Xenobiotic Metabolites Research Articles

XenoMet: A Corpus of Texts to Extract Data on Metabolites of Xenobiotics.

Understanding the biotransformation of xenobiotics in the human body is critical for a comprehensive assessment of drug effects since pharmacologically active drug metabolites may exhibit a range of biological effects that often differ from those of the original pharmaceutical agent. Studies of the biotransformation mechanisms of xenobiotics have resulted in numerous publications. Extracting information about the parent compounds (substrates) and their metabolites from the texts allows retrieval of information on their biological activities, molecular mechanisms of action, and toxicity. Manual curation of the names of xenobiotics, their metabolites, and biotransformation reactions in the text is a challenging task due to the large number of publications related to studies of pharmaceutical agents metabolism. Our aim is to create an annotated corpus of texts that can be used for automated extraction of the names of xenobiotics, including pharmaceutical agents that undergo biotransformation and their metabolites. Prior to manual annotation of the corpus, semiautomatic annotation was carried out based on the earlier developed rule-based method for parent compounds and their metabolites extraction. To create XenoMet, we automatically extracted relevant texts from PubMed using a query based on MeSH terms. The names of biotransformation reactions were recognized by using an in-house-developed dictionary. Then, we manually verified the extracted data by correcting errors in the named entity annotation and identified the associations between substrates and metabolites. We tested the applicability of XenoMet for the reconstruction of a metabolic tree and for the automated extraction of the chemical names of substrates, metabolites, and reactions of biotransformation. Classification of the named entities of metabolites, substrates, and biotransformation reactions by a conditional random fields approach using XenoMet as the training set provides an F1-score of 0.79.

Same, but different: Variations in fragment ions among stereoisomers of a 17α-methyl steroid in gas chromatography/electron ionization mass spectrometry.

Gas chromatography/electron ionization mass spectrometry (GC/EI-MS) is a well-established tool for the identification of unknown compounds such as new metabolites of xenobiotics. But it reaches the limits of confident structural assignment if it comes to stereoisomers. This work helps to overcome this difficulty by getting a deeper comprehension of composition of so far unspecific and also characteristic fragment ions in general and comparison among stereoisomers. Unit mass resolution mass spectra of various isotopologues of four 17α-methyl steroid diastereomers obtained by selectively introducing [2H9]-trimethylsilyl (TMS) groups or chemical syntheses were systematically compared. The impact of stereochemistry on variations of relative abundances has been assessed by statistical comparison from repeated measurements. Additionally, characterization of m/z 318 with high-resolution MS using gas chromatography/quadrupole time-of-flight MS (GC/QTOF-MS) was performed. The formation of fragment ions from TMS-derivatives after cleavage of methyl or TMS groups ([M-CH3]+, [M-TMSOH]•+, [M-CH3-TMSOH]+, [M-2x90]•+, [M-2x90-CH3]+) rarely arises from only one position in the molecule and composition of fragment ion signals is highly influenced by the stereochemistry of the A-ring at C3 and C5 of the steroid. Similarly, the formation of the characteristic fragment ion m/z 143 most likely consists of two different ways of formation. A possible structure for fragment ion m/z 318 was postulated. Stereoisomers showed differing fragmentation behaviors based on their configuration. These observations further illustrate that variations among stereoisomers in EI-MS fragmentation is no random underlying process but instead a pattern which needs to be understood in its complexity. This easily accessible technical approach can be applied on different molecule structures to further investigate the field of isomeric assignment in GC/EI-MS.

Metabolomic Fingerprints of Medical Therapy Versus Bariatric Surgery in Patients With Obesity and Type 2 Diabetes: The STAMPEDE Trial.

Roux-en-Y gastric bypass (RYGB) and sleeve gastrectomy (SG) are effective procedures to treat and manage type 2 diabetes (T2D). However, the underlying metabolic adaptations that mediate improvements in glucose homeostasis remain largely elusive. The purpose of this study was to identify metabolic signatures associated with biochemical resolution of T2D after medical therapy (MT) or bariatric surgery. Plasma samples from 90 patients (age 49.9 ± 7.6 years; 57.7% female) randomly assigned to MT (n = 30), RYGB (n = 30), or SG (n = 30) were retrospectively subjected to untargeted metabolomic analysis using ultra performance liquid chromatography with tandem mass spectrometry at baseline and 24 months of treatment. Phenotypic importance was determined by supervised machine learning. Associations between change in glucose homeostasis and circulating metabolites were assessed using a linear mixed effects model. The circulating metabolome was dramatically remodeled after SG and RYGB, with largely overlapping signatures after MT. Compared with MT, SG and RYGB profoundly enhanced the concentration of metabolites associated with lipid and amino acid signaling, while limiting xenobiotic metabolites, a function of decreased medication use. Random forest analysis revealed 2-hydroxydecanoate as having selective importance to RYGB and as the most distinguishing feature between MT, SG, and RYGB. To this end, change in 2-hydroxydecanoate correlated with reductions in fasting glucose after RYGB but not SG or MT. We identified a novel metabolomic fingerprint characterizing the longer-term adaptations to MT, RYGB, and SG. Notably, the metabolomic profiles of RYGB and SG procedures were distinct, indicating equivalent weight loss may be achieved by divergent effects on metabolism.

The breath volatilome is shaped by the gut microbiota.

The gut microbiota is widely implicated in host health and disease, inspiring translational efforts to implement our growing body of knowledge in clinical settings. However, the need to characterize gut microbiota by its genomic content limits the feasibility of rapid, point-of-care diagnostics. The microbiota produces a diverse array of xenobiotic metabolites that disseminate into tissues, including volatile organic compounds (VOCs) that may be excreted in breath. We hypothesize that breath contains gut microbe-derived VOCs that inform the composition and metabolic state of the microbiota. To explore this idea, we compared the breath volatilome and fecal gut microbiomes of 27 healthy children and found that breath VOC composition is correlated with gut microbiomes. To experimentally interrogate this finding, we devised a method for capturing exhaled breath from gnotobiotic mice. Breath volatiles are then profiled by gas-chromatography mass-spectrometry (GC-MS). Using this novel methodology, we found that the murine breath profile is markedly shaped by the composition of the gut microbiota. We also find that VOCs produced by gut microbes in pure culture can be identified in vivo in the breath of mice monocolonized with the same bacteria. Altogether, our studies identify microbe-derived VOCs excreted in breath and support a mechanism by which gut bacterial metabolism directly contributes to the mammalian breath VOC profiles.

Probing and gauging of D-Penicillamine xenobiotics in hepatic Wilson disease patients

D-penicillamine (PA) is the primary chelator of choice to treat Wilson disease (WD). There are limitations in obtaining comprehensive data on PA metabolites in biological specimens by conventional approaches. Hence, the aim of the present was to identify the major hepatic PA metabolites and draw clear conclusions of the drug's xenobiotic in WD. Urine samples were collected from children with hepatic WD (n = 63, aged 14.8 ± 4 years) 5 h after PA administration (16.3 ± 3.8 mg/kg/day) and age-matched healthy volunteers comprised as controls (n = 30). High-resolution 800 MHz nuclear magnetic resonance spectroscopy (NMR) and mass spectrometry was applied to reveal unambiguous appraisals of different excretory by-products of PA metabolism. Four new products comprising penicillamine disulphide (PD), penicillamine cysteine disulphide (PCD), S-methyl penicillamine (SMP), and N-acetyl penicillamine (NAP) of PA xenobiotic metabolites were identified using high-resolution NMR spectroscopy. Quantitative levels of PCD and SMP were approximately three-fold higher than those of PD and NAP, respectively. High-resolution NMR identifies the major PA metabolites with certainty. Reduction, sulfation, and methylation are the predominant pathways of PA metabolism. There is a potential application for assessing therapeutic monitoring of chelation in hepatic WD.

Abstract 3429: Using metabolomics to identify biomarkers mediating the associations of adiposity in childhood and early adulthood with mammographic breast density in premenopausal women

Abstract Introduction: Mammographic breast density (MBD), a strong predictor of breast cancer risk, is highly influenced by body mass index (BMI) in childhood and early adulthood, but the mechanisms elucidating this relationship are undetermined. To our knowledge, no study has explored the mediating role of biomarkers on the relationship between early-life adiposity and MBD. The goal of this study is to discover metabolites that mediate the relationship between BMI at ages 10 and 18 with MBD in premenopausal women. Methods: This study includes premenopausal women who had their screening mammogram at Washington University in St. Louis, MO, and provided a fasting blood sample. Metabolon performed untargeted metabolomic profiling, detecting 1,074 metabolites. Metabolites missing >300 observations were excluded, leaving 828 metabolites; the other missing values were imputed using the nearest neighbor method. To mitigate batch effect, we normalized the metabolite peak area data using ComBat. Volumetric percent density (VPD) was calculated in 700 women using Volpara software. BMI at age 10 was estimated using the Stunkard pictogram, and BMI at age 18 was calculated from self-reported weight at 18 and height at study initiation. To assess the mediating role of the 828 metabolites, we performed high dimensional mediation analysis using the hima R package adjusting for potential confounders. Missing values in the covariates and BMI measures included in the mediation analysis were imputed using multivariate imputation by chain equations. Associations were considered significant if FDR p-value <0.1. Results: Four metabolites (glutamate, beta-cryptoxanthin, phytanate, and cortolone glucuronide (1)) mediated the relationship between BMI at age 10 and VPD; and 2 metabolites (glutamate, beta-cryptoxanthin) mediated the relationship between BMI at age 18 and VPD. Glutamate and beta-cryptoxanthin significantly mediated the relationship between both BMI measures and VPD, but glutamate was the strongest mediator across both time points. Glutamate mediated 6.7% (FDR p-value=0.06) and 9.3% (FDR p-value=0.008) of the total effect between BMI at age 10 and 18, respectively, on VPD. Beta-cryptoxanthin mediated 4.1% (FDR p-value=0.06) and 6.3% (FDR p-value=0.04), of the total effect between BMI at age 10 and 18, respectively, on VPD. Additionally, phytanate mediated 2.6% (FDR p-value=0.06) and cortolone glucuronide (1) mediated 2.0% (FDR p-value=0.07) of the total effect between BMI at age 10 and VPD. Conclusion: Amino acid, lipid, cofactor/vitamin, and xenobiotic metabolites mediated the associations of BMI in early-life and VPD in premenopausal women. This innovative study offers insight into the biological mechanisms underlying the link between early-life adiposity and MBD, which can support future research into breast cancer prevention. Citation Format: Kayla R. Getz, Myung Sik Jeon, Lili Liu, Lei Liu, Chongliang Luo, Jingqin Luo, Adetunji T. Toriola. Using metabolomics to identify biomarkers mediating the associations of adiposity in childhood and early adulthood with mammographic breast density in premenopausal women [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 3429.

Mendelian Randomization Study With Clinical Follow-Up Links Metabolites to Risk and Severity of Pulmonary Arterial Hypertension.

Pulmonary arterial hypertension (PAH) exhibits phenotypic heterogeneity and variable response to therapy. The metabolome has been implicated in the pathogenesis of PAH, but previous works have lacked power to implicate specific metabolites. Mendelian randomization (MR) is a method for causal inference between exposures and outcomes. Using genome-wide association study summary statistics, we implemented MR analysis to test for potential causal relationships between serum concentration of 575 metabolites and PAH. Five metabolites were causally associated with the risk of PAH after multiple testing correction. Next, we measured serum concentration of candidate metabolites in an independent clinical cohort of 449 patients with PAH to check whether metabolite concentrations are correlated with markers of disease severity. Of the 5 candidates nominated by our MR work, serine was negatively associated and homostachydrine was positively associated with clinical severity of PAH via direct measurement in this independent clinical cohort. Finally we used conditional and orthogonal approaches to explore the biology underlying our lead metabolites. Rare variant burden testing was carried out using whole exome sequencing data from 578 PAH cases and 361 675 controls. Multivariable MR is an extension of MR that uses a single set of instrumental single-nucleotide polymorphisms to measure multiple exposures; multivariable MR is used to determine interdependence between the effects of different exposures on a single outcome. Rare variant analysis demonstrated that loss-of-function mutations within activating transcription factor 4, a transcription factor responsible for upregulation of serine synthesis under conditions of serine starvation, are associated with higher risk for PAH. Homostachydrine is a xenobiotic metabolite that is structurally related to l-proline betaine, which has previously been linked to modulation of inflammation and tissue remodeling in PAH. Our multivariable MR analysis suggests that the effect of l-proline betaine is actually mediated indirectly via homostachydrine. Our data present a method for study of the metabolome in the context of PAH, and suggests several candidates for further evaluation and translational research.

Characterizing Chemical Exposure Trends from NHANES Urinary Biomonitoring Data.

Xenobiotic metabolites are widely present in human urine and can indicate recent exposure to environmental chemicals. Proper inference of which chemicals contribute to these metabolites can inform human exposure and risk. Furthermore, longitudinal biomonitoring studies provide insight into how chemical exposures change over time. We constructed an exposure landscape for as many human-exposure relevant chemicals over as large a time span as possible to characterize exposure trends across demographic groups and chemical types. We analyzed urine data of nine 2-y cohorts (1999-2016) from the National Health and Nutrition Examination Survey (NHANES). Chemical daily intake rates (in milligrams per kilogram bodyweight per day) were inferred, using the R package bayesmarker, from metabolite concentrations in each cohort individually to identify exposure trends. Trends for metabolites and parents were clustered to find chemicals with similar exposure patterns. Exposure variation by age, gender, and body mass index were also assessed. Intake rates for 179 parent chemicals were inferred from 151 metabolites (96 measured in five or more cohorts). Seventeen metabolites and 44 parent chemicals exhibited fold-changes between any two cohorts (deltamethrin, di--octyl phthalate, and di-isononyl phthalate had the greatest exposure increases). Di-2-ethylhexyl phthalate intake began decreasing in 2007, whereas both di-isobutyl and di-isononyl phthalate began increasing shortly before. Intake for four parabens was markedly higher in females, especially reproductive-age females, compared with males and children. Cadmium and arsenobetaine exhibited higher exposure for individuals years of age and lower for individuals years of age. With appropriate analysis, NHANES indicates trends in chemical exposures over the past two decades. Decreases in exposure are observable as the result of regulatory action, with some being accompanied by increases in replacement chemicals. Age- and gender-specific variations in exposure were observed for multiple chemicals. Continued estimation of demographic-specific exposures is needed to both monitor and identify potential vulnerable populations. https://doi.org/10.1289/EHP12188.

Non-targeted LC–MS/MS metabolomic profiling of human plasma uncovers a novel Mediterranean diet biomarker panel

IntroductionConsumption of a Mediterranean diet (MD) has established health benefits, and the identification of novel biomarkers could enable objective monitoring of dietary pattern adherence.ObjectivesThe present investigation performed untargeted metabolomics on blood plasma from a controlled study of MD adherence, to identify novel blood-based metabolite biomarkers associated with the MD pattern, and to build a logistic regression model that could be used to characterise MD adherence.MethodsA hundred and thirty-five plasma samples from n = 58 patients collected at different time points were available. Using a 14-point scale MD Score (MDS) subjects were divided into ‘high’ or ‘low’ MDS adherence groups and liquid chromatography-mass spectrometry (LC–MS/MS) was applied for analysis.ResultsThe strongest association with MDS was pectenotoxin 2 seco acid (r = 0.53; ROC = 0.78), a non-toxic marine xenobiotic metabolite. Several lipids were useful biomarkers including eicosapentaenoic acid, the structurally related lysophospholipid (20:5(5Z,8Z,11Z,14Z,17Z)/0:0), a phosphatidylcholine (P-18:1(9Z)/16:0) and also xi-8-hydroxyhexadecanedioic acid. Two metabolites negatively correlated with MDS, these were the monoacylglycerides (0:0/16:1(9Z)/0:0) and (0:0/20:3(5Z,8Z,11Z)/0:0). By stepwise elimination we selected a panel of 3 highly discriminatory metabolites and developed a linear regression model which identified ‘high MDS’ individuals with high sensitivity and specificity [AUC (95% CI) 0.83 (0.76–0.97)].ConclusionOur study highlights the utility of metabolomics as an approach for developing novel panels of dietary biomarkers. Quantitative profiling of these metabolites is required to validate their utility for evaluating dietary adherence.

Imprinting and Reproductive Health: A Toxicological Perspective

This overview discusses the role of imprinting in the development of an organism, and how exposure to environmental chemicals during fetal development leads to the physiological and biochemical changes that can have adverse lifelong effects on the health of the offspring. There has been a recent upsurge in the use of chemical products in everyday life. These chemicals include industrial byproducts, pesticides, dietary supplements, and pharmaceutical products. They mimic the natural estrogens and bind to estradiol receptors. Consequently, they reduce the number of receptors available for ligand binding. This leads to a faulty signaling in the neuroendocrine system during the critical developmental process of ‘imprinting’. Imprinting causes structural and organizational differentiation in male and female reproductive organs, sexual behavior, bone mineral density, and the metabolism of exogenous and endogenous chemical substances. Several studies conducted on animal models and epidemiological studies provide profound evidence that altered imprinting causes various developmental and reproductive abnormalities and other diseases in humans. Altered metabolism can be measured by various endpoints such as the profile of cytochrome P-450 enzymes (CYP450’s), xenobiotic metabolite levels, and DNA adducts. The importance of imprinting in the potentiation or attenuation of toxic chemicals is discussed.

Xenobiotic metabolites modify immune responses of the cervicovaginal epithelium: potential mechanisms underlying barrier disruption.

Xenobiotic metabolites are exogenous biochemicals that can adversely impact reproductive health. We previously identified xenobiotics in cervicovaginal fluid during pregnancy in association with short cervix. In other organ systems, xenobiotics can modify epithelial barrier function. We hypothesise that xenobiotics dysregulate epithelial cell and macrophage immune responses as a mechanism to disrupt the cervicovaginal barrier. In vitro cell culture system. Laboratory within academic institution. Vaginal, ectocervical and endocervical epithelial cell lines and primary macrophages. Cells were treated with diethanolamine (2.5 mM), ethyl glucoside (5 mM) or tartrate (2.5 mM) for 24 h. Cytokines and matrix metalloproteinases were measured in cell supernatants (n = 3 per condition). One-way analysis of variance (ANOVA) with Dunnett's test for multiple comparisons was performed. Diethanolamine induces inflammatory cytokines, whereas ethyl glucoside and tartrate generally exert anti-inflammatory effects across all cells. Diethanolamine increases interleukin 6 (IL-6), IL-8, interferon γ-induced protein 10 kDa (IP-10), growth-regulated oncogene (GRO), fractalkine, matrix metalloproteinase 1 (MMP-1), MMP-9 and MMP-10 (p < 0.05 for all), factors involved in acute inflammation and recruitment of monocytes, neutrophils and lymphocytes. Ethyl glucoside and tartrate decrease multiple cytokines, including RANTES and MCP-1 (p < 0.05 for all), which serve as chemotactic factors. Vaginal cells exhibit heightened inflammatory tone compared with cervical cells and macrophages, with a greater number of differentially expressed analytes after xenobiotic exposure. Xenobiotic metabolites present in the cervicovaginal space during pregnancy modify immune responses, unveiling potential pathways through which environmental exposures may contribute to the pathogenesis of cervical remodelling preceding preterm birth. Future work identifying xenobiotic sources and routes of exposure offers the potential to modify environmental risks to improve pregnancy outcomes.

Straw return drives soil microbial community assemblage to change metabolic processes for soil quality amendment in a rice-wheat rotation system

Straw return has been widely implemented to sequester soil organic carbon (SOC) and enhance soil quality in rice-wheat cropping systems, however, the mechanism through which it influences microbial assemblages into mediating biochemical metabolic pathways in soil remains ambiguous. This study aimed at investigating the composition and assembly of soil microbial communities and the soil metabolome prevailing across four straw return practices (control: no straw return; RR: rice-straw return; WR: wheat-straw return; DR: both rice- and wheat-straw return) during wheat cultivation on a rice-wheat rotation field. Straw return primarily altered the abundance of lipids (LL), organic acids (OA), organic nitrogen compounds, and benzenoids, with DR having a greater impact on soil metabolites than WR or RR. Besides being predominantly present in the lipid (LM) and amino acid (AAM) metabolic pathways, these differentially expressed metabolites (DEMs) were also dispersed throughout the nucleotide, xenobiotic, and secondary metabolite pathways. Straw return substantially elevated homogeneous selection in the order DR > WR > RR > control. The links of taxa to LM and AAM occupied by 64.9% in the DEMs-microbial taxa correlation network, with majority of taxa being derived from the keystone modules of the microbial network. Furthermore, these taxa potentially modulated variations in microbiota assembly by 27–45.1%, soil metabolites by 13.3–70.7%, and soil nutrient properties by 24.8–49.6%; and their removal evidently mitigated the natural connectivity of the microbial network. Structural equation modeling depicted that straw return exerted positive effects on LL and OA by regulating microbial assembly. Therefore, our results demonstrated that straw return drive microbial community assembly to dominate the taxa mediating soil LM and AAM for enhancing SOC sequestration and soil quality.

The effect of vitamin B12 on DNA adduction by styrene oxide, a genotoxic xenobiotic

Vitamin B12 (cyano- or hydroxo-cobalamin) acts, via its coenzymes, methyl- and adenosyl-cobalamin, as a partner for enzymatic reactions in humans catalysed by methionine synthase and methylmalonyl-CoA mutase. As well as its association with pernicious anaemia, human B12 deficiency may also be a risk factor for neurological illnesses, heart disease and cancer. In the present work the effect of vitamin B12 (hydroxocobalamin) on the formation of DNA adducts by the epoxide phenyloxirane (styrene oxide), a genotoxic metabolite of phenylethene (styrene), has been studied using an in vitro model system. Styrene was converted to its major metabolite styrene oxide as a mixture of enantiomers using a microsomal fraction from the livers of Sprague-Dawley rats with concomitant inhibition of epoxide hydrolase. However, microsomal oxidation of styrene in the presence of vitamin B12 gave diastereoisomeric 2-hydroxy-2-phenylcobalamins. The quantitative formation of styrene oxide-DNA adducts was investigated using 2-deoxyguanosine or calf thymus DNA in the presence or absence of vitamin B12. Microsomal incubations containing either deoxyguanosine or DNA in the absence of vitamin B12 gave 2-amino-7-(2-hydroxy-1-phenylethyl)-1,7-dihydro-6H-purin-6-one [N7-(2-hydroxy-1-phenylethyl)-guanine], and 2-amino-7-(2-hydroxy-2-phenylethyl)-1,7-dihydro-6H-purin-6-one [N7-(2-hydroxy-2-phenylethyl)guanine] as the principal adducts. With deoxyguanosine the level of formation of guanine adducts was ca. 150 adducts/106 unmodified nucleoside. With DNA the adduct level was 36 pmol/mg DNA (ca. 1 adduct/0.83 × 105 nucleotides). Styrene oxide adducts from deoxyguanosine or DNA were not detected in microsomal incubations of styrene in the presence of vitamin B12. These results suggest that vitamin B12 could protect DNA against genotoxicity due to styrene oxide and other xenobiotic metabolites. However, this potential defence mechanism requires that the 2-hydroxyalkylcobalamins derived from epoxides are not ‘anti-vitamins’ and ideally liberate, and therefore, recycle vitamin B12. Otherwise, depletion of vitamin B12 leading to human deficiency could increase the risk of carcinogenesis initiated by genotoxic epoxides.

Metabolite Stability in Archived Neonatal Dried Blood Spots Used for Epidemiologic Research.

Epidemiologic studies of low-frequency exposures or outcomes using metabolomics analyses of neonatal dried blood spots (DBS) often require assembly of samples with substantial differences in duration of storage. Independent assessment of stability of metabolites in archived DBS will enable improved design and interpretation of epidemiologic research utilizing DBS. Neonatal DBS routinely collected and stored as part of the California Genetic Disease Screening Program between 1983 and 2011 were used. The study population included 899 children without cancer before age 6 years, born in California. High-resolution metabolomics with liquid-chromatography mass spectrometry was performed, and the relative ion intensities of common metabolites and selected xenobiotic metabolites of nicotine (cotinine and hydroxycotinine) were evaluated. In total, we detected 26,235 mass spectral features across 2 separate chromatography methods (C18 hydrophobic reversed-phase chromatography and hydrophilic-interaction liquid chromatography). For most of the 39 metabolites related to nutrition and health status, we found no statistically significant annual trends across the years of storage. Nicotine metabolites were captured in the DBS with relatively stable intensities. This study supports the usefulness of DBS stored long-term for epidemiologic studies of the metabolome. -Omics-based information gained from DBS may also provide a valuable tool for assessing prenatal environmental exposures in child health research.

Amine-Functionalized Natural Rubber/Mesostructured Silica Nanocomposites for Adsorptive Removal of Clofibric Acid in Aqueous Phase

This study is the first report on the synthesis, characterization and application of amine-functionalized mesoporous nanocomposites based on natural rubber (NR) and wormhole-like mesostructured silica (WMS). In comparison with amine-functionalized WMS (WMS-NH2), a series of NR/WMS-NH2 composites were synthesized via an in situ sol-gel method in which the organo-amine group was grafted onto the nanocomposite surface via co-condensation with 3-aminopropyltrimethoxysilane (APS) as the amine-functional group precursor. The NR/WMS-NH2 materials had a high specific surface area (115-492 m2 g-1) and total pore volume (0.14-1.34 cm3 g-1) with uniform wormhole-like mesoporous frameworks. The amine concentration of NR/WMS-NH2 (0.43-1.84 mmol g-1) was increased with an increase in the APS concentration, corresponding to high levels of functionalization with the amine groups of 53-84%. The H2O adsorption-desorption measurement revealed that NR/WMS-NH2 possessed higher hydrophobicity than WMS-NH2. The removal of clofibric acid (CFA), a xenobiotic metabolite of the lipid-lowering drug clofibrate, from the aqueous solution using WMS-NH2 and NR/WMS-NH2 materials was investigated using a batch adsorption experiment. The adsorption was a chemical process in which the pseudo-second order kinetic model expressed the sorption kinetic data better than the pseudo first-order and Ritchie-second kinetic order model. In addition, the CFA adsorption sorption equilibrium data of the NR/WMS-NH2 materials were fitted to the Langmuir isotherm model. The NR/WMS-NH2 with 5% amine loading had the highest CFA adsorption capacity (6.29 mg g-1).

Elucidating the Metabolism of 2,4-Dibromophenol in Plants.

Crops can be extensively exposed to organic pollutants, since soil is a major sink for pollutants discarded into the environment. This creates potential human exposure through the consumption of pollutant-accumulated foods. Elucidating the uptake and metabolism of xenobiotics in crops is essential for the assessment of dietary exposure risk in humans. However, for such experiments, the use of intact plants requires long-term experiments and complex sample preparation protocols that can be affected by various factors. Plant callus cultures combined with high-resolution mass spectrometry (HRMS) may provide a solution for the accurate and time-saving identification of metabolites of xenobiotics in plants, as it can avoid interference from the microbial or fungal microenvironment, shorten the treatment duration, and simplify the matrix effect of intact plants. 2,4-dibromophenol, a typical flame retardant and endocrine disrupter, was chosen as the model substance due to its widespread occurrence in soil and its uptake potential by plants. Herein, plant callus was generated from asepsis seeds and exposed to sterile 2,4-dibromophenol-containing culture medium. The results showed that eight metabolites of 2,4-dibromophenol were identified in the plant callus tissues after 120 h of incubation. This indicates that 2,4-dibromophenol was rapidly metabolized inthe plant callus tissues. Thus, the plant callus culture platform is an effective method to evaluate the uptake and metabolism of xenobiotics in plants.

Lipid environment determines the drug-stimulated ATPase activity of P-glycoprotein.

P-glycoprotein (Pgp), also known as ABCB1 or multidrug resistance protein 1 (MDR1), is expressed in the luminal membrane of the intestine, liver, and kidney where it regulates the absorption, distribution, metabolism, and excretion (ADME) of a wide range of xenobiotic compounds and metabolites, and at the blood-brain where it protects the sanctuary from uptake of toxic compounds and enhances excretion of β-amyloid and metabolites. Its expression in cancer cells has been linked to multidrug resistance against many chemotherapeutic agents leading to ineffective treatment and relapse. Besides chemotherapeutic drugs, lipids have been suggested to be transported by themselves or co-transported with drugs by Pgp. Here we tested the hypothesis that the plasma membrane lipid composition modulates how drugs interact with Pgp and may greatly affect both the affinity of the transport substrates and its maximum activity. Our general approach was to test varieties of synthetic lipid mixtures starting with the bilayer-forming phosphatidylcholine (PC) and supplementing with phospholipids carrying different head groups as well as cholesterol. We present the first results of Pgp interactions with PC, phosphatidylethanolamine (PE), sphingomyelin (SM), and cardiolipin which we found to act as positive effectors and increase the apparent affinity for substrates and increase Vmax, while others acted as negative effectors and decreased Vmax. The impact on the substrate binding and translocation mechanisms of Pgp will be discussed. The long-term goal is to establish a stable source of synthetic phospholipid mixtures supplemented with cholesterol that mimic Pgp activity in its native environment in the human body.

Xenobiotic Metabolites Decrease Over Time During Oral Immunotherapy in Children with Multiple Food Allergies

Oral immunotherapy therapy (OIT) is used to desensitize individuals to food allergies (FA); however, the biological mechanisms of OIT are still under investigation. This exploratory analysis was conducted to determine how metabolomic profiles of children with multiple FA change over the course of OIT.

Identifying xenobiotic metabolites with in silico prediction tools and LCMS suspect screening analysis.

Understanding the metabolic fate of a xenobiotic substance can help inform its potential health risks and allow for the identification of signature metabolites associated with exposure. The need to characterize metabolites of poorly studied or novel substances has shifted exposure studies towards non-targeted analysis (NTA), which often aims to profile many compounds within a sample using high-resolution liquid-chromatography mass-spectrometry (LCMS). Here we evaluate the suitability of suspect screening analysis (SSA) liquid-chromatography mass-spectrometry to inform xenobiotic chemical metabolism. Given a lack of knowledge of true metabolites for most chemicals, predictive tools were used to generate potential metabolites as suspect screening lists to guide the identification of selected xenobiotic substances and their associated metabolites. Thirty-three substances were selected to represent a diverse array of pharmaceutical, agrochemical, and industrial chemicals from Environmental Protection Agency's ToxCast chemical library. The compounds were incubated in a metabolically-active in vitro assay using primary hepatocytes and the resulting supernatant and lysate fractions were analyzed with high-resolution LCMS. Metabolites were simulated for each compound structure using software and then combined to serve as the suspect screening list. The exact masses of the predicted metabolites were then used to select LCMS features for fragmentation via tandem mass spectrometry (MS/MS). Of the starting chemicals, 12 were measured in at least one sample in either positive or negative ion mode and a subset of these were used to develop the analysis workflow. We implemented a screening level workflow for background subtraction and the incorporation of time-varying kinetics into the identification of likely metabolites. We used haloperidol as a case study to perform an in-depth analysis, which resulted in identifying five known metabolites and five molecular features that represent potential novel metabolites, two of which were assigned discrete structures based on in silico predictions. This workflow was applied to five additional test chemicals, and 15 molecular features were selected as either reported metabolites, predicted metabolites, or potential metabolites without a structural assignment. This study demonstrates that in some-but not all-cases, suspect screening analysis methods provide a means to rapidly identify and characterize metabolites of xenobiotic chemicals.

A prospective case–cohort analysis of plasma metabolites and breast cancer risk

BackgroundBreast cancer incidence rates have not declined despite an improvement in risk prediction and the identification of modifiable risk factors, suggesting the need to identify novel risk factors and etiological pathways involved in this cancer. Metabolomics has emerged as a promising tool to find circulating metabolites associated with breast cancer risk.MethodsUntargeted metabolomic analysis was done on prediagnostic plasma samples from a case–cohort study of 1695 incident breast cancer cases and a 1983 women subcohort drawn from Cancer Prevention Study 3. The associations of 868 named metabolites (per one standard deviation increase) with breast cancer were determined using Prentice-weighted Cox proportional hazards regression modeling.ResultsA total of 11 metabolites were associated with breast cancer at false discovery rate (FDR) < 0.05 with the majority having inverse association [ranging from RR = 0.85 (95% CI 0.80–0.92) to RR = 0.88 (95% CI 0.82–0.94)] and one having a positive association [RR = 1.14 (95% CI 1.06–1.23)]. An additional 50 metabolites were associated at FDR < 0.20 with inverse associations ranging from RR = 0.88 (95% CI 0.81–0.94) to RR = 0.91 (95% CI 0.85–0.98) and positive associations ranging from RR = 1.13 (95% CI 1.05–1.22) to RR = 1.11 (95% CI 1.02–1.20). Several of these associations validated the findings of previous metabolomic studies. These included findings that several progestogen and androgen steroids were associated with increased risk of breast cancer in postmenopausal women and four phospholipids, and the amino acids glutamine and asparagine were associated with decreased risk of this cancer in pre- and postmenopausal women. Several novel associations were also identified, including a positive association for syringol sulfate, a biomarker for smoked meat, and 3-methylcatechol sulfate and 3-hydroxypyridine glucuronide, which are metabolites of xenobiotics used for the production of pesticides and other products.ConclusionsOur study validated previous metabolite findings and identified novel metabolites associated with breast cancer risk, demonstrating the utility of large metabolomic studies to provide new leads for understanding breast cancer etiology. Our novel findings suggest that consumption of smoked meats and exposure to catechol and pyridine should be investigated as potential risk factors for breast cancer.