Impact of Dietary Lipid and Garlic on the Binding of 7,12-dimethylbenz[a]anthracene (DMBA) to Mammary DNA
The present studies determined the impact of dietary lipids in the presence or absence of supplemental garlic on the binding of DMBA to mammary cell DNA in female Sprague-Dawley rats. In all studies rats were fed for 2 weeks prior to DMBA treatment (25 mg/kg body weight). DMBA-DNA adducts were quantitated using a 32P-postlabeling technique. In experiment 1, rats were feed diets with or without 2% garlic and varying amounts of corn oil (5, 10, or 20%). Increasing dietary corn oil resulted in a proportional increase in DMBA-DNA binding. The depression in total and individual DMBA-DNA adducts resulting from garlic consumption was greatest in rats fed 20% corn oil. Experiment 2 examined the influence of source of lipid (15% corn, olive, coconut, or fish oil) added to basal diets containing 5% corn oil. Regardless of source, consumption of diets containing 20% lipid increased DMBA-DNA binding by approximately 100% compared to diets containing 5% dietary corn oil in experiment 2. Garlic depressed DMBA-DNA binding by 50, 29, and 70% when diets contained 20% corn, olive, or fish oil, respectively. Although coconut oil increased the formation of DMBA-DNA adducts, garlic failed to reduce the binding when this source of lipid was provided. These studies demonstrate an effect of several sources of lipids on the initiation phase of carcinogenesis. Furthermore, these studies suggest the effect of garlic is dependent upon the degree of unsaturation of the dietary lipid fed.