Effect of Types and Amount of Dietary Fat During the Initiation Phase of Hepatocarcinogenesis

Abstract

The effects of various levels of corn oil and lard fed during the initiation stage of azoxymethane (AOM)-induced hepatocarcinogenesis were studied in male Fischer 344 rats. The animals were fed diets containing 5%, 13.6%, and 23.5% corn oil or lard two weeks before, during, and until one week after injections of AOM (15 mg/kg body wt sc) once weekly for two weeks. One week after AOM treatment, groups of animals fed the 13.6% and 23.5% corn oil or lard diet were transferred to their respective 5% corn oil or lard diet and fed these diets until the termination of the study (34 wk). Immunohistochemical staining of glutathione S-transferase placental form was performed in the liver, and the number of glutathione S-transferase placental form-positive foci was determined. Density, average area, and unit area of foci were significantly inhibited in the animals fed the 13.6% and 23.5% lard diets compared with those fed the 13.6% and 23.5% corn oil diets. These results indicate that the effect of dietary fat during the initiation phase of AOM-induced hepatocarcinogenesis depends on the type of fat and its fatty acid composition. Additionally, the enhancing effect of a corn oil diet in hepatocarcinogenesis is mainly present during the initiation phase of carcinogenesis compared with a lard diet.