Garg M L, Thomson A B, Clandinin M T
Department of Foods and Nutrition, Faculty of Home Economics, Faculty of Medicine, University of Alberta, Edmonton, Canada.
J Nutr. 1988 Jun;118(6):661-8. doi: 10.1093/jn/118.6.661.
Male weanling rats were fed for 28 d a purified diet containing 20% (wt/wt) fat providing high levels of either saturated fat or alpha-linolenic acid or eicosapentaenoic and docosahexaenoic acids with or without 2% (wt/wt) cholesterol supplementation. Effect of diet on rate of desaturation of eicosatrienoic acid (20:3 omega 6) and lipid composition of liver microsomal membranes was examined. The desaturation of 20:3 omega 6 to arachidonic acid (20:4 omega 6) was higher in rats fed linseed oil and lower in rats fed fish oil than in control animals fed the beef tallow diet. The desaturation of 20:3 omega 6 was lower in rats fed beef tallow or linseed oil diets supplemented with cholesterol than in the respective unsupplemented diet. Inclusion of 2% (wt/wt) cholesterol in the fish oil diet failed to affect synthesis of 20:4 omega 6 from 20:3 omega 6. These in vitro changes in delta 5-desaturase activity are consistent with the diet-induced alterations observed in the fatty acid composition of microsomal membranes. Both free cholesterol and cholesterol ester in the microsomal membrane were higher in rats fed beef tallow or linseed oil diets supplemented with exogenous cholesterol than in the respective unsupplemented diet, and only free cholesterol was higher in rats fed the fish oil diet supplemented with cholesterol. Feeding fish oil appears to prevent both the inhibition of 20:4 omega 6 biosynthesis and the accumulation of cholesterol ester that were apparent when 2% cholesterol was added to either beef tallow or linseed oil diets.
雄性断乳大鼠喂食28天纯化饮食，该饮食含20%（重量/重量）脂肪，提供高水平的饱和脂肪、α-亚麻酸或二十碳五烯酸和二十二碳六烯酸，添加或不添加2%（重量/重量）胆固醇。研究了饮食对二十碳三烯酸（20:3ω6）去饱和率和肝微粒体膜脂质组成的影响。与喂食牛脂饮食的对照动物相比，喂食亚麻籽油的大鼠中20:3ω6去饱和为花生四烯酸（20:4ω6）的比例更高，而喂食鱼油的大鼠中该比例更低。喂食添加胆固醇的牛脂或亚麻籽油饮食的大鼠中，20:3ω6的去饱和率低于各自未添加胆固醇的饮食组。鱼油饮食中添加2%（重量/重量）胆固醇未能影响20:4ω6从20:3ω6的合成。δ5-去饱和酶活性的这些体外变化与微粒体膜脂肪酸组成中饮食诱导的改变一致。喂食添加外源性胆固醇的牛脂或亚麻籽油饮食的大鼠，其微粒体膜中的游离胆固醇和胆固醇酯均高于各自未添加胆固醇的饮食组，而喂食添加胆固醇的鱼油饮食的大鼠仅游离胆固醇含量更高。喂食鱼油似乎既能防止20:4ω6生物合成受到抑制，又能防止当向牛脂或亚麻籽油饮食中添加2%胆固醇时明显出现的胆固醇酯积累。
