Compound- and sex-specific effects on programming of energy and immune homeostasis in adult C57BL/6JxFVB mice after perinatal TCDD and PCB 153

Polychlorinated biphenyls and incident coronary heart disease-related outcomes in Great Lakes fish consumers

BACKGROUND

Exposure to polychlorinated biphenyls (PCBs) has been linked to risk factors for cardiovascular disease such as increased inflammation, accelerated atherosclerosis, diabetes, and sex hormone dysregulation. Furthermore, there is increasing evidence suggesting associations between internal dose of PCBs and cardiovascular outcomes.

OBJECTIVES

The purpose of this study is to investigate longitudinal associations of PCBs with coronary heart disease (CHD)-related outcomes in a cohort of Great Lakes sport fish consumers.

METHODS

The Great Lakes Sport Fish Consumer cohort was established in the early 1990's. Eight hundred nineteen participants were followed from 1993 to 2017. Serum PCBs were measured in 1994/1995 (baseline), in 2001, and in 2004, while health history questionnaires were administered in 1996, 2003, 2010, and 2017. Cox models were used to prospectively investigate associations of total PCBs and PCB groupings, based on aryl hydrocarbon receptor activity, with incident self-reported physician diagnosis of coronary heart disease (CHD), myocardial infarction (MI), and angina pectoris.

RESULTS

A 2-fold increase in phenobarbital-type PCBs was associated with a 72% increase in likelihood of self-reported incident diagnosis of CHD (HR=1.72, 95% CI: 1.06-2.81; p=0.0294). Similar results were observed for total PCBs (HR=1.68, 95% CI: 1.05-2.69; p=0.0306) and mixed methacholine/phenobarbital type (mixed-type) PCBs (HR=1.60, 95% CI: 1.02-2.52; p=0.0427), but not methacholine-type PCBs. PCBs were not strongly associated with risk of MI or angina.

CONCLUSIONS

This study presents evidence that exposure to PCBs increases the risk of developing coronary heart disease. Given the large number of risk factors and causal pathways for CHD, future research is required to better understand biological mechanisms of action for PCBs on CHD.

Exposure to PCB126 during the nursing period reversibly impacts early-life glucose tolerance

Polychlorinated biphenyls (PCBs) are persistent environmental organic pollutants known to have detrimental health effects. Using a mouse model, we previously demonstrated that PCB126 exposure before and during pregnancy and throughout the perinatal period adversely affected offspring glucose tolerance and/or body composition profiles. The purpose of this study was to investigate the glucose tolerance and body composition of offspring born to dams exposed to PCB126 during the nursing period only. Female ICR mice were bred, and half of the dams were exposed to either vehicle (safflower oil) or 1 µmole PCB126 per kg of body weight via oral gavage on postnatal days (PND) 3, 10, and 17 (n = 9 per group). Offspring body weight, lean and fat mass, and glucose tolerance were recorded every three weeks. PCB126 treatment did not alter dam nor offspring body weight (p > 0.05). PCB126-exposed male and female offspring displayed normal body composition (p > 0.05) relative to vehicle-exposed offspring. However, both male and female offspring that were exposed to PCB126 during the nursing period had significantly impaired glucose tolerance at 3 and 9 weeks of age (p < 0.05). At 6 and 12 weeks of age, no impairments in glucose tolerance existed in offspring (p > 0.05). Our current study demonstrates that exposure to PCB126 through the mother's milk does not affect short- or long-term body composition but impairs glucose tolerance in the short-term.

Gestational exposure to PCB-118 impairs placental angiogenesis and fetal growth

Maternal exposure to polychlorinated biphenyls (PCBs) results in adverse effects on fetal development. However, the underlying mechanism has not been sufficiently explored in respect to particular PCBs. Placental angiogenesis plays a crucial role in feto-maternal substances transportation and fetal development. The present study was conducted to investigate the effects of prenatal PCB118 exposure on placental angiogenesis and fetal growth. The pregnant dam received PCB118 at environmentally relevant doses (0, 20, or 100 μg/kg/day) intragastrically from gestational day (GD) 7.5-18.5 to establish an in vivo model. Compared with the control group, the fetal body and placental weights of the PCB118 (100 μg/kg/day) group were significantly decreased and the intrauterine growth retardation (IUGR) rates were increased both in the female and male fetus. Furthermore, we found that placental histology was significantly impaired and the number of blood vessels was decreased in the PCB118 group. Additionally, gestational exposure to PCB118 caused anomalous mRNA expression of the genes in the placenta regarding angiogenesis. These findings indicate that PCB118 may contribute to the occurrence of IUGR by provoking placental angiogenesis dysfunction. This study clarified the adverse effects and potential mechanism of prenatal PCBs exposure on fetal growth, providing a new theoretical and experimental basis for future treatment and prevention.

Developmental Exposure to Endocrine Disrupting Chemicals and Its Impact on Cardio-Metabolic-Renal Health

Developmental origin of health and disease postulates that the footprints of early life exposure are followed as an endowment of risk for adult diseases. Epidemiological and experimental evidence suggest that an adverse fetal environment can affect the health of offspring throughout their lifetime. Exposure to endocrine disrupting chemicals (EDCs) during fetal development can affect the hormone system homeostasis, resulting in a broad spectrum of adverse health outcomes. In the present review, we have described the effect of prenatal EDCs exposure on cardio-metabolic-renal health, using the available epidemiological and experimental evidence. We also discuss the potential mechanisms of their action, which include epigenetic changes, hormonal imprinting, loss of energy homeostasis, and metabolic perturbations. The effect of prenatal EDCs exposure on cardio-metabolic-renal health, which is a complex condition of an altered biological landscape, can be further examined in the case of other environmental stressors with a similar mode of action.

Prenatal exposure to persistent organic pollutants and childhood obesity: A systematic review and meta-analysis of human studies

We conducted a systematic review and meta-analysis of the associations between prenatal exposure to persistent organic pollutants (POPs) and childhood obesity. We focused on organochlorines (dichlorodiphenyltrichloroethane [DDT], dichlorodiphenyldichloroethylene [DDE], hexachlorobenzene [HCB], and polychlorinated biphenyls [PCBs]), perfluoroalkyl and polyfluoroalkyl substances (PFAS), and polybrominated diphenyl ethers (PBDEs) that are the POPs more widely studied in environmental birth cohorts so far. We search two databases (PubMed and Embase) through July/09/2021 and identified 33 studies reporting associations with prenatal organochlorine exposure, 21 studies reporting associations with prenatal PFAS, and five studies reporting associations with prenatal PBDEs. We conducted a qualitative review. Additionally, we performed random-effects meta-analyses of POP exposures, with data estimates from at least three prospective studies, and BMI-z. Prenatal DDE and HCB levels were associated with higher BMI z-score in childhood (beta: 0.12, 95% CI: 0.03, 0.21; I² : 28.1% per study-specific log increase of DDE and beta: 0.31, 95% CI: 0.09, 0.53; I² : 31.9% per study-specific log increase of HCB). No significant associations between PCB-153, PFOA, PFOS, or pentaPBDEs with childhood BMI were found in meta-analyses. In individual studies, there was inconclusive evidence that POP levels were positively associated with other obesity indicators (e.g., waist circumference).

Lack of Offspring Nrf2 Does Not Exacerbate the Detrimental Metabolic Outcomes Caused by In Utero PCB126 Exposure

Human environmental exposures to toxicants, such as polychlorinated biphenyls (PCBs), increase oxidative stress and disease susceptibility. Such exposures during pregnancy and/or nursing have been demonstrated to adversely affect offspring health outcomes. Nuclear factor erythroid-2-related factor 2 (Nrf2) regulates the antioxidant response and is involved in the detoxification of coplanar PCBs, like PCB126. The purpose of this study was to investigate glucose tolerance and body composition in PCB-exposed offspring expressing or lacking Nrf2. We hypothesized that offspring lacking Nrf2 expression would be more susceptible to the long-term health detriments associated with perinatal PCB exposure. During gestation, whole-body Nrf2 heterozygous (Het) and whole-body Nrf2 knockout (KO) mice were exposed to vehicle or PCB126. Shortly after birth, litters were cross-fostered to unexposed dams to prevent PCB exposure during nursing. Offspring were weaned, and their body weight, body composition, and glucose tolerance were recorded. At two months of age, PCB exposure resulted in a significant reduction in the average body weight of offspring born to Nrf2 Het dams (p < 0.001) that primarily arose from the decrease in average lean body mass in offspring (p < 0.001). There were no differences in average body weight of PCB-exposed offspring born to Nrf2 KO dams (p > 0.05), and this was because offspring of Nrf2 KO dams exposed to PCB126 during pregnancy experienced a significant elevation in fat mass (p = 0.002) that offset the significant reduction in average lean mass (p < 0.001). Regardless, the lack of Nrf2 expression in the offspring themselves did not enhance the differences observed. After an oral glucose challenge, PCB-exposed offspring exhibited significant impairments in glucose disposal and uptake (p < 0.05). Offspring born to Nrf2 Het dams exhibited these impairments at 30 min and 120 min, while offspring born to Nrf2 KO dams exhibited these impairments at zero, 15, 30, 60 and 120 min after the glucose challenge. Again, the interactions between offspring genotype and PCB exposure were not significant. These findings were largely consistent as the offspring reached four months of age and demonstrate that the lack of offspring Nrf2 expression does not worsen the metabolic derangements caused by in utero PCB exposure as we expected. Future directions will focus on understanding how the observed maternal Nrf2 genotypic differences can influence offspring metabolic responses to in utero PCB exposure.

Sublethal, sex-specific, osmotic, and metabolic impairments in embryonic and adult round stingrays from a location exposed to environmental contamination in southern California, USA

Organic contaminants are known to affect a suite of physiological processes across vertebrate clades. However, despite their ancient lineage and important roles in maintaining healthy ecosystems, elasmobranchs (sharks, skates, and rays) are understudied with regard to sublethal effects of contaminant exposure on metabolic processes. Perturbations resulting from contaminant exposure can divert energy away from maintaining physiological homeostasis, particularly during energetically challenging life stages, such as pregnancy and embryonic development. Using the round stingray (Urobatis halleri) as a model elasmobranch species, we captured adult males and pregnant females (matrotrophic histotrophy) and their embryos from two populations differing in their environmental exposure to organic contaminants (primarily polychlorinated biphenyls (PCBs)). Pregnant females from the PCB-exposed population experienced significant decreases from early- to late-pregnancy in tissue mass and quality not seen in reference females. PCB-exposed pregnant females also failed to maintain plasma urea concentrations as pregnancy progressed, which was accompanied by a loss in muscle protein content. Despite the energetic demands of late-term pregnancy, females had significantly greater liver lipid content than reproductively inactive adult males. PCB-exposed adult males also had high metabolic capacity (i.e., enzyme activity) for most substrate groupings of all sex-site groups, suggesting that males may be even more negatively impacted by contaminant exposure than pregnant females. Evidence that in utero exposure to PCBs via maternal offloading impairs embryo outcomes is accumulating. Embryos from the PCB-contaminated site had lower tissue quality measures and indications that sex-based differences were manifesting in utero as males had higher metabolic capacities than females. This study indicates that accumulated PCB contaminants are not physiologically inert in the stingray.

Endocrine, metabolic and apical effects of in utero and lactational exposure to non-dioxin-like 2,2',3,4,4',5,5'-heptachlorobiphenyl (PCB 180): A postnatal follow-up study in rats

PCB 180 is a persistent and abundant non-dioxin-like PCB (NDL-PCB). We determined the developmental toxicity profile of ultrapure PCB 180 in developing offspring following in utero and lactational exposure with the focus on endocrine, metabolic and retinoid system alterations. Pregnant rats were given total doses of 0, 10, 30, 100, 300 or 1000 mg PCB 180/kg bw on gestational days 7-10 by oral gavage, and the offspring were sampled on postnatal days (PND) 7, 35 and 84. Decreased serum testosterone and triiodothyronine concentrations on PND 84, altered liver retinoid levels, increased liver weights and induced 7-pentoxyresorufin O-dealkylase (PROD) activity were the sensitive effects used for margin of exposure (MoE) calculations. Liver weights were increased together with induction of the metabolizing enzymes cytochrome P450 (CYP) 2B1, CYP3A1, and CYP1A1. Less sensitive effects included decreased serum estradiol and increased luteinizing hormone levels in females, decreased prostate and seminal vesicle weight and increased pituitary weight in males, increased cortical bone area and thickness of tibial diaphysis in females and decreased cortical bone mineral density in males. Developmental toxicity profiles were partly different in male and female offspring, males being more sensitive to increased liver weight, PROD induction and decreased thyroxine concentrations. MoE assessment indicated that the 95^th percentile of current maternal PCB 180 concentrations do not exceed the estimated tolerable human lipid-based PCB 180 concentration. Although PCB 180 is much less potent than dioxin-like compounds, it shares several toxicological targets suggesting a potential for interactions.

Endocrine disrupting chemicals and metabolic disorders in the liver: What if we also looked at the female side?

Endocrine disrupting chemicals (EDCs) are linked to the worldwide epidemic incidence of metabolic disorders and fatty liver diseases, which affects quality of life and represents a high economic cost to society. Energy homeostasis exhibits strong sexual dimorphic traits, and metabolic organs respond to EDCs depending on sex, such as the liver, which orchestrates both drug elimination and glucose and lipid metabolism. In addition, fatty liver diseases show a strong sexual bias, which in part could also originate from sex differences observed in gut microbiota. The aim of this review is to highlight significant differences in endocrine and metabolic aspects of the liver, between males and females throughout development and into adulthood. It is also to illustrate how the male and female liver differently cope with exposure to various EDCs such as bisphenols, phthalates and persistent organic chemicals in order to draw attention to the need to include both sexes in experimental studies. Interesting data come from analyses of the composition and diversity of the gut microbiota in males exposed to the mentioned EDCs showing significant correlations with hepatic lipid accumulation and metabolic disorders but information on females is lacking or incomplete. As industrialization increases, the list of anthropogenic chemicals to which humans will be exposed will also likely increase. In addition to strengthening existing regulations, encouraging populations to protect themselves and promoting the substitution of harmful chemicals with safe products, innovative strategies based on sex differences in the gut microbiota and in the gut-liver axis could be optimistic outlook.

Exposure to pollutants altered glucocorticoid signaling and clock gene expression in female mice. Evidence of tissue- and sex-specificity

Environmental pollutants suspected of disrupting the endocrine system are considered etiologic factors in the epidemic of metabolic disorders. As regulation of energy metabolism relies on the integrated action of a large number of hormones, we hypothesized that certain chemicals could trigger changes in glucocorticoid signaling. To this end, we exposed C57Bl6/J female and male mice between 5 and 20 weeks of age to a mixture of 2,3,7,8- tetrachlorodibenzo-p-dioxin (20 pg/kg body weight/day [bw/d]), polychlorobiphenyl 153 (200 ng/kg bw/d), di-[2-ethylhexyl]-phthalate (500 μg/kg bw/d) and bisphenol A (40 μg/kg bw/d). In female mice fed a standard diet (ST), we observed a decrease in plasma levels of leptin as well as a reduced expression of corticoid receptors Nr3c1 and Nr3c2, of leptin and of various canonical genes related to the circadian clock machinery in visceral (VAT) but not subcutaneous (SAT) adipose tissue. However, Nr3c1 and Nr3c2 mRNA levels did not change in high-fat-fed females exposed to pollutants. In ST-fed males, pollutants caused the same decrease of Nr3c1 mRNA levels in VAT observed in ST-fed females but levels of Nr3c2 and other clock-related genes found to be down-regulated in female VAT were enhanced in male SAT and not affected in male VAT. The expression of corticoid receptors was not affected in the livers of both sexes in response to pollutants. In summary, exposure to a mixture of pollutants at doses lower than the no-observed adverse effect levels (NoAELs) resulted in sex-dependent glucocorticoid signaling disturbances and clock-related gene expression modifications in the adipose tissue of ST-fed mice.

Adipose Tissue and Endocrine-Disrupting Chemicals: Does Sex Matter?

Obesity and metabolic-related diseases, among which diabetes, are prominent public health challenges of the 21st century. It is now well acknowledged that pollutants are a part of the equation, especially endocrine-disrupting chemicals (EDCs) that interfere with the hormonal aspect. The aim of the review is to focus on adipose tissue, a central regulator of energy balance and metabolic homeostasis, and to highlight the significant differences in the endocrine and metabolic aspects of adipose tissue between males and females which likely underlie the differences of the response to exposure to EDCs between the sexes. Moreover, the study also presents an overview of several mechanisms of action by which pollutants could cause adipose tissue dysfunction. Indeed, a better understanding of the mechanism by which environmental chemicals target adipose tissue and cause metabolic disturbances, and how these mechanisms interact and sex specificities are essential for developing mitigating and sex-specific strategies against metabolic diseases of chemical origin. In particular, considering that a scenario without pollutant exposure is not a realistic option in our current societies, attenuating the deleterious effects of exposure to pollutants by acting on the gut-adipose tissue axis may constitute a new direction of research.

Metabolism-Disrupting Chemicals and the Constitutive Androstane Receptor CAR

During the last two decades, the constitutive androstane receptor (CAR; NR1I3) has emerged as a master activator of drug- and xenobiotic-metabolizing enzymes and transporters that govern the clearance of both exogenous and endogenous small molecules. Recent studies indicate that CAR participates, together with other nuclear receptors (NRs) and transcription factors, in regulation of hepatic glucose and lipid metabolism, hepatocyte communication, proliferation and toxicity, and liver tumor development in rodents. Endocrine-disrupting chemicals (EDCs) constitute a wide range of persistent organic compounds that have been associated with aberrations of hormone-dependent physiological processes. Their adverse health effects include metabolic alterations such as diabetes, obesity, and fatty liver disease in animal models and humans exposed to EDCs. As numerous xenobiotics can activate CAR, its role in EDC-elicited adverse metabolic effects has gained much interest. Here, we review the key features and mechanisms of CAR as a xenobiotic-sensing receptor, species differences and selectivity of CAR ligands, contribution of CAR to regulation hepatic metabolism, and evidence for CAR-dependent EDC action therein.

Air pollution exposure is associated with the gut microbiome as revealed by shotgun metagenomic sequencing

Animal work indicates exposure to air pollutants may alter the composition of the gut microbiota. This study examined relationships between air pollutants and the gut microbiome in young adults residing in Southern California. Our results demonstrate significant associations between exposure to air pollutants and the composition of the gut microbiome using whole-genome sequencing. Higher exposure to 24-hour O3 was associated with lower Shannon diversity index, higher Bacteroides caecimuris, and multiple gene pathways, including L-ornithine de novo biosynthesis as well as pantothenate and coenzyme A biosynthesis I. Among other pollutants, higher NO2 exposure was associated with fewer taxa, including higher Firmicutes. The percent variation in gut bacterial composition that was explained by air pollution exposure was up to 11.2% for O3 concentrations, which is large compared to the effect size for many other covariates reported in healthy populations. This study provides the first evidence of significant associations between exposure to air pollutants and the compositional and functional profile of the human gut microbiome. These results identify O3 as an important pollutant that may alter the human gut microbiome.

Indole-3-carbinol prevents colitis and associated microbial dysbiosis in an IL-22-dependent manner

Colitis, an inflammatory bowel disease, is caused by a variety of factors, but luminal microbiota are thought to play crucial roles in disease development and progression. Indole is produced by gut microbiota and is believed to protect the colon from inflammatory damage. In the current study, we investigated whether indole-3-carbinol (I3C), a naturally occurring plant product found in numerous cruciferous vegetables, can prevent colitis-associated microbial dysbiosis and attempted to identify the mechanisms. Treatment with I3C led to repressed colonic inflammation and prevention of microbial dysbiosis caused by colitis, increasing a subset of gram-positive bacteria known to produce butyrate. I3C was shown to increase production of butyrate, and when mice with colitis were treated with butyrate, there was reduced colonic inflammation accompanied by suppression of Th17 and induction of Tregs, protection of the mucus layer, and upregulation in Pparg expression. Additionally, IL-22 was increased only after I3C but not butyrate administration, and neutralization of IL-22 prevented the beneficial effects of I3C against colitis, as well as blocked I3C-mediated dysbiosis and butyrate induction. This study suggests that I3C attenuates colitis primarily through induction of IL-22, which leads to modulation of gut microbiota that promote antiinflammatory butyrate.

Prenatal dioxin exposure and glucose metabolism in the Seveso Second Generation study

BACKGROUND

Exposure to endocrine disrupting compounds such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) during susceptible developmental windows may alter risk of metabolic disease later in life. Animal studies of in utero and lactational TCDD exposure report associations with alterations in insulin sensitivity and energy homeostasis, but epidemiologic evidence is limited. We examined the relationship of prenatal TCDD exposure with markers of glucose homeostasis in the Seveso Second Generation study, a unique cohort of children born to TCDD-exposed women resulting from a 1976 explosion in Seveso, Italy.

METHODS

We included 426 children who were 18 years or older with complete follow-up data including a fasting blood draw. Insulin and glucose were measured and the updated homoeostatic model assessment was used to estimate insulin resistance (HOMA2-IR) and beta-cell function (HOMA2-B). Prenatal TCDD exposure was defined in two ways, as initial maternal serum TCDD concentration and TCDD estimated at pregnancy.

RESULTS

The children (222 female, 204 male) averaged 28.6 (±6.0) years. We found a 10-fold increase in TCDD estimated at pregnancy was inversely associated with insulin (adj-β = -1.24 μIU/mL, 95% confidence interval (CI): -2.38, -0.09) and HOMA2-B (adj-β = -10.2% decrease, 95% CI: -17.8, -1.9) among daughters, but not sons (insulin: adj-β = 0.57 μIU/mL, 95% CI: -0.84, 1.98, P for interaction = 0.04; and HOMA2-B: adj-β = 0.8% increase, 95% CI -10.7, 13.9, P for interaction = 0.11). Similar effect modification was observed for TCDD estimated at pregnancy and HOMA2-IR (P for interaction = 0.13). The models for initial maternal serum TCDD showed similar effect modification by child sex. The observed associations in daughters showed evidence of mediation by body mass index, which we have previously found to be associated with prenatal TCDD exposure in female offspring.

CONCLUSION

These results suggest prenatal exposure to TCDD is associated with lower insulin resistance and beta compensation in female offspring, and show evidence of mediation by body mass index.

Effects of perinatal dioxin exposure on development of children: a 3-year follow-up study of China cohort

The purpose of this study was to investigate the longitudinal effects of perinatal exposure to dioxin on physical growth in a 3-year follow-up study. In 2015, 27 mother-infant pairs living in an electronic waste (e-waste) dismantling region and 35 pairs living in a control region were enrolled in the present study. Breast milk samples were collected at 4 weeks after birth. Physical growth, including weight, height, and head and chest circumferences, was measured at 6 months and 3 years of age. Dioxin levels in the breast milk were measured by gas chromatography/high-resolution mass spectrometry. Levels of 2,3,7,8-tetrachlorodibenzo-p-dioxin and toxic equivalency values in maternal breast milk of polychlorinated dibenzodioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and PCDDs/PCDFs were significantly higher in women residing in the e-waste dismantling region. In 3-year-old boys, inverse associations were found between height and PCDDs-TEQ. In girls, positive associations were found between height and 2,3,7,8-TetraCDD, PCDDs-TEQ, and PCDDs/PCDFs-TEQ, and for weight and PCDDs-TEQ and PCDDs/PCDFs-TEQ at 3 years of age. In this study, sex-specific differences were observed in children, in whom dioxin exposure decreased growth in boys but increased growth in girls during the first 3 years of life.

Type 3 innate lymphoid cells are altered in colons of C57BL/6 mice with dioxin exposure

Type 3 innate lymphoid cells (ILC3s) are distributed in the gut and regulate inflammation by secreting cytokines, including interferon (IFN)-γ and interleukin (IL)-17. The maintenance and function of ILC3s involve the activity of aryl hydrocarbon receptor (AhR), a potent ligand of which is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), one of the most toxic dioxin congeners. Thus, TCDD exposure might affect ILC3s. To obtain in vivo evidence supporting this notion, we exposed female C57BL/6 mice orally to TCDD (low/high doses: 0.1/10 μg/kg body weight) during pregnancy and lactation periods, and after the exposure, evaluated the mothers and offspring for alterations in ILC3 differentiation and function in the colon. ILC3 frequency among colonic lamina propria lymphocytes was preferentially diminished in the offspring, and, in parallel, the median fluorescence intensity (MFI) of retinoic acid receptor-related orphan receptor (ROR)γt, which is associated with ILC3 differentiation, was also decreased in ILC3s. Conversely, the percentages of two subsets of the cells, one positive for natural cytotoxicity receptor NKp46 and the other for IL-17a, were increased in TCDD-exposed mothers and offspring. Moreover, the percentage of IFN-γ⁺ ILC3s was increased specifically in the mothers, but this was in conjunction with a significant decrease in the MFI of IFN-γ, which suggests that the IFN-γ⁺ ILC3 subset was functionally altered. In conclusion, maternal exposure to TCDD suppresses ILC3 differentiation in the offspring and influences ILC3 function in distinct manners in the mother and offspring. Our study provides new insights into the intergenerational interference of dioxins in colonic ILC3s.

Environmental exposures during pregnancy: Mechanistic effects on immunity

In human studies, it is well established that exposures during embryonic and fetal development periods can influence immune health. Coupled with genetic predisposition, these exposures can alter lifetime chronic and infectious disease trajectory, and, ultimately, life expectancy. Fortunately, as research advances, mechanisms governing long-term effects of prenatal exposures are coming to light and providing the opportunity for intervention and risk reduction. For instance, human association studies have provided a foundation for the association of prenatal exposure to particulate matter with early immunosuppression and later allergic disease in the offspring. Only recently, the mechanisms mediating this response have been revealed and there is much we have yet to discover. Although cellular immune response is understood for many exposure scenarios, molecular pathways are still unidentified. This review will provide commentary and synthesis of the current literature regarding environmental exposures during pregnancy and mechanisms determining immune outcomes. Shared mechanistic features and current gaps in the state of the science are identified and discussed. To such purpose, we address exposures by their immune effect type: immunosuppression, autoimmunity, inflammation and tissue damage, hypersensitivity, and general immunomodulation.

In utero dioxin exposure and cardiometabolic risk in the Seveso Second Generation Study

Background/Objectives:

In utero exposure to endocrine-disrupting compounds such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) may alter risk of obesity and related metabolic disease later in life. We examined the relationship of prenatal exposure to TCDD with obesity and metabolic syndrome (MetS) in children born to a unique cohort of TCDD-exposed women resulting from a 1976 explosion in Seveso, Italy.

Subjects/Methods:

In 2014, nearly 40 years after the explosion, we enrolled 611 post-explosion offspring, 2 to 39 years of age, in the Seveso Second Generation study. In utero TCDD exposure was defined primarily as TCDD concentration measured in maternal serum collected soon after the explosion and alternately as TCDD estimated at pregnancy. We measured height, weight, waist circumference, body fat, blood pressure, and fasting blood levels of lipids and glucose, which were combined to assess body mass index (BMI) and MetS.

Results:

Children (314 female, 297 male) averaged 23.6 (±6.0) years of age. Among the 431 children ≥18 years, a 10-fold increase in initial maternal TCDD concentration was inversely associated with BMI in daughters (adj-β=−0.99 kg/m²; 95% CI −1.86, −0.12), but not sons (adj-β=0.41 kg/m²; 95% CI −0.35, 1.18) (p-int=0.02). A similar relationship was found in the younger children (2-17 years); a 10-fold increase in initial maternal TCDD was inversely associated with BMI z-score (adj-β = −0.59 kg/m²; 95% CI −1.12, −0.06) among daughters, but not sons (adj-β = 0.04 kg/m²; 95% CI −0.34, 0.41) (p-int=0.03). In contrast, in sons only, initial maternal TCDD was associated with increased risk for MetS (adj-RR = 2.09, 95% CI 1.09, 4.02). Results for TCDD estimated at pregnancy were comparable.

Conclusions:

These results suggest prenatal TCDD exposure alters cardiometabolic endpoints in a sex-specific manner. In daughters, in utero TCDD is inversely associated with adiposity measures. In sons, in utero TCDD is associated with increased risk for MetS.

Endocrine Disrupting Chemicals: An Occult Mediator of Metabolic Disease

Endocrine disrupting chemicals (EDCs), a heterogeneous group of exogenous chemicals that can interfere with any aspect of endogenous hormones, represent an emerging global threat for human metabolism. There is now considerable evidence that the observed upsurge of metabolic disease cannot be fully attributed to increased caloric intake, physical inactivity, sleep deficit, and ageing. Among environmental factors implicated in the global deterioration of metabolic health, EDCs have drawn the biggest attention of scientific community, and not unjustifiably. EDCs unleash a coordinated attack toward multiple components of human metabolism, including crucial, metabolically-active organs such as hypothalamus, adipose tissue, pancreatic beta cells, skeletal muscle, and liver. Specifically, EDCs' impact during critical developmental windows can promote the disruption of individual or multiple systems involved in metabolism, via inducing epigenetic changes that can permanently alter the epigenome in the germline, enabling changes to be transmitted to the subsequent generations. The clear effect of this multifaceted attack is the manifestation of metabolic disease, clinically expressed as obesity, metabolic syndrome, diabetes mellitus, and non-alcoholic fatty liver disease. Although limitations of EDCs research do exist, there is no doubt that EDCs constitute a crucial parameter of the global deterioration of metabolic health we currently encounter.

Maternal exposure to TCDD during gestation advanced sensory-motor development, but induced impairments of spatial learning and memory in adult male rat offspring

2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) is an endocrine disrupting chemical (EDC) with high persistency. Even a low amount can pass the placental barrier during gestational exposure. Exposure to TCDD exposure can impair the development of the nervous system in children, leading to impaired learning ability in later-life. But the changes in neurobehavioral developments in infancy and childhood caused by TCDD are unknown. Pregnant Sprague-Dawley rats were given a consecutive daily dose of TCDD (200 or 800 ng/day/kg) or an equivalent volume of vehicle by gavage on gestational days 8-14 (GD 8-14) as the prenatal TCDD exposure model. In the offspring, early neurobehavioral development was assessed at postnatal day 5 (PND5) and eye-opening was monitored from PND10 onwards. Adult male offspring was tested by Morris Water Maze for spatial memory and learning ability evaluation. Hippocampus Nissl's staining and astrocyte GFAP immunohistochemistry were used to evaluate the activity of astrocytes. The results of the behavioral tests showed that gestational TCDD exposure induced premature motor activity and earlier eyes-opening, but lead to serious deficits of spatial memory and learning ability in the adult male offspring. Morphology and number of neurons in the hippocampus CA1 region was not affected, while the activity of astrocytes in the same region was significantly reduced. These data indicate that perinatal TCDD exposure induced premature neurobehavioral development but impaired the spatial learning and memory in adult male rat offspring. The decreased activity of astrocytes in the hippocampus may play a role in these adverse effects.

Analysis of Lipid Metabolism, Immune Function, and Neurobehavior in Adult C57BL/6JxFVB Mice After Developmental Exposure to di (2-ethylhexyl) Phthalate

Background: Developmental exposure to di (2-ethylhexyl) phthalate (DEHP) has been implicated in the onset of metabolic syndrome later in life. Alterations in neurobehavior and immune functions are also affected by phthalate exposure and may be linked to the metabolic changes caused by developmental exposure to DEHP. Objectives: Our goal was to study the effects of developmental exposure to DEHP in the context of metabolic syndrome by integrating different parameters to assess metabolic, neurobehavioral, and immune functions in one model. Methods: Female C57BL/6J mice were exposed to DEHP through the diet during gestation and lactation at doses ranging from 3.3 to 100,000 μg/kg body weight/day (μkd). During a 1-year follow-up period, a wide set of metabolic parameters was assessed in the F1 offspring, including weekly body weight measurements, food consumption, physical activity, glucose homeostasis, serum lipids, and endocrine profile. In addition, neurobehavioral and immune functions were assessed by sweet preference test, object recognition test, acute phase protein, and cytokines production. Animals were challenged with a high fat diet (HFD) in the last 9 weeks of the study. Results: Increased free fatty acids (FFA) and, high density lipoprotein (HDL-C) were observed in serum, together with a decrease in glycated hemoglobin levels in blood of 1-year old male DEHP-exposed offspring after HFD challenge. For the most sensitive endpoint measured (FFA), a lower bound of the 90%-confidence interval for benchmark dose (BMD) at a critical effect size of 5% (BMDL) of 2,160 μkd was calculated. No persistent changes in body weight or fat mass were observed. At 33,000 μkd altered performance was found in the object recognition test in males and changes in interferon (IFN)γ production were observed in females. Conclusions: Developmental exposure to DEHP combined with HFD in adulthood led to changes in lipid metabolism and neurobehavior in male offspring and cytokine production in female offspring. Our findings contribute to the evidence that DEHP is a developmental dyslipidemic chemical, however, more research is needed to further characterize adverse health outcomes and the mechanisms of action associated with the observed sex-specific effects.

Genetic background and window of exposure contribute to thyroid dysfunction promoted by low-dose exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin in mice

Genetic and environmental factors contribute to thyroid diseases. Although still debated, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is thought to induce thyroid dysfunction in humans and rodents. The data here reported point out the contribution of the exposure window and genetic background in mediating the low-dose TCDD effects on thyroid. Indeed, early (from E0.5 to PND30) and low-dose (0,001 μg/kg/day) TCDD exposure reduced the circulating fT4 and altered the expression of thyroid specific transcripts. The role of genetic components was estimated monitoring the same markers in Pax8^+/- and Nkx2-1^+/- mice, susceptible to thyroid dysfunction, exposed to 0, 1 μg/kg/day TCDD from E15.5 to PND60. Haploinsufficiency of either Pax8 or Nkx2-1 genes exacerbated the effects of the exposure impairing the thyroid enriched mRNAs in sex dependent manner. Such effect was mediated by mechanisms involving the Nkx2-1/p53/p65/IĸBα pathway in vitro and in vivo. Foetal exposure to TCDD impaired both thyroid function and genes expression while thyroid development and differentiation did not appear significantly affected. In mouse, stronger effects were related to earlier exposure or specific genetic background such as either Pax8 or Nkx2-1 haploinsufficiency, both associated to hypothyroidism in humans. Furthermore, our data underline that long exposure time are needed to model in vitro and in vivo results.

Mitochondria as target of endocrine-disrupting chemicals: implications for type 2 diabetes

Type 2 diabetes is a chronic, heterogeneous syndrome characterized by insulin resistance and pancreatic β-cell dysfunction or death. Among several environmental factors contributing to type 2 diabetes development, endocrine-disrupting chemicals (EDCs) have been receiving special attention. These chemicals include a wide variety of pollutants, from components of plastic to pesticides, with the ability to modulate endocrine system function. EDCs can affect multiple cellular processes, including some related to energy production and utilization, leading to alterations in energy homeostasis. Mitochondria are primarily implicated in cellular energy conversion, although they also participate in other processes, such as hormone secretion and apoptosis. In fact, mitochondrial dysfunction due to reduced oxidative capacity, impaired lipid oxidation and increased oxidative stress has been linked to insulin resistance and type 2 diabetes. Herein, we review the main mechanisms whereby metabolism-disrupting chemical (MDC), a subclass of EDCs that disturbs energy homeostasis, cause mitochondrial dysfunction, thus contributing to the establishment of insulin resistance and type 2 diabetes. We conclude that MDC-induced mitochondrial dysfunction, which is mainly characterized by perturbations in mitochondrial bioenergetics, biogenesis and dynamics, excessive reactive oxygen species production and activation of the mitochondrial pathway of apoptosis, seems to be a relevant mechanism linking MDCs to type 2 diabetes development.

Risk for animal and human health related to the presence of dioxins and dioxin-like PCBs in feed and food

The European Commission asked EFSA for a scientific opinion on the risks for animal and human health related to the presence of dioxins (PCDD/Fs) and DL-PCBs in feed and food. The data from experimental animal and epidemiological studies were reviewed and it was decided to base the human risk assessment on effects observed in humans and to use animal data as supportive evidence. The critical effect was on semen quality, following pre- and postnatal exposure. The critical study showed a NOAEL of 7.0 pg WHO2005-TEQ/g fat in blood sampled at age 9 years based on PCDD/F-TEQs. No association was observed when including DL-PCB-TEQs. Using toxicokinetic modelling and taking into account the exposure from breastfeeding and a twofold higher intake during childhood, it was estimated that daily exposure in adolescents and adults should be below 0.25 pg TEQ/kg bw/day. The CONTAM Panel established a TWI of 2 pg TEQ/kg bw/week. With occurrence and consumption data from European countries, the mean and P95 intake of total TEQ by Adolescents, Adults, Elderly and Very Elderly varied between, respectively, 2.1 to 10.5, and 5.3 to 30.4 pg TEQ/kg bw/week, implying a considerable exceedance of the TWI. Toddlers and Other Children showed a higher exposure than older age groups, but this was accounted for when deriving the TWI. Exposure to PCDD/F-TEQ only was on average 2.4- and 2.7-fold lower for mean and P95 exposure than for total TEQ. PCDD/Fs and DL-PCBs are transferred to milk and eggs, and accumulate in fatty tissues and liver. Transfer rates and bioconcentration factors were identified for various species. The CONTAM Panel was not able to identify reference values in most farm and companion animals with the exception of NOAELs for mink, chicken and some fish species. The estimated exposure from feed for these species does not imply a risk.

Perinatal exposure to endocrine disrupting compounds and the control of feeding behavior-An overview

Endocrine disrupting compounds (EDC) are ubiquitous environmental contaminants that can interact with steroid and nuclear receptors or alter hormone production. Many studies have reported that perinatal exposure to EDC including bisphenol A, PCB, dioxins, and DDT disrupt energy balance, body weight, adiposity, or glucose homeostasis in rodent offspring. However, little information exists on the effects of perinatal EDC exposure on the control of feeding behaviors and meal pattern (size, frequency, duration), which may contribute to their obesogenic properties. Feeding behaviors are controlled centrally through communication between the hindbrain and hypothalamus with inputs from the emotion and reward centers of the brain and modulated by peripheral hormones like ghrelin and leptin. Discrete hypothalamic nuclei (arcuate nucleus, paraventricular nucleus, lateral and dorsomedial hypothalamus, and ventromedial nucleus) project numerous reciprocal neural connections between each other and to other brain regions including the hindbrain (nucleus tractus solitarius and parabrachial nucleus). Most studies on the effects of perinatal EDC exposure examine simple crude food intake over the course of the experiment or for a short period in adult models. In addition, these studies do not examine EDC's impacts on the feeding neurocircuitry of the hypothalamus-hindbrain, the response to peripheral hormones (leptin, ghrelin, cholecystokinin, etc.) after refeeding, or other feeding behavior paradigms. The purpose of this review is to discuss those few studies that report crude food or energy intake after perinatal EDC exposure and to explore the need for deeper investigations in the hypothalamic-hindbrain neurocircuitry and discrete feeding behaviors.

Prenatal exposure to TCDD and atopic conditions in the Seveso second generation: a prospective cohort study

BACKGROUND

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a toxic environmental contaminant that can bioaccumulate in humans, cross the placenta, and cause immunological effects in children, including altering their risk of developing allergies. On July 10, 1976, a chemical explosion in Seveso, Italy, exposed nearby residents to a high amount of TCDD. In 1996, the Seveso Women's Health Study (SWHS) was established to study the effects of TCDD on women's health. Using data from the Seveso Second Generation Health Study, we aim to examine the effect of prenatal exposure to TCDD on the risk of atopic conditions in SWHS children born after the explosion.

METHODS

Individual-level TCDD was measured in maternal serum collected soon after the accident. In 2014, we initiated the Seveso Second Generation Health Study to follow-up the children of the SWHS cohort who were born after the explosion or who were exposed in utero to TCDD. We enrolled 677 children, and cases of atopic conditions, including eczema, asthma, and hay fever, were identified by self-report during personal interviews with the mothers and children. Log-binomial and Poisson regressions were used to determine the association between prenatal TCDD and atopic conditions.

RESULTS

A 10-fold increase in 1976 maternal serum TCDD (log10TCDD) was not significantly associated with asthma (adjusted relative risk (RR) = 0.93; 95% CI: 0.61, 1.40) or hay fever (adjusted RR = 0.99; 95% CI: 0.76, 1.27), but was significantly inversely associated with eczema (adjusted RR = 0.63; 95% CI: 0.40, 0.99). Maternal TCDD estimated at pregnancy was not significantly associated with eczema, asthma, or hay fever. There was no strong evidence of effect modification by child sex.

CONCLUSIONS

Our results suggest that maternal serum TCDD near the time of explosion is associated with lower risk of eczema, which supports other evidence pointing to the dysregulated immune effects of TCDD.

Childhood obesity and endocrine disrupting chemicals

The prevalence of obesity around the world has increased sharply. Strong evidence has emerged over the last decades that human exposure to numerous endocrine disrupting chemicals (EDCs) is the cause of obesity and obesity-related metabolic diseases. Many EDCs are manmade chemicals that are released into the environment. EDCs are exogenous compounds that interfere with hormonal regulation and normal endocrine systems, thereby affecting the health of animals and humans. The number of chemicals belonging to EDCs is increasing and some of them are very stable; they persist in the environment (persistent organic pollutants). Although they are banned, their concentrations have been continuously increasing over time. This review gives a brief introduction to common EDCs, and evidence of harmful effects of EDCs on obesity-related diseases; we focus in particular on EDCs' role in causing mitochondrial dysfunction.

Low-dose pollutant mixture triggers metabolic disturbances in female mice leading to common and specific features as compared to a high-fat diet

Environmental pollutants are potential etiologic factors of obesity and diabetes that reach epidemic proportions worldwide. However, it is important to determine if pollutants could exert metabolic defects without directly inducing obesity. The metabolic disturbances triggered in nonobese mice lifelong exposed to a mixture of low-dose pollutants (2,3,7,8-tetrachlorodibenzo-p-dioxine, polychlorinated biphenyl 153, diethylhexyl-phthalate, and bisphenol A) were compared with changes provoked by a high-fat high-sucrose (HFHS) diet not containing the pollutant mixture. Interestingly, females exposed to pollutants exhibited modifications in lipid homeostasis including a significant increase of hepatic triglycerides but also distinct features from those observed in diet-induced obese mice. For example, they did not gain weight nor was glucose tolerance impacted. To get more insight, a transcriptomic analysis was performed in liver for comparison. We observed that in addition to the xenobiotic/drug metabolism pathway, analysis of the hepatic signature illustrated that the steroid/cholesterol, fatty acid/lipid and circadian clock metabolic pathways were targeted in response to pollutants as observed in the diet-induced obese mice. However, the specific sets of dysregulated annotated genes (>1300) did not overlap more than 40% between both challenges with some genes specifically altered only in response to pollutant exposure. Collectively, results show that pollutants and HFHS affect common metabolic pathways, but by different, albeit overlapping, mechanisms. This is highly relevant for understanding the synergistic effects between pollutants and the obesogenic diet reported in the literature.

Increased Fetal Thymocytes Apoptosis Contributes to Prenatal Nicotine Exposure-induced Th1/Th2 Imbalance in Male Offspring Mice

Nicotine, a definite risk factor during pregnancy, is an immunomodulator. This study was designed to investigate the effects of prenatal nicotine exposure (PNE) on the balance of Th1/Th2 in offspring, and further explore the developmental origin mechanisms from the perspective of fetal thymocytes apoptosis. Pregnant Balb/c mice were administered 1.5 mg/kg nicotine subcutaneously twice per day from gestational day (GD) 9 to GD18. Results showed that PNE could cause a Th2 shift in male offspring, manifested as increased ratio of IgG1/IgG2a, IL-4 production in serum, and IL-4/IFN-γ expression ratio in spleen. Increased apoptosis of total thymocytes and CD4SP and reduced cell proportion of CD4SP were found in PNE male offspring on postnatal day (PND) 14 and PND 49. In the fetuses, decreased body weight and organ index of fetal thymus, histological changes in fetal thymus, reduced CD4SP proportion and increased fetal thymocyte apoptosis were observed in nicotine group. The increased mRNA expression of genes involved in Fas-mediated apoptotic pathway and protein expression of Fas were also detected. In conclusion, PNE could cause a Th2 shift in male offspring mediated by reduced CD4⁺ T cells output, which may result from the increasing apoptosis of total thymocytes and CD4SP.

Perinatal exposure to dioxins and dioxin-like compounds and infant growth and body mass index at seven years: A pooled analysis of three European birth cohorts

BACKGROUND

Dioxins and dioxin-like compounds are endocrine disrupting chemicals (EDCs). Experimental studies suggest perinatal exposure to EDCs results in later obesity. However, the few epidemiological investigations on dioxins are inconclusive. We investigated perinatal exposure to dioxins and dioxin-like compounds, infant growth and body mass index (BMI) in childhood.

METHODS

We pooled data from 3 European birth cohorts (Belgian, Norwegian, Slovak) with exposure assessment in cord blood or breast milk. Two cohorts had dioxin-like toxicity assessed using dioxin-responsive chemical-activated luciferase expression (DR-CALUX) bioassay and one cohort had measured concentrations of dioxins, furans and dioxin-like polychlorinated biphenols with CALUX relative potency values applied. Growth was cohort- and sex-specific change in weight-for-age z-score between birth and 24months (N=367). BMI was calculated at around 7years (median 7.17, interquartile range [IQR] 7.00-7.37years, N=251), and overweight defined according to international standards for children equivalent to adult BMI >25kg/m(2) (Cole and Lobstein, 2012). We fitted multivariate models using generalized estimating equations, and tested effect modification by sex, breastfeeding and cohort. Results per 10pgCALUXTEQ/g lipid increase in exposure.

RESULTS

Dioxin exposure was highest in the Belgian and lowest in the Norwegian cohort; median (IQR) of the pooled sample 13 (12.0) pgCALUXTEQ/g lipid. Perinatal exposure to dioxins and dioxin-like compounds appeared associated with increased growth between 0 and 24months (adjusted estimate for change in z-score: β=0.07, 95% CI: -0.01, 0.14). At 7years, dioxins exposure was associated with a statistically significant increase in BMI in girls (adjusted estimate for BMI units β=0.49, 95% CI: 0.07, 0.91) but not in boys (β=-0.03, 95% CI: -0.55, 0.49) (p-interaction=0.044). Furthermore, girls had a 54% (-6%, 151%) increased risk of overweight at 7years (p-interaction=0.023).

CONCLUSION

Perinatal exposure to dioxin and dioxin-like compounds was associated with increased early infant growth, and increased BMI in school age girls. Studies in larger sample sizes are required to confirm these sex-specific effects.

Effects of Perinatal Dioxin Exposure on Development of Children during the First 3 Years of Life

OBJECTIVE

To investigate the longitudinal effects of perinatal exposure to dioxin on neurodevelopment and physical growth of a birth cohort during the first 3 years of life.

STUDY DESIGN

A total of 217 mother-infant pairs living in a dioxin-contaminated area in Vietnam were followed up. Perinatal dioxin exposure of infants was estimated by the measurement of dioxin levels in breast milk of nursing mothers. Neurodevelopment of infants and children, including cognitive, language, and motor development, was determined at 4 months, 1 year, and 3 years of age. Physical growth, including weight, height, and head and abdominal circumferences, was measured at birth, 1 and 4 months, and 1 and 3 years of age. Multivariate mixed models were applied for analyzing repeated measures.

RESULTS

In boys, composite motor and gross motor scores were decreased with increasing exposure of 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TetraCDD). The high toxic equivalent of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDDs/PCDFs-TEQ) group showed a significant decrease in expressive communication score. In girls, there was no decreased score in any neurodevelopment aspects in high-exposure groups. All body size measures in boys were decreased in the high-exposure groups of 2,3,7,8-TetraCDD and PCDDs/PCDFs-TEQ. In girls, high 2,3,7,8-TetraCDD and PCDDs/PCDFs-TEQ exposure was associated with increased head and abdominal circumferences.

CONCLUSIONS

Perinatal dioxin exposure affects physical growth and neurodevelopment of infants and children in the first 3 years of life in a sex-specific manner.

Uppsala Consensus Statement on Environmental Contaminants and the Global Obesity Epidemic

Summary: From the lectures presented at the 2nd International Workshop on Obesity and Environmental Contaminants, which was held in Uppsala, Sweden, on 8–9 October 2015, it became evident that the findings from numerous animal and epidemiological studies are consistent with the hypothesis that environmental contaminants could contribute to the global obesity epidemic. To increase awareness of this important issue among scientists, regulatory agencies, politicians, chemical industry management, and the general public, the authors summarize compelling scientific evidence that supports the hypothesis and discuss actions that could restrict the possible harmful effects of environmental contaminants on obesity.