Presence of leptin and its receptor in the ram reproductive system and in vitro effect of leptin on sperm quality

Leptin is a 16 kDa hormone encoded by obese (OB) gene in adipocytes. This molecule not only regulates energy metabolism but also plays a role in the reproduction of mammals. Leptin and its receptor (OBR) have been found in male reproductive systems of human, bovine, equine and pig. The effects of leptin on sperm quality vary widely from different research findings. However, the presence of leptin and its receptor in the ram reproductive system and the in vitro effect of leptin on sperm quality have not reported yet. In the present study, we found that the OB was highly expressed in primary and secondary spermatocytes of the testes, OBR was highly expressed in secondary spermatocytes of the testes. The expressions of OB were in stereocilia of epididymis and in columnar cells of epididymal caput and cauda, the expressions of OBR were in columnar cells of epididymis and in stereocilia of epididymal corpus and cauda. The presence of both OB and OBR in testes, epididymis and sperm were confirmed through RT-PCR, immunolocalization and Western blot analyses. The RT-qPCR results indicated OB and OBR had higher expression levels in epididymal sperm than that of the ejaculated sperm in rams. When sperm were treated with 5 ng/mL leptin, the progressive motility (P < 0.01), straight-line velocity (VSL) (P < 0.05), average path velocity (VAP) (P < 0.05), membrane mitochondrial potential (MMP) (P < 0.01) and viability (P < 0.05) significantly increased, while DNA fragmentation index (DFI) and reactive oxygen species (ROS) significantly decreased compared to the control (P < 0.01), and the other semen parameters such as acrosome integrity and acrosome reaction rate had no significant changes between groups (P > 0.05). In conclusion, this is probably the first report describing localization of leptin and its receptors in the reproductive system of rams and their effects on sperm quality parameters. Our findings suggest that 5 ng/mL leptin treatment enhanced sperm motility, viability and MMP, and decrease DFI and ROS without obvious influence on the acrosome reaction in ram sperm. The potential mechanisms may be related to leptin's ability to reduce the oxidative stress and apoptosis of sperms and improve their mitochondrial function and energy supply, therefore, to maintain the physiological homeostasis of the sperm.

Exploring the ovine sperm transcriptome by RNAseq techniques. I Effect of seasonal conditions on transcripts abundance

Understanding the cell molecular changes occurring as a results of climatic circumstances is crucial in the current days in which climate change and global warming are one of the most serious challenges that living organisms have to face. Sperm are one of the mammals’ cells most sensitive to heat, therefore evaluating the impact of seasonal changes in terms of its transcriptional activity can contribute to elucidate how these cells cope with heat stress events. We sequenced the total sperm RNA from 64 ejaculates, 28 collected in summer and 36 collected in autumn, from 40 Manchega rams. A highly rich transcriptome (11,896 different transcripts) with 90 protein coding genes that exceed an average number of 5000 counts were found. Comparing transcriptome in the summer and autumn ejaculates, 236 significant differential abundance genes were assessed, most of them (228) downregulated. The main functions that these genes are related to sexual reproduction and negative regulation of protein metabolic processes and kinase activity. Sperm response to heat stress supposes a drastic decrease of the transcriptional activity, and the upregulation of only a few genes related with the basic functions to maintain the organisms’ homeostasis and surviving. Rams’ spermatozoids carry remnant mRNAs which are retrospectively indicators of events occurring along the spermatogenesis process, including abiotic factors such as environmental temperature.

The Hepatokine FGF21 Increases the Human Spermatozoa Motility

Lifestyle, environment and excess body weight are not only associated with an increased risk of metabolic disorders, such as type 2 diabetes, but also to other pathological processes, such as infertility. A hormone produced mainly by the liver called fibroblast growth factor 21 (FGF21) is closely linked to the energy status and is increased in patients suffering from obesity or insulin resistance. Recently, FGF21 has been shown to be associated with female fertility disorders, but no or few data about the role of FGF21 on human male fertility has been described. In the present study, FGF21 was measured in the seminal fluid at a lower level in comparison to the blood level. Thus, in the present in vitro study, we aimed to decipher the FGF21 system in human semen. To evaluate the putative role of FGF21 on spermatozoa function, we incubated human spermatozoa with increasing concentrations of recombinant human FGF21. The FGF21 in seminal fluid is potentially produced by male reproductive tract tissues. In spermatozoa, the FGF21 signal was transduced by the two main receptors FGFR1-c and FGFR3 and the cofactor β-klotho, which are colocalized in the middle piece of spermatozoa and stimulated the PI3K/Akt and MAPK pathways. Finally, in vitro treatment by FGF21 significantly increased sperm motility and ATP levels. Concomitantly, exposure to FGF21 improved the oxidative stress, as a lower ROS level was observed. Overall, these results seem to indicate that the metabolic factor, FGF21, positively modifies the activity and quality of the parameters of human spermatozoa.

When idiopathic male infertility is rooted in maternal malnutrition during the perinatal period in mice

Infertility represents a growing burden worldwide, with one in seven couples presenting difficulties conceiving. Amongst these, 10-15% of the men have idiopathic infertility that does not correlate with any defect in the classical sperm parameters measured. In the present study, we used a mouse model to investigate the effects of maternal undernutrition on fertility in male progeny. Our results indicate that mothers fed on a low protein diet during gestation and lactation produce male offspring with normal sperm morphology, concentration and motility but exhibiting an overall decrease of fertility when they reach adulthood. Particularly, in contrast to control, sperm from these offspring show a remarkable lower capacity to fertilize oocytes when copulation occurs early in the estrus cycle relative to ovulation, due to an altered sperm capacitation. Our data demonstrate for the first time that maternal nutritional stress can have long-term consequences on the reproductive health of male progeny by affecting sperm physiology, especially capacitation, with no observable impact on spermatogenesis and classical quantitative and qualitative sperm parameters. Moreover, our experimental model could be of major interest to study, explain, and ultimately treat certain categories of infertilities.

Adipokines expression profiles in both plasma and peri renal adipose tissue in Large White and Meishan sows: A possible involvement in the fattening and the onset of puberty

In pig, backfat deposition is strongly related to the growth and reproductive performance. However, the molecular regulatory mechanisms of adipose tissue are not clearly understood. Adipose tissue is now recognized as an important endocrine organ that secretes a variety of factors including adipokines. However, the regulation of expression pattern of these adipokines in both plasma and visceral white adipose tissue (WAT) in lean and fat pig is unclear. In the present study, we used two representative porcine breeds (Large White, LW; Meishan, MS) with contrasting backfat thickness and sexual maturity age. Using specific ELISA assays, we determined the plasma profile of eight adipokines, leptin, adiponectin, visfatin, apelin, chemerin, resistin, omentin and vaspin in LW and MS sows. By RT-qPCR and western-blot we also investigated the mRNA and protein levels of these adipokines and their cognate receptors (LEPR, ADIPOR1, ADIPOR2, CMKLR1, CCRL2, GPR1, APLNR, TLR4, ROR1, CAP1 and HSPA5) in the peri renal WAT, respectively. At both plasma and peri renal WAT level, we found that the amounts of leptin, chemerin, resistin and vaspin were higher whereas those of adiponectin and omentin were lower in MS than LW sows. Plasma and adipose tissue visfatin and apelin levels were not different between the two breeds. Moreover, we noted that the variations of peri renal WAT adipokines observed between MS and LW were similar at the protein and mRNA level except for chemerin and apelin suggesting post-transcriptional modifications for these two adipokines. Finally, among the eight adipokines studied, we showed that only the plasma concentrations of leptin and chemerin were positively and those of adiponectin, negatively associated with the thickness of fat and opposite correlation was found for the onset of puberty in both LW and MS animals. Taken together, these results support a potential involvement of adipokines in WAT regulation and its link with the onset of the puberty in sows.

Nerve growth factor-β effects on post-thaw bull semen quality: Effects of nerve growth factor-β added to extenders for cryopreservation of electro-ejaculated and epididymal bull semen

Nerve growth factor-β (NGF) is a seminal plasma protein associated with improved sperm membrane integrity and motility in mammalian species. The objective of this study was to compare post-thaw semen quality from both ejaculated and pididymal-collected bull sperm incubated with purified NGF prior to cryopreservation. Semen was obtained from Angus × Simmental crossbred bulls (n = 10) collected by electroejaculation, followed by castration and epididymal sperm collections 3 days later. Semen samples were incubated with extender having 0 ng/mL (CONT), 0.5 ng/mL (LOW), 5 ng/mL (MED), or 50 ng/mL (HIGH) of purified NGF prior to cryopreservation. Sperm motility was assessed in each sample prior to treatment and cryopreservation and at post-thaw. Flow cytometry was used for post-thaw assessment of sperm viability (SYBR-14/PI), acrosome integrity (FITC-PNA/PI), and chromatin stability (acridine orange). Values for post-thaw sperm motility and velocity variables were decreased, while linearity was increased in samples of the HIGH compared with CONT group (P < 0.01), but there were no differences in epididymal samples (P> 0.05). Samples from the HIGH group also had a lesser amplitude of lateral head displacement at 2.5 and 3 h post-thaw (P < 0.01). Post-thaw sperm viability, acrosome integrity, and DNA fragmentation index were not affected by NGF treatment in either ejaculated or epididymal sperm (P> 0.05). In conclusion, supplementation of freezing extender with NGF had minimal effects on post-thaw sperm quality in bulls. Results indicate NGF may have a function in preventing premature sperm hyperactivation in ejaculated, but not epididymal-collected spermatozoa. Fertility studies, both in vitro and in vivo, are warranted to ascertain the relevancy of these findings.

Insights into leptin signaling and male reproductive health: the missing link between overweight and subfertility?

Obesity stands as one of the greatest healthcare challenges of the 21st century. Obesity in reproductive-age men is ever more frequent and is reaching upsetting levels. At the same time, fertility has taken an inverse direction and is decreasing, leading to an increased demand for fertility treatments. In half of infertile couples, there is a male factor alone or combined with a female factor. Furthermore, male fertility parameters such as sperm count and concentration went on a downward spiral during the last few decades and are now approaching the minimum levels established to achieve successful fertilization. Hence, the hypothesis that obesity and deleterious effects in male reproductive health, as reflected in deterioration of sperm parameters, are somehow related is tempting. Most often, overweight and obese individuals present leptin levels directly proportional to the increased fat mass. Leptin, besides the well-described central hypothalamic effects, also acts in several peripheral organs, including the testes, thus highlighting a possible regulatory role in male reproductive function. In the last years, research focusing on leptin effects in male reproductive function has unveiled additional roles and molecular mechanisms of action for this hormone at the testicular level. Herein, we summarize the novel molecular signals linking metabolism and male reproductive function with a focus on leptin signaling, mitochondria and relevant pathways for the nutritional support of spermatogenesis.

The expression and distribution of a leptin receptor in the central nervous system, digestive organs, and gonads of the giant freshwater prawn, Macrobrachium rosenbergii

In the present study, the presence and distribution of leptin receptor (LEP-R) in central nervous system, digestive organs, gonads of giant freshwater prawn, Macrobrachium rosenbergii, were investigated with Western blot and immunohistochemistry. By Western blot a LEP-R with a molecular weight (MW) of 100 kDa was detected in the brain, thoracic ganglia, abdominal ganglia, hepatopancreas, all parts of the gastrointestinal tract, ovaries, and testes. In hepatopancreas and foregut, another intense positive band was detected at molecular weight of 30 kDa, which could be an isotype of LEP-R. By immunohistochemistry, LEP-R-ir was detected in the neurons, and neuropils in the brain, thoracic ganglia, and abdominal ganglia. In the gastrointestinal tract, there was intense LEP-R-ir in the apical part of the epithelial cells of the foregut, midgut, and hindgut. In addition, LEP-R-ir was found in the Restzellen(R)cells and Fibrillenzellen(F) cells in the hepatopancreas. In the ovary, LEP-R-ir was detected in early stage of oocytes and mature oocytes. Intense LEP-R-ir was observed in spermatogonia and spermatocytes of the small and orange claw male prawns. In addition, LEP-R was seen in the high epithelium of spermatic ducts from all male morphotypes. In summary, the detection of the LEP-R-ir suggests the existence of a LEP-R in several organs of M. rosenbergii. Through binding with leptin peptide, LEP-R may be an important signaling molecule that has critical functions in modulating and controlling food intake, energy expenditure, and reproduction in this prawn.

Effect of brain-derived neurotrophic factor (BDNF) on sperm quality of normozoospermic men

The neurotrophin family of proteins and their receptors act as important proliferative and pro-survival factors in differentiation of nerve cells and are thought to play key roles in the development of reproductive tissues and normal function of spermatozoa. The objective of the present study was to evaluate the effect of Brain-Derived Neurotrophic Factor (BDNF) on the sperm viability and motility, lipid peroxidation (LPO), mitochondrial activity and concentration of leptin, nitric oxide (NO) and insulin in normozoospermic men. Semen samples from 20 normozoospermic men were divided into three groups: (i) control, (ii) BDNF and (iii) BDNF + K252a. BDNF and K252a were added in the dose of 0.133 and 0.1 nM, respectively. Viability was assessed by eosin-nigrosin staining technique, and motility was observed by microscopy. NO concentration and mitochondrial activity were measured with flow cytometry, and LPO was analyzed using enzyme-linked immunosorbent assay (ELISA) kits. Results showed that exogenous BDNF at 0.133 nM could significantly (p < 0.05) influence viability, motility, NO concentration, mitochondrial activity and LPO content. Secretions of insulin and leptin by human sperm were increased in cells exposed to the exogenous BDNF, whereas viability, mitochondrial activity and insulin and leptin secretions were decreased in cells exposed to the K252.

Uteroplacental insufficiency reduces rat plasma leptin concentrations and alters placental leptin transporters: ameliorated with enhanced milk intake and nutrition

KEY POINTS

Uteroplacental insufficiency compromises maternal mammary development, milk production and pup organ development; this is ameliorated by cross-fostering, which improves pup growth and organ development and prevents adult diseases in growth-restricted (Restricted) offspring by enhancing postnatal nutrition. Leptin is transported to the fetus from the mother by the placenta; we report reduced plasma leptin concentrations in Restricted fetuses associated with sex-specific alterations in placental leptin transporter expression. Pup plasma leptin concentrations were also reduced during suckling, which may suggest reduced milk leptin transport or leptin reabsorption. Mothers suckled by Restricted pups had impaired mammary development and changes in milk fatty acid composition with no alterations in milk leptin; cross-fostering restored pup plasma leptin concentrations, which may be correlated to improved milk composition and intake. Increased plasma leptin and altered milk fatty acid composition in Restricted pups suckling mothers with normal lactation may improve postnatal growth and prevent adult diseases.

ABSTRACT

Uteroplacental insufficiency reduces birth weight and adversely affects fetal organ development, increasing adult disease risk. Cross-fostering improves postnatal nutrition and restores these deficits. Mothers with growth-restricted pups have compromised milk production and composition; however, the impact cross-fostering has on milk production and composition is unknown. Plasma leptin concentrations peak during the completion of organogenesis, which occurs postnatally in rats. Leptin is transferred to the fetus via the placenta and to the pup via the lactating mammary gland. This study investigated the effect of uteroplacental insufficiency on pup plasma leptin concentrations and placental leptin transporters. We additionally examined whether cross-fostering improves mammary development, milk composition and pup plasma leptin concentrations. Fetal growth restriction was induced by bilateral uterine vessel ligation surgery on gestation day 18 in Wistar Kyoto rats (termed uteroplacental insufficiency surgery mothers). Growth-restricted (Restricted) fetuses had reduced plasma leptin concentrations, persisting throughout lactation, and sex-specific alterations in placental leptin transporters. Mothers suckled by Restricted pups had impaired mammary development, altered milk fatty acid composition and increased plasma leptin concentrations, despite no changes in milk leptin. Milk intake was reduced in Restricted pups suckling uteroplacental insufficiency surgery mothers compared to Restricted pups suckling sham-operated mothers. Cross-fostering Restricted pups onto a sham-operated mother improved postnatal growth and restored plasma leptin concentrations compared to Restricted pups suckling uteroplacental insufficiency surgery mothers. Uteroplacental insufficiency alters leptin homeostasis. This is ameliorated with cross-fostering and enhanced milk fatty acid composition and consumption, which may protect the pups from developing adverse health conditions in adulthood.

Leptin and leptin-receptor polymorphisms in fertile and infertile men

The association of leptin (LEP) -2548G/A and/or leptin receptor (LEPR) Gln223Arg polymorphisms with male infertility and plasma FSH, LH, and testosterone (T) levels was examined. The genotypes and allele frequency distributions of LEP -2548G/A and LEPR Gln223Arg polymorphisms were investigated in 150 fertile and 150 infertile men by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Also, plasma levels of FSH, LH, and T were measured using commercial ELISA kits. Frequencies of AA, AG and GG genotypes of LEP-2548G/A polymorphism were statistically different in fertile and infertile men (p=0.012). The AG genotype showed a protective effect which could decrease risk of male infertility about 3 fold (p = 0.004). We did not observe any differences in frequencies of LEPR Gln223Arg alleles and genotypes between groups (p > 0.05). Sperm counts from infertile men with the AG and GG genotypes of the LEP polymorphism were significantly higher than AA genotype (p<0.05). Moreover, infertile men who carried the RR genotype of LEPR showed a statistically higher percentage of sperm with progressive motility than individuals with other genotypes (p = 0.004). There was no correlation between different combinations of LEP and LEPR genotypes and LH, FSH, and T levels (p > 0.05). Our study suggests that the LEP -2548G/A polymorphism may play a role in male fertility and the AG genotype may have a protective effect through increasing sperm counts. The distribution of genotypes of LEP -2548G/A polymorphism are different in fertile and infertile males and may be a useful tool in evaluation of male infertility.

ABBREVIATIONS

LEP: leptin; LEPR: leptin receptor; T: testosterone; FSH: follicle-stimulating hormone; LH: luteinizing hormone.

Leptin and leptin receptor are detectable in equine spermatozoa but are not involved in in vitro fertilisation

In human and swine, leptin (OB) has been identified in seminal plasma and leptin receptors (OB-R) on the cell surface of spermatozoa, indicating that spermatozoa are a target for OB. This hormone has also been detected in follicular fluid (FF) in women and mares, although its role requires further study. The aims of this study were to investigate the immunolocalisation and the expression of OB and OB-R in equine spermatozoa and to evaluate the involvement of OB in equine in vitro fertilisation (IVF). Since progesterone (P) and OB are both found in FF, the individual and combined effects of these two hormones were studied in equine IVF and compared with the results obtained from the use of FF for in vitro sperm preparation. For the first time, we were able to identify OB and OB-R mRNA and their corresponding proteins in equine spermatozoa. When spermatozoa were treated with OB, there was a decrease in the three motility parameters VSL, STR and LIN, commonly associated with hyperactivation, whilst the acrosome reaction rate increased (P < 0.05). The fertilisation rate was 51% with FF, 46.15% with P, 43.64% with P+OB and 0% with OB alone. The percentage of eight-cell stage embryos was 18.7% with FF, 17.1% with P and 16.7% with OB+P. OB alone did not permit oocyte fertilisation, indicating that, in the horse, OB is involved in capacitation and hyperactivation but not in sperm penetration.

The immobilization of human spermatozoa by STAT3 inhibitory compound V results from an excessive intracellular amount of reactive oxygen species

We previously showed that Stattic V (Stat3 inhibitory compound V) reduces human sperm motility and cellular ATP levels, increases intracellular Ca(2+) concentration, and promotes mitochondrial membrane depolarization resulting in increased levels of extracellular reactive oxygen species (ROS). As these alterations in cellular function are highly similar to what is observed in a cell undergoing apoptosis, our goal was to determine if the immobilizing effect of Stattic V on spermatozoa results from apoptosis or was because of an oxidative stress. To address this question, spermatozoa were incubated with Stattic V in combination with a caspase inhibitor, a proteasome inhibitor or a cell permeant ROS scavenger. Following incubation in different conditions, sperm motility was evaluated by CASA, acrosomal integrity by FITC conjugated Pisum sativum agglutinin (PSA-FITC) labeling, intracellular pH, and mitochondrial superoxide production by flow cytometry using BCECF and MitoSoxRed dye, respectively. Levels of reduced thiols were assessed by iodoacetamidofluorescein staining on total and on sperm surface proteins, and protein tyrosine phosphorylation was evaluated by western blot. The loss in sperm motility induced by Stattic V was associated with a slight intracellular acidification and an important increase in intracellular superoxide anion. Unlike caspase and proteasome inhibitors, low molecular weight thiols, such as N-acetyl-L-cysteine (NAC), prevented Stattic V-induced sperm immobilization and increase responsiveness to acrosome reaction inducers. NAC also efficiently prevented the production of superoxide anion, mitochondrial membrane depolarization, intracellular acidification and the oxidation of protein free thiols caused by Stattic V. These results show that the deleterious effects of Stattic V on sperm functions are caused directly or indirectly by excessive intracellular ROS production without causing sperm apoptosis or necrosis.

Peroxisome proliferator-activated receptor gamma signaling in human sperm physiology

Peroxisome proliferator-activated receptor gamma (PPARγ) is a member of the PPARs, which are transcription factors of the steroid receptor superfamily. PPARγ acts as an important molecule for regulating energy homeostasis, modulates the hypothalamic-pituitary-gonadal (HPG) axis, and is reciprocally regulated by HPG. In the human, PPARγ protein is highly expressed in ejaculated spermatozoa, implying a possible role of PPARγ signaling in regulating sperm energy dissipation. PPARγ protein is also expressed in Sertoli cells and germ cells (spermatocytes). Its activation can be induced during capacitation and the acrosome reaction. This mini-review will focus on how PPARγ signaling may affect fertility and sperm quality and the potential reversibility of these adverse effects.

Profiling signaling proteins in human spermatozoa: biomarker identification for sperm quality evaluation

OBJECTIVE

To determine the correlation between semen basic parameters and the expression and activity of signaling proteins.

DESIGN

In vitro studies with human spermatozoa.

SETTING

Academic research institute.

PATIENT(S)

Thirty-seven men provided semen samples for routine analysis.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Basic semen parameters tracked included sperm DNA fragmentation (SDF), the expression levels of 75 protein kinases, and the phosphorylation/cleavage patterns of 18 signaling proteins in human spermatozoa.

RESULT(S)

The results indicated that the phosphorylated levels of several proteins (Bad, GSK-3β, HSP27, JNK/SAPK, mTOR, p38 MAPK, and p53), as well as cleavage of PARP (at D214) and Caspase-3 (at D175), were significantly correlated with motility parameters. Additionally, the percentage of morphologically normal spermatozoa demonstrated a significant positive correlation with the phosphorylated levels of p70 S6 kinase and, in turn, head defects and the teratozoospermia index (TZI) showed a significant negative correlation with the phosphorylated levels of Stat3. There was a significant positive correlation between SDF and the teratozoospermia index, as well as the presence of head defects. In contrast, SDF negatively correlated with the percentage of morphologically normal spermatozoa and the phosphorylation of Akt and p70 S6 kinase. Subjects with varicocele demonstrated a significant negative correlation between head morphological defects and the phosphorylated levels of Akt, GSK3β, p38 MAPK, and Stat1. Additionally, 34 protein kinases were identified as expressed in their total protein levels in normozoospermic samples.

CONCLUSION(S)

This study contributed toward establishing a biomarker "fingerprint" to assess sperm quality on the basis of molecular parameters.

Male obesity is associated with changed spermatozoa Cox4i1 mRNA level and altered seminal vesicle fluid composition in a mouse model

The rate of obesity among men of reproductive age has tripled in the last three decades. Previously, we demonstrated that paternal obesity resulted in impaired preimplantation developmental kinetics, compromised post-compaction metabolism and decreased blastocyst cell number when embryos were generated in vivo. Subsequently, using in vitro fertilization we found embryos of obese males to have altered metabolism before compaction, reduced inner cell mass cell number and retarded fetal development--the difference between these two studies being the method of embryo generation and the presence or absence of seminal plasma, respectively. Here, we hypothesize that both sperm and seminal plasma are affected by obesity, compromising embryogenesis and pregnancy health in a cumulative manner. Epididymal sperm and seminal vesicle fluid were collected from normal and obese C57BL/6 mice. RNA and DNA were extracted from spermatozoa for qPCR and global methylation analysis, respectively. Proteomic (Luminex) and metabolomic (GC-MS) techniques were employed to analyse the composition of seminal vesicle fluid. Nuclear encoded cytochrome c oxidase subunit IV isoform 1 (Cox4i1) of the terminal enzyme in the mitochondrial respiratory chain demonstrated significantly increased RNA levels in the sperm of obese males (P< 0.05). Quantitative seminal plasma analysis identified significant changes in levels of the hormones insulin, leptin and estradiol between normal and obese males (P < 0.05). Further, the metabolite composition of seminal vesicle fluid was significantly affected by obesity. Consequently, this study has determined that obesity affects both sperm and seminal plasma composition. The interaction between sperm and seminal plasma warrants further analysis.

Postnatal leptin promotes organ maturation and development in IUGR piglets

Babies with intra-uterine growth restriction (IUGR) are at increased risk for experiencing negative neonatal outcomes due to their general developmental delay. The present study aimed to investigate the effects of a short postnatal leptin supply on the growth, structure, and functionality of several organs at weaning. IUGR piglets were injected from day 0 to day 5 with either 0.5 mg/kg/d leptin (IUGRLep) or saline (IUGRSal) and euthanized at day 21. Their organs were collected, weighed, and sampled for histological, biochemical, and immunohistochemical analyses. Leptin induced an increase in body weight and the relative weights of the liver, spleen, pancreas, kidneys, and small intestine without any changes in triglycerides, glucose and cholesterol levels. Notable structural and functional changes occurred in the ovaries, pancreas, and secondary lymphoid organs. The ovaries of IUGRLep piglets contained less oogonia but more oocytes enclosed in primordial and growing follicles than the ovaries of IUGRSal piglets, and FOXO3A staining grade was higher in the germ cells of IUGRLep piglets. Within the exocrine parenchyma of the pancreas, IUGRLep piglets presented a high rate of apoptotic cells associated with a higher trypsin activity. In the spleen and the Peyer's patches, B lymphocyte follicles were much larger in IUGRLep piglets than in IUGRSal piglets. Moreover, IUGRLep piglets showed numerous CD79(+) cells in well-differentiated follicle structures, suggesting a more mature immune system. This study highlights a new role for leptin in general developmental processes and may provide new insight into IUGR pathology.

Stattic V, a STAT3 inhibitor, affects human spermatozoa through regulation of mitochondrial activity

We have recently shown that many mediators of the JAK/STAT signaling pathway are present in ejaculated human spermatozoa. Among them, STAT3 is detected mainly in membranes and flagellar cytoskeletal fractions. In order to determine the importance of STAT3-mediated signaling, sperm were incubated with Stattic V, a specific inhibitor. Effects on motility were evaluated by CASA, sperm acrosomal integrity was evaluated by FITC conjugated lectin (PSA or PNA) staining, and protein phosphotyrosine content was assessed by Western blot using a monoclonal anti-phosphotyrosine antibody. INDO1-AM and JC-1 were used to measure sperm intracellular calcium and mitochondrial membrane potential, respectively, by flow cytometry, and reactive oxygen species (ROS) production was investigated by luminol-based assay. Percentages of motility and motility parameters were significantly affected by Stattic V. This later also significantly increased intracellular Ca(2+) levels, progesterone- and calcium ionophore (A23187)-induced acrosome reaction. On the other hand, a significant decrease in ATP content was measured when sperm were treated with Stattic V, associated with depolarization of mitochondrial membrane and elevated ROS production. These results suggest that STAT3 is involved in sperm functions, at least through regulation of mitochondrial activity. This further emphasizes that STAT3 mediates cellular activities in a manner different than strictly the activation of gene transcription.

Expression of ghrelin receptor (GHSR-1a) in rat epididymal spermatozoa and the effects of its activation

In this study we demonstrated the expression of the ghrelin receptor GHSR-1a in rat spermatids and epididymal spermatozoa, as well as some effects of ghrelin on the spermatozoa in vitro. For the demonstration of GHSR-1a the immunocytochemical, immunofluorescence and Western blotting techniques were applied using three different types of antibodies. The response of spermatozoa to ghrelin was tested in a series of in vitro experiments and their effects were evaluated using confocal microscopy and flow cytometry. GHSR-1a protein was found as expressed in the Golgi and acrosomes of spermatids and acrosome regions or the head cell membrane of epididymal spermatozoa. The GHSR-1a expression in spermatozoa was also confirmed by Western blot. No differences were found in percentage of spermatozoa showing annexin-V binding and expression of active form caspase-3 between control and ghrelin-treated spermatozoa. This result may indicate no pro-apoptotic effects of ghrelin neither at 10(-9) nor 10(-6)mol/L concentration. Ghrelin (10(-6)mol/L) increased free intracellular calcium ion concentration in the rat spermatozoa. Moreover, stimulation with 10(-6)mol/L ghrelin increased, while 10(-4)mol/L ghrelin decreased the number of spermatozoa showing progressive motility. In conclusion, the expression of the GHSR-1a receptor in spermatozoa, as well as ghrelin influences on sperm motility and intracellular calcium ion concentration suggest that such biological effects of ghrelin may be produced under in vivo conditions.

Progesterone activates Janus Kinase 1/2 and activators of transcription 1 (JAK1-2/STAT1) pathway in human spermatozoa

Ejaculated spermatozoa undergo capacitation and acrosome reaction by responding to extrinsic clues and activate signalling cascades to induce protein tyrosine phosphorylation. In the present study, we investigated the existence, the Janus kinase (JAK) and activator of transcription (STAT) pathway and determined its physiological relevance. JAK1 and STAT1 are localised on the equatorial region and the midpiece of their human spermatozoa, JAK2 is detected on the sperm tail. Capacitation leads to phosphorylation of JAK2 but not JAK1 and STAT1. In the uncapacitated sperm, phosphorylated JAK2 (pJAK2) is localised mainly in the tail region; in response to capacitation, the JAK2 is phosphorylated in the midpiece and the head region along with the tail. Progesterone (5 μm) leads to phosphorylation of JAK1, JAK2 and STAT1 in a time-dependent manner. In progesterone-treated spermatozoa, the JAK2 in the tail is hyperphosphorylated, the JAK2 in the head and the midpiece is dephosphorylated. We conclude that in human spermatozoa, the JAK1/2 pathway is activated upon capacitation and is further modulated by progesterone; the biological processes controlled by this pathway in sperm need to be elucidated.

Nitric oxide involvement in the acrosome reaction triggered by leptin in pig sperm

BACKGROUND

Nitric oxide (NO) is a signaling molecule produced by intracellular nitric oxide synthase (NOS) enzymes. This free radical appears to affect sperm capacitation, a maturation step preceding acrosome reaction. Recent studies have reported leptin ability to promote capacitation and acrosome reaction in pig male gametes.

METHODS

This study has investigated nitric oxide production in leptin-treated pig spermatozoa by fluorescence-activated cell sorting, while the intracellular NOS isoforms were assessed by Western blot analysis. In addition, acrosome status of treated-spermatozoa was evaluated by FITC-PNA staining.

RESULTS

Significant increases of nitric oxide levels and acrosome reaction extent were detected in leptin-treated spermatozoa, but both the effects were reversed in presence of L-NAME. Furthermore, the immunoblots of sperm extracts have evidenced three bands of ~160 Kd(bNOS), ~130 Kd (iNOS) and ~135 Kd (eNOS).

CONCLUSIONS

The identification of the three intracellular NOS isoforms suggests that pig spermatozoa could produce NO, while the augmented nitric oxide levels in leptin-treated male gametes indicates the capacity of the hormone to induce nitric oxide production. Furthermore, the inhibitory effect of L-NAME and of Ab-ObR on the promotion of acrosome reaction triggered by leptin suggests a possible involvement of NO in the hormone action.

Mediators of the Jak/STAT signaling pathway in human spermatozoa

In their journey to acquire the ability to fertilize the egg, numerous intracellular signaling systems are activated in spermatozoa, leading to an increase in protein tyrosine phosphorylation. Although the JAK/STAT signaling pathway is usually associated with the activation of transcription of specific genes, our laboratory previously demonstrated the presence of the IL6 receptor (IL6R) and the Janus kinase 1 (JAK1) in human spermatozoa, a cell that is mostly transcriptionally inactive. In order to determine the importance of the JAK/STAT signaling pathway, our objectives were to identify and characterize the mediators of this system in human sperm. Cell fractionation and surface biotinylation assays clearly demonstrated that IL6R is expressed at the sperm membrane surface. The kinase JAK1 is enriched in membrane fractions and is activated during human sperm capacitation as suggested by its increase in phosphotyrosine content. Many signal transducer and activator of transcription (STAT) proteins are expressed in human sperm, including STAT1, STAT3, STAT4, STAT5, and STAT6. Among them, only STAT1 and STAT5 were detected in the cytosolic fraction. All the detected STAT proteins were enriched in the cytoskeletal structures. STAT4 was present in the perinuclear theca, whereas JAK1, STAT1, and STAT5 were detected in the fibrous sheath. Indirect immunofluorescence studies showed that JAK1 and STAT1 colocalized in the neck region and that STAT4 is present at the equatorial segment and flagella. The presence of STAT proteins in sperm structural components suggests that their role is different from their well-known transcription factor activity in somatic cells, but further investigations are required to determine their role in sperm function.

Sperm storage in the female reproductive tract of Scotophilus heathii: role of androgen

The aim of the present study was to investigate the mechanism of androgen-mediated, prolonged sperm-storage in the female reproductive tract of the bat, Scotophilus heathii. The bat treated in vivo with flutamide, an androgen antagonist, showed loss of spermatozoa at the storage site, utero-tubal junction. Immunocytochemistry and Western blot analysis revealed the presence of increased expression of Bcl2 in the epithelial cell lining of the utero-tubal junction during the period of sperm-storage. Treatment with testosterone in vitro caused a significant dose-dependent increase in expression of the survival factor Bcl2, whereas treatment with flutamide together with testosterone caused a significant decline in Bcl2 in the utero-tubal junction of S. heathii. Together with the expression of Bcl2, the utero-tubal junction also expresses the death signal, caspase3. Expression of caspase3 decreased during January, but increased in February during the late stage of sperm storage. Androgen stimulated Bcl2 synthesis in the utero-tubal junction via the non-genomic MAP kinase signaling pathway. In conclusion, this study suggests that androgen promotes sperm storage in S. heathii by stimulating the survival factor Bcl2 in the utero-tubal junction. It is further hypothesized that a balance between the survival factor, Bcl2, and the death signal, caspase3, determines the duration of sperm storage in S. heathii.

Mechanisms of obesity-induced male infertility

Male infertility, characterized by hypogonadism, decreased semen quality or ejaculatory dysfunction, accounts for approximately 20% of infertility cases. Obesity and metabolic dysfunction have been identified, among other causal factors, to contribute to male infertility. In the context of the Western world's 'obesity epidemic', this article discusses three main biological mechanisms linking obesity to impaired male reproductive function: hypogonadism, testicular heat stress/hypoxia-induced apoptosis and endocrine disruption by 'obesogens'. Among these, obesity-induced hypogonadism is undoubtedly the most clinically significant and is easily assessed. Rapidly expanding areas of research in this area include leptin modulation of kisspeptins and hypothalamic-pituitary-testicular hormone pathways, and roles of other adipocytokines in male infertility, as well as the impact of exposure to obesogens on the quality of semen.

Evaluation of the leptin receptor in human spermatozoa

BACKGROUND

Leptin, a 167 amino acid peptide hormone, profoundly effects reproduction exerting its biological effects via interaction with the leptin receptor (ObR) which is widely expressed on peripheral tissues. In this study, we have attempted to assess leptin receptor expression in the spermatozoa of fertile males and those diagnosed with male factor infertility; both at the mRNA or protein levels.

METHODS

Semen samples were collected from fertile males and individuals with male factor infertility. In order to evaluate leptin receptor expression several techniques were utilized, including: reverse transcriptase-polymerase chain reaction (RT-PCR), immunostaining, flow cytometry, and western blotting. Mononuclear cells isolated from volunteers' peripheral blood were used as positive controls for leptin receptor expression.

RESULTS

leptin receptor was noted on mononuclear cells but we were unable to detect this receptor on spermatozoa at the protein level. Leptin receptor expression was detected on peripheral blood mononuclear cells (PBMCs) as positive controls; however it was not detectable on the spermatozoa of both groups by immunofluorescence microscopy or flow cytometry. Furthermore, positive expression of the ObR long isoform as assessed by RT-PCR was observed in the sperm of only four cases, whereas expression of beta-Actin, a house keeping gene, and HspA2, a testis specific gene, was present in all cases.

CONCLUSION

The long isoform of leptin receptor may not be present on human sperm. Species difference may be accounted for diverse reproductive physiology which depends on metabolic requirement. Leptin receptor expression at the mRNA level in some individuals may be related to contamination by other cells in semen.

The role of Mitogen activated protein kinase (MAPK) in sperm functions

The generation of mature spermatozoa in the epididymis includes the activation of the MAPK cascade in a complex manner. MAPKs are thought to be involved in the regulation of transcription and ectoplasmic specialization (ES) in the testis. MAPKs also regulate mature spermatozoa flagellar motility, hyperactivation and the acrosome reaction. Here we review the current data regarding the functions of MAPKs in spermatogenesis and in mature spermatozoa.