The high-level accumulation of n-3 polyunsaturated fatty acids in transgenic pigs harboring the n-3 fatty acid desaturase gene from Caenorhabditis briggsae

Livestock meat is generally low in n-3 polyunsaturated fatty acids (PUFAs), which are beneficial to human health. An alternative approach to increasing the levels of n-3 PUFAs in meat is to generate transgenic livestock animals. In this study, we describe the generation of cloned pigs that express the cbr-fat-1 gene from Caenorhabditis briggsae, encoding an n-3 fatty acid desaturase. Analysis of fatty acids demonstrated that the cbr-fat-1 transgenic pigs produced high levels of n-3 fatty acids from n-6 analogs; consequently, a significantly reduced ratio of n-6/n-3 fatty acids was observed. We demonstrated that the n-3 desaturase gene from C. briggsae was functionally expressed, and had a significant effect on the fatty acid composition of the transgenic pigs, which may allow the production of pork enriched in n-3 PUFAs.     

Effects of dietary fish oil substitution by Echium oil on enterocyte and hepatocyte lipid metabolism of gilthead seabream (Sparus aurata L.)

The fatty acid profile of vegetable oils (VOs), together with the poor ability of marine fish to convert polyunsaturated fatty acids (PUFA) to highly unsaturated fatty acids (HUFA), lead to important changes in the nutritional value of farmed fish fed VO, which include increased fat and 18:2n-6 and reduced n-3 HUFA. Echium oil (EO) has a good n-3/n-6 balance as well as an interesting profile with its high content of unusual fatty acids (SDA, 18:4n-3 and GLA, 18:3n-6) that are of increasing pharmacological interest. The effects of substituting 50 % of dietary fish oil (FO) by EO on gilthead seabream (Sparus aurata L.) enterocyte and hepatocyte lipid metabolism were studied. After 4 months of feeding, cell viability, total lipid contents and lipid class compositions were not affected by EO. The cells clearly reflected the fatty acid profile of the EO showing increased SDA, GLA and its elongation product 20:3n-6, and only minorly decreased n-3 HUFA compared to other VO. Metabolism of [1-¹⁴C]18:2n-6 and [1-¹⁴C]18:3n-3 was also unaffected by EO in terms of total uptake, incorporation, β-oxidation and elongation–desaturation activities.     

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

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

Metabolism of linoleic and α-linolenic acids in cultured cardiomyocytes: Effect of different N-6 and N-3 fatty acid supplementation

The metabolites of linoleic (LA) and -linolenic (ALA) acids are involved in coronary heart disease. Both n-6 and n-3 essential fatty acids (EFAs) are likely to be important in prevention of atherosclerosis since the common risk factors are associated with their reduced 6-desaturation. We previously demonstrated the ability of heart tissue to desaturate LA. In this study we examined the ability of cultured cardiomyocytes to metabolize both LA and ALA in vivo, in the absence and in the presence of gamma linolenic acid (GLA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) alone or combined together. In control conditions, about 25% of LA and about 90% of ALA were converted in PUFAs. GLA supplementation had no influence on LA conversion to more unsaturated fatty acids, while the addition of n-3 fatty acids, alone or combined together, significantly decreased the formation of interconversion products from LA. Using the combination of n-6 and n-3 PUFAs, GLA seemed to counterbalance partially the inhibitory effect of EPA and DHA on LA desaturation/elongation. The conversion of ALA to more unsaturated metabolites was greatly affected by GLA supplementation. Each supplemented fatty acid was incorporated to a significant extent into cardiomyocyte lipids, as revealed by gas chromatographic analysis. The n-6/n-3 fatty acid ratio was greatly influenced by the different supplementations; the ratio in GLA+EPA+DHA supplemented cardiomyocytes was the most similar to that recorded in control cardiomyocytes. Since important risk factors for coronary disease may be associated with reduced 6-desaturation of the parent EFAs, administration of n-6 or n-3 EFA metabolites alone could cause undesirable effects. Since they appear to have different and synergistic roles, only combined treatment with both n-6 and n-3 metabolites is likely to achieve optimum results.     

Comparison of stearidonic acid and alpha-linolenic acid on PGE2 production and COX-2 protein levels in MDA-MB-231 breast cancer cell cultures

The bioactivity of stearidonic acid (SDA, 18:4n-3) and alpha-linolenic acid (LNA, 18:3n-3) on cyclooxygenase-2 (COX-2) enzyme expression and prostaglandin E2 (PGE2) production has not been evaluated. This investigation examined the effects of SDA and LNA on PGE2 biosynthesis and COX-2 protein and mRNA levels in MDA-MB-231 human breast cancer cells. Cells were supplemented with SDA, LNA, linoleic acid and arachidonic acid (AA) at concentrations ranging from 10 to 200 microM. At 50 and 200 microM, both SDA and LNA treatments and their combinations reduced PGE2 production as compared with AA. At 50 microM, SDA treatment also lowered the COX-2 protein level as compared with the vehicle, but this reduction was not observed with the LNA treatment. Gas chromatographic analysis of fatty acids in cellular lipids of breast cancer cells revealed that SDA led to significantly greater concentrations of 20:5n-3 and other long-chain (LC) n-3 polyunsaturated fatty acids (PUFAs) (20:4n-3, 22:4n-3 and 22:5n-3) as compared with the LNA treatment. Both SDA and LNA reduced the level of 20:4n-6; however, SDA was more effective than LNA in decreasing the ratio of n-6/n-3 PUFAs in cells. In addition, SDA was more potent than LNA in suppressing the expression of the COX-2 gene, which was associated with the reduction in the levels of nuclear factor kappa B and peroxisome proliferator-activated receptor gamma mRNA. This study showed that although PGE2 production in MDA-MB-231 breast cancer cells was not significantly different between the SDA and LNA treatments, SDA was more effective than LNA in converting into LC n-3 PUFAs and in reducing COX-2 protein and mRNA levels.     

Metabolic engineering of soybean seeds for enhanced vitamin E tocochromanol content and effects on oil antioxidant properties in polyunsaturated fatty acid-rich germplasm

Soybean seeds produce oil enriched in oxidatively unstable polyunsaturated fatty acids (PUFAs) and are also a potential biotechnological platform for synthesis of oils with nutritional omega-3 PUFAs. In this study, we engineered soybeans for seed-specific expression of a barley homogentisate geranylgeranyl transferase (HGGT) transgene alone and with a soybean γ-tocopherol methyltransferase (γ-TMT) transgene. Seeds for HGGT-expressing lines had 8- to 10-fold increases in total vitamin E tocochromanols, principally as tocotrienols, with little effect on seed oil or protein concentrations. Tocochromanols were primarily in δ- and γ-forms, which were shifted largely to α- and β-tocochromanols with γ-TMT co-expression. We tested whether oxidative stability of conventional or PUFA-enhanced soybean oil could be improved by metabolic engineering for increased vitamin E antioxidants. Selected lines were crossed with a stearidonic acid (SDA, 18:4^Δ6,9,12,15)-producing line, resulting in progeny with oil enriched in SDA and α- or γ-linoleic acid (ALA, 18:3^Δ9,12,15 or GLA, 18:3^Δ6,9,12), from transgene segregation. Oil extracted from HGGT-expressing lines had ≥6-fold increase in free radical scavenging activity compared to controls. However, the oxidative stability index of oil from vitamin E-enhanced lines was ~15% lower than that of oil from non-engineered seeds and nearly the same or modestly increased in oil from the GLA, ALA and SDA backgrounds relative to controls. These findings show that soybean is an effective platform for producing high levels of free-radical scavenging vitamin E antioxidants, but this trait may have negative effects on oxidative stability of conventional oil or only modest improvement of the oxidative stability of PUFA-enhanced oil.     

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.     

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

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

Identification and functional characterization of polyunsaturated fatty acid elongase (McELOVL5) gene from pike eel (Muraenesox cinereus)

The cDNA coding for a polyunsaturated fatty acid elongase (McELOVL5) was isolated from the brain of the pike eel (Muraenesox cinereus) being based on available sequences in 23 types of fish. Four sequence variants were identified with different amino acid substitutions as compared with two clones of McELOVL5 gene (McELOVL5 11.7 and McELOVL5 12.4). When the two variants of McELOVL5 were expressed in Saccharomyces cerevisiae, the two recombinant yeasts elongated γ-linolenic acid (GLA, 18:3n-6) to di-homo-γ-linolenic acid (DGLA, 20:3n-6) but differed in the rate of GLA conversion to DGLA. Cells transformed with McELOVL5 12.4 also converted arachidonic acid (20:4n-6) and eicosapentaenoic acid (20:5n-3) to docosatetraenoic acid (22:4n-6) and docosapentaenoic acid (22:5n-3), respectively. However McELOVL5 11.7 lost its function for the elongation of C₂₀ fatty acids. The four sequence variants have changed substrate specificities. Three-dimensional models of the McELOVL5 proteins are suggested.     

Gene and protein expression profiling of the fat-1 mouse brain

Polyunsaturated fatty acids (PUFAs) are essential structural components of all cell membranes and, more so, of the central nervous system. Several studies revealed that n-3 PUFAs possess anti-inflammatory actions and are useful in the treatment of dyslipidemia. These actions explain the beneficial actions of n-3 PUFAs in the management of cardiovascular diseases, inflammatory conditions, neuronal dysfunction, and cancer. But, the exact molecular targets of these beneficial actions of n-3 PUFAs are not known. Mice engineered to carry a fat-1 gene from Caenorhabditis elegans add a double bond into an unsaturated fatty acid hydrocarbon chain and convert n-6 to n-3 fatty acids. This results in an abundance of n-3 eicosapentaenoic acid and docosapentaenoic acid specifically in the brain and a reduction in n-6 fatty acids of these mice that can be used to evaluate the actions of n-3 PUFAs. Gene expression profile, RT-PCR and protein microarray studies in the hippocampus and whole brain of wild-type and fat-1 transgenic mice revealed that genes and proteins concerned with inflammation, apoptosis, neurotransmission, and neuronal growth and synapse formation are specifically modulated in fat-1 mice. These results may explain as to why n-3 PUFAs are of benefit in the prevention and treatment of diseases such as Alzheimer's disease, schizophrenia and other diseases associated with neuronal dysfunction, low-grade systemic inflammatory conditions, and bronchial asthma. Based on these data, it is evident that n-3 PUFAs act to modulate specific genes and formation of their protein products and thus, bring about their various beneficial actions.     

Coexpression of Elo-like enzyme and Δ5, Δ4-desaturases derived from Thraustochytrium aureum ATCC 34304 and the production of DHA and DPA in Pichia pastoris

Thraustochytrium aureum ATCC 34304 produces a high level of polyunsaturated fatty acids (PUFAs), which are typically synthesized by strings of reactions catalyzed by desaturase and elongase enzymes. In this study, the genes related to the biosynthesis of PUFAs were investigated and targeted to enable optimization of the production of PUFAs. To the best of our knowledge, this is first study to evaluate the co-expression of genes TaElo, Tad5, and Tad4genes derived from T. aureum. We found that C22 PUFAs such as docosapentaenoic acid (DPA, C22:5n–6) and docosahexaenoic acid (DHA, 22:6n–3) were synthesized from γ-linolenic acid (GLA, C18:3n–6) and stearidonic acid (SDA, C18:4n–3), respectively, as exogenous substrates via a series of reactions catalyzed by an Elo-like enzyme and Δ5, Δ4-desaturase enzymes. In addition, the results of this study revealed that the TaElo gene could synthesize the Δ6-and Δ5-elongation products. Taken together, these results confirmed that the Elo-like enzyme was involved in multiple reactions leading to the production of PUFAs and that the TaElo, Tad5, and Tad4 genes were capable of functioning together to produce DPA and DHA using GLA and SDA.     

Alteration of plasma phospholipid fatty acid profile in patients with septic shock

In septic shock patients, alterations of plasma phospholipid fatty acid profile have never been described. The purpose of this monocentric, non-interventional, observational prospective study was to describe this fatty acid profile in the early phase of septic shock in intensive care unit. Thirty-seven adult patients with septic shock were included after the first day of stay in intensive care unit, before any form of artificial nutritional support. Plasma phospholipid fatty acid composition was determined by gas chromatography. All biological data from patients with septic shock were compared with laboratory reference values. Patients presented hypocholesterolemia and hypertriglyceridemia. They had low concentrations of phospholipid fatty acids specifically n-6 and n-3 polyunsaturated fatty acids (PUFAs) with a high n-6/n-3 ratio. Plasma phospholipid PUFA concentrations were strongly correlated with cholesterolemia. PUFAs/SFAs (saturated fatty acids) and PUFAs/MUFAs (monounsaturated fatty acids) ratios were low because of low percentage of n-6 and n-3 PUFAs and high percentage of SFAs and MUFAs. Low levels of plasma long chain PUFAs (≥20 carbons) were significantly associated with mortality at 28th day. In conclusion, plasma phospholipid FA profile of septic patients is very characteristic, close to that of acute respiratory distress syndrome and mortality is associated with long chain PUFA decrease. This profile could be explained by numerous non-exclusive physio-pathological processes 1) an activation of hepatic de novo lipogenesis that could contribute to hepatic steatosis, 2) an elevated adipose tissue lipolysis, 3) an increased free radical attack of FA by oxidative stress, 4) an over-production of inflammatory lipid mediators.     

Association of Plasma Phospholipid n-3 and n-6 Polyunsaturated Fatty Acids with Type 2 Diabetes: The EPIC-InterAct Case-Cohort Study

BackgroundWhether and how n-3 and n-6 polyunsaturated fatty acids (PUFAs) are related to type 2 diabetes (T2D) is debated. Objectively measured plasma PUFAs can help to clarify these associations.ConclusionsThese large-scale findings suggest an important inverse association of circulating plant-origin n-3 PUFA (ALA) but no convincing association of marine-derived n3 PUFAs (EPA and DHA) with T2D. Moreover, they highlight that the most abundant n6-PUFA (LA) is inversely associated with T2D. The detection of associations with previously less well-investigated PUFAs points to the importance of considering individual fatty acids rather than focusing on fatty acid class.     

Functional characterization of a delta 6-desaturase gene from the black seabream (<Emphasis Type="Italic">Acanthopagrus schlegeli</Emphasis>)

Delta 6-fatty acid desaturase (D6DES) is used in the synthesis of polyunsaturated fatty acids (PUFAs) from microorganisms to higher animals, including arachidonic acid (ARA) and eicosapentaenoic acid (EPA). A 1,338 bp full-length cDNA encoding D6DES was cloned from Acanthopagrus schlegeli (AsD6DES) through degenerate- and RACE-PCR methods. A recombinant vector expressing AsD6DES (pYES-AsD6DES) was subsequently constructed and transformed into Saccharomyces cerevisiae to test the enzymatic activity of AsD6DES towards the production of n-6 and n-3 fatty acids. The exogenously expressed AsD6DES produced γ-linolenic acid (18:3 n-6) and stearidonic acid (18:4n-3) at 26 and 36% from exogenous linoleic acid (18:2n-6) and α-linolenic acid (18:3n-3), respectively, indicating that it is essentially a delta 6-fatty acid desaturase.     

Gene transfer of the Caenorhabditis elegans n-3 fatty acid desaturase inhibits neuronal apoptosis

Previous studies have shown that n-3 polyunsaturated fatty acids (PUFAs) can exert an antiapoptotic effect on neurons. The present study was designed to investigate whether the Caenorhabditis elegans fat-1 gene encoding an n-3 fatty acid desaturase (an enzyme that converts n-6 PUFAs to corresponding n-3 PUFAs) can be expressed functionally in rat cortical neurons and whether its expression can change the ratio of n-6 : n-3 fatty acids in the cell membrane and exert an effect on neuronal apoptosis. Infection of primary rat cortical cultures with Ad-fat-1 resulted in high expression of the fat-1 gene. Lipid analysis indicated a decrease in the ratio of n-6 : n-3 PUFAs from 5.9 : 1 in control cells, to 1.45 : 1 in cells expressing the n-3 fatty acid desaturase. Accordingly, the levels of prostaglandin E2, an eicosanoid derived from n-6 PUFA, were significantly lower in cells infected with Ad-fat-1 when compared with control cells. Finally, there was a significant inhibition of growth factor withdrawal-induced apoptotic cell death in neurons expressing the fat-1 gene. These results demonstrate that expression of the fat-1 gene can inhibit apoptotic cell death in neurons and suggest that the change in the n-6 : n-3 fatty acid ratio may play a key role in this protective effect.     

Cloning and functional characterisation of a fatty acyl elongase from southern bluefin tuna (Thunnus maccoyii)

The synthesis of long chain polyunsaturated fatty acids (LCPUFA), such as eicosapentaenoic acid (EPA; 20:5n-3) and docosahexaenoic acid (DHA; 22:6n-3), involves fatty acyl desaturase and elongase enzymes. The marine fish species southern bluefin tuna (SBT) can accumulate large quantities of omega-3 (n-3) LCPUFA in its flesh but their capacity to synthesize EPA and DHA is uncertain. A cDNA, sbtElovl5, encoding a putative fatty acyl elongase was amplified from SBT liver tissue. The cDNA included an open reading frame (ORF) encoding 294 amino acids. Sequence comparisons and phylogenetic analyses revealed a high level of sequence conservation between sbtElovl5 and fatty acyl elongase sequences from other fish species. Heterologous expression of the sbtElovl5 ORF in Saccharomyces cerevisiae confirmed that it encoded a fatty acyl elongase capable of elongating C_18/20 polyunsaturated fatty acid (PUFA) substrates, but not C₂₂ PUFA substrates. For the first time in an Elovl5, the substrate competition occurring in nature was investigated. Higher activity towards n-3 PUFA substrates than omega-6 (n-6) PUFA substrates was exhibited, regardless of substrate chain length. The sbtElovl5 preferentially elongated 18:4n-3 and 18:3n-6 rather than 20:5n-3 and 20:4n-6. The sbtElovl5 enzyme also elongated saturated and monounsaturated fatty acids.     

Unsaturated fatty acids differ between hepatic colorectal metastases and liver tissue without tumour in humans: Results from a randomised controlled trial of intravenous eicosapentaenoic and docosahexaenoic acids

IntroductionMediators derived from the n-6 polyunsaturated fatty acid (PUFA) arachidonic acid oxidation have been shown to have tumour promoting effects in experimental models, while n-3 PUFAs are thought to be protective. Here we report fatty acid concentrations in hepatic colorectal metastases compared to liver tissue without tumour in humans.MethodsTwenty patients with colorectal liver metastasis were randomized to receive a 72 h infusion of parenteral nutrition with or without n-3 PUFAs. Histological samples from liver metastases and liver tissue without tumour were obtained from 15 patients at the time of their subsequent liver resection (mean 8 days (range 4–12) post-infusion) and the fatty acid composition determined by gas chromatography.ResultsThere were no significant differences in fatty acid composition between the two intervention groups. When data from all patients were combined, liver tissue without tumour had a higher content of both n-3 and n-6 PUFAs and a lower content of oleic acid and total n-9 fatty acids compared with tumour tissue (p<0.0001, 0.0002,<0.0001 and <0.0001, respectively). The n-6/n-3 PUFA ratio was found to be higher in tumour tissue than tissue without tumour (p<0.0001).ConclusionsHepatic colorectal adenocarcinoma metastases have a higher content of n-9 fatty acids and a lower content of n-6 and n-3 PUFAs than liver tissue without tumour.     

BIOCHEMICAL COMPOSITION AND FATTY ACID CONTENT OF FILAMENTOUS NITROGEN-FIXING CYANOBACTERIA

The biochemical composition and fatty acid content of twelve strains of filamentous, heterocystous, nitrogen-fixing cyanobacteria have been determined. When grown under diazotrophic conditions, protein, carbohydrate, lipid, and nucleic acids comprised 37–52%, 16–38%, 8–13%, and 8–11% of the dry weight, respectively. The presence of a combined nitrogen source resulted in an increase in the protein content of the cells and a decrease in the levels of lipids and carbohydrates, although biomass productivity was not affected significantly. Biochemical composition also changed during culture growth, with the highest levels of proteins and lipids occurring as the culture entered stationary phase, whereas the highest levels of carbohydrate and nucleic acids were found during the exponential phase. Total fatty acid levels in the strains assayed ranged between 3 and 5.7% of the dry weight. With regard to fatty acid composition, all strains showed high levels of polyunsaturated fatty acids (PUFAs) and saturated fatty acids (SAFAs), with values of 24–45% and 31–52% of total fatty acids, respectively, whereas the levels of monounsaturated fatty acids (MUFAs) were in general lower (11– 32%). Palmitic acid (16:0) was the most prevalent SAFA, whereas palmitoleic (16:1n- 7) and oleic acid (18:1n-9) were the most abundant MUFAs in all the strains. Among PUFAs, γ-linolenic acid (GLA, 18:3n-6) was present at high levels (18% of total fatty acids) in Nostoc sp. (Chile) and at lower levels (3.6% of total fatty acids) in Anabaenopsis sp. The presence of GLA has not been previously reported in these genera of cyanobacteria. The rest of the strains exhibited high levels (12–35% of total fatty acids) of α-linolenic acid (ALA, 18:3n-3). Linoleic acid (18:2n-6) was also present at a substantial level in most of the strains. Eicosapentaenoic acid (EPA, 20:5n-3) was also detected in Nostoc sp. (Albufera). Some filamentous nitrogen-fixing cyanobacteria therefore represent potential sources of commercially interesting fatty acids.