Pilot Metabolome-Wide Association Study of Benzo(a)pyrene in Serum From Military Personnel

B(a)P induces ovarian granulosa cell apoptosis via TRAF2-NFκB-Caspase1 axis during early pregnancy

Benzo(a)pyrene [B(a)P] is an environmental endocrine disruptor with reproductive toxicity. The corpus luteum (CL) of the ovary plays an important role in embryo implantation and pregnancy maintenance. Our previous studies have shown that B(a)P exposure affects embryo implantation and endometrial decidualization in mouse, but its effects and mechanisms on CL function remain unclear. In this study, we explore the mechanism of ovarian toxicity of B(a)P using a pregnant mouse model and an in vitro model of human ovarian granulosa cells (GCs) KGN. Pregnant mice were gavaged with corn oil or 0.2 mg/kg.bw B(a)P from pregnant day 1 (D1) to D7, while KGN cells were treated with DMSO, 1.0IU/mL hCG, or 1.0IU/mL hCG plus benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE), a B(a)P metabolite. Our findings revealed that B(a)P exposure damaged embryo implantation and reduced estrogen and progesterone levels in early pregnant mice. Additionally, in vitro, BPDE impaired luteinization in KGN cells. We observed that B(a)P/BPDE promoted oxidative stress (OS) and inflammation, leading to apoptosis rather than pyroptosis in ovaries and luteinized KGN cells. This apoptotic response was mediated by the activation of inflammatory Caspase1 through the cleavage of BID. Furthermore, B(a)P/BPDE inhibited TRAF2 expression and suppressed NFκB signaling pathway activation. The administration of VX-765 to inhibit the Caspase1 activation, over-expression of TRAF2 using TRAF2-pcDNA3.1 (+) plasmid, and BetA-induced activation of NFκB signaling pathway successfully alleviated BPDE-induced apoptosis and cellular dysfunction in luteinized KGN cells. These findings were further confirmed in the KGN cell treated with H2O2 and NAC. In conclusion, this study elucidated that B(a)P/BPDE induces apoptosis rather than pyroptosis in GCs via TRAF2-NFκB-Caspase1 during early pregnancy, and highlighting OS as the primary contributor to B(a)P/BPDE-induced ovarian toxicity. Our results unveil a novel role of TRAF2-NFκB-Caspase1 in B(a)P-induced apoptosis and broaden the understanding of mechanisms underlying unexplained luteal phase deficiency.

Prolonged exposure of environmental concentration benzo[a]pyrene promoted cancer stemness through AhR/PKA/SOX2 dependent pathway in small cell lung cancer

Benzo[a]pyrene (BaP) is commonly found in the environment as a result of incomplete combustion of organic materials and cigarette smoke. Epidemiological studies have consistently suggested that elderly smokers are at higher risk for small cell lung cancer (SCLC), with risks and clinical stages increasing with the intensity and duration of smoking. However, the underlying mechanism remains insufficiently investigated. Here, we established a positive correlation between smoking and BaP metabolite 3-hydroxybenzo[a]pyrene (3OH-BaP) in urine. The pooled standardized mean difference of urinary 3OH-BaP concentration for smokers versus nonsmokers was 5.18 (95 % CI 2.86-7.50). Clinical data suggested that smoking led to more lymph node metastasis, higher pathological N-stage, and worse overall survival in SCLC patients. We identified 75 genes that participate in BaP-associated cancer stemness of SCLC from Comparative Toxicogenomics Database and validated the expression of these candidate genes in SCLC patient samples. Protein kinase cAMP-activated catalytic subunit alpha (PRKACA) was found to be most upregulated in SCLC patients and in vitro experiments indicated that long-term exposure of SCLC cells to BaP, at the concentration equivalent to those detected in blood, increased PKA protein level. Further investigation revealed that PKA could directly interact with SOX2 and protect SOX2 from COP1-mediated ubiquitination and degradation. Upregulated SOX2 then contributed to the stemness and metastasis of SCLC cells while inhibition of aryl hydrocarbon receptor (AhR) signaling pathway abolished BaP induced PKA expression and downstream PKA/SOX2 axis. Our findings firstly pinpoint BaP exposure as a high-risk factor for SCLC and worse outcomes in patients, with the underlying mechanism being the activation of cancer stemness of SCLC via the AhR/PKA/SOX2 axis.

Non-additive mixture effects of benzo[a]pyrene and pesticides in vitro and in vivo: Role of AhR signaling

Polycyclic aromatic hydrocarbons (PAHs) and pesticides are two major groups of environmental contaminants which humans are simultaneously exposed to. However, potential mixture interactions of these groups of chemicals are not well-studied. In this study, the effects of binary mixtures of the PAH benzo[a]pyrene (B[a]P) and the commonly used pesticides chlorpyrifos, paraquat and tebuconazole on human liver HepG2 cells were investigated. The results showed that binary mixtures of B[a]P and paraquat or tebuconazole mainly caused additive effects on cell viability and cytochrome P4501a1 (CYP1A1) expression compared to single compound exposures. In contrast, the binary mixture with chlorpyrifos interacted antagonistically on cell viability and ROS production, whereas synergistic effects were observed for induction of CYP1A1 expression. B[a]P and chlorpyrifos also inhibited the activity of recombinant human CYP1A1 enzyme. To verify the synergistic in vitro results, zebrafish (Danio rerio) embryos were exposed to binary mixtures of B[a]P and chlorpyrifos. The mixtures caused synergistic induction of CYP1A expression, as well as synergistic developmental toxicity on multiple endpoints including non-inflated swim bladder, yolk-sac and pericardial edema, and spinal deformation. The effects were reduced upon morpholino-mediated knockdown of the aryl hydrocarbon receptor (AhR), indicating an AhR-dependence of the synergistic toxicity. Altogether, these data suggest that the combination of AhR activation and CYP1A1 inhibition is responsible for the underlying non-additive interaction between B[a]P and chlorpyrifos in vitro and in vivo.

Untargeted metabolomics reveals that multiple reproductive toxicants are present at the endometrium

BACKGROUND

Recent epidemiologic research shows many environmental chemicals exhibit endocrine disrupting effects on the female reproductive system. Few studies have examined exposure at reproductive organs. Our aim was to perform a preliminary untargeted metabolomic characterization of menstrual blood, a novel biofluid, to identify environmental toxins present in the endometrium and evaluate the suitability of this sample type for exposome research.

METHODS

Whole blood menstrual samples were collected from four women using a menstrual cup. Samples were analyzed for small molecules that include both environmental chemicals and endogenous metabolites using untargeted liquid chromatography with high-resolution mass spectrometry (LC-HRMS). Principal component analysis (PCA) and ANOVA was used to identify differences within and between individuals' menstrual blood metabolomic profiles, and the influence of the sample processing method. To assess the presence of environmental exposures, LC-HRMS chemical profiles were matched to the ToxCast chemical database, which includes 4557 commonly used commercial chemicals. Select compounds were confirmed by comparison to reference standards.

RESULTS

PCA of metabolome profiles showed analysis of menstrual blood samples were highly reproducible, with high variability in detected metabolites between participants and low variability between analytical replicates of an individual's sample. Endogenous metabolites detected in menstrual blood samples achieved good coverage of the human blood metabolome. We found 1748 annotations for environmental chemicals, including suspected reproductive toxicants such as phenols, parabens, phthalates, and organochlorines. Storage temperature for the first 24 h did not significantly influence global metabolomic profiles.

CONCLUSION

Our results show chemical exposures linked to reproductive toxicity and endocrine disruption are present in menstrual blood, a sampling medium for the endometrium.

Metabolomics for exposure assessment and toxicity effects of occupational pollutants: current status and future perspectives

INTRODUCTION

Work-related exposures to harmful agents or factors are associated with an increase in incidence of occupational diseases. These exposures often represent a complex mixture of different stressors, challenging the ability to delineate the mechanisms and risk factors underlying exposure-disease relationships. The use of omics measurement approaches that enable characterization of biological marker patterns provide internal indicators of molecular alterations, which could be used to identify bioeffects following exposure to a toxicant. Metabolomics is the comprehensive analysis of small molecule present in biological samples, and allows identification of potential modes of action and altered pathways by systematic measurement of metabolites.

OBJECTIVES

The aim of this study is to review the application of metabolomics studies for use in occupational health, with a focus on applying metabolomics for exposure monitoring and its relationship to occupational diseases.

METHODS

PubMed, Web of Science, Embase and Scopus electronic databases were systematically searched for relevant studies published up to 2021.

RESULTS

Most of reviewed studies included worker populations exposed to heavy metals such as As, Cd, Pb, Cr, Ni, Mn and organic compounds such as tetrachlorodibenzo-p-dioxin, trichloroethylene, polyfluoroalkyl, acrylamide, polyvinyl chloride. Occupational exposures were associated with changes in metabolites and pathways, and provided novel insight into the relationship between exposure and disease outcomes. The reviewed studies demonstrate that metabolomics provides a powerful ability to identify metabolic phenotypes and bioeffect of occupational exposures.

CONCLUSION

Continued application to worker populations has the potential to enable characterization of thousands of chemical signals in biological samples, which could lead to discovery of new biomarkers of exposure for chemicals, identify possible toxicological mechanisms, and improved understanding of biological effects increasing disease risk associated with occupational exposure.

Utilizing a Biology-Driven Approach to Map the Exposome in Health and Disease: An Essential Investment to Drive the Next Generation of Environmental Discovery

BACKGROUND

Recent developments in technologies have offered opportunities to measure the exposome with unprecedented accuracy and scale. However, because most investigations have targeted only a few exposures at a time, it is hypothesized that the majority of the environmental determinants of chronic diseases remain unknown.

OBJECTIVES

We describe a functional exposome concept and explain how it can leverage existing bioassays and high-resolution mass spectrometry for exploratory study. We discuss how such an approach can address well-known barriers to interpret exposures and present a vision of next-generation exposomics.

DISCUSSION

The exposome is vast. Instead of trying to capture all exposures, we can reduce the complexity by measuring the functional exposome-the totality of the biologically active exposures relevant to disease development-through coupling biochemical receptor-binding assays with affinity purification-mass spectrometry. We claim the idea of capturing exposures with functional biomolecules opens new opportunities to solve critical problems in exposomics, including low-dose detection, unknown annotations, and complex mixtures of exposures. Although novel, biology-based measurement can make use of the existing data processing and bioinformatics pipelines. The functional exposome concept also complements conventional targeted and untargeted approaches for understanding exposure-disease relationships.

CONCLUSIONS

Although measurement technology has advanced, critical technological, analytical, and inferential barriers impede the detection of many environmental exposures relevant to chronic-disease etiology. Through biology-driven exposomics, it is possible to simultaneously scale up discovery of these causal environmental factors. https://doi.org/10.1289/EHP8327.

High-Resolution Metabolomic Assessment of Pesticide Exposure in Central Valley, California

Pesticides are widely used in the agricultural Central Valley region of California. Historically, this has included organophosphates (OPs), organochlorines (OCs), and pyrethroids (PYRs). This study aimed to identify perturbations of the serum metabolome in response to each class of pesticide and mutual associations between groups of metabolites and multiple pesticides. We conducted high-resolution metabolomic profiling of serum samples from 176 older adults living in the California Central Valley using liquid chromatography with high-resolution mass spectrometry. We estimated chronic pesticide exposure (from 1974 to year of blood draw) to OPs, OCs, and PYRs from ambient sources at homes and workplaces with a geographic information system (GIS)-based model. Based on partial least-squares regression and pathway enrichment analysis, we identified metabolites and metabolic pathways associated with one or multiple pesticide classes, including mitochondrial energy metabolism, fatty acid and lipid metabolism, and amino acid metabolism. Utilizing an integrative network approach, we found that the fatty acid β-oxidation pathway is a common pathway shared across all three pesticide classes. The disruptions of the serum metabolome suggested that chronic pesticide exposure might result in oxidative stress, inflammatory reactions, and mitochondrial dysfunction, all of which have been previously implicated in a wide variety of diseases. Overall, our findings provided a comprehensive view of the molecular mechanisms of chronic pesticide toxicity, and, for the first time, our approach informs exposome research by moving from macrolevel population exposures to microlevel biologic responses.

Environmental Chemicals Altered in Association With Deployment for High Risk Areas

OBJECTIVE

A study was conducted using serum samples and high-resolution metabolomics (HRM) to test for changes in abundance of environmental chemicals in deployment in high-risk areas (Balad, Iraq; Bagram, Afghanistan).

METHODS

Pre and Post-deployment serum samples for deployment (cases) and matched controls stationed domestically were analyzed by HRM and bioinformatics for the relative abundance of 271 environmental chemicals.

RESULTS

Of the 271 chemicals, 153 were measurable in at least 80% of the samples in one of the pre- or post-deployment groups. Several pesticides and other chemicals were modestly elevated post-deployment in the Control as well as the Bagram and Balad samples. Similarly, small decreases were seen for some chemicals.

CONCLUSION

These results using serum samples show that for the 271 environmental chemicals studied, 56% were detected and small differences occurred with deployment to high-risk areas.

Benzo[a]pyrene Perturbs Mitochondrial and Amino Acid Metabolism in Lung Epithelial Cells and Has Similar Correlations With Metabolic Changes in Human Serum

OBJECTIVE

A study was conducted to identifymetabolic-related effects of benzo[a]pyrene (BaP) on human lung epithelial cells and validate these findings using human sera.

METHODS

Human lung epithelial cells were treated with BaP, and extracts were analyzed with a global metabolome-wide association study (MWAS) to test for pathways and metabolites altered relative to vehicle controls.

RESULTS

MWAS results showed that BaP metabolites were among the top metabolites differing between BaP-treated cells and controls. Pathway enrichment analysis further confirmed that fatty acid, lipid, and mitochondrial pathways were altered by BaP. Human sera analysis showed that lipids varied with BaP concentration. BaP associations with amino acid metabolism were found in both models.

CONCLUSIONS

These findings show that BaP has broad metabolic effects, and suggest that air pollution exacerbates disease processes by altered mitochondrial and amino acid metabolism.

Analysis of Postdeployment Serum Samples Identifies Potential Biomarkers of Exposure to Burn Pits and Other Environmental Hazards

OBJECTIVE

The potential health risks of deployment to sites with open burn pits remain poorly understood, in part, because personal exposure monitoring was not performed. Here, we investigated whether postdeployment serum samples contain biomarkers associated with exposure to burn pits.

METHODS

A total of 237 biomarkers were measured in 800 serum samples from deployed and never-deployed subjects. We used a regression model and a supervised vector machine to identify serum biomarkers with significant associations with exposures and deployment.

RESULTS

We identified 101 serum biomarkers associated with polycyclic aromatic hydrocarbons, dioxins or furans, and 54 biomarkers associated with deployment. Twenty-six of these biomarkers were shared in common by the exposure and deployment groups.

CONCLUSIONS

We identify a potential signature of exposure to open burn pits, and provide a framework for using postexposure sera to identify exposures when contemporaneous monitoring was inadequate.

Metabolome-Wide Association Study of Deployment to Balad, Iraq or Bagram, Afghanistan

OBJECTIVE

To use high-resolution metabolomics (HRM) to identify metabolic changes in military personnel associated with deployment to Balad, Iraq, or Bagram, Afghanistan.

METHODS

Pre- and post-deployment samples were obtained from the Department of Defense Serum Repository (DoDSR). HRM and bioinformatics were used to identify metabolic differences associated with deployment.

RESULTS

Differences at baseline (pre-deployment) between personnel deployed to Bagram compared with Balad or Controls included sex hormone and keratan sulfate metabolism. Deployment to Balad was associated with alterations to amino acid and lipid metabolism, consistent with inflammation and oxidative stress, and pathways linked to metabolic adaptation and repair. Difference associated with deployment to Bagram included lipid pathways linked to cell signaling and inflammation.

CONCLUSIONS

Metabolic variations in pre- and post-deployment are consistent with deployment-associated responses to air pollution and other environmental stressors.

Integrative Network Analysis Linking Clinical Outcomes With Environmental Exposures and Molecular Variations in Service Personnel Deployed to Balad and Bagram

OBJECTIVE

To develop a computational approach to link clinical outcomes with environmental exposures and molecular variations measured in Department of Defense (DOD) serum-repository samples.

METHODS

International Classification of Diseases, Ninth Division codes which corresponded to cardiopulmonary symptoms for service personnel were selected to test for associations with deployment-related inhalation hazards and metabolomics, micro-RNA, cytokine, plasma markers, and environmental exposure analyses for corresponding samples. xMWAS and Mummichog were used for integrative network and pathway analysis.

RESULTS

Comparison between 41 personnel exhibiting new cardio-pulmonary diagnoses after deployment start-date to 25 personnel exhibiting no symptoms identified biomarkers associated with cardiopulmonary conditions. Integrative network and pathway analysis showed communities of clinical, molecular, and environmental markers associated with fatty acid, lipid, nucleotide, and amino acid metabolism pathways.

CONCLUSIONS

The current proof of principle study establishes a computational framework for integrative analysis of deployment-related exposures, molecular responses, and health outcomes.

Use of Biomarkers to Assess Environmental Exposures and Health Outcomes in Deployed Troops

OBJECTIVE

This paper provides an overview of our Military Biomarkers Research Study (MBRS) designed to assess whether biomarkers can be used to retrospectively assess deployment exposures and health impacts related to deployment environmental exposures.

METHODS

The MBRS consists of four phases. Phase I was a feasibility study of stored sera. Phase II looks at associations between exposures and biomarkers. Phase III examines relationships of biomarkers and health outcomes, and Phase IV investigates in vitro biomarker changes associated with exposures to chemicals of interest. This paper briefly summarizes work already published and introduces the new reports contained in this supplement.

RESULTS

Novel biomarkers were identified. These were associated with deployment exposures.

CONCLUSIONS

Significant associations were noted between deployment exposures, microRNA biomarkers and metabolomic biomarkers, and deployment health outcomes.

Associations of Benzo(ghi)perylene and Heptachlorodibenzo-p-dioxin in Serum of Service Personnel Deployed to Balad, Iraq, and Bagram, Afghanistan Correlates With Perturbed Amino Acid Metabolism in Human Lung Fibroblasts

OBJECTIVE

A study was conducted to identify metabolic-related effects of benzo(ghi)perylene (BghiP) and 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin (HpCDD), on primary human fibroblasts to verify biological associations previously found in occupational health research.

METHODS

Human lung fibroblasts were exposed to BghiP or HpCDD and extracts were analyzed with a metabolome-wide association study to test for pathways and metabolites altered relative to controls. Gene expression was measured by quantitative-real time polymerase chain reaction.

RESULTS

Metabolic perturbations in amino-acid, oxidative stress, and fatty-acid pathways were observed for BghiP and HpCDD. HpCDD but not BghiP exposure increased gene expression of the amino acid transporters SLC7A5 and SLC7A11.

CONCLUSIONS

Exposure to polycyclic aromatic hydrocarbons (PAH) or dioxins perturbs amino acid pathways at physiologically relevant concentrations with different mechanisms. These findings imply an effect on central homeostatic systems by environmental exposures which could have implications on disease susceptibility.

Metabolome Wide Association Study of serum DDT and DDE in Pregnancy and Early Postpartum

The advancement of high-resolution metabolomics (HRM) and metabolome-wide-association study (MWAS) enables the readout of environmental effects in human specimens. We used HRM to understand DDT-induced alterations of in utero environment and potential health effects. Endogenous metabolites were measured in 397 maternal perinatal serum samples collected during 1959-1967 in the Child Health and Development Studies (CHDS) and in 16 maternal postnatal serum samples of mice treated with or without DDT. MWAS was performed to assess associations between metabolites and p,p'-DDT, o,p'-DDT and p,p'-DDE levels, followed by pathway analysis. Distinct metabolic profiles were found with p,p'-DDT and p,p'-DDE. Amino acids such arginine had a strong association with p,p'-DDT and o,p'-DDT in both women and mice, whereas lipids and acyl-carnitine intermediates were found exclusively associated with p,p'-DDE in CHDS women indicating mitochondrial impairment. It suggests that the role of serine and fatty acid metabolism on the causal disease pathway should be examined.

High-resolution metabolomic profiling of Alzheimer's disease in plasma

Background

Alzheimer’s disease (AD) is a complex neurological disorder with contributions from genetic and environmental factors. High‐resolution metabolomics (HRM) has the potential to identify novel endogenous and environmental factors involved in AD. Previous metabolomics studies have identified circulating metabolites linked to AD, but lack of replication and inconsistent diagnostic algorithms have hindered the generalizability of these findings. Here we applied HRM to identify plasma metabolic and environmental factors associated with AD in two study samples, with cerebrospinal fluid (CSF) biomarkers of AD incorporated to achieve high diagnostic accuracy.

Methods

Liquid chromatography‐mass spectrometry (LC–MS)‐based HRM was used to identify plasma and CSF metabolites associated with AD diagnosis and CSF AD biomarkers in two studies of prevalent AD (Study 1: 43 AD cases, 45 mild cognitive impairment [MCI] cases, 41 controls; Study 2: 50 AD cases, 18 controls). AD‐associated metabolites were identified using a metabolome‐wide association study (MWAS) framework.

Results

An MWAS meta‐analysis identified three non‐medication AD‐associated metabolites in plasma, including elevated levels of glutamine and an unknown halogenated compound and lower levels of piperine, a dietary alkaloid. The non‐medication metabolites were correlated with CSF AD biomarkers, and glutamine and the unknown halogenated compound were also detected in CSF. Furthermore, in Study 1, the unknown compound and piperine were altered in MCI patients in the same direction as AD dementia.

Conclusions

In plasma, AD was reproducibly associated with elevated levels of glutamine and a halogen‐containing compound and reduced levels of piperine. These findings provide further evidence that exposures and behavior may modify AD risks.

Connecting environmental exposure and neurodegeneration using cheminformatics and high resolution mass spectrometry: potential and challenges

Connecting chemical exposures over a lifetime to complex chronic diseases with multifactorial causes such as neurodegenerative diseases is an immense challenge requiring a long-term, interdisciplinary approach. Rapid developments in analytical and data technologies, such as non-target high resolution mass spectrometry (NT-HR-MS), have opened up new possibilities to accomplish this, inconceivable 20 years ago. While NT-HR-MS is being applied to increasingly complex research questions, there are still many unidentified chemicals and uncertainties in linking exposures to human health outcomes and environmental impacts. In this perspective, we explore the possibilities and challenges involved in using cheminformatics and NT-HR-MS to answer complex questions that cross many scientific disciplines, taking the identification of potential (small molecule) neurotoxicants in environmental or biological matrices as a case study. We explore capturing literature knowledge and patient exposure information in a form amenable to high-throughput data mining, and the related cheminformatic challenges. We then briefly cover which sample matrices are available, which method(s) could potentially be used to detect these chemicals in various matrices and what remains beyond the reach of NT-HR-MS. We touch on the potential for biological validation systems to contribute to mechanistic understanding of observations and explore which sampling and data archiving strategies may be required to form an accurate, sustained picture of small molecule signatures on extensive cohorts of patients with chronic neurodegenerative disorders. Finally, we reflect on how NT-HR-MS can support unravelling the contribution of the environment to complex diseases.

Multigenerational metabolic profiling in the Michigan PBB registry

Although polychlorinated biphenyls and polybrominated biphenyls are no longer manufactured the United States, biomonitoring in human populations show that exposure to these pollutants persist in human tissues. The objective of this study was to identify metabolic variations associated with exposure to 2,2'4,4',5,5'-hexabromobiphenyl (PBB-153) and 2,2'4,4',5,5'-hexachlorobiphenyl (PCB-153) in two generations of participants enrolled in the Michigan PBB Registry (http://pbbregistry.emory.edu/). Untargeted, high-resolution metabolomic profiling of plasma collected from 156 individuals was completed using liquid chromatography with high-resolution mass spectrometry. PBB-153 and PCB-153 levels were measured in the same individuals using targeted gas chromatography-tandem mass spectrometry and tested for dose-dependent correlation with the metabolome. Biological response to these exposures were evaluated using identified endogenous metabolites and pathway enrichment. When compared to lipid-adjusted concentrations for adults in the National Health and Nutrition Examination Survey (NHANES) for years 2003-2004, PCB-153 levels were consistent with similarly aged individuals, whereas PBB-153 concentrations were elevated (p<0.0001) in participants enrolled in the Michigan PBB Registry. Metabolic alterations were correlated with PBB-153 and PCB-153 in both generations of participants, and included changes in pathways related to catecholamine metabolism, cellular respiration, essential fatty acids, lipids and polyamine metabolism. These pathways were consistent with pathophysiological changes observed in neurodegenerative disease and included previously identified metabolomic markers of Parkinson's disease. To determine if the metabolic alterations detected in this study are replicated other cohorts, we evaluated correlation of PBB-153 and PCB-153 with plasma fatty acids measured in NHANES. Both pollutants showed similar associations with fatty acids previously linked to PCB exposure. Thus, the results from this study show metabolic alterations correlated with PBB-153 and PCB-153 exposure can be detected in human populations and are consistent with health outcomes previously reported in epidemiological and mechanistic studies.

The Exposome: Molecules to Populations

Derived from the term exposure, the exposome is an omic-scale characterization of the nongenetic drivers of health and disease. With the genome, it defines the phenome of an individual. The measurement of complex environmental factors that exert pressure on our health has not kept pace with genomics and historically has not provided a similar level of resolution. Emerging technologies make it possible to obtain detailed information on drugs, toxicants, pollutants, nutrients, and physical and psychological stressors on an omic scale. These forces can also be assessed at systems and network levels, providing a framework for advances in pharmacology and toxicology. The exposome paradigm can improve the analysis of drug interactions and detection of adverse effects of drugs and toxicants and provide data on biological responses to exposures. The comprehensive model can provide data at the individual level for precision medicine, group level for clinical trials, and population level for public health.

Membrane Remodeling as a Key Player of the Hepatotoxicity Induced by Co-Exposure to Benzo[a]pyrene and Ethanol of Obese Zebrafish Larvae

The rise in prevalence of non-alcoholic fatty liver disease (NAFLD) constitutes an important public health concern worldwide. Including obesity, numerous risk factors of NAFLD such as benzo[a]pyrene (B[a]P) and ethanol have been identified as modifying the physicochemical properties of the plasma membrane in vitro thus causing membrane remodeling—changes in membrane fluidity and lipid-raft characteristics. In this study, the possible involvement of membrane remodeling in the in vivo progression of steatosis to a steatohepatitis-like state upon co-exposure to B[a]P and ethanol was tested in obese zebrafish larvae. Larvae bearing steatosis as the result of a high-fat diet were exposed to ethanol and/or B[a]P for seven days at low concentrations coherent with human exposure in order to elicit hepatotoxicity. In this condition, the toxicant co-exposure raised global membrane order with higher lipid-raft clustering in the plasma membrane of liver cells, as evaluated by staining with the fluoroprobe di-4-ANEPPDHQ. Involvement of this membrane’s remodeling was finally explored by using the lipid-raft disruptor pravastatin that counteracted the effects of toxicant co-exposure both on membrane remodeling and toxicity. Overall, it can be concluded that B[a]P/ethanol co-exposure can induce in vivo hepatotoxicity via membrane remodeling which could be considered as a good target mechanism for developing combination therapy to deal with steatohepatitis.

Untargeted metabolomics reveals multiple metabolites influencing smoking-related DNA methylation

AIM

We conducted a joint metabolomic-epigenomic study to identify patterns of epigenetic associations with smoking-related metabolites.

PATIENTS & METHODS

We performed an untargeted metabolome-wide association study of smoking and epigenome-wide association studies of smoking-related metabolites among 180 male twins. We examined the patterns of epigenetic association linked to smoking-related metabolites using hierarchical clustering.

RESULTS

Among 12 annotated smoking-related metabolites identified from a metabolome-wide association study, we observed significant hypomethylation associated with increased level of N-acetylpyrrolidine, cotinine, 5-hydroxycotinine and nicotine and hypermethylation associated with increased level of 8-oxoguanine. Hierarchical clustering revealed common and unique epigenetic-metabolic associations related to smoking.

CONCLUSION

Our study suggested that a joint metabolome-epigenome approach can reveal additional details in molecular responses to the environmental exposure to understand disease risk.

Introduction to Department of Defense Research on Burn Pits, Biomarkers, and Health Outcomes Related to Deployment in Iraq and Afghanistan

OBJECTIVE

This paper provides an overview of our study that was designed to assess the health impact of environmental exposures to open pit burning in deployed troops.

METHODS

The rationale for the study and the structure of the research plan was laid out. An overview of each article in the supplement was provided. The cohort of deployed Service members was assessed for airborne exposure, relevant biomarkers, and health outcomes following deployment to Balad, Iraq, and/or Bagram, Afghanistan.

RESULTS

Polycyclic aromatic hydrocarbon (PAH) exposures were elevated, and serum biomarkers were statistically different postdeployment. Associations were noted between PAHs and dioxins and microRNAs. Some health outcomes were evident in deployers compared with nondeployers.

CONCLUSIONS

Future research will examine the associations between demographic variables, smoking status, biomarker levels, and related health outcomes.

Metabolic Pathways and Networks Associated With Tobacco Use in Military Personnel

OBJECTIVE

The aim of this study is to use high-resolution metabolomics (HRM) to identify metabolic pathways and networks associated with tobacco use in military personnel.

METHODS

Four hundred deidentified samples obtained from the Department of Defense Serum Repository were classified as tobacco users or nonusers according to cotinine content. HRM and bioinformatic methods were used to determine pathways and networks associated with classification.

RESULTS

Eighty individuals were classified as tobacco users compared with 320 nonusers on the basis of cotinine levels at least 10 ng/mL. Alterations in lipid and xenobiotic metabolism, and diverse effects on amino acid, sialic acid, and purine and pyrimidine metabolism were observed. Importantly, network analysis showed broad effects on metabolic associations not simply linked to well-defined pathways.

CONCLUSIONS

Tobacco use has complex metabolic effects that must be considered in evaluation of deployment-associated environmental exposures in military personnel.

Beyond genomics: understanding exposotypes through metabolomics

BACKGROUND

Over the past 20 years, advances in genomic technology have enabled unparalleled access to the information contained within the human genome. However, the multiple genetic variants associated with various diseases typically account for only a small fraction of the disease risk. This may be due to the multifactorial nature of disease mechanisms, the strong impact of the environment, and the complexity of gene-environment interactions. Metabolomics is the quantification of small molecules produced by metabolic processes within a biological sample. Metabolomics datasets contain a wealth of information that reflect the disease state and are consequent to both genetic variation and environment. Thus, metabolomics is being widely adopted for epidemiologic research to identify disease risk traits. In this review, we discuss the evolution and challenges of metabolomics in epidemiologic research, particularly for assessing environmental exposures and providing insights into gene-environment interactions, and mechanism of biological impact.

MAIN TEXT

Metabolomics can be used to measure the complex global modulating effect that an exposure event has on an individual phenotype. Combining information derived from all levels of protein synthesis and subsequent enzymatic action on metabolite production can reveal the individual exposotype. We discuss some of the methodological and statistical challenges in dealing with this type of high-dimensional data, such as the impact of study design, analytical biases, and biological variance. We show examples of disease risk inference from metabolic traits using metabolome-wide association studies. We also evaluate how these studies may drive precision medicine approaches, and pharmacogenomics, which have up to now been inefficient. Finally, we discuss how to promote transparency and open science to improve reproducibility and credibility in metabolomics.

CONCLUSIONS

Comparison of exposotypes at the human population level may help understanding how environmental exposures affect biology at the systems level to determine cause, effect, and susceptibilities. Juxtaposition and integration of genomics and metabolomics information may offer additional insights. Clinical utility of this information for single individuals and populations has yet to be routinely demonstrated, but hopefully, recent advances to improve the robustness of large-scale metabolomics will facilitate clinical translation.

Trends in the application of high-resolution mass spectrometry for human biomonitoring: An analytical primer to studying the environmental chemical space of the human exposome

Global profiling of xenobiotics in human matrices in an untargeted mode is gaining attention for studying the environmental chemical space of the human exposome. Defined as the study of a comprehensive inclusion of environmental influences and associated biological responses, human exposome science is currently evolving out of the metabolomics science. In analogy to the latter, the development and applications of high resolution mass spectrometry (HRMS) has shown potential and promise to greatly expand our ability to capture the broad spectrum of environmental chemicals in exposome studies. HRMS can perform both untargeted and targeted analysis because of its capability of full- and/or tandem-mass spectrum acquisition at high mass accuracy with good sensitivity. The collected data from target, suspect and non-target screening can be used not only for the identification of environmental chemical contaminants in human matrices prospectively but also retrospectively. This review covers recent trends and advances in this field. We focus on advances and applications of HRMS in human biomonitoring studies, and data acquisition and mining. The acquired insights provide stepping stones to improve understanding of the human exposome by applying HRMS, and the challenges and prospects for future research.

Computational Metabolomics: A Framework for the Million Metabolome

"Sola dosis facit venenum." These words of Paracelsus, "the dose makes the poison", can lead to a cavalier attitude concerning potential toxicities of the vast array of low abundance environmental chemicals to which humans are exposed. Exposome research teaches that 80-85% of human disease is linked to environmental exposures. The human exposome is estimated to include >400,000 environmental chemicals, most of which are uncharacterized with regard to human health. In fact, mass spectrometry measures >200,000 m/z features (ions) in microliter volumes derived from human samples; most are unidentified. This crystallizes a grand challenge for chemical research in toxicology: to develop reliable and affordable analytical methods to understand health impacts of the extensive human chemical experience. To this end, there appears to be no choice but to abandon the limitations of measuring one chemical at a time. The present review looks at progress in computational metabolomics to provide probability-based annotation linking ions to known chemicals and serve as a foundation for unambiguous designation of unidentified ions for toxicologic study. We review methods to characterize ions in terms of accurate mass m/z, chromatographic retention time, correlation of adduct, isotopic and fragment forms, association with metabolic pathways and measurement of collision-induced dissociation products, collision cross section, and chirality. Such information can support a largely unambiguous system for documenting unidentified ions in environmental surveillance and human biomonitoring. Assembly of this data would provide a resource to characterize and understand health risks of the array of low-abundance chemicals to which humans are exposed.

Deployment-Associated Exposure Surveillance With High-Resolution Metabolomics

OBJECTIVE

The aim of this study was to assess the suitability of high-resolution metabolomics (HRM) for measure of internal exposure and effect biomarkers from deployment-related environmental hazards.

METHODS

HRM provides extensive coverage of metabolism and data relevant to a broad spectrum of environmental exposures. This review briefly describes the analytic platform, workflow, and recent applications of HRM as a prototype environmental exposure surveillance system.

RESULTS

Building upon techniques available for contemporary occupational medicine and exposure sciences, HRM methods are able to integrate external exposures, internal body burden of environmental agents, and relevant biological responses with health outcomes.

CONCLUSIONS

Systematic analysis of existing Department of Defense Serum Repository samples will provide a high-quality, cross-sectional reference dataset for deployment-associated exposures while at the same time establishing a foundation for precision medicine.