Selective utilization of omega 6 and omega 3 polyunsaturated fatty acids by human skin fibroblasts

Incorporation of exogenous [14C] arachidonate by human skin fibroblasts was found to be significantly greater than that of either [14C]linoleate or alpha-[14C] linolenate. Arachidonate was preferentially esterified in the PI + PS and PE classes of phospholipids. Over 40% of the incorporated [14C] arachidonate was chain elongated in 24 hours. Cells were also grown in lipid-free medium to enhance PUFA desaturation and elongation and the utilization of various omega 6 and omega 3 metabolites examined. Whereas [14C] linoleate partitioned approximately 50:50 between PL and TAG, eicosatrienoate (20:3 omega 6) was selectively sequestered in TAG. Arachidonate and docosatetraenoate (22:4 omega 6) were preferentially incorporated into phospholipids; the PI + PS fraction was most highly enriched with arachidonate. Modification of alpha-[14C] linolenate was more extensive than that of [14C] linoleate. Docosapentaenoate (22:5 omega 3) was the major omega 3 [14C] PUFA of PI + PS and PE. Eicosapentaeonate was not selectively incorporated into phospholipids; within phospholipids the 20:5 omega 3 was primarily in PC. These results indicate that human skin fibroblasts exhibit acyl specificity in the esterification of polyunsaturated fatty acids, including preferential utilization of arachidonate rather than other prostaglandin precursors in the PI + PS fraction.

Preferential oxidation of linolenic acid compared to linoleic acid in the liver of catfish (Heteropneustes fossilis and Clarias batrachus)

The fate of [1(-14)C] linoleic acid and [1(-14)C] linolenic acid in the liver slices and also in the liver tissues of live carnivorous catfish, Heteropneustes fossilis and Clarias batrachus, was studied. Incorporation of the fatty acids into different lipid classes in the live fish differed greatly from the tissue slices, indicating certain physiological control operative in vivo. The extent of desaturation and chain elongation of linoleic and linolenic acids into long-chain polyunsaturated fatty acids was low. Linolenic acid was oxidized (thus labeling the saturated fatty acid with liberated 14C-acetyl-CoA) in preference to linoleic acid, and this oxidation also seemed to be under physiological control since both of the fatty acids were poorly oxidized in the tissue slices and in the killed fish. These fish can therefore recognize the difference in the acyl chain structures of linoleate and linolenate. The higher oxidation of linolenic acid and poor capacity for its conversion to longer chain, highly unsaturated derivatives indicates a higher demand for the dietary supply of these essential fatty acids in these two species.

AMP deaminase as a control system of glycolysis in yeast. Mechanism of the inhibition of glycolysis by fatty acid and citrate

The role of fatty acid and citrate on the interaction of the AMP deaminase (EC 3.5.4.6) reaction with glycolysis was investigated using permeabilized yeast cells. (a) Linolenate and citrate inhibited glycolytic flux and the recovery of the adenylate energy charge; however, linolenate remarkably retarded the depletion of the total adenylate pool, which was not at all affected by the addition of citrate. (b) Linolenate inhibited AMP deaminase activity in situ, resulting in the subsequent decrease in ammonium production, which reduced the activity of 6-phosphofructokinase (EC 2.7.1.11), whereas linolenate itself had no ability to inhibit the phosphofructokinase activity in the presence of excess ammonium concentration. (c) Citrate inhibited the activity of phosphofructokinase in situ in the presence and absence of ammonium ion, followed by an inhibition of glycolysis; however, AMP deaminase activity was not inhibited by citrate. The inhibition of glycolysis by fatty acids can be accounted for by the lowered activity of phosphofructokinase as a result of the decreased level of ammonium ion through the inhibition of the AMP deaminase reaction by these ligands, whereas the effect of citrate on glycolysis is a direct inhibition of phosphofructokinase without affecting the activity of AMP deaminase. Fatty acid and citrate, a principal metabolic product of fatty acid oxidation, can be responsible for the control of glycolysis in two different manners.

Decrease in essential fatty acid content of edible fats during the frying process

Degradation of sunflower oil, rapeseed oil, and lard during the frying operation was investigated by studying the loss of essential fatty acids compared to the accumulation of decomposition products. Linoleic and/or linolenic acid concentration was measured by GLC, and for detecting decomposition products determination of polymer content by GPC was chosen. Twelve laboratory experiments with different heating or frying conditions were run aimed at modelling practice and studying the effects of certain factors. The results indicated that loss of essential fatty acids being a parallel process to the accumulation of breakdown products is suitable both for detecting the decrease in nutritive value and for quality assessment of used frying fats. It was also found that the rate of deterioration is considerably affected by the nature of fat and the frying parameters. Study of the relationship between polymer content and the decrease in essential fatty acid concentration (using data from 110 samples) showed that high, linear correlation depending on the nature of fat can be found. Correlation coefficients and equations of regression lines were calculated.

Chemiluminescence of UV-irradiated linolenic acid and squalene

An emission spectral analysis was carried out on ultraweak chemiluminescence emitted from UVB-irradiated linolenic acid and squalene. The main emission species produced by the transition of (1 delta g) (1 delta g) dimer and an additional weak band near 477.5 nm (0, 0) by the transition of (1 delta g (1 epsilon g+) to (3 epsilon g-) (3 epsilon g-) were found by spectroscopic analysis of chemiluminescence in both cases of irradiated linolenic acid and of squalene. A distinct peak around 410-420 nm was observed in irradiated squalene and the emitter seems to be due to the excited carbonyl compound.

Influence of dietary essential fatty acid level on fatty acid composition in peripheral nerve and muscle

Two groups of rats of different lines were divided into two lots. The four lots, whose dams received a fat-controlled diet, were fed with diets containing different levels of essential unsaturated fatty acids, namely linoleic (18:2 (n-6)) and linolenic (18:2 (n-3)) acid, in the oil. Nerve and muscle fatty acids were analyzed at adulthood. When the linolenic acid level was less than 0.6 p. 100 of the total fatty acids in the diets (peanut oil and sunflower oil), the level of long-chain polyunsaturated fatty acids (PUFA) of the (n-3) series decreased. This decrease was associated with an increase in the PUFA of the (n-6) series. Total PUFA ((n-3) + (n-6)) remained similar in the same group of rats, whatever the diet. On the contrary, when dietary linolenic acid reached 7.6 p. 100 (soya oil) or 8.5 p. 100 (rapeseed oil) of the total fatty acids, in the presence of a very high linoleic acid level, the PUFA of the (n-6) series decreased and that of the (n-3) series increased in nerve and especially in muscle. It appears that preferential PUFA biosynthesis from linolenic acid occurred when the ratio (n-6)/(n-3) was low enough in the dietary oil.

Tissue distribution, uptake, and requirement for alpha-tocopherol of rainbow trout (Salmo gairdneri) fed diets with a minimal content of unsaturated fatty acids

The metabolism of and requirements for alpha-tocopherol in rainbow trout fed diets containing 1% linolenic acid as sole source of unsaturated fat and graded levels of tocopherol (0.06-10 mg/100 g) were examined. Fish grew 5-fold over a 16-week period. In liver, tocopherol was concentrated in mitochondria with little in cytosol. Orally administered [3H]-tocopherol was rapidly taken up by plasma and liver but uptake into erythrocytes and white muscle was much slower; in most tissues radioactivity reached a plateau after about 3 days but in red muscle radioactivity increased over a 10-day period. Activities of enzymes that prevent free radical initiated tissue damage did not change in tocopherol deficiency. Tocopherol-deficient trout had no gross or subcellular pathologies even though liver and muscle were severely depleted of the vitamin. Ascorbic acid-stimulated lipid peroxidation in liver organelles indicated a tocopherol requirement of 2-3 mg/100 g diet; the molar ratios of polyunsaturated fatty acids to tocopherol in livers of trout fed diets lacking or supplemented with tocopherol (100 mg/100 g) were 980 and 170, respectively.

Increased conversion of arachidonic acid to vasodilator prostanoids in spontaneously hypertensive rats

1. Vasodepressor responses to intravenous injection of prostacyclin, arachidonic acid, and nitroprusside were examined in anaesthetized, spontaneously hypertensive rats (SHR) of the Okamoto strain, and in their normotensive Wistar-Kyoto (WKY) controls. 2. Depressor responses to prostacyclin and nitroprusside did not differ significantly between the two strains. 3. The vasodepressor effects of arachidonic acid were greater and much more prolonged in SHR than in WKY. In rats treated with indomethacin (2 mg/kg) arachidonic acid induced only transient depressor responses which did not differ significantly between these strains. 4. It is concluded that SHR do not differ from WKY in their sensitivity to prostacyclin but they have enhanced ability to transform exogenous arachidonic acid into vasodilator prostanoids.

Relationship between essential fatty acid requirements of aquatic animals and the capacity for bioconversion of linolenic acid to highly unsaturated fatty acids

1. [1-14C]linolenic acid was injected into the rainbow trout, Salmo gairdnerii, ayu, Plecoglossus altivelis, eel, Anguilla japonica, red sea bream, Chrysophrys major, rockfish, Sebastiscus marmoratus, globefish, Fugu rubripes rubripes and prawn, Penaeus japonicus (molting stage D"1-D2), and the bioconversion of linolenic acid (18:3 omega 3) to highly unsaturated fatty acids such as eicosapentaenoic (20:5 omega 3) and docosahexaenoic (22:6 omega 3) acids was investigated. 2. Linolenic acid was converted to 20:5 omega 3 and 22:6 omega 3 intensively in the rainbow trout, moderately in the ayu, eel and prawn, but slightly in the red sea bream, rockfish and globefish. 3. These results were discussed in relation to the essential fatty acid requirements of the aquatic animals.

HEPATIC CHANGES INDUCED BY AN AQUEOUS EXTRACT OF ULTRAVIOLET-IRRADIATED LINOLENIC ACID

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