Highly hydrogenated dietary soybean oil modifies the responses to polychlorinated biphenyls in rats

The effects of dietary highly hydrogenated soybean oil (HSO) upon the changes caused by dietary polychlorinated biphenyls (PCBs) were examined in rats. Six groups of rats were fed the following diets for 30 d: a 20% soybean oil-containing diet (control diet), a diet in which a half of soybean oil was substituted with HSO (HSO-A diet), a diet in which cellulose powder was replaced with HSO (HSO-B diet) and these diets supplemented with 100 ppm PCBs (control + PCBs, HSO-A + PCBs and HSO-B + PCBs diets). Hepatic concentration of PCBs and relative liver weight were markedly decreased in rats fed with the HSO-A + PCBs diet compared with those fed with the other diets containing PCBs. Liver lipids and liver cholesterol were considerably decreased with a reciprocal increase in fecal sterol excretion by rats fed the HSO-A + PCBs and the HSO-B + PCBs diets compared with those fed with the control + PCBs diet. The fatty acid composition in hepatic phospholipids showed an independent increase of the saturated fatty acid content induced by dietary HSO and PCBs. Dietary PCBs also caused decreases in the amounts of monounsaturated and n-3 polyunsaturated fatty acids. These results suggest that dietary HSO prevents accumulation of PCBs in the liver and promotes the excretion of lipids stimulated by PCBs, accompanied by a change in fatty acid metabolism.