Tyburczy C, Lock A L, Dwyer D A, Destaillats F, Mouloungui Z, Candy L, Bauman D E
Department of Animal Science, Cornell University, Ithaca, NY 14853, USA.
J Dairy Sci. 2008 Oct;91(10):3850-61. doi: 10.3168/jds.2007-0893.
Trans fatty acids (FA) arise in ruminant-derived foods as a consequence of rumen biohydrogenation and are of interest because of their biological effects and potential role in chronic human diseases. Our objective was to compare 2 trans FA, elaidic acid (EA; trans-9 18:1) and vaccenic acid (VA; trans-11 18:1), with oleic acid (OA; cis-9 18:1) relative to plasma lipid transport and mammary utilization for milk fat synthesis. Three ruminally cannulated, Holstein dairy cows, 259 +/- 6 DIM (mean +/- SEM), were randomly assigned in a 3 x 3 Latin square design. Treatments were a 4-d abomasal infusion of 1) OA (45.5 g/d), 2) EA (41.7 g/d), and 3) VA (41.4 g/d). Milk samples were collected at each milking and blood samples were collected at the start and end of each treatment period. The proportions of total plasma FA associated with each plasma lipid fraction at baseline (pretreatment) were 62.6 +/- 0.6% phospholipids, 26.1 +/- 0.6% cholesterol esters, 9.8 +/- 0.4% triglycerides, and 1.5 +/- 0.1% nonesterified fatty acids; these values were unaffected by treatment. There were striking differences in the FA composition of the individual plasma lipid fractions and in the distribution of specific 18-carbon FA among the lipid fractions. Infusion of treatment isomers caused their specific increase in the various plasma lipid fractions but had no effect on milk production variables, including milk fat yield and content. Transfer efficiency of infused OA, EA, and VA to milk fat averaged 65.5 +/- 3.0%, 59.7 +/- 1.5%, and 54.3 +/- 0.6%, respectively. For the VA infusion, 24.6 +/- 1.1% of the transfer was accounted for by the increased yield of cis-9, trans-11 conjugated linoleic acid in milk fat, consistent with its endogenous synthesis from VA via the mammary enzyme Delta(9)-desaturase. Notably, linoleic acid (18:2n-6) and linolenic acid (18:3n-3) accounted for 47.7% of total plasma FA, but only 2.6% of FA in milk. Overall, results demonstrate clear differences in plasma transport and mammary uptake and utilization of 18-carbon FA, and these relate to the location, orientation, and number of double bonds.
反式脂肪酸（FA）产生于反刍动物源性食品中，是瘤胃生物氢化作用的结果，因其生物学效应以及在人类慢性疾病中的潜在作用而受到关注。我们的目标是比较两种反式脂肪酸，即反油酸（EA；反式-9 18:1）和vaccenic酸（VA；反式-11 18:1），与油酸（OA；顺式-9 18:1）在血浆脂质转运以及乳腺用于乳脂肪合成的利用方面的差异。三头安装了瘤胃瘘管的荷斯坦奶牛，产犊后259±6天（平均值±标准误），按照3×3拉丁方设计随机分配。处理方式为通过皱胃灌注4天的：1）OA（45.5克/天），2）EA（41.7克/天），以及3）VA（41.4克/天）。每次挤奶时采集牛奶样本，在每个处理期开始和结束时采集血液样本。在基线（预处理）时，与各血浆脂质组分相关的总血浆FA比例为：磷脂62.6±0.6%，胆固醇酯26.1±0.6%，甘油三酯9.8±0.4%，以及非酯化脂肪酸1.5±0.1%；这些值不受处理影响。各血浆脂质组分的FA组成以及特定18碳FA在脂质组分中的分布存在显著差异。灌注处理异构体导致它们在各种血浆脂质组分中特异性增加，但对牛奶生产变量没有影响，包括乳脂肪产量和含量。灌注的OA、EA和VA向乳脂肪的转移效率平均分别为65.5±3.0%、59.7±1.5%和54.3±0.6%。对于VA灌注，乳脂肪中顺式-9，反式-11共轭亚油酸产量增加占转移量的24.6±1.1%，这与其通过乳腺酶Δ(9)-去饱和酶从VA内源性合成一致。值得注意的是，亚油酸（18:2n-6）和亚麻酸（18:3n-3）占总血浆FA的47.7%，但在牛奶FA中仅占2.6%。总体而言，结果表明18碳FA在血浆转运以及乳腺摄取和利用方面存在明显差异，并且这些差异与双键的位置、方向和数量有关。
