EFFECT OF DIETARY LIPIDS ON ACTIVITIES OF HEPATIC-STEROID METABOLIZING ENZYMES (5-ALPHA-REDUCTASE AND AROMATASE) AND COMPOSITION OF MICROSOMES

The effects of dietary fat (saturated, omega-6 and omega-3 fatty acids ) on the activities of two key steroid metabolizing enzymes, 5 alpha-r eductase and aromatase, were examined in the present study. These enzy mes are widely speculated to be involved in the initiation of prostate and breast cancer. Weanling male Sprague Dawley rats were fed semi-pu rified diets containing 14% fat of either beef-fat (BF), safflower oil (SO) or fish oil (FO) for 7 wks and enzyme activity and hepatic micro somal phospholipid fatty acid composition were analyzed. 5 alpha-reduc tase and aromatase activities were differentially modulated by the die tary lipids. Animals fed the FO diet showed significantly higher 5 alp ha-reductase activity compared to those fed the BF diet. Rats fed the SO diet had the highest activity of microsomal aromatase compared to a nimals fed the BF or FO diet. Liver microsomal lipids of animals fed t he BF diet had a higher percentage of saturated (stearic, 18:0) and mo nounsaturated (oleic, 18:1) fatty acids compared to those of SO and FO fed groups while microsomes of animals fed BF-and SO diets contained higher percentages of omega-6 fatty acids compared with FO diet group. Feeding FO diet resulted in accumulation of significantly higher leve ls of omega-3 fatty acids (20:5, 22:5 and 22:6) in the microsomes comp ared to the BF or SO fed groups. The data suggest that dietary fatty a cids may play a role in steroid hormone action through modulating the activities of these two steroid metabolizing enzymes.