Endocrine-Disrupting Chemicals and Human Growth and Maturation

Prenatal Exposure to Multiple Endocrine-Disrupting Chemicals and Childhood BMI Trajectories in the INMA Cohort Study

BACKGROUND

Prenatal exposure to endocrine-disrupting chemicals (EDCs) may disrupt normal fetal and postnatal growth. Studies have mainly focused on individual aspects of growth at specific time points using single chemical exposure models. However, humans are exposed to multiple EDCs simultaneously, and growth is a dynamic process.

OBJECTIVE

The objective of this study was to evaluate the associations between prenatal exposure to EDCs and children's body mass index (BMI) growth trajectories using single exposure and mixture modeling approaches.

METHODS

Using data from the INfancia y Medio Ambiente (INMA) Spanish birth cohort (n = 1,911 ), prenatal exposure to persistent chemicals [hexachlorobenzene (HCB), 4-4'-dichlorodiphenyldichloroethylene (DDE), polychlorinated biphenyls (PCB-138, -150, and -180), 4 perfluoroalkyl substances (PFAS)] and nonpersistent chemicals (8 phthalate metabolites, 7 phenols) was assessed using blood and spot urine concentrations. BMI growth trajectories were calculated from birth to 9 years of age using latent class growth analysis. Multinomial regression was used to assess associations for single exposures, and Bayesian weighted quantile sum (BWQS) regression was used to evaluate the EDC mixture's association with child growth trajectories.

RESULTS

In single exposure models exposure to HCB, DDE, PCBs, and perfluorononanoic acid (PFNA) were associated with increased risk of belonging to a trajectory of lower birth size followed by accelerated BMI gain by 19%-32%, compared with a trajectory of average birth size and subsequent slower BMI gain [e.g., relative risk ratio (RRR) per doubling in DDE concentration = 1.19 (95% CI: 1.05, 1.35); RRR for PFNA = 1.32 (95% CI: 1.05, 1.66)]. HCB and DDE exposure were also associated with higher probability of belonging to a trajectory of higher birth size and accelerated BMI gain. Results from the BWQS regression showed the mixture was positively associated with increased odds of belonging to a BMI trajectory of lower birth size and accelerated BMI gain (odds ratio per 1-quantile increase of the mixture = 1.70 ; credible interval: 1.03, 2.61), with HCB, DDE, and PCBs contributing the most.

DISCUSSION

This study provides evidence that prenatal EDC exposure, particularly persistent EDCs, may lead to BMI trajectories in childhood characterized by accelerated BMI gain. Given that accelerated growth is linked to a higher disease risk in later life, continued research is important. https://doi.org/10.1289/EHP11103.

Association of perfluoroalkyl and polyfluoroalkyl substances with sex hormones in children and adolescents 6-19 Years of age

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) have raised concerns regarding sex hormones homeostasis disruption in critical windows including childhood and adolescence, but epidemiological evidence is limited. We aimed to explore the associations of total testosterone (TT), estradiol (E₂), and sex hormone binding globulin (SHBG) in children and adolescents with PFAS in 921 participants 6-19 years of age from NHANES 2013 to 2016. Multiple linear regression models and Bayesian Kernel Machine Regression (BKMR) models stratified by sex-age and sex-puberty-status groups were performed to explore the associations of the associations of individual or mixture of PFAS with sex hormone levels, respectively. Inverse associations were observed between n-PFOA and SHBG in female adolescents when the exposure was modeled as continuous (β = -0.20, 95% CI -0.33, -0.07) or categorized variable (P for trend = 0.005). In children, inverse associations were observed by BKMR in 6-11-year-old girls of high concentration, and in boys of low concentration of the PFAS mixture with TT. A positive association of PFAS mixture with SHBG was observed in boys. PFOS and PFNA were identified as major contributors to the associations in girls and boys, respectively. Although the 95% credible intervals included the null in adolescents, suggestive negative associations of PFAS mixture with TT and SHBG levels in adolescents aged 12-19 years were found by BKMR. Results by sex-puberty status presented a similar pattern, where significantly inverse associations between PFAS mixture and E₂ were observed in the pubertal. Our findings suggested the associations of either individual or mixture PFAS with decreased TT levels, and increased SHBG levels in U.S. children and adolescents, and with decreased E₂ levels in pubertal individuals. The associations were evident in children.

Associations between repeated measurements of childhood triclosan exposure and physical growth at 7 years

BACKGROUND

Epidemiological studies suggested that triclosan (TCS) exposure was ubiquitous among children and could affect their physical growth. However, most studies relied on TCS exposure at single time point, and the impacts of multiple time points TCS exposure were unclear.

OBJECTIVES

To estimate the associations between repeated TCS measurements in childhood (at ages 1, 2, 5, and 7 years) and physical growth at 7 years.

METHODS

This study included 206 children from Laizhou Wan Birth Cohort (LWBC), China. Urinary TCS concentrations were detected at age of 1, 2, 5, and 7 years, and physical growth including height, weight, waist circumference, and fat percentage was measured at 7 years. Multiple informant models were applied to examine the relationships of repeated TCS measurements in childhood with physical growth, and stratified analysis by gender was performed.

RESULTS

The detection rates of TCS at age of 1, 2, 5, and 7 years were above 60%, with median declining from 0.89 to 0.33 μg/g creatinine. We found TCS at 5 years was positively associated with waist-to-height ratio, and TCS at 7 years was positively associated with physical growth, including weight z-score, BMI z-score, waist circumference, waist-to-height ratio, and fat percentage. Moreover, the above associations for weight z-score, BMI z-score, and fat percentage significantly varied by the period of exposure (pint ˂ 0.05). After stratified by gender, positive associations were only found among boys.

CONCLUSIONS

In our study, TCS levels decreased as children's age increased. TCS exposures at age of 5 and 7 years were positively associated with physical growth at 7 years, and these associations were only significant in boys. Given the relatively small sample size, our findings should be interpreted with caution until confirmed by further investigation.

In utero exposure to endocrine disruptors and developmental neurotoxicity: Implications for behavioural and neurological disorders in adult life

Endocrine disrupting chemicals (EDCs) are a class of environmental toxicants that interfere with the endocrine system, resulting in developmental malformations, reproductive disorders, and alterations to immune and nervous system function. The emergence of screening studies identifying these chemicals in fetal developmental matrices such as maternal blood, placenta and amniotic fluid has steered research focus towards elucidation of in utero effects of exposure to these chemicals, as their capacity to cross the placenta and reach the fetus was established. The presence of EDCs, a majority of which are estrogen mimics, in the fetal environment during early development could potentially affect neurodevelopment, with implications for behavioural and neurological disorders in adult life. This review summarizes studies in animal models and human cohorts that aim to elucidate mechanisms of action of EDCs in the context of neurodevelopment and disease risk in adult life. This is a significant area of study as early brain development is heavily mediated by estrogen and could be particularly sensitive to EDC exposure. A network analysis presented using genes summarized in this review, further show a significant association with disorders such as major depressive disorder, alcoholic disorder, psychotic disorders and autism spectrum disorder. Functional outcomes such as alterations in memory, behaviour, cognition, learning memory, feeding behaviour and regulation of ion transport are also highlighted. Interactions between genes, receptors and signaling pathways like NMDA glutamate receptor activity, 5-hydroxytryptamine receptor activity, Ras-activated Ca₂⁺ influx and Grin2A interactions, provide further potential mechanisms of action of EDCs in mediating brain function. Taken together with the growing pool of human and animal studies, this review summarizes current status of EDC neurotoxicity research, limitations and future directions of study for researchers.

Potential long-term developmental toxicity of in utero and lactational exposure to Triclocarban (TCC) in hampering ovarian folliculogenesis in rat offspring

Triclocarban (TCC), an antimicrobial compound commonly added to a wide range of household and personal hygiene care products, is one of the most prevalent endocrine-disrupting substances (EDS). This study was conducted to elucidate whether in utero and lactational exposure to TCC could adversely affect folliculogenesis and the onset of puberty in female rat offspring. Twenty pregnant Sprague Dawley rats were equally divided into Control and TCC dam groups (supplemented daily with drinking water enriched with 0.5 mg/L of TCC) from gestational day5 to postnatal day21 (PND21). Female offspring, 20 from control and 20 from TCC dams, were subdivided into 4 subgroups (PND21, PND28, PND35 & PND42). The day of vaginal opening and first estrous cycle were determined. Ovarian sections of the offspring were processed for H&E staining and for immunohistochemical expression of Ki67, Caspase-3 and androgen receptors (AR) on the granulosa cells of ovarian follicles. Follicular count and atretic index were assessed besides, serum estradiol, progesterone, FSH and LH, C-reactive protein (CRP), malondialdehyde (MDA) and total antioxidant capacity (TAC) were measured. TCC offspring exhibited a significant delay in the onset of puberty and impedance of normal transition of the primordial follicles to more developed ones with altered cyctoarchitecture. Also, TCC decreased follicular count, proliferation and gonado-somatic index while it increased atretic index, apoptosis and AR of the granulosa cells along with disturbance of the feminine hormonal profile and oxidant/antioxidant balance. This study highlighted the potential long-term consequences of in utero and lactational exposure to TCC on the postnatal development of the ovary in rat offspring.

Stereological analysis and transcriptome profiling of testicular injury induced by di-(2-ethylhexyl) phthalate in prepubertal rats

Di-(2-ethylhexyl) phthalate (DEHP) is the most common phthalate that can affect the male reproductive system. DEHP exposure at the prepubertal stage could lead to the injury of immature testes, but the mechanism has not been fully clarified. In the present study, we elucidated the possible underlying mechanism of DEHP-induced prepubertal testicular injury through stereological analysis and transcriptome profiling. Compared with the control group, the DEHP-treated rats had lower body weight gain and decreased testicular weight and organ coefficient. Moreover, lower serum levels of testosterone and LH were observed in the DEHP group, in contrast to the increased FSH level. Additionally, the serum level of estradiol had no significant difference after DEHP exposure. Stereological analysis showed significant reduction in volumes of most testicular structures, especially in the seminiferous tubule and seminiferous epithelium, along with a vast decrease of spermatogenic cells and obvious structural damages with substantial pathological signs (germ cracks, cytoplasmic vacuolization, sloughing, multinucleated giant cell formation, chromatolysis desquamation and dissolution, pyknosis of nuclei) in the seminiferous tubule upon DEHP exposure at the prepubertal stage. Furthermore, transcriptome profiling identified 5548 differentially expressed genes (DEGs) upon DEHP exposure. Pathway enrichment analysis revealed several crucial signaling pathways related to retinol metabolism, oxidative phosphorylation, steroid hormone biosynthesis, and cell adhesion molecules (CAMs). In addition, seven DEGs selected from RNA-seq data were validated by quantitative real-time polymerase chain reaction (qRT-PCR), and the results showed the same trends as the RNA-seq results. In conclusion, the above findings provide basic morphological data and lay a foundation for systematic research on transcriptome profiling in prepubertal testicular injury induced by DEHP.

Effects of 2,3',4,4',5-pentachlorobiphenyl exposure during pregnancy on DNA methylation in the testis of offspring in the mouse

Polychlorinated biphenyls (PCBs) are persistent organic pollutants, and the widespread use of PCBs has had adverse effects on human and animal health. This study experiment explored the effects of 2,3',4,4',5-pentachlorobiphenyl (PCB118) on the mammalian reproductive system. PCB118 was administered to pregnant mice from 7.5 to 12.5 days of gestation; F1 mice were obtained and the reproductive system of F1 male mice was examined. PCB118 damaged the reproductive system in male F1 mice, as evidenced by negative effects on the testicular organ coefficient (testes weight/bodyweight), a decrease in the diameter of seminiferous tubules and a significant reduction in the anogenital distance in 35-day-old F1 mice. In addition, methylation levels of genomic DNA were reduced, with reductions in the expression of the DNA methyltransferases DNMT1, DNMT3A and DNMT3B, as well as that of the epigenetic regulatory factor ubiquitin like with PHD and ring finger domains 1 (Uhrf1). Together, the results of this study provide compelling evidence that exposure of pregnant mice to PCB118 during primordial germ cell migration in the fetus affects the reproductive system of the offspring and decreases global methylation levels in the testis.

Bioanalytical methodologies for clinical investigation of endocrine-disrupting chemicals: a comprehensive update

Endocrine-disrupting chemicals (EDCs) are xenobiotics that disrupt the endocrine system in humans at ecologically significant concentrations. Various substances are exposed to human health via routes including food, water, air and skin that result in disastrous maladies at low doses as well. Therefore EDCs need a meticulous strategy of analysis for dependable and consistent monitoring in humans. The management and risk assessment necessitate advancements in the detection methodologies of EDCs. Hyphenated MS-based chromatograph and other validated laboratory analysis methods are widely available and employed. Besides, in vitro bioassay techniques and biosensors are also used to conduct accurate toxicological tests. This article provides a revision of various bioanalytical detection methods and technologies for the clinical estimation of EDCs.

Assessment of the Emerging Threat Posed by Perfluoroalkyl and Polyfluoroalkyl Substances to Male Reproduction in Humans

Per-fluoroalkyl and polyfluoroalkyl substances (PFAS) are a diverse group of synthetic fluorinated chemicals used widely in industry and consumer products. Due to their extensive use and chemical stability, PFAS are ubiquitous environmental contaminants and as such, form an emerging risk factor for male reproductive health. The long half-lives of PFAS is of particular concern as the propensity to accumulate in biological systems prolong the time taken for excretion, taking years in many cases. Accordingly, there is mounting evidence supporting a negative association between PFAS exposure and an array of human health conditions. However, inconsistencies among epidemiological and experimental findings have hindered the ability to definitively link negative reproductive outcomes to specific PFAS exposure. This situation highlights the requirement for further investigation and the identification of reliable biological models that can inform health risks, allowing sensitive assessment of the spectrum of effects of PFAS exposure on humans. Here, we review the literature on the biological effects of PFAS exposure, with a specific focus on male reproduction, owing to its utility as a sentinel marker of general health. Indeed, male infertility has increasingly been shown to serve as an early indicator of a range of co-morbidities such as coronary, inflammatory, and metabolic diseases. It follows that adverse associations have been established between PFAS exposure and the incidence of testicular dysfunction, including pathologies such as testicular cancer and a reduction in semen quality. We also give consideration to the mechanisms that render the male reproductive tract vulnerable to PFAS mediated damage, and discuss novel remediation strategies to mitigate the negative impact of PFAS contamination and/or to ameliorate the PFAS load of exposed individuals.

Early-life exposure to multiple persistent organic pollutants and metals and birth weight: Pooled analysis in four Flemish birth cohorts

BACKGROUND AND AIMS

Prenatal chemical exposure has frequently been associated with reduced fetal growth although results have been inconsistent. Most studies associate single pollutant exposure to this health outcome, even though this does not reflect real life situations as humans are exposed to many pollutants during their life time. The objective of this study is to investigate the association between prenatal exposure to a mixture of persistent environmental chemicals and birth weight using multipollutant models.

METHODS

We combined exposure biomarker data measured in cord blood samples of 1579 women from four Flemish birth cohorts collected over a 10 years' time period. The common set of available and detectable exposure measures in these cohorts are three polychlorinated biphenyls (PCB) congeners (138, 153 and 180), hexachlorobenzene (HCB), dichlorodiphenyldichloroethylene (p,p'-DDE) and the metals cadmium and lead. Multiple linear regression (MLR), Bayesian Information Criterion (BIC), penalized regression using minimax concave penalty (MCP) and Bayesian Adaptive Sampling (BAS) were applied to assess the influence of multiple pollutants in a single analysis on birth weight, adjusted for a priori selected covariates.

RESULTS

In the pooled dataset, a median (P25-P75) birth weight and gestational age of 3420 (3140-3700) grams and 39 (39-40) weeks was observed respectively. The median contaminant levels in cord blood were: 15.8, 26.5, 18.0, 16.9 and 91.5 ng/g lipid for PCB 138, PCB 153, PCB 180, HCB and p,p'-DDE, respectively, 0.075 µg/L for cadmium and 9.7 µg/L for lead. According to the applied statistical methods for multipollutant assessment, p,p'-DDE and PCB 180 were most consistently associated with birth weight. In addition, PCB 153 was selected when applying MCP and BAS. An inverse association with birth weight was found for the PCB congeners, while an increased birth weight was observed for elevated levels of p,p'-DDE.

CONCLUSIONS

Assessing the health risk of combinations of exposure biomarkers reflects better real-world situations and thereby allows more effective risk assessment. Our results add to the existing evidence based on detrimental effects of PCBs on birth weight and indicate a possible increase in birth weight due to p,p'-DDE (while correcting for PCBs).

Proteomic Profiles of Thyroid Gland and Gene Expression of the Hypothalamic-Pituitary-Thyroid Axis Are Modulated by Exposure to AgNPs during Prepubertal Rat Stages

Silver nanoparticles (AgNPs) have potent antimicrobial activity and, for this reason, are incorporated into a variety of products, raising concern about their potential risks and impacts on human health and the environment. The developmental period is highly dependent on thyroid hormones (THs), and puberty is a sensitive period, where changes in the hormonal environment may have permanent effects. We evaluated the hypothalamic-pituitary (HP)-thyroid axis after exposure to low doses of AgNPs using a validated protocol to assess pubertal development and thyroid function in immature male rats. For stimulatory events of the HP-thyroid axis, we observed an increase in the expression of Trh mRNA and serum triiodothyronine. Negative feedback reduced the hypothalamic expression of Dio2 mRNA and increased the expression of Thra1, Thra2, and Thrb2 mRNAs. In the pituitary, there was a reduced expression of Mct-8 mRNA and Dio2 mRNA. For peripheral T3-target tissues, a reduced expression of Mct-8 mRNA was observed in the heart and liver. An increased expression of Dio3 mRNA was observed in the heart and liver, and an increased expression of Thrb2 mRNA was observed in the liver. The quantitative proteomic profile of the thyroid gland indicated a reduction in cytoskeletal proteins (Cap1, Cav1, Lasp1, Marcks, and Tpm4; 1.875 μg AgNP/kg) and a reduction in the profile of chaperones (Hsp90aa1, Hsp90ab1, Hspa8, Hspa9, P4hb) and proteins that participate in the N-glycosylation process (Ddost, Rpn1 and Rpn2) (15 μg AgNP/kg). Exposure to low doses of AgNPs during the window of puberty development affects the regulation of the HP-thyroid axis with further consequences in thyroid gland physiology.

A Meta-Analysis of Stressors from the Total Environment Associated with Children's General Cognitive Ability

General cognitive ability, often referred to as ‘general intelligence’, comprises a variety of correlated abilities. Childhood general cognitive ability is a well-studied area of research and can be used to predict social outcomes and perceived success. Early life stage (e.g., prenatal, postnatal, toddler) exposures to stressors (i.e., chemical and non-chemical stressors from the total (built, natural, social) environment) can impact the development of childhood cognitive ability. Building from our systematic scoping review (Ruiz et al., 2016), we conducted a meta-analysis to evaluate more than 100 stressors related to cognitive development. Our meta-analysis identified 23 stressors with a significant increase in their likelihood to influence childhood cognitive ability by 10% or more, and 80 stressors were observed to have a statistically significant effect on cognitive ability. Stressors most impactful to cognition during the prenatal period were related to maternal health and the mother’s ability to access information relevant to a healthy pregnancy (e.g., diet, lifestyle). Stressors most impactful to cognition during the early childhood period were dietary nutrients (infancy), quality of social interaction (toddler), and exposure to toxic substances (throughout early childhood). In conducting this analysis, we examined the relative impact of real-world exposures on cognitive development to attempt to understand the inter-relationships between exposures to both chemical and non-chemical stressors and early developmental life stages. Our findings suggest that the stressors observed to be the most influential to childhood cognitive ability are not permanent and can be broadly categorized as activities/behaviors which can be modified to improve childhood cognition. This meta-analysis supports the idea that there are complex relationships between a child’s total environment and early cognitive development.

Endocrine disrupting chemicals: exposure, effects on human health, mechanism of action, models for testing and strategies for prevention

Endocrine Disrupting Chemicals (EDCs) are a global problem for environmental and human health. They are defined as "an exogenous chemical, or mixture of chemicals, that can interfere with any aspect of hormone action". It is estimated that there are about 1000 chemicals with endocrine-acting properties. EDCs comprise pesticides, fungicides, industrial chemicals, plasticizers, nonylphenols, metals, pharmaceutical agents and phytoestrogens. Human exposure to EDCs mainly occurs by ingestion and to some extent by inhalation and dermal uptake. Most EDCs are lipophilic and bioaccumulate in the adipose tissue, thus they have a very long half-life in the body. It is difficult to assess the full impact of human exposure to EDCs because adverse effects develop latently and manifest at later ages, and in some people do not present. Timing of exposure is of importance. Developing fetus and neonates are the most vulnerable to endocrine disruption. EDCs may interfere with synthesis, action and metabolism of sex steroid hormones that in turn cause developmental and fertility problems, infertility and hormone-sensitive cancers in women and men. Some EDCs exert obesogenic effects that result in disturbance in energy homeostasis. Interference with hypothalamo-pituitary-thyroid and adrenal axes has also been reported. In this review, potential EDCs, their effects and mechanisms of action, epidemiological studies to analyze their effects on human health, bio-detection and chemical identification methods, difficulties in extrapolating experimental findings and studying endocrine disruptors in humans and recommendations for endocrinologists, individuals and policy makers will be discussed in view of the relevant literature.

Prenatal BPA and its analogs BPB, BPF, and BPS exposure and reproductive axis function in the male offspring of Sprague Dawley rats

Research in the past has indicated associated long-term and low levels of exposure of bisphenol A (BPA) in early life and neuroendocrine disorders, such as obesity, precocious puberty, diabetes, and hypertension. BPA and its analogs bisphenol B (BPB), bisphenol F (BPF), and bisphenol S (BPS) have been reported to have similar or even more toxic effect as compared to BPA. Exposure of rats to BPA and its analogs BPB, BPF, and BPS resulted in decreased sperm production, testosterone secretion, and histological changes in the reproductive tissues of male rats. In the present study, BPA, BPB, BPF, and BPS were administered in drinking water at concentrations of (5, 25, and 50 μg/L) from pregnancy day (PD) 1 to PD 21. Body weight (BW), hormonal concentrations, antioxidant enzymes, and histological changes were determined in the reproductive tissues. BPA and its analogs prenatal exposure to female rats induced significant statistical difference in the antioxidant enzymes, plasma testosterone, and estrogen concentrations in the male offspring when compared with the control. Histological parameters of both testis and epididymis revealed prominent changes in the reproductive tissues. The present study suggests that BPA and its analogs BPB, BPF, and BPS different concentrations led to marked alterations in the development of the male reproductive system.

In utero and lactational exposure to triclocarban: reproductive effects on female rat offspring

Triclocarban (TCC) is an antimicrobial compound widely used in personal care products such as soaps, toothpaste, and shampoo. This agent is incompletely removed by wastewater treatment and represents an environmental contaminant. Recent studies have shown that TCC is associated with some endocrine disruptions. The aim of the present study was to evaluate if TCC exposure during critical periods of development (gestation and lactation) could lead to adverse effects on reproductive and behavior parameters of female offspring. Pregnant female Wistar rats were divided into four groups (n = 8-11/group): Control; TCC 0.3 mg/kg (TCC 0.3); TCC 1.5 mg/kg; TCC 3.0 mg/kg (TCC 3.0); and treated daily by oral gavage from gestational day 0 to lactational day 21. The female pups (F1 generation) were weaned on post-natal day 21 and included in the study. No litter-mates were used for the same group. There was a decrease in estradiol levels in the TCC 0.3 and TCC 3.0 groups. Moreover, there was a decrease in progesterone levels and an increase in pre-implantation loss in the TCC 3.0 group in adulthood. It is suggested, in this study, that the decrease in progesterone biosynthesis could interfere with implantation process. The exposure window to TCC is an important factor, as we found alterations only in the offspring.

Pesticides With Potential Thyroid Hormone-Disrupting Effects: A Review of Recent Data

Plant Protection Products, more commonly referred to as pesticides and biocides, are used to control a wide range of yield-reducing pests including insects, fungi, nematodes, and weeds. Concern has been raised that some pesticides may act as endocrine disrupting chemicals (EDCs) with the potential to interfere with the hormone systems of non-target invertebrates and vertebrates, including humans. EDCs act at low doses and particularly vulnerable periods of exposure include pre- and perinatal development. Of critical concern is the number of pesticides with the potential to interfere with the developing nervous system and brain, notably with thyroid hormone signaling. Across vertebrates, thyroid hormone orchestrates metamorphosis, brain development, and metabolism. Pesticide action on thyroid homeostasis can involve interference with TH production and its control, displacement from distributor proteins and liver metabolism. Here we focused on thyroid endpoints for each of the different classes of pesticides reviewing epidemiological and experimental studies carried out both in in vivo and in vitro. We conclude first, that many pesticides were placed on the market with insufficient testing, other than acute or chronic toxicity, and second, that thyroid-specific endpoints for neurodevelopmental effects and mixture assessment are largely absent from regulatory directives.

Estimation of plasma levels of bisphenol-A & phthalates in fertile & infertile women by gas chromatography-mass spectrometry

Background & objectives:

Bisphenol-A (BPA) and phthalates are utilized widely in consumer products. Due to their ubiquitous presence in the environment, a concern is expressed worldwide about their possible effect on human reproductive health. This study was conducted to compare the internal exposure of BPA and phthalates (using their metabolites as biomarkers) in plasma samples of infertile and fertile women.

Methods:

A sensitive gas chromatographic-mass spectrometric (GC-MS) method was developed to simultaneously quantify BPA and four phthalate monoester metabolites [namely mono-methyl phthalate (MMP), mono-benzyl phthalate (MBzP), mono-2-ethylhexyl phthalate (MEHP) and mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP)] in human plasma. The method was validated using charcoal-stripped human plasma. Activated charcoal was also utilized to reduce contamination from reagents. The method was designed to account for and/or eliminate background contamination from all sources.

Results:

The limit of quantification for the method was 5 ng/ml for MMP and MBzP, while 1 ng/ml for BPA, MEHP and MEHHP, respectively. The precision and accuracy were well within the acceptable range. BPA was detectable in 77 per cent of plasma samples of infertile women and 29 per cent of fertile women. All the four phthalate metabolites were detected in plasma samples of both fertile and infertile women.

Interpretation & conclusions:

A GC-MS was developed and validated to estimate the BPA and four phthalate monoester metabolites in human plasma. It was utilised to analyse the plasma samples from fertile and infertile women. The infertile women showed significantly higher plasma concentrations of MBzP, BPA and MEHHP as compared to fertile women. The levels of MMP and MEHP were not significantly different between the two groups. Further studies need to be done to confirm these preliminary findings.

Prenatal epigenetics diets play protective roles against environmental pollution

It is thought that germ cells and preimplantation embryos during development are most susceptible to endogenous and exogenous environmental factors because the epigenome in those cells is undergoing dramatic elimination and reconstruction. Exposure to environmental factors such as nutrition, climate, stress, pathogens, toxins, and even social behavior during gametogenesis and early embryogenesis has been shown to influence disease susceptibility in the offspring. Early-life epigenetic modifications, which determine the expression of genetic information stored in the genome, are viewed as one of the general mechanisms linking prenatal exposure and phenotypic changes later in life. From atmospheric pollution, endocrine-disrupting chemicals to heavy metals, research increasingly suggests that environmental pollutions have already produced significant consequences on human health. Moreover, mounting evidence now links such pollution to relevant modification in the epigenome. The epigenetics diet, referring to a class of bioactive dietary compounds such as isothiocyanates in broccoli, genistein in soybean, resveratrol in grape, epigallocatechin-3-gallate in green tea, and ascorbic acid in fruits, has been shown to modify the epigenome leading to beneficial health outcomes. This review will primarily focus on the causes and consequences of prenatal environment pollution exposure on the epigenome, and the potential protective role of the epigenetics diet, which could play a central role in neutralizing epigenomic aberrations against environmental pollutions.

The effects of dexamethasone on 17β-HSD1 levels at the rat optic nerve

Dexamethasone (DEX) is associated with many inflammation and metabolic diseases. We analyzed the effects of DEX on the expression of estrogen metabolism enzyme 17β-HSD1 at the optic nerve. Rats were treated with different concentrations of intraperitoneal DEX. Western Blot analysis showed that 17β-HSD protein was expressed in the optic nerve tissue. The enzyme was detected by immunohistochemistry on the terminal foot of Muller cells from the ganglion cell layer of rat retina. ELISA analysis showed that the 17β-HSD1 protein expression of DEX-treated group is 2.4 fold comparing to the control group. The results indicated that DMXS sodium phosphate might modulate the expression of 17β-HSD1 protein in optic tissue. This study sheds light on understanding of the relationship among DEX, 17β-HSD presence and distribution of visual neural systems. At the same time, DEX treatment affects the athletic ability and memory of the animals. Compared with the control group, the experimental group showed slow response to stimulation, inertia, depression, cowardice and lack of appetite. The results of ethology experiments showed that all the parameters decreased by 15-30%.

Bisphenol A and pubertal height growth in school-aged children

BACKGROUND

Bisphenol A (BPA) is an environmental endocrine disruptor and is found in many consumer products. Studies suggest that BPA may perturb pubertal development, although evidence on BPA-influenced pubertal height growth is scarce.

METHODS

A total of 754 children aged 9-18 years from three schools (one elementary, one middle, and one high school) in Shanghai were included in this longitudinal study. Height was measured at enrolment (visit 1) and, subsequently, at 19 months after enrolment (visit 2). Age- and sex-specific Z scores for height were calculated (height Z score = [participant's height-sex- and age-specific population height mean]/sex- and age-specific population height standard deviation). Urine samples were collected at enrolment to measure BPA concentrations. We used multiple linear regression models or general estimating equation models (GEE) to estimate associations between urine BPA level and height Z score.

RESULTS

The geometric mean of urine BPA concentrations was 1.6 μg/L (95%CI: 1.4, 1.8) or 1.2 μg/g creatinine (95%CI: 1.0, 1.3). An inverse association between urine BPA level and height was observed in boys. After adjustment for potential confounders, height Z score at enrolment in boys decreased by 0.49 for the highest exposure level (above 10.9 μg/g creatinine as the 90th percentile), compared with the lowest BPA exposure (below 0.2 μg/g creatinine as the 25th percentile) (95%CI: -0.96, -0.01; p-trend = 0.024). The inverse association remained between BPA exposure and height Z score at visit 2. The GEE model showed that a 1-unit increase in log₁₀-transformed BPA concentrations was associated with a 0.15-point decrease in height Z score over the follow-up (95%CI: -0.30, -0.01). BPA was not associated with height growth in girls.

CONCLUSIONS

Our findings indicate an inverse association between urine BPA level and height growth in boys. These findings need to be confirmed in further studies.

Mate choice, sexual selection, and endocrine-disrupting chemicals

Humans have disproportionately affected the habitat and survival of species through environmental contamination. Important among these anthropogenic influences is the proliferation of organic chemicals, some of which perturb hormone systems, the latter referred to as endocrine-disrupting chemicals (EDCs). EDCs are widespread in the environment and affect all levels of reproduction, including development of reproductive organs, hormone release and regulation through the life cycle, the development of secondary sexual characteristics, and the maturation and maintenance of adult physiology and behavior. However, what is not well-known is how the confluence of EDC actions on the manifestation of morphological and behavioral sexual traits influences mate choice, a process that requires the reciprocal evaluation of and/or acceptance of a sexual partner. Moreover, the outcomes of EDC-induced perturbations are likely to influence sexual selection; yet this has rarely been directly tested. Here, we provide background on the development and manifestation of sexual traits, reproductive competence, and the neurobiology of sexual behavior, and evidence for their perturbation by EDCs. Selection acts on individuals, with the consequences manifest in populations, and we discuss the implications for EDC contamination of these processes, and the future of species.

Vitamin-caused faulty perinatal hormonal imprinting and its consequences in adult age

Lipid-soluble vitamins (vitamins A, D, E, and K) are actually hormones (exohormones), as they can be directly bound by hormone receptors or are in connection with molecules, which influence hormone receptors. Vitamin D is a transition between endo- and exohormones and the possibility of similar situation in case of other lipid-soluble hormones is discussed. The perinatal exposition with these “vitamins” can cause faulty perinatal hormonal imprinting with similar consequences as the faulty imprinting by the synthetic endohormones, members of the same hormone family or industrial, communal, or medical endocrine disruptors. The faulty imprinting leads to late (lifelong) consequences with altered hormone binding by receptors, altered sexuality, brain function, immunity, bone development, and fractures, etc. In addition, as hormonal imprinting is an epigenetic process, the effect of a single exposure by fat-soluble vitamins is inherited to the progeny generations. As vitamins are handled differently from hormones; however, perinatal treatments take place frequently and sometimes it is forced, the negative late effect of faulty perinatal vitamin-caused hormonal imprinting must be considered.

Specific effects of prenatal DEHP exposure on neuroendocrine gene expression in the developing hypothalamus of male rats

Endocrine disrupting chemicals may disrupt developing neuroendocrine systems, especially when the exposure occurs during a critical period. This study aimed to investigate whether prenatal exposure to di-(2-ethylhexyl) phthalate (DEHP), a major component of plasticizers used worldwide, disrupted the development of a network of genes important for neuroendocrine function in male rats. Pregnant rats were treated with corn oil (vehicle control), 2, 10 or 50 mg/kg DEHP by gavage from gestational day 14 to 19. The neuroendocrine gene expressions were quantified using a 48-gene Taqman qPCR array in the whole hypothalamus of neonatal rats (postnatal day 1) and in the anteroventral periventricular nucleus (AVPV), medial preoptic nucleus (MPN) and arcuate nucleus (ARC) of adult rats (postnatal day 70). Immunofluorescent signals of ERα and CYP19 were detected using the confocal microscopy in adult AVPV, MPN and ARC. The results showed that prenatal DEHP exposure perturbed somatic and reproductive development of offspring. Eleven genes were down-regulated in neonatal hypothalamus and showed non-monotonic dose-response relationships, that the 10 mg/kg DEHP dosage was associated with the greatest number of gene expression changes. Different from this, 14 genes were altered in adult AVPV, MPN and ARC and most of alterations were found in the 50 mg/kg DEHP group. Also, 50 mg/kg DEHP reduced ERα expression in the ARC, but no alterations were observed in CYP19 expression. These results indicated that prenatal DEHP exposure may perturb hypothalamic gene programming and the influences are permanent. The effects showed dependence on developmental stages and nuclei region.

Prenatal concentrations of Perfluoroalkyl substances and early communication development in British girls

Perfluoroalkyl substances (PFAS), found in many household products and classed as endocrine disrupting chemicals, can be transferred through the placenta and are associated with multiple developmental deficits in offspring. Using data from the Avon Longitudinal Study of Parents and Children (ALSPAC), we investigated the association between intrauterine exposure to PFAS and early communication development in 432 mother-daughter dyads at 15 and 38months of age. Concentrations of perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), perfluorohexane sulfonate (PFHxS), and perfluorononanoate (PFNA) were measured in maternal serum collected during pregnancy. Early communication development was measured with the ALSPAC-adapted MacArthur Communicative Development Inventories for Infants and Toddlers. The infant questionnaire measured verbal comprehension, vocabulary comprehension and production, nonverbal communication, and social development. The toddler questionnaire measured language, intelligibility, and communicative sub-scores. Multivariable linear regression was used to examine associations between each PFAS exposure and each communication sub-scale score. The association between maternal PFAS concentrations and early communication development at 15 and 38months of age varied by maternal age at delivery. In daughters of younger mothers (<25years of age), every 1ng/mL of PFOS was associated with a 3.82 point (95% confidence interval (CI): -6.18, -1.47) lower vocabulary score at 15months and a 0.80 point (95% CI: -1.74, 0.14) lower language score at 38months. Prenatal exposure to select PFAS was positively and negatively associated with communication development among girls, with inconsistent pattern of association across all measured PFAS and endpoints.

Environment, susceptibility windows, development, and child health

PURPOSE OF REVIEW

To illustrate the role of the exposome in child health while highlighting unique aspects of this research pertinent to children, such as the time dependency of environmental exposures on fetal programming, as well as the time-dependent nature of child behavior, diet, and motor function, which alter the probability of exposure to different compounds. Future environmental health research will be more hypothesis generating but will also need to heed lessons learned from other 'omic' sciences. The NIH Child Health Environmental Analysis Resource (CHEAR) is a major step toward providing the infrastructure needed to study the exposome and child health.

RECENT FINDINGS

Environmental exposures have overlapping mechanisms such as endocrine disruption and oxidative stress, among others. The nature of the long-term health impact of an exposure is dependent not only on dose, but also on the timing of exposure. Advances in exposure science, toxicology, and biostatistics will create new opportunities to identify and better define windows of susceptibility to environmental exposures.

SUMMARY

As exposure science matures, we will better understand the role of environment on health. Linking the exposome with genomics will unlock the root origins of multiple complex diseases.

Early puberty in 11-year-old girls: Millennium Cohort Study findings

OBJECTIVE

Early puberty in girls is linked to some adverse outcomes in adolescence and mid-life. We address two research questions: (1) Are socioeconomic circumstances and ethnicity associated with early onset puberty? (2) Are adiposity and/or psychosocial stress associated with observed associations?

DESIGN

Longitudinal data on 5839 girls from the UK Millennium Cohort Study were used to estimate associations between ethnicity, family income, adiposity and psychosocial stress with a marker of puberty.

MAIN OUTCOME MEASURE

Reported menstruation at age 11 years.

RESULTS

All quoted ORs are statistically significant. Girls in the poorest income quintile were twice as likely (OR=2.1), and the second poorest quintile nearly twice as likely (OR=1.9) to have begun menstruation compared with girls in the richest income quintile. Estimates were roughly halved on adjustment for Body Mass Index and markers of psychosocial stress (poorest, OR=1.5; second poorest, OR=1.5). Indian girls were over 3 times as likely compared with whites to have started menstruation (OR=3.5) and statistical adjustments did not attenuate estimates. The raised odds of menstruation for Pakistani (OR=1.9), Bangladeshi (OR=3.3) and black African (OR=3.0) girls were attenuated to varying extents, from about a third to a half, on adjustment for income and adiposity.

CONCLUSIONS

In contemporary UK, excess adiposity and psychosocial stress were associated with social inequalities in early puberty, while material disadvantage and adiposity were linked to ethnic inequalities in early puberty among girls.

Perinatal exposure to insecticide fipronil: effects on the reproductive system in male rats

Fipronil is an insecticide widely used in agriculture, veterinary medicine and public health that has recently been listed as a potential endocrine disrupter. In the present study we evaluated the effects of perinatal exposure to fipronil during the period of sexual brain differentiation and its later repercussions on reproductive parameters in male rats. Pregnant rats were exposed (via gavage) to fipronil (0.03, 0.3 or 3 mg kg–1) from Gestational Day 15 until Postnatal Day 7. Fipronil exposure did not compromise the onset of puberty. In adulthood, there was no effect on organ weight or sperm production. Furthermore, there were no adverse effects on the number of Sertoli cells per seminiferous tubule, testicular and epididymal histomorphometry or histopathology or expression patterns of androgen receptor in the testis. Similarly, no changes were observed in the sexual behaviour or hormone levels. However, in rats exposed to fipronil, changes in sperm motility were observed, with a decrease in motile spermatozoa and an increase in non-mobile spermatozoa, which can compromise sperm quality in these rats. Perinatal exposure to fipronil has long-term effects on sperm parameters, and the epididymis can be a target organ. Additional studies should be undertaken to identify the mechanisms by which fipronil affects sperm motility.

Para-Dichlorobenzene Exposure Is Associated with Thyroid Dysfunction in US Adolescents

OBJECTIVE

To examine the association between exposure to para-dichlorobenzene, measured as urinary concentrations of 2,5-dichlorophenol (2,5-DCP), and thyroid function in US adolescents.

STUDY DESIGN

A nationally representative subsample of 618 adolescents aged 12-19 years in the 2007-2008 and 2011-2012 National Health and Nutrition Examination Survey was analyzed for the association of urinary 2,5-DCP with serum thyroid function measures using multivariate logistic and general linear regression models.

RESULTS

After adjusting for potential confounders, we found a significantly positive association between urinary concentrations of 2,5-DCP and serum levels of thyroid-stimulating hormone and thyroglobulin in adolescents. Furthermore, urinary 2,5-DCP was associated with an increased prevalence of hypothyroidism in the study population.

CONCLUSIONS

This study demonstrates a potential relationship between para-dichlorobenzene exposure, measured as urinary 2,5-DCP, and thyroid dysfunction in adolescents; however, further studies are needed to confirm our findings and to elucidate mechanisms of action.

Thyroid Hormones and Timing of Pubertal Onset in a Longitudinal Cohort of Females, Northern California, 2006-11

BACKGROUND

Pubertal timing is regulated by a complex interplay of hormones. Few studies have evaluated the role of thyroid hormones in pubertal onset. We investigated the associations between blood concentrations of free and total thyroxine (FT4, TT4), free triiodothyronine, and thyroid stimulating hormone and pubertal onset among females.

METHODS

Participants included 323 Kaiser Permanente Northern California members followed at annual intervals during 2004-11, who provided a blood sample during the first 3 years of the study. Thyroid hormone concentrations were measured in serum in the first blood specimen available for each participant. Pubertal onset was defined as Tanner stage ≥2 for breast (thelarche) and pubic hair (pubarche) development. Associations between thyroid hormones and pubertal onset were assessed by multivariable logistic regression and Cox proportional hazards modelling.

RESULTS

At blood draw, participants were age 6.5-10.1 (median 7.7) years, 10% had reached thelarche, and 12% had reached pubarche. Participants were followed 0-5 years after blood draw (median 4). At most recent clinical visit, participants were age 6.7-14.7 (median 12.3) years, 92% had reached thelarche, and 89% had reached pubarche. No associations were identified between having reached thelarche or pubarche at time of blood draw and thyroid hormones. Examined longitudinally, higher concentrations of pre-pubertal FT4 and TT4 were associated with earlier pubarche (adjusted hazard ratio (HR) 1.41, 95% confidence interval (CI) 1.06, 1.86; per ng/dL and aHR 1.07, 95% CI 1.02, 1.12; per μg/dL respectively).

CONCLUSIONS

Higher pre-pubertal concentrations of FT4 and TT4 are associated with earlier pubarche.

Effects of environmental endocrine disruptors, including insecticides used for malaria vector control on reproductive parameters of male rats

The male reproductive system is sensitive to endocrine disrupting chemicals (EDCs) during critical developmental windows. Male Sprague-Dawley rats were exposed in utero-, during lactation- and directly to 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT), 1,1,-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) and a mixture of DDT, deltamethrin (DM), p-nonylphenol (p-NP) and phytoestrogens, at concentrations found in a malaria-area. After dosing for 104 days, histological assessments and reproductive-endpoints were assessed. The anogenital distance (AGD) (P=0.005) was shorter in the mixture-exposed group, while the prostate mass (P=0.018) was higher in the DDT-exposed group. A higher testicular mass and abnormal histology was observed in the DDT-(P=0.019), DDE-(P=0.047) and mixture-exposed (P<0.005) groups. This study shows that in utero-, lactational- and direct exposure to EDCs present in a malaria-area negatively affects male reproductive parameters in rats. These findings raise concerns to EDC-exposures to mothers living in malaria-areas and the reproductive health of their male offspring.

The Effects of Endocrine Disruptors on Adipogenesis and Osteogenesis in Mesenchymal Stem Cells: A Review

Endocrine-disrupting chemicals (EDCs) are prevalent in the environment, and epidemiologic studies have suggested that human exposure is linked to chronic diseases, such as obesity and diabetes. In vitro experiments have further demonstrated that EDCs promote changes in mesenchymal stem cells (MSCs), leading to increases in adipogenic differentiation, decreases in osteogenic differentiation, activation of pro-inflammatory cytokines, increases in oxidative stress, and epigenetic changes. Studies have also shown alteration in trophic factor production, differentiation ability, and immunomodulatory capacity of MSCs, which have significant implications to the current studies exploring MSCs for tissue engineering and regenerative medicine applications and the treatment of inflammatory conditions. Thus, the consideration of the effects of EDCs on MSCs is vital when determining potential therapeutic uses of MSCs, as increased exposure to EDCs may cause MSCs to be less effective therapeutically. This review focuses on the adipogenic and osteogenic differentiation effects of EDCs as these are most relevant to the therapeutic uses of MSCs in tissue engineering, regenerative medicine, and inflammatory conditions. This review will highlight the effects of EDCs, including organophosphates, plasticizers, industrial surfactants, coolants, and lubricants, on MSC biology.

Effect of in utero exposure to endocrine disruptors on fetal steroidogenesis governed by the pituitary-gonad axis: a study in rats using different ways of administration

The effects of endocrine disruptors on testicular steroidogenesis in fetal rats were investigated in a study involving in utero exposure. In the major part of this study, pregnant rats at gestational day (GD)15 were given a single oral administration of the test substance, and then the expression of the following mRNAs in GD20 fetuses was determined: testicular steroidogenic acute-regulatory protein (StAR), a cholesterol transporter mediating the rate-limiting step of steroidogenesis, a ß-subunit of pituitary luteinizing hormone (LH), and a regulator of gonadal steroidogenesis. Among the substances tested, only di(2-ethylhexyl)phthalate (DEHP) reduced the expression of fetal testicular StAR. The others listed below exhibited little effect on fetal StAR: 2,2',4,4'-tetrabromodiphenylether, tributyltin chloride, atrazine, permethrin, cadmium chloride (Cd), lead acetate (Pb) and methylmercury (CH3HgOH). None of them, including DEHP, lacked the ability to reduce the expression of pituitary LHß mRNA. The present study also examined the potential of metals as modifiers of fetal steroidogenesis by giving them to pregnant dams in drinking water during GD1 and GD20. Under these conditions, Cd and Pb at a low concentration (0.01 ppm) significantly attenuated the fetal testicular expression of StAR mRNA without a concomitant reduction in LHß. No such effect was detected with CH3HgOH even at 1 ppm. These results suggest that: 1) DEHP, Cd and Pb attenuate the fetal production of sex steroids by directly acting on the testis, and 2) chronic treatment during the entire gestational period is more useful than a single administration for determining the hazardous effect of a suspected endocrine disruptor on fetal steroidogenesis.

Burden of Growth Hormone Deficiency and Excess in Children

Longitudinal growth results from multifactorial and complex processes that take place in the context of different genetic traits and environmental influences. Thus, in view of the difficulties in comprehension of the physiological mechanisms involved in the achievement of normal height, our ability to make a definitive diagnosis of GH impairment still remains limited. There is a myriad of controversial aspects in relation to GH deficiency, mainly related to diagnostic controversies and advances in molecular biology. This might explain the diversity in therapeutic responses and may also serve as a rationale for new "nonclassical" treatment indications for GH. It is necessary to acquire more effective tools to reach an adequate evaluation, particularly while considering the long-term implications of a correct diagnosis, the cost, and safety of treatments. On the other hand, overgrowth constitutes a heterogeneous group of different pathophysiological situations including excessive somatic and visceral growth. There are overlaps in clinical and molecular features among overgrowth syndromes, which constitute the real burden for an accurate diagnosis. In conclusion, both GH deficiency and overgrowth are a great dilemma, still not completely solved. In this chapter, we review the most burdensome aspects related to short stature, GH deficiency, and excess in children, avoiding any details about well-known issues that have been extensively discussed in the literature.

Atrazine Exposure and Reproductive Dysfunction through the Hypothalamus-Pituitary-Gonadal (HPG) Axis

Endocrine disrupting chemicals (EDC) are exogenous agents that alter endogenous hormone signaling pathways. These chemicals target the neuroendocrine system which is composed of organs throughout the body that work alongside the central nervous system to regulate biological processes. Of primary importance is the hypothalamic-pituitary-gonadal (HPG) axis which is vital for maintaining proper reproductive function. Atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) is a pre-emergent herbicide used to prevent the growth of weeds on various crops. This herbicide is reported to widely contaminate potable water supplies everywhere it is applied. As such, the European Union banned the use of atrazine in 2004. Currently the United States Environmental Protection Agency regulates atrazine at 3 parts per billion (ppb; μg/L) in drinking water, while the World Health Organization recently changed their drinking water guideline to 100 ppb. Atrazine is implicated to be an EDC that alters reproductive dysfunction by targeting the HPG axis. However, questions remain as to the human health risks associated with atrazine exposure with studies reporting mixed results on the ability of atrazine to alter the HPG axis. In this review, the current findings for atrazine’s effects on the HPG axis are examined in mammalian, anuran, and fish models and in epidemiological studies.

Epidemiologic evidence for association between adverse environmental exposures in early life and epigenetic variation: a potential link to disease susceptibility?

A growing body of evidence suggests that the risk of development and progression of a variety of human chronic diseases depends on epigenetic modifications triggered by environmental cues during early life sensitive stages. Exposures to environmental factors such as adverse nutritional, psychological, and social conditions, as well as pollutants and substance abuse in early life, have been shown to be important determinants of epigenetic programming of chronic pathological conditions in human populations. Over the past years, it has become increasingly clear due to the epigenome-wide association studies (EWASs) that early life adverse environmental events may trigger widespread and persistent alterations in transcriptional profiling. Several candidate genes have been identified underlying these associations. In this context, DNA methylation is the most intensively studied epigenetic phenomenon. In this review, the clinical and epidemiological evidence for the role of epigenetic factors in mediating the link between early life experiences and long-term health outcomes are summarized.

Isolation and identification of a repressor TetR for 3,17β-HSD expressional regulation in Comamonas testosteroni

Comamonas testosteroni (C. testosteroni) is able to catabolize a variety of steroids and polycyclic aromatic hydrocarbons. 3,17β-Hydroxysteroid dehydrogenase (3,17β-HSD) from C. testosteroni is a key enzyme in steroid degradation. Understanding the mechanism of 3,17β-HSD gene (βhsd) induction may help us to elucidate its complete molecular regulation. Sequencing the C. testosteroni ATCC11996 genome lead us to identify the tetR (522 bp) downstream of βhsd. Two repeat sequences (RS; 13 bp), that are separated to each other by 1661 bp, were found upstream of βhsd. A bioinformatic analysis revealed that TetR family proteins act as transcriptional repressors which are sensitive to environmental signals. Since, C. testosteroni responds to environmental steroid induction and upregulates steroid catabolic genes, we hypothesized that TetR might act in C. testosteroni as repressor for βhsd expression. The tetR was cloned into different plasmids, including an EGFP reporter system, for functional characterization and/or overexpression. The data indicate that, indeed, TetR acts as a repressor for 3,17β-HSD expression. Testosterone in turn, which is known to induce βhsd expression, could not resolve TetR repression. To further substantiate TetR as repressor for βhsd expression, a tetR gene knock-out mutant of C. testosteroni was generated. TetR gene knock-out mutants showed the same basal low level of βhsd expression as the C. testosteroni wild type cells. Interestingly, testosterone induction leads to a strong increase in βhsd expression, especially in the tetR gene knock-out mutants. The result with the knock-out mutant, in principle, supports our hypothesis that TetR is a repressor for βhsd expression, but the exact role of testosterone in this context remains unknown. Finally, it turned out that TetR is obviously also involved in the regulation of the hsdA gene.

Bisphenol-A impairs myelination potential during development in the hippocampus of the rat brain

Myelin is the functional implication of oligodendrocytes (OLs), which is involved in insulation of axons and promoting rapid propagation of action potential in the brain. OLs are derived from oligodendrocyte progenitor cells (OPCs), which proliferate, differentiate, and migrate throughout the central nervous system. Defects in myelination process lead to the onset of several neurological and neurodegenerative disorders. Exposure to synthetic xenoestrogen bisphenol-A (BPA) causes cognitive dysfunction, impairs hippocampal neurogenesis, and causes onset of neurodevelopmental disorders. However, the effects of BPA on OPC proliferation, differentiation and myelination, and associated cellular and molecular mechanism(s) in the hippocampus of the rat brain are still largely unknown. We found that BPA significantly decreased bromodeoxyuridine (BrdU)-positive cell proliferation and number and size of oligospheres. We observed reduced co-localization of BrdU with myelination markers CNPase and platelet-derived growth factor receptor-α (PDGFR-α), suggesting impaired proliferation and differentiation of OPCs by BPA in culture. We studied the effects of BPA exposure during prenatal and postnatal periods on cellular and molecular alteration(s) in the myelination process in the hippocampus region of the rat brain at postnatal day 21 and 90. BPA exposure both in vitro and in vivo altered proliferation and differentiation potential of OPCs and decreased the expression of genes and levels of proteins that are involved in myelination. Ultrastructural electron microscopy analysis revealed that BPA exposure caused decompaction of myelinated axons and altered g-ratio at both the developmental periods as compared to control. These results suggest that BPA exposure both during prenatal and postnatal periods alters myelination in the hippocampus of the rat brain leading to cognitive deficits.

Epigenomic programing: a future way to health?

It is now generally accepted that the ‘central genome dogma’ (i.e. a causal chain going from DNA to RNA to proteins and downstream to biological functions) should be replaced by the ‘fluid genome dogma’, that is, complex feed-forward and feed-back cycles that interconnect organism and environment by epigenomic programing – and reprograming – throughout life and at all levels, sometimes also down the generations. The epigenomic programing is the net sum of interactions derived from own metabolism and microbiota as well as external factors such as diet, pharmaceuticals, environmental compounds, and so on. It is a growing body of results indicating that many chronic metabolic and degenerative disorders and diseases – often called ‘civilization diseases’ – are initiated and/or influenced upon by non-optimal epigenomic programing, often taking place early in life. In this context, the first 1,000 days of life – from conception into early infancy – is often called the most important period of life. The following sections present some major mechanisms for epigenomic programing as well as some factors assumed to be of importance. The need for more information about own genome and metagenome, as well as a substantial lack of adequate information regarding dietary and environmental databases are also commented upon. However, the mere fact that we can influence epigenomic health programing opens up the way for prophylactic and therapeutic interventions. The authors underline the importance of creating a ‘Human Gut Microbiota and Epigenomic Platform’ in order to facilitate interdisciplinary collaborations among scientists and clinicians engaged in host microbial ecology, nutrition, metagenomics, epigenomics and metabolomics as well as in disease epidemiology, prevention and treatment.