Oat lipids-induced covalent DNA modifications (I-compounds) in female Sprague-Dawley rats, as determined by 32P-postlabeling

Abstract

Previous studies have shown that the presence of oats in the diet contributes to formation of I-compounds (age-dependent covalent DNA modifications detected by 32P-postlabeling assay) in female Sprague-Dawley rat liver DNA. The current study explored the possible ingredients in oats responsible for the observed effects on DNA. Feeding AIN-76A diet containing 5% oat lipids (obtained by methanol extraction and dissolved in trioctanoin) in place of corn oil for 2 months successfully induced the formation of 3 oats-specific (spots 2–4) and 4 natural ingredient diet-specific I-compounds (spots 6–9) in liver DNA. Barley, an oatlike cereal, induced 3 of these spots at very low intensities but not the 3 oats-specific I-spots. Oral administration of oat lipids to weanling rats of both sexes for 7 days elicited trace amounts of the oats-specific spots and spot 9 in liver DNA. However, when oat lipids were given at 6 or 9 weeks of age, the oats-specific spots were detected at high levels in female but not in male rats. These oats-related DNA modifications were also present in 6-week-old female rats which had received oat lipids p.o. for 2 or 3 days or i.p. for 4 days. Rats given trioctanoin or extracts from natural ingredient Wayne diet (lacking oats) did not show any of these spots. On the other hand, rats treated with extracts from an oats-containing Teklad diet displayed a trace amount of one of these I-compounds. Oat lipids did not induce any extra spots in rat kidney DNA. Feeding of AIN diet supplemented with oats to female Syrian hamsters did not elicit any renal or hepatic DNA alterations, as detected by 32P-postlabeling. Rats fed oat lipids-supplemented AIN diet or Purina diet showed the highest levels of I-compounds overall in liver among all dietary groups and these two groups also had significantly higher hepatic DNA synthesis rates. Oat lipids enhanced kidney DNA synthesis also. The total hepatic or renal cytochrome P-450 contents were not significantly affected by different diets. These results demonstrate a novel link between a natural dietary ingredient and covalent DNA modifications and shed light on the origins of certain I-compounds.