title: Acid-labile protein-adducted heterocyclic aromatic amines in human blood are not viable biomarkers of dietary exposure: A systematic study.
abstract: Heterocyclic aromatic amines (HCA) are carcinogenic mutagens formed during cooking of protein-rich foods. HCA residues adducted to blood proteins have been postulated as biomarkers of HCA exposure. However, the viability of quantifying HCAs following hydrolytic release from adducts in vivo and correlation with dietary intake are unproven. To definitively assess the potential of labile HCA-protein adducts as biomarkers, a highly sensitive UPLC-MS/MS method was validated for four major HCAs: 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx) and 2-amino-3,7,8-trimethylimidazo[4,5-f]quinoxaline (7,8-DiMeIQx). Limits of detection were 1-5 pg/ml plasma and recoveries 91-115%. Efficacy of hydrolysis was demonstrated by HCA-protein adducts synthesised in vitro. Plasma and 7-day food diaries were collected from 122 fasting adults consuming their habitual diets. Estimated HCA intakes ranged from 0 to 2.5 mg/day. An extensive range of hydrolysis conditions was examined for release of adducted HCAs in plasma. HCA was detected in only one sample (PhIP, 9.7 pg/ml), demonstrating conclusively for the first time that acid-labile HCA adducts do not reflect dietary HCA intake and are present at such low concentrations that they are not feasible biomarkers of exposure. Identification of biomarkers remains important. The search should concentrate on stabilised HCA-peptide markers and use of untargeted proteomic and metabolomic approaches.
authors.affiliation: Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, 18-30 Malone Road, Belfast, BT9 5BN, United Kingdom. Electronic address: k.cooper@qub.ac.uk.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Cooper
authors.affiliation: Centre for Public Health, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, Belfast, BT12 6BA, United Kingdom.
authors.forename: Sarah F
authors.initials: SF
authors.lastname: Brennan
authors.affiliation: Centre for Public Health, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, Belfast, BT12 6BA, United Kingdom.
authors.forename: Jayne V
authors.initials: JV
authors.lastname: Woodside
authors.affiliation: Centre for Public Health, School of Medicine, Dentistry and Biomedical Science, Queen's University Belfast, Belfast, BT12 6BA, United Kingdom.
authors.forename: Marie
authors.initials: M
authors.lastname: Cantwell
authors.affiliation: Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, 18-30 Malone Road, Belfast, BT9 5BN, United Kingdom.
authors.forename: Xiaoxiao
authors.initials: X
authors.lastname: Guo
authors.affiliation: Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, 18-30 Malone Road, Belfast, BT9 5BN, United Kingdom.
authors.forename: Mark
authors.initials: M
authors.lastname: Mooney
authors.affiliation: Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, 18-30 Malone Road, Belfast, BT9 5BN, United Kingdom.
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Elliott
authors.affiliation: Institute for Global Food Security, School of Biological Sciences, Queen's University Belfast, 18-30 Malone Road, Belfast, BT9 5BN, United Kingdom.
authors.forename: Geraldine J
authors.initials: GJ
authors.lastname: Cuskelly
mesh_terms: D000588:Amines / Q000097:blood* / Q000737:chemistry; D002853:Chromatography, Liquid; D003430:Cross-Sectional Studies; D006571:Heterocyclic Compounds / Q000097:blood* / Q000737:chemistry; D006801:Humans; D006868:Hydrolysis; D053719:Tandem Mass Spectrometry
chemical_list: D000588:Amines; D006571:Heterocyclic Compounds
keywords: Heterocyclic amines; LC-MS/MS; PhIP; Plasma; Protein adducts; Serum albumin