Gut microbiota supports male reproduction via nutrition, immunity, and signaling

Microbial metabolites as engines of behavioral variation across animals

The microbiome, especially that present in the gut, has emerged as a key modulator of animal behavior. However, the extent of its influence across species and behavioral repertoires, as well as the underlying mechanisms, remains poorly understood. Increasing evidence suggests that microbial metabolites play an important role in driving behavioral variation. In this review, we synthesize findings from vertebrates to invertebrates, spanning both model and non-model organisms, to define key groups of microbial-derived metabolites involved in modulating seven distinct behaviors: nutrition, olfaction, circadian rhythms, reproduction, locomotion, aggression, and social interactions. We discuss how these microbial metabolites interact with host chemosensory systems, neurotransmitter signaling, and epigenetic modifications to shape behavior. Additionally, we highlight critical gaps in mechanistic understanding, including the need to map additional host receptors and signaling pathways, as well as the untapped potential of microbial biosynthetic gene clusters as sources for novel bioactive compounds. Advancing these areas will enhance understanding of the microbiome's role in behavioral modulation and open new avenues for microbiome-based interventions for behavioral disorders.

Technologies to improve sperm retrieval in men undergoing micro-TESE for NOA

ABSTRACT

Nonobstructive azoospermia (NOA) is considered the most challenging clinical scenario for infertile men and current treatments leave many men unsuccessful at being able to achieve a pregnancy with their partner using their own sperm. Microdissection testicular sperm extraction (micro-TESE) is the choice for men with NOA desiring to father children with their own gametes. Micro-TESE results in the highest numbers of sperm cells retrieved for use with in vitro fertilization/intracytoplasmic sperm injection. With suboptimal micro-TESE success rates of sperm retrieval and then pregnancy and live birth using the retrieved sperm with in vitro fertilization/intracytoplasmic sperm injection, advances to improve outcomes are necessary. This article comprehensively reviews the technologies investigated to date to improve the outcomes for men undergoing micro-TESE.

Causal relationships between gut microbiota and male reproductive inflammation and infertility: Insights from Mendelian randomization

The study observed interactions between gut microbiota and male reproductive health, noting that the causal relationships were previously unclear. It aimed to explore the potential cause-and-effect relationship between gut bacteria and male reproductive problems such as inflammation, infertility, and sperm functionality, using a two-sample Mendelian randomization method to examine these connections. The analysis found that certain bacterial genera, such as Erysipelatoclostridium (0.71 [0.55-0.92]), Parasutterella (0.74 [0.57-0.96]), Ruminococcaceae UCG-009 (0.77 [0.60-0.98]), and Slackia (0.69 [0.49-0.96]), showed protective effects against prostatitis. In contrast, other genera like Faecalibacterium (1.59 [1.08-2.34]), Lachnospiraceae UCG004 (1.64 [1.15-2.34]), Odoribacter (1.68 [1.01-2.81]), Paraprevotella (1.28 [1.03-1.60]), and Sutterella (1.58 [1.13-2.19]) were detrimental. Additionally, causal relationships were identified between 2 genera and orchitis and epididymitis, 3 genera and male infertility, and 5 genera and abnormal spermatozoa. Further analysis of sperm-related proteins revealed causal associations between specific bacterial genera and proteins such as SPACA3, SPACA7, SPAG11A, SPAG11B, SPATA9, SPATA20, and ZPBP4. The results remained robust after sensitivity analysis and reverse Mendelian randomization analysis. The study concluded that specific bacterial genera have causal roles in reproductive inflammation, infertility, and sperm-associated proteins. This provides a novel strategy for the early diagnosis and identification of therapeutic targets in reproductive inflammation and infertility.

Mechanisms of Hormonal, Genetic, and Temperature Regulation of Germ Cell Proliferation, Differentiation, and Death During Spermatogenesis

Spermatogenesis is a complex and highly regulated process involving the proliferation, differentiation, and apoptosis of germ cells. This process is controlled by various hormonal, genetic, and environmental factors, including temperature. In hormonal regulation, follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone (T) are essential for correct spermatogenesis development from the early stages and spermatogonia proliferation to germ cell maturation. Other hormones, like inhibin and activin, finely participate tuning the process of spermatogenesis. Genetic regulation involves various transcription factors, such as SOX9, SRY, and DMRT1, which are crucial for the development and maintenance of the testis and germ cells. MicroRNAs (miRNAs) play a significant role by regulating gene expression post-transcriptionally. Epigenetic modifications, including DNA methylation, histone modifications, and chromatin remodelling, are also vital. Temperature regulation is another critical aspect, with the testicular temperature maintained around 2-4 °C below body temperature, essential for efficient spermatogenesis. Heat shock proteins (HSPs) protect germ cells from heat-induced damage by acting as molecular chaperones, ensuring proper protein folding and preventing the aggregation of misfolded proteins during thermal stress. Elevated testicular temperature can impair spermatogenesis, increasing germ cell apoptosis and inducing oxidative stress, DNA damage, and the disruption of the blood-testis barrier, leading to germ cell death and impaired differentiation. The cellular mechanisms of germ cell proliferation, differentiation, and death include the mitotic divisions of spermatogonia to maintain the germ cell pool and produce spermatocytes. Spermatocytes undergo meiosis to produce haploid spermatids, which then differentiate into mature spermatozoa. Apoptosis, or programmed cell death, ensures the removal of defective germ cells and regulates the germ cell population. Hormonal imbalance, genetic defects, and environmental stress can trigger apoptosis during spermatogenesis. Understanding these mechanisms is crucial for addressing male infertility and developing therapeutic interventions. Advances in molecular biology and genetics continue to uncover the intricate details of how spermatogenesis is regulated at multiple levels, providing new insights and potential targets for treatment.

Vitamin B6 Alleviates Aflatoxin B1-Induced Impairment of Testis Development by Activating the PI3K/Akt Signaling Pathway

Aflatoxin B1 (AFB1) is a harmful environmental contaminant known to disrupt gut microbiota and cause health problems. In recent years, the role of vitamin B6 (VB6) in maintaining intestinal and reproductive health has attracted much attention. AFB1 has been found to damage the intestinal barrier and cause inflammation by disrupting the intestinal microbiota, particularly by increasing the abundance of Enterococcus. In mice treated with AFB1, serum metabolites were disturbed, VB6 serum levels were reduced, and testicular inflammation was exacerbated. Enterococcus exposure in mice leads to a reduction in serum VB6 levels, which is accompanied by intestinal and testicular damage. However, VB6 supplementation significantly ameliorated AFB1-induced intestinal and testicular injury. Transcriptomics and Western blotting showed that after AFB1 exposure, VB6 could increase the expression of phosphoinositide 3-kinase (PI3K) and kinase B (AKT) as well as their phosphorylated forms in the testes of mice. Based on the results, AFB1 leads to intestinal and testicular damage by disturbing the gut microbiota, and VB6 represents a potential therapeutic to counteract this damage. In conclusion, supplementation with adequate VB6 can ameliorate AFB1-induced intestinal and testicular damage, emphasizing the importance of VB6 intervention and providing a new perspective for the prevention and treatment of AFB1-related health issues.

Acupuncture mediates the "gut-testis axis" to improve asthenozoospermia

Background

Asthenozoospermia is a common cause of male infertility. Studies have shown that sperm quality and motility are affected by the gut-testis axis that can regulate testicular metabolism and function through the gut microbiota and its metabolites. Acupuncture is an important modality of complementary and alternative medicine. It can improve sperm motility, but it remains unclear whether acupuncture can enhance sperm vitality by influencing the gut-testis axis.

Methods

In this study, sperm quality, testicular pathology, and serum hormone levels were assessed using a cyclophosphamide-induced mouse model. Real-time PCR, a western blot analysis, and immunofluorescence techniques were used to assess the effects of acupuncture on the gut barrier and blood-testis barrier functions. In addition, gut microbiome and metabolomics were used to study the impact of acupuncture on the gut microbiota structure, serum, and testicular metabolites in asthenozoospermic mice. Further validation was obtained by performing a fecal microbiota transplantation (FMT).

Results

Acupuncture improved the sperm quality; ameliorated testicular pathology; increased serum testosterone (T), follicle-stimulating hormone (FSH), and luteinizing hormone (LH) levels; and repaired gut and blood-testis barrier damage in asthenozoospermic mice. The abundances of Bacteroidota, Firmicutes, Faecalibaculum, and Dubosiella were associated with sperm motility, as shown by a gut microbiome analysis. Serum metabolomics revealed that differentially expressed metabolites (DEMs), such as cytosine and N-oleyl-leucine, were closely related to sperm motility. Testicular metabolomics analysis revealed DEMs, such as 5-fluorouridine and 1-acetylimidazole, were also associated with sperm motility. Furthermore, reproductive function improvements in asthenozoospermic mice through acupuncture were achieved via an FMT.

Conclusion

Acupuncture may alleviate asthenozoospermia symptoms by modulating the gut-testis axis and repairing the gut-testis barrier.

Exploring the microbiome-gut-testis axis in testicular germ cell tumors

The microbiome-gut-testis axis has emerged as a significant area of interest in understanding testicular cancer, particularly testicular germ cell tumors (TGCTs), which represent the most common malignancy in young men. The interplay between the gut and testicular microbiomes is hypothesized to influence tumorigenesis and reproductive health, underscoring the complex role of microbial ecosystems in disease pathology. The microbiome-gut-testis axis encompasses complex interactions between the gut microbiome, systemic immune modulation, and the local microenvironment of the testis. Dysbiosis in the gut or testicular microbiomes may contribute to altered immune responses, inflammation, and hormonal imbalances, potentially playing a role in the pathogenesis of TGCTs. Concurrently, seminal microbiomes have been linked to variations in sperm quality, fertility potential, and possibly cancer susceptibility, underscoring the need for further evaluation. This review explores the emerging role of the microbiome-gut-testis axis in the context of testicular cancer, highlighting its implications for disease onset, progression, treatment efficacy, and toxicity. Identifying potential microbial biomarkers, followed by microbiota modulation to restore a balanced microbial community, might offer a novel supportive strategy for improving treatment efficacy in refractory TGCT patients while reducing chemotherapy-induced toxicity. We suggest a better understanding of the association between dysregulated microbial environments and TGCTs emphasizes potential pathways by which the gut microbiome might influence testicular cancer.

Ammonia and hydrogen sulfide - new insights into gut microbiota and male infertility through meta-analysis

Background

Ammonia (NH3) and hydrogen sulfide (H2S) are produced during digestion in the human gut, yet the impact of these internally generated gases on male reproduction have received limited attention in scientific research.

Methods

We systematically reviewed 935 scientific publications, spanning from 1947 to 2023, focusing on external or internal NH3 and/or H2S, male infertility, and gut microbiota. Meta-analysis was conducted to evaluate the summary relative risk (RR) and 95% confidence intervals (CIs) of combined studies.

Results

Our findings revealed that the internal NH3 and/or H2S were negatively related to the Lactobacillus, which is beneficial to male fertility, whereas NH3 and H2S were positively related to Bacteroides, which showed negative effects on male fertility. The meta-analysis comparing Lactobacillus and Bacteroides levels with NH3 showed statistically significant results (p<0.001).

Conclusions

The meta-analysis is the first to confirm these facts and explored the potential existence of a gut microbiota-inner gases-male fertility axis in the human gut.

Microbiota contribute to regulation of the gut-testis axis in seasonal spermatogenesis

Seasonal breeding is an important adaptive strategy for animals. Recent studies have highlighted the potential role of the gut microbiota in reproductive health. However, the relationship between the gut microbiota and reproduction in seasonal breeders remains unclear. In this study, we selected a unique single food source animal, the flying squirrel (Trogopterus xanthipes), as a model organism for studying seasonal breeding. By integrating transcriptomic, metabolomic, and microbiome data, we comprehensively investigated the regulation of the gut-metabolism-testis axis in seasonal breeding. Here, we demonstrated a significant spermatogenic phenotype and highly active spermatogenic transcriptional characteristics in the testes of flying squirrels during the breeding season, which were associated with increased polyamine metabolism, primarily involving spermine and γ-amino butyric acid. Moreover, an enrichment of Ruminococcus was observed in the large intestine during the breeding season and may contribute to enhanced methionine biosynthesis in the gut. Similar changes in Ruminococcus abundance were also observed in several other seasonal breeders. These findings innovatively revealed that reshaping the gut microbiota regulates spermatogenesis in seasonal breeders through polyamine metabolism, highlighting the great potential of the gut-testis axis in livestock animal breeding and human health management.

Boar semen microbiome: Insights and potential implications

The pioneers of next-generation sequencing technology and bioinformatic analyses initiated a new era in microbiology research by offering profound insights into bacterial microbiome communities. In the pig farming sector, while considerable attention has been devoted to the gut microbiome and the microbiome of the female reproductive tract, research on the microbiome of boar semen remains limited. Nonetheless, published studies have provided valuable insights, serving as important references and sparking ideas for further investigations into the seminal microbiome. Factors such as breed, seasons, feed additives, hygiene management, and antibiotic use are believed to exert a notable influence on the diversity and richness of bacterial genera in the boar seminal microbiome, potentially affecting semen quality. Moreover, current shifts towards sustainability in the swine industry, coupled with global guidelines concerning the prudent use of antibiotics in stored boar semen for artificial insemination, underscore the need for insights into factors influencing seminal bacteria. The objective of this review is to elucidate the current understanding of boar bacterial contents using conventional culture methods, as well as the boar seminal microbiome through metagenomics and bioinformatics. It also aims to review specific microbiome communities, such as those in the reproductive tract and gut, and their connections to semen quality. In addition, strategic enhancements for processing boar semen doses through alternative methods to improve seminal quality are proposed.

Exploring the hypothetical links between environmental pollutants, diet, and the gut-testis axis: The potential role of microbes in male reproductive health

The gut system, commonly referred to as one of the principal organs of the human "superorganism," is a home to trillions of bacteria and serves an essential physiological function in male reproductive failures or infertility. The interaction of the endocrine-immune system and the microbiome facilitates reproduction as a multi-network system. Some recent studies that link gut microbiota to male infertility are questionable. Is the gut-testis axis (GTA) real, and does it affect male infertility? As a result, this review emphasizes the interconnected links between gut health and male reproductive function via changes in gut microbiota. However, a variety of harmful (endocrine disruptors, heavy metals, pollutants, and antibiotics) and favorable (a healthy diet, supplements, and phytoconstituents) elements promote microbiota by causing dysbiosis and symbiosis, respectively, which eventually modify the activities of male reproductive organs and their hormones. The findings of preclinical and clinical studies on the direct and indirect effects of microbiota changes on testicular functions have revealed a viable strategy for exploring the GTA-axis. Although the GTA axis is poorly understood, it may have potential ties to reproductive issues that can be used for therapeutic purposes in the future.

Melatonin alleviates heat stress-induced spermatogenesis dysfunction in male dairy goats by regulating arachidonic acid metabolism mediated by remodeling the gut microbiota

BACKGROUND

Heat stress (HS) commonly occurring in summer has gradually become a factor threatening the reproductive performance of male dairy goats by reducing their fecundity. Despite the melatonin is applied to relieve HS, it is still unclear whether melatonin protects against reproductive damage induced by HS in dairy goats and how it works. The purpose of the present study is to evaluate the role of melatonin in alleviating HS-induced spermatogenesis dysfunction in male dairy goats and further explore its mechanism.

RESULTS

HS impaired spermatogenesis, sperm formation in the testes, and sperm maturation in the epididymis of dairy goats, resulting in decreased sperm quality. Melatonin rescued the decrease of sperm quality induced by HS via decreasing inflammatory and oxidative stress levels in testicular tissue and enhancing intercellular barrier function within the testes. Amplicon-based microbiota analysis revealed that despite gut microbiota differences between melatonin-treated dairy goats and NC dairy goats to some extent, melatonin administration tends to return the gut microbiota of male dairy goats under HS to the levels of natural control dairy goats. To explore whether the protective role of melatonin in sperm quality is mediated by regulating gut microbiota, fecal microbiota of HS dairy goats with or without melatonin treatment were transferred to HS mice, respectively. We found HS mice that had received fecal bacteria of HS dairy goats experienced serious testicular injury and dyszoospermia, while this phenomenon was ameliorated in HS mice that had received fecal bacteria of dairy goats treated with melatonin, indicating melatonin alleviates HS-induced spermatogenic damage in a microbiota dependent manner. We further found that the testicular tissue of both HS dairy goats and mice transplanted with HS dairy goat feces produced large amounts of arachidonic acid (AA)-related metabolites, which were closely associated with semen quality. Consistently, supplementation with AA has been shown to elevate the levels of inflammation and oxidative stress in the testicular tissue of mice, disrupting intercellular connections and ultimately leading to spermatogenic disorders.

CONCLUSION

This study has revealed that melatonin can effectively alleviate spermatogenic disorders in dairy goats caused by HS. This beneficial effect was primarily achieved through the modulation of gut microbiota, which subsequently inhibited the excessive synthesis of AA in testicular tissue. These discoveries are of great significance for preventing or improving the decline in male livestock reproductive performance caused by HS, enhancing the reproductive efficiency of elite male breeds, and ultimately improving the production efficiency of animal husbandry. Video Abstract.

The microbiota: a key regulator of health, productivity, and reproductive success in mammals

The microbiota, intensely intertwined with mammalian physiology, significantly impacts health, productivity, and reproductive functions. The normal microbiota interacts with the host through the following key mechanisms: acting as a protective barrier against pathogens, maintain mucosal barrier integrity, assisting in nutrient metabolism, and modulating of the immune response. Therefore, supporting growth and development of host, and providing protection against pathogens and toxic substances. The microbiota significantly influences brain development and behavior, as demonstrated by comprehensive findings from controlled laboratory experiments and human clinical studies. The prospects suggested that gut microbiome influence neurodevelopmental processes, modulate stress responses, and affect cognitive function through the gut-brain axis. Microbiota in the gastrointestinal tract of farm animals break down and ferment the ingested feed into nutrients, utilize to produce meat and milk. Among the beneficial by-products of gut microbiota, short-chain fatty acids (SCFAs) are particularly noteworthy for their substantial role in disease prevention and the promotion of various productive aspects in mammals. The microbiota plays a pivotal role in the reproductive hormonal systems of mammals, boosting reproductive performance in both sexes and fostering the maternal-infant connection, thereby becoming a crucial factor in sustaining mammalian existence. The microbiota is a critical factor influencing reproductive success and production traits in mammals. A well-balanced microbiome improves nutrient absorption and metabolic efficiency, leading to better growth rates, increased milk production, and enhanced overall health. Additionally, it regulates key reproductive hormones like estrogen and progesterone, which are essential for successful conception and pregnancy. Understanding the role of gut microbiota offers valuable insights for optimizing breeding and improving production outcomes, contributing to advancements in agriculture and veterinary medicine. This study emphasizes the critical ecological roles of mammalian microbiota, highlighting their essential contributions to health, productivity, and reproductive success. By integrating human and veterinary perspectives, it demonstrates how microbial communities enhance immune function, metabolic processes, and hormonal regulation across species, offering insights that benefit both clinical and agricultural advancements.

Effect of Probiotics on Sperm Quality in the Adult Mouse

The administration of probiotics for the treatment of different diseases has gained interest in recent years. However, few studies have evaluated their effects on reproductive traits. The objective of this study was to examine the effect of two mixtures of probiotics, a commercial probiotic (Vivomixx®) and a mix of Lacticaseibacillus rhamnosus GG and Faecalibacterium duncaniae A2-165, on sperm quality in a mouse model. Adult male mice (8 months old) were used for two experimental and one control groups (n = 5 each). The probiotics or physiological serum (control) was administered orally, twice a week, during 5 weeks. Sperm were collected from the cauda epididymis, and their total number, motility, kinematics, morphology, and acrosome integrity were assessed in recently collected samples and after a 60-min in vitro incubation. Results showed a higher percentage of normal sperm in both experimental groups, with fewer head abnormalities than in the control. Differences were found among groups in the morphometry of sperm heads, being more elongated in mice treated with probiotics. Sperm from probiotic-treated mice showed similar total motility when compared to the controls, although the proportion of progressively moving sperm and their vigor of motility were lower. Sperm swimming descriptors were measured with a CASA system. Velocity parameters were similar among groups whereas linearity was higher in mice treated with the commercial probiotic. These results suggest that the administration of probiotics may increase the proportion of sperm with normal morphology and lead to modifications in sperm head shape that may enhance sperm swimming. Studies using a longer administration period would be useful in further characterizing the effect of these probiotic mixtures on sperm quality and fertilization capacity.

Differential gene expression and gut microbiota composition in low-altitude and high-altitude goats

Previous studies have presented evidence suggesting that altitude exerts detrimental effects on reproductive processes, yet the underlying mechanism remains elusive. Our study employed two distinct goat breeds inhabiting low and high altitudes, and conducted a comparative analysis of mRNA profiles in testis tissues and the composition of gut microbiota. The results revealed a reduced testis size in high-altitude goats. RNA-seq analysis identified the presence of 214 differentially expressed genes (DEGs) in the testis. These DEGs resulted in a weakened immunosuppressive effect, ultimately impairing spermatogenesis in high-altitude goats. Additionally, 16S rDNA amplicon sequencing recognized statistically significant variations in the abundance of the genera Treponema, unidentified_Oscillospiraceae, Desulfovibrio, Butyricicoccus, Dorea, Parabacteroides between the two groups. The collective evidence demonstrated the gut and testis played a synergistic role in causing decreased fertility at high altitudes. Our research provides a theoretical basis for future investigations into the reproductive fitness of male goats.

Contribution of the seminal microbiome to paternal programming

The field of Developmental Origins of Health and Disease has primarily focused on maternal programming of offspring health. However, emerging evidence suggests that paternal factors, including the seminal microbiome, could potentially play important roles in shaping the developmental trajectory and long-term offspring health outcomes. Historically, the microbes present in the semen were regarded as inherently pathogenic agents. However, this dogma has recently been challenged by the discovery of a diverse commensal microbial community within the semen of healthy males. In addition, recent studies suggest that the transmission of semen-associated microbes into the female reproductive tract during mating has potentials to not only influence female fertility and embryo development but could also contribute to paternal programming in the offspring. In this review, we summarize the current knowledge on the seminal microbiota in both humans and animals followed by discussing their potential involvement in paternal programming of offspring health. We also propose and discuss potential mechanisms through which paternal influences are transmitted to offspring via the seminal microbiome. Overall, this review provides insights into the seminal microbiome-based paternal programing, which will expand our understanding of the potential paternal programming mechanisms which are currently focused primarily on the epigenetic modifications, oxidative stresses, and cytokines.

Effects of polycyclic aromatic hydrocarbons on the gut-testis axis

Polycyclic aromatic hydrocarbons (PAHs) are a large group of organic compounds which are comprised of two or more fused benzene rings. As a typical environmental pollutant, PAHs are widely distributed in water, soil, atmosphere and food. Despite extensive researches on the mechanisms of health damage caused by PAHs, especially their carcinogenic and mutagenic toxicity, there is still a lack of comprehensive summarization and synthesis regarding the mechanisms of PAHs on the gut-testis axis, which represents an intricate interplay between the gastrointestinal and reproductive systems. Thus, this review primarily focuses on the potential forms of interaction between PAHs and the gut microbiota and summarizes their adverse outcomes that may lead to gut microbiota dysbiosis, then compiles the possible mechanistic pathways on dysbiosis of the gut microbiota impairing the male reproductive function, in order to provide valuable insights for future research and guide further exploration into the intricate mechanisms underlying the impact of gut microbiota dysbiosis caused by PAHs on male reproductive function.

MicroRNA and Gut Microbiota Alter Intergenerational Effects of Paternal Exposure to Polyethylene Nanoplastics

Nanoplastics (NPs), as emerging contaminants, have been shown to cause testicular disorders in mammals. However, whether paternal inheritance effects on offspring health are involved in NP-induced reproductive toxicity remains unclear. In this study, we developed a mouse model where male mice were administered 200 nm polyethylene nanoparticles (PE-NPs) at a concentration of 2 mg/L through daily gavage for 35 days to evaluate the intergenerational effects of PE-NPs in an exclusive male-lineage transmission paradigm. We observed that paternal exposure to PE-NPs significantly affected growth phenotypes and sex hormone levels and induced histological damage in the testicular tissue of both F0 and F1 generations. In addition, consistent changes in sperm count, motility, abnormalities, and gene expression related to endoplasmic reticulum stress, sex hormone synthesis, and spermatogenesis were observed across paternal generations. The upregulation of microRNA (miR)-1983 and the downregulation of miR-122-5p, miR-5100, and miR-6240 were observed in both F0 and F1 mice, which may have been influenced by reproductive signaling pathways, as indicated by the RNA sequencing of testis tissues and quantitative real-time polymerase chain reaction findings. Furthermore, alterations in the gut microbiota and subsequent Spearman correlation analysis revealed that an increased abundance of Desulfovibrio (C21_c20) and Ruminococcus (gnavus) and a decreased abundance of Allobaculum were positively associated with spermatogenic dysfunction. These findings were validated in a fecal microbiota transplantation trial. Our results demonstrate that changes in miRNAs and the gut microbiota caused by paternal exposure to PE-NPs mediated intergenerational effects, providing deeper insights into mechanisms underlying the impact of paternal inheritance.

Obesity, Dietary Patterns, and Hormonal Balance Modulation: Gender-Specific Impacts

Understanding the intricate relationship between nutrition, hormonal balance, and gender-specific factors is crucial for developing targeted interventions to mitigate obesity-related endocrine disruptions and improve metabolic health. This narrative review examines the impact of various dietary patterns on hormonal regulation in both men and women, focusing on their effects on hormonal balance and metabolic health in the context of obesity. Calorie restriction, the Western diet, high-fat diets, low-CHO diets, plant-based diets, and the Mediterranean diet are analyzed in relation to their influence on obesity-related endocrine disruptions and metabolic health. Future research directions include investigating the specific mechanisms underlying dietary influences on hormonal regulation, addressing the gender-specific metabolic differences and body fat distribution, and exploring the dietary needs of individuals undergoing gender transition. Personalized dietary interventions tailored to individual metabolic and hormonal profiles are essential for optimizing health outcomes across the gender spectrum. By integrating gender-specific considerations into dietary recommendations, healthcare professionals can better support individuals in achieving optimal metabolic health and hormonal balance.

Fluoride induces pyroptosis via IL-17A-mediated caspase-1/11-dependent pathways and Bifidobacterium intervention in testis

Fluoride, a ubiquitous environmental pollutant, poses a significant public health threat. Our previous study revealed a correlation between fluoride-induced testicular pyroptosis and male reproductive dysfunction. However, the underlying mechanism remains unclear. Wild-type and interleukin 17A knockout mice were exposed to sodium fluoride (100 mg/L) in deionized drinking water for 18 weeks. Bifidobacterium intervention (1 × 109 CFU/mL, 0.2 mL/day, administered via gavage) commenced in the 10th week. Sperm quality, testicular morphology, key pyroptosis markers, spermatogenesis key genes, IL-17A signaling pathway, and pyroptosis pathway related genes were determined. The results showed that fluoride reduced sperm quality, damaged testicular morphology, affected spermatogenesis, elevated IL-17A levels, and induced testicular pyroptosis. Bifidobacterium intervention alleviated adverse reproductive outcomes. Fluoride-activated testicular pyroptosis through both typical and atypical pathways, with IL-17A involvement. Bifidobacterium supplementation attenuated pyroptosis by downregulating IL-17A, inhibiting NLRP3 and PYRIN-mediated caspase-1 and caspase-11 dependent pathways in testis, thereby alleviating fluoride-induced male reproductive damage. In summary, this study uncovers the mechanism underlying fluorine-induced testicular pyroptosis and illustrates the novel protecting feature of Bifidobacterium against fluoride-induced harm to male reproduction, along with its potential regulatory mechanism. These results provide fresh perspectives on treating male reproductive dysfunction resulting from fluoride or other environmental toxins.

A meta-analysis-based adverse outcome pathway for the male reproductive toxicity induced by microplastics and nanoplastics in mammals

The male reproductive toxicity of microplastics (MPs) and nanoplastics (NPs) has attracted great attention, but the latent mechanisms remain fragmented. This review performed the adverse outcome pathway (AOP) analysis and meta-analysis in 39 relevant studies, with the AOP analysis to reveal the cause-and-effect relationships of MPs/NPs-induced male reproductive toxicity and the meta-analysis to quantify the toxic effects. In the AOP framework, increased reactive oxygen species (ROS) is the molecular initiating event (MIE), which triggered several key events (KEs) at different levels. At the cellular level, the KEs included oxidative stress, mitochondrial dysfunction, sperm DNA damage, endoplasmic reticulum stress, apoptosis and autophagy of testicular cells, repressed expression of steroidogenic enzymes and steroidogenic acute regulatory protein, disrupted hypothalamic-pituitary-testicular (HPT) axis, and gut microbiota alteration. These KEs further induced the reduction of testosterone, impaired blood-testis barrier (BTB), testicular inflammation, and impaired spermatogenesis at tissue/organ levels. Ultimately, decreased sperm quality or quantity was noted and proved by meta-analysis, which demonstrated that MPs/NPs led to a decrease of 5.99 million/mL in sperm concentration, 14.62% in sperm motility, and 23.56% in sperm viability, while causing an increase of 10.65% in sperm abnormality rate. Overall, this is the first AOP for MPs/NPs-mediated male reproductive toxicity in mammals. The innovative integration of meta-analysis into the AOP analysis increases the rigorism of the results.

Gut microbiota-gonadal axis: the impact of gut microbiota on reproductive functions

The influence of gut microbiota on physiological processes is rapidly gaining attention globally. Despite being under-studied, there are available data demonstrating a gut microbiota-gonadal cross-talk, and the importance of this axis in reproduction. This study reviews the impacts of gut microbiota on reproduction. In addition, the possible mechanisms by which gut microbiota modulates male and female reproduction are presented. Databases, including Embase, Google scholar, Pubmed/Medline, Scopus, and Web of Science, were explored using relevant key words. Findings showed that gut microbiota promotes gonadal functions by modulating the circulating levels of steroid sex hormones, insulin sensitivity, immune system, and gonadal microbiota. Gut microbiota also alters ROS generation and the activation of cytokine accumulation. In conclusion, available data demonstrate the existence of a gut microbiota-gonadal axis, and role of this axis on gonadal functions. However, majority of the data were compelling evidences from animal studies with a great dearth of human data. Therefore, human studies validating the reports of experimental studies using animal models are important.

Probiotics for Inflammatory Bowel Disease; A Deep Dive into their Impact on Disease Course and Associated Health Risks

To date, the underlying pathology of inflammatory bowel disease (IBD) is undetermined. Disturbance of intestinal gut microbiota was implicated in many health diseases, including IBD. Increasing evidence suggests that probiotics play a beneficial role in restoring the balance of the gut ecosystem. This review searched multiple databases for relevant works that examined probiotics' possible benefits in adults with IBD. Probiotic mode of action in ulcerative colitis patients and Crohn's disease were examined with respect to probiotic strain, their benefits, and their advantages in adult cases. Eligible studies for inclusion were assessed and analyzed. They were effective in reducing IBD disease course, inducing and maintaining remission, particularly for ulcerative colitis patients, with good efficacy and safety profile. However, the evidence for Crohn's disease was lacking. Probiotics positively affect IBD-related risks, reducing the risk of gastrointestinal malignancy and optimizing treating them. Additionally, they improved reduced fertility odds for both genders. The osteoporosis risk among IBD patients was also reduced, although the duration of use and dose were still not established. There was an encouraging role for them in reducing IBD -cardiovascular risks among cases with acute myocardial infarction and those with chronic heart failure. Finally, they had novel use in reducing IBD-related depression and improved overall mental health. In conclusion, we recommend probiotics as an adjuvant therapeutic option for IBD therapy for ulcerative colitis; however, their role in Crohn's disease needs further research.

Comparative analysis of changes in diarrhea and gut microbiota in Beigang pigs

Increasing evidence indicated that the gut microbiota is a large and complex organic combination, which is closely related to the host health. Diarrhea is a disease with devastating effects on livestock that has been demonstrated to be associated with gut microbiota. Currently, studies on gut microbiota and diarrhea have involved multiple species, but changes in gut microbiota of Beigang pigs during diarrhea have not been characterized. Here, we described gut microbial changes of Beigang pigs during diarrhea. Results indicated that a total of 4423 OTUs were recognized in diarrheic and healthy Beigang pigs, and Firmicutes and Bacteroidota were the most dominant phyla regardless of health status. However, the major components of the gut microbiota changed between diarrheic and healthy Beigang pigs. Bacterial taxonomic analysis revealed that the relative abundances of 3 phyla (Synergistota, Actinobacteriota and Spirochaetota) and 30 genera increased significantly during diarrhea, whereas the relative abundances of 3 phyla (Patescibacteria, Bacteroidota and Fibrobacterota) and 41 genera decreased significantly. In conclusion, this study found significant changes in the gut microbiota of Beigang pigs during diarrhea. Meanwhile, this also lays the foundation for the prevention and treatment of diarrhea in Beigang pigs and the further discovery of more anti-diarrhea probiotics.

The gut metabolite 3-hydroxyphenylacetic acid rejuvenates spermatogenic dysfunction in aged mice through GPX4-mediated ferroptosis

BACKGROUND

Aging-related fertility decline is a prevalent concern globally. Male reproductive system aging is mainly characterized by a decrease in sperm quality and fertility. While it is known that intestinal physiology changes with age and that microbiota is shaped by physiology, the underlying mechanism of how the microbiota affects male reproductive aging is still largely unexplored.

RESULTS

Here, we utilized fecal microbiota transplantation (FMT) to exchange the fecal microbiota between young and old mice. Cecal shotgun metagenomics and metabolomics were used to identify differences in gut microbiota composition and metabolic regulation during aging. Our results demonstrated that FMT from young to old mice alleviated aging-associated spermatogenic dysfunction through an unexpected mechanism mediated by a gut bacteria-derived metabolite, 3-hydroxyphenylacetic acid (3-HPAA). 3-HPAA treatment resulted in an improvement of spermatogenesis in old mice. RNA sequencing analysis, qRT-PCR and Western blot revealed that 3-HPAA induced an upregulation of GPX4, thereby restraining ferroptosis and restoring spermatogenesis. These findings were further confirmed by in vitro induction of ferroptosis and inhibition of GPX4 expression.

CONCLUSIONS

Our results demonstrate that the microbiome-derived metabolite, 3-HPAA, facilitates spermatogenesis of old mice through a ferroptosis-mediated mechanism. Overall, these findings provide a novel mechanism of dysregulated spermatogenesis of old mice, and suggest that 3-HPAA could be a potential therapy for fertility decline of aging males in clinical practice. Video Abstract.

Male infertility and the human microbiome

The historical belief in urology was that the genitourinary system should be sterile in a normal, healthy, asymptomatic adult. This idea was perpetuated for decades until research revealed a diverse microbiota existing in human anatomical niches that contributed to both human health and disease processes. In recent years, the search for an etiology and modifiable risk factors in infertility has turned to the human microbiome as well. Changes in the human gut microbiome have been associated with changes in systemic sex hormones and spermatogenesis. Certain microbial species are associated with higher levels of oxidative stress, which may contribute to an environment higher in oxidative reactive potential. Studies have demonstrated a link between increased oxidative reactive potential and abnormal semen parameters in infertile men. It has also been hypothesized that antioxidant probiotics may be able to correct an imbalance in the oxidative environment and improve male fertility, with promising results in small studies. Further, the sexual partner's microbiome may play a role as well; studies have demonstrated an overlap in the genitourinary microbiomes in sexually active couples that become more similar after intercourse. While the potential applications of the microbiome to male fertility is exciting, there is a need for larger studies with uniform microbial sequencing procedures to further expand this topic.

Characterization of the semen, gut, and urine microbiota in patients with different semen abnormalities

Introduction

Semen quality is decreasing worldwide, leading to increased male infertility. This study analyzed the microbiota of the gut, semen, and urine in individuals with semen abnormalities to identify potential probiotics and pathogenic bacteria that affect semen parameters and help develop new methods for the diagnosis and treatment of patients with semen abnormalities.

Methods

We recruited 12 individuals with normal semen parameters (control group), 12 with asthenospermia but no semen hyperviscosity (Group_1), 6 with oligospermia (Group_2), 9 with severe oligospermia or azoospermia (Group_3), and 14 with semen hyperviscosity only (Group_4). The semen, gut, and urine microbiota were examined by analyzing the 16S ribosomal RNA gene sequence using next-generation sequencing.

Results

The gut microbes were clustered into the highest number of operational taxonomic units, followed by urine and semen. Furthermore, the α-diversity of gut microbes was highest and significantly different from that of urine and semen microbiota. The microbiota of the gut, urine, and semen were all significantly different from each other in terms of β-diversity. The gut abundance of Collinsella was significantly reduced in groups 1, 3, and 4. Furthermore, the gut abundance of Bifidobacterium and Blautia was significantly decreased in Group_1, while that of Bacteroides was significantly increased in Group_3. The abundance of Staphylococcus was significantly increased in the semen of groups 1 and 4. Finally, Lactobacillus abundance was significantly reduced in the urine of groups 2 and 4.

Discussion

This study comprehensively describes the differences in intestinal and genitourinary tract microbiota between healthy individuals and those with abnormal semen parameters. Furthermore, our study identified Collinsella, Bifidobacterium, Blautia, and Lactobacillus as potential probiotics. Finally, the study identified Bacteroides in the gut and Staphylococcus in semen as potential pathogenic bacteria. Our study lays the foundation of a new approach to the diagnosis and treatment of male infertility.

Moringa oleifera leaf ethanolic extract benefits cashmere goat semen quality via improving rumen microbiota and metabolome

Background

Artificial insemination (AI) is an effective reproductive technique to improve the performance of cashmere goats and prevent the spread of diseases, and the quality of the semen determines the success of AI. The potential of Moringa oleifera leaf powder (MOLP) and Moringa oleifera leaf ethanolic extract (MOLE) to improve semen quality has been reported, but the underlying mechanisms remain unclear. For the purpose, 18 mature male cashmere goats were randomly assigned into three groups: the control (CON), MOLP, and MOLE groups. The CON group received distilled water orally; the MOLP group was orally treated with 200 mg/kg body weight (BW) MOLP; and the MOLE group was orally treated with 40 mg/kg BW MOLE.

Results

Results showed that MOLE contained long-chain fatty acids and flavonoids. Treatment with MOLP and MOLE increased the activities of the serum catalase, superoxide dismutase, and glutathione peroxidase (P < 0.05), enhanced the total antioxidant capacity (P < 0.05), and reduced the serum malondialdehyde level (P < 0.05). At the same time, MOLE increased the contents of serum gonadotropin releasing hormone and testosterone (P < 0.05). Moreover, MOLE significantly increased sperm concentration, motility, and viability (P < 0.05). Meanwhile, MOLE raised the Chao1 index (P < 0.05) and altered the composition of the rumen microbiota; it also raised the relative abundance of Treponema (P < 0.05) and Fibrobacter (P < 0.05) and reduced the relative abundance of Prevotella (P < 0.1). Correlation analysis revealed the genus Prevotella was significantly negatively correlated with sperm concentration, as well as sperm motility and viability. Furthermore, MOLE significantly increased the rumen levels of the steroid hormones testosterone and dehydroepiandrosterone (P < 0.05), as well as the polyunsaturated fatty acids (PUFAs) alpha-Linolenic acid, gamma-Linolenic acid, docosapentaenoic acid, and 9-S-Hydroperoxylinoleicacid (P < 0.05).

Conclusions

Oral MOLE supplementation can improve semen quality by increasing the antioxidant capacity and altering the rumen microbiota and metabolites of cashmere goats. Moreover, the MOLP supplementation could enhance the antioxidant capacity of cashmere goats.