A preliminary study on the relationship between environmental endocrine disruptors and precocious puberty in girls

Temporal and geographic variability of bisphenol levels in humans: A systematic review and meta-analysis of international biomonitoring data

INTRODUCTION

Bisphenols are endocrine-disrupting chemicals known to contribute to chronic disease across the lifespan. With increased awareness of their health effects, changes in regulation and health behaviors have contributed to reductions in urinary bisphenol A (BPA) levels in the United States, Canada, and Europe. However, global trends in bisphenols outside these regions, especially bisphenol S (BPS) exposure, have been less studied.

AIM

We examine trends in urinary BPA and BPS concentration in non-occupationally exposed populations, where representative data at a country level is unavailable.

METHODS

We systematically reviewed studies published between 2000 and 2023 that included urinary bisphenol concentrations. We examined BPA and BPS concentration changes by sampling year, controlling for region, age, and pregnancy status, with and without a quadratic term and geometric mean, via mixed-effects meta-regression models with a random intercept and sensitivity analysis. We identified heterogeneity using Cochran's Q-statistic, I2 index, and funnel plots.

RESULTS

The final analytic sample consisted of 164 studies. We observed positive non-linear associations between time and BPA concentration internationally (beta: 0.02 ng/mL/year2, 95% CI: [0.01, 0.03]) and in Eastern and Pacific Asia (beta: 0.03 ng/mL/year2, 95% CI: [0.02, 0.05]). We also observed non-linear associations of time with both BPA and BPS concentrations in the Middle East and South Asia (beta: 0.13 ng/mL/year2, 95% CI: [0.01, 0.25] and beta: 0.29 ng/mL/year2, 95% CI: [-0.50, -0.08], respectively). In the sensitivity analyses excluding studies with geometric or arithmetic mean values, each displayed significant shifts from the main findings with some consistent outcomes occurring internationally and/or in specific regions. Heterogeneity was high across studies, suggesting possible bias in our estimations.

CONCLUSIONS

Our findings provide evidence for concern about increasing population exposure to BPA and BPS. Further studies estimating attributable disease burden and costs at regional and global levels are warranted to show these chemicals' impact on population health and economies.

Reproductive toxicity of bisphenol A and nitro-bisphenol A in male zebrafish at environmentally relevant concentrations

Bisphenol A (BPA) is a well-known endocrine-disrupting pollutant that poses significant environmental challenges globally. However, the toxicity of nitro-BPA (NBPA), the primary transformation product of BPA, remains poorly understood. This study employs a multi-omics approach, integrating in silico and bioinformatics analyses, to investigate and compare the male reproductive toxicity of BPA and NBPA in male zebrafish exposed to environmentally relevant concentrations. After 21 days of exposure, we observed a significant increase in cumulative egg production over five days in the NBPA 200 nM group compared to pre-exposure levels. Conversely, the gonadosomatic index of NBPA 200 nM group was significantly reduced by approximately 41.65 %. Our findings indicate that the activation of ESRRγ and inhibition of NR5A2 are critical molecular initiating events linked to male reproductive toxicity. Additionally, both BPA and NBPA were found to disrupt several key events within the steroid hormone biosynthesis pathway. This disruption includes the downregulation of genes encoding cytochrome P450 (CYP450) and hydroxysteroid dehydrogenase enzymes, as well as alterations in the levels of steroid hormones such as cholesterol and 25-hydroxycholesterol. Our study identifies biomolecular targets of BPA and NBPA at environmentally relevant concentrations that induce reproductive toxicity, enhancing our understanding of NBPA toxicity and are anticipated to inform the development of effective mitigation strategies.

The toxic effect of 2,6-di-tert-butylphenol on embryonic development in zebrafish (Danio rerio): Decreased survival rate, morphological abnormality, and abnormal vascular development

2,6-di-tert-butylphenol (2,6-DTBP) has been used extensively in plastics, rubber and polymer phenolic antioxidants. It is discharged into the aquatic environment through industrial waste. However, the toxicity assessment of 2,6-DTBP is insufficient. Here, zebrafish embryos were used as an animal model to investigate the toxicological effects of 2,6-DTBP. The results showed that 2,6-DTBP induced mitochondrial dysfunction and reactive oxygen species accumulation, which caused apoptosis, and further led to developmental toxicity of zebrafish embryos, such as delayed incubation, reduced survival rate, and increased malformation rate and heart rate. 2,6-DTBP can also cause morphological changes in the zebrafish endothelial cell (zEC) nucleus, inhibit zEC migration, trigger abnormal angiogenesis and zEC sprouting angiogenesis, and ultimately affect vascular development. In addition, 2,6-DTBP interfered with the endogenous antioxidant system, causing changes in activities of superoxide dismutase, catalase, and glutathione S-transferase and contents of malondialdehyde and glutathione. Transcriptome sequencing showed that 2,6-DTBP altered the mRNA levels of genes associated with vascular development, oxidative stress, apoptosis, extracellular matrix components and receptors. Integrative biomarker response assessment found that 12 μM 2,6-DTBP had the highest toxicity. These results indicated that 2,6-DTBP induced apoptosis through oxidative stress, leading to toxicity of zebrafish embryo development. This study contributes to understanding the effects of environmental 2,6-DTBP exposure on early development of aquatic organisms and draws public attention to the health risks posed by chemicals in aquatic organisms.

Tiny pills, big impacts: A systematic review on the endocrine disrupting effects of paediatric pharmaceuticals

Endocrine disrupting chemicals (EDCs) may impact children's health, with medicines as a possible exposure source. Objective: to assess the potential impact of substances in paediatric medications and essential oils on children as EDC. It is a systematic review of five databases including Medline following the PECOT approach. The review focused on publications about children exposed to medication (active ingredients or excipients of interest) and having developed clinical signs of endocrine dysfunction. Out of 946 studies identified, 28 studies were included. They revealed that parabens, lavender essential oils and anti-epileptics are the most identified pharmaceutical products. The reported outcomes relate to puberty, thyroid disorders, obesity and growth. The evidence indicates potential risks, but the overall quality of available data is limited. This systematic review exposes a lack of robust evidence linking paediatric medication exposure to EDC, predominantly relying on case reports. It cautions about potential conflicts of interest.

Multi-omic analysis of precocious puberty girls: pathway changes and metabolite validation

Objective

Precocious puberty (PP) is a prevalent endocrine disorder affecting the physical and mental wellbeing of children. Identifying the triggering factors of PP has become a central issue. This study seeks to investigate the metabolomic and transcriptomic alterations in PP.

Material and methods

First, 37 school-aged girls diagnosed with PP and 25 age-matched prepubertal control girls were recruited, and the fecal samples were collected for non-targeted metabolomic analysis to screen for differentially expressed metabolites (DEMs). Subsequently, an animal model of PP was constructed by danazol administration to neonatal female rats, and both fecal non-targeted metabolomics and serum next-generation transcriptomic sequencing were performed to screen DEMs and differentially expressed genes (DEGs) in PP. Moreover, the DEM co-existing in clinical and animal models was administrated to PP rats to explore the role of the target metabolite in PP.

Results

A total of 24 DEMs in PP clinical samples and 180 DEMs and 425 DEGs in PP animal samples were identified. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that these DEMs and DEGs were enriched in disease-associated pathways, including fatty acid synthesis, glycerolipid metabolism, pyrimidine metabolism, steroid hormone biosynthesis, progesterone-mediated oocyte maturation, and gonadotropin-releasing hormone (GnRH) signaling pathway, forming a tight DEM-DEG pathway regulatory network. Further DEM validation demonstrated that thymine supplementation delayed the opening of the vagina and development of PP in model rats.

Conclusion

This study reveals that the metabolomic and transcriptomic changes, along with enriched pathways, are implicated in PP based on clinical and animal analyses. The findings may provide new strategies and research avenues for PP treatment.

Persistent high exposure to exogenous phthalates and endogenous sex hormones associated with early pubertal onset among children: A 3.5-year longitudinal cohort study in China

BACKGROUND

Early onset of puberty could have significant impacts on childhood health, but the extent to which it was affected by phthalate esters (PAEs) and sex hormone disruption was not understood. The aim of this study is to investigate the associations between exposure to PAEs and sex hormone disruption and early onset of puberty in children.

METHODS

A longitudinal cohort study was conducted in China from May 2017 to Oct 2020, involving 740 children during consecutive visits. The onset of puberty was evaluated using Tanner definition, and early puberty was defined as an onset age less than the first 25 %, with cut-offs of 10.33 and 8.97 years for boys and girls, respectively. Serum testosterone (TT), estradiol (E₂) and urinary PAE metabolites were measured during three visits. Generalized linear models were used to explore the associations between PAE and sex hormones with the age of puberty onset, while log-binomial regressions were applied to assess the associations of persistent exposure to PAEs and sex hormones with early pubertal onset.

RESULTS

Approximately 86.0 % of boys and 90.2 % of girls completed puberty onset from pre-puberty, and more than 95 % of participants had PAE concentrations higher than the limit of detection. Boys showed higher exposure to PAE pollutants and higher TT levels. Persistent exposure to PAEs was positively associated with early pubertal onset in girls (ARR = 1.97, 95 %CI = 1.12, 3.46). Moreover, persistent exposure to PAEs and E₂ had synergistic associations with early pubertal onset in both boys (ARR = 4.77, 95 %CI = 1.06, 21.54) and girls (ARR = 7.07, 95 %CI = 1.51, 33.10). However, PAEs and TT had antagonistic associations only in boys (ARR = 0.44, 95 %CI = 0.07, 2.58).

CONCLUSION

Long-term exposure to PAEs might increase the risk of early pubertal onset, and it appears to work in synergy with E₂, while in antagonism with TT in boys' early pubertal onset. Reducing PAEs exposure might promote pubertal health.

A review of statistical strategies to integrate biomarkers of chemical exposure with biomarkers of effect applied in omic-scale environmental epidemiology

Humans are exposed to a growing list of synthetic chemicals, some of them becoming a major public health concern due to their capacity to impact multiple biological endpoints and contribute to a range of chronic diseases. The integration of endogenous (omic) biomarkers of effect in environmental health studies has been growing during the last decade, aiming to gain insight on the potential mechanisms linking the exposures and the clinical conditions. The emergence of high-throughput omic platforms has raised a list of statistical challenges posed by the large dimension and complexity of data generated. Thus, the aim of the present study was to critically review the current state-of-the-science about statistical approaches used to integrate endogenous biomarkers in environmental-health studies linking chemical exposures with health outcomes. The present review specifically focused on internal exposure to environmental chemical pollutants, involving both persistent organic pollutants (POPs), non-persistent pollutants like phthalates or bisphenols, and metals. We identified 42 eligible articles published since 2016, reporting 48 different statistical workflows, mostly focused on POPs and using metabolomic profiling in the intermediate layer. The outcomes were mainly binary and focused on metabolic disorders. A large diversity of statistical strategies were reported to integrate chemical mixtures and endogenous biomarkers to characterize their associations with health conditions. Multivariate regression models were the most predominant statistical method reported in the published workflows, however some studies applied latent based methods or multipollutant models to overcome the specific constraints of omic or exposure of data. A minority of studies used formal mediation analysis to characterize the indirect effects mediated by the endogenous biomarkers. The principles of each specific statistical method and overall workflow set-up are summarized in the light of highlighting their applicability, strengths and weaknesses or interpretability to gain insight into the causal structures underlying the triad: exposure, effect-biomarker and outcome.

Dysregulation of steroid metabolome in follicular fluid links phthalate exposure to diminished ovarian reserve of childbearing-age women

The widespread use of phthalates (PAEs) has drawn increasing attention due to their endocrine disruption and reproductive toxicity, while the steroid metabolome is essential for follicular development. However, the mechanism by which PAE exposure affects ovarian reserve through the steroid metabolome remains unclear. This study recruited 264 childbearing-age women in Tianjin (China) from April 2019 to August 2020 in a cross-sectional design. Target metabolome analysis of 16 steroids was performed in follicular fluid (FF) to compare diminished ovarian reserve (DOR) against normal ovarian reserve (NOR) women and differential steroids were identified using binary logistic analyses. Further analysis of eleven PAE metabolites (mPAEs) in FF was conducted, and the retrieved oocyte number (RON) representing ovarian reserve was counted. Multiple linear regression and quantile-based g-computation (qgcomp) models were used to associate individual mPAEs and mPAE mixture with the DOR-related differential steroids in FF. Mediation analysis was used to discuss the mediating effect of DOR-related steroids on the association between mPAEs and RON. Androstenedione (A4), corticosterone (CORT), cortisol (COR) and cortisone were significantly down-regulated in FF from women with DOR. Nine mPAEs with detection frequencies greater than 60% and median concentrations of 0.02-4.86 ng/mL were incorporated into statistical models. Negative associations with COR and CORT were found for mono-ethyl phthalate (mEP), mono-(2-ethyl-5-oxohexyl) phthalate (mEOHP), and mono-2-ethylhexyl phthalate (mEHP). A positive association with cortisone was found for mEOHP, mEHP, monobutyl phthalate (mBP), and mono (2-isobutyl) phthalate (miBP). The qgcomp and mediation analyses revealed that mEP and mEOHP not only significantly contributed to the decline of COR and CORT in the mixed exposure but also indirectly reduced RON through the mediating effects of COR and CORT. In conclusion, PAE exposure may decrease ovarian reserve by downregulating COR and CORT.

Oestrogenic Activity in Girls with Signs of Precocious Puberty as Exposure Biomarker to Endocrine Disrupting Chemicals: A Pilot Study

The relationship between endocrine disrupting chemical (EDC) exposure and Precocious Puberty (PP) was investigated in this pilot study, involving girls with signs of PP (P) and pre-pubertal girls (C). Risk factors for PP were assessed through questionnaires, while 17β-oestradiol (E2) levels and oestrogenic activity were quantified on sera. The oestrogenic activity, expressed as E2 equivalent concentration (EEQ), was applied as EDC exposure biomarker. Questionnaires showed a low EDC knowledge, a high EDC exposure, and a potential relationship between some habits at risk for EDC exposure and PP. EEQs were similar between C and P; however, they were significantly higher in girls living in an urban environment than in girls living in a rural environment, suggesting a potential higher EDC exposure in cities. The results of this pilot study highlighted the need to raise awareness on EDCs and can be considered a starting point to clarify the relationship between EDC exposure and PP.

Childhood obesity and central precocious puberty

Childhood obesity is a major public health problem worldwide, and the relationship between obesity and central precocious puberty has long been confirmed, however, the mechanisms underlying this association remain elusive. This review provides an overview of the recent progress regarding how childhood obesity impacts on hypothalamic-pituitary-gonadal axis and pubertal onset, focusing on adipokines (leptin and ghrelin), hormone (insulin), and lipid (ceramide), as well as critical signaling pathways (AMPK/SIRT, mTOR) that integrate the peripheral metabolism and central circuits. Notably, prevention of obesity and CPP is beneficial for the adult life of the children, thus we further summarize the potential strategies in treating and preventing childhood obesity and CPP. The updated understanding of metabolic stress and pediatric endocrine disease will arise the attention of society, and also contribute to preventing more serious comorbidities in the later period of life in children.