Paradoxical Protective Effect of Perfluorooctanesulfonic Acid Against High-Fat Diet-Induced Hepatic Steatosis in Mice

NAM-based analysis of contaminant short-term organ toxicity in HepaRG and RPTEC/TERT1 cells

New Approach Methodologies (NAMs), including cell culture and multi-level omics analyses, are promising alternatives to animal testing. To become useable for risk assessment purposes, they have to be applicable for different substance groups. One important group of substances is food contaminants, including synthetic chemicals, such as perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), and natural compounds, such as mycotoxins and pyrrolizidine alkaloids. We tested five known contaminants affecting the liver and/or the kidney - PFOS, PFOA, Aflatoxin B1 (AB1), lasiocarpine (Las), and cadmium chloride - using HepaRG and RPTEC/TERT1 cells at non-cytotoxic concentrations for 36 and 72 h. Our NAM-based testing protocol included marker protein analysis for cellular functions and targeted transcriptomics followed by bioinformatics pathway analysis. The effects observed were compared with established in vivo results. Protein analysis indicated various affected pathways in HepaRG cells, with generally fewer effects in RPTEC/TERT1 cells. The strongest transcriptional impact was noted for Las in HepaRG cells. This study demonstrated the test protocol's applicability across different substances, revealing significant differences between HepaRG and RPTEC/TERT1 cell lines. RPTEC/TERT1 cells, while expressing renal-specific CYP enzymes, were less suitable for detecting effects of substances requiring hepatic metabolic activation, like Las and AB1. Our data supports the concept of specific pathway toxicity, with pathway analysis enabling the prediction of effects based on mechanism rather than target organ. Employing multiple omics techniques provided comprehensive insights into various compound effects, including steatosis, reactive oxygen species production and DNA damage, highlighting the potential of an extended omics approach for advancing toxicological assessments.

Associations of perfluoroalkyl substances with metabolic-associated fatty liver disease and non-alcoholic fatty liver disease: NHANES 2017-2018

OBJECTIVES

This study investigated the potential effects of perfluoroalkyl substance (PFAS) in serum on MAFLD, NAFLD, and liver fibrosis.

METHODS

Our sample included 696 participants (≥ 18 years) from the 2017-2018 NHANES study with available serum PFASs, covariates, and outcomes. Using the first quartile of PFAS as the reference group, we used weighted binary logistic regression and multiple ordered logistic regression used to analyze the relationship between PFAS and MAFLD, NAFLD, and liver fibrosis and multiple ordinal logistic regression to investigate the relationship between PFAS and MAFLD, NAFLD, and liver fibrosis and calculated the odds ratio (OR) and 95% confidence interval for each chemical. Finally, stratified analysis and sensitivity analysis were performed according to gender, age, BMI, and serum cotinine concentration.

RESULTS

A total of 696 study subjects were included, including 212 NAFLD patients (weighted 27.03%) and 253 MAFLD patients (weighted 32.65%). The quartile 2 of serum PFOA was positively correlated with MAFLD and NAFLD (MAFLD, OR 2.29, 95% CI 1.05-4.98; NAFLD, OR 2.37, 95% CI 1.03-5.47). PFAS were not significantly associated with liver fibrosis after adjusting for potential confounders in MAFLD and NAFLD. Stratified analysis showed that PFOA was strongly associated with MAFLD, NAFLD, and liver fibrosis in males and obese subjects. In women over 60 years old, PFHxS was also correlated with MAFLD, NAFLD, and liver fibrosis.

CONCLUSION

The serum PFOA was positively associated with MAFLD and NAFLD in US adults. After stratified analysis, the serum PFHxS was correlated with MFALD, NAFLD, and liver fibrosis.

Association between per- and poly-fluoroalkyl substances and nonalcoholic fatty liver disease: A nested case-control study in northwest China

Per- and poly-fluoroalkyl substances (PFAS) have been reported to have hepatotoxic effects. However, it is unclear whether they are linked to non-alcoholic fatty liver disease (NAFLD). This nested case-control study focused on the epidemiological links between PFAS and the prevalence of NAFLD. We selected 476 new cases of NAFLD and 952 age- and sex-matched controls from the Jinchang cohort population between 2014 and 2019. Serum concentrations of PFAS were measured using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Only PFAS with a detection rate of ≥90 % were included for analysis, which included PFPeA, PFOA, PFNA, PFHxS, PFOS, and 9Cl-PF3ONS. The relationship between single and co-exposure to PFAS and the occurrence of NAFLD was evaluated using conditional logistic regression, Quantile g-computation (QgC), and Bayesian kernel machine regression (BKMR) model. Logistic regression indicated that PFPeA, PFOA, and 9Cl-PF3ONS were positive correlation with the incidence of NAFLD after adjusting for confounders, with odds ratios (OR) and 95 % confidence interval (CI) of 3.13 (95 % CI: 2.53, 3.86), 1.39 (95 % CI: 1.12, 1.73), and 1.41 (95 % CI: 1.20, 1.66), respectively. PFNA, PFHxS, and PFOS were nonlinearly and negatively associated with the incidence of NAFLD, with OR (95 % CI) of 0.53 (0.46, 0.62), 0.83 (0.73, 0.95), and 0.52 (0.44, 0.61), respectively. QgC showed a significant joint effect of PFAS mixture on NAFLD onset (OR: 1.52, 95 % CI: 1.24, 1.88). BKMR showed a weak positive trend between PFAS mixtures and NAFLD incidence. Positive correlations were primarily driven by PFPeA and 9Cl-PF3ONS, while negative correlations were mainly influenced by PFNA and PFOS. The BKMR model also suggested that there was an interaction between PFOS and PFNA and other four PFAS compounds. In conclusion, our findings suggest that individual and co-exposure to PFAS is associated with a risk of NAFLD onset.

Threats of per- and poly-fluoroalkyl pollutants to susceptible populations

Environmental exposure to per- and poly-fluoroalkyl substances (PFAS) has raised significant global health concerns due to potential hazards in healthy adults. However, the impact of PFAS on susceptible populations, including pregnant individuals, newborns, the older people, and those with underlying health conditions, has been overlooked. These susceptible groups often have physiological changes that make them less resilient to the same exposures. Consequently, there is an urgent need for a comprehensive understanding of the health risks posed by PFAS exposure to these populations. In this review, we delve into the potential health risks of PFAS exposure in these susceptible populations. Equally important, we also examine and discuss the molecular mechanisms that underlie this susceptibility. These mechanisms include the induction of oxidative stress, disruption of the immune system, impairment of cellular metabolism, and alterations in gut microbiota, all of which contribute to the enhanced toxicity of PFAS in susceptible populations. Finally, we address the primary research challenges and unresolved issues that require further investigation. This discussion aims to foster research for a better understanding of how PFAS affect susceptible populations and to pave the way for strategies to minimize their adverse effects.

Close association of PFASs exposure with hepatic fibrosis than steatosis: evidences from NHANES 2017-2018

Multiple animals and in vitro studies have demonstrated that perfluoroalkyl and polyfluoroalkyl substances (PFASs) exposure causes liver damage associated with fat metabolism. However, it is lack of population evidence for the correlation between PFAS exposure and nonalcoholic fatty liver disease (NAFLD). A cross-sectional analysis was performed of 1150 participants aged over 20 from the US. Liver ultrasound transient elastography was to identify the participants with NAFLD and multiple biomarkers were the indicators for hepatic steatosis and hepatic fibrosis. Logistics regression and restricted cubic splines models were used to estimate the association between PFASs and NAFLD. PFASs had not a significant association with NAFLD after adjustment. The hepatic steatosis indicators including fatty liver index, NAFLD liver fat score, and Framingham steatosis index were almost not significantly correlated with PFASs exposure respectively. But fibrosis indicators including fibrosis-4 index (FIB-4), NAFLD fibrosis score, and Hepamet fibrosis score were positively correlated with each type of PFASs exposure. After adjustment by gender, age, race, education, and poverty income rate, there was also a significant correlation between PFOS and FIB-4 with 0.07 (0.01, 0.13). The mixed PFASs were associated with FIB-4, with PFOS contributing the most (PIP = 1.000) by the Bayesian kernel machine regression model. The results suggested PFASs exposure appeared to be more closely associated with hepatic fibrosis than steatosis, and PFOS might be the main cause of PFASs associated with hepatic fibrosis.Key messagesCurrent exposure doses of PFAS did not significantly change the risk of developing NAFLD.PFASs exposure appeared to be more closely associated with hepatic fibrosis than steatosis.PFOS might be the main cause of PFASs associated with hepatic fibrosis.

Extracellular Vesicles altered by a Per- and Polyfluoroalkyl Substance Mixture: In Vitro Dose-Dependent Release, Chemical Content, and MicroRNA Signatures involved in Liver Health

Per- and polyfluoroalkyl substances (PFAS) have emerged as high priority contaminants due to their ubiquity and pervasiveness in the environment. Numerous PFAS co-occur across sources of drinking water, including areas of North Carolina (NC) with some detected concentrations above the Environmental Protection Agency's health advisory levels. While evidence demonstrates PFAS exposure induces harmful effects in the liver, the involvement of extracellular vesicles (EVs) as potential mediators of these effects has yet to be evaluated. This study set out to evaluate the hypothesis that PFAS mixtures induce dose-dependent release of EVs from liver cells, with exposures causing differential loading of microRNAs (miRNAs) and PFAS chemical signatures. To test this hypothesis, a defined PFAS mixture was prioritized utilizing data collected by the NC PFAS Testing Network. This mixture contained three substances, PFOS, PFOA, and PFHxA, selected based upon co-occurrence patterns and the inclusion of both short-chain (PFHxA) and long-chain (PFOA and PFOS) substances. HepG2 liver cells were exposed to equimolar PFAS, and secreted EVs were isolated from conditioned media and characterized for count and molecular content. Exposures induced a dose-dependent release of EVs carrying miRNAs that were differentially loaded upon exposure. These altered miRNA signatures were predicted to target mRNA pathways involved in hepatic fibrosis and cancer. Chemical concentrations of PFOS, PFOA, and PFHxA were also detected in both parent HepG2 cells and their released EVs, specifically within a 15-fold range after normalizing for protein content. This study therefore established EVs as novel biological responders and measurable endpoints for evaluating PFAS-induced toxicity.

Moderate body lipid accumulation in mice attenuated benzene-induced hematotoxicity via acceleration of benzene metabolism and clearance

Recent population and animal studies have revealed a correlation between fat content and the severity of benzene-induced hematologic toxicity. However, the precise impact of lipid deposition on benzene-induced hematotoxicity and the underlying mechanisms remain unclear. In this study, we established a mouse model with moderate lipid accumulation by subjecting the mice to an 8-week high-fat diet (45% kcal from fat, HFD), followed by 28-day inhalation of benzene at doses of 0, 1, 10, and 100 ppm. The results showed that benzene exposure caused a dose-dependent reduction of peripheral white blood cell (WBC) counts in both diet groups. Notably, this reduction was less pronounced in the HFD-fed mice, suggesting that moderate lipid accumulation mitigates benzene-related hematotoxicity. To investigate the molecular basis for this effect, we performed bioinformatics analysis of high-throughput transcriptome sequencing data, which revealed that moderate lipid deposition alters mouse metabolism and stress tolerance towards xenobiotics. Consistently, the expression of key metabolic enzymes, such as Cyp2e1 and Gsta1, were upregulated in the HFD-fed mice upon benzene exposure. Furthermore, we utilized a real-time exhaled breath detection technique to monitor exhaled benzene metabolites, and the results indicated that moderate lipid deposition enhanced metabolic activation and increased the elimination of benzene metabolites. Collectively, these findings demonstrate that moderate lipid deposition confers reduced susceptibility to benzene-induced hematotoxicity in mice, at least in part, by accelerating benzene metabolism and clearance.

Determination of in vitro hepatotoxic potencies of a series of perfluoroalkyl substances (PFASs) based on gene expression changes in HepaRG liver cells

Per- and polyfluoroalkyl substances (PFASs) are omnipresent and have been shown to induce a wide range of adverse health effects, including hepatotoxicity, developmental toxicity, and immunotoxicity. The aim of the present work was to assess whether human HepaRG liver cells can be used to obtain insight into differences in hepatotoxic potencies of a series of PFASs. Therefore, the effects of 18 PFASs on cellular triglyceride accumulation (AdipoRed assay) and gene expression (DNA microarray for PFOS and RT-qPCR for all 18 PFASs) were studied in HepaRG cells. BMDExpress analysis of the PFOS microarray data indicated that various cellular processes were affected at the gene expression level. From these data, ten genes were selected to assess the concentration-effect relationship of all 18 PFASs using RT-qPCR analysis. The AdipoRed data and the RT-qPCR data were used for the derivation of in vitro relative potencies using PROAST analysis. In vitro relative potency factors (RPFs) could be obtained for 8 PFASs (including index chemical PFOA) based on the AdipoRed data, whereas for the selected genes, in vitro RPFs could be obtained for 11-18 PFASs (including index chemical PFOA). For the readout OAT5 expression, in vitro RPFs were obtained for all PFASs. In vitro RPFs were found to correlate in general well with each other (Spearman correlation) except for the PPAR target genes ANGPTL4 and PDK4. Comparison of in vitro RPFs with RPFs obtained from in vivo studies in rats indicate that best correlations (Spearman correlation) were obtained for in vitro RPFs based on OAT5 and CXCL10 expression changes and external in vivo RPFs. HFPO-TA was found to be the most potent PFAS tested, being around tenfold more potent than PFOA. Altogether, it may be concluded that the HepaRG model may provide relevant data to provide insight into which PFASs are relevant regarding their hepatotoxic effects and that it can be applied as a screening tool to prioritize other PFASs for further hazard and risk assessment.

Resistance to obesity prevents obesity development without increasing spontaneous physical activity and not directly related to greater metabolic and oxidative capacity

There are evidence that obese-resistant animals are more physically active, due to a higher rate of lipid oxidation. Efficiency in such pathways can favor greater spontaneous physical activity and, consequently, less body fat deposition. The aim of study was characterizing the nutritional profile and spontaneous physical activity in the condition of Resistance to Obesity (OR). Wistar rats were randomized into standard diet (SD; n = 50) and high-fat diet (HFD; n = 50) groups, after obesity induction, were redistributed into Control (C), False-control (FC), Propensity to obesity (OP) and OR, and then spontaneous physical activity was evaluated. Analyzed parameters: body mass (BM), epididymal (EF), retroperitoneal (RF), visceral (VF) and respective summations (∑), adiposity index (AI), nutritional, morphological, biochemical and metabolic parameters and protein quantification. The comparison of the groups was performed by ANOVA one or two factors, with 5% significance adopted. OP and FC presented high final MC values compared to C and OR. OR had lower EF, RF, VF, ∑ and IA compared to OP. OR had similar values to C and higher HDL than FC and OP. In GTT, OR and C presented similar values and both were lower than OP in the 30 minutes. OP promoted higher values than C for glycemic AUC. OR had higher PPARγ content than C and OP, as well as levels similar to C for leptin and insulin. Spontaneous physical activity did not differ between groups. The results were not enough to show that OR animals have greater lipid oxidative capacity, as well as greater spontaneous physical activity.

Adverse Effects of Perfluorooctane Sulfonate on the Liver and Relevant Mechanisms

Perfluorooctane sulfonate (PFOS) is a persistent, widely present organic pollutant. PFOS can enter the human body through drinking water, ingestion of food, contact with utensils containing PFOS, and occupational exposure to PFOS, and can have adverse effects on human health. Increasing research shows that the liver is the major target of PFOS, and that PFOS can damage liver tissue and disrupt its function; however, the exact mechanisms remain unclear. In this study, we reviewed the adverse effects of PFOS on liver tissue and cells, as well as on liver function, to provide a reference for subsequent studies related to the toxicity of PFOS and liver injury caused by PFOS.

Exposure to per- and Polyfluoroalkyl Substances and Markers of Liver Injury: A Systematic Review and Meta-Analysis

BACKGROUND

Experimental evidence indicates that exposure to certain pollutants is associated with liver damage. Per- and polyfluoroalkyl substances (PFAS) are persistent synthetic chemicals widely used in industry and consumer products and bioaccumulate in food webs and human tissues, such as the liver.

OBJECTIVE

The objective of this study was to conduct a systematic review of the literature and meta-analysis evaluating PFAS exposure and evidence of liver injury from rodent and epidemiological studies.

METHODS

PubMed and Embase were searched for all studies from earliest available indexing year through 1 December 2021 using keywords corresponding to PFAS exposure and liver injury. For data synthesis, results were limited to studies in humans and rodents assessing the following indicators of liver injury: serum alanine aminotransferase (ALT), nonalcoholic fatty liver disease, nonalcoholic steatohepatitis, or steatosis. For human studies, at least three observational studies per PFAS were used to conduct a weighted z-score meta-analysis to determine the direction and significance of associations. For rodent studies, data were synthesized to qualitatively summarize the direction and significance of effect.

RESULTS

Our search yielded 85 rodent studies and 24 epidemiological studies, primarily of people from the United States. Studies focused primarily on legacy PFAS: perfluorooctanoic acid (PFOA), perfluorooctanesulfonic acid (PFOS), perfluorononanoic acid (PFNA), and perfluorohexanesulfonic acid. Meta-analyses of human studies revealed that higher ALT levels were associated with exposure to PFOA (z-score= 6.20, p<0.001), PFOS (z-score= 3.55, p<0.001), and PFNA (z-score= 2.27, p=0.023). PFOA exposure was also associated with higher aspartate aminotransferase and gamma-glutamyl transferase levels in humans. In rodents, PFAS exposures consistently resulted in higher ALT levels and steatosis.

CONCLUSION

There is consistent evidence for PFAS hepatotoxicity from rodent studies, supported by associations of PFAS and markers of liver function in observational human studies. This review identifies a need for additional research evaluating next-generation PFAS, mixtures, and early life exposures. https://doi.org/10.1289/EHP10092.

Xenobiotic-Induced Aggravation of Metabolic-Associated Fatty Liver Disease

Metabolic-associated fatty liver disease (MAFLD), which is often linked to obesity, encompasses a large spectrum of hepatic lesions, including simple fatty liver, steatohepatitis, cirrhosis and hepatocellular carcinoma. Besides nutritional and genetic factors, different xenobiotics such as pharmaceuticals and environmental toxicants are suspected to aggravate MAFLD in obese individuals. More specifically, pre-existing fatty liver or steatohepatitis may worsen, or fatty liver may progress faster to steatohepatitis in treated patients, or exposed individuals. The mechanisms whereby xenobiotics can aggravate MAFLD are still poorly understood and are currently under deep investigations. Nevertheless, previous studies pointed to the role of different metabolic pathways and cellular events such as activation of de novo lipogenesis and mitochondrial dysfunction, mostly associated with reactive oxygen species overproduction. This review presents the available data gathered with some prototypic compounds with a focus on corticosteroids and rosiglitazone for pharmaceuticals as well as bisphenol A and perfluorooctanoic acid for endocrine disruptors. Although not typically considered as a xenobiotic, ethanol is also discussed because its abuse has dire consequences on obese liver.

The role of maternal high fat diet on mouse pup metabolic endpoints following perinatal PFAS and PFAS mixture exposure

Per- and polyfluoroalkyl substances (PFAS) are a family of chemicals that are ubiquitous in the environment. Some of these chemicals, such as perfluorooctanesulfonic acid (PFOS), perfluorohexanesulfonate (PFHxS) and perfluorooctanoic acid (PFOA), are found in human sera and have been shown to cause liver steatosis and reduce postnatal survival and growth in rodents. The purpose of this work is to evaluate the impact of diet and PFAS exposure to mouse dam (mus musculus) on the risk to pup liver and metabolism endpoints later in life, as well as evaluate PFAS partitioning to pups. Timed-pregnant dams were fed a standard chow diet or 60 % kcal high fat diet (HFD). Dams were administered either vehicle, 1 mg/kg PFOA, 1 mg/kg PFOS, 1 mg/kg PFHxS, or a PFAS mixture (1 mg/kg of each PFOA, PFOS, and PFHxS) daily via oral gavage from gestation day 1 until postnatal day (PND) 20. At PND 21, livers of dams and 2 pups of each sex were evaluated for lipid changes while remaining pups were weaned to the same diet as the dam for an additional 10 weeks. Dam and pup serum at PND 21 and PND 90 were also evaluated for PFAS concentration, alanine aminotransferase (ALT), leptin and adiponectin, and glycosylated hemoglobin A1c. Perinatal exposure to a HFD, as expected, increased pup body weight, maternal liver weight, pup liver triglycerides, pup serum ALT, and pup serum leptin. PFOA and the PFAS mixture increased liver weights, and. treatment with all three compounds increased liver triglycerides. The maternal HFD increased dam and pup serum PFAS levels, however, was protective against PFOA-induced increase in serum ALT and observed increases in liver triglycerides. The PFAS mixture had very distinct effects when compared to single compound treatment, suggesting some cumulative effects, particularly when evaluating PFAS transfer from dam to pup. This data highlights the importance of diet and mixtures when evaluating liver effect of PFAS and PFAS partitioning.

An 'Omics Approach to Unraveling the Paradoxical Effect of Diet on Perfluorooctanesulfonic Acid (PFOS) and Perfluorononanoic Acid (PFNA)-Induced Hepatic Steatosis

Perfluoroalkyl substances (PFAS) are a family of toxicants universally detected in human serum and known to cause dyslipidemia in animals and humans. Hepatic steatosis, which is defined as lipid deposition in the liver, is known to be a consequence of poor diet. Similarly, PFAS are known to induce hepatic steatosis in animals on a low-fat chow. This study explored diet-PFAS interactions in the liver and their potential to modulate hepatic steatosis. Male C57BL/6J mice were fed with either a low-fat diet (10% kcal from fat, LFD) or a moderately high-fat diet (45% kcal from fat, HFD) with or without perfluorooctanesulfonic acid (3 ppm, PFOS) or perfluorononanoic acid (3 ppm, PFNA) in feed for 12 weeks. Livers were excised for histology and quantification of PFAS and lipids. The PFOS and PFNA coadministration with HFD reduced the hepatic accumulation of lipid and PFAS relative to the LFD treatment groups. Furthermore, transcriptomic analysis revealed that PFAS administration in the presence of an HFD significantly reduces expression of known hepatic PFAS uptake transporters, organic anion transporter proteins. Transcriptomics and proteomics further revealed several pathways related to lipid metabolism, synthesis, transport, and storage that were modulated by PFAS exposure and further impacted by the presence of dietary fat. Both dietary fat content and the chemical functional head group exerted significant influence on hepatic PFAS accumulation and the resulting biochemical signature, suggesting that diet and structure should be considered in the design and interpretation of research on PFAS induced hepatic steatosis.

Perfluorooctanesulfonic Acid and Perfluorohexanesulfonic Acid Alter the Blood Lipidome and the Hepatic Proteome in a Murine Model of Diet-Induced Obesity

Perfluoroalkyl substances (PFAS) represent a family of environmental toxicants that have infiltrated the living world. This study explores diet-PFAS interactions and the impact of perfluorooctanesulfonic acid (PFOS) and perfluorohexanesulfonic (PFHxS) on the hepatic proteome and blood lipidomic profiles. Male C57BL/6J mice were fed with either a low-fat diet (10.5% kcal from fat) or a high fat (58% kcal from fat) high carbohydrate (42 g/l) diet with or without PFOS or PFHxS in feed (0.0003% wt/wt) for 29 weeks. Lipidomic, proteomic, and gene expression profiles were determined to explore lipid outcomes and hepatic mechanistic pathways. With administration of a high-fat high-carbohydrate diet, PFOS and PFHxS increased hepatic expression of targets involved in lipid metabolism and oxidative stress. In the blood, PFOS and PFHxS altered serum phosphatidylcholines, phosphatidylethanolamines, plasmogens, sphingomyelins, and triglycerides. Furthermore, oxidized lipid species were enriched in the blood lipidome of PFOS and PFHxS treated mice. These data support the hypothesis that PFOS and PFHxS increase the risk of metabolic and inflammatory disease induced by diet, possibly by inducing dysregulated lipid metabolism and oxidative stress.

Increased toxicity and retention of perflourooctane sulfonate (PFOS) in humanized CYP2B6-Transgenic mice compared to Cyp2b-null mice is relieved by a high-fat diet (HFD)

PFOS is a persistent, fluorosurfactant used in multiple products. Murine Cyp2b's are induced by PFOS and high-fat diets (HFD) and therefore we hypothesized that human CYP2B6 may alleviate PFOS-induced steatosis. Cyp2b-null and hCYP2B6-Tg mice were treated with 0, 1, or 10 mg/kg/day PFOS by oral gavage for 21-days while provided a chow diet (ND) or HFD. Similar to murine Cyp2b10, CYP2B6 is inducible by PFOS. Furthermore, three ND-fed hCYP2B6-Tg females treated with 10 mg/kg/day PFOS died during the exposure period; neither Cyp2b-null nor HFD-fed mice died. hCYP2B6-Tg mice retained more PFOS in serum and liver than Cyp2b-null mice presumably causing the observed toxicity. In contrast, serum PFOS retention was reduced in the HFD-fed hCYP2B6-Tg mice; the opposite trend observed in HFD-fed Cyp2b-null mice. Hepatotoxicity biomarkers, ALT and ALP, were higher in PFOS-treated mice and repressed by a HFD. However, PFOS combined with a HFD exacerbated steatosis in all mice, especially in the hCYP2B6-Tg mice with significant disruption of key lipid metabolism genes such as Srebp1, Pparg, and Hmgcr. In conclusion, CYP2B6 is induced by PFOS but does not alleviate PFOS toxicity presumably due to increased retention. CYP2B6 protects from PFOS-mediated steatosis in ND-fed mice, but increases steatosis when co-treated with a HFD.

Associations between serum isomers of perfluoroalkyl acids and metabolic syndrome in adults: Isomers of C8 Health Project in China

BACKGROUND

Exposure to perfluoroalkyl acids (PFAAs) is known to be associated with metabolic disorders. However, whether PFAAs isomers are associated with metabolic syndrome (MetS) still remains unknown.

OBJECTIVES

To explore the associations between serum PFAAs isomers and MetS.

METHODS

We recruited 1,501 adults from a cross-sectional study, the "Isomers of C8 Health Project in China" to investigate the associations between PFAAs isomers and MetS. A total of 20 PFAAs including the isomers of PFOS and PFOA were detected. Logistic regression models and restricted cubic spline models were used to evaluate the relationship of serum PFAAs isomers exposure with MetS and its components as well after adjusting for covariates.

RESULTS

The MetS prevalence in our study was 43.0%. The serum levels of both PFOS and PFOA isomers were higher in participants with MetS than that with non-MetS (p < 0.05). We found positive associations for per natural log-transformed ng/mL of branched perfluorooctane sulfonate (br-PFOS) (odds ratio (OR) = 1.18, 95% confidence interval (CI): 1.01, 1.38)) linear perfluoronanoic acid (n-PFOA) (OR = 1.35, 95% CI: 1.16, 1.58) and perfluoro-6-methylpheptanoic acid (6 m-PFOA) (OR = 1.32, 95% CI: 1.11, 1.57) with higher odds of MetS after covariates adjustment, while null association was observed for linear isomers of PFOS (OR = 1.09, 95% CI: 0.94, 1.25). We found a nonlinear dose-response relationship with a "threshold" effect in serum br-PFOS isomers with MetS, in which the odds of MetS increased quickly with increasing serum br-PFOS isomers under low exposure (p for nonlinearity = 0.030).

CONCLUSION

We report new evidence of associations between PFAAs isomers and MetS and the nonlinearity of dose-response relationship with br-PFOS isomers. Our findings indicate that more attention is needed to pay on the nonlinearity of dose-response relationship when investigate the association of PFAAs isomers with human health.

Diet as an Exposure Source and Mediator of Per- and Polyfluoroalkyl Substance (PFAS) Toxicity

Per- and polyfluoroalkyl substances (PFAS) are ubiquitously found in the environment due to their widespread commercial use and high chemical stability. Humans are exposed primarily through ingestion of contaminated water and food and epidemiological studies over the last several decades have shown that PFAS levels are associated with adverse chronic health effects, including cardiometabolic disorders such as hyperlipidemia and non-alcoholic fatty liver disease. Perhaps the most well-established effects, as demonstrated in animal studies and human epidemiological studies, are the metabolic alterations PFAS exposure can lead to, especially on lipid homeostasis and signaling. This altered lipid metabolism has often been linked to conditions such as dyslipidemia, leading to fatty liver disease and steatosis. Western diets enriched in high fat and high cholesterol containing foods may be an important human exposure route of PFAS and may also act as an important modulator of associated toxicities. In fact, the chemical structure of PFAS resemble fatty acids and may activate some of the same signaling cascades critical for endogenous metabolism. In this review we aim to outline known dietary exposure sources of PFAS, describe the detrimental metabolic health effects associated with PFAS exposure, and focus on studies examining emerging interaction of dietary effects with PFAS exposure that further alter the dysregulated metabolic state.

Perfluorooctanesulfonic acid (PFOS) administration shifts the hepatic proteome and augments dietary outcomes related to hepatic steatosis in mice

Hepatic steatosis increases risk of fatty liver and cardiovascular disease. Perfluorooctanesulfonic acid (PFOS) is a persistent, bio-accumulative pollutant that has been used in industrial and commercial applications. PFOS administration induces hepatic steatosis in rodents and increases lipogenic gene expression signatures in cultured hepatocytes. We hypothesized that PFOS treatment interferes with lipid loss when switching from a high fat diet (HFD) to a standard diet (SD), and augments HFD-induced hepatic steatosis. Male C57BL/6 N mice were fed standard chow diet or 60% kCal high-fat diet (HFD) for 4 weeks to increase body weight. Then, some HFD mice were switched to SD and mice were further divided to diet only or diet containing 0.0003% PFOS, for six treatment groups: SD, HFD to SD (H-SD), HFD, SD + PFOS, H-SD + PFOS, or HFD + PFOS. After 10 weeks on study, blood and livers were collected. HFD for 14 weeks increased body weight and hepatic steatosis, whereas H-SD mice returned to SD measures. PFOS administration reduced body weight in mice fed a SD, but not H-SD or HFD. PFOS administration increased liver weight in H-SD + PFOS and HFD + PFOS mice. PFOS increased hepatic steatosis in H-SD and HFD groups. Hepatic mRNA expression and SWATH-MS proteomic analysis revealed that PFOS induced lipid and xenobiotic transporters, as well as metabolism pathways. Overall, the findings herein suggest that PFOS treatment did interfere with lipid loss associated with switch to a SD and similarly augmented hepatic lipid accumulation in mice established on an HFD.

Risk to human health related to the presence of perfluoroalkyl substances in food

The European Commission asked EFSA for a scientific evaluation on the risks to human health related to the presence of perfluoroalkyl substances (PFASs) in food. Based on several similar effects in animals, toxicokinetics and observed concentrations in human blood, the CONTAM Panel decided to perform the assessment for the sum of four PFASs: PFOA, PFNA, PFHxS and PFOS. These made up half of the lower bound (LB) exposure to those PFASs with available occurrence data, the remaining contribution being primarily from PFASs with short half-lives. Equal potencies were assumed for the four PFASs included in the assessment. The mean LB exposure in adolescents and adult age groups ranged from 3 to 22, the 95th percentile from 9 to 70 ng/kg body weight (bw) per week. Toddlers and 'other children' showed a twofold higher exposure. Upper bound exposure was 4- to 49-fold higher than LB levels, but the latter were considered more reliable. 'Fish meat', 'Fruit and fruit products' and 'Eggs and egg products' contributed most to the exposure. Based on available studies in animals and humans, effects on the immune system were considered the most critical for the risk assessment. From a human study, a lowest BMDL 10 of 17.5 ng/mL for the sum of the four PFASs in serum was identified for 1-year-old children. Using PBPK modelling, this serum level of 17.5 ng/mL in children was estimated to correspond to long-term maternal exposure of 0.63 ng/kg bw per day. Since accumulation over time is important, a tolerable weekly intake (TWI) of 4.4 ng/kg bw per week was established. This TWI also protects against other potential adverse effects observed in humans. Based on the estimated LB exposure, but also reported serum levels, the CONTAM Panel concluded that parts of the European population exceed this TWI, which is of concern.

Combined extracts of Moringa oleifera, Murraya koeingii leaves, and Curcuma longa rhizome increases energy expenditure and controls obesity in high-fat diet-fed rats

Background

LI85008F is a proprietary combination of leaf extracts of Moringa oleifera, Murraya koeingii, and extract of Curcuma longa rhizome. This herbal extract combination is an effective weight loss supplement for overweight and obese subjects. The present study aimed to investigate the thermogenic potential of the LI85008F in high-fat diet (HFD)-induced obese Sprague Dawley rats.

Methods

Seven rats received a regular diet (RD), and twenty-one rats received a high-fat diet (HFD) for 56 days. On day 28, the HFD-fed rats were randomized into three groups (n = 7). Starting from day 29 through day 56, one HFD-fed group received daily oral gavage of 0.5% Carboxymethylcellulose Sodium (CMC) alone (HFD), and the remaining two groups received 100 and 250 mg/kg LI85008F (LI85008F-100 and LI85008F-250, respectively).

Body weight, fat mass, fat cell size, liver weight, liver triglyceride were measured. The energy metabolism parameters were measured using indirect calorimetry. In serum, the metabolic and endocrine markers were analyzed. The adipogenic and thermoregulatory proteins expression in the white adipose tissue (WAT) were analyzed using an immunoblot assay.

Results

Supplementation with both doses of LI85008F significantly increased resting energy expenditure (REE) in the obese rats. The LI85008F-250 rats showed significant up-regulation of uncoupling protein-1 (UCP-1) expression, as compared with the HFD rats. LI85008F significantly reduced body weight gain, fat mass, fat cell size, liver weight, and hepatic triglycerides. Serum triglyceride, total cholesterol, glucose, leptin, and fat cell markers were significantly reduced in LI85008F-supplemented rats compared to the HFD rats.

Conclusion

The present data suggest that LI85008F reduces body fat mass and controls body weight gain via increasing energy metabolism in combination with reduced lipogenesis in diet-fed obese rats.

Understanding Environmental Contaminants' Direct Effects on Non-alcoholic Fatty Liver Disease Progression

PURPOSE OF REVIEW

Environmental contaminants are considered one of the major factors in the development and progression of NAFLD, the most common liver disease in the USA.

RECENT FINDINGS

The evolving knowledge of mechanisms of hepatic steatosis and steatohepatitis has recently been reviewed and characterized as ALD, NAFLD, and TAFLD. The most recent mechanistic studies on PFAS and PCBs have revealed a greater role for toxicants in the initiation of not only TAFLD but also NAFLD and the more progressive inflammatory stage of NAFLD, non-alcoholic steatohepatitis. In addition to insecticides, recent studies support a significant contribution of fungicides and herbicides to NAFLD. The mechanisms of PFAS, PCBs, and fungicides in contributing to the increased prevalence of NAFLD remain unclear. Addressing whether chronic, low-dose exposures could result in liver pathology and whether real-world exposure to mixtures of environmental contaminants pose a significant risk factor for NAFLD is paramount to understand the impact of NAFLD on populations today.

Perfluorobutanesulfonic Acid (PFBS) Induces Fat Accumulation in HepG2 Human Hepatoma

Per- and poly-fluoroalkyl substances, especially perfluorooctanesulfonic acid, have been extensively used for over 50 years. A growing body of evidence has emerged demonstrating the potential adverse effects of these substances, including its effect on the development of non-alcoholic fatty liver disease, as one of the most prevalent chronic liver diseases. Nonetheless, there is no report of effects of perfluorobutanesulfonic acid, the major replacement for perfluorooctanesulfonic acid, on non-alcoholic fatty liver disease. Therefore, the effects of perfluorobutanesulfonic acid exposure on fat accumulation in a human hepatoma cell line were examined. Cells were exposed to perfluorobutanesulfonic acid with or without 300 μmol/L fatty acid mixture (oleic acid:palmitic acid = 2:1) conjugated by bovine serum albumin as an inducer of steatosis for 48 hours. Perfluorobutanesulfonic acid at 200 μmol/L significantly increased the triglyceride level in the presence of fatty acid compared to the control, but not without fatty acid, which was abolished by a specific peroxisome proliferator-activated receptor gamma antagonist. Perfluorobutanesulfonic acid upregulated key genes controlling lipogenesis and fatty acid uptake. Perfluorobutanesulfonic acid treatment also promoted the production of reactive oxygen species, an endoplasmic reticulum stress marker and cytosolic calcium. In conclusion, perfluorobutanesulfonic acid increased fat accumulation, in part, via peroxisome proliferator-activated receptor gamma-mediated pathway in hepatoma cells.