Dietary intake of concentrated gamma-linolenic acid (GLA)-enriched oil suppresses cutaneous level of dihomo-gamma-linolenic acid (DGLA): possible in vivo inhibition of microsomal elongation of GLA to DGLA.

The dietary supplementation of normal guinea-pig diet with moderate levels of vegetable oils containing gamma-linolenic acid (GLA) is associated with elevation of epidermal levels of dihomo-gamma-linolenic acid (DGLA) and 15-hydroxyeicosatrienoic acid (15-lipoxygenase product of DGLA). However, supplementation of diet with higher level (70%) of GLA (GLA-70) resulted in marked decrease of epidermal level of DGLA. This nutritional observation prompted us to investigate in vitro the effects of varying concentrations of polyunsaturated fatty acids (PUFAs) on rat liver microsomal chain elongation of GLA into DGLA. Our data revealed that low concentrations of GLA (less than 100 microM) are stimulatory on the chain elongation while higher concentrations (greater than 100 microM) are inhibitory. The 18-carbon linoleic acid (precursor of GLA) was also markedly inhibitory at high concentrations. Interestingly, the longer chain 20-carbon n-3 PUFAs: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) exerted negligible effect. The results suggest that increased systemic presence of free PUFAs, such as may occur in vivo after dietary intake of high n-6 PUFA-containing vegetable oils, may explain the decreased level of DGLA in the epidermal tissue.     

Distribution and metabolism of dihomo-gamma-linolenic acid (DGLA, 20:3n-6) by oral supplementation in rats

We compared the dietary effects of dihomo-gamma-linolenic acid (DGLA) contained in the DGLA oil produced by a fungus with gamma-linolenic acid (GLA) on the fatty acid composition. Wistar rats were fed with three kinds of oil for two weeks as follows: (i) control group: corn oil; (ii) GLA group: borage oil; (iii) DGLA group: DGLA oil/safflower oil = 55:45. The DGLA concentrations in the liver, serum, and brain of the DGLA group were higher than those of the GLA oil group. We also examined the dose effect of DGLA. The DGLA levels in the liver, serum, and brain significantly increased with increasing dosage of DGLA in the diet. DGLA administration significantly increased the ratio of PGE1/PGE2 in the rat plasma. The mechanism for GLA administration to improve atopic eczema is thought to involve an increase in the concentration of DGLA metabolized from GLA, so these results suggest that the dietary effect of DGLA would be more dominant than GLA.     

Effect of n-3 and n-6 fatty acids on hepatic microsomal lipid metabolism: a time course study

The present study examines the time dependent effects of n-6 and n-3 polyunsaturated fatty acids on liver microsomal lipid metabolism in FVB mice fed a diet supplemented with a mixture of free fatty acids (mainly 18:3n-6 and 20:5n-3) at 25 mg/g diet. Significant changes in the fatty acid composition of total liver and microsomal lipids were observed after 7 days on the diets. Thereafter, some animals remained on the same diet while others were fed a diet supplemented with hydrogenated coconut oil (HCO). With the exception of 20:5n-3 which showed a slower recovery, establishment of the HCO pattern was rapid indicating that the diet-induced changes could be easily reversed. The unsaturation index, the cholesterol/phospholipid ratio and the microviscosity of the microsomal membranes were not affected by these dietary manipulations. Unsaturated fatty acid supplementation reduced the activity of ⁹ desaturase by 50%. Feeding the HCO diet to mice previously fed the EPA/GLA diet led to a progressive increase in ⁹ desaturase activity, reaching 80% of the day zero values after 14 days. The monoene content of hepatic total lipids reflected, in most cases, the changes in enzyme activity. This study shows that a low dose of a n-3 and n-6 free fatty acid mixture increases the quantities of members of the n-3 family, without loss of n-6 fatty acids in microsomal membranes and modifies the activity of ⁹ desaturase without altering the microsome physicochemical parameters.     

The effect of acetic acid concentration on the growth and production of gamma-linolenic acid byMucor circinelloides CBS 203.28 in fed-batch culture

The effect of different initial acetic acid concentrations on the growth of and lipid and gamma-linolenic acid (GLA) production byMucor circinelloides CBS 203.28 was determined in a 14 litre stirred tank reactor operated in a fedbatch, pH-stat mode with acetic acid as carbon source and pH titrant. Increased acetic acid concentrations in the culture resulted in a significant increase in the crude oil content of the biomass. By contrast, all the other parameters such as the biomass concentration, GLA and oil yield on acetic acid, the GLA content of the biomass and oil, the growth rate and volumetric rate of GLA production decreased with an increase in acetic acid concentration. The best results were obtained with acetic acid at 2 g/1, which gave 39.8 mg GLA/g biomass and 15.6% GLA in the neutral lipid fraction, amounting to 340 mg GLA/1 culture. A decrease in the glyco- and phospho-lipid fractions during the cultivation coincided with an increase in the neutral lipid fraction. The GLA content of the biomass remained within rather narrow limits of 3.5% to 4% of the biomass, irrespective of the oil content of the biomass. The fatty acid profile was not greatly affected by the acetic acid concentration. The hyphae of the fungus were characterized by the accumulation of large intracellular oil droplets and some septa delimited the hyphae.     

Sex differences in n-3 and n-6 fatty acid metabolism in EFA-depleted rats

We studied the effect of sex on the distribution of long-chain n-3 and n-6 fatty acids in essential fatty acid-deficient rats fed gamma-linolenate (GLA) concentrate and/or eicosapentaenoate and docosahexaenoate-rich fish oil (FO). Male and female weanling rats were rendered essential fatty acid deficient by maintaining them on a fat-free semisynthetic diet for 8 weeks. Thereafter, animals of each sex were separated into three groups (n = 6) and given, for 2 consecutive days by gastric intubation, 4 g/kg body wt per day of GLA concentrate (containing 84% 18:2n-6), n-3 fatty acid-rich FO (containing 18% 20:5n-3 and 52% 22:6n-3), or an equal mixture of the two oil preparations (GLA + FO). The fatty acid distributions in plasma and liver lipids were then examined. GLA treatment increased the levels of C-20 and C-22 n-6 fatty acids in all lipid fractions indicating that GLA was rapidly metabolized. However, the increases in 20:3n-6 were less in females than those in males, while those in 20:4n-6 were greater, suggesting that the conversion of 20:3n-6 to 20:4n-6 was more active in female than in male rats. FO treatment increased the levels of 20:5n-3 and 22:6n-3 and reduced those of 20:4n-6. The increase in n-3 fatty acids was greater in females than that in males and the reduction in 20:4n-6 was smaller. Consequently, the sum of total long-chain EFAs incorporated was greater in females than that in males. The administration of n-3 fatty acids also reduced the ratio of 20:4n-6 to 20:3n-6 in GLA + FO-treated rats indicating that n-3 fatty acids inhibited the activity of delta-5-desaturase. However, this effect was not affected by the sex difference.     

The effects of evening primrose oil, safflower oil and paraffin on plasma fatty acid levels in humans: Choice of an appropriate placebo for clinical studies on primrose oil

In a number of diseases, plasma levels of linoleic acid are normal or elevated while those of gamma-linolenic acid (18:3n-6, GLA) and further metabolites are below normal. Evening primrose oil (EPO), similar to safflower oil (SFO) except that it contains 8-9% of 18:3n-6, has been proposed as a therapeutic agent in these diseases, such as atopic eczema. There is argument as to whether an appropriate placebo for clinical studies on EPO should be an inert material such as paraffin, or a linoleic acid--containing oil such as SFO. We have therefore compared in normal humans the effects on plasma fatty acids of administering EPO, SFO and paraffin for 10 days. Paraffin had no effect on any fatty acid in any fraction. EPO raised the level of 20:3n-6 (dihomo-gamma-linolenic acid, DGLA) the immediate metabolite of GLA but had no significant effect on arachidonic acid. In surprising contrast, SFO raised the levels of linoleic and of arachidonic acids, without raising those of DGLA. This suggests that linoleic acid may be rapidly converted to arachidonic acid by a tightly linked enzyme sequence: GLA, in contrast, may be rapidly converted to DGLA but then only slowly on to arachidonic acid. These results are consistent with recent in vitro observations by others on rat hepatocytes and human fibroblasts.     

Long-chain conversion of [13C]linoleic acid and alpha-linolenic acid in response to marked changes in their dietary intake in men

We studied the long-chain conversion of [U-13C]alpha-linolenic acid (ALA) and linoleic acid (LA) and responses of erythrocyte phospholipid composition to variation in the dietary ratios of 18:3n-3 (ALA) and 18:2n-6 (LA) for 12 weeks in 38 moderately hyperlipidemic men. Diets were enriched with either flaxseed oil (FXO; 17 g/day ALA, n=21) or sunflower oil (SO; 17 g/day LA, n=17). The FXO diet induced increases in phospholipid ALA (>3-fold), 20:5n-3 [eicosapentaenoic acid (EPA), >2-fold], and 22:5n-3 [docosapentaenoic acid (DPA), 50%] but no change in 22:6n-3 [docosahexanoic acid (DHA)], LA, or 20:4n-6 [arachidonic acid (AA)]. The increases in EPA and DPA but not DHA were similar to those in subjects given the SO diet enriched with 3 g of EPA plus DHA from fish oil (n=19). The SO diet induced a small increase in LA but no change in AA. Long-chain conversion of [U-13C]ALA and [U-13C]LA, calculated from peak plasma 13C concentrations after simple modeling for tracer dilution in subsets from the FXO (n=6) and SO (n=5) diets, was similar but low for the two tracers (i.e., AA, 0.2%; EPA, 0.3%; and DPA, 0.02%) and varied directly with precursor concentrations and inversely with concentrations of fatty acids of the alternative series. [13C]DHA formation was very low (<0.01%) with no dietary influences.     

Dietary manipulation implicates lipid signaling in the regulation of germ cell maintenance in C. elegans

Reproduction in C. elegans relies on continuously proliferating germ cells which, during germline development, exit mitosis, undergo meiosis and differentiate into gametes. Supplementing the diet of C. elegans with dihommogamma-linolenic acid (20:3n-6, DGLA), a long chain omega-6 polyunsaturated fatty acid, results in sterile worms that lack germ cells. The effect is remarkably specific for DGLA, as eicosapentaenoic acid (20:5n-3, EPA) and other long-chain polyunsaturated fatty acids with similar physical properties have little or no effect on fertility. Germ cells undergoing mitosis during larval stages are especially sensitive to DGLA, but exposure to DGLA during adulthood also reduces germ cells and brood size, in part by inducing inappropriate apoptosis of meiotic germ cells. Mutant strains with defects in fatty acid desaturation and elongation display altered susceptibility to DGLA, indicating that the sterility effect of the dietary lipid depends on the amount of DGLA present in membranes as well as on the capacity to convert DGLA to other fatty acids. We propose that DGLA produces a signal that interacts with one or more pathways regulating germ cell survival. Our DGLA findings are the first report of a role for a specific fatty acid affecting the development and maintenance of germ cells in C. elegans.     

Gammalinolenic acid-enriched diet alters cutaneous eicosanoids

There are reports that vegetable oils containing gammalinolenic acid (GLA) may exert beneficial effects on inflammatory skin disorders. To determine whether or not dietary GLA exerts any modulatory role on cutaneous eicosanoids, guinea pigs were fed either a control diet containing safflower oil (less than 0.5% GLA) or borage oil, a GLA-rich diet containing 25% GLA. After an 8-week feeding period, epidermal samples from both animal groups were analyzed for fatty acid composition and tissue eicosanoids. Analysis of epidermal neutral lipids and phospholipids in borage oil-fed animals showed a marked increase in GLA and its elongase product, dihomogammalinolenic acid (DGLA). Similarly, analysis of epidermal eicosanoids in the borage oil-fed animals revealed significant increases in the amounts of the 15-hydroxy fatty acid (15-OH-20:3n-6) and prostaglandin PGE1, both metabolites of DGLA. Since these metabolites have anti-inflammatory potential, our results suggest that increased dietary GLA could result in the generation of local anti-inflammatory metabolites thus providing a non-toxic approach to suppression of cutaneous inflammatory skin disorders.     

Isolation and functional characterization of a delta 6-desaturase gene from the pike eel (Muraenesox cinereus)

Stearidonic acid (STA; 18:4n-3) and γ-linolenic acid (GLA; 18:3n-6) are significant intermediates in the biosynthetic pathway for the very-long-chain polyunsaturated fatty acids of eicosapentaenoic acid (EPA; 20:5n-3) and arachidonic acid (ARA; 20:4n-6), respectively. To develop a sustainable system for the production of dietary polyunsaturated fatty acids, we focused on the action of the enzyme delta 6-desaturase (D6DES) on the essential acids, linoleic acid (LA; 18:2n-6) and α-linolenic acid (ALA; 18:3n-3). A 1,335-bp full-length cDNA encoding D6DES (McD6DES) was cloned from Muraenesox cinereus using degenerate PCR and RACE-PCR methods. To investigate the enzymatic activity of McD6DES in the production of n-6 and n-3 fatty acids, a recombinant plasmid expressing McD6DES (pYES-McD6DES) was transformed into and expressed in Saccharomyces cerevisiae. The exogenously expressed McD6DES produced GLA and STA at conversion rates of 14.2% and 45.9%, respectively, from the exogenous LA and ALA substrates. These results indicate that McD6DES is essentially a delta 6-desaturase involved in very-long-chain polyunsaturated fatty acid synthesis.     

Identification of Δ9-elongation activity from <Emphasis Type="Italic">Thraustochytrium aureum</Emphasis> by heterologous expression in <Emphasis Type="Italic">Pichia pastoris</Emphasis>

The Δ9-elongase isolated from Thraustochytrium aureum, which contains a high level of polyunsaturated fatty acids (PUFAs), was demonstrated to be associated with the synthesis of C20 PUFAs. The TaELO gene contains a 825 bp ORF that encodes a protein of 274 amino acids that shares a high similarity with other PUFA elongases. The expression of the TaELO gene in Pichia pastoris resulted in the elongation of linoleic acid (LA, C18:2; n-6) and α-linolenic acid (ALA, C18:3; n-3) to eicosadienoic acid (EDA, C20:2; n-6) and eicosatrienoic acid (ETrA, C20:3; n-3), respectively. The endogenous conversion rate of LA and ALA to EDA and ETrA was 32.68 and 38.57%, respectively. In addition, TaELO was also able to synthesize eicosenoic acid (C20:1; n-9) from oleic acid (OA, C18:1; n-9), even though the conversion level was low (2.81%). Furthermore, TaELO was able to carry out the 6Δ-elongation of γ-linolenic acid (GLA, C18:3; n-6) to dihomo-γ-linolenic acid (DGLA, C20:3; n-6) and Δ5-elongation of eicosapentaenoic acid (EPA, C20:5; n-3) to docosapentaenoic acid (DPA, C22:5; n-3). The conversion rate of GLA to DGLA and EPA to DPA were 93 and 28.36%, respectively. The TaELO protein was confirmed to have multifunctional activities, such as Δ9, Δ6, and Δ5-elongations as well as the elongation of monounsaturated fatty acid.     

Effect of diets enriched in Delta6 desaturated fatty acids (18:3n-6 and 18:4n-3), on growth, fatty acid composition and highly unsaturated fatty acid synthesis in two populations of Arctic charr (Salvelinus alpinus L.)

This study aimed to test the hypothesis that diets containing relatively high amounts of the Delta6 desaturated fatty acids stearidonic acid (STA, 18:4n-3) and gamma-linolenic acid (GLA, 18:3n-6), may be beneficial in salmonid culture. The rationale being that STA and GLA would be better substrates for highly unsaturated fatty acid (HUFA) synthesis as their conversion does not require the activity of the reputed rate-limiting enzyme, fatty acid Delta6 desaturase. Duplicate groups of two Arctic charr (Salvelinus alpinus L.) populations with different feeding habits, that had been reported previously to show differences in HUFA biosynthetic capacity, were fed for 16 weeks on two fish meal based diets containing 47% protein and 21% lipid differing only in the added lipid component, which was either fish oil (FO) or echium oil (EO). Dietary EO had no detrimental effect on growth performance and feed efficiency, mortalities, or liver and flesh lipid contents in either population. The proportions of 18:2n-6, 18:3n-3, 18:3n-6, 18:4n-3, 20:3n-6 and 20:4n-3 in total lipid in both liver and flesh were increased by dietary EO in both populations. However, the percentages of 20:5n-3 and 22:6n-3 were reduced by EO in both liver and flesh in both strains, whereas 20:4n-6 was only significantly reduced in flesh. In fish fed FO, HUFA synthesis from both [1-(14)C]18:3n-3 and [1-(14)C]20:5n-3 was significantly higher in the planktonivorous Coulin charr compared to the demersal, piscivorous Rannoch charr morph. However, HUFA synthesis was increased by EO in Rannoch charr, but not in Coulin charr. In conclusion, dietary EO had differential effects in the two populations of charr, with HUFA synthesis only stimulated by EO in the piscivorous Rannoch morph, which showed lower activities in fish fed FO. However, the hypothesis was not proved as, irrespective of the activity of the HUFA synthesis pathway in either population, feeding EO resulted in decreased tissue levels of n-3HUFA and 20:4n-6. This has been observed previously in salmonids fed vegetable oils, and thus the increased levels of Delta6 desaturated fatty acids in EO did not effectively compensate for the lack of dietary HUFA.     

Changes in the content of gamma-linolenic C18:3 (n-6) and stearidonic C18:4 (n-3) acids in developing seeds of viper's bugloss Echium vulgare L

Changes in the composition of fatty acids (FA) were determined in lipid extracts isolated from developing ovaries containing ovules and developing seeds of Echium vulgare L. The samples were collected successively over 20 days beginning with the first day after flowering. The contents of the n-6 FA family members, i.e., gamma-linolenic (GLA) (C(18:3)) and linoleic (LA) (C(18:2)) acids changed in a parallel manner and reached the maximum of 13.9% and 24%, respectively, on the 12th day, after which they fell systematically down to 8.6% and 18.2%, respectively, on the 20th day after flowering. Starting with day 13, the content of alpha-linolenic acid (ALA) (C(18:3) n-3) begins to grow intensively, from 24.2% to 39.3% on the 20th day after flowering. The increase in the content of stearidonic acid (SDA) (C(18:4) n-3), up to 10.5% on the 20th day after flowering, occurred steadily as the seeds developed, and was independent of the changes in the content of GLA and LA. The pattern of changes in the content of SDA, GLA, LA and ALA during the development of seeds, and the occurrence of SDA in the seed oil of other plants, demonstrate that the biosynthesis of SDA in the seeds is critically dependent on the presence of ALA. The above condition indicates that SDA biosynthesis in the seeds of Echium vulgare follows the scheme LA --> simultaneous, competitive, action of Delta(6) and Delta(15) desaturases, leading to the formation of GLA and ALA, respectively, and then ALA (Delta(6) des) --> SDA. The biosynthesis according to the scheme: GLA (Delta(15) des) --> SDA is highly unlikely.     

Association between E-cadherin expression by human colon,bladder and breast cancer cells and the 13-HODE:15-HETE ratio. A possible role of their metastatic potential

The relationship between 15(S)-HETE and 13(S)-HODE from different human tumor cells exposed to n-6 and n-3 essential fatty acids (EFAs) and E-cadherin expression was studied. Colon cancer cells (HRT-18) exposed to gamma linoleic acid (18:3n-6, GLA) and eicosapentaenoic (20:5n-3, EPA) (50microM) showed an increased expression of E-cadherin. Breast cancer (MCF-7) exposed to EPA showed an increment whereas GLA had no effect on E-cadherin expression. No expression of E-cadherin was observed for urothelial cancer (T-24) after GLA or EPA treatment. Significant levels of 15(S)-HETE and 13(S)-HODE were detected after GLA or EPA treatment for all tumor lines. E-cadherin expression was inversely proportional to the 13(S)-HODE:15(S)-HETE ratio when cells were pretreated with GLA or EPA. Nevertheless, the liberation of these metabolites seems to be independent of the E-cadherin expression. The increase in the13(S)-HODE:15(S)-HETE correlates to a decrease in the expression of E-cadherin. Both factors may play a role in metastasis development.     

Assessment of blood measures of n-3 polyunsaturated fatty acids with acute fish oil supplementation and washout in men and women

Changes in n-3 highly unsaturated fatty acids (HUFA, ≥20 carbons and ≥3 carbon–carbon double bonds) at baseline, during fish oil supplementation (4 weeks) and during washout (8 weeks) were compared in venous plasma, erythrocytes, whole blood and fingertip prick blood (weeks 0, 4, 8 and 12) with additional weekly fingertip prick samples. Correlations between the various blood fractions were slightly stronger when n-3 HUFA status was expressed as the percentage of n-3 HUFA in total HUFA as compared with the sum of EPA and DHA. Increases and decreases in n-3 HUFA were more dramatic in plasma, and EPA responded rapidly (within 1 week) with fish oil supplementation and cessation. Sex differences in the proportions of n-3 HUFA in blood were also apparent at baseline with females (n=7) having a tendency for higher docosahexaenoic acid (DHA, 22:6n-3) relative to eicosapentaenoic acid (EPA, 20:5n-3) and n-3 docosapentaenoic acid (DPAn-3, 22:5n-3) as compared with males (n=9). Further n-3 biomarker research in larger populations is required.     

Long chain polyunsaturated fatty acids alter membrane-bound RANK-L expression and osteoprotegerin secretion by MC3T3-E1 osteoblast-like cells

Inflammation triggers an increase in osteoclast (bone resorbing cell) number and activity. Osteoclastogenesis is largely controlled by a triad of proteins consisting of a receptor (RANK), a ligand (RANK-L) and a decoy receptor (osteoprotegerin, OPG). Whilst RANK is expressed by osteoclasts, RANK-L and OPG are expressed by osteoblasts. The long chain polyunsaturated fatty acid (LCPUFA) arachidonic acid (AA, 20:4n-6) and its metabolite prostaglandin E2 (PGE2), are pro-inflammatory and PGE2 is a potent stimulator of RANKL expression. Various LCPUFAs such as eicosapentaenoic acid (EPA, 20:5n-3), docosahexaenoic acid (DHA, 22:6n-3) and gamma-linolenic acid (GLA, 18:3n-6) have anti-inflammatory activity. We aimed to determine if AA itself can stimulate RANKL expression and whether EPA, DHA and GLA inhibit RANKL expression in osteoblasts. MC3T3-E1/4 osteoblast-like cells were cultured under standard conditions with each of the LCPUFAs (5microg/ml) for 48h. Membrane-bound RANKL expression was measured by flow cytometry and OPG secretion measured by ELISA. In a second experiment, RANKL expression in MC3T3-E1/4 cells was stimulated by PGE2 treatment and the effect of EPA, DHA and GLA on membrane-bound RANKL expression and OPG secretion determined. The percentage of RANKL-positive cells was higher (p<0.05) than controls following treatment with AA or GLA but not after co-treatment with the cyclooxygenase inhibitor, indomethacin. DHA and EPA had no effect on membrane-bound RANKL expression under standard cell culture conditions. Secretion of OPG was lower (p<0.05) in AA-treated cells but not significantly different from controls in GLA, EPA or DHA treated cells. Treatment with prostaglandin E2 (PGE2) resulted in an increase (p<0.05) in the percentage of RANK-L positive cells and a decrease (p<0.05) in mean OPG secretion. The percentage of RANKL positive cells was significantly lower following co-treatment with PGE2 and either DHA or EPA compared to treatment with PGE2 alone. Mean OPG secretion remained lower than controls in cells treated with PGE2 regardless of co-treatment with EPA or DHA. Results from this study suggest COX products of GLA and AA induce membrane-bound RANKL expression in MC3T3-E1/4 cells. EPA and DHA have no effect on membrane-bound RANKL expression in cells cultured under standard conditions however both EPA and DHA inhibit the PGE2-induced increase in RANKL expression in MC3T3-E1/4 cells.     

Diets enriched in menhaden fish oil, seal oil, or shark liver oil have distinct effects on the lipid and fatty-acid composition of guinea pig heart

The purpose of this investigation was to determine whether diets supplemented with oils from three different marine sources, all of which contain high proportions of long-chain n-3 polyunsaturated fatty acids (PUFA), result in qualitatively distinct lipid and fatty acid profiles in guinea pig heart. Albino guinea pigs (14 days old) were fed standard, nonpurified guinea pig diets (NP) or NP supplemented with menhaden fish oil (MO), harp seal oil (SLO) or porbeagle shark liver oil (PLO) (10%, w/w) for 4-5 weeks. An n-6 PUFA control group was fed NP supplemented with corn oil (CO). All animals appeared healthy, with weight gains marginally lower in animals fed the marine oils. Comparison of relative organ weights indicated that only the livers responded to the diets, and that they were heavier only in the marine-oil fed guinea pigs. Heart total cholesterol levels were unaffected by supplementing NP with any of the oils, whereas all increased the triacylglycerol (TAG) content. The fatty-acid profiles of totalphospholipid (TPL), TAG and free fatty acid (FFA) fractions of heart lipids showed that feeding n-3 PUFA significantly altered the proportions of specific fatty-acid classes. For example, all marine-oil-rich diets were associated with increases in total monounsaturated fatty acids in TPL (p < 0.05), and with decreases in total saturates in TAG (p < 0.05). Predictably, the n-3 PUFA enriched regimens significantly increased the cardiac content of n-3 PUFA and decreased that of n-6 PUFA, although the extent varied among the diets. As a result, n-6/n-3 ratios were significantly lower in all myocardial lipid classes of marine-oil-fed guinea pigs. Analyses of the profiles of individual PUFA indicated that quantitatively, the fatty acids of the three marine oils were metabolized and/or incorporated into TPL, TAG and FFA in a diet-specific manner. In animals fed MO-enriched diets in which eicosapentaenoic acid (EPA) > docosahexacnoic acid (DHA), ratios of DHA /EPA in the hearts were 1.2, 2.2 and 1.5 in TPL, TAG and FFA, respectively. In SLO-fed guinea pigs in which dietary EPA DHA, ratios of DHA/EPA were 0.9, 3.4 and 2.1 in TPL, TAG and FFA, respectively. Feeding NP + PLO (DHA/EPA = 4.8), resulted in values for DHA/EPA in cardiac tissue of 2.1, 10.6 and 2.9 in TPL, TAG and FFA, respectively. In the TAG and FFA, proportions of n-3 docosapentaenoic acid (n-3 DPA) were equal to or higher than EPA in the SLO- and PLO-fed animals. The latter group exhibited the greatest difference between the DHA/n-3 DPA ratio in the diet and in cardiac TAG and FFA fractions (7, 3.4 and 3.1, respectively). Quantitative analysis indicated that 85% of the n-3 PUFA were in TPL, 7-11% were in TAG, and 2-6% were FFA. Specific patterns of distribution of EPA, DPA and DHA depended on the dietary oil. Both the qualitative and quantitative results of this study demonstrated that in guinea pigs, n-3 PUFA in different marine oils are metabolized and/or incorporated into cardiac lipids in distinct manners. In support of the concept that the diet-induced alterations reflect changes specifically in cardiomyocytes, we observed that direct supplementation of cultured guinea pig myocytes for 2-3 weeks with EPA or DHA produced changes in the PUFA profiles of their TPL that were qualitatively similar to those observed in tissue from the dietary study. The factors that regulate specific deposition of n-3 PUFA from either dietary oils or individual PUFA are not yet known, however the differences that we observed could in some manner be related to cardiac function and thus their relative potentials as health-promoting dietary fats.     

The effect of growth phase on the lipid class,fatty acid and sterol composition in the marine dinoflagellate,Gymnodinium sp. in batch culture

We have studied the effects of growth phase on the lipid composition in batch cultures of Gymnodinium sp. CS-380/3 over 43 days of culturing. The lipid content increased two fold, from late logarithmic (day 6) to linear growth phase (day 22) then decreased at stationary phase (day 43) while the lipid yield (mg l(-1)) increased 30-fold from day 6 to 30 mg l(-1) at day 43. Changes in fatty acid content mirrored those observed for the total lipid, while the sterol content continued to increase with culture age through to stationary phase. The largest changes occurred in the lipid classes, especially the polar lipids and triacylglycerols (oil). The proportion of triacylglycerols increased from 8% (of total lipids) at day 6 to 30% at day 43, with a concomitant decrease in the polar lipid fraction. The proportions of 16:0 and DHA [22:6(n-3)] increased while those of 18:5(n-3) and EPA [20:5(n-3)] decreased with increasing culture age. The proportion of the major sterol, dinosterol, decreased from 41% (day 6) to 29% (day 43), while the major dinostanol epimer (23R,24R) increased from 33% (day 6) to 38% (day 22). Despite small changes in the proportion of the main sterols, the same sterols were present at all stages of growth, indicating their value as a chemotaxonomic tool for distinguishing between strains within the same genus. Growth phase could be a useful variable for optimising the oil and DHA content with potential for aquaculture feeds and a source of DHA-rich oils for nutraceuticals.     

Double enrichment of chicken eggs with conjugated linoleic acid and n-3 fatty acids through dietary fat supplementation

Yolk fat fatty acid (FA) concentrations, sensory quality and firmness of eggs and laying hen performance were evaluated with respect to the combined inclusion in the diet of conjugated linoleic acid (CLA), high n-3 oil sources and high-oleic sunflower oil (HOSO). Nine diets were arranged factorially, with three levels of n-3 FA supplementation (2.9, 3.7 and 4.5 g/kg) from three different sources (two fish oils highly concentrated in eicosapentanoic (EPA) or docosahexanoic acid (DHA) and one algae oil with a very high-DHA content) in diets added with fixed amounts of CLA (2.5 g/kg) and HOSO (30 g/kg). A commercial feed with no CLA, n-3 or HOSO added, and another one containing 4.5 g/kg of high-DHA fish oil but not CLA or HOSO were also formulated. An increase in n-3 FA supplementation had little effect on proportions of CLA, monounsaturated FA, saturated FA or total polyunsaturated FA in yolk fat, but increased (P<0.005) long-chain n-3 FA and decreased (P<0.001) long-chain n-6 FA. An increment of dietary n-3 FA also impaired linearly (P<0.001) egg acceptability by consumers. An increment in the proportion of DHA with respect to total n-3 FA from 0.28 to 0.96 increased yolk concentrations of DHA (P<0.001) and total n-3 FA (P<0.01), but decreased (P<0.001) concentrations of EPA and docosapentanoic acid FA. Current data indicate that addition of HOSO to diets supplemented with moderate amounts of CLA and n-3 FA allows the production of double enriched eggs while maintaining sensory quality for consumers at acceptable levels.     

Comparison of bloodstream fatty acid composition from African-American women at gestation, delivery, and postpartum

Our aim was to examine the docosahexaenoic acid (DHA; 22:6n-3) status of pregnant African-American women reporting to the antenatal clinic at Wayne State University in a longitudinal study design. Fatty acid compositions of plasma and erythrocyte total lipid extracts were determined and food frequency surveys were administered at 24 weeks of gestation, delivery, and 3 months postpartum for participants (n = 157). DHA (mean +/- SD) in the estimated total circulating plasma was similar at gestation (384 +/- 162 mg) and delivery (372 +/- 155 mg) but was significantly lower at 3 months postpartum (178 +/- 81 mg). The relative weight percentage of DHA and docosapentaenoic acid n-6 (DPAn-6; 22:5n-6) decreased postpartum, whereas their respective metabolic precursors, eicosapentaenoic acid (EPA; 20:5n-3) and arachidonic acid (AA; 20:4n-6), increased. Similar results were found in erythrocytes. Dietary intake of DHA throughout the study was estimated at 68 +/- 75 mg/day. The relative amounts of circulating DHA and DPAn-6 were increased during pregnancy compared with 3 months postpartum, possibly via increased synthesis from EPA and AA. The low dietary intake and blood levels of DHA in this population compared with others may not support optimal fetal DHA accretion and subsequent neural development.