Rats were fed cholesterol-free or cholesterol-enriched diets containing olive oil or partially hydrogenated corn oil at the 10% level for ca. 30 days (c-18:1, 77.0% in the former diet and c-18:1,24.7% and t-18:1,42.5% in the latter). The linoleic acid content of these fat diets was made equivalent (1.7 energy %). After feeding cholesterol-free diets, trans fat compared to cis fat showed (a) no untoward effects on growth parameters, (b) a reduction of serum cholesterol levels without influencing concentrations of serum apolipoproteins A-1, B and E, (c) no effects on the bile flow and the concentration of biliary cholesterol and bile acids, (d) an increasing trend of fecal excretion of neutral and acidic steroids, both in terms of mg/day and mg/g feces, and (e) rather equivocal change in the composition of fecal, but not biliary steroids. Similar response patterns were also observed when cholesterol-enriched diets were fed except for a decrease in serum apo B and an ineffectiveness to increase fecal acidic steroids. Together with the results obtained from experiments simultaneously performed with safflower oil and completely hydrogenated corn oil, it seems that the steroid metabolism can be specifically modified by the geometry of dietary fats.

Male Wistar rats were fed cholesterol-free or cholesterol-enriched diets containing partially hydrogenated soybean oil with different levels oftrans-fatty acids or unhydrogenated soybean oil at the 10% level. The linoleic acid content of hydrogenated fat diets was adjusted to 3.6% of the total energy. Hydrogenated fat diets contained 29% and 41%trans-acids, mainly ast-18∶1.Trans-fats exerted no untoward effects on growth parameters, but increased liver weight. Dietary hydrogenated fats influenced neither the concentration nor composition of biliary steroids, irrespective of the presence or absence of cholesterol in the diet. In rats fed a cholesterol-free diet, daily fecal output of neutral and acidic steroids was enhanced by hydrogenated fats and the magnitude of augmentation was proportional to the dietary level oftrans-fatty acids. The increased fecal steroid excretion corresponded to an increase in total excreta. Hydrogenated fats also tended to enhance bile acid excretion when feeding a cholesterol-enriched diet. The results suggest that dietarytrans-fatty acids, in relation tocis-polyunsaturated fatty acids, provoke demonstrable change in steroid homeodynamics.

家庭用マーガリン15種, 業務用マーガリン33種, 学校給食用マーガリン5種, 業務用ショートニング26種, および健康な22～29歳の青年の血清の脂肪酸組成をGLCにより分析し, トランス型不飽和脂肪酸 (t酸) の種類と含量を測定した。水素添加製品中のt酸のほとんどは, t-18: 1であり, c, t-18: 2およびt, c-18: 2の割合はきわめてわずかで, t, t-18: 2はほとんど検出されなかった。t酸含量は, 家庭用マーガリンで平均13.7%, 業務用マーガリンで平均12.2%, 学校給食用マーガリンで平均15.5%, そして業務用ショートニングで平均14.3%であった。業務用製品でt酸含量が低かったのは, 強く水素添加したものが多かったため, あるいは, 原料として不飽和脂肪酸の少ない脂肪を用いたためであった。主として大学食堂で食事を摂っているヒト血清中のt酸含量は全脂質中では1%未満であった。各脂質画分間でわずかながら違いがあり, 遊離脂肪酸中で最も高かったが, それでも2～4%であった。