Beneficial effect of residential greenness on sperm quality and the role of air pollution: A multicenter population-based study

BACKGROUND

Poor sperm quality is a major cause of male infertility. However, evidence remains scarce on how greenness affects male sperm quality.

OBJECTIVES

To assess the associations of residential greenness with male sperm quality and the modification effect of air pollution exposure on the relationship.

METHODS

A total of 78,742 samples from 33,184 sperm donors from 6 regions across China during 2014-2020 were included and analyzed. Individual residential greenness exposures of study subjects were estimated using the Normalized Difference Vegetation Index (NDVI) during the entire (0-90 lag days) and two key stages (0-37, and 34-77 lag days) of sperm development. Contemporaneous personal exposure levels to air pollutants were estimated using a spatio-temporal deep learning method. Linear mixed models were employed to assess the impact of greenspace in relation to sperm quality. The modification effect of air pollution on the greenspace-sperm quality relationship was also estimated.

RESULTS

Per IQR increment in NDVI exposure throughout spermatogenesis were statistically associated with increasing sperm count by 0.0122 (95 % CI: 0.0007, 0.0237), progressive motility by 0.0162 (95 % CI: 0.0045, 0.0280), and total motility by 0.0147 (95 % CI: 0.0014, 0.0281), respectively. Similar results were observed when the model added air pollutants (PM1, PM2.5 or O3) for adjustment. Additionally, specific air pollutants, including PM1, PM2.5, and O3, were found to modify this association. Notably, the protective effects of greenness exposure were more pronounced at higher concentrations of PM1 and PM2.5 and lower concentrations of O3 (all Pinteraction < 0.05). Statistically significant positive effects of NDVI were observed on sperm motility in early spermatogenesis and sperm count in late spermatogenesis.

CONCLUSIONS

Exposure to residential greenness may have beneficial effects on sperm quality and air pollution modifies their relationship. These findings highlight the importance of adopting adaptable urban greenspace planning and policies to safeguard male fertility against environmental factors.

Impact of heat waves on semen quality: A retrospective study in Argentina between 2005 and 2023

Heat waves, defined as periods with daily temperatures surpassing the historical average for a specific region, have become more frequent worldwide in recent years. Previous studies have reported a negative association between temperature and semen quality, but the focus has mainly been on Asian and European populations. The study included 54,926 men (18-60 years) undergoing routine semen analysis between 2005 and 2023 at CEUSA-LAEH andrology unit, in Buenos Aires, Argentina. Hourly temperature readings were provided by the Servicio Meteorológico Nacional. R programming (R Studio v2022.07.2) was used to define heat waves, calculate key characteristics, visualize results, and perform statistical tests at the IBYME laboratory. During the period studied, a total of 124 days had heat waves (defined after at least 3 consecutive days with 32.3 °C and 22 °C). Men exposed to heat waves during spermatogenesis exhibited lower sperm number (concentration and count; P < 0.0001) and decreased normal morphology (percentage of normal sperm and normal motile count; P < 0.05) compared to those not exposed. These differences were most pronounced between semen samples from years with several heat waves (2013, 2023) and none (2005, 2007, 2016), displaying 4-5 times higher fold changes (P < 0.05). Further analysis employing multiple regression revealed a significantly negative association between semen quality and heat wave length, suggesting that a prolonged exposure may be more detrimental than an acute exposure. Subsequent analysis focusing on prolonged exposure (≥6-days heat wave) during spermatogenesis revealed a negative (P < 0.05) association between early exposure (spermatocytogenesis: 64-90 days prior semen collection) and semen quality. This study underscores the negative association between early exposure to heat waves during sperm development and semen quality, raising concerns about its possible association with the worldwide declining male fertility. A comprehensive collaborative approach is crucial, involving global governmental policies, sustainable practices, and coordinated efforts across scientific, healthcare, and policy domains.

Genotoxicity and cytotoxicity in male reproductive cells caused by sediment pollutants

In recent years, mounting evidence has highlighted a global decline in male semen quality, paralleling an increase in male infertility problems. Such developments in the male reproductive system are likely due to a range of environmental factors, which could negatively affect the outcomes of pregnancy, reproductive health, and the well-being of fetuses. Different environmental contaminants ultimately accumulate in riverbed sediments due to gravity, so these sediments are frequently considered hotspots for pollutants. Therefore, understanding the detrimental effects of river sediment pollution on human reproductive health is crucial. This study indicates male germ cells' high vulnerability to environmental contaminants. There is a strong positive correlation between the concentration of complex accumulated pollutants from human activities and the reproductive toxicity observed in human testicular embryonic cell lines NCCIT and NTERA-2. This toxicity is characterized by increased levels of reactive oxygen species, disruption of critical cellular functions, genotoxic impacts, and the induction of cell apoptosis. This research marks a significant step in providing in vitro evidence of the damaging effects of environmental pollutants on the human male germline.

Paternal exposures to endocrine-disrupting chemicals induce intergenerational epigenetic influences on offspring: A review

Endocrine-disrupting chemicals (EDCs) are ubiquitous in ecological environments and have become a great issue of public health concern since the 1990 s. There is a deep scientific understanding of the toxicity of EDCs. However, recent studies have found that the abnormal physiological functions of the parents caused by EDCs could be transmitted to their unexposed offspring, leading to intergenerational toxicity. We questioned whether sustained epigenetic changes occur through the male germline. In this review, we (1) systematically searched the available research on the intergenerational impacts of EDCs in aquatic and mammal organisms, including 42 articles, (2) summarized the intergenerational genetic effects, such as decreased offspring survival, abnormal reproductive dysfunction, metabolic disorders, and behavioral abnormalities, (3) summarized the mechanisms of intergenerational toxicity through paternal interactions, and (4) propose suggestions on future research directions to develop a deeper understanding of the ecological risk of EDCs.

What is driving the global decline of human fertility? Need for a multidisciplinary approach to the underlying mechanisms

An intense period of human population expansion over the past 250 years is about to cease. Total fertility rates are falling dramatically all over the world such that highly industrialized nations, including China and the tiger economies of SE Asia, will see their populations decline significantly in the coming decades. The socioeconomic, geopolitical and environmental ramifications of this change are considerable and invite a multidisciplinary consideration of the underlying mechanisms. In the short-term, socioeconomic factors, particularly urbanization and delayed childbearing are powerful drivers of reduced fertility. In parallel, lifestyle factors such as obesity and the presence of numerous reproductive toxicants in the environment, including air-borne pollutants, nanoplastics and electromagnetic radiation, are seriously compromising reproductive health. In the longer term, it is hypothesized that the reduction in family size that accompanies the demographic transition will decrease selection pressure on high fertility genes leading to a progressive loss of human fecundity. Paradoxically, the uptake of assisted reproductive technologies at scale, may also contribute to such fecundity loss by encouraging the retention of poor fertility genotypes within the population. Since the decline in fertility rate that accompanies the demographic transition appears to be ubiquitous, the public health implications for our species are potentially devastating.

Multivariate analyses on male factors and construction of a nomogram for predicting low in vitro fertilization rate

Low fertilization rate (LFR) and total fertilization failure (TFF) are often encountered in routine in vitro fertilization (IVF) procedure. To solve this problem, multivariate analyses on the relationship between male factors and in vitro fertilization rate were performed, and a nomogram for prediction of LFR was constructed. This retrospective study contained 2011 couples who received IVF treatment from January 2017 to December 2021. Man factors and in vitro fertilization rate were collected. Among these couples, 1347 cases had in vitro fertilization rates ≥30 % (control group), and 664 cases had in vitro fertilization rates <30 % (LFR group). Univariate analyses of male factors found that between the two groups there were significant differences (p < 0.05) in sperm progressive motility (SPR), sperm concentration (SC), total sperm number, normal sperm morphology rate (NSMR), DNA fragmentation index (DFI), sperm acrosin activity (SAA) and the clinical diagnosis of primary or secondary infertility. Multivariate logistic regression analyses showed that SPR, SAA, and SC were independent risk factors for LFR. An algorithm and a correspondent nomogram for predicting high LFR risk were constructed using data from the training cohort. The LFR nomogram exhibited an excellent discrimination power and a high fitting degree in both the training cohort (AUC = 0.90, 95 % CI: 0.88-0.92), (H-L: x2 = 5.43, p = 0.71) and validation cohort (AUC = 0.89, 95 % CI:0.87-0.92), (H-L: x2 = 7.85, p = 0.45), respectively. The decision curve analysis (DCA) demonstrated a high efficiency of the LFR nomogram for clinical utility. SPR, SAA, and SC are independent risk factors for LFR. The LFR nomogram established based on these factors could be a useful tool to predict high risk of LFR, and patients with high risk of LFR can be guided to direct ICSI procedure. Clinical application of the LFR nomogram may increase the in vitro fertilization rate by facilitating the decision making in IVF service.

Early or late menarche is associated with reduced fecundability in the Norwegian Mother, Father and Child Cohort Study

STUDY QUESTION

Is age at menarche associated with fecundability?

SUMMARY ANSWER

Both early (<11 years) and late (>15 years) menarche is associated with decreased fecundability.

WHAT IS KNOWN ALREADY

Previous studies on age at menarche and fecundability have been inconclusive. Women with early or late menarche are at increased risks of gynaecological and autoimmune diseases that may affect their ability to conceive.

STUDY DESIGN, SIZE, DURATION

We conducted a retrospective cohort study including 67 613 pregnant women, participating in the Norwegian Mother, Father and Child Cohort Study between 1999 and 2008, with self-reported information on age at menarche and time to pregnancy. We included planned pregnancies that were conceived either naturally or with the help of assisted reproductive technologies.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We calculated fecundability ratios (FRs) with 95% CIs representing the cycle-specific probability of conception by categories of age at menarche. FRs were adjusted for participants' pre-pregnancy body mass index, highest completed or ongoing education level, and age at initiation of trying to conceive.

MAIN RESULTS AND THE ROLE OF CHANCE

We observed a 7% lower probability of conceiving during any given menstrual cycle up to 12 cycles in women with early or late menarche. Among women with menarche >15 years, the adjusted FR was 0.93 (95% CI: 0.90-0.97), and among women with menarche <11 years, the adjusted FR was 0.93 (95% CI: 0.89-0.99), when compared to women with menarche between 12 and 14 years.

LIMITATIONS, REASONS FOR CAUTION

The study-population consisted of women pregnant in their second trimester, excluding those with persistent infertility. Recall of age at menarche and time to pregnancy may be inaccurate.

WIDER IMPLICATIONS OF THE FINDINGS

Both early (<11 years) and late (>15 years) menarche was associated with decreased fecundability. Women experiencing early menarche or late menarche may be counselled accordingly.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by the Norwegian Institute of Public Health, Oslo, Norway, and by Telemark Hospital Trust, Porsgrunn, Norway and was partly supported by the Research Council of Norway through its centres of excellence funding scheme (project number 262700) and the Research Council of Norway (project no. 320656). The project was co-funded by the European Union (ERC, BIOSFER, 101071773). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. M.C.M. has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement no. 947684). The authors report no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

PBA alleviates cadmium-induced mouse spermatogonia apoptosis by suppressing endoplasmic reticulum stress

OBJECTIVE

Endoplasmic reticulum (ER) stress mediates Cd-caused germ cell apoptosis in testis. The effects of 4-phenylbutyric acid (PBA), a classical chaperone, were investigated on Cd-induced apoptosis in mouse GC-1 spermatogonia cells.

METHODS

The cells were pretreated with PBA before Cd exposure. TUNEL and flow cytometry assays were applied to determine apoptosis. Some key biomarkers of ER stress were analyzed using RT-PCR and western blot.

RESULTS

as expected, the apoptotic cells exposed to Cd apparently increased. The mRNA and protein expression levels of GRP78 and ATF6α, were elevated in the Cd groups. Additional experiments displayed that Cd notably increased IRE1α and JNK phosphorylation, and upregulated XBP-1 mRNA and protein expression. Moreover, p-eIF2α and CHOP expressions were clearly elevated in the Cd groups. Interestingly, PBA almost completely inhibited ER stress and protected spermatogonia against apoptosis induced by Cd.

CONCLUSION

PBA alleviated Cd-induced ER stress and spermatogonia apoptosis, and may have the therapeutic role in Cd-induced male reproductive toxicity.

Taste receptor type 1 member 3 regulates Western diet-induced male infertility

Western diet (WD), characterized by a high intake of fats and sugary drinks, is a risk factor for male reproductive impairment. However, the molecular mechanisms underlying this remain unclear. Taste receptor type 1 member 3 (TAS1R3), activated by ligands of WD, is highly expressed in extra-oral tissues, particularly in the testes. Here, we investigated to determine the effects of WD intake on male reproduction and whether TAS1R3 mediates WD-induced impairment in male reproduction. Male C57BL/6 J wild-type (WT) and Tas1r3 knockout (KO) mice were fed either a normal diet and plain water (ND) or a 60 % high-fat-diet and 30 % (w/v) sucrose water (WD) for 18 weeks (n = 7-9/group). Long-term WD consumption significantly impaired sperm count, motility and testicular morphology in WT mice with marked Tas1r3 overexpression, whereas Tas1r3 KO mice were protected from WD-induced reproductive impairment. Testicular transcriptome analysis revealed downregulated AMP-activated protein kinase (AMPK) signaling and significantly elevated AMPK-targeted nuclear receptor 4A1 (Nr4a1) expression in WD-fed Tas1r3 KO mice. In vitro studies further validated that Tas1r3 knockdown in Leydig cells prevented the suppression of Nr4a1 and downstream steroidogenic genes (Star, Cyp11a1, Cyp17a1, and Hsd3b1) caused by high glucose, fructose, and palmitic acid levels, and maintained the levels of testosterone. Additionally, we analyzed the public human dataset to assess the clinical implications of our findings and confirmed a significant association between TAS1R3 and male-infertility-related diseases. Our findings suggest that TAS1R3 regulates WD-induced male reproductive impairment via the AMPK/NR4A1 signaling and can be a novel therapeutic target for male infertility.

Effects of temperature anomaly on sperm quality: A multi-center study of 33,234 men

Backgrounds

Global fertility rates continue to decline and sperm quality is a prime factor affecting male fertility. Both extreme cold and heat have been demonstrated to be associated with decreased sperm quality, but no epidemiological studies have considered human adaptation to long-term temperature. Our aim was to conduct a multi-center retrospective cohort study to investigate exposure-response relationship between temperature anomaly (TA) that deviate from long-term climate patterns and sperm quality.

Methods

A total of 78,952 semen samples measured in 33,234 donors from 6 provincial human sperm banks in China were collected. This study considered heat and cold acclimatization to prolonged exposure in humans and explored the exposure-response relationship between TAs and sperm quality parameters (sperm concentrations, sperm count, progressive motility, progressive sperm count, total motility and total motile sperm count) during the hot and cold seasons, respectively. Linear mixed models and generalized linear models were built separately for specific centers to pool in a meta-analysis to obtain the pooled effect of TA on sperm quality, considering repeated measurements data structure and spatial heterogeneity.

Results

We identified an inverted U-shaped exposure-response relationship between TA and sperm quality during the hot season. Significant negative effect of anomalous cold on sperm quality during the hot season was found after additional adjustment for Body mass index, marital status and childbearing history. The heat-related TA in hot season was significantly negatively associated with sperm concentration, progressive sperm count and total motile sperm count (all P-values<0.05). After adjusting the relative humidity, the cold-related TA in cold season was negatively associated with the sperm total motility (P-values<0.05).

Conclusions

Our results suggest both heat-related and cold-related TAs are associated with decreased sperm quality. The findings highlight the importance of reducing exposure to anomalous temperatures to protect male fertility.

Exploration of Lactiplantibacillus plantarum P101 ameliorated the alcohol-induced testicular dysfunction based on metabolome analysis

The decline in male sperm quality caused by multiple factors has become a widespread concern. Alcohol excessive consumption is one of the factors that induce testicular dysfunction. Testicular dysfunction caused by alcohol abuse is related to oxidative stress and inflammation. Probiotics can ameliorate alcohol-induced testicular dysfunction. However, the specific mechanism is not explicit. This study aimed to elucidate the underlying mechanism by which Lactiplantibacillus plantarum P101 ameliorates the alcohol-induced testicular dysfunction. The model of alcohol-induced testicular dysfunction in C57B/6 male mice was established according to the National Institute on Alcohol Abuse and Alcoholism, and Lactiplantibacillus plantarum P101 supplementation was orally administered to mice during the experiment. The results showed that Lactiplantibacillus plantarum P101 promoted androgen production, reduced testis inflammation, and improved testis antioxidant capacity, thereby improving sperm quality and sperm motility and ultimately ameliorating alcohol-induced testicular disorder. Three key metabolite pathways and six key metabolites were identified by metabolome analysis.

Redox mechanisms of environmental toxicants on male reproductive function

Humans and wildlife, including domesticated animals, are exposed to a myriad of environmental contaminants that are derived from various human activities, including agricultural, household, cosmetic, pharmaceutical, and industrial products. Excessive exposure to pesticides, heavy metals, and phthalates consequently causes the overproduction of reactive oxygen species. The equilibrium between reactive oxygen species and the antioxidant system is preserved to maintain cellular redox homeostasis. Mitochondria play a key role in cellular function and cell survival. Mitochondria are vulnerable to damage that can be provoked by environmental exposures. Once the mitochondrial metabolism is damaged, it interferes with energy metabolism and eventually causes the overproduction of free radicals. Furthermore, it also perceives inflammation signals to generate an inflammatory response, which is involved in pathophysiological mechanisms. A depleted antioxidant system provokes oxidative stress that triggers inflammation and regulates epigenetic function and apoptotic events. Apart from that, these chemicals influence steroidogenesis, deteriorate sperm quality, and damage male reproductive organs. It is strongly believed that redox signaling molecules are the key regulators that mediate reproductive toxicity. This review article aims to spotlight the redox toxicology of environmental chemicals on male reproduction function and its fertility prognosis. Furthermore, we shed light on the influence of redox signaling and metabolism in modulating the response of environmental toxins to reproductive function. Additionally, we emphasize the supporting evidence from diverse cellular and animal studies.

Impact of stress on male fertility: role of gonadotropin inhibitory hormone

Studies have implicated oxidative stress-sensitive signaling in the pathogenesis of stress-induced male infertility. However, apart from oxidative stress, gonadotropin inhibitory hormone (GnIH) plays a major role. The present study provides a detailed review of the role of GnIH in stress-induced male infertility. Available evidence-based data revealed that GnIH enhances the release of corticosteroids by activating the hypothalamic-pituitary-adrenal axis. GnIH also mediates the inhibition of the conversion of thyroxine (T4) to triiodothyronine (T3) by suppressing the hypothalamic-pituitary-thyroidal axis. In addition, GnIH inhibits gonadotropin-releasing hormone (GnRH), thus suppressing the hypothalamic-pituitary-testicular axis, and by extension testosterone biosynthesis. More so, GnIH inhibits kisspeptin release. These events distort testicular histoarchitecture, impair testicular and adrenal steroidogenesis, lower spermatogenesis, and deteriorate sperm quality and function. In conclusion, GnIH, via multiple mechanisms, plays a key role in stress-induced male infertility. Suppression of GnIH under stressful conditions may thus be a beneficial prophylactic and/or therapeutic strategy.

The spermiogram and correlation of seminal fluid parameters in patient attending fertility centre in Lagos, South West Nigeria

BACKGROUND

The determinant of the spermiogram of semen varies in different populations based on several factors ranging, from age to the pathological state of an individual to environmental factors. The aim of the study is to determine the spermiogram of patients that attend fertility clinics in southwest Nigeria and the relationship between the parameters.

METHODOLOGY

This is a cross-sectional study that recruited two hundred and ninety seven (297) patients from two fertility centers in Lagos, Nigeria for the period of January 2021 to November 2022. The sperm samples were collected following WHO standards. The spermiogram was analyzed using an automated sperm analyzer and the descriptive and inference statistics of the study were carried out using R packages (R version 4.2.0).

RESULTS

The result showed the mean age of 43.12±6.95years with median age of 42years. The mean of sperm count and concentration were 114×106 sperm cells and 42×106 per mL with the mean volume of the semen produced by the patients was 2.69mL and average motility (progressive and non-progressive) of the sperm is 47%±19%, 42%±17% has normal morphology. The distributions of the observed variables (seminal fluid parameters) were different from normal distributions in the studied population, such that almost all of them are skewed to the right. The degree of relationship between the sperm parameter were very weak. Nevertheless, specifically, there is a negative correlation between age and sperm count, age and motility, age and volume, and a positive correlation between age and abnormal morphology. The results showed that sperm morphology has a significant effect on motility while sperm morphology significantly depend on sperm count.

CONCLUSION

An increase in sperm volume and concentration improves the sperm morphology and boost the sperm motility, this may increasing the chance of fertility.

Low acrosin activity is associated with decreased Spam1/acrosin expression and GSH deficiency-caused premature acrosome release of human sperm cells

Low acrosin activity (LAA) is associated with sperm function anomaly and poor outcomes of in vitro fertilization. In this study, we confirm that 993 semen samples with LAA had a reduced sperm motility and low in vitro fertilization rate in comparison with 1332 normal controls (NC). Proteomic comparison between 11 LAA and 11 NC sperm samples identified 35 upregulated and 99 downregulated proteins in the LAA group. Indeed, proteomic data showed that acrosome enzymes Spam1 and Acrosin were among the downregulated proteins in the LAA group, which was validated by quantitative PCR and immunefluorescent staining of sperm cells. The KEEG pathway analysis revealed a deficiency of GSH and Gln biosynthesis in LAA sperm cells. Immunofluorescent staining of sperms and quantitative PCR verified downregulation of GLUL and GCLC, the key enzymes for GSH and Gln biosynthesis. Moreover, the results of ELISA assay confirmed low levels of GSH and Gln in LAA sperm cells. Mechanistic studies showed that addition of 10 mM H2O2 to semen samples led to a significant reduction of acrosin activity and sperm motility, most possibly by triggering premature acrosome release. In contrast, the presence of 20 mM GSH blocked the oxidative effects of H2O2. Since GSH counteracts the oxidative stress and Gln participates in TCA cycling, their deficiency may affect the redox balance as well as energy production of sperm cells. These findings shed new light on the pathological mechanisms of infertility associated with LAA. Male infertility patients could benefit from GSH supplement by improvement of acrosin activity and other sperm functions.

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.

Exposure to Fine Particulate Matter Constituents and Human Semen Quality Decline: A Multicenter Study

Exposure to fine particulate matter (PM < 2.5 μm in diameter [PM2.5]) may accelerate human sperm quality decline, although research on this association is limited. Our objective was to investigate the relationship between exposure to the chemical constituents of PM2.5 air pollution and decreased sperm quality and to further explore the exposure-response relationship. We conducted a multicenter population-based cohort study including 78,952 semen samples from 33,234 donors at 6 provincial human sperm banks (covering central, northern, southern, eastern, and southwestern parts of China) between 2014 and 2020. Daily exposure to PM2.5 chemical composition was estimated using a deep learning model integrating a density ground-based measure network at a 1 km resolution. Linear mixed models with subject- and center-specific intercepts were used to quantify the harmful impacts of PM2.5 constituents on semen quality and explore their exposure-response relationships. Per interquartile range (IQR) increase in PM2.5 exposure levels during spermatogenesis was significantly associated with decreased sperm concentration, progressive motility, and total motility. For PM2.5 constituents, per IQR increment in Cl- (β: -0.02, 95% CI: [-0.03, -0.00]) and NO3- (β: -0.05, 95% CI: [-0.08, -0.02]) exposure was negatively associated with sperm count, while NH4+ (β: -0.03, 95% CI: [-0.06, -0.00]) was significantly linked to decreased progressive motility. These results suggest that exposure to PM2.5 chemical constituents may adversely affect human sperm quality, highlighting the urgent need to reduce PM2.5 exposure.

Trend of change of sperm count and concentration over the last two decades: A systematic review and meta-regression analysis

BACKGROUND

Since the 1970s, several studies found that sperm concentration (SC) and total sperm count (TSC) constantly worsened over time, mainly in high-income countries.

OBJECTIVES

To evaluate whether the decreasing trend in sperm count is continuing in Western European countries and USA, we performed a systematic review and meta-regression analysis.

MATERIALS AND METHODS

Embase and Pubmed/Medline were searched papers published in English in the 2000-2020 period limiting the search to data collected in the USA and Western European countries.

RESULTS

We identified 62 articles and pooled information on 24,196 men (range 10-2,523), collected from 1993 to 2018. Considering all the studies, random-effects meta-regression analyses showed no significant trend for SC (slope per year -0.07 mil/mL, p-value = 0.86). Negative trends of SC were detected in Scandinavian countries (slope per year -1.11 mil/mL, 95% CI: -2.40 to +0.19; p-value = 0.09), but the findings were statistically not significant. No significant trends of SC were detected in Central Europe (slope per year +0.23, 95% CI -2.51 to +2.96; p-value = 0.87), the USA (slope per year +1.08, 95% CI -0.42 to +2.57; p-value = 0.16), and Southern Europe (slope per year +0.19, 95% CI -0.99 to +1.37; p-value = 0.75). We have analyzed separately findings from studies including sperm donors, fertile men, young unselected men (unselected men, study mean age < 25 years) and unselected men (unselected men, study mean age ≥ 25 years). No significant trends of SC were observed among sperm donors (slope per year -2.80, 95% CI -6.76 to +1.17; p-value 0.16), unselected men (slope per year -0.23, 95% CI -1.58 to +1.12; p-value 0.73), young unselected men (slope per year -0.49, 95% CI -1.76 to +0.79; p-value 0.45), fertile men (slope per year +0.29, 95% CI -1.09 to +1.67; p-value 0.68).

DISCUSSION AND CONCLUSION

The results of this analysis show no significant trends in SC, in USA, and selected Western European countries.

Environmental exposure to industrial air pollution is associated with decreased male fertility

OBJECTIVE

To understand how chronic exposure to industrial air pollution is associated with male fertility through semen parameters.

DESIGN

Retrospective cohort study.

PATIENTS

Men in the Subfertility, Health, and Assisted Reproduction cohort who underwent a semen analysis in the two largest healthcare systems in Utah from 2005-2017 with ≥1 measured semen parameter (N = 21,563).

INTERVENTION(S)

Residential histories for each man were constructed using locations from administrative records linked through the Utah Population Database. Industrial facilities with air emissions of nine endocrine-disrupting compound chemical classes were identified from the Environmental Protection Agency Risk-Screening Environmental Indicators microdata. Chemical levels were linked with residential histories for the 5 years before each semen analysis.

MAIN OUTCOME MEASURES

Semen analyses were classified as azoospermic or oligozoospermic (< 15 M/mL) using World Health Organization cutoffs for concentration. Bulk semen parameters such as concentration, total count, ejaculate volume, total motility, total motile count, and total progressive motile count were also measured. Multivariable regression models with robust standard errors were used to associate exposure quartiles for each of the nine chemical classes with each semen parameter, adjusting for age, race, and ethnicity, as well as neighborhood socioeconomic disadvantage.

RESULTS

After adjustment for demographic covariates, several chemical classes were associated with azoospermia and decreased total motility and volume. For exposure in the 4th relative to 1st quartile, significant associations were observed for acrylonitrile (βtotal motility = -0.87 pp), aromatic hydrocarbons (odds ratio [OR]azoospermia = 1.53; βvolume = -0.14 mL), dioxins (ORazoospermia = 1.31; βvolume = -0.09 mL; βtotal motility = -2.65 pp), heavy metals (βtotal motility = -2.78pp), organic solvents (ORazoospermia = 1.75; βvolume = -0.10 mL), organochlorines (ORazoospermia = 2.09; βvolume = -0.12 mL), phthalates (ORazoospermia = 1.44; βvolume = -0.09 mL; βtotal motility = -1.21 pp), and silver particles (ORazoospermia = 1.64; βvolume = -0.11 mL). All semen parameters significantly decreased with increasing socioeconomic disadvantage. Men who lived in the most disadvantaged areas had concentration, volume, and total motility of 6.70 M/mL, 0.13 mL, and 1.79 pp lower, respectively. Count, motile count, and total progressive motile count all decreased by 30-34 M.

CONCLUSION(S)

Several significant associations between chronic low-level environmental exposure to endocrine-disrupting compound air pollution from industrial sources and semen parameters were observed. The strongest associations were seen for increased odds of azoospermia and declines in total motility and volume. More research is needed to further explore additional social and exposure factors as well as expand on the risk posed to male reproductive health by the studied chemicals.

Obesity and male infertility

The worldwide prevalence of obesity is increasing among both sexes, with associated impacts on chronic health and medical comorbidities. Similarly, the effects of obesity on reproductive health are increasingly being recognized. Adiposity is associated with reduced fertility in men, with a complex and multifactorial etiology. The reported effects of obesity on semen parameters and impaired fertility are contrasting, with some studies showing a clear reduction in reproductive outcomes associated with increased body mass index, while others do not show such impacts. These controversies may be due to the complex pathophysiology and interplay between gonadotropins and end organs, as well as genetic and epigenetic changes and oxidative stress on male fertility and function. These different aspects have led to heterogeneous participants in studies and varying implications for assisted reproductive outcomes as well as offspring health. Treatment modalities to manage obesity include lifestyle, medical, and surgical options, with emerging and effective medical treatments showing promise in reproductive outcomes.

Trends in sperm quality by computer-assisted sperm analysis of 49,189 men during 2015-2021 in a fertility center from China

Background

Sperm quality, including semen volume, sperm count, concentration, and total and progressive motility (collectively, "semen parameters"), has declined in the recent decades. Computer-assisted sperm analysis (CASA) provides sperm kinematic parameters, and the temporal trends of which remain unclear. Our objective is to examine the temporal trend of both semen parameters and kinematic parameters in Shanghai, China, in the recent years.

Methods

This retrospective study analyzed semen parameters and kinematic parameters of 49,819 men attending our reproductive center by using CASA during 2015-2021. The total sample was divided into two groups: samples that surpassed the WHO guideline (2010) low reference limits ("above reference limit" group, ARL; n = 24,575) and samples that did not ("below reference limit" group, BRL; n = 24,614). One-way analysis of variance, Kruskal-Wallis test, independent samples t-test, and covariance analysis were used to assess the differences among groups. Year, age, and abstinence time were included in the multiple linear regression model of the ARL group to adjust the confounders and depict the trends in sperm quality.

Results

Among all the total sample and the ARL and BRL groups, the age of subjects increased in recent years. Semen volume and sperm count showed declined tendency with years in the total sample, the ARL and BRL groups, and the subgroup of age or abstinence time, whereas sperm velocities showed increased tendency with years on the contrary. The multiple linear regression model of the ARL group, adjusting for age and abstinence time, confirmed these trends. Semen volume (β1= -0.162; CI: -0.172, -0.152), sperm count (β1= -9.97; CI: -10.813, -9.128), sperm concentration (β1 = -0.535; CI: -0.772, -0.299), motility (β1 = -1.751; CI: -1.830, -1.672), and progressive motility (β1 = -1.12; CI: -0.201, -0.145) decreased with year, whereas curvilinear line velocity (VCL) (β1 = 3.058; CI: 2.912, 3.203), straight line velocity (VSL) (β1 = 2.075; CI: 1.990, 2.161), and average path velocity (VAP) (β1 = 2.305; CI: 2.224, 2.386) increased over time (all p < 0.001). In addition, VCL, VSL, and VAP significantly declined with age and abstinence time.

Conclusion

The semen parameters declined, whereas the kinematic parameters increased over the recent years. We propose that, although sperm count and motility declined over time, sperm motion velocity increased, suggesting a possible compensatory mechanism of male fertility.

Global trends in semen quality of young men: a systematic review and regression analysis

PURPOSE

Many studies have reported declines in semen quality mainly focused on total sperm counts (TSC) and sperm concentration (SC), ignoring the importance of progressive motile sperm (PR), total motile sperm (TM), and normal morphological sperm (NM). Therefore, we performed a comprehensive meta-analysis to explore the trend in semen quality of young men.

METHODS

We searched 3 English databases and 4 Chinese databases from January 1980 to August 2022. Random-effect meta-analyses and weighted linear regression models were conducted to perform the trend in semen quality.

RESULTS

Finally, 162 eligible studies including 264,665 men from 28 countries were got between 1978 and 2021. Significant decreases were observed in TSC (- 3.06 million/year, 95% CI - 3.28 to - 2.84), SC (- 0.47 million/ml/year, 95% CI - 0.51 to - 0.43), and PR (- 0.15%/year, 95% CI - 0.20 to - 0.09), and there was an upward trend in TM (0.28%/year, 95% CI 0.24 to 0.32). The results of meta-regression analyses indicated that age, continent, income, WHO criteria, and abstinence time significantly impacted on TSC, SC, PR, and TM. Positive regression coefficients were observed in some categories suggesting that outcomes might not be declining and even increasing in these subgroups.

CONCLUSIONS

Downward trends in semen quality among global young men were observed in our study, including TSC, SC, and PR. But TM did not appear to be trending down or even to be leveling off. More studies are needed to focus on the causes of the declines.

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.

Trends in semen parameters of infertile men in South Africa and Nigeria

There are conflicting reports on trends of semen parameters from different parts of the globe. However, in recent times there is dearth of information on the trend in Sub-Saharan countries. Therefore, in this study we aimed at determining the trends in semen parameters in Nigeria and South Africa between 2010 and 2019. A retrospective study of semen analyses of 17,292 men attending fertility hospitals in Nigeria and South Africa in 2010, 2015 and 2019. Patients who had undergone vasectomy and those who had a pH less than 5 or greater than 10 were excluded from this study. The following variables were assessed: ejaculate volume, sperm concentration, progressive motility, total progressively motile sperm count (TPMSC), total sperm count, and normal sperm morphology. Between 2010 and 2019, significant trends of decreasing values were observed in normal sperm morphology (- 50%), and the ejaculatory volume (- 7.4%), indicating a progressive deterioration of the values in both countries. In Nigeria, there were significant decreases in progressive motility (- 87%), TPMSC (- 78%), and sperm morphology (- 55%) between 2010 and 2019 (P < 0.001). Spearman`s rank correlation revealed significant negative associations between age and morphology (ρ =  - 0.24, P < 0.001), progressive motility (ρ =  - 0.31. P < 0.001), and TPMSC (ρ =  - 0.32, P < 0.001). Patients in South Africa were younger than those from Nigeria, with also a significantly higher sperm morphology, sperm concentration, progressive motility, total sperm count and TPMSC. Our findings provide a quantitative evidence of an alarming decreasing trend in semen parameters in Nigeria and South Africa from 2010 to 2019. It also proves that astheno- and teratozoospermia are the leading causes of male infertility in these regions. In addition to this, it also shows empirically that semen parameters decrease with advancement in age. These findings are the first report of temporal trends in semen parameters in Sub-Saharan countries, necessitating a thorough investigation on the underlying factors promoting this worrisome decline.

HE4 overexpression in mice leads to leydig cell hyperplasia and spermatogensis impairment: Pathological implications for oligospermia

Previous studies have shown that HE4 cancer biomarker promoted cancer cell proliferation and tumor growth in mouse xenograft models. Interestingly, HE4 levels are significantly increased in the seminal plasma of oligoasthenospermia patients, raising a question on HE4 role(s) in spermatogenesis. We constructed an HE4 overexpression mouse model (HE4-OE), and observed that HE4-OE male adult mice had small testes, low sperm counts, and elevated serum/testis testosterone levels. These mice exhibited disorganized seminiferous tubules and impaired spermatogenesis. HE4 overexpression concentrated in Leydig cells, and these cells had hyperplasia and increased testosterone biosynthesis. Mechanistic studies indicated that the impaired spermatogenesis was likely caused by a local and direct action of HE4 in the testis rather than by a hypothalamus/pituitary-initiated dysregulation. The new findings reveal a novel HE4 function in male reproductive system, and suggest the existence of a subtype of primary oligoasthenospermia characterized by HE4 overexpression, Leydig cell hyperplasia, and elevated testosterone levels.

Does Air Pollution Impact on Semen Parameters? Findings from a Real-Life, Cross-Sectional Study in Italian Infertile Men

PURPOSE

In industrialized countries, air pollutants levels have been monitored closely for environmental and research issues. Using Italian data, we aimed to investigate the association between air pollutants levels and semen parameters in a cohort of non-Finnish white-European men presenting for couple's infertility.

MATERIALS AND METHODS

Complete demographic and laboratory data from 1,152 infertile men consecutively assessed between January 2015 and January 2018 were analyzed. Semen analyses were based on the 2010 World Health Organization reference criteria. Health-significant comorbidities were scored with the Charlson Comorbidity Index (CCI). We analyzed the annual average level of the three main markers of air pollution (Pm10, Pm2.5, and NO₂) between 2014 and 2018. Descriptive statistics, linear and logistic regression analyses tested the association between air pollutants levels and semen parameters.

RESULTS

Of 1,152 men, 87 (7.55%) had normal sperm parameters at first semen analysis. Of 1,065 patients with abnormal semen analyses, 237 (22.25%), 324 (30.42%), and 287 (26.95%) patients presented 1, 2 or 3 abnormalities, respectively, and 217 (20.38%) were azoospermic. At linear regression analysis, Pm10, Pm2.5, and NO₂ were negatively associated with sperm morphology (Pm10: β=-0.5288 µg/m³, p=0.001; Pm2.5: β=-0.5240 µg/m³, p=0.019; NO₂: β=-0.4396 µg/m³, p<0.0001). Furthermore, the adjusted odds of normal sperm morphology <4% were 1.06 (95% confidence interval [CI], 1.03-1.09; p=0.007) for Pm10, 1.07 (95% CI, 1.03-1.11; p=0.007) for Pm 2.5, and 1.03 (95% CI, 1.02-1.05; p=0.001) for NO₂, respectively.

CONCLUSIONS

In a large homogenous cohort of infertile men, Pm10, Pm 2.5, and NO₂ levels were negatively associated with sperm morphology. Conversely, no clear association was observed with other macroscopic sperm parameters.

Machine learning-based clustering to identify the combined effect of the DNA fragmentation index and conventional semen parameters on in vitro fertilization outcomes

BACKGROUND

Previous studies have demonstrated an association between male sperm quality and assisted reproduction outcomes, focusing on the effects of individual parameters and reaching controversial conclusions. The WHO 6th edition manual highlights a new semen assay, the sperm DNA fragmentation index, for use after routine semen examination. However, the combined effect of the sperm DNA fragmentation index (DFI) and routine semen parameters remains largely unknown.

METHODS

We assessed the combined effect of the sperm DFI and conventional semen parameters on single fresh conventional IVF outcomes for infertile couples from January 1, 2017, to December 31, 2020. IVF outcomes were obtained from the cohort database follow-up records of the Clinical Reproductive Medicine Management System of the Third Affiliated Hospital of Guangzhou Medical University. An unsupervised K-means clustering method was applied to classify participants into several coexposure pattern groups. A multivariate logistic regression model was used for statistical analysis.

RESULTS

A total of 549 live births among 1258 couples occurred during the follow-up period. A linear exposure-response relationship was observed among the sperm DFI, sperm motility, and IVF outcomes. In multivariable adjustment, increased sperm DFI values and decreased sperm motility and semen concentration levels were associated with reduced odds of favourable IVF outcomes. Four coexposure patterns were generated based on the sperm DFI and the studied semen parameters, as follows: Cluster 1 (low sperm DFI values and high sperm motility and semen concentration levels), Cluster 2 (low sperm DFI values and moderate sperm motility and semen concentration levels), Cluster 3 (low sperm DFI values and low sperm motility and semen concentration levels) and Cluster 4 (high sperm DFI values and low sperm motility and semen concentration levels). Compared with those in Cluster 1, participants in Cluster 3 and Cluster 4 had lower odds of a live birth outcome, with odds ratios (95% confidence intervals [CIs]) of 0.733 (0.537, 0.998) and 0.620 (0.394, 0.967), respectively.

CONCLUSIONS

When combined with low sperm DFI values, there was no significant difference between high or moderate sperm concentration and motility levels, and both were associated with favourable IVF outcomes. Low sperm parameter levels, even when DFI values remain low, may still lead to poor IVF outcomes. Participants with high sperm DFI values and low sperm motility and semen concentration levels had the worst outcomes. Our findings offer a novel perspective for exploring the joint effects of sperm DFI and routine semen parameter values.

Association between ambient temperature and semen quality among sperm donation volunteers in South China

BACKGROUND

Potential adverse effects of non-optimum temperatures on human semen quality have drawn much concern worldwide; however, the exposure-response relationship remains less understood.

OBJECTIVES

To quantitatively assess the association between exposure to ambient temperature and semen quality in South China, and to identify potential critical exposure windows.

METHODS

We conducted a longitudinal study to investigate 11,050 volunteers who lived in Guangdong province, China and intended to donate sperm in the Guangdong provincial human sperm bank during 2016-2021. Exposure to ambient temperature during 0-90 days before semen collection was assessed by extracting daily temperatures from a validated grid dataset at each subject's residential address. Linear mixed models and linear regression models were used to perform exposure-response analyses.

RESULTS

During the study period, the 11,050 subjects underwent 44,564 semen analyses. Each 5 °C increase of lag 0-90 day exposure to ambient temperature was approximately linearly associated with a 3.11 (95 % confidence interval [CI]: 2.08, 4.14) × 10⁶/ml, 9.31 (4.83, 13.80) × 10⁶, 1.27 % (0.91 %, 1.62 %), 8.20 (5.33, 11.08) × 10⁶, 1.37 % (1.01 %, 1.74 %), 8.29 (5.52, 11.06) × 10⁶, 0.67 % (0.28 %, 1.05 %), and 4.50 (2.20, 6.80) × 10⁶ reduction in sperm concentration, total sperm number, total motility, total motile sperm number, progressive motility, total progressive sperm number, normal forms, and total normal form sperm number, respectively (all p < 0.001), which was not significantly modified by age (all p for effect modification > 0.05). We identified a critical exposure period of 10-14 days before semen collection for sperm motility, and 70-90 days before semen collection for sperm count and morphology.

CONCLUSIONS

Our study provides consistent evidence that higher ambient temperature was significantly associated with a reduction in semen quality in South China. The findings highlight the needs to reduce high temperature exposures during 3 months before ejaculation to maintain better semen quality.

Association between urinary phthalate levels and chronic pain in US adults, 1999-2004: A nationally representative survey

Introduction

Chronic pain is a public health concern throughout the world. Ascertaining and managing its risk factors helps develop well-directed treatment plans and prevention strategies. Phthalates (PAEs) exposure leads to various health problems. The present study aims to explore the potential correlation between urinary PAEs metabolites and chronic pain in adults.

Methods

The study population data were extracted from the National Health and Nutrition Examination Survey (NHANES) conducted from 1999 to 2004 in the United States. Seven urinary PAEs metabolites were used to assess long-term PAEs exposure. The assessment of chronic pain was determined by a self-report questionnaire. Weighted analyses were conducted to consider the complex sampling design. Models were adjusted by demographic data and lifestyle factors. Urinary PAEs metabolites were assessed as both continuous and categorical variables. Tertile 1 was considered as the reference. Stratified analyses were performed by gender and pain site. All data analyses were conducted with STATA, version 15.1. P < 0.05 was considered with statistical significance.

Results

A total of 4,196 participants were considered in our final analysis. Chronic pain prevalence reached 52.19% (n = 2,138) among the participants, with women accounting for a large proportion (57.75% vs. 42.25%). After multivariable logistic regression analysis, a higher prevalence of chronic pain was observed among participants in the third tertile of mono-(2-ethyl)-hexyl phthalate (MEHP) (OR = 1.23, 95% CI = 1.02-1.48, P = 0.034) and mono-benzyl phthalate (MBzP) (OR = 1.28, 95% CI = 1.04-1.58, P = 0.022) in our adjusted model. The logtransformed concentration of MBzP also showed a significant association with chronic pain prevalence (OR = 1.09, 95% CI = 1.01-1.18, P = 0.036) in the adjusted model. In further analysis, the positive correlations of urinary phthalate metabolites with chronic pain remained robust when stratified by gender and chronic pain site.

Conclusions

Our findings presented a positive correlation between urinary PAEs metabolites and chronic pain among adult participants, and more causal research should be conducted to ascertain the interactions between the two and to expound their underlying mechanisms.

Effect of ambient temperature variability on sperm quality: A retrospective population-based cohort study

BACKGROUNDS

Abnormal sperm quality in men is one of the common causes of infertility. Both ambient temperature and extreme heat exposure have been shown to be associated with sperm quality, but there is no epidemiological evidence for the effect of ambient temperature variability. Our aim was to investigate the association between ambient temperature variability exposure and a decline in sperm quality at different stages of sperm development.

METHODS

A total of 4912 semen samples collected from the Guangdong Human Sperm Bank between 1 January 2019 and 31 December 2019 were analyzed. We selected three exposure periods: the full-stage (0-90 lag days), early-stage (34-77 lag days) and late-stage (0-37 lag days) of sperm development, and then calculated the standard deviation of daily temperature (TVSD), the maximum day-to-day temperature difference (TVD_max) and the mean day-to-day temperature difference (TVD_mean) for the three exposure periods. A linear mixed model was used to explore the exposure response relationship between temperature variability exposure and sperm quality indicators (including sperm concentration, sperm count and sperm motility).

RESULTS

There was a significant negative association of decreased sperm count with the exposure to temperature variability during 0-90 days prior to sperm collection. (TVD_max: -0.041; -0.063, -0.019; TVD_mean: -0.237; -0.386, -0.088; TVSD: -0.103; -0.196, -0.011). We observed a significant association between the decline in sperm concentration, sperm count and per 1 °C increase in TVD_mean during early spermatogenesis. No significant association of temperature variability with sperm motility was found.

CONCLUSIONS

The results indicate that exposure to temperature variability during the entire period of sperm development is significantly associated with a decline in sperm counts. We found that mean day-to-day temperature differences had a detrimental effect on sperm counts in the early-stage. Our findings provide a scientific basis for public health policy and further mechanistic studies.

Impacts of traffic-related particulate matter pollution on semen quality: A retrospective cohort study relying on the random forest model in a megacity of South China

BACKGROUND

Emerging evidence shows the detrimental impacts of particulate matter (PM) on poor semen quality. High-resolution estimates of PM concentrations are conducive to evaluating accurate associations between traffic-related PM exposure and semen quality.

METHODS

In this study, we firstly developed a random forest model incorporating meteorological factors, land-use information, traffic-related variables, and other spatiotemporal predictors to estimate daily traffic-related PM concentrations, including PM_2.5, PM₁₀, and PM₁. Then we enrolled 1310 semen donors corresponding to 4912 semen samples during the study period from January 1, 2019, and December 31, 2019 in Guangzhou city, China. Linear mixed models were employed to associate individual exposures to traffic-related PM during the entire (0-90 lag days) and key periods (0-37 and 34-77 lag days) with semen quality parameters, including sperm concentration, sperm count, progressive motility and total motility.

RESULTS

The results showed that decreased sperm concentration was associated with PM₁₀ exposures (β: -0.21, 95 % CI: -0.35, -0.07), sperm count was inversely related to both PM_2.5 (β: -0.19, 95 % CI: -0.35, -0.02) and PM₁₀ (β: -0.19, 95 % CI: -0.33, -0.05) during the 0-90 days lag exposure window. Besides, PM_2.5 and PM₁₀ might diminish sperm concentration by mainly affecting the late phase of sperm development (0-37 lag days). Stratified analyses suggested that PBF and drinking seemed to modify the associations between PM exposure and sperm motility. We did not observe any significant associations of PM₁ exposures with semen parameters.

CONCLUSION

Our results indicate that exposure to traffic-related PM_2.5 and PM₁₀ pollution throughout spermatogenesis may adversely affect semen quality, especially sperm concentration and count. The findings provided more evidence for the negative associations between traffic-related PM exposure and semen quality, highlighting the necessity to reduce ambient air pollution through environmental policy.

The future of sperm: a biovariability framework for understanding global sperm count trends

The past 50 years have seen heated debate in the reproductive sciences about global trends in human sperm count. In 2017, Levine and colleagues published the largest and most methodologically rigorous meta-regression analysis to date and reported that average total sperm concentration among men from 'Western' countries has decreased by 59.3% since 1973, with no sign of halting. These results reverberated in the scientific community and in public discussions about men and masculinity in the modern world, in part because of scientists' public-facing claims about the societal implications of the decline of male fertility. We find that existing research follows a set of implicit and explicit assumptions about how to measure and interpret sperm counts, which collectively form what we term the Sperm Count Decline hypothesis (SCD). Using the study by Levine and colleagues, we identify weaknesses and inconsistencies in the SCD, and propose an alternative framework to guide research on sperm count trends: the Sperm Count Biovariability hypothesis (SCB). SCB asserts that sperm count varies within a wide range, much of which can be considered non-pathological and species-typical. Knowledge about the relationship between individual and population sperm count and life-historical and ecological factors is critical to interpreting trends in average sperm counts and their relationships to health and fertility.

Urinary concentrations of polycyclic aromatic hydrocarbon and phthalate metabolite mixtures in relation to semen quality among men attending an infertility clinic

Previous studies have reported that exposure to phthalates and polycyclic aromatic hydrocarbons (PAHs) is individually associated with altered semen quality, but no human studies have evaluated their joint effects of exposure mixtures, a more real-world scenario. We aimed to explore urinary metabolite mixtures of phthalates and PAHs in associations with semen quality. Repeated spot-urine samples gathered from 695 men attending a fertility clinic were analyzed for urinary metabolites of eight phthalates and ten monohydroxylated-PAHs (OH-PAHs). Principal component analysis (PCA)-multivariable linear regression (MLR) model, quantile g-computation (qg-comp), and Bayesian kernel machine regression (BKMR) were applied to estimate the associations of urinary mixtures of phthalate and OH-PAH metabolites with semen quality. The overall effects of urinary mixtures of phthalate and PAH metabolites on semen quality were not statistically significant. However, hydroxynaphthalene (OHNa) factor identified from PCA was monotonically associated with decreased total sperm count and sperm concentration, whereas di(2-ethylhexyl) phthalate (DEHP) factor was non-monotonically related to increased progressive sperm motility and total sperm motility. Qg-comp and BKMR models confirmed these findings and identified 2-OHNa and 2-OHFlu as the primary negative contributors, whereas MEOHP and MEHP as the primary positive contributors. Our findings suggest that exposure to mixtures of naphthalene and DEHP is associated with altered semen quality. The finding is warranted to confirm in further well-designed epidemiological studies.

Hindlimb unloading induces time-dependent disruption of testicular histology in mice

Mechanical unloading of the body in the hindlimb unloaded (HU) mice induces pathology in multiple organs, but the effects on testes are poorly characterized. We investigated the histology and Raman spectroscopy of the mouse testes following HU condition. We divided male, c57BL/6j mice into ground-based controls or experimental groups for two and four weeks of HU. The testes tissues were dissected after euthanasia to investigate histological and Raman spectroscopic analysis. We found an HU-induced atrophy of testes irrespective of the time duration (p < 0.05). Histological analysis revealed that the HU induced epithelial thinning, luminal widening, and spermatozoa decline in the seminiferous tubules of the mouse testes. In addition, we found a thickening of the epididymal epithelia and tunica albuginea. These changes were accompanied by a generalized depression in the Raman spectra, indicating an altered concentration and/or orientation of several molecules. We also report reduced signal intensities of hydroxyproline and tryptophan, potentially contributing to testicular pathology during HU. Taken together, our findings indicate that the two or four weeks of HU induce disruption of testicular architecture and molecular phenotypes. Our results may have implications for understanding and/or treating male infertility associated with prolonged bed rest and spaceflight.

Androgen Receptor Gene CAG Repeat Length Varies and Affects Semen Quality in an Ethnic-Specific Fashion in Young Men from Russia

Male infertility is a multi-factorial and multi-genetic disorder, and the prevalence of male infertility in the world is estimated at 5–35%. The search for the causes of male infertility allowed for identifying a number of genetic factors including a single X-linked gene of the androgen receptor (AR), and some of its alleles are assumed to negatively affect male fertility. Our aim was (1) to study the variability of the length of CAG repeats of the AR gene and possible associations in the AR CAG genetic variants with semen quality and reproductive hormone levels in a population-based cohort of men and (2) to estimate distributions of AR CAG repeat alleles and associations with semen parameters in different ethnic subgroups. The cohort of 1324 young male volunteers of different ethnicities (median age 23.0 years) was recruited from the general population of five cities of the Russian Federation, regardless of their fertility status. Semen quality (sperm concentration, motility and morphology), reproductive hormone levels (testosterone, estradiol, LH, FSH and inhibin B) and trinucleotide (CAG) n repeat polymorphism in exon 1 of the AR gene were evaluated. The semen samples were analyzed according to the WHO laboratory manual (WHO, 2010), serum hormones were measured by enzyme immunoassay, and the AR CAG repeat length was analyzed by direct sequencing of leukocyte DNA. The median AR CAG repeat length in men of our multi-ethnic population was 23 (range 6–39). In the entire study population, a significant difference (p ≤ 0.05) was found in the frequency distribution and the mean values for the CAG repeat length between the groups with normal (23.2 ± 3.3) and impaired semen quality (23.9 ± 3.2). Additionally, we demonstrated that the total sperm count, sperm concentration, progressive motility and normal morphology were lower in the category of long CAG repeats (CAG ≥ 25) compared with those in the category of short CAG repeats (CAG ≤ 19); however, hormonal parameters did not differ between the long and short CAG categories, with the exception of estradiol. Significant differences were observed in the AR CAG repeat length between the most common ethnic cohorts of Slavs (Caucasians), Buryats (Asians), and Yakuts (Asians). The Buryats and Yakuts had a higher number of CAG repeats than the Slavs (medians: Slavs—23; Buryats—24; Yakuts—25). The range of alleles differed among ethnicities, with the Slavs having the largest range (7–36 repeats, 24 alleles total), the Yakuts having the smallest range (18–32 repeats, 14 alleles total) and the Buryats having the middle range (11–39 repeats, 20 alleles total). The longer CAG repeats were associated with an impaired semen quality within the Slavic (CAG ≥ 25) and Buryat (CAG ≥ 28) groups, but this effect was not found in Yakuts. Hormonal parameters did not differ between the three CAG repeat categories in men of all ethnic groups. This is the largest Russian study of the distribution of AR CAG repeats and the search for association between length of AR CAG repeat tract and impaired spermatogenesis in men from the general population. Our results confirmed the association of longer CAG repeats with a risk of impaired semen quality, but this association can be modified by ethnic origin. Identification of the number of AR CAG repeats can be an effective tool to assess the risk of male subfertility and the control of androgen hormone therapy of reproductive diseases.

Role of p38 MAPK Signalling in Testis Development and Male Fertility

The testis is an important male reproductive organ, which ensures reproductive function via the secretion of testosterone and the generation of spermatozoa. Testis development begins in the embryonic period, continues after birth, and generally reaches functional maturation at puberty. The stress-activated kinase, p38 mitogen-activated protein kinase (MAPK), regulates multiple cell processes including proliferation, differentiation, apoptosis, and cellular stress responses. p38 MAPK signalling plays a crucial role in testis development by regulating spermatogenesis, the fate determination of pre-Sertoli, and primordial germ cells during embryogenesis, the proliferation of testicular cells in the postnatal period, and the functions of mature Sertoli and Leydig cells. In addition, p38 MAPK signalling is involved in decreased male fertility when exposed to various harmful stimuli. This review will describe in detail the biological functions of p38 MAPK signalling in testis development and male reproduction, together with its pathological role in male infertility.

Spatiotemporal trends in human semen quality

Over the past four decades, studies of various designs have reported spatial and temporal trends in human semen quality. Several standardized-methodology studies in homogeneous populations that compare specific cities within a country or a continent provide clear evidence of geographical differences in sperm production, even over short distances within the same country. Human sperm production is widely believed to be declining over time, but evidence from the scientific literature is less clear. Studies based on repeated cross-sectional data from a single centre have shown mixed results. Among the numerous retrospective studies conducted in a single centre, only some included homogeneous groups of men and appropriate methods, and most of them suggest a temporal decrease in human sperm production in the geographical areas considered. Conclusions reporting temporal trends in sperm production that came from existing retrospective multicentre studies based on individual semen data and those using means, medians or estimates of sperm production are questionable, owing to intrinsic limitations in the studies performed. Regardless of study design, studies on the percentage of motile or morphologically normal spermatozoa are still limited by the inherent variability in assessment. Overall, available data do not enable us to conclude that human semen quality is deteriorating worldwide or in the Western world, but that a trend is observed in some specific areas. To understand these trends and contrasts in sperm and semen quality, prospective studies should be encouraged and combined with assessment of the male exposome.

Several studies over the past few decades have suggested that sperm quality varies by geographical region and might be subject to a temporal decline worldwide. However, the data supporting these conclusions have come from studies of various methodologies and heterogeneous populations, making them unreliable. In this in-depth Review, Chevrier and colleagues discuss the data surrounding discussion of spatiotemporal trends in semen parameters and consider how these trends and the factors promoting them interact.

The vast literature on human semen quality trends is extremely heterogeneous in terms of the populations studied and study designs, and so these studies have been unable to draw firm conclusions.

Understanding the data around spatiotemporal semen trends requires a focus on the methodological choices and application of criteria to filter findings from the studies with optimal design.

Numerous appropriately designed studies suggest unambiguous geographical contrasts in human sperm production; however, evidence of a decline in sperm production is reliable only in specific populations and cities in which studies with a complete set of quality criteria have been conducted.

By contrast, suggestions of a worldwide drop in human semen quality on the basis of retrospective multicentre studies cannot be substantiated, owing to intrinsic limitations in the studies performed.

Many and varied factors of variation, in particular the diverse modalities of assessment, do not enable us to conclude that clear temporal trends of sperm motility and normal morphology are present.

Progress in our understanding of the highlighted trends and their causal factors requires prospective studies that minimize all known biases combined with the assessment of men’s exposome.

Bacteriospermia - A formidable player in male subfertility

Bacterial colonization of male reproductive tissues, cells, and fluids, and the subsequent impact of bacteria on the sperm architecture, activity, and fertilizing potential, has recently gained increased attention from the medical and scientific community. Current evidence strongly emphasizes the fact that the presence of bacteria in semen may have dire consequences on the resulting male fertility. Nevertheless, the molecular basis underlying bacteriospermia-associated suboptimal semen quality is sophisticated, multifactorial, and still needs further understanding. Bacterial adhesion and subsequent sperm agglutination and immobilization represent the most direct pathway of sperm-bacterial interactions. Furthermore, the release of bacterial toxins and leukocytic infiltration, associated with a massive outburst of reactive oxygen species, have been repeatedly associated with sperm dysfunction in bacteria-infested semen. This review serves as a summary of the present knowledge on bacteriospermia-associated male subfertility. Furthermore, we strived to outline the currently available methods for assessing bacterial profiles in semen and to outline the most promising strategies for the prevention and/or management of bacteriospermia in practice.

Low and high postpubertal ethanol use: damage on adulthood reproduction and offspring

Graphical abstract

Abstract

The relationship between adolescent ethanol uses and its impacts throughout life are not conclusive. Thus, we evaluated if the low and high consumption of ethanol at postpuberty interferes with the reproduction and ethanol-naive offspring and if the effects are dose-related. Female and male rats were divided into three groups: low drinker (L), high drinker (H) and control (C). The L and H groups were exposed to ethanol up to 10 % from 65 to 80 days with withdrawal after this period. The ethanol consumed by low drinkers was 1.41 ± 0.21 g/kg/day and by high drinkers 4.59 ± 0.45 g/kg/day. The study was conducted in two phases. The first phase verified the reproductive capacity in adulthood on generations (litter size and sex ratio). Data were collected over 10 years. The second phase analyzed the parent reproductive parameters (body weight, reproductive organ weight, sperm parameters and estrous cycle) and the pup development. We observed a reduced litter size in both drinker groups. Gestational body weight gain and feed consumption were lower in L and H. We observed an alteration in reproductive organs weight in both sexes of H. Females presented a longer estrous cycle duration. Males presented an increase in abnormal sperm, a decrease in sperm count and accelerated transit time. The ethanol-naive offspring development was also impaired. We conclude that low and high postpubertal alcohol use impairs long-term reproductive parameters, even after alcohol withdrawal. There is also impaired ethanol-naive offspring. Besides, the effects are dose-related.

Lay summary

The effects of alcohol use have been reported in several studies. However, better knowledge about early alcohol use and its impact on reproduction in adulthood, after abstinence and on ethanol-naive offspring could help improve preventive measures and mechanisms of action. One of the methods used was retrospective analysis which allows to evaluate the effects of postpubertal ethanol use on the reproductive capacity of rats over generations. Despite our limitations, we verified that the post-adolescent period acts as a susceptibility window, and lifestyle at this age modulates the long-term reproductive parameters. The early ethanol use impairs reproduction function since sperm parameters and the estrous cycle have been altered. The dose of alcohol also contributes to damage on the drinkers’ reproduction and on the physical development of ethanol-naive offspring. Future studies are necessary to identify the mechanism involved in long-term alcohol use effects, even in withdrawal, as well as ethanol-naive offspring outcomes.

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.

Targeted Analysis of HSP70 Isoforms in Human Spermatozoa in the Context of Capacitation and Motility

HSP70s constitute a family of chaperones, some isoforms of which appear to play a role in sperm function. Notably, global proteomic studies analyzing proteins deregulated in asthenozoospermia, a main cause of male infertility characterized by low sperm motility, showed the dysregulation of some HSP70 isoforms. However, to date, no clear trend has been established since the variations in the abundance of HSP70 isoforms differed between studies. The HSPA2 isoform has been reported to play a key role in fertilization, but its dysregulation and possible relocation during capacitation, a maturation process making the spermatozoon capable of fertilizing an oocyte, is debated in the literature. The aim of the present study was to investigate the fate of all sperm HSP70 isoforms during capacitation and in relation to sperm motility. Using Multiple-Reaction Monitoring (MRM) mass spectrometry, we showed that the relative abundance of all detected isoforms was stable between non-capacitated and capacitated spermatozoa. Immunofluorescence using two different antibodies also demonstrated the stability of HSP70 isoform localization during capacitation. We also investigated spermatozoa purified from 20 sperm samples displaying various levels of total and progressive sperm motility. We showed that the abundance of HSP70 isoforms is not correlated to sperm total or progressive motility.

Distinctive features of the hypothalamic-pituitary-gonadal axis and the level of dopamine in men of the European and Asian North

In recent years, there has been a decrease in reproductive potential, especially among residents of the Arctic territories, having the greatest stress from various body systems, including the state of the hormonal regulation of the male reproductive system. The study of the dopamine levels and the content of sex hormones in the male population of various Arctic regions is relevant due to the increased stress on the part of the dopaminergic system and the hypothalamic-pituitary-gonadal axis in residents of the Northern regions, as well as the lack of information about their interaction among the apparently healthy population. The aim of the investigation is to study the possible effect of various plasma concentrations of the dopamine on the content of sex hormones and sex-steroid-binding β-globulin (SHBG) in apparently healthy men in the Arctic zone of the Russian Federation, taking into account the territory of residence. There were examined 181 men aged 22-60 years, living in the territories of the European and Asian North. The levels of sex hormones, SHBG, and dopamine were determined by the enzyme-linked immunosorbent assay. The inhabitants of the Asian North in comparison with the men of the European North have higher levels of dopamine, luteinizing hormone, progesterone, prolactin, estradiol and SHBG with decreased serum levels of free fractions of testosterone. Reference levels of dopamine in men from the European North are combined with the stimulatory effect of dopamine on LH levels, which may indicate an increase steroidogenesis. The high levels of dopamine in men from the Asian North are combined with increased level of estradiol, which may be related to the effect of dopamine on testosterone aromatization. The separate region with its ecological differences is characterized by the presence of features of compensatory-adaptive reactions of an organism in male representatives on the part of the dopaminergic system and the hypothalamic-pituitary-gonadal axis. The identified features can help in carrying out preventive measures aimed at preserving the male reproductive potential of the inhabitants of the Arctic territories.

Impacts of endocrine disrupting chemicals on reproduction in wildlife and humans

Endocrine disrupting chemicals (EDCs) are ubiquitous in aquatic and terrestrial environments. The main objective of this review was to summarize the current knowledge of the impacts of EDCs on reproductive success in wildlife and humans. The examples selected often include a retrospective assessment of the knowledge of reproductive impacts over time to discern how the effects of EDCs have changed over the last several decades. Collectively, the evidence summarized here within reinforce the concept that reproduction in wildlife and humans is negatively impacted by anthropogenic chemicals, with several altering endocrine system function. These observations of chemicals interfering with different aspects of the reproductive endocrine axis are particularly pronounced for aquatic species and are often corroborated by laboratory-based experiments (i.e. fish, amphibians, birds). Noteworthy, many of these same indicators are also observed in epidemiological studies in mammalian wildlife and humans. Given the vast array of reproductive strategies used by animals, it is perhaps not surprising that no single disrupted target is predictive of reproductive effects. Nevertheless, there are some general features of the endocrine control of reproduction, and in particular, the critical role that steroid hormones play in these processes that confer a high degree of susceptibility to environmental chemicals. New research is needed on the implications of chemical exposures during development and the potential for long-term reproductive effects. Future emphasis on field-based observations that can form the basis of more deliberate, extensive, and long-term population level studies to monitor contaminant effects, including adverse effects on the endocrine system, are key to addressing these knowledge gaps.

Effects of mobile phone use on semen parameters: a cross-sectional study of 1634 men in China

Mobile phones play an irreplaceable role in modern people's lives. However, the radiofrequency electromagnetic radiation produced by mobile phones has also caused increasing concern. A cross-sectional study was conducted to investigate the effect of radiofrequency electromagnetic radiation produced by mobile phones on semen parameters in 1634 men who underwent semen examination at the Department of Reproductive Endocrinology, Women's Hospital, School of Medicine, Zhejiang University, China. Analysis of variance and multivariate linear regression were used to explore differences among different groups. A P <0.05 was considered statistically significant. The results showed significant associations among different groups of daily mobile phone use time and daily duration of phone calls in the percentage of progressively motile spermatozoa (P =0.004 and P =0.007), rapid progressively motile spermatozoa (P =0.012 and P =0.006) and total motile spermatozoa (P =0.004 and P =0.046). After adjustments for the confounding effects of age and body mass index by multiple linear regression, the results showed that the daily duration of mobile phone use had a negative effect on sperm motility. However, there was no statistically significant correlation between daily phone call duration and sperm motility. Therefore, the daily duration of mobile phone use may negatively affect sperm motility and impair male fertility.

Obesity and male infertility: multifaceted reproductive disruption

Background

The global prevalence of obesity has soared to a concerning height in the past few decades. Interestingly, the global decline in semen quality is a parallel occurrence that urges researchers to evaluate if obesity is among the most essential causatives of male infertility or subfertility.

Main body

Obesity may alter the synchronized working of the reproductive-endocrine milieu, mainly the hypothalamic-pituitary-gonadal (HPG) axis along with its crosstalks with other reproductive hormones. Obesity-mediated impairment in semen parameters may include several intermediate factors, which include physical factors, essentially increased scrotal temperature due to heavy adipose tissue deposits, and systemic inflammation and oxidative stress (OS) initiated by various adipose tissue-derived pro-inflammatory mediators. Obesity, via its multifaceted mechanisms, may modulate sperm genetic and epigenetic conformation, which severely disrupt sperm functions. Paternal obesity reportedly has significant adverse effects upon the outcome of assisted reproductive techniques (ARTs) and the overall health of offspring. Given the complexity of the underlying mechanisms and rapid emergence of new evidence-based hypotheses, the concept of obesity-mediated male infertility needs timely updates and pristine understanding.

Conclusions

The present review comprehensively explains the possible obesity-mediated mechanisms, especially via physical factors, OS induction, endocrine modulation, immune alterations, and genetic and epigenetic changes, which may culminate in perturbed spermatogenesis, disrupted sperm DNA integrity, compromised sperm functions, and diminished semen quality, leading to impaired male reproductive functions.

The Association of HLA-G Gene Polymorphism and Its Soluble Form With Male Infertility

Successful reproduction depends on many factors. Male factors contribute to infertility in approximately 50% of couples who fail to conceive. Seminal plasma consists of secretions from different accessory glands containing a mixture of various cytokines, chemokines, and growth factors, which together can induce a local immune response that might impact on a male’s as well as a female’s fertility. Human leukocyte antigen (HLA)-G expression has been suggested as an immunomodulatory molecule that influences pregnancy outcome. The HLA-G gene encodes either membrane-bound or/and soluble proteins. The aim of this study was the evaluation of HLA-G polymorphisms and their impact on soluble HLA-G (sHLA-G) production. We tested the HLA-G polymorphism in three positions: rs1632947: c.-964G>A; rs1233334: c.-725G>C/T in the promoter region; rs371194629: c.∗65_∗66insATTTGTTCATGCCT in the 3′ untranslated region. We tested two cohorts of men: 663 who participated in in vitro fertilization (test material was blood or sperm), and 320 fertile controls who possessed children born after natural conception (test material was blood). Since 50% of men visiting assisted reproductive clinics have abnormal semen parameters, we wondered if men with normal sperm parameters differ from those with abnormal parameters in terms of HLA-G polymorphism and secretion of sHLA-G into semen. We found that certain rs1632947-rs1233334-rs371194629 HLA-G haplotypes and diplotypes were associated with male infertility, while others were protective. Normozoospermic men with the A-C-del haplotype and A-C-del/A-C-del diplotype secreted the most sHLA-G into semen (574.1 IU/mL and 1047.0 IU/mL, respectively), while those with the G-C-ins haplotype and G-C-ins/G-C-ins diplotype – the least (80.8 IU/mL and 75.7 IU/mL, respectively). Men with the remaining haplotypes/diplotypes secreted sHLA-G at an intermediate level. However, only in one haplotype, namely G-C-ins, did we observe strong significant differences in the concentration of sHLA-G in the semen of men with teratozoospermia compared to men with normal sperm parameters (p = 0.009). In conclusion, fertile men differ in the profile of HLA-G polymorphism from men participating in IVF. Among all HLA-G haplotypes, the most unfavorable for male fertility is the G-C-ins haplotype, which determines the secretion of the lowest concentration of the soluble HLA-G molecule. This haplotype may reduce sperm parameters.

Oxidative Stress and Male Infertility: Evidence From a Research Perspective

Male fertility potential can be influenced by a variety of conditions that frequently coincide. Spermatozoa are particularly susceptible to oxidative damage due to their limited antioxidant capacity and cell membrane rich in polyunsaturated fatty acids (PUFAs). The role of oxidative stress (OS) in the etiology of male infertility has been the primary focus of our Stellenbosch University Reproductive Research Group (SURRG) over the last 10 years. This review aims to provide a novel insight into the impact of OS on spermatozoa and male reproductive function by reviewing the OS-related findings from a wide variety of studies conducted in our laboratory, along with those emerging from other investigators. We will provide a concise overview of the production of reactive oxygen species (ROS) and the development of OS in the male reproductive tract along with the physiological and pathological effects thereof on male reproductive functions. Recent advances in methods and techniques used for the assessment of OS will also be highlighted. We will furthermore consider the current evidence regarding the association between OS and ejaculatory abstinence period, as well as the potential mechanisms involved in the pathophysiology of various systemic diseases such as obesity, insulin resistance, hypertension, and certain mental health disorders which have been shown to cause OS induced male infertility. Finally, special emphasis will be placed on the potential for transferring and incorporating research findings emanating from different experimental studies into clinical practice.

Association between exposure to ambient air pollution and semen quality in adults: a meta-analysis

Air pollution has become a global concern and may be hazardous to human reproductive capacity, but the impact of exposure to air pollutants on semen quality remains controversial. We performed the meta-analysis to examine the association between air pollution exposure and semen quality. We searched PubMed, Web of Science Core Collection, and Cochrane Library databases (before December 2019). We selected original epidemiological studies on humans, written and published in English, that provided quantitative information to determine the associations between air pollution and sperm parameters. A random-effects model was used when the pooled effect estimates were found to be heterogeneous (I² > 50% or P < 0.05), otherwise, a fixed-effects model was applied. Publication bias was not evaluated for less than 10 included articles. Our meta-analysis showed that the standardised mean differences (SMDs) (95% confidence interval, 95% CI) of sperm concentration, sperm count, and sperm total motility were -0.17 (-0.20, -0.13), -0.05 (-0.08, -0.02), and -0.33 (-0.54, -0.11), respectively. However, exposure to air pollution was not related to sperm progressive motility (SMD = 0.00, 95% CI: -0.13, 0.12). The results indicated that exposure to air pollutants at a higher level was associated with impaired semen quality, including declined sperm concentration, reduced sperm count, and declined total motility. The results suggested that high level of air pollution exposure had a negative effect on semen quality. Improvement of air quality is important for enhancing semen quality.

Adverse effects of antiepileptic drugs on hormones of the hypothalamic-pituitary-gonadal axis in males: A review

The HPG axis is critical in the maintenance of spermatogenesis and sexual function in males. The GnRH-releasing neurons of the hypothalamus are the axis's main hierarchical element. These neurons make connections with different areas of the brain to regulate the release of GnRH. Neurotransmitters have a critical in the connections between these neurons. So, neurotransmitters can inhibit or stimulate the release of GnRH by affecting GnRH-releasing neurons. In neurological disorders, neurotransmitter's activities inevitably change; therefore, these changes can affect the HPG axis via affecting GnRH-releasing neurons, just like in epilepsy. Many investigations have attracted attention to be decreased fertility potential in males with epilepsy. It has been stated that changes in the HPG axis hormone levels have been found in these patients. Moreover, it has also been observed that sperm quality decreased in patients. It has been emphasized that a decrease in sperm quality may be related to both epilepsy and AEDs. It has been shown that AEDs caused decreased sperm quality by impairing the HPG axis, so they act like endocrine-disrupting chemicals. AEDs can affect fertility and cause additive adverse effects in terms of sperm quality together with epilepsy. Therefore, it is crucial to investigate the adverse reproductive effects of AEDs, which are frequently used during reproductive ages, and determine the role of the HPG axis on potential reproductive pathologies.