ORIGINAL ARTICLE Chemopreventive effects from prebiotic inulin towards microbial 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine bioactivation L. Vanhaecke, C. Grootaert, W. Verstraete and T. Van de Wiele Laboratory of Microbial Ecology and Technology (LabMET), Faculty of Bioscience Engineering, Ghent University – UGent, Coupure Links 653, Ghent, Belgium Introduction Dietary epidemiological studies implicate heterocyclic amines (HCA), mutagenic ⁄ carcinogenic compounds formed from high-protein diets during cooking, as risk factors in the aetiology of human cancer (Felton et al. 2005). Of the 19 heterocyclic amines identified so far, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is the most mass abundant HCA produced during the cooking of beef, pork and chicken (Felton et al. 1986; Murray et al. 1993; Sinha et al. 1995; Wong et al. 2005). Experimentally, PhIP is a potent mutagen and genotoxin and has been shown to produce mammary gland, prostate and colon tumours in rats (Ito et al. 1991; Shirai et al. 1997; Sugimura 2000). In humans, less is known about the potential role of PhIP and related HCA in tumour development. Several studies have shown that individuals who eat well-done meat have an elevated risk of breast (Zheng et al. 1998) and colorectal (Sinha 1999; Gunter et al. 2005) cancers. In realizing its mutagenic potential, PhIP requires meta- bolic activation by drug-metabolizing enzymes (Aeschbacher and Turesky 1991). In common with other genotoxic aro- matic amines, PhIP is metabolically activated via oxidation of the exocyclic amino group, a reaction mainly mediated by the cytochrome P450 isoenzyme CYP1A2 (Crofts et al. 1998; Turesky et al. 2002). While PhIP is biotransformed into a large number of derivates by mammalian enzyme Keywords cancer, genotoxic, heterocyclic amines, human colonic bacteria, SHIME. Correspondence Tom Van de Wiele, Laboratory of Microbial Ecology and Technology, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium. E-mail: tom.vandewiele@ugent.be 2008 ⁄ 0666: received 18 April 2008, revised 25 June 2008 and accepted 07 July 2008 doi:10.1111/j.1365-2672.2008.04015.x Abstract Aims: Using a Simulator of the Human Intestinal Microbial Ecosystem (SHIME), we investigated the chemopreventive potential of prebiotic chicory inulin towards the in vitro bioactivation of 2-amino-1-methyl-6-phenylimi- dazo[4,5-b]pyridine (PhIP) by human intestinal microbiota. Methods and Results: HPLC data revealed that inulin significantly decreased the formation of the genotoxic PhIP-M1 metabolite, with the highest inhibitory activity in the colon ascendens (87% decrease). Interestingly, this chemopre- ventive effect correlated with alterations of bacterial community composition and metabolism in the different colon compartments. Conventional culture- based techniques and PCR-DGGE analysis on the SHIME colon suspension revealed significant bifidogenic effects during inulin treatment, whereas the overall microbial community kept relatively unchanged. Additionally, the pro- duction of short-chain fatty acids increased with 12%, 3% and 7%, while ammonia concentrations decreased with 3%, 4% and 3% in the ascending, transverse and descending colon compartments, respectively. Conclusions: These results indicate that the prebiotic effects from inulin may also purport protective effects towards microbial PhIP bioactivation. Significance and Impact of the Study: As the colonic microbiota may contri- bute significantly to the carcinogenic potential of PhIP, the search for dietary constituents that decrease the formation of this harmful metabolite, may help in preventing its risk towards human health. Journal of Applied Microbiology ISSN 1364-5072 474 Journal compilation ª 2009 The Society for Applied Microbiology, Journal of Applied Microbiology 106 (2009) 474–485 ª 2009 The Authors