The endocrine disrupting chemical tolylfluanid alters adipocyte metabolism via glucocorticoid receptor activation

Impacts of tolylfluanid on implantation and placental development: Disruption of mitochondrial function and implantation-related gene expression in vitro and in vivo

Tolylfluanid is a widely used pesticide and antifouling agent in agricultural and marine industries and is recognized as a potential endocrine disruptor. However, the toxicological effects of tolylfluanid on the placenta development was not elucidated. This study used trophoblastic cell (HTR-8/SVneo cell) and endometrial cell (T HESCs) lines as in vitro model and mouse models as in vivo model to investigate the toxic effects of tolylfluanid on implantation-associated cell and placenta development during early pregnancy. Experimental results indicated that both cell lines exhibited reduced viability upon tolylfluanid exposure. Various in vitro experiments were conducted at <1 mg/L concentration. The results indicate that tolylfluanid can arrest cell cycle and induce apoptosis in endometrial and trophoblastic cells, abnormally regulate Ca2+ homeostasis and MAPK signaling pathways, and disrupt mitochondrial function. In vivo experiments, subchronic tolylfluanid exposure to mouse during puberty and pregnancy period impaired placenta development, resulting in reduced fetal and placental weight, abnormal placental structures, and altered gene expression. Specifically, a decrease in the ratio of labyrinth/junctional zones and changes in placenta gene expression patterns after tolylfluanid exposure were similar to characters of adverse pregnancy outcomes such as preeclampsia and fetal growth restriction (FGR). This study suggests that tolylfluanid exposure may have negative outcomes on female reproduction, and highlights the need for stricter regulation and monitoring of tolylfluanid use to protect women's reproductive health. This is the first study indicating the adverse effects of tolylfluanid on implantation and placental development during pregnancy.

Application of In Vitro Models for Studying the Mechanisms Underlying the Obesogenic Action of Endocrine-Disrupting Chemicals (EDCs) as Food Contaminants-A Review

Obesogenic endocrine-disrupting chemicals (EDCs) belong to the group of environmental contaminants, which can adversely affect human health. A growing body of evidence supports that chronic exposure to EDCs can contribute to a rapid increase in obesity among adults and children, especially in wealthy industrialized countries with a high production of widely used industrial chemicals such as plasticizers (bisphenols and phthalates), parabens, flame retardants, and pesticides. The main source of human exposure to obesogenic EDCs is through diet, particularly with the consumption of contaminated food such as meat, fish, fruit, vegetables, milk, and dairy products. EDCs can promote obesity by stimulating adipo- and lipogenesis of target cells such as adipocytes and hepatocytes, disrupting glucose metabolism and insulin secretion, and impacting hormonal appetite/satiety regulation. In vitro models still play an essential role in investigating potential environmental obesogens. The review aimed to provide information on currently available two-dimensional (2D) in vitro animal and human cell models applied for studying the mechanisms of obesogenic action of various industrial chemicals such as food contaminants. The advantages and limitations of in vitro models representing the crucial endocrine tissue (adipose tissue) and organs (liver and pancreas) involved in the etiology of obesity and metabolic diseases, which are applied to evaluate the effects of obesogenic EDCs and their disruption activity, were thoroughly and critically discussed.

Adipogenic Activity of Chemicals Used in Plastic Consumer Products

Bisphenols and phthalates, chemicals frequently used in plastic products, promote obesity in cell and animal models. However, these well-known metabolism-disrupting chemicals (MDCs) represent only a minute fraction of all compounds found in plastics. To gain a comprehensive understanding of plastics as a source of exposure to MDCs, we characterized the chemicals present in 34 everyday products using nontarget high-resolution mass spectrometry and analyzed their joint adipogenic activities by high-content imaging. We detected 55,300 chemical features and tentatively identified 629 unique compounds, including 11 known MDCs. Importantly, the chemicals extracted from one-third of the products caused murine 3T3-L1 preadipocytes to proliferate, and differentiate into adipocytes, which were larger and contained more triglycerides than those treated with the reference compound rosiglitazone. Because the majority of plastic extracts did not activate the peroxisome proliferator-activated receptor γ and the glucocorticoid receptor, the adipogenic effects are mediated via other mechanisms and, thus, likely to be caused by unknown MDCs. Our study demonstrates that daily-use plastics contain potent mixtures of MDCs and can, therefore, be a relevant yet underestimated environmental factor contributing to obesity.

Inappropriately sweet: Environmental endocrine-disrupting chemicals and the diabetes pandemic

Afflicting hundreds of millions of individuals globally, diabetes mellitus is a chronic disorder of energy metabolism characterized by hyperglycemia and other metabolic derangements that result in significant individual morbidity and mortality as well as substantial healthcare costs. Importantly, the impact of diabetes in the United States is not uniform across the population; rather, communities of color and those with low income are disproportionately affected. While excessive caloric intake, physical inactivity, and genetic susceptibility are undoubted contributors to diabetes risk, these factors alone fail to fully explain the rapid global rise in diabetes rates. Recently, environmental contaminants acting as endocrine-disrupting chemicals (EDCs) have been implicated in the pathogenesis of diabetes. Indeed, burgeoning data from cell-based, animal, population, and even clinical studies now indicate that a variety of structurally distinct EDCs of both natural and synthetic origin have the capacity to alter insulin secretion and action as well as global glucose homeostasis. This chapter reviews the evidence linking EDCs to diabetes risk across this spectrum of evidence. It is hoped that improving our understanding of the environmental drivers of diabetes development will illuminate novel individual-level and policy interventions to mitigate the impact of this devastating condition on vulnerable communities and the population at large.

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.

Glucocorticoid and mineralocorticoid receptors and corticosteroid homeostasis are potential targets for endocrine-disrupting chemicals

Endocrine-disrupting chemicals (EDCs) have received significant concern, since they ubiquitously exist in the environment and are able to induce adverse health effects on human and wildlife. Increasing evidence shows that the glucocorticoid receptor (GR) and the mineralocorticoid receptor (MR), members of the steroid receptor subfamily, are potential targets for EDCs. GR and MR mediate the actions of glucocorticoids and mineralocorticoids, respectively, which are two main classes of corticosteroids involved in many physiological processes. The effects of EDCs on the homeostasis of these two classes of corticosteroids have also gained more attention recently. This review summarized the effects of environmental GR/MR ligands on receptor activity, and disruption of corticosteroid homeostasis. More than 130 chemicals classified into 7 main categories were reviewed, including metals, metalloids, pesticides, bisphenol analogues, flame retardants, other industrial chemicals and pharmaceuticals. The mechanisms by which EDCs interfere with GR/MR activity are primarily involved in ligand-receptor binding, nuclear translocation of the receptor complex, DNA-receptor binding, and changes in the expression of endogenous GR/MR genes. Besides directly interfering with receptors, enzyme-catalyzed synthesis and prereceptor regulation pathways of corticosteroids are also important targets for EDCs. The collected evidence suggests that corticosteroids and their receptors should be considered as potential targets for safety assessment of EDCs. The recognition of relevant xenobiotics and their underlying mechanisms of action is still a challenge in this emerging field of research.

Multiple pesticides in mothers' hair samples and children's measurements at birth: Results from the French national birth cohort (ELFE)

BACKGROUND

A growing body of studies now suggests that the general population is continuously and ubiquitously exposed to numerous pesticides. However, studies investigating the possible role of environmental exposure to pesticides on fetal growth have focused on a limited set of substances, despite the hundreds of modern pesticides currently available.

AIM

To explore the relation between maternal hair concentrations of 64 pesticides and metabolites and their newborns' measurements at birth, with data from the ELFE French nationwide birth cohort.

METHODS

We measured 64 compounds (10-100% detection) in bundles of hair 9 cm long collected at birth from 311 women who gave birth in France in 2011. We assessed their associations with birth weight, length, and head circumference, adjusted for potential confounders, and used elastic net regularization to simultaneously select the strongest predictors of measurements at birth. Selected variables were multiply imputed for missing values, and unpenalized estimators were assessed by standard linear regression.

RESULTS

We observed statistically significant associations between maternal hair concentrations of seven pesticides or pesticide metabolites and birth measurements (weight: fipronil sulfone; length: TCPy, bitertanol, DEP, and isoproturon; head circumference: tebuconazole and prochloraz). Analyses restricted to boys identified 12 additional compounds: 8 independently associated with birth weight (3Me4NP, DCPMU, DMST, fipronil, mecoprop, propoxur, fenhexamid, and thiabendazole), 2 with birth length (dieldrin and β-endosulfan), and 6 with head circumference (β-endosulfan, β-HCH, fenuron, DCPMU, propoxur, and thiabendazole).

CONCLUSION

Our results suggest that prenatal exposure to 19 pesticides or metabolites from various chemical families may influence measurements at birth. As with any exploratory research findings, results should be interpreted cautiously, until they are replicated or verified by further epidemiological or mechanistic studies.

Organophosphorus pesticide triazophos: A new endocrine disruptor chemical of hypothalamus-pituitary-adrenal axis

The organophosphorus pesticide, triazophos (TAP) was banned to use in agriculture in several countries due to its high toxicity. However, TAP was still widely used and frequently detected in foods. Recently, many studies reported the endocrine-disrupting effect of pesticides, especially the hypothalamic-pituitary-thyroid and hypothalamic-pituitary-gonadal axis. In this study, adult male Wistar rats were exposed to TAP at the dose of 0.164 and 1.64 mg/kg bodyweight (~1/500th and 1/50th of LD₅₀) for 24 weeks and serum contents of hormones were measured. TAP exposure significantly reduced serum contents of adrenocorticotropic hormone, corticosterone and epinephrine in rats (p < .05), leading to the delay in glucose homeostasis during the insulin tolerance test and decrease in serum contents of total cholesterol, triglyceride and low density lipoprotein. Molecular docking results suggested TAP may be an antagonist of glucocorticoid receptor which decreased significantly in the liver of rats, resulting in the decreased expression of 11β-hydroxysteroid dehydrogenase 1 and PEPCK1. This study revealed that TAP is a potential endocrine disruptor, especially in the hypothalamus-pituitary-adrenal system and may disturb the metabolism by affecting glucocorticoid receptor. This study provided new evidence about the toxicity of TAP and it was necessary to strictly control the usage of TAP in food.

Developmental exposure to the endocrine disruptor tolylfluanid induces sex-specific later-life metabolic dysfunction

Endocrine-disrupting chemicals (EDCs) are implicated in the developmental mis-programming of energy metabolism. This study examined the impact of combined gestational and lactational exposure to the fungicide tolylfluanid (TF) on metabolic physiology in adult offspring. C57BL/6 J dams received standard rodent chow or the same diet containing 67 mg/kg TF. Offspring growth and metabolism were assessed up to 22 weeks of age. TF-exposed offspring exhibited reduced weaning weight. Body weight among female offspring remained low throughout the study, while male offspring matched controls by 17 weeks of age. Female offspring exhibited reduced glucose tolerance, markedly enhanced systemic insulin sensitivity, reduced adiposity, and normal gluconeogenic capacity during adulthood. In contrast, male offspring exhibited impaired glucose tolerance with unchanged insulin sensitivity, no differences in adiposity, and increased gluconeogenic capacity. These data indicate that developmental exposure to TF induces sex-specific metabolic disruptions that recapitulate key aspects of other in utero growth restriction models.

Environmentally relevant concentrations of bifenthrin affect the expression of estrogen and glucocorticoid receptors in brains of female western mosquitofish

In recent decades, pyrethroid pesticides have been deemed a safer alternative to previously used pesticides. While some evidence supports this assumption in mammals and birds, exposure to certain pyrethroids can affect concentrations of hormones vital to reproduction in fish. Thus, we hypothesized that pyrethroid exposure impacts fish reproductive behavior and the expression of genes associated with reproduction. We tested our hypothesis by examining effects of the widely used pyrethroid pesticide, bifenthrin, on the reproductive behaviors of the broadly distributed livebearing western mosquitofish, Gambusia affinis. We exposed sexually mature female fish to one of five environmentally relevant concentrations of bifenthrin and conducted behavioral assays to assess reproductive, social, and space use behaviors before and after exposure. We did not detect changes in behaviors measured in response to bifenthrin. However, exposure was associated with increased expression of an estrogen receptor gene (ER-α) and glucocorticoid receptor (GR) in brain tissue at bifenthrin concentrations at concentrations of 5.90 and 24.82 ng/L, and 5.90 and 12.21 ng/L, respectively. Our study supports the perspective that the use of multiple endpoints through integrative approaches is essential for understanding the cumulative impact of pollutants. Integrating physiological, morphological, and behavioral investigations of nonlethal concentrations of pollutants like bifenthrin may heighten our potential to predict their impact on individuals, populations, and communities.

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.

Organotins in obesity and associated metabolic disturbances

The objective of the present study was to review the mechanisms of organotin-induced adipogenesis, obesity, and associated metabolic disturbances. Peroxisome proliferator-activated receptor γ (PPARγ) and retinoid X receptor α (RXRα) activation is considered as the key mechanism of organotin-induced adipogenesis. Particularly, organotin exposure results in increased adipogenesis both in cell and animal models. Moreover, transgenerational inheritance of organotin-induced obese phenotype was demonstrated in vivo. At the same time, the existing data demonstrate that organotin compounds (OTCs) induces aberrant expression of PPARγ-targeted genes, resulting in altered of adipokine, glucose transporter, proinflammatory cytokines levels, and lipid and carbohydrate metabolism. The latter is generally characterized by hyperglycemia and insulin resistance. Other mechanisms involved in organotin-induced obesity may include estrogen receptor and corticosteroid signaling, altered DNA methylation, and gut dysfunction. In addition to cellular effects, organotin exposure may also affect neural circuits of appetite regulation, being characterized by neuropeptide Y (NPY) up-regulation in parallel with of pro-opiomelanocortin (POMC), Agouti-related protein (AgRP), and cocaine and amphetamine regulated transcript (CART) down-regulation in the arcuate nucleus. These changes result in increased orexigenic and reduced anorexigenic signaling, leading to increased food intake. The existing data demonstrate that organotins are potent adipogenic agents, however, no epidemiologic studies have been performed to reveal the association between organotin exposure and obesity and the existing indirect human data are contradictory.

Cellular fatty acid level regulates the effect of tolylfluanid on mitochondrial dysfunction and insulin sensitivity in C2C12 skeletal myotubes

Previous research suggests that the endocrine disrupting chemical tolylfluanid (TF) may promote metabolic dysfunction and insulin resistance in humans. The potential impact of TF on skeletal muscle metabolism has yet to be fully investigated. The purpose of this study was to determine whether TF can promote insulin resistance and metabolic dysfunction in mammalian skeletal muscle cells. C2C12 murine skeletal myotubes were exposed to 1 ppm TF for 24 h. To examine the potential effect of cellular fatty acid levels on TF-dependent regulation of mitochondrial metabolism and insulin signaling, we treated skeletal myotubes with 0.25 mM or 1.0 mM oleic acid (OA) during TF exposure trials. Tolylfluanid (1-10 ppm) reduced lipid accumulation by approximately 20% in 0.25 and 1.0 mM OA treated cells. The addition of 0.25 mM OA completely inhibited the TF-dependent reduction in maximal mitochondrial oxygen consumption rate (OCR) while 1.0 mM OA exacerbated the TF-dependent reduction in mitochondrial OCR. Exposing skeletal myotubes to 1 ppm TF promoted an 80% reduction in mitochondrial membrane potential, which was completely inhibited by 0.25 mM OA and partially inhibited by1.0 mM OA. The addition of 0.25 mM OA promoted a TF-dependent increase in insulin-dependent P-Akt (Ser473). In contrast, the addition of 1.0 mM OA promoted a significant reduction in insulin-dependent P-Akt (Ser473). Further, the addition of 1 ppm TF significantly reduced insulin-dependent mTORC1 activity regardless of OA concentration. Finally, TF significantly reduced insulin-dependent protein synthesis in the 1 mM OA treated cells only. Our results demonstrate that the effect of 1 ppm TF on mitochondrial function and insulin-dependent protein synthesis in skeletal myotubes was largely dependent upon cellular fatty acid levels.

Transgenerational effects of polychlorinated biphenyls: 1. Development and physiology across 3 generations of rats

BACKGROUND

Polychlorinated biphenyls (PCBs) are persistent organic environmental contaminants and known endocrine-disrupting chemicals (EDCs). Previous studies demonstrated that developmental exposure to the weakly estrogenic PCB mixture Aroclor 1221 (A1221) in Sprague-Dawley rats altered sexual development, adult reproductive physiology and body weight. The current study tested the hypothesis that prenatal A1221 exposure not only disrupts these endpoints within an exposed individual's (F₁ generation) lifespan, but may also affect subsequent generations (F₂-F₃).

METHODS

We treated pregnant female rats on embryonic days (E) 16 and E18 with A1221 (1 mg/kg), estradiol benzoate (50 μg/kg, positive estrogenic control), or vehicle (3% DMSO in sesame oil, negative control). Endpoints related to sexually dimorphic developmental trajectories of reproductive and developmental physiology were measured, and as adults, reproductive endocrine status was assessed, in the F₁, F₂, and F₃ generations.

RESULTS

Significant effects of transgenerational EDCs were found for body weight and serum hormones. The A1221 descendants had significantly higher body weight in the F₂-maternal lineage throughout postnatal development, and in F₃-maternal lineage animals after weaning. In females, generation- and lineage-specific effects of exposure were found for serum progesterone and estradiol. Specifically, serum progesterone concentrations were lower in F₂-A1221 females, and higher in F₃-A1221 females, compared to their respective F₂- and F₃-vehicle counterparts. Serum estradiol concentrations were higher in F₃-A1221 than F₃-vehicle females. Reproductive and adrenal organ weights, birth outcomes, sex ratio, and estrous cycles, were unaffected. It is notable that effects of A1221 were only sometimes mirrored by the estrogenic control, EB, indicating that the mechanism of action of A1221 was likely via non-estrogenic pathways.

CONCLUSIONS

PCBs caused body weight and hormonal effects in rats that were not observed in the directly exposed F₁ offspring, but emerged in F₂ and F₃ generations. Furthermore, most effects were in the maternal lineage; this may relate to the timing of exposure of the F₁ fetuses at E16 and 18, when germline (the future F₂ generation) epigenetic changes diverge in the sexes. These results showing transgenerational effects of EDCs have implications for humans, as we are now in the 3rd generation since the Chemical Revolution of the mid-twentieth century, and even banned chemicals such as PCBs have a persistent imprint on the health of our descendants.

Inhibition of the Mitochondrial Pyruvate Carrier by Tolylfluanid

Several recent studies have suggested that compounds known as endocrine-disrupting chemicals (EDCs) can promote obesity by serving as ligands for nuclear receptors, including the peroxisome proliferator-activated receptor γ (PPARγ) and the glucocorticoid receptor (GR). Thiazolidinedione insulin sensitizers, which act as ligands for PPARγ, also interact with and regulate the activity of the mitochondrial pyruvate carrier (MPC). We evaluated whether several EDCs might also affect MPC activity. Most of the EDCs evaluated did not acutely affect pyruvate metabolism. However, the putative endocrine disruptors tributyltin (TBT) and tolylfluanid (TF) acutely and markedly suppressed pyruvate metabolism in isolated mitochondria. Using mitochondria isolated from brown adipose tissue in mice with adipocyte-specific deletion of the MPC2 protein, we determined that the effect of TF on pyruvate metabolism required MPC2, whereas TBT did not. We attempted to determine whether the obesogenic effects of TF might involve MPC2 in adipose tissue. However, we were unable to replicate the published effects of TF on weight gain and adipose tissue gene expression in wild-type or fat-specific MPC2 knockout mice. Treatment with TF modestly enhanced adipogenic gene expression in vitro but had no effect on GR activation or phosphorylation in cultured cells. These data suggest that TF may affect mitochondrial pyruvate metabolism via the MPC complex but also call into question whether this compound affects GR activity and is obesogenic in mice.

Diet-dependence of metabolic perturbations mediated by the endocrine disruptor tolylfluanid

Emerging evidence implicates environmental endocrine-disrupting chemicals (EDCs) in the pathogenesis of metabolic diseases such as obesity and diabetes; however, the interactions between EDCs and traditional risk factors in disease pathogenesis remain incompletely characterized. The present study interrogates the interaction of the EDC tolylfluanid (TF) and traditional dietary stressors in the promotion of metabolic dysfunction. Eight-week-old male C57BL/6 mice were fed a high-fat, high-sucrose diet (HFHSD) or a high-sucrose diet (HSD), with or without TF supplementation at 100 μg/g, for 12 weeks. Food intake, body weight and visceral adiposity were quantified. Glucose homeostasis was interrogated by intraperitoneal glucose and insulin tolerance tests at 9 and 10 weeks of exposure, respectively. After 12 weeks of dietary exposure, metabolic cage analyses were performed to interrogate nutrient handling and energy expenditure. In the background of an HFHSD, TF promoted glucose intolerance; however, weight gain and insulin sensitivity were unchanged, and visceral adiposity was reduced. In the background of an HSD, TF increased visceral adiposity; however, glucose tolerance and insulin sensitivity were unchanged, while weight gain was reduced. Thus, these analyses reveal that the metabolic perturbations induced by dietary exposure to TF, including the directionality of alterations in body weight gain, visceral adiposity and glucose homeostasis, are influenced by dietary macronutrient composition, suggesting that populations may exhibit distinct metabolic risks based on their unique dietary characteristics.

Polluted Pathways: Mechanisms of Metabolic Disruption by Endocrine Disrupting Chemicals

PURPOSE OF REVIEW

Environmental toxicants are increasingly implicated in the global decline in metabolic health. Focusing on diabetes, herein, the molecular and cellular mechanisms by which metabolism disrupting chemicals (MDCs) impair energy homeostasis are discussed.

RECENT FINDINGS

Emerging data implicate MDC perturbations in a variety of pathways as contributors to metabolic disease pathogenesis, with effects in diverse tissues regulating fuel utilization. Potentiation of traditional metabolic risk factors, such as caloric excess, and emerging threats to metabolism, such as disruptions in circadian rhythms, are important areas of current and future MDC research. Increasing evidence also implicates deleterious effects of MDCs on metabolic programming that occur during vulnerable developmental windows, such as in utero and early post-natal life as well as pregnancy. Recent insights into the mechanisms by which MDCs alter energy homeostasis will advance the field's ability to predict interactions with classical metabolic disease risk factors and empower studies utilizing targeted therapeutics to treat MDC-mediated diabetes.

Endocrine-disrupting chemicals and the regulation of energy balance

Energy balance involves the adjustment of food intake, energy expenditure and body fat reserves through homeostatic pathways. These pathways include a multitude of biochemical reactions, as well as hormonal cues. Dysfunction of this homeostatic control system results in common metabolism-related pathologies, which include obesity and type 2 diabetes mellitus. Metabolism-disrupting chemicals (MDCs) are a particular class of endocrine-disrupting chemicals that affect energy homeostasis. MDCs affect multiple endocrine mechanisms and thus different cell types that are implicated in metabolic control. MDCs affect gene expression and the biosynthesis of key enzymes, hormones and adipokines that are essential for controlling energy homeostasis. This multifaceted spectrum of actions precludes compensatory responses and favours metabolic disorders. Herein, we review the main mechanisms used by MDCs to alter energy balance. This work should help to identify new MDCs, as well as novel targets of their action.

Metabolism disrupting chemicals and metabolic disorders

The recent epidemics of metabolic diseases, obesity, type 2 diabetes(T2D), liver lipid disorders and metabolic syndrome have largely been attributed to genetic background and changes in diet, exercise and aging. However, there is now considerable evidence that other environmental factors may contribute to the rapid increase in the incidence of these metabolic diseases. This review will examine changes to the incidence of obesity, T2D and non-alcoholic fatty liver disease (NAFLD), the contribution of genetics to these disorders and describe the role of the endocrine system in these metabolic disorders. It will then specifically focus on the role of endocrine disrupting chemicals (EDCs) in the etiology of obesity, T2D and NAFLD while finally integrating the information on EDCs on multiple metabolic disorders that could lead to metabolic syndrome. We will specifically examine evidence linking EDC exposures during critical periods of development with metabolic diseases that manifest later in life and across generations.

Evaluation of tetrabromobisphenol A effects on human glucocorticoid and androgen receptors: A comparison of results from human- with yeast-based in vitro assays

The incidence of immune-related diseases increased over the last years in industrialized countries, suggesting a contribution of environmental factors. Impaired glucocorticoid action has been associated with immune disorders. Thus, there is an increasing interest to identify chemicals disrupting glucocorticoid action. The widely used flame retardant tetrabromobisphenol A (TBBPA) was reported earlier to potently inhibit glucocorticoid receptor (GR) and moderately androgen receptor (AR) activity in yeast-based reporter gene assays. To further characterize possible GR disrupting effects of TBBPA, transactivation experiments using a human HEK-293 cell-based reporter gene assay and cell-free receptor binding experiments were performed in the present study. Both, transactivation and GR binding experiments failed to detect any activity of TBBPA on GR function. Molecular docking calculations supported this observation. Additionally, the current study could confirm the antiandrogenic activity of TBBPA seen in the yeast assay, although the effect was an order of magnitude less pronounced in the HEK-293 cell-based system. In conclusion, TBBPA does not directly affect GR function and, considering its rapid metabolism and low concentrations found in humans, it is unlikely to cause adverse effects by acting through AR. This study emphasizes the use of cell-free assays in combination with cell-based assays for the in vitro evaluation of endocrine disrupting chemicals.

[Impact on human health of endocrine disruptors present in environmental water bodies: is there an association with obesity?]

There is growing evidence that endocrine disruptors (ED) may adversely affect humans. Surface and underground water are the main sources for obtaining potable water, however they can be contaminated with ED, which are not completely removed by conventional water and sewage treatment processes. Some health problems are related to the exposure of humans to ED, obesity being one of them. There is currently an increase in the prevalence of obesity worldwide, a fact that is considered a concern in view of its potential impact on the health care system, since obesity is the major risk factor of the leading chronic diseases including diabetes and cardiovascular disease. By means of a review of the literature, this paper sought to gather scientific publications linking exposure to ED with obesity, in order to verify the importance of removal of ED from water bodies, thereby preserving the population's health and aquatic biota. Most of the selected studies suggest an association between ED and obesity in humans.

Endocrine-Disrupting Effects of Pesticides through Interference with Human Glucocorticoid Receptor

Many pesticides have been identified as endocrine-disrupting chemicals (EDCs) due to their ability to bind sex-steroid hormone receptors. However, little attention has been paid to the ability of pesticides to interfere with other steroid hormone receptors such as glucocorticoid receptor (GR) that plays a critical role in metabolic, endocrine, immune, and nervous systems. In this study, the glucocorticoidic and antiglucocorticoidic effects of 34 pesticides on human GR were investigated using luciferase reporter gene assay. Surprisingly, none of the test chemicals showed GR agonistic activity, but 12 chemicals exhibited apparent antagonistic effects. Bifenthrin, λ-cyhalothrin, cypermethrin, resmethrin, o,p'-DDT, p,p'-DDT, methoxychlor, ethiofencarb, and tolylfluanid showed remarkable GR antagonistic properties with RIC20 values lower than 10(-6) M. The disruption of glucocorticoid-responsive genes in H4IIE and J774A.1 cells was further evaluated on these 12 GR antagonists. In H4IIEcells, four organochlorine insecticides, bifenthrin, and 3-PBA decreased cortisol-induced PEPCK gene expression, while o,p'-DDT and methoxychlor inhibited cortisol-stimulated Arg and TAT gene expression. Cypermethrin and tolyfluanid attenuated cortisol-induced TAT expression. In J774A.1 cells, λ-cyhalothrin, resmethrin, 3-PBA, o,p'-DDT, p,p'-DDT, p,p'-DDE, methoxychlor- and tolylfluanid-reduced cortisol-stimulated GILZ expression. Furthermore, molecular docking simulation indicated that different interactions may stabilize the binding between molecules and GR. Our findings suggest that comprehensive screening and evaluation of GR antagonists and agonists should be considered to better understand the health and ecological risks of man-made chemicals such as pesticides.

EDC-2: The Endocrine Society's Second Scientific Statement on Endocrine-Disrupting Chemicals

The Endocrine Society's first Scientific Statement in 2009 provided a wake-up call to the scientific community about how environmental endocrine-disrupting chemicals (EDCs) affect health and disease. Five years later, a substantially larger body of literature has solidified our understanding of plausible mechanisms underlying EDC actions and how exposures in animals and humans-especially during development-may lay the foundations for disease later in life. At this point in history, we have much stronger knowledge about how EDCs alter gene-environment interactions via physiological, cellular, molecular, and epigenetic changes, thereby producing effects in exposed individuals as well as their descendants. Causal links between exposure and manifestation of disease are substantiated by experimental animal models and are consistent with correlative epidemiological data in humans. There are several caveats because differences in how experimental animal work is conducted can lead to difficulties in drawing broad conclusions, and we must continue to be cautious about inferring causality in humans. In this second Scientific Statement, we reviewed the literature on a subset of topics for which the translational evidence is strongest: 1) obesity and diabetes; 2) female reproduction; 3) male reproduction; 4) hormone-sensitive cancers in females; 5) prostate; 6) thyroid; and 7) neurodevelopment and neuroendocrine systems. Our inclusion criteria for studies were those conducted predominantly in the past 5 years deemed to be of high quality based on appropriate negative and positive control groups or populations, adequate sample size and experimental design, and mammalian animal studies with exposure levels in a range that was relevant to humans. We also focused on studies using the developmental origins of health and disease model. No report was excluded based on a positive or negative effect of the EDC exposure. The bulk of the results across the board strengthen the evidence for endocrine health-related actions of EDCs. Based on this much more complete understanding of the endocrine principles by which EDCs act, including nonmonotonic dose-responses, low-dose effects, and developmental vulnerability, these findings can be much better translated to human health. Armed with this information, researchers, physicians, and other healthcare providers can guide regulators and policymakers as they make responsible decisions.

Increase in intracellular Ca(2+) level by phenylsulfamide fungicides, tolylfluanid and dichlofluanid, in rat thymic lymphocytes

Tolylfluanid, a phenylsulfamide fungicide, is one of the many pesticides that are frequently detected in crops. Therefore, its health risk is a concern. Micromolar concentrations of tolylfluanid induce chromosomal aberrations and micronuclei in mammalian lymphocytes. The findings prompted us to study the cellular actions of tolylfluanid and another frequently detected pesticide, dichlofluanid, at submicromolar and micromolar concentrations. Of the cellular actions of chemicals, the action on cellular Ca(2+) homeostasis is important since Ca(2+) is involved in cell signaling and death. Consequently, in this study, the effects of phenylsulfamide fungicides were examined on rat thymocytes by using fluorescent probes in order to further characterize the cellular actions of phenylsulfamide fungicides. Both phenylsulfamide fungicides exhibited biphasic, early and late, increase in intracellular Ca(2+) levels. The early phase was dependent on intracellular Ca(2+) release and increased membrane Ca(2+) permeability. The late phase was owing to Ca(2+) influx via activation of store-operated Ca(2+) channels and the further increase of membrane ionic permeability. Voltage-dependent Ca(2+) channels were not involved. The increases in intracellular Ca(2+) levels by phenylsulfamide fungicides were observed at drug concentrations of 0.1 μM or more (up to 10 μM). Thus, it is plausible that micromolar concentrations of phenylsulfamide fungicides deregulate intracellular Ca(2+) homeostasis in rat thymocytes. Both phenylsulfamide fungicides at 10 μM promoted the transition from intact living cells to living cells with phosphatidylserine-exposed membranes. This was not the case for phenylsulfamide fungicides at 3 μM. The potency of tolylfluanid was similar to that of dichlofluanid. Although the information on residual concentrations of tolylfluanid and dichlofluanid is very limited, their residual concentrations do not reach micromolar levels. It is unlikely that humans will develop adverse effects on exposure to phenylsulfamide fungicides under present environmental conditions.

Silencing Mediator of Retinoid and Thyroid Hormone Receptors (SMRT) regulates glucocorticoid action in adipocytes

Local modulation of glucocorticoid action in adipocytes regulates adiposity and systemic insulin sensitivity. However, the specific cofactors that mediate glucocorticoid receptor (GR) action in adipocytes remain unclear. Here we show that the silencing mediator of retinoid and thyroid hormone receptors (SMRT) is recruited to GR in adipocytes and regulates ligand-dependent GR function. Decreased SMRT expression in adipocytes in vivo increases expression of glucocorticoid-responsive genes. Moreover, adipocytes with decreased SMRT expression exhibit altered glucocorticoid regulation of lipolysis. We conclude that SMRT regulates the metabolic functions of GR in adipocytes in vivo. Modulation of GR-SMRT interactions in adipocytes represents a novel approach to control the local degree of glucocorticoid action and thus influence adipocyte metabolic function.

Dietary exposure to the endocrine disruptor tolylfluanid promotes global metabolic dysfunction in male mice

Environmental endocrine disruptors are implicated as putative contributors to the burgeoning metabolic disease epidemic. Tolylfluanid (TF) is a commonly detected fungicide in Europe, and previous in vitro and ex vivo work has identified it as a potent endocrine disruptor with the capacity to promote adipocyte differentiation and induce adipocytic insulin resistance, effects likely resulting from activation of glucocorticoid receptor signaling. The present study extends these findings to an in vivo mouse model of dietary TF exposure. After 12 weeks of consumption of a normal chow diet supplemented with 100 parts per million TF, mice exhibited increased body weight gain and an increase in total fat mass, with a specific augmentation in visceral adipose depots. This increased adipose accumulation is proposed to occur through a reduction in lipolytic and fatty acid oxidation gene expression. Dietary TF exposure induced glucose intolerance, insulin resistance, and metabolic inflexibility, while also disrupting diurnal rhythms of energy expenditure and food consumption. Adipose tissue endocrine function was also impaired with a reduction in serum adiponectin levels. Moreover, adipocytes from TF-exposed mice exhibited reduced insulin sensitivity, an effect likely mediated through a specific down-regulation of insulin receptor substrate-1 expression, mirroring effects of ex vivo TF exposure. Finally, gene set enrichment analysis revealed an increase in adipose glucocorticoid receptor signaling with TF treatment. Taken together, these findings identify TF as a novel in vivo endocrine disruptor and obesogen in mice, with dietary exposure leading to alterations in energy homeostasis that recapitulate many features of the metabolic syndrome.

Metabolic disruption in context: Clinical avenues for synergistic perturbations in energy homeostasis by endocrine disrupting chemicals

The global epidemic of metabolic disease is a clear and present danger to both individual and societal health. Understanding the myriad factors contributing to obesity and diabetes is essential for curbing their decades-long expansion. Emerging data implicate environmental endocrine disrupting chemicals (EDCs) in the pathogenesis of metabolic diseases such as obesity and diabetes. The phenylsulfamide fungicide and anti-fouling agent tolylfluanid (TF) was recently added to the list of EDCs promoting metabolic dysfunction. Dietary exposure to this novel metabolic disruptor promoted weight gain, increased adiposity, and glucose intolerance as well as systemic and cellular insulin resistance. Interestingly, the increase in body weight and adipose mass was not a consequence of increased food consumption; rather, it may have resulted from disruptions in diurnal patterns of energy intake, raising the possibility that EDCs may promote metabolic dysfunction through alterations in circadian rhythms. While these studies provide further evidence that EDCs may promote the development of obesity and diabetes, many questions remain regarding the clinical factors that modulate patient-specific consequences of EDC exposure, including the impact of genetics, diet, lifestyle, underlying disease, pharmacological treatments, and clinical states of fat redistribution. Currently, little is known regarding the impact of these factors on an individual's susceptibility to environmentally-mediated metabolic disruption. Advances in these areas will be critical for translating EDC science into the clinic to enable physicians to stratify an individual's risk of developing EDC-induced metabolic disease and to provide direction for treating exposed patients.

Laminin α4 deficient mice exhibit decreased capacity for adipose tissue expansion and weight gain

Obesity is a global epidemic that contributes to the increasing medical burdens related to type 2 diabetes, cardiovascular disease and cancer. A better understanding of the mechanisms regulating adipose tissue expansion could lead to therapeutics that eliminate or reduce obesity-associated morbidity and mortality. The extracellular matrix (ECM) has been shown to regulate the development and function of numerous tissues and organs. However, there is little understanding of its function in adipose tissue. In this manuscript we describe the role of laminin α4, a specialized ECM protein surrounding adipocytes, on weight gain and adipose tissue function. Adipose tissue accumulation, lipogenesis, and structure were examined in mice with a null mutation of the laminin α4 gene (Lama4^−/−) and compared to wild-type (Lama4^+/+) control animals. Lama4^−/− mice exhibited reduced weight gain in response to both age and high fat diet. Interestingly, the mice had decreased adipose tissue mass and altered lipogenesis in a depot-specific manner. In particular, epididymal adipose tissue mass was specifically decreased in knock-out mice, and there was also a defect in lipogenesis in this depot as well. In contrast, no such differences were observed in subcutaneous adipose tissue at 14 weeks. The results suggest that laminin α4 influences adipose tissue structure and function in a depot-specific manner. Alterations in laminin composition offers insight into the roll the ECM potentially plays in modulating cellular behavior in adipose tissue expansion.

Environmental endocrine disruption of energy metabolism and cardiovascular risk

Rates of metabolic diseases have increased at an astounding rate in recent decades. Even though poor diet and physical inactivity are central drivers, these lifestyle changes alone fail to fully account for the magnitude and rapidity of the epidemic. Thus, attention has turned to identifying novel risk factors, including the contribution of environmental endocrine disrupting chemicals. Epidemiologic and preclinical data support a role for various contaminants in the pathogenesis of diabetes. In addition to the vascular risk associated with dysglycemia, emerging evidence implicates multiple pollutants in the pathogenesis of atherosclerosis and cardiovascular disease. Reviewed herein are studies linking endocrine disruptors to these key diseases that drive significant individual and societal morbidity and mortality. Identifying chemicals associated with metabolic and cardiovascular disease as well as their mechanisms of action is critical for developing novel treatment strategies and public policy to mitigate the impact of these diseases on human health.

Adipocytes under assault: environmental disruption of adipose physiology

The burgeoning obesity epidemic has placed enormous strains on individual and societal health mandating a careful search for pathogenic factors, including the contributions made by endocrine disrupting chemicals (EDCs). In addition to evidence that some exogenous chemicals have the capacity to modulate classical hormonal signaling axes, there is mounting evidence that several EDCs can also disrupt metabolic pathways and alter energy homeostasis. Adipose tissue appears to be a particularly important target of these metabolic disruptions. A diverse array of compounds has been shown to alter adipocyte differentiation, and several EDCs have been shown to modulate adipocyte physiology, including adipocytic insulin action and adipokine secretion. This rapidly emerging evidence demonstrating that environmental contaminants alter adipocyte function emphasizes the potential role that disruption of adipose physiology by EDCs may play in the global epidemic of metabolic disease. Further work is required to better characterize the molecular targets responsible for mediating the effects of EDCs on adipose tissue. Improved understanding of the precise signaling pathways altered by exposure to environmental contaminants will enhance our understanding of which chemicals pose a threat to metabolic health and how those compounds synergize with lifestyle factors to promote obesity and its associated complications. This knowledge may also improve our capacity to predict which synthetic compounds may alter energy homeostasis before they are released into the environment while also providing critical evidentiary support for efforts to restrict the production and use of chemicals that pose the greatest threat to human metabolic health. This article is part of a Special Issue entitled: Modulation of Adipose Tissue in Health and Disease.

The hijacking of cellular signaling and the diabetes epidemic: mechanisms of environmental disruption of insulin action and glucose homeostasis

The burgeoning epidemic of metabolic disease causes significant societal and individual morbidity and threatens the stability of health care systems around the globe. Efforts to understand the factors that contribute to metabolic derangements are critical for reversing these troubling trends. While excess caloric consumption and physical inactivity superimposed on a susceptible genetic background are central drivers of this crisis, these factors alone fail to fully account for the magnitude and rapidity with which metabolic diseases have increased in prevalence worldwide. Recent epidemiological evidence implicates endocrine disrupting chemicals in the pathogenesis of metabolic diseases. These compounds represent a diverse array of chemicals to which humans are exposed via multiple routes in adulthood and during development. Furthermore, a growing ensemble of animal- and cell-based studies provides preclinical evidence supporting the hypothesis that environmental contaminants contribute to the development of metabolic diseases, including diabetes. Herein are reviewed studies linking specific endocrine disruptors to impairments in glucose homeostasis as well as tying these compounds to disturbances in insulin secretion and impairments in insulin signal transduction. While the data remains somewhat incomplete, the current body of evidence supports the hypothesis that our chemically polluted environment may play a contributing role in the current metabolic crisis.