Polluted Pathways: Mechanisms of Metabolic Disruption by Endocrine Disrupting Chemicals

Association of per- and polyfluoroalkyl substances with the antioxidant bilirubin across pregnancy

BACKGROUND

In mechanistic and preliminary human studies, prenatal exposure to per- and polyfluoroalkyl substances (PFAS) is associated with oxidative stress, a potential contributor to maternal liver disease. Bilirubin is an endogenous antioxidant abundant in the liver that may serve as a physiological modulator of oxidative stress in pregnant people. Hence, our objective was to estimate the association between repeated measures of PFAS and bilirubin during pregnancy.

METHODS

The study population included 332 participants in the Atlanta African American Maternal-Child Cohort between 2014 and 2020. Serum samples were collected up to two times (early pregnancy: 6-18 gestational weeks; late pregnancy: 21-36 gestational weeks) for the measurement of perfluorohexane sulfonate (PFHxS), perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), and total bilirubin. We analyzed single PFAS with linear mixed effect regression and a mixture of the four PFAS with quantile g-computation. Models were repeated with a multiplicative interaction term to explore effect modification by study visit.

RESULTS

Overall, PFHxS was positively associated with bilirubin (β = 0.08, 95 % CI = 0.01, 0.15). We also found during late pregnancy, there was a positive association of PFHxS and the PFAS mixture with bilirubin (β = 0.12, 95 % CI = 0.02, 0.22; ψ = 0.19, 95 % CI = 0.03, 0.34, respectively). Finally, study visit modified the PFOA-bilirubin association (interaction p-value = 0.09), which was greater during early pregnancy (β = 0.08, 95 % CI = 0.01, 0.15).

CONCLUSION

In a prospective cohort of pregnant African Americans, an increase in PFOA, PFHxS, and the PFAS mixture was associated with an increase in bilirubin. Our results suggest that, depending on pregnancy stage, prenatal PFAS exposure disrupts the maternal liver antioxidant capacity.

Effects of Inorganic Arsenic on Type 2 Diabetes Mellitus In Vivo: the Roles and Mechanisms of miRNAs

Accumulating studies have shown that chronic exposure to iAs correlates with an increased incidence of diabetes. In recent years, miRNA dysfunction has emerged both as a response to iAs exposure and independently as candidate drivers of metabolic phenotypes such as T2DM. However, few miRNAs have been profiled during the progression of diabetes after iAs exposure in vivo. In the present study, high iAs (10 mg/L NaAsO2) exposure mice models of C57BKS/Leprdb (db/db) and C57BLKS/J (WT) were established through the drinking water, the exposure duration was 14 weeks. The results showed that high iAs exposure induced no significant changes in FBG levels in either db/db or WT mice. FBI levels, C-peptide content, and HOMA-IR levels were significantly increased, and glycogen levels in the livers were significantly lower in arsenic-exposed db/db mice. HOMA-β% was decreased significantly in WT mice exposed to high iAs. In addition, more different metabolites were found in the arsenic-exposed group than the control group in db/db mice, mainly involved in the lipid metabolism pathway. Highly expressed glucose, insulin, and lipid metabolism-related miRNAs were selected, including miR-29a-3p, miR-143-3p, miR-181a-3p, miR-122-3p, miR-22-3p, and miR-16-3p. And a series of target genes were chosen for analysis, such as ptp1b, irs1, irs2, sirt1, g6pase, pepck and glut4. The results showed that, the axles of miR-181a-3p-irs2, miR-181a-3p-sirt1, miR-22-3p-sirt1, and miR-122-3p-ptp1b in db/db mice, and miR-22-3p-sirt1, miR-16-3p-glut4 in WT mice could be considered promising targets to explore the mechanisms and therapeutic aspects of T2DM after exposure to high iAs.

Stress and human health in diabetes: A report from the 19th Chicago Biomedical Consortium symposium

Stress and diabetes coexist in a vicious cycle. Different types of stress lead to diabetes, while diabetes itself is a major life stressor. This was the focus of the Chicago Biomedical Consortium's 19th annual symposium, "Stress and Human Health: Diabetes," in November 2022. There, researchers primarily from the Chicago area met to explore how different sources of stress - from the cells to the community - impact diabetes outcomes. Presenters discussed the consequences of stress arising from mutant proteins, obesity, sleep disturbances, environmental pollutants, COVID-19, and racial and socioeconomic disparities. This symposium showcased the latest diabetes research and highlighted promising new treatment approaches for mitigating stress in diabetes.

RISING STARS: Sex differences in toxicant-associated fatty liver disease

Based on biological sex, the consequential health outcomes from exposures to environmental chemicals or toxicants can differ in disease pathophysiology, progression, and severity. Due to basal differences in cellular and molecular processes resulting from sexual dimorphism of organs including the liver and additional factors influencing 'gene-environment' interactions, males and females can exhibit different responses to toxicant exposures. Associations between environmental/occupational chemical exposures and fatty liver disease (FLD) have been well-acknowledged in human epidemiologic studies and their causal relationships demonstrated in experimental models. However, studies related to sex differences in liver toxicology are still limited to draw any inferences on sex-dependent chemical toxicity. The purpose of this review is to highlight the present state of knowledge on the existence of sex differences in toxicant-associated FLD (TAFLD), discuss potential underlying mechanisms driving these differences, implications of said differences on disease susceptibility, and emerging concepts. Chemicals of interest include various categories of pollutants that have been investigated in TAFLD, namely persistent organic pollutants, volatile organic compounds, and metals. Insight into research areas requiring further development is also discussed, with the objective of narrowing the knowledge gap on sex differences in environmental liver diseases. Major conclusions from this review exercise are that biological sex influences TAFLD risks, in part due to (i) toxicant disruption of growth hormone and estrogen receptor signaling, (ii) basal sex differences in energy mobilization and storage, and (iii) differences in chemical metabolism and subsequent body burden. Finally, further sex-dependent toxicological assessments are warranted for the development of sex-specific intervention strategies.

Perfluorooctane sulfonate-induced oxidative stress contributes to pancreatic β-cell apoptosis by inhibiting cyclic adenosine monophosphate pathway: Prevention by pentoxifylline

Endocrine-disrupting chemical perfluorooctane sulfonate (PFOS) acute exposure stimulates insulin secretion from pancreatic β-cells. However, chronic exposure to PFOS on pancreatic β-cells, its role in insulin secretion, and the underlying mechanisms have not been studied. We used rat insulinoma INS-1 and human 1.1b4 islet cells to investigate the chronic effects of PFOS on glucose-stimulated insulin secretion and toxicity implicated in the downregulation of β-cell functionality. Chronic exposure of INS-1 cells or human pancreatic 1.1b4 β-cells to PFOS stimulated the small G-protein RAC1-guanosine triphosphate-dependent nicotinamide adenine dinucleotide phosphate oxidase (NOX2/gp91phox) subunit expression and activation. Upregulated NOX2/gp91phox activation led to elevated reactive oxygen species (ROS) production with a decrease in the cyclic adenosine monophosphate/protein kinase A (cAMP/PKA) pathway in both cell types. Inhibition of cAMP/PKA signaling induces β-cell mitochondrial dysfunction and endoplasmic stress via the loss of PDX1-SERCA2B and glucose-stimulated insulin release. Inhibiting RAC1-NOX2/gp91phox activation or elevating cAMP by pentoxifylline, a Food and Drug Administration-approved phosphodiesterase inhibitor, significantly reduced PFOS-induced ROS production and restored insulin secretory function of pancreatic β-cells. Enhanced secretory function in pentoxifylline-treated cells was associated with increased stability of PDX1-SERCA2B protein levels. Intriguingly, inhibition of cAMP/PKA signaling impaired pentoxifylline-induced insulin secretion caused by the activation of ROS production and mitochondrial dysfunction. Overall, our findings show that PFOS has a new and first-ever direct chronic effect on pancreatic β-cell failure through increased RAC1-NOX2/gp91phox activation and pentoxifylline-induced cAMP/PKA signaling, which inhibits PFOS-mediated mitochondrial dysfunction.

Critical Overview on Endocrine Disruptors in Diabetes Mellitus

Diabetes mellitus is a major public health problem in all countries due to its high human and economic burden. Major metabolic alterations are associated with the chronic hyperglycemia that characterizes diabetes and causes devastating complications, including retinopathy, kidney failure, coronary disease and increased cardiovascular mortality. The most common form is type 2 diabetes (T2D) accounting for 90 to 95% of the cases. These chronic metabolic disorders are heterogeneous to which genetic factors contribute, but so do prenatal and postnatal life environmental factors including a sedentary lifestyle, overweight, and obesity. However, these classical risk factors alone cannot explain the rapid evolution of the prevalence of T2D and the high prevalence of type 1 diabetes in particular areas. Among environmental factors, we are in fact exposed to a growing amount of chemical molecules produced by our industries or by our way of life. In this narrative review, we aim to give a critical overview of the role of these pollutants that can interfere with our endocrine system, the so-called endocrine-disrupting chemicals (EDCs), in the pathophysiology of diabetes and metabolic disorders.

Relationships Between Urinary Metals and Diabetes Traits Among Mexican Americans in Starr County, Texas, USA

Hispanics/Latinos have higher rates of type 2 diabetes (T2D), and the origins of these disparities are poorly understood. Environmental endocrine-disrupting chemicals (EDCs), including some metals and metalloids, are implicated as diabetes risk factors. Data indicate that Hispanics/Latinos may be disproportionately exposed to EDCs, yet they remain understudied with respect to environmental exposures and diabetes. The objective of this study is to determine how metal exposures contribute to T2D progression by evaluating the associations between 8 urinary metals and measures of glycemic status in 414 normoglycemic or prediabetic adults living in Starr County, Texas, a Hispanic/Latino community with high rates of diabetes and diabetes-associated mortality. We used multivariable linear regression to quantify the differences in homeostatic model assessments for pancreatic β-cell function, insulin resistance, and insulin sensitivity (HOMA-β, HOMA-IR, HOMA-S, respectively), plasma insulin, plasma glucose, and hemoglobin A1c (HbA1c) associated with increasing urinary metal concentrations. Quantile-based g-computation was utilized to assess mixture effects. After multivariable adjustment, urinary arsenic and molybdenum were associated with lower HOMA-β, HOMA-IR, and plasma insulin levels and higher HOMA-S. Additionally, higher urinary copper levels were associated with a reduced HOMA-β. Lastly, a higher concentration of the 8 metal mixtures was associated with lower HOMA-β, HOMA-IR, and plasma insulin levels as well as higher HOMA-S. Our data indicate that arsenic, molybdenum, copper, and this metal mixture are associated with alterations in measures of glucose homeostasis among non-diabetics in Starr County. This study is one of the first to comprehensively evaluate associations of urinary metals with glycemic measures in a high-risk Mexican American population.

Metabolic Signatures of Youth Exposure to Mixtures of Per- and Polyfluoroalkyl Substances: A Multi-Cohort Study

BACKGROUND

Exposure to per- and polyfluoroalkyl substances (PFAS) is ubiquitous and has been associated with an increased risk of several cardiometabolic diseases. However, the metabolic pathways linking PFAS exposure and human disease are unclear.

OBJECTIVE

We examined associations of PFAS mixtures with alterations in metabolic pathways in independent cohorts of adolescents and young adults.

METHODS

Three hundred twelve overweight/obese adolescents from the Study of Latino Adolescents at Risk (SOLAR) and 137 young adults from the Southern California Children's Health Study (CHS) were included in the analysis. Plasma PFAS and the metabolome were determined using liquid-chromatography/high-resolution mass spectrometry. A metabolome-wide association study was performed on log-transformed metabolites using Bayesian regression with a g-prior specification and g-computation for modeling exposure mixtures to estimate the impact of exposure to a mixture of six ubiquitous PFAS (PFOS, PFHxS, PFHpS, PFOA, PFNA, and PFDA). Pathway enrichment analysis was performed using Mummichog and Gene Set Enrichment Analysis. Significance across cohorts was determined using weighted Z -tests.

RESULTS

In the SOLAR and CHS cohorts, PFAS exposure was associated with alterations in tyrosine metabolism (meta-analysis p = 0.00002 ) and de novo fatty acid biosynthesis (p = 0.03 ), among others. For example, when increasing all PFAS in the mixture from low (∼ 30 th percentile) to high (∼ 70 th percentile), thyroxine (T4), a thyroid hormone related to tyrosine metabolism, increased by 0.72 standard deviations (SDs; equivalent to a standardized mean difference) in the SOLAR cohort (95% Bayesian credible interval (BCI): 0.00, 1.20) and 1.60 SD in the CHS cohort (95% BCI: 0.39, 2.80). Similarly, when going from low to high PFAS exposure, arachidonic acid increased by 0.81 SD in the SOLAR cohort (95% BCI: 0.37, 1.30) and 0.67 SD in the CHS cohort (95% BCI: 0.00, 1.50). In general, no individual PFAS appeared to drive the observed associations.

DISCUSSION

Exposure to PFAS is associated with alterations in amino acid metabolism and lipid metabolism in adolescents and young adults. https://doi.org/10.1289/EHP11372.

Exploring the Effects of Metabolism-Disrupting Chemicals on Pancreatic α-Cell Viability, Gene Expression and Function: A Screening Testing Approach

Humans are constantly exposed to many environmental pollutants, some of which have been largely acknowledged as key factors in the development of metabolic disorders such as diabetes and obesity. These chemicals have been classified as endocrine-disrupting chemicals (EDCs) and, more recently, since they can interfere with metabolic functions, they have been renamed as metabolism-disrupting chemicals (MDCs). MDCs are present in many consumer products, including food packaging, personal care products, plastic bottles and containers, and detergents. The scientific literature has ever-increasingly focused on insulin-releasing pancreatic β-cells as one of the main targets for MDCs. Evidence highlights that these substances may disrupt glucose homeostasis by altering pancreatic β-cell physiology. However, their potential impact on glucagon-secreting pancreatic α-cells remains poorly known despite the essential role that this cellular type plays in controlling glucose metabolism. In the present study, we have selected seven paradigmatic MDCs representing major toxic classes, including bisphenols, phthalates, perfluorinated compounds, metals, and pesticides. By using an in vitro cell-based model, the pancreatic α-cell line αTC1-9, we have explored the effects of these compounds on pancreatic α-cell viability, gene expression, and secretion. We found that cell viability was moderately affected after bisphenol-A (BPA), bisphenol-F (BPF), and perfluorooctanesulfonic acid (PFOS) exposure, although cytotoxicity was relatively low. In addition, all bisphenols, as well as di(2-ethylhexyl) phthalate (DEHP) and cadmium chloride (CdCl₂), promoted a marked decreased on glucagon secretion, together with changes in the expression of glucagon and/or transcription factors involved in cell function and identity, such as Foxo1 and Arx. Overall, our results indicated that most of the selected chemicals studied caused functional alterations in pancreatic α-cells. Moreover, we revealed, for the first time, their direct effects on key molecular aspects of pancreatic α-cell biology.

Screening of Metabolism-Disrupting Chemicals on Pancreatic α-Cells Using In Vitro Methods

Metabolism-disrupting chemicals (MDCs) are endocrine disruptors with obesogenic and/or diabetogenic action. There is mounting evidence linking exposure to MDCs to increased susceptibility to diabetes. Despite the important role of glucagon in glucose homeostasis, there is little information on the effects of MDCs on α-cells. Furthermore, there are no methods to identify and test MDCs with the potential to alter α-cell viability and function. Here, we used the mouse α-cell line αTC1-9 to evaluate the effects of MDCs on cell viability and glucagon secretion. We tested six chemicals at concentrations within human exposure (from 0.1 pM to 1 µM): bisphenol-A (BPA), tributyltin (TBT), perfluorooctanoic acid (PFOA), triphenylphosphate (TPP), triclosan (TCS), and dichlorodiphenyldichloroethylene (DDE). Using two different approaches, MTT assay and DNA-binding dyes, we observed that BPA and TBT decreased α-cell viability via a mechanism that depends on the activation of estrogen receptors and PPARγ, respectively. These two chemicals induced ROS production, but barely altered the expression of endoplasmic reticulum (ER) stress markers. Although PFOA, TPP, TCS, and DDE did not alter cell viability nor induced ROS generation or ER stress, all four compounds negatively affected glucagon secretion. Our findings suggest that αTC1-9 cells seem to be an appropriate model to test chemicals with metabolism-disrupting activity and that the improvement of the test methods proposed herein could be incorporated into protocols for the screening of diabetogenic MDCs.

In vitro biochemical assessment of mixture effects of two endocrine disruptors on INS-1 cells

4-tert-Octylphenol (4-tOP) is a component of non-ionic surfactants alkylphenol polyethoxylates while triclosan (TCS) is an antibacterial present in personal care products. Both compounds can co-exist in environmental matrices such as soil and water. The mixture effects of these micropollutants in vitro remains unknown. INS-1 cells were exposed to 20 µM or 30 µM 4-tOP and 8 µM or 12.5 µM TCS as well as equimolar mixture of the chemicals (Mix) in total concentration of 12.5 µM or 25 µM for 48 h. Mitochondrial related parameters were investigated using high content analytical techniques. The cytotoxicity of the chemicals (IC₅₀) varied according to TCS > Mix > 4-tOP. Increased glucose uptake and loss of mitochondrial membrane potential were recorded in TCS and Mix treated cells. Fold values of glucose-galactose assay varied according to dinitrophenol > TCS > 4-tOP > Mix in decreasing order of mitochondrial toxicity. The loss of the intracellular Ca²⁺ influx by all the test substances and Mix was not substantial whereas glibenclamide and diazoxide increased the intracellular Ca²⁺ influx when compared with the Blank. The recorded increase in Ca²⁺ influx by diazoxide which contrasted with its primary role of inhibiting insulin secretion need be re-investigated. It is concluded that the toxic effects of TCS and Mix but not 4-tOP on INS-1 cells was mitochondria-mediated.

In Vitro Assays to Identify Metabolism-Disrupting Chemicals with Diabetogenic Activity in a Human Pancreatic β-Cell Model

There is a need to develop identification tests for Metabolism Disrupting Chemicals (MDCs) with diabetogenic activity. Here we used the human EndoC-βH1 β-cell line, the rat β-cell line INS-1E and dispersed mouse islet cells to assess the effects of endocrine disruptors on cell viability and glucose-stimulated insulin secretion (GSIS). We tested six chemicals at concentrations within human exposure (from 0.1 pM to 1 µM). Bisphenol-A (BPA) and tributyltin (TBT) were used as controls while four other chemicals, namely perfluorooctanoic acid (PFOA), triphenylphosphate (TPP), triclosan (TCS) and dichlorodiphenyldichloroethylene (DDE), were used as “unknowns”. Regarding cell viability, BPA and TBT increased cell death as previously observed. Their mode of action involved the activation of estrogen receptors and PPARγ, respectively. ROS production was a consistent key event in BPA-and TBT-treated cells. None of the other MDCs tested modified viability or ROS production. Concerning GSIS, TBT increased insulin secretion while BPA produced no effects. PFOA decreased GSIS, suggesting that this chemical could be a “new” diabetogenic agent. Our results indicate that the EndoC-βH1 cell line is a suitable human β-cell model for testing diabetogenic MDCs. Optimization of the test methods proposed here could be incorporated into a set of protocols for the identification of MDCs.

Emerging concepts and opportunities for endocrine disruptor screening of the non-EATS modalities

Endocrine disrupting chemicals (EDCs) are ubiquitous in the environment and involve diverse chemical-receptor interactions that can perturb hormone signaling. The Organization for Economic Co-operation and Development has validated several EDC-receptor bioassays to detect endocrine active chemicals and has established guidelines for regulatory testing of EDCs. Focus on testing over the past decade has been initially directed to EATS modalities (estrogen, androgen, thyroid, and steroidogenesis) and validated tests for chemicals that exert effects through non-EATS modalities are less established. Due to recognition that EDCs are vast in their mechanisms of action, novel bioassays are needed to capture the full scope of activity. Here, we highlight the need for validated assays that detect non-EATS modalities and discuss major international efforts underway to develop such tools for regulatory purposes, focusing on non-EATS modalities of high concern (i.e., retinoic acid, aryl hydrocarbon receptor, peroxisome proliferator-activated receptor, and glucocorticoid signaling). Two case studies are presented with strong evidence amongst animals and human studies for non-EATS disruption and associations with wildlife and human disease. This includes metabolic syndrome and insulin signaling (case study 1) and chemicals that impact the cardiovascular system (case study 2). This is relevant as obesity and cardiovascular disease represent two of the most significant health-related crises of our time. Lastly, emerging topics related to EDCs are discussed, including recognition of crosstalk between the EATS and non-EATS axis, complex mixtures containing a variety of EDCs, adverse outcome pathways for chemicals acting through non-EATS mechanisms, and novel models for testing chemicals. Recommendations and considerations for evaluating non-EATS modalities are proposed. Moving forward, improved understanding of the non-EATS modalities will lead to integrated testing strategies that can be used in regulatory bodies to protect environmental, animal, and human health from harmful environmental chemicals.

Advances in organophosphorus pesticides pollution: Current status and challenges in ecotoxicological, sustainable agriculture, and degradation strategies

Organophosphorus pesticides (OPPs) are one of the most widely used types of pesticide that play an important role in the production process due to their effects on preventing pathogen infection and increasing yield. However, in the early development and application of OPPs, their toxicological effects and the issue of environmental pollution were not considered. With the long-term overuse of OPPs, their hazards to the ecological environment (including soil and water) and animal health have attracted increasing attention. Therefore, this review first clarified the classification, characteristics, applications of various OPPs, and the government's restriction requirements on various OPPs. Second, the toxicological effects and metabolic mechanisms of OPPs and their metabolites were introduced in organisms. Finally, the existing methods of degrading OPPs were summarized, and the challenges and further addressing strategy of OPPs in the sustainable development of agriculture, the environment, and ecology were prospected. However, methods to solve the environmental and ecological problems caused by OPPs from the three aspects of use source, use process, and degradation methods were proposed, which provided a theoretical basis for addressing the stability of the ecological environment and improving the structure of the pesticide industry in the future.

An investigation into the biological effects of indirect potable reuse water using zebrafish embryos

Advanced treatment technologies are being assessed as a proactive measure to assist with the transformation of treated wastewater into a source of water for potable water production. We investigated the biological effects along an advanced water treatment pilot plant, using zebrafish embryos throughout early development. The study compared phenotypic observations with global transcriptome responses, enabling us to keep an open mind about the chemicals that might influence the biological activity. There was no evidence of acute toxicity at any treatment stage, but skeletal, cardiovascular and pigmentation changes occurred in a small proportion of embryos along the treatment process, and in a tap water; not detected in the aquarium water control. Reverse osmosis (RO) reduced the concentration of measured chemical contaminants in the water the most, while eliminating the occurrence of abnormalities detected in fish embryos. Conversely, advanced oxidation reversed the benefits of RO treatment by increasing the frequency of teratogenic and sub-lethal abnormalities seen. Using the molecular responses of zebrafish embryos to different IPR water, we report the bioactivity within the water at different stages of advanced treatment and associate these to perturbed biological functions. Transcriptomic analysis revealed alterations to the retinoid system, which was consistent with the observed teratogenic effects. Changes to tryptophan metabolism (associated with the production of melatonin required for the control of normal circadian rhythms) and somatolactin-beta (associated with normal pigmentation in fish) were also found. We show that underexplored forms of biological activity occur in treated wastewater effluent, and/or may be created depending on the type of advanced treatment process used. By integrating the available analytical chemistry we highlight chemical groups associated to this response. Our study shows that more detailed and in-depth characterisation of chemicals and biological pathways associated with advanced treatment water systems are needed to mitigate possible risks to downstream organisms.

Developmental origins of metabolic diseases

Almost 2 billion adults in the world are overweight, and more than half of them are classified as obese, while nearly one-third of children globally experience poor growth and development. Given the vast amount of knowledge that has been gleaned from decades of research on growth and development, a number of questions remain as to why the world is now in the midst of a global epidemic of obesity accompanied by the "double burden of malnutrition," where overweight coexists with underweight and micronutrient deficiencies. This challenge to the human condition can be attributed to nutritional and environmental exposures during pregnancy that may program a fetus to have a higher risk of chronic diseases in adulthood. To explore this concept, frequently called the developmental origins of health and disease (DOHaD), this review considers a host of factors and physiological mechanisms that drive a fetus or child toward a higher risk of obesity, fatty liver disease, hypertension, and/or type 2 diabetes (T2D). To that end, this review explores the epidemiology of DOHaD with discussions focused on adaptations to human energetics, placental development, dysmetabolism, and key environmental exposures that act to promote chronic diseases in adulthood. These areas are complementary and additive in understanding how providing the best conditions for optimal growth can create the best possible conditions for lifelong health. Moreover, understanding both physiological as well as epigenetic and molecular mechanisms for DOHaD is vital to most fully address the global issues of obesity and other chronic diseases.

Epigenetic Modifications Associated with Exposure to Endocrine Disrupting Chemicals in Patients with Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) remains a significant clinical and public health issue due to its increasing prevalence and the possibility for numerous short- and long-term complications. The growing incidence of GDM seems to coincide with the widespread use of endocrine disrupting chemicals (EDCs). The extensive production and common use of these substances in everyday life has resulted in constant exposure to harmful substances from the environment. That may result in epigenetic changes, which may manifest themselves also after many years and be passed on to future generations. It is important to consider the possible link between environmental exposure to endocrine disrupting chemicals (EDCs) during pregnancy, epigenetic mechanisms and an increased risk for developing gestational diabetes mellitus (GDM). This manuscript attempts to summarize data on epigenetic changes in pregnant women suffering from gestational diabetes in association with EDCs. There is a chance that epigenetic marks may serve as a tool for diagnostic, prognostic, and therapeutic measures.

Human Pluripotent Stem Cells: A Unique Tool for Toxicity Testing in Pancreatic Progenitor and Endocrine Cells

Diabetes prevalence is increasing worldwide, and epidemiological studies report an association between diabetes incidence and environmental pollutant exposure. There are >84,000 chemicals in commerce, many of which are released into the environment without a clear understanding of potential adverse health consequences. While in vivo rodent studies remain an important tool for testing chemical toxicity systemically, we urgently need high-throughput screening platforms in biologically relevant models to efficiently prioritize chemicals for in depth toxicity analysis. Given the increasing global burden of obesity and diabetes, identifying chemicals that disrupt metabolism should be a high priority. Pancreatic endocrine cells are key regulators of systemic metabolism, yet often overlooked as a target tissue in toxicology studies. Immortalized β-cell lines and primary human, porcine, and rodent islets are widely used for studying the endocrine pancreas in vitro, but each have important limitations in terms of scalability, lifespan, and/or biological relevance. Human pluripotent stem cell (hPSC) culture is a powerful tool for in vitro toxicity testing that addresses many of the limitations with other β-cell models. Current in vitro differentiation protocols can efficiently generate glucose-responsive insulin-secreting β-like cells that are not fully mature, but still valuable for high-throughput toxicity screening in vitro. Furthermore, hPSCs can be applied as a model of developing pancreatic endocrine cells to screen for chemicals that influence endocrine cell formation during critical windows of differentiation. Given their versatility, we recommend using hPSCs to identify potential β-cell toxins, which can then be prioritized as chemicals of concern for metabolic disruption.

From bench to bedside: Biosensing strategies to evaluate endocrine disrupting compounds based on epigenetic events and their potential use in medicine

The relationship between endocrine system disorders and health risks due to chemical environmental compounds has become a growing concern in recent years. Involuntary exposure to endocrine disruptors (EDCs) is associated with the worldwide increase of diseases such as cancer, obesity, diabetes, and neurocortical disorders. EDCs are compounds that target the nuclear hormonereceptors (NHR) leading to epigenetic changes. Consequently, the use of biosensing strategies based on epigenetic events have a great potential to provide outstanding information about the exposition of EDCs and their evaluation in human health. This review addresses the novel trends in biosensing EDCs evaluation based on DNA methylation assays associated with different human diseases.

20th Pollutant Responses in Marine Organisms (PRIMO 20): Global issues and fundamental mechanisms caused by pollutant stress in marine and freshwater organisms

The 20th Pollutant Responses in Marine Organisms (PRIMO 20) conference provided a forum for scientists from around the world to communicate novel toxicological research findings specifically focused on aquatic organisms, by combining applied and basic research at the intersection of environmental and mechanistic toxicology. The work highlighted in this special issue of Aquatic Toxicology, a special issue of Marine Environmental Research, and presented through posters and presentations, encompass important and emerging topics in freshwater and marine toxicology. This includes multiple types of emerging contaminants including microplastics and UV filtering chemicals. Other studies aimed to further our understanding of the effects of endocrine disrupting chemicals, pharmaceuticals, and personal care products. Further research presented in this virtual issue examined the interactive effects of chemicals and pathogens, while the final set of manuscripts demonstrates continuing efforts to combine traditional biomonitoring, data from -omic technologies, and modeling for use in risk assessment and management. An additional goal of PRIMO meetings is to address the link between environmental and human health. Several articles in this issue of Aquatic Toxicology describe the appropriateness of using aquatic organisms as models for human health, while the keynote speakers, as described in the editorial below, presented research that highlighted bioaccumulation of contaminants such as PFOS and mercury from fish to marine mammals and coastal human populations such as the Gullah/GeeChee near Charleston, South Carolina, USA.

Bisphenol-A exposure during pregnancy alters pancreatic β-cell division and mass in male mice offspring: A role for ERβ

Bisphenol-A (BPA) is a widespread endocrine disrupting chemical that constitutes a risk factor for type 2 diabetes mellitus (T2DM). Data from animal and human studies have demonstrated that early exposure to BPA results in adverse metabolic outcomes in adult life. In the present work, we exposed pregnant heterozygous estrogen receptor β (ERβ) knock out (BERKO) mice to 10 μg/kg/day BPA, during days 9-16 of pregnancy, and measured β-cell mass and proliferation in wildtype (WT) and BERKO male offspring at postnatal day 30. We observed increased pancreatic β-cell proliferation and mass in WT, yet no effect was produced in BERKO mice. Dispersed islet cells in primary culture treated with 1 nM BPA showed an enhanced pancreatic β-cell replication rate, which was blunted in pancreatic β-cells from BERKO mice and mimicked by the selective ERβ agonist WAY200070. This increased β-cell proliferation was found in male adult as well as in neonate pancreatic β-cells, suggesting that BPA directly impacts β-cell division at earliest stages of life. These findings strongly indicate that BPA during pregnancy upregulates pancreatic β-cell division and mass in an ERβ-dependent manner. Thus, other natural or artificial chemicals may use this ERβ-mediated pathway to promote similar effects.

Stress, Sex, and Sugar: Glucocorticoids and Sex-Steroid Crosstalk in the Sex-Specific Misprogramming of Metabolism

Early-life exposures to environmental insults can misprogram development and increase metabolic disease risk in a sex-dependent manner by mechanisms that remain poorly characterized. Modifiable factors of increasing public health relevance, such as diet, psychological stress, and endocrine-disrupting chemicals, can affect glucocorticoid receptor signaling during gestation and lead to sex-specific postnatal metabolic derangements. Evidence from humans and animal studies indicate that glucocorticoids crosstalk with sex steroids by several mechanisms in multiple tissues and can affect sex-steroid-dependent developmental processes. Nonetheless, glucocorticoid sex-steroid crosstalk has not been considered in the glucocorticoid-induced misprogramming of metabolism. Herein we review what is known about the mechanisms by which glucocorticoids crosstalk with estrogen, androgen, and progestogen action. We propose that glucocorticoid sex-steroid crosstalk is an understudied mechanism of action that requires consideration when examining the developmental misprogramming of metabolism, especially when assessing sex-specific outcomes.

Prostate cancer early diagnosis: circulating microRNA pairs potentially beyond single microRNAs upon 1231 serum samples

The accuracy of prostate-specific antigen or clinical examination in prostate cancer (PCa) screening is in question, and circulating microRNAs (miRNAs) can be alternatives to PCa diagnosis. However, recent circulating miRNA biomarkers either are identified upon small sample sizes or cannot have robust diagnostic performance in every aspect of performance indicators. These may decrease applicability of potential biomarkers for the early detection of PCa. We reviewed recent studies on blood-derived miRNAs for prostate cancer diagnosis and carried out a large case study to understand whether circulating miRNA pairs, rather than single circulating miRNAs, could contribute to a more robust diagnostic model to significantly improve PCa diagnosis. We used 1231 high-throughput miRNA-profiled serum samples from two cohorts to design and verify a model based on class separability miRNA pairs (cs-miRPs). The pairwise model was composed of five circulating miRNAs coupled to miR-5100 and miR-1290 (i.e. five miRNA pairs, 5-cs-miRPs), reaching approximately 99% diagnostic performance in almost all indicators (sensitivity = 98.96%, specificity = 100%, accuracy = 99.17%, PPV = 100%, NPV = 96.15%) shown by a test set (n = 484: PCa = 384, negative prostate biopsies = 100). The nearly 99% diagnostic performance was also verified by an additional validation set (n = 140: PCa = 40, healthy controls = 100). Overall, the 5-cs-miRP model had 1 false positive and 7 false negatives among the 1231 serum samples and was superior to a recent 2-miRNA model (so far the best for PCa diagnosis) with 18 false positives and 80 false negatives. The present large case study demonstrated that circulating miRNA pairs could potentially bring more benefits to PCa early diagnosis for clinical practice.

Endocrine-Disrupting Chemicals and Insulin Resistance in Children

The purpose of this article is to review the evidence linking background exposure to endocrine-disrupting chemicals (EDCs) with insulin resistance in children. Although evidence in children is scarce since very few prospective studies exist even in adults, evidence that EDCs might be involved in the development of insulin resistance and related diseases such as obesity and diabetes is accumulating. We reviewed the literature on both cross-sectional and prospective studies in humans and experimental studies. Epidemiological studies show a statistical link between exposure to pesticides, polychlorinated bisphenyls, bisphenol A, phthalates, aromatic polycyclic hydrocarbides, or dioxins and insulin resistance.

The GOLIATH Project: Towards an Internationally Harmonised Approach for Testing Metabolism Disrupting Compounds

The purpose of this project report is to introduce the European "GOLIATH" project, a new research project which addresses one of the most urgent regulatory needs in the testing of endocrine-disrupting chemicals (EDCs), namely the lack of methods for testing EDCs that disrupt metabolism and metabolic functions. These chemicals collectively referred to as "metabolism disrupting compounds" (MDCs) are natural and anthropogenic chemicals that can promote metabolic changes that can ultimately result in obesity, diabetes, and/or fatty liver in humans. This project report introduces the main approaches of the project and provides a focused review of the evidence of metabolic disruption for selected EDCs. GOLIATH will generate the world's first integrated approach to testing and assessment (IATA) specifically tailored to MDCs. GOLIATH will focus on the main cellular targets of metabolic disruption-hepatocytes, pancreatic endocrine cells, myocytes and adipocytes-and using an adverse outcome pathway (AOP) framework will provide key information on MDC-related mode of action by incorporating multi-omic analyses and translating results from in silico, in vitro, and in vivo models and assays to adverse metabolic health outcomes in humans at real-life exposures. Given the importance of international acceptance of the developed test methods for regulatory use, GOLIATH will link with ongoing initiatives of the Organisation for Economic Development (OECD) for test method (pre-)validation, IATA, and AOP development.

Consensus on the key characteristics of endocrine-disrupting chemicals as a basis for hazard identification

Endocrine-disrupting chemicals (EDCs) are exogenous chemicals that interfere with hormone action, thereby increasing the risk of adverse health outcomes, including cancer, reproductive impairment, cognitive deficits and obesity. A complex literature of mechanistic studies provides evidence on the hazards of EDC exposure, yet there is no widely accepted systematic method to integrate these data to help identify EDC hazards. Inspired by work to improve hazard identification of carcinogens using key characteristics (KCs), we have developed ten KCs of EDCs based on our knowledge of hormone actions and EDC effects. In this Expert Consensus Statement, we describe the logic by which these KCs are identified and the assays that could be used to assess several of these KCs. We reflect on how these ten KCs can be used to identify, organize and utilize mechanistic data when evaluating chemicals as EDCs, and we use diethylstilbestrol, bisphenol A and perchlorate as examples to illustrate this approach.

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.

Association of urinary phthalate metabolites and phenolics with adipokines and insulin resistance related markers among women of reproductive age

Chemicals such as phthalates and phenolics have been associated with metabolic markers in humans. However, most studies have only looked at a limited number of chemicals, and little is known about their potential effects on adipokines in humans. In the present study, the associations between dozens of urinary chemicals, including phthalate metabolites and phenolics, and markers related to insulin resistance as well as major adipokines, were assessed among the women of reproductive age (n = 459, between 20 and 48 years of age) recruited from major cities in Korea between 2015 and 2016. Adipokines such as adiponectin and leptin, and insulin resistance related markers such as glucose and insulin, were analyzed in serum. Associations between urinary chemicals and the adipokines or insulin resistance related markers were assessed in two steps. First, ordinary least squares (OLS) regression was used to assess the association of each urinary chemical with the adipokines or insulin resistance related markers (single-pollutant model). Second, several chemicals were selected using elastic net regression and were subsequently analyzed with OLS regression model (multi-pollutant model), considering simultaneous exposure to multiple chemicals. In both single- and multi-pollutant models, several urinary chemicals consistently showed significant associations with adipokines or the insulin resistance related markers. The sum of di-(2-ethylhexyl) phthalate metabolites (ΣDEHPm) and ethyl paraben (EtP) were associated with increased serum adiponectin levels. Urinary ΣDEHPm levels also showed positive associations with fasting glucose. Moreover, urinary mono-methyl phthalate (MMP), mono-isobutyl phthalate (MiBP), and bisphenol S (BPS) levels showed positive associations with the homeostasis model assessment for insulin resistance (HOMA-IR). Interestingly, urinary propyl paraben (PrP) levels showed a negative association with HOMA-IR, in both models. Our observations show that among many consumer chemicals, phthalates may affect serum adipokines, and thus glucose, and insulin resistance in adult females. Further confirmation is warranted in other populations.

Environmental neglect: endocrine disruptors as underappreciated but potentially modifiable diabetes risk factors

Type 2 diabetes prevalence is increasing dramatically across the globe, imposing a tremendous toll on individuals and healthcare systems. Reversing these trends requires comprehensive approaches to address both classical and emerging diabetes risk factors. Recently, environmental toxicants acting as endocrine-disrupting chemicals (EDCs) have emerged as novel metabolic disease risk factors. EDCs implicated in diabetes pathogenesis include various inorganic and organic molecules of both natural and synthetic origin, including arsenic, bisphenol A, phthalates, polychlorinated biphenyls and organochlorine pesticides. Indeed, evidence implicates EDC exposures across the lifespan in metabolic dysfunction; moreover, specific developmental windows exhibit enhanced sensitivity to EDC-induced metabolic disruption, with potential impacts across generations. Importantly, differential exposures to diabetogenic EDCs likely also contribute to racial/ethnic and economic disparities. Despite these emerging links, clinical practice guidelines fail to address this underappreciated diabetes risk factor. Comprehensive approaches to stem the tide of diabetes must include efforts to address its environmental drivers.

Di-n-butyl phthalate induced autophagy of uroepithelial cells via inhibition of hedgehog signaling in newborn male hypospadias rats

Maternal exposure to di-n-butyl phthalate (DBP) induces hypospadias via regulation of autophagy in uroepithelial cells. Here, we use gene express analysis to explore the underlying molecular mechanisms. Pregnant rats received DBP orally at a dose of 750 mg/kg/day during gestational days 14-18. Gene expression analysis showed an increased expression of the hedgehog interacting protein (HhIP) gene. In DBP-induced hypospadiac male offspring, immunohistochemistry (IHC) staining and Western blot analysis confirmed increased expression of the HhIP protein and inhibited hedgehog signaling. in vitro experiments suggest the involvement of the reactive oxygen species (ROS)-HhIP-Gli1-autophagy axis in DBP-treated primary rat urethral epithelial cells. Taken together, our findings show that prenatal exposure to DBP induces abnormal hedgehog signaling and autophagy in uroepithelial cells that may play important roles in the development of hypospadias.

Assessment of the endocrine-disrupting effects of organophosphorus pesticide triazophos and its metabolites on endocrine hormones biosynthesis, transport and receptor binding in silico

Triazophos (TAP) was a widely used organophosphorus insecticide in developing countries. TAP could produce specific metabolites triazophos-oxon (TAPO) and 1-phenyl-3-hydroxy-1,2,4-triazole (PHT) and non-specific metabolites diethylthiophosphate (DETP) and diethylphosphate (DEP). The objective of this study involved computational approaches to discover potential mechanisms of molecular interaction of TAP and its major metabolites with endocrine hormone-related proteins using molecular docking in silico. We found that TAP, TAPO and DEP showed high binding affinity with more proteins and enzymes than PHT and DETP. TAP might interfere with the endocrine function of the adrenal gland, and TAP might also bind strongly with glucocorticoid receptors and thyroid hormone receptors. TAPO might disrupt the normal binding of androgen receptor, estrogen receptor, progesterone receptor and adrenergic receptor to their natural hormone ligands. DEP might affect biosynthesis of steroid hormones and thyroid hormones. Meanwhile, DEP might disrupt the binding and transport of thyroid hormones in the blood and the normal binding of thyroid hormones to their receptors. These results suggested that TAP and DEP might have endocrine disrupting activities and were potential endocrine disrupting chemicals. Our results provided further reference for the comprehensive evaluation of toxicity of organophosphorus chemicals and their metabolites.

Identifying sex differences arising from polychlorinated biphenyl exposures in toxicant-associated liver disease

Exposures to persistent environmental pollutants like polychlorinated biphenyls (PCBs) has been associated with liver diseases such as toxicant-associated steatohepatitis (TASH). However, previously published PCB hepatotoxicity studies evaluated mostly male animal models. Moreover, epidemiologic studies on PCB-exposed cohorts evaluating sex differences are scarce. Therefore, the objective of this study was to examine hepato-toxicological responses of PCB exposures in the context of sex-dependent outcomes. Male and female C57Bl/6 mice were exposed to Aroclor 1260 (20 mg/kg), and PCB126 (20 μg/kg), by gavage for two weeks. Female mice appeared to be more sensitive to PCB-induced hepatotoxic effects as manifested by increased liver injury markers, namely, hepatic Serpine1 expression. Additionally, compared to their male counterparts, PCB-exposed females exhibited dysregulated hepatic gene expression favoring lipid accumulation rather than lipid breakdown; accompanied by dyslipidemia. Sex differences were also observed in the expression and activation of PCB targets such as the epidermal growth factor receptor (EGFR) while PCB-induced pancreatic toxicity was similar in both sexes. Importantly, PCB exposure appeared to cause pro-androgenic, anti-estrogenic along with sex-dependent thyroid hormone effects. The overall findings demonstrated that the observed PCB-mediated hepatotoxicity was sex-dependent; confirming the existence of sex differences in environmental exposure-induced markers of TASH and warrants further investigation.

Exposure to bisphenol A: current levels from food intake are toxic to human cells

In the present work, cell lines of different origin were exposed to BPA levels from food intake reported elsewhere. Specifically, we used an in vitro assay to determine cytotoxicity of BPA in three cell lines: MCF7 (breast cancer), PC3 (prostate cancer) and 3T3-L1 (mouse fibroblast). Cytotoxic effects were observed at concentrations higher than 50 μg/mL which is above the involuntary exposure level of BPA described before in fresh, canned and frozen foods and beverages. Furthermore, medial inhibitory concentrations (IC50) of 85.17 μg/mL and 88.48 μg/mL were observed for PC3 and 3T3-L1, respectively, and a slightly lower IC50 of 64.67 μg/mL for MCF7. These results highlight BPA's toxicity potential at current levels from food intake. The cell line-dependent divergent response to BPA reported herein is discussed.

Interventions to Address Environmental Metabolism-Disrupting Chemicals: Changing the Narrative to Empower Action to Restore Metabolic Health

Metabolic disease rates have increased dramatically over the last four decades. Classic understanding of metabolic physiology has attributed these global trends to decreased physical activity and caloric excess; however, these traditional risk factors insufficiently explain the magnitude and rapidity of metabolic health deterioration. Recently, the novel contribution of environmental metabolism-disrupting chemicals (MDCs) to various metabolic diseases (including obesity, diabetes, and non-alcoholic fatty liver disease) is becoming recognized. As this burgeoning body of evidence has matured, various organic and inorganic pollutants of human and natural origin have emerged as metabolic disease risk factors based on population-level and experimental data. Recognition of these heretofore underappreciated metabolic stressors now mandates that efforts to mitigate the devastating consequences of metabolic disease include dedicated efforts to address environmental drivers of disease risk; however, there have not been adequate recommendations to reduce exposures or to mitigate the effects of exposures on disease outcomes. To address this knowledge gap and advance the clinical translation of MDC science, herein discussed are behaviors that increase exposures to MDCs, interventional studies to reduce those exposures, and small-scale clinical trials to reduce the body burden of MDCs. Also, we discuss evidence from cell-based and animal studies that provide insights into MDC mechanisms of action, the influence of modifiable dietary factors on MDC toxicity, and factors that modulate MDC transplacental carriage as well as their impact on metabolic homeostasis. A particular emphasis of this discussion is on critical developmental windows during which short-term MDC exposure can elicit long-term disruptions in metabolic health with potential inter- and transgenerational effects. While data gaps remain and further studies are needed, the current state of evidence regarding interventions to address MDC exposures illuminates approaches to address environmental drivers of metabolic disease risk. It is now incumbent on clinicians and public health agencies to incorporate this knowledge into comprehensive strategies to address the metabolic disease pandemic.

History of the Obesogen Field: Looking Back to Look Forward

The Obesogen field developed from two separate scientific research areas, endocrine disruptors and the Developmental Origins of Health and Disease (DOHaD). Endocrine Disrupting Chemicals (EDCs) are exogenous chemicals or mixtures of chemicals that interfere with the action of hormones. Exposure to EDCs during early development (DOHaD) has been shown to increase susceptibility to a variety of diseases including infertility, asthma, breast and prostate cancer, early puberty, susceptibility to infections, heart disease, autoimmune disease, and attention deficit hyperactivity disorder/learning disability. The effects of EDCs on obesity and fat cell development first gained attention around the turn of the twenty-first century. In 2002 Dr. Paula Baillie-Hamilton wrote the first review article focusing on environmental chemicals and obesity. She suggested that the obesity epidemic correlated with the increased production of chemicals after World War II. Baillie-Hamilton identified studies showing that exposures to a variety of chemicals led to weight gain. Shortly after that a commentary on an article showing that nonylphenol would increase fat cell differentiation in vitro noted the Baillie-Hamilton article and made the point that perhaps obesity was due in part to exposure to EDCs. In 2006 the field of DOHaD/EDCs and obesity made a giant leap forward when Dr. Bruce Blumberg published a paper showing that tributyltin could lead to weight gain in mice and coined the term obesogen for a chemical that caused weight gain and lead to obesity. In 2011, the NIEHS developed the first funding initiative focused on obesogens. In the following years there have been several workshops focused on obesogens. This paper describes these early days that lead to the obesogen hypotheses and the growth of the field for a decade, leading to its prominence today, and provides some insight into where the field is moving.

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.

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.

Retinoid X Receptor Activation During Adipogenesis of Female Mesenchymal Stem Cells Programs a Dysfunctional Adipocyte

Early life exposure to endocrine-disrupting chemicals (EDCs) is an emerging risk factor for the development of obesity and diabetes later in life. We previously showed that prenatal exposure to the EDC tributyltin (TBT) results in increased adiposity in the offspring. These effects linger into adulthood and are propagated through successive generations. TBT activates two nuclear receptors, the peroxisome proliferator-activated receptor (PPAR) γ and its heterodimeric partner retinoid X receptor (RXR), that promote adipogenesis in vivo and in vitro. We recently employed a mesenchymal stem cell (MSC) model to show that TBT promotes adipose lineage commitment by activating RXR, not PPARγ. This led us to consider the functional consequences of PPARγ vs RXR activation in developing adipocytes. We used a transcriptomal approach to characterize genome-wide differences in MSCs differentiated with the PPARγ agonist rosiglitazone (ROSI) or TBT. Pathway analysis suggested functional deficits in TBT-treated cells. We then compared adipocytes differentiated with ROSI, TBT, or a pure RXR agonist IRX4204 (4204). Our data show that RXR activators ("rexinoids," 4204 and TBT) attenuate glucose uptake, blunt expression of the antidiabetic hormone adiponectin, and fail to downregulate proinflammatory and profibrotic transcripts, as does ROSI. Finally, 4204 and TBT treatment results in an inability to induce markers of adipocyte browning, in part due to sustained interferon signaling. Taken together, these data implicate rexinoids in the development of dysfunctional white adipose tissue that could potentially exacerbate obesity and/or diabetes risk in vivo. These data warrant further screening and characterization of EDCs that activate RXR.

Effects of Perinatal Exposure to Dibutyltin Chloride on Fat and Glucose Metabolism in Mice, and Molecular Mechanisms, in Vitro

BACKGROUND

The organotin dibutyltin (DBT) is used in the manufacture of polyvinyl chloride (PVC) plastics, in construction materials, and in medical devices. Previous animal studies showed detrimental effects of DBT during in utero development at relatively high doses, but little was known about the effects of DBT exposure at environmentally relevant doses on endpoints such as obesity and metabolic disease.

OBJECTIVES

We tested the potential obesogenic effects of DBT using in vitro and in vivo models.

METHODS

We evaluated the effects of DBT on nuclear receptor activation and adipogenic potential using human and mouse multipotent mesenchymal stromal stem cells (MSCs). We also evaluated the effects of perinatal exposure to environmentally relevant doses of DBT in C57BL/6J mice.

RESULTS

DBT activated human and mouse PPARγ and RXRα in transient transfection assays, increased expression of adipogenic genes, promoted adipogenic differentiation and increased lipid accumulation in mouse and human MSCs, in vitro. DBT-induced adipogenic differentiation was abolished by the PPARγ antagonist T0070907, indicating that DBT was acting primarily through PPARγ. Perinatal exposure to low doses of DBT led to increased fat storage, decreased glucose tolerance, and increased circulating leptin levels in male, but not female, mice.

CONCLUSIONS

DBT acted as an obesogen by inducing lipid accumulation in human and mouse MSCs through a PPARγ-dependent pathway. In vivo exposure to biologically relevant doses of DBT during perinatal development led to increased fat storage, elevated leptin levels in plasma, and glucose intolerance in mice. Based on these findings, we posit that monitoring of DBT levels in human samples may aid in understanding and potentially preventing the rising rates of metabolic disorders in human populations. https://doi.org/10.1289/EHP3030.

Underutilized and Under Threat: Environmental Policy as a Tool to Address Diabetes Risk

PURPOSE OF REVIEW

Diabetes is a burgeoning threat to public health in the USA. Importantly, the burden of diabetes is not equally borne across society with marked disparities based on geography, race/ethnicity, and income. The etiology of global and population-specific diabetes risk remains incompletely understood; however, evidence linking environmental toxicants acting as endocrine-disrupting chemicals (EDCs), such as particulate matter and arsenic, with diabetes suggests that environmental policies could play an important role in diabetes risk reduction.

RECENT FINDINGS

Evidence suggests that disproportionate exposures to EDCs may contribute to subgroup-specific diabetes risk; however, no federal policies regulate EDCs linked to diabetes based upon diabetogenic potential. Nevertheless, analyses of European Union data indicate that such regulation could reduce diabetes-associated costs and disease burden. Federal laws only regulate EDCs indirectly. The accumulating evidence linking these chemicals with diabetes risk should encourage policymakers to adopt stricter environmental standards that consider both health and economic impacts.

Persistent Endocrine-Disrupting Chemicals and Fatty Liver Disease

PURPOSE OF REVIEW

Non-alcoholic fatty liver disease (NAFLD) is the most prominent chronic liver disease in Western countries, affecting approximately 25% of the population worldwide. Sex-specific differences in the development of NAFLD are apparent. While obesity and insulin resistance are major contributors to the increasing prevalence of NAFLD, a growing body of literature suggests that exposure to persistent endocrine-disrupting chemicals (pEDCs) may also play a role. This review summarizes recent (2011 and later) scientific literature investigating exposures to pEDCs, specifically persistent organic pollutants (POPs), and NAFLD, with a focus on sex-specific associations.

RECENT FINDINGS

The overwhelming majority of studies were conducted in single-sex animal models and provide biological evidence that exposures to 2,3,7,8-tetrachlorodibenzo-p-dioxin polychlorinated biphenyls, and other POPs or POP mixtures are negatively associated with liver health. There were four cross-sectional epidemiological studies in humans that reported associations for several POPs, including polychlorinated biphenyls and perfluorinated chemicals, with elevated liver enzymes. Only one of these studies, using a sample of gastric bypass surgery patients, examined sex-specific associations of POPs and liver enzymes, finding adverse associations among women only. The noticeable lack of studies investigating how differences (i.e., biochemical, physiological, and behavioral) between men and women may influence associations of pEDCs and NAFLD represents a large research gap in environmental health. Sexual dimorphism in metabolic processes throughout the body, including the liver, is established but often overlooked in the designs and analyses of studies. Other factors identified in this review that may also act to modulate associations of environmental chemicals and NAFLD are reproductive status and dietary nutrient intakes, which also remain understudied in the literature. Despite knowledge of sexual dimorphism in the actions of pEDCs, as well as in metabolic processes related to NAFLD development, few experimental or epidemiological studies have investigated sex-dependent associations. Future studies, especially those in humans, should be designed to address this research need. Consideration of other factors, such as reproductive status, dietary intakes, and mixtures of chemicals with varying endocrine-disrupting capabilities, should be explored.

Lipid Metabolism Alteration by Endocrine Disruptors in Animal Models: An Overview

Exposure to potential Endocrine Disrupting Chemicals (EDCs) pose a documented risk to both wildlife and human health. Many studies so far described declining sperm counts, genital malformations, early puberty onset, highlighting the negative impact on reproduction caused by the exposure to many anthropogenic chemicals. In the last years, increasing evidence suggested that these compounds, other than altering reproduction, affect metabolism and induce the onset of obesity and metabolic disorders. According to the "environmental obesogens" hypothesis, evidence exists that exposure to potential EDCs during critical periods when adipocytes are differentiating, and organs are developing, can induce diseases that manifest later in the life. This review summarizes the effects occurring at the hepatic level in different animal models, describing morphological alterations and changes of molecular pathways elicited by the toxicant exposure. Results currently available demonstrated that these chemicals impair normal metabolic processes via interaction with members of the nuclear receptor superfamily, including steroid hormone receptors, thyroid hormone receptors, retinoid X receptors, peroxisome proliferator-activated receptors, liver X receptors, and farnesoid X receptors. In addition, novel results revealed that EDC exposure can either affect circadian rhythms as well as up-regulate the expression of signals belonging to the endocannabinoid system, in both cases leading to a remarkable increase of lipid accumulation. These results warrant further research and increase the interest toward the identification of new mechanisms for EDC metabolic alterations. The last part of this review article condenses recent evidences on the ability of potential EDCs to cause "transgenerational effects" by a single prenatal or early life exposure. On this regard, there is compelling evidence that epigenetic modifications link developmental environmental insults to adult disease susceptibility. This review will contribute to summarize the mechanisms underlying the insurgence of EDC-induced metabolic alterations as well as to build integrated strategies for their better management. In fact, despite the large number of results obtained so far, there is still a great demand for the development of frameworks that can integrate mechanistic and toxicological/epidemiological observations. This would increase legal and governmental institution awareness on this critical environmental issue responsible for negative consequences in both wild species and human health.

Environmental Pollutants and Metabolic Disorders: The Multi-Exposure Scenario of Life

Obesity and diabetes have reached epidemic proportions the past few decades and continue to progress worldwide with no clear sign of decline of the epidemic. Obesity is of high concern because it is the main risk factor for a number of non-communicable diseases such as cardiovascular diseases and type 2 diabetes. Metabolic diseases constitute a major challenge as they are associated with an overall reduced quality of life and impose a heavy economic burden on countries. These are multifactorial diseases and it is now recognized that environmental exposure to man-made chemical pollutants is part of the equation. Yet, risk assessment procedures are based on a one-by-one chemical evaluation which does not meet the specificities of the multi-exposure scenario of life, e.g., a combined and long-term exposure to even the smallest amounts of chemicals. Indeed, it is assumed that environmental exposure to chemicals will be negligible based on the low potency of each chemical and that they do not interact. Within this mini-review, strong evidences are brought that exposure to low levels of multiple chemicals especially those shown to interfere with hormonal action, the so-called endocrine disrupting compounds do trigger metabolic disturbances in conditions in which no effect was expected if considering the concentration of each individual chemical in the mixture. This is known as the cocktail effect. It means that risk assessment procedures are not protective enough and thus that it should be revisited for the sake of Public Health.

Timing of Exposure and Bisphenol-A: Implications for Diabetes Development

Bisphenol-A (BPA) is one of the most widespread endocrine disrupting chemicals (EDCs). It is used as the base compound in the production of polycarbonate and other plastics present in many consumer products. It is also used as a building block in epoxy can coating and the thermal paper of cash register receipts. Humans are consistently exposed to BPA and, in consequence, this compound has been detected in the majority of individuals examined. Over the last decade, an enlarging body of evidence has provided a strong support for the role of BPA in the etiology of diabetes and other metabolic disorders. Timing of exposure to EDCs results crucial since it has important implications on the resulting adverse effects. It is now well established that the developing organisms are particularly sensitive to environmental influences. Exposure to EDCs during early life may result in permanent adverse consequences, which increases the risk of developing chronic diseases like diabetes in adult life. In addition to that, developmental abnormalities can be transmitted from one generation to the next, thus affecting future generations. More recently, it has been proposed that gestational environment may also program long-term susceptibility to metabolic disorders in the mother. In the present review, we will comment and discuss the contributing role of BPA in the etiology of diabetes. We will address the metabolic consequences of BPA exposure at different stages of life and comment on the final phenotype observed in different whole-animal models of study.

Endocrine disrupting chemicals, 4-nonylphenol, bisphenol A and butyl benzyl phthalate, impair metabolism of estradiol in male and female rats as assessed by levels of 15α-hydroxyestrogens and catechol estrogens in urine

Bisphenol A (BPA), 4-nonylphenol (NP) and butyl benzyl phthalate (BBP), termed endocrine-disrupting chemicals, are known to mimic estrogen activity. The effects of these chemicals on 17β-estradiol (E₂ ) metabolism in vivo in rats were examined. Male and female rats were given NP (250 mg kg^-1  day^-1 ), BPA (250 μg kg^-1  day^-1 ) or BBP (500 mg kg^-1  day^-1 ) by gavage for 14 days, followed by a single intraperitoneal injection of E₂ (5 mg kg^-1 ) on the final day. The urinary excretion over 72 hours of 2-hydroxyestrone 1-N-acetylcysteine thioether, 2-hydroxyestrone 4-N-acetylcysteine thioether, 4-hydroxyestrone 2-N-acetylcysteine thioether, 2-hydroxy-17β-estradiol (2-OHE₂ ), 2-hydroxyestrone (2-OHE₁ ), 4-hydroxy-17β-estradiol, 4-hydroxyestrone, 15α-hydroxyestriol (E₄ ), 15α-hydroxy-17β-estradiol and 15α-hydroxyestrone was measured. Increases in urinary excretion of 2-OHE₁ and decreases in E₄ were observed in males treated with NP or BBP. Decreases in urinary excretion of 2-OHE₂ and E₄ were observed in males treated with BPA. Decreases in urinary excretion of 2-OHE₁ and 2-OHE₂ were observed in females treated with BBP. Normalized liver and weights were increased in both sexes treated with NP or BBP. Histologic observations revealed marked changes in the distal tubules and collecting ducts in the kidneys of rats exposed to NP and BBP, and hypertrophy in the hepatocytes of the centrilobular zone of the liver. No BPA-related effects on organ weight and on liver or kidney histopathology were found. These results suggest that the 14 day oral dosing of NP and BBP disrupted E₂ metabolism, resulting from marked morphological and functional alterations in the liver and kidneys. In addition, BPA could induce metabolic and endocrine disruption.

Environmental Toxicant Exposures and Type 2 Diabetes Mellitus: Two Interrelated Public Health Problems on the Rise

Rates of type 2 diabetes mellitus (T2DM) are rising rapidly across the globe and the impact of this devastating disease threatens to plague the 21^st century. While some contributing factors are well-recognized (e.g. sedentary lifestyles and caloric excess), others diabetes-promoting risk factors are less established or poorly appreciated. The latter category includes environmental exposures to diabetogenic contaminants. Herein we review some of the latest concepts and mechanisms by which environmental exposures may contribute to rising rates of T2DM with a particular focus on mechanisms involving mitochondrial dysfunction and imbalances in reactive oxygen species (ROS). Furthermore, while the pathogenesis of diabetes includes impairments in insulin sensitivity as well as insulin secretion, we will specifically delve into the links between environmental exposures to toxicants such as arsenic and disruptions in insulin release from pancreatic β-cells. Since β-cell death or dysfunction lies at the heart of both T2DM as well as type 1 diabetes mellitus (T1DM), environmental endocrine disrupting chemicals (EDCs) that disrupt the production or regulated release of the glucose-lowering hormone insulin are likely contributors to diabetes risk. Importantly, understanding the contribution of toxicants to diabetes risk as well as improved understanding of their mechanisms of action offer unique opportunities to modulate diabetes risk via targeted therapeutics or public policy interventions to reduce and remediate exposures.