Fatty acid desaturase 2 (FADS2) but not FADS1 desaturates branched chain and odd chain saturated fatty acids

Branched chain fatty acids (BCFA) and linear chain/normal odd chain fatty acids (n-OCFA) are major fatty acids in human skin lipids, especially sebaceous gland (SG) wax esters. Skin lipids contain variable amounts of monounsaturated BCFA and n-OCFA, in some reports exceeding over 20% of total fatty acids. Fatty acid desaturase 2 (FADS2) codes for a multifunctional enzyme that catalyzes Δ4-, Δ6- and Δ8-desaturation towards ten unsaturated fatty acids but only one saturate, palmitic acid, converting it to 16:1n-10; FADS2 is not active towards 14:0 or 18:0. Here we test the hypothesis that FADS2 also operates on BCFA and n-OCFA. MCF-7 cancer cells stably expressing FADS1 or FADS2 along with empty vector control cells were incubated with anteiso-15:0, iso-16:0, iso-17:0, anteiso-17:0, iso-18:0, or n-17:0. BCFA were Δ6-desaturated by FADS2 as follows: iso-16:0 → iso-6Z-16:1, iso-17:0 → iso-6Z-17:1, anteiso-17:0 → anteiso-6Z-17:1 and iso-18:0 → iso-6Z-18:1. anteiso-15:0 was not desaturated in either FADS1 or FADS2 cells. n-17:0 was converted to both n-6Z-17:1 by FADS2 Δ6-desaturation and n-9Z-17:1 by SCD Δ9-desaturation. We thus establish novel FADS2-coded enzymatic activity towards BCFA and n-OCFA, expanding the number of known FADS2 saturated fatty acid substrates from one to six. Because of the importance of FADS2 in human skin, our results imply that dysfunction in activity of sebaceous FADS2 may play a role in skin abnormalities associated with skin lipids.     

Apocryphal FADS2 activity promotes fatty acid diversification in cancer

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Fatty acid composition of chicken breast meat is dependent on genotype-related variation of FADS1 and FADS2 gene expression and desaturating activity

In Western countries the dietary guidance emphasizes the need to decrease the intake of saturated fatty acids and to replace them with polyunsaturated fatty acids (PUFA), particularly long chain n-3 PUFA (LC-PUFA). The production of poultry meat having a lower fat content and healthier fatty acid (FA) profile is a hot topic for the poultry industry, and the possibility to identify genotypes able to produce meat with a higher LC-PUFA content deserves attention. The aims of the present study were to evidence in chicken (i) a genotype-related different expression of the desaturating enzymes delta-6 (Δ6, EC 1.14.99.25), delta-5 (Δ5, EC 1.14.19.) and delta-9 (Δ9, EC 1.14.19.1); (ii) the impact of the hypothesized different expression on the meat FA composition; (iii) the distribution of desaturase products in the different lipid classes. Slow (SG), medium (MG) and fast (FG) growing chickens fed the same diet were evaluated either for the relative expression of FADS1, FADS2 and SCD1 genes in liver (by q-PCR), or for the FA composition of breast meat. MG and particularly SG birds showed a greater expression of FADS2 and FADS1 genes, a higher Δ6 and Δ5 activity (estimated using desaturase indices), and consequently a higher LC-PUFA content in the breast meat than FG birds. The relationship between genotype and desaturating ability was demonstrated, with a significant impact on the PUFA content of breast meat. Due to the high consumption rate of avian meat, the identification of the best genotypes for meat production could represent an important goal not only for the food industry, but also for the improvement of human nutrition.     

Polyunsaturated fatty acid production by marine bacteria

Polyunsaturated fatty acids are important in maintaining human health. Limitations associated with current sources of ω-3 fatty acids and ω-6 fatty acids, from animal and plant sources, have led to increased interest in microbial production. Marine bacteria may provide a suitable alternative, although the isolation of production strains and the identification of operating conditions must be addressed before manufacturing processes become economically viable. Marine isolate 560 was identified as an eicosapentaenoic acid (EPA) producer via GC/MS. The isolate was initially identified as Vibrio cyclitrophicus by 16S rRNA sequencing. Statistically based experimental designs were applied to the optimisation of medium components and environmental factors for the production of EPA. A Plackett–Burman design was used to screen for the effect of temperature, pH, and media components. Subsequently, the concentrations of NaCl, yeast extract, and peptone, identified as significant factors, were optimised using a central composite design. The predicted optimal combination of media components for maximum EPA production (4.8 mg/g dry weight) was determined as 7.9 g/l peptone, 16.2 g/l NaCl, and 6.2 g/l yeast extract. On transfer of this process to bioreactor cultivation, where a range of pH and DO values were tested, the maximum amount of EPA produced increased to 7.5 mg/g dry weight and 10 % of the total fatty acid.     

Polyunsaturated fatty acid status of Dutch vegans and omnivores

We compared the polyunsaturated fatty acid (PUFA) status of Dutch vegans and omnivores to investigate whether disparities can be explained by different diets and long chain PUFA (LCP) synthesis rates. Dietary intakes and fatty acid compositions of erythrocytes (RBC), platelets (PLT), plasma cholesterol esters (CE) and plasma triglycerides (TG) of 12 strict vegans and 15 age- and sex-matched omnivores were determined. Vegans had higher omega 6 (CE, TG), 18:2 omega 6 (RBC, CE, TG), 18:3 omega 6 (TG), 20:3 omega 6 (TG), 22:4 omega 6 (TG), 22:5 omega 3 (RBC, PLT), 22:5 omega 3/22:6 omega 3 (RBC, PLT) and 22:5 omega 6/22:6 omega 3 (RBC, PLT), and lower 22:4 omega 6 (RBC, PLT), 22:4 omega 6/22:5 omega 6 (RBC, PLT), omega 3 (CE), LCP omega 3 (CE, TG), 20:5 omega 3 (RBC, PLT, CE), 22:5 omega 3 (TG) and 22:6 omega 3 (all compartments). Vegans had lower 20:4 omega 6 (TG) after normalization of PUFA to 100%, and normalization of eicosanoid precursors to 100% revealed similar 20:4 omega 6 (all), higher 20:3 omega 6 (TG) and lower 20:5 omega 3 (all). High omega 6 (notably 18:2 omega 6) and low omega 3 (notably 20:5 omega 3, 22:6 omega 3) status in Dutch vegans derives from low dietary LCP omega 3 and 18:3 omega 3/18:2 omega 6 ratio. Higher 18:3 omega 6 and 20:3 omega 6 in their TG may reflect higher hepatic 20:4 omega 6 production rate, whereas higher 20:4 omega 6 and 22:4 omega 6 in omnivores indicates 20:4 omega 6 intake from meat.     

Changes in rat n-3 and n-6 fatty acid composition during pregnancy are associated with progesterone concentrations and hepatic FADS2 expression

The mechanisms responsible for changes to long-chain polyunsaturated fatty acid (LC PUFA) status during pregnancy have not been fully elucidated. Tissue samples were collected from virgin and pregnant (day 12 and 20) female rats. LC PUFA status, sex hormone concentrations and hepatic mRNA expression of FADS1, FADS2 and elongase were assessed. Day 20 gestation females had higher plasma and liver docosahexaenoic acid and lower arachidonic acid content than virgin females (P<0.05). There was higher FADS2 mRNA expression during pregnancy (P=0.051). Progesterone and oestradiol concentrations positively correlated with hepatic FADS2 mRNA expression (P=0.043, P=0.004). Progesterone concentration positively correlated with hepatic n-6 docosapentaenoic acid content (P=0.006), and inversely correlated with intermediates in LC PUFA synthesis including n-3 docosapentaenoic acid, γ-linolenic acid and 20:2n-6 (P<0.05). Changes in progesterone and oestradiol during pregnancy may promote the synthesis of LC PUFA via increased FADS2 expression.     

Polyunsaturated fatty acid biosynthesis: a microsomal-peroxisomal process.

The synthesis of 22-carbon fatty acids, with their first double bond at position 4, requires the participation of enzymes in both peroxisomes and the endoplasmic reticulum as well as the controlled movement of fatty acids between these two cellular compartments. It has been observed that there is generally an inverse relationship between rates of peroxisomal beta-oxidation vs those for the microsomal esterification of fatty acids into 1-acyl-sn-glycero-3-phosphocholine. With a variety of different substrates it was found that when a fatty acid is produced in peroxisomes, with its first double bond at position 4, its preferred metabolic fate is to move to microsomes for esterification rather than to serve as a substrate for continued degradation. The required movement, and the associated reactions, in peroxisomes and microsomes is not restricted to the synthesis of 4,7,10,13,16-docosapentaenoic acid and 4,7,10,13,16,19-docosahexaenoic acid. When microsomes and peroxisomes were incubated with NAD, NADPH and malonyl-CoA it was found that 6,9,12-octadecatrienoic acid was metabolized to linoleate. Collectively our findings suggest that there may be considerably more recycling of fatty acids between peroxisomes and the endoplasmic reticulum than was previously recognized.     

Variants of the FADS1 FADS2 gene cluster, blood levels of polyunsaturated fatty acids and eczema in children within the first 2 years of life

Background

Association of genetic-variants in the FADS1-FADS2-gene-cluster with fatty-acid-composition in blood of adult-populations is well established. We analyze this genetic-association in two children-cohort-studies. In addition, the association between variants in the FADS-gene-cluster and blood-fatty-acid-composition with eczema was studied.

Methods and Principal Findings

Data of two population-based-birth-cohorts in the Netherlands and Germany (KOALA, LISA) were pooled (n = 879) and analyzed by (logistic) regression regarding the mutual influence of single-nucleotide-polymorphisms (SNPs) in the FADS-gene-cluster (rs174545, rs174546, rs174556, rs174561, rs3834458), on polyunsaturated fatty acids (PUFA) in blood and parent-reported eczema until the age of 2 years. All SNPs were highly significantly associated with all PUFAs except for alpha-linolenic-acid and eicosapentaenoic-acid, also after correction for multiple-testing. All tested SNPs showed associations with eczema in the LISA-study, but not in the KOALA-study. None of the PUFAs was significantly associated with eczema neither in the pooled nor in the analyses stratified by study-cohort.

Conclusions and Significance

PUFA-composition in young children''s blood is under strong control of the FADS-gene-cluster. Inconsistent results were found for a link between these genetic-variants with eczema. PUFA in blood was not associated with eczema. Thus the hypothesis of an inflammatory-link between PUFA and eczema by the metabolic-pathway of LC-PUFAs as precursors for inflammatory prostaglandins and leukotrienes could not be confirmed by these data.     

Polyunsaturated fatty acid biosynthesis in Saccharomyces cerevisiae: expression of ethanol tolerance and the FAD2 gene from Arabidopsis thaliana.

The Arabidopsis thaliana delta-12 fatty acid desaturase gene (FAD2) was overexpressed in Saccharomyces cerevisiae by using the GAL1 promoter. S. cerevisiae harboring the FAD2 gene was capable of forming hexadecadienoyl (16:2) and linoleoyl (18:2) residues in the membrane lipid when cultured in medium containing galactose. Gas-liquid chromatography analysis of total lipids indicated that the transformed S. cerevisiae accumulated these dienoic fatty acyl residues and that they accounted for approximately 50% of the total fatty acyl residues. Phospholipid analysis of this strain indicated that the oleoyl (18:1) residue binding phosphatidylcholine (PC) was mostly converted to the 18:2 residue binding PC, whereas 50% of the palmitoleoyl (16:1) residue binding PC was converted to the 16:2 residue binding PC. A marked effect on the unsaturation of 16:1 and 18:1 was observed when S. cerevisiae harboring the FAD2 gene was cultured at 8 degrees C. To assess the ethanol tolerance of S. cerevisiae producing polyunsaturated fatty acids, the cell viability of this strain in the presence of ethanol was examined. The results indicated that S. cerevisiae cells overexpressing the FAD2 gene had greater resistance to 15% (vol/vol) ethanol than did the control cells.     

Cloning and characterization of chicken adipocyte fatty acid binding protein gene

Fatty acid binding proteins (FABPs) are members of a superfamily of lipid-binding proteins and occur intracellularly in vertebrates and invertebrates. This study was designed to clone and characterize the adipocyte fatty acid binding protein (A-FABP) gene in the chicken. PCR primers were designed according to mammalian A-FABP gene sequence to amplify partial cDNA of A-FABP gene from chicken adipose tissues, and the full length of the gene was cloned by 5'RACE and 3'RACE. Analysis of sequence showed that the cDNA of the chicken A-FABP gene was 74 and 73% homologous with porcine and human A-FABP gene, respectively. The similarity was 77, 28, and 23% at the predicted amino acid level with human A-FABP, human L-FABP, and human I-FABP, respectively. RT-PCR and Northern blot analysis indicated that the chicken A-FABP gene, similar to that of the mammal, is only expressed in fat tissues. This is the first report to identify and characterize A-FABP gene in the chicken.     

Polyunsaturated fatty acid metabolism in neuroblastoma cells in culture.

Neuroblastoma cell cultures took up linoleic and linolenic acids at approximately equal rates, and incorporated them into a variety of lipid fractions, principally cellular phospholipids. Linoleic acid was preferentially incorporated into choline phosphoglycerides, while most of the radioactivity derived from linolenic acid entered ethanolamine phosphoglycerides. There was no evidence for direct transfer of fatty acids between these two phosphoglyceride fractions. When, after the addition of cytosine arabinoside, cell division was arrested, the entry of labelled fatty acids into ethanolamine and serine phosphoglycerides was reduced, suggesting that these lipids are involved in the formation of new cell membranes. In the ethanolamine phosphoglyceride fraction, phosphatidal ethanolamine (plasmalogen) was the principal acceptor for the higher polyunsaturated fatty acids of the φ 3 series. The ratio of labelled fatty acids entering ethanolamine plasmalogens to that entering ethanolamine phosphoglycerides increased following the addition of cytosine arabinoside, suggesting plasmalogens to be involved in formation of cell processes. The first step in the metabolism of both linoleic and linolenic acid was the addition of a two-carbon unit. Conversion of linoleic acid to higher polyunsaturated fatty acids was slower than the conversion of linolenic acid to its higher analogues. This contrasted with the behaviour of dissociated cultures of normal brain cells which were able to form higher analogues of linoleic and linolenic acids at nearly equal rates.     

Polyunsaturated fatty acid supplements modulate mast cell membrane microdomain composition

In the present study, the lipid raft composition of a canine mastocytoma cell line (C2) was analyzed. Lipid rafts were well separated from non-raft plasma membranes using a detergent-free isolation technique. To study the influence of n-3 and n-6 polyunsaturated fatty acids (PUFA) on raft fatty acid composition in comparison to non-raft cell membrane, C2 were supplemented with one of the following: α-linolenic acid, eicosapentaenoic acid, docosahexaenoic acid, linoleic acid or arachidonic acid. Enrichment of the culture medium with a specific PUFA resulted in an increase in the content of this fatty acid both in rafts and non-raft membranes. Contents of cholesterol and protein were found not to be affected by the changes in the fatty acid profiles. In conclusion, our data provide strong evidence that PUFA modulate lipid composition and physiological properties of membrane micro domains of mast cells which in turn may have effects on mast cell function.