) in pubertal development, male hypogonadism, and the effect of testosterone (Te) replacement therapy (TRT) remains unclear. We aimed to investigate the total OCN (tOCN) concentrations in male patients with Klinefelter syndrome (KS), a model of adult hypergonadotropic hypogonadism.

METHODS

This retrospective longitudinal study investigated 254 male patients with KS (47,XXY) between 2007 and 2021 at an academic referral center, categorized as (1) prepubertal, (2) pubertal, and (3) adults. All prepubertal patients were Te-naïve. Adult patients were subcategorized as (1) eugonadal, (2) hypogonadal, and (3) receiving TRT. We also analyzed 18 adult patients with available tOCN levels before and 3 months after TRT commencement.

RESULTS

The tOCN levels varied throughout the lifespan according to pubertal status, were highest in eugonadal and significantly lower in TRT subjects, correlated with both LH (p = 0.017) and FSH levels (p = 0.004) in adults, and significantly declined after 3 months of TRT (p = 0.006) in the adult KS cohort. HPG-axis hormones levels demonstrated no correlation in prepubertal boys. Adjustment for age and body mass index confirmed previous results and revealed significant inverse correlations with total Te (p = 0.004), calculated free Te (p = 0.016), the Te/LH (p = 0.010), and calculated free Te/LH ratios (p = 0.031).

CONCLUSION

In KS, a model of male hypergonadotropic hypogonadism, tOCN levels were not associated with gonadal function during normal prepuberty and pubertal development but were associated with worse testicular function and a higher degree of HPG stimulation in adults. TRT acutely reduced tOCN levels in adults.

Investigation of miR-26b and miR-27b expressions and the effect of quercetin on fibrosis in experimental pulmonary fibrosis

In this study, investigation of the effects of Quercetin on Bleomycin-induced pulmonary fibrosis and fibrosis-associated molecules miR-26b and miR-27b was aimed. Control group was given 10% saline on the 0th day, and saline was administered for 21 days starting from the 8th day. Group 2 was given 50 mg/kg Quercetin for 21 days starting from the 8th day. Group 3 was given 10 mg/kg Bleomycin Sulfate on day 0, and sacrificed on the 22nd and 29th day. Group 4 was given 10 mg/kg Bleomycin Sulfate on the 0th day, and was given 50 mg/kg Quercetin for 14 days, and 21 days starting from day 8. Lung tissues were examined using light and electron microscopic, immunohistochemical and molecular biological methods. Injury groups revealed impaired alveolar structure, collagen accumulation and increased inflammatory cells in interalveolar septum. Fibrotic response was decreased and the alveolar structure was improved with Quercetin treatment. α-SMA expressions were higher in the injury groups, but lower in the treatment groups compared to the injury groups. E-cadherin expressions were decreased in the injury groups and showed stronger immunoreactivity in the treatment groups compared to the injury groups. miR-26b and miR-27b expressions were lower in the injury groups than the control groups, and higher in the treatment groups than the injury groups. Quercetin can be considered as a new treatment agent in the idiopathic pulmonary fibrosis, since it increases the expression levels of miR-26b and miR-27b which decrease in fibrosis, and has therapeutic effects on the histopathological changes.

High Salt Diet Impairs Male Fertility in Mice via Modulating the Skeletal Homeostasis

Male reproductive functions and bone health are both adversely affected by the high salt diet (HSD). Nevertheless, the underlying mechanism via which it alters the sperm function remains largely unknown. This study examines the mechanism by which HSD affects male fertility by impairing bone health. For investigating the same, male BALB/c mice were categorized into three groups-HSD group (fed with 4% NaCl), a low salt diet (LSD) group (fed with 0.4% NaCl), and a control group (fed with a normal diet) for 6 weeks and thereafter assessed for various sperm parameters, bone turnover markers, and testosterone levels. Furthermore, the quantitative assessment of testosterone biosynthesis enzymes was performed. Interestingly, we observed that mice fed with HSD showed significant alterations in sperm parameters-motility, count, and vitality, including morphological changes compared to both the LSD and the control groups. In addition, serum analysis showed an increase in bone resorption markers and a decrease in bone formation markers in the HSD group (p < 0.05). Further, HSD caused a decrease in the testosterone level and mRNA expression of testosterone biosynthesis enzymes. Importantly, a significant decrease in bone formation marker osteocalcin (OC) was observed to coincide with the dip in testosterone level in the HSD group. Given that OC plays a key role in maintaining male fertility, the above findings suggest that a decrease in OC levels may affect the testosterone biosynthesis pathway, reducing testosterone hormone secretion and thereby resulting in decreased spermatogenesis. The study for the first time delineates and bridges the mechanism of HSD-mediated bone loss (results in a deficiency of OC) with decreased testosterone biosynthesis and thus impaired male fertility.

Rifaximin Protects against Malathion-Induced Rat Testicular Toxicity: A Possible Clue on Modulating Gut Microbiome and Inhibition of Oxidative Stress by Mitophagy

Testicular dysfunction is caused by chronic exposure to environmental pollution, such as malathion, which causes oxidative stress, promoting cell damage. Autophagy is a key cellular process for eliminating malfunctioning organelles, such as the mitochondria (mitophagy), an eminent source of reactive oxygen species (ROS). Autophagy is crucial for protection against testicular damage. Rifaximin (RFX) is a non-absorbable antibiotic that can reshape the gut microbiome, making it effective in different gastrointestinal disorders. Interestingly, the gut microbiome produces short chain fatty acids (SCFAs) in the circulation, which act as signal molecules to regulate the autophagy. In this study, we investigated the regulatory effects of RFX on gut microbiota and its circulating metabolites SCFA and linked them with the autophagy in testicular tissues in response to malathion administration. Moreover, we divided the groups of rats that used malathion and RFX into a two-week group to investigate the mitophagy process and a four-week group to study mitochondriogenesis. The current study revealed that after two weeks of cotreatment with RFX, apoptosis was inhibited, oxidative stress was improved, and autophagy was induced. More specifically, PINK1 was overexpressed, identifying mitophagy activation. After four weeks of cotreatment with RFX, there was an increase in acetate and propionate-producing microflora, as well as the circulating levels of SCFAs. In accordance with this, the expression of PGC-1α, a downstream to SCFAs action on their receptors, was activated. PGC-1α is an upstream activator of mitophagy and mitochondriogenesis. In this sense, the protein expression of TFAM, which regulates the mitochondrial genome, was upregulated along with a significant decrease in apoptosis and oxidative stress. Conclusion: we found that RFX has a positive regulatory effect on mitophagy and mitochondria biogenesis, which could explain the novel role played by RFX in preventing the adverse effects of malathion on testicular tissue.

The effect of Vitamin D on testosterone and uncarboxylated osteocalcin levels in aged male rats

There is a well-established complex interaction between vitamin D metabolism and bone and gonad functions. In this study, we aimed to investigate the potential effects of vitamin D therapy on testosterone and osteocalcin (OC) levels in aged male rats. Forty-five adult male rats were divided into three groups in this study. Unlike the control group, the two experimental groups received 50 IU/kg/day and 100 IU/kg/day of vitamin D₃ (cholecalciferol), respectively, for a 4-week period using the gavage method. Testicular tissue and blood samples from rats were collected under general anesthesia at the end of the 4-week period. Testicular tissue samples were examined using light and electron microscopy. Additionally, serum testosterone and OC levels were measured in blood samples. The 50 IU/kg dose of cholecalciferol increased testosterone and OC levels, which were lower than normal due to aging, and regulated the organization of the seminiferous tubule epithelium and interstitium more effectively than the 100 IU/kg dose of cholecalciferol. Male fertility functions and bone health, which degrade due to aging, were increased due to the use of exogenous vitamin D, although the higher dose was not associated with more effective results.

Distribution of Aquaporin-4 channels in hippocampus and prefrontal cortex in mk-801-treated balb/c mice

Functional disorders of the glymphatic system and Aquaporin-4 (AQP-4) channels take part in the pathophysiology of neurodegenerative disease. The aim of this study was to describe the distribution of AQP-4 channels in the prefrontal cortex and hippocampus in a mouse model of NMDA receptor blocking agent-induced schizophrenia-like behavior model. NMDA receptor antagonist MK-801 was used to produce the experimental schizophrenia model. MK-801 injections were administered for eleven days to Balb/c mice intraperitoneally. Beginning from the sixth day of injection, the spatial learning and memory of the mice were tested by the Morris water maze (MWM) task. A group of mice was injected with MK-801 for ten days without the MWM task. Hippocampus and prefrontal specimens were collected from this group. Tissue samples were stained immunohistochemically and AQP-4 channels were examined by electron microscope. Time to find the platform was significantly longer at MK-801 injected group than the control group at the MWM task. Also, time spent at the target quadrant by the MK-801 group was shorter compared to the control group. AQP-4 expression increased significantly at MK-801 group glial cells, neuronal perikaryon, perineuronal and pericapillary spaces. In the MK-801 group, there was remarkable damage in neurons and glial cells. Increased AQP-4 channel expression and neurodegeneration at the MK-801 group induced with schizophrenia-like behavior model. MK-801 induced NMDA receptor blockade causes a decline in cognitive and memory functions. Increased AQP-4 expression at the prefrontal cortex and hippocampus to elicit and transport products of synaptic neurotransmitters and end metabolites is suggested.

Are there sex differences in the reaction of undercarboxylated osteocalcin to hypoglycemia?

There has been increasing evidence in recent years for the hypothesis of bones as endocrine organs. Osteocalcin, long considered just a marker of new bone formation, is now seen as the first hormone produced by bones, and seems to be associated with regulating glucose metabolism and reproduction. The aim of this work was to monitor changes of osteocalcin in reaction to hypoglycemia, and determine if there are differences in such reactions between the sexes. The study included 61 healthy probands with physiological calciophosphate metabolism (30 men and 31 women). We applied to each of them an insulin tolerance test, and then monitored levels of undercarboxylated osteocalcin and reactions to hypoglycemia at regular time intervals. We found differences in the reaction to hypoglycemia between the sexes. In men there was a significant decline in undercarboxylated osteocalcin between the 30 and 40 min (p<0.0015), which reflects a reaction to a glycemic decline between 25-30 min, followed by reversal. Low undercarboxylated osteocalcin in men lasted up to 90 min, after which they returned to levels before the test. In women we did not find any significant changes in undercarboxylated osteocalcin levels. Changes in undercarboxylated osteocalcin induced by hypoglycemia indicate a relationship between bones and glucose metabolism. There was an interesting difference between the sexes. However, a definitive conclusion about the role of osteocalcin in human metabolism will require numerous future studies.

Skeletal endocrinology: where evolutionary advantage meets disease

The regulation of whole-body homeostasis by the skeleton is mediated by its capacity to secrete endocrine signaling molecules. Although bone-derived hormones confer several adaptive benefits, their physiological functions also involve trade-offs, thus eventually contributing to disease. In this manuscript, we discuss the origins and functions of two of the best-studied skeletal mediators, fibroblast growth factor 23 and osteocalcin, in an evolutionary context. Moreover, we provide a theoretical framework seeking to explain the broad involvement of these two hormones in amniote physiology as well as their potential to fuel the development and progression of diseases. Vice versa, we outline which perturbations might be amenable to manipulation of these systems and discuss limitations and ongoing challenges in skeletal endocrine research. Finally, we summarize unresolved questions and potential future studies in this thriving field.

Vitamin K in Vertebrates' Reproduction: Further Puzzling Pieces of Evidence from Teleost Fish Species

Vitamin K (VK) is a fat-soluble vitamin that vertebrates have to acquire from the diet, since they are not able to de novo synthesize it. VK has been historically known to be required for the control of blood coagulation, and more recently, bone development and homeostasis. Our understanding of the VK metabolism and the VK-related molecular pathways has been also increased, and the two main VK-related pathways-the pregnane X receptor (PXR) transactivation and the co-factor role on the γ-glutamyl carboxylation of the VK dependent proteins-have been thoroughly investigated during the last decades. Although several studies evidenced how VK may have a broader VK biological function than previously thought, including the reproduction, little is known about the specific molecular pathways. In vertebrates, sex differentiation and gametogenesis are tightly regulated processes through a highly complex molecular, cellular and tissue crosstalk. Here, VK metabolism and related pathways, as well as how gametogenesis might be impacted by VK nutritional status, will be reviewed. Critical knowledge gaps and future perspectives on how the different VK-related pathways come into play on vertebrate's reproduction will be identified and proposed. The present review will pave the research progress to warrant a successful reproductive status through VK nutritional interventions as well as towards the establishment of reliable biomarkers for determining proper nutritional VK status in vertebrates.