Multiomics Analysis of PCB126's Effect on a Mouse Chronic-Binge Alcohol Feeding Model.

BACKGROUND: Environmental pollutants, including polychlorinated biphenyls (PCBs) have been implicated in the pathogenesis of liver disease. Our group recently demonstrated that PCB126 promoted steatosis, hepatomegaly, and modulated intermediary metabolism in a rodent model of alcohol-associated liver disease (ALD). OBJECTIVE: To better understand how PCB126 promoted ALD in our previous model, the current study adopts multiple omics approaches to elucidate potential mechanistic hypotheses. METHODS: Briefly, male C57BL/6J mice were exposed to 0.2mg/kg polychlorinated biphenyl (PCB) 126 or corn oil vehicle prior to ethanol (EtOH) or control diet feeding in the chronic-binge alcohol feeding model. Liver tissues were collected and prepared for mRNA sequencing, phosphoproteomics, and inductively coupled plasma mass spectrometry for metals quantification. RESULTS: Principal component analysis showed that PCB126 uniquely modified the transcriptome in EtOH-fed mice. EtOH feeding alone resulted in >4,000 differentially expressed genes (DEGs), and PCB126 exposure resulted in more DEGs in the EtOH-fed group (907 DEGs) in comparison with the pair-fed group (503 DEGs). Top 20 significant gene ontology (GO) biological processes included "peptidyl tyrosine modifications," whereas top 25 significantly decreasing GO molecular functions included "metal/ion/zinc binding." Quantitative, label-free phosphoproteomics and western blot analysis revealed no major significant PCB126 effects on total phosphorylated tyrosine residues in EtOH-fed mice. Quantified hepatic essential metal levels were primarily significantly lower in EtOH-fed mice. PCB126-exposed mice had significantly lower magnesium, cobalt, and zinc levels in EtOH-fed mice. DISCUSSION: Previous work has demonstrated that PCB126 is a modifying factor in metabolic dysfunction-associated steatotic liver disease (MASLD), and our current work suggests that pollutants also modify ALD. PCB126 may, in part, be contributing to the malnutrition aspect of ALD, where metal deficiency is known to contribute and worsen prognosis. https://doi.org/10.1289/EHP14132.

Sex-specific effects of acute chlordane exposure in the context of steatotic liver disease, energy metabolism and endocrine disruption.

Chlordane is an organochlorine pesticide (OCP) that is environmentally persistent. Although exposures to OCPs including chlordane have been associated with elevated liver enzymes, current knowledge on OCPs' contribution to toxicant-associated steatotic liver disease (TASLD) and underlying sex-specific metabolic/endocrine disruption are still widely limited. Therefore, the objective of this study was to investigate the sex-dependent effects of chlordane in the context of TASLD. Age-matched male and female C57BL/6 mice were exposed to chlordane (20 mg/kg, one-time oral gavage) for two weeks. Female mice generally exhibited lower bodyfat content but more steatosis and hepatic lipid levels, consistent with increased hepatic mRNA levels of genes involved in lipid synthesis and uptake. Surprisingly, chlordane-exposed females demonstrated lower hepatic cholesterol levels. With regards to metabolic disruption, chlordane exposure decreased expression of genes involved in glycogen and glucose metabolism (Pklr, Gck), while chlordane-exposed females also exhibited decreased gene expression of HNF4A, an important regulator of liver identity and function. In terms of endocrine endpoints, chlordane augmented plasma testosterone levels in males. Furthermore, chlordane activated hepatic xenobiotic receptors, including the constitutive androstane receptor, in a sex-dependent manner. Overall, chlordane exposure led to altered hepatic energy metabolism, and potential chlordane-sex interactions regulated metabolic/endocrine disruption and receptor activation outcomes.

Investigating the Acute Metabolic Effects of the N-Methyl Carbamate Insecticide, Methomyl, on Mouse Liver.

Many pesticides have been identified as endocrine and metabolism-disrupting chemicals with hepatotoxic effects. However, data are limited for insecticides in the n-methyl carbamate class, including methomyl. Here, we investigate the liver and systemic metabolic effects of methomyl in a mouse model. We hypothesize that methomyl exposure will disrupt xenobiotic and intermediary metabolism and promote hepatic steatosis in mice. Male C57BL/6 mice were exposed daily to 0-5 mg/kg methomyl for 18 days. Mice were fed water and regular chow diet ad libitum. Metabolic phenotyping was performed, and tissue samples were collected. Effects were generally greatest at the highest methomyl dose, which induced Cyp1a2. Methomyl decreased whole body weight while the liver:body weight and testes:body weight ratios were increased. Hepatic steatosis increased while plasma LDL decreased. Fasting blood glucose and the glucose tolerance test area under the curve decreased along with hepatic glycogen stores. Methomyl, however, did not increase liver oxidative stress or injury. Collectively, these data demonstrate that methomyl disrupts hepatic xenobiotic and intermediary metabolism while increasing the testes:body weight ratio, suggesting that it may be an endocrine disrupting chemical. Besides methomyl's known action in cholinesterase inhibition, it may be involved in aryl hydrocarbon receptor activation. The potential impact of n-methyl carbamate insecticides on metabolic health and diseases, including toxicant-associated steatotic liver disease (TASLD), warrants further investigation.

Investigating the effects of long-term Aroclor 1260 exposure on fatty liver disease in a diet-induced obesity mouse model.

Introduction: Polychlorinated biphenyls (PCBs) are persistent environmental toxicants that have been implicated in numerous health disorders including liver diseases such as non-alcoholic fatty liver disease (NAFLD). Toxicant-associated NAFLD, also known as toxicant-associated fatty liver disease (TAFLD), consists of a spectrum of disorders ranging from steatosis and steatohepatitis to fibrosis and hepatocellular carcinoma. Previously, our group demonstrated that 12-week exposure to the PCB mixture, Aroclor 1260, exacerbated steatohepatitis in high-fat diet (HFD)-fed mice; however, the longer-term effects of PCBs on TAFLD remain to be elucidated. This study aims to examine the longer-term effects of Aroclor 1260 (>30 weeks) in a diet-induced obesity model to better understand how duration of exposure can impact TAFLD. Methods: Male C57BL/6 mice were exposed to Aroclor 1260 (20 mg/kg) or vehicle control by oral gavage at the beginning of the study period and fed either a low-fat diet (LFD) or HFD throughout the study period. Results: Aroclor 1260 exposure (>30 weeks) led to steatohepatitis only in LFD-fed mice. Several Aroclor 1260 exposed LFD-fed mice also developed hepatocellular carcinoma (25%), which was absent in HFD-fed mice. The LFD+Aroclor1260 group also exhibited decreased hepatic Cyp7a1 expression and increased pro-fibrotic Acta2 expression. In contrast, longer term Aroclor 1260 exposure in conjunction with HFD did not exacerbate steatosis or inflammatory responses beyond those observed with HFD alone. Further, hepatic xenobiotic receptor activation by Aroclor 1260 was absent at 31 weeks post exposure, suggesting PCB redistribution to the adipose and other extra-hepatic tissues with time. Discussion: Overall, the results demonstrated that longer-term PCB exposure worsened TAFLD outcomes independent of HFD feeding and suggests altered energy metabolism as a potential mechanism fueling PCB mediated toxicity without dietary insult. Additional research exploring mechanisms for these longer-term PCB mediated toxicity in TAFLD is warranted.

Can Zinc Supplementation Attenuate High Fat Diet-Induced Non-Alcoholic Fatty Liver Disease?

The pathogenesis of non-alcoholic fatty liver disease (NAFLD), the most prevalent chronic liver disease, is associated with zinc deficiency. Previous studies show zinc supplementation improves steatosis and glucose metabolism, but its therapeutic effects in patients with established NAFLD remain unclear. We developed an in vivo model to characterize the effects of zinc supplementation on high-fat diet (HFD) induced NAFLD and hypothesized that the established NAFLD would be attenuated by zinc supplementation. Male C57BL/6J mice were fed a control diet or HFD for 12 weeks. Mice were then further grouped into normal and zinc-supplemented diets for 8 additional weeks. Body composition and glucose tolerance were determined before and after zinc supplementation. At euthanasia, plasma and liver tissue were collected for characterization and downstream analysis. As expected, 12 weeks of HFD resulted in reduced glucose clearance and altered body composition. Eight weeks of subsequent zinc supplementation did not alter glucose handling, plasma transaminases, steatosis, or hepatic gene expression. Results from our model suggest 8-week zinc supplementation cannot reverse established NAFLD. The HFD may have caused NAFLD disease progression beyond rescue by an 8-week period of zinc supplementation. Future studies will address these limitations and provide insights into zinc as a therapeutic agent for established NAFLD.

The environmental pollutant, polychlorinated biphenyl 126, alters liver function in a rodent model of alcohol-associated liver disease.

BACKGROUND: The prevalence of alcohol-associated liver disease (ALD), a subtype of fatty liver disease (FLD), continues to rise. ALD is a major cause of preventable death. Polychlorinated biphenyl (PCB) 126 is an environmentally relevant, dioxin-like pollutant whose negative metabolic effects have been well documented. In human and animal studies, PCB has been associated with the severity of nonalcoholic fatty liver disease (NAFLD). However, few studies have investigated whether exposures to environmental toxicants can worsen ALD. Thus, the objective of the current study was to develop an alcohol-plus-toxicant model to study how an environmental pollutant, PCB 126, impacts rodent ALD pathology. METHODS: Briefly, male C57BL/6J mice were exposed to 0.2 mg/kg PCB 126 or corn oil vehicle four days prior to ethanol feeding using the chronic-binge (10-plus-one) model. RESULTS: Concentrations of macromolecules, including hepatic lipids, carbohydrates, and protein (albumin) were impacted. Exposure to PCB 126 exacerbated hepatic steatosis and hepatomegaly in mice exposed to the chemical and fed an ethanol diet. Gene expression and the analysis of blood chemistry showed a potential net increase and retention of hepatic lipids and reductions in lipid oxidation and clearance capabilities. Depletion of glycogen and glucose was evident, which contributes to disease progression by generating systemic malnutrition. Granulocytic immune infiltrates were present but driven solely by ethanol feeding. Hepatic albumin gene expression and plasma levels were decreased by ~50% indicating a potential compromise of liver function. Finally, gene expression analyses indicated that the aryl hydrocarbon receptor and constitutive androstane receptor were activated by PCB 126 and ethanol, respectively. CONCLUSIONS: Various environmental toxicants are known to modify or enhance FLD in high-fat diet models. Findings from the present study suggest that they interact with other lifestyle factors such as alcohol consumption to reprogram intermediary metabolism resulting in exacerbated ethanol-associated systemic malnutrition in ALD.

Associations Between Residential Exposure to Volatile Organic Compounds and Liver Injury Markers.

Occupational exposures to volatile organic compounds (VOCs) have been associated with numerous health complications including steatohepatitis and liver cancer. However, the potential impact of environmental/residential VOC exposures on liver health and function is largely unknown. To address this knowledge gap, the objective of this cross-sectional study is to investigate associations between VOCs and liver injury biomarkers in community residents. Subjects were recruited from six Louisville neighborhoods, and informed consent was obtained. Exposure biomarkers included 16 creatinine-adjusted urinary metabolites corresponding to 12 parent VOCs. Serological disease biomarkers measured included cytokertain-18 (K18 M65 and M30), liver enzymes, and direct bilirubin. Associations between exposure and disease biomarkers were assessed using generalized linear models. Smoking status was confirmed through urinary cotinine levels. The population comprised of approximately 60% females and 40% males; White persons accounted 78% of the population; with more nonsmokers (n = 413) than smokers (n = 250). When compared with nonsmokers, males (45%) and Black persons (26%) were more likely to be smokers. In the overall population, metabolites of acrolein, acrylonitrile, acrylamide, 1,3-butadiene, crotonaldehyde, styrene, and xylene were positively associated with alkaline phosphatase. These associations persisted in smokers, with the exception of crotonaldehyde, and addition of N,N-dimethylformamide and propylene oxide metabolites. Although no positive associations were observed for K18 M30, the benzene metabolite was positively associated with bilirubin, irrespective of smoking status. Taken together, the results demonstrated that selected VOCs were positively associated with liver injury biomarkers. These findings will enable better risk assessment and identification of populations vulnerable to liver disease.