Flutamide Alters the Expression of Chemerin, Apelin, and Vaspin and Their Respective Receptors in the Testes of Adult Rats

Obesity, White Adipose Tissue, and Adipokines Signaling in Male Reproduction

Currently, obesity is a global pandemic characterized by systemic metabolic complications that negatively impact several organs, including white adipose tissue (WAT) and the tissues of the male reproductive system. Since the discovery of leptin in 1994, WAT has been recognized as a dynamic endocrine organ for secreting a series of molecules with hormonal functions, collectively called adipokines. The link between obesity, WAT, adipokines, and the male reproductive system is direct and little explored. With changes in nutritional status, WAT undergoes morphofunctional changes, and the secretion of adipokines is altered, negatively impacting reproductive mechanisms, including steroidogenesis and spermatogenesis. In this review, we address in an updated way the structural and functional characteristics of WAT as well as the link between obesity and changes in the signaling pathways of the adipokines leptin, adiponectin, resistin, visfatin, apelin, chemerin, omentin-1, vaspin, and asprosin in male reproduction. Understanding the relationship between obesity, these adipokines, and reproductive dysfunction can contribute to new strategies for the treatment of subfertility and male infertility.

Novel insights into the mechanisms of seasonal cyclicity of testicles by proteomics and transcriptomics analyses in goose breeder lines

Spermatogenesis is a crucial indicator of geese reproduction performance and production. The testis is the main organ responsible for sperm production, and the egg-laying cycle in geese is a complex physiological process that demands precise orchestration of hormonal cues and cellular events within the testes, however, the seasonal changes in the transcriptomic and proteomic profiles of goose testicles remain unclear. To explore various aspects of the mechanisms of the seasonal cyclicity of testicles in different goose breeds, in this study, we used an integrative transcriptomic and proteomic approach to screen the key genes and proteins in the testes of 2 goose males, the Hungarian white goose and the Wanxi white goose, at 3 different periods of the laying cycle: beginning of laying cycle (BLC), peak of laying cycle (PLC), and end of laying cycle (ELC). The results showed that a total of 9,273 differentially expressed genes and 4,543 differentially expressed proteins were identified in the geese testicles among the comparison groups. The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis suggested that the DEGs, in the comparison groups, were mainly enrichment in metabolic pathways, neuroactive ligand-receptor interaction, cyctokine-cyctokine receptor interaction, calcium signaling pathway, apelin signaling pathway, ether lipid metabolism, cysteine, and methionine metabolism. While the DEPs, in the 3 comparison groups, were mainly involved in the ribosome, metabolic pathways, carbon metabolism, proteasome, endocytosis, lysosome, regulation of actin cytoskeleton, oxidative phosphorylation, nucleocytoplasmic transport, and tight junction. The protein-protein interaction network analysis (PPI) indicated that selected DEPs, such as CHD1L, RAB18, FANCM, TAF5, TSC1/2, PHLDB2, DNAJA2, NCOA5, DEPTOR, TJP1, and RAPGEF2, were highly associated with male reproductive regulation. Further, the expression trends of 4 identified DEGs were validated by qRT-PCR. In conclusion, this work offers a new perspective on comprehending the molecular mechanisms and pathways involved in the seasonal cyclicity of testicles in the Hungarian white goose and the Wanxi white goose, as well as contributing to improving goose reproductive performance.

Comparative expression and localization of visfatin, chemerin, and chemerin receptor proteins in a heat-stressed mouse testis

The adipokines, visfatin, chemerin, and its receptor are expressed in the testis. It has also been shown that heat-stress alters the secretion and expression of other adipokines. Testicular heat-stress is now well known to cause the impairment in the testis. It has also been documented that heat-stress changes the expression of genes and proteins in the testis. To the best of our knowledge, the expression and localization of visfatin chemerin and its receptor have not been investigated in the heat-stressed testis. Therefore, the present study has investigated the expression and localization of these proteins in the heat-stressed testis. The expression of visfatin and chemerin and receptor exhibits a differential repossess against the heat stress. Visfatin expression was up-regulated while chemerin and chemerin receptor was down-regulated in the heat-stressed testis as shown by western blot analysis. The immunolocalization of visfatin and chemerin showed increased abundance in the seminiferous tubules of heat-stressed mice testis. Furthermore, abundance of visfatin, chemerin, and its receptor showed a decrease in abundance in the Leydig cells of heat-stressed testis. The decreased abundance of these proteins in the Leydig cells coincides with decreased 3β-HSD immunostaining along with decreased testosterone levels. These results suggest that heat-stress might decrease testosterone secretion by modulating visfatin and chemerin in the Leydig cells. The increased abundance of visfatin and chemerin in the primary spermatocytes, round spermatid, and multinucleated germ cells also coincides with increased immunostaining of active caspase-3. Moreover, expression of Bcl-2 was down-regulated, and expression of active caspase-3 and HSP70 were up-regulated along with increased oxidative stress in the heat-stressed testis, suggesting stimulated apoptosis. In conclusion, our results showed that visfatin, chemerin, and its receptor are differentially expressed in the testis under heat-stress and within the testis also it might differentially regulate testosterone biosynthesis in the Leydig cells and apoptosis in the seminiferous tubules.

Androgens and Notch signaling cooperate in seminiferous epithelium to regulate genes related to germ cell development and apoptosis

It was reported previously that in adult males disruption of both androgen and Notch signaling impairs spermatid development and germ cell survival in rodent seminiferous epithelium. To explain the molecular mechanisms of these effects, we focused on the interaction between Notch signaling and androgen receptor (AR) in Sertoli cells and investigate its role in the control of proteins involved in apical ectoplasmic specializations, actin remodeling during spermiogenesis, and induction of germ cell apoptosis. First, it was revealed that in rat testicular explants ex vivo both testosterone and Notch signaling modulate AR expression and cooperate in the regulation of spermiogenesis-related genes (Nectin2, Afdn, Arp2, Eps8) and apoptosis-related genes (Fasl, Fas, Bax, Bcl2). Further, altered expression of these genes was found following exposure of Sertoli cells (TM4 cell line) and germ cells (GC-2 cell line) to ligands for Notch receptors (Delta-like1, Delta-like4, and Jagged1) and/or Notch pathway inhibition. Finally, direct interactions of Notch effector, Hairy/enhancer-of-split related with YRPW motif protein 1, and the promoter of Ar gene or AR protein were revealed in TM4 Sertoli cells. In conclusion, Notch pathway activity in Sertoli and germ cells regulates genes related to germ cell development and apoptosis acting both directly and indirectly by influencing androgen signaling in Sertoli cells.

Apelin receptor antagonist (ML221) treatment has a stimulatory effect on the testicular proliferation, antioxidants system and steroidogenesis in adult mice

The expression of apelin and its receptor (APJ) has been shown in the hypothalamus-pituitary-testicular axis. It has also been suggested apelin and APJ are neuropeptide factors. The presence of apelin and APJ in the seminiferous tubules and interstitium might be predicted to act as a local regulator of testicular activity, although the function is not well known in the mice testis. In the present study, we have investigated the effects of APJ, antagonist, ML221 on the gonadotropin levels, testicular steroidogenesis, proliferation, apoptosis and antioxidant system. Our results showed that inhibition of APJ by ML221 increased the sperm concentration, circulating testosterone, FSH, LH levels and intra-testicular testosterone concentration. Furthermore, ML221 treatment stimulates the germ cell proliferation and antioxidant system in the testis. The expression of BCL2, AR was up-regulated whereas, the expression of BAX and active caspase3 was down-regulated after ML221 treatment. Immunohistocehmical analysis of AR also showed increase abundance in the spermatogonia, primary spermatocytes and Leydig cells of 150 μg/kg dose group. These findings suggest that in adult testis, the apelin system might have an inhibitory role in germ cell proliferation and a stimulatory role in apoptosis. It might also be suggested that the apelin system could be involved in the disposal mechanism for damaged germ cells during spermatogenesis via the down-regulation of AR.

Apelin is found in human sperm and testis and is raised in inflammatory pathological conditions

Apelin/APJ receptor (R) is involved in many oxidative stress-induced pathological conditions. Since this system is not yet explored in male reproduction, we studied apelin/APJ-R in human semen and testis. Semen of 41 infertile patients with varicocele, genitourinary infections, unexplained infertility and 12 fertile men was analysed (WHO guidelines, 2021). Apelin was quantified by ELISA in seminal fluid and spermatozoa, interleukin (IL)-1β in seminal fluid. Apelin/APJ-R were immunolocalized in spermatozoa and testis. Apelin was present in spermatozoa and its levels were negatively correlated with normal sperm morphology% (r = -0.857; p < 0.001), and positively with IL-1β levels (r = 0.455; p < 0.001). Apelin and IL-1β concentrations were increased in patients' samples with varicocele (apelin p < 0.01; IL-1β p < 0.05) and infections (apelin p < 0.01; IL-1β p < 0.001). By logistic regression analysis, apelin (OR 1.310; p = 0.011) and IL-1β (OR 1.572; p = 0.005) were predictors of inflammatory diseases (varicocele, infections). Apelin and APJ-R immunofluorescence labels were weak in sperm tail of fertile men and intense along tail, cytoplasmic residues and post-acrosomal sheath of sperm from infertile men. In testis, apelin and APJ-R labels were evident in Leydig cells and weak inside the seminiferous tubule. Apelin/APJ-R system is present in human spermatozoa and testicular tissue and probably involved in human fertility.

The role of apelinergic system in metabolism and reproductive system in normal and pathological conditions: an overview

Lifestyle changes have made metabolic disorders as one of the major threats to life. Growing evidence demonstrates that obesity and diabetes disrupt the reproductive system by affecting the gonads and the hypothalamus-pituitary-gonadal (HPG) axis. Apelin, an adipocytokine, and its receptor (APJ) are broadly expressed in the hypothalamus nuclei, such as paraventricular and supraoptic, where gonadotropin-releasing hormone (GnRH) is released, and all three lobes of the pituitary, indicating that apelin is involved in the control of reproductive function. Moreover, apelin affects food intake, insulin sensitivity, fluid homeostasis, and glucose and lipid metabolisms. This review outlined the physiological effects of the apelinergic system, the relationship between apelin and metabolic disorders such as diabetes and obesity, as well as the effect of apelin on the reproductive system in both gender. The apelin-APJ system can be considered a potential therapeutic target in the management of obesity-associated metabolic dysfunction and reproductive disorders.

Presence and localization of apelin and its cognate receptor in canine testes using immunohistochemical and RT-PCR techniques

Apelin, a member of the adipokine family, is a novel endogenous peptide which regulates the male reproductive system of mammals by interacting with a specific receptor. Recent studies have highlighted that apelin may play a role in the regulation of reproduction by reducing testosterone production and inhibiting LH secretion. To the best of our knowledge, there is no available data on the presence of the apelin and its receptor in canine testes. Therefore, the aim of this study was to reveal the presence of apelin and evaluate its distribution in the canine testes using immunohistochemical and RT-PCR techniques. For this purpose, five fertile and healthy male dogs were subjected to elective orchiectomy. The immunohistochemical reaction revealed the presence of apelin and its receptor in the canine testes. Apelin was localized in spermatids and spermatozoa with a positive signal in the "acrosomal bodies". As regards the apelin receptor, a positive immunoreaction was detected in the cytoplasm of the cells localized near to the basal membrane of the seminiferous tubules and in the cytoplasm of Leydig cells. The RT-PCR analysis showed the presence of transcripts for apelin and apelin receptor in all of the samples under study. A 35kDa band confirmed apelin receptor protein expression in all of the samples analysed. In conclusion, the paracrine and endocrine role of apelin and its cognate receptor on male reproduction reported in humans and laboratory animals could also be hypothesized in dogs.

Chemerin: A Functional Adipokine in Reproductive Health and Diseases

As a multifaceted adipokine, chemerin has been found to perform functions vital for immunity, adiposity, and metabolism through its three known receptors (chemokine-like receptor 1, CMKLR1; G-protein-coupled receptor 1, GPR1; C-C motif chemokine receptor-like 2, CCRL2). Chemerin and the cognate receptors are also expressed in the hypothalamus, pituitary gland, testis, ovary, and placenta. Accumulating studies suggest that chemerin participates in normal reproduction and underlies the pathological mechanisms of certain reproductive system diseases, including polycystic ovary syndrome (PCOS), preeclampsia, and breast cancer. Herein, we present a comprehensive review of the roles of the chemerin system in multiple reproductive processes and human reproductive diseases, with a brief discussion and perspectives on future clinical applications.

Melatonin inhibits testosterone synthesis in Roosters Leydig cells by regulating lipolysis of lipid droplets

Leydig cells are important component of testis cells, which can synthesize testosterone with free cholesterol derived from lipid droplets (LDs). It is well known that melatonin could regulate synthesis of testosterone. However, it is still unclear whether melatonin participates in the synthesis of testosterone by regulating the lipolysis of LDs in Leydig cells. The purpose of this study was to elucidate the effect of melatonin on synthesis of testosterone in roosters Leydig cells by regulating lipolysis of LDs. The results showed that melatonin decreased synthesis of testosterone and intracellular free cholesterol in roosters Leydig cells. Exogenous addition of 22-OH-Cholesterol counteracted the inhibitory effect of melatonin on synthesis of testosterone. Furthermore, melatonin increased the LDs content and expression of perilipin 1 (PLIN1), and decreased expression of hormone-sensitive lipase (HSL) and triacylglycerol hydrolase (ATGL) in roosters Leydig cells. In addition, silencing PLIN1 reversed the inhibitory effect of melatonin on synthesis of testosterone in roosters Leydig cells by increasing free cholesterol content and expression of HSL and ATGL, and decreasing the lipid droplet content. Activation of cAMP/PKA pathway by using the pathway activators Forskolin and 8-Bromo-cAMP attenuated the inhibitory effect of melatonin on synthesis of testosterone accompanied by increasing level of free cholesterol content and expression of HSL and ATGL, and decreasing level of lipid droplet content and expression of PLIN1 in roosters Leydig cells. These results suggested that melatonin could inhibit the synthesis of testosterone in roosters Leydig cells by reducing the content of intracellular free cholesterol in which expression of PLIN1 and cAMP/PKA pathway were inhibited to reduce the lipolysis of LDs.

Review: Vaspin (SERPINA12) Expression and Function in Endocrine Cells

Proper functioning of the body depends on hormonal homeostasis. White adipose tissue is now known as an endocrine organ due to the secretion of multiple molecules called adipokines. These proteins exert direct effects on whole body functions, including lipid metabolism, angiogenesis, inflammation, and reproduction, whereas changes in their level are linked with pathological events, such as infertility, diabetes, and increased food intake. Vaspin-visceral adipose tissue-derived serine protease inhibitor, or SERPINA12 according to serpin nomenclature, is an adipokine discovered in 2005 that is connected to the development of insulin resistance, obesity, and inflammation. A significantly higher amount of vaspin was observed in obese patients. The objective of this review was to summarize the latest findings about vaspin expression and action in endocrine tissues, such as the hypothalamus, pituitary gland, adipose tissue, thyroid, ovary, placenta, and testis, as well as discuss the link between vaspin and pathologies connected with hormonal imbalance.

Flutamide treatment reveals a relationship between steroidogenic activity of Leydig cells and ultrastructure of their mitochondria

Our present knowledge on interrelation between morphology/ultrastructure of mitochondria of the Leydig cell and its steroidogenic function is far from satisfactory and needs additional studies. Here, we analyzed the effects of blockade of androgen receptor, triggered by exposure to flutamide, on the expression of steroidogenic proteins (1) and ultrastructure of Leydig cells' constituents (2). We demonstrated that increase in the expression level of steroidogenic (StAR, CYP11A1, 3β-HSD, and CYP19A1) proteins (and respective mRNAs) in rat testicular tissue as well as elevation of intratesticular sex steroid hormone (testosterone and estradiol) levels observed in treated animals correspond well to morphological alterations of the Leydig cell ultrastructure. Most importantly, up-regulation of steroidogenic proteins' expression apparently correlates with considerable multiplication of Leydig cell mitochondria and subsequent formation of local mitochondrial networks. Interestingly, we showed also that the above-mentioned processes were associated with elevated transcription of Drp1 and Mfn2 genes, encoding proteins implicated in mitochondrial dynamics. Collectively, our studies emphasize the importance of mitochondrial homeostasis to the steroidogenic function of Leydig cells.

Metabolic Syndrome: the Influence of Adipokines on the L-Arginine-NO Synthase-Nitric Oxide Signaling Pathway

Metabolic syndrome includes the following symptoms: obesity, hyperlipidemia, hypertension, insulin resistance, and cardiovascular disease. The purpose of this review is to elucidate the role of adipokines in the regulation of the L-arginine-NO-synthas-NO signaling pathway in the pathogenesis of metabolic syndrome. The main questions raised in the review are: how adipokine secretion changes, how the level of their receptors is regulated, and which signaling pathways are involved in the transmission of adipokine signals when coupled to the L-arginine-NO-synthase-NO signaling cascade. Adipokines are peptide hormones that transmit a signal from adipose tissue to targets in the brain, blood vessels, liver, pancreas, muscles, and other tissues. Some adipokines have anti-inflammatory and insulin-sensitive effects: adiponectin, omentin, adipolin, chemerin, progranulin. Others have the negative inflammatory effect in the development ofmetabolic syndrome: visfatin, vaspin, apelin. Adipokines primarily regulate the expression and activity of endothelial NO-synthase. They either activate an enzyme involving 5-AMP protein kinase or Akt kinase, increasing its activity and synthesis of NO in the tissues of healthy patients: adiponectin, adipolin, omentin, or inhibit the activity of eNOS, which leads to a decrease in NO-synthase and suppression of mRNA bioavailability: vaspin, visfatin, apelin in metabolic syndrome, and a decrease in its activity leads to dissociation and endothelial dysfunction. It should be noted that the bioavailability of NO formed by NO-synthase is affected at many levels, including: the expression ofNO-synthase mRNA and its protein; the concentration of L-arginine; the level of cofactors of the reaction; and to detect the maximum activity of endothelial NO-synthase, dimerization of the enzyme is required, posttranslational modifications are important, in particular, phosphorylation of endothelial NO-synthase by serine 1177 with the participation of 5-AMP protein kinase, Akt kinase and other kinases. It should be noted that the participation of adiponectin, omentin, and kemerin in the regulation of the L-arginine-NO-synthase-NO cascade in metabolic syndrom opens up certain opportunities for the development of new approaches for the correction of disorders observed in this disease. The review analyzes the results of research searching in PubMed databases, starting from 2001 and up to 2020 using keywords and adipokine names, more than half of the references of the last 5 years. 

Expression and localization of apelin and its receptor in the testes of diabetic mice and its possible role in steroidogenesis

Type 1 diabetes mellitus (T1DM) is a metabolic disorder with severe hyperglycemia, one of the complications of which is testicular dysfunctions, androgen deficiency and decreased male fertility. In the diabetic testes, the expression and signaling pathways of leptin and a number of other adipokines are significantly changed. However, there is no information on the localization and expression of adipokine, apelin and its receptor (APJ) in the diabetic testes, although there is information on the involvement of apelin in the regulation of reproductive functions. The aim of this study was to investigate the expression and localization of apelin and APJ in the testes of mice with streptozotocin-induced T1DM and to estimate the effects of agonist (apelin-13) and antagonist (ML221) of APJ on the testosterone production by diabetic testis explants in the in vitro conditions. We first detected the expression of apelin and its receptor in the mouse testes, and showed an increased intratesticular expression of apelin and APJ along with the reduced testosterone secretion in T1DM. Using imunohistochemical approach, we showed that apelin and APJ are localized in the Leydig and germ cells, and in diabetes, the amount of these proteins was significantly higher than in the control mice. The diabetic testes had a decrease in germ cell proliferation (the reduced PCNA and GCNA levels) and an increase in apoptosis (the increased active caspase-3 and decreased BCL2 levels). These results suggest an involvement of apelin and APJ in T1DM-induced testicular pathogenesis. Treatment of the cultured testis explants with ML221 significantly increased the testosterone secretion, whereas apelin-13 was ineffective. Thus, hyperapelinemia in the testes can significantly contribute to testicular pathogenesis in T1DM, and pharmacological inhibition of apelin receptors can improve testicular steroidogenesis.

Evaluation of maternal high-fat diet and Quercetin-3-O-rutinoside treatment on the reproductive profile of diet naïve male offspring

BACKGROUND

Male infertility and reproductive dysfunctions have become major global health problems. Although several causative factors have been attributed to this challenge, of importance are alterations in maternal-foetal environment, diet-induced transcriptional changes and dysregulation in chemical signaling via hypothalamic-gonadal axis.

AIM

The present study investigated the impact of maternal high-fat diet (HFD) consumption and the putative role of Quercetin-3-O-rutinoside on reproductive functions of male offspring rats at critical developmental stages with a quest to unravel the underpinned molecular changes.

MATERIALS AND METHODS

Fifty-six pregnant rats (previously fed normal diet ND) or 45% HFD) were maintained on supplemented chow (150 mg/kg QR) - ND/QR, HFD/QR throughout gestation. Subsequently, dams (n = 7) and offspring (n = 6) were sacrificed at post-natal day (PND) 21, 28 and 35, respectively, and the blood, placenta, hypothalamus (HT), and testicular samples were processed for molecular analysis of Gonadotropin-releasing hormone (GnRH), Luteinizing hormone (LH), testosterone, chemerin, chemokine-like receptor 1 (CMKLR1), tumour necrosis factor α (TNF-α), interleukin 1β (IL-1β) and nuclear factor kappa B (NF-κB).

KEY FINDINGS

We observed a significant decrease in GnRH level in the HFD group at PND21 and PND28 in male offspring and treatment with QR significantly reduced GnRH. There was a significant reduction in LH levels in the HFD group at PND 21 in the male offspring accompanied by a significant decrease in testosterone level at PND 28 and PND35 which appears to be age dependent. In the HT, Chemerin and CMKLR1 was significantly upregulated in the HFD group at PND 21 and PND 35 respectively while CMKLR1 was significantly downregulated in the HFD group of the placenta and testis at PND 21. TNF-α, IL-1β and NF-κB were also expressed in the placenta, HT and testis at PND 21.

SIGNIFICANCE

Male fertility is affected by maternal HFD consumption while chemerin, CMKLR1 and TNF-α, may play a significant role in male steroidogenesis. Treatment with QR had little or no ameliorative effect on HFD induced alterations in male reproductive functions.