Alternatives for the worse: Molecular insights into adverse effects of bisphenol a and substitutes during human adipocyte differentiation

Endocrine disruption of adipose physiology: Screening in SGBS cells

The increasing use of industrial chemicals has raised concerns regarding exposure to endocrine-disrupting chemicals (EDCs), which interfere with developmental, reproductive and metabolic processes. Of particular concern is their interaction with adipose tissue, a vital component of the endocrine system regulating metabolic and hormonal functions. The SGBS (Simpson Golabi Behmel Syndrome) cell line, a well-established human-relevant model for adipocyte research, closely mimics native adipocytes' properties. It responds to hormonal stimuli, undergoes adipogenesis and has been successfully used to study the impact of EDCs on adipose biology. In this study, we screened human exposure-relevant doses of various EDCs on the SGBS cell line to investigate their effects on viability, lipid accumulation and adipogenesis-related protein expression. Submicromolar doses were generally well tolerated; however, at higher doses, EDCs compromised cell viability, with cadmium chloride (CdCl2) showing the most pronounced effects. Intracellular lipid levels remained unaffected by EDCs, except for tributyltin (TBT), used as a positive control, which induced a significant increase. Analysis of adipogenesis-related protein expression revealed several effects, including downregulation of fatty acid-binding protein 4 (FABP4) by dibutyl phthalate, upregulation by CdCl2 and downregulation of perilipin 1 and FABP4 by perfluorooctanoic acid. Additionally, TBT induced dose-dependent upregulation of C/EBPα, perilipin 1 and FABP4 protein expression. These findings underscore the importance of employing appropriate models to study EDC-adipocyte interactions. Conclusions from this research could guide strategies to reduce the negative impacts of EDC exposure on adipose tissue.

Addressing chemically-induced obesogenic metabolic disruption: selection of chemicals for in vitro human PPARα, PPARγ transactivation, and adipogenesis test methods

Whilst western diet and sedentary lifestyles heavily contribute to the global obesity epidemic, it is likely that chemical exposure may also contribute. A substantial body of literature implicates a variety of suspected environmental chemicals in metabolic disruption and obesogenic mechanisms. Chemically induced obesogenic metabolic disruption is not yet considered in regulatory testing paradigms or regulations, but this is an internationally recognised human health regulatory development need. An early step in the development of relevant regulatory test methods is to derive appropriate minimum chemical selection lists for the target endpoint and its key mechanisms, such that the test method can be suitably optimised and validated. Independently collated and reviewed reference and proficiency chemicals relevant for the regulatory chemical universe that they are intended to serve, assist regulatory test method development and validation, particularly in relation to the OECD Test Guidelines Programme. To address obesogenic mechanisms and modes of action for chemical hazard assessment, key initiating mechanisms include molecular-level Peroxisome Proliferator-Activated Receptor (PPAR) α and γ agonism and the tissue/organ-level key event of perturbation of the adipogenesis process that may lead to excess white adipose tissue. Here we present a critical literature review, analysis and evaluation of chemicals suitable for the development, optimisation and validation of human PPARα and PPARγ agonism and human white adipose tissue adipogenesis test methods. The chemical lists have been derived with consideration of essential criteria needed for understanding the strengths and limitations of the test methods. With a weight of evidence approach, this has been combined with practical and applied aspects required for the integration and combination of relevant candidate test methods into test batteries, as part of an Integrated Approach to Testing and Assessment for metabolic disruption. The proposed proficiency and reference chemical list includes a long list of negatives and positives (20 chemicals for PPARα, 21 for PPARγ, and 11 for adipogenesis) from which a (pre-)validation proficiency chemicals list has been derived.

Exposure to BPA and BPS during pregnancy disrupts the bone mineralization in the offspring

Exposure to plastic-derived estrogen-mimicking endocrine-disrupting bisphenols can have a long-lasting effect on bone health. However, gestational exposure to bisphenol A (BPA) and its analogue, bisphenol S (BPS), on offspring's bone mineralization is unclear. The effects of in-utero bisphenol exposure were examined on the offspring's bone parameters. BPA and BPS (0.0, 0.4 μg/kg bw) were administered to pregnant Wistar rats via oral gavage from gestational day 4-21. Maternal exposure to BPA and BPS increased bone mineral content and density in the offspring aged 30 and 90 days (P < 0.05). Plasma analysis revealed that alkaline phosphatase, and Gla-type osteocalcin were significantly elevated in the BPS-exposed offspring (P < 0.05). The expression of BMP1, BMP4, and their signaling mediators SMAD1 mRNAs were decreased in BPS-exposed osteoblast SaOS-2 cells (P < 0.05). The expression of extracellular matrix proteins such as ALPL, COL1A1, DMP1, and FN1 were downregulated (P < 0.05). Bisphenol co-incubation with noggin decreased TGF-β1 expression, indicating its involvement in bone mineralization. Altered mineralization could be due to dysregulated expression of bone morphogenetic proteins and signalling mediators in the osteoblast cells. Thus, bisphenol exposure during gestation altered growth and bone mineralization in the offspring, possibly by modulating the expression of Smad-dependent BMP/TGF-β1 signalling mediators.

Exploring BPA alternatives - Environmental levels and toxicity review

Bisphenol A alternatives are manufactured as potentially less harmful substitutes of bisphenol A (BPA) that offer similar functionality. These alternatives are already in the market, entering the environment and thus raising ecological concerns. However, it can be expected that levels of BPA alternatives will dominate in the future, they are limited information on their environmental safety. The EU PARC project highlights BPA alternatives as priority chemicals and consolidates information on BPA alternatives, with a focus on environmental relevance and on the identification of the research gaps. The review highlighted aspects and future perspectives. In brief, an extension of environmental monitoring is crucial, extending it to cover BPA alternatives to track their levels and facilitate the timely implementation of mitigation measures. The biological activity has been studied for BPA alternatives, but in a non-systematic way and prioritized a limited number of chemicals. For several BPA alternatives, the data has already provided substantial evidence regarding their potential harm to the environment. We stress the importance of conducting more comprehensive assessments that go beyond the traditional reproductive studies and focus on overlooked relevant endpoints. Future research should also consider mixture effects, realistic environmental concentrations, and the long-term consequences on biota and ecosystems.

Structural Studies on the Binding Mode of Bisphenols to PPARγ

Bisphenol A (BPA) and bisphenol B (BPB) are widely used in the production of plastics, and their potential adverse health effects, particularly on endocrine disruption and metabolic health, have raised concern. Peroxisome proliferator-activated receptor gamma (PPARγ) plays a pivotal role in metabolic regulation and adipogenesis, making it a target of interest in understanding the development of obesity and associated health impacts. In this study, we employ X-ray crystallography and molecular dynamics (MD) simulations to study the interaction of PPARγ with BPA and BPB. Crystallographic structures reveal the binding of BPA and BPB to the ligand binding domain of PPARγ, next to C285, where binding of partial agonists as well as antagonists and inverse agonists of PPARγ signaling has been previously observed. However, no interaction of BPA and BPB with Y437 in the activation function 2 site is observed, showing that these ligands cannot stabilize the active conformation of helix 12 directly. Furthermore, free energy analyses of the MD simulations revealed that I341 has a large energetic contribution to the BPA and BPB binding modes characterized in this study.

Single and mixture effects of bisphenol A and benzophenone-3 on in vitro T helper cell differentiation

Immune homeostasis is key to guarantee that the immune system can elicit effector functions against pathogens and at the same time raise tolerance towards other antigens. A disturbance of this delicate balance may underlie or at least trigger pathologies. Endocrine disrupting chemicals (EDCs) are increasingly recognized as risk factors for immune dysregulation. However, the immunotoxic potential of specific EDCs and their mixtures is still poorly understood. Thus, we aimed to investigate the effect of bisphenol A (BPA) and benzophenone-3 (BP-3), alone and in combination, on in vitro differentiation of T helper (TH)17 cells and regulatory T (Treg) cells. Naïve T cells were isolated from mouse lymphoid tissues and differentiated into the respective TH population in the presence of 0.001-10 μM BP-3 and/or 0.01-100 μM BPA. Cell viability, proliferation and the expression of TH lineage specific transcription factors and cytokines was measured by flow cytometry and CBA/ELISA. Moreover, the transcription of hormone receptors as direct targets of EDCs was quantified by RT-PCR. We found that the highest BPA concentration adversely affected TH cell viability and proliferation. Moreover, the general differentiation potential of both TH populations was not altered in the presence of both EDCs. However, EDC exposure modulated the emergence of TH17 and Treg cell intermediate states. While BPA and BP-3 promoted the development of TH1-like TH17 cells under TH17-differentiating conditions, TH2-like Treg cells occurred under Treg polarization. Interestingly, differential effects could be observed in mixtures of the two tested compounds compared with the individual compounds. Notably, estrogen receptor β expression was decreased under TH17-differentiating conditions in the presence of BPA and BP-3 as mixture. In conclusion, our study provides solid evidence for both, the immune disruptive potential and the existence of cumulative effects of real nature EDC mixtures on T cell in vitro differentiation.

Upregulation of GOLPH3 mediated by Bisphenol a promotes colorectal cancer proliferation and migration: evidence based on integrated analysis

Background

The interaction between environmental endocrine-disrupting chemicals, such as Bisphenol A (BPA), and their influence on cancer progression, particularly regarding the GOLPH3 gene in colorectal cancer, remains unclear.

Methods

We performed an integrated analysis of transcriptional profiling, clinical data, and bioinformatics analyses utilizing data from the Comparative Toxicogenomics Database and The Cancer Genome Atlas. The study employed ClueGO, Gene Set Enrichment Analysis, and Gene Set Variation Analysis for functional enrichment analysis, alongside experimental assays to examine the effects of BPA exposure on colorectal cancer cell lines, focusing on GOLPH3 expression and its implications for cancer progression.

Results

Our findings demonstrated that BPA exposure significantly promoted the progression of colorectal cancer by upregulating GOLPH3, which in turn enhanced the malignant phenotype of colorectal cancer cells. Comparative analysis revealed elevated GOLPH3 protein levels in cancerous tissues versus normal tissues, with single-cell analysis indicating widespread GOLPH3 presence across various cell types in the cancer microenvironment. GOLPH3 was also associated with multiple carcinogenic pathways, including the G2M checkpoint. Furthermore, our investigation into the colorectal cancer microenvironment and genomic mutation signature underscored the oncogenic potential of GOLPH3, exacerbated by BPA exposure.

Conclusion

This study provides novel insights into the complex interactions between BPA exposure and GOLPH3 in the context of colorectal cancer, emphasizing the need for heightened awareness and measures to mitigate BPA exposure risks. Our findings advocate for further research to validate these observations in clinical and epidemiological settings and explore potential therapeutic targets within these pathways.

Relationship of bisphenol A substitutes bisphenol F and bisphenol S with adiponectin/leptin ratio among children from the environment and development of children cohort

BACKGROUND

Bisphenol A (BPA) is known as an obesogenic endocrine disruptor. Bisphenol S (BPS) and F (BPF) are substitutes that have recently replaced BPA.

OBJECTIVES

To investigate the relationships of urinary bisphenols (BPA, BPS and BPF) with adiposity measurements (obesity, BMI z-score, and fat mass), serum adipokine levels (adiponectin and leptin), and adiponectin/leptin ratio (A/L ratio) in 6- and 8-year-old children.

METHODS

A total of 561 children who participated in the Environment and Development of Children cohort (482 and 516 children visited at age 6 and 8, respectively) at Seoul National University Children's Hospital during 2015-2019 were included. Urinary BPA levels were log-transformed. BPS levels were categorized into three groups (non-detected, lower-half, and higher-half of detected), and BPF levels were classified into two groups (non-detected and detected).

RESULTS

The urinary BPS higher-half group had a higher BMI z-score (β = 0.160, P= 0.044), higher fat mass (β = 0.104, P< 0.001), lower adiponectin concentration (β =- 0.069, P< 0.001), higher leptin concentration (β = 0.360, P< 0.001), and lower A/L ratio (β =- 0.428, P< 0.001) compared with the non-detected group. The urinary BPF-detected group had a higher fat mass (β = 0.074, P< 0.001), lower adiponectin concentration (β =- 0.069, P< 0.001), higher leptin concentration (β = 0.360, P< 0.001), and lower A/L ratio (β =- 0.428, P< 0.001) compared with the non-detected group. The BPA levels showed no consistent associations with outcomes, except for isolated associations of BPA at age 6 with a higher BMI z-score at age 6 (P= 0.016) and leptin at age 8 (P= 0.021).

CONCLUSIONS

Increased exposure to BPS and BPF is associated with higher fat mass and leptin concentration, lower serum adiponectin, and lower A/L ratio in children. These findings suggest potential adverse effects of BPA substitutes on adiposity and adipokines. No consistent association of BPA exposure with outcomes could be partly explained by the decreasing BPA levels over time.

Bisphenol A analogues and metabolic syndrome in women with polycystic ovary syndrome

Bisphenols (BPs) have become a chemical group of special interest due to their ability to interfere with the endocrine system and their ubiquitous presence in the environment. As some of them possess mild estrogenic and anti-androgenic effects, they might be associated with the diagnosis of polycystic ovary syndrome (PCOS). Acting on multiple tissues, BPs exposure may lead to metabolic derangements characteristic for metabolic syndrome (MetS). Therefore, the aim of this study was to determine the potential relationship between exposure to some BPA analogues and features of the MetS in women with PCOS. Serum BPE, BPC, BPG, BPM, BPP, BPZ, BPFL, and BPBP concentrations did not differ significantly between the PCOS (n = 135) and the control subjects (n = 104). However, women whose serum BPM and BPP concentrations were in the highest tertile were more likely to be diagnosed with PCOS (adjusted OR; [95%CI] 0.43; [0.20; 0.89], P < 0.001 and 0.56; [0.27; 0.96], P = 0.049, consequently). Serum concentrations of BPs were not associated with the MetS diagnosis in the PCOS group. There was a negative correlation between the concentrations of serum BPBP and total serum cholesterol (r = - 0.153; P = 0.019), BPE and serum testosterone (r = - 0.160; P = 0.014) as well as BPC and HDL-cholesterol (r = - 0.138; P = 0.036). There was a positive correlation between the concentrations of BPP and serum triglycerides (r = 0.138; P = 0.036). Our results point to the potential association between exposure to BPM, BPP, and the diagnosis of PCOS, along with the impact of BPBP, BPE, BPC, and BPP on the metabolic features of the MetS.

Gestational exposure to bisphenol S induces microvesicular steatosis in male rat offspring by modulating metaflammation

Prenatal exposure to endocrine-disrupting bisphenol A (BPA) shows a long-lasting programming effect on an organ's metabolic function and predisposes it to the risk of adult metabolic diseases. Although a reduced contaminant risk due to "BPA-free" exposure is proposed, limited data on a comparative assessment of gestational exposure to BPS and BPA and their effects on metaflammation in predisposing liver metabolic disease is reported. Pregnant Wistar rats were exposed to BPS and BPA (0.0, 0.4, 4.0 μg/kg bw) via gavage from gestational day 4 to 21, and effects were assessed in the 90 d male offspring. Prenatal BPS-exposed offspring showed a more obesogenic effect than BPA, including changes in body fat distribution, feed efficiency, and leptin signalling. The BPS exposure induced the adipocyte hypertrophy of visceral adipose to a greater extent than BPA. The adipose hypertrophy was augmented by tissue inflammation, endoplasmic reticulum (ER) stress, and apoptosis due to increased expression of pro-inflammatory (IL6, IL1β, CRP, COX2) cytokines, ER stress modulator (CHOP), and apoptotic effector (Caspase 3). The enlarged, stressed, inflamed adipocytes triggered de novo lipogenesis in the bisphenol-exposed offspring liver due to increased expression of cholesterol and lipid biogenesis mediators (srebf1, fasn, acaca, PPARα) concomitant with elevated triacylglycerol (TG) and cholesterol (TC), resulted in impaired hepatic clearance of lipids. The lipogenic effects were also promoted by increased expression of HSD11β1. BPS exposure increased absolute liver weight, discoloration, altered liver lobes more than in BPA. Liver histology showed numerous lipid droplets, and hepatocyte ballooning, upregulated ADRP expression, an increased expression of pro-inflammatory mediators (IL6, CRP, IL1β, TNFα, COX2), enhanced lipid peroxidation in the BPS-exposed offspring's liver suggest altered metaflammation leads to microvesicular steatosis. Overall, gestational BPS exposure demonstrated a higher disruption in metabolic changes than BPA, involving excess adiposity, liver fat, inflammation, and predisposition to steatosis in the adult male offspring.

Bisphenol A (BPA) and Cardiovascular or Cardiometabolic Diseases

Bisphenol A (BPA; 4,4'-isopropylidenediphenol) is a well-known endocrine disruptor. Most human exposure to BPA occurs through the consumption of BPA-contaminated foods. Cardiovascular or cardiometabolic diseases such as diabetes, obesity, hypertension, acute kidney disease, chronic kidney disease, and heart failure are the leading causes of death worldwide. Positive associations have been reported between blood or urinary BPA levels and cardiovascular or cardiometabolic diseases. BPA also induces disorders or dysfunctions in the tissues associated with these diseases through various cell signaling pathways. This review highlights the literature elucidating the relationship between BPA and various cardiovascular or cardiometabolic diseases and the potential mechanisms underlying BPA-mediated disorders or dysfunctions in tissues such as blood vessels, skeletal muscle, adipose tissue, liver, pancreas, kidney, and heart that are associated with these diseases.

Development of new approach methods for the identification and characterization of endocrine metabolic disruptors-a PARC project

In past times, the analysis of endocrine disrupting properties of chemicals has mainly been focused on (anti-)estrogenic or (anti-)androgenic properties, as well as on aspects of steroidogenesis and the modulation of thyroid signaling. More recently, disruption of energy metabolism and related signaling pathways by exogenous substances, so-called metabolism-disrupting chemicals (MDCs) have come into focus. While general effects such as body and organ weight changes are routinely monitored in animal studies, there is a clear lack of mechanistic test systems to determine and characterize the metabolism-disrupting potential of chemicals. In order to contribute to filling this gap, one of the project within EU-funded Partnership for the Assessment of Risks of Chemicals (PARC) aims at developing novel in vitro methods for the detection of endocrine metabolic disruptors. Efforts will comprise projects related to specific signaling pathways, for example, involving mTOR or xenobiotic-sensing nuclear receptors, studies on hepatocytes, adipocytes and pancreatic beta cells covering metabolic and morphological endpoints, as well as metabolism-related zebrafish-based tests as an alternative to classic rodent bioassays. This paper provides an overview of the approaches and methods of these PARC projects and how this will contribute to the improvement of the toxicological toolbox to identify substances with endocrine disrupting properties and to decipher their mechanisms of action.

The fat accumulation promotion effects of dihydrxytetraphenylmethane and its underlying mechanisms via transcriptome analysis

Dihydrxytetraphenylmethane, also known as Bisphenol BP (BPBP), has been increasingly used in industrial production and more frequently detected in the environment as an alternative plasticizer of BPA. However, there are no reports about BPBP in food safety or its effects on cellular lipogenesis. The purpose of this research was to investigate the influence and potential mechanisms of BPBP on adipogenesis in 3T3-L1 cells. Cells were treated with 4 concentrations (0.01, 0.1, 1, and 10 μM) of BPBP and the results showed that treatment with at low concentrations (0.01 μM) promoted cell fat differentiation and triglyceride accumulation. RNA-seq data showed that a total of 370 differentially expressed genes between control and the low-dose BPBP-treated group were determined, including 227 upregulated genes and 143 downregulated genes. Some key genes related to adipocyte differentiation and adipogenesis were significantly enriched after BPBP treatment, including PPAR-γ, Adipoq, Nr1h3 and Plin1. Pathway analyses suggest that the activation of PPAR-γ signaling pathway may be key for BPBP to promote adipocyte differentiation and fat accumulation. Our work provides evidence for the potential obesogenic effect of BPBP and may call for further research on the safety of the chemical in food products.

BPA and its alternatives BPF and BPAF exaggerate hepatic lipid metabolism disorders in male mice fed a high fat diet

Alternatives to Bisphenol A (BPA), such as BPF and BPAF, have found increasing industrial applications. However, toxicological research on these BPA analogues remains limited. This study aimed to investigate the effects of BPA, BPF, and BPAF exposure on hepatotoxicity in mice fed with high-fat diets (HFD). Male mice were exposed to the bisphenols at a dose of 0.05 mg per kg body weight per day (mg/kg bw/day) for eight consecutive weeks, or 5 mg/kg bw/day for the first week followed by 0.05 mg/kg bw/day for seven weeks under HFD. The low dose (0.05 mg/kg bw/day) was corresponding to the tolerable daily intake (TDI) of BPA and the high dose (5 mg/kg bw/day) was corresponding to its no observed adverse effect level (NOAEL). Biochemical analysis revealed that exposure to these bisphenols resulted in liver damage. Metabolomics analysis showed disturbances of fatty acid and lipid metabolism in bisphenol-exposed mouse livers. BPF and BPAF exposure reduced lipid accumulation in HFD mouse liver by lowering glyceride and cholesterol levels. Transcriptomics analysis demonstrated that expression levels of genes related to fatty acid synthesis and metabolism were changed, which might be related to the activation of the PPAR signaling pathway. Besides, a feedback regulation mechanism might exist to maintain hepatic metabolic homeostasis. For the first time, this study demonstrated the effects of BPF and BPAF exposure in HFD-mouse liver. Considering the reality of the high prevalence of obesity nowadays and the ubiquitous environmental distribution of bisphenols, this study provides insight and highlights the adverse effects of BPA alternatives, further contributing to the consideration of the safe use of such compounds.

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.

Bisphenol A alternatives continuously contribute to the endocrine disruption in cetaceans

The bans on bisphenol A (BPA) have facilitated the widespread use of BPA alternatives and shifted environmental contamination profiles of bisphenols (BPs). However, the continued reports of toxicities of emerging BPA alternatives have raised questions about whether the shifting profiles are contributed to mitigate BPs-mediated endocrine-disruption effects (EDEs). Cetaceans are commonly used as the ideal sentinel species for monitoring marine pollutants of concern and determining potential health effects, but far less is known about BP loads and BPs-mediated EDEs in cetaceans. Here we measured the hepatic concentrations of six BPs in eight stranded cetacean species (n = 41) in the South China Sea, between 2007 and 2020. The large-bodied whales generally showed higher ∑BPs concentrations than the small-bodied dolphins. In Indo-Pacific finless porpoises (Neophocaena phocaenoides) (n = 33), BPA concentrations first increased (2007-2014) and then decreased (2014-2020), while ∑BP_Alternatives concentrations increased from 2007 to 2020. It appears that the alternatives gradually replaced BPA, probably due to the BPA-related bans in China. In order to examine the hormone disruption of BPA and its alternatives in finless porpoises, five blubber hormones (cortisol, progesterone, testosterone, triiodothyronine and tetraiodothyronine), which are proven to be validated endocrine biomarkers, were measured in 21 samples. Tetraiodothyronine, testosterone, and cortisol were significantly and positively correlated with BPA and its alternatives, suggesting that the interference of endocrine hormone homeostasis may continue to occur despite the changes of BP profiles in finless porpoises. This is the first investigation of the relationship between hormone and BP concentrations in cetaceans and represents a substantial advance in understanding BPs-mediated endocrine effects on cetaceans.

The p-Phthalates Terephthalic Acid and Dimethyl Terephthalate Used in the Manufacture of PET Induce In Vitro Adipocytes Dysfunction by Altering Adipogenesis and Thermogenesis Mechanisms

Public health concerns associated with the potential leaching of substances from Polyethylene terephthalate (PET) packaging have been raised due to the role of phthalates as endocrine-disrupting chemicals or obesogens. In particular, changes in the environment such as pH, temperature, and irradiation can improve contaminant migration from PET food packaging. In this study, the in vitro effects of p-phthalates terephthalic acid (TPA) and dimethyl terephthalate (DMT) on murine adipocytes (3T3-L1) were evaluated using concentrations that might be obtained in adult humans exposed to contaminated sources. TPA and, in particular, DMT exposure during 3T3-L1 differentiation increased the cellular lipid content and induced adipogenic markers PPAR-γ, C/EBPß, FABP4, and FASN, starting from low nanomolar concentrations. Interestingly, the adipogenic action of TPA- and DMT-induced PPAR-γ was reverted by ICI 182,780, a specific antagonist of the estrogen receptor. Furthermore, TPA and DMT affected adipocytes’ thermogenic program, reducing pAMPK and PGC-1α levels, and induced the NF-κB proinflammatory pathway. Given the observed effects of biologically relevant chronic concentrations of these p-phthalates and taking into account humans’ close and constant contact with plastics, it seems appropriate that ascertaining safe levels of TPA and DMT exposure is considered a high priority.

Testicular toxicity of bisphenol compounds: Homeostasis disruption of cholesterol/testosterone via PPARα activation

The widespread application of bisphenols (BPs) has made them ubiquitous in the environment. Although the side effects of bisphenol A (BPA) substitutes have received increasing attention, studies on their reproductive toxicity remain lacking. In this research, the effects of BPA and its substitutes, including bisphenol S (BPS), bisphenol F (BPF), and bisphenol AF (BPAF), on the male reproductive system were evaluated. Results proved that these BPs disturbed germ cell proliferation, induced germ cell apoptosis, and perturbed sperm physiologies and spermatogenesis, which resulted from the disruption of testosterone (T) biosynthesis in Leydig cells (LCs). Importantly, in vitro and in vivo studies indicated that the exhausted cholesterol in LCs accounted for the reduced T production. Furthermore, the knockdown of peroxisome proliferator-activated receptor alpha (PPARα) remarkably ameliorated the downregulation of cholesterogenesis-related genes (i.e., Hmgcs1, Hmgcr, and Srebf2), indicating that PPARα played a critical role in BPs-induced testicular dysfunction. Overall, our studies indicated that BPS, BPF, and BPAF could induce testicular toxic effects similar to that of BPA, which were associated with the PPARα pathway.

Bisphenol analogues induced metabolic effects through eliciting intestinal cell heterogeneous response

The metabolic effects of endocrine-disrupting chemicals, such as bisphenol analogues, have drawn increasing attention. Bisphenol A (BPA) usage is associated with the occurrence of many metabolic diseases. With the restricted use of BPA, alternatives like bisphenol F (BPF) and bisphenol AF (BPAF) have been greatly introduced for industrial manufacture, and brings new hazard to public health. To understand how bisphenol analogues induced metabolic effects, zebrafish are continuous exposed to environmental level (0.5 μg/L) of BPA, BPF and BPAF since embryonic stage, and identified hepatic steatosis and insulin resistance at 60-day post fertilization. Hepatic transcriptional profile indicated that pancreatic disease pathways were activated by BPA, but were inhibited by BPF. At the same time, increased lipid secretion and gluconeogenesis pathways in zebrafish liver was found post BPAF exposure. Significant inflammatory response, histological injury and increased mucus secretion was detected in zebrafish intestine post exposure of three bisphenol analogues. Single-cell RNA sequencing of zebrafish intestinal cells revealed activation of lipid uptake and absorption pathways in enterocyte lineages, which well explained the hepatic steatosis induced by BPA and BPF. Besides, genes related to carbohydrate metabolism, diabetes and insulin resistance were activated in intestinal immune cell types by three bisphenol analogues. These findings indicated that BPA and its alternatives could lead to abnormal lipid and carbohydrate metabolism of zebrafish through inducing cell heterogeneous changes in gut, and revealed both molecular and cellular mechanism in mediating this effect.

Di-(2-ethylhexyl) phthalate substitutes accelerate human adipogenesis through PPARγ activation and cause oxidative stress and impaired metabolic homeostasis in mature adipocytes

The obesity pandemic is presumed to be accelerated by endocrine disruptors such as phthalate-plasticizers, which interfere with adipose tissue function. With the restriction of the plasticizer di-(2-ethylhexyl)-phthalate (DEHP), the search for safe substitutes gained importance. Focusing on the master regulator of adipogenesis and adipose tissue functionality, the peroxisome proliferator-activated receptor gamma (PPARγ), we evaluated 20 alternative plasticizers as well as their metabolites for binding to and activation of PPARγ and assessed effects on adipocyte lipid accumulation. Among several compounds that showed interaction with PPARγ, the metabolites MINCH, MHINP, and OH-MPHP of the plasticizers DINCH, DINP, and DPHP exerted the highest adipogenic potential in human adipocytes. These metabolites and their parent plasticizers were further analyzed in human preadipocytes and mature adipocytes using cellular assays and global proteomics. In preadipocytes, the plasticizer metabolites significantly increased lipid accumulation, enhanced leptin and adipsin secretion, and upregulated adipogenesis-associated markers and pathways, in a similar pattern to the PPARγ agonist rosiglitazone. Proteomics of mature adipocytes revealed that both, the plasticizers and their metabolites, induced oxidative stress, disturbed lipid storage, impaired metabolic homeostasis, and led to proinflammatory and insulin resistance promoting adipokine secretion. In conclusion, the plasticizer metabolites enhanced preadipocyte differentiation, at least partly mediated by PPARγ activation and, together with their parent plasticizers, affected the functionality of mature adipocytes similar to reported effects of a high-fat diet. This highlights the need to further investigate the currently used plasticizer alternatives for potential associations with obesity and the metabolic syndrome.

The Mixture of Bisphenol-A and Its Substitutes Bisphenol-S and Bisphenol-F Exerts Obesogenic Activity on Human Adipose-Derived Stem Cells

Bisphenol A (BPA) and its substitutes, bisphenol F (BPF) and S (BPS), have previously shown in vitro obesogenic activity. This study was designed to investigate their combined effect on the adipogenic differentiation of human adipose-derived stem cells (hASCs). Cells were exposed for 14 days to an equimolar mixture of bisphenols (MIX) (range 10 nM–10 µM). Oil Red staining was used to measure intracellular lipid accumulation, quantitative real-time polymerase chain reaction (qRT-PCR) to study gene expression of adipogenic markers (PPARγ, C/EBPα, LPL, and FABP4), and Western Blot to determine their corresponding proteins. The MIX promoted intracellular lipid accumulation in a dose-dependent manner with a maximal response at 10 µM. Co-incubation with pure antiestrogen (ICI 182,780) inhibited lipid accumulation, suggesting that the effect was mediated by the estrogen receptor. The MIX also significantly altered the expression of PPARγ, C/EBPα, LPL, and FABP4 markers, observing a non-monotonic (U-shaped) dose-response, with maximal gene expression at 10 nM and 10 µM and lesser expression at 1 µM. This pattern was not observed when bisphenols were tested individually. Exposure to MIX (1–10 µM) also increased all encoded proteins except for FABP4, which showed no changes. Evaluation of the combined effect of relevant chemical mixtures is needed rather than single chemical testing.

Thyroid endocrine disruption and hepatotoxicity induced by bisphenol AF: Integrated zebrafish embryotoxicity test and deep learning

Bisphenol AF (BPAF) is an emerging contaminant prevalent in the environment as one of main substitutes of bisphenol A (BPA). It was found that BPAF exhibited estrogenic effects in zebrafish larvae in our previous study, while little is known about its effects on the thyroid and liver. A 7 d zebrafish embryotoxicity test was conducted to study the potential thyroid disruption and hepatotoxicity of BPAF. BPAF decreased levels of thyroid hormones and deiodinases but increased expressions of transthyretin at 12.5 and 125 μg/L after 7 d exposure, indicating that both the metabolism and transport of thyroid hormones were perturbed. The thyroid hormone receptor (TR) levels decreased significantly upon exposure to ≥12.5 μg/L BPAF, implying that BPAF acts as a TR antagonist, which coincided well with the prediction from the Direct Message Passing Neural Network. The liver impairment (mainly cell necrosis of hepatocytes) and apoptosis were triggered by 125 μg/L and ≥12.5 μg/L BPAF respectively, accompanied by the increased activities of caspase 3 and caspase 9. Thus BPAF might not be a safe alternative to BPA given the thyroid and liver toxicity. DMPNN appears useful to screen for thyroid disrupting activity from molecular structures.

Obesity III: Obesogen assays: Limitations, strengths, and new directions

There is increasing evidence of a role for environmental contaminants in disrupting metabolic health in both humans and animals. Despite a growing need for well-understood models for evaluating adipogenic and potential obesogenic contaminants, there has been a reliance on decades-old in vitro models that have not been appropriately managed by cell line providers. There has been a quick rise in available in vitro models in the last ten years, including commercial availability of human mesenchymal stem cell and preadipocyte models; these models require more comprehensive validation but demonstrate real promise in improved translation to human metabolic health. There is also progress in developing three-dimensional and co-culture techniques that allow for the interrogation of a more physiologically relevant state. While diverse rodent models exist for evaluating putative obesogenic and/or adipogenic chemicals in a physiologically relevant context, increasing capabilities have been identified for alternative model organisms such as Drosophila, C. elegans, zebrafish, and medaka in metabolic health testing. These models have several appreciable advantages, including most notably their size, rapid development, large brood sizes, and ease of high-resolution lipid accumulation imaging throughout the organisms. They are anticipated to expand the capabilities of metabolic health research, particularly when coupled with emerging obesogen evaluation techniques as described herein.

Are BPA Substitutes as Obesogenic as BPA?

Metabolic diseases, such as obesity, Type II diabetes and hepatic steatosis, are a significant public health concern affecting more than half a billion people worldwide. The prevalence of these diseases is constantly increasing in developed countries, affecting all age groups. The pathogenesis of metabolic diseases is complex and multifactorial. Inducer factors can either be genetic or linked to a sedentary lifestyle and/or consumption of high-fat and sugar diets. In 2002, a new concept of “environmental obesogens” emerged, suggesting that environmental chemicals could play an active role in the etiology of obesity. Bisphenol A (BPA), a xenoestrogen widely used in the plastic food packaging industry has been shown to affect many physiological functions and has been linked to reproductive, endocrine and metabolic disorders and cancer. Therefore, the widespread use of BPA during the last 30 years could have contributed to the increased incidence of metabolic diseases. BPA was banned in baby bottles in Canada in 2008 and in all food-oriented packaging in France from 1 January 2015. Since the BPA ban, substitutes with a similar structure and properties have been used by industrials even though their toxic potential is unknown. Bisphenol S has mainly replaced BPA in consumer products as reflected by the almost ubiquitous human exposure to this contaminant. This review focuses on the metabolic effects and targets of BPA and recent data, which suggest comparable effects of the structural analogs used as substitutes.

The Emerging Plasticizer Alternative DINCH and Its Metabolite MINCH Induce Oxidative Stress and Enhance Inflammatory Responses in Human THP-1 Macrophages

The use of the plasticizer bis(2-ethylhexyl)phthalate (DEHP) and other plasticizers in the manufacture of plastic products has been restricted due to adverse health outcomes such as obesity, metabolic syndrome, and asthma, for which inflammation has been described to be a driving factor. The emerging alternative plasticizer 1,2-cyclohexanedioic acid diisononyl ester (DINCH) still lacks information regarding its potential effects on the immune system. Here, we investigated the effects of DINCH and its naturally occurring metabolite monoisononylcyclohexane-1,2-dicarboxylic acid ester (MINCH) on the innate immune response. Human THP-1 macrophages were exposed to 10 nM–10 μM DINCH or MINCH for 4 h, 16 h, and 24 h. To decipher the underlying mechanism of action, we applied an untargeted proteomic approach that revealed xenobiotic-induced activation of immune-related pathways such as the nuclear factor κB (NF-κB) signaling pathway. Key drivers were associated with oxidative stress, mitochondrial dysfunction, DNA damage repair, apoptosis, and autophagy. We verified increased reactive oxygen species (ROS) leading to cellular damage, NF-κB activation, and subsequent TNF and IL-1β release, even at low nM concentrations. Taken together, DINCH and MINCH induced cellular stress and pro-inflammatory effects in macrophages, which may lead to adverse health effects.