Characterizing the obesogenic and fatty liver-inducing effects of Acetyl tributyl citrate (ATBC) plasticizer using both in vivo and in vitro models

Identification and quantification of acetyl tributyl citrate (ATBC) metabolites using human liver microsomes and human urine

Plasticizers are chemicals that make plastics flexible, and phthalates are commonly used. Due to the toxic effects of phthalates, there is increasing use of non-phthalate plasticizers like acetyl tributyl citrate (ATBC). ATBC has emerged as a safer alternative, yet concerns about its long-term safety persist due to its high leachability and potential endocrine-disrupting effects. This study aims to identify ATBC metabolites using human liver microsomes and suspect screening methods, and to explore potential urinary biomarkers for ATBC exposure. Using ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry, we identified ATBC metabolites, including acetyl dibutyl citrate (ADBC), tributyl citrate (TBC), and dibutyl citrate (DBC). Urine samples from 15 participants revealed the presence of ADBC in 5, TBC in 11, and DBC in all samples, with DBC concentrations pointedly higher than the other metabolites. These metabolites show promise as biomarkers for ATBC exposure, though further validation with human data is required. Our results underscore the need for comprehensive studies on ATBC metabolism, exposure pathways, and urinary excretion to accurately assess human exposure levels.

A systematic review and meta-analysis of environmental contaminant exposure impacts on weight loss and glucose regulation during calorie-restricted diets in preclinical studies: Persistent organic pollutants may impede glycemic control

Epidemiological evidence links chemical exposure with type 2 diabetes (T2DM) risk and prevalence. Chemical exposure may therefore also limit success of weight loss or restoration of glycemic control during calorie restricted diets. Few human studies examine this hypothesis. This systematic review and clustered meta-analysis examines preclinical evidence that exposure to anthropogenic environmental contaminants impedes weight loss and resumption of glycemic control during calorie restriction. Of five eligible papers from 212 unique citations, four used C57BL/6 mice and one used Sprague Dawley rats. In four the animals received high fat diets to induce obesity and impaired glycemic control. All examined persistent organic pollutants (POPs). Polychlorinated biphenyl (PCB) 77 exposure did not affect final mass (standardised mean difference (SMD) = -0.35 [-1.09, 0.39]; n = 5 (experiments); n = 3 (papers)), or response to insulin in insulin tolerance tests (SMD = -1.54 [-3.25, 0.16] n = 3 (experiments); n = 2 (papers)), but impaired glucose control in glucose tolerance tests (SMD = -1.30 [-1.96, -0.63]; n = 6 (experiments); n = 3 (papers)). The impaired glycemic control following perfluoro-octane sulphonic acid (PFOS) exposure and enhanced mass loss following dichlorodiphenyltrichloroethane (DDT) exposure have not been replicated. Animal studies thus suggest some chemical groups, especially PCB and PFOS, could impair glucose control management during calorie restriction, similar to conclusions from limited existing clinical studies. We discuss the research that is urgently required to inform weight management services that are now the mainstay prevention initiative for T2DM.

Leachates from plastics and bioplastics reduce lifespan, decrease locomotion, and induce neurotoxicity in Caenorhabditis elegans

Plastic pollution continuously accumulates in the environment and poses a global threat as it fragments into microplastics and nanoplastics that can harm ecosystems. To reduce the accumulation of microplastic and nanoplastic pollution, bioplastics made from biodegradable materials are promoted as a more sustainable alternative because it can degrade faster than plastics. However, plastics also leach out chemicals as they degrade and disintegrate, but the potential toxicity of these chemicals leaching out from plastics and especially bioplastics is poorly explored. Here, we determined the composition of leachates from plastics and bioplastics and tested their toxicity in Caenorhabditis elegans. LC-MS analysis of the leachates revealed that bioplastics leached a wider array of chemicals than their counterpart plastics. Toxicity testing in our study showed that the leachates from plastics and bioplastics reduced lifespan, decreased locomotion, and induced neurotoxicity in C. elegans. Leachates from bioplastics reduced C. elegans lifespan more compared to leachates from plastics: by 7%-31% for bioplastics and by 6%-15% for plastics. Leachates from plastics decreased locomotion in C. elegans more compared to leachates from bioplastics: by 8%-34% for plastics and by 11%-24% for bioplastics. No changes were observed in the ability of the C. elegans to respond to mechanical stimuli. The leachates induced neurotoxicity in the following neurons at varying trends: cholinergic neurons by 0%-53% for plastics and by 30%-42% for bioplastics, GABAergic neurons by 3%-29% for plastics and by 10%-23% for bioplastics, and glutamatergic neurons by 3%-11% for plastics and by 15%-29% for bioplastics. Overall, our study demonstrated that chemicals leaching out from plastics and bioplastics can be toxic, suggesting that both plastics and bioplastics pose ecotoxicological and human health risks.

Association of Di(2-ethylhexyl) Terephthalate and Its Metabolites with Nonalcoholic Fatty Liver Disease: An Epidemiology and Toxicology Study

As an alternative plasticizer to conventional phthalates, di(2-ethylhexyl) terephthalate (DEHTP) has attracted considerable concerns, given its widespread detection in the environment and humans. However, the potential toxicity, especially liver toxicity, posed by DEHTP remains unclear. In this study, based on the 2017-2018 National Health and Nutrition Examination Survey, two metabolites of DEHTP, i.e., mono(2-ethyl-5-hydroxyhexyl) terephthalate (MEHHTP) and mono(2-ethyl-5-carboxypentyl) terephthalate (MECPTP), were found to be present in the urine samples of nearly all representative U.S. adults. Moreover, a positive linear correlation was observed between the concentrations of the two metabolites and the risk of nonalcoholic fatty liver disease (NAFLD) in the population. Results of weighted quantile sum and Bayesian kernel machine regression indicated that MEHHTP contributed a greater weight to the risk of NAFLD in comparison with 12 conventional phthalate metabolites. In vitro experiments with hepatocyte HepG2 revealed that MEHHTP exposure could increase lipogenic gene programs, thereby promoting a dose-dependent hepatic lipid accumulation. Activation of liver X receptor α may be an important regulator of MEHHTP-induced hepatic lipid disorders. These findings provide new insights into the liver lipid metabolism toxicity potential of DEHTP exposure in the population.

Di-2-ethylhexyl phthalate disrupts hepatic lipid metabolism in obese mice by activating the LXR/SREBP-1c and PPAR-α signaling pathways

Di-2-ethylhexyl phthalate (DEHP), a widely utilized plasticizer, has been described as a potential obesogen based on in vivo disruption of hepatic lipid homeostasis and in vitro promotion of lipid accumulation. However, limited literature exists regarding the specific ramifications of DEHP exposure on obese individuals, and the precise mechanisms underlying the adverse effects of DEHP exposure remain unclear. This study aimed to assess the impact of DEHP on hepatic lipid metabolism in obese mice by comparing them to normal mice. Following a 10-week DEHP exposure period, the obese mice exhibited higher blood lipid levels, more severe hepatic steatosis, and more infiltrations of inflammatory cells in liver tissue than normal mice. Interestingly, the body weight of the mice exhibited no significant alteration. In addition, transcriptomic analyses revealed that both lipogenesis and fatty acid oxidation contributed to hepatic lipid metabolism dysregulation following DEHP exposure. More specifically, alterations in the transcription of genes associated with hepatic lipid metabolism were linked to the different responses to DEHP exposure observed in normal and obese mice. Additionally, the outcomes of in vitro experiments validated the in vivo findings and demonstrated that DEHP exposure could modify hepatic lipid metabolism in normal mice by activating the LXR/SREBP-1c signaling pathway to promote lipogenesis. At the same time, DEHP exposure led to inhibition of the Camkkβ/AMPK pathway to suppress β-fatty acid oxidation. Conversely, in obese mice, DEHP exposure was found to be associated with the stimulation of both lipogenesis and fatty acid oxidation via activation of the LXR/SREBP-1c and PPAR-α signaling pathways, respectively. The findings presented in this study first elucidate the contrasting mechanisms underlying DEHP-induced liver damage in obese and normal mice, thereby offering valuable insights into the pathogenesis of DEHP-induced liver damage in individuals with obesity.

Comparative toxicity of beach mesoplastics from South Spain: An in vitro approach

Plastics, particularly mesoplastics, dominate beach debris and act as carriers of hazardous chemicals, either initially present in plastics or absorbed from the surrounding environment. In this study, mesoplastics were collected from five beaches in the southern region of Spain to investigate their potential impact on marine life. In vitro assays employing fish liver cells (PLHC-1) were conducted to evaluate the toxicity of methanolic extracts derived from intact mesoplastics and after simulated photodegradation. LC-MS analysis of the methanolic extracts revealed the presence of organophosphate esters, phthalates, and phthalate alternatives. The extracts from photodegraded plastics generally showed higher cytotoxicity, ability to generate reactive oxygen species (ROS), and genotoxicity (micronuclei formation) than those from intact mesoplastics. All the extracts induced EROD activity in PLHC-1 cells, indicating the presence of significant amounts of CYP1A inducers in beach mesoplastics. Thus, mesoplastics contain chemicals able to induce cytotoxicity and genotoxicity in PLHC-1 cells, and further photodegradation of mesoplastics facilitates the release of additional chemicals, increasing the overall toxicity. This work also highlights the usefulness of cell-based assays to better define the risks of plastic pollution.

Evaluating the risk of phthalate and non-phthalate plasticizers in dust samples from 100 Japanese houses

Phthalates are widely used as plasticizer and associated with various health issues. Recently, non-phthalate plasticizers are replacing phthalates; however, the exposure to these substances and the risk in Japan is unclear. In this study, we assessed the concentrations of phthalates, non-phthalate plasticizers, and phthalate degradation products in house dust and determined their respective exposure risks via oral and dermal routes. Twelve phthalates, seven non-phthalate plasticizers, and two degradation products were determined in the house dust obtained from 100 Japanese homes. The median concentration of di(2-ethylhexyl) phthalate (DEHP), accounting for 85 % of the total concentration of phthalates and non-phthalate plasticizers detected in this study, was 2.1 × 103 μg/g of dust. Apart from DEHP, diisononyl phthalate (DINP) and di(2-ethylhexyl) terephthalate (DEHT) were the most abundant in the house dust, accounting for 6.2 % (median: 1.7 × 102 μg/g of dust) and 6.1 % (median: 1.7 × 102 μg/g of dust) of the total concentrations, respectively. DEHP and DEHT concentrations in house dust were higher in apartment and small houses (floor area: ≤30 m2 or 31-60 m2 for DEHP and 31-60 m2 for DEHT) than in detached and large houses (floor area: ≥121 m2). Conversely, di-n-butyl phthalate (DnBP) concentrations were significantly higher in detached and large houses (floor area: ≥121 m2) than in apartment and small houses (floor area: ≤30 m2). The total hazard quotient (HQ), using the maximum concentration in house dust, revealed that oral and dermal exposure to house dust was 1.3 × 10-6-0.11 for adults (all substances) and 1.6 × 10-5-2.2 × 10-2 for preschool children (except for DnBP and DEHP), suggesting no risk. The HQs for DnBP and DEHP exposure via house dust for preschool children using the maximum values were 0.46 and 1.2, and 6.0 × 10-3 and 0.18 using the median values, indicating that risk of DEHP exposure should be exhaustively determined by considering other exposure routes that were not evaluated in this study, such as diet.

Efficient analysis of toxicity and mechanisms of environmental pollutants with network toxicology and molecular docking strategy: Acetyl tributyl citrate as an example

The study aims to promote network toxicology strategy to efficiently investigate the putative toxicity and underlying molecular mechanisms of environmental pollutants through an example of exploring brain injury induced by ATBC exposure. By utilizing ChEMBL, STITCH, GeneCards, and OMIM databases, we identified 213 potential targets associated with ATBC exposure and brain injury. Further refinements via STRING and Cytoscape software highlight 23 core targets, including AKT1, CASP3, and HSP90AA1. GO and KEGG pathway analysis conducted through DAVID and FUMA databases reveal that core targets of ATBC-induced brain toxicity are predominantly enriched in cancer signaling and neuroactive ligand receptor interaction pathways. Molecular docking was performed with Autodock, which confirmed robust binding between ATBC and core targets. Together, these findings suggest that ATBC may impact the occurrence and development of brain cancer and brain related inflammation, whereas pose risks for cognitive impairment and neurodegeneration, by modulating the apoptosis and proliferation of brain cancer cells, activating inflammatory signaling pathways, and regulating neuroplasticity. This research provides a theoretical basis for understanding the molecular mechanism of ATBC-induced brain toxicity, as well as establishing a foundation for the prevention and treatment of prostatic diseases associated with exposure to plastic products containing ATBC and certain ATBC-overwhelmed environments. Moreover, our network toxicology approach also expedites the elucidation of toxicity pathways for uncharacterized environmental chemicals.

Novel insights into perfluorinated compound-induced hepatotoxicity: Chronic dietary restriction exacerbates the effects of PFBS on hepatic lipid metabolism in mice

Perfluorobutane sulfonates (PFBS) have garnered extensive utilization because of their distinctive physicochemical properties. The liver acts as a key target organ for toxicity within the body and is vital for regulating metabolic processes, particularly lipid metabolism. However, there is currently a significant research gap regarding the influences of PFBS on hepatic lipid metabolism, especially in individuals with different dietary statuses. Here, the objective of this research was to examine the effects of PFBS on hepatic function under different dietary conditions. The results suggested that the levels of liver injury biomarkers were significantly upregulated, e.g., transaminase (GPT, GOT), while liver lipid levels were downregulated after exposure to PFBS at concentration of 50 μg/L for 42 days. Moreover, restricted diet further intensified the adverse effects of PFBS on the liver. Metabolomics analysis identified significant alterations in lipid-related metabolites in PFBS-induced hepatotoxicity, PFBS exposure induced a decrease in lysophosphatidylethanolamine and lysophosphatidylcholine. PFBS exposure caused an increase in aldosterone and prostaglandin f2alpha under restricted diet. In PFBS treatment group, histidine metabolism, beta-alanine metabolism, and arginine biosynthesis were the main pathway for PFBS toxicity. Aldosterone-regulated sodium reabsorption as a vital factor in inducing PFBS toxicity in the RD-PFBS treatment group. The analysis of 16S rRNA sequencing revealed that exposure to PFBS resulted in imbalance of gut microbial communities. PFBS exposure induced a decrease in Akkermansia and Lactobacillus, but an increase in Enterococcus. PFBS exposure caused the abundance of Lachnospiraceae_NK4A136_group was significantly elevated under restricted diet. Additionally, disruptions in the expression of genes involved in lipid production and consumption may significantly contribute to lipid imbalance in the liver. This study underscores the importance of recognizing the harmful impact of PFBS on liver function, along with the biotoxicity of contaminant influenced by dietary habits.