Effects of high-fat diet on the patterns of prostatic cancer induced in rats by N-nitrosobis(2-oxopropyl)amine and testosterone

Abstract

Controversial views exist on the link between prostatic cancer and consumption of high-fat (HF) diet. This topic was examined in experimental prostatic cancer induced in rats by N-nitrosobis(2-oxopropyl)amine (BOP). Groups of Wistar-derived MRC rats were fed a semipurified diet containing either 5% (low fat = LF) or 24.6% (HF) corn oil for life, beginning after weaning. In the short-term study, treatment with testosterone significantly increased the rate of cellular DNA synthesis (as determined by autoradiographs after tritiated thymidine injection) that was not influenced by the level of dietary fat. HF diet alone depressed the rate significantly in the dorsal lobe only. There was a significant increase in the plasma level of estradiol, a decrease in the level of luteinizing hormone, but no changes in the level of follicle-stimulating hormone (FSH) in rats treated with testosterone, with no differences between the HF and LF groups. However, HF in the absence of testosterone depressed the serum FSH level. In the carcinogenicity experiment, all rats fed HF or LF diet developed prostatic cancers (mostly adenocarcinomas). The incidence, however, was significantly higher in testosterone-treated rats. Dietary fat did not influence the incidence, histological patterns, or anatomical distribution of tumors, and there were no differences in the parameters between the HF- and LF-fed groups. Long-term administration of testosterone significantly lowered serum levels of luteinizing hormone but did not change the FSH level and affected estradiol levels to a variable extent. These values were not influenced by dietary fat. However, in the HF-BOP group, significantly higher levels of FSH were found compared with the values in the LF-BOP group. We concluded that (a) under the described experimental conditions, dietary fat, fed ad libitum, does not influence the patterns of prostatic cancer induced in rats by BOP; (b) testosterone alters the serum levels of estradiol and luteinizing hormone; and (c) both testosterone and estradiol could be involved in carcinogenesis.