不同年龄阶段小鼠脑聚集二十二碳六烯酸及脂肪酸去饱和酶的变化

Investigation on changes in brain accretion of docosahexaenoic acid and fatty acid desaturases in mice with different ages

【目的】探讨生命早期不同年龄阶段脑摄取、聚集二十二碳六烯酸(DHA)(C22:6n-3)及相关去饱和酶的变化。【方法】使用6～8周龄清洁级C57BL/6J雌性小鼠,分别给予n-3多不饱和脂肪酸(n-3PUFAs)缺乏饲料和含n-3PUFAs饲料喂养6周,然后雌雄合笼交配繁殖,新生仔鼠分别于生后7、21d和42d时取血、脑和肝脏。采用甲酯化-气相色谱分析对血浆、脑和肝脏中脂肪酸谱进行分析;采用荧光定量PCR方法对脑和肝脏中脂肪酸去饱和酶1(FADS1)和脂肪酸去饱和酶2(FADS2)基因mRNA表达进行检测。【结果】对不同年龄小鼠组织脂肪酸的比较发现,脑中DHA和总n-3PUFAs含量在两种不同饲料组均随年龄增加而升高;而肝中的含量则随年龄增加而降低。与n-3PUFAs缺乏组相比,饲料中添加n-3PUFAs可使仔鼠生后7、21d和42d时脑和肝脏中DHA和总n-3PUFAs含量均显著升高;升高的程度在脑组织中随年龄增加而降低,而在肝脏组织中则不随年龄变化。对不同年龄段FADS表达的比较发现,FADS1和FADS2mRNA在脑组织中的表达量于42d时显著高于7d和21d,而在肝组织中的表达量于各年龄段之间无显著性差异。与n-3PUFAs缺乏组相比,饲料中添加n-3PUFAs可使仔鼠生后7d和21d时脑组织FADS1和FADS2表达水平显著降低,而42d时的表达无变化;肝组织中这两种酶mRNA水平在7d和21d时无变化,42d时FADS1显著降低。【结论】发育期脑对DHA的聚集需求随着年龄增大而逐渐减少;FADS在脑中的表达水平随年龄增大而升高。同时,饲料n-3PUFAs缺乏状态对脑聚集DHA以及FADS的影响在年龄小时更明显。

【Objective】 To investigate brain accretion of docosahexaenoic acid（DHA） at different ages and the expressional changes in related fatty acid desaturases（FADS）.【Methods】 3~4 weeks old C57BL/6J female mice were fed with two types of diets,n-3 PUFA deficient diet and n-3 PUFA containing diet.Followed by 6-week feeding,the mice were mated for breeding new pups.At postnatal 7 d,21 d and 42 d respectively,new pups were sacrificed and the blood,brain and liver were gathered.Fatty acids in the tissues were analyzed by gas chromatography and expressed as percent（%） of the total fatty acids.The mRNA expressions of FADS1 and FADS2 in the brain and liver were assayed by real-time RT-PCR.【Results】 In both n-3 PUFA deficient and containing diet groups,the levels of DHA and total n-3 PUFAs increased in the brain and decreased in the liver with age increasing.Compared to the mice with n-3 PUFA deficient diet,the levels of DHA and total n-3 PUFAs in both the brain and liver at 7 d,21 d and 42 d were significantly increased in mice fed with n-3 PUFA diets.The percentage change in DHA level in the brain became minor with the age increased,whereas no differences were shown in the liver among the three ages.The levels of FADS1 and FADS2 mRNA were higher at 42 d than those at 7 d and 21 d in the brain,and no differences in FADS mRNA were found in the liver among the three ages.In mice with the n-3 PUFA diet,FADS1 and FADS2 mRNA levels were reduced in the brain at 7 d and 21 d with no changes at 42 d,and did not change at 7 d and 21 d with decreased level of FADS1 mRNA in the liver.【Conclusion】 Brain accretion of DHA decreases and FADS expression increases with the age increasing.Diet n-3 PUFA deficiency affects brain accretion of DHA and the expression of FADS to a larger extent in an early age.