Metabolism of all trans 9,12-[1-14C]octadecadienoic acid in the developing brain

Trans fatty acids. 2. Fatty acid composition of the brain and other organs in the mature female pig

Female pigs were fed from three wk of age and up to two years a diet containing partially hydrogenated fish oil (PHFO, 28% trans monoenoic fatty acids), partially hydrogenated soybean oils (PHSBO, 36% trans fatty acids) or lard. No consistent differences were found between PHFO and PHSBO with regard to incorporation of trans fatty acids in organ lipids, but trans incorporations were highly organ-specific. No trans fatty acids were detected in brain phosphatidylethanolamine (PE). The incorporation of monoenoic trans isomers, as a percentage of total cis + trans, in other organs was highest in subcutaneous adipose tissue and liver mitochondria PE, followed by blood lipids with the lowest level in heart PE. The percentage of trans isomers compared with that of dietary lipids was consistently lower for 20:1, compared with 18:1 in organs from PHFO-fed pigs. The only effect of dietary trans fatty acids on the fatty acid pattern of brain PE was an increased level of 22:5n-6. Heart PE and total serum lipids of pigs fed the hydrogenated fats contained higher levels of 18:2n-6, and these lipids of the PHFO-fed group also contained slightly elevated amounts of 20:3n-6, 18:3n-3 and 20:5n-3. Liver mitochondria PE of the PHFO group also contained higher levels of 20:3n-6 and 22:5n-6. Dietary trans fatty acids caused a consistent decrease of saturated fatty acids compensated by increased levels of monoenes.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of different acids with delta 9,12-dienoic structures on delta 9 desaturation activity in rat liver microsomes

The effect of oral administration, for 24 or 48 hr, of different octadeca fatty acids containing a 9,12-dienoic structure on the fatty acid composition and delta 9 desaturation activity of liver microsomes of rat fed a fat-free diet was studied. The ethyl esters of linoelaidic and gamma-linolenic acids, the methyl ester of linoleic acid and free columbinic acid were administered to rats maintained on a fat-free diet. The supplementation of the fat-free diet with linoelaidate produced no relevant changes in the fatty acid composition pattern of liver microsomes and did not modify the percentage of conversion of palmitic to palmitoleic acid. The addition of linoleate or gamma-linolenate to the fat-free diet returned liver microsome delta 9 desaturation activity toward the control and partially restored the liver microsome fatty acid spectrum found in the fat-free diet. Columbinic acid (5-trans-9-cis,12-cis-18:3), which cannot be transformed into arachidonic acid, also decreased the delta 9 desaturation activity enhanced by the fat-free diet and evoked changes in the microsomal fatty acid composition similar to those produced by the omega 6 fatty acids. These results suggest that the modulation of delta 9 desaturase activity evoked by dietary administration of unsaturated acids of omega 6 series would depend on the cis double bond configuration of these acids.

Effect of dietary fatty acids on delta 5 desaturase activity and biosynthesis of arachidonic acid in rat liver microsomes

The effect of different fatty acids supplemented to a fat-free diet on the activity of delta 5 desaturase was studied. Fat-free diet produces a reduction in the conversion of eicosa-8,11,14-trienoic acid to arachidonic acid. The addition of the cis-omega 6 acids, linoleic, gamma-linolenic or arachidonic to the diet produces an increase of eicosatrienoic acid desaturation, shifting delta 5 desaturase activity towards the controls on a balanced diet. This reactivation is apparently produced by induction of enzyme biosynthesis since linoleate effect was suppressed by simultaneous cycloheximide injection. On the contrary, no changes in delta 5 desaturation activity were found when the diet was supplemented with palmitic or 9-trans,12-trans-linoleic acid. The changes on the activity of delta 5 desaturase were compared with the fatty acid composition of plasma and liver microsomes.

Interrelationship between dietary trans Fatty acids and the 6- and 9-desaturases in the rat

Studies are reported on the effects of dietary trans fatty acids on the 6- and 9-acyl desaturase activities in the liver microsomes of rats fed essential fatty acid (EFA)-deficient and non-EFA-deficient diets. In experiment I, weanling male rats were fed a semisynthetic diet with either 10% safflower oil (SAF) or 10% hydrogenated coconut oil (HCO). At the age of one year, half of the dietary fat was replaced by a supplement containing elaidate, linolelaidate and cis, trans-trans,cis-18:2 (TRANS) for 12 weeks. In experiment II, male rats which were kept from weaning on a 10% (SAF + TRANS, or 5% HCO + 5% TRANS. Feeding TRANS depressed the 6-desaturase activity in the liver microsomes, especially in the EFA-deficient rats (HCO + TRANS group of experiment I). Unlike the 6-deaturase activity, the 9-desaturase activity was not inhibited by the dietary trans fatty acids and was significantly stimulated in the non-EFA-deficient rats (SAF + TRANS group of experiment I and HCO + TRANS groups of experiment II). This was evidence by incubation reaction and by comparisons of fatty acid consumptions and microsomal fatty acid levels, showing extra biosynthesis of 16:1 and 18:1 when TRANS was fed. The biosynthesis of essential (n-6) fatty acids was depressed by the TRANS supplement in EFA-deficient as well as in non-EFA-deficient animals.

The influence of trans-acids on desaturation and elongation of fatty acids in developing brain

trans-Monounsaturated acids account for up to 3% of the total octadecenoic acyl chains of human brain lipids. To investigate the influence of trans-acids on desaturation and chain elongation of fatty acids, in vitro and in vivo experiments with rat brain were performed. In the in vitro assays of delta 9 desaturation, delta 6 desaturation and chain elongation, trans,trans-dienoic acid was inhibitory, particularly to chain elongation. Slight differences between the inhibitory effects of trans-monoenoic acids and their cis-isomers were observed. In an in vivo model, unlabeled fatty acid (stearate, oleate, elaidate, linoleate, linoelaidate, arachidonate, or trans-monoene from margarine) was injected simultaneously with [1-14C] linoleic acid into the brains of suckling rats. Linoelaidate and oleate inhibited desaturation and elongation of linoleate, whereas elaidate, stearate and trans-monoene from margarine were stimulatory. While the demonstration of differences between cis and trans monenic isomers required relatively high levels of the test acids, it appears that trans-acids can influence desaturation and elongation enzymes that lead to acyl chain modification in the central nervous system.

Positional specificity of trans fatty acids in fetal lecithin

Differences in the positional incorporation of 9-trans[1-(14)C] octadecenoic (elaidic) and 9-trans,12-trans[1-(14)C] octadecadienoic (linoelaidic) acids in fetal lecithin of rats were demonstrated. On the 20th day of gestation, a 14C-labeled albumin complex of elaidic or linoelaidic acid was injected into the jugular vein of pregnant rats. For comparative purposes, 9-cis[1-(14)C] octadecenoic (oleic) or 9-cis,12-cis[1-(14)C] octadecadienoic (linoleic acid) was injected into the maternal circulation of rats. Animals were killed 6 hr later. Distribution of label in total lipids and phospholipids (PL) of fetal issue was measured by TLC. Irrespective of the label, the highest percentage of total radioactivity was associated with PL-59 to 67%. Within PL, the major portion of radioactivity was found in choline phosphoglycerides (CPG)-53 to 67%, and in ethanolamine phosphoglycerides (EPG)-18 to 33%. While linoelaidic acid was predominantly esterified in the 2-position of CPG, elaidic acid was nearly equally distributed between positions 1 and 2 of lecithin. Distribution of radioactivity within fatty acid methyl esters (FAME) of CPG measured by radio-GLC suggested that oleic and possibly linoleic acids may be converted to nervonic and arachidonic acid, respectively, in the rat by the 20th day of gestation. Following injection of elaidate, radioacivity of FAME was distributed between palmitate and elaidic acid indicating that rat fetal tissue may metabolize elaidic acid via beta-oxidation. In contrast, following injection of linoelaidate, radioactivity of FAME was primarily associated with tt-18:2, suggesting little biotransformation to other fatty acids by fetal tissues.

Effects of dietary trans acids on the biosynthesis of arachidonic acid in rat liver microsomes

Effects of dietary trans acids on the interconversion of linoleic acid was studied using the liver microsomal fraction of rats fed a semipurified diet containing fat supplements of safflower oil (SAFF), hydrogenated coconut oil (HCO) at 5 and 20 at and 20% levels or a 5% level of a supplement containing 50.3% linolelaidic and 24.3% elaidic acids devoid of cis,cis-linoleic acid (TRANS). Growth rate was suppressed to greater extent with the animals fed the 20% than the 5% level of the HCO-supplemented diets and still further by the TRANS diet compared to the groups fed the SAFF diets. Food intake was greater in the groups fed the HCO than the SAFF-supplemented diets, demonstrating the marked effect of an essential fatty acid (EFA) deficiency on feed efficiency. In contrast to an EFA deficiency produced by the HCO supplement, which stimulated the in vitro liver microsomal biosynthesis of arachidonic acid, diets containing the TRANS supplement exacerabated the EFA deficiency and depressed 6-desaturase activity of the liver microsomal fraction. The liver microsomal fraction of the animals receiving this supplement also was more sensitive to fatty acid inhibition of the desaturation of linoleic acid than those obtained from animals fed either the SAFF or HCO diets. It is suggested that dietary trans acids alter the physical properties of the 6-desaturase enzyme system, suppressing its activity, which increases the saturation of the tissue lipids and, in turn, the requirement for EFA or polyunsaturated fatty acids.