Dietary trans fatty acids affect docosahexaenoic acid concentrations in plasma and liver but not brain of pregnant and fetal rats

The aim of the present study was to investigate the maternal-fetal transpor t, incorporation, and effects on liver delta-6 fatty-acid desaturase activi ty of dietary trans fatty acids in pregnant rats. Three groups of six rats each were fed three experimental diets containing approximately 0%, 15%, an d 30% of trans fatty acids but containing the same proportion of linoleic ( 18:2 n-6) and alpha-linolenic (18:3 n-3) acids for 10 wk. On d 20 of pregna ncy, the animals from each group were killed. We determined the fatty acid profiles in plasma, brain, and liver microsomes of pregnant rats, as well a s in placenta and fetal liver and brain. No changes were found in the numbe r of fetuses of the pregnant rats. Trans fatty acids were incorporated in h igh concentrations in placenta and in maternal and fetal tissues, except br ain, strongly elevating the linoleic acid proportion and lowering that of d ocosahexaenoic acid. The delta-6 fatty-acid desaturase activity in the live r microsomes of the pregnant rats was inhibited by trans isomers. In conclu sion, high intakes of trans fatty acids partially inhibit liver delta-6 fat ty-acid desaturase in pregnant rats, which may explain, in part, the low co ncentrations of docosahexaenoic acid in pregnant and fetal tissues. However , the fatty acid composition of both fetal and pregnant rat brain remains m ostly unaffected regardless of the dietary trans fatty acid content.