The gut microbiome, a key constituent of the colonic environment, has been implicated as an important modulator of human health. The eukaryotic epigenome is postulated to respond to environmental ...stimuli through alterations in chromatin features and, ultimately, gene expression. How the host mediates epigenomic responses to gut microbiota is an emerging area of interest. Here, we profile the gut microbiome and chromatin characteristics in colon epithelium from mice fed either an obesogenic or control diet, followed by an analysis of the resultant changes in gene expression.
The obesogenic diet shapes the microbiome prior to the development of obesity, leading to altered bacterial metabolite production which predisposes the host to obesity. This microbiota-diet interaction leads to changes in histone modification at active enhancers that are enriched for binding sites for signal responsive transcription factors. These alterations of histone methylation and acetylation are associated with signaling pathways integral to the development of colon cancer. The transplantation of obesogenic diet-conditioned microbiota into germ free mice, combined with an obesogenic diet, recapitulates the features of the long-term diet regimen. The diet/microbiome-dependent changes are reflected in both the composition of the recipient animals' microbiome as well as in the set of transcription factor motifs identified at diet-influenced enhancers.
These findings suggest that the gut microbiome, under specific dietary exposures, stimulates a reprogramming of the enhancer landscape in the colon, with downstream effects on transcription factors. These chromatin changes may be associated with those seen during colon cancer development.
Because the signaling eicosanoids, epoxyeicosatrienoic acids (EETs) and HETEs, are esterified to membrane phospholipids, we asked which long-chain acyl-CoA synthetase (ACSL) isoforms would activate ...these molecules and whether the apparent FA substrate preferences of each ACSL isoform might differ depending on whether it was assayed in mammalian cell membranes or as a purified bacterial recombinant protein. We found that all five ACSL isoforms were able to use EETs and HETEs as substrates and showed by LC-MS/MS that ACSLs produce EET-CoAs. We found differences in substrate preference between ACS assays performed in COS7 cell membranes and recombinant purified proteins. Similarly, preferences and Michaelis-Menten kinetics for long-chain FAs were distinctive. Substrate preferences identified for the purified ACSLs did not correspond to those observed in ACSL-deficient mouse models. Taken together, these data support the concept that each ACSL isoform exhibits a distinct substrate preference, but apparent substrate specificities depend upon multiple factors including membrane character, coactivators, inhibitors, protein interactions, and posttranslational modification.
Fatty liver disease is an emerging public health problem without effective therapies, and chronic hepatic inflammation is a key pathologic mediator in its progression. Cytochrome P450 (CYP) ...epoxygenases metabolize arachidonic acid to biologically active epoxyeicosatrienoic acids (EETs), which have potent anti-inflammatory effects. Although promoting the effects of EETs elicits anti-inflammatory and protective effects in the cardiovascular system, the contribution of CYP-derived EETs to the regulation of fatty liver disease-associated inflammation and injury is unknown. Using the atherogenic diet model of non-alcoholic fatty liver disease/non-alcoholic steatohepatitis (NAFLD/NASH), our studies demonstrated that induction of fatty liver disease significantly and preferentially suppresses hepatic CYP epoxygenase expression and activity, and both hepatic and circulating levels of EETs in mice. Furthermore, mice with targeted disruption of Ephx2 (the gene encoding soluble epoxide hydrolase) exhibited restored hepatic and circulating EET levels and a significantly attenuated induction of hepatic inflammation and injury. Collectively, these data suggest that suppression of hepatic CYP-mediated EET biosynthesis is an important pathological consequence of fatty liver disease-associated inflammation, and that the CYP epoxygenase pathway is a central regulator of the hepatic inflammatory response in NAFLD/NASH. Future studies investigating the utility of therapeutic strategies that promote the effects of CYP-derived EETs in NAFLD/NASH are warranted.
Background Sensitization to cockroach allergens is a major risk factor for asthma. The cockroach allergen Bla g 1 has multiple repeats of approximately 100 amino acids, but the fold of the protein ...and its biological function are unknown. Objective We sought to determine the structure of Bla g 1, investigate the implications for allergic disease, and standardize cockroach exposure assays. Methods nBla g 1 and recombinant constructs were compared by using ELISA with specific murine IgG and human IgE. The structure of Bla g 1 was determined by x-ray crystallography. Mass spectrometry and nuclear magnetic resonance spectroscopy were used to examine the ligand-binding properties of the allergen. Results The structure of an rBla g 1 construct with comparable IgE and IgG reactivity to the natural allergen was solved by x-ray crystallography. The Bla g 1 repeat forms a novel fold with 6 helices. Two repeats encapsulate a large and nearly spherical hydrophobic cavity, defining the basic structural unit. Lipids in the cavity varied depending on the allergen origin. Palmitic, oleic, and stearic acids were associated with nBla g 1 from cockroach frass. One unit of Bla g 1 was equivalent to 104 ng of allergen. Conclusions Bla g 1 has a novel fold with a capacity to bind various lipids, which suggests a digestive function associated with nonspecific transport of lipid molecules in cockroaches. Defining the basic structural unit of Bla g 1 facilitates the standardization of assays in absolute units for the assessment of environmental allergen exposure.
Prostate cancer eventually recurs during androgen deprivation therapy despite castrate levels of serum androgens. Expression of androgen receptor and androgen receptor-regulated proteins suggests ...androgen receptor activation in recurrent prostate cancer. Many groups have pursued mechanisms of ligand-independent androgen receptor activation but we found high levels of testicular androgens in recurrent prostate cancer tissue using RIA.
Prostate specimens from 36 men were procured preserving blood flow to prevent ischemia and cyropreserved immediately. Recurrent prostate cancer specimens from 18 men whose cancer recurred locally during androgen deprivation therapy and androgen-stimulated benign prostate specimens from 18 men receiving no hormonal treatments were studied. Tissue levels of testosterone and dihydrotestosterone were measured in each specimen using liquid chromatography/electrospray tandem mass spectrometry. Testosterone and dihydrotestosterone levels were compared with clinical variables and treatment received.
Testosterone levels were similar in recurrent prostate cancer (3.75 pmol/g tissue) and androgen-stimulated benign prostate (2.75 pmol/g tissue, Wilcoxon two-sided, P=0.30). Dihydrotestosterone levels decreased 91% in recurrent prostate cancer (1.25 pmol/g tissue) compared with androgen-stimulated benign prostate (13.7 pmol/g tissue; Wilcoxon two-sided, P < 0.0001) although dihydrotestosterone levels in most specimens of recurrent prostate cancer were sufficient for androgen receptor activation. Testosterone or dihydrotestosterone levels were not related to metastatic status, antiandrogen treatment, or survival (Wilcoxon rank sum, all P > 0.2).
Recurrent prostate cancer may develop the capacity to biosynthesize testicular androgens from adrenal androgens or cholesterol. This surprising finding suggests intracrine production of dihydrotestosterone and should be exploited for novel treatment of recurrent prostate cancer.
Evidence suggests that inflammation increases risk for ovarian cancer. Aspirin has been shown to decrease ovarian cancer risk, though the mechanism is unknown. Studies of inflammatory markers, lipid ...molecules such as arachidonic acid, linoleic acid, and alpha-linoleic acid metabolites, and development of ovarian cancer are essential to understand the potential mechanisms.
We conducted a nested case-control study (157 cases/156 matched controls) within the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial. Unconditional logistic regression was used to estimate the association between prediagnostic serum levels of 31 arachidonic acid/linoleic acid/alpha-linoleic acid metabolites and risk of ovarian cancer.
Five of the 31 arachidonic acid/linoleic acid/alpha-linoleic acid (free fatty acids) metabolites were positively associated with ovarian cancer risk: 8-HETE tertile 3 vs. 1: OR 2.53 (95% confidence interval CI 1.18-5.39),
0.02, 12,13-DHOME 2.49 (1.29-4.81), 0.01, 13-HODE 2.47 (1.32-4.60), 0.005, 9-HODE 1.97 (1.06-3.68), 0.03, 9,12,13-THOME 2.25 (1.20-4.21), 0.01. In analyses by subtype, heterogeneity was suggested for 8-HETE serous OR (95% CI): 2.53 (1.18-5.39) vs. nonserous OR (95% CI): 1.15 (0.56-2.36),
0.1 and 12,13-EpOME 1.95 (0.90-4.22) vs. 0.82 (0.39-1.73), 0.05.
Women with increased levels of five fatty acid metabolites (8-HETE, 12,13-DHOME, 13-HODE, 9-HODE, and 9,12,13-THOME) were at increased risk of developing ovarian cancer in the ensuing decade. All five metabolites are derived from either arachidonic acid (8-HETE) or linoleic acid (12,13-DHOME, 13-HODE, 9-HODE, 9,12,13-THOME) via metabolism through the LOX/cytochrome P450 pathway.
The identification of these risk-related fatty acid metabolites provides mechanistic insights into the etiology of ovarian cancer and indicates the direction for future research.
Eicosanoids are a class of bioactive lipids produced from the oxygenation of polyunsaturated fatty acid precursors, including the primary omega-6 fatty acids (linoleic acid LA and arachidonic acid ...AA) and omega-3 fatty acids (docosahexaenoic acid DHA and eicosapentaenoic acid EPA) 12. Namely, 1 participant previously categorized as AGA was recategorized as SGA, and 2 participants previously categorized as LGA were recategorized as AGA. ...our final distribution of outcome groups was 31 SGA cases, 31 AGA controls, and 28 LGA cases. Eicosanoid quantification A panel of eicosanoids and fatty acids was measured in plasma samples by the Mass Spectrometry Research and Support Group at the National Institute of Environmental Health Sciences (Research Triangle, NC, US) in 2018. The eicosanoid pathway is defined by a fatty acid precursor—linoleic acid (LA), arachidonic acid (AA), docosahexaenoic acid (DHA), or eicosapentaenoic acid (EPA)—that is metabolized by an enzyme—cytochrome P450 (CYP), lipoxygenase (LOX), or cyclooxygenase (COX).
The androgen receptor (AR) mediates the growth of benign and malignant prostate in response to dihydrotestosterone (DHT). In patients undergoing androgen deprivation therapy for prostate cancer, AR ...drives prostate cancer growth despite low circulating levels of testicular androgen and normal levels of adrenal androgen. In this report, we demonstrate the extent of AR transactivation in the presence of 5α-androstane-3α,17β-diol (androstanediol) in prostate-derived cell lines parallels the bioconversion of androstanediol to DHT. AR transactivation in the presence of androstanediol in prostate cancer cell lines correlated mainly with mRNA and protein levels of 17β-hydroxysteroid dehydrogenase 6 (17β-HSD6), one of several enzymes required for the interconversion of androstanediol to DHT and the inactive metabolite androsterone. Levels of retinol dehydrogenase 5, and dehydrogenase/reductase short-chain dehydrogenase/reductase family member 9, which also convert androstanediol to DHT, were lower than 17β-HSD6 in prostate-derived cell lines and higher in the castration-recurrent human prostate cancer xenograft. Measurements of tissue androstanediol using mass spectrometry demonstrated androstanediol metabolism to DHT and androsterone. Administration of androstanediol dipropionate to castration-recurrent CWR22R tumor-bearing athymic castrated male mice produced a 28-fold increase in intratumoral DHT levels. AR transactivation in prostate cancer cells in the presence of androstanediol resulted from the cell-specific conversion of androstanediol to DHT, and androstanediol increased LAPC-4 cell growth. The ability to convert androstanediol to DHT provides a mechanism for optimal utilization of androgen precursors and catabolites for DHT synthesis.
The biomarker 8-iso-prostaglandin F2α (8-iso-PGF2α) is regarded as the gold standard for detection of excessive chemical lipid peroxidation in humans. However, biosynthesis of 8-iso-PGF2α via ...enzymatic lipid peroxidation by prostaglandin-endoperoxide synthases (PGHSs), which are significantly induced in inflammation, could lead to incorrect biomarker interpretation. To resolve the ambiguity with this biomarker, the ratio of 8-iso-PGF2α to prostaglandin F2α (PGF2α) is established as a quantitative measure to distinguish enzymatic from chemical lipid peroxidation in vitro, in animal models, and in humans. Using this method, we find that chemical lipid peroxidation contributes only 3% to the total 8-iso-PGF2α in the plasma of rats. In contrast, the 8-iso-PGF2α levels in plasma of human males are generated >99% by chemical lipid peroxidation. This establishes the potential for an alternate pathway of biomarker synthesis, and draws into question the source of increases in 8-iso-PGF2α seen in many human diseases. In conclusion, increases in 8-iso-PGF2α do not necessarily reflect increases in oxidative stress; therefore, past studies using 8-iso-PGF2α as a marker of oxidative stress may have been misinterpreted. The 8-iso-PGF2α/PGF2α ratio can be used to distinguish biomarker synthesis pathways and thus confirm the potential change in oxidative stress in the myriad of disease and chemical exposures known to induce 8-iso-PGF2α.
•We evaluated class-specific mixtures of phenol, phthalate, and organophosphate ester biomarkers in maternal urine.•We assessed the bioactive lipids called oxylipins from several biosynthetic ...pathways in maternal plasma.•Higher consumer product chemicals were associated with certain pro-inflammatory oxylipins.•Consumer product chemicals may promote inflammation related to lipid metabolism during pregnancy.
Exposure to consumer product chemicals during pregnancy may increase susceptibility to pregnancy disorders by influencing maternal inflammation. However, effects on specific inflammatory pathways have not been well characterized. Oxylipins are a diverse class of lipids that act as important mediators and biomarkers of several biological pathways that regulate inflammation. Adverse pregnancy outcomes have been associated with circulating oxylipin levels in pregnancy. In this study, we aimed to determine the longitudinal associations between plasma oxylipins and urinary biomarkers of three classes of consumer product chemicals among pregnant women.
Data come from a study of 90 pregnant women nested within the LIFECODES cohort. Maternal plasma and urine were collected at three prenatal visits. Plasma was analyzed for 61 oxylipins, which were grouped according to biosynthetic pathways that we defined by upstream: 1) fatty acid precursor, including linoleic, arachidonic, docosahexaenoic, or eicosapentaenoic acid; and 2) enzyme pathway, including cyclooxygenase (COX), lipoxygenase (LOX), or cytochrome P450 (CYP). Urine was analyzed for 12 phenol, 12 phthalate, and 9 organophosphate ester (OPE) biomarkers. Linear mixed effect models were used for single-pollutant analyses. We implemented a novel extension of quantile g-computation for longitudinal data to examine the joint effect of class-specific chemical mixtures on individual plasma oxylipin concentrations.
We found that urinary biomarkers of consumer product chemicals were positively associated with pro-inflammatory oxylipins from several biosynthetic pathways. Importantly, these associations depended upon the chemical class of exposure biomarker. We estimated positive associations between urinary phenol biomarkers and oxylipins produced from arachidonic acid by LOX enzymes, including several important pro-inflammatory hydroxyeicosatetraenoic acids (HETEs). On average, mean concentrations of oxylipin produced from the arachidonic acid/LOX pathway were 48%–71% higher per quartile increase in the phenol biomarker mixture. For example, a simultaneous quartile increase in all urinary phenols was associated with 53% higher (95% confidence interval CI: 11%, 111%) concentrations of 12-HETE. The positive associations among phenols were primarily driven by methyl paraben, 2,5-dichlorophenol, and triclosan. Additionally, we observed that phthalate and OPE metabolites were associated with higher concentrations of oxylipins produced from linoleic acid by CYP enzymes, including the pro-inflammatory dihydroxy-octadecenoic acids (DiHOMEs). Associations among DiHOME oxylipins were driven by metabolites of benzylbutyl and di-isodecyl phthalate, and by the metabolite of tris(1,3-dichloro-2-propyl) phosphate among OPEs. We also observed inverse associations between phthalate and OPE metabolites and oxylipins produced from other pathways; however, adjusting for a plasma indicator of dietary fatty acid intake attenuated those results.
Our findings support the hypothesis that consumer product chemicals may have diverse impacts on inflammation processes in pregnancy. Certain pro-inflammatory oxylipins were generally higher among participants with higher urinary chemical biomarker concentrations. Associations varied by class of chemical and by the biosynthetic pathway of oxylipin production, indicating potential specificity in the inflammatory effects of these environmental chemicals during pregnancy that warrant investigation in larger studies.
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