Fatty acid changes in liver choline and ethanolamine glycerophospholipids in aspirin-treated rats fed linoleate, gamma-linolenate and fish oil

The effects of dietary linoleic acid, gamma-linolenic acid and marine fatty acids on the development of aspirin-induced gastric hemorrhage and the distribution of liver glycerophospholipid fatty acids in fat-deficient growing rats were studied. Aspirin (100 mg/day)-treated and nontreated rats were fed for 7 days, a mixed diet of 2.5% safflower oil and 7.5% hydrogenated coconut oil (SFO/HCO) or 7.5% fish oil (SFO/FO), or 2.5% gamma-linolenate concentrate and 7.5% fish oil (GLA/FO). Gastric hemorrhage was induced in animals by aspirin treatment to various extents. It was not affected by FO feeding, but was significantly alleviated by GLA feeding. Aspirin treatment reduced the proportions of 20:4n-6 in liver phosphatidylcholine. FO feeding (in SFO/FO and GLA/FO rats) further reduced the 20:4n-6 level and replaced it by n-3 fatty acids. GLA feeding, on the other hand, elevated the proportion of 20:4n-6. As a result, the reduction of 20:4n-6 by fish oil feeding, was less significant in GLA/FO rats than in SFO/FO rats. The degree of gastric hemorrhage appeared to relate negatively to the levels of 20:4n-6 in liver phosphatidylcholine, and to the sum of 20:4n-6 and 20:5n-3 when FO was included in the diet. It is suggested that long-chain polyunsaturated fatty acids (20:4n-6 and 20:5n-3) per se in addition to being precursors of prostaglandins, may also affect the development of gastric hemorrhage, possibly by modulating the permeability of cell membranes in the gastric mucosa.     

Modulation of cholesterol concentration in Caco-2 cells by incubation with different n-6 fatty acids

Incorporation of exogenous cholesterol was compared in human adenocarcinoma colon cells (Caco-2) after incubation with 100 microM of either linoleic acid (LA, 18:2n-6), gamma-linolenic acid (GLA, 18:3n-6), arachidonic acid (AA, 20:4n-6) or adrenic acid (or n-6 docosatetraenoic acid, DTA, 22:4n-6). In both cells 7 days after seeding and 14 days after confluency, incubation with LA significantly raised the proportion of 18:2n-6 but not its long-chain metabolites in cellular phospholipid. Incubation with GLA increased the levels of 18:3n-6, 20:3n-6, and 20:4n-6. Incubation with AA increased the levels of 20:4n-6 and 22:4n-6, and incubation with DTA increased the levels of 22:4n-6 as well as its retro-conversion metabolite, 20:4n-6. A subsequent addition of cholesterol (180 microM) to the medium significantly raised the cellular cholesterol level but less so in the cells 7 days after seeding incubated with GLA. The increase in cellular cholesterol level was generally greater in the cells of 7 days after seeding, particularly those incubated with long-chain highly unsaturated n-6 fatty acids, than in those of 14 days after confluency. These findings suggest that the cell growth and the extent of unsaturation in cell membrane phospholipid fatty acids modulate the incorporation of the exogenous cholesterol into the Caco-2 cells.     

Effect of n-6 and n-3 polyunsaturated fatty acids ingestion on rat liver membrane-associated enzymes and fluidity

The influences of diets having different fatty acid compositions on the fatty-acid content, desaturase activities, and membrane fluidity of rat liver microsomes have been analyzed. Weanling male rats (35–45 g) were fed a fat-free semisynthetic diet supplemented with 10% (by weight) marine fish oil (FO, 12.7% docosahexaenoic acid and 13.8% eicosapentaenoic acid), evening primrose oil (EPO, 7.8% γ-linolenic acid and 70.8% linoleic acid) or a mixture of 5% FO-5% EPO. After 12 weeks on the respective diets, animals fed higher proportions of (n-3) polyunsaturated fatty acids (FO group) consistently contained higher levels of 20:3(n-6), 20:5(n-3), 22:5(n-3), and 22:6(n-3), and lower levels of 18:2(n-6) and 20:4(n-6), than those of the EPO (a rich source of (n-6) polyunsaturated fatty acids) or the FO + EPO groups. Membrane fluidity, as estimated by the reciprocal of the order parameter S_DPH, was higher in the FO than in the EPO or the FO + EPO groups, and the n-6 fatty-acid desaturation system was markedly affected.     

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.     

An alternative n-3 fatty acid elongation pathway utilising 18:3n-3 in barramundi (Lates calcarifer)

Desaturase and elongase are two key enzyme categories in the long-chain polyunsaturated fatty acid (LCPUFA) pathway that convert dietary α-linolenic acid (18:3n-3) to docosahexaenoic acid (22:6n-3). The Δ6 desaturase is considered as rate limiting in the conversion. In a previous study in barramundi we demonstrated that the desaturase had a low Δ6 activity but noted that the enzyme also possessed Δ8 ability that utilised 20-carbon fatty acids. This observation suggests that an alternative pathway may exist in the barramundi via elongases to form 20-carbon metabolites from 18:3n-3 to 20:3n-3 and then Δ6/8 desaturase to 20:4n-3. Cloning of the barramundi elongation of very long-chain fatty acid gene (ELOVL) and heterologous expression of the corresponding elongase were performed to examine activity with regard to time course, substrate concentration and substrate preference. Results revealed that the barramundi elongase showed a broad range of substrate specificity including 18-carbon PUFA (including 18:3n-3 and 18:2n-6), 20- and 22-carbon LCPUFA, with greater activity towards omega-3 (n-3) than n-6 fatty acids. The findings from this study provide molecular evidence for an alternative n-3 fatty acid elongation pathway utilising 18:3n-3 in barramundi.     

Effects of calcium deprivation on n-6 fatty acid metabolism in growing rats

Two separate experiments examining the effects of calcium deficiency on plasma and liver fatty acids in rats were conducted. In Experiment I, weanling male Sprague-Dawley rats were fed a calcium-deficient diet with or without the supplementation of 5 or 20 g/kg calcium for 22 days. There were no significant differences in plasma and liver fatty acid distribution between the two calcium-supplemented groups. However, calcium deficiency significantly elevated the levels of 18:3n-6 in plasma and liver cholesteryl esters and liver phospholipids, while it reduced the levels of 20:3n-6 in plasma cholesteryl esters. In Experiment II, weanling rats were fed a calcium-deficient diet supplemented with 5 g/kg calcium for 22 days. After overnight fast, animals were given by intragastric feeding a dose of 4 g/kg body wt gamma-linolenic acid concentrate (containing 92% 18:3n-6 ethyl ester), and were killed 22 hr later. The levels of 18:3n-6 were significantly higher, whereas the levels of 20:3n-6 were either not changed or lower than those in calcium-supplemented group. In both experiments, the ratios of (20:3n-6 + 20:4n-6)/18:3n-6 in plasma and liver lipids were significantly reduced in calcium-deficient rats. These results suggest that calcium may play an important and specific role in the process of elongation of 18:3n-6 to 20:3n-6.     

The esterification and modification of n-3 and n-6 polyunsaturated fatty acids by hepatocytes and liver microsomes of turbot (Scophthalmus maximus)

The present study was undertaken to establish whether the formation of 22:6n-3 from 18:3n-3 and/or 20:5n-3 can occur in turbot liver and if this conversion is consistent with the operation of a Delta4 desaturase-independent pathway. At the same, time the effects of feeding a diet devoid of long chain polyunsaturated fatty acids (PUFA) on the patterns of esterification and modification of 18:3n-3, 20:5n-3 and 18:2n-6 by turbot hepatocytes and liver microsomes were examined. For this purpose, two groups of fish (25-30 g) were employed: one was fed a commercial diet containing fish oil (FO) and thus rich in long chain n-3 PUFA and the other was fed an experimental diet based on olive oil (OO). After 5 months of feeding, hepatocytes and liver microsomes isolated from individuals in the two groups of fish were incubated with [1-(14)C]-PUFA [either 18:3n-3, 20:5n-3 or 18:2n-6]. After 3 h of incubation, most radioactivity from all three radiolabelled substrates incorporated into lipids by hepatocytes and microsomes was recovered in the original substrate. The formation of desaturation products of n-3 radiolabelled substrates was higher in hepatocytes isolated from OO-fed than FO-fed fish. Small amounts of radiolabelled 22:6n-3 were formed from [1-(14)C]18:3n-3 and [1-(14)C]20:5n-3, but only by hepatocytes from fish fed OO, which also synthesised a small amount of radiolabelled 24:6n-3 from 14C-20:5n-3. Elongation products predominated over desaturation products in hepatic microsomes from both groups of fish studied, particularly in microsomes from fish fed FO. The results confirm that regardless of the long chain PUFA content of the diet, the production of 22:6n-3 in turbot liver from 18:3n-3 and/or 20:5n-3, and of 20:4n-6 from 18:2n-6, is very limited. The presence of radiolabelled 24:6n-3 in microsomes coupled with the absence of radiolabelled 22:6n-3 suggests that the formation of 22:6n-3 that does occur in turbot liver cells, may involve C24 intermediates and peroxisomal beta-oxidation.     

Interactions of saturated, n-6 and n-3 polyunsaturated fatty acids to modulate arachidonic acid metabolism

Anti-thrombotic effects of omega-3 (n-3) fatty acids are believed to be due to their ability to reduce arachidonic acid levels. Therefore, weanling rats were fed n-3 acids in the form of linseed oil (18:3n-3) or fish oil (containing 20:5n-3 and 22:6n-3) in diets containing high levels of either saturated fatty acids (hydrogenated beef tallow) or high levels of linoleic acid (safflower oil) for 4 weeks. The effect of diet on the rate-limiting enzyme of arachidonic acid biosynthesis (delta 6-desaturase) and on the lipid composition of hepatic microsomal membrane was determined. Both linseed oil- or fish oil-containing diets inhibited conversion of linoleic acid to gamma-linolenic acid. Inhibition was greater with fish oil than with linseed oil, only when fed with saturated fat. delta 6-Desaturase activity was not affected when n-3 fatty acids were fed with high levels of n-6 fatty acids. Arachidonic acid content of serum lipids and hepatic microsomal phospholipids was lower when n-3 fatty acids were fed in combination with beef tallow but not when fed with safflower oil. Similarly, n-3 fatty acids (18:3n-3, 20:5n-3, 22:5n-3, and 22:6n-3) accumulated to a greater extent when n-3 fatty acids were fed with beef tallow than with safflower oil. These observations indicate that the efficacy of n-3 fatty acids in reducing arachidonic acid level is dependent on the linoleic acid to saturated fatty acid ratio of the diet consumed.     

Reduction of hyperlipidemia in the LA/N-corpulent rat by dietary fish oil containing n-3 fatty acids

The LA/N rat, when homozygous for the corpulent gene (cp/cp), is obese, hyperphageous, hyperinsulinemic, hypertriglyceridemic and prone to the development of vascular and myocardial lesions. The hypertriglyceridemia, which in 3-month-old cp/cp males is 282 +/- 42 mg/dl and in females, 512 +/- 83 mg/dl, results from the presence of a large triacylglycerol-rich VLDL. The moderate hypercholesterolemia in these animals is largely due to markedly elevated HDL levels, which reach 172 +/- 21 mg total lipid/dl in males and 154 +/- 22 mg total lipid/dl in females. The LA/N-cp rat is thus an interesting animal model of endogenous hypertriglyceridemia in which to examine the hypolipidemic effects of pharmacological agents and also dietary oil supplements containing the n-3 fatty acids. In this study, 1-month-old male and female cp/cp rats were fed a normal low fat laboratory chow supplemented with either 10% olive oil or 10% redfish (Sebastes marinus) oil ad libitum for a period of 2 months. The redfish oil contained 4.9 +/- 0.1% of its total fatty acids as eicosapentaenoic (20:5(n-3)) and 2.3 +/- 0.5% as docosahexaenoic acid (22:6(n-3)), the predominant fatty acids being gondoic (20:1(n-3)), 21.9 +/- 0.9% and cetoleic acid (22:1(n-11)), 21.7 +/- 1.7%, which are of dietary origin. Daily caloric intake was similar to the oil-fed versus control rats. However, the oil-fed animals weighed significantly more than the controls after 2 months of oil supplementation. Redfish oil reduced serum triacylglycerols by 54% in males and 45% in females after 2 months. VLDL levels, after the same time period, were reduced by 44% in males and 39% in females. HDL lipid mass was significantly reduced in both sexes (by 27% in males and 49% in females). However, the levels remained above those of male LA/N +/+ rats of the same age and Long-Evens rats. Olive oil feeding significantly reduced serum cholesterol, triacyglycerols and phospholipids in male but only cholesterol and phospholipids in female animals. This oil had no significant effect upon VLDL total lipid levels in either sex, but significantly increased the particle diameter with a concomitant reduction in the cholesterol and phospholipid content. HDL total lipid levels were unaffected: However, HDL total cholesterol increased significantly in males only. Both oils markedly reduced serum LDL levels in both sexes.(ABSTRACT TRUNCATED AT 400 WORDS)     

The pathway from arachidonic to docosapentaenoic acid (20:4n-6 to 22:5n-6) and from eicosapentaenoic to docosahexaenoic acid (20:5n-3 to 22:6n-3) studied in testicular cells from immature rats

The concentration-dependent metabolism of 1-(14)C-labelled precursors of 22:5n-6 and 22:6n-3 was compared in rat testis cells. The amounts of [(14)C]22- and 24-carbon metabolites were measured by HPLC. The conversion of [1-(14)C]20:5n-3 to [3-(14)C]22:6n-3 was more efficient than that of [1-(14)C]20:4n-6 to [3-(14)C]22:5n-6. At low substrate concentration (4 microM) it was 3.4 times more efficient, reduced to 2.3 times at high substrate concentration (40 microM). The conversion of [1-(14)C]22:5n-3 to [1-(14)C]22:6n-3 was 1.7 times more efficient than that of [1-(14)C]22:4n-6 to [1-(14)C]22:5n-6 using a low, but almost equally efficient using a high substrate concentration. When unlabelled 20:5n-3 was added to a cell suspension incubated with [1-(14)C]20:4n-6 or unlabelled 22:5n-3 to a cell suspension incubated with [1-(14)C]22:4n-6, the unlabelled n-3 fatty acids strongly inhibited the conversion of [1-(14)C]20:4n-6 or [1-(14)C]22:4n-6 to [(14)C]22:5n-6. In the reciprocal experiment, unlabelled 20:4n-6 and 22:4n-6 only weakly inhibited the conversion of [1-(14)C]20:5n-3 and [1-(14)C]22:5n-3 to [(14)C]22:6n-3. The results indicate that if both n-6 and n-3 fatty acids are present, the n-3 fatty acids are preferred over the n-6 fatty acids in the elongation from 20- to 22- and from 22- to 24-carbon atom fatty acids. In vivo the demand for 22-carbon fatty acids for spermatogenesis in the rat may exceed the supply of n-3 precursors and thus facilitate the formation of 22:5n-6 from the more abundant n-6 precursors.     

Hydrolysis of long-chain, n-3 fatty acid enriched chylomicrons by cardiac lipoprotein lipase

The hydrolysis of chylomicrons enriched in long-chain n-3 fatty acids by cardiac lipoprotein lipase was studied. In 60 min, 24.8% of the triacylglycerol fatty acids were released as free fatty acids. The fatty acids were hydrolyzed at different rates. DHA (docosahexaenoic acid, 22:6n-3) and EPA (eicosapentaenoic acid, 20:5n-3) were released at rates significantly less than average. Stearic acid (18:0), 20:1n-9, and alpha-linolenic acid (18:3n-3) were released significantly faster than average. There was no relationship between the rate of release of a fatty acid and the number of carbons or the number of double bonds. Lipoprotein lipase selectively hydrolyzes the fatty acids of chylomicron triacylglycerols. This selectively will result in remnants that are relatively depleted in 18:0, 20:1, and 18:3 and relatively enriched in 20:5 and 22:6.     

Comparison of 20-, 22-, and 24-carbon n-3 and n-6 polyunsaturated fatty acid utilization in differentiated rat brain astrocytes

Astrocytes convert n-6 fatty acids primarily to arachidonic acid (20:4n-6), whereas n-3 fatty acids are converted to docosapentaenoic (22:5n-3) and docosahexaenoic (22:6n-3) acids. The utilization of 20-, 22- and 24-carbon n-3 and n-6 fatty acids was compared in differentiated rat astrocytes to determine the metabolic basis for this difference. The astrocytes retained 81% of the arachidonic acid ([(3)H]20:4n-6) uptake and retroconverted 57% of the docosatetraenoic acid ([3-(14)C]22:4n-6) uptake to 20:4n-6. By contrast, 68% of the eicosapentaenoic acid ([(3)H]20:5n-3) uptake was elongated, and only 9% of the [3-(14)C]22:5n-3 uptake was retroconverted to 20:5n-3. Both tetracosapentaenoic acid ([3-(14)C]24:5n-3) and tetracosatetraenoic acid ([3-(14)C]24:4n-6) were converted to docosahexaenoic acid (22:6n-3) and 22:5n-6, respectively. Therefore, the difference in the n-3 and n-6 fatty acid products formed is due primarily to differences in the utilization of their 20- and 22-carbon intermediates. This metabolic difference probably contributes to the preferential accumulation of docosahexaenoic acid in the brain.     

Evidence for peroxisomal retroconversion of adrenic acid (22:4(n-6)) and docosahexaenoic acids (22:6(n-3)) in isolated liver cells

The intracellular localization of the oxidation of [2-14C]adrenic acid (22:4(n-6)) and [1-14C]docosahexaenoic acid (22:6(n-3)) was studied in isolated liver cells. The oxidation of 22:4(n-6) was 2-3-times more rapid than the oxidation of 22:6(n-3), [1-14C]arachidonic acid (20:4(n-6)) or [1-14C]oleic acid (18:1). (+)-Decanoylcarnitine and lactate, both known to inhibit mitochondrial beta-oxidation, reduced the oxidation of 18:1 distinctly more efficiently than with 22:4(n-6) and 22:6(n-3). In liver cells from rats fed a diet containing partially hydrogenated fish oil, the oxidation of 22:6(n-6) and 22:6(n-3) was increased by 30-40% compared with cells from rats fed a standard pellet diet. With 18:1 as substrate, the amount of fatty acid oxidized was very similar in cells from animals fed standard pellets or partially hydrogenated fish oil. Shortened fatty acids were not produced from [5,6,8,9,11,12,14,15-3H]arachidonic acid. In hepatocytes from rats starved and refed 20% fructose, a large fraction of 14C from 22:4 was recovered in 14C-labelled C14-C18 fatty acids. Oxidation of 22:4 thus caused a high specific activity of the extramitochondrial pool of acetyl-CoA. The results suggest that 22:4(n-6) and to some extent 22:6(n-3) are oxidized by peroxisomal beta-oxidation and by this are retroconverted to arachidonic acid and eicosapentaenoic acid.     

Effects of n-3 polyunsaturated dietary supplementation on the reproductive capacity of male turkeys

To measure the effects of dietary n-3 polyunsaturated fatty acid (PUFA) supplementation on the reproductive capacity of adult male turkeys in industrial flocks, the males of 22 commercial farms were fed either a standard diet or a fish oil diet enriched in n-3 PUFAs. The fatty acid composition of the spermatozoa and reproductive performance were measured throughout the reproductive period. The fish oil diet very effectively increased the percentage of n-3 fatty acids (FA) (22:5n-3 and 22:6n-3) in spermatozoa and correspondingly decreased the percentage of n-6 PUFAs (20:4-6 and 22:4n-6): the n-3/n-6 ratio in spermatozoa fatty acids were 0.04-0.07 with the standard diet and 0.32-0.4 with the fish oil diet. These changes did not affect the spermatozoa content of n-9 PUFAs, particularly of 22:3n-9 which is abundant in turkey spermatozoa (9-12% of the total fatty acids). The supplementation was effective in the middle as at the end of the reproductive period. The reproductive capacity of males was modified by the diet and the positive effect of the n-3 supplemented diet increased with age (increase in hatching rates of nearly 2 points at 48-58 weeks for males fed fish oil diet). These results indicate that an increase in the dietary ratio of n-3/n-6 PUFAs is valuable to sustain the reproductive capacity of male turkeys especially when they are getting older.     

Conservation of Docosahexaenoic Acid in Rod Outer Segments of Rat Retina During n-3 and n-6 Fatty Acid Deficiency

We investigated the mechanism by which rat retina conserves docosahexaenoic acid during essential fatty acid deficiency. Weanling female albino rats were fed diets containing either 10% by weight hydrogenated coconut oil, safflower oil, or linseed oil for 15 weeks. Plasma and rod outer segment (ROS) membranes were prepared for fatty acid and phospholipid molecular species analysis. In addition, retinas were removed for morphometric analysis. We found the following: (1) Plasma phospholipids and cholesterol esters from coconut oil, safflower oil, and linseed oil diet groups were enriched in 20:3(n-9), 20:4(n-6), and 20:5(n-3), respectively. The levels of these 20-carbon fatty acids in the ROS, however, were only slightly affected by diet. (2) The fatty acids and molecular species of ROS phospholipids from the safflower oil and coconut oil groups showed a selective replacement of 22:6(n-3) with 22:5(n-6), as evidenced by a reduction of the 22:6(n-3)-22:6(n-3) molecular species and an increase in the 22:5(n-6)-22:6(n-3) species. (3) The renewal rate of ROS integral proteins, determined by autoradiography, was 10% per day for each diet group. (4) Morphometric analysis of retinas showed no differences in the outer nuclear layer area or in ROS length between the three groups. We conclude that the conservation of 22:6(n-3) in ROS is not accomplished through reductions in the rate of membrane turnover, the total amount of ROS membranes, or in the number of rod cells. The retina may conserve 22:6(n-3) through recycling within the retina or between the retina and the pigment epithelium, or through the selective uptake of 22-carbon polyunsaturated fatty acids from the circulation.     

High contents of 24:6(n-3) and 20:1(n-13) fatty acids in the brittle star Amphiura elandiformis from Tasmanian coastal sediments

The presence of long-chain polyunsaturated fatty acids (PUFA; ca. 9% of total fatty acids) in marine sediments near Dover, southern Tasmania, Australia prompted a search for their likely source. Analysis of a number of different species of benthic fauna isolated from these sediments revealed that the brittle star Amphiura elandiformis contained abundant PUFA including high contents of the uncommon long-chain fatty acid 24:6(n-3), but much smaller amounts of the more common animal PUFA 22:6(n-3). This is the first report of the lipid composition of this animal. Identifications of the unsaturated fatty acids were confirmed by formation of DMOX derivatives which gave characteristic and easily interpreted mass spectra. The 24:6(n-3) PUFA has been identified in some genera of brittle stars, but not others. It is rarely found in significant amounts in other marine animals. DMDS adducts were used to identify the positions of double bonds in the monounsaturated fatty acids. The major 20:1 isomer was identified as the rarely reported 20:1(n-13) fatty acid. The two fatty acids 20:1(n-13) and 24:6(n-3) may be useful biomarkers in food-web studies for identifying a brittle star diet and for recognising contributions of organic detritus from this benthic animal to marine sediments.     

Platelet phospholipid n-3 PUFA negatively associated with plasma homocysteine in middle-aged and geriatric hyperlipaemia patients

Studies showed that increased dietary intake of n-3 polyunsaturated fatty acids (PUFA) has a cardiovascular beneficial effect. Increased plasma phospholipid (PL) docosahexaenoic acid (22:6n-3) is associated with decreased plasma homocysteine (Hcy). The aim of this study was to investigate the relationship between platelet PL fatty acid and plasma Hcy in middle-aged and geriatric hyperlipaemia patients (50 males, 31 females) and 65 healthy subjects (43 males, 22 females) in Hangzhou, China. Plasma Hcy demonstrated significant positive correlation with adrenic acid (22:4n-6) (r = 0.188, P = 0.018) and negative correlation with 22:6n-3 (r = -0.277, P = 0.001) and the ratio of n-3/n-6 (r = -0.231, P = 0.003) in sex-, age- and BMI-controlled partial correlation analysis. The present results suggest that increased ratio of n-3/n-6 PUFA in platelet PL is associated with decreased thrombotic risks such as plasma Hcy in middle-aged and geriatric hyperlipaemia patients in Hangzhou.     

The influence of dietary essential fatty acids on uterine C20 and C22 fatty acid composition.

The effect of dietary fatty acids on uterine fatty acid composition was studied in rats fed control diet or semi-synthetic diet supplemented with 1.5 microliter/g/day evening primrose oil (EPO) or fish oil (FO). Diet-related changes in uterine lipid were detected within 21 days. Changes of 2- to 20-fold were detected in the uterine n-6 and n-3 essential fatty acids (EFA) and in certain saturated and monounsaturated fatty acids. The FO diet was associated with higher uterine C20 and C22 n-3, and the EPO diet, with higher uterine n-6 fatty acid. High uterine C18:2 n-6 was detected in neutral lipid (NL) of rats fed high concentrations of this fatty acid, but there was little evidence of selective incorporation or retention of C18:2 n-6 by uterine NL. The incorporation of EFA into uterine phospholipids (PL) was greater than NL EFA incorporation, and uterine PL n-3/n-6 ratios showed greater diet dependence. Tissue/diet fatty acid ratios in NL and PL also indicated preferential incorporation/synthesis of C16:1 n-9, and C16:0, and there was greater incorporation of C12:0 and C14:0 into uteri of rats fed EPO and FO. Replacement of 50-60% of arachidonate with n-3 EFA in uterine PL may inhibit n-6 EFA metabolism necessary for uterine function at parturition.     

Adrenoleukodystrophy. The chain shortening of erucic acid (22:1(n-9)) and adrenic acid (22:4(n-6)) is deficient in neonatal adrenoleukodystrophy and normal in X-linked adrenoleukodistrophy skin fibroblasts

The metabolism of long chain unsaturated fatty acids was studied in cultured fibroblasts from patients with X-linked adrenoleukodystrophy (ALD) and with neonatal ALD. By using [14-14C] erucic acid (22:1(n-9)) as substrate it was shown that the peroxisomal beta-oxidation, measured as chain shortening, was impaired in cells from patients with neonatal ALD. The beta-oxidation of adrenic acid (22:4(n-6)), measured as acid-soluble products, was also reduced in the neonatal ALD cells. The peroxisomal beta-oxidation of [14-14C]erucic acid (22:1(n-9)) and [2-14C]adrenic acid (22:4(n-6)) was normal in cells from X-ALD patients. The beta-oxidation, esterification and chain elongation of [1-14C]arachidonic acid (20:4(n-6)) and [1-14C]eicosapentaenoic acid (20:5(n-3)) was normal in both X-linked ALD and in neonatal ALD. Previous studies suggest that the activation of very long chain fatty acids by a lignoceryl (24:0)-CoA ligase is deficient in X-linked ALD, while the peroxisomal beta-oxidation enzymes are deficient in neonatal ALD. The present results suggest that the peroxisomal very long-chain acyl-CoA ligase is not required for activation of unsaturated C20 and C22 fatty acids and that these fatty acids can be efficiently activated by the long chain acyl-(palmityl)-CoA ligase.     

Age-related changes of n-3 and n-6 polyunsaturated fatty acids in the anterior cingulate cortex of individuals with major depressive disorder

Accumulating evidence finds a relative deficiency of peripheral membrane fatty acids in persons with affective disorders such as unipolar and bipolar depression. Here we sought to investigate whether postmortem brain fatty acids within the anterior cingulate cortex (BA-24) varied according to the presence of major depression at the time of death. Using capillary gas chromatography we measured fatty acids in a depressed group (n=12), and in a control group without lifetime history of psychiatric diagnosis (n=14). Compared to the control group, the depressed group showed significantly lower concentrations of numerous saturated and polyunsaturated fatty acids including both the n-3 and n-6 fatty acids. Additionally, significant correlations between age at death and precursor (or metabolites) in the n-3 fatty acid pathway were demonstrated in the depressed group but not in control subjects. In the n-6 fatty acid family, the ratio of 20:3(n-6)/18:2(n-6) was higher in patients than in control groups, whereas the ratio of 20:4(n-6)/20:3(n-6) was relatively decreased in patients. Lastly, a significant negative correlation between age and the ratio of 20:4(n-6) to 22:6(n-3) was found in patients, but not in controls. Taken together, decreases in 22:6(n-3) may be caused, at least in part, by the diminished formation of 20:5(n-3), which is derived from 20:4(n-3) through a Δ5 desaturase reaction. The present findings from postmortem brain tissue raise the possibility that an increased ratio of 20:4(n-6) to 22:6(n-3) may provide us with a biomarker for depression. Future research should further investigate these relationships.