Interaction of volatile organic compounds and underlying liver disease: a new paradigm for risk

Air Pollution and Oral Health: An Overall Insight From Genetic Causality

BACKGROUND

A growing body of epidemiological data consistently links air pollution to various adverse health outcomes. However, the potential connection between air pollution and the risk of oral diseases remains underexplored.

METHODS

This study utilized a two-sample Mendelian randomization approach to assess the causal relationship between air pollution and oral diseases. Six categories of air pollution were considered as exposures: nitrogen oxides (NOx), nitrogen dioxide (NO2), particulate matter (PM2.5, PM2.5-10, PM10), and PM2.5 absorbance. The outcomes included 18 oral health-related diseases drawn from the Finngen R10 dataset, the Gene-Lifestyle Interactions in Dental Endpoints consortium, and the Oncoarray oral cavity and oropharyngeal cancer consortium. Sensitivity analyses were performed to validate the primary inverse-variance weighted estimates using methods such as weighted median, weighted mode, and MR Egger.

RESULTS

The inverse-variance weighted analysis demonstrated a detrimental effect of air pollution on multiple oral health conditions, yielding 5 positive associations including PM2.5 with oral leukoplakia, gingivitis and periodontitis; PM2.5-10 with pulp and periapical diseases, and NO2 with gingivitis and periodontitis, and oral cavity, salivary glands and jaws diseases. Sensitivity tests showed no evidence of heterogeneity or pleiotropy, affirming the robustness of the findings.

CONCLUSION

This study highlights the detrimental impact of air pollution on oral health, emphasizing the need for further research into the underlying mechanisms and interactions. These findings reinforce the importance of implementing environmental interventions to mitigate the associated risks for oral health.

Association between volatile organic compounds exposure and cardiometabolic function: a population-based study

Background

The Cardiometabolic Index (CMI) is a new metric used to assess an individual's cardiovascular and metabolic status. Volatile Organic Compounds (VOCs) are common environmental pollutants associated with cardiovascular diseases and lipid metabolism disorders. This study aims to investigate the relationship between VOC exposure and CMI.

Methods

Data from NHANES (2011-2020) were used to assess the impact of VOC exposure on cardiometabolic function. Multivariable linear regression was used to analyze the association between VOCs and the CMI. Restricted cubic spline models were applied to model the nonlinear relationship between VOCs and CMI. BKMR (bayesian kernel machine regression), WQS (weighted quantile sum), and Q-gcomp (quantile g-computation) models were employed to explore the association between VOC mixture exposure and CMI. Subgroup analyses were conducted to investigate the relationship between VOCs and CMI across different subgroups.

Results

Multiple linear regression analysis confirmed the significantly positive associations between the highest quartile concentrations of CEMA, 3HPMA, MHBMA3, and HMPMA compared to the lowest quartile (β = 0.43, 95% CI = 0.20, 0.67, P for trend < 0.001; β = 0.30, 95% CI = 0.05, 0.55, P for trend = 0.006; β = 0.37, 95% CI = 0.14, 0.61, P for trend < 0.001; β = 0.28, 95% CI = 0.01, 0.55, P for trend = 0.010). AAMC and SBMA showed a nonlinear relationship with CMI. Results from mixture exposure models indicated that CEMA contributed most significantly to the impact on CMI. BKMR, WQS, and Q-gcomp models showed a positive trend between overall VOC exposure and CMI. Subgroup analysis revealed significant interactions of BMI and diabetes status in the relationship between VOC exposure and CMI, especially among individuals with BMI ≥ 30 and those with diabetes.

Conclusion

This study found significant positive associations between specific VOC exposures and CMI. Additionally, BMI and diabetes status play important roles in moderating the relationship between VOC exposure and CMI. These findings highlight the potential impact of environmental VOCs on cardiovascular and metabolic health which provides new evidence for public health interventions.

Environmental Pollutants, Occupational Exposures, and Liver Disease

Environmental pollutants significantly impact liver disease development, progression, and outcomes. This review examines the complex relationship between environmental exposures and liver pathology, from malignant conditions like hepatocellular carcinoma to steatotic and cholestatic liver diseases. Key environmental factors include air pollutants, volatile organic compounds, persistent organic pollutants, heavy metals, and per- and polyfluoroalkyl substances. These compounds can act through multiple mechanisms, including endocrine disruption, metabolic perturbation, oxidative stress, and direct hepatotoxicity. The impact of these exposures is often modified by factors such as sex, diet, and genetic predisposition. Recent research has revealed that even low-level exposures to certain chemicals can significantly affect liver health, particularly when combined with other risk factors. The emergence of exposomics as a research tool promises to enhance our understanding of how environmental factors influence liver disease. Importantly, exposure effects can vary by demographic and socioeconomic factors, highlighting environmental justice concerns. Implementation of this knowledge in clinical practice requires new diagnostic approaches, healthcare system adaptations, and increased awareness among medical professionals. In conclusion, this review provides a comprehensive examination of current evidence linking environmental exposures to liver disease and discusses implications for clinical practice and public health policy.

Association of occupational noise exposure and shift work with non-alcoholic fatty liver disease: a cross-sectional study of male workers in the Chinese automobile manufacturing industry

OBJECTIVE

This study aimed to determine the relationship between occupational noise, shift work and non-alcoholic fatty liver disease (NAFLD) in male workers in the automobile manufacturing industry.

DESIGN

Cross-sectional study.

SETTING

This study was carried out at the Guangzhou Twelfth People's Hospital using data from April to September 2022.

PARTICIPANTS

A total of 4672 eligible participants were included in the study.

PRIMARY AND SECONDARY OUTCOME MEASURES

Diagnosis of NAFLD was made using ultrasound. Noise was detected according to the Measurement of Physical Factors in the Workplace-Part 8: Noise. Environmental noise intensity was assessed using an EDGE personal noise dosimeter manufactured by CASELLA (UK). The working status of workers was investigated by questionnaire.

RESULTS

The OR of NAFLD was 1.39 (1.03, 1.88) in the cumulative noise exposure (CNE)≥95 group compared with CNE<85 group. Improved risk of NAFLD in workers with shift work compared with those without shift work (OR=1.35, 95% CI: 1.09, 1.68). As stratified analyses showed, the ORs of NAFLD prevalence related to occupational noise and shift work exposure appear to be increased in young workers. When both shift work and noise exposure work are present simultaneously, the synergy index between them was 0.47 (95% CI: 0.25, 0.89). Combined effects analysis revealed that the OR of NAFLD was 2.02 (95% CI: 1.34, 2.99) in CNE≥95 and cumulative length of night shifts work>2920 hours.

CONCLUSION

Occupational noise exposure may be an independent risk factor for NAFLD. It may synergistically affect disease when combined with night shift work, particularly among younger workers. These findings underscore the importance for companies to prioritise the management and training of younger workers, along with targeted occupational health education initiatives, as crucial measures for reducing the incidence of NAFLD.

The association analysis between exposure to volatile organic compounds and fatty liver disease in US Adults

BACKGROUND

Limited epidemiological research has explored the associations between ambient volatile organic compounds (VOCs) and fatty liver disease (FLD). This study aimed to explore the associations between VOCs and FLD and liver function biomarkers. We obtained urinary concentrations of VOCs metabolites from NHANES.

METHODS

Weighted logistic regression models were employed to investigate the relationships between VOCs and FLD risk, including alcoholic FLD (AFLD) and non-alcoholic FLD (NAFLD). The associations of VOCs and liver function biomarkers were also investigated using weighted linear regression.

RESULTS

Among the 2050 participants, 774 were classified as having FLD. After adjustment, each log-transformed SD increase in N-Acetyl-S-(2-carboxyethyl)-l-cysteine (CEMA), 2-Aminothiazoline-4-carboxylicacid (ATCA), and trans-trans-muconic-acid (MUCA) had a OR (95%CI) of 1.30 (1.06-1.61; P-trend=0.014), 1.34 (1.12-1.61; P-trend=0.002), and 1.22 (1.01-1.47; P-trend=0.035), respectively. ATCA and MUCA were associated with higher risks of NAFLD (OR=1.47, 95%CI: 1.20-1.79, and OR=1.26, 95%CI: 1.02-1.56, respectively). VOCs were positively associated with gamma glutamyl transaminase (GGT) and C-reactive protein (CRP), while inversely associated with albumin, total protein and alanine aminotransferase (ALT) (P < 0.05).

CONCLUSIONS

Urinary metabolites of VOCs have been found to be strongly correlated with a higher risk of FLD and NFALD, and impaired liver function. These novel findings merit further prospective studies to comprehend the effect of VOCs on liver diseases.

Cilostazol attenuates mirabegron-induced hepatic and renal toxicity in rats: regulation of metabolic, oxidative, and inflammatory pathways

BACKGROUND

Mirabegron (MIRG) is a type of β3 adrenoceptor agonist that is considered an alternative therapy for the treatment of overactive bladder (OAB) symptoms. Cilostazol (CITZ) is a selective inhibitor of phosphodiesterase (III) that has various pharmacological effects.

OBJECTVE

The current study aimed to highlight the regulatory effects of CITZ on MIRG-induced toxicity.

MATERIALS AND METHODS

Male rats were divided into six groups. Blood samples were collected to determine different hepatic and kidney function levels along with serum protein electrophoresis and inflammatory factor levels. Histopathological studies and oxidative stress (OS) were also assessed. Kidney and hepatic damage were detected following the administration of MIRG, especially at high doses, due to elevated OS, inflammation, and apoptotic marker levels.

RESULTS

Rats receiving CITZ exhibited significant improvements in both hepatic and kidney functions, with decreased inflammation and OS.

CONCLUSION

CITZ administration plays a beneficial role in alleviating hepatic and nephrotoxicity induced by MIRG by inhibiting OS and inflammation.

Air pollution exposure and prevalence of non-alcoholic fatty liver disease and related cirrhosis: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

A systematic review and meta-analysis were used to investigate the relationship between air pollution exposure and the prevalence of non-alcoholic fatty liver disease (NAFLD) and its related cirrhosis. Through this study, we hope to clarify the potential public health risks of air pollution as an environmental exposure factor.

METHODS

Through a comprehensive and systematic search of the EMBASE, PubMed, Web of Science, and Cochrane library databases, studies published up to March 30, 2024, that met the eligibility criteria were identified. The meta-analysis aimed to determine the association between air pollution exposure and NAFLD risk. Subgroup analyses were conducted based on regional economic development after adjusting for confounding factors. The combined odds ratio (OR) was calculated, publication bias was assessed using funnel plots, and consideration was given to heterogeneity among study-specific relative risks.

RESULTS

This review included 14 observational studies (including 7 cohort studies and 7 cross-sectional studies) involving 43,475,41 participants. The pooled analysis showed that PM2.5, NOx, PM10, PM2.5-10, passive smoking, PM1, and air pollution from solid fuels were positively associated with the incidence and prevalence of NAFLD and its related cirrhosis. The risk ratios for PM2.5, NOx, PM10, PM2.5-10, passive smoking, and air pollution from solid fuels for NAFLD and its related cirrhosis were 1.33 (95 % CI: 1.25, 1.42), 1.19 (95 % CI: 1.14, 1.23), 1.27 (95 % CI: 1.05, 1.55), 1.05 (95 % CI: 1.00, 1.11), 1.53 (95 % CI: 1.12, 2.09), 1.50 (95 % CI: 0.86, 2.63), and 1.18 (95 % CI: 0.85, 1.63), respectively. In contrast, the risk ratio for O3 was 0.75 (95 % CI: 0.69, 0.83), suggesting that O3 may lower the incidence and prevalence of NAFLD and its related cirrhosis. We also conducted subgroup analyses based on the level of national development to examine the impact of PM2.5 on NAFLD and its related cirrhosis. The results showed that the risk of NAFLD and its related cirrhosis associated with PM2.5 in developing countries was 1.41 (95 % CI: 1.29, 1.53), which was higher than 1.20 (95 % CI: 1.12, 1.29) in developed countries.

CONCLUSION

The study findings show that PM2.5, NOx, PM10, PM2.5-10, passive smoking, PM1, and air pollution from solid fuels can increase an individual's risk of developing NAFLD and its related cirrhosis; while O3 can reduce the risk. In developing countries, the risk level of NAFLD and its related cirrhosis due to PM2.5 is higher than that in developed countries.

Volatile organic compounds exposure in relation to glucose homeostasis and type 2 diabetes in older adults from the NHANES

The impact of volatile organic compounds (VOCs) on type 2 diabetes (T2D) among older adults is unknown. The multiple linear regression model and the multiple binary logistic regression were used to evaluate the relationships between mVOCs and glucose homeostasis/T2D, respectively. Among the 19 mVOCs, the higher levels of urinary N-acetyl-S-(2-hydroxypropyl)-L-cysteine (2HPMA, compound CID:44146439) and N-acetyl-S-(2-hydroxypropyl)-L-cysteine (HPMMA, compound CID:107774684) were significantly associated with higher odds of T2D (OR = 1.16, 95% confidence interval [CI]:1.01-1.34 for 2HPMA; and OR = 1.27, 95% CI:1.04-1.54 for HPMMA). In addition, higher concentrations of multiple mVOCs in urine were significantly correlated with glucose homeostasis biomarkers, including 2HPMA and 2-thioxothiazolidine-4-carboxylic acid (TTCA, compound CID:3034757) with fasting glucose, HPMMA and mandelic acid (MA, compound CID:1292) with HbA1c, phenylglyoxylic acid (PGA, compound CID:11915) with serum insulin, HbA1c and HOMA-IR. Our findings suggested that exposure to VOCs were associated with increased odds of T2D in older adults, which might be mediated by impaired glucose homeostasis. Mitigating VOCs should be a necessary component of public health strategies aimed at reducing the burden of type 2 diabetes.

Association of urinary volatile organic compounds and chronic kidney disease in patients with diabetes: real-world evidence from the NHANES

BACKGROUND

Chronic kidney disease (CKD) is common in patients with diabetes mellitus (DM). Volatile organic compounds (VOCs) are widespread pollutants that may impact DM development.

OBJECTIVE

This study aims to explore the association between urinary VOC metabolites and CKD in patients with DM.

METHODS

Adult National Health and Nutrition Examination Survey (NHANES) 2011 to 2018 participants with DM were included in this study. CKD was defined as an estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2 or urine albumin-to-creatinine ratio (UACR) ≥ 30 mg/g. Multivariable regression models were used to analyze the associations between urinary VOC metabolites and CKD.

RESULTS

A total of 1,295 participants with DM and a mean age of 59 years were included. After adjustment for demographic and clinical characteristics, elevated levels of N-acetyl-S-(2-carbamoylethyl)-L-cysteine (AAMA) (tertile 2: adjusted odds ratio (aOR)  =   1.81, 95% confidence interval (CI): 1.15-2.85, p  =  0.012), N-acetyl-S-(N-methylcarbamoyl)-L-cysteine (AMCC) (tertile 2: aOR   =  1.84, 95% CI: 1.10-3.08, p  =  0.021), DHBMA (tertile 3: aOR  =  1.93, 95% CI: 1.12-3.35, p  =   0.020), and phenylglyoxylic acid (PGA) (tertile 3: aOR   =  1.71, 95% CI: 1.11-2.63, p  =  0.017) were significantly associated with increased likelihood of CKD.

CONCLUSION

Specific urinary VOC metabolite levels are positively associated with an increased risk of CKD in patients with DM. These findings suggest that monitoring urinary VOC metabolites could be important for the prevention and management of CKD in this population. Future longitudinal studies should focus on establishing causality and elucidating the underlying mechanisms of these associations.

Hepatotoxicity of N-nitrosodin-propylamine in larval zebrafish by upregulating the Wnt pathway

N-nitrosodin-propylamine is an organic compound mainly used in organic synthesis. As a typical pollutant, the accidental release of N-nitrosodin-propylamine may cause environmental pollution, especially water environment pollution. In the present study, we used the zebrafish model for the first time to evaluate the developmental toxicity of this drug in the liver. Zebrafish larvae fertilized at 72hpf showed a range of toxic responses after 72hpf exposure to the drug. These include increased mortality, delayed absorption of yolk sac nutrients, shorter body length, abnormal liver morphology, gene disruption, and altered expression of various indicators with increasing dose. Studies on the mechanism of toxicity showed that N-nitrosodin-propylamine exposure increased the level of oxidative stress, increased the level of apoptosis in hepatocytes, and up-regulated the transcriptional expression level of Wnt signaling pathway genes. Astaxanthin and IWR-1 can effectively save the liver toxicity in zebrafish caused by N-nitrosodin-propylamine. Our study showed that the drug exposure induced hepatotoxicity in zebrafish larvae through the up-regulation of Wnt signaling pathway, oxidative stress and apoptosis.

NMR-based metabolomics for investigating urinary profiles of metal carpentry workers exposed to welding fumes and volatile organic compounds

Introduction

Metal carpentry includes a wide range of work activities such as welding and cutting metallic components, use of solvents and paints. Therefore, the employees in these types of activities are mainly exposed to welding fumes and volatile organic solvents. Here, we present an NMR-based metabolomic approach for assessing urinary profiles of workers in the same company that are exposed to two different risk factors.

Methods

The study enrolled 40 male subjects exposed to welding fumes, 13 male subjects exposed to volatile organic compounds of a metal carpentry company, and 24 healthy volunteers. All samples were collected, in the middle of the working week at fast. Thirty-five urinary metabolites belonging to different chemical classes such as amino acids, organic acids and amines were identified and quantified. Results were processed by multivariate statistical analysis for identifying significant metabolites for each working group examined, compared to controls.

Results

Workers exposed to welding fumes displayed urinary increase in glutamine, tyrosine, taurine, creatine, methylguanidine and pseudouridine associated to oxidative impairment, while workers exposed to volatile organic compounds showed higher urinary levels of branched chain aminoacids.

Conclusion

Our work identified specific urinary profile related to each occupational exposure, even if it is below the threshold limit values.

The association between exposure to volatile organic chemicals and serum α-Klotho in USA middle to old aged population: A cross-sectional study from NHANES 2011-2016

BACKGROUND

Volatile Organic Compounds (VOCs) constitute an omnipresent category of environmental contaminants. Numerous studies have identified associations between various VOCs and human diseases. The anti-aging protein α-Klotho has been shown to exert protective influences across a variety of disease origins and progressions. This study aims to explore the relationship between serum α-Klotho levels and exposure to VOCs in humans.

METHODS

This analysis utilized data from 1672 participants aged from 40 to 79 years in 2011-2016 NHANES. Exposure to VOCs was assessed through measurements of urinary VOC metabolites (mVOCs), with 16 mVOCs selected for analysis. Multivariate generalized linear models (GLM), restricted cubic splines (RCS), weighted quantile sum (WQS) regression models, and Bayesian kernel machine regression (BKMR) models were employed to examine the connection between serum α-Klotho and individual mVOCs and mVOCs mixtures, as well as to identify the primary monomeric mVOCs responsible for these associations.

RESULTS

Our research revealed that 8 mVOCs exhibited inverse associations with serum α-Klotho levels in GLM and RCS models. Particularly noteworthy, N-Acetyl-S-(2-cyanoethyl)-L-cysteine (CYMA), a metabolite of acrylonitrile, emerged as the most influential mVOC in both WQS and BKMR models. Furthermore, the mVOCs mixture was found to be negatively correlated with serum α-Klotho. The detrimental effects of mVOCs on serum α-Klotho were observed to significantly diminish in individuals with elevated serum vitamin D levels.

CONCLUSION

Our study highlights a significant inverse relationship between serum α-Klotho and the mixture of mVOCs, indicating that exposure to VOCs may impact the molecular pathways of aging and related diseases by influencing α-Klotho concentrations. Remarkably, the attenuation of this association by high serum vitamin D levels implies potential therapeutic strategies. Our study underscores the importance of minimizing VOCs exposure to mitigate the adverse effects on α-Klotho. Further research is warranted to elucidate the underlying mechanisms of these relationships.

Association between Volatile Organic Compound Exposure and Sex Hormones in Adolescents: The Mediating Role of Serum Albumin

The associations between VOCs and sex hormones in adolescents remain unclear, and the role of serum albumin in these associations deserves to be explored. We conducted cross-sectional analyses using generalized linear models (GLMs), weighted quantile sum (WQS) regression, and mediation analysis, based on data from 584 adolescents from the National Health and Nutrition Examination Survey (NHANES). The GLM analyses revealed that seven kinds of mVOCs potentially affected sex hormone levels. According to the WQS regression results, 2-aminothiazoline-4-carboxylic acid (ATCA) was the major contributor to the significant associations of mixed mVOC exposure with testosterone, estradiol, and free androgen index in males; N-acetyl-S-(N-methylcarbamoyl)-L-cysteine (AMCC) was the major contributor to the significant associations of mixed mVOC exposure with sex hormone-binding globulin in males; and N-acetyl-S-(benzyl)-L-cysteine (BMA) was the major contributor to the significant associations of mixed mVOC exposure with the ratio of testosterone to estradiol in females. Moreover, serum albumin could mediate up to 9.2% of the associations between mixed exposure to mVOCs and sex hormones. Our findings could provide a reference for studies on the mechanisms underlying the effects of VOCs on sex hormones in adolescents and emphasize the necessity of reducing exposure to ATCA, AMCC, BMA, and their parent compounds.

Exploring occupational toxicant exposures in patients with metabolic dysfunction-associated steatotic liver disease: A prospective pilot study

BACKGROUND

Metabolic dysfunction-associated steatotic liver disease (MASLD) has been traditionally associated with insulin resistance and obesity. Recently, pollutants have been shown to contribute to the development of MASLD. Given the global burden of MASLD, understanding whether pollutants are merely associated with steatosis or contribute to its progression to advanced chronic liver disease (ACLD) and hepatocellular carcinoma (HCC) is critical. Workers exposed to occupational toxicants represent an ideal population for assessing the potentially hazardous consequences of professional exposure. Confirming a link between occupational exposure and ACLD/HCC may not only provide further elements in understanding MASLD, but also contribute to preventive strategies for exposed workers.

OBJECTIVE

This study aimed to assess the prevalence of self-reported occupational exposure to toxicants in patients with MASLD.

METHODS

This hospital-based prospective pilot study included 201 patients with MASLD. Data on workplace toxicant exposure were collected systematically using a structured questionnaire. Subsequently, patients with ACLD and/or HCC (n = 55) were compared to controls (n = 146). Logistic regression analysis and propensity score models were used to investigate the associations between self-reported occupational exposure and ACLD and/or HCC.

RESULTS

Patients with ACLD/HCC reported exposure to metals, halogenated refrigerants, pain/resins, and fuel emissions more often than the controls. After controlling for confounders, durations of 21-30 years and >30 years of occupational exposure to toxicants showed odds ratios (ORs) of 2.31 (95 % confidence interval [CI]: 1.09-4.88, p = 0.029) and 4.47 (95 % CI: 2.57-7.78, p<0.001), respectively.

CONCLUSIONS

In this pilot study, patients with MASLD complications were more likely to report workplace toxicant exposure. Our results warrant future multicentre confirmatory studies, as implementing prevention policies may reduce the risk of life-threatening diseases among exposed populations.

Does ambient air pollution influence biochemical markers of liver injury? Findings of a cross-sectional population-based survey

BACKGROUND

There is limited evidence supporting an adverse effect of ambient air pollution on the liver.

OBJECTIVES

To test the association between exposure to residential air pollution and serum biochemical indicators of liver injury.

METHODS

We used a nationally representative sample of 32,989 participants aged 3-79 years old who participated in the Canadian Health Measures Survey between 2007 and 2019. Cross-sectional associations were assessed by generalized linear mixed models incorporating survey-specific sampling weights.

RESULTS

The joint effect of an interquartile range (IQR) increase in nitrogen dioxide (NO2), ozone (O3) and fine particulate matter (PM2.5) was positively and significantly associated with all measures of liver injury adjusting for age, sex, education, income, smoking, alcohol consumption, body mass index (BMI), total cholesterol, diabetes, hypertension, and physical activity. The ranking of effect sizes from largest to smallest percent increases were 8.72% (95% confidence interval [CI] 7.56, 9.88) for alanine aminotransferase (ALT), 5.54% (95%CI 3.31, 7.77) for gamma-glutamyl transferase (GGT), 4.81% (95%CI 3.87, 5.74) for aspartate aminotransferase (AST), 2.46% (95%CI 0.26, 4.65) for total bilirubin (TBIL) and 1.18% (95%CI 0.62, 1.75) for alkaline phosphatase (ALP). Findings were not significantly different when stratified by age (≤16, >16 yr), sex, smoking (current, other), cholesterol (≤6.18, >6.18 mmol/l) and BMI (<30, ≥30 kg/m2).

DISCUSSION

These findings suggest that ambient air pollution may have a relatively small impact on the liver, but these changes may have significant impact from a population health perspective, considering the ubiquitous nature of air pollution, or for individuals exposed to very high levels of air pollution.

Multi-omics analysis reveals hepatic lipid metabolism profiles and serum lipid biomarkers upon indoor relevant VOC exposure

As a widespread indoor air pollutant, volatile organic compound (VOC) caused various adverse health effects, especial the damage to liver, which has become a growing public concern. However, the current toxic data are intrinsically restricted in the single or major VOC species. Limited knowledge is available regarding toxic effects, biomarkers and underlying mechanisms of real indoor VOC-caused liver damage. Herein, an indoor relevant VOC exposure model was established to evaluate the hepatic adverse outcomes. Machine learning and multi-omics approaches, including liver lipidomic, serum lipidomic and liver transcriptomic, were utilized to uncover the characteristics of liver damage, serum lipid biomarkers, and involved mechanism stimulated by VOC exposure. The result showed that indoor relevant VOC led to the abnormal hepatic lipid metabolism, mainly manifested as a decrease in triacylglycerol (TG) and its precursor substance diacylglycerol (DG), which could be contributed to the occurrence of hepatic adverse outcomes. In terms of serum lipid biomarkers, five lipid biomarkers in serum were uncovered using machine learning to reflect the hepatic lipid disorders induced by VOC. Multi-omics approaches revealed that the upregulated Dgkq disturbed the interconversion of DG and phosphatidic acid (PA), leading to a TG downregulation. The in-depth analysis revealed that VOC down-regulated FoxO transcription factor, contributing to the upregulation of Dgkq. Hence, this study can provide valuable insights into the understanding of liver damage caused by indoor relevant VOC exposure model VOC exposure, from the perspective of multi-omics analysis.

RISING STARS: Sex differences in toxicant-associated fatty liver disease

Based on biological sex, the consequential health outcomes from exposures to environmental chemicals or toxicants can differ in disease pathophysiology, progression, and severity. Due to basal differences in cellular and molecular processes resulting from sexual dimorphism of organs including the liver and additional factors influencing 'gene-environment' interactions, males and females can exhibit different responses to toxicant exposures. Associations between environmental/occupational chemical exposures and fatty liver disease (FLD) have been well-acknowledged in human epidemiologic studies and their causal relationships demonstrated in experimental models. However, studies related to sex differences in liver toxicology are still limited to draw any inferences on sex-dependent chemical toxicity. The purpose of this review is to highlight the present state of knowledge on the existence of sex differences in toxicant-associated FLD (TAFLD), discuss potential underlying mechanisms driving these differences, implications of said differences on disease susceptibility, and emerging concepts. Chemicals of interest include various categories of pollutants that have been investigated in TAFLD, namely persistent organic pollutants, volatile organic compounds, and metals. Insight into research areas requiring further development is also discussed, with the objective of narrowing the knowledge gap on sex differences in environmental liver diseases. Major conclusions from this review exercise are that biological sex influences TAFLD risks, in part due to (i) toxicant disruption of growth hormone and estrogen receptor signaling, (ii) basal sex differences in energy mobilization and storage, and (iii) differences in chemical metabolism and subsequent body burden. Finally, further sex-dependent toxicological assessments are warranted for the development of sex-specific intervention strategies.

Western diet unmasks transient low-level vinyl chloride-induced tumorigenesis; potential role of the (epi-)transcriptome

BACKGROUND & AIMS

Vinyl chloride (VC) monomer is a volatile organic compound commonly used in industry. At high exposure levels, VC causes liver cancer and toxicant-associated steatohepatitis. However, lower exposure levels (i.e., sub-regulatory exposure limits) that do not directly damage the liver, enhance injury caused by Western diet (WD). It is still unknown if the long-term impact of transient low-concentration VC enhances the risk of liver cancer development. This is especially a concern given that fatty liver disease is in and of itself a risk factor for the development of liver cancer.

METHODS

C57Bl/6 J mice were fed WD or control diet (CD) for 1 year. During the first 12 weeks of feeding only, mice were also exposed to VC via inhalation at sub-regulatory limit concentrations (<1 ppm) or air for 6 h/day, 5 days/week.

RESULTS

Feeding WD for 1 year caused significant hepatic injury, which was exacerbated by VC. Additionally, VC increased the number of tumors which ranged from moderately to poorly differentiated hepatocellular carcinoma (HCC). Transcriptomic analysis demonstrated VC-induced changes in metabolic but also ribosomal processes. Epitranscriptomic analysis showed a VC-induced shift of the modification pattern that has been associated with metabolic disease, mitochondrial dysfunction, and cancer.

CONCLUSIONS

These data indicate that VC sensitizes the liver to other stressors (e.g., WD), resulting in enhanced tumorigenesis. These data raise concerns about potential interactions between VC exposure and WD. It also emphasizes that current safety restrictions may be insufficient to account for other factors that can influence hepatotoxicity.

Pulmonary and neurological health effects associated with exposure to representative composite manufacturing emissions and corresponding alterations in circulating metabolite profiles

Cured-in-place pipe (CIPP) technology is increasingly being utilized to repair aging and damaged pipes, however, there are concerns associated with the public health hazards of emissions. CIPP installation involves the manufacture of a new plastic composite pipe at the worksite and includes multiple variable components including resin material, curing methods, and operational conditions. We hypothesize styrene-based composite manufacturing emissions (CMEs) will induce greater pulmonary inflammatory responses and oxidative stress, as well as neurological toxicity compared with nonstyrene CMEs. Further, these CME-toxicological responses will be sex- and time-dependent. To test the hypothesis, representative CMEs were generated using a laboratory curing chamber and characterized using thermal desorption-gas chromatography-mass spectrometry and photoionization detector. Styrene was released during staying, isothermal curing, and cooling phases of the process and peaked during the cooling phase. Male and female C57BL6/J mice were utilized to examine alterations in pulmonary responses and neurotoxicity 1 day and 7 days following exposure to air (controls), nonstyrene-CMEs, or styrene-CMEs. Serum styrene metabolites were increased in mice exposed to styrene-CMEs. Metabolic and lipid profiling revealed alterations related to CIPP emissions that were resin-, time-, and sex-dependent. Exposure to styrene-CMEs resulted in an influx of lymphocytes in both sexes. Expression of inflammatory and oxidative stress markers, including Tnfα, Vcam1, Ccl2, Cxcl2, Il6, Cxcl1, Tgfβ1, Tgmt2, and Hmox1, displayed alterations following exposure to emissions. These changes in pulmonary and neurological markers of toxicity were dependent on resin type, sex, and time. Overall, this study demonstrates resin-specific differences in representative CMEs and alterations in toxicity endpoints, which can potentially inform safer utilization of composite manufacturing processes.

Plasma Cytokeratin-18 Fragment Level Reflects the Metabolic Phenotype in Obesity

There is growing interest in the non-invasive identification and monitoring of the outcome of liver damage in obese patients. Plasma cytokeratin-18 (CK-18) fragment levels correlate with the magnitude of hepatocyte apoptosis and have recently been proposed to independently predict the presence of non-alcoholic steatohepatitis (NASH). The aim of the study was to analyze the associations of CK-18 with obesity and related complications: insulin resistance, impaired lipid metabolism and the secretion of hepatokines, adipokines and pro-inflammatory cytokines. The study involved 151 overweight and obese patients (BMI 25-40), without diabetes, dyslipidemia or apparent liver disease. Liver function was assessed based on alanine aminotransferase (ALT), gamma-glutamyl transferase (GGT) and the fatty liver index (FLI). CK-18 M30 plasma levels, FGF-21, FGF-19 and cytokines were determined by ELISA. CK-18 values >150 U/l were accompanied by high ALT, GGT and FLI, insulin resistance, postprandial hypertriglyceridemia, elevated FGF-21 and MCP-1 and decreased adiponectin. ALT activity was the strongest independent factor influencing high CK-18 plasma levels, even after an adjustment for age, sex and BMI [β coefficient (95%CI): 0.40 (0.19-0.61)]. In conclusion, the applied CK-18 cut-off point at 150 U/l allows to distinguish between two metabolic phenotypes in obesity.

Associations between residential volatile organic compound exposures and liver injury markers: The role of biological sex and race

While occupational exposures to volatile organic compounds (VOCs) have been linked to steatohepatitis and liver cancer in industrial workers, recent findings have also positively correlated low-dose, residential VOC exposures with liver injury markers. VOC sources are numerous; factors including biological make up (sex), socio-cultural constructs (gender, race) and lifestyle (smoking) can influence both VOC exposure levels and disease outcomes. Therefore, the current study's objective is to investigate how sex and race influence associations between residential VOC exposures and liver injury markers particularly in smokers vs. nonsmokers. Subjects (n = 663) were recruited from residential neighborhoods; informed consent was obtained. Exposure biomarkers included 16 urinary VOC metabolites. Serological disease biomarkers included liver enzymes, direct bilirubin, and hepatocyte death markers (cytokeratin K18). Pearson correlations and generalized linear models were conducted. Models were adjusted for common liver-related confounders and interaction terms. The study population constituted approximately 60% females (n = 401) and 40% males (n = 262), and a higher percent of males were smokers and/or frequent drinkers. Both sexes had a higher percent of White (75% females, 82% males) vs. Black individuals. Positive associations were identified for metabolites of acrolein, acrylamide, acrylonitrile, butadiene, crotonaldehyde, and styrene with alkaline phosphatase (ALP), a biomarker for cholestatic injury; and for the benzene metabolite with bilirubin; only in females. These associations were retained in female smokers. Similar associations were also observed between these metabolites and ALP only in White individuals (n = 514). In Black individuals (n = 114), the styrene metabolite was positively associated with aspartate transaminase. Interaction models indicated that positive associations for acrylamide/crotonaldehyde metabolites with ALP in females were dose-dependent. Most VOC associations with K18 markers were negative in this residential population. Overall, the findings demonstrated that biological sex, race, and smoking status influence VOC effects on liver injury and underscored the role of biological-social-lifestyle factor(s) interactions when addressing air pollution-related health disparities.

The association analysis between exposure to volatile organic chemicals and obesity in the general USA population: A cross-sectional study from NHANES program

BACKGROUND

Increasing evidence have been provided that the exposure to environment pollutants was associated obesity, while whether the exposure to volatile organic chemicals (VOC) was associated with obesity or abdominal obesity is yet to be clarified.

METHOD

A cross-sectional study using data from the 6 survey cycles (2005-2006, 2011-2018, 2017-2020) of NHANES program was performed. Obesity and abdominal obesity were identified as a BMI >30 and a waist circumference >102 cm for men or >88 cm for women respectively. The quantile logistic regression method was used to analyze the association between VOC metabolites (VOCs) in urine and obesity, and the quantile regression method was used for the association analysis between VOCs in urine and BMI, as well as waist circumference.

RESULTS

A total of 17 524 participants (4965 obesity, 7317 abdominal obesity) were included, and participants in the obesity or abdominal obesity groups showed higher VOCs in urine than that in the control group. The CEMA was identified as the risk factor for obesity and abdominal obesity in all the 4 models, and its detected OR for obesity in the Q2 to Q4 of model 3 was 1.169 (Q2, p < 0.05), 1.306 (Q3, p < 0.001) and 1.217 (Q4, p < 0.01) respectively. And its OR for abdominal obesity in the Q2 to Q4 of model 3 was 1.222 (Q2, p < 0.01), 1.448 (Q3, p < 0.001) and 1.208 (Q4, p < 0.05) respectively. A significantly positive association between CEMA and BMI, as well as waist circumference, was also detected.

CONCLUSION

In this study, we found that the exposure to VOC (Acrolein, Acrylamide, Acrylonitrile, 1,3-Butadiene, Crotonaldehyde, Cyanide, N,N-Dimethylformamide, Ethylbenzene, styrene, Propylene oxide, Toluene and Xylene) was significantly associated with obesity or abdominal obesity. And also, more prospective studies and related experimental researches should be carried out to further demonstrate the conclusion of this study.

Exposure to volatile organic compounds and polycyclic aromatic hydrocarbons is associated with the risk of non-alcoholic fatty liver disease in Korean adolescents: Korea National Environmental Health Survey (KoNEHS) 2015-2017

Non-alcoholic fatty liver disease (NAFLD) is one of the most frequent liver diseases among adolescents. Several animal studies have suggested that volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) increase NAFLD risk. However, few epidemiological studies have confirmed the association between VOCs, PAHs and NAFLD in the general adolescent population. Therefore, we analyzed 798 adolescents from the Korean National Environmental Health Survey (KoNEHS), 2015-2017, to examine the associations of urinary metabolites of VOCs and PAHs with serum alanine aminotransferase (ALT) activity and NAFLD prevalence. We performed linear regression, logistic regression, and Bayesian kernel machine regression (BKMR) to evaluate the association of urinary VOCs and PAHs metabolites with ALT levels and NAFLD prevalence. After adjusting for all covariates, urinary benzylmercapturic acid and 2-hydroxyfluorene levels were found to increase ALT activity and NAFLD prevalence. Additionally, the BKMR analyses showed a significantly positive overall effect on ALT activity and NAFLD prevalence with urinary concentrations of VOCs and PAHs metabolites, with 2-hydroxyfluorene as the biggest contributor. Our study suggests that exposure to low-level VOCs and PAHs may have a detrimental effect on NAFLD risk in adolescents. Given the increasing prevalence of NAFLD in adolescents, future cohort studies are confirmed to comprehend the effect of these chemicals on NAFLD risk.

Association of volatile organic compounds co-exposure with bone health indicators and potential mediators

Limited evidence was found in the associations of volatile organic compound (VOC) exposure with bone health indicators. This study aimed to explore the associations of individual and combined metabolites of VOCs (mVOCs) in urine, a representative of the internal exposure level of VOCs, with bone mineral density (BMD), osteoporosis (OP) and fracture, and potential mediators. Data of the National Health Examination and Nutrition Survey 2005-2006 and 2013-2014 was used. Multiple linear and logistic regression modeling were performed to analyze the associations of individual mVOC with bone health indicators. The least absolute shrinkage and selection operator (LASSO) regression was adopted to select mVOCs that were more relevant to bone health indicators for further weight quantile sum (WQS) analysis used for analyzing the associations between multiple VOC co-exposure and bone health indicators. Mediation analysis was used to identify potential mediators. Seventeen mVOC members with detection rate of >50% in urine of all 3478 participants aged ≥20 years (1829 females) were involved. Levels of most mVOCs were higher in women than men. Eight mVOCs were negatively associated with BMDs, and two and four mVOCs were positively associated with OP and fracture risks, respectively. WQS regression revealed decreased femoral neck BMD (β = -0.010 g/cm², 95% CI: -0.020, -0.0001) and total spine BMD (β = -0.015 g/cm², 95% CI: -0.028, -0.002) in response to increasing mVOC mixture levels. And alkaline phosphatase (ALP), body mass index (BMI), fasting insulin (FI) and high-density lipoprotein (HDL), were mediators in the associations with proportions of mediating effect ranging from 4.6% to 10.2%. Individual and combined VOC (co-)exposure were associated with reduced BMDs in American adults. ALP, BMI, FI and HDL were demonstrated to be mediators in the association of multiple VOC co-exposure with BMD.

Protective effect of Moringa oleifera Lam. leaf extract against oxidative stress, inflammation, depression, and apoptosis in a mouse model of hepatic encephalopathy

The present study aimed to assess the antioxidative, anti-inflammatory, antiapoptotic, and anti-depression impacts of Moringa oleifera Lam. leaf ethanolic extract (MOLE) in the hippocampus and cerebral cortex of CCl4-induced hepatic encephalopathy mouse model. High-performance liquid chromatography was used to detect marker compounds: rutin and β-sitosterol. Animals were divided into four groups: vehicle group, CCl4-treated group, MOLE-treated group, and (CCl4 + MOLE) group treated with MOLE for 14 days before CCl4-induced neurotoxicity. MOLE decreased alanine aminotransferase, aspartate aminotransferase, corticosterone, and ammonia levels in serum and improved the antioxidant status of CCl4-treated mice in the hippocampus and cerebral cortex. It reduced the expression of toll-like receptor 4 (TLR4), TLR2, myeloid differentiation primary response 88 (MYD88), and nuclear factor-kappa B (NF-κB) genes and the protein levels of the pro-inflammatory cytokines. MOLE also attenuated apoptosis, as revealed by the reduced expression of caspase3, and prevented histological deterioration. Furthermore, MOLE attenuated CCl4-induced anxiety and depression-like behavioral changes. Collectively, MOLE modulates neuroinflammation, oxidative stress, TLR4/2-MyD88/NF-κB signaling, and apoptosis in the hippocampus and cerebral cortex of the hepatic encephalopathy experimental model.

Environmental Toxicants and NAFLD: A Neglected yet Significant Relationship

The liver is an organ of vital importance in the body; it is the center of metabolic activities and acts as the primary line of defense against toxic compounds. Exposure to environmental toxicants is an unavoidable fallout from rapid industrialization across the world and is even higher in developing countries. Technological development and industrialization have led to the release of toxicants such as pollutant toxic gases, chemical discharge, industrial effluents, pesticides and solvents, into the environment. In the last few years, a growing body of evidence has shed light on the potential impact of environmental toxicants on liver health, in particular, on non-alcoholic fatty liver disease (NAFLD) incidence and progression. NAFLD is a multifactorial disease linked to metabolic derangement including diabetes and other complications. Environmental toxicants including xenobiotics and pollutants may have a direct or indirect steatogenic/fibrogenic impact on the liver and should be considered as risk factors associated with NAFLD. This review discusses the contribution of environmental toxicants toward the increasing disease burden of NAFLD.

Assessing volatile organic compounds exposure and prostate-specific antigen: National Health and Nutrition Examination Survey, 2001-2010

Background

Volatile organic compounds (VOCs) are a large group of chemicals widely used in people's daily routines. Increasing evidence revealed the VOCs' accumulating toxicity. However, the VOCs toxicity in male prostate has not been reported previously. Thus, we comprehensively evaluated the association between VOCs and prostate-specific antigen (PSA).

Methods

A total of 2016 subjects were included in our study from the National Health and Nutrition Examination Survey with VOCs, PSA, and other variables among U.S. average population. We constructed XGBoost Algorithm Model, Regression Model, and Generalized linear Model (GAM) to analyze the potential association. Stratified analysis was used to identify high-risk populations.

Results

XGBoost Algorithm model identified blood chloroform as the most critical variable in the PSA concentration. Regression analysis suggested that blood chloroform was a positive association with PSA, which showed that environmental chloroform exposure is an independent risk factor that may cause prostate gland changes [β, (95% CI), P = 0.007, (0.003, 0.011), 0.00019]. GAM observed the linear relationship between blood chloroform and PSA concentration. Meanwhile, blood chloroform linear correlated with water chloroform in the lower dose range, indicating that the absorption of water may be the primary origin of chloroform. Stratified associations analysis identified the high-risk group on the chloroform exposures.

Conclusion

This study revealed that blood chloroform was positively and independently associated with total PSA level, suggesting that long-term environmental chloroform exposure may cause changes in the prostate gland.

The effects of chemical mixtures on lipid profiles in the Korean adult population: threshold and molecular mechanisms for dyslipidemia involved

A scarcity of research assesses the effects of exposure to a combination of chemicals on lipid profiles as well as molecular mechanisms related to dyslipidemia. A cross-sectional study of 3692 adults aims to identify the association between chemical mixtures, including blood and urine 26 chemicals, and lipid profiles among Korean adults (aged ≥ 18) using linear regression models, weighted quantile sum (WQS) regression, quantile g-computation (qgcomp), and Bayesian kernel machine regression (BKMR). In silico toxicogenomic data-mining, we assessed molecular mechanisms linked with dyslipidemia, including genes, miRNAs, pathways, biological processes, and diseases. In the linear regression models, heavy metals, volatile organic compound metabolites, and phthalate metabolites were found to be related to HDL-C, triglycerides, LDL-C, total lipids, and total cholesterol, and significant trends were observed for these chemical quartiles (p < 0.01). The WQS index was significantly linked with HDL-C, triglycerides, LDL-C, total cholesterol, and total lipids. The qgcomp index also found a significant association between chemicals and HDL-C, triglycerides, and total lipids. In BKMR analysis, the overall effect of the chemical mixture was significantly associated with HDL-C, triglycerides, total cholesterol, and total lipids. We found that mixed chemicals interacted with the PPARA gene and were linked with dyslipidemia. Several pathways ("SREBF and miR33 in cholesterol," "estrogen receptor pathway and lipid homeostasis," and "regulation of PGC-1α"), "negative regulation of hepatocyte apoptotic process," "negative regulation of sequestering of triglycerides," "regulation of hepatocyte apoptotic process," and "negative regulation of cholesterol storage," and "abdominal obesity metabolic syndrome" were identified as key molecular mechanisms that may be affected by mixed chemicals and implicated in the development of dyslipidemia. The highest interaction and expression of miRNAs involved in the process of dyslipidemia were also described. Especially, the cutoff levels for chemical exposure levels related to lipid profiles were also provided.

Adsorptive removal of some Cl-VOC's as dangerous environmental pollutants using feather-like γ-Al2O3 derived from aluminium waste with life cycle analysis

Herein, we designed a cost-effective preparation method of nanocomposite γ-Al₂O₃ derived from Al-waste. The produced material has a feather-like morphology, and its adsorption of some chlorinated volatile organic compounds (Cl-VOC's) such as benzyl chloride, chloroform and carbon tetrachloride (C₇H₇Cl, CHCl₃ and CCl₄) was investigated due to their potential carcinogenic effect on humans. It showed a characteristic efficiency towards the adsorptive removal of these compounds over a long period, i.e., eight continuous weeks, at ambient temperature and atmospheric pressure. After 8-weeks, the adsorbed amounts of these compounds were determined as: 325.3 mg C₇H₇Cl, 247.6 mg CHCl₃ and 253.3 mg CCl₄ per g of γ-Al₂O_3, respectively. CCl₄ was also found to be dissociatively adsorbed on the surface of γ-Al₂O₃, whereas CHCl₃ and C₇H₇Cl were found to be associatively adsorbed. The prepared γ-Al₂O₃ has a relatively high surface area (i.e., 192.2 m². g^-1) and mesoporosity with different pore diameters in the range of 25-47 Å. Furthermore, environmental impacts of the nanocomposite γ-Al₂O₃ preparation were evaluated using life cycle assessment. For prepartion of adsorbent utilising 1 kg of scrap aluminium wire, it was observed that potential energy demand was 288 MJ, climate change potential was 19 kg CO₂ equivalent, acidification potential was 0.115 kg SO₂ equivalent and eutrophication potential was 0.018 kg PO₄^3- equivalent.

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.

Airborne fine particulate matter in Japan induces lipid synthesis and inhibits autophagy in HepG2 cells

Inhalation of particulate matter with a diameter less than 2.5 µm has been reported to exacerbates fatty liver disease. However, the components and mechanisms of particulate matter involved in hepatic lipid metabolism and autophagy have not been fully elucidated. We found that atmospheric particulate matter in Japan stimulated lipogenesis in hepatocytes even when its lipid component was removed. Furthermore, we demonstrated that particulate matter did not promote autophagosome formation but inhibited autophagic degradation in hepatocytes. In previous toxicity experiments, particulate matter collected from atmosphere often contained contaminants originating from filters. In this study, we exposed the powdery particulate matter with less contaminants collected using a cyclone and impactor system to HepG2 cells, human hepatocyte. This particulate matter induced lipogenesis and endoplasmic reticulum stress in HepG2 cells as well as previous reports of particulate matter in the USA and China. On the other hand, when autophagic flux were examined in detail, the particulate matter did not promote autophagosome formation, but inhibited autophagic degradation. Since these effects were similar to those of palmitate, a fatty acid, we prepared particulate matter in which lipid component was removed by acetone and compared the effects on HepG2 cells with those of untreated one. The particulate matter without lipid component induced lipid droplets as well as did the untreated one although it induced less endoplasmic reticulum stress. These results suggest that hepatic lipid synthesis is stimulated not only by the uptake of lipid but also by other components in the particulate matter.

Environmental exposure as a risk-modifying factor in liver diseases: Knowns and unknowns

Liver diseases are considered to predominantly possess an inherited or xenobiotic etiology. However, inheritance drives the ability to appropriately adapt to environmental stressors, and disease is the culmination of a maladaptive response. Thus “pure” genetic and “pure” xenobiotic liver diseases are modified by each other and other factors, identified or unknown. The purpose of this review is to highlight the knowledgebase of environmental exposure as a potential risk modifying agent for the development of liver disease by other causes. This exercise is not to argue that all liver diseases have an environmental component, but to challenge the assumption that the current state of our knowledge is sufficient in all cases to conclusively dismiss this as a possibility. This review also discusses key new tools and approaches that will likely be critical to address this question in the future. Taken together, identifying the key gaps in our understanding is critical for the field to move forward, or at the very least to “know what we don't know.”

Environmental toxicant-induced maladaptive mitochondrial changes: A potential unifying mechanism in fatty liver disease?

Occupational and environmental exposures to industrial chemicals are well known to cause hepatotoxicity and liver injury. However, despite extensive evidence showing that exposure can lead to disease, current research approaches and regulatory policies fail to address the possibility that subtle changes caused by low level exposure to chemicals may also enhance preexisting conditions. In recent years, the conceptual understanding of the contribution of environmental chemicals to liver disease has progressed significantly. Mitochondria are often target of toxicity of environmental toxicants resulting in multisystem disorders involving different cells, tissues, and organs. Here, we review persistent maladaptive changes to mitochondria in response to environmental toxicant exposure as a mechanism of hepatotoxicity. With better understanding of the mechanism(s) and risk factors that mediate the initiation and progression of toxicant-induced liver disease, rational targeted therapy can be developed to better predict risk, as well as to treat or prevent this disease.

Inhalation exposure to 2-ethyl-1-hexanol causes hepatomegaly and transient lipid accumulation without induction of peroxisome proliferator-activated receptor alpha in mice

2-Ethyl-1-hexanol (2EH) is a volatile organic compound known to cause sick building syndrome. However, 2EH-induced hepatotoxicity has been mainly evaluated in experiments orally administering 2EH as a metabolite of di(2-ethylhexyl) phthalate. To evaluate the hepatotoxicity risk of 2EH as an indoor air pollutant, we exposed 10-wk-old male ICR mice to 2EH by inhalation for 8 h/d, 5 d/wk for 3 months (0, 20, 60, or 150 ppm) or 6 months (0, 0.5, 10, or 100 ppm). In both experiments, relative liver weights significantly increased in the highest exposure groups. The 3-month exposure increased histopathological lipid droplets in the liver in a dose-dependent manner, hepatic triglyceride at all exposure levels, hepatic phospholipid at 150 ppm, and microsomal triglyceride transfer protein at 60 and 150 ppm; however, these changes were not observed following the 6-month of exposure. Following the 3-month exposure, alanine transaminase and peroxisomal bifunctional proteins, known markers of liver injury and peroxisome proliferation, respectively, remained unaltered. Therefore, in the present study, the inhalation concentration range of 2EH induced a toxic hypertrophic change, revealing a limited role of peroxisome proliferator-activated receptor alpha (PPARα). The liver weights may have presumably increased via a mechanism independent of PPARα activation.

Joint effects of ethnic enclave residence and ambient volatile organic compounds exposure on risk of gestational diabetes mellitus among Asian/Pacific Islander women in the United States

BACKGROUND

Asian/Pacific Islander (API) communities in the United States often reside in metropolitan areas with distinct social and environmental attributes. Residence in an ethnic enclave, a socially distinct area, is associated with lower gestational diabetes mellitus (GDM) risk, yet exposure to high levels of air pollution, including volatile organic compounds (VOCS), is associated with increased GDM risk. We examined the joint effects of ethnic enclaves and VOCs to better understand GDM risk among API women, the group with the highest prevalence of GDM.

METHODS

We examined 9069 API births in the Consortium on Safe Labor (19 hospitals, 2002-2008). API ethnic enclaves were defined as areas ≥66th percentile for percent API residents, dissimilarity (geographic dispersal of API and White residents), and isolation (degree that API individuals interact with another API individual). High levels of 14 volatile organic compounds (VOC) were defined as ≥75th percentile. Four joint categories were created for each VOC: Low VOC/Enclave (reference group), Low VOC/No Enclave, High VOC/Enclave, High VOC/No Enclave. GDM was reported in medical records. Hierarchical logistic regression estimated odds ratios (OR) and 95% confidence intervals (95%CI) between joint exposures and GDM, adjusted for maternal factors and area-level poverty. Risk was estimated for 3-months preconception and first trimester exposures.

RESULTS

Enclave residence was associated with lower GDM risk regardless of VOC exposure. Preconception benzene exposure was associated with increased risk when women resided outside enclaves [High VOC/No Enclave (OR:3.45, 95%CI:1.77,6.72)], and the effect was somewhat mitigated within enclaves, [High VOC/Enclave (OR:2.07, 95%:1.09,3.94)]. Risks were similar for 12 of 14 VOCs during preconception and 10 of 14 during the first trimester.

CONCLUSIONS

API residence in non-enclave areas is associated with higher GDM risk, regardless of VOC level. Ethnic enclave residence may mitigate effects of VOC exposure, perhaps due to lower stress levels. The potential benefit of ethnic enclaves warrants further study.

Liver function alterations among workers in the shoe industry due to combined low-level exposure to organic solvents

This study aimed to investigate the potential hepatotoxicity, nephrotoxic, and hematotoxic effects of simultaneous occupational low-level exposure of shoe workers to a mixture of organic solvents. The study included 16 male and 55 female workers and non-exposed subjects (n = 60) in the control group. Along with a standard sets of hematological, liver enzymes (aspartate aminotransferase (AST), alanine aminotransferase (ALT) and gamma-glutamyl transpeptidase (GGT), bilirubin total, bilirubin direct, blood glucose, urea, and creatinine were analyzed in all participants. Indoor air quality was monitored using a Gasmet Dx - 4000 multi-component analyzer. Despite the concentration levels of individual chemicals in shoe production units were below the permissible limits, the equivalent exposure (Em) values calculated based on the American Conference of Governmental Industrial Hygienists (ACGIH) and National Institute of Occupational Safety and Health (NIOSH) occupational exposure limits were higher than 1. Statistically significant increase of biochemical parameters (aspartate aminotransferase (AST), gamma-glutamyl transpeptidase (GGT), total bilirubin, and direct bilirubin) was obtained in exposed workers of both genders compared with controls (p < 0.001). Calculated liver damage risk scores were significantly higher in both females and males compared with controls (p < 0.001). The multivariate logistic regression analysis showed that direct bilirubin was the most important predictor of organic solvent mixture exposure in the studied group of workers. These results suggest that combined exposure to organic solvents even at low concentrations may lead to hepatotoxicity.

Associations between blood volatile organic compounds, and changes in hematologic and biochemical profiles, in a population-based study

OBJECTIVE

To investigate the influence of volatile organic compound (VOC) levels in blood, on hematological and serum biochemical parameters in the Canadian population.

METHODS

We tested the association between seven selected VOCs and hematological profiles and serum tests reflecting liver and kidney function and glucose metabolism using a cross-sectional study design in 3950 participants of the Canadian Health Measures Survey from 2012 to 2015. We used generalized linear mixed models adjusting for age, sex, smoking, alcohol consumption, BMI, education and household income.

RESULTS

An increase in blood concentration equivalent to the geometric mean for benzene, ethylbenzene, toluene, m-, p-xylenes, styrene, and total xylenes was associated with 0.68% (95% CI 0.36, 1.0) to 0.91% (95% CI 0.52, 1.3) increase in hemoglobin, and a 1.79% (95% CI 0.96, 2.62) to 4.11% (95% CI 3.11, 5.11) increase in total white blood cell count. Ethylbenzene, toluene, m-, p-xylenes and styrene were positively associated with increased platelet counts. A geometric mean increase for all VOCs was associated with decreases in creatinine. m- and p-xylenes were associated with a significant change in every measured blood cell count and liver function parameter, and in creatinine. Ethylbenzene was also positively associated with an increase in every measured hematologic parameter, two of the three liver function tests, and creatinine. Results were similar when stratified by age, but differed by smoking status and sex.

CONCLUSIONS

This study provides evidence that VOCs in blood, at levels found in the Canadian population, may influence blood cell counts and indicators of liver and kidney function, including an inverse association between serum VOC and creatinine. This novel finding merits further investigation to understand the impact of VOCs on human physiology and population health.

Adipose tissue-liver crosstalk during pathologic changes caused by vinyl chloride metabolites in mice

Volatile organic compounds (VOCs), such as vinyl chloride (VC), can be directly toxic at high concentrations. However, we have shown that 'nontoxic' exposures to VC and its metabolite chloroethanol (CE) enhances experimental non-alcoholic fatty liver disease (NAFLD), suggesting an unpredicted interaction. Importantly, VOC exposure has been identified as a potential risk factor for the development of obesity and its sequelae in humans. As there is a known axis between adipose and hepatic tissue in NAFLD, the impact of CE on white adipose tissue (WAT) inflammation and lipolysis was investigated. Mice were administered CE (or vehicle) once, after 10 weeks of being fed high-fat or low-fat diet (LFD). CE significantly enhanced hepatic steatosis and inflammation caused by HFD. HFD significantly increased the size of epididymal fat pads, which was enhanced by CE. The relative size of adipocyte lipid droplets increased by HFD + CE, which was also correlated with increased expression of lipid-associated proteins (e.g., PLINs). CE also enhanced HFD-induced indices of WAT inflammation, and ER stress. Hepatic-derived circulating FGF21, a major modulator of WAT lipolysis, which is hypothesized to thereby regulate hepatic steatosis, was significantly increased by CE in animals fed HFD. Taken together these data support the hypothesis that environmental toxicant exposure can exacerbate the severity of NAFLD/NASH, involving the liver-adipose axis in this process. Specifically, CE enhances local inflammation and alters lipid metabolism and WAT-mediated hepatic steatosis due to changes in WAT lipolysis.

Blood BTEXS and heavy metal levels are associated with liver injury and systemic inflammation in Gulf states residents

INTRODUCTION

Exposures to volatile organic compounds and metals have previously been associated with liver diseases including steatohepatitis, although more data are needed. Benzene, toluene, ethylbenzene, xylenes, styrene (BTEXS) and metals were measured in blood samples collected between May 2012-July 2013 from volunteers participating in home visits for the Gulf Long-term Follow-up (GuLF) Study. This cross-sectional analysis evaluates associations of exposure biomarkers with serum liver injury and adipocytokine biomarkers in a sample of 214 men.

METHODS

Adult nonsmoking men without a history of liver disease or heavy alcohol consumption were included. The serologic disease biomarkers evaluated were the hepatocellular injury biomarker, cytokeratin 18 [whole (CK18 M65) and caspase-cleaved fragment (CK18 M30)]; and adipocytokines. Confounder-adjusted beta coefficients were determined using linear regression models for the overall sample (primary endpoints) and for obesity-classified sub-groups (secondary endpoints). A product interaction term between the exposure of interest and a dichotomized indicator of obesity was included to determine the disease modifying effects of obesity on the biomarker associations.

RESULTS

The study sample was 57% white and 51% obese. In the overall sample, lead was positively associated with CK18 M30 (β = 21.7 ± 6.0 (SE), p = 0.0004); IL-1β (β = 32.8 ± 5.2, p < 0.0001); IL-6 (β = 72.8 ± 18.3, p = 0.0001); and IL-8 (β = 140.8 ± 42.2, p = 0.001). Cadmium exposures were associated with increased IL-1β (β = 77.8 ± 26.3, p = 0.003) and IL-8 (β = 419.5 ± 201.2, p = 0.04). There were multiple significant interactions between obesity and exposure to lead, cadmium, benzene and toluene in relation to outcome biomarkers. Among obese participants (n = 108), benzene, lead, and cadmium were each positively associated with CK18 M30, IL-1β, IL-6, and IL-8. In obese subjects, lead was also inversely associated with leptin, and toluene was positively associated with IL-1β.

CONCLUSION

For the overall sample, heavy metal exposures were associated with liver injury (lead only) and/or systemic inflammation (lead and cadmium). Obesity modified the associations between BTEXS and heavy metal exposures on several of the outcome variables. In the obesity subgroup, liver injury was positively associated with lead, cadmium and benzene exposures; systemic inflammation was increased with lead, cadmium, benzene, and toluene exposures; and leptin was inversely associated with lead exposures. The cross-sectional design of this study makes it difficult to determine causality, and all results should be interpreted cautiously. Nonetheless, the potential impact of exposures to lead, cadmium, benzene and toluene in steatohepatitis, an obesity-associated inflammatory liver disease, warrants further investigation.

Hepatic Injury Caused by the Environmental Toxicant Vinyl Chloride is Sex-Dependent in Mice

Vinyl chloride (VC), a common industrial chemical, has been associated with hemangiosarcoma and toxicant-associated steatohepatitis (TASH) in men working at rubber-production plants. Our group previously demonstrated that chronic VC inhalation at environmentally relevant levels (< 1 ppm) in male mice exacerbated hepatic injury caused by high-fat diet (HFD) feeding. Because VC studies on TASH have only been performed in male models, the objective of this study is to examine VC inhalation in female mice in the context of TASH mechanisms. Male and female C57Bl/6 mice were fed either a low-fat diet or HFD and exposed to VC or room air using an inhalation chamber, for 12 weeks (6 h, 5 days/week); and plasma and liver samples were collected after euthanasia. Compared with males, females were less susceptible to HFD+VC-induced obesogenic effects demonstrated by lower body weight and fat composition. Histological analysis revealed that whereas VC exacerbated HFD-induced steatosis in males, this effect was absent in females. In addition, females were more resistant to VC-induced hepatic inflammation whereas males had increased liver weights and higher hepatic Tnfα mRNA levels. Systemic markers of hepatic injury, namely alanine aminotransaminase and thrombin/antithrombin levels were increased by HFD+VC co-exposures only in males. In addition, females did not show significant cell death as previously reported in males. Taken together, the results suggested that VC inhalation led to sex-dependent liver and metabolic toxicity. This study implicated the importance of assessing sex differences in environmental basic science and epidemiologic studies to better identify at-risk populations in both men and women.

Vinyl Chloride and High-Fat Diet as a Model of Environment and Obesity Interaction

Vinyl chloride (VC), an abundant environmental contaminant, causes steatohepatitis at high levels, but is considered safe at lower levels. Although several studies have investigated the role of VC as a direct hepatotoxicant, the concept that VC modifies sensitivity of the liver to other factors, such as nonalcoholic fatty liver disease (NAFLD) caused by high-fat diet (HFD) is novel. This protocol describes an exposure paradigm to evaluate the effects of chronic, low-level exposure to VC. Mice are acclimated to low-fat or high-fat diet one week prior to the beginning of the inhalation exposure and remain on these diets throughout the experiment. Mice are exposed to VC (sub-OSHA level: <1 ppm) or room air in inhalation chambers for 6 hours/day, 5 days/week, for up to 12 weeks. Animals are monitored weekly for body weight gain and food consumption. This model of VC exposure causes no overt liver injury with VC inhalation alone. However, the combination of VC and HFD significantly enhances liver disease. A technical advantage of this co-exposure model is the whole-body exposure, without restraint. Moreover, the conditions more closely resemble a very common human situation of a combined exposure to VC with underlying nonalcoholic fatty liver disease and therefore support the novel hypothesis that VC is an environmental risk factor for the development of liver damage as a complication of obesity (i.e., NAFLD). This work challenges the paradigm that the current exposure limits of VC (occupational and environmental) are safe. The use of this model can shed new light and concern on the risks of VC exposure. This model of toxicant-induced liver injury can be used for other volatile organic compounds and to study other interactions that may impact the liver and other organ systems.

Outcomes and Toxicology of Herbal Drugs in Alcoholic Hepatitis - A Single Center Experience from India

Background and Aims: We aimed to study clinical outcomes and liver biopsy features of alcoholic hepatitis (AH) patients on complementary and alternative medicines (CAMs) and to analyze the retrieved drugs for chemical and toxic components linked to drug-induced liver injury. Methods: We retrospectively assessed clinical, biochemical and liver biopsy features of AH patients on CAM with drug-induced liver injury (AH-CAM, n = 27) and compared them to a control group (classical AH, n = 29) on standard of care. Patients without liver biopsy evaluation and other causes for liver disease were excluded. Samples of the CAMs (n = 42) from patients were retrieved and assessed for chemical and toxins. Results: All were males, and significantly worse clinical presentation, biochemical severity, and liver disease scores were notable in patients with AH-CAM. Traditional Ayurvedic-polyherbal formulations were the most commonly used CAM. On liver histology, varying grades of severe-necrosis, severe hepatocellular, canalicular, cholangiolar cholestasis with predominant lymphocytic-portal-inflammation and varying grades of interface-hepatitis were noted in AH-CAM. Analysis of CAMs revealed presence of heavy metals up to 100,000 times above detectable range and adulterants, such as antibiotics, chemotherapy agents, nonsteroidal anti-inflammatory drugs, alcohols, antidepressants, anxiolytics, and recreational drugs. On follow up, a significantly higher number of patients with AH on CAM died at end of 1, 3- and-6-months compared to controls (37% vs. 83%, 29% vs. 62%, 18% vs. 52% respectively; p < 0.001). Conclusions: Patients with AH and CAM-related drug-induced liver injury have extremely poor short-term survival in the absence of liver transplantation compared to those patients with AH on evidence-based management. Early transplant referral and educating on and curbing of CAM use in severe liver disease through strict monitoring of unregulated traditional health practices can help ease the burden of liver-related death.

Rapamycin attenuates liver injury caused by vinyl chloride metabolite chloroethanol and lipopolysaccharide in mice

Vinyl chloride (VC) is a prevalent environmental toxicant that is rapidly metabolized within the liver. Its metabolites have been shown to directly cause hepatic injury at high exposure levels. We have previously reported that VC metabolite, chloroethanol (CE), potentiates liver injury caused by lipopolysaccharide (LPS). Importantly, that study showed that CE alone, while not causing damage per se, was sufficient to alter hepatic metabolism and increase mTOR phosphorylation in mice, suggesting a possible role for the mTOR pathway. Here, we explored the effect of an mTOR inhibitor, rapamycin, in this model. C57BL/6 J mice were administered CE, followed by rapamycin 1 h and LPS 24 h later. As observed previously, the combination of CE and LPS significantly enhanced liver injury, inflammation, oxidative stress, and metabolic dysregulation. Rapamycin attenuated not only inflammation, but also restored the metabolic phenotype and protected against CE + LPS-induced oxidative stress. Importantly, rapamycin protected against mitochondrial damage and subsequent production of reactive oxygen species (ROS). The protective effect on mitochondrial function by rapamycin was mediated, by restoring the integrity of the electron transport chain at least in part, by blunting the deactivation of mitochondrial c-src, which is involved mitochondrial ROS production by electron transport chain leakage. Taken together, these results further demonstrate a significant role of mTOR-mediated pathways in VC-metabolite induced liver injury and provide further insight into VC-associated hepatic damage. As mTOR mediated pathways are very complex and rapamycin is a more global inhibitor, more specific mTOR (i.e. mTORC1) inhibitors should be considered in future studies.

In vitro profiling of endothelial volatile organic compounds under resting and pro-inflammatory conditions

INTRODUCTION

The evaluation of volatile organic compounds(VOCs) emitted by human body offers a unique tool to set up new non-invasive devices for early diagnosis and long-lasting monitoring of most human diseases. However, their cellular origin and metabolic fate have not been completely elucidated yet, thus limiting their clinical application. Endothelium acts as an interface between blood and surrounding tissues. As such, it adapts its physiology in response to different environmental modifications thus playing a role in the pathogenesis of many metabolic and inflammatory diseases.

OBJECTIVES

Since endothelium specifically reshapes its physiologic functions upon environmental changes the objective of this study was to evaluate if and how pro-inflammatory stimuli affect VOC metabolism in endothelial cell in culture.

METHODS

Gas chromatography with mass spectrometric detection was applied to profile VOCs in the headspace of cultured endothelial cells (EC) in the absence or presence of the pro-inflammatory stimulus lipopolysaccharide (LPS).

RESULTS

We observed that, under resting conditions, EC affected the amount of 58 VOCs belonging to aldehyde, alkane and ketone families. Among these, LPS significantly altered the amount of 15 VOCs. ROC curves show a perfect performance (AUC = 1) for 10 metabolites including 1-butanol, 3-methyl-1-butanol and 2-ethyl-1-hexanol.

DISCUSSION

The emission and uptake of the aforementioned VOCs disclose potential unexplored metabolic pathways for EC that deserve to be investigated. Overall, we identified new candidate VOC potentially exploitable, upon experimental confirm in in vivo model of disease, as potential biomarkers of sepsis and pro-inflammatory clinical settings.

Vinyl chloride-induced interaction of nonalcoholic and toxicant-associated steatohepatitis: Protection by the ALDH2 activator Alda-1

Vinyl chloride (VC), an abundant environmental contaminant causes steatohepatitis at high levels, but is considered safe at lower (i.e., sub-OSHA) levels. However, we have previously shown that even lower VC levels exacerbate experimental nonalcoholic fatty liver disease (NAFLD) caused by high-fat diet (HFD). Mitochondrial oxidative injury and subsequent metabolic dysfunction appeared to play key roles in mediating this interaction. Mitochondrial aldehyde dehydrogenase 2 (ALDH2) serves as a key line of defense against endogenous and exogenous reactive aldehydes. The current study therefore tests the hypothesis that allosteric activation of ALDH2 with Alda-1 will protect against VC-enhanced NAFLD. Mice were exposed to low VC concentrations (<1 ppm), or room air for 6 h/day, 5 days/week for 12 weeks, while on HFD or low-fat control diet (LFD). Some mice received Alda-1 (20 mg/kg i.p., 3 × /week) for the last 3 weeks of diet/VC exposure. Indices of liver injury, oxidative stress, metabolic and mitochondrial (dys)function were measured. As observed previously, low-dose VC did not cause liver injury in control mice; while liver injury caused by HFD was enhanced by VC. VC decreased hepatic ALDH2 activity of mice fed HFD. Alda-1 attenuated oxidative stress, liver injury, and dysmetabolism in mice exposed to HFD+VC under these conditions. Importantly, alterations in mitochondrial function caused by VC and HFD were diminished by Alda-1. Previous studies have indicated that liver injury caused by HFD is mediated, at least in part, by enhanced mitochondrial autophagy (mitophagy). Here, Alda-1 suppressed PINK1/PARKIN-mediated mitophagy. Taken together, these results support the hypothesis that ALDH2 is a critical defense against mitochondrial injury caused by VC in experimental NAFLD. The ALDH2 activator Alda-1 conferred protection against liver damage under these conditions, most likely via increasing clearance of aldehydes and preserving mitochondrial respiratory function.

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VC, combined with HFD impairs ALDH2 function, causing an accumulation of endogenous aldehydes and oxidative stress in vivo.

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VC metabolite chloroacetaldehyde directly blocks ALDH2 activity in vitro.

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Alda-1 treatment reverses pre-established liver injury, oxidative stress and metabolic dysregulation caused by VC and HFD.

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Alda-1 increases overall autophagy caused by VC+HFD, but decreases mitophagy, likely to preserve mitochondrial function.

Noninvasive evaluation of nonalcoholic fatty liver disease: Current evidence and practice

With the increasing number of individuals with diabetes and obesity, nonalcoholic fatty liver disease (NAFLD) is becoming increasingly prevalent, affecting one-quarter of adults worldwide. The spectrum of NAFLD ranges from simple steatosis or nonalcoholic fatty liver (NAFL) to nonalcoholic steatohepatitis (NASH). NAFLD, especially NASH, may progress to fibrosis, leading to cirrhosis and hepatocellular carcinoma. NAFLD can impose a severe economic burden, and patients with NAFLD-related terminal or deteriorative liver diseases have become one of the main groups receiving liver transplantation. The increasing prevalence of NAFLD and the severe outcomes of NASH make it necessary to use effective methods to identify NAFLD. Although recognized as the gold standard, biopsy is limited by its sampling bias, poor acceptability, and severe complications, such as mortality, bleeding, and pain. Therefore, noninvasive methods are urgently needed to avoid biopsy for diagnosing NAFLD. This review discusses the current noninvasive methods for assessing NAFLD, including steatosis, NASH, and NAFLD-related fibrosis, and explores the advantages and disadvantages of measurement tools. In addition, we analyze potential noninvasive biomarkers for tracking disease processes and monitoring treatment effects, and explore effective algorithms consisting of imaging and nonimaging biomarkers for diagnosing advanced fibrosis and reducing unnecessary biopsies in clinical practice.

Proteomic Analysis Reveals Novel Mechanisms by Which Polychlorinated Biphenyls Compromise the Liver Promoting Diet-Induced Steatohepatitis

Environmental pollution contributes to fatty liver disease pathogenesis. Polychlorinated biphenyl (PCB) exposures have been associated with liver enzyme elevation and suspected steatohepatitis in cohort studies. Male mice treated with the commercial PCB mixture, Aroclor 1260 (20 mg/kg), and fed high fat diet (HFD) for 12 weeks developed steatohepatitis. Receptor-based modes of action including inhibition of the epidermal growth factor (EGF) receptor were previously proposed, but other mechanisms likely exist. Objectives were to identify and validate the pathways, transcription factors, and mechanisms responsible for the steatohepatitis associated with PCB and HFD coexposures. Comparative proteomics analysis was performed in archived mouse liver samples from the aforementioned chronic exposure study. Pathway and transcription factor analysis (TFA) was performed, and selected results were validated. Liver proteomics detected 1103 unique proteins. Aroclor 1260 upregulated 154 and downregulated 93 of these. Aroclor 1260 + HFD coexposures affected 55 pathways including glutathione metabolism, intermediary metabolism, and cytoskeletal remodeling. TFA of Aroclor 1260 treatment demonstrated alterations in the function of 42 transcription factors including downregulation of NRF2 and key nuclear receptors previously demonstrated to protect against steatohepatitis (e.g., HNF4α, FXR, PPARα/δ/γ, etc.). Validation studies demonstrated that Aroclor 1260 significantly reduced HNF4α protein levels, while Aroclor 1260 + HFD reduced expression of the HNF4α target gene, albumin, in vivo. Aroclor 1260 attenuated EGF-dependent HNF4α phosphorylation and target gene activation in vitro. Aroclor 1260 reduced levels of NRF2, its target genes, and glutathione in vivo. Aroclor 1260 attenuated EGF-dependent NRF2 upregulation, in vitro. Aroclor 1260 indirectly activated hepatic stellate cells in vitro via induction of hepatocyte-derived TGFβ. PCB exposures adversely impacted transcription factors regulating liver protection, function, and fibrosis. PCBs, thus, compromised the liver by reducing its protective responses against nutritional stress to promote diet-induced steatohepatitis. The identified mechanisms by which environmental pollutants influence fatty liver disease pathogenesis require confirmation in humans.