Metabolic modulation induced by oestradiol and DHT in immature rat Sertoli cells cultured in vitro

Molecular insights into Sertoli cell function: how do metabolic disorders in childhood and adolescence affect spermatogonial fate?

Male infertility is a major public health concern globally with unknown etiology in approximately half of cases. The decline in total sperm count over the past four decades and the parallel increase in childhood obesity may suggest an association between these two conditions. Here, we review the molecular mechanisms through which obesity during childhood and adolescence may impair future testicular function. Several mechanisms occurring in obesity can interfere with the delicate metabolic processes taking place at the testicular level during childhood and adolescence, providing the molecular substrate to hypothesize a causal relationship between childhood obesity and the risk of low sperm counts in adulthood.

pH Homeodynamics and Male Fertility: A Coordinated Regulation of Acid-Based Balance during Sperm Journey to Fertilization

pH homeostasis is crucial for spermatogenesis, sperm maturation, sperm physiological function, and fertilization in mammals. HCO3- and H+ are the most significant factors involved in regulating pH homeostasis in the male reproductive system. Multiple pH-regulating transporters and ion channels localize in the testis, epididymis, and spermatozoa, such as HCO3- transporters (solute carrier family 4 and solute carrier family 26 transporters), carbonic anhydrases, and H+-transport channels and enzymes (e.g., Na+-H+ exchangers, monocarboxylate transporters, H+-ATPases, and voltage-gated proton channels). Hormone-mediated signals impose an influence on the production of some HCO3- or H+ transporters, such as NBCe1, SLC4A2, MCT4, etc. Additionally, ion channels including sperm-specific cationic channels for Ca2+ (CatSper) and K+ (SLO3) are directly or indirectly regulated by pH, exerting specific actions on spermatozoa. The slightly alkaline testicular pH is conducive to spermatogenesis, whereas the epididymis's low HCO3- concentration and acidic lumen are favorable for sperm maturation and storage. Spermatozoa pH increases substantially after being fused with seminal fluid to enhance motility. In the female reproductive tract, sperm are subjected to increasing concentrations of HCO3- in the uterine and fallopian tube, causing a rise in the intracellular pH (pHi) of spermatozoa, leading to hyperpolarization of sperm plasma membranes, capacitation, hyperactivation, acrosome reaction, and ultimately fertilization. The physiological regulation initiated by SLC26A3, SLC26A8, NHA1, sNHE, and CFTR localized in sperm is proven for certain to be involved in male fertility. This review intends to present the key factors and characteristics of pHi regulation in the testes, efferent duct, epididymis, seminal fluid, and female reproductive tract, as well as the associated mechanisms during the sperm journey to fertilization, proposing insights into outstanding subjects and future research trends.

Insights Into Antioxidant Strategies to Counteract Radiation-Induced Male Infertility

Significance: Radiotherapy, which employs ionizing radiation to destroy or prevent the multiplication of tumor cells, has been increasingly used in the treatment of neoplastic diseases, especially cancers. However, radiation collaterally leads to prolonged periods of sperm count suppression, presumably due to impaired spermatogenesis by depleting the germ cell pool, which has long-term side effects for male reproduction. Recent Advances: Studies of antioxidant compounds as a potential strategy for male fertility preservation have been performed mainly from animal models, aiming to prevent and restore the male germinal tissue and its function, particularly against the oxidative stress effects of radiation. Evidence in preclinical and clinical trials has shown that inhibitors of the renin-angiotensin system and other drugs, such as statins and metformin, are candidates for ameliorating radiation-induced damage to several tissues, including the testis and prostate. Critical Issues: Research for developing an ideal radioprotective agent is challenging due to toxicity in the normal tissue, tumor radioresistance, cellular response to radiation, costs, regulation, and timeline development. Moreover, male radioprotection experiments in humans, mainly clinical trials, are scarce and use few individuals. This scenario is reflected in the slow progress of innovation in the radioprotection field. Future Directions: Expanding human studies to provide clues on the efficacy and safety of radioprotective compounds in the human reproductive system is necessary. Drug repurposing, frequently used in clinical practice, can be a way to shorten the development pipeline for innovative approaches for radioprotection or radiomitigation of the repercussions of radiotherapy in the male reproductive system.

The Effect of Different Exercise Modalities on Sertoli-germ Cells Metabolic Interactions in High-fat Diet-induced Obesity Rat Models: Implication on Glucose and Lactate Transport, Igf1, and Igf1R-dependent Pathways

The study aimed to uncover a unique aspect of obesity-related metabolic disorders in the testicles induced by a high-fat diet (HFD) and explored the potential mitigating effects of exercise modalities on male fertility. Thirty mature male Wistar rats were randomly assigned to control, HFD-sole, moderate-intensity exercise with HFD (HFD+MICT), high-intensity continuous exercise with HFD (HFD+HICT), and high-intensity interval exercise with HFD (HFD+HIIT) groups (n=6/group). Intracytoplasmic carbohydrate (ICC) storage, expression levels of GLUT-1, GLUT-3, MCT-4, Igf1, and Igf1R, and testicular lactate and lactate dehydrogenase (LDH) levels were assessed. ICC storage significantly decreased in HFD-sole rats, along with decreased mRNA and protein levels of GLUT-1, GLUT-3, MCT-4, Igf1, and Igf1R. The HFD-sole group exhibited a notable reduction in testicular lactate and LDH levels (p<0.05). Conversely, exercise, particularly HIIT, upregulated ICC storage, expression levels of GLUT-1, GLUT-3, MCT-4, Igf1, and Igf1R, and enhanced testicular lactate and LDH levels. These results confirm that exercise, especially HIIT, has the potential to mitigate the adverse effects of HFD-induced obesity on testicular metabolism and male fertility. The upregulation of metabolite transporters, LDH, lactate levels, Igf1, and Igf1R expression may contribute to maintaining metabolic interactions and improving the glucose/lactate conversion process. These findings underscore the potential benefits of exercise in preventing and managing obesity-related male fertility issues.

GHB toxicokinetics and renal monocarboxylate transporter expression are influenced by the estrus cycle in rats

BACKGROUND

The illicit use and abuse of gamma-hydroxybutyric acid (GHB) occurs due to its sedative/hypnotic and euphoric effects. Currently, there are no clinically available therapies to treat GHB overdose, and care focuses on symptom treatment until the drug is eliminated from the body. Proton- and sodium-dependent monocarboxylate transporters (MCTs (SLC16A) and SMCTs (SLC5A)) transport and mediate the renal clearance and distribution of GHB. Previously, it has been shown that MCT expression is regulated by sex hormones in the liver, skeletal muscle and Sertoli cells. The focus of the current study is to evaluate GHB toxicokinetics and renal monocarboxylate transporter expression over the estrus cycle in females, and in the absence of male and female sex hormones.

METHODS

GHB toxicokinetics and renal transporter expression of MCT1, SMCT1 and CD147 were evaluated in females over the estrus cycle, and in ovariectomized (OVX) female, male and castrated (CST) male rats. GHB was administered iv bolus (600 and 1000 mg/kg) and plasma and urine samples were collected for six hours post-dose. GHB concentrations were quantified using a validated LC/MS/MS assay. Transporter mRNA and protein expression was quantified by qPCR and Western Blot.

RESULTS

GHB renal clearance and AUC varied between sexes and over the estrus cycle in females with higher renal clearance and a lower AUC in proestrus females as compared to males (intact and CST), and OVX females. We demonstrated that renal MCT1 membrane expression varies over the estrus cycle, with the lowest expression observed in proestrus females, which is consistent with the observed changes in GHB renal clearance.

CONCLUSIONS

Our results suggest that females may be less susceptible to GHB-induced toxicity due to decreased exposure resulting from increased renal clearance, as a result of decreased renal MCT1 expression.

Effect of Sex and Cross-Sex Hormone Treatment on Renal Monocarboxylate-Transporter Expression in Rats

Proton- and sodium-dependent monocarboxylate transporters (MCTs/SMCTs) are determinants of renal clearance through the renal reabsorption of monocarboxylate substrates. Prior studies with intact females and males, ovariectomized females and castrated males have revealed the hormonal regulation of renal monocarboxylate-transporter expression, prompting investigation into the regulatory role of individual hormones. The aim of the present study is to evaluate the effect of exogenous sex and cross-sex hormones on renal MCT1, MCT4, CD147 and SMCT1 mRNA and membrane-bound protein expression. Ovariectomized (OVX) females and castrated (CST) male Sprague Dawley rats received estrogen and/or progesterone, testosterone, or a corresponding placebo treatment for 21 days prior to kidney collection. The quantitative measurement of mRNA and membrane-protein levels were conducted using qPCR and Western blot. Quantitative analysis revealed the combination estrogen/progesterone treatment reduced membrane MCT1 and 4 expression and increased SMCT1 expression, while testosterone administration increased MCT1 membrane-protein expression. Correlation analysis indicated that plasma 17β-estradiol was negatively correlated with MCT1 and MCT4 membrane expression, while testosterone was positively correlated. In contrast, SMCT1 membrane expression was positively correlated with 17β-estradiol and progesterone concentrations. MCT1, MCT4, CD147 and SMCT1 renal expression are significantly altered in response to female and male sex hormones following sex and cross-sex hormone treatment in OVX and CST rats. Further studies are needed to understand the complex role of sex hormones, sex hormone receptors and the impact of puberty on MCT/SMCT regulation.

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.

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.

Effects of Pgam1-mediated glycolysis pathway in Sertoli cells on Spermatogonial stem cells based on transcriptomics and energy metabolomics

Spermatogenesis is a complex process involving a variety of intercellular interactions and precise regulation of gene expression. Spermatogenesis is sustained by a foundational Spermatogonial stem cells (SSCs) and in mammalian testis. Sertoli cells (SCs) are the major component of SSC niche. Sertoli cells provide structural support and supply energy substrate for developing germ cells. Phosphoglycerate mutase 1 (Pgam1) is a key enzyme in the glycolytic metabolism and our previous work showed that Pgam1 is expressed in SCs. In the present study, hypothesized that Pgam1-depedent glycolysis in SCs plays a functional role in regulating SSCs fate decisions. A co-culture system of murine SCs and primary spermatogonia was constructed to investigate the effects of Pgam1 knockdown or overexpression on SSCs proliferation and differentiation. Transcriptome results indicated that overexpression and knockdown of Pgam1 in SCs resulted in up-regulation of 458 genes (117 down-regulated, 341 up-regulated) and down-regulation of 409 genes (110 down-regulated, 299 up-regulated), respectively. Further analysis of these DEGs revealed that GDNF, FGF2 and other genes that serve key roles in SSCs niche maintenance were regulated by Pgam1. The metabolome results showed that a total of 11 and 16 differential metabolites were identified in the Pgam1 gene overexpression and knockdown respectively. Further screening of these metabolites indicated that Sertoli cell derived glutamate, glutamine, threonine, leucine, alanine, lysine, serine, succinate, fumarate, phosphoenolpyruvate, ATP, ADP, and AMP have potential roles in regulating SSCs proliferation and differentiation. In summary, this study established a SCs-SSCs co-culture system and identified a list of genes and small metabolic molecules that affect the proliferation and differentiation of SSCs. This study provides additional insights into the regulatory mechanisms underlying interactions between SCs and SSCs during mammalian spermatogenesis.

Stress Hormone Corticosterone Controls Metabolic Mitochondrial Performance and Inflammatory Signaling of In Vitro Cultured Sertoli Cells

Stress, as a physiological response, is a major factor that affects several processes, including reproductive functions. The main hormonal players of stress are cortisol (humans) and corticosterone (rodents). Sertoli cells (SCs), as key contributors for the testicular homeostasis maintenance, are extensively challenged by different hormones, with glucocorticoid corticosterone being the signaling modulator that may impact these cells at different levels. We aimed to characterize how corticosterone modulates SCs energy balance, putting the mitochondrial performance and signaling output in perspective as the cells can disperse to the surroundings. TM4 mouse SCs were cultured in the absence and presence of corticosterone (in nM: 20, 200, and 2000). Cells were assessed for extracellular metabolic fluxes, mitochondrial performance (cell respirometry, mitochondrial potential, and mitochondrial complex expressions and activities), and the expression of androgen and corticosteroid receptors, as well as interleukine-6 (IL-6) and glutathione content. Corticosterone presented a biphasic impact on the extracellular fluxes of metabolites. Low sub-physiological corticosterone stimulated the glycolytic activity of SCs. Still, no alterations were perceived for lactate and alanine production. However, the lactate/alanine ratio was decreased in a dose-dependent mode, opposite to the mitochondrial complex II activity rise and concurrent with the decrease of IL-6 expression levels. Our results suggest that corticosterone finely tuned the energetic profile of mouse SCs, with sub-physiological concentrations promoting glycolytic expenditure, without translating into cell redox power and mitochondrial respiratory chain performance. Corticosterone deeply impacted the expression of the pro-inflammatory IL-6, which may alter cell-to-cell communication in the testis, in the last instance and impact of the spermatogenic performance.

TGF-β3 induces lactate production in Sertoli cell through inhibiting Notch pathway

BACKGROUNDS

In the testis, spermatocytes and spermatids rely on lactate produced by Sertoli cells (SCs) as energy source. TGF-β3 is one of the generally accepted paracrine regulatory factors of SC-created blood-testis barrier (BTB), yet its role in SC glycolysis and lactate production still remains unclear.

OBJECTIVES

To investigate the effect of TGF-β3 on glycolysis and lactate production in SCs and determine the role of Lgl2 and Notch signaling activity during this process.

MATERIALS AND METHODS

Primary cultured rat Sertoli cells and TM4 cells were treated with different concentrations of TGF-β3. In some experiments, cells were transfected with siRNA specifically targeting Lgl2 and then treated with TGF-β3 or DAPT. Lactate concentration, glucose and glutamine consumption in the culture medium, activity of PFK, LDH, and Gls, ATP level, oxygen consumption, extracellular acidification and mitochondrial respiration complex activity were detected using commercial kits. The protein level of Lgl2, LDH, MCT4, and activity of Akt, ERK, p38 MAPK, and Notch pathway were detected by Western blot. The stage-specific expression of Jagged1 was examined by immunohistochemistry and qPCR after LCM. Spermatogenesis in rat testis injected with recombinant Jagged1 (re-Jagged1) was observed by HE staining and lactate concentration in testis lysate was measured at different day point after re-Jagged1 treatment.

RESULTS

Significant enhancement of lactate concentration was detected in culture medium of both primary SCs and TM4 cells treated with TGF-β3 at 3 or 5 ng/ml. Besides, other parameters of glycolysis, i.e. glucose and Gln consumption, enzyme activity of PFK, LDH, and Gls, displayed different levels of increment in primary SCs and TM4 cells after TGF-β3 treatment. Mitochondria respiration of SCs was shown to decrease in response to TGF-β3. Lgl2, MCT4, activity of ERK and p38 MAPK were up-regulated, whereas Akt and Notch pathway activity were inhibited by TGF-β3. Silencing of Lgl2 in SCs affected lactate production and attenuated the above effects of TGF-β3 on SC glycolysis except for Gln consumption, Gls activity, and activity of Akt, ERK, and p38. DAPT treatment in SCs antagonized glycolysis suppression caused by Lgl2-silencing. In vivo analysis revealed a stage-specific expression of Jagged1 in contrary with TGF-β3. Activating Notch signaling by re-Jagged1 resulted in restorable hypospermatogenesis and lowered lactate level in rat testis.

CONCLUSION

TGF-β3 induces lactate production in Sertoli cell through upregulating Lgl2, which weakened the Notch signaling activity and intensified glycolysis in SCs. Thus, besides the known function of TGF-β3 as the BTB regulator, TGF-β3-Lgl2-Notch maybe considered as an important pathway controlling Sertoli cell glycolysis and spermatogenesis. This article is protected by copyright. All rights reserved.

Differential response of hepatocellular carcinoma glycolytic metabolism and oxidative stress markers after exposure to human amniotic membrane proteins

BACKGROUND

The human Amniotic Membrane (hAM) has been studied as a potential therapeutic option in cancer, namely in hepatocellular carcinoma. Previously, our research group evaluated the effect of human Amniotic Membrane Protein Extracts (hAMPE) in cancer therapy, demonstrating that hAMPE inhibit the metabolic activity of human hepatocellular carcinoma cell lines: Hep3B2.1-7, HepG2 and Huh7. Therefore, and considering the close relationship between metabolic activity and oxidative stress, the aim of this study was to evaluate the effect of hAMPE treatment in glucose metabolism and its role in oxidative stress of hepatocellular carcinoma.

METHODS AND RESULTS

Glucose uptake and lactate production was assessed by 1 H-NMR, and the expression of several mediators of the glycolytic pathway was evaluated by Western blot or fluorescence. Total antioxidant capacity (TAC) and biomarkers of oxidative stress effects in proteins were detected. Our results showed that hAMPE treatment increased glucose consumption on Hep3B2.1-7, HepG2, and Huh7 through the increase of GLUT1 in Hep3B2.1-7 and Huh7, and GLUT3 in HepG2 cells. It was observed an increased expression of 6-phosphofrutokinase (PFK-1L) in all cell lines though glucose was not converted to lactate on HepG2 and Huh7 cells, suggesting that hAMPE treatment may counteract the Warburg effect observed in carcinogenesis. In Hep3B2.1-7, hAMPE treatment induced an increase in expression of lactate dehydrogenase (LDH) and monocarboxylate transporter isoform 4 (MCT4). We further detected that hAMPE enhances the TAC of culture media after 2 and 8 h. This was followed by a degree of protection against proteins nitration and carbonylation.

CONCLUSIONS

Overall, this work highlights the potential usefulness of hAMPE as anticancer therapy through the modulation of the glycolytic and oxidative profile in human hepatocellular carcinoma.

Male Infertility in the XXI Century: Are Obesogens to Blame?

The permanent exposure to environmental contaminants promoting weight gain (i.e., obesogens) has raised serious health concerns. Evidence suggests that obesogens are one of the leading causes of the marked decline in male fertility and are key players in shaping future health outcomes, not only for those who are directly exposed to them, but also for upcoming generations. It has been hypothesized that obesogens affect male fertility. By using an interdisciplinary strategy, combining in silico, in vitro, in vivo and epidemiological findings, this review aims to contribute to the biological understanding of the molecular transformations induced by obesogens that are the basis of male infertility. Such understanding is shaped by the use of Adverse Outcomes Pathways, a new approach that may shift the paradigm of reproductive toxicology, contributing to the improvement of the diagnosis and management of the adverse effects of obesogens in male fertility.

The Impact of Endocrine-Disrupting Chemicals in Male Fertility: Focus on the Action of Obesogens

The current scenario of male infertility is not yet fully elucidated; however, there is increasing evidence that it is associated with the widespread exposure to endocrine-disrupting chemicals (EDCs), and in particular to obesogens. These compounds interfere with hormones involved in the regulation of metabolism and are associated with weight gain, being also able to change the functioning of the male reproductive axis and, consequently, the testicular physiology and metabolism that are pivotal for spermatogenesis. The disruption of these tightly regulated metabolic pathways leads to adverse reproductive outcomes. The permanent exposure to obesogens has raised serious health concerns. Evidence suggests that obesogens are one of the leading causes of the marked decline of male fertility and key players in shaping the future health outcomes not only for those who are directly exposed but also for upcoming generations. In addition to the changes that lead to inefficient functioning of the male gametes, obesogens induce alterations that are “imprinted” on the genes of the male gametes, establishing a link between generations and contributing to the transmission of defects. Unveiling the molecular mechanisms by which obesogens induce toxicity that may end-up in epigenetic modifications is imperative. This review describes and discusses the suggested molecular targets and potential mechanisms for obesogenic–disrupting chemicals and the subsequent effects on male reproductive health.

In vivo and in vitro short-term bisphenol A exposures disrupt testicular energy metabolism and negatively impact spermatogenesis in zebrafish

This study investigated the in vitro and short-term in vivo effects of Bisphenol A (BPA) on testicular energy metabolism and morphology in the zebrafish (Danio rerio). Testes were incubated in vitro for 1 h or fish were exposed in vivo to BPA in the tank water for 12 h. Testicular lactate, glycogen and cholesterol were measured and ¹⁴C-deoxy-d-glucose uptake and activity of lactate dehydrogenase (LDH), alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were determined. In addition, testis samples from the in vivo exposures were subject to digital analysis of testicular cells using Ilastik software and the Pixel Classification module and estimation of apoptosis by Terminal deoxynucleotidyl transferase (TdT) dUTP Nick-End Labeling (TUNEL) immunohistochemical analysis. Our results from in vitro studies showed that BPA at 10 pM and 10 μM decreased testicular lactate content, glycogen content and LDH activity, but increased testicular AST activity. In addition, only BPA at 10 pM significantly decreased testicular ALT activity and cholesterol content. However, ¹⁴C-deoxy-d-glucose uptake was not changed. Furthermore, our results from in vivo studies showed that 10 pM BPA but not 10 μM BPA reduced testicular content of lactate and glycogen. In addition, both BPA concentrations decreased AST activity, whereas only BPA at 10 μM reduced ALT activity. However, LDH activity was not changed. Additionally, both concentrations of BPA induced spermatocyte apoptosis and a decrease in the proportion of the surface area of spermatids and spermatozoa. Collectively these data suggest that short-term BPA exposure affects energy metabolism and spermatogenesis in male zebrafish.

Impacts of Immunometabolism on Male Reproduction

The physiological process of male reproduction relies on the orchestration of neuroendocrine, immune, and energy metabolism. Spermatogenesis is controlled by the hypothalamic-pituitary-testicular (HPT) axis, which modulates the production of gonadal steroid hormones in the testes. The immune cells and cytokines in testes provide a protective microenvironment for the development and maturation of germ cells. The metabolic cellular responses and processes in testes provide energy production and biosynthetic precursors to regulate germ cell development and control testicular immunity and inflammation. The metabolism of immune cells is crucial for both inflammatory and anti-inflammatory responses, which supposes to affect the spermatogenesis in testes. In this review, the role of immunometabolism in male reproduction will be highlighted. Obesity, metabolic dysfunction, such as type 2 diabetes mellitus, are well documented to impact male fertility; thus, their impacts on the immune cells distributed in testes will also be discussed. Finally, the potential significance of the medicine targeting the specific metabolic intermediates or immune metabolism checkpoints to improve male reproduction will also be reassessed.

MicroRNA-125a-5p modulates the proliferation and apoptosis of TM4 Sertoli cells by targeting RAB3D and regulating the PI3K/AKT signaling pathway

Sertoli cells are cells that provide protection and nutrition for developing sperm. Each stage of sperm development occurs on the surface of Sertoli cells. MicroRNA (MiR)-125a-5p is involved in male reproduction. The current research aimed to probe the role of miR-125a-5p in Sertoli cell function. Functionally, miR-125a-5p knockdown facilitated Sertoli cell proliferation, while miR-125a-5p overexpression suppressed Sertoli cell proliferation, as evidenced by 5-ethynyl-20-deoxyuridine incorporation assay. Additionally, miR-125a-5p knockdown inhibited Sertoli cell apoptosis, while miR-125a-5p upregulation facilitated Sertoli cell apoptosis, as evidenced by flow cytometry analysis. Computationally, we identified four predicted mRNA targets of miR-125a-5p. Based on the results of luciferase reporter assay, miR-125a-5p was confirmed to bind to the predicted sequence in the Ras-related protein Rab-3D (RAB3D) 3'UTR. Rescue experiments showed that miR-125a-5p suppressed the proliferative ability of TM4 Sertoli cells and facilitated their apoptosis by targeting RAB3D. Finally, our data confirmed that miR-125a-5p and RAB3D modulated activation of the PI3K/AKT pathway. In conclusion, our data showed that miR-125a-5p regulated Sertoli cell proliferation and apoptosis by targeting RAB3D and regulating the PI3K/AKT pathway.

Sex hormones regulate lipid metabolism in adult Sertoli cells: A genome-wide study of estrogen and androgen receptor binding sites

Optimal functioning of Sertoli cells is crucial for spermatogenesis which is under tight regulation of sex hormones, estrogen and androgen. Adult rat Sertoli cells expresses estrogen receptor beta (ERβ) and androgen receptor (AR), both of which regulate gene transcription by binding to the DNA. The present study is aimed to acquire a genome-wide map of estrogen- and androgen-regulated genes in adult Sertoli cells. ChIP-Seq was performed for ERβ and AR in Sertoli cells under physiological conditions. 30,859 peaks in ERβ and 9,594 peaks in AR were identified with a fold enrichment >2 fold. Pathway analysis for the genes revealed metabolic pathways to be significantly enriched. Since Sertoli cells have supportive functions and provide energy substrates to germ cells during spermatogenesis, significantly enriched metabolic pathways were explored further. Peaks of the genes involved in lipid metabolism, like fatty acid, glyceride, leucine, and sphingosine metabolism were validated. Motif analysis confirmed the presence of estrogen- and androgen-response elements (EREs and AREs). Moreover, transcript levels of enzymes involved in the lipid metabolic pathways were significantly altered in cultured Sertoli cells treated with estrogen and androgen receptor agonists, demonstrating functional significance of these binding sites. This study elucidates a mechanism by which sex hormones regulate lipid metabolism in Sertoli cells by transcriptionally controlling the expression of these genes, thereby shedding light on the roles of these hormones in male fertility.

The Molecular Mechanism of Sex Hormones on Sertoli Cell Development and Proliferation

Sustaining and maintaining the intricate process of spermatogenesis is liable upon hormones and growth factors acting through endocrine and paracrine pathways. The Sertoli cells (SCs) are the major somatic cells present in the seminiferous tubules and are considered to be the main regulators of spermatogenesis. As each Sertoli cell supports a specific number of germ cells, thus, the final number of Sertoli cells determines the sperm production capacity. Similarly, sex hormones are also major regulators of spermatogenesis and they can determine the proliferation of Sertoli cells. In the present review, we have critically and comprehensively discussed the role of sex hormones and some other factors that are involved in Sertoli cell proliferation, differentiation and maturation. Furthermore, we have also presented a model of Sertoli cell development based upon the recent advancement in the field of reproduction. Hence, our review article provides a general overview regarding the sex hormonal pathways governing Sertoli cell proliferation and development.

Transcriptomic, proteomic and metabolomic profiling unravel the mechanisms of hepatotoxicity pathway induced by triphenyl phosphate (TPP)

Triphenyl phosphate (TPP) has been found in various environmental media and in biota suggesting widespread human exposure. However, there is still insufficient information on the hepatotoxicity mechanisms of health risk exposed to TPP. In this study, TPP could induce human normal liver cell (L02) apoptosis, injury cell ultrastructure and elevate the levels of reactive oxygen species (ROS). The integrated multi-omic (transcriptomic, proteomic, and metabolomic) analysis was used to further investigate the mechanisms. Transcriptomic analysis revealed that TPP exposure markedly affected cell apoptosis, oncogene activation, REDOX homeostasis, DNA damage and repair. Additionally, proteomic analysis found that the related proteins associated with apoptosis, oxidative stress, metabolism and membrane structure were affected. And metabolomic analysis verified that the related metabolic pathways, such as glycolysis, citrate cycle, oxidative phosphorylation, lipid and protein metabolism, were also significantly disrupted. Based on the multi-omic results, a hypothesized network was constructed to discover the key molecular events in response to TPP and illustrate the mechanism of TPP-induced hepatotoxicity in L02 cells. Therefore, molecular responses could be elucidated at multiple biological levels, and multi-omic analysis could provide scientific tools for exploring potential mechanisms of toxicity and chemical risk assessment.

Monocarboxylate Transporters (SLC16): Function, Regulation, and Role in Health and Disease

The solute carrier family 16 (SLC16) is comprised of 14 members of the monocarboxylate transporter (MCT) family that play an essential role in the transport of important cell nutrients and for cellular metabolism and pH regulation. MCTs 1-4 have been extensively studied and are involved in the proton-dependent transport of L-lactate, pyruvate, short-chain fatty acids, and monocarboxylate drugs in a wide variety of tissues. MCTs 1 and 4 are overexpressed in a number of cancers, and current investigations have focused on transporter inhibition as a novel therapeutic strategy in cancers. MCT1 has also been used in strategies aimed at enhancing drug absorption due to its high expression in the intestine. Other MCT isoforms are less well characterized, but ongoing studies indicate that MCT6 transports xenobiotics such as bumetanide, nateglinide, and probenecid, whereas MCT7 has been characterized as a transporter of ketone bodies. MCT8 and MCT10 transport thyroid hormones, and recently, MCT9 has been characterized as a carnitine efflux transporter and MCT12 as a creatine transporter. Expressed at the blood brain barrier, MCT8 mutations have been associated with an X-linked intellectual disability, known as Allan-Herndon-Dudley syndrome. Many MCT isoforms are associated with hormone, lipid, and glucose homeostasis, and recent research has focused on their potential roles in disease, with MCTs representing promising novel therapeutic targets. This review will provide a summary of the current literature focusing on the characterization, function, and regulation of the MCT family isoforms and on their roles in drug disposition and in health and disease. SIGNIFICANCE STATEMENT: The 14-member solute carrier family 16 of monocarboxylate transporters (MCTs) plays a fundamental role in maintaining intracellular concentrations of a broad range of important endogenous molecules in health and disease. MCTs 1, 2, and 4 (L-lactate transporters) are overexpressed in cancers and represent a novel therapeutic target in cancer. Recent studies have highlighted the importance of MCTs in glucose, lipid, and hormone homeostasis, including MCT8 in thyroid hormone brain uptake, MCT12 in carnitine transport, and MCT11 in type 2 diabetes.

pH and male fertility: making sense on pH homeodynamics throughout the male reproductive tract

In the male reproductive tract, ionic equilibrium is essential to maintain normal spermatozoa production and, hence, the reproductive potential. Among the several ions, HCO3- and H+ have a central role, mainly due to their role on pH homeostasis. In the male reproductive tract, the major players in pH regulation and homeodynamics are carbonic anhydrases (CAs), HCO3- membrane transporters (solute carrier 4-SLC4 and solute carrier 26-SLC26 family transporters), Na+-H+ exchangers (NHEs), monocarboxylate transporters (MCTs) and voltage-gated proton channels (Hv1). CAs and these membrane transporters are widely distributed throughout the male reproductive tract, where they play essential roles in the ionic balance of tubular fluids. CAs are the enzymes responsible for the production of HCO3- which is then transported by membrane transporters to ensure the maturation, storage, and capacitation of the spermatozoa. The transport of H+ is carried out by NHEs, Hv1, and MCTs and is essential for the electrochemical balance and for the maintenance of the pH within the physiological limits along the male reproductive tract. Alterations in HCO3- production and transport of ions have been associated with some male reproductive dysfunctions. Herein, we present an up-to-date review on the distribution and role of the main intervenient on pH homeodynamics in the fluids throughout the male reproductive tract. In addition, we discuss their relevance for the establishment of the male reproductive potential.

Multiple signaling pathways in Sertoli cells: recent findings in spermatogenesis

The functions of Sertoli cells in spermatogenesis have attracted much more attention recently. Normal spermatogenesis depends on Sertoli cells, mainly due to their influence on nutrient supply, maintenance of cell junctions, and support for germ cells' mitosis and meiosis. Accumulating evidence in the past decade has highlighted the dominant functions of the MAPK, AMPK, and TGF-β/Smad signaling pathways during spermatogenesis. Among these pathways, the MAPK signaling pathway regulates dynamics of tight junctions and adherens junctions, proliferation and meiosis of germ cells, proliferation and lactate production of Sertoli cells; the AMPK and the TGF-β/Smad signaling pathways both affect dynamics of tight junctions and adherens junctions, as well as the proliferation of Sertoli cells. The AMPK signaling pathway also regulates lactate supply. These signaling pathways combine to form a complex regulatory network for spermatogenesis. In testicular tumors or infertile patients, the activities of these signaling pathways in Sertoli cells are abnormal. Clarifying the mechanisms of signaling pathways in Sertoli cells on spermatogenesis provides new insights into the physiological functions of Sertoli cells in male reproduction, and also serves as a pre-requisite to identify potential therapeutic targets in abnormal spermatogenesis including testicular tumor and male infertility.

Treatment with, Resveratrol, a SIRT1 Activator, Prevents Zearalenone-Induced Lactic Acid Metabolism Disorder in Rat Sertoli Cells

Zearalenone (ZEA) interferes with the function of the male reproductive system, but its molecular mechanism has yet to be completely elucidated. Sertoli cells (SCs) are important in the male reproductive system. Silencing information regulator 1 (SIRT1) is a cell metabolism sensor and resveratrol (RSV) is an activator of SIRT1. In this study we investigated whether SIRT1 is involved in the regulation of ZEA-induced lactate metabolism disorder in SCs. The results showed that the cytotoxicity of ZEA toward SCs increased with increasing ZEA concentration. Moreover, ZEA induced a decrease in the production of lactic acid and pyruvate of SCs and inhibited the expression of glycolytic genes and lactic acid production-related proteins. ZEA also led to a decreased expression of SIRT1 in energy receptors and decreased ATP levels in SCs. However, the ZEA-induced cytotoxicity and decline in lactic acid production in SCs were alleviated by the use of RSV, which is an activator of SIRT1. In summary, ZEA decreased lactic acid production in SCs, while the treatment with an SIRT1 activator, RSV, restored the inhibition of lactic acid production in SCs and reduced cytotoxicity of ZEA toward SCs.

Knockout of MCT1 results in total absence of spermatozoa, sex hormones dysregulation, and morphological alterations in the testicular tissue

Lactate is a key metabolite for the normal occurrence of spermatogenesis. In the testis, lactate is produced by the Sertoli cells and transported to germline cells. Monocarboxylate transporters (MCTs) are key players in that process. Among the family of MCTs, MCT1 is at least partly responsible for lactate uptake by the germ cells. We aimed to perform a first assessment of the role of MCT1 in male reproductive potential. Mct1 conditional knockout (cKO) mice were used for morphometric evaluation, testicular morphology, and sperm parameter assessment. Serum steroid hormones levels were also measured. cKO animals showed a decrease in gonadosomatic index, testis weight, and seminiferous tubular diameters. Deletion of MCT1 also causes morphological changes in the organization of the seminiferous tubules and on Sertoli cell morphology. These changes resulted in failure of spermatogenesis with depletion of germ cells and total absence of spermatozoa. MCT1 cKO animals presented also hormonal dysregulation, with a decrease in serum 17β-estradiol levels. In conclusion, MCT1 is pivotal for male reproductive potential. Absence of MCT1 results in maintenance of undifferentiated spermatogonia pool and compromised sperm production.

Exposure to Pb and Cd alters MCT4/CD147 expression and MCT4/CD147-dependent lactate transport in mice Sertoli cells cultured in vitro

Sertoli cells (SCs) provide lactate as an energy substrate to develop germ cells during spermatogenesis. Lead (Pb) and cadmium (Cd) can induce SC toxicity. However, the mechanisms remain unclear. This study aimed to investigate the molecular mechanisms by which Pb and Cd alter lactate transport and production by SCs. Mouse SC line (15P-1 cells) were cultured in the absence and presence of lead acetate (PbAc, 1, 10, 20 and 30 μM) or cadmium chloride (CdCl₂, 0.5, 5, 10 and 15 μM) for 24 h. The results showed that PbAc exposure significantly decreased lactate dehydrogenase (LDH) activity and mRNA level, intracellular and extracellular lactate, and MCT4 and CD147 protein levels but increased MCT4 and CD147 mRNA levels. However, PbAc did not alter the glucose uptake, glucose transporters 1 (GLUT1) and 3 (GLUT3) mRNA expression of SCs. Thus, PbAc mainly decreased lactate production by inhibiting LDH activity. In CdCl₂-treated SCs, intracellular lactate content increased but extracellular lactate content decreased significantly, P < .05. The glucose uptake, LDH activity, and mRNA expression of GLUT1, GLUT3 and LDH, all significantly increased. But the mRNA and protein levels of MCT4 and CD147 significantly decreased. Moreover, the fluorescence intensity of co-localizations of the MCT4-CD147 complex dose-dependently decreased in the cell membrane. Thus, CdCl₂ may reduce lactate export by suppressing MCT4 and CD147 expression. These results suggest that PbAc and CdCl₂ disrupt lactate production and transport in mouse SCs by disturbing glycolysis or inhibiting MCT4-CD147 transporter expression and co-localizations.

Alteration in sperm characteristics, endocrine balance and redox status in rats rendered diabetic by streptozotocin treatment: attenuating role of Loranthus micranthus

Objectives:Loranthus micranthus is widely used in Nigerian folklore treatment of male infertility and diabetes complications. We investigated this claim in rats rendered diabetic by streptozotocin (STZ).

Methods: Induction of diabetes mellitus in adult male Wistar rats was by intraperitoneal injection of STZ (60 mg/kg). The diabetic rats were thereafter treated orally once/day with 5 mg/kg Gilbenclamide or L. micranthus (100 mg/kg or 200 mg/kg) and monitored for 14 days. Clinical observations, hormonal profile, oxidative stress parameters, glucose metabolism enzymes, histopathological examination, apoptotic marker immunoreactivity and western blotting in testes and sperm parameters were evaluated to examine effects of L. micranthus on STZ-diabetic rats.

Results:L. micranthus treatment significantly reduced the blood glucose level (45.9% and 84.7% on the 7th and 14th post-treatment days, respectively); increased antioxidant status, improved microarchitecture of testes, reduced lipid peroxidation and increased BCl-2 protein expression in diabetic rats relative to control. Furthermore, treatment with L. micranthus increased steroidogenic enzymes activities, levels of steroid hormones and improved sperm quality, relative to control.

Conclusion: The anti-diabetic and aphrodisiac properties exhibited by L. micranthus could be contingent on its ability to restore a balance to the compromised redox status that characterizes male reproductive dysfunction in diabetes.

Maternal exposure to traffic pollutant causes impairment of spermatogenesis and alterations of genome-wide mRNA and microRNA expression in F2 male mice

Male spermatogenesis dysfunctions are associated with environmental pollutants, but the detailed mechanisms remain poorly understood. In this study, healthy C57BL/6 J mice were used to establish an animal model of maternal exposure to traffic pollutant during pregnancy, and the toxic effects on the reproductive system of F2 male mice were analysed using mRNA and miRNA microarray. Our results showed that 54 miRNAs and 1927 mRNAs were significantly altered in the exposed group. Gene Ontology (GO) analysis revealed that the most significant GO terms for biological process, molecular function and cellular component were myeloid cell differentiation, growth factor binding and main axon. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis demonstrated that the biosynthesis of amino acids was the most significant pathway and that the cytokine-cytokine receptor interaction was the most abundant pathway (37 genes). Protein-protein interaction (PPI) and the miRNA-mRNA network were constructed with Cytoscape. The hub genes, Tnf, Il10 and Gapdh, were closely related to immuno-regulation and their miRNA regulators were reversely changed. Together, our results indicate that maternal exposure to traffic pollutant can cause spermatogenesis damage in F2 male mice possibly through the destroyed immunoprivileged environment in testis mediated by the aberrant expression of miRNA and mRNA.

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.

Molecular Mechanisms and Signaling Pathways Involved in the Nutritional Support of Spermatogenesis by Sertoli Cells

Sertoli cells play a central role in spermatogenesis. They maintain the blood-testis barrier, an essential feature of seminiferous tubules which creates the proper environment for the occurrence of the spermatogenesis. However, this confinement renders germ cells almost exclusively dependent on Sertoli cells' nursing function and support. Throughout spermatogenesis, differentiating sperm cells become more specialized, and their biochemical machinery is insufficient to meet their metabolic demands. Although the needs are not the same at all differentiation stages, Sertoli cells are able to satisfy their needs. In order to maintain the seminiferous tubule energetic homeostasis, Sertoli cells react in response to several metabolic stimuli, through signaling cascades. The AMP-activated kinase, sensitive to the global energetic status; the hypoxia-inducible factors, sensitive to oxygen concentration; and the peroxisome proliferator-activated receptors, sensitive to fatty acid availability, are pathways already described in Sertoli cells. These cells' metabolism also reflects the whole-body metabolic dynamics. Metabolic diseases, including obesity and type II diabetes mellitus, induce changes that, both directly and indirectly, affect Sertoli cell function and, ultimately, (dys)function in male reproductive health. Insulin resistance, increased estrogen synthesis, vascular disease, and pubic fat accumulation are examples of metabolic-related conditions that affect male fertility potential. On the other hand, malnutrition can also induce negative effects on male sexual function. In this chapter, we review the molecular mechanisms associated with the nutritional state and male sexual (dys)function and the central role played by the Sertoli cells.

Evaluation of the Purity of Sertoli Cell Primary Cultures

The purity of the primary cultures of Sertoli cells is a factor for the validation of the studies using this methodological approach. There is a probability of contamination of these cultures with other testicular cellular types, such as peritubular cells and germ cells (that represent a large percentage of the volume of the seminiferous tubules).For the evaluation of the purity of cultures, the immunocytochemistry technique (immunoperoxidase or immunofluorescence) is frequently used to label a protein marker specific for the Sertoli cells within the testicular environment. The expression of several protein markers can be used, with different particularities, being that vimentin is often used as a marker for Sertoli cells. Vimentin is expressed independently of the differentiation state of the cells and is observed around the nuclei and in the cytoplasm of Sertoli cells.

Assessing Sertoli Cell Metabolic Activity

Nuclear magnetic resonance (NMR)-based metabolomics is widely used in the research of metabolic conditions of complex biological systems under various conditions, and its use has been found in the field of male fertility. Here we describe the implementation of total and targeted NMR-based metabolomics in the research on Sertoli cell metabolism. Main principles and techniques of cell medium, cellular extracts, and intact cells are explained, as well as some classical experiments that can give complementary information on the Sertoli cell metabolism.

Enantiomeric Recognition of d- and l-Lactate by CEST with the Aid of a Paramagnetic Shift Reagent

A previous report demonstrated that EuDO3A could be used as an NMR shift reagent for imaging extracellular lactate produced by cancer cells using CEST imaging. In this work, a series of heptadentate macrocyclic YbDO3A-trisamide complexes with δ-chiral carbons in the three pendant side-arms were examined as shift reagents for lactate detection. High resolution 1H NMR spectra and DFT calculations provided evidence for the formation of stereoselective lactate·YbDO3A-trisamide complexes each with a different CEST signature. This stereoselectivity allowed discrimination of d- versus l-lactate by both high-resolution NMR and CEST. This work demonstrates that lanthanide-based paramagnetic shift reagents can be designed to detect important metabolites by CEST MRI selectively.

Toxicological effects of tris(2-chloropropyl) phosphate in human hepatic cells

Organophosphate flame retardants (OPFRs) are widely used as flame retardants which are ubiquitous in various environment media. As many of OPFRs are toxic and persistent, concerns have been raised in regards to their environmental impact. In this study, the toxicological effects of tris(2-chloropropyl) phosphate (TCPP) in human L02 cells was investigated by cell proliferation and apoptosis, oxidative stress, metabolomic and proteomic responses as well as gene expressions related to apoptosis. Results showed that TCPP did not significantly affect the L02 cell apoptosis, however, a significant increase of ROS production was observed in L02 cells with TCPP treatment compared with that in control group (p < 0.05). The expression levels of Bcl-2 family-encoding genes (Bax, Hrk and Bax/Bcl-2) were up-regulated significantly in 10^-4 M group (p < 0.05). Metabolomic and proteomic responses indicated that TCPP mainly caused disturbance in cell growth/division and gene expression, energy and material metabolism, signal transduction, defense and cytoskeleton, which was further confirmed by the western blot analysis.

The effects of the obesogen tributyltin on the metabolism of Sertoli cells cultured ex vivo

Human exposure to environmental contaminants is widespread. Some of these contaminants have the ability to interfere with adipogenesis, being thus considered as obesogens. Recently, obesogens have been singled out as a cause of male infertility. Sertoli cells (SCs) are essential for male fertility and their metabolic performance, especially glucose metabolism, is under a tight endocrine control, being essential for the success of spermatogenesis. Herein, we studied the impact of the model obesogen tributyltin in the metabolic profile of SCs. For that, ex vivo-cultured rat SCs were exposed to increasing doses of tributyltin. SCs proliferation was evaluated by the sulforhodamine B assay and the maturation state of the cells was assessed by the expression of specific markers (inhibin B and the androgen receptor) by quantitative polymerase chain reaction. The metabolic profile of SCs was established by studying metabolites consumption/production by nuclear magnetic resonance spectroscopy and by analyzing the expression of key transporters and enzymes involved in glycolysis by Western blot. The proliferation of SCs was only affected in the cells exposed to the highest dose (1000 nM) of tributyltin. Notably, SCs exposed to 10 nM tributyltin decreased the consumption of glucose and pyruvate, as well as the production of lactate. The decreased lactate production hampers the development of germ cells. Intriguingly, the lowest levels of tributyltin were more prone to modulate the expression of key players of the glycolytic pathway. This is the first study showing that tributyltin reprograms glucose metabolism of SCs under ex vivo conditions, suggesting new targets and mechanisms through which obesogens modulate the metabolism of SCs and thus male (in)fertility.

Neonatal hypothyroidism affects testicular glucose homeostasis through increased oxidative stress in prepubertal mice: effects on GLUT3, GLUT8 and Cx43

Thyroid hormones (THs) play an important role in maintaining the link between metabolism and reproduction and the altered THs status is associated with induction of oxidative stress in various organs like brain, heart, liver and testis. Further, reactive oxygen species play a pivotal role in regulation of glucose homeostasis in several organs, and glucose utilization by Leydig cells is essential for testosterone biosynthesis and thus is largely dependent on glucose transporter 8 (GLUT8). Glucose uptake by Sertoli cells is mediated through glucose transporter 3 (GLUT3) under the influence of THs to meet energy requirement of developing germ cells. THs also modulate level of gap junctional protein such as connexin 43 (Cx43), a potential regulator of cell proliferation and apoptosis in the seminiferous epithelium. Although the role of transient neonatal hypothyroidism in adult testis in terms of testosterone production is well documented, the effect of THs deficiency in early developmental period and its role in testicular glucose homeostasis and oxidative stress with reference to Cx43 in immature mice remain unknown. Therefore, the present study was conducted to evaluate the effect of neonatal hypothyroidism on testicular glucose homeostasis and oxidative stress at postnatal days (PND) 21 and 28 in relation to GLUT3, GLUT8 and Cx43. Hypothyroidism induced by 6-propyl-2-thiouracil (PTU) markedly decreased testicular glucose level with considerable reduction in expression level of GLUT3 and GLUT8. Likewise, lactate dehydrogenase (LDH) activity and intratesticular concentration of lactate were also decreased in hypothyroid mice. There was also a rise in germ cell apoptosis with increased expression of caspase-3 in PTU-treated mice. Further, neonatal hypothyroidism affected germ cell proliferation with decreased expression of proliferating cell nuclear antigen (PCNA) and Cx43. In conclusion, our results suggest that neonatal hypothyroidism alters testicular glucose homeostasis via increased oxidative stress in prepubertal mice, thereby affecting germ cell survival and proliferation.

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.

Repeated exposure to iron oxide nanoparticles causes testicular toxicity in mice

The aim of this study was to determine whether repeated exposure to iron oxide nanoparticles (Fe₂ O₃ -NPs) could be toxic to mice testis. Fe₂ O₃ -NPs (25 and 50 mg/kg) were intraperitoneally administered into mice once a week for 4 weeks. Our study showed that Fe₂ O₃ -NPs have the ability to cross the blood-testis barrier to get into the testis. The findings showed that exposure resulted in the accumulation of Fe₂ O₃ -NPs which was evidenced from the iron content and accumulation in the testis. Furthermore, 25 and 50 mg/kg Fe₂ O₃ -NPs administration increased the reactive oxygen species, lipid peroxidation, protein carbonyl content, glutathione peroxidase activity, and nitric oxide levels with a concomitant decrease in the levels of antioxidants-superoxide dismutase, catalase, glutathione, and vitamin C. Increased expression of Bax, cleaved-caspase-3, and cleaved-PARP confirms apoptosis. Serum testosterone levels increased with increased concentration of Fe₂ O₃ -NPs exposure. In addition, the histopathological lesions like vacuolization, detachment, and sloughing of germ cells were also observed in response to Fe₂ O₃ -NPs treatment. The data from our study entailed that testicular toxicity caused by Fe₂ O₃ -NPs exposure may be associated with Fe₂ O₃ -NPs accumulation leading to oxidative stress and apoptosis. Therefore, precautions should be taken in the safe use of Fe₂ O₃ -NPs to avoid complications in the fertility of males. Further research will unravel the possible molecular mechanisms on testicular toxicity of Fe₂ O₃ -NPs. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 594-608, 2017.

Obesogens and male fertility

In the last decades, several studies evidenced a decrease in male fertility in developed countries. Although the aetiology of this trend in male reproductive health remains a matter of debate, environmental compounds that predispose to weight gain, namely obesogens, are appointed as contributors because of their action as endocrine disruptors. Obesogens favour adipogenesis by an imbalance of metabolic processes and can be found virtually everywhere. These compounds easily accumulate in tissues with high lipid content. Obesogens change the functioning of male reproductive axis, and, consequently, the testicular physiology and metabolism that are pivotal for spermatogenesis. The disruption of these tightly regulated metabolic pathways leads to adverse reproductive outcomes. Notably, adverse effects of obesogens may also promote disturbances in the metabolic performance of the following generations, through epigenetic modifications passed by male gametes. Thus, unveiling the molecular pathways by which obesogens induce toxicity that may end up in epigenetic modifications is imperative. Otherwise, a transgenerational susceptibility to metabolic diseases may be favoured. We present an up-to-date overview of the impact of obesogens on testicular physiology, with a particular focus on testicular metabolism. We also address the effects of obesogens on male reproductive parameters and the subsequent consequences for male fertility.

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.

Ghrelin acts as energy status sensor of male reproduction by modulating Sertoli cells glycolytic metabolism and mitochondrial bioenergetics

Ghrelin is a growth hormone-releasing peptide that has been suggested to interfere with spermatogenesis, though the underling mechanisms remain unknown. We studied the effect of ghrelin in human Sertoli cells (hSCs) metabolic phenotype. For that, hSCs were exposed to increasing concentrations of ghrelin (20, 100 and 500 pM) mimicking the levels reported in obese, normal weight, and severely undernourished individuals. The metabolite production/consumption was determined. The protein levels of key glycolysis-related transporters and enzymes were assessed. The lactate dehydrogenase (LDH) activity was measured. Mitochondrial complexes protein levels and mitochondria membrane potential were also measured. We showed that hSCs express the growth hormone secretagogue receptor. At the concentration present in the plasma of normal weight men, ghrelin caused a decrease of glucose consumption and mitochondrial membrane potential in hSCs, though LDH activity and lactate production remained unchanged, illustrating an alteration of glycolytic flux efficiency. Exposure of hSCs to levels of ghrelin found in the plasma of severely undernourished individuals decreased pyruvate consumption and mitochondrial complex III protein expression. All concentrations of ghrelin decreased alanine and acetate production by hSCs. Notably, the effects of ghrelin levels found in severely undernourished individuals were more pronounced in hSCs metabolic phenotype highlighting the importance of a proper eating behavior to maintain male reproductive potential. In conclusion, ghrelin acts as an energy status sensor for hSCs in a dose-dependent manner, showing an inverse association with the production of lactate, thus controlling the nutritional support of spermatogenesis.

Melatonin intake since weaning ameliorates steroidogenic function and sperm motility of streptozotocin-induced diabetic rats

Melatonin may be used as an antioxidant in therapy against systemic sequelae caused by oxidative stress in diabetes. However, as melatonin has a major role in regulating reproductive activity, its consequence on reproductive parameters under diabetes needs to be better clarified. We have studied whether prior and concomitant treatment of juvenile Wistar rats with low doses of melatonin interferes in reproductive damage induced by experimental diabetes after 1 and 8 weeks. The consequences of melatonin administration since weaning on reproductive parameters of healthy rats at adulthood were also evaluated. Melatonin was provided in drinking water (10 μg/kg b.w./day) after weaning (5-week-old). Diabetes was induced by streptozotocin injection (4.5 mg/100 g b.w.) at 13-week-old rats, and rats were euthanized 1 and 8 weeks after disease onset. Diabetes decreased circulating testosterone levels (~35% to 1 week; ~62% to 2 months; p < 0.01) but did not affect testes sperm counts. Two months of diabetes reduced the sperm reserve and led to atrophy of epididymal cauda. Both 1-week and 2-month diabetes impaired sperm motility, decreased the number of spermatozoa with progressive movement, and increased the number of immotile sperm. Melatonin intake reduced serum testosterone levels ~29% in healthy 14-week-old and ~23% in 21-week-old rats and reduced daily testicular sperm production ~26% in the latter disease stage, but did not interfere in sperm reserves and transit time for both experimental periods. Exogenous melatonin prevented the serum testosterone decrease and damage to sperm motility in diabetic rats and attenuated reduction in sperm counts and transit time induced by 1-week diabetes but did not avoid this decrease at 2-month diabetes. Low doses of melatonin administered prior to and during experimental diabetes attenuated damage to testicular steroidogenic activity and preserved sperm motility, but not sperm reserves in the rat. Our data indicated a differential action of melatonin in normoglycemic and hyperglycemic conditions, particularly in sperm motility and testosterone production by Leydig cells.

Hormone responsiveness of cultured Sertoli cells obtained from adult rats after their rapid isolation under less harsh conditions

During adulthood, testicular Sertoli cells (Sc) coordinate all stages of germ cell (Gc) development involved in sperm production. However, our understanding about the functions of adult Sc is limited because of the difficulties involved in the process of isolating these cells from the adult testis, mainly because of the presence of large number of advanced Gc which interfere with Sc isolation at this age. Most of our knowledge about Sc function are derived from studies which used pre-pubertal rat Sc (18 ± 2-day old) as it is easy to isolate and culture Sc at this age. To this end, we established a less time consuming and less harsh procedure of isolating Sc from adult (60 days of age) rat testis for facilitating research on Sc-mediated regulation of spermatogenesis during adulthood. The cells were isolated using collagenase digestion at higher temperature, reducing the exposure time of cells to the enzyme. Step-wise digestion with intermittent removal of small clusters of tissue helped in increasing the yield of Sc. Isolated Sc were cultured and treated with FSH and testosterone (T) to evaluate their hormone responsiveness in terms of lactate, E2 , cAMP production. Adult Sc were found to be active and produced high amounts of lactate in a FSH-independent manner. FSH-mediated augmentation of cAMP and E2 production by adult Sc was less as compared with that by pre-pubertal Sc obtained from 18-day-old rats. Androgen-binding ability of adult Sc was significantly higher than pre-pubertal Sc. Although T treatment remarkably augmented expression of Claudin 11, it failed to augment lactate production by adult Sc. This efficient and rapid procedure for isolation and culture of functionally viable adult rat Sertoli cells may pave the way for determining their role in regulation and maintenance of spermatogenesis.

Metabolic alterations in bladder cancer: applications for cancer imaging

Treatment planning, outcome and prognosis are strongly related to the adequate tumor staging for bladder cancer (BC). Unfortunately, a large discrepancy exists between the preoperative clinical and final pathologic staging. Therefore, an advanced imaging-based technique is crucial for adequate staging. Although Magnetic Resonance Imaging (MRI) is currently the best in vivo imaging technique for BC staging because of its excellent soft-tissue contrast and absence of ionizing radiation it lacks cancer-specificity. Tumor-specific positron emission tomography (PET), which is based on the Warburg effect (preferential uptake of glucose by cancer cells), exploits the radioactively-labeled glucose analogs, i.e., FDG. Although FDG-PET is highly cancer specific, it lacks resolution and contrast quality comparable with MRI. Chemical Exchange Saturation Transfer (CEST) MRI enables the detection of low concentrations of metabolites containing protons. BC is an attractive target for glucose CEST MRI because, in addition to the typical systemic administration, glucose might also be directly applied into the bladder to reduce toxicity-related complications. As a first stage of the development of a contrast-specific BC imaging technique we have studied glucose uptake by bladder epithelial cells and have observed that glucose is, indeed, consumed by BC cells with higher intensity than by non-transformed urothelial cells. This effect might be partly explained by increased expression of glucose transporters GLUT1 and GLUT3 in transformed cells as compared to normal urothelium. We also detected higher lactate production by BC cells which is another cancer-specific manifestation of the Warburg effect. In addition, we have observed other metabolic alterations in BC cells as compared to non-transformed cells: in particular, increased pyruvate synthesis. When glucose was substituted by glutamine in culture media, preferential uptake of glutamine by BC cells was observed. The preferential uptake of glucose by BC cells gives an opportunity to develop NMR based imaging procedures where glucose or its derivatives can serve as a contrasting agent. In addition, metabolic alterations observed in BC cells could provide the basis for development of new anti-cancer therapeutics.