Transcript Laboratory of Microbial Ecology and Technology (LabMET)

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
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Colonmicrobiota and health
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Aid in digestion
Fermentation to useful VFA
Immunostimulation
Vitamin production
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Colonization resistance
Production of healthpromoting metabolites
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Production of toxins
Pathogen colonization
Aetiology in colorectal
cancer
(geno-)toxic compounds
from food (contaminants)
Recent (!): microbiota
stimulate fat uptake and
synthesis
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Metabolic potency
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Microbiota
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500 species, 1011 CFU/mL
High enzymatic diversity
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Saccharolytic and proteolytic fermentation
Conversion of food components
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Conversion of xenobiotics
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Deconjugation of phase II metabolites from liver and
enterocytes
Reductive, hydrolytic, degradative, even oxidative
Detoxification
<-> Toxification
More metabolic conversions than in liver !?
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Example 1: phytoestrogens
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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
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Example 2:
Heterocyclic aromatic amines
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Intestinal bacteria convert IQ
to hydroxylated metabolite
4'
Rumney et al. (1993)
5'
3'
2'
1'
6
7
CH3
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N
6'
5
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Intestinal bacteria convert
procarcinogen PHIP
Vanhaecke et al. (2006) Journal of
Agricultural and Food Chemistry
N
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2
NH 2
N
3'
4'
2'
1' 6
5'
7
CH 3
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N
2
6'
5
N
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N
10
NH
12
OH
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Example 3: mycotoxins
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Conversion of
zearalenone to zearalenol
Increase in estrogenic
properties
Relationship with
aetiology of cancer
development
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Colon microbiota may toxify xenobiotics
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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
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Case study: polycyclic aromatic hydrocarbons
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Food:
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Grilled, broiled... meat
 0.35 - 99 g B(a)P / kg
Environment:
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Atmospheric PAH deposition
on soil: 50 g.ha-1.yr-1
Soil ingestion (EPA):
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Adults: 50 mg.d-1
Children: 200 mg.d-1
Occasionally: 1-20 g.d-1
Inhalation of dust and
subsequent ingestion
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Incubation of PAH in SHIME
Simulator of Human Intestinal Microbial Ecosystem
• pure PAH compounds
• PAH contaminated soil
Stomach
Small
Colon
intestine
• Colon microbiota bioactivate PAH
• Hydroxylated PAH metabolites
• Estrogenic property
• Not considered in current risk assessment !!!
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SHIME: colon microbiota activate PAHs
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LC-ESI-MS: hydroxylation of PAHs in colon
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1-OH pyrene: 4.3 µg/L
7-OH B(a)P: 1.9 µg/L
Stomach
Small intestine
Colon
Inactivated colon
3,00
nM EE2 equivalence
2,50
2,00
1,50
1,00
0,50
0,00
naphthalene
phenanthrene
pyrene
benzo(a)pyrene
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Playground soil : 50 ppm PAH
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estrogenicity
25
% EE2 equivalence
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Lowest concentration in colon
Highest estrogenic activity
Risk assessment !!!
PAH release
µg PAH/L released
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20
15
10
5
0
stomach
small intestine
colon
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Manipulate bioactivation with pro- and prebiotics
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Probiotic: Lactobacillus amylovorus
 Incubate 40 µM B(a)P in colon suspension
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Prebiotic: oligofructose DP 3-60 (inulin)
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With / without 107 CFU/mL L. amylovorus
Short term effect
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 ?
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Chemopreventive effect: probiotic
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L. amylovorus lowers estrogenicity from B(a)P
incubated colon samples
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Chemopreventive effect: prebiotic
Proximal colon start-up
Proximal colon inulin
120
120
100
100
80
60
40
20
-11
-10
-9
-8
log mol L-1
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Distal colon inulin
80
60
40
0
-12
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Distal colon start-up
20
0
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EE2
% EE2 equivalence
% EE2 equivalence
EE2
-7
-6
-5
-12
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-9
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-6
-5
log mol L-1
Proximal colon: 40% decrease in estrogenicity
Distal colon: no significant decrease
Similar effects with phenanthrene and pyrene
Inulin exerts chemopreventive effect in proximal colon
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Prebiotic effects from inulin
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26% increase in SCFA (towards propionic and butyric
acid)
Significant increase in Bifidobacteria
Morecolon
pronounced
effects in proximal colon
ascendens
Start-up
Treatment
Control
60
50
µmol/g
40
30
20
10
0
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Chemopreventive effect from functional food
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Take into account interindividual variability
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Steer microbial community to health-promoting composition
Minimize hazardous bioactivation of ingested contaminants
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Take home messages
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Metabolic potency from gut microbiota
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Modulate hazardous bioactivation through diet
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Consider this process in risk assessment
Bacterial players in biological activation
Process conditions
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
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Contact information
LabMET – Ghent University
Coupure Links 653
B-9000 Gent
+32 9 264.59.76
[email protected]
http://labMET.ugent.be
http://www.shimetec.be
http://www.food2know.be
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