Heterocyclic amines (HAs) are formed at ppb level during cooking of meat and fish. Epidemiological studies have shown a correlation between the intake of fried meat and cancer. The carcinogenicity of HAs has been shown in mice, rats and non-human primates. The human risk of HA intake is not clarified, but depends on the level of exposure, dietary factors influencing their uptake and biotransformation, and on the capacity of the individual to handle HAs. Exposure will be determined by new methods for analysis of HAs in foods and for biomarkers of internal and bioactive dose. Endogenous handling will be studied using cloning techniques; critical human enzymes and polymorphisms/genetic susceptibility in the bioactivation and detoxification of HAs and individual DNA repair capacity will be characterised. Exogenous dietary factors modifying the biological handling will be investigated.
The overall objective is to increase our understanding of the impact of exposure to heterocyclic amines on human health. Three major objectives can be identified: Improvement of (i) the assessments of exposure to HAs, (ii) the understanding of endogenous factors modifying the health effects of HAs, and (iii) the understanding of exogenous (dietary) factors modifying the health effects of HAs.
Exposure: Analytical methods for the determination of HAs in foods have been optimised and harmonised. Preliminary results of the most popular meat and fish dishes in Austria and in Sweden show that the precursors content in the meat has a marked influence on the formation of HAs during cooking. An analytical method for PhIP in human hair as a long-term biomarker for exposure to HAs has been developed. Ametabolite of PhIP, 5-OH-PhIP, was found in urine of exposed rats. Urinary mutagenic activity was measured after ingestion of meat with a defined amount of HAs, and two HAs were identified. The induction of tumours in Min-mice by PhIP has been performed.
Endogenous factors: V79 cell lines that co-express human enzymes have been genetically engineered and used to study the mutagenicity of HAs. Genotoxicity of HAs has been investigated with special emphasis on aminocarbolines in short-term tests. The metabolism of MeA€C has been studied in hepatic microsomes from rats and from humans. The mutagenicity of extracts of fried foods was studied through incubation with Lactobacillus strains. Germ-free rats were inoculated with human intestinal microflora and fed a standard or an experimental diet for four weeks to determine the genotoxic response.
Exogenous factors: New genetically altered V-79 cells have been used in two test systems, and it was possible to obtain positive effects with HAs. An improved protocol for the measurement of PhIP-induced DNA damage in mice and rats was established. Effects of Brassica vegetables on IQ induced liver foci in rats were studied; it is possible to use this method to investigate protective effects of vegetables. The effect of Brussels sprouts on urinary mutagenicity, induced by hamburgers, was monitored in a HA sensitive Salmonella strain. Preliminary findings showed that the HA induced effects decline after consumption of the vegetables.