Of Mice and Men
Mice are often used to test whether substances in food are harmful to humans. This requires that mice and humans metabolize substances in the same way. This may not be perfectly true (after all mice and men are different). The health risk associated with harmful substances in food may therefore be underestimated. Researchers at the Norwegian Institute of Public Health have adopted a mouse type where human enzymes have been inserted to examine whether people may be more sensitive to certain carcinogenic substances from heat-treated foods. They have obtained a better model to assess negative health effects in humans from substances in food using these mice.
Heat-processing of food can lead to the formation of carcinogenic substances. The formation of carcinogenic substances - so-called food mutagens — usually occurs at high temperatures when frying or grilling.
There are enzymes called sulfotransferases (SULT) in several places in the human body. These are only found in the livers of normal laboratory mice. SULT-enzymes can make some substances in food less harmful, but they can also transform harmless substances into carcinogenic substances.
The SULT enzymes transfer sulfate groups to various acceptor molecules. They are involved in posttranslational sulfation of proteins and sulfate conjugation of exogenous chemicals and bile acids.
Humans have SULT-enzymes in many organs while normal mice only have them in the liver. Using results from laboratory mice to predict health risk to humans consuming food mutagens can therefore be underestimated.
The mice received the food mutagen often found in highest quantities in the crust of meat and fish. The researchers wanted to study tumor development in the intestines of the modified mice, and compare this with tumour development in normal mice given the same food mutagen.
The results showed that the incidence of intestinal tumors increased from 31 per cent to 80 per cent in modified mice after consuming substances from the meat crust.
This shows that normal laboratory mice are not a perfect model for assessing the health risk to humans following ingestion of food mutagens from well-done meat and fish.