Apiaceous vegetable consumption decreases PhIP-induced DNA adducts and increases methylated PhIP metabolites in the urine metabolome in rats.
BACKGROUND
Heterocyclic aromatic amines, such as 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), are carcinogenic compounds produced during heating of protein-containing foods. Apiaceous vegetables inhibit PhIP-activating enzymes, whereas cruciferous vegetables induce both PhIP-activating and -detoxifying enzymes.


OBJECTIVE
We investigated the effects of these vegetables, either alone or combined, on PhIP metabolism and colonic DNA adduct formation in rats.


METHODS
Male Wistar rats were fed cruciferous vegetables (21%, wt:wt), apiaceous vegetables (21%, wt:wt), or a combination of both vegetables (10.5% wt:wt of each). Negative and positive control groups were fed an AIN-93G diet. After 6 d, all groups received an intraperitoneal injection of PhIP (10 mg · kg body weight(-1)) except for the negative control group, which received only vehicle. Urine was collected for 24 h after the injection for LC-tandem mass spectrometry metabolomic analyses. On day 7, rats were killed and tissues processed.


RESULTS
Compared with the positive control, cruciferous vegetables increased the activity of hepatic PhIP-activating enzymes [39.5% and 45.1% for cytochrome P450 (CYP) 1A1 (P = 0.0006) and CYP1A2 (P < 0.0001), respectively] and of uridine 5'-diphospho-glucuronosyltransferase 1A (PhIP-detoxifying) by 24.5% (P = 0.0267). Apiaceous vegetables did not inhibit PhIP-activating enzymes, yet reduced colonic PhIP-DNA adducts by 20.4% (P = 0.0496). Metabolomic analyses indicated that apiaceous vegetables increased the relative abundance of urinary methylated PhIP metabolites. The sum of these methylated metabolites inversely correlated with colonic PhIP-DNA adducts (r = -0.43, P = 0.01). We detected a novel methylated urinary PhIP metabolite and demonstrated that methylated metabolites are produced in the human liver S9 fraction.


CONCLUSIONS
Apiaceous vegetables did not inhibit the activity of PhIP-activating enzymes in rats, suggesting that the reduction in PhIP-DNA adducts may involve other pathways. Further investigation of the importance of PhIP methylation in carcinogen metabolism is warranted, given the inverse correlation of methylated PhIP metabolites with a biomarker of carcinogenesis and the detection of a novel methylated PhIP metabolite.
Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN.
Jae Kyeom
JK
Kim
Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN.
Daniel D
DD
Gallaher
Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN.
Chi
C
Chen
Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN.
Dan
D
Yao
Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN trudo@umn.edu.
Sabrina P
SP
Trudo
D000818:Animals; D015239:Arylsulfotransferase / Q000235:genetics / Q000378:metabolism; D001711:Biotransformation; D002273:Carcinogens / Q000633:toxicity; D002853:Chromatography, Liquid; D003106:Colon / Q000187:drug effects / Q000378:metabolism; D019363:Cytochrome P-450 CYP1A1 / Q000235:genetics / Q000378:metabolism; D019388:Cytochrome P-450 CYP1A2 / Q000235:genetics / Q000378:metabolism; D018736:DNA Adducts / Q000378:metabolism*; D014453:Glucuronosyltransferase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000378:metabolism* / Q000633:toxicity* / Q000652:urine; D008099:Liver / Q000187:drug effects / Q000378:metabolism; D008297:Male; D055442:Metabolome / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D053719:Tandem Mass Spectrometry; D014675:Vegetables; D000099148:UGT1A1 Enzyme
D015239:Arylsulfotransferase; D002273:Carcinogens; D019363:Cytochrome P-450 CYP1A1; D019388:Cytochrome P-450 CYP1A2; D018736:DNA Adducts; D014453:Glucuronosyltransferase; D007093:Imidazoles; C502239:2-amino-1-methyl-6-phenolimidazo(4,5-b)pyridine-DNA adduct; C499946:Ugt1a1 protein, rat; D000099148:UGT1A1 Enzyme; C049584:2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine; C573795:Sult1a1 protein, rat
2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine; DNA adducts; N-methyltransferase; apiaceous vegetables; biotransformation enzymes; cruciferous vegetables; heterocyclic aromatic amines; metabolomics