Regulation of expression of Sertoli cell glucose transporters 1 and 3 by FSH, IL1β, and bFGF at two different time-points in pubertal development

Regulation and Role of Adiponectin Secretion in Rat Ovarian Granulosa Cells

Adiponectin is an important adipokine involved in glucose and lipid metabolism, but its secretion and potential role in regulating glucose utilization during ovarian development remains unclear. This study aims to investigate the mechanism and effects of follicle-stimulating hormones (FSHs) on adiponectin secretion and its following impact on glucose transport in the granulosa cells of rat ovaries. A range of experimental techniques were utilized to test our research, including immunoblotting, immunohistochemistry, immunofluorescence, ELISA, histological staining, real-time quantitative PCR, and transcriptome analysis. The immunohistochemistry results indicated that adiponectin was primarily located in the granulosa cells of rat ovaries. In primary granulosa cells cultured in vitro, both Western blot and immunofluorescence assays demonstrated that FSH significantly induced adiponectin secretion within 2 h of incubation, primarily via the PKA signaling pathway rather than the PI3K/AKT pathway. Concurrently, the addition of the AdipoR1/AdipoR2 dual agonist AdipoRon to the culture medium significantly stimulated the protein expression of GLUT1 in rat granulosa cells, resulting in enhanced glucose absorption. Consistent with these in vitro findings, rats injected with eCG (which shares structural and functional similarities with FSH) exhibited significantly increased adiponectin levels in both the ovaries and blood. Moreover, there was a notable elevation in mRNA and protein levels of AdipoRs and GLUTs following eCG administration. Transcriptomic analysis further revealed a positive correlation between the expression of the intraovarian adiponectin system and glucose transporter. The present study represents a novel investigation, demonstrating that FSH stimulates adiponectin secretion in ovarian granulosa cells through the PKA signaling pathway. This mechanism potentially influences glucose transport (GLUT1) and utilization within the ovaries.

Glucose transporters (GLUTs): Underreported yet crucial molecules in unraveling testicular toxicity

Glucose transporters (GLUTs) are crucial in maintaining glucose homeostasis and supporting energy production in various tissues, including the testes. This review article delves into the distribution and function of GLUTs in distinct testicular cell types, namely Leydig cells, Sertoli cells, germ cells, and spermatozoa, shedding light on their significance in the context of male reproductive health-an issue of mounting global concern. Furthermore, this article examines the implications of GLUT dysregulation in testicular dysfunction. Altered GLUT expression has been associated with impaired steroidogenesis, spermatogenesis, sperm count, and motility in various animal models. Lastly, the article underscores the potential therapeutic implications of targeting GLUTs concerning testicular toxicity. Insights gleaned from studies in diabetes and cancer suggest that modulating GLUT expression and translocation could present novel strategies for mitigating testicular dysfunction and safeguarding male fertility. In summary, the intricate interplay between GLUTs, glucose metabolism, and testicular health underscores the significance of sustaining testicular glucose homeostasis for male reproductive health. Manipulating GLUTs presents an innovative avenue to address testicular dysfunction, potentially revolutionizing therapeutic strategies to restore male fertility and overall reproductive well-being. Future research in this field holds great promise for advancing male fertility treatments and reproductive health interventions.

Diabetes-induced male infertility: potential mechanisms and treatment options

Male infertility is a physiological phenomenon in which a man is unable to impregnate a fertile woman during a 12-month period of continuous, unprotected sexual intercourse. A growing body of clinical and epidemiological evidence indicates that the increasing incidence of male reproductive problems, especially infertility, shows a very similar trend to the incidence of diabetes within the same age range. In addition, a large number of previous in vivo and in vitro experiments have also suggested that the complex pathophysiological changes caused by diabetes may induce male infertility in multiple aspects, including hypothalamic-pituitary-gonadal axis dysfunction, spermatogenesis and maturation disorders, testicular interstitial cell damage erectile dysfunction. Based on the above related mechanisms, a large number of studies have focused on the potential therapeutic association between diabetes progression and infertility in patients with diabetes and infertility, providing important clues for the treatment of this population. In this paper, we summarized the research results of the effects of diabetes on male reproductive function in recent 5 years, elaborated the potential pathophysiological mechanisms of male infertility induced by diabetes, and reviewed and prospected the therapeutic measures.

Glycolysis as key regulatory step in FSH-induced rat Sertoli cell proliferation: Role of the mTORC1 pathway

The definitive number of Sertoli cells (SCs), achieved during the proliferative periods, defines the spermatogenic capacity in adulthood. It is recognized that FSH is the main mitogen targeting SC and that it exerts its action, at least partly, through the activation of the PI3K/Akt/mTORC1 pathway. mTORC1 controls a large number of cellular functions, including glycolysis and cell proliferation. Interestingly, recent evidence revealed that the glycolytic flux might modulate mTORC1 activity and, consequently, cell cycle progression. Although mature SC metabolism has been thoroughly studied, several aspects of metabolism regulation in proliferating SC are still to be elucidated. The objective of this study was to explore whether aerobic glycolysis is regulated by FSH through mTORC1 pathway in proliferating SC, and to assess the involvement of glycolysis in the regulation of SC proliferation. The present study was carried out utilizing 8-day-old rat SC cultures. The results obtained show that FSH enhances glycolytic flux through the induction of 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3) and lactate dehydrogenase A (LDHA) in an mTORC1 dependent manner. In addition, PFKFB3 and LDH inhibitors prevent FSH from activating mTORC1 and stimulating SC proliferation and glycolysis, presumably through mTORC1 pathway inhibition. In summary, FSH simultaneously regulates SC proliferation and glycolysis in an mTORC1 dependent manner, and glycolysis seems to cooperate with FSH in the stimulation of both cellular functions through the modulation of the same signalling pathway. Therefore, a positive feedback between the mTORC1 pathway and glycolysis triggered by FSH is hypothesized.

Melatonin improves oxidative state and lactate metabolism in rodent Sertoli cells

Antioxidant actions of melatonin and its impact on testicular function and fertility have already been described. Considering that Sertoli cells contribute to provide structural support and nutrition to germ cells, we evaluated the effect of melatonin on oxidative state and lactate metabolism in the immature murine TM4 cell line and in immature hamster Sertoli cells. A prooxidant stimulus applied to rodent Sertoli cells expressing MT1/MT2 receptors, increased lipid peroxidation whereas decreased antioxidant enzymes (superoxide dismutase 1, catalase, peroxiredoxin 1) expression and catalase activity. These changes were prevented by melatonin. Furthermore, melatonin stimulated lactate dehydrogenase (LDH) expression/activity via melatonin receptors, and increased intracellular lactate production in rodent Sertoli cells. Interestingly, oral melatonin supplementation in infertile men positively regulated LDHA testicular mRNA expression. Overall, our work provides insights into the potential benefits of melatonin on Sertoli cells contributing to testicular development and the future establishment of a sustainable spermatogenesis.

Environmentally relevant doses of endocrine disrupting chemicals affect male fertility by interfering with sertoli cell glucose metabolism in mice

The growing global deterioration in several aspects of human health has been partly attributed to hazardous effects of endocrine-disrupting chemicals (EDCs) exposure. Therefore, experts and government regulatory agencies have consistently advocated for studies on the combined effects of EDCs that model human exposure to multiple environmental chemicals in real life. Here, we investigated how low concentrations of bisphenol A (BPA), and phthalates compounds affect the Sertoli cell glucose uptake/lactate production in the testis and male fertility. An EDC mixture containing a detected amount of each chemical compound in humans, called daily exposure (DE), and DE increased in magnitude by 25 (DE25), 250 (DE250), and 2500 (DE2500), and corn oil (control) were administered for six weeks to male mice. We found that DE activated estrogen receptor beta (Erβ) and glucose-regulated protein 78 (Grp 78) and disrupted the estradiol (E2) balance. In addition, DE25, DE250, and DE2500 doses of the EDC mixture via binding with Sertoli cells' estrogen receptors (ERs) inhibited the glucose uptake and lactate production processes by downregulating glucose transporters (GLUTs) and glycolytic enzymes. As a result, endoplasmic reticulum stress (ERS), marked by unfolded protein response (UPR) activation, was induced. The accompanying upregulation of activating transcription factor 4 (ATF4), inositol requiring enzyme-1 (IRE1), C/EBP homologous protein (CHOP), and mitogen-activated protein kinase (MAPK) signaling promoted antioxidant depletion, testicular cell apoptosis, abnormal regulation of the blood-testis barrier, and decreased sperm count. Therefore, these findings suggest that human and wildlife exposure to multiple environmental chemicals can produce a wide range of reproductive health complications in male mammals.

Environmentally relevant perinatal exposure to DBP accelerated spermatogenesis by promoting the glycolipid metabolism of Sertoli cells in male offspring mice

Since Sertoli cells (SCs) play an essential role in providing energy for spermatogenesis, the present study aimed to investigate the effects of maternal exposure to plasticizer Dibutyl phthalate (DBP) on the onset of spermatogenesis in male offspring through the metabolism pathway as well as the underlying molecular mechanism. Here, pregnant mice were treated with 0 (control), 50, 250, or 500 mg/kg/day DBP in 1 mL/kg corn oil administered daily by oral gavage from gestation day (GD) 12.5 to parturition. The in vivo results showed that 50 mg/kg/day DBP exposure could promote the expression of glucose metabolism-related proteins (GLUT3, LDHA, and MCT4) in the testis of 22 days male offspring. The in vitro results demonstrated that 0.1 mM monobutyl phthalate (MBP, the active metabolite of DBP) promoted the lactate production, glucose consumption, and glycolytic flux of immature SCs, which was paralleled by the upregulated expression of glucose metabolism-related proteins (GLUT1, GLUT3, LDHA, and MCT4). On the other hand, DBP/MBP increased fatty acid (FA) uptake, FA β-oxidation, and ATP production by promoting the expression of CD36 in immature SCs, which might accelerate the maturity of SCs to support the onset of spermatogenesis. Therefore, our findings provided a new perspective on glycolipid metabolism to explain prenatal DBP exposure leading to earlier onset of spermatogenesis in male offspring mice.

Abnormalities in sex hormones and sexual dysfunction in males with diabetes mellitus: A mechanistic insight

Diabetes is a considerate metabolic disorder that can lead to a series of complications, involving the malfunctioning of the reproductive system of males. It has been observed that there is a gradual rise in male diabetic patients and almost half of the diabetic males have low semen quality and decrease reproductive function. In diabetic conditions, prolonged hyperglycemia leads to oxidative stress, diabetic neuropathy, and insulin resistance. Insulin resistance and its deficiency can impair the hypothalamus, pituitary gland, gonads, and perigonads. This causes a decrease in the secretion of gonadal steroids such as GnRH (gonadotropin-releasing hormone), FSH (follicle-stimulating hormone), LH (luteinizing hormone), and Testosterone. Moreover, it also causes damage to the testicles, spermatogenic and stromal cells, seminiferous tubules, and various structural injuries to male reproductive organs. During spermatogenesis, glucose metabolism plays an important role, because the fundamental activities of cells and their specific features, such as motility and mature sperm fertilization activity, are maintained by glucose metabolism. All these activities can influence the fertility and reproductive health of males. But the glucose metabolism is primarily disrupted in diabetic conditions. Until now, there has been no medicine focusing on the reproductive health of diabetic people. In this chapter, we review the consequences of diabetes on the reproductive system of males and all the pathways involved in the dysfunction of the reproductive system. This will help interpret the effects of DM on male reproductive health.

Simultaneous regulation of lactate production and fatty acid metabolism by Resveratrol in rat Sertoli cells

Sertoli cells provide structural and nutritional support for germ cell development. They actively metabolize glucose and convert it into lactate, which is an important source of energy for germ cells. They also oxidize fatty acids (FA), stored as triacylglycerides (TAGs) within lipid droplets (LD), to fulfill their own energy requirements. So, the combined regulation of lactate production and FA metabolism may be relevant to the physiology of seminiferous tubules. Resveratrol (RSV) is a nutritional supplement found primarily in red grape skin that exhibits multiple beneficial health effects: it is cardioprotective, anti-inflammatory, anticancer, and antiaging. The aim of this study was to evaluate the effect of RSV in Sertoli cells lactate production and lipid metabolism. Sertoli cell cultures obtained from 20-day-old rats were incubated for different times with 10 or 50 μM RSV. RSV treatment increased lactate production and glucose consumption. These increments were accompanied by a rise in GLUT1 expression, which is the main glucose transporter in Sertoli cells. On the other hand, RSV decreased LD content and TAG levels. In addition, an increase in ATGL and FAT/CD36 mRNA levels was observed, which suggests augmented cytoplasmatic FA availability. RSV treatment also increased P-ACC levels, which might indicate that RSV promotes FA transport into the mitochondria to be oxidized. An enhanced expression of LCAD and MCAD, enzymes that participate in the oxidation of FA, was also observed. Altogether, these results suggest that RSV simultaneously regulates Sertoli cells lactate production and lipid metabolism, ensuring an adequate energetic balance both in germ and Sertoli cells.

Adverse Birth and Child Outcomes in Children Fathered by Men Treated with Antidiabetics Prior to Conception: A Nationwide Cohort Study

BACKGROUND

The safety of fathers' use of antidiabetic drugs in terms of child outcomes is an important clinical question. We aimed to assess the risk of adverse birth and early childhood outcomes after fathers' use of antidiabetics prior to conception.

METHODS

A nationwide cohort study based on Danish health registries. The study comprised all live born singleton children in Denmark (1997 through 2018). Children were categorized according to fathers' filled prescriptions for antidiabetic drugs three months prior to conception. Exposed cohorts: children born after paternal use of insulin or non-insulin anti-hyperglycemic agents. The unexposed constituted children born by fathers not treated with antidiabetics prior to conception. We examined adverse birth outcomes (preterm birth, small for gestational age (SGA)), and adverse childhood outcomes in the first year of life (major congenital malformations (MCMs), and infections diagnosed at a hospital).

RESULTS

A total of 1,318,684 children were included. In all, 5527 children were born after paternal use of insulin, 2121 after use of non-insulin anti-hyperglycemic agents, and 1,311,036 were unexposed. After fathers' use of insulin we did not find increased risk of adverse outcomes. After fathers' use of metformin, the adjusted OR of MCMs was 1.40 (95% CI 1.11-1.76). After fathers' use of sulfonylureas, the adjusted OR of SGA was 1.80 (95% CI 1.11-2.93), and for child gastrointestinal infections the adjusted HR was 1.76 (95% CI 1.04-2.99).

CONCLUSIONS

Fathers' use of insulin was reassuring. Metformin and sulfonylureas were associated with selected adverse outcomes. Our findings suggest an additional 14 MCMs per 1000 fathers exposed to metformin prior to conception. As there is no meaningful supporting biological rationale, these findings should be confirmed in a different population prior to clinical consequences being drawn.

Molecular mechanisms regulating spermatogenesis in vertebrates: Environmental, metabolic, and epigenetic factor effects

The renewal of the natural resources is one of the most concerning aspects of modern farming. In animal production, there are many barriers breeders and researchers have to overcome to develop new practices to improve reproductive potential and hasten sexual maturation of the commercially viable species, while maintaining meat quality and sustainability. With the utilization of molecular biology techniques, there have been relevant advances in the knowledge of spermatogenesis, especially in mammals, resulting in new possibilities to control male fertility and the selection of desirable characteristics. Most of these discoveries have not been implemented in animal production. In this review, recent studies are highlighted on the molecular pathways involved in spermatogenesis in the context of animal production. There is also exploration of the interaction between environmental factors and spermatogenesis and how this knowledge may revolutionize animal production techniques. Furthermore, new insights are described about the inheritance of desired characteristics in mammals and there is a review of nefarious actions of pollutants, nutrition, and metabolism on reproductive potential in subsequent generations. Even though there are these advances in knowledge base, results from recent studies indicate there are previously unrecognized environmental effects on spermatogenesis. The molecular mechanisms underlying this interaction are not well understood. Research in spermatogenesis, therefore, remains pivotal as a pillar of animal production sustainability.

Evaluation of testicular glycogen storage, FGF21 and LDH expression and physiological parameters of sperm in hyperglycemic rats treated with hydroalcoholic extract of Securigera Securidaca seeds, and Glibenclamide

Structural and physiological changes in sperm and semen parameters reduce fertility in diabetic patients. Securigera Securidaca (S. Securidaca) seed is a herbal medicine with hypoglycemic, antioxidant, and anti-hypertensive effects. The question now is whether this herbal medicine improves fertility in diabetic males. The study aimed to evaluate the effects of hydroalcoholic extract of S. Securidaca seeds (HESS), glibenclamide and a combination of both on fertility in hyperglycemic rats by comparing histological and some biochemical changes in testicular tissue and sperm parameters. The treatment protocol included administration of three doses of HESS and one dose of glibenclamide, as well as treatment with both in diabetic Wistar diabetic rats and comparison of the results with untrated groups. The quality of the testicular tissue as well as histometric parameters and spermatogenesis indices were evaluated during histopathological examination. Epididymal sperm analysis including sperm motility, viability, abnormalities, maturity, and chromatin structure were studied. The effect of HESS on the expression of LDH and FGF21 genes and tissue levels of glycogen, lactate, and total antioxidant capacity in testicular tissue was investigated and compared with glibenclamide. HESS improved sperm parameters in diabetic rats but showed little restorative effect on damaged testicular tissue. In this regard, glibenclamide was more effective than the highest dose of HESS and its combination with HESS enhanced its effectiveness so that histological tissue characteristics and sperm parameters were were comparable to those of healthy rats. The expression level of testicular FGF21 gene increased in diabetic rats, which intensified after treatment with HESS as well as glibenclamide. The combination of HESS and glibenclamide restored the expression level of testicular LDH gene, as well as tissue storage of glycogen, lactate and LDH activity, and serum testosterone to the levels near healthy control. S. Securidaca seeds can be considered as an effective supplement in combination with hypoglycemic drugs to prevent infertility complications in diabetes.

Different continuous exercise training intensities induced effect on sertoli-germ cells metabolic interaction; implication on GLUT-1, GLUT-3 and MCT-4 transporting proteins expression level

Despite other tissues, the effect of different exercise training protocols (ETPs) on the expression levels of metabolic substrates transmembrane transporters in the testicular tissue, remains completely unexplored. Thus, the effects of low, moderate and high-intensity ETPs on the SCs and germ cells potentials in GLUT-1, GLUT-3 and MCT-4 expression levels was investigated in this study. The animals were assigned into 4 groups, including sedentary control, low-intensity continuous (LICT), moderate-intensity (MICT) and high-intensity (HICT) ETPs-induced groups (n = 6/group). The GLUT-1, GLUT-3 and MCT-4 expressions, cytoplasmic carbohydrate storages of SCs and germ cells, the SCs survival and the spermatogenesis and spermiogenesis rates were assessed. The LICT and MICT did not significantly alter the protein expression levels of GLUT-3 and MCT-4 in the SCs and germ cells, while decreased the GLUT-1 protein content versus the sedentary control animals. In contrast, the HICT remarkably suppressed the GLUT-1 and MCT-4 in both SCs, and germ cells and diminished GLUT-3 in SCs and increased in the germ cells. No significant changes were revealed in the cytoplasmic carbohydrate storage in the LICT and MICT groups, while significantly diminished in the HICT group. The HICT group showed a failed spermatogenesis and spermiogenesis, which were not demonstrated in the sedentary control, LICT and MICT groups. In conclusion, the HICT, by reducing the GLUT-1, GLUT-3 and MCT-4 protein contents in the SCs and reducing the SCs survival, can suppress the glucose transmembrane transport and inhibit the lactate export from SCs, which in turn, ends with failed spermatogenesis and spermiogenesis.

Metformin mitigates impaired testicular lactate transport/utilisation and improves sexual behaviour in streptozotocin-induced diabetic rats

CONTEXT

Lactate is the preferred energy substrate for developing testicular germ cells. Diabetes is associated with impaired testicular lactate transport/utilisation, and poor sexual behaviour.

OBJECTIVE

To examine the effects of metformin on parameters involved in testicular lactate production, transport/utilisation, and sexual behaviour in diabetic state.

METHODS

Male Sprague-Dawley rats were assigned into normal control (NC), diabetic control (DC), and metformin-treated diabetic group (n = 6/group). Metformin (300 mg/kg b.w./day) was administrated orally for 4 weeks.

RESULTS

Intra-testicular glucose and lactate levels, and lactate dehydrogenase (LDH) activity increased, while the mRNA transcript levels of genes responsible for testicular glucose and lactate transport/utilisation (glucose transporter 3, monocarboxylate transporter 4 (MCT4), MCT2, and LDH type C) decreased in DC group. Furthermore, penile nitric oxide increased, while cyclic guanosine monophosphate decreased, with impaired sexual behaviour in DC group. Treatment with metformin improved these parameters.

CONCLUSIONS

Metformin increases testicular lactate transport/utilisation and improves sexual behaviour in diabetic state.

Immunodistribution of RFamide-related peptide-3 (RFRP-3) during the seminiferous epithelium cycle in a desert rodent Psammomys obesus

The Sand rat, Psammomys obesus, living northwest of the Algerian Sahara, presents a seasonal reproductive cycle. The purposes of this study were firstly to determine the stages of seminiferous epithelium cycle (SEC) by histological and morphometric analysis and secondly to investigate, for the first time, the testicular expression of RFamide-related peptide-3 (RFRP-3) during the SEC by immunohistochemistry. The results showed that the SEC consists of 14 stages according to the tubular morphology method. RFRP-3 was observed in both testicular compartments: the tubular and the interstitial. Leydig cells exhibited the highest RFRP-3 signal (30.73 % ± 4.80) compared to Sertoli cells (13-15 %). In the germline, RFRP-3 was detected during the late prophase I of meiosis in late pachytene, diplotene and metaphasic spermatocytes I. In addition, only round and triangular spermatids were positive during spermiogenesis. Referring to the SEC, it was found that the increased staining of RFRP-3 in spermatocytes I coincided with late pachytene of XI and XII stages (16.90 % ± 0.69 and 16.61 % ± 0.28, respectively). In spermatids, the labeling decreased in the triangular ones at stage IX (8.04 % ± 0.42). These results suggest the involvement of RFRP-3 in the control of SEC in P. obesus.

A Brazilian pulp and paper mill effluent disrupts energy metabolism in immature rat testis and alters Sertoli cell secretion and mitochondrial activity

Our objective was to investigate whether the pulp and paper mill industry effluent could affect the testis and Sertoli cells in a fast exposure period. For this, the present study was carried out in immature rats at 10-day-old. Testis treated in vitro with 4% effluent for 1 h presented changes in energy metabolism in terms of a decrease in lactate content and glucose uptake. Elevation in GSH content, as an antioxidant defense mechanism, was also detected. Sertoli cells treated with 4% effluent for 1 hour showed alterations in the mitochondrial metabolism that favor the decoupling of oxidative phosphorylation and the generation of oxygen reactive species and also a time and concentration-dependent delay secretion of acidic vesicles. Our results showed that pollutants present in the pulp and paper mill effluents, in a short time of exposure, are capable of inducing alterations in important metabolic functions in the testis and in Sertoli cells that are crucial for the correct progression of spermatogenesis and fertility.

Neural Deletion of Glucose Transporter Isoform 3 Creates Distinct Postnatal and Adult Neurobehavioral Phenotypes

We created a neural-specific conditional murine glut3 (Slc2A3) deletion (glut3 ^{flox/flox/nestin-Cre+}) to examine the effect of a lack of Glut3 on neurodevelopment. Compared with age-matched glut3 ^flox/flox = WT and heterozygotes (glut3 ^{flox/+/nestin-Cre+}), we found that a >90% reduction in male and female brain Glut3 occurred by postnatal day 15 (PN15) in glut3 ^{flox/flox/nestin-Cre+} This genetic manipulation caused a diminution in brain weight and cortical thickness at PN15, a reduced number of dendritic spines, and fewer ultrasonic vocalizations. Patch-clamp recordings of cortical pyramidal neurons revealed increased frequency of bicuculline-induced paroxysmal discharges as well as reduced latency, attesting to a functional synaptic and cortical hyperexcitability. Concomitant stunting with lower glucose concentrations despite increased milk intake shortened the lifespan, failing rescue by a ketogenic diet. This led to creating glut3 ^{flox/flox/CaMK2α-Cre+} mice lacking Glut3 in the adult male limbic system. These mice had normal lifespan, displayed reduced IPSCs in cortical pyramidal neurons, less anxiety/fear, and lowered spatial memory and motor abilities but heightened exploratory and social responses. These distinct postnatal and adult phenotypes, based upon whether glut3 gene is globally or restrictively absent, have implications for humans who carry copy number variations and present with neurodevelopmental disorders.SIGNIFICANCE STATEMENT Lack of the key brain-specific glucose transporter 3 gene found in neurons during early postnatal life results in significant stunting, a reduction in dendritic spines found on neuronal processes and brain size, heightened neuronal excitability, along with a shortened lifespan. When occurring in the adult and limited to the limbic system alone, lack of this gene in neurons reduces the fear of spatial exploration and socialization but does not affect the lifespan. These features are distinct heralding differences between postnatal and adult phenotypes based upon whether the same gene is globally or restrictively lacking. These findings have implications for humans who carry copy number variations pertinent to this gene and have been described to present with neurodevelopmental disorders.

Comparative proteomic analysis of maternal peripheral plasma and umbilical venous plasma from normal and gestational diabetes mellitus pregnancies

Gestational diabetes mellitus (GDM) increases many health risks in offspring. The study aims to investigate the underlying mechanism in fetal risk of GDM.We collected maternal peripheral plasma and umbilical venous plasma samples from 4 GDM and 4 control patients during their delivery at a university-based women's hospital. An isobaric tag for relative and absolute quantitation-labeled proteomics analysis was performed. The enzyme-linked immunosorbent assay was used to confirm the change of cholesteryl ester transfer protein (CETP). Bioinformatic analysis was performed with Ingenuity Pathway Analysis (IPA) software package.We identified 19 up-regulated proteins and 15 down-regulated proteins in GDM peripheral plasma, 29 up-regulated proteins and 69 down-regulated proteins in GDM umbilical venous plasma. CETP concentration was significantly lower in both GDM peripheral plasma and umbilical venous plasma. Upstream regulator analysis predicted follicle-stimulating hormone (FSH) as the activated regulator of differentially expressed proteins.The protein profiles in both GDM peripheral plasma and umbilical venous plasma between normal and GDM patients were significantly different. The results indicated that CETP and FSH might associates with health problem of GDM offspring.

Research Trends and Hotspots Analysis Related to the Effects of Xenobiotics on Glucose Metabolism in Male Testes

This study aimed to integrate and analyze the existing studies and to explore research trends and hotspots related to the effects of xenobiotics on glucose metabolism in male testes. All articles were retrieved from the PubMed database, from an inception date up to 10 June 2017. CiteSpace software (version 5.1.R8 SE) was used for the co-word cluster analysis. A total of 165 eligible publications were included in this study. In 1949⁻1959, only two articles were published. After 1960, the number of articles increased steadily. These articles were published in 97 journals, in particular, in the Indian Journal of Experimental Biology (11 articles, 6.7%). Most of the authors (87.0%) only published one article. Only a few established research teams, mostly from the USA, worked consistently in this field. The main xenobiotics that had been studied were medicine and common environmental pollutants, e.g., gossypol, cadmium, di-n-butyl phthalate, and alpha-chlorohydrin. The hotspot keywords were Sertoli cell, lactate dehydrogenase, 6-phosphate dehydrogenase, oxidative stress, and glucose metabolism. The focus of research had been changed overtime. This is the first bibliometric study between xenobiotics and glucose metabolism in the male testes. The findings suggest that environmental pollutants have become a huge concern, and related research should be strengthened.

Glucose and glutamine handling in the Sertoli cells of transgenic rats overexpressing regucalcin: plasticity towards lactate production

Sertoli cells (SCs) possess the unparalleled ability to provide the germ line with growth factors and nutrients. Although SCs can oxidize amino acids, e.g., glutamine, they mostly metabolize glucose, producing high amounts of lactate, the germ cells preferential substrate. Regucalcin (RGN) is a calcium-binding protein that has been indicated as a regulator of cell metabolism. In this study, we investigated glucose and glutamine handling in the SCs of transgenic rats overexpressing RGN (Tg-RGN) comparatively with wild-type (Wt) littermates. Primary SCs isolated from adult Tg-RGN animals and maintained in culture for 24 hours, produced and exported more lactate, despite consuming less glucose. These observations were underpinned by increased expression of alanine transaminase, and augmented glutamine consumption, suggesting that alternative routes are contributing to the enhanced lactate production in the SCs of Tg-RGN rats. Moreover, lactate seems to be used by germ cells, with diminished apoptosis being detected in the seminiferous tubules of Tg-RGN animals cultured ex vivo. The obtained results showed a distinct metabolism in the SCs of Wt and Tg-RGN rats widening the roles assigned to RGN in spermatogenesis. These findings also highlighted the plasticity of SCs metabolism, a feature that would be exploited in the context of male infertility.

The hypothalamic neuropeptide orexin A- a possible regulator in glucose homeostasis and germ cell kinetics in adult mice testes

Orexin A (OXA), a hypothalamic neuropeptide, regulates food intake, sleep-wake cycle and energy balance by binding to its receptor (OX1R). Apart from brain, OXA and OX1R are also present in peripheral organs including reproductive tissues. Mammalian reproduction depends on uptake and proper utilization of glucose in the testes. This study, therefore, examined role of OXA/OX1R system in regulation of glucose homeostasis in adult mouse testis under in vivo and ex vivo conditions. Binding of OXA to OX1R was blocked using an OX1R antagonist, SB-334867. Mice were given a single bilateral intratesticular injection of the antagonist at doses of 4 and 12μg/mouse and sacrificed 24 h post-injection. In order to understand the direct role of OXA in testes of adult mice, an ex vivo experiment was performed where binding of OXA to OX1R in the testis was blocked by using the same OX1R antagonist. The antagonist treatment affected testicular glucose and lactate concentration with concomitant down-regulation in the expression of glucose transporters 3 and 8. A decreased activity in lactate dehydrogenase enzyme and imbalance between germ cell survival and proliferation were also noted in testes in treated mice. The results of ex vivo study supported the results obtained from in vivo study. The findings thus suggest involvement of OXA/OX1R system in regulation of testicular glucose homeostasis and germ cell kinetics in adult mice.

Role of FSH glycan structure in the regulation of Sertoli cell inhibin production

Variations in follicle-stimulating hormone (FSH) carbohydrate composition and structure are associated with important structural and functional changes in Sertoli cells (SCs) during sexual maturation. The aim of the present study was to investigate the impact of FSH oligosaccharide structure and its interaction with gonadal factors on the regulation of monomeric and dimeric inhibin production at different maturation stages of the SC. Recombinant human FSH (rhFSH) glycosylation variants were isolated according to their sialylation degree (AC and BA) and complexity of oligosaccharides (CO and HY). Native rhFSH stimulated inhibin α-subunit (Pro-αC) but did not show any effect on inhibin B (INHB) production in immature SCs isolated from 8-day-old rats. Activin A stimulated INHB and had a synergistic effect on FSH to stimulate Pro-αC. The less acidic/sialylated rhFSH charge analogues, BA, were the only charge analogue mix that stimulated INHB as well as the most potent stimulus for Pro-αC production. Native rhFSH stimulated both Pro-αC and INHB in SCs at a more advanced maturation stage, isolated from 20-day-old rats. In these cells, all rhFSH glycosylation variants increased INHB and Pro-αC production, even in the presence of growth factors. The BA preparation exerted a more marked stimulatory effect on INHB and Pro-αC than the AC. Glycoforms bearing high mannose and hybrid-type oligosaccharides, HY, stimulated INHB and Pro-αC more effectively than those bearing complex oligosaccharides, CO, even in the presence of gonadal growth factors. These findings demonstrate the modulatory effect of FSH oligosaccharide structure on the regulation of inhibin production in the male gonad.

Germ cells regulate 3-hydroxybutyrate production in rat Sertoli cells

Paracrine regulation of Sertoli cell function by germ cells is an outstanding characteristic of testicular physiology. It has been demonstrated that Sertoli cells produce ketone bodies and that germ cells may use them as energy source. The aim of the study was to analyze a possible regulation by germ cells of ketogenesis in Sertoli cells. Cultures of Sertoli cells (SC) obtained from 31-day-old rats were co-cultured with germ cells (GC). The results presented herein show that the presence of GC stimulated 3-hydroxybutyrate production and increased mRNA levels of two enzymes involved in ketogenesis-carnitine palmitoyltransferase 1a (CPT1a) and mitochondrial 3-hydroxy-3-methylglutaryl-CoA (mHMGCoA) synthase- in SC. Additionally, GC increased monocarboxylate transporter 4 (Mct4) expression in SC, a transporter involved in ketone bodies exit. To evaluate if the observed effects might be mediated by soluble factors, SC cultures were incubated with germinal cell-conditioned medium (GCCM) or with two growth factors, bFGF and IGF1, which are known to be secreted by GC. We observed that GCCM and bFGF stimulated ketone bodies production but that IGF1 did not modify it. Also, we observed that GCCM and bFGF increased Cpt1a and Mct4 mRNA levels. In summary, results presented herein demonstrate that Sertoli cells are able to produce ketone bodies and that its production is regulated in a paracrine way by germ cells. This study adds new information about communication between Sertoli cells and developing germ cells.

PPARγ activation regulates lipid droplet formation and lactate production in rat Sertoli cells

Sertoli cells provide the structural and nutritional support for germ cell development; they actively metabolize glucose and convert it to lactate, which is an important source of energy for germ cells. Furthermore, Sertoli cells can oxidize fatty acids, a metabolic process that is assumed to fulfill their own energy requirements. Fatty acids are stored as triacylglycerides within lipid droplets. The regulation of fatty acid storage in conjunction with the regulation of lactate production may thus be relevant to seminiferous tubule physiology. Our aim is to evaluate a possible means of regulation by the PPARγ activation of lipid droplet formation and lactate production. Sertoli cell cultures obtained from 20-day-old rats were incubated with Rosiglitazone (10 μM), a PPARγ activator, for various periods of time (6, 12, 24 and 48 h). Increased triacylglycerides levels and lipid droplet content were observed, accompanied by a rise in the expression of genes for proteins involved in fatty acid storage, such as the fatty acid transporter Cd36, glycerol-3-phosphate-acyltransferases 1 and 3, diacylglycerol acyltransferase 1 and perilipins 1, 2 and 3, all proteins that participate in lipid droplet formation and stabilization. However, PPARγ activation increased lactate production, accompanied by an augmentation in glucose uptake and Glut2 expression. These results taken together suggest that PPARγ activation in Sertoli cells participates in the regulation of lipid storage and lactate production thereby ensuring simultaneously the energetic metabolism for the Sertoli and germ cells.

1,25(OH)2 vitamin D3 signalling on immature rat Sertoli cells: gamma-glutamyl transpeptidase and glucose metabolism

1α,25-Dihydroxyvitamin D₃ (1,25-D₃) is critical for the maintenance of normal male reproduction since reduced fertility is observed in vitamin D-deficient rats. Gamma-glutamyl transpeptidase (GGT) is a membrane-bound enzyme that is localized on Sertoli cells and catalyses the transfer of the gamma-glutamyl residues to an amino acid or peptide acceptor. Sertoli cells are also responsible for providing nutrients, as lactate, to the development of germ cells. The aim of this study was to investigate the effect and the mechanism of action of 1,25-D₃ on GGT on Sertoli cell functions from 30-day-old immature rat testis. Results demonstrated that 1,25-D₃ stimulates GGT activity at Sertoli cells plasma membrane through a PKA-dependent mechanism of action, which was not dependent of active de novo protein synthesis. The hormone increases glucose uptake, as well as lactate production and release by Sertoli cells without altering the reactive oxygen species (ROS) generation. In addition, 1,25-D₃ did not change reduced glutathione (GSH) amount or oxygen consumption, and diminished Sertoli cell death. These findings demonstrate that 1,25-D₃ stimulatory effect on GGT activity, glucose uptake, LDH activity and lactate production seem to be an important contribution of Sertoli cells for germ cells nutrition and for a full and active ongoing spermatogenesis.

Impact of uteroplacental insufficiency on postnatal rat male gonad

Prenatal events such as intrauterine growth restriction can affect gonadal development of the offspring and have an impact on reproductive health. To investigate the effects of intrauterine growth restriction induced by uterine artery ligation on the postnatal rat testis. Pregnant rats underwent uterine artery ligation at day 19 of gestation. Offspring were killed at 5, 20 and 40 days post-partum (dpp). At killing, one gonad was snap-frozen in liquid nitrogen and processed for RNA and steroid extraction. The other gonad was formalin-fixed for histology. Gene expression was analyzed by TaqMan Low-Density Array. Intratesticular testosterone, estradiol and serum gonadotrophins were measured. Thirty genes were dysregulated in intrauterine growth-restricted rats compared to controls, among which markers of Sertoli cell and Leydig cell function, cell metabolism and growth factors. Testis weights were significantly reduced at 5 and 20 dpp in intrauterine growth-restricted rats and caught-up by 40 dpp Accordingly, Sertoli cell number was significantly lower in 5 dpp intrauterine growth-restricted rats. At 20 dpp, intratesticular testosterone was significantly increased in intrauterine growth-restricted rats, whereas serum gonadotrophins were unchanged. IUGR altered the gene expression in the rat testes up to peripubertal age and reduced testis size and Sertoli cell number in neonatal age. Multiple mechanisms encompassing genetic changes and steroid production by the testis may be involved in the catch-up growth phase that restored testis size by 40 dpp Permanent consequences on organ function and gamete integrity cannot be excluded and deserve further investigations.

Participation of HIFs in the regulation of Sertoli cell lactate production

Hypoxia Inducible Factors (HIFs) are master regulators of glycolytic metabolism. HIFs consist of a constitutive HIFbeta (HIFβ) subunit and a HIFalpha (HIFα) subunit, whose half-life depends on prolyl-hydroxylases activity. Inhibition of prolyl-hydroxylases by hypoxia or transition metals, or augmentation of HIFα subunit levels by hormonal stimuli lead to a higher HIF transcriptional activity. On the other hand, it is well known that lactate produced by Sertoli cells is delivered to and used by germ cells as an energy substrate. The aim of this work was to investigate whether HIFs participate in the regulation of lactate production in rat Sertoli cells and whether they are involved in the FSH mechanism of action. In order to reach a higher HIF transcriptional activity, Sertoli cells were treated with CoCl2. We observed that a higher HIF transcriptional activity leads to an augmentation of: lactate production, glucose uptake and LDH activity. Besides, an increase in Glut1, Pkm2 and Ldha mRNA levels was observed. These findings suggested that HIFs may participate in the modulation of Sertoli cell nutritional function. As FSH regulates lactate production, we evaluated whether HIFs were involved in FSH action. Sertoli cells were stimulated with FSH in the absence or presence of LW6, a drug which promotes HIFα subunit degradation. On the one hand, we observed that FSH increases HIF1α protein, Hif1α and Hif2α mRNA levels and, on the other hand, that LW6 inhibits FSH-stimulated lactate production, glucose uptake, Glut1, Pkm2 and Ldha expression. It is proposed that HIFs are key components of the intricate pathways utilized by FSH to regulate the provision of lactate for germ cells. Considering that FSH is the master endocrine regulator of Sertoli cells, it is not surprising that this hormone may employ several regulatory mechanisms to fulfill the nourishing functions of this cell type.

Localization, expression and role of Orexin A and its receptor in testes of neonatal mice

Orexin A (OXA), a hypothalamic neuropeptide, and its receptor (OX1R) are primarily expressed in lateral hypothalamus and are involved in the control of various biological functions. Expressions of OXA and OX1R have also been reported in peripheral organs like gastrointestinal and genital tracts. In the present study, expressions of OXA and OX1R have been observed in the testis of Parkes strain neonatal mice by semi-quantitative RT-PCR and western blot analyses. Immunohistochemical study also revealed their presence on spermatogonia, Sertoli cells and in the interstitium of the testis. In order to understand the role of OXA and OX1R in testicular development, an in vitro study was also performed. For this, binding of OXA to OX1R was blocked using OX1R specific antagonist, SB-334867. Eighteen mice were sacrificed and their testes were cultured in complete media containing vehicle and two doses (0.1 and 4.0μg/ml media) of SB-334867 for 72h in CO₂ incubator at 37°C. At the end of culture period, testes were used for western blot and RT-PCR analyses to study the expression of various markers of gonadal development, such as steroidogenic factor 1 (SF-1), Wilms' tumor 1 (Wt1), Mullerian inhibiting substance (MIS) and stem cell factor (SCF). Further, expressions of OXA, OX1R and glucose transporter 3 (GLUT 3) were also studied. A marked increase in the expression of SF-1 and a decrease in the expression of Wt1 at both transcript and protein levels were noted, while there was a decrease in the expression of SCF and MIS at transcript level at both doses of the antagonist; this suggests that blockage of OXA binding to OX1R by SB-334867 affects testicular development. The decrease in expressions of OXA, OX1R and GLUT 3 in the test is in response to both doses of the antagonist points to their down-regulation causing inefficient uptake of glucose by the testicular cells, thereby affecting gonadal development. In conclusion, our results suggest that the binding of OXA to OX1R is important for the development of the testis.

Immunohistochemical localization of GLUT3, MCT1, and MCT2 in the testes of mice and rats: the use of different energy sources in spermatogenesis

Lactate represents a preferential energy substrate of germ cells rather than glucose. Testicular Sertoli cells are believed to produce lactate and pyruvate and to supply these to germ cells, particularly spermatocytes and spermatids. Monocarboxylate transporter (MCT), responsible for the transport of lactate and other monocarboxylates via the cell membrane, is abundant in the testes and sperm (MCT1, MCT2, and MCT4). For the uptake of glucose, germ cells within the seminiferous tubules and sperm have been known to intensely express GLUT3. The present study investigated expression profiles of MCTs and GLUTs and revealed their cellular and subcellular localization in the mouse and rat testis. An in situ hybridization analysis showed significant expressions of MCT1, MCT2, and GLUT3 mRNA in the testis. Immunohistochemically, spermatogonia, spermatocytes, and spermatids expressed MCT1 on their cell surfaces in a stage-dependent manner: in some seminiferous tubules, an intense expression of MCT1 was unique to the spermatogonia. MCT2 was restricted to the tails of elongated spermatids and sperm. An intense immunoreactivity for GLUT3 was shared by spermatocytes, spermatids, and sperm. Sertoli cells were devoid of any immunoreactivities for MCT1, MCT2, and GLUT3. The predominant energy source of germ cells may be lactate and other monocarboxylates--especially for spermatogonia, but glucose and other hexoses may be responsible for an energy supply to spermatocytes and spermatids.

Possible Role of GnIH as a Mediator between Adiposity and Impaired Testicular Function

The aim of the present study was to evaluate the roles of gonadotropin-inhibitory hormone (GnIH) as an endocrine link between increasing adiposity and impaired testicular function in mice. To achieve this, the effect of GnIH on changes in nutrients uptake and hormonal synthesis/action in the adipose tissue and testis was investigated simultaneously by in vivo study and separately by in vitro study. Mice were treated in vivo with different doses of GnIH for 8 days. In the in vitro study, adipose tissue and testes of mice were cultured with different doses of GnIH with or without insulin or LH for 24 h at 37°C. The GnIH treatment in vivo showed increased food intake, upregulation of glucose transporter 4 (GLUT4), and increased uptake of triglycerides (TGs) in the adipose tissue. These changes may be responsible for increased accumulation of fat in white adipose tissue, resulting in increase in the body mass. Contrary to the adipose tissue, treatment with GnIH both in vivo and in vitro showed decreased uptake of glucose by downregulation of glucose transporter 8 (GLUT8) expressions in the testis, which in turn resulted in the decreased synthesis of testosterone. The GnIH treatment in vivo also showed the decreased expression of insulin receptor protein in the testis, which may also be responsible for the decreased testicular activity in the mice. These findings thus suggest that GnIH increases the uptake of glucose and TGs in the adipose tissue, resulting in increased accumulation of fat, whereas simultaneously in the testis, GnIH suppressed the GLUT8-mediated glucose uptake, which in turn may be responsible for decreased testosterone synthesis. This study thus demonstrates GnIH as mediator of increasing adiposity and impaired testicular function in mice.

Mammalian target of rapamycin controls glucose consumption and redox balance in human Sertoli cells

OBJECTIVE

To study the role of mammalian target of rapamycin (mTOR) in the regulation of human Sertoli cell (hSC) metabolism, mitochondrial activity, and oxidative stress.

DESIGN

Experimental study.

SETTING

University research center and private assisted reproductive technology centers.

PATIENT(S)

Six men with anejaculation (psychological, vascular, neurologic) and conserved spermatogenesis.

INTERVENTION(S)

Testicular biopsies were used from patients under treatment for recovery of male gametes. Primary hSCs cultures were established from each biopsy and divided into a control group and one treated with rapamycin, the inhibitor of mTOR, for 24 hours.

MAIN OUTCOME MEASURE(S)

Cytotoxicity of hSCs to rapamycin was evaluated by sulforhodamine B assay. The glycolytic profile of hSCs was assessed by proton nuclear magnetic resonance and by studying protein expression of key glycolysis-related transporters and enzymes. Expression of mitochondrial complexes and citrate synthase activity were determined. Protein carbonylation, nitration, lipid peroxidation, and sulfhydryl protein group contents were quantified. The mTOR signaling pathway was studied.

RESULT(S)

Rapamycin increased glucose consumption by hSCs, maintaining lactate production. Alanine production by rapamycin-exposed hSCs was affected, resulting in an unbalanced intracellular redox state. Rapamycin-exposed hSCs had decreased expression of mitochondrial complex III and increased lipid peroxidation, whereas other oxidative stress markers were unaltered. Treatment of hSCs with rapamycin down-regulated phospho-mTOR (Ser-2448) levels, illustrating an effective partial inhibition of mTORC1. Protein levels of downstream signaling molecule p-4E-BP1 were not altered, suggesting that during treatment it became rephosphorylated.

CONCLUSION(S)

We show that mTOR regulates the nutritional support of spermatogenesis by hSCs and redox balance in these cells.

Novel molecular mechanisms involved in hormonal regulation of lactate production in Sertoli cells

The aim of the study was to analyze molecular mechanisms involved in FSH and basic fibroblast growth factor (bFGF) regulation of lactate production in rat Sertoli cells. The regulation of the availability of pyruvate, which is converted to lactate, could be a mechanism utilized by hormones to ensure lactate supply to germ cells. On one hand, the regulation of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase (PFKFB) expression could result in increased glycolysis, while an increase in pyruvate availability may also result from a lower conversion to acetyl-CoA by negative regulation of pyruvate dehydrogenase complex (PDC) activity by phosphorylation. Sertoli cell cultures obtained from 20-day-old rats were used. Stimulation of the cultures with FSH or bFGF showed that FSH increases Pfkfb1 and Pfkfb3 expression while bFGF increases Pfkfb1 mRNA levels. Additionally, we observed that FSH-stimulated lactate production was inhibited in the presence of a PFKFB3 inhibitor, revealing the physiological relevance of this mechanism. As for the regulation of PDC, analysis of pyruvate dehydrogenase kinase (Pdk) expression showed that FSH increases Pdk3 and decreases Pdk4 mRNA levels while bFGF increases the expression of all Pdks. In addition, we showed that bFGF increases phosphorylated PDC levels and that bFGF-stimulated lactate production is partially inhibited in the presence of a PDK inhibitor. Altogether, these results add new information regarding novel molecular mechanisms involved in hormonal regulation of lactate production in Sertoli cells. Considering that lactate is essential for the production of energy in spermatocytes and spermatids, these mechanisms might be relevant in maintaining spermatogenesis and male fertility.

Leptin modulates human Sertoli cells acetate production and glycolytic profile: a novel mechanism of obesity-induced male infertility?

Human feeding behavior and lifestyle are gradually being altered, favoring the development of metabolic diseases, particularly type 2 diabetes and obesity. Leptin is produced by the adipose tissue acting as a satiety signal. Its levels have been positively correlated with fat mass and hyperleptinemia has been proposed to negatively affect male reproductive function. Nevertheless, the molecular mechanisms by which this hormone affects male fertility remain unknown. Herein, we hypothesize that leptin acts on human Sertoli cells (hSCs), the "nurse cells" of spermatogenesis, altering their metabolism. To test our hypothesis, hSCs were cultured without or with leptin (5, 25 and 50ng/mL). Leptin receptor was identified by qPCR and Western blot. Protein levels of glucose transporters (GLUT1, GLUT2 and GLUT3), phosphofructokinase, lactate dehydrogenase (LDH) and monocarboxylate transporter 4 (MCT4) were determined by Western Blot. LDH activity was assessed and metabolite production/consumption determined by proton nuclear magnetic resonance. Oxidative damage was evaluated by assessing lipid peroxidation, protein carbonilation and nitration. Our data shows that leptin receptor is expressed in hSCs. The concentration of leptin found in lean, healthy patients, upregulated GLUT2 protein levels and concentrations of leptin found in lean and obese patients increased LDH activity. Of note, all leptin concentrations decreased hSCs acetate production illustrating a novel mechanism for this hormone action. Moreover, our data shows that leptin does not induce or protect hSCs from oxidative damage. We report that this hormone modulates the nutritional support of spermatogenesis, illustrating a novel mechanism that may be linked to obesity-induced male infertility.

Metabolic fingerprints in testicular biopsies from type 1 diabetic patients

Diabetes mellitus (DM) is a metabolic disease that has grown to pandemic proportions. Recent reports have highlighted the effect of DM on male reproductive function. Here, we hypothesize that testicular metabolism is altered in type 1 diabetic (T1D) men seeking fertility treatment. We propose to determine some metabolic fingerprints in testicular biopsies of diabetic patients. For that, testicular tissue from five normal and five type 1 diabetic men was analyzed by high-resolution magic-angle spinning (HR-MAS) nuclear magnetic resonance (NMR) spectroscopy. mRNA and protein expression of glucose transporters and glycolysis-related enzymes were also evaluated. Our results show that testes from diabetic men presented decreased levels of lactate, alanine, citrate and creatine. The mRNA levels of glucose transporter 1 (GLUT1) and phosphofructokinase 1 (PFK1) were decreased in testes from diabetic men but only GLUT3 presented decreased mRNA and protein levels. Lactate dehydrogenase (LDH) and glutamate pyruvate transaminase (GPT) protein levels were also found to be decreased in testes from diabetic men. Overall, our results show that T1D alters glycolysis-related transporters and enzymes, compromising lactate content in the testes. Moreover, testicular creatine content was severely depressed in T1D men. Since lactate and creatine are essential for germ cells development and support, the data discussed here open new insights into the molecular mechanism by which DM promotes subfertility/infertility in human males.

Cyclooxygenase and prostaglandins in somatic cell populations of the testis

Prostaglandins (PGs) are synthesized through the action of the rate-limiting enzyme cyclooxygenase (COX) and further specific enzymes. The development ofCox-deficient mice in the 1990s gave insights into the reproductive roles of PGs. FemaleCox-knockout mice were subfertile or infertile. Interestingly, fertility was not affected in male mice deficient inCox, suggesting that PGs may not be critical for the functioning of the testis. However, this conclusion has recently been challenged by observations of important roles for PGs in both physiological and pathological processes in the testis. The two key somatic cell types in the testis, Leydig and Sertoli cells, express the inducible isoenzyme COX2 and produce PGs. Testicular COX2 expression in these somatic cells is regulated by hormonal input (FSH, prolactin (PRL), and testosterone) as well as by IL1β. PGs modulate steroidogenesis in Leydig cells and glucose uptake in Sertoli cells. Hence, the COX2/PG system in Leydig and Sertoli cells acts as a local modulator of testicular activity, and consequently may regulate spermatogenic efficiency. In addition to its expression in Leydig and Sertoli cells, COX2 has been detected in the seminiferous tubule wall, and in testicular macrophages and mast cells of infertile patients. These observations highlight the possible relevance of PGs in testicular inflammation associated with idiopathic infertility. Collectively, these data indicate that the COX2/PG system plays crucial roles not only in testicular physiology (i.e., development, steroidogenesis, and spermatogenesis), but more importantly in the pathogenesis or maintenance of infertility status in the male gonad. Further studies of these actions could lead to new therapeutic approaches to idiopathic male infertility.

Free German abstract

A German translation of this abstract is freely available athttp://www.reproduction-online.org/content/149/4/R169/suppl/DC1.

Free Spanish abstract

A Spanish translation of this abstract is freely available athttp://www.reproduction-online.org/content/149/4/R169/suppl/DC2.

High-energy diets: a threat for male fertility?

Male fertility is declining in developed countries, as well as in developing countries. External factors linked to lifestyle, such as eating disorders, negatively affect spermatogenesis, both at central and gonadal levels. The overconsumption of high-energy diets (HED) alters the functioning of the male reproductive axis and consequently affects the testicular physiology, disrupting its metabolism and bioenergetic capacity. Testicular metabolism presents unique characteristics, partly because of its cellular heterogeneity and to the specific functions that each cell type plays within the testicular environment. Disruption of the tightly regulated metabolic pathways leads to adverse reproductive outcomes, such as inefficient energy supply to germ cells, sperm defects or spermatogenesis arrest. Testicular metabolic alterations induced by HED intake may also lead to mitochondrial dysfunction, which is closely associated to reactive oxygen species (ROS) overproduction and oxidative stress. ROS easily target spermatozoa DNA and lipids, contributing to decreased sperm quality. Thus, understanding the detrimental effects of HED overconsumption on the pathways underlying testicular metabolism and sperm production is imperative; otherwise, one may favour a transgenerational amplification of subfertility. Herein, we present an up-to-date overview of the effects of HED on testicular metabolism, sperm parameters and the subsequent consequences for male fertility.

Metformin and male reproduction: effects on Sertoli cell metabolism

BACKGROUND AND PURPOSE

Metformin is commonly used to treat type 2 diabetes (T2D). While new clinical applications have been ascribed to metformin, including treatment of anovulatory infertility, its effects on male reproduction have not been investigated. The Sertoli cell (SC) is crucial for germ cell development, exerting metabolic control of spermatogenesis, therefore, we investigated the effects of metformin on SC metabolism.

EXPERIMENTAL APPROACH

Rat SCs were cultured in the absence and presence of metformin (5, 50 and 500 μM). mRNA and protein levels of glucose transporters (GLUT1 and GLUT3), phosphofructokinase 1 (PFK 1), lactate dehydrogenase (LDH) and monocarboxylate transporter 4 (MCT4) were determined by quantitative PCR and Western blot respectively. LDH activity was assessed and metabolite production/consumption determined by (1) H-NMR.

KEY RESULTS

Metformin (50 μM) decreased mRNA and protein levels of GLUT1, GLUT3, MCT4 and PFK 1 but did not affect LDH mRNA or protein levels. However, although glucose consumption was maintained in metformin-treated cells, LDH activity, lactate and alanine production were increased, indicating an enhanced glycolytic flux. No metabolic cytotoxicity was detected in SCs exposed to supra-pharmacological concentration of metformin.

CONCLUSIONS AND IMPLICATIONS

Our results indicate that metformin: (i) decreases mRNA and protein levels of glycolysis-related transporters in SCs but increases their activity; and (ii) stimulates alanine production, which induces antioxidant activity and maintains the NADH/NAD(+) equilibrium. The increased lactate in metformin-treated SCs provides nutritional support and has an anti-apoptotic effect in developing germ cells. Thus, metformin can be considered as a suitable antidiabetic drug for male patients of reproductive age with T2D.

Melatonin alters the glycolytic profile of Sertoli cells: implications for male fertility

Melatonin co-operates with insulin in the regulation of glucose homeostasis. Within the testis, glucose metabolism in the somatic Sertoli cells (SCs) is pivotal for spermatogenesis. Since the effects of melatonin on male reproductive physiology remain largely unknown, we hypothesized that melatonin may affect spermatogenesis by modulating SC metabolism, interacting with insulin. To test our hypothesis, rat SCs were maintained in culture for 24 h in the presence of insulin, melatonin or both and metabolite production/consumption was determined by proton nuclear magnetic resonance ((1)H-NMR). Protein levels of glucose transporters (GLUT1 and GLUT3), phosphofructokinase 1, lactate dehydrogenase (LDH) and monocarboxylate transporter 4 were determined by western blot. LDH activity was also assessed. SCs treated with melatonin showed an increase in glucose consumption via modulation of GLUT1 levels, but decreased LDH protein expression and activity, which resulted in lower lactate production. Moreover, SCs exposed to melatonin produced and accumulated less acetate than insulin-exposed cells. The combined treatment (insulin plus melatonin) increased acetate production by SCs, but intracellular acetate content remained lower than in insulin exposed cells. Finally, the intracellular redox state, as reflected by intracellular lactate/alanine ratio, was maintained at control levels in SCs by melatonin exposure (i.e. melatonin, alone or with insulin, increased the lactate/alanine ratio versus cells treated with insulin). Furthermore, SCs exposed to insulin plus melatonin produced more lactate and maintained the protein levels of some glycolysis-related enzymes and transporters at control levels. These findings illustrate that melatonin regulates SCs metabolism, and thus may affect spermatogenesis. Since lactate produced by SCs provides nutritional support and has an anti-apoptotic effect in developing germ cells, melatonin supplementation may be an effective therapy for diabetic male individuals facing subfertility/infertility.

Nutritional signals and reproduction

There is extensive evidence that nutrition influences reproductive function in various mammalian species (agricultural animals, rodents and human). However, the mechanisms underlying the relationship between nutrition, energy metabolism and reproductive function are poorly understood. This review considers nutrient sensors as a molecular link between food molecules and consequences for female and male fertility. It focuses on the roles and the molecular mechanisms of some of the relevant hormones, such as insulin and adipokines, and of energy substrates (glucose, fatty acids and amino acids), in the gonadotropic axis (central nervous system and gonads). A greater understanding of the interactions between nutrition and fertility is required for both better management of the physiological processes and the development of new molecules to prevent or cure metabolic diseases and their consequences for fertility.

Integrating microRNAs into the complexity of gonadotropin signaling networks

Follicle-stimulating hormone (FSH) is a master endocrine regulator of mammalian reproductive functions. Hence, it is used to stimulate folliculogenesis in assisted reproductive technologies (ART), both in women and in breeding animals. However, the side effects that hormone administration induces in some instances jeopardize the success of ART. Similarly, the luteinizing hormone (LH) is also of paramount importance in the reproductive function because it regulates steroidogenesis and the LH surge is a pre-requisite to ovulation. Gaining knowledge as extensive as possible on gonadotropin-induced biological responses could certainly lead to precise selection of their effects in vivo by the use of selective agonists at the hormone receptors. Hence, over the years, numerous groups have contributed to decipher the cellular events induced by FSH and LH in their gonadal target cells. Although little is known on the effect of gonadotropins on microRNA expression so far, recent data have highlighted that a microRNA regulatory network is likely to superimpose on the signaling protein network. No doubt that this will dramatically alter our current understanding of the gonadotropin-induced signaling networks. This is the topic of this review to present this additional level of complexity within the gonadotropin signaling network, in the context of recent findings on the microRNA machinery in the gonad.

Effect of white tea (Camellia sinensis (L.)) extract in the glycolytic profile of Sertoli cell

PURPOSE

Many health benefits have been attributed to tea (Camellia sinensis (L.)), and tea infusions are used as dietary agent and included in food supplements. Herein, we report the effect of a white tea (WTEA) extract in Sertoli cell (SC) metabolism. The SC is responsible for the nutritional support of the developing germ cells.

METHODS

An aqueous WTEA extract was prepared and analyzed by (1)H-NMR. Rat SCs were cultured with or without the WTEA extract. mRNA and protein levels of glucose transporters (GLUT1 and GLUT3), phosphofructokinase, lactate dehydrogenase (LDH) and monocarboxylate transporter 4 were determined by qPCR and western blot. LDH activity was assessed and metabolite production/consumption determined by (1)H-NMR.

RESULTS

WTEA-exposed SCs presented decreased protein and mRNA levels of GLUT1 and decreased glucose uptake. However, intracellular LDH activity was increased and SC lactate production was stimulated by the presence of the WTEA extract. Interestingly, alanine production was also found to be stimulated in WTEA extract-exposed SCs.

CONCLUSION

WTEA extract altered the glycolytic profile of cultured SCs, stimulating lactate production. Since lactate is used as metabolic substrate and has an anti-apoptotic effect in the developing germ cells, the supplementation with WTEA extract may be advantageous to improve male reproductive health.

Diabetes, insulin-mediated glucose metabolism and Sertoli/blood-testis barrier function

Blood testis barrier (BTB) is one of the tightest blood-barriers controlling the entry of substances into the intratubular fluid. Diabetes Mellitus (DM) is an epidemic metabolic disease concurrent with falling fertility rates, which provokes severe detrimental BTB alterations. It induces testicular alterations, disrupting the metabolic cooperation between the cellular constituents of BTB, with dramatic consequences on sperm quality and fertility. As Sertoli cells are involved in the regulation of spermatogenesis, providing nutritional support for germ cells, any metabolic alteration in these cells derived from DM may be responsible for spermatogenesis disruption, playing a crucial role in fertility/subfertility associated with this pathology. These cells have a glucose sensing machinery that reacts to hormonal fluctuations and several mechanisms to counteract hyper/hypoglycemic events. The role of DM on Sertoli/BTB glucose metabolism dynamics and the metabolic molecular mechanisms through which DM and insulin deregulation alter its functioning, affecting male reproductive potential will be discussed.