The Association between Mortality and Male Infertility: Systematic Review and Meta-analysis

Male infertility risk and plasma lipidome: a Mendelian randomization study

Background

In recent years, the decline in sperm quality in men has become a global trend. There is a close relationship between sperm quality and pregnancy outcome. There is a large body of literature supporting the role of plasma lipidome in male infertility, while the complex mechanisms between them and male infertility are still less clear. Systematic study of the causal relationship between plasma lipidome and MI can help to provide new therapeutic ideas and targets for male infertility.

Methods

In this study, we used a two-sample Mendelian randomization analysis based on Genome-wide association studies pooled data of 179 causal relationships between plasma lipidome and male infertility. We used employed the inverse variance weighted method as the main analysis to assess causality between exposure and outcome, in addition to MR-Egger, Weighted median as complementary methods, and tests for multiplicity and heterogeneity.

Results

We identified 13 plasma lipidome comprising 4 types of plasma lipidome that were associated with male infertility. Among these, 9 plasma lipidome were found to be protective factors, while 4 were risk factors. Notably, the largest proportion of these plasma lipidome were triglyceride types, with Sphingomyelin (d40:1) exhibiting the strongest association with male infertility.

Conclusion

These findings contribute to the current better understanding of male infertility and provide new perspectives on the underlying etiology of male infertility as well as prevention and treatment strategies. In addition, clinical trial validation is needed to assess the potential of these plasma lipidome as biomarkers.

Male Infertility: New Developments, Current Challenges, and Future Directions

There have been many significant scientific advances in the diagnostics and treatment modalities in the field of male infertility in recent decades. Examples of these include assisted reproductive technologies, sperm selection techniques for intracytoplasmic sperm injection, surgical procedures for sperm retrieval, and novel tests of sperm function. However, there is certainly a need for new developments in this field. In this review, we discuss advances in the management of male infertility, such as seminal oxidative stress testing, sperm DNA fragmentation testing, genetic and epigenetic tests, genetic manipulations, artificial intelligence, personalized medicine, and telemedicine. The role of the reproductive urologist will continue to expand in future years to address different topzics related to diverse questions and controversies of pathophysiology, diagnosis, and therapy of male infertility, training researchers and physicians in medical and scientific research in reproductive urology/andrology, and further development of andrology as an independent specialty.

Interplay between male gonadal function and overall male health

The process-of-male reproduction is intricate, and various medical conditions-have the potential to disrupt spermatogenesis. Moreover, infertility in males can serve as an indicator of-potential future health issue. Numerous conditions with systemic implications have been identified, encompassing genetic factors (such as Klinefelter Syndrome), obesity, psychological stress, environmental factors, and others. Consequently, infertility assessment-presents an opportunity for comprehensive health counseling, extending-beyond discussions about reproductive goals. Furthermore, male infertility has been suggested as a harbinger of future health problems, as poor semen quality and a diagnosis of-male infertility are associated with an increased risk of hypogonadism, cardiometabolic disorders, cancer, and even mortality. This review explores the existing-literature on the relationship between systemic illnesses and male fertility, impacting both clinical-outcomes and semen parameters. The majority of the literature analyzed, which compared gonadal function with genetic, chronic, infectious or tumoral diseases, confirm the association between overall male health and infertility.

Frequency, morbidity and equity - the case for increased research on male fertility

Currently, most men with infertility cannot be given an aetiology, which reflects a lack of knowledge around gamete production and how it is affected by genetics and the environment. A failure to recognize the burden of male infertility and its potential as a biomarker for systemic illness exists. The absence of such knowledge results in patients generally being treated as a uniform group, for whom the strategy is to bypass the causality using medically assisted reproduction (MAR) techniques. In doing so, opportunities to prevent co-morbidity are missed and the burden of MAR is shifted to the woman. To advance understanding of men's reproductive health, longitudinal and multi-national centres for data and sample collection are essential. Such programmes must enable an integrated view of the consequences of genetics, epigenetics and environmental factors on fertility and offspring health. Definition and possible amelioration of the consequences of MAR for conceived children are needed. Inherent in this statement is the necessity to promote fertility restoration and/or use the least invasive MAR strategy available. To achieve this aim, protocols must be rigorously tested and the move towards personalized medicine encouraged. Equally, education of the public, governments and clinicians on the frequency and consequences of infertility is needed. Health options, including male contraceptives, must be expanded, and the opportunities encompassed in such investment understood. The pressing questions related to male reproductive health, spanning the spectrum of andrology are identified in the Expert Recommendation.

Deteriorating Semen Quality: The Role of the Environment

Since the end of the last century, several reports have suggested that semen quality is declining, especially in Western countries. Furthermore, cross-sectional studies using similar protocols have suggested regional differences in semen quality of young and fertile men. Reasons for these regional differences and local adverse trends in semen quality are unknown, but environmental factors are suspected to have a role. Besides adulthood environmental exposures, those occurring during testicular development may also affect semen quality. Longitudinal follow-up studies and mixture risk analyses are needed to study the effect of fetal, childhood, and adult life environment on semen quality.

Kidney function impairment in men with primary infertility: A case-control analysis

BACKGROUND

Infertile men have a worse overall health status than their fertile counterparts.

OBJECTIVE

We aimed to (1) compare kidney function in men presenting for primary couple's infertility with that of fertile men and (2) assess kidney function impairment toward sperm quality in infertile men.

MATERIALS AND METHODS

In this case-control study, 387 consecutive white-European infertile men were matched by age with 134 same-ethnicity fertile men. Complete clinical and laboratory data were available for each patient. The Chronic Kidney Disease Epidemiology Collaboration function was used for estimated glomerular filtration rate calculation. Kidney functional impairment was defined as an estimated glomerular filtration rate <90 mL/min per 1.73 m2 , according to the Kidney Disease Improving Global Outcomes criteria. Multivariable logistic regression analysis was used to (1) assess the association between kidney function impairment and infertility status and (2) investigate the association between kidney function and semen analysis abnormalities in infertile men.

RESULTS

After matching, 34 (8.8%) infertile men depicted at least a mild unknown impairment of kidney function compared to only four (3%) fertile men, with four (3%) of the infertile presenting with an overt kidney function impairment (estimated glomerular filtration rate <60 mL/min per 1.73 m2 ). There were no differences in terms of age, body mass index and rate of comorbidities between the two groups (all p > 0.05). After adjusting for major confounders, infertility status was associated with a higher risk of reduced estimated glomerular filtration rate (odds ratio 3.20; 95% confidence interval 1.21-5.2; p = 0.002). Conversely, estimated glomerular filtration rate was not associated with sperm abnormalities in infertile men.

CONCLUSIONS

Mild kidney function impairment was found in 9% of asymptomatic and unaware men presenting for primary couple's infertility investigation. This novel finding corroborates growing data on a significant association of male infertility with a poorer overall male health status and the need for tailored preventive strategies.

Male infertility

Clinical infertility is the inability of a couple to conceive after 12 months of trying. Male factors are estimated to contribute to 30-50% of cases of infertility. Infertility or reduced fertility can result from testicular dysfunction, endocrinopathies, lifestyle factors (such as tobacco and obesity), congenital anatomical factors, gonadotoxic exposures and ageing, among others. The evaluation of male infertility includes detailed history taking, focused physical examination and selective laboratory testing, including semen analysis. Treatments include lifestyle optimization, empirical or targeted medical therapy as well as surgical therapies that lead to measurable improvement in fertility. Although male infertility is recognized as a disease with effects on quality of life for both members of the infertile couple, fewer data exist on specific quantification and impact compared with other health-related conditions.

Reproduction as a window for health in men

Male factor infertility is widely considered a harbinger for a man's general health. Failure of reproduction often accompanies other underlying processes, with growing evidence suggesting that a diagnosis of infertility increases the likelihood of developing future cardiac, metabolic, and oncologic diseases. The goal of this review is to provide a comprehensive overview of the research on male fertility as a marker for current and future health. A multidisciplinary approach is essential, and there is growing consensus that the male fertility evaluation offers an opportunity to better men's wellness beyond their immediate reproductive ambitions.

The Renaissance of Male Infertility Management in the Golden Age of Andrology

Infertility affects nearly 186 million people worldwide and the male partner is the cause in about half of the cases. Meta-regression data indicate an unexplained decline in sperm concentration and total sperm count over the last four decades, with an increasing prevalence of male infertility. This suggests an urgent need to implement further basic and clinical research in Andrology. Andrology developed as a branch of urology, gynecology, endocrinology, and, dermatology. The first scientific journal devoted to andrological sciences was founded in 1969. Since then, despite great advancements, andrology has encountered several obstacles in its growth. In fact, for cultural reasons, the male partner has often been neglected in the diagnostic and therapeutic workup of the infertile couple. Furthermore, the development of assisted reproductive techniques (ART) has driven a strong impression that this biotechnology can overcome all forms of infertility, with a common belief that having a spermatozoon from a male partner (a sort of sperm donor) is all that is needed to achieve pregnancy. However, clinical practice has shown that the quality of the male gamete is important for a successful ART outcome. Furthermore, the safety of ART has been questioned because of the high prevalence of comorbidities in the offspring of ART conceptions compared to spontaneous conceptions. These issues have paved the way for more research and a greater understanding of the mechanisms of spermatogenesis and male infertility. Consequently, numerous discoveries have been made in the field of andrology, ranging from genetics to several "omics" technologies, oxidative stress and sperm DNA fragmentation, the sixth edition of the WHO manual, artificial intelligence, management of azoospermia, fertility in cancers survivors, artificial testis, 3D printing, gene engineering, stem cells therapy for spermatogenesis, and reconstructive microsurgery and seminal microbiome. Nevertheless, as many cases of male infertility remain idiopathic, further studies are required to improve the clinical management of infertile males. A multidisciplinary strategy involving both clinicians and scientists in basic, translational, and clinical research is the core principle that will allow andrology to overcome its limits and reach further goals. This state-of-the-art article aims to present a historical review of andrology, and, particularly, male infertility, from its "Middle Ages" to its "Renaissance", a golden age of andrology.

Counseling for the man with severe male infertility

PURPOSE OF REVIEW

This review summarize the proper counseling for men with severe male factor infertility.

RECENT FINDINGS

Men who are experiencing infertility should have a semen analysis, the results of which may imply additional investigations, including genetic and hormonal. Moreover, possible modifiable factors that may harm men's reproductive health should be carefully evaluated. Finally, different treatment options are available.

SUMMARY

Approximately 15% of couples struggle with infertility. Complete evaluations of both men and women are required to determine the etiology of infertility and determine appropriate treatment.

Translational Bioinformatics for Human Reproductive Biology Research: Examples, Opportunities and Challenges for a Future Reproductive Medicine

Since 1978, with the first IVF (in vitro fertilization) baby birth in Manchester (England), more than eight million IVF babies have been born throughout the world, and many new techniques and discoveries have emerged in reproductive medicine. To summarize the modern technology and progress in reproductive medicine, all scientific papers related to reproductive medicine, especially papers related to reproductive translational medicine, were fully searched, manually curated and reviewed. Results indicated whether male reproductive medicine or female reproductive medicine all have made significant progress, and their markers have experienced the progress from karyotype analysis to single-cell omics. However, due to the lack of comprehensive databases, especially databases collecting risk exposures, disease markers and models, prevention drugs and effective treatment methods, the application of the latest precision medicine technologies and methods in reproductive medicine is limited.

Bibliometric analysis and visualization of literature on assisted reproduction technology

Introduction

Assisted reproductive technology (ART) is a method that uses various techniques to process sperm or ova. Assisted reproductive technology involves removing ova from a woman's ovaries, combining them with sperm in the laboratory, and returning them to the woman's body or donating them to another woman.

Methods

Based on the web of science core collection database, we firstly analyzed the quantity and quality of publications in the field of ART, secondly profiled the publishing groups in terms of country, institution, author's publication and cooperation network, and finally sorted out and summarized the hot topics of research.

Results

In total, 6,288 articles on ART were published between 2001 and 2022 in 1,013 journals. Most of these published articles represent the global research status, potential hotspots and future research directions. Publications and citations of research on assisted reproductive technology have steadily increased over the past few decades. Academic institutions in Europe and the United States have been leading in assisted reproductive technology research. The countries, institutions, journals, and authors with the most published articles were the United States (1864), Harvard Univ (108), Fertility and Sterility (819), and Stern, Judy E. (64). The most commonly used keywords are Assisted reproductive technology (3303) and in-vitro Fertilization (2139), Ivf (1140), Pregnancy (1140), Women (769), Intracytoplasmic Sperm injection (644), In Fertilization (632), Risk (545), and Outcome (423).

Conclusion

Frozen embryo transfer, intracytoplasmic sperm injection, and in vitro fertilization are the main research topics and hotspots in the field of assisted reproductive technology.

The impact of different WHO reference criteria for semen analysis in clinical practice: who will benefit from the new 2021 thresholds for normal semen parameters?

Background

In 2021, the World Health Organization (WHO) has provided the latest update on processing and evaluating semen analysis.

Objectives

To assess (i) the rate of discordance in semen parameters categorization across three different WHO reference values (namely WHO21, 2010 and 1999) and (ii) the clinical differences among discordant semen analyses from a cohort of primary infertile men.

Materials and methods

Data from 788 infertile men were analyzed. Semen parameters were interpreted based on WHO21, WHO10, and WHO99 reference criteria. Pregnancy outcomes with assisted reproductive techniques (ART) were available for 110 (14%) patients. Descriptive statistics was applied to describe potential differences among the three consecutive WHO references criteria.

Results

Semen parameters categorizations were highly different across the three groups (p < 0.001). Of all, 271 (42.2%) patients had normal semen parameters according to WHO10 but were pathologic when considered with WHO21 reference criteria (namely, men with increased semen abnormalities). Infertile men with increased semen abnormalities had lower testicular volume (p < 0.001) but higher FSH (p < 0.01) and LH (p < 0.001) values than those who had no change in terms of semen parameters categorization. Negative ART outcomes were more frequently reported in men with worsening semen parameters compared with those with confirmed semen parameters at WHO21 versus WHO10 (26.8% vs. 49%, p = 0.03). Conversely, infertile men with worsening semen parameters at WHO21 versus WHO99 were similar in terms of clinical and hormonal characteristics compared with those with the same rate of semen abnormalities.

Conclusions

One out of three infertile men showed worsened semen categorization according to WHO21 versus WHO10. Infertile men with worsening of semen parameters had worse clinical and hormonal characteristics than those with confirmed numbers of semen abnormalities. Moreover, live birth rates were lower in men with worsening semen abnormalities as for WHO21.

Triglycerides/Glucose Index is Associated with Sperm Parameters and Sperm DNA Fragmentation in Primary Infertile Men: A Cross-Sectional Study

Study question: we aimed to investigate the relationship between the tyg index and both semen and hormonal characteristics in a cohort of primary infertile men. Summary answer: almost one in two primary infertile men presented with a triglycerides/glucose index (tyg) suggestive of insulin resistance (ir). overall, patients with tyg suggestive of ir showed worse clinical, hormonal, and semen parameters. What is already known: male factor infertility (MFI) is often associated with metabolic disorders such as diabetes mellitus and metabolic syndrome, where insulin resistance (IR) plays a relevant pathological role. Recently, TyG has been suggested as a user-friendly IR marker. Study Design: serum hormones and the sperm DNA fragmentation index (SDF) were measured in every patient. The semen analysis was based on 2010 WHO reference criteria. Glucose and insulin levels were measured for every man after a 12-h overnight fast, and the homeostatic model assessment index (HOMA-IR) was then calculated and categorized using a 2.6 threshold. Similarly, fasting glucose and triglycerides levels were measured and the TyG index was calculated and categorized using an 8.1 threshold. Descriptive statistics and logistic regression models tested the association between the TyG and semen and hormonal characteristics. Participants: complete demographic, clinical, and laboratory data from 726 consecutive white European primary infertile men were considered for this analysis. Main results and the role of chance: the median (IQR) age was 39 (35–43) years. A TyG and HOMA suggestive for IR was found in 339 (46.6%) and 154 (21.2%) men, respectively. During the Spearman’s test, the TyG index was highly correlated with HOMA-IR (rho = 0.46, p < 0.001). Compared to men with a normal TyG, men with TyG > 8.1 were older, had greater BMI and CCI scores, and lower total testosterone and sperm concentration, but higher DFI, and presented a greater proportion of NOA (all p < 0.01). The multivariable logistic regression analysis showed that men with TyG > 8.1 were at higher risk of SDF > 30 (OR 1.92 (CI: 1.2–2.9)) and NOA (OR 1.78 (CI: 1.1–2.8)). Wider implications of the findings: the Tyng index may act as a reliable marker of IR in the clinical work-up of primary infertile men in real-life settings.

The sixth edition of the WHO manual on semen examination: ensuring quality and standardization in basic examination of human ejaculates

A basic semen investigation has established principles that are necessary for ascertaining reliable and internationally comparable results. Although these principles have been present in the WHO manual since its inception, the baseline issue across most published studies and practice in reproductive medicine (in which the male is considered) is repetitive failure to adhere to these principles, thereby leading to relevant comparable data and accuracy. To address this failure, the sixth edition of the WHO manual includes revised basic methods, and a complementary formal standard of the International Standards Organization (ISO23162:2021) for basic semen examination has been published. Perhaps the most significant change in the sixth edition is the reintroduction of the four-category distinction of sperm motility, which causes additional work for laboratories in changing reporting parameters but is clinically important. Another essential change is the widened focus from mainly a prognostic tool for medically assisted reproduction to additionally raising awareness of semen examination as a measure of male reproductive functions and general male health.

Male fertility as a marker for health

Male reproduction is a complex biological process, and male factor infertility is increasingly recognized as a biomarker for overall male health. Emerging data suggest associations between male reproduction and medical disease (genetic, infectious, chronic comorbid conditions), psychological disease, environmental exposures, dietary habits, medications and substances of abuse, and even socioeconomic factors. There is also evidence that a diagnosis of male fertility is associated with future disease risk including cancer, metabolic disease and mortality. As such, there is a growing view that the male fertility evaluation is an opportunity to improve a man's health beyond his immediate reproductive goals, and also highlights the necessity of a multidisciplinary approach.

Meiotic Cohesin and Variants Associated With Human Reproductive Aging and Disease

Successful human reproduction relies on the well-orchestrated development of competent gametes through the process of meiosis. The loading of cohesin, a multi-protein complex, is a key event in the initiation of mammalian meiosis. Establishment of sister chromatid cohesion via cohesin rings is essential for ensuring homologous recombination-mediated DNA repair and future proper chromosome segregation. Cohesin proteins loaded during female fetal life are not replenished over time, and therefore are a potential etiology of age-related aneuploidy in oocytes resulting in decreased fecundity and increased infertility and miscarriage rates with advancing maternal age. Herein, we provide a brief overview of meiotic cohesin and summarize the human genetic studies which have identified genetic variants of cohesin proteins and the associated reproductive phenotypes including primary ovarian insufficiency, trisomy in offspring, and non-obstructive azoospermia. The association of cohesion defects with cancer predisposition and potential impact on aging are also described. Expansion of genetic testing within clinical medicine, with a focus on cohesin protein-related genes, may provide additional insight to previously unknown etiologies of disorders contributing to gamete exhaustion in females, and infertility and reproductive aging in both men and women.