Glycolysis and mitochondrial respiration in mouse LDHC-null sperm

Synergistic protective effects of 3,4-dihydroxyphenylglycol and hydroxytyrosol in male rats against induced heat stress-induced reproduction damage

Testicular heat stress disrupts spermiogenesis and damages testicular tissue. The study aims to assess 3,4-dihydroxyphenylglycol (DHPG) and hydroxytyrosol (HT) from olive oil as antioxidants to reduce heat-induced testicular damage. Seven groups of 35 male rats were used. Group I got normal saline. Group 2 had HS (43 °C for 20 min/day) and normal saline for 60 days. Groups 3-7 had HS and DHPG/HT doses (0.5 mg/kg DHPG, 1 mg/kg DHPG, 5 mg/kg HT, 0.5 mg/kg DHPG + 5 mg/kg HT, and 1 mg/kg DHPG + 5 mg/kg HT). The evaluation included tests on testicular tissue, sperm quality, oxidative status, gene activity, and fertility after 60 days. After DHPG and HT treatment, sperm motility, viability, and plasma membrane functionality, as well as levels of total antioxidant capacity (TAC), glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase (CAT), and Bcl-2 gene expression, and in vivo fertility indexes increased. Meanwhile, abnormal morphology and DNA damage decreased, along with levels of glutathione (GSH), nitric oxide (NO), and malondialdehyde (MDA), and Bax, caspase-3, and caspase-9 gene expression, compared to the HS group. The study found that DHPG and HT have a more substantial synergistic effect when used together, improving reproductive health.

Adenylate kinase phosphate energy shuttle underlies energetic communication in flagellar axonemes

The complexities of energy transfer mechanisms in the flagella of mammalian sperm flagella have been intensively investigated and demonstrate significant diversity across species. Enzymatic shuttles, particularly adenylate kinase (AK) and creatine kinase (CK), are pivotal in the efficient transfer of intracellular ATP, showing distinct tissue- and species-specificity. Here, the expression profiles of AK and CK were investigated in mice and found to fall into four subgroups, of which Subgroup III AKs were observed to be unique to the male reproductive system and conserved across chordates. Both AK8 and AK9 were found to be indispensable to male reproduction after analysis of an infertile male cohort. Knockout mouse models showed that AK8 and AK9 were central to promoting sperm motility. Immunoprecipitation combined with mass spectrometry revealed that AK8 and AK9 interact with the radial spoke (RS) of the axoneme. Examination of various human and mouse sperm samples with substructural damage, including the presence of multiple RS subunits, showed that the head of radial spoke 3 acts as an adapter for AK9 in the flagellar axoneme. Using an ATP probe together with metabolomic analysis, it was found that AK8 and AK9 cooperatively regulated ATP transfer in the axoneme, and were concentrated at sites associated with energy consumption in the flagellum. These findings indicate a novel function for RS beyond its structural role, namely, the regulation of ATP transfer. In conclusion, the results expand the functional spectrum of AK proteins and suggest a fresh model regarding ATP transfer within mammalian flagella.

Ameliorative effects of omega-3 and omega-6 on spermatogenesis, testicular antioxidant status and in vivo fertility index in heat-stressed rats

The current study aimed to investigate the use of omega-6 (ω6) or omega-3 (ω3) in reducing heat-induced damage to the testicles. This is due to the known detrimental effects of heat and the potential protective properties of ω6 and ω3. In the study, 48 male rats were divided into eight groups, each containing 6 rats. Group I (control) received normal saline. Group 2 was exposed to high temperatures (43 °C for 20 min/day) and also received normal saline for 60 days. Groups 3-7 underwent identical HS conditions and received varying doses of ω6 or ω3 (0.5 mg/kg DHPG, 1 mg/kg DHPG, 5 mg/kg HT, 0.5 mg/kg DHPG + 5 mg/kg HT, and 1 mg/kg DHPG + 5 mg/kg HT), respectively. After 60 days, various tests were conducted on the testicular tissue, sperm quality, oxidative status, gene activity, and in vivo fertility indexes to evaluate the effects of the treatments. Treatment with ω6 and ω3 could reduce abnormal morphology and DNA damage while increasing total and progressive motility, characteristics motility, viability, and plasma membrane functional impairment compared with HS-exposed groups. Antioxidant status levels in testicular tissue were improved after administration of ω6 and ω3. Furthermore, after receiving ω6 and ω3, there were significantly lower expression levels of P53 and Caspase-3 and significantly higher expression levels of Bcl-2 compared to the HS-exposed group. Furthermore, the results showed that administration of ω6 and ω3 to rats exposed to HS could increase their in vivo fertility indexes compared to the group not exposed to HS. According to our data, all doses of ω6 and ω3 (particularly doses of ω6-1.25 and ω3-300) can improve the testicular damage, testicular antioxidant defense mechanism, regulate germ cell apoptosis, and increase in vivo fertility indexes.

IRF4 Knockdown Inhibits the Chronic Rhinosinusitis Without Nasal Polyps Development by Regulating NLRP3/Caspase-1/GSDMD-Mediated Pyroptosis

Chronic rhinosinusitis without nasal polyps (CRSsNP) is a CRS phenotype. However, the mechanisms of CRSsNP remains unclear. Differentially expressed genes (DEGs) were obtained from the GSE36830 and GSE198950 datasets through the GEO2R tool. The six hub genes were screened by the protein-protein interaction (PPI) network analysis and Cytoscape software. Then we constructed the mouse models of CRS and verified the expression levels of hub genes by reverse transcription quantitative PCR (RT-qPCR). Hematoxylin-eosin (HE) staining was employed to observe pathological alterations in mouse tissues. Casepase-3 expression was detected by immunohistochemistry (IHC). The levels of TNF-α, IL-12, IL-6, IL-1β, LDH, and IL-18 were evaluated using enzyme-linked immunosorbent assay (ELISA). Pyroptosis-related protein expressions were measured by western blotting. Cell counting kit-8 (CCK-8) and flow cytometry were performed to assess the proliferation and apoptosis of lipopolysaccharide (LPS)-induced NP69 cells. Six hub DEGs were identified. The expression levels of IRF4, IKZF1, and CD79A were obviously increased in CRSsNP, while those of ADH6, ADH1A, and LDHC were significantly decreased. IRF4 knockdown attenuated the pathologic features of CRSsNP. IRF4 knockdown reduced levels of the TNF-α, IL-12, IL-6 IL-1β, LDH, and IL-18 as well as the proteins expression of Casepase-1, GSDMD, and NLRP3 both in vivo and in vitro, implying that inflammation and pyroptosis were inhibited. IRF4 knockdown hinders the development of CRSsNP by inhibiting the inflammatory response and NLRP3/Caspase-1/GSDMD-mediated pyroptosis, which offers novel promising treatment strategies for clinical intervention.

Cancer testis antigens: Emerging therapeutic targets leveraging genomic instability in cancer

Cancer care has witnessed remarkable progress in recent decades, with a wide array of targeted therapies and immune-based interventions being added to the traditional treatment options such as surgery, chemotherapy, and radiotherapy. However, despite these advancements, the challenge of achieving high tumor specificity while minimizing adverse side effects continues to dictate the benefit-risk balance of cancer therapy, guiding clinical decision making. As such, the targeting of cancer testis antigens (CTAs) offers exciting new opportunities for therapeutic intervention of cancer since they display highly tumor specific expression patterns, natural immunogenicity and play pivotal roles in various biological processes that are critical for tumor cellular fitness. In this review, we delve deeper into how CTAs contribute to the regulation and maintenance of genomic integrity in cancer, and how these mechanisms can be exploited to specifically target and eradicate tumor cells. We review the current clinical trials targeting aforementioned CTAs, highlight promising pre-clinical data and discuss current challenges and future perspectives for future development of CTA-based strategies that exploit tumor genomic instability.

Testicular ACE regulates sperm metabolism and fertilization through the transcription factor PPARγ

Testis angiotensin-converting enzyme (tACE) plays a critical role in male fertility, but the mechanism is unknown. By using ACE C-domain KO (CKO) mice which lack tACE activity, we found that ATP in CKO sperm was 9.4-fold lower than WT sperm. Similarly, an ACE inhibitor (ACEi) reduced ATP production in mouse sperm by 72%. Metabolic profiling showed that tACE inactivation severely affects oxidative metabolism with decreases in several Krebs cycle intermediates including citric acid, cis-aconitic acid, NAD, α-ketoglutaric acid, succinate, and L-malic acid. We found that sperms lacking tACE activity displayed lower levels of oxidative enzymes (CISY, ODO1, MDHM, QCR2, SDHA, FUMH, CPT2, and ATPA) leading to a decreased mitochondrial respiration rate. The reduced energy production in CKO sperms leads to defects in their physiological functions including motility, acrosine activity, and fertilization in vitro and in vivo. Male mice treated with ACEi show severe impairment in reproductive capacity when mated with female mice. In contrast, an angiotensin II receptor blocker (ARB) had no effect. CKO sperms express significantly less peroxisome proliferators-activated receptor gamma (PPARγ) transcription factor, and its blockade eliminates the functional differences between CKO and WT sperms, indicating PPARγ might mediate the effects of tACE on sperm metabolism. Finally, in a cohort of human volunteers, in vitro treatment with the ramipril or a PPARγ inhibitor reduced ATP production in human sperm and hence its motility and acrosine activity. These findings may have clinical significance since millions of people take ACEi daily, including men who are reproductively active.

Deficiency in AK9 causes asthenozoospermia and male infertility by destabilising sperm nucleotide homeostasis

BACKGROUND

Asthenozoospermia is the primary cause of male infertility; however, its genetic aetiology remains poorly understood. Adenylate kinase 9 (AK9) is highly expressed in the testes of humans and mice and encodes a type of adenosine kinase that is functionally involved in cellular nucleotide homeostasis and energy metabolism. We aimed to assess whether AK9 is involved in asthenozoospermia.

METHODS

One-hundred-and-sixty-five Chinese men with idiopathic asthenozoospermia were recruited. Whole-exome sequencing (WES) and Sanger sequencing were performed for genetic analyses. Papanicolaou staining, Haematoxylin and eosin staining, scanning electron microscopy, and transmission electron microscopy were used to observe the sperm morphology and structure. Ak9-knockout mice were generated using CRISPR-Cas9. Sperm adenosine was detected by liquid chromatography-mass spectrometry. Targeted sperm metabolomics was performed. Intracytoplasmic sperm injection (ICSI) was used to treat patients.

FINDINGS

We identified five patients harbouring bi-allelic AK9 mutations. Spermatozoa from men harbouring bi-allelic AK9 mutations have a decreased ability to sustain nucleotide homeostasis. Moreover, bi-allelic AK9 mutations inhibit glycolysis in sperm. Ak9-knockout male mice also presented similar phenotypes of asthenozoospermia. Interestingly, ICSI was effective in bi-allelic AK9 mutant patients in achieving good pregnancy outcomes.

INTERPRETATION

Defects in AK9 induce asthenozoospermia with defects in nucleotide homeostasis and energy metabolism. This sterile phenotype could be rescued by ICSI.

FUNDING

The National Natural Science Foundation of China (82071697), Medical Innovation Project of Fujian Province (2020-CXB-051), open project of the NHC Key Laboratory of Male Reproduction and Genetics in Guangzhou (KF202004), Medical Research Foundation of Guangdong Province (A2021269), Guangdong Provincial Reproductive Science Institute Innovation Team grants (C-03), and Outstanding Young Talents Program of Capital Medical University (B2205).

Methylprednisolone improves the quality of liquid preserved boar spermatozoa in vitro and reduces polymorphonuclear neutrophil chemotaxis and phagocytosis

After artificial insemination, immune cells such as polymorphonuclear neutrophils will be recruited into the genital tract and induce endometrial inflammation, adversely affecting the spermatozoa. This study aimed to analyze the effect of methylprednisolone (MPS) on boar spermatozoa quality of in vitro liquid preservation and chemotaxis and phagocytosis of polymorphonuclear neutrophils toward boar spermatozoa. Various concentrations of MPS were added to the extender and analyzed for their effects on spermatozoa motility, kinetic parameters, abnormality rate, total antioxidant capacity (T-AOC) levels, H₂O₂ content, mitochondrial membrane potential and acrosome integrity. Testing of MPS on chemotaxis and phagocytosis of polymorphonuclear neutrophils toward spermatozoa induced by lipopolysaccharide (LPS). The results showed that an extender containing 2 × 10^-7 mol/mL MPS was the most effective for preserving boar spermatozoa during in vitro liquid preservation at 17°C. It effectively improved spermatozoa motility, kinetic parameters, T-AOC levels, mitochondrial membrane potential and acrosome integrity, reducing the abnormality rate and H₂O₂ content. Meanwhile, the chemotaxis and phagocytosis of polymorphonuclear neutrophils toward spermatozoa under LPS induction were inhibited in a concentration-dependent manner. In conclusion, MPS has positive implications for improving in vitro liquid preserved boar spermatozoa quality, inhibiting chemotaxis and phagocytosis of polymorphonuclear neutrophils toward spermatozoa.

Glucose Starvation Inhibits Ferroptosis by Activating the LKB1/AMPK Signaling Pathway and Promotes the High Speed Linear Motility of Dairy Goat Sperm

In mammals, sperm acquire fertilization ability after capacitation in vitro or when in the female reproductive tract. The motility patterns of sperm undergo continuous changes from the moment of ejaculation until fertilization in the female reproductive tract. In vitro, hyperactivated motility can be induced through high glucose mediums, while in vivo, it is induced by oviduct fluids. Conversely, sperm maintain linear motility in seminal plasma or uterine fluids that contain low glucose levels. In dairy goat sperm, energy metabolism associated with capacitation depends on the energy sources in vitro, seminal plasma, or the female reproductive tract, especially the glucose levels. However, there is little experimental knowledge that glucose levels affect sperm energy metabolism in dairy goats. To clarify these hypotheses, we incubated dairy goat spermatozoa with different concentrations of rotenone-glucose (ROT), carbonyl cyanide 4-(trifluoromethoxy) phenylhydrazone (FCCP), and tigecycline (TIG) in vitro. Sperm motility attributes, ATP content, pyruvate and lactate levels, mitochondrial permeability transition pore fluorescence intensity, mitochondrial membrane potential (MMP), and protein synthesis were analyzed. Sperm motility patterns changed from circular to linear under low glucose conditions compared with those in high glucose conditions and showed a significant improvement in progressive motility and straight line speed, whereas lactate and pyruvate levels and MMP decreased remarkably. Incubation of spermatozoa with ROT, FCCP, and TIG inhibited sperm mitochondrial activity, protein synthesis, oxidative phosphorylation, and ATP levels, thereby reducing sperm motility, including the progressive motility, straight line speed, and total motility. Simultaneously, incubation of spermatozoa with Compound C under low glucose conditions significantly decreased the ATP levels and MMP, as well as liver kinase B1 and AMPK protein expression. Under low glucose conditions, sperm mainly produce ATP through mitochondrial OXPHOS to achieve high speed linear movement, inhibit ferroptosis through the LKB1/AMPK signaling pathway, and further maintain energy metabolism homeostasis.

Deciphering sperm functions using biological networks

The global human population is exponentially increasing, which requires the production of quality food through efficient reproduction as well as sustainable production of livestock. Lack of knowledge and technology for assessing semen quality and predicting bull fertility is hindering advances in animal science and food animal production and causing millions of dollars of economic losses annually. The intent of this systemic review is to summarize methods from computational biology for analysis of gene, metabolite, and protein networks to identify potential markers that can be applied to improve livestock reproduction, with a focus on bull fertility. We provide examples of available gene, metabolic, and protein networks and computational biology methods to show how the interactions between genes, proteins, and metabolites together drive the complex process of spermatogenesis and regulate fertility in animals. We demonstrate the use of the National Center for Biotechnology Information (NCBI) and Ensembl for finding gene sequences, and then use them to create and understand gene, protein and metabolite networks for sperm associated factors to elucidate global cellular processes in sperm. This study highlights the value of mapping complex biological pathways among livestock and potential for conducting studies on promoting livestock improvement for global food security.

Metabolomic analysis reveals spermatozoa and seminal plasma differences between Duroc and Liang guang Small-spotted pig

The Liang guang Small-spotted pig is a well-known Chinese indigenous pig that is valued for its exceptional meat quality. However, the Liang guang Small-spotted pig has a lower semen storage capacity, shorter storage time and worse semen quality compared to Duroc. Pig sperm used for artificial insemination (AI) loses part of vitality and quality when being stored in commercial solutions. Serious vitality losses and short shelf life of the semen are particularly prominent in Liang guang Small-spotted pig. In this study, the metabolites in seminal plasma and spermatozoa of Duroc and Liang guang Small-spotted pigs were identified using UHPLC-Q-TOF/MS technology. The findings indicated forty distinct metabolites concentrating on energy metabolic substrates and antioxidant capacity in Liang guang Small-spotted pig and Duroc seminal plasma, including D-Fructose, succinate, 2-dehydro-3-deoxy-d-gluconate, alanine betaine, citrate, carnitine, acetylcarnitine and so on. Seventeen different metabolites were explored, with a focus on glycerophospholipid metabolism in Liang guang Small-spotted pig and Duroc spermatozoa, primarily including glycerol 3-phosphate, acetylcarnitine, phosphatidylcholine (PC) 16:0/16:0, palmitoyl sphingomyelin, acetylcholine, choline, glycerophosphocholine, betaine, L-carnitine, creatinine and others. This study reveals the metabolite profile of spermatozoa and seminal plasma among different pig breeds and might be valuable for understanding the mechanisms that lead to sperm storage capacity. Metabolites involved in energy metabolism, antioxidant capacity and glycerophospholipid metabolism might be key to the poor sperm storage capacity in Liang guang Small-spotted pig.

Bioenergetic changes in response to sperm capacitation and two-way metabolic compensation in a new murine model

The acquisition of fertilizing ability by mammalian spermatozoa, known as "capacitation," includes processes that depend on particular metabolic pathways. This has led to the hypothesis that ATP demands might differ between capacitated and non-capacitated cells. Mouse sperm can produce ATP via OXPHOS and aerobic glycolysis, an advantageous characteristic considering that these cells have to function in the complex and variable environment of the female reproductive tract. Nonetheless, despite evidence showing that both metabolic pathways play a role in events associated with mouse sperm capacitation, there is contradictory evidence regarding changes promoted by capacitation in this species. In addition, the vast majority of studies regarding murine sperm metabolism use Mus musculus laboratory strains as model, thus neglecting the wide diversity of sperm traits of other species of Mus. Focus on closely related species with distinct evolutionary histories, which may be the result of different selective pressures, could shed light on diversity of metabolic processes. Here, we analyzed variations in sperm bioenergetics associated with capacitation in spermatozoa of the steppe mouse, Mus spicilegus, a species with high sperm performance. Furthermore, we compared sperm metabolic traits of this species with similar traits previously characterized in M. musculus. We found that the metabolism of M. spicilegus sperm responded to capacitation in a manner similar to that of M. musculus sperm. However, M. spicilegus sperm showed distinct metabolic features, including the ability to perform cross-pathway metabolic compensation in response to either respiratory or glycolytic inhibition, thus revealing a delicate fine-tuning of its metabolic capacities.

Ldha-Dependent Metabolic Programs in Sertoli Cells Regulate Spermiogenesis in Mouse Testis

Sertoli cells play indispensable roles in spermatogenesis by providing the advanced germ cells with structural, nutritional, and regulatory support. Lactate is regarded as an essential Sertoli-cell-derived energy metabolite that nurses various types of spermatogenic cells; however, this assumption has not been tested using genetic approaches. Here, we have reported that the depletion of lactate production in Sertoli cells by conditionally deleting lactate dehydrogenase A (Ldha) greatly affected spermatogenesis. Ldha deletion in Sertoli cells significantly reduced the lactate production and resulted in severe defects in spermatogenesis. Spermatogonia and spermatocytes did not show even mild impairments, but the spermiogenesis of Ldha conditional knockout males was severely disrupted. Further analysis revealed that 2456 metabolites were altered in the sperm of the knockout animals, and specifically, lipid metabolism was dysregulated, including choline, oleic acid, and myristic acid. Surprisingly, choline supplementation completely rescued the spermiogenesis disorder that was caused by the loss of Ldha activities. Collectively, these data have demonstrated that the interruption of Sertoli-cell-derived lactate impacted sperm development through a choline-mediated mechanism. The outcomes of these findings have revealed a novel function of lactate in spermatogenesis and have therapeutic applications in treating human infertility.

Impaired fertility in 4930590J08Rik mutant male mice is associated with defective sperm energy metabolism

Testis-specifically expressed genes are important for male reproduction according to their unique expression patterns. However, the functions of most of these genes in reproduction are unclear. Here, we showed that mouse 4930590J08Rik was a testis-specifically expressed gene. 4930590J08Rik knockout mice exhibited a delay in the first wave of spermatogenesis and a reduction of cauda epididymal sperm. Furthermore, knockout spermatozoa exhibited defective acrosome reactions and decreased progressive motility, which led to impaired in vivo fertilization. Transcriptome analysis of testes revealed that most of the differentially expressed genes in knockout testes were associated with metabolic processes. 4930590J08Rik knockout sperm exhibited oxidative phosphorylation deficiency and were highly dependent on increased anaerobic glycolysis to compensate for ATP demands. Taken together, the 4930590J08Rik-disrupted mouse partially mimics the phenotypes of human asthenospermia and oligozoospermia, which provides a new model for further understanding the pathogenesis of idiopathic male infertility.

Cancer-testis antigen lactate dehydrogenase C4 as a novel biomarker of male infertility and cancer

A unique lactate dehydrogenase (LDH) isoenzyme designated as lactate dehydrogenase C4 (LDH-C4) is found in mammalian mature testis and spermatozoa. Thus far, LDH-C4 has been well studied with regard to its gene and amino acid sequences, structure, biological properties, and peptide synthesis. Accumulating evidence has shown that LDH-C4 is closely related to spermatic energy metabolism and plays a critical role in sperm motility, capacitation, and fertilization. Defects in the catalytic activity of LDH-C4 are key to pathophysiological abnormalities underlying infertility. LDH-C4 was originally thought to be present only in mature testis and spermatozoa; however, recent studies have implicated LDH-C4 as a cancer-testis antigen (CTA), owing to its aberrant transcription in a broad spectrum of human neoplasms. This review highlights the recent findings on LDH-C4 with particular emphasis on its role in male infertility and tumors.

The effect of cryopreservation media on the quality of β-thalassemia mouse spermatozoa

Background

The mouse model of human diseases is commonly used for biomedical study, including β-thalassemia (β-thal), an inherited hemoglobin disorder. Maintaining the mice strain by natural mating systems is costly and seems impractical, especially during the COVID-19 pandemic. Sperm-freezing is a cost-effective solution for β-thal mouse colony management.

Aim

To determine appropriate cryopreservation media for β-thal mouse spermatozoa to establish a β-thal mouse sperm bank.

Methods

The epididymal spermatozoa of C57BL/6 wild-type (WT) and β-globin gene knockout thalassemia (BKO) mice were frozen in four freezing media: I) raffinose-skim milk-monothioglycerol (MTG), II) raffinose-skim milk-glutamine, III) raffinose-egg yolk-glycerol, and IV) egg yolk-TES-Tris. The sperm quality was assessed prior to and following freeze-thawing.

Results

Compared with WT counterparts, the viable spermatozoa before freezing exhibiting elevated levels of oxidative stress were significantly greater in BKO (p = 0.01). After thawing, the membrane integrity of BKO spermatozoa preserved in I was significantly lower (p = 0.001). The sperm viability and membrane integrity of BKO males were also inferior when media III and IV were used (p = 0.008-0.027). The amount of oxidative stress in the spermatozoon of BKO mice was significantly greater when preserved in I, III, and IV (p = 0.002-0.044). Comparing freezing media, the motility and acrosome integrity of WT and BKO spermatozoa preserved in IV were significantly higher than those in other media (p < 0.001 to p = 0.01). Spermatozoa with the highest mitochondrial membrane potential were observed in I in both genotypes (p = 0.012 to p > 0.05). The viability, membrane integrity, and oxidative stress of post-thaw BKO spermatozoa did not significantly differ among freezing solutions.

Conclusion

Irrespective of freezing media, spermatozoa of BKO males are rather more sensitive to cryopreservation than those of WT. Raffinose-skim milk-MTG/glutamine, raffinose-egg yolk-glycerol, and egg yolk-TES-Tris can all be used to preserve BKO mouse spermatozoa. However, with slightly better sperm characteristics, egg yolk-TES-Tris may be a diluent of choice for BKO mouse sperm cryopreservation. The addition of a reducing agent to thawing media is also strongly recommended to efficiently prevent oxidative stress and therefore improve frozen-thawed sperm survival.

Capacitation promotes a shift in energy metabolism in murine sperm

In mammals, sperm acquire fertilization ability after a series of physiological and biochemical changes, collectively known as capacitation, that occur inside the female reproductive tract. In addition to other requirements, sperm bioenergetic metabolism has been identified as a fundamental component in the acquisition of capacitation. Mammalian sperm produce ATP through two main metabolic processes, oxidative phosphorylation (OXPHOS) and aerobic glycolysis that are localized to two different flagellar compartments, the midpiece, and the principal piece, respectively. In mouse sperm, the occurrence of many events associated with capacitation relies on the activity of these two energy-producing pathways, leading to the hypothesis that some of these events may impose changes in sperm energetic demands. In the present study, we used extracellular flux analysis to evaluate changes in glycolytic and respiratory parameters of murine sperm that occur as a consequence of capacitation. Furthermore, we examined whether these variations affect sperm ATP sustainability. Our results show that capacitation promotes a shift in the usage ratio of the two main metabolic pathways, from oxidative to glycolytic. However, this metabolic rewiring does not seem to affect the rate at which the sperm consume ATP. We conclude that the probable function of the metabolic switch is to increase the ATP supply in the distal flagellar regions, thus sustaining the energetic demands that arise from capacitation.

Responses of sperm mitochondria functionality in animals to thermal stress: The mitigating effects of dietary natural antioxidants

The reproductive consequences of global warming representing heat stress (HS) have been widely received more attention in the last decades. HS induced significant influence on the male reproductive cell, especially sperm functionally. Reduction in the sperm function induced by HS leads to failure of fertility potential. The main effects of HS on sperm are reducing sperm motility, increased abnormalities and changes in the fluidity of the membrane as well as cell morphology. Moreover, the destruction of mitochondrial function could be the result of adverse influences of HS. The protein contents and enzymes of mitochondria were lowered after the exposure of sperm to HS. Some natural antioxidants were used for improving sperm mitochondrial function under HS conditions. In this review, it was highlighted the potential influences of HS on sperm function through reduction in ATP Synthesis yield, mitochondrial activity, mitochondrial protein contents and mitochondrial enzymes, which involves the interference of mitochondrial remodelling in sperm of animals.

The sodium-glucose cotransporter isoform 1 (SGLT-1) is important for sperm energetics, motility, and fertility†

Glucose is a key substrate for supporting sperm energy production and function. Previous studies have demonstrated that sperm glucose uptake is facilitated by several isoforms of the glucose transporters (GLUT). Here, we report that sperm also expresses the Na+-dependent sodium glucose cotransporter (SGLT). This was first suggested by our observation that genetic deletion of the testis-specific Na,K-ATPase α4, which impairs the sperm plasma membrane Na+ gradient, reduces glucose uptake and ATP production. Immunoblot analysis revealed the presence of an SGLT in sperm, with specific expression of isoform 1 (SGLT-1), but not of isoform 2 (SGLT-2). Immunocytochemistry identified SGLT-1 in the mid- and principal piece of the sperm flagellum. Inhibition of SGLT-1 with the isotype-selective inhibitor phlorizin significantly reduced glucose uptake, glycolytic activity, and ATP production in noncapacitated and capacitated sperm from wild-type mice. Phlorizin also decreased total sperm motility, as well as other parameters of sperm movement. In contrast, inhibition of SGLT-1 had no significant effect on sperm hyperactivation, protein tyrosine phosphorylation, or acrosomal reaction. Importantly, phlorizin treatment impaired the fertilizing capacity of sperm. Altogether, these results demonstrate that mouse sperm express a functional SGLT transport system that is important for supporting sperm energy production, motility, and fertility.

Energy Metabolism and Hyperactivation of Spermatozoa from Three Mouse Species under Capacitating Conditions

Mammalian sperm differ widely in sperm morphology, and several explanations have been presented to account for this diversity. Less is known about variation in sperm physiology and cellular processes that can give sperm cells an advantage when competing to fertilize oocytes. Capacitation of spermatozoa, a process essential for mammalian fertilization, correlates with changes in motility that result in a characteristic swimming pattern known as hyperactivation. Previous studies revealed that sperm motility and velocity depend on the amount of ATP available and, therefore, changes in sperm movement occurring during capacitation and hyperactivation may involve changes in sperm bioenergetics. Here, we examine differences in ATP levels of sperm from three mouse species (genus Mus), differing in sperm competition levels, incubated under non-capacitating and capacitating conditions, to analyse relationships between energetics, capacitation, and swimming patterns. We found that, in general terms, the amount of sperm ATP decreased more rapidly under capacitating conditions. This descent was related to the development of a hyperactivated pattern of movement in two species (M. musculus and M. spicilegus) but not in the other (M. spretus), suggesting that, in the latter, temporal dynamics and energetic demands of capacitation and hyperactivation may be decoupled or that the hyperactivation pattern differs. The decrease in ATP levels during capacitation was steeper in species with higher levels of sperm competition than in those with lower levels. Our results suggest that, during capacitation, sperm consume more ATP than under non-capacitating conditions. This higher ATP consumption may be linked to higher velocity and lateral head displacement, which are associated with hyperactivated motility.

Lactate Dehydrogenase A or B Knockdown Reduces Lactate Production and Inhibits Breast Cancer Cell Motility in vitro

Background: Lactate dehydrogenase (LDH) plays an important role in cancer pathogenesis and enhanced expression/activity of this enzyme has been correlated with poor prognosis. In this study we determined the expression profile of LDH-A and B in normal as well as in endocrine-resistant and -responsive breast cancer cells and the effect of their knockdown on LDH activity, lactate production, proliferation and cell motility.

Methods: Knockdown experiments were performed using siRNA and shRNA. The expression profile of LDH and signaling molecules was determined using PCR and western blotting. Intracellular LDH activity and extracellular lactate levels were measured by a biochemical assay. Cell motility was determined using wound healing, while proliferation was determined using MTT assay.

Results: LDH-A was expressed in all of the tested cell lines, while LDH-B was specifically expressed only in normal and endocrine-resistant breast cancer cells. This was correlated with significantly enhanced LDH activity and lactate production in endocrine resistant breast cancer cells when compared to normal or endocrine responsive cancer cells. LDH-A or -B knockdown significantly reduced LDH activity and lactate production, which led to reduced cell motility. Exogenous lactate supplementation enhanced cell motility co-incident with enhanced phosphorylation of ERK1/2 and reduced E-cadherin expression. Also, LDH-A or -B knockdown reduced ERK 1/2 phosphorylation.

Conclusion: Enhanced cell motility in endocrine resistant breast cancer cells is at least in part mediated by enhanced extracellular lactate levels, and LDH inhibition might be a promising therapeutic target to inhibit cancer cell motility.

In-cell structures of conserved supramolecular protein arrays at the mitochondria-cytoskeleton interface in mammalian sperm

Spatial organization of mitochondria is vital for cellular function. In many specialized cell types, mitochondria are immobilized at specific subcellular loci through interactions with the cytoskeleton. One of the most striking mitochondrial configurations occurs in mammalian sperm, where mitochondria wrap around the flagellum. Malformation of the mitochondrial sheath causes infertility, but the molecular structures underlying this intricate arrangement are unknown. Here, we analyzed the mitochondrial sheath in sperm from three mammalian species. We find that although mitochondrial dimensions and cristae architecture vary across species, molecular assemblies mediating intermitochondria and mitochondria–cytoskeleton interactions are conserved. These findings yield important insight into sperm physiology and evolution and are relevant for other polarized cell types, such as muscles, neurons, photoreceptors, and hair cells.

Mitochondria–cytoskeleton interactions modulate cellular physiology by regulating mitochondrial transport, positioning, and immobilization. However, there is very little structural information defining mitochondria–cytoskeleton interfaces in any cell type. Here, we use cryofocused ion beam milling-enabled cryoelectron tomography to image mammalian sperm, where mitochondria wrap around the flagellar cytoskeleton. We find that mitochondria are tethered to their neighbors through intermitochondrial linkers and are anchored to the cytoskeleton through ordered arrays on the outer mitochondrial membrane. We use subtomogram averaging to resolve in-cell structures of these arrays from three mammalian species, revealing they are conserved across species despite variations in mitochondrial dimensions and cristae organization. We find that the arrays consist of boat-shaped particles anchored on a network of membrane pores whose arrangement and dimensions are consistent with voltage-dependent anion channels. Proteomics and in-cell cross-linking mass spectrometry suggest that the conserved arrays are composed of glycerol kinase-like proteins. Ordered supramolecular assemblies may serve to stabilize similar contact sites in other cell types in which mitochondria need to be immobilized in specific subcellular environments, such as in muscles and neurons.

A drastic shift in the energetic landscape of toothed whale sperm cells

Mammalian spermatozoa are a notable example of metabolic compartmentalization.¹ Energy in the form of ATP production, vital for motility, capacitation, and fertilization, is subcellularly separated in sperm cells. While glycolysis provides a local, rapid, and low-yielding input of ATP along the flagellum fibrous sheath, oxidative phosphorylation (OXPHOS), far more efficient over a longer time frame, is concentrated in the midpiece mitochondria.² The relative weight of glycolysis and OXPHOS pathways in sperm function is variable among species and sensitive to oxygen and substrate availability.^3-5 Besides partitioning energy production, sperm cell energetics display an additional singularity: the occurrence of sperm-specific gene duplicates and alternative spliced variants, with conserved function but structurally bound to the flagellar fibrous sheath.^6,7 The wider selective forces driving the compartmentalization and adaptability of this energy system in mammalian species remain largely unknown, much like the impact of ecosystem resource availability (e.g., carbohydrates, fatty acids, and proteins) and dietary adaptations in reproductive physiology traits.⁸ Here, we investigated the Cetacea, an iconic group of fully aquatic and carnivorous marine mammals, evolutionarily related to extant terrestrial herbivores.⁹ In this lineage, episodes of profound trait remodeling have been accompanied by clear genomic signatures.^10-14 We show that toothed whales exhibit impaired sperm glycolysis, due to gene and exon erosion, and demonstrate that dolphin spermatozoa motility depends on endogenous fatty acid β-oxidation, but not carbohydrates. Such unique energetic rewiring substantiates the observation of large mitochondria in toothed whale spermatozoa and emphasizes the radical physiological reorganization imposed by the transition to a carbohydrate-depleted marine environment.

Sperm Functional Genome Associated With Bull Fertility

Bull fertility is an important economic trait in sustainable cattle production, as infertile or subfertile bulls give rise to large economic losses. Current methods to assess bull fertility are tedious and not totally accurate. The massive collection of functional data analyses, including genomics, proteomics, metabolomics, transcriptomics, and epigenomics, helps researchers generate extensive knowledge to better understand the unraveling physiological mechanisms underlying subpar male fertility. This review focuses on the sperm phenomes of the functional genome and epigenome that are associated with bull fertility. Findings from multiple sources were integrated to generate new knowledge that is transferable to applied andrology. Diverse methods encompassing analyses of molecular and cellular dynamics in the fertility-associated molecules and conventional sperm parameters can be considered an effective approach to determine bull fertility for efficient and sustainable cattle production. In addition to gene expression information, we also provide methodological information, which is important for the rigor and reliability of the studies. Fertility is a complex trait influenced by several factors and has low heritability, although heritability of scrotal circumference is high and that it is a known fertility maker. There is a need for new knowledge on the expression levels and functions of sperm RNA, proteins, and metabolites. The new knowledge can shed light on additional fertility markers that can be used in combination with scrotal circumference to predict the fertility of breeding bulls. This review provides a comprehensive review of sperm functional characteristics or phenotypes associated with bull fertility.

Effect of glucose concentration and cryopreservation on mitochondrial functions of bull spermatozoa and relationship with sire conception rate

Mitochondrial function is essential for sperm viability, not only from a sperm metabolism perspective, but also for improvement of sperm storage in liquid and frozen states. Bull sperm have notable metabolic variability with energy production for motility and subsequently for fertilizing capacity resulting from both glycolysis and oxidative phosphorylation. The objective of this study was to determine mitochondrial function of sperm using high-throughput Seahorse Analyzer technology in fresh semen and subsequent to freezing-thawing when there was incubation in media commonly used for sperm storage (relatively large glucose concentration) and female tract (relatively small glucose concentration). Additionally, there were determinations whether there were differences in values for fertility variables by regressing sire conception rate on values for mitochondrial variables when there was evaluation of semen from bulls with varying fertility. Media with larger concentrations of glucose inhibited mitochondrial function in fresh sperm, as indicated by less maximal oxygen consumption, spare respiratory capacity and coupling efficiency when compared to sperm in the media containing less glucose. Furthermore, there was greater (P <  0.05) mitochondrial function in cryopreserved-thawed compared to fresh samples with there being no effect of incubation media. These results indicate that mitochondrial damage from cryopreservation cannot be simply overcome post-thawing with glucose supplementation of bull semen incubation media. The increase in mitochondrial function is likely due to "non-productive" oxygen consumption to maintain the mitochondrial proton gradient. Furthermore, there was a negative association of mitochondrial proton leakage with sire conception rate indicating this could be a potential biomarker of bull fertility.

Impact of Cryopreservation on Spermatozoa Freeze-Thawed Traits and Relevance OMICS to Assess Sperm Cryo-Tolerance in Farm Animals

Sperm cryopreservation is a powerful tool for the livestock breeding program. Several technical attempts have been made to enhance the efficiency of spermatozoa cryopreservation in different farm animal species. However, it is well-recognized that mammalian spermatozoa are susceptible to cryo-injury caused by cryopreservation processes. Moreover, the factors leading to cryo-injuries are complicated, and the cryo-damage mechanism has not been methodically explained until now, which directly influences the quality of frozen–thawed spermatozoa. Currently, the various OMICS technologies in sperm cryo-biology have been conducted, particularly proteomics and transcriptomics studies. It has contributed while exploring the molecular alterations caused by cryopreservation, identification of various freezability markers and specific proteins that could be added to semen diluents before cryopreservation to improve sperm cryo-survival. Therefore, understanding the cryo-injury mechanism of spermatozoa is essential for the optimization of current cryopreservation processes. Recently, the application of newly-emerged proteomics and transcriptomics technologies to study the effects of cryopreservation on sperm is becoming a hotspot. This review detailed an updated overview of OMICS elements involved in sperm cryo-tolerance and freeze-thawed quality. While also detailed a mechanism of sperm cryo-injury and utilizing OMICS technology that assesses the sperm freezability potential biomarkers as well as the accurate classification between the excellent and poor freezer breeding candidate.

Spermatogonial Gene Networks Selectively Couple to Glutathione and Pentose Phosphate Metabolism but Not Cysteine Biosynthesis

In adult males, spermatogonia maintain lifelong spermatozoa production for oocyte fertilization. To understand spermatogonial metabolism we compared gene profiles in rat spermatogonia to publicly available mouse, monkey, and human spermatogonial gene profiles. Interestingly, rat spermatogonia expressed metabolic control factors Foxa1, Foxa2, and Foxa3. Germline Foxa2 was enriched in Gfra1Hi and Gfra1Low undifferentiated A-single spermatogonia. Foxa2-bound loci in spermatogonial chromatin were overrepresented by conserved stemness genes (Dusp6, Gfra1, Etv5, Rest, Nanos2, Foxp1) that intersect bioinformatically with conserved glutathione/pentose phosphate metabolism genes (Tkt, Gss, Gc l c , Gc l m, Gpx1, Gpx4, Fth), marking elevated spermatogonial GSH:GSSG. Cystine-uptake and intracellular conversion to cysteine typically couple glutathione biosynthesis to pentose phosphate metabolism. Rat spermatogonia, curiously, displayed poor germline stem cell viability in cystine-containing media, and, like primate spermatogonia, exhibited reduced transsulfuration pathway markers. Exogenous cysteine, cysteine-like mercaptans, somatic testis cells, and ferroptosis inhibitors counteracted the cysteine-starvation-induced spermatogonial death and stimulated spermatogonial growth factor activity in vitro.

Cancer/testis antigen LDHC promotes proliferation and metastasis by activating the PI3K/Akt/GSK-3β-signaling pathway and the in lung adenocarcinoma

The cancer/testis antigen lactate dehydrogenase-C4 (LDHC) is a specific isoenzyme of the LDH family that regulates invasion and metastasis in some malignancies; however, little is known regarding its role in progression of lung adenocarcinoma (LUAD). Thus, we investigated LDHC expression by immunohistochemistry, and analyzed its clinical significance in 88 LUAD specimens. The role and molecular mechanisms subserving LDHC in cellular proliferation, migration, and invasion were explored both in vitro and in vivo. As a result, we found that high LDHC expression was significantly correlated with clinicopathological features of aggressive LUAD and a poor prognosis. Overexpression of LDHC induced LUAD cells to produce lactate and ATP, increased their metastatic and invasive potential-, and accelerated xenograft tumor growth. We further demonstrated that overexpression of LDHC affected the expression of cell proliferation-related proteins (cyclin D1 and c-Myc) and epithelial-mesenchymal transition (EMT)-related proteins (MMP-2, MMP-9, E-cadherin, Vimentin, Twist, Slug, and Snail) both in vitro and in vivo. Finally, excessive activation of LDHC enhanced the phosphorylation levels of AKT and GSK-3β, revealing activation of the PI3K/Akt/GSK-3β oncogenic-signaling pathways. Treatment with a PI3K inhibitor reversed the effects of LDHC overexpression by inhibiting cellular proliferation, migration, and invasion, with diminished levels of p-Akt and p-GSK3β. PI3K inhibition also reversed cell proliferation-related and EMT-related proteins in LDHC-overexpressing A549 cells. In conclusion, LDHC promotes proliferation, migration, invasion, and EMT in LUAD cells via activation of the PI3K/Akt/GSK-3β pathway.

Red LED Light Acts on the Mitochondrial Electron Chain of Donkey Sperm and Its Effects Depend on the Time of Exposure to Light

This work aimed to investigate how stimulation of donkey sperm with red LED light affects mitochondrial function. For this purpose, freshly diluted donkey semen was stimulated with red light for 1, 5, and 10 min, in the presence or absence of oligomycin A (Omy A), a specific inhibitor of mitochondrial ATP synthase, or FCCP, a specific disruptor of mitochondrial electron chain. The results obtained in the present study indicated that the effects of red LED light on fresh donkey sperm function are related to changes in mitochondria function. In effect, irradiation of donkey sperm resulted in an increase in mitochondrial membrane potential (MMP), the activity of cytochrome C oxidase and the rate of oxygen consumption. In addition, in the absence of oligomycin A and FCCP, light-stimulation augmented the average path velocity (VAP) and modified the structure of motile sperm subpopulations, increasing the fastest and most linear subpopulation. In contrast, the presence of either Omy A or FCCP abolished the aforementioned effects. Interestingly, our results also showed that the effects of red light depend on the exposure time applied, as indicated by the observed differences between irradiation protocols. In conclusion, our results suggest that exposing fresh donkey sperm to red light modulates the function of their mitochondria through affecting the activity of the electron chain. However, the extent of this effect depends on the irradiation pattern and does not exclude the existence of other mechanisms, such as those related to thermotaxis.

Genome-Wide Epigenetic Signatures of Adaptive Developmental Plasticity in the Andes

High-altitude adaptation is a classic example of natural selection operating on the human genome. Physiological and genetic adaptations have been documented in populations with a history of living at high altitude. However, the role of epigenetic gene regulation, including DNA methylation, in high-altitude adaptation is not well understood. We performed an epigenome-wide DNA methylation association study based on whole blood from 113 Peruvian Quechua with differential lifetime exposures to high altitude (>2,500) and recruited based on a migrant study design. We identified two significant differentially methylated positions (DMPs) and 62 differentially methylated regions (DMRs) associated with high-altitude developmental and lifelong exposure statuses. DMPs and DMRs were found in genes associated with hypoxia-inducible factor pathway, red blood cell production, blood pressure, and others. DMPs and DMRs associated with fractional exhaled nitric oxide also were identified. We found a significant association between EPAS1 methylation and EPAS1 SNP genotypes, suggesting that local genetic variation influences patterns of methylation. Our findings demonstrate that DNA methylation is associated with early developmental and lifelong high-altitude exposures among Peruvian Quechua as well as altitude-adaptive phenotypes. Together these findings suggest that epigenetic mechanisms might be involved in adaptive developmental plasticity to high altitude. Moreover, we show that local genetic variation is associated with DNA methylation levels, suggesting that methylation associated SNPs could be a potential avenue for research on genetic adaptation to hypoxia in Andeans.

Analysis of metabolic flux in felid spermatozoa using metabolomics and 13C-based fluxomics†

Spermatozoa from three feline species-the domestic cat (Felis catus), the cheetah (Acinonyx jubatus), and the clouded leopard (Neofelis nebulosa)-were analyzed using metabolomic profiling and 13C-based fluxomics to address questions raised regarding their energy metabolism. Metabolic profiles and utilization of 13C-labeled energy substrates were detected and quantified using gas chromatography-mass spectrometry (GC-MS). Spermatozoa were collected by electroejaculation and incubated in media supplemented with 1.0 mM [U13C]-glucose, [U13C]-fructose, or [U13C]-pyruvate. Evaluation of intracellular metabolites following GC-MS analysis revealed the uptake and utilization of labeled glucose and fructose in sperm, as indicated by the presence of heavy ions in glycolytic products lactate and pyruvate. Despite evidence of substrate utilization, neither glucose nor fructose had an effect on the sperm motility index of ejaculated spermatozoa from any of the three felid species, and limited entry of pyruvate derived from these hexose substrates into mitochondria and the tricarboxylic acid cycle was detected. However, pathway utilization was species-specific for the limited number of individuals (four to seven males per species) assessed in these studies. An inhibitor of fatty acid beta-oxidation (FAO), etomoxir, altered metabolic profiles of all three felid species but decreased motility only in the cheetah. While fluxomic analysis provided direct evidence that glucose and fructose undergo catabolic metabolism, other endogenous substrates such as endogenous lipids may provide energy to fuel motility.

The protein phosphatase isoform PP1γ1 substitutes for PP1γ2 to support spermatogenesis but not normal sperm function and fertility†

Four isoforms of serine/threonine phosphatase type I, PP1α, PP1β, PP1γ1, and PP1γ2, are derived from three genes. The PP1γ1 and PP1γ2 isoforms are alternately spliced transcripts of the protein phosphatase 1 catalytic subunit gamma gene (Ppp1cc). While PP1γ1 is ubiquitous in somatic cells, PP1γ2 is expressed exclusively in testicular germ cells and sperm. Ppp1cc knockout male mice (-/-), lacking both PP1γ1 and PP1γ2, are sterile due to impaired sperm morphogenesis. Fertility and normal sperm function can be restored by transgenic expression of PP1γ2 alone in testis of Ppp1cc (-/-) mice. The purpose of this study was to determine whether the PP1γ1 isoform is functionally equivalent to PP1γ2 in supporting spermatogenesis and male fertility. Significant levels of transgenic PP1γ1 expression occurred only when the transgene lacked a 1-kb 3΄UTR region immediately following the stop codon of the PP1γ1 transcript. PP1γ1 was also incorporated into sperm at levels comparable to PP1γ2 in sperm from wild-type mice. Spermatogenesis was restored in mice expressing PP1γ1 in the absence of PP1γ2. However, males from the transgenic rescue lines were subfertile. Sperm from the PP1γ1 rescue mice were unable to fertilize eggs in vitro. Intrasperm localization of PP1γ1 and the association of the protein regulators of the phosphatase were altered in epididymal sperm in transgenic PP1γ1 compared to PP1γ2. Thus, the ubiquitous isoform PP1γ1, not normally expressed in differentiating germ cells, could replace PP1γ2 to support spermatogenesis and spermiation. However, PP1γ2, which is the PP1 isoform in mammalian sperm, has an isoform-specific role in supporting normal sperm function and fertility.

Impact of quercetin supplementation on testicular functions in summer heat-stressed rabbits

<p>The current study was designed to determine the effects of dietary quercetin on epididymal sperm and testicular changes in male rabbits during summer heat stress (HS). Twelve adult male New Zealand white rabbits were submitted to summer heat conditions (temperature-humidity index 29.9±1.2). One group was fed a basal ration (BR; n = 6), whereas the other group was fed the same basal diet supplemented with quercetin (30 mg/kg d; Que-BR; n = 6) for 60 d, and both groups were sacrificed at the end of the experiment. Epididymis and testicles isolation was done for sperm, histopathology and apoptosis assessments. The results showed that quercetin improved epididymis weight, but did not affect other testicular dimensions except testicular length. A significant improvement was observed in epididymal sperm motility, concentration, kinematic parameters, viability, mitochondrial potential and acrosome integrity in Que-BR compared to the BR group. Lowered serum malondialdehyde level was observed in quercetin supplemented rabbits. Moreover, the quercetin supplementation maintained the interstitial stroma, seminiferous tubules architecture, germinal and Sertoli cells under HS, decreasing the apoptotic germ cell rate in seminiferous tubules. In conclusion, HS condition affects the sperm and testes configurations in rabbits and dietary quercetin minimises oxidative stress, which in turn protects the testes and sperm against HS induced damage.</p>

Faster and more efficient swimming: energy consumption of murine spermatozoa under sperm competition†

ATP supply is essential for sperm performance and increases in ATP content coevolve with enhanced sperm swimming velocity as a response to sperm competition in rodents. ATP content is the balance between production and consumption but, although ATP production has received much attention, little is known about ATP consumption. The rate of ATP consumption is crucial for the propagation of the flagellar wave, becoming a main determinant of the time and distance sperm could move before exhausting their reserves. A high yield in distance per unit of ATP consumed (efficiency) could provide advantages in sperm competition. We characterized sperm ATP consumption rate in a group of mouse species with different sperm competition levels to understand its impact on swimming velocity, duration, and yield of sperm ATP reserves. Interspecific comparisons revealed that sperm of species with higher sperm competition levels had high ATP consumption rates and faster swimming velocity. Moreover, sperm that consumed ATP at a faster rate swam more efficiently, since they were able to cover more distance per unit of ATP consumed. Our results suggest that by coupling the advantages of higher ATP turnover rates to increased efficiency of ATP expenditure, sperm would respond to increasingly competitive environments while maintaining a positive ATP balance.

Protamine and other proteins in sperm and seminal plasma as molecular markers of bull fertility

Fertility is the most important aspect in the efforts to increase livestock populations. Protamine and various proteins in sperm and seminal plasma are the results of the molecular analysis which can be used as a marker of fertility. Each of the proteins plays an important role in the normal function of sperm, starting from the formation of sperm structure, motility, capacitation, cell protection, acrosome reactions, successful fertilization, egg activation, and embryonic development. Finally, these molecular components can be a marker of fertility and can help to diagnose the cases of infertility/subfertility in livestock in the field.

Imbalanced testicular metabolism induced by thyroid disorders: New evidences from quantitative proteome

Thyroid dysfunctions, such as hypothyroidism and hyperthyroidism, are the second most prevalent endocrinopathies and are associated to reproductive disorders in men. Several genes are differentially modulated by thyroid hormones in testes and imbalances in thyroid hormone levels are also associated to alterations on sperm functionality. Imbalances on antioxidant defense mechanism and stress oxidative have been pointed out as the main factors for the impairments on male reproductive function. To clarify this issue, we investigated the expression and activity of antioxidant enzymes in testis, followed by their proteomic profile in attempt to characterize the mechanisms involved in the alterations induced by hypo- or hyperthyroidism in adult male rats. Hypothyroidism reduced the Gsr transcript expression and the activity of CAT and GSR enzymes, while the hyperthyroidism reduced the Gpx4 var2 transcript expression. Among 1082 identified proteins, 123 and 37 proteins were downregulated by hypothyroidism compared to euthyroid and hyperthyroid condition, respectively, being 36 proteins commonly reduced in both comparisons and one exclusively in hypo-hyperthyroidism comparison. A network containing 29 nodes and 68 edges was obtained in protein-protein interaction analysis and the functional enrichment analysis of differentially expressed proteins revealed significant alterations for several functions in hypo-euthyroid and hypo-hyperthyroid comparisons, such as ATP metabolic process, coenzyme binding, sperm part, peroxiredoxin activity, mitochondrial protein complex, intramolecular oxidoreductase activity, binding of sperm to zona pellucida, glutathione transferase activity, response to testosterone. Thus, there is a correlation between thyroid disorders and impaired antioxidant defense mechanism, resulting in reproductive dysfunctions, as infertility, mainly observed in hypothyroidism.

Influence of the genetic background on the reproductive phenotype of mice lacking Cysteine-Rich Secretory Protein 1 (CRISP1)

Epididymal sperm protein CRISP1 has the ability to both regulate murine CatSper, a key sperm calcium channel, and interact with egg-binding sites during fertilization. In spite of its relevance for sperm function, Crisp1-/-mice are fertile. Considering that phenotypes can be influenced by the genetic background, in the present work mice from the original mixed Crisp1-/- colony (129/SvEv*C57BL/6) were backcrossed onto the C57BL/6 strain for subsequent analysis of their reproductive phenotype. Whereas fertility and fertilization rates of C57BL/6 Crisp1-/- males did not differ from those reported for mice from the mixed background, several sperm functional parameters were clearly affected by the genetic background. Crisp1-/- sperm from the homogeneous background exhibited defects in both the progesterone-induced acrosome reaction and motility not observed in the mixed background, and normal rather than reduced protein tyrosine phosphorylation. Additional studies revealed a significant decrease in sperm hyperactivation as well as in cAMP and protein kinase A (PKA) substrate phosphorylation levels in sperm from both colonies. The finding that exposure of mutant sperm to a cAMP analog and phosphodiesterase inhibitor overcame the sperm functional defects observed in each colony indicated that a common cAMP-PKA signaling defect led to different phenotypes depending on the genetic background. Altogether, our observations indicate that the phenotype of CRISP1 null males is modulated by the genetic context and reveal new roles for the protein in both the functional events and signaling pathways associated to capacitation.

Uncovering sperm metabolome to discover biomarkers for bull fertility

Background

Subfertility decreases the efficiency of the cattle industry because artificial insemination employs spermatozoa from a single bull to inseminate thousands of cows. Variation in bull fertility has been demonstrated even among those animals exhibiting normal sperm numbers, motility, and morphology. Despite advances in research, molecular and cellular mechanisms underlying the causes of low fertility in some bulls have not been fully elucidated. In this study, we investigated the metabolic profile of bull spermatozoa using non-targeted metabolomics. Statistical analysis and bioinformatic tools were employed to evaluate the metabolic profiles high and low fertility groups. Metabolic pathways associated with the sperm metabolome were also reported.

Results

A total of 22 distinct metabolites were detected in spermatozoa from bulls with high fertility (HF) or low fertility (LF) phenotype. The major metabolite classes of bovine sperm were organic acids/derivatives and fatty acids/conjugates. We demonstrated that the abundance ratios of five sperm metabolites were statistically different between HF and LF groups including gamma-aminobutyric acid (GABA), carbamate, benzoic acid, lactic acid, and palmitic acid. Metabolites with different abundances in HF and LF bulls had also VIP scores of greater than 1.5 and AUC- ROC curves of more than 80%. In addition, four metabolic pathways associated with differential metabolites namely alanine, aspartate and glutamate metabolism, β-alanine metabolism, glycolysis or gluconeogenesis, and pyruvate metabolism were also explored.

Conclusions

This is the first study aimed at ascertaining the metabolome of spermatozoa from bulls with different fertility phenotype using gas chromatography-mass spectrometry. We identified five metabolites in the two groups of sires and such molecules can be used, in the future, as key indicators of bull fertility.

Aberrant expression of sperm‑specific glycolytic enzymes are associated with poor sperm quality

The energy required for normal sperm function is mainly generated by glycolysis and oxidative phosphorylation. Testis‑specific glycolytic enzymes are expressed in germ cells and present in mature spermatozoa. The objective of the present study was to investigate the association between aberrant expression of glycolytic enzymes and human sperm quality. In silico analysis of glyceraldehyde‑3‑phosphate dehydrogenase, testis‑specific (GAPDHS), phosphoglycerate kinase 2 (PGK2) and lactate dehydrogenase (LDHC) identified that they were exclusively expressed in post‑meiotic germ cells and this was validated in human testes using immunohistochemistry. Compared with the testes of young adults, markedly lower expression levels of these glycolytic enzymes were observed in the testes of elderly adults. Similarly, low levels were observed in immature and asthenozoospermic spermatozoa. The expression levels of GAPDHS, PGK2 and LDHC in the spermatozoa were closely correlated with progressive sperm motility. The results indicated that the expression of GAPDHS, PGK2 and LDHC in sperm may be associated with sperm quality, and there may be a similar molecular mechanism underlying sperm quality in immature and asthenozoospermic spermatozoa. This study reveals a close association of glycolytic enzymes with sperm quality. The data may greatly contribute to the molecular evaluation of sperm quality and the diagnosis and treatment of asthenozoospermia.

The age-related changes and differences in energy metabolism and glutamate-glutamine recycling in the d-gal-induced and naturally occurring senescent astrocytes in vitro

Previously, we successfully established a d-galactose (d-gal)-induced astrocyte aging model in vitro. However, whether the changes in the aged astrocytes induced by d-gal are similar to those occurred in naturally are unknown. Therefore, in current study, we simultaneously established d-gal-induced and naturally aged astrocyte aging models in vitro to explore the age-related changes and to compare the differences in these two astrocyte aging models. The Seahorse Extracellular Flux Analyzer was used to examine the mitochondrial metabolism and glycolysis activities of the young and senescent astrocytes. The results showed that the mitochondrial ATP-linked oxygen consumption rates (OCRs) were decreased markedly both in the d-gal-induced and naturally occurring senescent astrocytes. The basal glycolysis activity was increased in the naturally occurring senescent astrocytes, whereas it was decreased in the d-gal-induced senescent astrocytes. Western blot analysis showed that isocitrate dehydrogenase 3 (IDH3), succinate dehydrogenase (SDH) and malate dehydrogenase 2 (MDH2) were markedly decreased both in these two aging models, whereas the iron‑sulfur cluster assembly enzyme (ISCU) was up-regulated in the naturally occurring senescent astrocytes but was down-regulated in the d-gal-induced senescent astrocytes. The expression levels of glial glutamate transporter-1 (GLT-1), glutamine synthetase (GS) and γ-aminobutyric acid type B receptor subunit 2 (GABA_BR2) were also markedly decreased in these two aging models. In addition, the PI3K/AKT signaling pathway was to be inactivated both in the d-gal-induced and naturally occurring senescent astrocytes. These results indicate that the age-related changes in d-gal-induced senescent astrocytes are not fully consistent with those in naturally occurring senescent astrocytes, and it may be not suitable to use d-gal-induced senescent astrocytes to replace the naturally occurring senescent astrocytes to explore the aging mechanisms under some circumstances.

Localization of MIF-II on mammalian spermatozoa: A study revealing its structure, function and motility inhibitory pathway

Motility of spermatozoa is a crucial factor for determining semen quality. Here we report motility inhibitory factor (MIF-II) from goat epididymal plasma, revealing its structure, function, localization and motility inhibitory pathway. Structural characterization with MALDI revealed novelty of this protein while circular dichroism data confirmed its alpha helical nature. Higher dilutions of MIF-II antibody increased cauda sperm motility and induced immature/immotile caput sperm motility as tested microscopically. Higher number of sperm cells and lower dilutions of antibody induced agglutination in cauda sperm showing surface localization. Indirect immuno-fluorescence showed MIF-II localization throughout the caput sperm surface which relocated more towards acrosomal region with maturation. ELISA assay revealed gradual increase and decrease in concentration of MIF-II in epididymal plasma and plasma membrane respectively from caput to cauda. Signaling cascade that leads to sperm motility inhibition elevates nitric oxide levels through cAMP dependent pathway. MIF-II treatment doesn't alter sperm surface morphology. Expression pattern of MIF-II during epididymal maturation goes hand-in-hand with gaining motility potential as well as dormancy of spermatozoa before ejaculation. Both MIF-II and its antibody inhibit fertilization in-vitro thus expected to open new gateway for future male infertility and contraceptive development research.

Mitochondrial ATP is required for the maintenance of membrane integrity in stallion spermatozoa, whereas motility requires both glycolysis and oxidative phosphorylation

To investigate the hypothesis that oxidative phosphorylation is a major source of ATP to fuel stallion sperm motility, oxidative phosphorylation was suppressed using the mitochondrial uncouplers CCCP and 2,4,-dinitrophenol (DNP) and by inhibiting mitochondrial respiration at complex IV using sodium cyanide or at the level of ATP synthase using oligomycin-A. As mitochondrial dysfunction may also lead to oxidative stress, production of reactive oxygen species was monitored simultaneously. All inhibitors reduced ATP content, but oligomycin-A did so most profoundly. Oligomycin-A and CCCP also significantly reduced mitochondrial membrane potential. Sperm motility almost completely ceased after the inhibition of mitochondrial respiration and both percentage of motile sperm and sperm velocity were reduced in the presence of mitochondrial uncouplers. Inhibition of ATP synthesis resulted in the loss of sperm membrane integrity and increased the production of reactive oxygen species by degenerating sperm. Inhibition of glycolysis by deoxyglucose led to reduced sperm velocities and reduced ATP content, but not to loss of membrane integrity. These results suggest that, in contrast to many other mammalian species, stallion spermatozoa rely primarily on oxidative phosphorylation to generate the energy required for instance to maintain a functional Na⁺/K⁺ gradient, which is dependent on an Na⁺-K⁺ antiporter ATPase, which relates directly to the noted membrane integrity loss. Under aerobic conditions, however, glycolysis also provides the energy required for sperm motility.

Heat Stress Reduces Sperm Motility via Activation of Glycogen Synthase Kinase-3α and Inhibition of Mitochondrial Protein Import

The adverse effects of high environmental temperature exposure on animal reproductive functions have been concerned for many decades. However, the molecular basis of heat stress (HS)-induced decrease of sperm motility has not been entirely elucidated. We hypothesized that the deteriorate effects of HS may be mediated by damage of mitochondrial function and ATP synthesis. To test this hypothesis, we use mature boar sperm as model to explore the impacts of HS on mitochondrial function and sperm motility. A 6 h exposure to 42°C (HS) induced significant decrease in sperm progressive motility. Concurrently, HS induced mitochondrial dysfunction that is indicated by decreased of membrane potential, respiratory chain complex I and IV activities and adenosine triphosphate (ATP) contents. Exogenous ATP abolished this effect suggesting that reduced of ATP synthesis is the committed step in HS-induced reduction of sperm motility. At the molecular level, the mitochondrial protein contents were significantly decreased in HS sperm. Notably, the cytochrome c oxidase subunit 4, which was synthesized in cytoplasm and translocated into mitochondria, was significantly lower in mitochondria of HS sperm. Glycogen synthase kinase-3α (GSK3α), a negative regulator of sperm motility that is inactivated by Ser21 phosphorylation, was dephosphorylated after HS. The GSK3α inhibitor CHIR99021 was able to abolish the effects of HS on sperm and their mitochondria. Taken together, our results demonstrate that HS affects sperm motility through downregulation of mitochondrial activity and ATP synthesis yield, which involves dephosphorylation of GSK3α and interference of mitochondrial remodeling.

mtDNA polymorphism and metabolic inhibition affect sperm performance in conplastic mice

Whereas a broad link exists between nucleotide substitutions in the mitochondrial genome (mtDNA) and a range of metabolic pathologies, exploration of the effect of specific mtDNA genotypes is on-going. Mitochondrial DNA mutations are of particular relevance for reproductive traits, since they are expected to have profound effects on male specific processes as a result of the strict maternal inheritance of mtDNA. Sperm motility is crucially dependent on ATP in most systems studied. However, the importance of mitochondrial function in the production of the ATP necessary for sperm function remains uncertain. In this study, we test the effect of mtDNA polymorphisms upon mouse sperm performance and bioenergetics by using five conplastic inbred strains that share the same nuclear background while differing in their mitochondrial genomes. We found that, while genetic polymorphisms across distinct mtDNA haplotypes are associated with modification in sperm progressive velocity, this effect is not related to ATP production. Furthermore, there is no association between the number of mtDNA polymorphisms and either (a) the magnitude of sperm performance decrease, or (b) performance response to specific inhibition of the main sperm metabolic pathways. The observed variability between strains may be explained in terms of additive effects of single nucleotide substitutions on mtDNA coding sequences, which have been stabilized through genetic drift in the different laboratory strains. Alternatively, the decreased sperm performance might have arisen from the disruption of the nuclear DNA/mtDNA interactions that have coevolved during the radiation of Mus musculus subspecies.

Evidence for Rapid Oxidative Phosphorylation and Lactate Fermentation in Motile Human Sperm by Hyperpolarized 13C Magnetic Resonance Spectroscopy

Poor sperm motility is a common cause of male infertility for which there are no empirical therapies. Sperm motility is powered by adenosine triphosphate but the relative importance of lactate fermentation and Oxidative Phosphorylation (OxPhos) is debated. To study the relationship between energy metabolism and sperm motility we used dissolution Dynamic Nuclear Polarization (dDNP) for the first time to show the rapid conversion of ¹³C₁-pyruvate to lactate and bicarbonate, indicating active glycolytic and OxPhos metabolism in sperm. The magnitude of both lactate and bicarbonate signals were positively correlated with the concentration of progressively motile sperm. After controlling for sperm concentration, increased progressive sperm motility generated more pyruvate conversion to lactate and bicarbonate. The technique of dDNP allows ‘snapshots’ of sperm metabolism to be tracked over the different stages of their life. This may provide help to uncover the causes of poor sperm motility and suggest new approaches for novel treatments or therapies.

Expression of lactate dehydrogenase C correlates with poor prognosis in renal cell carcinoma

Lactate dehydrogenase C is an isoenzyme of lactate dehydrogenase and a member of the cancer-testis antigens family. In this study, we aimed to investigate the expression and functional role of lactate dehydrogenase C and its basic mechanisms in renal cell carcinoma. First, a total of 133 cases of renal cell carcinoma samples were analysed in a tissue microarray, and Kaplan-Meier survival curve analyses were performed to investigate the correlation between lactate dehydrogenase C expression and renal cell carcinoma progression. Lactate dehydrogenase C protein levels and messenger RNA levels were significantly upregulated in renal cell carcinoma tissues, and the patients with positive lactate dehydrogenase C expression had a shorter progression-free survival, indicating the oncogenic role of lactate dehydrogenase C in renal cell carcinoma. In addition, further cytological experiments demonstrated that lactate dehydrogenase C could prompt renal cell carcinoma cells to produce lactate, and increase metastatic and invasive potential of renal cell carcinoma cells. Furthermore, lactate dehydrogenase C could induce the epithelial-mesenchymal transition process and matrix metalloproteinase-9 expression. In summary, these findings showed lactate dehydrogenase C was associated with poor prognosis in renal cell carcinoma and played a pivotal role in the migration and invasion of renal cell carcinoma cells. Lactate dehydrogenase C may act as a novel biomarker for renal cell carcinoma progression and a potential therapeutic target for the treatment of renal cell carcinoma.

Altered expression profile of glycolytic enzymes during testicular ischemia reperfusion injury is associated with the p53/TIGAR pathway: effect of fructose 1,6-diphosphate

Background. Testicular ischemia reperfusion injury (tIRI) is considered the mechanism underlying the pathology of testicular torsion and detorsion. Left untreated, tIRI can induce testis dysfunction, damage to spermatogenesis and possible infertility. In this study, we aimed to assess the activities and expression of glycolytic enzymes (GEs) in the testis and their possible modulation during tIRI. The effect of fructose 1,6-diphosphate (FDP), a glycolytic intermediate, on tIRI was also investigated. Methods. Male Sprague-Dawley rats were divided into three groups: sham, unilateral tIRI, and tIRI + FDP (2 mg/kg). tIRI was induced by occlusion of the testicular artery for 1 h followed by 4 h of reperfusion. FDP was injected peritoneally 30 min prior to reperfusion. Histological and biochemical analyses were used to assess damage to spermatogenesis, activities of major GEs, and energy and oxidative stress markers. The relative mRNA expression of GEs was evaluated by real-time PCR. ELISA and immunohistochemistry were used to evaluate the expression of p53 and TP53-induced glycolysis and apoptosis regulator (TIGAR). Results. Histological analysis revealed tIRI-induced spermatogenic damage as represented by a significant decrease in the Johnsen biopsy score. In addition, tIRI reduced the activities of hexokinase 1, phosphofructokinase-1, glyceraldehyde 3-phosphate dehydrogenase, and lactate dehydrogenase C. However, mRNA expression downregulation was detected only for hexokinase 1, phosphoglycerate kinase 2, and lactate dehydrogenase C. ATP and NADPH depletion was also induced by tIRI and was accompanied by an increased Malondialdehyde concentration, reduced glutathione level, and reduced superoxide dismutase and catalase enzyme activities. The immunoexpression of p53 and TIGAR was markedly increased after tIRI. The above tIRI-induced alterations were attenuated by FDP treatment. Discussion. Our findings indicate that tIRI-induced spermatogenic damage is associated with dysregulation of GE activity and gene expression, which were associated with activation of the TIGAR/p53 pathway. FDP treatment had a beneficial effect on alleviating the damaging effects of tIRI. This study further emphasizes the importance of metabolic regulation for proper spermatogenesis.