Polychlorinated biphenyls (PCBs) are persistent organic pollutants that are linked to adverse health outcomes. PCB tissue levels are determinants of PCB toxicity; however, it is unclear how factors, such as an altered metabolism and/or a fatty liver, affect PCB distribution in vivo. We determined the congener-specific disposition of PCBs in mice with a liver-specific deletion of cytochrome P450 reductase (KO), a model of fatty liver with impaired hepatic metabolism, and wild-type (WT) mice. Eight-week-old male WT (MWT, n = 3), male KO (MKO, n = 5), female WT (FWT, n = 4), and female KO mice (FKO, n = 4) were exposed orally to Aroclor 1254. PCBs were quantified in adipose, blood, brain, and liver tissues by gas chromatography-mass spectrometry. The ΣPCB levels followed the rank order adipose > liver ∼ brain > blood in WT and adipose ∼ liver > brain > blood in KO mice. PCB levels were much higher in the liver of KO than WT mice, irrespective of the sex. A comparison across exposure groups revealed minor genotype and sex-dependent differences in the PCB congener profiles (cos Θ > 0.92). Within each exposure group, tissue profiles showed small differences between tissues (cos Θ = 0.85 to 0.98). These differences were due to a decrease in metabolically more labile PCB congeners and an increase in congeners resistant to metabolism. The tissue-to-blood ratio of PCBs decreased for adipose, increased for the brain, and remained constant for the liver with an increase in chlorination. While these ratios did not follow the trends predicted using a composition-based model, the agreement between experimental and calculated partition coefficients was reasonable. Although the distribution of PCBs differs between KO and WT mice, the magnitude of the partitioning of PCBs from the blood into tissues can be approximated using composition-based models.

Perchlorate is a pervasive, water-soluble contaminant that competitively inhibits the sodium/iodide symporter, reducing the available iodide for thyroid hormone synthesis. Insufficient iodide uptake can lead to hypothyroidism and metabolic syndromes. Because metabolism, obesity and non-alcoholic fatty liver disease (NAFLD) are tightly linked, we hypothesized that perchlorate would act as an obesogen and cause NAFLD via accumulation of lipids in liver of developing threespine stickleback (Gasterosteus aculeatus). We performed an upshift/downshift exposure regime (clean water to perchlorate treated water or perchlorate treated water to clean water) on stickleback embryos at two concentrations (30 mg/L and 100 mg/L) plus the control (0 mg/L) over the course of 305 days. Adult stickleback were euthanized, H&E stained and analyzed for liver morphology. Specifically, we counted the number of lipid droplets, and measured the area of each droplet and the total lipid area of a representative section of liver. We found that perchlorate treated fish had more and larger lipid droplets, and a larger percentage of lipid in their liver than control fish. These data indicate that perchlorate causes NAFLD and hepatic steatosis in stickleback at concentrations commonly found at contaminated sites. These data also indicate the potential of perchlorate to act as an obesogen. Future studies should investigate the obesogenic capacity of perchlorate by examining organ specific lipid accumulation and whether perchlorate induces these effects at concentrations commonly found in drinking water. Work is also needed to determine the mechanisms by which perchlorate induces lipid accumulation.

Exposure to ambient particular matters (PM) has been associated with the development of non-alcoholic fatty liver disease (NAFLD), but the underlying mechanism remains unclear. Given that microRNA (miRNA) is recognized as a key regulator of lipid metabolism and a potential mediator of environmental cues, this study aimed to explore the role of miRNA-mRNA regulation underlying abnormal lipid metabolism triggered by PM₂.₅liposoluble extracts. We confirmed that 72-h exposure to liposoluble extracts of PM₂.₅ from Nanjing at 25 μg/cm² induced lipid accumulation in HepG2 cells by promoting uptake of free fatty acids (FFAs). Notably, lipid accumulation induced by PM₂.₅ liposoluble extracts was associated with decreased expression of miR-26a and consequent upregulation of fatty acid translocase (FAT, also known as CD36). Using gain- and loss-of-function assays, we demonstrated that miR-26a negatively regulated CD36 to mediate lipid accumulation in HepG2 cells. We further confirmed that miR-26a directly acted on the 3′ untranslated region (3′UTR) of CD36. Furthermore, overexpression of miR-26a abolished steatosis in HepG2 cells treated with PM₂.₅ liposoluble extracts by suppressing CD36. In addition, we demonstrated that PM₂.₅ liposoluble extracts caused inflammation in HepG2 cells by raising p65 phosphorylation, thereby fuelling the transition from simple non-alcoholic fatty liver to non-alcoholic steatohepatitis. In conclusion, this study demonstrated a novel mechanism by which miR-26a-CD36 pathway mediated lipid accumulation induced by PM₂.₅ liposoluble extracts in hepatocytes. Lipid accumulation and inflammation induced by PM₂.₅ liposoluble extracts implied the potential role of PM₂.₅ in developing NAFLD.

We aimed to investigate the associations between chemical mixtures and the risk of nonalcoholic fatty liver disease (NAFLD) in this study. A total of 127 exposure analytes within 13 chemical mixture groups were included in the current analysis. Associations between chemical mixture exposure and prevalence of NAFLD were examined using weighted quantile sum (WQS) regressions. NAFLD was diagnosed by hepatic steatosis index (HSI) and US fatty liver index (USFLI). In USFLI-NAFLD cohort, chemical mixtures positively associated with NAFLD development included urinary metals (OR: 1.10, 95% CI: 1.04–1.16), urinary perchlorate, nitrate and thiocyanate (OR: 1.06, 95% CI: 1.02–1.11), urinary pesticides (OR: 1.24, 95% CI: 1.09–1.40), urinary phthalates (OR: 1.18, 95% CI: 1.09–1.28), urinary polyaromatic hydrocarbons (PAHs) (OR: 1.08, 95% CI: 1.03–1.14), and urinary pyrethroids, herbicides, and organophosphate pesticides metabolites (OR: 1.32, 95% CI: 1.15–1.51). All of the above mixtures were also statistically significant in WQS regressions in the HSI-NAFLD cohort. Besides, some chemical mixtures were only significant in HSI-NAFLD cohort including urinary arsenics (OR: 1.07, 95% CI: 1.02–1.12), urinary phenols (OR: 1.10, 95% CI: 1.02–1.19) and blood polychlorinated dibenzo-p-dioxins (OR: 1.10, 95% CI: 1.03–1.17). Three types of chemical mixtures only showed significant associations in the healthy lifestyle score (HLS) of 3–4 subgroup, including urinary perchlorate, nitrate and thiocyanate, urinary PAHs and blood polychlorinated dibenzo-p-dioxins. In conclusion, the exposure of specific types of chemical mixtures were associated with elevated NAFLD risk, and the effects of some chemical mixtures on NAFLD development exhibited differences in participants with different lifestyles.

Epidemiological studies have demonstrated that the general population’s exposure to bisphenol A (BPA) substitutes is ubiquitous. Bisphenol F (BPF), one of the main BPA substitutes, is increasingly replacing BPA in plastics for food and beverage applications. Accumulating evidence suggests that BPA exposure is associated with nonalcoholic fatty liver disease (NAFLD)-like changes. However, the potential effects of BPF on lipid homeostasis remain poorly understood. In the present study, an epidemiological analysis with LC-MS-MS revealed that the BPF concentrations in the serum of NAFLD patients were significantly higher than those in a control group. Supporting this result, using Oil Red O, BODIPY 493/503, LipidTox Deep Red staining and gas chromatography-time-of-flight mass spectrometry (TOF-MS) assays, we found that BPF exposure induced NAFLD-like changes, with obvious lipid droplet deposition, triglyceride (TG) and fatty acids increase in mouse livers. Meanwhile, lipid droplet deposition and TG increase induced by BPF were also observed in HepG2 cells, accompanied by autophagic flux blockade, including autophagosome accumulation and the decreased degradation of SQSTM1/p62. Using adenoviruses dual-reporter plasmid RFP-GFP-LC3, RFP-GFP-PLIN2 transfection, AO staining, and EGFR degradation assays, we demonstrated that BPF treatment impaired lysosomal degradative capacity, since BPF treatment obviously impaired lysosomal acidification, manifested as decreased lysosomal hydrolase cathepsin L (CTSL) and mature cathepsin D (CTSD) in HepG2 and mouse liver issues. Additionally, v-ATPase D, a multi-subunit enzyme that mediates acidification of eukaryotic intracellular organelles, significantly decreased after BPF exposure in both the vitro and in vivo studies.This study ascertained a novel mechanism involving dysfunctional of lysosomal degradative capacity induced by BPF, which contributes to lipophagic disorders and causes lipid droplet deposition. This work provides evidence that lysosomes may be a target organelle where BPF exerts its potential toxicity; therefore, novel intervention strategies targeting lysosome are promising for BPF-induced NAFLD-like changes.

Finding the potential environmental obesogens is crucial to explain the prevalence of obesity and the related pathologies. Increasing evidence has showed that many chemicals with endocrine disrupting effects can disturb lipid metabolism. Whether 4-hexylphenol (4-HP), a widely-used surfactant and a potential endocrine disrupting chemical (EDC), is associated to influence adipogenesis and hepatic lipid accumulation remained to be elucidated. In this study, both the 3T3-L1 differentiation model and oleic acid (OA)-treated HepG2 cells were used to investigate the effects of 4-HP on lipid metabolism, and the underlying estrogen receptor (ER)-involved mechanism was explored using MVLN assay, molecular docking simulation and the antagonist test. The results based on lipid droplet staining and triglyceride accumulation assay showed that 4-HP treatment promoted the adipogenic differentiation of 3T3-L1 cells and increased hepatic cellular OA accumulation in exposure concentration-dependent manners. The study on the elaborated transcription networks indicated that 4-HP activated peroxisome proliferator-activated receptor γ (PPARγ) as well as the subsequent adipogenic gene program in 3T3-L1 cells. This chemical also induced the increase of OA uptake and decreases of de novo lipogenesis and fatty acid oxidation in HepG2 cells. The agonistic activity of 4-HP in triggering ER-mediated pathway was shown to correlate with its perturbation in lipid metabolism, as evidenced by the enhanced development of mature lipid-laden adipocytes and suppression of excessive hepatic lipid accumulation upon its co-treatment with ER antagonist. Altogether, these findings provide new insights into the potential health impacts of 4-HP exposure as it may relate to obesity and nonalcoholic fatty liver disease.

Interactions between the intestine and the liver, the so-called ‘gut-liver axis’, play a crucial role in the onset of hepatic steatosis and non-alcoholic fatty liver disease. However, not much is known about the impact of environmental pollutants on the gut-liver axis and consequent hepatic steatosis. Bisphenol A (BPA), a widely used plasticiser, is an important environmental contaminant that affects gut microbiota. We hypothesised that BPA induces hepatic steatosis by promoting gut microbiota dysbiosis and activating the gut-liver axis. In this study, male CD-1 mice were fed with diet containing BPA (50 μg/kg body weight/day) for 24 weeks. Dietary exposure to BPA increased lipid contents and fat accumulation in the liver. Analysis of 16 S rRNA gene sequencing revealed that the diversity of gut microbiota reduced and the composition of gut microbiota was altered in the BPA-fed mice. Further, the abundance of Proteobacteria, a marker of dysbacteria, increased, whereas the abundance of Akkermansia, a gut microbe associated with increased gut barrier function and reduced inflammation, markedly decreased. Expression levels of intestinal tight junction proteins (zona occludens-1 and occludin) also decreased drastically, leading to increased intestinal permeability and elevated levels of endotoxins. Furthermore, BPA up-regulated the expression of Toll-like receptor 4 (TLR4) and phosphorylation of nuclear factor-kappa B (NF-κB) in the liver and increased the production of inflammatory cytokines, including interleukin-1β, interleukin-18, tumour necrosis factor-α, and interleukin-6. Take together, our work indicated that dietary intake of BPA induced hepatic steatosis, and this was closely related to dysbiosis of gut microbiota, elevated endotoxin levels, and increased liver inflammation through the TLR4/NF-κB pathway.

This work aimed at predicting the toxic effects of phenolic compounds in Ba River on the health of female sharpbelly (Hemiculter lucidus) by the de novo transcriptomic analysis of the liver. Sharpbelly, a native fish living in freshwater ecosystem of East Asia, were sampled upstream, near, and downstream of a wastewater discharge to the Ba river. Based on the occurrence of bisphenol A (BPA), nonylphenol (NP), and 4-tert-octylphenol (4-t-OP) in the water and fish sampled from each site, up-, mid-, and down-stream were interpreted as control, high, and low treatment groups, respectively. In the mid-stream group the Fulton’s condition factor (CF) and body weight were remarkably increased by approximate 20%; the gonado-somatic index (GSI) and hepatosomatic index (HSI) in mid-stream fish showed a similar increasing trend but lacking of statistical difference. Exposure to wastewater effluent caused 160 and 162 differentially expressed genes (DEGs) in up-mid and down-mid stream groups, respectively. Two sets of DEGs were primarily enriched in the signaling pathways of drug metabolism, endocrine system, cellular process, and lipid metabolism in the mid-stream sharpbelly, which may alter the fish behavior, disrupt the reproductive function, and lead to hypothyroidism, hepatic steatosis, etc. Taken together, our results linked the disrupted signaling pathways with activities of phenolic compounds to predict the potential effects of wastewater effluent on the health of wild fish.

Perfluorooctanoic acid (PFOA) has applications in numerous industrial products and is an industrial waste that is persistently present in the environment. Exposure to PFOA results in nonalcoholic fatty liver disease (NAFLD). However, the underlying mechanisms remain unclear. In this study, male C57BL/6 mice were exposed to PFOA (1 mg/kg/day) for 4 weeks to evaluate the effect of PFOA, and the human liver cell line (L-02) was used to observe the direct effect of PFOA in vitro. After PFOA exposure, the expression of genes related to hepatic lipogenesis, the NLRP3 inflammasome, and autophagy were measured. We found that exposure to PFOA induced lipid accumulation and stimulated lipogenesis in both mouse livers and L-02 cells. In addition, increased NLRP3 aggregation and enhanced production of IL-1β occurred after PFOA treatment. We also found that PFOA exposure induced autophagosome formation and p62 accumulation, indicating blockage of autophagic flux. Rapamycin alleviated PFOA-induced lipid accumulation and NLRP3 inflammasome activation by activating autophagic flux. Conversely, chloroquine, an autophagic flux inhibitor, exacerbated PFOA-induced lipid accumulation and NLRP3 inflammasome activation. Collectively, these results provide evidence to show that PFOA-induced blockade of autophagic flux causes an increase in lipid synthesis and inflammation in vivo and in vitro.