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【目的】探讨饲料中鱼油n-3多不饱和脂肪酸(n-3 PUFAs)含量对小鼠脑组织中二十二碳六烯酸(DHA)的影响,同时观察肝、脑组织中△5和△6去饱和酶表达的变化。【方法】使用3~4周龄C57BL/6J雌性小鼠,分别给予4种不同含量的鱼油n-3 PUFAs(占总脂肪酸含量的百分比分别为2.8%、5.4%、10.0%和23.0%)饲料喂养3个月,饲料中n-6/n-3 PUFAs比值分别为20∶1、10∶1、5∶1、1∶1,以n-3 PUFAs缺乏饲料为对照。应用气相色谱分析对血浆、肝脏和脑组织中脂肪酸进行测定;采用实时荧光定量PCR(RT-PCR)对小鼠肝脏和脑组织中△5和△6去饱和酶mR-NA表达进行分析。【结果】与n-3 PUFA缺乏饲料组相比,含鱼油n-3 PUFAs饲料喂养组小鼠血浆、肝脏及脑组织中的DHA及总n-3 PUFAs含量均明显增加,而花生四烯酸(AA)及总n-6 PUFAs含量降低;同时AA/DHA比值以及∑n-6/∑n-3 PUFAs比值降低。饲料中鱼油n-3 PUFAs含量变化对脑聚集DHA的影响存在着一定的剂量-效应关系。进一步发现,在肝组织中,n-3 PUFAs饲料喂养各组△6去饱和酶mRNA表达量较对照组均显著降低;而在脑组织中,只有n-6/n-3PUFAs(1∶1)组△5、△6去饱和酶mRNA表达量较对照组显著降低。【结论】脑组织中DHA的聚集随饲料中鱼油n-3 PUFAs含量的升高而增加;脑中△6和△5去饱和酶的表达在高含量鱼油n-3 PUFAs摄入时才受到抑制,提示膳食摄入DHA需要在很高含量时,才有可能满足脑的需求。
【Objective】 To investigate the effect of n-3 polyunsaturated fatty acids (n-3 PUFAs) in diet on the level of docosahexaenoic acid (DHA) in brain of mice, △ 6 desaturase expression changes. 【Method】 Four-week-old C57BL / 6J female mice were fed with 4 different concentrations of fish oil n-3 PUFAs (2.8%, 5.4%, 10.0% and 23.0% of the total fatty acid content) The feed n-6 / n-3 PUFAs ratios were 20: 1, 10: 1, 5: 1 and 1: 1 respectively. The n-3 PUFAs deficient diets were used as control. The fatty acids in plasma, liver and brain were determined by gas chromatography. The expression of △ 5 and △ 6 desaturase mR-NA in liver and brain of mice were analyzed by real-time fluorescence quantitative PCR (RT-PCR). 【Result】 Compared with n-3 PUFA-deficient diet group, the content of DHA and total n-3 PUFAs in plasma, liver and brain tissue of n-3 PUFAs diet-fed group increased significantly, while arachidonic acid (AA) and total n-6 PUFAs decreased, while AA / DHA ratio and Σn-6 / Σn-3 PUFAs ratio decreased. There is a certain dose-effect relationship between the changes of n-3 PUFAs content in fish oil and brain DHA. It was further found that mRNA expression of △ 6 desaturase in n-3 PUFAs diet group was significantly lower than that in control group in n-3 PUFAs diet, while only n-6 / n-3 PUFAs (1: 1) Group △ 5, △ 6 desaturase mRNA expression was significantly lower than the control group. 【Conclusion】 The accumulation of DHA in brain tissue increased with the increase of dietary n-3 PUFAs in fish oil. The expression of △ 6 and △ 5 desaturase in brain was inhibited only when high levels of fish oil n-3 PUFAs were ingested , Suggesting that dietary intake of DHA is needed at very high levels to meet the brain’s needs.