Differences in Lipid Characteristics Among Populations: Low-Temperature Adaptability of Ayu, Plecoglossus altivelis

The lipid and fatty acid compositions of the total lipids of three cultured populations (migratory between fresh and salt water, Lake Biwa landlocked, and Setogawa River forms) of ayu, Plecoglossus altivelis, were investigated to clarify the difference in lipid characteristics and temperature adaptability among the three groups. Triacylglycerols were the dominant depot lipids of the three populations, while phospholipids, such as phosphatidylcholine and phosphatidylethanolamine, were found to be the major components of the polar lipids, and their lipid classes are similar to each other. The major fatty acids in the triacylglycerols of all specimens were 16:0, 18:0, 16:1n-7, 18:1n-7, 18:1n-9, 18:2n-6 (linoleic acid), 20:5n-3 (EPA, icosapentaenoic acid), and 22:6n-3 (DHA, docosahexaenoic acid), similar to the tissue phospholipids of the three populations, 16:0, 18:0, 16:1n-7, 18:1n-7, 18:1n-9, 18:2n-6, 20:4n-6, EPA, and DHA. All classes had high levels of 18:2n-6, which originates from their dietary lipids. Compared with the lower DHA levels of the triacylglycerols, the higher levels in the phospholipids suggest their selective accumulation or a biosynthetic pathway to DHA as in freshwater fish. Two populations (the migratory and Setogawa River forms) adapted to lower temperatures with comparatively high levels of polyunsaturated fatty acids (PUFA) for their membrane fluidities. With significantly higher levels of n-3 PUFA and total PUFA, the mean DHA content in the lipids of the Setogawa River form (the population that adapted to lower temperatures) was significantly higher than that of the migratory form. From these results, we concluded that the Setogawa River population actively concentrates long-chain PUFA in its polar lipids and has high adaptability to low temperature.     

Cholesterol,Lipid Content,and Fatty Acid Composition of Different Tissues of Farmed Cobia (<Emphasis Type="Italic">Rachycentron canadum</Emphasis>) from China

Marine fishes are rich in n-3 polyunsaturated fatty acids (PUFA), especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are extremely important for human health. The objective of our work was to determine the content and composition of lipids and fatty acids in the different tissues of cobia from China and to evaluate their nutritional value. The results showed that cobia from China was rich in lipids; the neutral lipid content was above 82%; the content of cholesterol and phospholipid was low. Eighteen fatty acids were identified. Myristic (C14:0), palmitic (C16:0), and stearic acids (C18:0) were the main saturated acids; palmitoleic (C16:1n-7) and oleic acid (C18:1n-9) were the main monounsaturated fatty acids. EPA and DHA were the main PUFA; n-3 and n-6 PUFA were present as 12–18% and 2.6–3.2% of the total fatty acids, respectively. The n-6/n-3 ratio was in the range from 0.18 to 0.22, which was far lower than that (5:1) recommended by WHO/FAO. Therefore, cobia lipids from China have a high nutritional value.     

High Arachidonic Acid Levels in the Tissues of Herbivorous Fish Species (<Emphasis Type="Italic">Siganus fuscescens,Calotomus japonicus</Emphasis> and <Emphasis Type="Italic">Kyphosus bigibbus</Emphasis>)

The lipid and fatty acid compositions in the various organs (muscle, liver, other viscera) and stomach contents of three common herbivorous fish species in Japan, Siganus fuscescens, Calotomus japonicus and Kyphosus bigibbus, were examined to explore the stable 20:4n-6 (arachidonic acid, ARA) sources. Triacylglycerol (TAG), phosphatidylethanolamine (PtdEtn), and phosphatidylcholine (PtdCho) were the dominant lipid classes, while the major FA contents were 16:0, 18:1n-9, 16:1n-7, 14:0, 18:0, 18:1n-7, and some PUFA, including ARA, 20:5n-3 (eicosapentaenoic acid, EPA), 22:5n-3 (docosapentaenoic acid, DPA), and 22:6n-3 (docosahexaenoic acid, DHA). The amounts of these fatty acids were varied among species and their lipid classes. Phospholipids contained higher levels of PUFA than TAG. However, ARA in both phospholipids and TAG was markedly present in the muscle and viscera of all specimens, particularly in C. japonicus and K. bigibbus. Moreover, their ARA levels were higher than the levels of DHA and EPA. The observed high ARA level is unusual in marine fish and might be characteristic of herbivorous fish. Furthermore, ARA was the dominant PUFA in the stomach contents of the three species, suggesting that the high ARA level originated from their food sources. The above indicates that these three herbivorous fishes are ARA-rich marine foods and have potential utilization as stable ARA resources.     

Lipid Content and Fatty Acid Composition of 15 Marine Fish Species from the Southeast Coast of Brazil

Lipid content and fatty acid composition were determined in edible meat of fifteen marine fish species caught on the Southeast Brazilian coast and two from East Antarctic. Most of the fish had lipid amounts lower than 10% of their total weight. Palmitic acid (C16:0) predominated, accounting for 54–63% of the total amount of saturated fatty acids. Oleic acid (C18:1n-9) was the most abundant (49–69%) monounsaturated fatty acid, and docosahexaenoic acid (DHA) was the predominant polyunsaturated fatty acid (PUFA), accounting for 31–84% of n-3 PUFA. n-3 PUFA level were highest in Antarctic fish meat, comprising 45% of the total fatty acid content, which consisted of mainly EPA (16.1 ± 1.5 g/100 g lipids) and DHA (24.8 ± 2.4 g/100 g lipids). The amounts of EPA + DHA in g/100 g of lipids on the Southeast Brazilian coast and Antarctic fish species investigated were found to be similar: 42.0 ± 1.7 for Bonito cachorro, 41.0 ± 2.3 for Atum, and 39.4 ± 1.8 for peixe porco, respectively. All the studied species exhibited an n-3/n-6 ratio higher than 3, which confirms the great importance of Southeast Brazilian coast fish as a significant dietary source of n-3 PUFA.     

Incorporation of n-3 fatty acids into plasma lipid fractions, and erythrocyte membranes and platelets during dietary supplementation with fish, fish oil, and docosahexaenoic acid-rich oil among healthy young men

The effects of n-3 fatty acid supplementation in the form of fresh fish, fish oil, and docosahexaenoic acid (DHA) oil on the fatty acid composition of plasma lipid fractions, and platelets and erythrocyte membranes of young healthy male students were examined. Altogether 59 subjects (aged 19–32 yr, body mass index 16.8–31.3 kg/m²) were randomized into the following diet groups: (i) control group; (ii) fish diet group eating fish meals five times per week [0.38±0.04 g eicosapentaenoic acid (EPA) and 0.67±0.09 g DHA per day]; (iii) DHA oil group taking algae-derived DHA oil capsules (1.68 g/d DHA oil group taking algae-derived DHA oil capsules (1.68 g/d DHA in triglyceride form); and (iv) fish oil group (1.33 g EPA and 0.95 g DHA/d as free fatty acids) for 14 wk. The fatty acid composition of plasma lipids, platelets, and erythrocyte membranes was analyzed by gas chromatography. The subjects kept 4-d food records four times during the study to estimate the intake of nutrients. In the fish diet, in DHA oil, and in fish oil groups, the amounts of n-3 fatty acids increased and those of n-6 fatty acids decreased significantly in plasma lipid fractions and in platelets and erythrocyte membranes. A positive relationship was shown between the total n-3 polyunsaturated fatty acids (PUFA) and EPA and DHA intake and the increase in total n-3 PUFA and EPA and DHA in all lipid fractions analyzed. DHA was preferentially incorporated into phospholipid (PL) and triglyceride (TG) and there was very little uptake in cholesterol ester (CE), while EPA was preferentially incorporated into PL and CE. The proportion of EPA in plasma lipids and platelets and erythrocyte membranes increased also by DHA supplementation, and the proportion of linoleic acid increased in platelets and erythrocyte membranes in the DHA oil group as well. These results suggest retroconversion of DHA to EPA and that DHA also interferes with linoleic acid metabolism.     

Characteristics of the Fatty Acid Composition of a Deep-Sea Vent Gastropod, <Emphasis Type="Italic">Ifremeria nautilei</Emphasis>

Neutral and polar lipids in the soft parts of a gastropod species, Ifremeria nautilei, collected from deep-sea hydrothermal vents, were examined to assess the trophic relationships in hydrothermal vents. The vent gastropod obtains many of its lipids from symbiotic chemosynthetic microorganisms. The major polyunsaturated fatty acids (PUFA) both in the triacylglycerols and phospholipids of the gastropod consist of a limited number of n-3 and n-6 PUFA: arachidonic acid (20:4n-6), icosapentaenoic acid (20:5n-3), and docosapentaenoic acid (22:5n-3), without docosahexaenoic acid (DHA, 22:6n-3). Noticeable levels of various n-6 PUFA, such as 18:2n-6,9, 20:2n-6,9, 20:3n-6,9,12, and 20:3n-6,9,15 with significant levels of 16:1n-6 and 18:1n-6 indicate the biosynthetic characteristic of the endosymbionts. The lack of DHA in all specimens suggests a limitation of its lipid biosynthesis ability with its symbionts. This finding with regard to the lipids is unusual for a marine animal in the grazing or detrital food chain because many marine animal lipids evidently contain high levels of DHA with low levels of n-6 fatty acids. Such contradictory findings lead to some new insights into the absence of a biosynthetic pathway for DHA in I. nautilei, and provide evidence that DHA in this species is dispensable. Similar to herbivorous gastropods, the lack of DHA with significant levels of n-6 PUFA in this species also indicates its selective assimilation of specific microorganisms, such as chemosynthetic bacteria in hydrothermal vents, because significant levels of DHA were found in carnivorous mollusk lipids.     

Fatty Acid and Lipid Profiles with Emphasis on n-3 Fatty Acids and Phospholipids from Ciona intestinalis

In order to establish Ciona intestinalis as a new bioresource for n‐3 fatty acids‐rich marine lipids, the animal was fractionated into tunic and inner body tissues prior to lipid extraction. The lipids obtained were further classified into neutral lipids (NL), glycolipids (GL) and phospholipids (PL) followed by qualitative and quantitative analysis using GC‐FID, GC–MS, ¹H NMR, 2D NMR, MALDI‐TOF‐MS and LC–ESI–MS methods. It was found that the tunic and inner body tissues contained 3.42–4.08 % and 15.9–23.4 % of lipids respectively. PL was the dominant lipid class (42–60 %) irrespective of the anatomic fractions. From all lipid fractions and classes, the major fatty acids were 16:0, 18:1n‐9, C20:1n‐9, C20:5n‐3 (EPA) and C22:6n‐3 (DHA). The highest amounts of long chain n‐3 fatty acids, mainly EPA and DHA, were located in PL from both body fractions. Cholestanol and cholesterol were the dominant sterols together with noticeable amounts of stellasterol, 22 (Z)‐dehydrocholesterol and lathosterol. Several other identified and two yet unidentified sterols were observed for the first time from C. intestinalis. Different molecular species of phosphatidylcholine (34 species), sphingomyelin (2 species), phosphatidylethanolamine (2 species), phosphatidylserine (10 species), phosphatidylglycerol (9 species), ceramide (38 species) and lysophospholipid (5 species) were identified, representing the most systematic PL profiling knowledge so far for the animal. It could be concluded that C. intestinalis lipids should be a good alternative for fish oil with high contents of n‐3 fatty acids. The lipids would be more bioavailable due to the presence of the fatty acids being mainly in the form of PL.     

Positional distribution of ω3 Fatty acids in marine lipid triacylglycerols by high-resolution13C nuclear magnetic resonance spectroscopy

The positional distribution [α(1,3)-acyl and ß(2)-acyl] of ω3 fatty acids [18:4(n-3), 20:4(n-3), 20:5(n-3), 22:5(n-3) and 22:6(n-3)] in depot fat of Atlantic salmon (Salmo salar), harp seal oil and cod liver oil triacylglycerols has been examined by¹³C nuclear magnetic resonance (NMR) spectroscopy. The positional distribution data can be defined from the spectrum of the carbonyl (C1 carbon) and the methylene (C2 and glyceryl carbon) regions. In depot fat of Atlantic salmon and cod liver oil, docosahexaenoic acid (DHA) was concentrated in the ß-position of the triacylglycerides with 72.6 and 74.4%, respectively. Only 3.2% of DHA and 4.6% of eicosapentaenoic acid (EPA) were esterified to the ß-position of the triacylglycerides in harp seal oil. EPA is nearly randomly distributed in cod liver oil and muscle lipids of Atlantic salmon, with 37.8 and 39.7%, respectively, in the ß-position. In general, the¹³C NMR-derived data were in accordance with corresponding data reported in the literature obtained by conventional techniques.     

Concentration and purification of stearidonic,eicosapentaenoic, and docosahexaenoic acids from cod liver oil and the marine microalgaIsochrysis galbana

n-3 Polyunsaturated fatty acids (n-3 PUFA) from the marine microalgaIsochrysis galbana were concentrated and purified by a two-step process—formation of urea inclusion compounds followed by preparative high-performance liquid chromatography. These methods had been developed previously with fatty acids from cod liver oil. By the urea inclusion compounds method, a mixture that contained 94% (w/w) stearidonic (SA), eicosapentaenoic (EPA), plus docosahexaenoic (DHA) acids (4:1 urea/fatty acid ratio and 4°C crystallization final temperature) was obtained from cod liver oil fatty acids. Further purification of SA, EPA, and DHA was achieved with reverse-phase C₁₈ columns. These isolations were scaled up to a semi-preparative column. A PUFA concentrate was isolated fromI. galbana with methanol/water (80:20, w/w) or ethanol/water (70:30, w/w). With methanol/water, a 96% EPA fraction with 100% yield was obtained, as well as a 94% pure DHA fraction with a 94% yield. With ethanol/water as the mobile phase, EPA and DHA fractions obtained were 92% pure with yields of 84 and 88%, respectively.     

Lipidic pattern of 25 Mexican marine fishes with special emphasis in their n-3 fatty acids as nutraceuticals components

The aim of this study was to characterize and to evaluate the lipidic composition of mexican marine fishes with special emphasis in n-3 fatty acids as nutraceuticals. The edible portion of 25 species: humidity (H), crude protein (CP), total lipids (TL) and fatty acids (FA). The average content (g/100g edible portion) of H was 75.20, PC was 18.40, TL was 3.60. Four n-3 FA were identified in all the samples and they were found in the next abundance order (mg/100g edible portion): C22:6n-3 (DHA)(229.60), C20:5 n-3 (EPA)(52.10), C18:3 n-3 (ALA)(11.80) and C20:3 n-3 (2.25). By their origin and climate there were no difference. By their biologycal classification, n-3 FA content was higher in bony fishes than cartilaginous fishes. It was detected a proportional relation with the n-3 FA concentration and total lipid content. According to their ecotic distribution there were numerical differences in DHA content (mg/100g edible portion) between pelagics (420.70), benthopelagics (125.30) and demersals fishes (225.40). Fatty fishes had higher content of EPA and DHA (mg/100g edible portion) (109.27 and 552.72) than semifatty fishes (56.12 and 226.29) and leanness (15.95 and 96.52), respectively. Bony, fatty and pelagic fishes had a higher content of EPA+DHA. According with the international recommendation values (200 to 600 mg EPA+DHA/day) the 44% of the analyzed species could be considered as functional foods due to their high content of EPA + DHA in a range of 220 to 1300 mg/100g.     

Eicosapentaenoic acid,but not docosahexaenoic acid,increases mitochondrial fatty acid oxidation and upregulates 2,4-dienoyl-CoA reductase gene expression in rats

The aim of the present study was to investigate whether eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) was responsible for the triglyceride-lowering effect of fish oil. In rats fed a single dose of EPA as ethyl ester (EPA-EE), the plasma concentration of triglycerides was decreased at 8 h after acute administration. This was accompanied by an increased hepatic fatty acid oxidation and mitochondrial 2,4-dienoyl-CoA reductase activity. The steady-state level of 2,4-dienoyl-CoA reductase mRNA increased in parallel with the enzyme activity. An increased hepatic long-chain acyl-CoA content, but a reduced amount of hepatic malonyl-CoA, was obtained at 8 h after acute EPA-EE treatment. On EPA-EE supplementation, both EPA (20:5n-3) and docosapentaenoic acid (DPA, 22:5n-3) increased in the liver, whereas the hepatic DHA (22:6n-3) concentration was unchanged. On DHA-EE supplementation retroconversion to EPA occurred. No statistically significant differences were found, however, for mitochondrial enzyme activities, malonyl-CoA, long-chain acyl-CoA, plasma lipid levels, and the amount of cellular fatty acids between DHA-EE treated rats and their controls at any time point studied. In cultured rat hepatocytes, the oxidation of [1-¹⁴C]palmitic acid was reduced by DHA, whereas it was stimulated by EPA. In thein vivo studies, the activities of phosphatidate phosphohydrolase and acetyl-CoA carboxylase were unaffected after acute EPA-EE and DHA-EE administration, but the fatty acyl-CoA oxidase, the rate-limiting enzyme in peroxisomal fatty acid oxidation, was increased after feeding these n-3 fatty acids. The hypocholesterolemic properties of EPA-EE may be due to decreased 3-hydroxy-3-methylglutaryl-CoA reductase activity. Furthermore, replacement of the ordinary fatty acids, i.e., the monoenes (16:1n-7, 18:1n-7, and 18:1n-9) with EPA and some conversion to DPA concomitant with increased fatty acid oxidation is probably the mechanism leading to changed fatty acid composition. In contrast, DHA does not stimulate fatty acid oxidation and, consequently, no such displacement mechanism operates. In conclusion, we have obtained evidence that EPA, and not DHA, is the fatty acid primarily responsible for the triglyceride-lowering effect of fish oil in rats.     

Daily Intake of Cod or Salmon for 2?Weeks Decreases the 18:1n-9/18:0 Ratio and Serum Triacylglycerols in Healthy Subjects

Intake of fish and omega-3 (n-3) fatty acids is associated with a reduced concentration of plasma triacylglycerols (TAG) but the mechanisms are not fully clarified. Stearoyl-CoA desaturase-1 (SCD1) activity, governing TAG synthesis, is affected by n-3 fatty acids. Peripheral blood mononuclear cells (PBMC) display expression of genes involved in lipid metabolism. The aim of the present study was to estimate whether intake of lean and fatty fish would influence n-3 fatty acids composition in plasma phospholipids (PL), serum TAG, 18:1n-9/18:0 ratio in plasma PL, as well as PBMC gene expression of SCD1 and fatty acid synthase (FAS). Healthy males and females (n = 30), aged 20–40, consumed either 150 g of cod, salmon, or potato (control) daily for 15 days. During intervention docosahexaenoic acid (DHA, 22:6n-3) increased in the cod group (P < 0.05), while TAG concentration decreased (P < 0.05). In the salmon group both eicosapentaenoic acid (EPA, 20:5n-3) and DHA increased (P < 0.05) whereas TAG concentration and the 18:1n-9/18:0 ratio decreased (P < 0.05). Reduction of the 18:1n-9/18:0 ratio was associated with a corresponding lowering of TAG (P < 0.05) and an increase in EPA and DHA (P < 0.05). The mRNA levels of SCD1 and FAS in PBMC were not significantly altered after intake of cod or salmon when compared with the control group. In conclusion, both lean and fatty fish may lower TAG, possibly by reducing the 18:1n-9/18:0 ratio related to allosteric inhibition of SCD1 activity, rather than by influencing the synthesis of enzyme protein.     

Differential utilization of eicosapentaenoic acid and docosahexaenoic acid in human plasma

It has recently been shown that the ω3 fatty acid status in humans can be predicted by the concentration of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids in plasma phospholipids [Bjerve, K.S., Brubakk, A.M., Fougner, K.J., Johnsen, H., Midjthell, K., and Vik, T. (1993)Am. J. Clin. Nutr., in press]. In countries with low intake of ω3 fatty acids, the level of EPA in plasma phospholipids is often only about one-fifth the concentration of DHA. The purpose of this study was to investigate whether this difference in the concentration of these two fatty acids was due to a selective loss of EPA relative to DHA or to a lower dietary intake of EPA. Seven female volunteers ingested four grams of MaxEPA daily for 2 wk and in the following 4 wk they ate a diet almost completely devoid of the long-chain ω3 fatty acids. The concentrations of the ω3 fatty acids in the plasma cholesteryl esters, triglycerides and phospholipids and the high density lipoprotein phospholipids were examined at weekly intervals throughout the study. There was a more rapid rise in the concentration of EPA than in DHA levels in the supplementation period in all lipid fractions, but there was a disproportionate rise in DHA relative to EPA in the plasma lipids compared with the ratio in the supplement. In the depletion phase there was a rapid disappearance of EPA from all fractions, such that pre-trial levels were reached by one week post-supplementation. The disappearance of DHA was slower, particularly for the plasma phospholipids: at 4 wk post-supplementation, the DHA concentration in this fraction was still 40% above the pre-trial value. It is suggested that the low plasma EPA values relative to DHA are the result of increased β-oxidation of EPA and/or low dietary intake, rather than a rapid conversion of EPA to DHA. One practical result of this experiment is that, compared with DHA, the maintenance of increased EPA levels in plasma (and therefore tissues) would require constant inputs of EPA due to its more rapid loss from the plasma.     

N-3 Polyunsaturated Fatty Acids Modulate In-Vitro T Cell Function in Type I Diabetic Patients

In this work, we assessed the in-vitro effects of eicosapentaenoic acid (EPA; C20:5n-3) and docosahexaenoic acid (DHA; C22:6n-3) (final concentration, 15 microM) on T cell blastogenesis, interleukin-2 and -4 (IL-2, IL-4) secretion, fatty acid composition and intracellular oxidative status in type I diabetic patients with or without complications. Con A stimulated lymphocyte proliferation, glucose uptake, intracellular reduced glutathione levels and catalase activity were lower in diabetics as compared to controls, regardless to the presence of complications. EPA and DHA diminished T-lymphocyte proliferation and IL-2 production but enhanced IL-4 secretion in both diabetic and control groups. No changes in the levels of reduced glutathione and in the activities of catalase and SOD were observed in control T cells cultured in the presence of EPA and DHA. However, in diabetic patients, addition of n-3 PUFA to culture induced an increase in T cell levels of reduced glutathione and hydroperoxide, and in activities of catalase and SOD. Low levels of arachidonic acid (C20:4n-6) were found in plasma membrane phospholipids of lymphocytes from diabetic patients compared to controls. Incubation of lymphocytes with EPA and DHA was associated with an incorporation of these fatty acids in membrane phospholipids. In conclusion, the beneficial effects of n-3 PUFA on T cell functions in type I diabetes could be attributed to their suppressive action and modulation of cytokine secretion, and to the improvement of intracellular oxidative status.     

Polyunsaturated fatty acids exert antiarrhythmic actions as free acids rather than in phospholipids

Previous studies have shown that exogenous free n-3 polyunsaturated fatty acids (PUFA) can prevent tachyarrhythmias caused by specific agents in isolated cardiac myocytes. However, the question as to whether incorporation of the n-3 PUFA into membrane phospholipids has the same immediate protective effects remained to be answered. To answer this question, we increased the content of n-3 PUFA in the phospholipids of cultured neonatal rat myocytes by growing them 2–3 d in a culture to which eicosapentaenoic acid (EPA) or docosahexaenoic acid (DHA) in 15 μM concentration was added. Analysis of the fatty acid composition of membrane phospholipids revealed a significantly higher level of EPA and DHA (from 0.2 to 7.6% and from 1.2 to 6.5%) in cells supplemented with EPA or DHA, respectively. The responses of the myocytes grown in normal media or in media enriched with the PUFA to arrhythmogenic agents were examined after free fatty acids were removed from the medium and the cells. The arrhythmogenic agents used were the β-adrenergic agonist isoproterenol or an elevated extracellular concentration of calcium. The results showed that there was no significant difference in the induction of tachyarrhythmias by isoproterenol or by elevated [Ca²⁺]_o in cells grown in media enriched with PUFA, as compared with cells grown in normal media in the absence of the free PUFA. Under the conditions of this study, only the unesterified PUFA were able to protect the cardiomyocytes against induced arrhythmias. There was no antiarrhythmic effect due to an increased fraction of EPA or DHA in membrane phospholipids.     

The fatty acid composition of three unicellular algal species used as food sources for larvae of the American oyster (Crassostrea virginica)

The total lipid and fatty acid content of 3 algal species,Pyramimonas virginica, Pseudoisochrysis paradoxa andChlorella sp., which have been successful as food sources for rearing larvae of the American oyster,Crassostrea virginica, was determined. Of the fatty acids of ω6 and ω3 families which have been shown to be essential fatty acids for normal growth in many animals, only the ω6 fatty acids were found to be higher in these 3 species of algae than in the traditional oyster larvae diet which consists of the algaeMonochrysis lutheri andIsochrysis galbana. The major fatty acid constituents of the total lipids of the 3 species were the C12, C14, C16 and C18 saturated fatty acids and the C16 and C18 mono- and polyunsaturated acids. These components constituted 70–93% of the total lipid in cultures of all ages. There were modest amounts of C20 and C22 polyunsaturated acids; some of these existed only in trace amounts. InP. virginica andChlorella sp., hexadecanoic acid was dominant (23–39%). The presence of large quantities of tetradecanoic acid (22–26%) and oleic acid (17–21%) was characteristic ofP. paradoxa. Chlorella sp. had the highest proportion of octadecatrienoic acid (18∶3ω3) which accounted for up to 17% of the total lipids. γ-Linolenic acid (18∶3ω6) was found only inChlorella sp., but in the 5th-day culture only. The lowest proportion of total polyethylenic acid was inP. paradoxa; however, lipid analyses showed this alga had the most lipid/individual cell. Some variations were observed in the fatty acid composition with age of the culture. Contribution No. 883 of the Virginia Institute of Marine Science, Gloucester Point, VA 23062.     

Incorporation of exogenous docosahexaenoic acid into various bacterial phospholipids

Incorporation of exogenous docosahexaenoic acid (DHA) into bacterial phospholipids was examined as a method for DHA-linked phospholipid production. The cultivation of 23 bacterial strains in medium with DHA showed that an eicosapentaenoic acid-producing bacteriumShewanella sp. strain SCRC-2738 (strain SCRC-2738),Bacillus subtilis W23,B. cereus, an Antarctic marine bacterium strain S-7 (strain S-7), photosynthesis bacterium (PSB)Rhodopseudomonas capsulatus utilized for the production of larval marine fish,Pseudomonas aeruginosa, Staphylococcus aureus, Serratia marcescens andEscherichia coli K12 all incorporated DHA into their polar lipids. The polar lipids of the strain SCRC-2738, strain S-7, PSB andE. coli K12 were identified to be phospholipids. DHA was localized at thesn-2 position in the phospholipids of the four strains. Incorporation of exogenous DHA into their phospholipids produced an increase in saturated fatty acids and a decrease in monounsaturated fatty acids exceptE. coli K12. The strain SCRC-2738 incorporated the largest amount of DHA into their phospholipids among the tested bacterial strains in this study: DHA was 16% of the total fatty acids in the phosphatidylethanolamine (PE) and 29% in the phosphatidylglycerol (PG). In the PSB, incorporated DHA was 12% of the total fatty acids in the PE, 10% in the PG and phosophatidylcholine so that the PSB was nutritionally fortified.     

Polyunsaturated fatty acids increase the sensitivity of 36B10 rat astrocytoma cells to radiation-induced cell kill

Polyunsaturated fatty acids (PUFA) such as γ-linolenic acid (GLA, 18:3n-6), eicosapentaenoic acid (EPA, 20: 5n-3), and docosahexaenoic acid (DHA, 22:6n-3) have been shown to be cytotoxic to tumor cells. The objective of this work was to study the effect of PUFA on the radiation response of a 36B10 rat astrocytoma cell line. Supplementation of the astrocytoma cells with 15–45 μM GLA, EPA, or DHA produced marked changes in the fatty acid profiles of their phospholipids and neutral lipids. The methylene bridge index of these lipids increased significantly. These PUFA also exerted cytotoxic effects, as determined using the clonogenic cell survival assay. While GLA and DHA produced a moderate cell-killing effect, EPA was extremely cytotoxic, especially at a concentration of 45 μM. The monounsaturated oleic acid (OA, 18:1n-9) did not affect cell survival. Further, all three PUFA, and particularly GLA, increased the radiation-induced cell kill; OA did not enhance the effect of radiation. α-Tocopherol acetate blocked the enhanced radiation sensitivity of GLA- and DHA-supplemented cells. In conclusion, GLA, EPA, and DHA supplementation prior to, during, and after irradiation can enhance the radiation-induced cytotoxicity of rat astrocytoma cells. GLA and DHA supplementation post-irradiation also enhanced the radiation response of the 36B10 cells. Because GLA maximally increases the radioresponsiveness of a rat astrocytoma, this PUFA might prove useful in increasing the therapeutic efficacy of radiation in the treatment of certain gliomas.     

Is the Fatty Acid Composition of Freshwater Zoobenthic Invertebrates Controlled by Phylogenetic or Trophic Factors?

We studied the fatty acid (FA) content and composition of ten zoobenthic species of several taxonomic groups from different freshwater bodies. Special attention was paid to essential polyunsaturated fatty acids, eicosapentaenoic acid (EPA, 20:5n-3), docosahexaenoic acid (DHA, 22:6n-3), and arachidonic acid (ARA, 20:4n-6); and the n-3/n-6 and DHA/ARA ratios, which are important for consumers of higher trophic levels, i.e., fish. The content and ratios of these FA varied significantly in the studied zoobenthic species, consequently, the invertebrates were of different nutritional quality for fish. Eulimnogammarus viridis (Crustacea) and Dendrocoelopsis sp. (Turbellaria) had the highest nutrition value for fish concerning the content of EPA and DHA and n-3/n-6 and DHA/ARA ratios. Using canonical correspondence analysis we compared the FA profiles of species of the studied taxa taking into account their feeding strategies and habitats. We gained evidence that feeding strategy is of importance to determine fatty acid profiles of zoobenthic species. However, the phylogenetic position of the zoobenthic species is also responsible and may result in a similar fatty acid composition even if species or populations inhabit different water bodies or have different feeding strategies.     

Differential Impact of Sex on Seasonal Changes in Mantle and Tentacle Phospholipids and Triacylglycerols in Sepia officinalis

The aim of the present work was to study the effect of season on phospholipids and triacylglycerols (TAG) of mantle and tentacles of female and male wild Sepia officinalis. The identified phospholipids were phosphatidylethanolamine (PtdEtn), phosphatidylcholine (PtdCho), phosphatidylserine (PtdSer), and phosphatidylinositol (PtdIns), and PtdEtn was the major fraction. Results showed apparent seasonal variation of phospholipid content, particularly with female samples. Fatty acid composition of phospholipid classes showed a differentiation much more in the proportions than in the diversity of fatty acids. Results showed that the major saturated fatty acids were 16:0 and 18:0, the major monounsaturated fatty acids were 18:1 and 20:l, and the major polyunsaturated fatty acids were docosahexaenoic acid (22:6n-3) (DHA) and eicosapentaenoic acid (20:5n-3) (EPA). The results relative to TAG demonstrated significant variations. Principal component analysis confirmed the seasonal and sexual effects. This study could be appropriate for the improvement of consistent monitoring of phospholipid and TAG accumulation in cephalopod, which might be important for both physiological studies and food industries.