The association of bisphenol A exposure with premature ovarian insufficiency: a case-control study

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.

Mechanism Exploration of Environmental Pollutants on Premature Ovarian Insufficiency: a Systematic Review and Meta-analysis

As a public health problem, premature ovarian insufficiency leads to infertility or sub-fertility. In addition to premature ovarian insufficiency (POI) increases the lifetime risk of bone fragility, cardiovascular disease, and cognitive impairment. To investigate the effects of environmental pollutants on the occurrence of POI and explore its mechanism, we conducted a computer search for articles published in electronic databases by December 13, 2022. Three reviewers independently examined all included studies and scored the qualities of included studies using the Newcastle-Ottawa Scale criteria. In this meta-analysis, eight clinical studies as well as ten preclinical findings showed a pooled OR of 2.331 and 95% CI of 1.968-2.760. This confirms that environmental pollutants, including POPs, heavy metals, PAEs, PAHs, cosmetic and pharmaceutical products, and cigarette smoke, are indeed significant risk factors for POI. In addition, it is demonstrated from the results of this study that signaling pathway of calcium and PI3K Akt and Xpnpep2, Col1, Col3, Col4, Cx43, Egr3, Tff1, and Ptgs2 genes may all be involved in the process. Environmental pollutants, including POPs, heavy metals, PAEs, PAHs, cosmetic and pharmaceutical products, and cigarette smoke, are indeed significant risk factors for POI.

In utero bisphenol A exposure disturbs germ cell cyst breakdown through the PI3k/Akt signaling pathway and BDNF expression

PURPOSE

To determine the influence of the environmental endocrine disruptor bisphenol A (BPA) on germ cell cyst breakdown and explore the possible mechanisms regulating this activity.

METHODS

BPA (2 μg/kg/d or 20 μg/kg/d) or tocopherol-stripped corn oil (vehicle control) was administered to pregnant mice by gavage at gestational day 11, and the offspring (prenatally treated mice) were sacrificed and ovariectomized at postnatal day (PND) 4 and PND22. Ovarian morphology was documented in the first filial (F1) generation female offspring, and the follicles were analyzed and classified morphologically on PND 4. To discover differentially expressed genes and associated target pathways, we used RNA-seq, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, and Gene Ontology (GO) analysis. The mRNA expression of key steroid hormone synthesis-related genes was evaluated by Q-PCR in forskolin-induced KGN cells. Western blotting (WB) and qRTPCR were used to determine the protein and gene expression levels of brain-derived neurotrophic factor (BDNF).

RESULTS

BPA, a typical endocrine disrupting chemical (EDC), decreased the expression of the key steroid hormone synthesis-related genes P450scc and aromatase, while the expression of Star increased significantly and caused no significant difference in the expression of Cyp17a1 or HSD3β in forskolin-induced KGN cells. Moreover, we confirmed that in utero exposure to environmentally relevant concentrations of BPA (2 μg/kg/d and 20 μg/kg/d) could significantly disrupt germ cell cyst breakdown, leading to the generation of fewer primordial follicles than in the control group. The factors mediating the inhibitory effects included the PI3K-Akt signaling pathway and a significant downregulation of BDNF.

CONCLUSIONS

These findings indicate that in utero exposure to BPA at low doses, which are lower than recommended as 'safe' dosages, may influence the formation of primordial follicles by inhibiting the expression of steroid hormone synthesis-related genes and partly by regulating the BDNF-mediated PI3K/Akt pathway.

Bisphenol-A and Female Fertility: An Update of Existing Epidemiological Studies

Humans interfere with a variety of endocrine disruptors on a daily basis, which may result in adverse health effects. Among them, Bisphenol-A (BPA) is the most debated endocrine disruptor, despite being widely studied, regarding its effects on fertility. The aim of this review was to investigate the interrelation of BPA and female fertility. PubMed (Medline) was searched from 2013 until 2022 to identify epidemiological studies that report the association of BPA with fertility parameters, in vitro fertilization (IVF) outcomes, polycystic ovarian syndrome (PCOS) and endometriosis. Regarding general fertility, most studies report an inverse association between BPA and ovarian reserve markers, namely antral follicle count (AFC) and anti-Müllerian hormone (AMH). The BPA and estradiol (E2) levels did not correlate significantly in the majority of studies. No definite conclusions can be reached regarding BPA and IVF endpoints or endometriosis. Lastly, most studies report higher prevalence of PCOS in women with higher BPA concentrations, although no casualty has been proven. Although most studies fail to reach definite conclusion regarding the impact of BPA on fertility, there is accumulating evidence suggesting a negative role of BPA in female reproductive health.

Endocrine disrupting chemicals impact on ovarian aging: Evidence from epidemiological and experimental evidence

Endocrine-disrupting chemicals (EDCs) are ubiquitous in daily life, but their harmful effects on the human body have not been fully explored. Recent studies have shown that EDCs exposure could lead to infertility, menstrual disorder and menopause, resulting in subsequent effects on female health. Therefore, it is of great significance to clarify and summarize the impacts of EDCs on ovarian aging for explaining the etiology of ovarian aging and maintaining female reproductive health. Here in this review, we focused on the impacts of ten typical environmental contaminants on the progression of ovarian aging during adult exposure, including epidemiological data in humans and experimental models in rodents, with their clinical phenotypes and underlying mechanisms. We found that both persistent (polychlorinated biphenyls, perfluoroalkyl and polyfluoroalkyl substances) and non-persistent (phthalates) EDCs exposure could increase an overall risk of ovarian aging, leading to the diminish of ovarian reserve, decline of fertility or fecundity, irregularity of the menstrual cycle and an earlier age at menopause, and/or premature ovarian insufficiency/failure in epidemiological studies. Among these, the loss of follicles can also be validated in experimental studies of some EDCs, such as BPA, phthalates, parabens and PCBs. The underlying mechanisms may involve the impaired ovarian follicular development by altering receptor-mediated pro-apoptotic pathways, inducing signal transduction and cell cycle arrest and epigenetic modification. However, there were inconsistent results in the impacts on fertility/fecundity, menstrual/estrous cycle and hormone changes response to different EDCs, and differences between human and animal studies. Our review summarizes the current state of knowledge on ovarian disrupters, highlights their risks to ovarian aging and identifies knowledge gaps in humans and animals. We therefore propose that females adopt healthy lifestyle changes to minimize their exposure to both persistent and non-persistent chemicals, that have the potential damage to their reproductive function.