浓缩鱼油对高脂血患者血脂和血小板聚集及体外血栓形成的影响

本文报导204例高脂血患者服用富含二十碳五烯酸(EPA)和二十二碳六烯酸(DHA)浓缩鱼油对血脂和载脂蛋白水平、血小板聚集率及体外血栓形成的影响。受试者每人每日服浓缩鱼油胶丸18粒(相当摄入EPA+DHA 3.7g),连服10周。试验期间受试者的生活与饮食习惯与试验前一致,禁服降脂药和血小板聚集抑制药。结果表明:血清甘油三酯(TG)、总胆固醇(TC)、载脂蛋白(apo)B水平及血小板聚集率均显著降低,血清高密度脂蛋白胆固醇(HDL-C)水平明显升高;体外血栓形成的血栓长度和湿或干重均显著减小;高血压患者的收缩压和舒张压亦较前明显降低;服后血浆脂肪酸含量变化显著,可诱导血小板聚集的花生四烯酸(AA,C20∶4,φ6)含量显著降低,而具有降血脂、抑制血小板聚集和扩血管作用的EPA和DHA含量成倍升高。     

浓缩鱼油对兔血小板聚集和凝血时间及组织脂肪酸含量的影响

本文观察兔给予浓缩鱼油后血小板聚集和凝血时间及组织脂肪酸含量的变化。27头雄性青紫兰兔分为三组(橄榄油对照组、鱼油Ⅰ组和鱼油Ⅱ组)。鱼油Ⅰ组以灌胃法给予浓缩鱼油2ml/天/头,鱼油Ⅱ组以同法给予4ml/天/头,对照组给予橄榄油4ml/天/头,实验期均为10周。结果表明,与对照组相比,鱼油Ⅰ、Ⅱ组的血小板聚集率明显降低(P<0.001),凝血时间显著延长(P<0.001)。鱼油组动物的血浆、血小板、心肌及主动脉均含廿碳五烯酸(EPA)和廿二碳六烯酸(DHA),这些组织的(ω-3/ω-6族脂肪酸的比值明显高于对照组,脂肪酸分布的模式与实验动物的血小板聚集率及凝血时间的变化吻合。     

不同类型脂肪对高脂血家兔动脉粥样硬化形成的影响

本文观察了饱和脂肪(猪油)、单不饱和脂肪(橄揽油)和ω—3多不饱和脂肪(鱼油)对高脂血家兔血脂、血小板聚集、体外血栓形成及动脉粥样硬化(AS)形成的影响。雄性大耳家兔分为:猪油组、橄榄油组和鱼油组,每组9只。实验3个月期间各组每天每只分别给予猪油、橄榄油和鱼油2ml(内含胆固醇0.5g和维生素E10mg)。猪油组血清总胆固醇(TC)明显高于橄榄油组和鱼油组(P<0.01),后两组无显著差异;鱼油组血小板聚集率和血栓干重显著低于橄榄油组;鱼油组血浆过氧化脂质水平明显高于另两组;橄榄油组不仅血浆过氧化脂质水平低,且主动脉AS斑块面积亦显著低于另两组;鱼油组AS斑块面积小于猪油组,但无显著差异。     

鱼油补充对中老年人血清多不饱和脂肪酸构成脂联素水平及抗氧化能力影响的随机对照研究

目的探讨不同剂量鱼油补充对中老年人血清多不饱和脂肪酸(PUFA)构成、脂联素水平及抗氧化能力的影响。方法以240名45~70岁中老年人为对象,随机分成对照组(不服鱼油),鱼油低、中、高剂量组[分别每日服1、2、4粒鱼油胶囊(每粒含182mg EPA+129mg DHA)]4组,干预12w,干预前后进行问卷调查、体格测量并采集空腹静脉血。测定血清脂肪酸、脂联素、血糖、丙二醛(MDA)、总超氧化物歧化酶(SOD)及谷胱甘肽过氧化物酶(GSH-Px)含量。结果 201人完成试验。干预前对象的基线资料及血清学指标组间无差异;干预后对照组各指标无明显变化,鱼油各组血清二十碳五烯酸(EPA)、二十二碳六烯酸(DHA)及n-3 PUFA显著上升,高于对照组(P0.05),n-6/n-3PUFA则均低于对照组(P0.05);干预后鱼油中、高剂量组血清脂联素显著上升,血糖显著下降,与对照组相比有统计学差异(P0.05);血清MDA明显下降;各鱼油组总SOD及GSH-Px含量显著上升,中剂量组的GSH-Px及高剂量组的总SOD、GSH-Px均高于对照组(P0.05)。结论一定剂量鱼油补充可显著升高中老年人血清EPA、DHA、脂联素、总SOD及GSH-Px水平并降低n-6/n-3PUFA、血糖及MDA含量,以高剂量组(1.24g/d)最为明显。     

鱼油联合锌硒对衰老模型小鼠学习记忆障碍及淀粉样前体蛋白酶解通路的保护作用

目的探讨鱼油联合锌硒对衰老模型小鼠学习记忆障碍及淀粉样前体蛋白(amyloid precursor protein,APP酶解通路的保护作用。方法在体外细胞实验中,用0.1μmol/L的二十碳五烯酸(EPA)、二十二碳六烯酸(DHA)、锌(Zn)、硒(Se)分别处理高分化的PC12细胞及APP695稳定转染的CHO细胞,共分为正常对照、抑制剂、EPA、DHA、EPA+DHA+Se、EPA+DHA+Se+Zn 6组。使用酶联免疫吸附测定方法(ELISA)测定细胞培养上清液中β、γ-分泌酶活性及Aβ_(1-40)含量。在体内试验中,将60只两月龄雄性昆明小鼠随机分为正常对照、衰老、鱼油、鱼油+硒、鱼油+锌+硒及阳性对照6个组。连续腹腔注射200 mg/kg D-半乳糖建立衰老模型,采用ELISA法检测血清中β、γ-分泌酶活性;使用Morris水迷宫及跳台方法检测鱼油联合锌硒对衰老模型小鼠学习记忆障碍的保护作用。结果体外细胞实验显示,EPA、DHA处理组与正常对照组相比细胞上清液中β、γ-分泌酶活性受到抑制,Aβ1-40的含量降低;EPA、DHA、Zn、Se联合应用对细胞上清液中β、γ-分泌酶活性抑制作用增强。小鼠动物实验显示,与衰老组比较,鱼油、锌、硒处理组能够抑制血清β、γ-分泌酶活性;且鱼油联合锌硒抑制效果增强。行为学测试结果表明,鱼油联合锌硒缓解衰老模型小鼠学习记忆障碍。结论鱼油联合锌、硒对APP酶解通路具有较好的保护作用,并能减轻小鼠学习记忆障碍。[营养学报,2020,42(1):56-60]     

硝酸甘油对妊高征患者血流变学、血小板聚集的影响

目的:拟用硝酸甘油(Ng)治疗妊高征(PIH),评价其对PIH患者血流变学、血小板聚集的影响。方法:选取晚期正常妊娠妇女(正常组Ⅰ组:11例),中、重度妊高征患者34例[PIH组,其中单用硫酸镁(Mg)治疗Ⅱ组:11例;单用硝酸甘油(Ng)治疗Ⅲ组:11例;联合用药(Mg+Ng)治疗Ⅳ组:12例]。采用血液粘度仪在高、低切变率下测血流变学,硫酸铵沉淀法测纤维蛋白原(Fn),魏式法测血沉(ESR),常规法测红细胞压积(Hct),血小板聚集仪测血小板聚集(PAg)。结果:①血流变学:产前:PIH组较Ⅰ组全血粘度(BV),红细胞聚集指数(RE)、血浆粘度(PV)、Hct、ESR、血沉方程K值(Kesr)、Fn均增高(P<0.05)差异显著;产后各组无明显差别,Ⅲ、Ⅳ组治疗后BV、ESR、Kesr、Fn下降,差异显著(P<0.05),余下指标及Ⅱ组各指标改变不明显。②血小板聚集:产前:PIH组较Ⅰ组增高,差异显著(P<0.05),产后:各组无明显差别;Ⅲ、Ⅳ组治疗后较用前降低,差异显著(P<0.01),Ⅱ组改变不明显。结论:硝酸甘油作为NO供体治疗妊高征时,能改变血流变,抑制血小板聚集。     

饮食n-3脂肪酸对小鼠脑脂类中多不饱和脂肪酸构成的影响

【目的】观察饮食鱼油n-3多不饱和脂肪酸(n-3 PUFAs)对脑内不同脂类中PUFAs构成的影响。【方法】使用C57BL/6J雌性小鼠,在胎儿期和幼年期分别给予不同种类高脂饲料(18%脂肪,供能比为36%)喂养-高脂豆油饲料、高脂鱼油饲料和高脂豆油:鱼油(5∶1)混合饲料,以正常饲料(6%脂肪来自豆油,供能比为12%)为对照,时间为4个月。采用薄层层析分离脑组织中各主要脂类成份,然后采用甲酯化-气相色谱分析对各脂类成份中的脂肪酸进行测定。【结果】鱼油饲料喂养改变了小鼠脑内主要脂类中PUFAs的构成。在磷脂中,虽然5种PUFAs在各饲料组之间差异均无显著性(P>0.05),但二十二碳六烯酸(DHA)/花生四烯酸(AA)(1.94±0.41)以及n-3/n-6 PUFAs比值(2.31±0.75)在鱼油组较其它三组显著升高(P<0.05);在甘油一和二酯中,与豆油组相比,鱼油组和豆油:鱼油混合组LA含量(0.31±0.09%,0.65±0.58%)降低,而鱼油组DHA/AA(2.60±1.66)以及n-3/n-6 PUFAs比值(2.31±0.75)升高(P<0.05);在甘油三酯中,与豆油组相比,鱼油组和豆油:鱼油混合组AA含量(1.62±0.53%,1.12±0.36%)和EPA含量(0.98±0.58%,1.34±0.31%)显著降低,而DHA/AA比值(1.14±0.21,1.46±0.58)升高(P<0.05),但DHA含量在三组之间无差异(P>0.05);在游离脂肪酸中,5种PUFAs在各饲料组之间无差异(P>0.05)。【结论】饮食鱼油n-3 PUFAs摄入增多虽然不影响脑内DHA的聚积,但改变了DHA/AA以及n-3/n-6PUFAs的比值。甘油酯类可能是脑摄取、聚积DHA的主要直接来源之一。     

六种试验在动脉粥样硬化和血栓性疾病的统计学观察

对6种试验综合检测血栓性疾病的血小板功能进行统计分析,发现各个检测项目敏感性不一。最敏感的是β-TG及血小板粘附性,其次为PF_1及TXB_2,其次为血小板聚集及6—酮—PGF_(1α)。同时全血粘度及血浆粘度也有显著或非常显著增高。     

前列腺素与心血管疾病

PG对心血管的作用,TXA_2是目前知道的使血小板聚集、血管收缩的最强烈的物质,比血管紧张素Ⅱ强100倍。而PGI_2则是抗血小板聚集,血管舒张最强的物质。然而它们极不稳定,TXA_2半衰期约30秒,而且90％在肺循环中灭活。FGI_2在37℃血液中半衰期也只有2～3分钟,故限制了临床应用。 1.对冠状动脉硬化,血栓形成的作用:在用PG防治冠状动脉硬化,血栓形成方面,由于TXA_2和PGI_2性质极不稳定,人们把注意力集中于研究抑制TXA_2合成酶,使TXA_2减少,或增强PGI_2合成酶的活性,或合成稳定的可供口服的PGI_2。目前临床应用阿斯匹林,消炎痛等非类固醇抗炎药物,是环氧化酶的抑制剂。它阻断花生四烯酸转变成前列腺素内过氧化物,从而阻断了TXA_2的产生。由于动脉硬化患者,其血管内膜能产生PGI_2的内皮细胞很少,而血小板释放TXA_2占优势。阿     

浓缩鱼油升高大鼠血清高密度脂蛋白胆固醇机理的探讨

本文从酶学方面探讨了富含廿碳五烯酸甲酯(EPA-M)和廿二碳六烯酸甲酯(DHA-M)浓缩鱼油升高大鼠血清高密度脂蛋白胆固醇(HDL-C)的机理。实验分三组(高脂组、高脂+橄榄油组和高脂+鱼油组)。后两组动物分别以灌胃法给予橄榄油与浓缩鱼油,每头0.5ml/d,高脂组不喂其它油脂,实验期6周。结果显示,鱼油组大鼠血清HDL-C水平显著高于高脂组和橄榄油组(P<0.01),H-DL-C的变化是由于高密度脂蛋白亚属Ⅱ胆固醇(HDL_2-C)水平升高,而高密度脂蛋白亚属薑胆固醇(HDL_3-C)水平无显著改变。鱼油组大鼠血清卵磷脂胆固醇酰基转移酶(LCAT)及肝素化后血浆脂蛋白脂酶(LPL)活性显著高于高脂组和橄榄油组(P<0.01),肝素化后血浆肝内皮细胞脂酶(HEL)活性显著低于其它两个对照组(P<0.05)。以上结果表明,浓缩鱼油可能通过激活LCAT和LPL活性促使HDL生成增加;同时抑制HEL活性,减少HDL的分解,从而传大鼠血清HDL-C水平升高。     

Olive oil, corn oil, and n-3 fatty acids differently affect lipids, lipoproteins, platelets, and superoxide formation in type II hypercholesterolemia.

To evaluate which dietary fat may provide the best response in terms of plasma lipids and lipoproteins and also of platelet aggregability and superoxide formation by white blood cells, 12 type II patients were randomly allocated to three different diets, which provided polyunsaturated fatty acids (corn oil), monounsaturated fatty acids (olive oil), and a supplementation of ethyl esters of n-3 fatty acids to a prudent diet. Olive oil and, more significantly, n-3 ethyl esters lowered total cholesterol best (-2.2% and -5.8%, respectively); the latter diet, as expected, also significantly lowered triglyceridemia (-21.4%). The corn-oil diet exerted a small, statistically significant reduction of high-density-lipoprotein cholesterol (HDL) (-4.3%), and it also lowered plasma total apo B concentrations (-3.8%). n-3 ethyl esters significantly raised both total (+3.1%) and particularly HDL2 cholesterol (+24%). Platelet reactivity was insignificantly reduced by the three regimens, but all three significantly reduced thrombin-stimulated formation of thromboxane B2. Finally, only the n-3 fatty acid supplementation significantly reduced O2- generation by adherent monocytes. Dietary unsaturated fatty acids are generally effective on the plasma lipid and lipoproteins in type II patients, but significant differences may be found between the three tested regimens.     

茶油对动物血脂和血小板功能的影响

本文报道了富含油酸的茶油对兔和大鼠的血脂与血小板功能的影响。 新西兰雌兔22头,分3组,饲常备饲料。每日以灌胃法分别给予茶油、红花油和椰子油5ml(含0.5克胆固醇),饲养8周。结果表明,茶油组血清胆固醇(TC),低密度脂蛋白胆固醇(LDL-C)水平显著低于椰子油组,高密度脂蛋白胆固醇(HDL-C)/TC的比值显著高于其他两组;红花油组的TC,LDL-C虽也较低,但与椰子油组无明显差异。茶油组的血小板聚集率和血栓素B_2(TXB_2)水平亦显著低于椰子油组,6-酮前列腺素F_(1α)(6-Keto-PGF_(1α))水平与其他两组差别不明显,但TXB_2/6-Keto-PGF_(1α)比值较低。 Wistar雄性大鼠120只,分4组,分别饲予15％茶油,红花油和椰子油及1％胆固醇配制的半合成饲料9周。结果表明:茶油可降低大鼠的血小板聚集率及TXB_2/6-Keto-PGF_(1α)比值,并使血小板膜中的MUFA含量增高和PUFA含量减少。 基于本实验结果,作者在文中对茶油有利于预防心血管疾病的可能途径进行了讨论。     

Effect of dietary n-3 fatty acids on weight gain and liver polar lipid fatty acid composition of fingerling channel catfish

A 10-wk experiment was conducted to determine the effect of supplementing a 5% tristearin basal diet with linoleic acid [18:2(n-6)], linolenic acid [18:3(n-3)], an n-3 highly unsaturated fatty acid (n-3 HUFA) mixture, cod liver oil, corn oil or linseed oil on growth and fatty acid composition of the liver polar lipid fraction of fingerling channel catfish (Ictalurus punctatus). The lowest weight gain was observed in fish fed the basal diet. Weight gain was improved by certain levels of supplemental n-3 fatty acids. Fish fed a diet containing 2% 18:3(n-3) grew at the same rate as fish fed a diet containing 2.5% cod liver oil plus 2.5% corn oil. The best growth rate was observed in fish fed diets containing either 5% cod liver oil or 5% linseed oil. Growth rate was depressed by supplementation with 4% 18:3(n-3) or 1.25% n-3 HUFA mix. No improvement in growth rate was observed with dietary 18:2(n-6). Dietary linolenate was converted to docosahexaenoic acid [22:6(n-3)]. The ratio of 20:3(n-9) to 22:6(n-3) of the fish showing good growth was less than 0.4. The data obtained in this experiment indicate that n-3 fatty acids are essential for channel catfish and that the 18:3(n-3) or n-3 HUFA dietary requirement is 1.0-2.0% or 0.5-0.75%, respectively.     

Effect of dietary olive oil, corn oil and medium-chain triglycerides on the lipid composition of rat red blood cell membranes

The effects of dietary olive oil, corn oil and medium-chain triglycerides (MCT) on factors that characterized erythrocyte membrane lipid fluidity were studied. Weanling rats were fed for 3 or 5 wk high fat diets (10%) containing olive oil, corn oil or a mixture of MCT with olive oil or corn oil. Total phospholipids and phosphatidylcholine of erythrocyte ghosts obtained from olive oil-fed animals, as compared to those fed corn oil, showed an increase in long-chain polyunsaturated fatty acids (PUFA) of the (n-6) and (n-3) series and a decrease in saturated fatty acids. The addition of MCT to the olive oil diet induced an increase in palmitic, palmitoleic and delta-5,8,11-eicosatrienoic acids and a decrease in long-chain PUFA of the (n-6) series in erythrocyte membrane phospholipids. Conversely, rats fed a mixture of MCT and corn oil, as compared to those fed exclusively corn oil, showed increase in long-chain PUFA of the (n-6) and (n-3) series, with no changes in saturated fatty acid levels. The cholesterol/phosphorus molar ratio showed only a slight increase with MCT supplementation. Olive oil feeding induced important changes in fatty acid composition of erythrocyte membrane phospholipids as compared to corn oil feeding without modifying the cholesterol/phosphorus ratio and MCT feeding slightly affected red blood cell membrane lipid composition.     

Effect of Erabu sea snake (Laticauda semifasciata) lipids on the swimming endurance of aged mice

The effect of Erabu sea snake (Laticauda semifasciata) lipids on the swimming endurance was investigated in aged mice. Fifty three-week-old male Crlj:CD-1 (ICR) mice were fed one of three experimental diets containing either 6% lard, 6% fish oil, or 6% sea snake lipids for 16 wk. The swimming exercise was carried out in an acrylic plastic tank filled with 25 cm of water maintained at 23(o)C. Swimming times to exhaustion were measured with a load of 2% of their body weights attached to the tails of the mice. The swimming times to exhaustion of the group that were fed the sea snake lipid diet tended to be longer than those of the lard diet group, and were significantly improved compared with the fish oil diet group (p<0.05). The plasma and muscle lactate levels were significantly lower in the sea snake lipid diet group than in the lard and fish oil diet groups (p<0.05). The liver glycogen and plasma glucose levels of the sea snake lipid diet group did not differ markedly from those of the lard diet group (p>0.05), and were significantly higher than those of the fish oil diet group (p<0.05). These results suggest that an intake of sea snake lipids but not the fish oil, which is also rich in n-3 polyunsaturated fatty acids (n-3 PUFAs), is useful for improving the swimming endurance of aged mice by attenuating lactate production and/or enhancing lactate clearance during swimming exercise, and the n-3 PUFAs contained in the sea snake lipids did little or nothing for this improved endurance.     

Menhaden oil inhibited gamma-glutamyltransferase-positive altered hepatic foci in female Sprague-Dawley rats

Feeding menhaden oil, high in n-3 fatty acids, or a mixture of lard and corn oil with a polyunsaturated-to-monounsaturated fatty acid ratio of 1:1 was hypothesized to inhibit promotion of hepatocarcinogenesis in rats by decreasing hepatic prostaglandin (PG) levels. Ten-day-old female Sprague-Dawley rats were injected with diethylnitrosamine (DEN, 15 mg/kg body wt ip). At 4 wk of age, rats were fed fumonisin B1(50 mg/kg diet) for 5 wk in diets containing 14% lard + 6% corn oil, 10% lard + 10% corn oil, 14% menhaden oil + 6% corn oil, and 7% menhaden oil + 13% corn oil. Plasma alanine aminotransferase activity was 20% lower in rats fed 10% lard than in rats fed the other diets (P < 0.05). In menhaden oil-fed rats, total plasma cholesterol concentrations decreased 26% (P < 0.05) and hepatic phospholipid C20:5n-3, C22:5n-3, and C22:6n-3 fatty acid concentrations increased compared with lard-fed rats. Hepatic n-3 fatty acids were threefold greater in rats fed 10% lard than in rats fed 14% lard. The liver-associated natural killer cell activity in rats fed menhaden oil was 58% lower than in rats fed lard (P < 0.03). Rats fed lard had threefold (P < 0.05) greater area of _-glutamyltransferase-positive altered hepatic foci (AHF) than did rats fed menhaden oil. There was no significant difference in placental glutathione S-transferase-positive AHF among the groups. Hepatic PGF2alpha production was 60-80% greater in rats fed 14% lard than in rats fed the other diets (P < 0.05). Hepatic PGE2 was 48% less in rats fed 14%; menhaden oil than in rats fed 14% lard (P < 0.05). Although gamma-glutamyltransferase-positive focal area was inhibited by menhaden oil, only 14% menhaden oil inhibited PGE2. Feeding 10% lard inhibited PGF2alpha, but not the development of AHF. Therefore, decreased hepatic PGs did not explain the inhibition of carcinogenesis.     

三种食用油对大鼠血脂、血小板功能、生物膜及脂质过氧化的影响

采用成年ＳＤ大鼠，分别喂给猪油、米糠油和玉米油，观察其对血脂、血小板功能、生物膜及脂质过氧化的影响。结果表明，与猪油组比较，米糠油和玉米油组血清ＴＣ、ＴＧ、ＬＤＬ－Ｃ、ＴＣ／ＨＤＬ－Ｃ均较低，血浆６－Ｋ－ＰＧＦ１２／ＴＸＢ２比值较高，血小板聚集率较低，膜磷脂中多不饱和脂肪酸含量较多，膜流动性较大，心、肝、脑组织中ＭＤＡ含量较高，肝超氧化物歧化酶活性较低，易于脂质过氧化。米糠油和玉米油组之间则无明显差异。     

Effect of lipids extracted from a salted herring roe food product on maze-behavior in mice

Male mice (11 mo old) were fed 5% lard, fish oil, or Kazunoko (salted fish roe product) lipids for 4 mo to investigate their effects on maze behavior. The time required and distance traveled to reach the maze exit, and number of times that a mouse strayed into blind alleys in the maze, and the fatty acid compositions of brain lipids after the maze-behavior experiment were measured. The Kazunoko lipid group showed a significant improvement in all three parameters compared with the lard diet group, but the fish oil group showed only a significant decrease in the number of times that a mouse strayed into blind alleys compared with the lard diet group. The mice in the fish oil and Kazunoko lipid groups had significantly lower levels of arachidonic acid and higher percentages of docosahexaenoic acid in brain lipids compared with animals in the lard group. The mice in the Kazunoko lipid group had significantly lower levels of arachidonic acid in brain lipids than those in the fish oil group but the percentages of docosahexaenoic acid were not significantly different between these two diet groups. Our results suggest that an intake of Kazunoko lipids may suppress the percentage of n-6 fatty acids in brain lipids and this diet can be even more effective than fish oil as a supplement to improve learning capacity in mice.     

鱼油对小鼠脑磷脂中脂肪酸组成的影响

昆明种小鼠随机分成两组，对照组和鱼油组，按小鼠处死时间，对照组分三个亚组，鱼油组分四个亚组。取小鼠脑组织，采用气相色谱法测其脑磷脂中脂肪酸组成，考察鱼油中ｎ一３系多不饱和脂肪酸对小鼠大脑的影响，结果表明：鱼油可使小鼠脑重增加（Ｐ＜０．０５），使脑磷脂中饱和脂肪酸，单不饱和脂肪酸和ｎ一６系多不饱和脂肪酸水平降低，使ｎ一３系多不饱和脂肪酸水平上升（Ｐ＜０．０５）。停用鱼油两周后，其脑磷脂中脂肪酸水平与对照组的水平接近，即鱼油对脑磷脂中脂肪酸组成的影响作用逐渐减弱。由此推论，在人脑早期形成发育过程中，适时、适量、持续补充人体必需ｎ一３系多不饱和脂肪酸是必要的。