Stearidonic acid, an inhibitor of the 5-lipoxygenase pathway. A comparison with timnodonic and dihomogammalinolenic acid.

Leukotrienes have been shown to play an important role as mediators in various disease processes, including asthma and inflammation; thus, their synthesis is tightly regulated. The major precursor of leukotrienes is arachidonic acid (20:4n-6). Fatty acids which are structurally similar to 20:4n-6, such as eicosatrienoic acid (20:3n-6; dihomogammalinolenic acid) and eicosapentaenoic acid (20:5n-3; timnodonic acid) have been found to inhibit leukotriene biosynthesis. Because of the structural similarity of octadecatetraenoic acid (18:4n-3; stearidonic acid) with 20:4n-6, the present study was undertaken to determine whether stearidonic acid also exerts an inhibitory effect on the 5-lipoxygenase pathway. Human leukocytes were incubated with 18:4n-3 (20 microM or 10 microM), 20:5n-3 (20 microM) or 20:3n-6 (20 microM) and subsequently stimulated with 1 microM ionophore A23187 and 20:4n-6 (20 microM or 10 microM). The 5-lipoxygenase products were then measured by high-performance liquid chromatography. Leukotriene synthesis was reduced by 50% with 20 microM 18:4n-3 and by 35% with 10 microM 18:4n-3. Formation of 5S,12S-di-hydroxy-eicosatetraenoic acid and of 5-hydroxy-eicosatetraenoic acid was decreased by 25% with 20 microM 18:4n-3 and by 3% with 10 microM 18:4n-3. The inhibition observed with 20 microM 18:4n-3 appeared to be of the same order as that observed with 20 microM 20:5n-3; the inhibition observed with 18:4n-3 was shown to be dose-dependent. The inhibition produced by 20 microM 20:3n-6 was greater than that observed with either 20 microM 18:4n-3 or with 20 microM 20:5n-3.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibitory effect of stearidonic acid (18:4 n-3) on platelet aggregation and arachidonate oxygenation.

The effect of stearidonic acid (18:4 n-3) present in fish and some plant oils, such as black currant seed oil, was studied on human platelets. When added to platelets simultaneously with collagen, arachidonic acid or endoperoxide mimetic U46619, 18:4 n-3 appeared as a weak inhibitor of platelet aggregation. In addition, 18:4 n-3 did not alter the metabolism of exogenous arachidonic acid. In contrast, when preincubated with platelets after precoating onto albumin, 18:4 n-3 inhibited platelet aggregation induced by thrombin, collagen, arachidonic acid or U46619, and was as potent as eicosapentaenoic acid (20:5 n-3) tested under similar conditions. Stearidonic acid also altered the endogenous arachidonate oxygenation stimulated by low doses of thrombin, but to a significantly lesser extent than did 20:5 n-3. It seems therefore that, in addition to competing with endogenous arachidonate metabolism, 18:4n-3 may affect platelet aggregation by another mechanism.

Routine gas chromatographic/mass spectrometric analysis of fatty acid methyl esters using the ion trap detector.

About 60 long-chain fatty acids occur naturally in lipids of biological tissues and fluids, oils, fats and waxes. The ion trap detector (ITD) offers a convenient but powerful means for the routine analysis by gas chromatography/mass spectrometry of such fatty acids as their methyl esters (FAMES). Enhanced [M + 1]+ ions may be formed at higher sample levels of 50 ng or more. However, spectra still retain a predominantly electron impact (EI) character. Using the classical mass spectral performance test compound methyl stearate as an example, good library comparisons were obtained for spectra run over a dynamic range of 2 pg to 225 ng, when a mid-range ITD spectrum run on 7.5 ng was used as a reference. Almost equally good spectral comparisons were found with literature reference spectra run on both quadrupole and sector conventional mass spectrometers. Using human plasma phospholipid FAMES as an example, along with an ITD-generated EI spectral library of FAMES standards, it was seen that for most of the components present the mass spectral library comparison was good enough to permit identification based on mass spectrometry alone. For all components, a combination of gas chromatographic retention index and mass spectral information permitted an unequivocal identification.

Rat brain slices produce and liberate kynurenic acid upon exposure to L-kynurenine.

The incorporation of L-kynurenine (L-KYN) into kynurenic acid (KYNA) was examined in rat brain slices. KYNA was measured in the slices and in the incubation medium after purification by ion-exchange and HPLC chromatography. In pilot experiments, the formation of KYNA was confirmed by gas chromatography. KYNA was produced stereoselectively from L-KYN, and approximately 90% of the newly synthesized KYNA was recovered from the incubation medium. Intracellular KYNA was not actively retained by the tissue and was lost from the cells upon repeated washes. Thus, regulation of the levels of extracellular KYNA appears to occur at the level of L-KYN uptake and/or kynurenine transaminase, the biosynthetic enzyme of KYNA. KYNA production from L-KYN was linear up to 4 h and reached a plateau at a L-KYN concentration of 250 microM. The process was effectively inhibited by the transaminase inhibitor aminooxyacetic acid (IC50, approximately 25 microM), and showed pronounced regional distribution (hippocampus greater than cortical areas greater than thalamus much greater than cerebellum). The conversion of L-KYN to KYNA was dependent on oxygenation and on the presence of glucose in the incubation medium. Neither deletion of Ca2+ or Mg2+ nor addition of 20 mM Mg2+ had any effect. However, KYNA production was significantly attenuated in the absence of Cl- or in the presence of 50 mM K+ in the incubation medium. In Na+-free medium, the production of KYNA from L-KYN was increased by 30%.(ABSTRACT TRUNCATED AT 250 WORDS)

Black currant seed oil feeding and fatty acids in liver lipid classes of guinea pigs.

Guinea pigs were fed one of three diets containing 10% black currant seed oil (a source of gamma-linolenic (18:3 n-6) and stearidonic (18:4 n-3) acids), walnut oil or lard for 40 days. The fatty acid composition of liver triglycerides, free fatty acids, cholesteryl esters, phosphatidylinositol, phosphatidylserine, cardiolipin, phosphatidylcholine and phosphatidylethanolamine were determined. Dietary n-3 fatty acids found esterified in liver lipids had been desaturated and elongated to longer chain analogues, notably docosapentaenoic acid (22:5 n-3) and docosahexaenoic acid (22:6 n-3). When the diet contained low amounts of n-6 fatty acids, proportionately more of the n-3 fatty acids were transformed. Significantly more eicosapentaenoic acid (EPA) (20:5 n-3) was incorporated into triglycerides, cholesteryl esters, phosphatidylcholine and phosphatidylethanolamine of the black currant seed oil group compared with the walnut oil group. Feeding black currant seed oil resulted in significant increases of dihomogamma-linolenic acid (20:3 n-6) in all liver lipid classes examined, whereas the levels of arachidonic acid (20:4 n-6) remained relatively stable. The ratio dihomo-gamma-linolenic acid/arachidonic acid was significantly (2.5-fold in PI to 17-fold in cholesteryl esters) higher in all lipid classes from the black currant seed oil fed group.

Alternative lipids to usual omega 6 PUFAS: gamma-linolenic acid, alpha-linolenic acid, stearidonic acid, EPA, etc.

The intravenous administration of parenteral fat emulsions is widely used in total parenteral nutrition (TPN) to supply essential fatty acids and concentrated energy in a relatively small volume of isotonic solution. They contain very high amounts of linoleic acid and usually about 8% of alpha-linolenic acid calculated in the fat phase (10 or 20% of the total emulsion). Most of the time one emulsion is given as the sole source of fat, giving direct venous entry to a fatty acid composition substantially different from that encountered in a normal diet. Since the latter greatly influences the fatty acid composition of phospholipids which are critical determinants of membrane structural properties influencing a variety of membrane functions (Fig. 1) (enzyme activity, membrane transport, receptor function) and functional precursors of intracellular and intercellular mediators (diacylglycerols, prostaglandins, leukotrienes, hydroxy fatty acids), do we provide the right fatty acid at the right place and the right time for efficient cell cell interaction? In other words, given the three roles of fatty acids--energetic, structural, functional--are we using the best strategy to avoid imbalances between the three roles?

Evolution of lipid composition in skin treated with blackcurrant seed oil.

Synopsis This report utilizes a new procedure based on epidermal stripping to analyse unlabelled skin fatty acids. This technique was applied to the study of human dry skin treated with blackcurrant seed oil, an essential fatty acid rich lipid also containing gamma linolenic acid. In human dry skin the usual fatty acids were found in the stratum corneum as in normal skin outer layers. Among the saturated series no significant difference was observed in the C16 chain but a smaller quantity of C18:0 was detected. In the unsaturated series a marked fall of linoleic acid as well as a higher level of C16:1 in the stratum corneum appeared as the major significant events that could characterize dry skin. gamma linolenic acid was detectable neither in normal nor in dry skin. alpha linolenic acid was found but not consistently. After multiple applications of blackcurrant seed oil in an emulsion preparation, impregnation of the stratum corneum was complete, and essential or other fatty acids contained in the oil (particularly linoleic and linolenic acids) were found in combination with endogenous lipids. Possibly they contribute to enhance the protective effect of the stratum corneum.

Analysis of volatile fatty acids in biological specimens by capillary column gas chromatography.

A method was developed to analyze and quantify volatile fatty acids (VFA) such as acetic, propionic, butyric, isobutyric, valeric and isovaleric acids in biological specimens. To obtain good sample transfer into the chromatographic system an organic solvent had to be used together with an aqueous milieu, thus improving wetting properties of the liquid sample plug introduced into the column. Sample preparation was carried out under alkaline conditions in order to exclude or minimize sample losses due to sample transfer during the extraction and work-up procedure. A cold on-column injection was applied to avoid irregular discrimination of the various acids due to sample splitting and an automatic injection technique was used to accommodate the large number of samples generated from biological origin. Connection of a pre-column of wide internal diameter (0.53 mm) to the analytical column (0.32 m) was optimized and adapted to the nature of the injection solvent mixture consisting of acetonitrile, water and hydrochloric acid. To obtain well-separated and correctly quantifiable gas chromatographic peaks, it was essential to perform the chromatography under acidic aqueous conditions. Standard resolution conditions and response factors were evaluated. The chromatographic results of applying this method to biological specimens from both rats and humans are provided.

Characterization of gamma-linolenic acid in Ribes seed.

The total lipid content of fruit seeds of the Ribes family ranges by weight from 18.3% in goose-berries (Ribes uva crispa) to 30.5% in black currants (Ribes nigrum). Isolation procedures and analytical methods (gas chromatography, mass spectrometry, high performance thin layer chromatography and stereospecific analysis) demonstrate that the oils from Ribes seeds contain up to 19% by weight of gamma-linolenic acid (gamma-LA, C18:3, n-6) in black currant oil. This last Ribes species thus constitutes one of the richest natural sources in gamma-LA yet described. These oils appear promising for critically ill patients who seem unable to convert linoleic acid into subsequent EFA fractions.

On-line gas chromatographic evaluation of iodine values in edible fats and oils.

A method is reported where an on-line evaluation of gas-chromatographic data allows direct calculation of iodine values of fats and oils. Iodine values are printed out in the final analysis report of fatty acid methyl ester gas chromatographic analysis. For this purpose a simple equation was established which included double-bond increments of fatty acids, mean molecular weights and molecular weight contributions of each single component of the mixture. In a further step, a computer program was developed (Spectra-Physics 4100 Integrator) that allowed the final on-line print-out of the results. To evaluate the reliability of the method, comparative analyses by titration were carried out. No significant differences in the results could be observed.