Transcript No Slide Title

Human in vitro digestion models
powerful tools to predict maximum oral (relative) bioavailability
Esther F.A. Brandon
Centre for Substances and Integrated Risk Assessment
National Institute for Public Health and the Environment (RIVM)
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Humans are exposed to many compounds
food, medicines
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environment
air water soil
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Outline of presentation
• bioaccessibility and bioavailability
• in vitro digestion models
• examples
– lead from paint in top
– folic acid from dietary supplements
• validation
• conclusions
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Oral exposure: bioaccessibility and bioavailability
External
exposure
mouth
Exposure to contaminant in a matrix
Ingestion of matrix + contaminant
oesophagus,
stomach,
small intestine
FB = Fraction released from matrix = bioaccessible fraction
small intestine
portal vein
FA= Fraction of FB absorbed by small intestine
liver
systemic
circulation
FH = Fraction of FA after the liver without being metabolised
F = Fraction reaching systemic circulation = bioavailable fraction
Internal exposure F = FB x FA x FH
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Oral exposure
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release depends on type of oral contact
release depends on type of matrix
release from matrix  exposure
release from matrix can be
measured by sampling
– one way to study release after
oral exposure is using
in vitro digestion models
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In vitro digestion model
• principle
 various compartments of the human gastrointestinal tract
(mouth to small intestine) are simulated
 digestive juices are prepared artificially based on human
physiology
 matrix is introduced in mouth compartment, then transferred
to the stomach and finally to the small intestine
 transit times depend on the input of the risk assessor and
human physiology
 sampling compartment based on site of absorption
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In vitro digestion models
+ matrix
+ saliva
+ gastric juice
rotate
5 min at
37 C
empty
test tube
+ duodenal juice
+ bile
(+ NaHCO3)
step 1:
“mouth”
rotate
2 h at
37 C
step 2:
“stomach”
centrifuge (5 min 2750 g)
separate chyme and pellet
rotate
2 h at
37 C
step 3:
“small intestine”
+
chyme
pellet
analysis of
compound
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Developed in vitro digestion models
• for application of compounds in food and
supplements
 fasted conditions
 fed conditions
• for application of consumer products
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sucking
sucking and then swallowing
direct swallowing under fasted conditions
direct swallowing under fed conditions
• for application of soil
 fasted conditions
 fed conditions
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Different products and compounds tested
• mycotoxins from food
• folic acid from dietary supplements and enriched food products
• folate from natural food sources
• azo dyes in textile
• lead in street chalk and paint scraped from tops
• benzoic acid in finger paint
• lead and arsenic from contaminated soils
• lead from house dust
www.greenpeace.org.uk
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example - lead in paint scraped from top
• paint: lead level 14.4-15.2 mg/g
• situation simulated: ingestion of scraped of paint
– bioaccessibility under fasted conditions ~9.5%
– bioaccessibility under fed conditions ~4%
• large difference between external and internal exposure
• based on risk assessment this top is not safe for children
(11 mg paint leads to exceeding the TDI)
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Validation
• for lead and arsenic from soil (Oomen et al,. 2006)
• the mycotoxins aflatoxin B1 and ochratoxin A investigating
different adsorbents (Versantvoort et al., 2004)
Although relevant in vivo data are scarce, we succeeded to
preliminary validate the model for some cases
These cases showed good correlation and never
underestimated the bioavailability
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Scientific conclusions
• internal exposure can be considerably less than external
exposure
• bioaccessibility/bioavailability is highly dependent on
matrix and compound
• bioaccessibility can easily be measured experimentally
• the outcome should be interpreted as indicative
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Relevancy for industry, policy makers and upholders
• more accurate risk
assessment of ingested
contaminants
industry
Dutch Food and Consumer
Product Safety Authority
new product or sample
survey from a batch
random sample survey or
for ad hoc situations
in vitro digestion model for
relevant exposure scenario
• more accurate exposure
assessment for other
compounds, e.g.
vitamins
internal exposure value for
realistic worst case scenario
risk assessment
product safe?
yes or no
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Acknowledgment
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Agnes Oomen (Centre for Substances and Integrated Risk Assessment, RIVM)
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Adrienne Sips (Centre for Substances and Integrated Risk Assessment, RIVM)
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Carolien Versantvoort (Centre for Substances and Integrated Risk Assessment, RIVM)
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Cathy Rompelberg (Centre for Nutrition and Health, RIVM)
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Marco Blokland and co-workers (Laboratory for Food and Residue Analyses , RIVM)
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Peter Bragt and Martien Spanjer (Food and Consumer Product Safety Authority)
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Bülent Kabak (University of Cukurova, Turkey)
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Paula Alvito (Food Safety and Nutrition Centre, Portugal)
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Karin Ljung (Swedish University of Agricultural Sciences, Sweden)
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Rawad Massoud (Utrecht University, The Netherlands)
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RIVM reports and articles
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Kabak B, Brandon EFA, Vara I, Sizoo EA, Blokland MH, van Egmond HP, Sips
AJAM. Effects of probiotic bacteria on the bioaccessibility of aflatoxin B1 and
ochratoxin A using an in vitro digestion model under fed conditions. In preparation.
Oomen AG, Brandon EFA, Swartjes FA, Sips AJAM (2006). How can information on
oral bioavailability improve human health risk assessment for lead-contaminated
soils? Implementation and scientific basis. RIVM report 711701042, Bilthoven, the
Netherlands. Available at http://www.rivm.nl/bibliotheek/rapporten/711701042.pdf
Brandon EFA, Oomen AG, Rompelberg CJM, Versantvoort CHM, van Engelen JGM,
Sips AJAM (2006). Consumer product in vitro digestion model: bioaccessibility of
contaminants and its application in risk assessment. Reg Toxicol Pharmacol 44: 161171.
Versantvoort CHM, Oomen AG, van de Kamp E, Rompelberg CJM, Sips AJAM
(2005). Applicability of an in vitro digestion model in assessing the bioaccessibility of
mycotoxins from food. Food Chem Toxicol 43: 31-40.
Versantvoort CHM, van de Kamp E, Rompelberg CJM. Development and applicability
of an in vitro digestion model in assessing the bioaccessibility of contaminants from
food (2004). RIVM report 320102002, Bilthoven, the Netherlands. Available at
http://www.rivm.nl/bibliotheek/rapporten/320102002.pdf
Oomen AG, Rompelberg CJM, Bruil MA, Dobbe CJG, Pereboom DPKH, Sips AJAM
(2003). Development of an in vitro digestion model for estimating the bioaccessibility
of soil contaminants. Arch Environ Contam Toxicol 44: 281-287.
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