DELTA-6-DESATURASE ACTIVITY IN LIVER-MICROSOMES OF RATS FED DIETS ENRICHED WITH CHOLESTEROL AND OR OMEGA-3 FATTY-ACIDS
DELTA-6-DESATURASE ACTIVITY IN LIVER-MICROSOMES OF RATS FED DIETS ENRICHED WITH CHOLESTEROL AND OR OMEGA-3 FATTY-ACIDS
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DOI：
10.1042/bj2490351
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发表时间：
1988-01-15
影响因子：
4.1
通讯作者：
CLANDININ, MT
中科院分区：
文献类型：
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作者：
GARG, ML;SEBOKOVA, E;CLANDININ, MT
研究了喂食富含亚麻子油（富含C18：3，ω 3脂肪酸）或鱼油（富含C20：5，ω 3和C22：6，ω 3脂肪酸）的半纯化饮食，补充和不补充胆固醇对大鼠肝微粒体组分的亚油酸（C18：2，ω 6）去饱和作用的影响。动物喂养的饮食补充牛脂被用作等能量控制。亚麻籽油和鱼油饮食，不添加胆固醇，降低C18：2，ω 6脂肪酸向γ-脂肪酸的转化。亚麻酸（C18：3，ω 6）。喂食含有鱼油的饮食的动物的Δ 6-去饱和的减少显著大于喂食亚麻籽油饮食的动物。当与牛脂饮食组合喂养时，胆固醇补充的主要作用是降低C18：2，ω 6的去饱和速率，而当胆固醇与高ω 3脂肪酸饮食（亚麻籽油或鱼油）一起沿着喂养时，Δ 6-去饱和不受影响。Δ 6-去饱和酶的体外活性与在该酶所位于的微粒体膜上观察到的脂肪酸组成一致。与饲喂牛脂的组相比，膳食亚麻籽油和鱼油降低了大鼠肝微粒体的花生四烯酸（C20：4，ω 6）含量，伴随着膜二十碳五烯酸（C20：5，ω 3）和二十二碳六烯酸（C22：6，ω 3）含量的增加。在牛脂或亚麻籽油饮食中加入胆固醇导致膜C20：4，ω 6-脂肪酸含量降低，同时C18：2，ω 6-脂肪酸含量增加。然而，向鱼油饮食中添加胆固醇并不改变C20：4，ω 6脂肪酸的微粒体膜含量。因此，提示（1）在食用鱼油后通常观察到的前列腺素E2、血栓烷和前列环素水平的降低可能至少部分是由于抑制了C20：4，ω 6-脂肪酸从C18：2，ω 6脂肪酸的合成;和（2）食用鱼油防止了膳食胆固醇引起的C20：4，ω 6-脂肪酸水平的进一步降低，这在胆固醇与高饱和脂肪或C18：3，ω 3脂肪酸的膳食组合喂养时是明显的。
The effect of feeding semipurified diets enriched in linseed (rich in C18:3,.omega.3 fatty acid) or fish (rich in C20:5,.omega.3 and C22:6,.omega.3 fatty acid) oil with and without cholesterol supplementation on the desaturation of linoleic acid (C18:2,.omega.6) by rat liver microsomal fractions was investigated. Animals fed diets supplemented with beef tallow were used as equal-energy controls. Both linseed-oil and fish-oil diets, without added cholesterol, decrease conversion of C18:2,.omega.6 fatty acid to .gamma.-linolenic acid (C18:3,.omega.6). Reduction in .DELTA.6-desaturation was significantly greater for animals fed the diet containing fish oil than with animals fed the linseed-oil diet. The major effect of cholesterol supplementation was to decrease the rate of desaturation of C18:2,.omega.6, when fed in combination with the beef-tallow diet, whereas .DELTA.6-desaturation was unaffected when cholesterol was fed along with diets high in .omega.3 fatty acids (linseed oil or fish oil). The activity of the .DELTA.6-desaturase in vitro is consistent with the fatty acid composition observed for the microsomal membranes on which this enzyme is localized. Dietary linseed oil and fish oil lowered the arachidonic (C20:4,.omega.6) acid content of rat liver microsomes, with an accompanying increase in membrane eicosapentaenoic (C20:5,.omega.3) and docosahexaenoic (C22:6,.omega.3) acid content, in comparison with the group fed beef tallow. Inclusion of cholesterol into the beef-tallow or linseed-oil diets resulted in decreased membrane C20:4,.omega.6-fatty-acid content, with concomitant increase in C18:2,.omega.6-fatty-acid content. However, addition of cholesterol to the fish-oil diet did not alter the microsomal membrane content of C20:4,.omega.6 fatty acid. Thus it is suggested that (1) the decrease in prostaglandin E2, thromboxane and prostacyclin levels generally observed after fish-oil consumption may be at least partly due to inhibition of C20:4,.omega.6-fatty-acid synthesis from C18:2,.omega.6 fatty acid; and (2) consumption of fish oil prevents the further decrease in C20:4.omega.6-fatty-acid levels by dietary cholesterol that is apparent when cholesterol is fed in combination with diets high in saturated fat or C18:3,.omega.3 fatty acid.