Effect of varying dietary fat levels on rat growth and oxidative DNA damage

Dietary fat has previously been shown to have somewhat complicated relation ships to levels of oxidative stress in rats. In this study, we examined the effects of five different dietary fat intakes on levels of oxidative DNA d amage in rats. Animals fed diets containing 3%, 5%, 10%, or 15% corn oil ha d body weights that were similar after 20 weeks. Animals fed a 20% fat diet , however, had significantly higher mean body weight than any other group. Levels of 5-hydroxymethyl-2'-deoxyuridine, one marker of oxidative DNA dama ge, had different relationships to dietary fat in blood and mammary gland. In blood, levels increased with dietary fat levels, and the highest levels were observed with the 20% fat diet (65% higher levels than with the 3% fat diet). In mammary gland, a plateau-type effect was observed, with maximal levels of oxidative DNA damage being obtained using 10% fat (representing a 68% increase relative to the 3% fat diet). This could be a result of induc tion of compensatory mechanisms in response to a high fat diet in mammary g land but not in the short-lived nucleated blood cells. Oxidative DNA damage levels in blood thus appear to be a marker of dietary fat intake. In mamma ry gland, however, levels of DNA damage are consistent with previously obse rved promotional effects of dietary fat on mammary gland tumorigenesis at l ower levels of fat intake with little or no incremental promoting effects a t higher levels of fat intake.