Di-(2-ethylhexyl) phthalate metabolites in urine show age-related changes and associations with adiposity and parameters of insulin sensitivity in childhood

Status of phthalate esters pollution in facility agriculture across China: Spatial distribution, risk assessment, and remediation measures

The pervasive utilization of phthalate esters (PAEs) in plastic products has led to an emergent concern regarding the PAEs contamination in environmental matrices. However, the overall understanding of PAEs pollution in facility agriculture and its relevant risks remain limited. In this paper, the characteristics, health risks, and remediation measures of PAEs pollution in facility agriculture across China were analyzed. In general, PAEs pollution in facility agriculture soil in SWC and vegetables in SC were more serious than that in the other six regions (p < 0.05). The total level of six PAEs ranged from 0.053 to 5.663 mg·kg-1 in soil samples, nd (not detectable) to 12.540 mg·kg-1 in vegetable samples, with mean values of 0.951 mg·kg-1 and 2.458 mg·kg-1, respectively. DEHP and DnBP were dominant in both soil and vegetable samples with a total contribution of over 70 % of the six PAEs, but their concentrations were a little lower in soil samples. The PAEs concentrations of leafy, root, and fruit vegetables exhibited a descending trend. Correlation analysis revealed that the relationships between soil and vegetable PAEs concentrations remained inconclusive, lacking clear correlations. Furthermore, risk assessments indicated that the hazard quotient (HQ) for both total and individual PAEs in the vast majority of vegetable samples remained within acceptable thresholds. Meanwhile, all values for carcinogenic risks (CR) were confined within the range of 10-4. In conclusion, the study outlines remediation measures aimed at precluding and mitigating the environmental risks associated with PAEs exposure. These findings furnish a scientific foundation for the targeted assessment and judicious management of PAEs pollution within facility agriculture landscape of China.

Associations of early life phthalate exposures with adolescent lipid levels and insulin resistance: The HOME Study

BACKGROUND

Early-life phthalate exposures may disrupt metabolic processes; however few prospective studies have assessed whether these associations extend to cardiometabolic outcomes during adolescence.

METHODS

Among 183 mother-adolescent pairs in a prospective cohort study that enrolled pregnant women in Cincinnati, OH (2003-2006), we quantified nine phthalate metabolites in spot urine samples collected twice from mothers during pregnancy and up to seven times from children. At age 12 years, we assessed triglycerides, high-density (HDL) and low-density (LDL) lipoprotein cholesterol, insulin, and glucose from fasting serum samples and calculated homeostatic model assessment of insulin resistance (HOMA-IR). Using multiple informant models, we estimated covariate-adjusted associations between urinary phthalate concentrations at each time period and cardiometabolic biomarkers at age 12 years, including modification by child sex.

RESULTS

Although most associations were weak or null, monoethyl phthalate (MEP), mono-n-butyl phthalate (MnBP), mono-isobutyl phthalate (MiBP), and monobenzyl phthalate (MBzP) concentrations were generally associated with lower LDL at age 12 years. A 10-fold increase in 4- and 12-year MEP was associated with -15.3 mg/dL (95% CI: 27.5, -3.13 mg/dL) and -11.8 mg/dL (-22.0, -1.51 mg/dL) lower LDL, respectively. Discrepant associations were observed in females versus males: a 10-fold increase in 3-year MEP concentrations was associated with 12.0 mg/dL (95% CI: 7.11, 31.1 mg/dL) higher LDL levels in males and -30.4 mg/dL (95% CI: 50.9, -9.8 mg/dL) lower LDL levels in females. Some urinary phthalate concentrations were cross-sectionally associated with HOMA-IR.

CONCLUSIONS

Early-life phthalate biomarker concentrations may be inversely associated with LDL during early adolescence in an exposure-period and sex-dependent manner.

Gestational and Lactational Co-Exposure to DEHP and BPA Impairs Hepatic Function via PI3K/AKT/FOXO1 Pathway in Offspring

Di-(2-Ethylhexyl) phthalate (DEHP) and bisphenol A (BPA) present significant environmental endocrine-disrupting chemical properties. Although studies have implied reproductive impairment from exposure to BPA and DEHP, no study to date has shown the effect and mechanism of hepatic function after gestational and lactational co-exposure to DEHP and BPA in offspring. A total of 36 perinatal rats were randomly divided into four groups, DEHP (600 mg/kg/day), BPA (80 mg/kg/day), DEHP combined with BPA (600 mg/kg/day + 80 mg/kg/day), and control. Notably, 11 chemical targets were screened after identifying eight substances associated with chemically-induced hepatic damage. Molecular docking simulations revealed a high-scoring combination of eight metabolic components and targets of the PI3K/AKT/FOXO1 signaling pathway. The DEHP and BPA combination disrupted hepatic steatosis, ultimately affecting systemic the glucose and the lipid metabolic homeostasis with significant toxicity. Mechanistically, co-exposure to DEHP and BPA causes liver dysfunction and hepatic insulin resistance via PI3K/AKT/FOXO1 pathway in offspring. This is the first study of the hepatic function and mechanism of co-exposure to DEHP and BPA that combines metabolomics, molecular docking, and traditional toxicity assessment methods.

Prenatal exposure to phthalate and decreased body mass index of children: a systematic review and meta-analysis

Phthalates are well-known endocrine-disrupting chemicals. Many detrimental health effects of phthalates were investigated, but studies on the association of phthalates with obesity in children showed inconsistent results. Thus, this systematic review and meta-analysis were performed to clarify whether prenatal and postnatal exposures to phthalates are associated with physical growth disturbances in children. We performed the systematic review and meta-analysis following the PRISMA 2020 statement guidelines, and found 39 studies that met our inclusion criteria, including 22 longitudinal and 17 cross-sectional studies. We observed a significant negative association between the prenatal exposure to DEHP and the body mass index (BMI) z-score of the offspring (β = - 0.05; 95% CI: - 0.10, - 0.001) in the meta-analysis, while no significant association between the prenatal exposure to DEHP and the body fat percentage of the offspring was observed (β = 0.01; 95% CI: - 0.41, 0.44). In the systematic review, studies on the association between phthalates exposure in childhood and obesity were inconsistent. Prenatal exposure to phthalates was found to be associated with decreased BMI z-score in children, but not associated with body fat percentage. Our findings suggest that phthalates disturb the normal muscle growth of children, rather than induce obesity, as previous studies have hypothesized.

Effect of Di-(2-ethylhexyl) phthalate on the hypothalamus-pituitary-thyroid axis in adolescent rat

Di-(2-ethylhexyl) phthalate (DEHP) is extensively used in many personal care and consumer products, which results in widespread human exposure. Limited studies have suggested that exposure to DEHP may affect thyroid function, but little is known about the effect and mechanisms of DEHP exposure on the hypothalamic-pituitary-thyroid axis (HPTA). The present study was conducted to elucidate the potential mechanisms underlying DEHP disrupting the function of the HPTA. DEHP was administered to Wistar rats by gavage at 0, 5, 50, and 500 mg/kg/day for consecutive 28 days and then the rats were sacrificed within 24 h following the last dose. The hormone levels of HPTA were quantified with radioimmunoassay and enzyme-linked immunosorbent assay, the protein levels of thyrotropin-releasing hormone receptor (TRHR) and thyroid-stimulating hormone receptor (TSHR) were analyzed by Western blot and immunohistochemistry, and the expression levels of TRHR and TSHR mRNA were measured by quantitative real-time PCR. The low dose of DEHP increased the body weights of rats. Serum levels of T3, T4, FT3 and FT4 as well as protein and mRNA levels of TSHR decreased in rats treated with 50 mg/kg or 500 mg/kg DEHP compared with those of controls. Although the protein levels of TRH in the hypothalamus or protein and mRNA levels of TRHR in pituitary were up-regulated, serum levels of TSH did not change statistically in rats treated with DEHP. Therefore, DEHP can produce thyroid toxicity and may interfere with the secretion of pituitary TSH. In conclusion, DEHP could interfere with the balance of HPTA of adolescent rats, and disturb the homeostasis of thyroid related hormones and the expression levels of receptors.

The possible thyroid disruptive effect of di-(2-ethyl hexyl) phthalate and the potential protective role of selenium and curcumin nanoparticles: a toxicological and histological study

Di-(2-ethylhexyl) phthalate (DEHP) is one of the ubiquitous pollutants worldwide. This study aimed to clarify the potential thyroid disrupting effect of DEHP and explore the probable ameliorative effects of selenium nanoparticles (Se-NPs) and curcumin nanoparticles (CUR-NPs). Forty-two male albino rats were divided into seven groups (n = 6): Group I (negative control); group (II) orally received DEHP (500 mg/kg BW, dissolved in corn oil); Group (III) orally received Se-NPs (.2 mg/kg BW) in combination with DEHP; Group (IV) orally received CUR-NPs (15 mg/kg BW) alongside with DEHP; Group V (corn oil); Group VI (Se-NPs) and Group VII (CUR-NPs). The duration of the experiment was 30 days. DEHP administration significantly decreased serum free T4 and significantly increased serum free T3 as compared to control group, whereas thyroid-stimulating hormone showed no significant change. DEHP disrupted redox status leading to accumulation of malondialdehyde and depletion of reduced glutathione. Histologically, the effect of DEHP on thyroid follicles was confirmed by light and electron microscopic examination and morphometric analysis. Se-NPs slightly improved thyroid parameters as well as redox status. CUR-NPS reinstated the values of all studied thyroid parameters to nearly control levels. This research provides Se-NPs and CUR-NPs as novel protective agents against DEHP-thyroid disrupting effects.

Role of epidemiology in risk assessment: a case study of five ortho-phthalates

BACKGROUND

The association between environmental chemical exposures and chronic diseases is of increasing concern. Chemical risk assessment relies heavily on pre-market toxicity testing to identify safe levels of exposure, often known as reference doses (RfD), expected to be protective of human health. Although some RfDs have been reassessed in light of new hazard information, it is not a common practice. Continuous surveillance of animal and human data, both in terms of exposures and associated health outcomes, could provide valuable information to risk assessors and regulators. Using ortho-phthalates as case study, we asked whether RfDs deduced from male reproductive toxicity studies and set by traditional regulatory toxicology approaches sufficiently protect the population for other health outcomes.

METHODS

We searched for epidemiological studies on benzyl butyl phthalate (BBP), diisobutyl phthalate (DIBP), dibutyl phthalate (DBP), dicyclohexyl phthalate (DCHP), and bis(2-ethylhexyl) phthalate (DEHP). Data were extracted from studies where any of the five chemicals or their metabolites were measured and showed a statistically significant association with a health outcome; 38 studies met the criteria. We estimated intake for each phthalate from urinary metabolite concentration and compared estimated intake ranges associated with health endpoints to each phthalate's RfD.

RESULT

For DBP, DIBP, and BBP, the estimated intake ranges significantly associated with health endpoints were all below their individual RfDs. For DEHP, the intake range included associations at levels both below and above its RfD. For DCHP, no relevant studies could be identified. The significantly affected endpoints revealed by our analysis include metabolic, neurodevelopmental and behavioral disorders, obesity, and changes in hormone levels. Most of these conditions are not routinely evaluated in animal testing employed in regulatory toxicology.

CONCLUSION

We conclude that for DBP, DIBP, BBP, and DEHP current RfDs estimated based on male reproductive toxicity may not be sufficiently protective of other health effects. Thus, a new approach is needed where post-market exposures, epidemiological and clinical data are systematically reviewed to ensure adequate health protection.

A critical review on human internal exposure of phthalate metabolites and the associated health risks

Phthalates (PAEs) are popular synthetic chemicals used as plasticizers and solvents for various products, such as polyvinyl chloride or personal care products. Human exposure to PAEs is associated with various diseases, resulting in PAE biomonitoring in humans. Inhalation, dietary ingestion, and dermal absorption are the major human exposure routes. However, estimating the actual exposure dose of PAEs via an external route is difficult. As a result, estimation by internal exposure has become the popular analytical methods to determine the concentrations of phthalate metabolites (mPAEs) in human matrices (such as urine, serum, breast milk, hair, and nails). The various exposure sources and patterns result in different composition profiles of PAEs in biomatrices, which vary from country to country. Nevertheless, the mPAEs of diethyl phthalate (DEP), di-n-butyl phthalate (DnBP), di-iso-butyl phthalate (DiBP), and di-(2-ethylhexyl) phthalate (DEHP) are predominant in the urine. These mPAEs have greater potential health risks for humans. Children have been observed to exhibit higher exposure risks to several mPAEs than adults. Besides age, other influencing factors for phthalate exposure are gender, jobs, and residential areas. Although many studies have reported biological monitoring of PAEs, only a few reviews that adequately summarized the reports are available. The current review appraised available studies on mPAE quantitation in human biomatrices and estimated the dose and health risks of phthalate exposure. While some countries lack biomonitoring data, some countries' data do not reflect the current PAE exposure. Thence, future studies should involve frequent PAE biomonitoring to accurately estimate human exposure to PAEs, which will contribute to health risk assessments of human exposure to PAEs. Such would aid the formulation of corresponding regulations and restrictions by the government.

Urinary di(2-ethylhexyl)phthalate metabolite ratios in obese children of South Korea

Phthalate exposure has been reported to be more associated with obesity in children than in adults. The concentration of di(2-ethylhexyl)phthalate (DEHP) was high temporal variability in spot urine, so additional tools of assessing DEHP exposure were required. Therefore, we used relative metabolite ratios (RMRs) as well as concentrations, and RMRs did not need to be corrected to the creatinine concentration. We aimed to evaluate the levels of urinary DEHP metabolites and their RMRs in obese children in South Korea, and to investigate the potential of RMRs for assessing the risks for childhood obesity. We analyzed the four urinary DEHP metabolites (mono-2-ethylhexyl phthalate (MEHP), mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP), and mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP)) in 240 children aged 5-16 years, using isotope dilution GC-MS/MS. The children were placed into three groups ("normal weight," "overweight," and "obese") according to body mass index (BMI) percentiles. We statistically compared the concentrations and RMRs of DEHP metabolites among these groups. The obese group had lower MEHP levels, and higher secondary metabolite (MEHHP, MEOHP, and MECPP) levels, than the normal weight group. DEHP metabolite levels did not differ significantly between the normal weight and obese groups, whereas RMR_A2 (as the ratio of the molar concentrations of MEOHP to MEHHP) was found to be negatively associated with BMI percentile (β= -0.236, p <0.01) and weight percentile (β= -0.282, p<0.001). Therefore, we suggest that RMRs are an additional tool for assessing the health risks of DEHP.

Intrauterine exposure to low-dose DBP in the mice induces obesity in offspring via suppression of UCP1 mediated ER stress

Dibutyl phthalate (DBP) is recognized as an environmental endocrine disruptor that has been detected in fetal and postnatal samples. Recent evidence found that in utero DBP exposure was associated with an increase of adipose tissue weight and serum lipids in offspring, but the precise mechanism is unknown. Here we aimed to study the effects of in utero DBP exposure on obesity in offspring and examine possible mechanisms. SPF C57BL/6J pregnant mice were gavaged with either DBP (5 mg /kg/day) or corn oil, from gestational day 12 until postnatal day 7. After the offspring were weaned, the mice were fed a standard diet for 21 weeks, and in the last 2 weeks 20 mice were selected for TUDCA treatment. Intrauterine exposure to low-dose DBP promoted obesity in offspring, with evidence of glucose and lipid metabolic disorders and a decreased metabolic rate. Compared to controls, the DBP exposed mice had lower expression of UCP1 and significantly higher expression of Bip and Chop, known markers of endoplasmic reticulum (ER) stress. However, TUDCA treatment of DBP exposed mice returned these parameters nearly to the levels of the controls, with increased expression of UCP1, lower expression of Bip and Chop and ameliorated obesity. Intrauterine exposure of mice to low-dose DBP appears to promote obesity in offspring by inhibiting UCP1 via ER stress, a process that was largely reversed by treatment with TUDCA.

Artificial neural networks allow response prediction in squamous cell carcinoma of the scalp treated with radiotherapy

BACKGROUND

Epithelial neoplasms of the scalp account for approximately 2% of all skin cancers and for about 10-20% of the tumours affecting the head and neck area. Radiotherapy is suggested for localized cutaneous squamous cell carcinomas (cSCC) without lymph node involvement, multiple or extensive lesions, for patients refusing surgery, for patients with a poor general medical status, as adjuvant for incompletely excised lesions and/or as a palliative treatment. To date, prognostic risk factors in scalp cSCC patients are poorly characterized.

OBJECTIVE

To identify patterns of patients with higher risk of postradiotherapy recurrence.

METHODS

A retrospective observational study was performed on scalp cSCC patients with histological diagnosis who underwent conventional radiotherapy (50-120 kV) (between 1996 and 2008, follow-up from 1 to 140 months, median 14 months). Out of the 79 enrolled patients, 22 (27.8%) had previously undergone a surgery. Two months after radiotherapy, 66 (83.5%) patients achieved a complete remission, 6 (7.6%) a partial remission, whereas 2 (2.5%) proved non-responsive to the treatment and 5 cases were lost to follow-up. Demographical and clinical data were preliminarily analysed with classical descriptive statistics and with principal component analysis. All data were then re-evaluated with a machine learning-based approach using a 4th generation artificial neural networks (ANNs)-based algorithm.

RESULTS

Artificial neural networks analysis revealed four scalp cSCC profiles among radiotherapy responsive patients, not previously described: namely, (i) stage T2 cSCC type, aged 70-80 years; (ii) frontal cSCC type, aged <70 years; (iii) non-recurrent nodular or nodulo-ulcerated, stage T3 cSCC type, of the vertex and treated with >60 Grays (Gy); and (iv) flat, occipital, stage T1 cSCC type, treated with 50-59 Gy. The model uncovering these four predictive profiles displayed 85.7% sensitivity, 97.6% specificity and 91.7% overall accuracy.

CONCLUSIONS

Patient profiling/phenotyping with machine learning may be a new, helpful method to stratify patients with scalp cSCCs who may benefit from a RT-treatment.

Association of phthalate exposure with precocious and delayed pubertal timing in girls and boys: a systematic review and meta-analysis

Exposure to phthalate derivatives has adverse effects on the health and development of humans, especially for children. A growing body of evidence supports the idea that exposure to phthalates can change an individual's physiological set point and the time of puberty in both genders. In this systematic review and meta-analysis, recent studies were evaluated to obtain systematic and regulation results in relation to puberty status and phthalate exposure in girls and boys. We searched English-language papers using Scopus, ISI, and PubMed databases as search engines, with no restriction of time, until the end of July 2019. A comprehensive literature search for an association between phthalate exposure and signs of puberty as well as levels of different types of hormones was carefully performed. Of the 67 studies retained for full-text screening, 39 studies were eligible for data management and extraction. For conducting a meta-analysis, four studies had appropriate effect size and metrics for pooling in the meta-analysis. Our findings revealed that low and high exposure to phthalates could alter pubertal development in both genders; the effects were either early or delayed puberty such as changes in the pubarche, thelarche, and menarche time, as well as in testicular volume. We statistically analyzed the association of pubic-hair development, breast development, and menarche time with exposure to phthalates in girls. For example, the pooled odds ratios of mono (2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) and mono (2-ethyl-5-oxohexyl) phthalate (MEOHP) in relation to breast development were (OR: 1.48, 95% CI: 1.11-1.85) and (OR: 1.52, 95% CI: 1.15-1.58) (P-value < 0.001), respectively. In addition, we analyzed the correlation between pubic-hair development and testicular volume with exposure to phthalates in boys. To the best of our knowledge, this is the first systematic review and meta-analysis of its kind for girls and boys. In conclusion, we found that a positive association exists between phthalate exposure and pubertal timing in the pediatric age group. Therefore, prevention of exposure to phthalates and reduction of their use should be underscored in the strategies for primordial prevention of pubertal timing and related consequences.

The endocrine disruptor DEHP and the ECS: analysis of a possible crosstalk

Studies of the last decade associated the environmental contamination by di-(2-ethylhexyl)-phthalate (DEHP) with obesity and endocrine malfunction. DEHP was found to interact with several receptors - among them are receptors of the endocannabinoid system (ECS) with high expression levels in adipose tissue. Furthermore, the correlation for BMI and body fat to the serum endocannabinoid level raises the question if the obesogenic and endocrine-disrupting DEHP effects are mediated via the ECS. We therefore characterized the ECS in a human cell model of adipogenesis using the SGBS preadipocytes to subsequently investigate if DEHP exposure affects the intrinsic ECS. The receptors of the ECS and the endocannabinoid-metabolizing enzymes were upregulated during normal adipogenesis, accompanied by an increasing secretion of the adipokines adiponectin and leptin. DEHP affected the secretion of both adipokines but not the ECS, suggesting DEHP to alter the endocrine function of adipocytes without the involvement of the intrinsic ECS.

Association between the exposure to phthalates and adiposity: A meta-analysis in children and adults

BACKGROUND

Exposure to environmental chemicals has become one of the major concerns in the past decades. Phthalates are a family of synthetic organic chemicals used in the manufacture of plastics, solvents, and personal care products. These compounds are considered as endocrine-disrupting compounds (EDCs) since they may interfere with the endocrine system and disrupt its physiologic function.

AIM

The purpose of this work is to synthesize results from published literature on the association between the exposure to phthalates and adiposity in adults and children.

METHODS

We searched PubMed from inception up to 01 August 2019, to retrieve original papers reporting data on the association between EDCs and adiposity, using the following search expression: (("Endocrine disruptor" OR Endocrine disruptor[mh] OR phthalate) AND (Obesity OR Overweight OR BMI OR "Body fat" OR Adipose tissue[mh] OR Body size[mh] OR "body size" OR "body weight" OR Anthropometry OR "anthropometric measures")) AND (humans[mh]). The study variables and characteristics were collected during data extraction, namely the study design, sample, exposure, outcome, descriptive and association measures. Study quality was assessed using the STROBE template for observational studies. Although studies examined several adiposity measures, Body Mass Index (BMI) and Waist Circumference (WC) were the most commonly used, therefore, we used the beta coefficients regarding BMI and WC, and odds ratios when BMI outcome was categorical to perform the meta-analysis. Data from the studies were combined using fixed effects meta-analyses to compute summary regression coefficients or odds ratios and corresponding 95% confidence intervals (95% CI). Heterogeneity between studies was assessed by the I2 statistic.

RESULTS

In the systematic review we found 29 publications addressing the association between phthalate compounds and adiposity. The vast majority of the included studies reported associations that were not statistically significant. For most of the phthalate compounds there were few studies providing compatible measures and therefore it was not possible to combine the results in a meta-analysis. Both for BMI and WC, the meta-analysis for MiBP, MCPP and MbzP showed negative associations and null association for MBP in children, although none of them was significant. For MEP, positive but not significant associations were found both in children and adults. Conversely, for MEHP a negative association was found also in children and adults although it did not reach statistical significance. Only for MECPP a significant association was found for obesity in adults (OR = 1.67 (95% CI 1.30; 2.16).

CONCLUSION

In general, a positive association between phthalates and adiposity measures was found, especially in adults. However, most of the results did not reach statistical significance and the inconsistencies found between studies did not allow to reach a definitive conclusion. Additionally, we cannot exclude a possible effect of publication bias.

Association of exposure to phthalates with cardiometabolic risk factors in children and adolescents: a systematic review and meta-analysis

Recent studies revealed controversial results on the association of exposure to phthalates with cardiometabolic risk factors in children and adolescents. Therefore, this systematic review and meta-analysis was conducted in this regard. At first, we searched English-language papers in Scopus, Web of Science, and PubMed databases, with no restriction of time, till the end of the year 2018. We performed a comprehensive literature search for association between phthalate exposure and cardiometabolic risk factors including obesity, hypertension, hyperglycemia, and dyslipidemia. Among 99 published papers found in scientific databases, 17 cohort, 15 cross-sectional, and three case-control studies were included in the meta-analysis. We observed a significant association between the concentrations of phthalates and their metabolites with body mass index (BMI), BMI z-score, waist circumference (WC), and low-density lipoprotein cholesterol (LDL-C), triglyceride (TG), and glucose in serum. In addition, significant association was observed between prenatal phthalate exposure and birth weight. To the best of our knowledge, this is the first meta-analysis of its kind. It shows positive association between phthalate exposure and some cardiometabolic risk factors in children and adolescents. Therefore, prevention of exposure to phthalates and reduction of their use should be underscored in strategies for primordial prevention of cardiovascular diseases. Recent studies revealed controversial results on the association of exposure to phthalates with cardiometabolic risk factors in children and adolescents. Therefore, this systematic review and meta-analysis was conducted in this regard.

Serum beta-carotene modifies the association between phthalate mixtures and insulin resistance: The National Health and Nutrition Examination Survey 2003-2006

Animal models suggest a protective role of antioxidants against the adverse effect of di-2-ethylhexyl phthalate (DEHP) on insulin resistance. However, no epidemiologic study has examined the effects observed in the animal model. We conduct a study to examine associations of urinary concentrations of phthalate metabolites (individually and as a mixture) with insulin resistance, along with potential effect modification by serum antioxidant concentrations. This cross-sectional study included 1605 participants (51% males) aged 12-85 from the National Health and Nutrition Examination Surveys (2003-2006). Urinary concentrations of 9 phthalate metabolites were measured from spot urine samples. Antioxidant (vitamin A, C, E, and carotenoids) concentrations were measured from a fasting serum sample. We used Bayesian Kernel Machine Regression (BKMR) to evaluate associations between phthalate metabolite mixtures and insulin resistance, and examined whether serum antioxidant levels modified these associations, while accounting for the correlations of multiple concurrent exposures. A change in urinary ΣDEHP concentrations from the 25th to the 75th percentile was associated with a higher log HOMA-IR of 0.07 (95% CI = 0.01, 0.14) (4.85% increase in HOMA-IR). In contrast, the same change in urinary monoethyl phthalate (MEP) was associated with a lower HOMA-IR of -0.07 (95% CI = -0.14, -0.02) (6.68% decrease in HOMA-IR). The positive association between ΣDEHP and HOMA-IR became weaker at higher concentrations of serum β-carotene. The relationship between MEP and HOMA-IR, however, was not modified by the serum antioxidants examined. The remaining phthalate metabolites were unrelated to HOMA-IR. In this cross-sectional study, the positive association between DEHP exposure and insulin resistance weakened among participants with higher concentrations of serum β-carotene. As this is the first human report on the protective role of serum β-carotene on DEHP induced insulin resistance, future studies are needed.

Phthalate exposure and metabolic effects: a systematic review of the human epidemiological evidence

OBJECTIVE

We performed a systematic review of the epidemiology literature to identify the metabolic effects associated with phthalate exposure.

DATA SOURCES AND STUDY ELIGIBILITY CRITERIA

Six phthalates were included in the review: di(2‑ethylhexyl) phthalate (DEHP), diisononyl phthalate (DINP), dibutyl phthalate (DBP), diisobutyl phthalate (DIBP), butyl benzyl phthalate (BBP), and diethyl phthalate (DEP). The initial literature search (of PubMed, Web of Science, and Toxline) included all studies of metabolic effects in humans, and outcomes were selected for full systematic review based on data availability.

STUDY EVALUATION AND SYNTHESIS METHODS

Studies of diabetes and insulin resistance were evaluated using criteria defined a priori for risk of bias and sensitivity by two reviewers using a domain-based approach; studies identified with a pre-defined critical deficiency were excluded. Evidence was synthesized by outcome and phthalate and strength of evidence was summarized using a structured framework. Studies of obesity and renal effects received "screening level" reviews to determine whether full systematic review was warranted.

RESULTS

The primary outcomes reviewed here are (number of included/excluded studies in parentheses): type 2 diabetes (1/3), insulin resistance (13/3), and impaired glucose tolerance and blood glucose in pregnancy (4/2). For DEHP exposure, there was consistency among studies of insulin resistance and coherence with the single included study of diabetes, as well as an observed exposure-response gradient observed in a study of insulin resistance. This evidence is considered moderate. Similarly, for DBP and DIBP exposure, the evidence is considered moderate due to strong positive associations in the diabetes study and coherent results for insulin resistance. For DINP, BBP, and DEP, the evidence is considered slight. No association was reported in the single study of diabetes with BBP and DEP exposure (DINP was not investigated). The available evidence does indicate an association between exposure to these phthalates and insulin resistance, but the small number of studies and the lack of coherence with diabetes decreases confidence. The screening level reviews for obesity and renal effects determined that the currently available evidence is inadequate to assess the associations between these outcomes and phthalate exposure.

CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS

Overall, these results support that phthalate exposure at levels seen in human populations may have metabolic effects. Given the mechanistic support, the large effect sizes for incident diabetes in the single available study, and the coherence with insulin resistance, the association between phthalate exposure and diabetes risk should be considered when assessing the risks and costs of exposure to specific phthalates in humans. The views expressed are those of the authors and do not necessarily represent the views or policies of the U.S. EPA.

Phthalate exposure and female reproductive and developmental outcomes: a systematic review of the human epidemiological evidence

OBJECTIVE

We performed a systematic review of the epidemiology literature to identify the female reproductive and developmental effects associated with phthalate exposure.

DATA SOURCES AND STUDY ELIGIBILITY CRITERIA

Six phthalates were included in the review: di(2-ethylhexyl) phthalate (DEHP), diisononyl phthalate (DINP), dibutyl phthalate (DBP), diisobutyl phthalate (DIBP), butyl benzyl phthalate (BBP), and diethyl phthalate (DEP). The initial literature search (of PubMed, Web of Science, and Toxline) included all studies of female reproductive and developmental effects in humans, and outcomes were selected for full systematic review based on data availability.

STUDY EVALUATION AND SYNTHESIS METHODS

For each outcome, studies were evaluated using criteria defined a priori for risk of bias and sensitivity by two reviewers using a domain-based approach. Evidence was synthesized by outcome and phthalate and strength of evidence was summarized using a structured framework.

RESULTS

The primary outcomes reviewed here are (number of included/excluded studies in parentheses): pubertal development (5/13), time to pregnancy (3/4), preterm birth (8/12), and spontaneous abortion (5/0). Among these outcomes, preterm birth had moderate evidence of a positive association with phthalate exposure (specifically DEHP, DBP, and DEP). Exposure levels for BBP, DIBP, and DINP were generally lower than for the phthalates with an observed effect, which may partially explain the difference due to lower sensitivity. Other phthalate/outcome combinations were considered to have slight or indeterminate evidence of an association.

CONCLUSIONS AND IMPLICATIONS OF KEY FINDINGS

Overall, these results support that some phthalates may be associated with higher odds of preterm birth in humans, though there is some remaining inconsistency. More evidence is needed on the mechanism and relevant exposure window for this association. The views expressed are those of the authors and do not necessarily represent the views or policies of the U.S. EPA.

Systematic review and meta-analysis on the association between phthalates exposure and insulin resistance

This study aims to provide an overview of human studies on the association of exposure to phthalates and insulin resistance. We systematically searched human studies available until 15 January 2018.We conducted a literature search in Scopus, ISI Web of Science, PubMed, Google Scholar, and Cochrane Collaboration. We used the following keywords to identify relevant articles: "phthalate", "phthalate ester", "metabolic syndrome", "insulin resistance", "glucose intolerance", and "diabetes". For analyzing data, we conducted meta-analysis using the Stata software. We appraised each study to examine the sources of heterogeneity, including difference in clinical outcomes and exposure measurements. To determine the robustness and whether some of the factors have the highest impact on the results of the present meta-analysis, several sensitivity analyses were conducted. Sensitivity analysis showed that by removing studies with the highest weight and age groups, no change was observed in heterogeneity. Moreover, with excluding the study conducted in Europe, the results remained unchanged and constant. In addition, the funnel plot and Egger's tests were executed to access publication bias. Both the funnel plots and Egger's test did not show any evidence of publication bias (P = 0.31). In the random effects meta-analysis of all studies (n = 8), the pooled correlation coefficient between phthalate exposure and HOMA-IR was 0.10 (95% CI; 0.07-0.12, P < 0.001), with significant heterogeneity (P < 0.001, I² = 85.5%). Our findings revealed positive association between exposure to phthalate metabolites and increased HOMA-IR; this association remained significant even after adjusting the analysis for multiple confounding variables.

Urinary phthalate metabolites among children in Saudi Arabia: Occurrences, risks, and their association with oxidative stress markers

Phthalates have been used as plasticizers in numerous consumer applications and therefore, their metabolites have been detected in human urine worldwide. Despite concerns regarding their potential adverse health effects, few exposure assessments have been conducted among young populations in Middle Eastern countries. In this study, children (n = 109, aged 3-9 years) were recruited from four elementary schools in Riyadh, Saudi Arabia, in 2017, and major phthalate metabolites were measured in their urine. Their parents were asked to complete a questionnaire on their behalf to assess potential exposure sources of phthalates. In addition to 18 phthalate metabolites, malondialdehyde (MDA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) were measured in urine samples by LC/MS/MS. Among the children of Saudi Arabia, urinary levels of monoisobutyl phthalate (MiBP) and monobutyl phthalate (MnBP) were higher than those reported previously in children worldwide. Monoethyl phthalate (MEP) was also detected at high levels. Several phthalate metabolites showed significant associations with the levels of MDA or 8-OHdG. Hazard quotients (HQs) derived for certain phthalates were greater than one. In particular, the HQs for di(2-ethylhexyl) phthalate (DEHP) were greater than one in 34% of the participating children. Levels of monocyclohexyl phthalate (MCHP), monoisodecyl phthalate (MiDP), mono(2-ethylhexyl) phthalate (MEHP), and mono[2-(carboxymethyl)hexyl] phthalate (MCMHP) in the urine samples were positively associated with the consumption frequency of certain foods. Very high levels of exposure to phthalates, along with positive associations with oxidative stress markers, outline the importance of follow-up investigations for identification of phthalate exposure sources and potential health implications among the young population of Saudi Arabia.

Early-life exposure to endocrine disrupting chemicals associates with childhood obesity

Increasing prevalence of childhood obesity poses threats to the global health burden. Because this rising prevalence cannot be fully explained by traditional risk factors such as unhealthy diet and physical inactivity, early-life exposure to endocrine disrupting chemicals (EDCs) is recognized as emerging novel risk factors for childhood obesity. EDCs can disrupt the hormone-mediated metabolic pathways, affect children's growth and mediate the development of childhood obesity. Many organic pollutants are recently classified to be EDCs. In this review, we summarized the epidemiological and laboratory evidence related to EDCs and childhood obesity, and discussed the possible mechanisms underpinning childhood obesity and early-life exposure to non-persistent organic pollutants (phthalates, bisphenol A, triclosan) and persistent organic pollutants (dichlorodiphenyltrichloroethane, polychlorinated biphenyls, polybrominated diphenyl ethers, per- and polyfluoroalkyl substances). Understanding the relationship between EDCs and childhood obesity helps to raise public awareness and formulate public health policy to protect the youth from exposure to the harmful effects of EDCs.

Percentage fractions of urinary di(2-ethylhexyl) phthalate metabolites: Association with obesity and insulin resistance in Korean girls

OBJECTIVE

We assessed the associations of percentage fractions of urinary di(2-ethylhexyl) phthalate (DEHP) metabolites with obesity and insulin resistance in Korean girls.

METHODS

In total, 137 girls, aged 6 to 13 years (65 overweight cases and 72 controls), were recruited. Anthropometric indices and the homeostatic model assessment of insulin resistance (HOMA-IR) index were determined. Four major urinary DEHP metabolites were analyzed in spot urine samples by gas chromatography-tandem mass spectrometry, including mono(2-ethylhexyl) phthalate, mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono(2-ethyl-5-oxohexyl) phthalate (MEOHP), and mono(2-ethyl-5-carboxypentyl) phthalate.

RESULTS

There were no significant differences in the urinary concentrations of the DEHP metabolites between the overweight and control groups. The percentage fraction of MEHHP (MEHHP%) among all DEHP metabolites was significantly higher in the overweight prepubertal girls than in the controls (P = 0.035). MEHHP% was positively associated with the body mass index percentile, waist circumference, body fat percentage, and HOMA-IR index in the prepubertal girls. After adjusting for covariates, the prepubertal girls in a higher MEHHP% quartile were found to have a higher odds ratio for central obesity than those in a lower quartile (odds ratios: 5.05 for quartile 3; 7.30 for quartile 4). The relative rate of MEHHP oxidation to MEOHP was negatively associated with the body mass index percentile and waist circumference in the prepubertal girls. However, no such association was observed in the pubertal girls.

CONCLUSIONS

MEHHP% was positively associated with obesity and insulin resistance in prepubertal girls. Further studies are necessary to elucidate the causal links between altered phthalate metabolism and increased susceptibility to insulin resistance in children.

Temporal Trends of Urinary Phthalate Concentrations in Two Populations: Effects of REACH Authorization after Five Years

Phthalates are widely used in the industrial manufacture of many products. Some phthalates have shown reproductive toxicity in humans, acting as endocrine disruptors, so they were included in the authorization process defined in Reg. CE 1907/2006 (REACH). Two groups of population were recruited, before and after the inclusion of some phthalates in the authorization list in REACH: the first group of 157 volunteers was studied in 2011 and the second, 171 volunteers, in 2016. Each subject completed a questionnaire about personal lifestyle, working activities and use of chemical products. The main urinary metabolites of five phthalates were analyzed by HPLC/MS/MS: mono(2-ethylhexyl)phthalate (MEHP) and mono(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) for di(2-ethylhexyl)phthalate (DEHP) exposure; monoethylphthalate (MEP) for diethylphtahate (DEP); monobenzylphthalate (MBzP) for butylbenzylphtahalate (BBP) and dibenzylphthalate (DBzP), mono-n-butylphthalate (MnBP) for butylbenzylphtahalate (BBP) and di-n-butylphthalate (DnBP). The results show a significant difference for all metabolites between the two periods, with the exception of MEP in women. The comparison of the two sets of results shows a decrease in urinary metabolites excretion from 2011 to 2016, statistically significant for the three phthalates included in Annex XIV of REACH. DEP, not currently included in the list for authorization, maintains a constant presence in the daily life of the population, particularly for women.

Perinatal Exposure to an Environmentally Relevant Mixture of Phthalates Results in a Lower Number of Neurons and Synapses in the Medial Prefrontal Cortex and Decreased Cognitive Flexibility in Adult Male and Female Rats

The growth and organization of the developing brain are known to be influenced by hormones, but little is known about whether disruption of hormones affects cortical regions, such as mPFC. This region is particularly important given its involvement in executive functions and implication in the pathology of many neuropsychiatric disorders. Here, we examine the long-term effects of perinatal exposure to endocrine-disrupting compounds, the phthalates, on the mPFC and associated behavior. This investigation is pertinent as humans are ubiquitously exposed to phthalates through a variety of consumer products and phthalates can readily cross the placenta and be delivered to offspring via lactation. Pregnant dams orally consumed an environmentally relevant mixture of phthalates at 0, 200, or 1000 μg/kg/d through pregnancy and for 10 d while lactating. As adults, offspring were tested in an attentional set-shifting task, which assesses cognitive flexibility. Brains were also examined in adulthood for stereological quantification of the number of neurons, glia, and synapses within the mPFC. We found that, independent of sex, perinatal phthalate exposure at either dose resulted in a reduction in neuron number, synapse number, and size of the mPFC and a deficit in cognitive flexibility. Interestingly, the number of synapses was correlated with cognitive flexibility, such that rats with fewer synapses were less cognitively flexible than those with more synapses. These results demonstrate that perinatal phthalate exposure can have long-term effects on the cortex and behavior of both male and female rats.SIGNIFICANCE STATEMENT Humans globally are exposed on a daily basis to a variety of phthalates, which are endocrine-disrupting chemicals. The effects of phthalate exposure on the developing brain, especially on cognitively relevant regions, such as the mPFC, are not known. Here, we use a rat model of human prenatal exposure to an environmentally relevant mixture of phthalates and find that there is an appreciable reduction in neuron number, synapse number, and size of the mPFC and a deficit in cognitive flexibility. These results may have serious implications for humans given that the mPFC is involved in executive functions and is implicated in the pathology of many neuropsychiatric disorders.

Prenatal and Childhood Exposure to Phthalate Diesters and Thyroid Function in a 9-Year Follow-up Birth Cohort Study: Taiwan Maternal and Infant Cohort Study

BACKGROUND

Phthalates are widely used in industry, personal care products, and medications. Recent studies have suggested that phthalate exposure alters thyroid hormones. However, longitudinal studies concerning the association between phthalate exposure and thyroid function in children are scant. Therefore, we examined the association between pre- and postnatal phthalate exposure and thyroid function in children born in 2000-2001.

METHODS

We studied 181 mother-child pairs in central Taiwan and followed-up the children from 2000 to 2009 at 2, 5, and 8 years old. We measured serum levels of thyroxine (T4), free T4, triiodothyronine (T3), and thyroid-stimulating hormone in children by using radioimmunoassay. We quantified seven phthalate metabolites, representing the five most commonly used phthalates, in maternal and child urine samples by using liquid chromatography-tandem mass spectrometry. The metabolites were monoethylhexyl phthalate (MEHP), mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP) derived from di(2-ethylhexyl) phthalate (DEHP), monomethyl phthalate (MMP), monoethyl phthalate (MEP), monobutyl phthalate (MBP), and monobenzyl phthalate (MBzP). We constructed a linear mixed model to examine these associations after adjustments for covariates.

RESULTS

The T4 levels were inversely associated with maternal urinary MEHHP (β = -0.028 [95% confidence interval (CI) = -0.051, -0.006]) and MEOHP (β = -0.027 [-0.050, -0.003]), with similar T3 levels being observed in boys, even when the children exposure levels were considered spontaneously. In the girls, the free T4 levels were inversely associated with levels of maternal urinary MEP (β = -0.042), maternal urinary MBzP (β = -0.050), and children's urinary MEHP (β = -0.027).

CONCLUSIONS

Early life phthalate exposure was associated with decreased thyroid hormone levels in young children.

Current Knowledge on Endocrine Disrupting Chemicals (EDCs) from Animal Biology to Humans, from Pregnancy to Adulthood: Highlights from a National Italian Meeting

Wildlife has often presented and suggested the effects of endocrine disrupting chemicals (EDCs). Animal studies have given us an important opportunity to understand the mechanisms of action of many chemicals on the endocrine system and on neurodevelopment and behaviour, and to evaluate the effects of doses, time and duration of exposure. Although results are sometimes conflicting because of confounding factors, epidemiological studies in humans suggest effects of EDCs on prenatal growth, thyroid function, glucose metabolism and obesity, puberty, fertility, and on carcinogenesis mainly through epigenetic mechanisms. This manuscript reviews the reports of a multidisciplinary national meeting on this topic.

Urinary phthalate metabolite concentrations in girls with premature thelarche

In girls, breast development before eight years of age is called "premature thelarche (PT)". There are few studies in literature that show the interaction between PT and phthalate exposure. The aim of this study was to determine the urinary levels of di-(2-ethylhexyl) phthalate (DEHP) metabolites and other phthalate metabolites in girls with PT. PT group consisted of 29 newly diagnosed subjects. Control group comprised of healthy age-matched girls (n = 25). Urinary phthalate metabolite concentrations were measured by liquid chromatography/tandem mass spectroscopy (LC-MS/MS). The urinary concentrations of mono-(2-ethyl-hexyl)phthalate (MEHP) in the PT group (33.96 ± 6.88 μg/g creatinine) were found to be significantly higher compared to control group (11.54 ± 1.39 μg/g creatinine, p = 0.002). In PT group, %MEHP was also markedly higher vs. control (17.84 ± 3.31 vs. 6.44 ± 1.13, p = 0.001). Our results suggest that DEHP is more efficiently converted to MEHP in girls with PT, the importance of which needs to be further elucidated.

Correction and Republication: Effect of Di-(2-ethylhexyl) phthalate on the hypothalamus-pituitary-thyroid axis in adolescent rat

Di-(2-ethylhexyl) phthalate (DEHP) is extensively used in many personal care and consumer products, which has resulted in widespread human exposure. Limited studies have suggested that exposure to DEHP may affect thyroid function, but little is known about the effect and mechanisms of DEHP exposure on the hypothalamic-pituitary-thyroid axis (HPTA). The present study was conducted to elucidate the potential mechanisms in which DEHP disrupts the function of the HPTA. Wistar rats were administered DEHP by gavage at 0, 5, 50, and 500 mg/kg/day for 28 days and then sacrificed within 24 h following the last dose. Hormones of HPTA was quantified with radioimmunoassay and enzyme-linked immunosorbent assay, protein levels of thyrotropin-releasing hormone receptor (TRHR) and thyroid-stimulating hormone receptor (TSHR) were analyzed by Western blot and immunohistochemistry, expression levels of TRHR and TSHR mRNA were measured by quantitative real-time PCR. Rats treated with DEHP resulted in increased bodyweight, on the HPTA, down-regulated the protein levels of TRH in the hypothalamus, up-regulated the protein and mRNA levels of TRHR in the pituitary, down-regulated mRNA expression of TSHR in the thyroid, while the difference of TSH in various dose groups was not statistically significant and T3, T4, FT3, FT4 levels in serum were decreased compared with control. DEHP could interfere with the balance of HPTA of adolescent rats, and increase the body weight, down-regulate the homeostasis of thyroid related hormones and receptors expression levels.

Effects of Perinatal Exposure to Phthalates and a High-Fat Diet on Maternal Behavior and Pup Development and Social Play

Humans are ubiquitously exposed to many phthalates, a class of endocrine-disrupting chemicals commonly used in many consumer goods, and diet, especially fatty food, is presumed to be a major source of exposure. Here, we use a rat model of human prenatal exposure to investigate the potential interactive effects of an environmentally relevant mixture of phthalates and a maternal high-fat diet (HFD). From gestation through postnatal day (P)10, dams consumed the mixture of phthalates (0, 200, or 1000 μg/kg/d) and were fed a control diet or HFD. In males, perinatal exposure to the mixture of phthalates decreased prepubertal body weight and, in a dose-specific manner, periadolescent social play behavior. A dose-specific effect from phthalates with HFD was also seen in increased time alone in females during social play. HFD resulted in dams consuming more calories, having greater gestational weight gain, and licking and nursing their pups more, such that an early postnatal HFD generally increased pup body weight. There also was a tendency for increased oxidative stress markers at P10 within the medial prefrontal cortex of males exposed to the relatively high dose of phthalates and HFD. Effects on gene expression were inconsistent at P10 and P90 in both the medial prefrontal cortex and hypothalamus. Overall, this study demonstrates that phthalates and a maternal HFD only rarely interacted, except in oxidative stress markers in males. Additionally, perinatal exposure to an environmentally relevant mixture of phthalates can have a modest, but lasting, impact on social behaviors in both males and females.

Risks and benefits related to alimentary exposure to xenoestrogens

Xenoestrogens are widely diffused in the environment and in food, thus a large portion of human population worldwide is exposed to them. Among alimentary xenoestrogens, phytoestrogens (PhyEs) are increasingly being consumed because of their potential health benefits, although there are also important risks associated to their ingestion. Furthermore, other xenoestrogens that may be present in food are represented by other chemicals possessing estrogenic activities, that are commonly defined as endocrine disrupting chemicals (EDCs). EDCs pose a serious health concern since they may cause a wide range of health problems, starting from pre-birth till adult lifelong exposure. We herein provide an overview of the main classes of xenoestrogens, which are classified on the basis of their origin, their structures and their occurrence in the food chain. Furthermore, their either beneficial or toxic effects on human health are discussed in this review.

Immune System: An Emerging Player in Mediating Effects of Endocrine Disruptors on Metabolic Health

The incidence of metabolic disorders like type 2 diabetes and obesity continues to increase. In addition to the well-known contributors to these disorders, such as food intake and sedentary lifestyle, recent research in the exposure science discipline provides evidence that exposure to endocrine-disrupting chemicals like bisphenol A and phthalates via multiple routes (e.g., food, drink, skin contact) also contribute to the increased risk of metabolic disorders. Endocrine-disrupting chemicals (EDCs) can disrupt any aspect of hormone action. It is becoming increasingly clear that EDCs not only affect endocrine function but also adversely affect immune system function. In this review, we focus on human, animal, and in vitro studies that demonstrate EDC exposure induces dysfunction of the immune system, which, in turn, has detrimental effects on metabolic health. These findings highlight how the immune system is emerging as a novel player by which EDCs may mediate their effects on metabolic health. We also discuss studies highlighting mechanisms by which EDCs affect the immune system. Finally, we consider that a better understanding of the immunomodulatory roles of EDCs will provide clues to enhance metabolic function and contribute toward the long-term goal of reducing the burden of environmentally induced diabetes and obesity.

Early-Life Phthalate Exposure and Adiposity at 8 Years of Age

BACKGROUND

Early-life phthalate exposure may influence child adiposity, but prior studies have not determined if there are periods of enhanced vulnerability to phthalates.

OBJECTIVE

To examine the relationship between child adiposity at 8 y of age and repeated urinary biomarkers of phthalate exposure from gestation through childhood to determine if there are distinct periods of vulnerability.

METHODS

In 219 mother-child pairs from Cincinnati, Ohio, we quantified nine urinary phthalate metabolites up to two times prenatally and six times from 1-8 y of age. We measured child body mass index (BMI), waist circumference, and percent body fat at 8 y of age. To identify periods of vulnerability, we used two statistical methods to estimate phthalate-adiposity associations at each visit, test differences in phthalate-adiposity associations across visits, and model trajectories of phthalate concentrations for children at different levels of adiposity.

RESULTS

Prenatal phthalate concentrations were not associated with excess child adiposity. Monobenzyl phthalate (MBzP) concentrations during pregnancy and childhood were inversely associated with adiposity. The associations of di(2-ethylhexyl) phthalate (∑DEHP) metabolites and monoethyl phthalate (MEP) with child adiposity depended on the timing of exposure. A 10-fold increase in ∑DEHP at 1 and 5 y was associated with a 2.7% decrease [95% confidence interval (CI): -4.8, -0.5] and 2.9% increase (95% CI: 0.3, 5.5) in body fat, respectively. MEP concentrations at 5 and 8 y of age were associated with higher child adiposity, but earlier childhood concentrations were not.

CONCLUSION

In this cohort, we did not find evidence of an obesogenic effect of prenatal phthalate exposure. Positive associations between postnatal MEP and ∑DEHP concentrations depended on the timing of exposure. https://doi.org/10.1289/EHP1022.

Association between urinary phthalates and metabolic abnormalities in obese Thai children and adolescents

BACKGROUND

Several endocrine disruptors (including phthalates) are considered to be a cause of obesity. However, the current evidence has not conclusively established an association between phthalates and metabolic abnormalities, especially in children. The objective of the study was to evaluate the association between urinary phthalate metabolites and metabolic abnormalities in obese Thai children and adolescents.

METHODS

This cross-sectional case-control study was conducted in participants aged 7-18 years and divided into two groups: normal weight and overweight/obesity. Spot urine concentrations of two phthalate metabolites (monomethyl phthalate [MMP] and mono-n-buthyl phthalate [MBP]) were measured by high performance liquid chromatography (HPLC). Anthropometric data, including weight, height, body mass index (BMI), waist circumference (WC), hip circumference (HC), waist-to-hip ratio (WHR) and waist-to-height ratio (WHTR), were measured and calculated. Fasting plasma glucose, insulin, HbA1c, lipid profiles and hepatic transaminase were analyzed, and insulin resistance indices were calculated.

RESULTS

One hundred and fifty-five participants were included. The median MMP level in the normal weight and the overweight/obesity groups were 0 (0, 459.83) and 0 (0, 1623.50) μg/g Cr, respectively (p=0.933). The median MBP level in the normal weight and the overweight/obesity groups were 233.6 (118.1, 633.62) and 206.94 (7.4, 427.7) μg/g Cr, respectively (p=0.083). After adjusting for age, gender and puberty, there was no correlation between MBP and all anthropometric data and metabolic profiles. Participants with hypertriglyceridemia had lower MBP levels than those with normal TG level. MMP levels were not significantly different between the participants with normal and abnormal weight of all metabolic parameters.

CONCLUSIONS

Participants with hypertriglyceridemia had lower MBP levels than those with normotriglyceridemia. However, it cannot show the correlation between phthalate and metabolic parameters.

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.

Endocrine disrupting chemicals and growth of children

According to the "environmental obesogen hypothesis", early-life (including in utero) exposure to endocrine disrupting chemicals (EDCs) may disturb the mechanisms involved in adipogenesis or energy storage, and thus may increase the susceptibility to overweight and obesity. Animal models have shown that exposure to several of these chemicals could induce adipogenesis and mechanisms have been described. Epidemiological studies are crucial to know whether this effect could also be observed in humans. We aimed at summarizing the literature in epidemiology on the relationship between EDCs exposure and child's growth. Overall, epidemiological studies suggest that pre- and/or early postnatal exposure to some EDCs may increase the risk of overweight or obesity during childhood. In that review, we present some limitations of these studies, mainly in exposure assessment, that currently prevent to conclude about causality. Recent advances in epidemiology should bring further knowledge.

The influence of phthalates and bisphenol A on the obesity development and glucose metabolism disorders

The prevalence of obesity and type 2 diabetes mellitus epidemics presents a great health problem worldwide. Beside the changes in diet and decreased physical activity, there is growing interest in endocrine disrupting chemicals that may have effects on these conditions. Among them, the role of certain phthalates and bisphenol A is confirmed. We have summarized the existing literature on this issue including cross-sectional, follow up epidemiological studies and in vivo and in vitro studies. Most data support the effects of bisphenol A and some phthalates, such as di-2-ethyl-hexyl phthalate, diethyl phthalate, dibuthyl phthalate, dimethyl phthalate, dibenzyl phthalate, diisononyl phthalate and others on the development obesity and type 2 diabetes mellitus. These endocrine disrupting chemicals interfere with different cell signaling pathways involved in weight and glucose homeostasis. Since the data are rather inconsistent, there is a need for new, well-designed prospective studies.

Human exposure to endocrine disrupting compounds: Their role in reproductive systems, metabolic syndrome and breast cancer. A review

Endocrine disrupting chemicals (EDCs) are released into the environment from different sources. They are mainly used in packaging industries, pesticides and food constituents. Clinical evidence, experimental models, and epidemiological studies suggest that EDCs have major risks for humans by targeting different organs and systems in the body (e.g. reproductive system, breast tissue, adipose tissue, pancreas, etc.). Due to the ubiquity of human exposure to these compounds the aim of this review is to describe the most recent data on the effects induced by phthalates, bisphenol A and parabens in a critical window of exposure: in utero, during pregnancy, infants, and children. The interactions and mechanisms of toxicity of EDCs in relation to human general health problems, especially those broadening the term of endocrine disruption to 'metabolic disruption', should be deeply investigated. These include endocrine disturbances, with particular reference to reproductive problems and breast, testicular and ovarian cancers, and metabolic diseases such as obesity or diabetes.

In utero exposure to di-(2-ethylhexyl) phthalate induces metabolic disorder and increases fat accumulation in visceral depots of C57BL/6J mice offspring

Excessive visceral fat accumulation is associated with metabolic disorders. Di-(2-ethylhexyl) phthalate (DEHP), a candidate environmental obesogen, affects lipid metabolism and adipogenesis. Perinatal exposure to DEHP may be associated with metabolic disorders of dams and offspring. The aim of the present study was to explore the effects of exposure of pregnant dams to DEHP on the metabolism and fat distribution of their offspring, and to determine the mechanisms for these effects. Pregnant C57BL/6J mice were administered DEHP via gavage (0.05 or 500 mg/kg/day) from gestational days 1-19. Pups were sacrificed at nine weeks of age. Serum leptin, insulin, lipid and fasting glucose levels, and the weights of the inguinal (subcutaneous) and gonadal (visceral) fat pads were determined. mRNA expression levels of two developmental genes, T-box 15 (Tbx15) and glypican 4 (Gpc4) were detected in fat tissues. A 100% abortion rate was exhibited in 500 mg/kg DEHP-treated dams, whereas exposure to 0.05 mg/kg DEHP did not affect reproductive outcomes. Pups from the 0.05 mg/kg exposure group were used for subsequent experimentation. Serum leptin, insulin, lipid and fasting glucose concentrations in these pups were significantly higher than those of control pups (P<0.05). Although no significant change in body weight was detected, the visceral fat weights of DEHP-exposed pups were significantly higher than those of control pups (P<0.05). Compared with controls, mRNA expression levels of Tbx15 in subcutaneous fat and Gpc4 in visceral fat were significantly increased among DEHP-exposed pups (P<0.01). The present results suggest that in utero exposure to an environmentally safe dose of DEHP may lead to excessive visceral fat accumulation and metabolic disorders in offspring and that aberrant expression of Tbx15 and Gpc4 may have an important role in these effects.

Life without plastic: A family experiment and biomonitoring study

Exposure to bisphenol-A (BPA) and phthalates has been associated with negative health outcomes in animal and human studies, and human bio-monitoring studies demonstrate widespread exposure in the US and Europe. Out of concern for the environment and health, individuals may attempt to modify their environment, diet, and consumer choices to avoid such exposures, but these natural experiments are rarely if ever quantitatively evaluated. The aim of the study was to evaluate the difference in urinary concentrations of BPA and phthalate metabolites following an exposure reduction intervention among an Austrian family of five. Urine samples were taken shortly after the family had removed all plastic kitchenware, toys, and bathroom products, and started a concerted effort to eat less food packaged in plastic. Two-months later, urine samples were collected at a follow-up visit, and concentrations of BPA and phthalate metabolites were compared. Shortly after removal of plastic urinary concentrations of BPA were below limit of quantification in all samples. Phthalate concentrations were low, however, 10 of 14 investigated metabolites could be found above limit of quantification. After the two-month intervention, phthalate urinary concentrations had declined in some but not all family members. In the mother most phthalate metabolites increased. The low levels might be partly due to the environmentally conscious lifestyle of the family and partly due to the fact that body levels had dropped already because of the delay of four days between finishing removal and first measurement. Further two months avoidance of dietary exposure and exposure to environmental plastics reduced urinary concentrations for all but one metabolite in the oldest son only, but decreased somewhat in all family members except the mother.

Age and Gender Differences in Urinary Levels of Eleven Phthalate Metabolites in General Taiwanese Population after a DEHP Episode

Introduction

In 2011, the Taiwan FDA disclosed illegal di(2-ethylhexyl phthalate) (DEHP) and dibutyl phthalate (DBP) use in beverage and nutrition supplements. We aim to determine phthalate exposure and other relevant factors in a sample of the general Taiwanese population in order to evaluate actual phthalate exposure levels after this disclosure of DEHP use.

Method

We selected subjects aged 7 years old and older in 2013 from the general Taiwanese population. First morning urine samples from each participant were collected to analyze 11 phthalate metabolites representing 7 parent phthalates using on-line liquid chromatography/ tandem mass spectrometry. An interview questionnaire was applied to obtain participant demographic characteristics, lifestyle, and other relevant factors.

Results

The median levels of metabolites of DEHP, including mono-ethylhexyl phthalate (MEHP), mono-(2-ethyl-5-oxohexyl) phthalate (MEOHP), mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono-(2-ethyl-5-carboxypentyl) phthalate (MECPP), DBP (DnBP and DiBP), including mono-n-butyl phthalate (MnBP) and mono-iso-butyl phthalate (MiBP), and mono-ethyl phthalate (MEP) in urine samples of 290 adults/ 97 minors (<18 years) were 7.9/ 6.1, 12.6/ 17.8, 22.0/ 25.8, 25.4/ 30.8, 18.1/ 23.6, 9.4/ 13.6 and 14.5/ 12.4 μg/g creatinine, respectively. Women (≧18 years) were exposed to significantly higher levels of MEHHP (P=0.011), MECPP (P=0.01), MnBP (P=0.001) and MEP (P<0.001) than men (≧18 years), whereas no gender difference was observed in minors. We found significant higher level of MEP (creatinine-unadjusted) in subject aged between 18 to 40 years old (P<0.001), especially for women. Exposure levels of MEOHP (P<0.001), MECPP (P=0.002) and MnBP (P=0.044) in minors were significantly higher than those of adults. High frequency usage of food preservation film and bags, and personal care products are potential sources of phthalates exposure in general Taiwanese.

Conclusion

Our findings indicated that DEHP and DBP exposure in a sample of the general Taiwanese population varied by age and gender, possibly affected by different lifestyles, and continuing bio-monitoring surveillance is warranted.