Emken E A, Adlof R O, Gulley R M
National Center for Agricultural Utilization Research, Agricultural Research Service, US Department of Agriculture, Peoria, IL 61604.
Biochim Biophys Acta. 1994 Aug 4;1213(3):277-88. doi: 10.1016/0005-2760(94)00054-9.
The purpose of this study was to investigate the effect of dietary linoleic acid (18:2(n - 6)) on the conversion of 18:2(n - 6) and 18:3(n - 3) to their respective n - 6 and n - 3 metabolites; to compare the incorporation of these fatty acids into human plasma lipids; to evaluate the importance of dietary 18:3(n - 3) as a precursor for the biosynthesis of long-chain length n - 3 fatty acids. The approach used was to feed young adult male subjects (n = 7) diets containing 2 levels of linoleic acid (SAT diet, 15 g/day; PUFA diet, 30 g/day) for 12 days. A mixture of triacylglycerols containing deuterated linolenic (18:3(n - 3)) and linoleic (18:2(n - 6)) acids was fed and blood samples were drawn over a 48 h period. Concentrations of deuterated 18:3(n - 3) in plasma total lipid ranged from 309.2 to 606.4 microgram/ml and concentrations of 18:2(n - 6) ranged from 949.2 to 1743.3 micrograms/ml. The sum of the deuterated n - 3 long-chain length fatty acid metabolites in plasma total lipid were 116 +/- 4.3 micrograms/ml (SAT diet) and 41.6 +/- 12.4 micrograms/ml (PUFA diet). The total deuterated n - 6 fatty acid metabolites were 34.6 +/- 12.2 micrograms/ml (SAT diet) and 9.8 +/- 5.9 micrograms/ml (PUFA diet). The total percent conversion of deuterated 18:3(n - 3) to n - 3 fatty acid metabolites and deuterated 18:2(n - 6) to n - 6 fatty acid metabolites were 11-18.5% and 1.0-2.2%, respectively. The percentages for deuterated 20:5(n - 3), 22:5(n - 3) and 22:6(n - 3) (6.0%, 3.5%, and 3.8%) were much higher than for 20:3(n - 6) and 20:4(n - 6) (0.9% and 0.5%). Overall, conversion of deuterated 18:3(n - 3) and 18:2(n - 6) was reduced by 40-54% when dietary intake of 18:2(n - 6) was increased from 15 to 30 g/day. Comparison of the deuterated 18:3(n - 3) and 18:2(n - 6) data for plasma triacylglycerol and phosphatidylcholine (PC) indicated that 18:2(n - 6) was preferentially incorporated into PC. Dietary 18:2(n - 6) intake did not alter acyltransferase selectivity but activity was reduced when 18:2(n - 6) intake was increased. Based on these results, conversion of the 18:3(n - 3) in the US diet (2 g) is estimated to provide 75-85% of the long-chain length n - 3 fatty acids needed to meet daily requirements for some (but not all) adults.
本研究的目的是调查膳食亚油酸（18:2(n - 6)）对18:2(n - 6)和18:3(n - 3)向其各自的n - 6和n - 3代谢产物转化的影响；比较这些脂肪酸在人体血浆脂质中的掺入情况；评估膳食18:3(n - 3)作为长链n - 3脂肪酸生物合成前体的重要性。采用的方法是让年轻成年男性受试者（n = 7）食用含2种亚油酸水平的饮食（饱和脂肪酸饮食，15克/天；多不饱和脂肪酸饮食，30克/天），持续12天。喂食含氘代亚麻酸（18:3(n - 3)）和亚油酸（18:2(n - 6)）的三酰甘油混合物，并在48小时内采集血样。血浆总脂质中氘代18:3(n - 3)的浓度范围为309.2至606.4微克/毫升，18:2(n - 6)的浓度范围为949.2至1743.3微克/毫升。血浆总脂质中氘代n - 3长链脂肪酸代谢产物的总和为116±4.3微克/毫升（饱和脂肪酸饮食）和41.6±12.4微克/毫升（多不饱和脂肪酸饮食）。氘代n - 6脂肪酸代谢产物的总量为34.6±12.2微克/毫升（饱和脂肪酸饮食）和9.8±5.9微克/毫升（多不饱和脂肪酸饮食）。氘代18:3(n - 3)向n - 3脂肪酸代谢产物和氘代18:2(n - 6)向n - 6脂肪酸代谢产物的总转化率分别为11 - 18.5%和1.0 - 2.2%。氘代20:5(n - 3)、22:5(n - 3)和22:6(n - 3)的百分比（6.0%、3.5%和3.8%）远高于20:3(n - 6)和20:4(n - 6)（0.9%和0.5%）。总体而言，当膳食中18:2(n - 6)的摄入量从15克/天增加到30克/天时，氘代18:3(n - 3)和18:2(n - 6)的转化率降低了40 - 54%。血浆三酰甘油和磷脂酰胆碱（PC）的氘代18:3(n - 3)和18:2(n - 6)数据比较表明，18:2(n - 6)优先掺入PC。膳食18:2(n - 6)摄入量未改变酰基转移酶的选择性，但当18:2(n - 6)摄入量增加时，其活性降低。基于这些结果，估计美国饮食中（2克）的18:3(n - 3)转化可提供满足部分（但不是全部）成年人每日需求所需长链n - 3脂肪酸的75 - 85%。
