In utero exposure to benzo[a]pyrene increases adiposity and causes hepatic steatosis in female mice, and glutathione deficiency is protective

Assessment of developmental neurotoxicology-associated alterations in neuronal architecture and function using Caenorhabditis elegans

Few of the many chemicals that regulatory agencies are charged with assessing for risk have been carefully tested for developmental neurotoxicity (DNT). To speed up testing efforts, as well as to reduce the use of vertebrate animals, great effort is being devoted to alternate laboratory models for testing DNT. A major mechanism of DNT is altered neuronal architecture resulting from chemical exposure during neurodevelopment. Caenorhabditis elegans is a nematode that has been extensively studied by neurobiologists and developmental biologists, and to a lesser extent by neurotoxicologists. The developmental trajectory of the nervous system in C. elegans is easily visualized, normally entirely invariant, and fully mapped. Therefore, we hypothesized that C. elegans could be a powerful in vivo model to test chemicals for the potential to alter developmental patterning of neuronal architecture. To test whether this might be true, we developed a novel C. elegans DNT testing paradigm that includes exposure throughout development, examines all major neurotransmitter neuronal types for architectural alterations, and tests behaviors specific to dopaminergic, cholinergic, and glutamatergic functions. We used this paradigm to characterize the effects of early-life exposures to the developmental neurotoxicants lead, cadmium, and benzo(a)pyrene (BaP) on dopaminergic, cholinergic, and glutamatergic architecture. We also assessed whether exposures would alter neuronal specification as assessed by expression of reporter genes diagnostic of specific neurotransmitters. We identified no cases in which the apparent neurotransmitter type of the neurons we examined changed, but many in which neuronal morphology was altered. We also found that neuron-specific behaviors were altered during C. elegans mid-adulthood for populations with measured morphological neurodegeneration in earlier stages. The functional changes were consistent with the morphological changes we observed in terms of type of neuron affected. We identified changes consistent with those reported in the mammalian DNT literature, strengthening the case for C. elegans as a DNT model, and made novel observations that should be followed up in future studies.

New insight into PAH4 induced hepatotoxicity and the dose-response assessment in rats model

PAH4 (sum of benzo[a]pyrene, chrysene, benz[a]anthracene and benzo[b]fluoranthene) has been proposed as better marker than benzo[a]pyrene to assess total PAHs exposure in foodstuffs. However, the toxicological behaviors of PAH4 combined exposure remain unclear. This study aimed to investigate PAH4 toxicity effects with non-targeted metabolomics approach and evaluate the external and internal dose-response relationships based on benchmark dose (BMD) analysis. Male Sprague-Dawley rats were treated by gavage with vehicle (corn oil) or four doses of PAH4 (10, 50, 250, 1000 μg/kg·bw) for consecutive 30 days. After the final dose, the liver, blood and urine samples of rats were subsequently collected for testing. The concentrations of urinary mono-hydroxylated PAHs metabolites (OH-PAHs) including 3-hydroxybenzo[a]pyrene (3-OHB[a]P), 3-hydroxychrysene (3-OHCHR) and 3-hydroxybenz[a]anthracene (3-OHB[a]A) were determined to reflect internal PAH4 exposure. Our results showed PAH4 exposure increased relative liver weight and serum aspartate aminotransferase (AST) activity and caused hepatocyte swelling and degeneration, implying hepatotoxicity induced by PAH4. Serum metabolomics suggested PAH4 exposure perturbed lipid metabolism through upregulating the expression of glycerolipids metabolites, which was evidenced by markedly increased serum triglyceride (TG) level and hepatic TG content. Additionally, urinary OH-PAHs concentrations presented strong positive correlations with the external dose, indicating they were able to reflect PAH4 exposure. Furthermore, PAH4 exposure led to a dose-response increase of hepatic TG content, based on which the 95% lower confidence value of BMDs for external and internal doses were estimated as 5.45 μg/kg·bw and 0.11 μmol/mol·Cr, respectively. In conclusion, this study suggested PAH4 exposure could induce hepatotoxicity and lipid metabolism disorder, evaluating the involved dose-response relationships and providing a basis for the risk assessment of PAHs.

Regulation of Benzo[a]pyrene-Induced Hepatic Lipid Accumulation through CYP1B1-Induced mTOR-Mediated Lipophagy

Metabolic dysfunction-associated steatotic liver disease (MASLD) is caused by lipid accumulation within the liver. The pathogenesis underlying its development is poorly understood. Benzo[a]pyrene (B[a]P) is a polycyclic aromatic hydrocarbon and a group 1 carcinogen. The aryl hydrocarbon receptor activation by B[a]P induces cytochrome P450 (CYP) enzymes, contributing to hepatic lipid accumulation. However, the molecular mechanism through which the B[a]P-mediated induction of CYP enzymes causes hepatic lipid accumulation is unknown. This research was conducted to elucidate the role of CYP1B1 in regulating B[a]P-induced lipid accumulation within hepatocytes. B[a]P increased hepatic lipid accumulation, which was mitigated by CYP1B1 knockdown. An increase in the mammalian target of rapamycin (mTOR) by B[a]P was specifically reduced by CYP1B1 knockdown. The reduction of mTOR increased the expression of autophagic flux-related genes and promoted phagolysosome formation. Both the expression and translocation of TFE3, a central regulator of lipophagy, were induced, along with the expression of lipophagy-related genes. Conversely, enhanced mTOR activity reduced TFE3 expression and translocation, which reduced the expression of lipophagy-related genes, diminished phagolysosome production, and increased lipid accumulation. Our results indicate that B[a]P-induced hepatic lipid accumulation is caused by CYP1B1-induced mTOR and the reduction of lipophagy, thereby introducing novel targets and mechanisms to provide insights for understanding B[a]P-induced MASLD.

Glucocorticoids and intrauterine programming of nonalcoholic fatty liver disease

Accumulating epidemiological and experimental evidence indicates that nonalcoholic fatty liver disease (NAFLD) has an intrauterine origin. Fetuses exposed to adverse prenatal environments (e.g., maternal malnutrition and xenobiotic exposure) are more susceptible to developing NAFLD after birth. Glucocorticoids are crucial triggers of the developmental programming of fetal-origin diseases. Adverse intrauterine environments often lead to fetal overexposure to maternally derived glucocorticoids, which can program fetal hepatic lipid metabolism through epigenetic modifications. Adverse intrauterine environments program the offspring's glucocorticoid-insulin-like growth factor 1 (GC-IGF1) axis, which contributes to postnatal catch-up growth and disturbs glucose and lipid metabolism. These glucocorticoid-driven programming alterations increase susceptibility to NAFLD in the offspring. Notably, after delivery, offspring often face an environment distinct from their in utero life. The mismatch between the intrauterine and postnatal environments can serve as a postnatal hit that further disturbs the programmed endocrine axes, accelerating the onset of NAFLD. In this review, we summarize the current epidemiological and experimental evidence demonstrating that NAFLD has an intrauterine origin and discuss the underlying intrauterine programming mechanisms, focusing on the role of overexposure to maternally derived glucocorticoids. We also briefly discuss potential early life interventions that may be beneficial against fetal-originated NAFLD.

Hepatokines, bile acids and ketone bodies are novel Hormones regulating energy homeostasis

Current views show that an impaired balance partly explains the fat accumulation leading to obesity. Fetal malnutrition and early exposure to endocrine-disrupting compounds also contribute to obesity and impaired insulin secretion and/or sensitivity. The liver plays a major role in systemic glucose homeostasis through hepatokines secreted by hepatocytes. Hepatokines influence metabolism through autocrine, paracrine, and endocrine signaling and mediate the crosstalk between the liver, non-hepatic target tissues, and the brain. The liver also synthetizes bile acids (BAs) from cholesterol and secretes them into the bile. After food consumption, BAs mediate the digestion and absorption of fat-soluble vitamins and lipids in the duodenum. In recent studies, BAs act not simply as fat emulsifiers but represent endocrine molecules regulating key metabolic pathways. The liver is also the main site of the production of ketone bodies (KBs). In prolonged fasting, the brain utilizes KBs as an alternative to CHO. In the last few years, the ketogenic diet (KD) became a promising dietary intervention. Studies on subjects undergoing KD show that KBs are important mediators of inflammation and oxidative stress. The present review will focus on the role played by hepatokines, BAs, and KBs in obesity, and diabetes prevention and management and analyze the positive effects of BAs, KD, and hepatokine receptor analogs, which might justify their use as new therapeutic approaches for metabolic and aging-related diseases.

Metabolism-Disrupting Chemicals Affecting the Liver: Screening, Testing, and Molecular Pathway Identification

The liver is the central metabolic organ of the body. The plethora of anabolic and catabolic pathways in the liver is tightly regulated by physiological signaling but may become imbalanced as a consequence of malnutrition or exposure to certain chemicals, so-called metabolic endocrine disrupters, or metabolism-disrupting chemicals (MDCs). Among different metabolism-related diseases, obesity and non-alcoholic fatty liver disease (NAFLD) constitute a growing health problem, which has been associated with a western lifestyle combining excessive caloric intake and reduced physical activity. In the past years, awareness of chemical exposure as an underlying cause of metabolic endocrine effects has continuously increased. Within this review, we have collected and summarized evidence that certain environmental MDCs are capable of contributing to metabolic diseases such as liver steatosis and cholestasis by different molecular mechanisms, thereby contributing to the metabolic syndrome. Despite the high relevance of metabolism-related diseases, standardized mechanistic assays for the identification and characterization of MDCs are missing. Therefore, the current state of candidate test systems to identify MDCs is presented, and their possible implementation into a testing strategy for MDCs is discussed.

Antibiotics administration alleviates the high fat diet-induced obesity through altering the lipid metabolism in young mice

Currently, there is a global trend of rapid increase in obesity, especially among adolescents. The antibiotics cocktails (ABX) therapy is commonly used as an adjunctive treatment for gut microbiota related diseases, including obesity. However, the effects of broad-spectrum antibiotics alone on young obese hosts have rarely been reported. In the present study, the 3-week-old C57BL/6J male mice fed a high-fat diet (HFD) were intragastric administration with ampicillin, vancomycin, metronidazole or neomycin for 30 days. The lipid metabolites in plasma were assessed by biochemical assay kits, and genes related to lipid metabolite in the white adipose were assessed by qPCR. To further analyze the underlying mechanisms, the expression of genes related to lipid metabolism, inflammatory reactions and oxidative stress in the liver were determined by qPCR assay. In addition, the expression of oxidative damage-associated proteins in the liver were detected by western blot. The results showed that oral antibiotics exposure could reduce body weight and fat index in HFD-fed mice, concurrent with the increase of white adipose lipolysis genes and the decrease of hepatic lipogenic genes. Furthermore, antibiotics treatment could clearly reverse the HFD-induced elevation of oxidative damage-related proteins in the liver. Together, these findings will provide valuable clues into the effects of antibiotics on obesity.

Prenatal exposure to a mixture of PAHs causes the dysfunction of islet cells in adult male mice: Association with type 1 diabetes mellitus

Polycyclic aromatic hydrocarbons (PAHs) have been detected throughout the human body. Whether exposure to PAHs is associated with the incidence of type 1 diabetes mellitus should be investigated. To this end, pregnant mice were exposed to mixed PAHs (5, 50, or 500 μg/kg) once every other day during gestation. The adult male offspring displayed impaired glucose tolerance and reduced serum levels of glucagon and insulin. Immunohistochemical staining revealed increased numbers of apoptotic β-cells and a reduced β-cell mass in these males. The downregulated expression of pancreatic estrogen receptor α, androgen receptor, and transcription factor PDX1 was responsible for impacting β-cell development. The relatively reduced α-cell area was associated with downregulated ARX expression. The transcription of Isn2 and Gcg in pancreatic tissue was downregulated, which indicated that the function of β-cells and α-cells was impaired. Methylation levels in the Isn2 promotor were significantly elevated in mice prenatally exposed to 500 µg/kg PAHs, which was consistent with the change in its mRNA levels. The number of macrophages infiltrating islets was significantly increased, indicating that prenatal PAH exposure might reduce islet cell numbers in an autoimmune manner. This study shows that prenatal exposure to PAHs may promote the pathogenesis of type 1 diabetes mellitus.

Glutathione deficiency decreases lipid droplet stores and increases reactive oxygen species in mouse oocytes†

Glutathione (GSH) is a tripeptide thiol antioxidant that has been shown to be important to overall reproductive health. Glutamate cysteine ligase, the rate-limiting enzyme in GSH synthesis consists of a catalytic and a modifier (GCLM) subunit. We previously showed that oxidative stress in the ovary and oocytes of Gclm-/- mice is associated with accelerated age-related decline in ovarian follicles and decreased female fertility due to preimplantation embryonic mortality. Mammalian preimplantation development is a highly regulated and energy-intensive process that primarily relies on coordination between lipid droplets (LDs) and mitochondria to maintain cellular homeostasis. In this study, we hypothesized that GSH deficiency in oocytes increases oxidative stress, leading to increased mitochondrial dysfunction and decreased LD consumption, thereby decreasing oocyte developmental competence. We observed that Gclm-/- oocytes have increased oxidative stress, primarily in the form of mitochondrial superoxide and decreased subcortical mitochondrial clusters. Further, Gclm-/- oocytes have decreased mitochondrial membrane potential (ΔΨm) compared with Gclm+/+. We surmise this is likely due to the decreased availability of LDs, as we observed a significant decrease in LD content in Gclm-/- oocytes compared with Gclm+/+. The decreased oocyte LD content is likely related to an altered serum lipidome, with Gclm-/- serum having relatively lower unsaturated fatty acids and triglycerides than that of Gclm+/+ and Gclm+/- females. Altogether these data support that decreased LDs and increased oxidative stress are primary drivers of decreased oocyte developmental competence in GSH-deficient oocytes.

Hepatotoxicity in young adult mouse offspring after prenatal exposure to benzo(a)pyrene, and protective effect of atorvastatin

OBJECTIVES

Benzo[a]pyrene (BaP) is an environmental contaminant that interrupts the antioxidant defense and thus leads to oxidative stress and DNA damage in the liver. Atorvastatin (ATV) for reducing cholesterol has antioxidant and anti-apoptotic activities. This study investigated the effects of prenatal exposure of BaP on liver toxicity and the protective role of ATV in reducing liver toxicity.

MATERIALS AND METHODS

In this study, rats were distributed randomly to seven groups: I. Saline control; II. ATV (10 mg/kg); III. Corn oil; IV and V. BaP (10 and 20 mg/kg); VI and VII. ATV + BaP (10 and 20 mg/kg). BaP and ATV were administrated from gestation day 7-16 (GD7-GD16), orally. Ten weeks after the birth, female offspring were examined for oxidative stress markers, liver enzymes, and histology.

RESULTS

Data revealed that BaP significantly induced oxidative stress (decreased glutathione and increased malondialdehyde level), and disrupted the tissue structure of the liver. Moreover, alanine aminotransferase, aspartate aminotransferase, and alkaline phosphatase increased in the offspring. ATV treatment along with BaP during gestation was able to bring the antioxidant status and serum liver enzymes levels relatively close to normal. As well as, histological findings showed that ATV was able to improve liver tissue structure caused by BaP.

CONCLUSION

Based on the above studies we concluded that ATV at a low dose during gestation was able to reduce liver damage caused by BaP with antioxidant properties.

Obesity II: Establishing causal links between chemical exposures and obesity

Obesity is a multifactorial disease with both genetic and environmental components. The prevailing view is that obesity results from an imbalance between energy intake and expenditure caused by overeating and insufficient exercise. We describe another environmental element that can alter the balance between energy intake and energy expenditure: obesogens. Obesogens are a subset of environmental chemicals that act as endocrine disruptors affecting metabolic endpoints. The obesogen hypothesis posits that exposure to endocrine disruptors and other chemicals can alter the development and function of the adipose tissue, liver, pancreas, gastrointestinal tract, and brain, thus changing the set point for control of metabolism. Obesogens can determine how much food is needed to maintain homeostasis and thereby increase the susceptibility to obesity. The most sensitive time for obesogen action is in utero and early childhood, in part via epigenetic programming that can be transmitted to future generations. This review explores the evidence supporting the obesogen hypothesis and highlights knowledge gaps that have prevented widespread acceptance as a contributor to the obesity pandemic. Critically, the obesogen hypothesis changes the narrative from curing obesity to preventing obesity.

The Role of Persistent Organic Pollutants in Obesity: A Review of Laboratory and Epidemiological Studies

Persistent organic pollutants (POPs) are considered as potential obesogens that may affect adipose tissue development and functioning, thus promoting obesity. However, various POPs may have different mechanisms of action. The objective of the present review is to discuss the key mechanisms linking exposure to POPs to adipose tissue dysfunction and obesity. Laboratory data clearly demonstrate that the mechanisms associated with the interference of exposure to POPs with obesity include: (a) dysregulation of adipogenesis regulators (PPARγ and C/EBPα); (b) affinity and binding to nuclear receptors; (c) epigenetic effects; and/or (d) proinflammatory activity. Although in vivo data are generally corroborative of the in vitro results, studies in living organisms have shown that the impact of POPs on adipogenesis is affected by biological factors such as sex, age, and period of exposure. Epidemiological data demonstrate a significant association between exposure to POPs and obesity and obesity-associated metabolic disturbances (e.g., type 2 diabetes mellitus and metabolic syndrome), although the existing data are considered insufficient. In conclusion, both laboratory and epidemiological data underline the significant role of POPs as environmental obesogens. However, further studies are required to better characterize both the mechanisms and the dose/concentration-response effects of exposure to POPs in the development of obesity and other metabolic diseases.

Activation of the aryl hydrocarbon receptor by clozapine induces preadipocyte differentiation and contributes to endothelial dysfunction

BACKGROUND

The superior therapeutic benefit of clozapine is often associated with metabolic disruptions as obesity, insulin resistance, tachycardia, higher blood pressure, and even hypertension.

AIMS

These adverse vascular/ metabolic events under clozapine are similar to those caused by polycyclic aromatic hydrocarbons (PAHs), and clozapine shows structural similarity to well-known ligands of the aryl hydrocarbon receptor (AhR). Therefore, we speculated that the side effects caused by clozapine might rely on AhR signaling.

METHODS

We examined clozapine-induced AhR activation by luciferase reporter assays in hepatoma HepG2 cells and we proved upregulation of the prototypical AhR target gene Cyp1A1 by realtime-PCR (RT-PCR) analysis and enzyme activity. Next we studied the physiological role of AhR in clozapine's effects on human preadipocyte differentiation and on vasodilatation by myography in wild-type and AhR-/- mice.

RESULTS

In contrast to other antipsychotic drugs (APDs), clozapine triggered AhR activation and Cyp1A1 expression in HepG2 cells and adipocytes. Clozapine induced adipogenesis via AhR signaling. After PGF2α-induced constriction of mouse aortic rings, clozapine strongly reduced the maximal vasorelaxation under acetylcholine in rings from wild-type mice, but only slightly in rings from AhR-/- mice. The reduction was also prevented by pretreatment with the AhR antagonist CH-223191.

CONCLUSION

Identification of clozapine as a ligand for the AhR opens new perspectives to explain common clozapine therapy-associated adverse effects at the molecular level.

Curcumin Suppresses the Lipid Accumulation and Oxidative Stress Induced by Benzo[a]pyrene Toxicity in HepG2 Cells

Benzo[a]pyrene (B[a]P) is a potentially hepatotoxic group-1 carcinogen taken up by the body through ingestion of daily foods. B[a]P is widely known to cause DNA and protein damages, which are closely related to cell transformation. Accordingly, studies on natural bioactive compounds that attenuate such chemical-induced toxicities have significant impacts on public health. This study aimed to uncover the mechanism of curcumin, the major curcuminoid in turmeric (Curcuma longa), in modulating the lipid accumulation and oxidative stress mediated by B[a]P cytotoxicity in HepG2 cells. Curcumin treatment reduced the B[a]P-induced lipid accumulation and reactive oxygen spicies (ROS) upregulation and recovered the cell viability. Cytochrome P450 family 1 subfamily A polypeptide 1 (CYP1A1) and Cytochrome P450 subfamily B polypeptide 1 (CYP1B1) downregulation resulting from decreased aryl hydrocarbon receptor (AhR) translocation into nuclei attenuated the effects of B[a]P-induced lipid accumulation and repressed cell viability, respectively. Moreover, the curcumin-induced reduction in ROS generation decreased the nuclear translocation of Nuclear factor erythroid-2-related factor 2 (Nrf2) and the expression of phase-II detoxifying enzymes. These results indicate that curcumin suppresses B[a]P-induced lipid accumulation and ROS generation which can potentially induce nonalcoholic fatty liver disease (NAFLD) and can shed a light on the detoxifying effect of curcumin.

Transcriptomic changes in western mosquitofish (Gambusia affinis) liver following benzo[a]pyrene exposure

Widely distributed western mosquitofish (Gambusia affinis) has been used as a new model species for hazard assessment of environmental stressors such as polycyclic aromatic hydrocarbons (PAHs). However, most of the PAH studies using G. affinis rely on targeted biomarker-based analysis, and thus may not adequately address the complexity of the toxic mechanisms of the stressors. In the present study, the whole transcriptional sequencing of G. affinis liver after exposure to a PAH model, benzo[a]pyrene (BaP) (100 μg/L), for 20 days was performed by using the HiSeq XTen sequencers. In total, 58,156,233 and 51,825,467 clean nucleotide reads were obtained in the control and BaP-exposed libraries, respectively, with average N50 lengths of 1419 bp. In addition, after G. affinis was exposed for 20 days, 169 genes were upregulated, and 176 genes were downregulated in liver. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were applied to all the genes to determine the genes' biological functions and processes. The results clearly showed that the differentially expressed genes were mainly related to immune pathways and metabolic correlation pathways. Interestingly, almost all the pathways related with the immunity were upregulated, while the metabolism pathways were downregulated. Lastly, quantitative real-time PCR (qRT-PCR) was performed to measure expressional levels of twelve genes confirmed through the DGE analysis. These results demonstrate that BaP damages immunity and enhances the consumption of all available energy storage to activate mechanisms of the detoxification in G. affinis. Up until now, the present study is the first time that a whole transcriptome sequencing analysis in the liver of G. affinis exposed to BaP has been reported.

Spironolactone reversed hepato-ovarian triglyceride accumulation caused by letrozole-induced polycystic ovarian syndrome: tissue uric acid-a familiar foe

Polycystic ovarian syndrome (PCOS) is a complex endocrine disease among women of reproductive age and is one of the main causes of infertility. Non-alcoholic fatty liver disease (NAFLD), the most prominent chronic liver disease in adults, is characterized by excess hepatic triglyceride (TG) accumulation. PCOS women have increased risk of NAFLD and uric acid has been documented to have a positive correlation with subclinical tissue damage and might be the link in the cystic. Spironolactone (SPL) is a mineralocorticoid receptor (MR) blocker that has been in wide clinical use for some decades. In this research, we investigated the effects of SPL on ovarian and hepatic tissue damage in experimental PCOS rats induced by letrozole (LET). A total of eighteen adult female Wistar rats were used for this study and the animals divided into 3 groups are treated with vehicle, LET (1 mg/kg), and LET+SPL (SPL; 0.25 mg/kg), p.o. once daily respectively for 21 uninterrupted days. Results showed that LET treatment induced features of PCOS characterized by increased plasma testosterone (T) and luteinizing hormone (LH) together with increased body weight. Abnormal ovarian and hepatic histomorphological changes were also observed with elevated uric acid (UA) and TG accumulation in both tissues respectively. Treatment with SPL however attenuated the elevated testosterone in the LET-induced PCOS model accompanied with a reversal in the observed ovarian and hepatic UA, TG accumulation, and altered histomorphological changes. Taken together, spironolactone reversed the PCOS-induced ovarian and hepatic tissue damage by suppressing tissue UA and TG accumulation.

Hepatic Tumor Formation in Adult Mice Developmentally Exposed to Organotin

BACKGROUND

Tributyltin (TBT) is a persistent and bioaccumulative environmental toxicant. Developmental exposure to TBT has been shown to cause fatty liver disease (steatosis), as well as increased adiposity in many species, leading to its characterization as an obesogen.

OBJECTIVE

We aimed to determine the long-term effects of developmental TBT exposure on the liver.

METHODS

C57BL/6J mice were exposed to a dose of TBT (0.5 mg / kg body weight per day; 3.07 μ M ) below the current developmental no observed adverse effect level (NOAEL) via drinking water, or drinking water alone, provided to the dam from preconception through lactation. Sires were exposed during breeding and lactation. Pups from two parity cycles were included in this study. Animals were followed longitudinally, and livers of offspring were analyzed by pathological evaluation, immunohistochemistry, immunoblotting, and RNA sequencing.

RESULTS

Developmental exposure to TBT led to increased adiposity and hepatic steatosis at 14 and 20 weeks of age and increased liver adenomas at 45 weeks of age in male offspring. Female offspring displayed increased adiposity as compared with males, but TBT did not lead to an increase in fatty liver or tumor development in female offspring. Liver tumors in male mice were enriched in pathways and gene signatures associated with human and rodent nonalcoholic fatty liver disease (NAFLD) and hepatocellular carcinoma (HCC). This includes down-regulation of growth hormone receptor (GHR) and of STAT5 signaling, which occurred in response to TBT exposure and preceded liver tumor development.

CONCLUSIONS

These data reveal a previously unappreciated ability of TBT to increase risk for liver tumorigenesis in mice in a sex-specific manner. Taken together, these findings provide new insights into how early life environmental exposures contribute to liver disease in adulthood. https://doi.org/10.1289/EHP5414.

Prepregnancy obesity is associated with cognitive outcomes in boys in a low-income, multiethnic birth cohort

Background

Maternal obesity and high gestational weight gain (GWG) disproportionally affect low-income populations and may be associated with child neurodevelopment in a sex-specific manner. We examined sex-specific associations between prepregnancy BMI, GWG, and child neurodevelopment at age 7.

Methods

Data are from a prospective low-income cohort of African American and Dominican women (n = 368; 44.8% male offspring) enrolled during the second half of pregnancy from 1998 to 2006. Neurodevelopment was measured using the Wechsler Intelligence Scale for Children (WISC-IV) at approximately child age 7. Linear regression estimated associations between prepregnancy BMI, GWG, and child outcomes, adjusting for race/ethnicity, marital status, gestational age at delivery, maternal education, maternal IQ and child age.

Results

Overweight affected 23.9% of mothers and obesity affected 22.6%. At age 7, full-scale IQ was higher among girls (99.7 ± 11.6) compared to boys (96.9 ± 13.3). Among boys, but not girls, prepregnancy overweight and obesity were associated with lower full-scale IQ scores [overweight β: − 7.1, 95% CI: (− 12.1, − 2.0); obesity β: − 5.7, 95% CI: (− 10.7, − 0.7)]. GWG was not associated with full-scale IQ in either sex.

Conclusions

Prepregnancy overweight and obesity were associated with lower IQ among boys, but not girls, at 7 years. These findings are important considering overweight and obesity prevalence and the long-term implications of early cognitive development.

Mechanisms of Environmental Contributions to Fatty Liver Disease

PURPOSE

Fatty liver disease (FLD) affects over 25% of the global population and may lead to liver-related mortality due to cirrhosis and liver cancer. FLD caused by occupational and environmental chemical exposures is termed "toxicant-associated steatohepatitis" (TASH). The current review addresses the scientific progress made in the mechanistic understanding of TASH since its initial description in 2010.

RECENT FINDINGS

Recently discovered modes of actions for volatile organic compounds and persistent organic pollutants include the following: (i) the endocrine-, metabolism-, and signaling-disrupting chemical hypotheses; (ii) chemical-nutrient interactions and the "two-hit" hypothesis. These key hypotheses were then reviewed in the context of the steatosis adverse outcome pathway (AOP) proposed by the US Environmental Protection Agency. The conceptual understanding of the contribution of environmental exposures to FLD has progressed significantly. However, because this is a new research area, more studies including mechanistic human data are required to address current knowledge gaps.

Effects of first-generation in utero exposure to diesel engine exhaust on second-generation placental function, fatty acid profiles and foetal metabolism in rabbits: preliminary results

Atmospheric pollution has major health effects on directly exposed subjects but intergenerational consequences are poorly characterized. We previously reported that diesel engine exhaust (DE) could lead to structural changes in the placenta of in utero exposed rabbits (first generation, F1). The effects of maternal exposure to DE were further studied on second-generation (F2) rabbits. Pregnant F0 females were exposed to filtered, diluted DE (1 mg/m³, median particle diameter: 69 nm) or clean filtered air (controls) for 2 h/day, 5 days/week by nose-only exposure during days 3–27 post-conception (dpc). Adult female offspring (F1) were mated to control males: F1 tissues and F2 foeto-placental units were collected at 28 dpc and placental structure and gene expression (microarray) analysed. Fatty acid profiles were determined in foetal and maternal plasma, maternal liver and placenta. In F1, compared to controls, hepatic neutral lipid contents were increased in exposed animals without change in the blood biochemistry. In F2, the placental lipid contents were higher, with higher monounsaturated fatty acids and reduced pro-inflammatory arachidonic acid (AA), without placental structural changes. Conversely, the proportion of anti-inflammatory n-3 polyunsaturated fatty acids in F2 plasma was increased while that of AA was decreased. Gene set enrichment analyses (GSEA) of F2 placenta transcriptomic data identified that the proteasome complex and ubiquitin pathways genes were over-represented and ion channel function and inflammation pathways genes were under-represented in exposed animals. These preliminary results demonstrate that diesel engine exhaust exposure and in utero indirect exposure should be considered as a programming factor within the context of the DOHaD (Developmental Origins of Health and Disease) with a probable intergenerational transmission.

Diet and Contaminants: Driving the Rise to Obesity Epidemics?

The obesity epidemic is spreading worldwide without reversal trend and despite specific policies oriented to dietary habits and lifestyle, which seem to have modest effects. Genetic factors only partly explain the rise, whereas environmental factors seem to play a key role, mainly by gene-environment interactions through epigenetic mechanisms. A number of animal and human studies point to maternal diet, intestinal microbiota and chemicals introduced as contaminants with food, all factors able to increase the risk of obesity. Widely diffused toxics (mainly BPA, phthalates, pesticides) are able to promote obesity in children and adults, mainly by acting on the differentiation pathway linking multipotent stromal stem cell to mature adipocyte, modulating epigenetic factors and influencing a series of mechanisms finally leading to altered dietary habits, increased adipocyte formation and fat storage. Furthermore, the adipose tissue is an important target for several chemicals (mainly POPs) which represent a threat to metabolic health. In conclusion, besides excessive individual energy intake and inadequate lifestyle, other broadly diffused and modifiable factors (mainly ingestion of toxic chemicals with food) seem to have a critical role in the rapid epidemiological growing of obesity, also considering trans-generational transmission of risk and later development of obesity due to exposure during early life. Further studies are needed, to better assess interactions between cumulative effects of toxic food contaminants and modification of diet and lifestyle, and to verify the efficacy of primary prevention strategies acting on all these factors and potentially able to reverse the continuous rising of the obesity epidemic.

Exposure to environmental level phenanthrene induces a NASH-like phenotype in new born rat

More and more evidence indicates that persistent organic pollutants (POPs) are a risk factor for non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH). Phenanthrene (Phe) is a kind of POP which existed extensively in the environment, but whose toxicity on mammals has so far received less focus. Subcutaneously injection of Phe (0.5, 5, 50 μg/kg) for 21 days induced significant NAFLD/NASH symptoms in new born rats. Exposure to environmental levels of Phe decreased body weight and liver-somatic index; impaired histology of liver; influenced the peroxisome proliferator-activated receptor gamma (PPARγ) signaling and lipid metabolism in liver; stimulated oxidative stress in the rats' liver; induced the variation of NFκB pathway and liver inflammatory response; and caused liver fibrosis via transforming growth factor β1 (tgfβ1). We speculated that the subcutaneously injected Phe was transferred to the liver through blood circulation, which may have induced the elevation of PPARγ directly or indirectly, leading to liver steatosis. Excess lipid, acting as the first hit, stimulated the second hit factors - oxidative stress, inflammatory response and lipid peroxidation, and finally resulted in steatohepatitis and liver fibrosis.

Endocrine Disruptors and Developmental Origins of Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is a growing epidemic worldwide, particularly in countries that consume a Western diet, and can lead to life-threatening conditions such as cirrhosis and hepatocellular carcinoma. With increasing prevalence of NAFLD in both children and adults, an understanding of the factors that promote NAFLD development and progression is crucial. Environmental agents, including endocrine-disrupting chemicals (EDCs), which have been linked to other diseases, may play a role in NAFLD development. Increasing evidence supports a developmental origin of liver disease, and early-life exposure to EDCs could represent one risk factor for the development of NAFLD later in life. Rodent studies provide the strongest evidence for this link, but further studies are needed to define whether there is a causal link between early-life EDC exposure and NAFLD development in humans. Elucidating the molecular mechanisms underlying development of NAFLD in the context of developmental EDC exposures may identify biomarkers for people at risk, as well as potential intervention and/or therapeutic opportunities for the disease.

Cross-Talk Between Bile Acids and Gastro-Intestinal and Thermogenic Hormones: Clues from Bariatric Surgery

Obesity is rapidly increasing and has reached epidemic features worldwide. It´s linked to insulin resistance, systemic low-grade inflammation and common pathogenic pathways with a number of comorbidities (including cancer), leading to high mortality rates. Besides change of lifestyles (diet and physical exercise) and pharmacological therapy, bariatric surgery is able to rapidly improve several metabolic and morphologic features associated with excessive fat storage, and currently represents an in vivo model to study the pathogenic mechanisms underlying obesity and obesity-related complications. Studies on obese subjects undergoing bariatric surgery find that the effects of surgery are not simply secondary to gastric mechanical restriction and malabsorption which induce body weight loss. In fact, some surgical procedures positively modify key pathways involving the intestine, bile acids, receptor signaling, gut microbiota, hormones and thermogenesis, leading to systemic metabolic changes. Furthermore, bariatric surgery represents a suitable model to evaluate the gene-environment interaction and some epigenetic mechanisms linking obesity and insulin resistance to metabolic diseases.

Obesogenic endocrine disruptors and obesity: myths and truths

Obesogenic endocrine disruptors, also known as obesogens, are chemicals potentially involved in weight gain by altering lipid homeostasis and promoting adipogenesis and lipid accumulation. They included compounds to which human population is exposed over daily life such as pesticides/herbicides, industrial and household products, plastics, detergents and personal care products. The window of life during which the exposure happens could lead to different effects. A critical window is during utero and/or neonatal period in which the obesogens could cause subtle changes in gene expression and tissue organization or blunt other levels of biological organization leading to increased susceptibility to diseases in the adulthood. Some of the reasons for this increased sensitivity include the lack of the protective mechanisms that are available in adult such as DNA repair mechanisms, a competent immune system, detoxifying enzymes, liver metabolism and the blood/brain barrier still not fully functional in the fetus or newborn. The mechanisms of action of obesogens lay on their ability to increase the number and/or the size of the adipocytes and to alter appetite, satiety and food preferences. The ability of obesogens to increase fat deposition results in an increased capacity for their own retention due to their lipophilic properties; thus prolonging the exposure and increasing the detrimental metabolic consequences.

Ovarian effects of prenatal exposure to benzo[a]pyrene: Roles of embryonic and maternal glutathione status

Females deficient in the glutamate cysteine ligase modifier subunit (Gclm) of the rate-limiting enzyme in glutathione synthesis are more sensitive to ovarian follicle depletion and tumorigenesisby prenatal benzo[a]pyrene (BaP) exposure than Gclm+/+ mice. We investigated effects of prenatal exposure to BaP on reproductive development and ovarian mutations in Kras, a commonly mutated gene in epithelial ovarian tumors. Pregnantmice were dosed from gestational day 6.5 through 15.5 with 2mg/kg/day BaP or vehicle. Puberty onset occurred 5 days earlier in F1 daughters of all Gclm genotypes exposed to BaP compared to controls. Gclm+/- F1 daughters of Gclm+/- mothers and wildtype F1 daughters of wildtype mothers had similar depletion of ovarian follicles following prenatal exposure to BaP, suggesting that maternal Gclm genotype does not modify ovarian effects of prenatal BaP. We observed no BaP treatment or Gclm genotype related differences in ovarian Kras codon 12 mutations in F1 offspring.

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.

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.

Fat, epigenome and pancreatic diseases. Interplay and common pathways from a toxic and obesogenic environment

The worldwide obesity epidemic is paralleled by a rise in the incidence of pancreatic disorders ranging from "fatty" pancreas to pancreatitis and cancer. Body fat accumulation and pancreatic dysfunctions have common pathways, mainly acting through insulin resistance and low-grade inflammation, frequently mediated by the epigenome. These mechanisms are affected by lifestyle and by the toxic effects of fat and pollutants. An early origin is common, starting in pediatric age or during the fetal life in response to nutritional factors, endocrine disruptor chemicals (EDCs) or parental exposure to toxics. A "fatty pancreas" is frequent in obese and is able to induce pancreatic damage. The fat is a target of EDCs and of the cytotoxic/mutagenic effects of heavy metals, and is the site of bioaccumulation of lipophilic and persistent pollutants related with insulin resistance and able to promote pancreatic cancer. Increased Body Mass Index (BMI) can act as independent risk factor for a more severe course of acute pancreatitis and obesity is also a well-known risk factor for pancreatic cancer, that is related with BMI, insulin resistance, and duration of exposure to the toxic effects of fat and/or of environmental pollutants. All these mechanisms involve gene-environment interactions through epigenetic factors, and might be manipulated by primary prevention measures. Further studies are needed, pointing to better assess the interplays of modifiable factors on both obesity and pancreatic diseases, and to verify the efficacy of primary prevention strategies involving lifestyle and environmental exposure to toxics.