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Chemopreventive Effects of Pro- and Prebiotics on Microbial Bioactivation of Ingested Contaminants

This study explores how inulin and Lactobacillus amylovorus supplementation in the human gut microbiota can lower the microbial bioactivation of dietary aromatic contaminants to estrogenic metabolites. The manipulation of the microbial community through functional foods can have chemopreventive effects, minimizing the hazardous bioactivation of ingested contaminants. The study provides insights into the potential of probiotics and prebiotics in reducing the risk of hormone-related cancers.

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Chemopreventive Effects of Pro- and Prebiotics on Microbial Bioactivation of Ingested Contaminants

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  1. Chemopreventive effects of pro- and prebiotics towards microbial bioactivation of ingested contaminants Inulin and Lactobacillus amylovorus supplemented to human gut microbiota lower the microbial bioactivation of dietary aromatic contaminants to estrogenic metabolites Tom Van de Wiele, Lynn Vanhaecke, Charlotte Boeckaert, Heidi Jacobs, Willy Verstraete Laboratory Microbial Ecology and Technology Ghent University - Belgium

  2. Aid in digestion Fermentation to useful VFA Immunostimulation Vitamin production Colonization resistance Production of health-promoting metabolites Production of toxins Pathogen colonization Aetiology in colorectal cancer (geno-)toxic compounds from food (contaminants) Recent (!): microbiota stimulate fat uptake and synthesis Colonmicrobiota and health

  3. Metabolic potency • Microbiota • 500 species, 1011 CFU/mL • High enzymatic diversity • Saccharolytic and proteolytic fermentation • Conversion of food components • Conversion of xenobiotics • Deconjugation of phase II metabolites from liver and enterocytes • Reductive, hydrolytic, degradative, even oxidative • Detoxification <-> Toxification • More metabolic conversions than in liver !?

  4. Example 1: phytoestrogens • Gut bacteria convert isoxanthohumol to hoppein • Most powerful phytoestrogen • Food supplements • Hormone substitution therapy • Prevention of hormone related cancers (breast/prostate) • Possemiers et al. (2006) Journal of Nutrition

  5. Example 2: Heterocyclic aromatic amines • Intestinal bacteria convert IQ to hydroxylated metabolite • Rumney et al. (1993) • Intestinal bacteria convert procarcinogen PHIP • Vanhaecke et al. (2006) Journal of Agricultural and Food Chemistry

  6. Example 3: mycotoxins • Conversion of zearalenone to zearalenol • Increase in estrogenic properties • Relationship with aetiology of cancer development

  7. Colon microbiota may toxify xenobiotics • Oral exposure to food and environmental contaminants • Enormous microbial metabolic potency • If toxification significantly contributes to total risk from ingested contaminant... • Can we do something about it ? • Manipulate microbial community ? • Functional foods: probiotics, prebiotics

  8. Case study: polycyclic aromatic hydrocarbons • Food: • Grilled, broiled... meat • 0.35 - 99 g B(a)P / kg • Environment: • Atmospheric PAH deposition on soil: 50 g.ha-1.yr-1 • Soil ingestion (EPA): • Adults: 50 mg.d-1 • Children: 200 mg.d-1 • Occasionally: 1-20 g.d-1 • Inhalation of dust and subsequent ingestion

  9. Incubation of PAH in SHIME • Simulator of Human Intestinal Microbial Ecosystem • pure PAH compounds • PAH contaminated soil Small intestine Stomach Colon • Colon microbiota bioactivate PAH • Hydroxylated PAH metabolites • Estrogenic property • Not considered in current risk assessment !!!

  10. SHIME: colon microbiota activate PAHs • LC-ESI-MS: hydroxylation of PAHs in colon • 1-OH pyrene: 4.3 µg/L • 7-OH B(a)P: 1.9 µg/L

  11. Playground soil : 50 ppm PAH • Lowest concentration in colon • Highest estrogenic activity • Risk assessment !!!

  12. Manipulate bioactivation with pro- and prebiotics • Probiotic: Lactobacillus amylovorus • Incubate 40 µM B(a)P in colon suspension • With / without 107 CFU/mL L. amylovorus • Short term effect • Prebiotic: oligofructose DP 3-60 (inulin) • SHIME run: • Start-up: 2 weeks • Treatment: 3 weeks inulin (2.5 g/d) • Incubate 40 µM B(a)P in colon suspension • Compare start-up with treatment period • Long term effect • Chemopreventive effect as added-value ?

  13. Chemopreventive effect: probiotic • L. amylovorus lowers estrogenicity from B(a)P incubated colon samples

  14. Chemopreventive effect: prebiotic • Proximal colon: 40% decrease in estrogenicity • Distal colon: no significant decrease • Similar effects with phenanthrene and pyrene • Inulin exerts chemopreventive effect in proximal colon

  15. Prebiotic effects from inulin • 26% increase in SCFA (towards propionic and butyric acid) • Significant increase in Bifidobacteria • More pronounced effects in proximal colon

  16. Chemopreventive effect from functional food • Take into account interindividual variability • Steer microbial community to health-promoting composition • Minimize hazardous bioactivation of ingested contaminants

  17. Take home messages • Metabolic potency from gut microbiota • Consider this process in risk assessment • Bacterial players in biological activation • Process conditions • Modulate hazardous bioactivation through diet • Chemopreventive process: how does it work • Inhibition of bioactivation reactions • Inhibition of responsible microorganism • Sorption to dietary fibres lower bioavailability • Chemopreventive effects are an added-value • Manipulation of community through functional food

  18. Contact information LabMET – Ghent University Coupure Links 653 B-9000 Gent +32 9 264.59.76 tom.vandewiele@ugent.be http://labMET.ugent.be http://www.shimetec.be http://www.food2know.be

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