Essential role of germ cell glycerol-3-phosphate phosphatase for sperm health, oxidative stress control and male fertility in mice

OBJECTIVES

Obesity, diabetes and high-calorie diets are associated with defective sperm function and lowered male fertility. Mature spermatozoa primarily use fructose and glucose, and glucose and glycerol metabolism are important for sperm function. We recently discovered a novel mammalian enzyme, glycerol-3-phosphate (Gro3P) phosphatase (G3PP), and showed that it operates the glycerol shunt by hydrolyzing Gro3P to glycerol, and regulates glucose, lipid and energy metabolism in pancreatic β-cells and liver. We now observed that G3PP expression is the highest in the testis and spermatozoa, and investigated its role in male fertility.

METHODS

We examined G3PP expression during spermatogenesis in mouse and assessed male fertility and spermatozoon function in conditional germ cell specific G3PP-KO (cG3PP-KO) mice and tamoxifen-inducible conditional germ cell G3PP-KO (icG3PP-KO) mice. We also determined the structural and metabolic parameters and oxidative stress in the spermatozoa from icG3PP-KO and control mice.

RESULTS

G3PP expression in mouse spermatocytes and spermatids markedly increases during spermatogenesis. Male cG3PP-KO mice, in which germ cell G3PP is deleted from embryonic stage, are infertile due to dysfunctional sperm with reduced motility and capacitation, and elevated spontaneous acrosomal reaction and oxidative stress. However, icG3PP-KO male mice do not have altered fertility, due to the presence of ∼10% normal spermatozoa. icG3PP-KO spermatozoa display significantly reduced functionality and morphological and ultrastructural alterations. The icG3PP-KO spermatozoa show reduced glycerol production, elevated levels of Gro3P and reactive oxygen species (ROS), and oxidative stress that is associated with increased mitochondrial membrane potential.

CONCLUSIONS

Germ cell G3PP deletion leads to the generation of spermatozoa that are functionally and structurally abnormal, likely due to the build-up of Gro3P that increases mitochondrial membrane potential, ROS, and oxidative stress and alters spermatozoa function. Overall, the results indicate that G3PP and the glycerol shunt are essential for normal spermatozoa function and male fertility.

Metabolomics analysis of human spermatozoa reveals impaired metabolic pathways in asthenozoospermia

BACKGROUND

Infertility is a major health issue, affecting 15% of reproductive-age couples with male factors contributing to 50% of cases. Asthenozoospermia (AS), or low sperm motility, is a common cause of male infertility with complex aetiology, involving genetic and metabolic alterations, inflammation and oxidative stress. However, the molecular mechanisms behind low motility are unclear. In this study, we used a metabolomics approach to identify metabolic biomarkers and pathways involved in sperm motility.

METHODS

We compared the metabolome and lipidome of spermatozoa of men with normozoospermia (n = 44) and AS (n = 22) using untargeted LC-MS and the metabolome of seminal fluid using 1H-NMR. Additionally, we evaluated the seminal fluid redox status to assess the oxidative stress in the ejaculate.

RESULTS

We identified 112 metabolites and 209 lipids in spermatozoa and 27 metabolites in the seminal fluid of normozoospermic and asthenozoospermic men. PCA analysis of the spermatozoa's metabolomics and lipidomics data showed a clear separation between groups. Spermatozoa of asthenozoospermic men presented lower levels of several amino acids, and increased levels of energetic substrates and lysophospholipids. However, the metabolome and redox status of the seminal fluid was not altered inAS.

CONCLUSIONS

Our results indicate impaired metabolic pathways associated with redox homeostasis and amino acid, energy and lipid metabolism in AS. Taken together, these findings suggest that the metabolome and lipidome of human spermatozoa are key factors influencing their motility and that oxidative stress exposure during spermatogenesis or sperm maturation may be in the aetiology of decreased motility in AS.

In vivo glycerol metabolism in patients with glycerol kinase deficiency

Glycerol kinase deficiency (GKD) is an X-linked recessive disorder due to glycerol kinase (GK) gene mutations resulting in hyperglycerolermia, hyperglyceroluria, and "pseudohypertriglyceridemia." In vivo glycerol metabolism has not been assessed in GKD. A 62-year-old man with suspected GKD and his extended family underwent whole exome sequencing and fasting blood work with two modes of lipid measurements: (1) standard lipase-based methodology and (2) nuclear magnetic resonance (NMR). Two overnight fasted men with GKD and a heterozygote female carrier then underwent 13C3-glycerol infusion. Affected family members had a novel two-nucleotide deletion in exon 5 of the GK gene (c.373_374del). Compared to their family members (n = 14), men with GKD (n = 5) had significantly lower total cholesterol levels (3.72 ± 0.70 vs. 4.77 ± 0.85 mmol/L, p = 0.024). Compared to NMR, lipase-based assays overreported triglycerides (5.28 ± 1.38 vs. 0.81 ± 0.32, mmol/L, p < 0.001) and underreported low-density lipoprotein cholesterol values (0.93 ± 0.23 vs. 2.18 ± 0.42 mmol/L, p = 0.001) in GKD. Men with GKD could not convert glycerol into glucose or triglycerides, which was preserved in the heterozygote carrier. Glycolytic metabolism of glycerol to lactate persisted in GKD, but it was reduced by a magnitude and, possibly, due to homologous glycerol kinases encoded by other genes. In summary, we report a novel GK pathogenic variant; affected men cannot convert circulating glycerol to glucose or triglycerides and have lower cholesterol levels. These results offer a human model for potentially targeting glycerol kinase to treat conditions associated with hyperglycemia and hyperlipidemia and warrant further investigation.

Aquaporins in sepsis- an update

Aquaporins (AQPs), a family of membrane proteins that facilitate the transport of water and small solutes, have garnered increasing attention for their role in sepsis, not only in fluid balance but also in immune modulation and metabolic regulation. Sepsis, characterized by an excessive and dysregulated immune response to infection, leads to widespread organ dysfunction and significant mortality. This review focuses on the emerging roles of aquaporins in immune metabolism and their potential as therapeutic targets in sepsis, with particular attention to the modulation of inflammatory responses and organ protection. Additionally, it explores the diverse roles of aquaporins across various organ systems, highlighting their contributions to renal function, pulmonary gas exchange, cardiac protection, and gastrointestinal barrier integrity in the context of sepsis. Recent studies suggest that AQPs, particularly aquaglyceroporins like AQP3, AQP7, AQP9, and AQP10, play pivotal roles in immune cell metabolism and offer new therapeutic avenues for sepsis treatment. In the context of sepsis, immune cells undergo metabolic shifts to meet the heightened energy demands of the inflammatory response. A key adaptation is the shift from oxidative phosphorylation (OXPHOS) to aerobic glycolysis, where pyruvate is converted to lactate, enabling faster ATP production. AQPs, particularly aquaglyceroporins, may facilitate this process by transporting glycerol, a substrate that fuels glycolysis. AQP3, for example, enhances glucose metabolism by transporting glycerol and complementing glucose uptake via GLUT1, while also regulating O-GlcNAcylation, a post-translational modification that boosts glycolytic flux. AQP7 could further contributes to immune cell energy production by influencing lipid metabolism and promoting glycolysis through p38 signaling. These mechanisms could be crucial for maintaining the energy supply needed for an effective immune response during sepsis. Beyond metabolism, AQPs also regulate key immune functions. AQP9, highly expressed in septic patients, is essential for neutrophil migration and activation, both of which are critical for controlling infection. AQP3, on the other hand, modulates inflammation through the Toll-like receptor 4 (TLR4) pathway, while AQP1 plays a role in immune responses by activating the PI3K pathway, promoting macrophage polarization, and protecting against lipopolysaccharide (LPS)-induced acute kidney injury (AKI). These insights into the immunoregulatory roles of AQPs suggest their potential as therapeutic targets to modulate inflammation in sepsis. Therapeutically, AQPs present promising targets for reducing organ damage and improving survival in sepsis. For instance, inhibition of AQP9 with compounds like HTS13286 or RG100204 has been shown to reduce inflammation and improve survival by modulating NF-κB signaling and decreasing oxidative stress in animal models. AQP5 inhibition with methazolamide and furosemide has demonstrated efficacy in reducing immune cell migration and lung injury, suggesting its potential in treating acute lung injury (ALI) in sepsis. Additionally, the regulation of AQP1 through non-coding RNAs (lncRNAs and miRNAs) may offer new strategies to mitigate organ damage and inflammatory responses. Moreover, AQPs have emerged as potential biomarkers for sepsis progression and outcomes. Altered expression of AQPs, such as AQP1, AQP3, and AQP5, correlates with sepsis severity, and polymorphisms in AQP5 have been linked to better survival rates and improved outcomes in sepsis-related acute respiratory distress syndrome (ARDS). This suggests that AQP expression could be used to stratify patients and tailor treatments based on individual AQP profiles. In conclusion, AQPs play a multifaceted role in the pathophysiology of sepsis, extending beyond fluid balance to crucial involvement in immune metabolism and inflammation. Targeting AQPs offers novel therapeutic strategies to mitigate sepsis-induced organ damage and improve patient survival. Continued research into the metabolic and immune functions of AQPs will be essential for developing targeted therapies that can be translated into clinical practice.

Gut-gonad crosstalk in mice exposed to a "chemical cocktail" combining metabolomics and microbial profile by amplicon sequencing

Testes are very prone to be damaged by environmental pollutants, but there is a lack of information about the impact of "chemical cocktails" (CC) on the testicular metabolome and the possible influence in the gut-gonad crosstalk. For this, BALB/c mice were given flumequine and diclofenac orally in food and potentially toxic trace elements (Cd, Hg, As) in drinking water. A mice group was supplemented with selenium, a well-known antagonist against many pollutants. Our results revealed that the steroid 5-alpha-androstan-17-beta-ol propionate, suggested as a parameter of androgenicity independent of testosterone levels, proline that improves reproductive indicators in male rabbits affected by environmental stress) among others metabolites are only present after CC exposure with rodent and selenium supplemented diet. Selenium also antagonized the up-or down-regulation of anandamide (20:l, n-9) (p < 0.001 and FC 0.54 of CC vs C but p > 0,05 and FC 0.74 of CC-Se vs C), that regulates gonadotropin-releasing hormones in mammals, 2,3-dinor-11b-PGF2a (p < 0.001 and FC 0.12 of CC vs C but p > 0,05 and FC 0.34 of CC-Se vs C), which has been related with reproductive hormones, besides others testicular metabolites altered by the exposure to the CC and reversed the levels to control. Moreover, numerous significant associations between gut microbes and testicular metabolites indicated a possible impact of pollutants in the testes mediated by gut microbiota due to a gut-gonad crosstalk.

Proximate analysis and GC-MS phytochemical profiling of aqueous extracts of Doryopteris raddiana, a plant used by the Mbya-Guaraní as a contraceptive

Doryopteris raddiana (Presl) Fée, a traditional contraceptive in Mbya culture, lacks scientific scrutiny regarding its chemical composition and contraceptive efficacy. Employing X-ray fluorescence, Fourier-transform infrared spectroscopy, and thermal analysis, we explored the plant's organs. Multielemental analysis excluded toxic elements. Key phytoconstituents identified by gas chromatography-mass spectrometry in the extracts obtained through infusion were glycerine, 1,3-dimethyl propane, and catechol in leaves; glycerine, cis-13-octadecenoic acid methyl ester, and 2-deoxy-D-erythro-pentose in stems and roots. Among these chemicals, glycerine emerged as the sole constituent with contraceptive potential, particularly intravaginally. Extract activity tests conducted on ram spermatozoa exhibited a reduction in the percentage of rapid spermatozoa but no significant impact on total motility, progressive motility, or viability. The reported data would only weakly support the advocated contraceptive action of this fern upon vaginal application, not through the oral administration of its decoction.

Addition of Vitamin C Mitigates the Loss of Antioxidant Capacity, Vitality and DNA Integrity in Cryopreserved Human Semen Samples

Cryopreservation of human spermatozoa is a necessity for males suffering from infertility who cannot produce fresh semen for insemination. However, current ART cryopreservation protocols are associated with losses of sperm motility, vitality and DNA integrity, which are thought to be linked to the induction of oxidative damage and the toxic properties of commercial cryoprotectants (CPAs). Preventing or mitigating these losses would be hugely beneficial to sperm survival during ART. Therefore, in this in vitro investigation, lipid peroxidation, production of reactive oxygen species, movement characteristics, antioxidant capacity, vitality, and DNA integrity were examined in semen samples both pre- and post-cryopreservation with CPA supplementation. The findings revealed a 50% reduction in antioxidant capacity with CPA addition, which was accompanied by significant increases in generation of reactive oxygen species and formation of lipid aldehydes. These changes were, in turn, correlated with reductions in sperm viability, motility and DNA integrity. Antioxidant supplementation generated bell-shaped dose-response curves with both resveratrol and vitamin C, emphasising the vulnerability of these cells to both oxidative and reductive stress. At the optimal dose, vitamin C was able to significantly enhance vitality and reduce DNA damage recorded in cryopreserved human spermatozoa. An improvement in sperm motility did not reach statistical significance, possibly because additional pathophysiological mechanisms limit the potential effectiveness of antioxidants in rescuing this aspect of sperm function. The vulnerability of human spermatozoa to reductive stress and the complex nature of sperm cryoinjury will present major challenges in creating the next generation of cryoprotective media.

A Metabolomic Analysis to Assess the Responses of the Male Gonads of Mytilus galloprovincialis after Heavy Metal Exposure

In recent years, metabolomics has become a valuable new resource in environmental monitoring programs based on the use of bio-indicators such as Mytilus galloprovincialis. The reproductive system is extremely susceptible to the effects of environmental pollutants, and in a previous paper, we showed metabolomic alterations in mussel spermatozoa exposed to metal chlorides of copper, nickel, and cadmium, and the mixture with these metals. In order to obtain a better overview, in the present work, we evaluated the metabolic changes in the male gonad under the same experimental conditions used in the previous work, using a metabolomic approach based on GC-MS analysis. A total of 248 endogenous metabolites were identified in the male gonads of mussels. Statistical analyses of the data, including partial least squares discriminant analysis, enabled the identification of key metabolites through the use of variable importance in projection scores. Furthermore, a metabolite enrichment analysis revealed complex and significant interactions within different metabolic pathways and between different metabolites. Particularly significant were the results on pyruvate metabolism, glycolysis, and gluconeogenesis, and glyoxylate and dicarboxylate metabolism, which highlighted the complex and interconnected nature of these biochemical processes in mussel gonads. Overall, these results add new information to the understanding of how certain pollutants may affect specific physiological functions of mussel gonads.

Male Sex Hormones, Metabolic Syndrome, and Aquaporins: A Triad of Players in Male (in)Fertility

Infertility is becoming a chronic and emerging problem in the world. There is a resistant stigma that this health condition is mostly due to the female, although the literature supports that the responsibility for the onset of infertility is equally shared between both sexes in more or less equal proportions. Nevertheless, male sex hormones, particularly testosterone (T), are key players in male-related infertility. Indeed, hypogonadism, which is also characterized by changes in T levels, is one of the most common causes of male infertility and its incidence has been interconnected to the increased prevalence of metabolic diseases. Recent data also highlight the role of aquaporin (AQP)-mediated water and solute diffusion and the metabolic homeostasis in testicular cells suggesting a strong correlation between AQPs function, metabolism of testicular cells, and infertility. Indeed, recent studies showed that both metabolic and sexual hormone concentrations can change the expression pattern and function of AQPs. Herein, we review up-to-date information on the involvement of AQP-mediated function and permeability in men with metabolic syndrome and testosterone deficit, highlighting the putative mechanisms that show an interaction between sex hormones, AQPs, and metabolic syndrome that may contribute to male infertility.

CFTR modulates aquaporin-mediated glycerol permeability in mouse Sertoli cells

The cystic fibrosis transmembrane conductance regulator (CFTR) is an anion channel that is crucial for fluid homeodynamics throughout the male reproductive tract. Previous evidence shed light on a potential molecular partnership between this channel and aquaporins (AQPs). Herein, we explore the role of CFTR on AQPs-mediated glycerol permeability in mouse Sertoli cells (mSCs). We were able to identify the expression of CFTR, AQP3, AQP7, and AQP9 in mSCs by RT-PCR, Western blot, and immunofluorescence techniques. Cells were then treated with CFTRinh-172, a specific CFTR inhibitor, and its glycerol permeability was evaluated by stopped-flow light scattering. We observed that CFTR inhibition decreased glycerol permeability in mSCs by 30.6% when compared to the control group. A DUOLINK proximity ligation assay was used to evaluate the endogenous protein-protein interactions between CFTR and the various aquaglyceroporins we identified. We positively detected that CFTR is in close proximity with AQP3, AQP7, and AQP9 and that, through a possible physical interaction, CFTR can modulate AQP-mediated glycerol permeability in mSCs. As glycerol is essential for the control of the blood-testis barrier and elevated concentration in testis results in the disruption of spermatogenesis, we suggest that the malfunction of CFTR and the consequent alteration in glycerol permeability is a potential link between male infertility and cystic fibrosis.

Follicle-stimulating hormone signaling in Sertoli cells: a licence to the early stages of spermatogenesis

Follicle-stimulating hormone signaling is essential for the initiation and early stages of spermatogenesis. Follicle-stimulating hormone receptor is exclusively expressed in Sertoli cells. As the only type of somatic cell in the seminiferous tubule, Sertoli cells regulate spermatogenesis not only by controlling their own number and function but also through paracrine actions to nourish germ cells surrounded by Sertoli cells. After follicle-stimulating hormone binds to its receptor and activates the follicle-stimulating hormone signaling pathway, follicle-stimulating hormone signaling will establish a normal Sertoli cell number and promote their differentiation. Spermatogonia pool maintenance, spermatogonia differentiation and their entry into meiosis are also positively regulated by follicle-stimulating hormone signaling. In addition, follicle-stimulating hormone signaling regulates germ cell survival and limits their apoptosis. Our review summarizes the aforementioned functions of follicle-stimulating hormone signaling in Sertoli cells. We also describe the clinical potential of follicle-stimulating hormone treatment in male patients with infertility. Furthermore, our review may be helpful for developing better therapies for treating patients with dysfunctional follicle-stimulating hormone signaling in Sertoli cells.

Pesticides and Male Fertility: A Dangerous Crosstalk

In recent decades, an increasing incidence of male infertility has been reported. Interestingly, and considering that pesticides have been used for a long time, the high incidence of this pathological state is concomitant with the increasing use of these chemicals, suggesting they are contributors for the development of human infertility. Data from literature highlight the ability of certain pesticides and/or their metabolites to persist in the environment for long periods of time, as well as to bioaccumulate in the food chain, thus contributing for their chronic exposure. Furthermore, pesticides can act as endocrine disrupting chemicals (EDCs), interfering with the normal function of natural hormones (which are responsible for the regulation of the reproductive system), or even as obesogens, promoting obesity and associated comorbidities, like infertility. Several in vitro and in vivo studies have focused on the effects and possible mechanisms of action of these pesticides on the male reproductive system that cause sundry negative effects, even though through diverse mechanisms, but all may lead to infertility. In this review, we present an up-to-date overview and discussion of the effects, and the metabolic and molecular features of pesticides on somatic cells and germinal tissues that affect germ cell differentiation.

Effects of Dietary Crude Glycerin Concentration on Testicular Morphology and Oxidative Stress Markers and on Plasma Testosterone Concentrations

We evaluated the effects of feeding 6%, 12% or 18% crude glycerin, containing 80.5% glycerol, on testicular histomorphometry and markers of oxidative stress and on plasma testosterone concentrations in lambs. Body weight, testicular biometric measurements, gonadosomatic index and net weight of the testicles were higher for the treated groups (P <0.05) compared with a control group that did not receive dietary glycerin. The mean total length of seminiferous tubules was higher in the 6% group (P <0.05), while the mean total tubular and seminiferous epithelium volumes increased in all treated groups (P <0.05). The volume of Leydig cells increased in the 12% group, while their number per gram of testicle decreased (P <0.05). There was a decrease in mean nuclear diameter and mean volume of Leydig cells, and an increase in the mean number of these cells per gram of testicle, in the 18% group (P <0.05). Plasma testosterone concentrations were unaffected. There was desquamation of seminiferous epithelium and vacuolation of Sertoli cells in the treated groups. Variable degrees of spermatocyte necrosis and the presence of giant cells were seen in all groups and there was intense vacuolation of Sertoli cells in the 12% and 18% groups. Superoxide dismutase and catalase production increased most in the 12% and 18% groups (P <0.05), while glutathione production was higher in the 18% group (P <0.05). Mean nitric oxide concentration decreased in all treated groups (P <0.05), while malondialdehyde production was higher in the 18% group than in the control and 6% groups (P <0.05). We conclude that the inclusion of 6% glycerin in the diet of lambs results in changes in testicular morphology that have been previously associated with improved reproductive function, but without evidence of oxidative stress.

Differential abundances of AQP3 and AQP5 in reproductive tissues from dogs with and without cryptorchidism

Aquaporins (AQPs) are integral transmembrane proteins facilitating transport of water and small solutes, such as glycerol and urea, between cells. In male reproductive tracts, AQPs maintain a milieu conducive for sperm formation, maturation, and storage. The aim of this study was to clarify effects of testicular and epidydimal function on male fertility by investigating localisation and abundances of AQP3 and AQP5 in testes and epididymal segments from dogs with and without unilateral cryptorchidism. Immunohistochemistry results indicated AQP3 and AQP5 have different distribution patterns in reproductive tissues of dogs with and without unilateral cryptorchidism. The AQP3, an aquaglyceroprotein, is present in different germ and Sertoli cells in testis of dogs without cryptorchidism. The AQP5 protein was not detected in germ cells but was present in Sertoli and Leydig cells and in endothelia of blood vessels. In cryptorchid dogs, AQP3 was detected in early-developing germ and Sertoli cells, and AQP5 had a distribution pattern similar to testes of dogs without cryptorchidism. In the epididymis, AQP3 and AQP5 were localised in epithelial cells of dogs with and without cryptorchidism in a cell-specific manner. The AQP3 and AQP5 protein was in larger abundance in the gonads from dogs with and without cryptorchidism. In contrast, AQP3 and AQP5 abundance increased in each segment of the cryptorchid epididymis, likely as a compensatory mechanism associated with the pathologic condition. These results indicate involvement of AQP3 and AQP5 in spermatogenesis and sperm maturation. Results from the present study indicate dogs are a useful for comparative reproductive biology studies.

Aquaporins and (in)fertility: More than just water transport

Aquaporins (AQPs) are a family of channel proteins that facilitate the transport of water and small solutes across biological membranes. They are widely distributed throughout the organism, having a number of key functions, some of them unexpected, both in health and disease. Among the various diseases in which AQPs are involved, infertility has been overlooked. According to the World Health Organization (WHO) infertility is a global public health problem with one third of the couples suffering from subfertility or even infertility due to male or female factors alone or combined. Thus, there is an urgent need to unveil the molecular mechanisms that control gametes production, maturation and fertilization-related events, to more specifically determine infertility causes. In addition, as more couples seek for fertility treatment through assisted reproductive technologies (ART), it is pivotal to understand how these techniques can be improved. AQPs are heterogeneously expressed throughout the male and female reproductive tracts, highlighting a possible regulatory role for these proteins in conception. In fact, their function, far beyond water transport, highlights potential intervention points to enhance ART. In this review we discuss AQPs distribution and structural organization, functions, and modulation throughout the male and female reproductive tracts and their relevance to the reproductive success. We also highlight the most recent advances and research trends regarding how the different AQPs are involved and regulated in specific mechanisms underlying (in)fertility. Finally, we discuss the involvement of AQPs in ART-related processes and how their handling can lead to improvement of infertility treatment.

Diet during early life defines testicular lipid content and sperm quality in adulthood

Childhood obesity is a serious concern associated with ill health later in life. Emerging data suggest that obesity has long-term adverse effects upon male sexual and reproductive health, but few studies have addressed this issue. We hypothesized that exposure to high-fat diet during early life alters testicular lipid content and metabolism, leading to permanent damage to sperm parameters. After weaning (day 21 after birth), 36 male mice were randomly divided into three groups and fed with a different diet regimen for 200 days: a standard chow diet (CTRL), a high-fat diet (HFD) (carbohydrate: 35.7%, protein: 20.5%, and fat: 36.0%), and a high-fat diet for 60 days, then replaced by standard chow (HFD_t). Biometric and metabolic data were monitored. Animals were then euthanized, and tissues were collected. Epididymal sperm parameters and endocrine parameters were evaluated. Testicular metabolites were extracted and characterized by 1H-NMR and GC-MS. Testicular mitochondrial and antioxidant activity were evaluated. Our results show that mice fed with a high-fat diet, even if only until early adulthood, had lower sperm viability and motility, and higher incidence of head and tail defects. Although diet reversion with weight loss during adulthood prevents the progression of metabolic syndrome, testicular content in fatty acids is irreversibly affected. Excessive fat intake promoted an overaccumulation of proinflammatory n-6 polyunsaturated fatty acids in the testis, which is strongly correlated with negative effects upon sperm quality. Therefore, the adoption of high-fat diets during early life correlates with irreversible changes in testicular lipid content and metabolism, which are related to permanent damage to sperm quality later in life.

Sperm selection strategies and their impact on assisted reproductive technology outcomes

The application of assisted reproductive technologies (ART) has revolutionised the treatment of human infertility, giving hope to the patients previously considered incapable of establishing pregnancy. While semen analysis is performed to access whether a sample has an adequate number of viable, motile and morphologically normal sperm cells able to achieve fertilisation, sperm selection techniques for ART aim to isolate the most competent spermatozoon which is characterised by the highest fertilising potential. Based on the semen analysis results, the correct sperm selection technique must be chosen and applied. In this review, different sperm selection strategies for retrieving spermatozoa with the highest fertilising potential and their impact on ART outcomes are discussed. In addition, advantages and disadvantages of each method and the best suited techniques for each clinical scenario are described.

Estrogen Modulates Glycerol Permeability in Sertoli Cells through Downregulation of Aquaporin-9

High 17β-Estradiol (E2) levels are known to cause alterations of spermatogenesis and environments throughout the male reproductive tract. Sertoli cells (SCs) ensure an adequate environment inside the seminiferous tubule. Glycerol stands as essential for the maintenance of blood⁻testis barrier created by SCs, however, the role of E2 in this process is not known. Herein, we hypothesized that the effect of E2 on glycerol permeability in mouse SCs (mSCs) could be mediated by aquaglyceroporins. The expression of aquaglyceroporins was assessed by RT-PCR and qRT-PCR. Glycerol permeability was evaluated by stopped-flow light scattering. We were able to identify the expression of AQP3 and AQP9 in mSCs where AQP9 is more abundant than AQP3. Our results show that high E2 levels decrease AQP9 mRNA abundance with no influence on AQP3 in mSCs. Interestingly, high E2 levels decreased mSCs' permeability to glycerol, while downregulating AQP9 expression, thus suggesting a novel mechanism by which E2 modulates fluid secretion in the testis. In conclusion, E2 is an important regulator of mSCs physiology and secretion through changes in AQP9 expression and function. Thus, alterations in glycerol permeability induced by E2 may be the cause for male infertility in cases associated with the presence of high E2 levels.