Association between maternal exposure to di(2-ethylhexyl) phthalate and reproductive hormone levels in fetal blood: the Hokkaido study on environment and children's health

Phthalate Metabolites in Maternal and Cord Plasma and Their Relations to Other Selected Endocrine Disruptors and Steroids

Endocrine disruptors (EDs) are known to have harmful effects on the human endocrine system; special effort is actually given to the exposure during pregnancy. Humans are usually exposed to a mixture of EDs, which may potentiate or antagonize each other, and the combined effect may be difficult to estimate. The main phthalate monoesters monoethyl-, mono-n-butyl-, monoisobutyl-, monobenzyl-, mono-(2-ethylhexyl)-, mono-(2-ethyl-5-hydroxyhexyl)- and mono-(2-ethyl-5-oxohexyl) phthalate were determined in 18 maternal (37th week of pregnancy) and cord plasma samples using liquid chromatography-tandem mass spectrometry. Previously determined levels of selected bisphenols, parabens and steroids were also considered in this study. In cord blood, there were significantly higher mono-n-butyl phthalate levels than in maternal blood (p=0.043). The results of multiple regression models showed that maternal plasma phthalates were negatively associated with cord plasma androstenedione, testosterone and dehydroepiandrosterone and positively associated with estradiol and estriol. For estriol, a cumulative association was also observed for Σbisphenols. To the best of our knowledge, this is the first pilot study evaluating the effect of prenatal exposure by multiple EDs on newborn steroidogenesis. Our results confirmed phthalate accumulation in the fetal area and disruption of fetal steroidogenesis. This preliminary study highlights the negative impacts of in utero EDs exposure on fetal steroidogenesis.

[Environmental Chemical Exposure and Its Effects on Infants' Reproductive Hormones]

In recent years, the birthrate has been continuously declining in Japan. The main causes of the decline are social factors. On the other hand, there is increasing evidence that many environmental chemicals show endocrine disrupting properties. Thus, we hypothesized that exposure to these chemicals would also be a causal for the fertility crisis. In this review, we examined current evidence that focused on environmental chemical exposure in utero and its association with reproductive hormones in children. We have included the findings from a prospective birth cohorts, the Hokkaido Study on Environment and Children's Health Sapporo cohort. According to the literature, environmental chemical levels in utero, such as polychlorinated biphenyl, dioxins, perfluorinated chemical substances, phthalates, and bisphenol A were somewhat associated with the levels of reproductive hormones, such as testosterone, estradiol, progesterone, inhibin B, and insulin-like factor-3 in cord blood, in early childhood and adolescence. The literature also suggests the association between exposure to these chemicals and brain-sexual differentiation or the anogenital distance, which suggests the disruption of androgen shower during the developmental stage in the fetal period. There are still knowledge gaps on whether these hormones at an early stage affect the pubertal development and reproductive functions in later life. In addition, alternative chemicals are produced after banning one type. The health effects of alternative chemicals should be evaluated. Effects of exposure to a mixture of the chemicals should also be examined in future studies. In conclusion, the prevention of environmental chemical hazards in relation to human reproductive function is important. It would be one of the countermeasures to the falling birthrate caused by fertility issues.

Melatonin protects prepuberal testis from deleterious effects of bisphenol A or diethylhexyl phthalate by preserving H3K9 methylation

A growing number of couples experience fertility issues with almost half being due to malefactors. The exposure to toxic environmental contaminants, such as endocrine disruptors (EDs), has been shown to negatively affect male fertility. EDs are present in the environment, and exposure to these toxins results in the failure of spermatogenesis. The deleterious effects of EDs on spermatogenesis have been well documented, whereas improvement of infertility associated with spermatogenesis defects remains a great challenge. Herein, we report that in vitro exposure of prepuberal mouse testes to two well-known endocrine disruptors (EDs), bisphenol A (BPA) or diethylhexyl phthalate (DEHP), impairs spermatogenesis with perturbing self-renewal, spermatogonia activity, and meiosis. Evidence indicates that such effects are likely due, at least in part, to decreased G9a-dependent H3K9 di-methylation. Of note, we found that melatonin (MLT) protected the testis from the negative ED impacts with preserving spermatogonia stem and meiotic cells, along with maintaining normal H3K9 di-methylation in these cells. Taken together, this work documents that BPA and EDHP adversely affect prepuberal spermatogenesis and perturb crucial epigenetic activities in male germ cells and highlight the protective ability of MLT.

Transcriptomics and metabonomics analyses of maternal DEHP exposure on male offspring

The objectives of this study were to evaluate the effect of maternal Di-2-ethylhexyl phthalate (DEHP) exposure on male offspring and to explore the mechanism of changes with the metabolic alterations and differential genes. Pregnant female Sprague-Dawley (SD) rats were intragastrically administered with 600 mg/kg body weight of DEHP or corn oil (CON) throughout pregnancy and lactation. The growth of male offspring was investigated until 14 weeks old, the indices of blood were detected, and mechanism was studied using metabonomics and transcriptomics. Compared with the CON group, body weight, body length, food intake, body fat weight, Lee's index, organ coefficient, blood lipids, and oral glucose tolerance test (OGTT) of male offspring were not significantly changed in maternal DEHP group. However, serum biochemical indexes such as alanine transaminase (ALT), total protein (TP), albumin (ALB), blood urea nitrogen (BUN), and creatinine (CREA) were markedly reduced in maternal DEHP group (p < 0.05). In addition, insulin level was elevated and catalase (CAT) level was decreased notably in maternal DEHP group compared with the CON group (p < 0.05). Furthermore, thyroxine (T₄) level was lower and thyroid stimulating hormone (TSH) level was higher in maternal DEHP group (p < 0.05). Metabonomics revealed seven principal metabolites were identified, including increased L-allothreonine, creatine, uric acid, retinyl ester, L-palmitoylcarnitine, and decreased glycocholic acid and LysoPC (18:3). Transcriptomics displayed 35 differential genes were involved in the mechanism of maternal DEHP exposure. Therefore, this research confirms the effect of a certain dose of maternal DEHP exposure on male offspring and understands exactly the mechanism of these changes with metabonomics and transcriptomics.

Sex-related differences in the associations between maternal dioxin-like compounds and reproductive and steroid hormones in cord blood: The Hokkaido study

BACKGROUND

Prenatal exposure to dioxin-like compounds (DLCs) irreversibly affects fetal reproductive and steroid hormone synthesis.

OBJECTIVE

This study aimed to assess the relationships between maternal DLCs and cord blood reproductive and steroid hormones.

METHODS

Participants in this study were pregnant women who enrolled in the Sapporo Cohort of the Hokkaido Study between 2002 and 2005. We quantified 29 DLCs during the 2nd and 3rd trimesters in maternal blood. Additionally, we measured the concentrations of progesterone, estradiol (E2), testosterone (T), androstenedione, dehydroepiandrosterone (DHEA), cortisol, cortisone, sex hormone-binding globulin (SHBG), luteinizing hormone (LH), follicle-stimulating hormone (FSH), prolactin, inhibin B, and insulin-like factor-3 (INSL3) in cord blood samples.

RESULTS

Data from 183 mother-child pairs were analyzed. We observed sex-dependent associations of DLCs on T/E2 ratios, DHEA, cortisol, cortisone, adrenal androgen/glucocorticoid (AA/GC: sum of DHEA and androstenedione)/(sum of cortisol and cortisone) ratios and SHBG. An increase in maternal DLCs related to decreased T/E2 ratios and SHBG and inhibin B levels, and increased AA/GC ratios and FSH and DHEA levels in male cord blood samples. However, an increase in maternal mono-ortho polychlorinated biphenyls related to increased cortisol, cortisone, and SHBG levels, and decreased DHEA levels and AA/GC ratios in female cord blood samples.

CONCLUSIONS

Prenatal exposure to DLCs alters steroidogenesis and suppresses the secretion of inhibin B in male cord blood. Relationships between maternal DLCs and cord blood hormones differ between boys and girls. Further studies are required to clarify whether the effects of in utero exposure to DLCs on adrenal hormones extend into infancy and puberty.

Cord Blood Bisphenol A Levels and Reproductive and Thyroid Hormone Levels of Neonates: The Hokkaido Study on Environment and Children's Health

BACKGROUND

Bisphenol A (BPA) is widely used and BPA exposure is nearly ubiquitous in developed countries. While animal studies have indicated adverse health effects of prenatal BPA exposure including reproductive dysfunction and thyroid function disruption possibly in a sex-specific manner, findings from epidemiologic studies have not been enough to prove these adverse effects. Given very limited research on human, the aim of this study was to investigate associations between cord blood BPA levels and reproductive and thyroid hormone levels of neonates and whether associations differed by neonate sex.

METHODS

The study population included 514 participants of the Hokkaido study recruited from 2002 to 2005 at one hospital in Sapporo, Japan. The BPA level in cord blood was determined by ID-LC/MS/MS, and the limit of quantification was 0.040 ng/ml. We measured nine types of reproductive hormone levels in cord blood, and thyroid hormone levels were obtained from neonate mass screening test data. There were 283 subjects, who had both BPA and hormone levels measurements, included for the final analyses.

RESULTS

The geometric mean of cord blood BPA was 0.051 ng/ml. After adjustment, BPA level was negatively associated with prolactin (PRL) (β = -0.38). There was an interaction between infant sex and BPA levels on PRL; a weak negative association was found in boys (β = -0.12), whereas a weak positive association was found in girls (β = 0.14). BPA level showed weak positive association with testosterone, estradiol, and progesterone levels in boys. No association was found between BPA and thyroid hormone levels.

CONCLUSIONS

Our findings suggested that fetal BPA levels might be associated with changes in certain reproductive hormone levels of neonates in a sex-specific manner, though further investigations are necessary.

[Importance of Two Birth Cohorts (n=20,926 and n=514): 15 Years' Experience of the Hokkaido Study on Environment and Children's Health: Malformation, Development and Allergy]

Since "Our Stolen Future" by Theo Colborn was published in 1996, global interest on the impact of chemical substances, such as the endocrine-disrupting action of chemicals, has increased. In Japan, "The Hokkaido Study on Environment and Children's Health: Malformation, Development and Allergy" was launched in 2001. It was a model of Japan Environment and Children's Study of the Ministry of the Environment. In a large-scale, Hokkaido cohort, we obtained the consent of 20,926 mothers at the organogenesis stage with the cooperation of 37 obstetrics clinics in Hokkaido. We tracked the effects of endocrine disruptors on developmental disorders. In a small-scale Sapporo cohort, we observed in detail the neuropsychiatric development of children with the consent of 514 mothers in their late pregnancy. We examined how prenatal exposure to low concentrations of environmental chemicals affect the development of organs and the postnatal development of children. Maternal exposure to POPs, such as PCB/dioxins and perfluorinated alkyl substances, has affected not only children's birth size, thyroid functions, and sex hormone levels, but also postnatal neurodevelopment, infection, and allergy among others. The associations of short-half-life substances, such as DEHP and BPA, with obesity, ASD, and ADHD have been investigated. Gene-environment interactions have been found for smoking, caffeine, folic acid, and PCB/dioxin. In 2015, our center was officially designated as the WHO Collaborating Centre for Environmental Health and Prevention of Chemical Hazards, and we continue to the contribute to the global perspectives of child health.

Association between fetal exposure to phthalate endocrine disruptor and genome-wide DNA methylation at birth

BACKGROUND

Phthalic acid esters are ubiquitous and antiandrogenic, and may cause systemic effects in humans, particularly with in utero exposure. Epigenetic modification, such as DNA methylation, has been hypothesized to be an important mechanism that mediates certain biological processes and pathogenic effects of in utero phthalate exposure.

OBJECTIVE

The aim of this study was to examine the association between genome-wide DNA methylation at birth and prenatal exposure to phthalate.

METHODS

We studied 64 infant-mother pairs included in TMICS (Taiwan Maternal and Infant Cohort Study), a long-term follow-up birth cohort from the general population. DNA methylation levels at more than 450,000 CpG sites were measured in cord blood samples using Illumina Infinium HumanMethylation450 BeadChips. The concentrations of three metabolites of di-(2-ethylhexyl) phthalate (DEHP) were measured using liquid chromatography tandem-mass spectrometry (LC-MS/MS) in urine samples collected from the pregnant women during 28-36 weeks gestation.

RESULTS

We identified 25 CpG sites whose methylation levels in cord blood were significantly correlated with prenatal DEHP exposure using a false discovery rate (FDR) of 5% (q-value < 0.05). Via gene-set enrichment analysis (GSEA), we also found that there was significant enrichment of genes involved in the androgen response, estrogen response, and spermatogenesis within those genes showing DNA methylation changes in response to exposure. Specifically, PA2G4, HMGCR, and XRCC6 genes were involved in genes in response to androgen.

CONCLUSIONS

Phthalate exposure in utero may cause significant alterations in the DNA methylation in cord blood. These changes in DNA methylation might serve as biomarkers of maternal exposure to phthalate in infancy and potential candidates for studying mechanisms via which phthalate may impact on health in later life. Future investigations are warranted.

Effects of prenatal di(2-ethylhexyl) phthalate exposure on childhood allergies and infectious diseases: The Hokkaido Study on Environment and Children's Health

Phthalates are widely used in consumer products, and experimental studies suggest that exposure to phthalates increase the risk of allergies. However, epidemiologic evidence on the associations between prenatal phthalate exposure and allergies/infectious diseases and cord blood immunoglobulin E (IgE) levels is limited. This study aimed to evaluate the associations between maternal mono(2-ethylhexyl) phthalate (MEHP) levels and cord blood IgE levels at birth (n=127), as well as the risk of allergies/infectious diseases in participants up to 7years of age; the participants were 1.5 (n=248), 3.5 (n=222), 7 (n=184) years of age. Maternal blood MEHP level in the second trimester was measured using gas chromatography-mass spectrometry. Participant characteristics were obtained from the medical birth records and self-administered questionnaires during pregnancy and after delivery. Wheeze and eczema were defined according to the Japanese version of the International Study of Asthma and Allergies in Childhood and the American Thoracic Society-Division of Lung Diseases questionnaire, respectively. Infectious diseases were defined using questionnaires for each specified age. To evaluate the associations between maternal MEHP and allergies or infectious diseases, we used logistic regression analysis and generalized estimating equations analysis. Maternal MEHP levels were negatively associated with cord blood IgE levels and increased risks of allergies and infectious diseases up to 7years of age. This is the first study to investigate the effects of prenatal MEHP exposure on IgE levels at birth and allergies/infectious diseases up to 7years of age. Further epidemiological studies should focus on other phthalate metabolites and their health effects on larger populations.

Birth cohorts in Asia: The importance, advantages, and disadvantages of different-sized cohorts

Asia contains half of the world's children, and the countries of Asia are the most rapidly industrializing nations on the globe. Environmental threats to the health of children in Asia are myriad. Several birth cohorts were started in Asia in early 2000, and currently more than 30 cohorts in 13 countries have been established for study. Cohorts can contain from approximately 100-200 to 20,000-30,000 participants. Furthermore, national cohorts targeting over 100,000 participants have been launched in Japan and Korea. The aim of this manuscript is to discuss the importance of Asian cohorts, and the advantages and disadvantages of different-sized cohorts. As for case, one small-sized (n=514) cohort indicate that even relatively low level exposure to dioxin in utero could alter birth size, neurodevelopment, and immune and hormonal functions. Several Asian cohorts focus prenatal exposure to perfluoroalkyo substances and reported associations with birth size, thyroid hormone levels, allergies and neurodevelopment. Inconsistent findings may possibly be explained by the differences in exposure levels and target chemicals, and by possible statistical errors. In a smaller cohort, novel hypotheses or preliminary examinations are more easily verifiable. In larger cohorts, the etiology of rare diseases, such as birth defects, can be analyzed; however, they require a large cost and significant human resources. Therefore, conducting studies in only one large cohort may not always be the best strategy. International collaborations, such as the Birth Cohort Consortium of Asia, would cover the inherent limitation of sample size in addition to heterogeneity of exposure, ethnicity, and socioeconomic conditions.

Impacts of prenatal triclosan exposure on fetal reproductive hormones and its potential mechanism

BACKGROUND

Triclosan (TCS) has been widely detected in pregnant women. The reproductive endocrine-disrupting effects of TCS have been observed in humans and animals. Little is known about the potential impact of prenatal TCS exposure on fetal reproductive development as well as its potential mechanism.

OBJECTIVES

We investigated the potential effect of prenatal TCS exposure on fetal reproductive hormones in cord blood and its potential mechanism in relation to placental steroidogenic enzymes.

METHODS

Urinary TCS was detected among 537 healthy pregnant women from a prospective cohort in China. Four reproductive hormones in cord blood, namely E₂ (n=430), T (n=424), LH (n=428) and FSH (n=373), and three steroidogenic enzymes in placenta, namely P450arom (n=233), 3β-HSD (n=227) and 17β-HSD (n=222), were measured.

RESULTS

Prenatal TCS exposure was associated with increased testosterone concentrations in cord blood in a dose-dependent manner. Infants with prenatal TCS levels >0.6μg/L had, on average, a 0.23ng/mL (95% CI: 0.05, 0.45, p=0.02) higher testosterone concentrations in cord blood compared to those with prenatal TCS levels <0.1μg/L. Of note, prenatal TCS exposure was associated with increased testosterone and decreased E₂ concentrations in cord blood among male infants. Adverse associations were found between the prenatal TCS exposure and concentrations of three placental steroidogenic enzymes. 3β-HSD and P450arom demonstrated mediating effects in the association between prenatal TCS exposure and testosterone concentrations in cord blood.

CONCLUSIONS

Our findings suggested potential impacts of prenatal TCS exposure on reproductive hormones in cord blood mediated by steroidogenic enzymes, and male infants were more vulnerable.

Phthalates Exert Multiple Effects on Leydig Cell Steroidogenesis

Humans are significantly exposed to phthalates via food packaging, cosmetics and medical devices such as tubings and catheters. Testicular Leydig cells (LCs) are suggested to be among the main targets of phthalate toxicity in the body. However, their sensitivity to phthalates is species-dependent. This paper describes the response of the LCs from different species (mouse, rat and human) to phthalate exposure in different experimental paradigms (in vivo, ex vivo and in vitro), with particular focus on mechanisms of phthalate action on LC steroidogenesis. A comprehensive analysis of the impact of phthalate diesters and phthalate monoesters on LCs in different stages of their development is presented and possible mechanisms of phthalates action are discussed. Finally novel, not yet fully elucidated sites of action of phthalate monoesters on the backdoor pathway of 5α-dihydrotestosterone biosynthesis in immature mouse LCs and their effects on steroidogenesis and redox state in adult mouse LCs are reported.

Prenatal organochlorine pesticide exposure and the disruption of steroids and reproductive hormones in cord blood: The Hokkaido study

Certain organochlorine pesticides (OCPs) are designated as persistent organic pollutants and are regulated in many countries. The effects of OCPs on pediatric endocrinology are a concern; however, only limited data exist from human studies on maternal OCP exposure and its effects on infants' hormone levels. This study was conducted as part of the Hokkaido Study Sapporo Cohort, a prospective birth cohort study in Japan. Participants included 514 women who enrolled at 23-35weeks of gestation between 2002 and 2005; maternal blood samples were collected in late pregnancy, and 29 OCPs were measured. Reproductive and steroid hormone levels in cord blood were also determined. Characteristics of mothers and their infants were obtained from self-administered questionnaires and medical records. Ultimately, 232 samples with both OCP and hormone data were analyzed. Fifteen of 29 investigated OCPs were detected in over 80% of the samples, with p,p'-dichlorodiphenyldichloroethylene showing the highest concentration (median value: 619pg/g-wet). The association between OCPs and sex hormone levels varied by sex. Linear regression models after sex stratification showed that chlordanes, cis-hexachlorobenzene, heptachlor epoxide, Mirex, and toxaphenes in maternal blood were inversely associated with testosterone, cortisol, cortisone, sex hormone-binding globin, prolactin, and androstenedione-dehydroepiandrosterone (DHEA) and testosterone-androstenediones ratios among boys. Furthermore, these OCPs were positively correlated with DHEA, follicle stimulating hormone (FSH), and adrenal androgen-glucocorticoid and FSH-inhibin B ratios among boys. In categorical quartile models, testosterone and DHEA were inversely and positively associated with OCPs, respectively. Estradiol-testosterone and adrenal androgen-glucocorticoid ratios tended to increase with increasing OCP concentrations in the higher quartile, while the testosterone-androstenedione ratio tended to decrease. Sex hormone-binding globulin and prolactin showed an inverse association with OCPs. Among girls, the linear regression model showed that only p,p'-dichlorodiphenyltrichloroethane was inversely associated with the level of DHEA and the adrenal androgen-glucocorticoid ratio, but was positively associated with cortisone levels. However, no associations were observed using the quartile categorical model. These results suggest that prenatal exposure to OCPs disrupt reproductive hormones of fetuses in utero among boys, even at relatively low levels.

Children's environmental health based on birth cohort studies of Asia

Numerous studies have explored the associations between environmental pollutants and pediatric health. Recent studies have investigated the issue in Asia, but no systematic review has been published to date. This study aims to elucidate the issue by summarizing relevant epidemiologic evidence for cohorts in Asia, using information from the Birth Cohort Consortium of Asia (BiCCA). Environmental pollutants include mercury, environmental tobacco smoke (ETS), polychlorinated biphenyls (PCB), perfluoroalkyl substances (PFAS) and phthalates. This study sought to classify the effects of such compounds on fetal growth and pregnancy outcomes, neurodevelopment and behavioral problems, allergic disease and immune function and the endocrine system and puberty. These evidences showed ETS has been associated with infant birth weight, children's neurodevelopment and allergy disease; mercury and PCB have been shown to affect children's neurodevelopment; phthalate has effects on endocrine function; PFAS alters children's neurodevelopment, the endocrine system, and the allergic response. However, more consistent and coordinated research is necessary to understand the whole picture of single environmental and/or co-exposure and children's health. Therefore, harmonization and international collaboration are also needed in Asia.

Associations between Urinary Phthalate Metabolites and Serum Anti-Müller Hormone Levels in U.S. Men Based on National Health and Nutrition Examination Survey 2003-2004

Anti-Müller hormone (AMH) plays an important role in reproductive development and has a wide potential clinical application value. Phthalates have been widely found in human living environment and have negative effects on human reproduction. This study aimed to explore the relationship between urinary phthalate metabolites and serum AMH level in the general male population. Cross-sectional analyses were performed with a population of 489 men aged more than 12 years who participated in National Health and Nutrition Examination Survey (NHANES) 2003-2004 by Centers for Disease Control and Prevention, the United States. NHANES public data (demographic and socioeconomic information, examinations, and laboratory tests) were analyzed using Kruskal-Wallis test, Wilcoxon test and multivariable regression. Results showed that the urine concentration of mono (3-carboxypropyl) phthalate (MCPP) of 12-20 age group was significantly positively correlated with serum AMH concentration in the model without any covariates (p < 0.05). In the 60-year-old group, the monomethyl phthalate (MEP), mono (2-ethyl-5-carboxypentyl) phthalate (MECPP) concentrations were significantly correlated with serum AMH concentrations in models both with and without covariates (all p < 0.05). It could be concluded that exposure to phthalates might have negative effects on AMH level, especially in seniors. AMH could be used as a marker of exposure to phthalates in aged males. How exposure to phthalates affected AMH level and what the potential long-term health consequences of their relationship are needs more investigation.

Phthalate and bisphenol A exposure during in utero windows of susceptibility in relation to reproductive hormones and pubertal development in girls

BACKGROUND

Over the past several decades, the age of pubertal onset in girls has shifted downward worldwide. As early pubertal onset is associated with increased risky behavior and psychological issues during adolescence and cardiometabolic disease and cancer in adulthood, this is an important public health concern. Exposure to endocrine disrupting chemicals during critical windows of in utero development may play a role in this trend. Our objective was to investigate trimester-specific phthalate and BPA exposure in relation to pubertal development among girls in the Early Life Exposure in Mexico to Environmental Toxicants (ELEMENT) birth cohort.

METHODS

We measured maternal urinary phthalate metabolites and BPA in samples collected during the first, second, and third trimesters of pregnancy. To assess reproductive development among their female children, we measured serum testosterone, estradiol, dehydroepiandrosterone sulfate (DHEA-S), inhibin B, and sex hormone-binding globulin (SHBG), and assessed sexual maturation, including Tanner staging for breast and pubic hair development and menarche status, at age 8-13 years (n = 120). We used linear and logistic regression to examine measures of trimester-specific in utero exposure as predictors of peripubertal hormone levels and pubertal onset, respectively. In secondary analyses, we evaluated estimated exposure at the midpoint of the first trimester and rates of change in exposure across pregnancy in relation to outcomes.

RESULTS

Several phthalate metabolites measured throughout in utero development were associated with higher serum testosterone concentrations, while a number of metabolites measured in the third trimester were associated with higher DHEA-S. For example, an interquartile range (IQR) increase in mean monoethyl phthalate (MEP) levels across pregnancy was associated with 44% higher peripubertal testosterone (95% CI: 13-83%), while an IQR increase in di-2-ethylhexyl phthalate metabolites (ΣDEHP) specifically in the third trimester was associated with 25% higher DHEA-S (95%CI: 4.7-47%). In IQR increase in mean mono-2-ethylhexyl phthalate (MEHP) levels across pregnancy was associated with lower odds of having a Tanner Stage >1 for breast development (OR = 0.32, 95%CI: 0.11-0.95), while MEHP in the third trimester was associated with higher odds of having a Tanner Stage >1 for pubic hair development (OR = 3.76, 95%CI: 1.1-12.8). Results from secondary analyses were consistent with findings from our main analysis.

CONCLUSION

These findings suggest that female reproductive development may be more vulnerable to the effects of phthalate or BPA exposure during specific critical periods of in utero development. This highlights the need for comprehensive characterizations of in utero exposure and consideration of windows of susceptibility in developmental epidemiological studies. Future research should consider repeated measures of in utero phthalate and BPA exposure within each trimester and across pregnancy.

Inhibitory effects of fifteen phthalate esters in human cDNA-expressed UDP-glucuronosyltransferase supersomes

Phthalate esters (PAEs) have been extensively used in industry as plasticizers and there remains concerns about their safety. The present study aimed to determine the inhibition of phthalate esters (PAEs) on the activity of the phase II drug-metabolizing enzymes UDP-glucuronosyltransferases (UGTs). In vitro recombinant UGTs-catalyzed glucuronidation of 4-methylumbelliferone was used to investigate the inhibition potentials of PAEs towards various s UGTs. PAEs exhibited no significant inhibition of UGT1A1, UGT1A3, UGT1A8, UGT1A10, UGT2B15, and UGT2B17, and limited inhibition of UGT1A6, UGT1A7 and UGT2B4. However, UGT1A9 was strongly inhibited by PAEs. In silico docking demonstrated a significant contribution of hydrogen bonds and hydrophobic interactions contributing to the inhibition of UGT by PAEs. The K_i values were 15.5, 52.3, 23.6, 12.2, 5.61, 2.79, 1.07, 22.8, 0.84, 73.7, 4.51, 1.74, 0.58, 6.79, 4.93, 6.73, and 7.23 μM for BBOP-UGT1A6, BBZP-UGT1A6, BBOP-UGT1A7, BBZP-UGT1A7, DiPP-UGT1A9, DiBP-UGT1A9, DCHP-UGT1A9, DBP-UGT1A9, BBZP-UGT1A9, BBOP-UGT1A9, DMEP-UGT1A9, DPP-UGT1A9, DHP-UGT1A9, DiBP-UGT2B4, DBP-UGT2B4, DAP-UGT2B4, and BBZP-UGT2B4, respectively. In conclusion, exposure to PAEs might influence the metabolic elimination of endogenous compounds and xenobiotics through inhibiting UGTs.

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.

Impact of phthalate and BPA exposure during in utero windows of susceptibility on reproductive hormones and sexual maturation in peripubertal males

BACKGROUND

Phthalates and BPA are endocrine disrupting chemicals (EDCs) widely used in consumer products. Evidence suggests that phthalate and BPA exposure alters steroid hormone levels in adults, while in utero exposure has been associated with altered fetal reproductive development in boys. However, the impact of exposure during distinct critical windows of in utero development on hormone concentrations and sexual maturation during the pubertal transition has not been examined. The objective of this study was to assess trimester-specific in utero phthalate and BPA exposure in relation to measures of reproductive development among peripubertal boys in a Mexico City birth cohort.

METHODS

We measured maternal urinary phthalate metabolites and BPA during the first, second, and third trimesters of pregnancy. We measured serum levels of testosterone, estradiol, dehydroepiandrosterone sulfate (DHEA-S), inhibin B, and sex hormone-binding globulin (SHBG), and assessed sexual maturation (Tanner staging and testicular volume) among male children at age 8-14 years (n = 109). Linear and logistic regression were used to investigate trimester-specific in utero exposure as predictors of peripubertal hormone levels and sexual maturation, respectively. In sensitivity analyses we evaluated estimated exposure at 7 weeks gestation and rates of change in exposure across pregnancy in relation to outcomes.

RESULTS

Exposure to phthalates during the third trimester was associated with reduced odds of having a Tanner stage >1 for pubic hair development (e.g. MBzP OR = 0.18 per interquartile range (IQR) increase; 95% CI:0.03-0.97) and higher peripubertal SHBG levels (e.g. MBzP 15.2%/IQR; 95% CI:3.2-28%), while first and second trimester phthalates were not. In contrast, exposure to DEHP during the first trimester was associated with higher estradiol (11%/IQR; 95% CI:1.5-22%), while second or third trimester DEHP exposure was not. Sensitivity analyses yielded similar findings.

CONCLUSIONS

Associations between in utero phthalate and BPA exposure and peripubertal measures of male reproductive development are dependent on the timing of that exposure during gestation. These findings suggest that future epidemiological studies relating in utero EDC exposure to pubertal outcomes should consider windows of susceptibility.

In Utero and Lactational Exposure Study in Rats to Identify Replacements for Di(2-ethylhexyl) Phthalate

Di(2-ethylhexyl) phthalate (DEHP) and other phthalates are ubiquitous environmental contaminants with endocrine disrupting properties. Two novel plasticizers, 1,4 butanediol dibenzoate (BDB) and dioctyl succinate (DOS), have been proposed as potential replacements. Both have desirable properties as plasticizers and minimal in vitro biological effects. Herein, we present an in utero and lactational exposure study comparing DEHP with BDB, DOS, and 1,2-cyclohexane dicarboxylic acid diisononyl ester (DINCH), a commercial alternative. Timed-pregnant Sprague-Dawley rats were gavaged with vehicle or one of these chemicals at 30 or 300 mg/kg/day from gestational day 8 until postnatal day (PND) 21. The offspring were examined for effects on developmental and endocrine markers until PND 46. DEHP treatment (300 mg/kg) decreased heart weights in dams and induced a significant decrease in anogenital index and an increase in hemorrhagic testes and multinucleated gonocytes in PND 3 male pups. An increase in the incidence of hemorrhagic testes was also observed on PND 8 after exposure to DINCH (30 and 300 mg/kg). The only other effects observed were decreases in serum alanine transaminase and magnesium in BDB 30 exposed dams. These data suggest that both BDB and DOS are viable alternative plasticizers.

Mono-2-ethylhexyl phthalate associated with insulin resistance and lower testosterone levels in a young population

Phthalates are commonly used as plasticizers and are reported to associate with testicular dysfunction or insulin resistance in different studies, but the concurrent relationship between phthalate exposure, testosterone levels, and insulin resistance in the young population is not well understood. We recruited 786 subjects aged 12-30 years from a population-based sample of Taiwanese adolescents and young adults from 2006 to 2008. Generalized additive models were used to evaluate glucose homeostasis and testicular function in relation to seven urinary phthalate metabolites among adolescents (aged 12-20) and young adults (aged 20-30) in Taiwan. We observed a trend toward a decrease in male testosterone and an increase in urinary mono-2-ethylhexyl phthalate (MEHP) levels across four quartiles of homeostasis model assessment of insulin resistance (HOMA-IR). After adjusting for potential covariates, generalized additive models further showed that log-transformed insulin and HOMA-IR were raised by 0.055 [95% confidence interval (CI), 0.027-0.082] and 0.056 (95% CI, 0.027-0.084), respectively, with a one-unit increase in log-transformed MEHP in young adults. In male adults (aged 22-30), the log-testosterone levels were reduced by 0.018 (95% CI, 0.001-0.036), with a one-unit of increase in log-transformed MEHP. Such relationships were not observed in adolescents. In conclusion, this study demonstrated age-related associations of urinary MEHP metabolites with impaired metabolic homeostasis of glucose that were only observed in young adults. In addition, MEHP exposure was concurrently associated with lower testosterone levels in young, male adults.

Prenatal and childhood exposure to phthalate diesters and sex steroid hormones in 2-, 5-, 8-, and 11-year-old children: A pilot study of the Taiwan Maternal and Infant Cohort Study

Background

Phthalate diesters are commonly used and have been well established as environmental endocrine disruptors. However, few studies have examined their effects on sex steroid hormones in children. We followed children over time to examine the association between pre- and post-natal phthalate exposure and sex steroid hormone levels at 2, 5, 8, and 11 years of age.

Methods

We recruited 430 pregnant women from central Taiwan from 2000 to 2001 and assessed their children at birth, 2, 5, 8, and 11 years of age. We studies children with at least one measurement for both phthalate and hormone levels during each any of the follow-up time point (n = 193). Estradiol, free testosterone, testosterone, and progesterone were measured from venous blood. Three monoesters of di-2-ethylhexyl phthalate (DEHP), mono-benzyl phthalate, mono-n-butyl phthalate, mono-ethyl phthalate, and mono-methyl phthalate were measured in maternal urine collected during the 3rd trimester and child urine collected at each follow-up point. The sum of mono-2-ethylhexyl phthalate (∑MEHP) was calculated by summing the concentrations of the three DEHP monoesters. Generalized estimating equation regression analysis with repeated measures was used to estimate associations between phthalate metabolites and hormone levels.

Results

After adjustment for potential confounders, maternal ∑MEHP level was associated with decreased levels of progesterone in girls (β = −0.309 p = 0.001). The child ∑MEHP concentration was associated with decreased levels of progesterone for girls (β = −0.194, p = 0.003) and with decreased levels of free testosterone for boys (β = −0.124, p = 0.004).

Conclusions

Early-life DEHP exposure may alter sex steroid hormones of children over time, which may pose potential reproductive health risks.

•

Prenatal phthalate exposure was associated with decreased PG levels in girls.

•

Postnatal DEHP exposure was related to decreased free TT in boys and PG in girls.

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Use of phthalate-containing products in developing children should be limited.

Effects of maternal acrolein exposure during pregnancy on testicular testosterone production in fetal rats

Acrolein has been reported to have diverse toxic effects on various organs, including the reproductive system. However, little is known regarding the effects of maternal acrolein exposure on testicular steroidogenesis in male offspring. The present study investigated the effects of acrolein on fetal testosterone production and associated genes. Pregnant Sprague-Dawley rats were intraperitoneally injected with vehicle (normal saline) or 1, 2 or 5 mg/kg acrolein from gestational day (GD) 14–20, and fetal testes were examined on GD 21. Fetal body and testicular weights were markedly reduced in pups following exposure to high doses of acrolein (5 mg/kg) in late pregnancy. Notably, in utero exposure of 5 mg/kg acrolein significantly decreased the testicular testosterone level and downregulated the expression levels of steroidogenic acute regulatory protein (StAR) and 3β-hydroxysteroid dehydrogenase (3β-HSD), whereas the levels of other steroidogenic enzymes, including scavenger receptor class B, cholesterol side-chain cleavage enzyme and steroid 17 alpha-hydroxylase/17,20 lyase, were unaffected. Furthermore, the 3β-HSD immunoreactive area in the interstitial region of the fetal testes was reduced at a 5 mg/kg dose, whereas the protein expression levels of 4-hydroxynonenalwere dose-dependently increased following maternal exposure to acrolein. mRNA expression levels of insulin-like factor 3, a critical gene involved in testicular descent, were unaltered following maternal acrolein exposure. Taken together, the results of the present study suggested that maternal exposure to high doses of acrolein inhibited fetal testosterone synthesis, and abnormal expression of StAR and 3β-HSD may be associated with impairment of the steroidogenic capacity.

The Hokkaido Birth Cohort Study on Environment and Children's Health: cohort profile-updated 2017

The Hokkaido Study on Environment and Children's Health is an ongoing study consisting of two birth cohorts of different population sizes: the Sapporo cohort and the Hokkaido cohort. Our primary study goals are (1) to examine the effects of low-level environmental chemical exposures on birth outcomes, including birth defects and growth retardation; (2) to follow the development of allergies, infectious diseases, and neurobehavioral developmental disorders and perform a longitudinal observation of child development; (3) to identify high-risk groups based on genetic susceptibility to environmental chemicals; and (4) to identify the additive effects of various chemicals, including tobacco smoking. The purpose of this report is to update the progress of the Hokkaido Study, to summarize the recent results, and to suggest future directions. In particular, this report provides the basic characteristics of the cohort populations, discusses the population remaining in the cohorts and those who were lost to follow-up at birth, and introduces the newly added follow-up studies and case-cohort study design. In the Sapporo cohort of 514 enrolled pregnant women, various specimens, including maternal and cord blood, maternal hair, and breast milk, were collected for the assessment of exposures to dioxins, polychlorinated biphenyls, organochlorine pesticides, perfluoroalkyl substances, phthalates, bisphenol A, and methylmercury. As follow-ups, face-to-face neurobehavioral developmental tests were conducted at several different ages. In the Hokkaido cohort of 20,926 enrolled pregnant women, the prevalence of complicated pregnancies and birth outcomes, such as miscarriage, stillbirth, low birth weight, preterm birth, and small for gestational age were examined. The levels of exposure to environmental chemicals were relatively low in these study populations compared to those reported previously. We also studied environmental chemical exposure in association with health outcomes, including birth size, neonatal hormone levels, neurobehavioral development, asthma, allergies, and infectious diseases. In addition, genetic and epigenetic analyses were conducted. The results of this study demonstrate the effects of environmental chemical exposures on genetically susceptible populations and on DNA methylation. Further study and continuous follow-up are necessary to elucidate the combined effects of chemical exposure on health outcomes.

Prenatal di(2-ethylhexyl) phthalate exposure and disruption of adrenal androgens and glucocorticoids levels in cord blood: The Hokkaido Study

Di(2-ethylhexyl) phthalate (DEHP) is known for its endocrine disrupting properties. We previously demonstrated that prenatal DEHP exposure is associated with decreased progesterone levels and testosterone/estradiol ratio in the cord blood. However, evidence of the effects of prenatal DEHP exposure on adrenal androgen and glucocorticoids in infants is scarce. Thus, the objectives of this study were to investigate the association between prenatal DEHP exposure and adrenal androgen and glucocorticoids, and to discuss its effects on steroid hormone profiles in infants. This is part of a birth cohort study: The Hokkaido Study on Environment and Children's Health, Sapporo Cohort. Among the 514 participants, 202 mother-infant pairs with available data on maternal mono(2-ethylhexyl) phthalate (MEHP), adrenal androgen (dehydroepiandrostenedione [DHEA] and androstenedione) and glucocorticoid (cortisol and cortisone) cord blood levels were included in this study. After adjusting for potential confounders, a linear regression analysis showed that maternal MEHP levels were associated with reduced cortisol and cortisone levels and glucocorticoid/adrenal androgen ratio, whereas increased DHEA levels and DHEA/androstenedione ratio. In a quartile model, when comparing the adjusted least square means in the 4th quartile of MEHP with those in the 1st quartile, cortisol and cortisone levels and glucocorticoid/adrenal androgen ratio decreased, whereas DHEA/androstenedione and cortisol/cortisone ratios increased. Significant p-value trends for cortisol and cortisone levels, cortisol/cortisone ratio, and glucocorticoid/adrenal androgen ratio were observed. In combination with the previous results of reduced progesterone levels and testosterone/estradiol ratio, prenatal exposure to DEHP altered the steroid hormone profiles of infants. Further studies investigating the long-term effects of DEHP exposure on growth, neurodevelopment, and gonad and reproductive function are required.

Direct and transgenerational effects of low doses of perinatal di-(2-ethylhexyl) phthalate (DEHP) on social behaviors in mice

Di-(2-ethylhexyl) phthalate (DEHP) is an endocrine disrupting chemical commonly used as a plasticizer in medical equipment, food packaging, flooring, and children’s toys. DEHP exposure during early development has been associated with adverse neurobehavioral outcomes in children. In animal models, early exposure to DEHP results in abnormal development of the reproductive system as well as altered behavior and neurodevelopment. Based on these data, we hypothesized that developmental exposure to DEHP would decrease social interactions and increase anxiety-like behaviors in mice in a dose-dependent manner, and that the effects would persist over generations. C57BL/6J mice consumed one of three DEHP doses (0, 5, 40, and 400 μg/kg body weight) throughout pregnancy and during the first ten days of lactation. The two higher doses yielded detectable levels of DEHP metabolites in serum. Pairs of mice from control, low, and high DEHP doses were bred to create three dose lineages in the third generation (F3). Average anogenital index (AGI: anogenital distance/body weight) was decreased in F1 males exposed to the low dose of DEHP and in F1 females exposed to the highest dose. In F1 mice, juvenile pairs from the two highest DEHP dose groups displayed fewer socially investigative behaviors and more exploratory behaviors as compared with control mice. The effect of DEHP on these behaviors was reversed in F3 mice as compared with F1 mice. F1 mice exposed to low and medium DEHP doses spent more time in the closed arms of the elevated plus maze than controls, indicating increased anxiety-like behavior. The generation-dependent effects on behavior and AGI suggest complex mechanisms by which DEHP directly impacts reproductive and neurobehavioral development and influences germline-inherited traits.

Prenatal di-2-ethylhexyl phthalate exposure and cord blood adipokine levels and birth size: The Hokkaido study on environment and children's health

Di-2-ethylhexyl phthalate (DEHP) is one of the most widely used phthalates. Metabolites of DEHP are detectable in majority of the population. Findings on adverse health outcomes, particularly birth weight in association with prenatal exposure to DEHP remain equivocal. Besides, there is insufficient evidence to address influence on metabolic function from epidemiological studies. Thus, our objective was to investigate cord blood adipokine levels and birth size in association with prenatal DEHP exposure in prospective birth cohort study. Mono-2-methylhexyl phthalate (MEHP), primary metabolite of DEHP was determined as exposure by using maternal blood sample of 3rd trimester. Leptin and adiponectin levels in cord blood were measured as markers of metabolic function. Birth weight and length were obtained from birth record. Association between maternal MEHP levels and cord blood adiponectin and leptin levels, birth weight and ponderal index (PI) were examined for 167 mother-child pairs who had both MEHP and cord blood adipokine measurements. The median MEHP level was 8.81ng/ml and the detection rate was 100%. There was no sex difference in MEHP levels. Both leptin and adiponectin levels were higher in girls than in boys. MEHP level was positively associated with adiponectin level among boys and was negatively associated with leptin level among girls. MEHP level were negatively associated with PI only in girls and this could be due to decreased leptin level. This study suggested that prenatal DEHP exposure may be associated with cord blood adipokine and birth size. The influence potentially be sex-specific and could be more significant in girls.

Chronic exposure of adult, postnatal and in utero rat models to low-dose 137Cesium: impact on circulating biomarkers

The presence of 137Cesium (137Cs) in the environment after nuclear accidents at Chernobyl and more recently Fukushima Daiichi raises many health issues for the surrounding populations chronically exposed through the food chain. To mimic different exposure situations, we set up a male rat model of exposure by chronic ingestion of a 137Cs concentration likely to be ingested daily by residents of contaminated areas (6500 Bq.l-1) and tested contaminations lasting 9 months for adult, neonatal and fetal rats. We tested plasma and serum biochemistry to identify disturbances in general indicators (lipids, proteins, carbohydrates and electrolytes) and in biomarkers of thyroid, heart, brain, bone, kidney, liver and testis functions. Analysis of the general indicators showed increased levels of cholesterol (+26%), HDL cholesterol (+31%), phospholipids B (+15%) and phosphorus (+100%) in the postnatal group only. Thyroid, heart, brain, bone and kidney functions showed no blood changes in any model. The liver function evaluation showed changes in total bilirubin (+67%) and alkaline phosphatase (-11%) levels, but only for the rats exposed to 137Cs intake in adulthood. Large changes in 17β-estradiol (-69%) and corticosterone (+36%) levels affected steroidogenesis, but only in the adult model. This study showed that response profiles differed according to age at exposure: lipid metabolism was most radiosensitive in the postnatal model, and steroid hormone metabolism was most radiosensitive in rats exposed in adulthood. There was no evidence of deleterious effects suggesting a potential impact on fertility or procreation.

Implications of Applying Minimal Risk Standards in Clinical Research to Information Provision in Prenatal and Pre-conception Care

BACKGROUND

There have long been minimal risk thresholds beneath which risks may not need to be discussed in clinical research. This threshold concept may be applied to clinical practice. Our research explored application of minimal risk standards in research regulations to providing information in prenatal and pre-conception care.

METHODS

A case study approach applied minimal risk standards in research regulations to prenatal and pre-conception care with respect to the risks of excess alcohol consumption, folic acid insufficiency, exposure to phthalate plasticizers, and exposure to brominated flame retardants (BFRs).

RESULTS

Excess alcohol consumption and folic acid insufficiency were found to be above the minimal risk standards as outlined in research regulations, while exposure to phthalates and BFRs requires more evidence to determine whether they are above minimal risk. However, applying the minimal risk standard based on the daily life of a healthy adult or a fetus in a healthy pregnant woman, phthalates and BFRs are at the minimal risk threshold regardless of their potential harm since all pregnant women may be exposed to these chemicals in their daily life. Nevertheless, if there is demonstration of sufficient evidence of harm, they may be above minimal risk if such harm can be reduced by individual choice to avoid exposure.

CONCLUSION

The minimal risk concept in research regulations as applied to clinical practice may be useful to help clinicians and professional organizations determine what risks need be discussed in prenatal and pre-conception care.

In vitro functional screening as a means to identify new plasticizers devoid of reproductive toxicity

Plasticizers are indispensable additives providing flexibility and malleability to plastics. Among them, several phthalates, including di (2-ethylhexyl) phthalate (DEHP), have emerged as endocrine disruptors, leading to their restriction in consumer products and creating a need for new, safer plasticizers. The goal of this project was to use in vitro functional screening tools to select novel non-toxic plasticizers suitable for further in vivo evaluation. A panel of novel compounds with satisfactory plasticizer properties and biodegradability were tested, along with several commercial plasticizers, such as diisononyl-cyclohexane-1,2-dicarboxylate (DINCH®). MEHP, the monoester metabolite of DEHP was also included as reference compound. Because phthalates target mainly testicular function, including androgen production and spermatogenesis, we used the mouse MA-10 Leydig and C18-4 spermatogonial cell lines as surrogates to examine cell survival, proliferation, steroidogenesis and mitochondrial integrity. The most promising compounds were further assessed on organ cultures of rat fetal and neonatal testes, corresponding to sensitive developmental windows. Dose-response studies revealed the toxicity of most maleates and fumarates, while identifying several dibenzoate and succinate plasticizers as innocuous on Leydig and germ cells. Interestingly, DINCH®, a plasticizer marketed as a safe alternative to phthalates, exerted a biphasic effect on steroid production in MA-10 and fetal Leydig cells. MEHP was the only plasticizer inducing the formation of multinucleated germ cells (MNG) in organ culture. Overall, organ cultures corroborated the cell line data, identifying one dibenzoate and one succinate as the most promising candidates. The adoption of such collaborative approaches for developing new chemicals should help prevent the development of compounds potentially harmful to human health.

Endocrine disruption: In silico perspectives of interactions of di-(2-ethylhexyl)phthalate and its five major metabolites with progesterone receptor

Background

Di-(2-ethylhexyl)phthalate (DEHP) is a common endocrine disrupting compound (EDC) present in the environment as a result of industrial activity and leaching from polyvinyl products. DEHP is used as a plasticizer in medical devices and many commercial and household items. Exposure occurs through inhalation, ingestion, and skin contact. DEHP is metabolized to a primary metabolite mono-(2-ethylhexyl)phthalate (MEHP) in the body, which is further metabolized to four major secondary metabolites, mono(2-ethyl-5-hydroxyhexyl)phthalate (5-OH-MEHP), mono(2-ethyl-5-oxyhexyl)phthalate (5-oxo-MEHP), mono(2-ethyl-5-carboxypentyl)phthalate (5-cx-MEPP) and mono[2-(carboxymethyl)hexyl]phthalate (2-cx-MMHP). DEHP and its metabolites are associated with developmental abnormalities and reproductive dysfunction within the human population. Progesterone receptor (PR) signaling is involved in important reproductive functions and is a potential target for endocrine disrupting activities of DEHP and its metabolites. This study used in silico approaches for structural binding analyses of DEHP and its five indicated major metabolites with PR.

Methods

Protein Data bank was searched to retrieve the crystal structure of human PR (Id: 1SQN). PubChem database was used to obtain the structures of DEHP and its five metabolites. Docking was performed using Glide (Schrodinger) Induced Fit Docking module.

Results

DEHP and its metabolites interacted with 19-25 residues of PR with the majority of the interacting residues overlapping (82-95 % commonality) with the native bound ligand norethindrone (NET). DEHP and each of its five metabolites formed a hydrogen bonding interaction with residue Gln-725 of PR. The binding affinity was highest for NET followed by DEHP, 5-OH-MEHP, 5-oxo-MEHP, MEHP, 5-cx-MEPP, and 2-cx-MMHP.

Conclusion

The high binding affinity of DEHP and its five major metabolites with PR as well as a high rate of overlap between PR interacting residues among DEHP and its metabolites and the native ligand, NET, suggested their disrupting potential in normal PR signaling, resulting in adverse reproductive effects.

Effects of prenatal phthalate exposure on thyroid hormone levels, mental and psychomotor development of infants: The Hokkaido Study on Environment and Children's Health

Di (2-ethylhexyl) phthalate (DEHP) is commonly used phthalates and concerns of adverse effects of prenatal DEHP exposure on neonatal thyroid hormone (TH) and neurodevelopment are increasing. However, there is no report regarding association between prenatal DEHP exposure and infant neurodevelopment including TH levels in Japanese population. Thus the aim of present study was to evaluate the associations between prenatal DEHP exposure and mental and psychomotor development of infants 6 and 18months along with investigating influence on neonatal free thyroxine (FT4) and thyroid stimulating hormone (TSH) levels in the prospective birth cohort study. Maternal blood samples collected between 23 and 41weeks of gestation was analyzed for mono (2-ethylhexyl) phthalate (MEHP), metabolite of DEHP levels. Neonatal FT4 and TSH were obtained from mass screening data. Infant neurodevelopment was assessed by Bayley Scale of Infant Development second edition at 6 and 18month of age. For the final analysis, 328 participants were included. The median levels of maternal MEHP was 10.6ng/ml, neonatal TSH and FT4 was 2.20 μU/ml and 2.03ng/ml, respectively. We did not find any associations between prenatal DEHP exposure and neonatal TH levels or infant mental and psychomotor development at 6 and 18month. In this study, prenatal DEHP exposure did not show adverse effects on infant TH levels or mental and psychomotor development in early life stage. However, our previous study revealed negative effects of prenatal DEHP exposure on sex hormone levels, continuous investigation on neurodevelopment in later life in association with prenatal DEHP exposure is necessary.

Association of perfluoroalkyl substances exposure in utero with reproductive hormone levels in cord blood in the Hokkaido Study on Environment and Children's Health

BACKGROUND

Exposure to perfluoroalkyl substances (PFASs) may disrupt reproductive function in animals and humans. Although PFASs can cross the human placental barrier, few studies evaluated the effects of prenatal PFAS exposure on the fetus' reproductive hormones.

OBJECTIVE

To explore the associations of prenatal exposure to perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) with cord blood reproductive hormones.

METHODS

In the prospective birth cohort (Sapporo cohort of the Hokkaido study), we included 189 mother-infant pairs recruited in 2002-2005 with both prenatal maternal and cord blood samples. PFOS and PFOA levels in maternal blood after the second trimester were measured via liquid chromatography-tandem mass spectrometry. We also measured cord blood levels of the fetuses' reproductive hormones, including estradiol (E2), total testosterone (T), progesterone (P4), inhibin B, insulin-like factor 3, steroid hormone binding globulin, follicle-stimulating hormone, and luteinizing hormone, and prolactin (PRL).

RESULTS

The median PFOS and PFOA levels in maternal serum were 5.2ng/mL and 1.4ng/mL, respectively. In the fully adjusted linear regression analyses of the male infants, maternal PFOS levels were significantly associated with E2 and positively, and T/E2, P4, and inhibin B inversely; PFOA levels were positively associated with inhibin B levels. Among the female infants, there were significant inverse associations between PFOS levels and P4 and PRL levels, although there were no significant associations between PFOA levels and the female infants' reproductive hormone levels.

CONCLUSIONS

These results suggest that the fetal synthesis and secretion of reproductive hormones may be affected by in utero exposure to measurable levels of PFOS and PFOA.

Di(2-Ethylhexyl) Phthalate Exposure In Utero Damages Sertoli Cell Differentiation Via Disturbance of Sex Determination Pathway in Fetal and Postnatal Mice

Mice may share similar mechanism with human underlying reproductive toxicity induced by di(2-ethylhexyl) phthalate (DEHP), which is not supposed to be associated with decreased testicular testosterone. Pregnant mice were exposed to DEHP by gavage, with the dosage regime beginning at human relevant exposure level. After in utero DEHP exposure, loss of Sertoli cells and germ cells were observed in the male pups at postnatal days 21. And SRY-related HMG box 9 (SOX9), Fibroblast growth factor-9 (FGF9), and Double-sex and Mab-3 related transcripttion factor 1 (DMRT1) proteins were significantly downregulated by DEHP at 2 mg/kg/d and above, suggesting the depression of Sertoli cell differentiation. The repression of Sox9 genes expression was supported by whole-mount in situ hybridization and real-time real-time-quantitative PCR. The expressions of Cyp11α1 and Star were not significantly affected by in utero DEHP exposure, indicating the absence of effects on testosterone biosynthesis. Furthermore, the testosterone-independent pathway regulating Sertoli cells differentiation was disturbed in fetus by DEHP at 2 mg/kg/d and above during the critical time window of sex determination, involving Gadd45g → Gata4/Fog2 → Sry → Sox9 → Fgf9 The results suggest that in utero DEHP exposure damaged Sertoli cells in the postnatal life of mice offspring via disturbance of the differentiation regulating pathway, potentially inducing declines in spermatogenesis.

Impacts of Perinatal Dioxin Exposure on Motor Coordination and Higher Cognitive Development in Vietnamese Preschool Children: A Five-Year Follow-Up

Dioxin concentrations remain elevated in the environment and in humans residing near former US Air Force bases in South Vietnam. Our previous epidemiological studies showed adverse effects of dioxin exposure on neurodevelopment for the first 3 years of life. Subsequently, we extended the follow-up period and investigated the influence of perinatal dioxin exposure on neurodevelopment, including motor coordination and higher cognitive ability, in preschool children. Presently, we investigated 176 children in a hot spot of dioxin contamination who were followed up from birth until 5 years old. Perinatal dioxin exposure levels were estimated by measuring dioxin levels in maternal breast milk. Dioxin toxicity was evaluated using two indices; toxic equivalent (TEQ)-polychlorinated dibenzo-p-dioxins/furans (PCDDs/Fs) and concentration of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Coordinated movements, including manual dexterity, aiming and catching, and balance, were assessed using the Movement Assessment Battery for Children, Second Edition (Movement ABC-2). Cognitive ability was assessed using the nonverbal index (NVI) of the Kaufman Assessment Battery for Children, Second Edition (KABC-II). In boys, total test and balance scores of Movement ABC-2 were significantly lower in the high TEQ- PCDDs/Fs group compared with the moderate and low exposure groups. NVI scores and the pattern reasoning subscale of the KABC-II indicating planning ability were also significantly lower in the high TCDD exposure group compared with the low exposure group of boys. However, in girls, no significant differences in Movement ABC-2 and KABC-II scores were found among the different TEQ-PCDDs/Fs and TCDD exposure groups. Furthermore, in high risk cases, five boys and one girl highly exposed to TEQ-PCDDs/Fs and TCDD had double the risk for difficulties in both neurodevelopmental skills. These results suggest differential impacts of TEQ-PCDDs/Fs and TCDD exposure on motor coordination and higher cognitive ability, respectively. Moreover, high TEQ-PCDDs/Fs exposure combined with high TCDD exposure may increase autistic traits combined with developmental coordination disorder.

Human exposure to endocrine disrupting chemicals and fertility: A case-control study in male subfertility patients

BACKGROUND

Dioxins, PCBs, chlorinated pesticides, brominated flame retardants, bisphenol A, triclosan, perfluorinated compounds and phthalates are known as endocrine disrupting chemicals (EDCs).

OBJECTIVES

The aim of our study was to investigate whether higher exposure to EDCs is associated with increased subfertility in men.

METHODS

We measured biomarkers of exposure in 163 men, recruited through four fertility clinics. According to WHO guidelines, we used a total motility count (TMC) of 20 million as cut-off value. We assigned patients to the case group when two semen samples - collected at least one week apart - had a TMC<20 and to the control group when both samples had a TMC≥20. To estimate the risk of subfertility and alteration in sex hormone concentrations we used multivariable-adjusted analysis, using logistic and linear regressions, respectively.

RESULTS

For an IQR increase in serum oxychlordane, the odds ratio for subfertility was 1.98 (95% CI: 1.07; 3.69). Furthermore, men with serum levels of BDE209 above the quantification limit had an odds of 7.22 (1.03; 50.6) for subfertility compared with those having values below the LOQ. Urinary levels of phthalates and triclosan were negatively associated with inhibin B and positively with LH. Urinary bisphenol A correlated negatively with testosterone levels.

CONCLUSIONS

Our study in men showed that internal body concentrations of endocrine disrupting chemicals are associated with an increased risk of subfertility together with alterations in hormone levels. The results emphasize the importance to reduce chemicals in the environment in order to safeguard male fertility.

Obstetrical outcomes and biomarkers to assess exposure to phthalates: A review

Studies of the effects on pregnancy outcomes of in utero exposure to phthalates, contaminants that are widely present in the environment, have yielded conflicting results. In addition, the mode of assessment of exposure varies between studies. The aim of this review was therefore to establish a current state of knowledge of the phthalates and metabolites involved in unfavorable pregnancy outcomes. Extant data were analyzed to determine which biomarker is the best suited to assess the relation between in utero exposure to phthalates and pregnancy outcomes. This review of the literature was conducted using the database of PubMed. A search was made of studies investigating exposure to phthalates and the following birth outcomes: preterm birth (gestational age <37 weeks), change in gestational age, change in body size at birth (birth weight, length, head circumference), anti-androgenic function, decreased anogenital distance, cryptorchidism, hypospadias and congenital malformation. The methodological approach adopted in each study was examined, in particular the methods used for exposure assessment (biomarkers and/or questionnaire). Thirty-five studies were included. Premature birth and decreased anogenital distance were the most commonly reported outcomes resulting from a moderate level of exposure to phthalates. The principal metabolites detected and involved were primary metabolites of di-2(ethylhexyl)-phthalate (DEHP) and di-n-butyl-phthalate (DnBP). No clear conclusion could be drawn with regard to gestational age at birth, body size at birth and congenital malformations. In epidemiological studies, maternal urine is the most suitable matrix to assess the association between in utero exposure to phthalates and pregnancy outcomes: in contrast to other matrices (cord blood, amniotic fluid, meconium and milk), sampling is easy, non-invasive and, can be repeated to assess exposure throughout pregnancy. Oxidative metabolites are the most relevant biomarkers since they are not prone to external contamination. Further epidemiological studies are required during pregnancy to i) determine the role of phthalates other than DEHP [currently replaced by various substitution products, in particular diisononyl-phthalate (DiNP)]; ii) establish the effect of phthalates on other outcomes (body size adjusted for gestational age, and congenital malformations); iii) determine the pathophysiological pathways; and iv) identify the most suitable time for biomarker determination of in utero exposure to phthalates.

Prenatal phthalate exposure and reproductive function in young men

BACKGROUND

Prenatal exposure to phthalates is suggested to negatively impact male reproductive function, but human data are lacking.

OBJECTIVES

To study associations between prenatal exposure to diethylhexyl phthalate (DEHP) and diisononyl phthalate (DiNP), and reproductive parameters of adolescent men.

METHODS

Using linear regression models adjusted for potential confounders, we studied associations between levels of DEHP- and DiNP metabolites in maternal sera from mean 12 weeks of pregnancy, and testicular size, semen quality and reproductive hormones in 112 adolescent sons, recruited from the general population.

RESULTS

Men in the highest exposure tertile of one DiNP metabolite [mono-(carboxy-iso-octyl) phthalate], compared with men in the lowest tertile had: 4.3mL (95% CI: 0.89, 7.6mL; p<0.001) lower total testicular volume; 30% (95% CI: 3.6, 63%; p=0.02) higher levels of follicle-stimulating hormone; and 0.87mL (95% CI: 0.28, 1.5mL; p=0.004) lower semen volume. Men in the highest exposure tertile of one DEHP metabolite [mono-(2-ethyl-5-hydroxylhexyl) phthalate] had 0.70mL (95% CI: 0.090, 1.3mL; p=0.03) lower semen volume than men in the lowest exposure tertile. The levels of two DiNP metabolites [mono-(hydroxy-iso-nonyl) phthalate and mono-(oxo-iso-nonyl) phthalate] were linearly associated with luteinizing hormone (p<0.01).

CONCLUSION

Prenatal levels of some metabolites of DEHP and DiNP seemed negatively associated with reproductive function of adolescent men.

Effects of prenatal Leydig cell function on the ratio of the second to fourth digit lengths in school-aged children

Prenatal sex hormones can induce abnormalities in the reproductive system and adversely impact on genital development. We investigated whether sex hormones in cord blood influenced the ratio of the second to fourth digit lengths (2D/4D) in school-aged children. Of the 514 children who participated in a prospective cohort study on birth in Sapporo between 2002 and 2005, the following sex hormone levels were measured in 294 stored cord blood samples (135 boys and 159 girls); testosterone (T), estradiol (E), progesterone, LH, FSH, inhibin B, and insulin-like factor 3 (INSL3). A total of 350 children, who were of school age and could be contacted for this survey, were then requested via mail to send black-and-white photocopies of the palms of both the left and right hands. 2D/4D was calculated in 190 children (88 boys and 102 girls) using photocopies and derived from participants with the characteristics of older mothers, a higher annual household income, higher educational level, and fewer smokers among family members. 2D/4D was significantly lower in males than in females (p<0.01). In the 294 stored cord blood samples, T, T/E, LH, FSH, Inhibin B, and INSL3 levels were significantly higher in samples collected from males than those from females. A multivariate regression model revealed that 2D/4D negatively correlated with INSL3 in males and was significantly higher in males with <0.32 ng/mL of INSL3 (p<0.01). No correlations were observed between other hormones and 2D/4D. In conclusion, 2D/4D in school-aged children, which was significantly lower in males than in females, was affected by prenatal Leydig cell function.