Bisphenol A exposure during pregnancy disrupts glucose homeostasis in mothers and adult male offspring

Systematic Review and Meta-Analysis of Early-Life Exposure to Bisphenol A and Obesity-Related Outcomes in Rodents

BACKGROUND

Early-life exposure to bisphenol A (BPA) has been implicated to play a role in the development of obesity.

OBJECTIVE

A systematic review with meta-analyses of experimental rodent studies was conducted to answer the following question: does early-life exposure to BPA affect the obesity-related outcomes body weight, fat (pad) weight, and circulating and tissue levels of triglycerides, free fatty acids (FFA), and leptin?

METHODS

The methodology was prespecified in a rigorous protocol using the Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE) approach. Using PubMed and EMBASE, we identified 61 articles that met the inclusion criteria. The risk of bias and the methodological quality of these articles were assessed using the SYRCLE Risk of Bias tool, and a confidence-rating methodology was used to score the quality of evidence. Meta-analyses were performed using random effect models and standardized mean differences (SMDs), or, where possible, mean differences (MDs) were calculated.

RESULTS

Overall summary estimates indicated significant positive associations between BPA and fat weight [SMD=0.67 (95% CI: 0.53, 0.81)], triglycerides [SMD=0.97 (95% CI: 0.53, 1.40)], and FFA [SMD=0.86 (95% CI: 0.50, 1.22)], and a nonsignificant positive association with leptin levels [MD=0.37 (95% CI: -0.14, 0.87)] and a significant negative association with body weight were estimated [MD=-0.22 (95% CI: -0.37, -0.06)]. Subgroup analyses revealed stronger positive associations for most outcome measures in males and at doses below the current U.S. reference dose of 50μg/kg/d compared with doses above the reference dose. It should be noted that there was substantial heterogeneity across studies for all outcomes assessed and that there was insufficient information to assess risk of bias for most studies.

CONCLUSIONS

Findings from our systematic review suggest that early-life exposure to BPA may increase adiposity and circulating lipid levels in rodents. https://doi.org/10.1289/EHP1233.

Bisphenol S Alters the Lactating Mammary Gland and Nursing Behaviors in Mice Exposed During Pregnancy and Lactation

High doses of estrogenic pharmaceuticals were once prescribed to women to halt lactation. Yet, the effects of low-level xenoestrogens on lactation remain poorly studied. We investigated the effects of bisphenol S (BPS), an estrogen receptor (ER) agonist, on the lactating mammary gland; the arcuate nucleus, a region of the hypothalamus important for neuroendocrine control of lactational behaviors; and nursing behavior in CD-1 mice. Female mice were exposed to vehicle, 2 or 200 µg BPS/kg/d from pregnancy day 9 until lactational day (LD) 20, and tissues were collected on LD21. Tissues were also collected from a second group at LD2. BPS exposure significantly reduced the fraction of the mammary gland comprised of lobules, the milk-producing units, on LD21, but not LD2. BPS also altered expression of Esr1 and ERα in the mammary gland at LD21, consistent with early involution. In the arcuate nucleus, no changes were observed in expression of signal transducer and activator of transcription 5, a marker of prolactin signaling, or ERα, suggesting that BPS may act directly on the mammary gland. However, observations of nursing behavior collected during the lactational period revealed stage-specific effects on both pup and maternal nursing behaviors; BPS-treated dams spent significantly more time nursing later in the lactational period, and BPS-treated pups were less likely to initiate nursing. Pup growth and development were also stunted. These data indicate that low doses of BPS can alter lactational behaviors and the maternal mammary gland. Together, they support the hypothesis that pregnancy and lactation are sensitive to low-dose xenoestrogen exposures.

Imidacloprid insecticide exposure induces stress and disrupts glucose homeostasis in male rats

In the present study, we evaluated the stress response in adult rats who were administered imidacloprid (IMI) orally in two doses (0.5 and 1.0mg/kg bw for 60days). It led to an alteration in the levels of cortisone and catecholamines and induced behavioral deficits, particularly in the animals exposed to the dose of 1.0mg/kg. IMI was further analyzed for the effect on glucose homeostasis in developing and adult rats at a dose of 1.0mg/kg bw where it elicited a hyperglycemic effect. Moreover, we observed an alteration in the mRNA levels of glucose transporters. Histopathological and immunohistochemical data displayed structural perturbations in pancreatic tissue with a decline in the expression of insulin and GLUT4, particularly in the developing rats. Collectively, IMI treatment resulted in stress represented by behavioral and biochemical changes, particularly at a dose of 1.0mg/kg bw. Moreover, IMI perturbed the glucose regulation through hyperglycemic activity in both developing and adult rats, an observation clearly evident in the developing rats.

Sex- and Dose-Specific Effects of Maternal Bisphenol A Exposure on Pancreatic Islets of First- and Second-Generation Adult Mice Offspring

BACKGROUND

Exposure to the environmental endocrine disruptor bisphenol A (BPA) is ubiquitous and associated with the increased risk of diabetes and obesity. However, the underlying mechanisms remain unknown. We recently demonstrated that perinatal BPA exposure is associated with higher body fat, impaired glucose tolerance, and reduced insulin secretion in first- (F1) and second-generation (F2) C57BL/6J male mice offspring.

OBJECTIVE

We sought to determine the multigenerational effects of maternal bisphenol A exposure on mouse pancreatic islets.

METHODS

Cellular and molecular mechanisms underlying these persistent changes were determined in F1 and F2 adult offspring of F0 mothers exposed to two relevant human exposure levels of BPA (10μg/kg/d-LowerB and 10mg/kg/d-UpperB).

RESULTS

Both doses of BPA significantly impaired insulin secretion in male but not female F1 and F2 offspring. Surprisingly, LowerB and UpperB induced islet inflammation in male F1 offspring that persisted into the next generation. We also observed dose-specific effects of BPA on islets in males. UpperB exposure impaired mitochondrial function, whereas LowerB exposure significantly reduced β-cell mass and increased β-cell death that persisted in the F2 generation. Transcriptome analyses supported these physiologic findings and there were significant dose-specific changes in the expression of genes regulating inflammation and mitochondrial function. Previously we observed increased expression of the critically important β-cell gene, Igf2 in whole F1 embryos. Surprisingly, increased Igf2 expression persisted in the islets of male F1 and F2 offspring and was associated with altered DNA methylation.

CONCLUSION

These findings demonstrate that maternal BPA exposure has dose- and sex-specific effects on pancreatic islets of adult F1 and F2 mice offspring. The transmission of these changes across multiple generations may involve either mitochondrial dysfunction and/or epigenetic modifications. https://doi.org/10.1289/EHP1674.

Molecular mechanisms involved in the non-monotonic effect of bisphenol-a on ca2+ entry in mouse pancreatic β-cells

In regulatory toxicology, the dose-response relationship is a key element towards fulfilling safety assessments and satisfying regulatory authorities. Conventionally, the larger the dose, the greater the response, following the dogma “the dose makes the poison”. Many endocrine disrupting chemicals, including bisphenol-A (BPA), induce non-monotonic dose response (NMDR) relationships, which are unconventional and have tremendous implications in risk assessment. Although several molecular mechanisms have been proposed to explain NMDR relationships, they are largely undemonstrated. Using mouse pancreatic β-cells from wild-type and oestrogen receptor ERβ−/− mice, we found that exposure to increasing doses of BPA affected Ca²⁺ entry in an NMDR manner. Low doses decreased plasma membrane Ca²⁺ currents after downregulation of Cav2.3 ion channel expression, in a process involving ERβ. High doses decreased Ca²⁺ currents through an ERβ-mediated mechanism and simultaneously increased Ca²⁺ currents via oestrogen receptor ERα. The outcome of both molecular mechanisms explains the NMDR relationship between BPA and Ca²⁺ entry in β-cells.

The role of polycarbonate monomer bisphenol-A in insulin resistance

Bisphenol A (BPA) is a synthetic unit of polycarbonate polymers and epoxy resins, the types of plastics that could be found in essentially every human population and incorporated into almost every aspect of the modern human society. BPA polymers appear in a wide range of products, from liquid storages (plastic bottles, can and glass linings, water pipes and tanks) and food storages (plastics wraps and containers), to medical and dental devices. BPA polymers could be hydrolyzed spontaneously or in a photo- or temperature-catalyzed process, providing widespread environmental distribution and chronic exposure to the BPA monomer in contemporary human populations. Bisphenol A is also a xenoestrogen, an endocrine-disrupting chemical (EDC) that interferes with the endocrine system mimicking the effects of an estrogen and could potentially keep our endocrine system in a constant perturbation that parallels endocrine disruption arising during pregnancy, such as insulin resistance (IR). Gestational insulin resistance represents a natural biological phenomenon of higher insulin resistance in peripheral tissues of the pregnant females, when nutrients are increasingly being directed to the embryo instead of being stored in peripheral tissues. Gestational diabetes mellitus may appear in healthy non-diabetic females, due to gestational insulin resistance that leads to increased blood sugar levels and hyperinsulinemia (increased insulin production from the pancreatic beta cells). The hypothesis states that unnoticed and constant exposure to this environmental chemical might potentially lead to the formation of chronic low-level endocrine disruptive state that resembles gestational insulin resistance, which might contribute to the development of diabetes. The increasing body of evidence supports the major premises of this hypothesis, as exemplified by the numerous publications examining the association of BPA and insulin resistance, both epidemiological and mechanistic. However, to what extent BPA might contribute to the development of diabetes in the modern societies still remains unknown. In this review, I discuss the chemical properties of BPA and the sources of BPA contamination found in the environment and in human tissues. I provide an overview of mechanisms for the proposed role of bisphenol A in insulin resistance and diabetes, as well as other related diseases, such as cardiovascular diseases. I describe the transmission of BPA effects to the offspring and postulate that gender related differences might originate from differences in liver enzyme levels, such as UDP-glucuronosyltransferase, which is involved in BPA processing and its elimination from the organism. I discuss the molecular mechanisms of BPA action through nuclear and membrane-bound ER receptors, non-monotonic dose response, epigenetic modifications of the DNA and propose that chronic exposure to weak binders, such as BPA, may mimic the effects of strong binders, such as estrogens.

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.

Hepatic Lipid Accumulation and Nrf2 Expression following Perinatal and Peripubertal Exposure to Bisphenol A in a Mouse Model of Nonalcoholic Liver Disease

BACKGROUND

Exposure to chemicals during critical windows of development may re-program liver for increased risk of nonalcoholic fatty liver disease (NAFLD). Bisphenol A (BPA), a plastics component, has been described to impart adverse effects during gestational and lactational exposure. Our work has pointed to nuclear factor E2-related factor 2 (Nrf2) being a modulator of hepatic lipid accumulation in models of NAFLD.

OBJECTIVES

To determine if chemical exposure can prime liver for steatosis via modulation of NRF2 and epigenetic mechanisms.

METHODS

Utilizing BPA as a model exposure, pregnant CD-1 mice were administered 25μg/kg/day BPA via osmotic minipumps from gestational day 8 through postnatal day (PND)16. The offspring were weaned on PND21 and exposed to same dose of BPA via their drinking water through PND35. Tissues were collected from pups at week 5 (W5), and their littermates at week 39 (W39).

RESULTS

BPA increased hepatic lipid content concomitant with increased Nrf2 and pro-lipogenic enzyme expression at W5 and W39 in female offspring. BPA exposure increased Nrf2 binding to a putative antioxidant response element consensus sequence in the sterol regulatory-element binding protein-1c (Srebp-1c) promoter. Known Nrf2 activators increased SREBP-1C promoter reporter activity in HepG2 cells. Methylated DNA immunoprecipitation-PCR and pyrosequencing revealed that developmental BPA exposure induced hypomethylation of the Nrf2 and Srebp-1c promoters in livers of W5 mice, which was more prominent in W39 mice than in others.

CONCLUSION

Exposure to a xenobiotic during early development induced persistent fat accumulation via hypomethylation of lipogenic genes. Moreover, increased Nrf2 recruitment to the Srebp-1c promoter in livers of BPA-exposed mice was observed. Overall, the underlying mechanisms described a broader impact beyond BPA exposure and can be applied to understand other models of NAFLD. https://doi.org/10.1289/EHP664.

Bile Acids and Tryptophan Metabolism Are Novel Pathways Involved in Metabolic Abnormalities in BPA-Exposed Pregnant Mice and Male Offspring

Increasing evidence has demonstrated that exposure to endocrine-disrupting chemicals impacts maternal and fetal health, but the underlying mechanisms are still unclear. We previously showed that dietary exposure to 10 µg/kg body weight (bw)/d and 10 mg/kg bw/d of bisphenol A (BPA) during pregnancy induced metabolic abnormalities in F1 male offspring and gestational glucose intolerance in F0 pregnant mice. The aim of this study was to elucidate the underlying etiologies of BPA exposure-induced metabolic disease by analyzing the male fetal liver metabolome. Using the Metabolon Discover HD4 Platform, our laboratory identified metabolic pathways that were altered by BPA exposure, including biochemicals in lipid and amino acid metabolism. Specifically, primary and secondary bile acids were increased in liver from BPA-exposed embryonic day 18.5 male fetuses. We subsequently showed that increased bile acid was associated with a defective farnesoid X receptor-dependent negative feedback mechanism in BPA-exposed fetuses. In addition, through metabolomics, we observed that BPA-exposed fetuses had elevated tryptophan levels. Independent liquid chromatography and mass spectrometry measurement revealed that BPA-exposed dams also had increased tryptophan levels relative to those of controls. Because several key enzymes in tryptophan catabolism are vitamin B6 dependent and vitamin B6 deficiencies have been linked to gestational diabetes, we tested the impact of vitamin B6 supplementation and showed that it rescued gestational glucose intolerance in BPA-exposed pregnant mice. Our study has therefore identified two pathways (bile acid and tryptophan metabolism) that potentially underlie BPA-induced maternal and fetal metabolic disease.

Effect of Bisphenol-A (BPA) on insulin signal transduction and GLUT4 translocation in gastrocnemius muscle of adult male albino rat

Environmental estrogens bind to estrogen receptors, mimic estrogenic actions, and have adverse effects on human health like Bisphenol - A (BPA) which is used as a monomer in the production of polycarbonate plastics (PC) and epoxy resins which are used in variety of canned foods. Skeletal muscle plays an essential role in maintaining systemic glucose metabolism. In the present study, we investigated the possible effects of BPA on insulin signalling molecules and GLUT4 translocation in the gastrocnemius muscle of adult male rat. Rats were divided into four groups - Group I: Control (vehicle-corn oil treated), Group II, III and IV were administered with BPA (10, 100 and 400mg/kg b.wt/day, respectively) through oral gavage. Fasting blood glucose level of BPA treated groups showed a significant increase, oral glucose tolerance and insulin tolerance were also impaired in these animals. BPA significantly decreased the protein levels of insulin signalling molecules like IR, IRS-1, Akt, AS160 and its phosphorylated forms and blunts GLUT4 translocation by altering the levels of v- and t- SNARE proteins that assist the translocation process, thereby decreasing glucose uptake and oxidation in the gastrocnemius muscle. These results suggest that BPA has detrimental effects on insulin signalling molecules and GLUT4 translocation in the gastrocnemius muscle and thus impairs glucose homeostasis.

Is bisphenol A an environmental obesogen?

Bisphenol A (BPA) is an endocrine disruptor with an oestrogenic activity that is widely produced for the manufacture of polycarbonate plastic, epoxy resin, and thermal paper. Its ubiquitous presence in the environment contributes to broad and continuous human exposure, which has been associated with deleterious health effects. Despite numerous controversial discussions and a lack of consensus about BPA's safety, growing evidence indicates that BPA exposure positively correlates with an increased risk of developing obesity. An updated analysis of the epidemiological, in vivo, and in vitro studies indicates that BPA should be considered an obesogenic environmental compound. Precisely, BPA exposure during all life stages correlates with increased body weight and/or body mass index. Developmental periods that include prenatal, infancy, and childhood appear to be critical windows with increased sensitivity to BPA effects. Finally, blood analysis and in vitro data clearly demonstrate that BPA promotes adipogenesis, lipid and glucose dysregulation, and adipose tissue inflammation, thus contributing to the pathophysiology of obesity. Future prevention efforts should now be employed to avoid BPA exposure, and more research to determine in depth the critical time windows, doses, and impact of long-term exposure of BPA is warranted in order to clarify its risk assessment.

Epigenetics in formation, function, and failure of the endocrine pancreas

Background

Epigenetics, in the broadest sense, governs all aspects of the life of any multicellular organism, as it controls how differentiated cells arrive at their unique phenotype during development and differentiation, despite having a uniform (with some exceptions such as T-cells and germ cells) genetic make-up. The endocrine pancreas is no exception. Transcriptional regulators and epigenetic modifiers shape the differentiation of the five major endocrine cell types from their common precursor in the fetal pancreatic bud. Beyond their role in cell differentiation, interactions of the organism with the environment are also often encoded into permanent or semi-permanent epigenetic marks and affect cellular behavior and organismal health. Epigenetics is defined as any heritable – at least through one mitotic cell division – change in phenotype or trait that is not the result of a change in genomic DNA sequence, and it forms the basis that mediates the environmental impact on diabetes susceptibility and islet function.

Scope of review

We will summarize the impact of epigenetic regulation on islet cell development, maturation, function, and pathophysiology. We will briefly recapitulate the major epigenetic marks and their relationship to gene activity, and outline novel strategies to employ targeted epigenetic modifications as a tool to improve islet cell function.

Major conclusions

The improved understanding of the epigenetic underpinnings of islet cell differentiation, function and breakdown, as well as the development of innovative tools for their manipulation, is key to islet cell biology and the discovery of novel approaches to therapies for islet cell failure.

Is bisphenol A exposure associated with the development of glucose intolerance and increased insulin resistance in Thais?

Bisphenol A (BPA), the monomeric component of polycarbonate plastics, reportedly possesses endocrine-disrupting effects. Exposure to low levels of BPA during more vulnerable periods leads to abnormalities related to sexual development in experimental animals. Moreover, recently a few epidemiological studies in Caucasians have demonstrated the association of BPA exposure with type 2 diabetes. Therefore, in the present study we examined the association of BPA exposure and abnormal glucose tolerance in Thais. This is a cross-sectional study of 240 participants aged at least 50 years, randomly selected by computer-generated random numbers within each glucose tolerance status from an oral glucose tolerance study of 661 participants. There were 80 participants in each group of type 2 diabetes, impaired glucose tolerance (IGT) and normal glucose tolerance (NGT). Serum BPA was measured by competitive ELISA. The detection rate of BPA was significantly higher in participants with IGT compared to those with NGT ( p < 0.05), while no difference was found between participants with type 2 diabetes and NGT. When participants with type 2 diabetes were stratified into those with fasting plasma glucose (FPG) under the diabetic threshold (<126 mg/dL) and those over (≥126 mg/dL), it was found that those with FPG under the diabetic threshold had measurable rates of BPA comparable to those with IGT, and rates significantly higher than the NGT group ( p < 0.05), while those with FPG over the diabetic threshold did not have higher rates of measurable BPA compared with the NGT group. In conclusion, BPA exposure is not uncommon in Thais. There is an association between BPA exposure and IGT, but not type 2 diabetes.

Inhalation Toxicity of Bisphenol A and Its Effect on Estrous Cycle, Spatial Learning, and Memory in Rats upon Whole-Body Exposure

Bisphenol A (BPA) is a monomer used in a polymerization reaction in the production of polycarbonate plastics. It has been used in many consumer products, including plastics, polyvinyl chloride, food packaging, dental sealants, and thermal receipts. However, there is little information available on the inhalation toxicity of BPA. Therefore, the aim of this study was to determine its inhalation toxicity and effects on the estrous cycle, spatial learning, and memory. Sprague-Dawley rats were exposed to 0, 10, 30, and 90 mg/m³ BPA, 6 hr/day, 5 days/week for 8 weeks via whole-body inhalation. Mortality, clinical signs, body weight, hematology, serum chemistry, estrous cycle parameters, performance in the Morris water maze test, and organ weights, as well as gross and histopathological findings, were compared between the control and BPA exposure groups. Statistically significant changes were observed in serum chemistry and organ weights upon exposure to BPA. However, there was no BPA-related toxic effect on the body weight, food consumption, hematology, serum chemistry, organ weights, estrous cycle, performance in the Morris water maze test, or gross or histopathological lesions in any male or female rats in the BPA exposure groups. In conclusion, the results of this study suggested that the no observable adverse effect level (NOAEL) for BPA in rats is above 90 mg/m³/6 hr/day, 5 days/week upon 8-week exposure. Furthermore, BPA did not affect the estrous cycle, spatial learning, or memory in rats.

Perinatal Exposure to Low-Dose Bisphenol-A Disrupts the Structural and Functional Development of the Hypothalamic Feeding Circuitry

Bisphenol-A (BPA) is a component of polycarbonate and other plastics to which humans are regularly exposed at low levels. BPA is characterized as an endocrine disruptor because of observations of its estrogenic activity in various experimental models. We have previously shown evidence of disrupted hypothalamic feeding circuitry and leptin sensitivity in adult BPA-exposed animals subjected to a high-fat diet, but because these animals were already exhibiting a diet-induced obese phenotype, we could not rule out the possibility that these observations were simply consequences of the obesity, not a preexisting phenotype produced by BPA exposure. Here, we studied leptin sensitivity and hypothalamic structure in young BPA-exposed animals before the onset of a body weight or metabolic phenotype. Pregnant and lactating CD-1 mice were exposed to either BPA or diethylstilbestrol (DES) at low, environmentally relevant doses via their diet. Studies of leptin function and neurobiology were conducted on offspring at several time points. Young adult offspring from this experiment were resistant to leptin-induced suppression of food intake, body weight loss, and hypothalamic pro-opiomelanocortin (POMC) upregulation. Both male and female BPA-exposed mice showed a reduced density of POMC projections into the paraventricular nucleus of the hypothalamus (PVN). BPA- and DES-exposed pups had respectively delayed and blunted postnatal leptin surges, and POMC projections into the PVN were rescued in female BPA-exposed animals given daily injections of supplemental leptin. Our findings suggest that BPA, a putative obesogen, may exert its effects through developmental programming of the hypothalamic melanocortin circuitry, permanently altering the neurobiology of metabolic homeostasis.

Trimester-Specific Urinary Bisphenol A Concentrations and Blood Glucose Levels Among Pregnant Women From a Fertility Clinic

CONTEXT

Women with a history of infertility are at increased risk of impaired glucose tolerance during pregnancy. Studies suggest higher urinary bisphenol A (BPA) concentrations are associated with diabetes in nonpregnant populations, but the association between BPA and glucose levels among pregnant women is unclear.

OBJECTIVE

To assess trimester-specific urinary BPA concentrations in relation to blood glucose levels among subfertile women.

DESIGN

Environment and Reproductive Health Study, an ongoing prospective cohort study.

SETTING

A fertility center in a teaching hospital.

PATIENTS

A total of 245 women contributed at least one urine sample during first and/or second trimesters, delivered a singleton or twin pregnancy, and had available blood glucose data (2005 to 2015).

MAIN OUTCOME MEASURE

Blood glucose levels after a nonfasting 50-g glucose challenge test at 24 to 28 weeks of gestation.

RESULTS

The specific gravity-adjusted geometric mean urinary BPA concentrations during first and second trimesters were 1.39 and 1.27 µg/L, respectively. Second-trimester BPA concentrations were positively associated with blood glucose (P, trend = 0.01). Specifically, the adjusted mean glucose levels (95% confidence interval) for women in the highest quartile of second-trimester BPA concentrations was 119 (112, 126) mg/dL compared with 106 (100, 112) mg/dL for women in the lowest quartile. No associations were observed between first-trimester BPA concentrations and glucose levels.

CONCLUSIONS

BPA exposure during the second trimester may have adverse effect on blood glucose levels among subfertile women. As the findings represent the first report suggesting a potential etiologically relevant window for BPA and glucose in humans, further studies are needed.

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.

Bisphenol a induces steatosis in HepaRG cells using a model of perinatal exposure

Human exposure to bisphenol A (BPA) could favor obesity and related metabolic disorders such as hepatic steatosis. Investigations in rodents have shown that these deleterious effects are observed not only when BPA is administered during the adult life but also with different protocols of perinatal exposure. Whether perinatal BPA exposure could pose a risk in human is currently unknown, and thus appropriate in vitro models could be important to tackle this major issue. Accordingly, we determined whether long-term BPA treatment could induce steatosis in human HepaRG cells by using a protocol mimicking perinatal exposure. To this end, the kinetics of expression of seven proteins differentially expressed during liver development was determined during a 4-week period of cell culture required for proliferation and differentiation. By analogy with data reported in rodents and humans, our results indicated that the period of cell culture around day 15 and day 18 after seeding could be considered as the "natal" period. Consequently, HepaRG cells were treated for 3 weeks with BPA (from 0.2 to 2000 nM), with a treatment starting during the proliferating period. BPA was able to induce steatosis with a nonmonotonic dose response profile, with significant effects on neutral lipids and triglycerides observed for the 2 nM concentration. However, the expression of many enzymes involved in lipid and carbohydrate homeostasis was unchanged in exposed HepaRG cells. The expression of other potential BPA targets and enzymes involved in BPA biotransformation was also determined, giving answers as well as new questions regarding the mechanisms of action of BPA. Hence, HepaRG cells provide a valuable model that can prove useful for the toxicological assessment of endocrine disruptors on hepatic metabolisms, in particular in the developing liver. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1024-1036, 2017.

Bisphenol S (BPS) Alters Maternal Behavior and Brain in Mice Exposed During Pregnancy/Lactation and Their Daughters

Estrogenic endocrine disrupting chemicals have been shown to disrupt maternal behavior in rodents. We investigated the effects of an emerging xenoestrogen, bisphenol S (BPS), on maternal behavior and brain in CD-1 mice exposed during pregnancy and lactation (F0 generation) and in female offspring exposed during gestation and perinatal development (F1 generation). We observed different effects in F0 and F1 dams for a number of components of maternal behavior, including time on the nest, time spent on nest building, latency to retrieve pups, and latency to retrieve the entire litter. We also characterized expression of estrogen receptor α in the medial preoptic area (MPOA) and quantified tyrosine hydroxylase immunoreactive cells in the ventral tegmental area, 2 brain regions critical for maternal care. BPS-treated females in the F0 generation had a statistically significant increase in estrogen receptor α expression in the caudal subregion of the central MPOA in a dose-dependent manner. In contrast, there were no statistically significant effects of BPS on the MPOA in F1 dams or the ventral tegmental area in either generation. This work demonstrates that BPS affects maternal behavior and brain with outcomes depending on generation, dose, and postpartum period. Many studies examining effects of endocrine disrupting chemicals view the mother as a means by which offspring can be exposed during critical periods of development. Here, we demonstrate that pregnancy and lactation are vulnerable periods for the mother. We also show that developmental BPS exposure alters maternal behavior later in adulthood. Both findings have potential public health implications.

Maternal bisphenol A exposure alters rat offspring hepatic and skeletal muscle insulin signaling protein abundance

BACKGROUND

The obesogenic and diabetogenic effects of the environmental toxin bisphenol A during critical windows of development are well recognized. Liver and skeletal muscle play a central role in the control of glucose production, utilization, and storage.

OBJECTIVES

We hypothesized that maternal bisphenol A exposure disrupts insulin signaling in rat offspring liver and skeletal muscle. We determined the protein expression of hepatic and skeletal muscle insulin signaling molecules including insulin receptor beta, its downstream target insulin receptor substrate 1 and glucose transporters (glucose transporter 2, glucose transporter 4), and hepatic glucose-regulating enzymes phosphoenolpyruvate carboxykinase and glucokinase.

STUDY DESIGN

Rat dams had ad libitum access to filtered drinking water (control) or drinking water with bisphenol A from 2 weeks prior to mating and through pregnancy and lactation. Offspring litters were standardized to 4 males and 4 females and nursed by the same dam. At weaning, bisphenol A exposure was removed from all offspring. Glucose tolerance was tested at 6 weeks and 6 months. Liver and skeletal muscle was collected from 3 week old and 10 month old offspring for protein expression (Western blot) of insulin receptor beta, insulin receptor substrate 1, glucose transporter 2, glucose transporter 4, phosphoenolpyruvate carboxykinase, and glucokinase.

RESULTS

Male, but not female, bisphenol A offspring had impaired glucose tolerance at 6 weeks and 6 months. Both male and female adult offspring had higher glucose-stimulated insulin secretion as well as the ratio of stimulated insulin to glucose. Male bisphenol A offspring had higher liver protein abundance of the 200 kDa insulin receptor beta precursor (2-fold), and insulin receptor substrate 1 (1.5-fold), whereas glucose transporter 2 was 0.5-fold of the control at 3 weeks of age. In adult male bisphenol A offspring, the abundance of insulin receptor beta was higher (2-fold) and glucose transporter 4 was 0.8-fold of the control in skeletal muscle. In adult female bisphenol A offspring, the skeletal muscle protein abundance of glucose transporter 4 was 0.4-fold of the control.

CONCLUSION

Maternal bisphenol A had sex- and tissue-specific effects on insulin signaling components, which may contribute to increased risk of glucose intolerance in offspring. Glucose transporters were consistently altered at both ages as well as in both sexes and may contribute to glucose intolerance. These data suggest that maternal bisphenol A exposure should be limited during pregnancy and lactation.

Bisphenol A Is More Potent than Phthalate Metabolites in Reducing Pancreatic β-Cell Function

Bisphenol A (BPA) and phthalates are common environmental contaminants that have been proposed to influence incidence and development of types 1 and 2 diabetes. Thus, effects of BPA and three phthalate metabolites (monoisobutyl phthalate (MiBP), mono-n-butyl phthalate (MnBP), and mono-(2-ethylhexyl) phthalate (MEHP)) were studied in the pancreatic β-cell line INS-1E, after 2–72 h of exposure to 5–500 μM. Three endpoints relevant to accelerated development of types 1 or 2 diabetes were investigated: β-cell viability, glucose-induced insulin secretion, and β-cell susceptibility to cytokine-induced cell death. BPA and the phthalate metabolites reduced cellular viability after 72 h of exposure, with BPA as the most potent chemical. Moreover, BPA, MEHP, and MnBP increased insulin secretion after 2 h of simultaneous exposure to chemicals and glucose, with potency BPA > MEHP > MnBP. Longer chemical exposures (24–72 h) showed no consistent effects on glucose-induced insulin secretion, and none of the environmental chemicals affected susceptibility to cytokine-induced cell death. Overall, BPA was more potent than the investigated phthalate metabolites in affecting insulin secretion and viability in the INS-1E pancreatic β-cells. In contrast to recent literature, concentrations with relevance to human exposures (1–500 nM) did not affect the investigated endpoints, suggesting that this experimental model displayed relatively low sensitivity to environmental chemical exposure.

Pancreatic impairment and Igf2 hypermethylation induced by developmental exposure to bisphenol A can be counteracted by maternal folate supplementation

Increasing evidence indicates that bisphenol A (BPA), a widely manufactured environmental pollutant, can induce changes in DNA methylation paatterns, which is a potential mechanism linking this environmental exposure to disease development. We investigated the influence of developmental exposure to BPA on pancreatic DNA methylation patterns and whether maternal folate supplementation can modify the epigenetic status and pancreatic impairment induced by BPA. Our results showed that maternal dietary folate supplementation in rats exposed to BPA counteracted the observed BPA-induced pancreatic impairments in the offspring, which included disrupted insulin secretion and glucose intolerance, and impaired morphology and ultrastructure of β cells. Moreover, these pancreatic dysfunctions were shown to be associated with low expression and DNA hypermethylation of insulin-like growth factor-2 (Igf2) in islets induced by exposure to BPA during the developmental period. Importantly, maternal dietary folate supplementation was demonstrated to negate this Igf2 DNA hypermethylation in the offspring, which was consistent with the upregulation of Igf2 expression. Overall, our results suggest that early developmental exposure to BPA alters the DNA methylation of Igf2, that these altered methylation patterns are associated with impaired β-cell function in the offspring and that these effects can be counteracted by maternal folate supplementation. Copyright © 2017 John Wiley & Sons, Ltd.

Early life programming and the risk of non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is associated with obesity, insulin resistance, type 2 diabetes and cardiovascular disease and can be considered the hepatic manifestation of the metabolic syndrome. NAFLD represents a spectrum of disease, from the relatively benign simple steatosis to the more serious non-alcoholic steatohepatitis, which can progress to liver cirrhosis, hepatocellular carcinoma and end-stage liver failure, necessitating liver transplantation. Although the increasing prevalence of NAFLD in developed countries has substantial implications for public health, many of the precise mechanisms accounting for the development and progression of NAFLD are unclear. The environment in early life is an important determinant of cardiovascular disease risk in later life and studies suggest this also extends to NAFLD. Here we review data from animal models and human studies which suggest that fetal and early life exposure to maternal under- and overnutrition, excess glucocorticoids and environmental pollutants may confer an increased susceptibility to NAFLD development and progression in offspring and that such effects may be sex-specific. We also consider studies aimed at identifying potential dietary and pharmacological interventions aimed at reducing this risk. We suggest that further human epidemiological studies are needed to ensure that data from animal models are relevant to human health.

Delayed onset of puberty in male offspring from bisphenol A-treated dams is followed by the modulation of gene expression in the hypothalamic–pituitary–testis axis in adulthood

Bisphenol A (BPA) is a synthetic endocrine-disrupting chemical of high prevalence in the environment, which may affect the function of the hypothalamic–pituitary–testis (HPT) axis in adult rats. The aim of the present study was to evaluate whether exposure to BPA during hypothalamic sexual differentiation at doses below the reproductive no observable adverse effect level of the World Health Organization causes changes in the regulation of the HPT axis. For this, 0.5 or 5 mg kg−1 BPA was injected subcutaneously to the mothers from gestational day 18 to postnatal day (PND) 5. In adulthood (PND90), the mRNA expression of genes related to HPT axis was evaluated in hypothalamus, pituitary and testis. Hypothalamic expression of gonadotrophin-releasing hormone (Gnrh) and estrogen receptor 2 (Esr2) mRNA was increased in both BPA-treated groups compared to control group. In the pituitary, follicle stimulating hormone beta subunit (Fshb) and androgen receptor (Ar) mRNA expression was increased compared to control group in rats treated with 0.5 mg kg−1 of BPA, whereas estrogen receptor 1 (Esr1) mRNA expression was only increased in the group treated with 5 mg kg−1 of BPA, compared to control group. In the testis, there was increased expression of FSH receptor (Fshr) and inhibin beta B subunit (Inhbb) transcripts only in rats treated with 0.5 mg kg−1 of BPA. Serum testosterone and LH concentrations were increased in the group treated with 5 mg kg−1 of BPA. The results of the present study demonstrate for the first time that perinatal exposure to low doses of BPA during the critical period of hypothalamic sexual differentiation modifies the activity of the HPT axis in the offspring, with consequences for later life in adult rats.

Epigenetic control of β-cell function and failure

Type 2 diabetes is a highly heritable disease, but only ∼15% of this heritability can be explained by known genetic variant loci. In fact, body mass index is more predictive of diabetes than any of the common risk alleles identified by genome-wide association studies. This discrepancy may be explained by epigenetic inheritance, whereby changes in gene regulation can be passed along to offspring. Epigenetic changes throughout an organism's lifetime, based on environmental factors such as chemical exposures, diet, physical activity, and age, can also affect gene expression and susceptibility to diabetes. Recently, novel genome-wide assays of epigenetic marks have resulted in a greater understanding of how genetics, epigenetics, and the environment interact in the development and inheritance of diabetes.

A pathway of bisphenol A affecting mineral element contents in plant roots at different growth stages

Bisphenol A (BPA), an environmental endocrine disruptor, is an important industrial raw material. The wide use of BPA has increased the risk of BPA release into the environment, and it has become a new environmental pollutant. In this work, the ecological deleterious effects of this new pollutant on soybean roots at different growth stages were investigated by determining the contents of mineral elements (P, K, Ca, and Mg) and analyzing root activity and the activities of critical respiratory enzymes (hexokinase, phosphofructokinase, pyruvate kinase, and isocitrate dehydrogenase). Our results revealed that low dose (1.5mg/L) of BPA increased the levels of P, K, Mg, and Ca in soybean roots at different growth stages. Whereas, high doses (6.0 and 12.0mg/L) of BPA decreased the levels of P, K, and Mg contents in a dose-dependent manner. BPA had a promotive effect on the content of Ca in soybean roots. Synchronous observation showed that the aforementioned dual response to BPA were also observed in the root activity and respiratory enzyme activities. The effects of BPA on the mineral element contents, root activity and respiratory enzyme activities in soybean roots at different growth stages followed the order: flowering and podding stage>seed-filling stage>seedling stage (mineral element contents); seedling stage>flowering and podding stage>seed-filling stage (root activity and respiratory enzyme activities). In a word, the response of plant root activity and respiratory enzyme activities to BPA pollution is a pathway of BPA affecting mineral element contents in plant roots.

Molecular targets of developmental exposure to bisphenol A in diabesity: a focus on endoderm-derived organs

Several studies associate foetal human exposure to bisphenol A (BPA) to metabolic/endocrine diseases, mainly diabesity. They describe the role of BPA in the disruption of pancreatic beta cell, adipocyte and hepatocyte functions. Indeed, the complexity of the diabesity phenotype is due to the involvement of different endoderm-derived organs, all targets of BPA. Here, we analyse this point delineating a picture of different mechanisms of BPA toxicity in endoderm-derived organs leading to diabesity. Moving from epidemiological data, we summarize the in vivo experimental data of the BPA effects on endoderm-derived organs (thyroid, pancreas, liver, gut, prostate and lung) after prenatal exposure. Mainly, we gather molecular data evidencing harmful effects at low-dose exposure, pointing to the risk to human health. Although the fragmentation of molecular data does not allow a clear conclusion to be drawn, the present work indicates that the developmental exposure to BPA represents a risk for endoderm-derived organs development as it deregulates the gene expression from the earliest developmental stages. A more systematic analysis of BPA impact on the transcriptomes of endoderm-derived organs is still missing. Here, we suggest in vitro toxicogenomics approaches as a tool for the identification of common mechanisms of BPA toxicity leading to the diabesity in organs having the same developmental origin.

Morphofunctional Changes in the Thyroid Gland of Pubertal and Postpubertal Rats Exposed to Low Dose of DDT

Consumption of low dose DDT from birth until puberty suppressed functional activity of the thyroid gland in rats and leads to destructive changes in the organ during the postpubertal period with compensatory stimulation of secretory activity of thyrocytes aimed at normalization of thyroxin production.

Do environmental pollutants increase obesity risk in humans?

OBJECTIVES

Obesity has become a global epidemic and threat to public health. A good understanding of the causes can help attenuate the risk and spread. Environmental pollutants may have contributed to the rising global obesity rates. Some research reported associations between chemical pollutants and obesity, but findings are mixed. This study systematically examined associations between chemical pollutants and obesity in human subjects.

METHODS

Systematic review of relevant studies published between 1 January 1995 and 1 June 2016 by searching PubMed and MEDLINE®.

RESULTS

Thirty-five cross-sectional (n = 17) and cohort studies (n = 18) were identified that reported on associations between pollutants and obesity measures. Of them, 16 studies (45.71%) reported a positive association; none reported a sole inverse association; three (8.57%) reported a null association only; six (17.14%) reported both a positive and null association; seven (20.00%) reported a positive and inverse association; and three studies (8.57%) reported all associations (positive, inverse and null). Most studies examined the association between multiple different pollutants, different levels of concentration and in subsamples, which results in mixed results. Thirty-three studies reported at least one positive association between obesity and chemicals, such as polychlorinated biphenyls, biphenyl A, dichlorodiphenyltrichloroethane, dichlorodiphenyldichloroethylene and more. Certain chemicals, such as biphenyl A, were more likely to have high ORs ranging from 1.0 to 3.0, whereas highly chlorinated polychlorinated biphenyls were more likely to have negative ORs. Effects of chemicals on the endocrine system and obesity might vary by substance, exposure level, measure of adiposity and subject characteristics (e.g. sex and age).

CONCLUSIONS

Accumulated evidences show positive associations between pollutants and obesity in humans. Future large, long-term, follow-up studies are needed to assess impact of chemical pollutants on obesity risk and related mechanisms.

Maternal Triclosan consumption alters the appetite regulatory network on Wistar rat offspring and predispose to metabolic syndrome in the adulthood

The objectives of this study were to evaluate the effects of maternal oral exposure to the antibacterial Triclosan (TCS) during gestation and lactation on the metabolic status of the adult offspring and on the expression of main genes controlling the appetite regulatory network. Pregnant rats were fed ad-libitum with ground food + TCS (1 mg/kg) from day 14 of gestation to day 20 of lactation (n=3) or ground food (n=3). After litter reduction, 12 males and 12 females born from the TCS exposed rats (TCS, n=24) or not (Control, n=24) were used to evaluate monthly body weight, food intake, plasma levels of cholesterol, glucose and triglycerides, and the hypothalamic mRNA expression of agouti-related protein (Agrp), neuropeptide Y (Npy) and propiomelanocortin (Pomc). Body weight for rats in the TCS group was 12.5% heavier for males at 4 months (p<0.001) and 19% heavier for females at 8 months (p=0.01). Food intake was significantly higher for rats in the TCS group at 5 months of age (p<0.01). Cholesterol and glucose levels were significantly higher for rats in the TCS group at 8 months (p<0.05). mRNA expression of Npy and Agrp were significantly increased in hypothalami of rats in the TCS group at 2 months for males or 8 months for females (p<0.05). In conclusion, low doses of oral TCS consumption by the pregnant and lactating dam increase the hypothalamic expression of the orexigenic neuropeptides Npy and Agrp in the offspring and alter their metabolic status during adulthood, resembling development of the metabolic syndrome.

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

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

The association between bisphenol A exposure and type-2 diabetes: a world systematic review

The present study was conducted to systematically review, analyze, and interpret all the relevant evidence in the literature on the possible link between exposure to bisphenol A (BPA) and the risk of type-2 diabetes mellitus (T2DM). We developed a comprehensive search strategy and used it to search Web of Science, Scopus, PubMed, and Google Scholar up to March 31, 2016, producing 3108 hits, of which 13 original papers were included. Findings of these studies were quite controversial; few studies indicated a significant positive association between BPA exposure and T2DM, while some other failed to detect such a relationship. Overall, it can be suggested that chance is unlikely the plausible explanation for the observed association between BPA exposure and T2DM. This was mainly because even in the negative studies some clues could be found in favor of a statistically significant relationship between BPA and T2DM. Additionally, some of the studies had shortcomings in defining the exposure and outcome measures, which, if present, might have led to underestimating the relationship between BPA exposure and T2DM. The theoretical plausibility of such a relationship found earlier in animal studies also supports this point. However, more definitive answer requires the conduct of future longitudinal studies, in which the possible association between BPA exposure and T2DM is assessed over much longer periods of time with more temporally robust BPA measurements. In addition, it would be quite beneficial if future studies be conducted in areas where data is still lacking (e.g., South America, Australia/Oceania, and Europe). Graphical abstract ᅟ.

Influence of Bisphenol A on Type 2 Diabetes Mellitus

Bisphenol A (BPA) is an organic synthetic compound employed to produce plastics and epoxy resins. It is used as a structural component in polycarbonate beverage bottles and as coating for metal surface in food containers and packaging. The adverse effects of BPA on human health are widely disputed. BPA has been recently associated with a wide variety of medical disorders and, in particular, it was identified as potential endocrine-disrupting compound with diabetogenic action. Most of the clinical observational studies in humans reveal a positive link between BPA exposure, evaluated by the measurement of urinary BPA levels, and the risk of developing type 2 diabetes mellitus. Clinical studies on humans and preclinical studies on in vivo, ex vivo, and in vitro models indicate that BPA, mostly at low doses, may have a role in increasing type 2 diabetes mellitus developmental risk, directly acting on pancreatic cells, in which BPA induces the impairment of insulin and glucagon secretion, triggers inhibition of cell growth and apoptosis, and acts on muscle, hepatic, and adipose cell function, triggering an insulin-resistant state. The current review summarizes the available evidences regarding the association between BPA and type 2 diabetes mellitus, focusing on both clinical and preclinical studies.

Developmental Bisphenol A Exposure Modulates Immune-Related Diseases

Bisphenol A (BPA), used in polycarbonate plastics and epoxy resins, has a widespread exposure to humans. BPA is of concern for developmental exposure resulting in immunomodulation and disease development due to its ability to cross the placental barrier and presence in breast milk. BPA can use various mechanisms to modulate the immune system and affect diseases, including agonistic and antagonistic effects on many receptors (e.g., estrogen receptors), epigenetic modifications, acting on cell signaling pathways and, likely, the gut microbiome. Immune cell populations and function from the innate and adaptive immune system are altered by developmental BPA exposure, including decreased T regulatory (Treg) cells and upregulated pro- and anti-inflammatory cytokines and chemokines. Developmental BPA exposure can also contribute to the development of type 2 diabetes mellitus, allergy, asthma and mammary cancer disease by altering immune function. Multiple sclerosis and type 1 diabetes mellitus may also be exacerbated by BPA, although more research is needed. Additionally, BPA analogs, such as bisphenol S (BPS), have been increasing in use, and currently, little is known about their immune effects. Therefore, more studies should be conducted to determine if developmental exposure BPA and its analogs modulate immune responses and lead to immune-related diseases.

Effects of In Utero Exposure to Ethinyl Estradiol on Tamoxifen Resistance and Breast Cancer Recurrence in a Preclinical Model

Background

Responses to endocrine therapies vary among patients with estrogen receptor (ER+) breast cancer. We studied whether in utero exposure to endocrine-disrupting compounds might explain these variations.

Methods

We describe a novel ER+ breast cancer model to study de novo and acquired tamoxifen (TAM) resistance. Pregnant Sprague Dawley rats were exposed to 0 or 0.1 ppm ethinyl estradiol (EE2), and the response of 9,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumors to 15 mg/kg TAM, with (n = 17 tumors in the controls and n = 20 tumors in EE2 offspring) or without 1.2 g/kg valproic acid and 5 mg/kg hydralazine (n = 24 tumors in the controls and n = 32 tumors in EE2 offspring) in the female offspring, was assessed. One-sided Chi2 tests were used to calculate P values. Comparisons of differentially expressed genes between mammary tumors in in utero EE2-exposed and control rats, and between anti-estrogen-resistant LCC9 and -sensitive LCC1 human breast cancer cells, were also performed.

Results

In our preclinical model, 54.2% of mammary tumors in the control rats exhibited a complete response to TAM, of which 23.1% acquired resistance with continued anti-estrogen treatment and recurred. Mammary tumors in the EE2 offspring were statistically significantly less likely to respond to TAM (P = .047) and recur (P = .007). In the EE2 offspring, but not in controls, adding valproic acid and hydralazine to TAM prevented recurrence (P < .001). Three downregulated and hypermethylated genes (KLF4, LGALS3, MICB) and one upregulated gene (ETV4) were identified in EE2 tumors and LCC9 breast cancer cells, and valproic acid and hydralazine normalized the altered expression of all four genes.

Conclusions

Resistance to TAM may be preprogrammed by in utero exposure to high estrogen levels and mediated through reversible epigenetic alterations in genes associated with epithelial-mesenchymal transition and tumor immune responses.

Epigenetic disruption and glucose homeostasis changes following low-dose maternal bisphenol A exposure

Developmental exposure to bisphenol A (BPA) has been linked to impaired glucose homeostasis and pancreatic function in adulthood, which has been hypothesized to result from the disruption of pancreatic β-cell development at early life. Here we evaluated whether maternal BPA exposure disrupts β-cell development and glucose tolerance and the role of epigenetic modifications of key regulator in this process. We found that maternal exposure to BPA (10 μg kg-1 d-1) reduced the pancreatic β-cell mass and the expression of pancreatic and duodenal homeobox 1 (Pdx1) at birth, as well as the expression of Pdx1 at gestational day (GD) 15.5. In parallel with the decreased expression of Pdx1, histones H3 and H4 deacetylation, along with demethylation of histone 3 lysine 4 (H3K4) and methylation of histone 3 lysine 9 (H3K9), were found at the promoter of Pdx1, while no significant changes in DNA methylation status were detected at this region. Moreover, these alterations were observed in adult life along with impaired glucose tolerance. We conclude that maternal exposure to BPA reduces pancreatic β-cell mass at birth by reducing PDX1+ progenitors during fetal development through altering the histone modifications of Pdx1, which can be propagated to later life and increase the susceptibility to glucose intolerance.

Environmental Contaminants and Pancreatic Beta-Cells

Despite health policies as well as clinical and research efforts, diabetes prevalence is still rising around the world. A multitude of causes have been suggested for this increase, mostly related to familial background, the occidental diet which is rich in fat/carbohydrates, and sedentary life style. Type 2 diabetes involves malfunctions of the primary pancreatic beta-cells, usually attributed to local damage; however, it can be associated with other stressful environmental agents, such as chemical contaminants from food, plastic and air, among others. Indeed, exposure to these chemical agents during perinatal and adolescent life can increase the risk of developing cardiometabolic diseases later in life. This review explores data showing which environmental chemical agents may produce injury in beta-cells and further impair the insulinotropic process of type 2 diabetes. Additionally, it points the need to also consider unusual causes of metabolic diseases, such as environmental contaminants.

Polycystic ovary syndrome and environmental toxins

Polycystic ovary syndrome (PCOS) is the most common, heterogeneous, and multifactorial endocrine disorder in premenopausal women. The pathophysiology of this endocrinopathy is still unclear; however, the heterogeneity of its features within ethnic races, geographic location, and families suggests that environment and lifestyle are of prime importance. This work is mainly focused on the possible role of the most common and studied environmental toxins for this syndrome in the pathogenesis of PCOS. Plasticizers, such as bisphenol A (BPA) or phthalates, which belong to the categories of endocrine disrupting chemicals (EDCs) and advanced glycation end products (AGEs), affect humans' health in everyday, industrialized life; therefore special attention should be paid to such exposure. Timing of exposure to EDCs is crucial for the intensity of adverse health effects. It is now evident that fetuses, infants, and/or young children are the most susceptible groups, especially in the early development periods. Prenatal exposure to EDCs that mimic endogenous hormones may contribute to the altered fetal programming and in consequence lead to PCOS and other adverse health effects, potentially transgenerationally. Acute or prolonged exposure to EDCs and AGEs through different life cycle stages may result in destabilization of the hormonal homeostasis and lead to disruption of reproductive functions. They may also interfere with metabolic alterations such as obesity, insulin resistance, and compensatory hyperinsulinemia that can exacerbate the PCOS phenotype and contribute to PCOS consequences such as type 2 diabetes and cardiovascular disease. Since wide exposure to environmental toxins and their role in the pathophysiology of PCOS are supported by extensive data derived from diverse scientific models, protective strategies and strong recommendations should be considered to reduce human exposure to protect present and future generations from their adverse health effects.

Perinatal BPA exposure alters body weight and composition in a dose specific and sex specific manner: The addition of peripubertal exposure exacerbates adverse effects in female mice

Body weight (BW) and body composition were examined in CD-1 mice exposed perinatally or perinatally and peripubertally to 0, 0.25, 2.5, 25, or 250μg BPA/kg BW/day. Our goal was to identify the BPA dose (s) and the exposure window(s) that increased BW and adiposity, and to assess potential sex differences in this response. Both perinatal exposure alone and perinatal plus peripubertal exposure to environmentally relevant levels of BPA resulted in lasting effects on body weight and body composition. The effects were dose specific and sex specific and were influenced by the precise window of BPA exposure. The addition of peripubertal BPA exposure following the initial perinatal exposure exacerbated adverse effects in the females but appeared to reduce differences in body weight and body composition between control and BPA exposed males. Some effects of BPA on body weight and body composition showed a non-linear dose response.

Bisphenol-A and metabolic diseases: epigenetic, developmental and transgenerational basis

Exposure to environmental toxicants is now accepted as a factor contributing to the increasing incidence of obesity and metabolic diseases around the world. Such environmental compounds are known as 'obesogens'. Among them, bisphenol-A (BPA) is the most widespread and ubiquitous compound affecting humans and animals. Laboratory animal work has provided conclusive evidence that early-life exposure to BPA is particularly effective in predisposing individuals to weight gain. Embryonic exposure to BPA is reported to generate metabolic disturbances later in life, such as obesity and diabetes. When BPA administration is combined with a high-fat diet, there is an exacerbation in the development of metabolic disorders. Remarkably, upon BPA exposure of gestating females, metabolic disturbances have been found both in the offspring and later in life in the mothers themselves. When considering the metabolic effects generated by an early developmental exposure to BPA, one of the questions that arises is the role of precursor cells in the etiology of metabolic disorders. Current evidence shows that BPA and other endocrine disruptors have the ability to alter fat tissue development and growth by affecting the capacity to generate functional adipocytes, as well as their rate of differentiation to specific cell types. Epigenetic mechanisms seem to be involved in the BPA-induced effects related to obesity, as they have been described in both in vitro and in vivo models. Moreover, recent reports also show that developmental exposure to BPA generates abnormalities that can be transmitted to future generations, in a process called as transgenerational epigenetic inheritance.

Bisphenol A affects early bovine embryo development and metabolism that is negated by an oestrogen receptor inhibitor

Increasing evidence supports an association between exposure to endocrine disruptors, such as the xenoestrogen bisphenol A (BPA), a commonly used plasticiser, and the developmental programming of offspring health. To date however animal studies to investigate a direct causal have mainly focussed on supra-environmental BPA concentrations, without investigating the effect on the early embryo. In this study we investigated the effect of acute BPA exposure (days 3.5 to 7.5 post-fertilisation) at environmentally relevant concentrations (1 and 10 ng/mL) on in vitro bovine embryo development, quality and metabolism. We then examined whether culturing embryos in the presence of the oestrogen receptor inhibitor fulvestrant could negate effects of BPA and 17β-oestradiol (E2). Exposure to BPA or E2 (10 ng/mL) decreased blastocyst rate and the percentage of transferrable quality embryos, without affecting cell number, lineage allocation or metabolic gene expression compared to untreated embryos. Notably, blastocysts exposed to BPA and E2 (10 ng/mL) displayed an increase in glucose consumption. The presence of fulvestrant however negated the adverse developmental and metabolic effects, suggesting BPA elicits its effects via oestrogen-mediated pathways. This study demonstrates that even acute exposure to an environmentally relevant BPA concentration can affect early embryo development and metabolism. These may have long-term health consequences on an individual.

An Emerging Role of micro-RNA in the Effect of the Endocrine Disruptors

Endocrine-disrupting chemicals (EDCs) are diverse natural and synthetic chemicals that may alter various mechanisms of the endocrine system and produce adverse developmental, reproductive, metabolic, and neurological effects in both humans and wildlife. Research on EDCs has revealed that they use a variety of both nuclear receptor-mediated and non-receptor-mediated mechanisms to modulate different components of the endocrine system. The molecular mechanisms underlying the effects of EDCs are still under investigation. Interestingly, some of the effects of EDCs have been observed to pass on to subsequent unexposed generations, which can be explained by the gametic transmission of deregulated epigenetic marks. Epigenetics is the study of heritable changes in gene expression that occur without a change in the DNA sequence. Epigenetic mechanisms, including histone modifications, DNA methylation, and specific micro-RNAs (miRNAs) expression, have been proposed to mediate transgenerational transmission and can be triggered by environmental factors. MiRNAs are short non-coding RNA molecules that post-transcriptionally repress the expression of genes by binding to 3′-untranslated regions of the target mRNAs. Given that there is mounting evidence that miRNAs are regulated by hormones, then clearly it is important to investigate the potential for environmental EDCs to deregulate miRNA expression and action.

Food contaminants and programming of type 2 diabetes: recent findings from animal studies

It is now accepted that the way our health evolves with aging is intimately linked to the quality of our early life. The present review highlights the emerging data of Developmental Origins of Health and Disease field on developmental disruption by toxicants and their subsequent effect on type 2 diabetes. We report adverse neonatal effects of several food contaminants during pregnancy and lactation, among them bisphenol A, chlorpyrifos, perfluorinated chemicals on pancreas integrity and functionality in later life. The described alterations, in conjunction with disruption of β cell mass in early life, can lead to dysregulation of glucose metabolism, insulin synthesis, which facilitates the development of insulin resistance and progression of diabetes in the adult. Despite limited and often inconclusive epidemiologic and experimental data, more recent data clearly show that infants appear to be at increased risk of type 2 diabetes in later life. This may be a result of continued exposure to chemical food contaminants during the critical window of pancreas development. In societies already burdened with increased incidence of non-communicable chronic diseases, there is a clear need for information regarding the potential harmful effects of chemical food contaminants on adult health diseases.

Environmentally Relevant Dose of Bisphenol A Does Not Affect Lipid Metabolism and Has No Synergetic or Antagonistic Effects on Genistein's Beneficial Roles on Lipid Metabolism

Both bisphenol A (BPA, an endocrine disrupting chemicals) and genistein (a phytoestrogen mainly derived from leguminosae) are able to bind to estrogen receptors, but they are considered to have different effects on metabolic syndrome, surprisingly. We here investigate the effects of an environmentally relevant dose of BPA alone and the combined effects with genistein on lipid metabolism in rats. Eight groups of adult male Wistar rats, fed with either standard chow diet or high-fat diet, were treated with BPA (50μg/kg/day), genistein (10mg/kg/day), and BPA plus genistein for 35 weeks, respectively. Metabolic parameters in serum and liver were determined; the hematoxylin/eosin and oil Red O staining were used to observe liver histologically; gene expressions related to hepatic lipid metabolism were analyzed by Real-time PCR; protein expressions of PPARγ, PPARα and LC3 in liver were analyzed by western blotting. No difference of body weight gain, total energy intake, liver weight/body weight or body fat percentage in both STD- and HFD-fed sub-groups was observed after treatment with BPA, genistein, or BPA plus genistein (P>0.05). Genistein alleviated lipid metabolism disorder and decreased the mRNA and protein expression of PPARγ (P<0.05), and increased the protein expression of LC3II (P<0.05) in liver of HFD-fed rats. However, BPA treatment had no effect on lipid metabolism in rats alone (P>0.05) or combined with genistein. Our findings suggest that long-term environmentally relevant dose of BPA did not affect lipid metabolism, and had no synergetic or antagonistic roles on genistein’s beneficial function on hepatic lipid metabolism.

Effect of bisphenol A on SOCS-3 and insulin signaling transduction in 3T3-L1 adipocytes

The aim of the present study was to investigate whether environmental endocrine disrupting chemical, bisphenol A (BPA), affects secretion of suppressor of cytokine signaling 3 (SOCS-3) and insulin signaling transduction in 3T3-L1 adipocytes. 3T3-L1 adipocytes were treated for 0, 2, 6, 12 and 24 h with BPA at 80 µM in serum‑deprived medium. Reverse transcription-quantitative polymerase chain reaction and western blotting were performed to detect the mRNA expression levels of SOCS‑3 and protein expression levels of SOCS‑3, insulin receptor substrate 1 (IRS‑1), phosphorylated (p)‑IRS‑1, Akt and p‑Akt. The levels of p‑IRS‑1, Akt and p‑Akt in cultures treated for 6 h with BPA were also analyzed by immunofluorescence. The SOCS‑3 mRNA and protein expression levels were decreased in the 6, 12 and 24 h groups. The levels of p‑IRS‑1 and p‑Akt protein were markedly downregulated, while the level of IRS‑1 and Akt protein remained unaltered among these groups, which was consistent with the results observed using immunofluorescence. BPA may inhibit insulin signal transduction and result in the occurrence of insulin resistance via promoting the expression of SOCS-3.

Eryptosis-inducing activity of bisphenol A and its analogs in human red blood cells (in vitro study)

Bisphenols are important chemicals that are widely used in the manufacturing of polycarbonates, epoxy resin and thermal paper, and thus the exposure of humans to these substances has been noted. The purpose of this study was to assess eryptotic changes in human erythrocytes exposed (in vitro) to bisphenol A (BPA) and its selected analogs, i.e.,bisphenol F (BPF), bisphenol S (BPS) and bisphenol AF (BPAF). The erythrocytes were incubated with compounds studied at concentrations ranging from 1 to 250μg/mL for 4, 12 or 24h. The results showed that BPA and its analogs increased cytosolic calcium ions level with the strongest effect noted for BPAF. It has also been revealed that all bisphenols analyzed, and BPAF and BPF in particular increased phosphatidylserine translocation in red blood cells, which confirmed that they exhibited eryptotic potential in this cell type. Furthermore, it was shown that BPA and its analogs caused significant increase in calpain and caspase-3 activities, while the strongest effect was noted for BPAF. BPS, which is the main substituent of bisphenol A in polymers and thermal paper production exhibited similar eryptotic potential to BPA. Eryptotic changes in human erythrocytes were provoked by bisphenols at concentrations, which may influence the human body during occupational exposure or subacute poisoning with these compounds.