Nicotinamide phosphoribosyltransferase production in human spermatozoa is influenced by maturation stage

Exogenous visfatin suppresses pituitary gonadotrophins and stimulates testosterone secretion in a male mouse

Visfatin expression has been shown in the testis and pituitary. However, the role of visfatin in the pituitary and testis axis is fragmentary. Furthermore, no study has shown the effects of visfatin on the pituitary gonadotrophins and testicular steroid hormonal secretions in a male mouse. The present study has investigated the effects of exogenous visfatin (most likely a state of hypervisfatinemia) on the gonadotrophins, testosterone, estradiol, androstenedione, and progesterone in a male mouse. The exogenous visfatin was given for 35 days, which covers one spermatogenic cycle. The circulating testosterone was elevated after visfatin treatment, along with down-regulation of AR and steroidogenic markers in the testis. However, the expression of CYP17 was up-regulated in visfatin-treated testis. Visfatin treatment also elevated apoptosis in the different germ cells of the testis. The levels of circulating LH and FSH were also suppressed after visfatin treatment. The immunolocalization of AR exhibited decreased abundance in the pituitary of visfatin-treated mice; thus, it can be suggested that pituitary gonadotrophins secretion might be suppressed by direct action of visfatin rather than via elevated testosterone. In conclusion, our results showed that exogenous visfatin suppresses gonadotrophins and stimulates testicular testosterone secretions in a differential manner. Visfatin has inhibitory effects on pituitary gonadotrophins secretion and stimulatory effects on testosterone secretion from the testis. Thus, conditions similar to hypervisfatinemia likely impair the release of hormones from the pituitary and testis.

Comparative transcriptome analysis of bull X- and Y-spermatozoa

Sex-sorted bovine semen is a major breakthrough in the dairy sector. The current flow cytometer-based technology for sex-sorting of bovine semen is proprietary, slow, expensive, and associated with lower conception rates. Therefore, developing alternative technologies is crucial for advancing milk production globally through use of sexed semen. However, lack of a comprehensive omics dataset hinders the ability to comprehend significant differences between the sorted sperm types and develop robust biomarkers for sex-sorting. Here, we reported the RNA-Seq analysis of unsorted, X- and Y-sperm in Bos indicus cattle. The differential gene expression analysis revealed significant upregulation of 47 genes in bovine Y-sperm and downregulation of 20 genes in comparison to X-sperm (adjusted p value < 0.05). Sixteen percent of the transcripts were unique to X-sperm, whereas 20.7% were unique to Y-sperm. The top 22 differentially expressed genes (DEGs) were validated using qPCR. A significant up- or down-regulation was detected in 21 of the 22 genes when comparing bovine Y-sperm to X-sperm (p < 0.01 and p < 0.05). The transcriptome dataset, the first in the league of bovine X- and Y-sperm, will aid in biomarker discovery for sex-sorting of bovine semen and improved fertility outcomes.

Intra-testicular visfatin inhibition disrupts androgen and estrogen signalling in the mouse testis

Visfatin is expressed in the testis of chicken, humans and rodents; however, direct role of visfatin in the adult testis has not been studied. We investigated testicular responses after intra-testicular injection of FK866. The effects of visfatin inhibition were accessed at 24 hrs and 1 week post FK866 treatment. The testicular histoarchitecture were degenerated after 24 hrs of FK866 treatment along with supressed testosterone and proliferating markers and resumption in these parameters showed after 1 week. The expression of AR and ERα were down-regulated after 1 week of FK866 treatment. The expression of BCl2 was down-regulated along with a slight elevation of caspase3 after 24 hrs; however, both proteins still showed suppressed expression after 1 week. Furthermore, ERβ expression, 3βHSD, and 17βHSD were down-regulated in both groups compared to the control. Despite the down-regulation of some factors, the testicular proliferation and histoarchitecture showed resumption in the testis after 1 week of FK866 treatment. This could be due to increased testosterone secretion by suppressing aromatase expression. In conclusion, our result is the first report on the direct role of visfatin in the adult testis. Visfatin has a stimulatory role in testosterone synthesis and proliferation in the testis. Moreover, some deregulated factors in the testis after 1 week of FK866 treatment, despite normal histoarchitecture treatment, could be a compensatory mechanism after visfatin inhibitions.

Evidence of the inhibitory role of visfatin in the testicular activity of mice during the infantile stage

Adipokines have emerged as regulators of gonadal function in many mammalian and non-mammalian species. In the present study, we have investigated the developmental expression of testicular and ovarian visfatin along with its possible role in the testicular activity infantile stages. Previously, our group has the extensive role of ovarian visfatin in relation to steroidogenesis, proliferation, and apoptosis in female mice. To the best of our knowledge, no study has shown the role of visfatin in mice testis. Our results from the previous study and present study showed that visfatin in the testis and ovaries are developmentally regulated. To unravel the role of visfatin, we have used FK866, as visfatin inhibitor. FK866 was used as a visfatin inhibitor, to decipher the role of visfatin in the testis of mice. Our results showed that visfatin expression in the testis was developmentally regulated in the testis. Leydig cells as well as germ have shown the presence of visfatin in mice testis, which suggest its role in testicular steroidogenesis and spermatogenesis. Furthermore, visfatin inhibition by FK866 significantly increased the testosterone secretion, and expression of AR, Bcl2, and ERα. The expression of GCNA was upregulated by FK866 treatment. These results suggest that visfatin has an inhibitory role in testicular steroidogenesis and germ cell proliferation in the infantile stage. Further research is required to define the precise role of visfatin in infantile mice testis.

Seminal plasma visfatin levels negatively correlate with sperm concentration

Introduction: Visfatin is involved in nicotinamide adenine dinucleotide biosynthesis, with a possible role in spermatogenesis. We investigated seminal plasma visfatin levels and its possible correlations with sperm parameters (concentration, motility, morphology) and BMI.

Materials and methods: We included 79 semen samples obtained from men from infertile couples presenting for sperm analysis. The samples were divided into 2 groups: a group of 35 samples with normal sperm parameters and another group of 44 samples with at least one abnormal sperm parameter. Seminal plasma visfatin levels were determined using commercially available enzyme-linked immunosorbent assay kits.

Results: Demographic data and body mass index (BMI) were similar in our subjects. As expected, the sperm parameters were significantly different between the 2 groups we studied. Visfatin levels did not differ between groups (66.6 ng/ml in normal samples and 72.7 ng/ml in abnormal samples, p=0.114) and did not correlate with sperm motility, sperm morphology, and BMI. However, a negative correlation between visfatin levels and sperm concentration (r=−0.28; p=0.014) and sperm count (r=−0.3; p=0.009), respectively, was detected.

Conclusions: Visfatin was detected in all human seminal plasma samples. Although its levels were similar in subjects with and without normal sperm parameters, a role for visfatin in sperm physiology cannot be ruled out at this point and further research is required.

New Aspects of Corpus Luteum Regulation in Physiological and Pathological Conditions: Involvement of Adipokines and Neuropeptides

The corpus luteum is a small gland of great importance because its proper functioning determines not only the appropriate course of the estrous/menstrual cycle and embryo implantation, but also the subsequent maintenance of pregnancy. Among the well-known regulators of luteal tissue functions, increasing attention is focused on the role of neuropeptides and adipose tissue hormones-adipokines. Growing evidence points to the expression of these factors in the corpus luteum of women and different animal species, and their involvement in corpus luteum formation, endocrine function, angiogenesis, cells proliferation, apoptosis, and finally, regression. In the present review, we summarize the current knowledge about the expression and role of adipokines, such as adiponectin, leptin, apelin, vaspin, visfatin, chemerin, and neuropeptides like ghrelin, orexins, kisspeptin, and phoenixin in the physiological regulation of the corpus luteum function, as well as their potential involvement in pathologies affecting the luteal cells that disrupt the estrous cycle.

Adipokines in metabolic and reproductive functions in birds: An overview of current knowns and unknowns

Adipose tissue is now recognized as an active endocrine organ, which synthesizes and secretes numerous peptides factors called adipokines. In mammals, they exert pleiotropic effects affecting energy metabolism but also fertility. In mammals, secretion of adipokines is altered in adipose tissue dysfunctions and may participate to obesity-associated disorders. Thus, adipokines are promising candidates both for novel pharmacological treatment strategies and as diagnostic tools. As compared to mammals, birds exhibit several unique physiological features, which make them an interesting model for comparative studies on endocrine control of metabolism and adiposity and reproductive functions. Some adipokines such as leptin and visfatin may have different roles in avian species as compared to mammals. In addition, some of them found in mammals such as CCL2 (chemokine ligand 2), resistin, omentin and FGF21 (Fibroblast Growth factor 21) have not yet been mapped to the chicken genome model and among its annotated gene models. This brief review aims to summarize data (structure, metabolic and reproductive roles and molecular mechanisms involved) related to main avian adipokines (leptin, adiponectin, visfatin, and chemerin) and we will briefly discuss the adipokines that are still lacking in avian species.

Reproductive roles of novel adipokines apelin, visfatin, and irisin in farm animals

The adipose tissue has a substantial impact on reproduction in mammals, specifically in females. As an energy depository organ, it is precisely associated with the reproductive success of mammals. Adipose tissue secretes many single molecules that are called 'adipokines' which mainly act as endocrine hormones. Adipokines homeostasis is fundamental to energy regulation, metabolic and cardiovascular diseases. The endocrine function of adipokines is influential for the long-term control of energy metabolism and performs an important function in metabolic state and fertility modulation. During the last years, new roles for adipokines have been appearing in the field of fertility. The adipokines have functions in reproduction at levels of the hypothalamus, the pituitary, and the gonads in humans, rodents, and other animals. Normal levels of adipokines are indispensable to protect the integrity of the hypothalamus-hypophysis-gonadal axis, regular ovulatory processes, and successful embryo implantation. Leptin and adiponectin are the most studied adipokines, but also the novel adipokines; apelin, visfatin, and irisin are important adipokines having several functions within the reproductive tract. Due to the known and unknown effects of these novel adipokines in the reproduction of farm animals, in this review, we will highlight the reproductive functions of apelin, visfatin, and irisin and summarize the known reproductive effects in farm animals to introduce the gaps for future studies in farm animals.

Exploratory Analysis in the Differences in Blood Serum and Seminal Plasma of Adipose-Tissue Related Peptides in Obese and Non-Obese Men and Their Correlations With Semen Parameters

OBJECTIVES

Evaluating the relationship between circulating metabolic biomarkers and semen parameters in obese, overweight and normal-weight patients.

METHODS

Patients were recruited at the "Andrology and Pathophysiology of Reproduction Unit", in Santa Maria Goretti Hospital. Divided into three groups were 98 participants (obese, overweight and normal-weight patients) according to BMI and were analyzed for three adipokines and six hormone peptides in blood serum and seminal plasma using Luminex assay. Standard semen analysis was performed for ejaculate volume, sperm concentration, total sperm count, motility, morphology and leukocytes.

RESULTS

In all groups of subjects, we observed a higher concentration of blood serum c-peptide, GIP, PAI-1, leptin, ghrelin and GLP-1 in comparison to seminal plasma; differently, higher levels in seminal plasma were observed for insulin and visfatin. In comparison to the non-obese subjects, obese subjects showed a higher blood serum concentration of c-peptide, GLP-1, GIP and leptin and a higher concentration of seminal plasma of GIP and insulin. Total sperm count, progressive motility, motility, and atypical forms directly correlated with PAI-1 and visfatin, whereas GLP-1 directly correlated only with total progressive motility.

CONCLUSION

Obese men showed a different pattern of blood serum and seminal plasma adipokines and hormone peptides concentrations in comparison to normal-weight men. Furthermore, these molecules correlated with functional seminal parameters. Our findings support the option to consider these molecules as new biomarkers and pharmacological targets for a new therapeutic approach in male infertility. However, further studies identifying other potential biomarkers of male infertility with important clinical implication and characterizing their mechanisms of action are mandatory.

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

Adipokines influence energy metabolism and have effects on male reproduction, including spermatogenesis and/or Sertoli cell maturation; however, the relationship between these active proteins and androgens in testicular cells is limited. Here, we studied the impact of short-term exposure to flutamide (an anti-androgen that blocks androgen receptors) on the expression of chemerin, apelin, vaspin and their receptors (CCRL2, CMKLR1, GPR1, APLNR, GRP78, respectively) in adult rat testes. Moreover, the levels of expression of lipid metabolism-modulating proteins (PLIN1, perilipin1; TSPO, translocator protein) and intercellular adherens junction proteins (nectin-2 and afadin) were determined in testicular cells. Plasma levels of adipokines, testosterone and cholesterol were also evaluated. Gene expression techniques used included the quantitative real-time polymerase chain reaction (qRT-PCR), Western blot (WB) and immunohistochemistry (IHC). The androgen-mediated effects observed post-flutamide treatment were found at the gonadal level as chemerin, apelin, and vaspin gene expression alterations at mRNA and protein levels were detected, whereas the cellular targets for these adipokines were recognised by localisation of respective receptors in testicular cells. Plasma concentrations of all adipokines were unchanged, whereas plasma cholesterol content and testosterone level increased after flutamide exposure. Differential distribution of adipokine receptors indicates potential para- or autocrine action of the adipokines within the rat testes. Additionally, changes in the expression of PLIN1 and TSPO, involved in the initial step of testosterone synthesis in Leydig cells, suggest that testicular cells represent a target of flutamide action. Increase in the gene expression of PLIN1 and TSPO and higher total plasma cholesterol content indicates enhanced availability of cholesterol in Leydig cells as a result of androgen-mediated effects of flutamide. Alterations in adherens junction protein expression in the testis confirm the flutamide efficacy in disruption of androgen signalling and presumably lead to impaired para- and autocrine communication, important for proper functioning of adipokines.

New Insights into Adipokines as Potential Biomarkers for Type-2 Diabetes Mellitus

A large number of studies have been focused on investigating serum biomarkers associated with risk or diagnosis of type-2 diabetes mellitus. In the last decade, promising studies have shown that circulating levels of adipokines could be used as a relevant biomarker for diabetes mellitus progression as well as therapeutic future targets. Here, we discuss the possible use of recently described adipokines, including apelin, omentin-1, resistin, FGF-21, neuregulin-4 and visfatin, as early biomarkers for diabetes. In addition, we also include recent findings of other well known adipokines such as leptin and adiponectin. In conclusion, further studies are needed to clarify the pathophysiological significance and clinical value of these biological factors as potential biomarkers in type-2 diabetes and related dysfunctions.

Involvement of Novel Adipokines, Chemerin, Visfatin, Resistin and Apelin in Reproductive Functions in Normal and Pathological Conditions in Humans and Animal Models

It is well known that adipokines are endocrine factors that are mainly secreted by white adipose tissue. Their central role in energy metabolism is currently accepted. More recently, their involvement in fertility regulation and the development of some reproductive disorders has been suggested. Data concerning the role of leptin and adiponectin, the two most studied adipokines, in the control of the reproductive axis are consistent. In recent years, interest has grown about some novel adipokines, chemerin, visfatin, resistin and apelin, which have been found to be strongly associated with obesity and insulin-resistance. Here, we will review their expression and role in male and female reproduction in humans and animal models. According to accumulating evidence, they could regulate the secretion of GnRH (Gonadotropin-Releasing Hormone), gonadotropins and steroids. Furthermore, their expression and that of their receptors (if known), has been demonstrated in the human and animal hypothalamo-pituitary-gonadal axis. Like leptin and adiponectin, these novel adipokines could thus represent metabolic sensors that are able to regulate reproductive functions according to energy balance changes. Therefore, after investigating their role in normal fertility, we will also discuss their possible involvement in some reproductive troubles known to be associated with features of metabolic syndrome, such as polycystic ovary syndrome, gestational diabetes mellitus, preeclampsia and intra-uterine growth retardation in women, and sperm abnormalities and testicular pathologies in men.

Putative Effects of Obesity on Linear Growth and Puberty

Childhood obesity is a major public health problem that has grown to epidemic proportions throughout the world. Obesity is influenced by genetic and environmental factors. The nutritional status plays an important role in growth and body weight regulation. Excess adiposity during childhood can affect the process of growth and puberty. Obese children are frequently tall for their age, with accelerated epiphyseal growth plate maturation despite low growth hormone levels. Several regulatory hormones may affect the process of linear growth in the constellation of obesity, as high levels of insulin and leptin are observed in obese children. Leptin can act as a skeletal growth factor, with a direct effect on skeletal growth centers. The finding that overweight children, especially girls, tend to mature earlier than lean children has led to the hypothesis that the degree of body fatness may trigger the neuroendocrine events that lead to the onset of puberty. Leptin receptors have been identified in the hypothalamus, as well as in gonadotrope cells, ovarian follicular cells, and Leydig cells. The increased leptin and androgen levels seen in obese children may be implicated in their earlier onset of puberty and accelerated pubertal growth. This review is focused on the interaction between childhood obesity and growth and pubertal processes.
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NAD+ Intermediates: The Biology and Therapeutic Potential of NMN and NR

Research on the biology of NAD+ has been gaining momentum, providing many critical insights into the pathogenesis of age-associated functional decline and diseases. In particular, two key NAD+ intermediates, nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN), have been extensively studied over the past several years. Supplementing these NAD+ intermediates has shown preventive and therapeutic effects, ameliorating age-associated pathophysiologies and disease conditions. Although the pharmacokinetics and metabolic fates of NMN and NR are still under intensive investigation, these NAD+ intermediates can exhibit distinct behavior, and their fates appear to depend on the tissue distribution and expression levels of NAD+ biosynthetic enzymes, nucleotidases, and presumptive transporters for each. A comprehensive concept that connects NAD+ metabolism to the control of aging and longevity in mammals has been proposed, and the stage is now set to test whether these exciting preclinical results can be translated to improve human health.

Chicken Is a Useful Model to Investigate the Role of Adipokines in Metabolic and Reproductive Diseases

Reproduction is a complex and essential physiological process required by all species to produce a new generation. This process involves strict hormonal regulation, depending on a connection between the hypothalamus-pituitary-gonadal axis and peripheral organs. Metabolic homeostasis influences the reproductive functions, and its alteration leads to disturbances in the reproductive functions of humans as well as animals. For a long time, adipose tissue has been recognised as an endocrine organ but its ability to secrete and release hormones called adipokines is now emerging. Adipokines have been found to play a major role in the regulation of metabolic and reproductive processes at both central and peripheral levels. Leptin was initially the first adipokine that has been described to be the most involved in the metabolism/reproduction interrelation in mammals. In avian species, the role of leptin is still under debate. Recently, three novel adipokines have been discovered: adiponectin (ADIPOQ, ACRP30), visfatin (NAMPT, PBEF), and chemerin (RARRES2, TIG2). However, their mode of action between mammalian and nonmammalian species is different due to the different reproductive and metabolic systems. Herein, we will provide an overview of the structure and function related to metabolic and reproductive mechanisms of the latter three adipokines with emphasis on avian species.