Functional Characterization of Polyunsaturated Fatty Acid Delta 6-Desaturase and Elongase Genes from the Black Seabream (Acanthopagrus schlegelii)

Fatty acid delta 6-desaturase (D6DES) and elongases are key enzymes in the synthesis of polyunsaturated fatty acids (PUFAs) including arachidonic acid (ARA) and eicosapentaenoic acid (EPA) from microorganisms to higher animals. To identify the genes encoding D6DES and elongases for PUFAs, we isolated each cDNA with a high similarity to the D6DES and ELOVL5-like elongases of mammals and fishes via degenerate PCR and RACE-PCR from Acanthopagrus schlegelii. A recombinant vector expressing AsD6DES was subsequently constructed and transformed into Saccharomyces cerevisiae to test the enzymatic activity toward n-6 and n-3 fatty acids in the PUFA biosynthesis. The heterologously expressed AsD6DES produced γ-linolenic acid (GLA, C_18:3 n-6) and stearidonic acid (STA, C_18:4 n-3) at conversion rates of 26.3–35.6 % from exogenous linoleic acid (LA, C_18:2 n-6) and α-linolenic acid (ALA, C_18:3 n-3) substrates, respectively. When AsELOVL5 was expressed in yeast, it conferred an ability to elongate GLA to di-homo-γ-linolenic acid (DGLA, C_20:3 n-6). In addition, AsELOVL5 showed an ability to convert ARA (C_20:4 n-6) and EPA (C_20:5 n-3) to dodecylthioacetic acid (DTA, C_22:4 n-6) and docosapentaenoic acid (DPA, C_22:5 n-3), respectively. In these results, the AsD6DES encodes a delta 6-fatty acid desaturase and the AsELOVL5 encoding a long-chain fatty acid elongase shows activity to enlongate C₁₈Δ6/C₂₀Δ5, but not C₂₂.     

Accumulation of trans C18:1 Fatty Acids in the Rumen after Dietary Algal Supplementation Is Associated with Changes in the Butyrivibrio Community

Optimization of the fatty acid composition of ruminant milk and meat is desirable. Dietary supplementation of algae was previously shown to inhibit rumen biohydrogenation, resulting in an altered milk fatty acid profile. Bacteria involved in biohydrogenation belong to the Butyrivibrio group. This study was aimed at relating accumulation of biohydrogenation intermediates with shifts in Butyrivibrio spp. in the rumen of dairy cows. Therefore, an experiment was performed with three rumen-fistulated dairy cows receiving a concentrate containing algae (9.35 g/kg total dry matter [DM] intake) for 20 days. Supplementation of the diet with algae inhibited biohydrogenation of C_18:2 omega 6 (n-6) and C_18:3 n-3, resulting in increased concentrations of biohydrogenation intermediates, whereas C_18:0 decreased. Addition of algae increased ruminal C_18:1 trans fatty acid concentrations, mainly due to 6- and 20-fold increases in C_18:1 trans 11 (t11) and C_18:1 t10. The number of ciliates (5.37 log copies/g rumen digesta) and the composition of the ciliate community were unaffected by dietary algae. In contrast, supplementation of the diet with algae changed the composition of the bacterial community. Primers for the Butyrivibrio group, including the genera Butyrivibrio and Pseudobutyrivibrio, were specifically designed. Denaturing gradient gel electrophoresis showed community changes upon addition of algae without affecting the total amount of Butyrivibrio bacteria (7.06 log copies/g rumen DM). Clone libraries showed that algae affected noncultivated species, which cluster taxonomically between the genera Butyrivibrio and Pseudobutyrivibrio and might play a role in biohydrogenation. In addition, 20% of the clones from a randomly selected rumen sample were related to the C_18:0-producing branch, although the associated C_18:0 concentration decreased through supplementation of the diet with algae.     

Influence of α-tocopherol supplementation on trans-18:1 and conjugated linoleic acid profiles in beef from steers fed a barley-based diet

The current study was conducted to determine the effect of different α-tocopherol (vitamin E) inclusion levels on trans(t)-18:1 and conjugated linoleic acid (CLA) profiles in subcutaneous and intramuscular fat of steers fed a barley-based diet. Fifty-six feedlot steers were offered a barley-based finisher diet (73% steam rolled barley, 22% barley silage and 5% supplement as-fed basis) with four levels of supplementary dl-α-tocopheryl acetate (340, 690, 1040 or 1740 IU/steer per day) for 120 days. Adding vitamin E to the diet had little effect on the overall fatty acid composition of intramuscular fat. The proportion of individual and total t,t- and cis(c),t-CLA, n-3 fatty acids, total polyunsaturated fatty acids (PUFA), mono-unsaturated fatty acids and saturated fatty acids to PUFA ratio in subcutaneous fat were not influenced (P > 0.05) by dietary vitamin E supplementation. Increasing levels of vitamin E led to linear reductions in t6-/t7-/t8-18:1 and t10-18:1 (P < 0.05), and linear increase in t11-/t10-18:1 ratio (P < 0.05) in subcutaneous fat. The content of 20:3n-6 and total n-6 in subcutaneous fat decreased (P < 0.05) linearly with increasing amounts of vitamin E. The subcutaneous fat n-6:n-3 ratio showed a quadratic (P < 0.05) response to vitamin E. In conclusion, although vitamin E supplementation has some potential to reduce t10-18:1 formation and increase t11-/t10-18:1 ratio in subcutaneous fat of cattle fed barley-based diets, the changes in the present study were limited and may not have been sufficient to impact on human health.     

Maintenance of lower proportions of (n − 6) eicosanoid precursors in phospholipids of human plasma in response to added dietary (n − 3) fatty acids

Competition between the (n ? 3) and (n ? 6) types of highly unsaturated fatty acids can diminish the abundance of (n ? 6) eicosanoid precursors in a tissue, which in turn can diminish the intensity of tissue responses that are mediated by (n ? 6) eicosanoids. The mixture of 20- and 22-carbon highly unsaturated fatty acids maintained in the phospholipids of human plasma is related to the dietary intake of 18:2 (n ? 6) and 18:3 (n ?3) by empirical hyperbolic equations in a manner very similar to the relationship reported for laboratory rats (Lands, W.E.M., Morris, A. and Libelt, B. (1990) Lipids 25, 505–516). Analytical results from volunteers ingesting self-selected diets showed an inter-individual variance for the proportion of (n ? 6) eicosanoid precursors in the fatty acids of plasma phospholipids of about 5%, but the variance among multiple samples taken from the same individual throughout the day was less (about 3%), closer to the experimental variance of the analytical procedure (about 1%). The reproducibility of the results makes it likely that analysis of fatty-acid composition of plasma lipids from individuals will prove useful in estimating the diet-related tendency for severe thrombotic, arthritic of other disorders that are mediated by (n ? 6) eicosanoids. Additional constants and terms were included in the equations to account for the effects of 20- and 22-carbon highly unsaturated (n ? 3) fatty acids in the diet. A lower constant for the 20- and 22-carbon (n ? 3) fatty acids compared to that for the 18-carbon (n ? 3) fatty acid in decreasing the ability of dietary 18:2 (n ? 6) to maintain 20:4 (n ? 6) in tissue lipids confirmed the greater competitive effectiveness of the more highly unsaturated n ? 3 fatty acids in the elongation/ desaturation process. Also, a lower constant for direct incorporation of 20-carbon fatty acids of the n ? 6 vs. the n ? 3 type indicated a greater competitive effectiveness of 20:4 (n ? 6) relative to 20:5 (n ? 3) in reesterification after release from tissue lipids. The equations may be used in reverse to estimate the dietary intakes of the (n ? 3) and (n ? 6) fatty acids by using the composition of the fatty acids that had been maintained in plasma lipids.     

Influences of stearidonic acid-enriched soybean oil on the blood and organ biochemical parameters in rats

In this study, we administered various diets of stearidonic acid (SDA, 18:4n?3) soybean oil to rats and examined the subsequent blood and organ biochemical parameters. Male Wistar rats (seven rats/group, six groups total) were fed diets supplemented with a test oil for 4 weeks. Diets containing test oils were: FFC diet (fish-oil-free control diet), C diet (control group, assuming a Japanese diet), SDA25 diet (25% 18:4n?3 soybean oil in the C diet), SDA50 (50% 18:4n?3 soybean oil in the C diet), ALA diet (34% flaxseed oil in the C diet), and EPA+DHA diet (34% fish oil in the C diet). The intake of 18:4n?3 showed increased relative efficiency of 20:5n?3 accretions in serum and liver triacylglycerol and significantly decreased the serum triacylglycerol level in rats. The results suggested that the consumption of 18:4n?3 soybean oil may modify the lipid and fatty acid profiles of body fats, even when EPA and DHA derived from fish is consumed.     

Low C18 to C20 fatty acid elongase activity and limited conversion of stearidonic acid, 18:4(n–3), to eicosapentaenoic acid, 20:5(n–3), in a cell line from the turbot, Scophthalmus maximus

The TF cell line, derived from a top predatory, carnivorous marine teleost, the turbot (Scophthalmus maximus), is known to have a limited conversion of C₁₈ to C₂₀ polyunsaturated fatty acids (PUFA). To illuminate the underlying processes, we studied the conversions of stearidonic acid, 18:4(n–3), and its elongation product, 20:4(n–3), in TF cells and also in a cell line, AS, derived from Atlantic salmon (Salmo salar), by adding unlabelled (25 μM), U-¹⁴C (1 μM) or deuterated (d5; 25 μM) fatty acids. Stearidonic acid, 18:4(n–3), was metabolised to 20:5(n–3) in both cells lines, but more so in AS than in TF cells. Δ5 desaturation was more active in TF cells than in AS cells, whereas C₁₈ to C₂₀ elongation was much reduced in TF as compared to AS cells. Only small amounts of docosahexaenoic acid (22:6(n–3)) were produced by both cell lines, although there was significant production of 22:5(n–3) in both cultures, especially when 20:4(n–3) was supplemented. We conclude that limited elongation of C₁₈ to C₂₀ fatty acids rather than limited fatty acyl Δ5 desaturation accounts for the limited rate of conversion of 18:3(n–3) to 20:5(n–3) in the turbot cell line, as compared to the Atlantic salmon cell line. The results can account for the known differences in conversions of C₁₈ to C₂₀ PUFA by the turbot and the Atlantic salmon in vivo.     

The role of lipid components of the diet in the regulation of the fatty acid composition of the rat liver endoplasmic reticulum and lipid peroxidation

The fatty acid compositions of the lipids and the lipid peroxide concentrations and rates of lipid peroxidation were determined in suspensions of liver endoplasmic reticulum isolated from rats fed on synthetic diets in which the fatty acid composition had been varied but the remaining constituents (protein, carbohydrate, vitamins and minerals) kept constant. Stock diet and synthetic diets containing no fat, 10% corn oil, herring oil, coconut oil or lard were used. The fatty acid composition of the liver endoplasmic reticulum lipid was markedly dependent on the fatty acid composition of the dietary lipid. Feeding a herring-oil diet caused incorporation of 8.7% eicosapentaenoic acid (C_20:5) and 17% docosahexaenoic acid (C_22:6), but only 5.1% linoleic acid (C_18:2) and 6.4% arachidonic acid (C_20:4), feeding a corn-oil diet caused incorporation of 25.1% C_18:2, 17.8% C_20:4 and 2.5% C_22:6 fatty acids, and feeding a lard diet caused incorporation of 10.3% C_18:2, 13.5% C_20:4 and 4.3% C_22:6 fatty acids into the liver endoplasmic-reticulum lipids. Phenobarbitone injection (100mg/kg) decreased the incorporation of C_20:4 and C_22:6 fatty acids into the liver endoplasmic reticulum of rats fed on a lard, corn-oil or herring-oil diet. Microsomal lipid peroxide concentrations and rates of peroxidation in the presence of ascorbate depended on the nature and quantity of the polyunsaturated fatty acids in the diet. The lipid peroxide content was 1.82±0.30nmol of malonaldehyde/mg of protein and the rate of peroxidation was 0.60±0.08nmol of malonaldehyde/min per mg of protein after feeding a fat-free diet, and the values were increased to 20.80nmol of malonaldehyde/mg of protein and 3.73nmol of malonaldehyde/min per mg of protein after feeding a 10% herring-oil diet in which polyunsaturated fatty acids formed 24% of the total fatty acids. Addition of α-tocopherol to the diets (120mg/kg of diet) caused a very large decrease in the lipid peroxide concentration and rate of lipid peroxidation in the endoplasmic reticulum, but addition of the synthetic anti-oxidant 2,6-di-t-butyl-4-methylphenol to the diet (100mg/kg of diet) was ineffective. Treatment of the animals with phenobarbitone (1mg/ml of drinking water) caused a sharp fall in the rate of lipid peroxidation. It is concluded that the polyunsaturated fatty acid composition of the diet regulates the fatty acid composition of the liver endoplasmic reticulum, and this in turn is an important factor controlling the rate and extent of lipid peroxidation in vitro and possibly in vivo.     

Fatty acid composition of Ruditapes decussatus spat fed on different microalgae diets

The fatty acid composition of the Ruditapes decussatus spat fed on three different microalgal diets during 4 weeks was determined. The fatty acid pattern of each diet was also analysed. The diets used were Isochrysis galbana, clone T-ISO, Tetraselmis suecica, and Phaeodactylum tricornutum. The fatty acid composition of the spat was usually well correlated with that of the diet supplied. Major differences among spat cultures were found in 14:0, 16:0, 16:1n-9, 16:1n-7, 18:1n-9, 18:2n-6, 18:3n-3, 18:4n-3, 20:5n-3, 22:5n-6 and 22:6n-3 fatty acids. These differences were correlated with the particular fatty acid content of each diet supplied. It has been shown that R. decussatus spat have a very low capacity to elongate and desaturate linolenic acid to n-3 PUFA, so when 20:5n-3 or 22:6n-3 were not present in the diet, they were also absent, at least in measurable amounts, in the clams. The absence of any of the “essential” fatty acids, 20:5n-3 in T-ISO or 22:6n-3 in Tetraselmis, did not limit spat growth, so their role as “essential” fatty acids might be a matter for discussion. Finally, the nutritive value of each diet was discussed in terms of its fatty acid composition.     

Comparisons Between the Kinetic Behaviour of the Muscle Carnitine Palmitoyltransferase I of a Higher and Lower Vertebrate

The V_max of rat muscle mitochondrial CPT I toward the coenzyme A derivatives of 16:0, 16:1n-7, 18:1n-9, and 22:6n-3 were far lower than those recorded previously for this enzyme in rat liver at the same temperature (37°C). However, the V_max of 7.0 nmol · min⁻¹ · mg mitochondrial protein⁻¹ for linoleoyl CoA (18:2n-6), which was the greatest recorded for the five acyl CoAs examined in muscle, was similar to that in liver. These comparisons presumably reflect a difference in the essential fatty acid requirements of these two rat tissues. Although the V_max values for CPT I in the musculature of a lower vertebrate (larval lamprey) at 20°C were similar to those exhibited toward the coenzyme A derivatives of 16:0, 16:1n-7, 18:1n-9, and 22:6n-3 by the CPT I of rat musculature at 37°C, the corresponding V_max toward 18:2n-6 (3.2 nmol · min⁻¹ · mg mitochondrial protein⁻¹) was lower. The latter relatively low activity may spare from oxidation this essential fatty acid, which is in low abundance in the diet of larval lampreys. Although the V_max values toward the four nonessential fatty acids in larval lamprey muscle were similar to those in rat muscle, the corresponding K_0.5 values were lower, thus indicating that the musculature of larval lampreys has a high capacity for energy generation through β-oxidation.     

Fatty acid composition in matrix vesicles and in microvilli from femurs of chicken embryos revealed selective recruitment of fatty acids

Hypertrophic chondrocytes participate in matrix mineralization by releasing matrix vesicles (MVs). These MVs, by accumulating Ca²⁺ and phosphate initiate the formation of hydroxyapatite. To determine the types of lipids essential for mineralization, we analyzed fatty acids (FAs) in MVs, microvilli and in membrane fractions of chondrocytes isolated from femurs of chicken embryos. The FA composition in the MVs was almost identical to that in microvilli, indicating that the MVs originated from microvilli. These fractions contained more monounsaturated FAs especially oleic acid than in membrane homogenates of chondrocytes. They were enriched in 5,8,11-eicosatrienoic acid (20:3n−9), in eicosadienoic acid (20:2n−6), and in arachidonic acid (20:4n−6). In contrast, membrane homogenates from chondrocytes were enriched in 20:1n−9, 18:3n−3, 22:5n−3 and 22:5n−6. Due to their relatively high content in MVs and to their selective recruitment within microvilli from where MV originate, we concluded that 20:2n−6 and 20:3n−9 (pooled values), 18:1n−9 and 20:4n−6 are essential for the biogenesis of MVs and for bone mineralization.     

Influence of pumpkin seed cake and extruded linseed on milk production and milk fatty acid profile in Alpine goats

The aim was to determine the effect of substituting pumpkin seed cake (PSC) or extruded linseed (ELS) for soya bean meal in goats’ diets on milk yield, milk composition and fatty acids profile of milk fat. In total, 28 dairy goats were divided into three groups. They were fed with concentrate mixtures containing soya bean meal (Control; n=9), ELS (n=10) or PSC (n=9) as main protein sources in the trial lasting 75 days. Addition of ELS or PSC did not influence milk yield and milk gross composition in contrast to fatty acid profile compared with Control. Supplementation of ELS resulted in greater branched-chain fatty acids (BCFA) and total n-3 fatty acids compared with Control and PSC (P<0.05). Total n-3 fatty acids were accompanied by increased α-linolenic acid (ALA, C18:3n-3; 0.56 g/100 g fatty acids) and EPA (C20:5n-3; 0.12 g/100 g fatty acids) proportions in milk of the ELS group. In contrast, ELS and PSC resulted in lower linoleic acid (LA, C18:2n-6; 2.10 and 2.28 g/100 g fatty acids, respectively) proportions compared with Control (2.80 g/100 g fatty acids; P<0.05). Abovementioned resulted in lower LA/ALA ratio (3.81 v. 7.44 or 6.92, respectively; P<0.05) with supplementation of ELS compared with Control or PSC. The PSC diet decreased total n-6 fatty acids compared with the Control (2.96 v. 3.54 g/100 g fatty acids, P<0.05). Oleic acid (c9-C18:1), CLA (c9,t11-18:2) and t10-,t11-C18:1 did not differ between treatments (P⩾0.08), although stearic acid (C18:0) increased in ELS diets compared with Control (12.7 v. 10.2 g/100 g fatty acids, P<0.05). Partially substituted soya bean meal with ELS in hay-based diets may increase beneficial n-3 fatty acids and BCFA accompanied by lowering LA/ALA ratio and increased C18:0. Pumpkin seed cake completely substituted soya bean meal in the diet of dairy goats without any decrease in milk production or sharp changes in fatty acid profile that may have a commercial or a human health relevancy.     

Effects of Temperature and Dietary Lipids on Phospholipid Fatty Acids and Membrane Fluidity in Steinernema carpocapsae

The phospholipid composition of Steinernema carpocapsae was studied in relation to diet and culture temperature. When reared at 18 and 27.5 C on Galleria mellonella or on an artificial diet supplemented with lard, linseed oil, or fish oil as lipid sources, nematode phospholipids contained an abundance of 20-carbon polyunsaturated fatty acids, with eicosapentaenoic acid (20:5(n - 3)) predominant, regardless of the fatty acid composition of the diet. Because the level of linolenic acid (18:3(n - 3)) in nematode phospholipids was very low and because eicosapentaenoic acid was present even when its precursor (linolenic acid) was undetectable in the diet, S. carpocapsae likely produces n - 3 polyunsaturated fatty acids by de novo biosynthesis, a pathway seldom reported in eukaryotic animals. Reduction of growth temperature from 25 to 18 C increased the proportion of 20:5(n - 3) but not other polyunsaturated fatty acids. A fluorescence polarization technique revealed that vesicles produced from phospholipids of nematodes reared at 18 C were less ordered than those from nematodes reared at 27.5 C, especially in the outermost region of the bilayer. Dietary fish oil increased fluidity in the outermost region but increased rigidity in deeper regions. Therefore, S. carpocapsae appears to modify its membrane physical state in response to temperature, and eicosapentaenoic acid may be involved in this response. The results also indicate that nematode membrane physical state can be modified dietarily, possibly to the benefit of host-finding or survival of S. carpocapsae at low temperatures.     

Gamma-linolenic acid alters the composition of mitochondrial membrane subfractions,decreases outer mitochondrial membrane binding of hexokinase and alters carnitine palmitoyltransferase I properties in the Walker 256 rat tumour

Gamma-linolenic acid (GLA) is known to be an inhibitor of Walker 256 tumour growth in vivo and causes changes in both mitochondrial structure and cellular metabolism. The aim of the present study was to investigate in greater detail the changes in energy metabolism and ultrastructure induced by GLA in this tumour model. A diet containing 5.5% GLA, which is sufficient to cause a 45% decrease in tumour growth, was found to almost double the triacylglycerol (TAG) content of the tumour and to increase the quantity of 20:3 n?6, 20:4 n?6, 22:4 n?6 and 22:5 n?6 in the TAG fraction as determined by gas chromatography–mass spectrometry (GCMS) analysis. Morphometric analysis of the tumour by electron microscopy confirmed this increase in TAG content, identifying a doubling of lipid droplet content in the GLA dietary group. The surface density of mitochondrial cristae was reduced, along with a reduction in the number of contact sites (CS) and matrix granules. These three parameters are likely indicators of a reduction in mitochondrial metabolic activity. Measurement of hexokinase activity identified that much of the total hexokinase activity was in the mitochondrially bound form (66.5%) in the control tumour and that GLA caused a decrease in the amount of enzyme in the bound form (39.3%). The fatty acyl chain composition of the tumour mitochondrial subfractions, outer membranes (OM), CSs and inner membranes (IM) was determined by GCMS. All subfractions showed considerable increases in 20:3 n?6 and decreases in 18:1 n?9, 18:2 n?6 and 22:6 n?3, when exposed to GLA diet. These changes were reflected in a large increase in the n?6/n?3 ratio in the GLA OM vs. the control OM, 21.299 vs. 6.747, respectively. The maximal activity of OM carnitine palmitoyltransferase I (CPT I) was found to be decreased by 61.6% in the GLA diet group. This was accompanied by a decrease in malonyl CoA sensitivity and a decrease in affinity for 16:0 CoA substrate. Such changes in CPT I may be the cause of cytoplasmic acyl CoA accumulation seen in this tumour model. These effects, together with previously reported increases in lipid peroxidation, lead to the conclusion that GLA may cause inhibition of tumour cell growth through separate but interlinked pathways, all of which eventually lead to apoptosis and a decrease in tumour development. The influence of mitochondrial OM fatty acyl chain composition upon two important enzymes of energy metabolism, hexokinase and CPT I, both of which have been linked to apoptosis, is of considerable importance for future studies on fatty acid-induced cell death.     

DHA status of vegetarians

The aim of the present study was to evaluate the influence of pregnancy in adolescents on the fatty acid composition of the erythrocyte membrane, which was used as a proxy for status of n-3 and n-6 polyunsaturated fatty acids (PUFA), and also on the composition of plasma non-esterified fatty acids (NEFA) mobilized from the adipose tissue. Two matched groups of healthy adolescents (14–19 years) from Rio de Janeiro, Brazil, were compared: pregnant (n=26; 32.7±3.9 weeks of gestation, mean±SD) and non-pregnant (n=20). Blood samples were collected after an overnight fast. Mean dietary intakes of total fat and n-3 and n-6 PUFA (energy %) were not different between pregnant and non-pregnant adolescents, and the consumption of food sources of docosahexaenoic acid (DHA) was low. Fasting total NEFA and NEFA 18:2n-6, 18:3n-6 and 20:4n-6 (g/100 g fatty acids) were higher in pregnant than in non-pregnant adolescents. Although erythrocyte 20:4n-6 was lower in pregnant adolescents, there were no differences in DHA (g/100 g fatty acids), in DHA status indices (22:5n-6/22:4n-6 and 22:6n-3/22:5n-6 ratios) and in the index of n-3+n-6 PUFA status ([Σn-3+Σn-6]/[Σn-7+Σn-9]) in erythrocytes as compared with those of non-pregnant adolescents. In conclusion, pregnancy did not have an adverse effect on erythrocyte DHA content or on DHA and n-3+n-6 PUFA status indices in the adolescents studied.     

Comparison of lipid content and fatty acid composition in muscle and liver of two notothenioid fishes from Admiralty Bay (Antarctica): an eco-physiological perspective

During Antarctic summer, total lipids (g/100 g dry matter) in Notothenia coriiceps (n=18) and Lepidonotothen nudifrons (n=10) were low (6.1 and 4.7 in muscle), which is typical of Antarctic benthic species. The liver of female N. coriiceps was heavier and contained more lipids per dry weight than the liver of males. The fatty acid composition of N. coriiceps and L. nudifrons was dominated by polyunsaturated fatty acids (PUFA, respectively, 44 and 49% of total fatty acids in muscle, 31 and 46% in liver), which included primarily C20:5n-3 (18 and 19% in muscle, 13 and 18% in liver) and C22:6n-3 (15 and 19% in muscle, 12 and 20% in liver). In L. nudifrons, the levels of some unsaturated fatty acids increased with age and size. The high percent unsaturation (PUFA+MUFA, 78 and 80% in muscle, 82 and 80% in liver) is a response to low water temperature (-0.4°C). Fish fatty acid profiles reflect fatty acid profiles of the diet (amphipods, macroalgae and fish).     

Incorporation of bacterial fatty acids and changes in a wax ester-based omnivory index during a long-term incubation experiment with Calanus glacialis Jaschnov

We traced the incorporation of fatty acid biomarkers into Calanus glacialis Jaschnov (CV) during a long-term incubation experiment using bacterivorous dinoflagellates and diatoms as food. Copepods fed Oxyrrhis marina Dujardin during a 3-week acclimation period developed an omnivorous lipid composition, relative to wild-captured copepods, characterized by significant losses of polyunsaturated fatty acids (PUFA) and diatom fatty acids [16:4(n−1), 20:5(n−3)], and increases in saturated fatty acids (SFA) and 18:1(n−7). Levels of a wax ester-based omnivory index [unsaturation coefficient (UC)], verified by gas chromatography (GC), also decreased in response to the relatively PUFA-poor dinoflagellate. After half of the copepods were switched to a diet comprised of the diatom Thalassiosira hispida Syvertsen (PUFA-rich), the data showed reversal to a more herbivorous lipid composition (increases in UC and relative amounts of PUFA and diatom fatty acids). We assert that UC, derived from routine thin-layer chromatography analysis (Iatroscan) can quickly determine in situ feeding strategies (i.e., degree of omnivory) of wax ester-storing copepods. None of the eight odd and/or branched fatty acids (OBFA) initially detected in C. glacialis increased in response to a diet of O. marina which was rich in these compounds [mainly iso (i)-15:0 and anteiso (ai)-15:0]. Lack of transfer of these and other fatty acids [e.g., 22:6(n−3)] could be related to the physiological state of the copepods (early diapause). We suggest that the bacterial fatty acid 18:1(n−7) may be more useful in inferring connections between Calanus spp. and the microbial food web than the odd and/or branched chains.     

Temperature-induced plasticity in membrane and storage lipid composition: thermal reaction norms across five different temperatures

Temperature is a key environmental factor inducing phenotypic plasticity in a wide range of behavioral, morphological, and life history traits in ectotherms. The strength of temperature-induced responses in fitness-related traits may be determined by plasticity of the underlying physiological or biochemical traits. Lipid composition may be an important trait underlying fitness response to temperature, because it affects membrane fluidity as well as availability of stored energy reserves. Here, we investigate the effect of temperature on lipid composition of the springtail Orchesella cincta by measuring thermal reaction norms across five different temperatures after four weeks of cold or warm acclimation. Fatty acid composition in storage and membrane lipids showed a highly plastic response to temperature, but the responses of single fatty acids revealed deviations from the expectations based on HVA theory. We found an accumulation of C_18:2n6 and C_18:3n3 at higher temperatures and the preservation of C_20:4n6 across temperatures, which is contrary to the expectation of decreased unsaturation at higher temperatures. The thermal response of these fatty acids in O. cincta differed from the findings in other species, and therefore shows there is interspecific variation in how single fatty acids contribute to HVA. Future research should determine the consequences of such variation in terms of costs and benefits for the thermal performance of species.     

Cox-2 expression, PGE2 and cytokines production are inhibited by endogenously synthesized n-3 PUFAs in inflamed colon of fat-1 mice

There is great interest in the role of polyunsaturated fatty acids (PUFAs) in promoting (n-6 class) or inhibiting (n-3 class) inflammation. Mammalian cells are devoid of desaturase that converts n-6 to n-3 PUFAs. Consequently, essential n-3 fatty acids must be supplied with the diet. We have studied the effect of endogenously produced n-3 PUFAs on colitis development in fat-1 transgenic mice carrying the Caenorhabditis elegans fat-1 gene encoding n-3 desaturase. Colonic cell lipid profile was measured by capillary gas chromatography in fat-1 and wild-type (WT) littermates fed standard diet supplemented with 10% (w/w) safflower oil rich (76%) in n-6 polyunsaturated linoleic acid (LA). Experimental colitis was induced by administrating 3% dextran sodium sulphate (DSS). Colitis was scored by histopatological analysis. Cyclooxygenase-2 (Cox-2) expression was evaluated by real time polymerase chain reaction. Prostaglandin E₂ (PGE₂) levels and cytokine production were determined by enzyme and microsphere-based immunoassays, respectively. The n-6/n-3 PUFA ratios in colonic cells of fat-1 mice were markedly lower (9.83±2.62) compared to WT (54.5±9.24, P<.001). Results also showed an attenuation of colonic acute and chronic inflammation in fat-1 mice with significant decreases in PGE₂ production (P<.01) and Cox-2 expression (P<.01). High levels of colitis-induced proinflammatory cytokines, interleukin (IL)-18, IL-1α, IL-1β, IL-6, monocytes chemotactic proteins 1, 2 and 3 (MCP 1,2,3), matrix metalloproteinase 9 and tumor necrosis factor α (TNF-α) were down-regulated in DSS acutely and chronically treated fat-1 mice. The expression of fat-1 gene in the colon was associated with endogenous n-3 PUFAs production, decreased Cox-2 expression, increased PGE₂ and cytokine production.     

Comparison of growth and lipid composition in the green abalone, Haliotis fulgens, provided specific macroalgal diets

Lipid composition of abalone was examined over a one-year interval. A feeding trial was designed to cover a full reproductive cycle in young adult green abalone, Haliotis fulgens, consisting of five diet treatments: the macrophytic algal phaeophyte Egregia menziesii, rhodophyte Chondracanthus canaliculatus, chlorophyte Ulva lobata, a composite of the three algae and a starvation control. The lipid class, fatty acid, sterol and 1-O-alkyl glyceryl ether profiles were determined for foot, hepatopancreas/gonad tissues and larvae. The major fatty acids were 16:0, 18:0, 18:1(n-7)c, 18:1(n-9)c, 20:4(n-6), 20:5(n-3) and 22:5(n-3), as well as 14:0 for abalone fed brown and red algae. 4,8,12-Trimethyltridecanoic acid, derived from algae, was detected for the first time in H. fulgens (hepatopancreas complex, 1.2–13.9%; larvae, 0.5% of total fatty acids). Diacylglyceryl ethers were present in larvae (0.6% of total lipid). The major 1-O-alkyl glycerols were 16:0, 16:1 and 18:0. Additionally, 18:1(n-9) was a major component in hepatopancreas/gonad and larvae. The major sterol was cholesterol (96–100% of total sterols). Highest growth rates were linked to temperature and occurred in abalone fed the phaeophyte E. menziesii (43 μm·day^–1, 56 mg·day^–1 yearly mean), an alga containing the highest levels of C₂₀ polyunsaturated fatty acids and the highest ratio of 20:4(n-6) to 20:5(n-3). This study provides evidence of the influence of diet and temperature on seasonal changes in abalone lipid profiles, where diet is most strongly related to body mass and temperature to shell length. The allocation of lipids to specific tissues in green abalone clarifies their lipid metabolism. These results provide a basis for improving nutrition of abalone in mariculture through formulation of artificial feeds.     

Mapping Quantitative Trait Loci for Omega-3 Fatty Acids in Asian Seabass

Omega-3 fatty acids are essential fatty acids for human health. Therefore, increasing both percentage of omega-3 and a better fatty acid profile in fish fillets is one of the breeding goals in aquaculture. However, it is difficult to increase the omega-3 content in fish fillets, as the phenotypic selection of these traits is not easily feasible. To facilitate the genetic improvement of the Asian seabass for optimal fatty acid profiles, a genome-wide scan for quantitative trait loci (QTL) affecting fatty acid level in the flesh of the Asian seabass was performed on an F₂ family containing 314 offspring. All family members were genotyped using 123 informative microsatellites and 22 SNPs. High percentages of n-3 polyunsaturated fatty acids (PUFA), especially C22:6 (DHA 16.48?±?3.09 %) and C20:5 (EPA 7.19?±?0.86 %) were detected in the flesh. One significant and 54 suggestive QTL for different fatty acids and a water content trait were detected on the whole genome. QTL for C18:0b was located on linkage groups (LG) 5. QTL for total n-3 PUFA content in flesh were mapped onto LG6 and LG23 with the phenotypic variance explained ranging from 3.8 to 6.3 %. Four QTL for C22:6 were detected on LG6, LG23, and LG24, explaining 3.9 to 4.9 % of the phenotypic variance, respectively. Mapping of QTL for contents of different fatty acids is the first step towards improving the omega-3 content in the fillets of fish by using marker-assisted selection and is important for understanding the biology of fatty acid deposition.