Urinary bisphenol A and S are associated with diminished ovarian reserve in women from an infertility clinic in Northern China

Preconception exposure to bisphenol A and its alternatives: Effects on female fecundity mediated by oxidative stress and ovarian reserve

BACKGROUND

Various 'Bisphenol A (BPA)-free' alternatives have emerged in numerous personal products in recent years. However, it remains unclear whether BPA analogs affect female fecundity and possible biological mechanisms.

OBJECTIVES

We aimed to evaluate the relationships of bisphenol analogs with female fecundability and infertility and whether oxidative stress, inflammation, and ovarian reserve may play a mediation role in such associations.

METHODS

This prospective preconception cohort study included 957 couples who attempted pregnancy. BPA and six alternatives were measured in women's urine samples. Bisphenol analogs-outcome associations were estimated using discrete-time Cox hazards and logistic regression models. A quantile g-computation (QGC) methodology was further applied to assess the joint effects of co-exposure to bisphenol analogs on fecundity. We also quantified three biomarkers, including malondialdehyde (MDA), C-reactive protein and Anti-Müllerian hormone (AMH), to explore possible biological pathways.

RESULTS

Using an integrated analytical approach consisting of both single-pollutant and mixture models, we found that BPA and bisphenol AP (BPAP) were significantly associated with decreased fecundability (adjusted fecundability ratio (aFR) = 0.87, 95%CI: 0.81, 0.94 for BPA; aFR = 0.64, 95%CI: 0.48, 0.84 for BPAP) and increased risk of infertility (adjusted odd ratio (aOR) = 1.23, 95%CI: 1.06, 1.44 for BPA; aOR = 2.27, 95%CI: 1.29, 3.99 for BPAP) after controlling for other bisphenol analogs. The link between BPA and prolonged time to pregnancy was more prominent in overweight or obese women and those who had regular menstrual cycles. Bisphenol AF was associated with impaired fecundity in women aged 35 years or older. The mixed effects of bisphenol analogs on fecundity were statistically non-significant. Mediation analysis revealed a significant indirect effect of urinary MDA and serum AMH in bisphenol analogs-induced impaired fecundity, with all average causal mediation effects (ACME) showing statistical significance (PACME < 0.05).

CONCLUSIONS

Our prospective preconception cohort study suggests that BPA and BPAP may be associated with impaired female fecundity. Increased oxidative stress and decreased ovarian reserve may be the underlying pathways.

The impact of Bisphenol-A on human reproductive health

Bisphenol-A (BPA) is a recognized endocrine-disrupting chemical used to produce several consumer goods and products. There has been widespread exposure to BPA because of increased industrial production and use of BPA-containing products. As a result of these exposures, BPA is found in several human body fluids and can cause endocrine disruption by interfering with hormone signaling pathways and epigenetic modifications. Therefore, human reproductive health and development have been adversely affected by BPA. This review aimed to consolidate existing knowledge on the impact of BPA on human reproductive health, examining its effects on both males and females. To achieve this, we systematically searched four databases for studies that associated BPA with reproductive health (male and female), after which we retrieved the important information from the selected articles. There was an association of reproductive health diseases with high BPA exposure. In males, BPA was associated with increased sperm alterations, altered reproductive hormone levels, and testicular atrophy. In females, there was an association of BPA exposure with hormonal imbalances, reduced ovarian reserve, and increased likelihood of conditions such as fibroids, polycystic ovarian syndrome, endometriosis and infertility. BPA's pervasive presence and its harmful effects on reproductive health underscore the need for global regulation and public awareness. Although substantial evidence from animal and in vitro studies supports the detrimental effects of BPA, there is a need for more human-focused research, particularly in developing countries, to confirm these findings. This review advocates for increased regulatory measures to limit BPA exposure.

Associations of bisphenol and phthalate exposure and anti-Müllerian hormone levels in women of reproductive age

Background

In women, exposure to endocrine disrupting chemicals might accelerate the depletion of the ovarian reserve and might be associated with accelerative reproductive aging and fertility. We examined the longitudinal associations of exposure to bisphenols and phthalates with anti-Müllerian hormone concentrations.

Methods

Pregnant women of 18 years or older that resided in Rotterdam between 2002 and 2006 were eligible for participation in this longitudinal prospective cohort study. We measured urinary bisphenol and phthalate concentration at three time-points in pregnancy among 1405 women, of whom 1322 women had serum Anti-Müllerian Hormone (AMH) measurements 6 and/or 9 years postpartum. We performed linear regression models to assess the association of urinary bisphenol and phthalate metabolites with AMH after 6 and 9 years, and linear mixed-effect model to assess the association with AMH over time. Models were adjusted for sociodemographic and lifestyle factors.

Findings

In our multivariable linear regression models we observed associations of higher urinary pregnancy-averaged mono-isobutyl phthalate (mIBP), mono-(2-ethyl-5-oxohexyl) phthalate (mEOHP), and monobenzyl phthalate (mBzBP) with lower serum AMH after both 6 and 9 years. However, these associations did not remain after adjustment for multiple testing. No significant associations of bisphenol A with AMH were present in our study sample. In our linear mixed-effects models, higher mIBP, mono-(2-ethyl-5-hydroxyhexyl) phthalate (mEHHP), mEOHP, and mBzBP were associated with lower overall AMH levels (differences -0.07 (95% CI -0.13, -0.02), -0.09 (-0.15, -0.02), -0.08 (95% CI -0.14, -0.02), and -0.08 (-0.13, -0.03) μg/L per doubling in mIBP, mEHHP, mEOHP, and mBzBP respectively) (all False Discovery Rate adjusted p-values < 0.05).

Interpretation

We identify decreases in indices of ovarian reserve in relationship to prenatal phthalate exposures. Studies are needed replicating our results among large multi-ethnic non-pregnant populations and assessing transgenerational effects of exposure on ovarian reserve.

Funding

This study was supported by the Erasmus Medical Center and Erasmus University Rotterdam, the Netherlands Organisation for Health Research and Development, the European Research Council, the Dutch Heart Foundation, the Dutch Diabetes Foundation, the European Union's Horizon 2020 Research and Innovation Program, the National Institutes of Health, Ansh Labs Webster, and the Royal Netherlands Academy of Arts and Sciences.

Urinary concentrations of bisphenol A and its alternatives: Potential predictors of and associations with antral follicle count among women from an infertility clinic in Northern China

BACKGROUND

Experimental studies have suggested exposure to bisphenol A (BPA) and its alternatives, such as bisphenol F (BPF) and bisphenol S (BPS), may exert adverse effects on ovarian reserve, but human evidence is limited. Moreover, the potential predictors of exposure to bisphenols among women seeking infertility treatment have not been reported.

OBJECTIVE

To explore whether individual or mixture of BPA, BPF, and BPS were related to antral follicle count (AFC), and further identify the predictors of exposure to bisphenols among women seeking assisted reproductive treatment.

METHODS

A total of 111 women from a reproductive center in Shenyang, China were enrolled in this study from September 2020 to February 2021. The concentrations of urinary BPA, BPF, and BPS were measured using ultra-high-performance liquid chromatography-triple quadruple mass spectrometry (UHPLC-MS/MS). AFC was measured by two infertility physicians through transvaginal ultrasonography on the 2-5 days of a natural cycle. Demographic characteristics, dietary habits, and lifestyles were obtained by questionnaires. The associations between individual and mixture of urinary bisphenols concentrations (BPA, BPF, and BPS) and AFC were assessed by the Poisson regression models and the quantile-based g-computation (QGC) model, respectively. The potential predictors of exposure to bisphenols were identified by the multivariate linear regression models.

RESULTS

After adjusting for confounders, elevated urinary concentrations of BPA, BPF and BPS were associated with reduced AFC (β = -0.016; 95%CI: -0.025, -0.006 in BPA; β = -0.017; 95%CI: -0.029, -0.004 in BPF; β = -0.128; 95%CI: -0.197, -0.060 in BPS). A quantile increase in the bisphenols mixture was negatively associated with AFC (β = -0.101; 95%CI: -0.173, -0.030). Intake of fried food had higher urinary concentrations of BPF, BPS, and total bisphenols (∑BPs) than women who did not eat, and age was related to increased urinary BPF concentrations.

CONCLUSION

Our findings indicated that exposure to individual BPA, BPF, BPS and bisphenol mixtures were associated with impaired ovarian reserve. Furthermore, the intake of fried food, as identified in this study, could serve as an important bisphenols exposure route for reproductive-aged women.

Exposure to bisphenol A affects transcriptome-wide N6-methyladenine methylation in ovarian granulosa cells

Bisphenol A (BPA) is an endocrine disruptor of potential reproductive toxicities. Increasingly research elucidated that BPA exposure to the environment would change the epigenetic modifications of transcriptome, but the mechanism by which BPA affects m6A methylation in interfering with female reproductive health remains uncertain. Therefore, this study preliminarily proposed and tested the hypothesis that BPA exposure alters the m6A modification level in transcripts in female ovarian granulosa cells. After BPA was exposed to granulosa cells for 24 h, RNA methylation related regulatory genes (such as METTL3, METTL14, ALKBH5, FTO) and the global m6A levels showed significant differences. Next, we applied MERIP-seq analysis to obtain information on the genome-wide m6A modification changes and identified 1595 differentially methylated mRNA transcripts, and 50 differentially methylated lncRNA transcripts. Further joint analysis of gene common expression showed that 33 genes were hypermethylated and up-regulated, 71 were hypermethylated and down-regulated, 49 were hypomethylated and up-regulated, and 20 were hypomethylated and down-regulated. Enriched Gene Ontology (GO) and biological pathway analysis revealed that these unique genes were mainly enriched in lipid metabolism, cell proliferation, and apoptosis related pathways. Six of these genes (mRNAs IMPA1, MCOLN1, DCTN3, BRCA2, and lncRNAs MALAT1, XIST) were validated using RT-qPCR and IGV software. Through comprehensive analysis of epitranscriptome and protein-protein interaction (PPI) data, lncRNAs MALAT1 and XIST are expected to serve as new markers for BPA interfering with the female reproductive system. In brief, these data show a novel and necessary connection between the damage of BPA exposure on female ovarian granulosa cells and RNA methylation modification.

The adverse role of endocrine disrupting chemicals in the reproductive system

Reproductive system diseases pose prominent threats to human physical and mental well-being. Besides being influenced by genetic material regulation and changes in lifestyle, the occurrence of these diseases is closely connected to exposure to harmful substances in the environment. Endocrine disrupting chemicals (EDCs), characterized by hormone-like effects, have a wide range of influences on the reproductive system. EDCs are ubiquitous in the natural environment and are present in a wide range of industrial and everyday products. Currently, thousands of chemicals have been reported to exhibit endocrine effects, and this number is likely to increase as the testing for potential EDCs has not been consistently required, and obtaining data has been limited, partly due to the long latency of many diseases. The ability to avoid exposure to EDCs, especially those of artificially synthesized origin, is increasingly challenging. While EDCs can be divided into persistent and non-persistent depending on their degree of degradation, due to the recent uptick in research studies in this area, we have chosen to focus on the research pertaining to the detrimental effects on reproductive health of exposure to several EDCs that are widely encountered in daily life over the past six years, specifically bisphenol A (BPA), phthalates (PAEs), polychlorinated biphenyls (PCBs), parabens, pesticides, heavy metals, and so on. By focusing on the impact of EDCs on the hypothalamic-pituitary-gonadal (HPG) axis, which leads to the occurrence and development of reproductive system diseases, this review aims to provide new insights into the molecular mechanisms of EDCs' damage to human health and to encourage further in-depth research to clarify the potentially harmful effects of EDC exposure through various other mechanisms. Ultimately, it offers a scientific basis to enhance EDCs risk management, an endeavor of significant scientific and societal importance for safeguarding reproductive health.

Bisphenols-A Threat to the Natural Environment

Negative public sentiment built up around bisphenol A (BPA) follows growing awareness of the frequency of this chemical compound in the environment. The increase in air, water, and soil contamination by BPA has also generated the need to replace it with less toxic analogs, such as Bisphenol F (BPF) and Bisphenol S (BPS). However, due to the structural similarity of BPF and BPS to BPA, questions arise about the safety of their usage. The toxicity of BPA, BPF, and BPS towards humans and animals has been fairly well understood. The biodegradability potential of microorganisms towards each of these bisphenols is also widely recognized. However, the scale of their inhibitory pressure on soil microbiomes and soil enzyme activity has not been estimated. These parameters are extremely important in determining soil health, which in turn also influences plant growth and development. Therefore, in this manuscript, knowledge has been expanded and systematized regarding the differences in toxicity between BPA and its two analogs. In the context of the synthetic characterization of the effects of bisphenol permeation into the environment, the toxic impact of BPA, BPF, and BPS on the microbiological and biochemical parameters of soils was traced. The response of cultivated plants to their influence was also analyzed.

Subfertility as Overlapping of Nutritional, Endocrine, Immune, and Cardiometabolic Dysregulations-A Study Focused on Biochemical Endophenotypes of Subfertile Couples

Subfertility is a global health issue, and as many as 30% of cases are attributed to unexplained reasons. A hypercaloric, high-fat diet stimulates the expansion of pro-inflammatory gut microbiota with a consequent rise in circulating lipopolysaccharides. Adverse gut microbiota remodeling can exacerbate insulin resistance, while sex and thyroid hormones may influence the variability in gut microbiota. This cross-sectional study included 150 participants and was designed to determine a biochemical, nutritional-related pattern that may distinguish subfertile from fertile individuals and couples. A panel of 28 biomarkers was assessed. Four biochemical phenotypes of unexplained subfertility were found, including two metabolic and two immune, when assessed using binary logistic regression models. Two phenotypes were distinguished in women: cardio-metabolic with atherogenic dyslipidemia (LowHDL-cholesterol: OR = 10.9; p < 0.05) and autoimmune thyroid disorder (Highanti-thyroid-peroxidase: OR = 5.5; p < 0.05) and two in men: hepato-metabolic with elevated liver injury enzymes (HighHOMA-IR: OR = 6.1; p < 0.05) and immune type-2 response (HighIgE: OR = 6.4; p < 0.05). The chances of a couple's subfertility rose with the number of laboratory components of metabolic syndrome in the couple (OR = 1.7; p < 0.05) and if at least one partner had an elevated total IgE level (>100 kU/L) (OR = 6.5; p < 0.05). This study found that unexplained subfertility may be accompanied by mutually overlapping immune and metabolic dysregulations in individuals and couples. We propose one-time laboratory diagnostics taking into account the lipid profile, insulin resistance, anti-thyroid-peroxidase, and total IgE in both males and females with unexplained subfertility. This may allow for a one-time assessment of targeted medical and nutritional interventions and help optimize patients' health. The gut-organ axes related to subfertility are discussed in the context of the obtained results.