Dietary oat lipids-induced novel DNA modifications and suppression of altered hepatic foci formation

Previous studies have shown that the presence of several hepatic I-compound s, i.e., age-dependent covalent DNA modifications, is related to the presen ce of a natural ingredient, i.e., oats, in the diet. To demonstrate the bio logical significance of these novel DNA modifications, the effect of oat li pids on tumor initiation and promotion was examined in a rat fiver tumor mo del. Female Sprague-Dawley rats were treated with a single dose of diethyln itrosamine, a hepatic carcinogen, 24 hours after a 70% partial hepatectomy, then subjected to dietary phenobarbital promotion. Diets containing 10% oa r lipids or corn oil were given during the initiation or the promotion stag e of the tumorigenesis. At the end of the feeding, hepatic I-compounds were measured by P-32 postlabeling, and the number and volume of enzyme-altered hepatic foci, which served as preneoplastic markers, were measured in seri al sections of liver by the method of quantitative stereology. Rats receivi ng oat lipids supplemented diets had five- To sixfold higher levels of I-co mpounds in their liver DNA than those receiving control diets. Meanwhile, r ats receiving diets containing oat lipids during promotion had significantl y smaller numbers and reduced volume of altered hepatic foci compared with those fed the control diet containing corn oil. These observations support the hypothesis that some I-compounds, e.g., the oats-specific I-compounds, are novel DNA modifications related to nutrient metabolism. The diet contai ning oat lipids may have chemopreventive activities, as demonstrated in thi s model system.