Grandgirard A, Bourre J M, Julliard F, Homayoun P, Dumont O, Piciotti M, Sebedio J L
INRA, Station de Recherches sur la Qualité des Aliments de l'Homme, Unité de Nutrition Lipidique, Dijon, France.
Lipids. 1994 Apr;29(4):251-8. doi: 10.1007/BF02536329.
During heat treatment, polyunsaturated fatty acids and specifically 18:3n-3 can undergo geometrical isomerization. In rat tissues, 18:3 delta 9c,12c,15t, one of the trans isomers of linolenic acid, can be desaturated and elongated to give trans isomers of eicosapentaenoic and docosahexaenoic acids. The present study was undertaken to determine whether such compounds are incorporated into brain structures that are rich in n-3 long-chain polyunsaturated fatty acids. Two fractions enriched in trans isomers of alpha-linolenic acid were prepared and fed to female adult rats during gestation and lactation. The pups were killed at weaning. Synaptosomes, brain microvessels and retina were shown to contain the highest levels (about 0.5% of total fatty acids) of the trans isomer of docosahexaenoic acid (22:6 delta 4c,7c,10c,13c,16c,19t). This compound was also observed in myelin and sciatic nerve, but to a lesser extent (0.1% of total fatty acids). However, the ratios of 22:6 trans to 22:6 cis were similar in all the tissues studied. When the diet was deficient in alpha-linolenic acid, the incorporation of trans isomers was apparently doubled. However, comparison of the ratios of trans 18:3n-3 to cis 18:3n-3 in the diet revealed that the cis n-3 fatty acids were more easily desaturated and elongated to 22:6n-3 than the corresponding trans n-3 fatty acids. An increase in 22:5n-6 was thus observed, as has previously been described in n-3 fatty acid deficiency. These results encourage further studies to determine whether or not incorporations of such trans isomers into tissues may have physiological implications.
在热处理过程中，多不饱和脂肪酸，尤其是18:3n-3会发生几何异构化。在大鼠组织中，亚麻酸的反式异构体之一18:3 Δ9c,12c,15t可去饱和并延长，生成二十碳五烯酸和二十二碳六烯酸的反式异构体。本研究旨在确定此类化合物是否会掺入富含n-3长链多不饱和脂肪酸的脑结构中。制备了两个富含α-亚麻酸反式异构体的组分，并在妊娠和哺乳期喂给成年雌性大鼠。幼崽在断奶时处死。结果显示，突触体、脑微血管和视网膜中二十二碳六烯酸反式异构体（22:6 Δ4c,7c,10c,13c,16c,19t）的含量最高（约占总脂肪酸的0.5%）。在髓鞘和坐骨神经中也观察到了这种化合物，但含量较低（占总脂肪酸的0.1%）。然而，在所研究的所有组织中，22:6反式与22:6顺式的比例相似。当饮食中α-亚麻酸缺乏时，反式异构体的掺入量明显增加一倍。然而，比较饮食中反式18:3n-3与顺式18:3n-3的比例发现，顺式n-3脂肪酸比相应的反式n-3脂肪酸更容易去饱和并延长为22:6n-3。因此，观察到22:5n-6增加，这与之前n-3脂肪酸缺乏时的描述一致。这些结果促使进一步研究此类反式异构体掺入组织是否具有生理意义。
