Nutritional and medical importance of gamma-linolenic acid

Ethanol extract of seeds of Oenothera odorata induces vasorelaxation via endothelium-dependent NO-cGMP signaling through activation of Akt-eNOS-sGC pathway

AIM OF STUDY

The vasorelaxant effect of ethanol extract of seeds of Oenothera odorata (Onagraceae) (one species of evening primroses) (ESOO) and its mechanisms involved were defined.

MATERIALS AND METHODS

Changes in vascular tension, guanosine 3',5'-cyclic monophosphate (cGMP) levels, and Akt expression were measured in carotid arterial rings from rats. Seeds of Oenothera odorata were extracted with ethanol (94%) and the extract was filtered, concentrated and stored at -70°C.

RESULTS

ESOO relaxed endothelium-intact, but not endothelium-denuded, carotid arterial rings in a concentration-dependent manner. Similarly, ESOO increased cGMP levels of the carotid arterial rings. Pretreatment of endothelium-intact arterial rings with L-NAME, an inhibitor of nitric oxide synthase (NOS), or ODQ, an inhibitor of soluble guanylyl cyclase (sGC), blocked the ESOO-induced vasorelaxation and increase in cGMP levels. Nominally Ca(2+)-free but not L-typed Ca(2+) channel inhibition attenuated the ESOO-induced vasorelaxation. Thapsigargin, Gd(3+), and 2-aminoethyl diphenylborinate, modulators of store-operated Ca(2+) entry (SOCE), significantly attenuated the ESOO-induced vasorelaxation and increase in cGMP levels. Further, wortmannin, an inhibitor of Akt, attenuated the ESOO-induced vasorelaxation and increases in cGMP levels and phosphorylated Akt2 expression. K(+) channel blockade with TEA, 4-aminopyridine, and glibenclamide attenuated the ESOO-induced vascular relaxation.

CONCLUSION

Taken together, the present study demonstrates that ESOO relaxes vascular smooth muscle via endothelium-dependent NO-cGMP signaling through activation of the Akt-eNOS-sGC pathway.

Differential temperature effect on the production of enhanced gamma linolenic acid in Mucor rouxii CFR-G15

Mucor rouxii CFR-G15, a locally isolated phycomycetous fungus, on cultivation at room temperature produced more than 30% (w/w) lipid in their dry cell weight, in which 14.2% accounted to be GLA content of the total fatty acids. It was observed that when incubation temperature lowered at 14°C, GLA content of the mycelium increased significantly (P<0.05) from 14.2% to 21.97%. In order to optimize the cultural conditions for high biomass and lipid production with high GLA content, the fungus was grown in association of two different temperatures and supply of additional glucose in culture medium. Maximum lipid and GLA were obtained 23.56 and 19.5% respectively, when the culture was grown at 28°C for four days and followed by addition of glucose (5%), and lowered the incubation temperature to 14°C for another four days. The presence of GLA in the oil obtained from M. rouxii CFR-G15 was confirmed by the gas chromatography-mass spectrometry. Gamma linolenic acid (GLA, n-6) is gaining importance in pharmaceutical and nutraceutical industries because of clinical evidence demonstrated that it has various beneficial effects in human health. In this paper temperature played a major role in enhancing the GLA content which has been described.

Identification and functional analysis of the genes encoding Delta6-desaturase from Ribes nigrum

Gamma-linolenic acid (gamma-linolenic acid, GLA; C18:3 Delta(6, 9, 12)) belongs to the omega-6 family and exists primarily in several plant oils, such as evening primrose oil, blackcurrant oil, and borage oil. Delta(6)-desaturase is a key enzyme involved in the synthesis of GLA. There have been no previous reports on the genes encoding Delta(6)-desaturase in blackcurrant (Ribes nigrum L.). In this research, five nearly identical copies of Delta(6)-desaturase gene-like sequences, named RnD8A, RnD8B, RnD6C, RnD6D, and RnD6E, were isolated from blackcurrant. Heterologous expression in Saccharomyces cerevisiae and/or Arabidopsis thaliana confirmed that RnD6C/D/E were Delta(6)-desaturases that could use both alpha-linolenic acids (ALA; C18:3 Delta(9,12,15)) and linoleic acid (LA; C18:2 Delta(9,12)) precursors in vivo, whereas RnD8A/B were Delta(8)-sphingolipid desaturases. Expression of GFP tagged with RnD6C/D/E showed that blackcurrant Delta(6)-desaturases were located in the mitochondrion (MIT) in yeast and the endoplasmic reticulum (ER) in tobacco. GC-MS results showed that blackcurrant accumulated GLA and octadecatetraenoic acids (OTA; C18:4 Delta(6,9,12,15)) mainly in seeds and a little in other organs and tissues. RT-PCR results showed that RnD6C and RnD6E were expressed in all the tissues at a low level, whereas RnD6D was expressed at a high level only in seeds, leading to the accumulation of GLA and OTA in seeds. This research provides new insights to our understanding of GLA synthesis and accumulation in plants and the evolutionary relationship of this class of desaturases, and new clues as to the amino acid determinants which define precise enzyme activity.

Altered lipid profile, oxidative status and hepatitis B virus interactions in human hepatocellular carcinoma

Altered membrane integrity in hepatocellular carcinoma (HCC) tissue was indicated by an elevation in cholesterol and significant decrease in phosphatidylcholine (PC). The resultant decreased phosphatidylcholine/phosphatidylethanolamine (PC/PE) and increased cholesterol/phospholipid ratios are associated with decreased fluidity in the carcinoma tissue. The lower PC was associated with a decrease in the quantitative levels of the saturated (C16:0, C18:0), omega6 (C18:2, C20:4) and omega3 (C22:5, C22:6) fatty acids (FAs), resulting in reduced long-chain polyunsaturated fatty acids (LCPUFAs), total PUFA and an increase in omega6/omega3 FA ratio. In PE, the saturated and omega3 (C22:5, C22:6) FAs were reduced while the total omega6 FA level was not affected, leading to an increased omega6/omega3 FA ratio. Increased levels of C18:1omega9, C20:2omega6 and reduction of 22:6omega3 in PC and PE suggest a dysfunctional delta-6 desaturase. The reduced PC/PE ratio resulted in a decreased C20:4omega6 (PC/PE) ratio, implying a shift towards synthesis of the 2-series eicosanoids. Lipid peroxidation was reduced in both hepatitis B negative (HBV(-)) and positive (HBV(+)) HCC tissues. Glutathione (GSH) was decreased in HCC while HBV had no effect, suggesting an impairment of the GSH redox cycle. In contrast HBV infection enhanced GSH in the surrounding tissue possibly to counter oxidative stress as indicated by the increased level of conjugated dienes. Apart from the reduced LCPUFA, the low level of lipid peroxidation in the carcinoma tissue was associated with increased superoxide dismutase and glutathione peroxidase activity. The disruption of the redox balance, resulting in increased cellular antioxidant capacity, could create an environment for resistance to oxidative stress in the carcinoma tissue. Alterations in membrane cholesterol, phospholipids, FA parameters, C20:4omega6 membrane distribution and low lipid peroxidation are likely to be important determinants underlying the selective growth advantage of HCC cells.

Polyunsaturated fatty acids and cardiovascular disease

Replacing saturated with polyunsaturated (PUFAs) rather than monounsaturated fatty acids or carbohydrates results in cardiovascular prevention over a wide range of intakes. The mechanisms by which PUFAs reduce cardiovascular risk are manifold, and the extent and precise nature of their activities is the subject of several investigations, spanning from in vitro mechanistic studies to human intervention trials. This article reviews the most up-to-date evidence of the association between PUFA consumption and reduced cardiovascular mortality.

Lipid formation and γ-linolenic acid production by Mucor circinelloides and Rhizopus sp., grown on vegetable oil

The fungi strains were tested in Bioscreen automated system to select the best nutritional source. Following, shaking submserse cultures were studied in media containing sole carbon or nitrogen source. The growth of these strains improved in media containing vegetable oil, with high concentration of lipids. The high concentration of γ-linolenic acid was obtained with M. circinelloides in culture containing sesame oil.

Suppression of superoxide anion and elastase release by C18 unsaturated fatty acids in human neutrophils

The structure-activity relationship of 18-carbon fatty acids (C(18) FAs) on human neutrophil functions and their underlying mechanism were investigated. C(18) unsaturated (U)FAs potently inhibited superoxide anion production, elastase release, and Ca(2+) mobilization at concentrations of <10 microM in formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP)-activated human neutrophils. However, neither saturated FA nor esterified UFAs inhibited these neutrophil functions. The inhibitory potencies of C(18) UFAs decreased in the following order: C(18):1 > C(18):2 > C(18):3 > C(18):4. Notably, the potency of attenuating Ca(2+) mobilization was closely correlated with decreasing cellular responses. The inhibitions of Ca(2+) mobilization by C(18) UFAs were not altered in a Ca(2+)-containing Na(+)-deprived medium. Significantly, C(18) UFAs increased the activities of plasma membrane Ca(2+)-ATPase (PMCA) in neutrophils and isolated cell membranes. In contrast, C(18) UFAs failed to alter either the cAMP level or phosphodiesterase activity. Moreover, C(18) UFAs did not reduce extracellular Ba(2+) entry in FMLP- and thapsigargin-activated neutrophils. In summary, the inhibition of neutrophil functions by C(18) UFAs is attributed to the blockade of Ca(2+) mobilization through modulation of PMCA. We also suggest that both the free carboxy group and the number of double bonds of the C(18) UFA structure are critical to providing the potent anti-inflammatory properties in human neutrophils.

Multi-targeted therapy of cancer by omega-3 fatty acids

Omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acids (PUFAs) are essential fatty acids necessary for human health. Currently, the Western diet contains a disproportionally high amount of n-6 PUFAs and low amount of n-3 PUFAs, and the resulting high n-6/n-3 ratio is thought to contribute to cardiovascular disease, inflammation, and cancer. Studies in human populations have linked high consumption of fish or fish oil to reduced risk of colon, prostate, and breast cancer, although other studies failed to find a significant association. Nonetheless, the available epidemiological evidence, combined with the demonstrated effects of n-3 PUFAs on cancer in animal and cell culture models, has motivated the development of clinical interventions using n-3 PUFAs in the prevention and treatment of cancer, as well as for nutritional support of cancer patients to reduce weight loss and modulate the immune system. In this review, we discuss the rationale for using long-chain n-3 PUFAs in cancer prevention and treatment and the challenges that such approaches pose in the design of clinical trials.

[Efficacy of omega-6 essential fatty acid treatment before and after photorefractive keratectomy]

PURPOSE

Following PRK, a regression or the appearance of haze is often observed. This type of problem may be caused by an anomalous response by the stroma, probably mediated by keratocytes. Controlling keratocyte apoptosis therefore affects the outcome and stability of PRK. Inhibiting the transmission of the apoptosis signal from the damaged corneal epithelium to the keratocytes attenuates cell activation. This can be achieved by using a systemic product that will control the release of the mediators of the inflammation and stimulate tear production. The aim of this prospective, randomized study was to test the effects of a supplement containing omega-6 fatty acids (linoleic and (-linolenic acid), (-carotene, group B vitamins and trace elements (copper, zinc), when administered both before and after PRK.

METHODS

Eighty subjects undergoing PRK were randomly divided into two groups. The group treated with omega-6 fatty acids included 18 females and 22 males, with a mean age of 32 years; the control group comprised 20 females and 20 males (mean age, 30 years). Statistical evaluation of the results was carried out on Schirmer test and fluorescein staining values and the state of the epithelium.

RESULTS

In the Schirmer tests, a comparison between the two groups of patients who underwent surgery (groups 1 and 2) showed a statistically significant difference after 7, 15, and 30 days' treatment in favor of the group treated with omega-6 fatty acids. The values relating to the fluorescein staining test and the state of the epithelium showed a statistically significant difference in favor of the group treated with omega-6 fatty acids.

CONCLUSION

These results confirm the real advantages of using omega-6 essential fatty acids to optimize and stabilize the outcome of PRK.

Clinical effects of undershirts coated with borage oil on children with atopic dermatitis: a double-blind, placebo-controlled clinical trial

It has been reported that gamma-linolenic acid contained in borage oil is effective against atopic dermatitis. The clinical effects of undershirts coated with borage oil rich in gamma-linolenic acid on atopic dermatitis were evaluated. Thirty-two children, aged 1-10 years, were involved in the clinical control study. Sixteen had worn undershirts coated with borage oil everyday for 2 weeks, and 16 had worn non-coated undershirts as a placebo. Their symptoms were assessed on a 4-point scale. Those children who had worn undershirts coated with borage oil for 2 weeks showed improvements in their erythema and itch, which were statistically significant. Transepidermal water loss from the back was decreased. In the placebo group, there were no statistically significant differences. The undershirts coated with borage oil were found to be statistically effective, and had no side-effects on children with mild atopic dermatitis.

Ethanol-induced changes in expression profiles of cell growth, fatty acid and desaturase genes of Mucor rouxii

We investigated the response of Mucor rouxii to ethanolic stress conditions. A differential response was found that was dependent on growth phase and ethanol concentration. 5% (v/v) ethanol showed an inhibitory effect on the mycelial growth of all stages. However, the ethanol sensitivity was specifically observed in active growing phases (12 and 21 h-grown cultures), in which the biomass and ratio of unsaturated/saturated fatty acids (UFA/SFA) decreased greatly after ethanol exposure compared to non-ethanol adding culture. With respect to different ethanol concentrations, M. rouxii was tolerant to low ethanol concentrations (about 1-3%, v/v) such that there was not much change in biomass and UFA/SFA ratio, in contrast to the 5% ethanol-added culture. We also showed the molecular basis of this response mechanism, demonstrating that expression of Delta(9)-, Delta(12)- and Delta(6)-desaturase genes, responsible for fatty acid desaturation in M. rouxii, were coordinately down-regulated upon exposure to ethanol stress.

Identification of a novel delta9-fatty acid desaturase gene and its promoter from oil-producing fungus Rhizopus arrhizus

Reverse Transcriptional Polymerase Chain Reaction (RT-PCR), Rapid Amplification of the cDNA ends (RACE) and Thermal asymmetric interlaced (TAIL)-PCR were used successfully to clone the open reading frame (1,377 bp) of delta9-fatty acid desaturase gene (named as RAD9) and its promoter region from oil-producing fungi Rhizopus arrhizus. Functional identification of the protein was done by sub-cloning RAD9 into the expression vector pYES2.0 to generate a recombinant plasmid pYRAD9, which was then subsequently transformed into Saccharomyces cerevisiae delta9-fatty acid desaturase mutation strain L8-14C to be expressed under the control of GAL1 promoter. The transformant containing RAD9 named as L8-14C-pYRAD9 could grow on the synthetic minimal medium plate with out oleic acid supplement. Fatty acid analysis also showed that the transformant contained 16:1 and 18:1. This indicated that pYRAD9 could successfully complement the mutation of L8-14C. Computational analysis of the nucleotide sequence of RAD9 promoter showed several basic transcriptional elements including a CAAT box, a GC box, a CACCC box, two TATA boxes and also several putative target-binding sites for transcription factors, which have been reported to be involved in the regulation of lipid metabolism. Preliminary functional analysis of this promoter in S. cerevisiae was done using lacZ report gene.

Disruption of the fatty acid Delta6-desaturase gene in the oil-producing fungus Mortierella isabellina by homologous recombination

The gamma-linolenic acid-producing fungus Mortierella isabellina 6-22 is an important industrial strain. To clarify the biosynthetic pathways for polyunsaturated fatty acids in this strain, a disruption vector pD4MI6, including 5' and 3' regions of the fatty acid Delta(6)-desaturase open reading frame as homologous recombination elements and the Escherichia coli hygromycin B (HmB) phosphotransferase gene (hph) as selectable marker, was successfully constructed. Following transformation of pD4MI6 into the hygromycin B-sensitive recipient strain M. isabellina 6-22-4, a Delta(6)-desaturase gene-defective mutant strain was selected that was unable to produce gamma-linolenic acid as determined by gas chromatography and molecular analysis. The morphology and physiology of the mutant, such as colony shape, color, and growth rate, were changed dramatically compared with that of strain M. isabellina 6-22-4.

Changes in hepatic gene expression related to innate immunity, growth and iron metabolism in GH-transgenic amago salmon (Oncorhynchus masou) by cDNA subtraction and microarray analysis, and serum lysozyme activity

Growth hormone (GH) transgenic amago salmon (Oncorhynchus masou) were generated with a construct containing the sockeye salmon GH1 gene fused to the metallothionein-B (MT-B) promoter from the same species. This transgene directed significant growth enhancement with transgenic fish reaching approximately four to five times greater weight than control salmon in F(2) and F(3) generations. This drastic growth enhancement by GH transgene is well known in fish species compared with mammals, however, such fish can show morphological abnormalities and physiological disorders like other GH transgenic animals. GH is known to have many acute effects, but currently there are no data describing the chronic effects of over-expression of GH on various hepatic genes in GH transgenic fish. Hepatic gene expression is anticipated to play very important roles in many physiological functions and growth performance of transgenic and control salmon. To examine these effects, we performed subtractive hybridization (using cDNA generated from liver RNA) in both directions to identify genes both increased and decreased in transgenic salmon relative to controls (576 clones were isolated and sequenced in total). Heme oxygenase, vitelline envelope protein, Acyl-coA binding protein, NADH dehydrogenase, mannose binding lectin-associated serine protease, hemopexin-like protein, leucyte-derived chemotaxin2 (LECT2), and many other genes were obtained in higher clone frequencies suggesting enhanced expression. In contrast, complement C3-1, lectin, rabin, alcohol dehydrogenase, Tc1-like transposase, Delta6-desaturase, and pentraxin genes were obtained in lower frequencies. Microarray analysis was also performed to obtain quantitative expression data for these subtracted cDNA clones. Analysis of fish across seasons was also conducted using both F(2) and F(3) salmon. Results of the microarray data essentially corresponded with those of the subtraction data when both F(2) and F(3) fish were completely immature, but the expression pattern was changed when fish approached maturation. Genes showing enhanced expression in GH transgenic fish in F(2) and F(3) by array analysis were vitelline envelope protein, hemopexin-like protein, heme-oxygenase, inter alpha-trypsin inhibitor, LECT2, GTP cyclohydrolase I feedback regulatory protein (GFRP), and bikunin. Reduced expression genes were lectin, Delta6-desaturase, apolipoprotein, and pentraxin. In particular, lectin was found to be highly suppressed in all F(2) and immature F(3) salmon. Further, serum lysozyme activity, one of innate immunity, was significantly (p<0.05) decreased in both F(2) and F(3) GH transgenic fish. These results indicate that the GH transgene fish had altered hepatic gene expression relating to iron-metabolism, innate immunity, reproduction, and growth.

Conjugated linoleic acid and black currant seed oil in the treatment of canine atopic dermatitis: A preliminary report

Although conjugated linoleic acid (CLA) shows inhibitory effects on histamine release, eicosanoid production and pruritus in laboratory rodents, its use in canine atopic dermatitis (AD) has not been reported. The aims of this study were to assess the efficacy of CLA, black currant seed oil (BSO) or a combination of both, compared to placebo, in dogs with AD and to evaluate any changes in fatty acid metabolism with these treatments. Twenty-four dogs with AD were randomly allocated to four groups, and were treated orally each day for two months with either 1 mL/10 kg CLA (80% purity), 1 mL/10 kg pure BSO, 1 mL/10 kg CLA+1 mL/10 kg BSO, or 1 mL/10 kg sugar syrup (placebo). Serum was obtained on days 0, 30 and 60 for analysis of CLA metabolites, linoleic acid (LA), gamma-linolenic acid (GLA), dihomo-gamma-linolenic acid (DGLA) and arachidonic acid (AA). At the same time point, the owners were asked to assess pruritus and the veterinarians evaluated any skin lesions present. Although the best clinical results occurred with BSO treatment alone, improvement of clinical signs and pruritus was not significant with any of the treatments. Serum levels of GLA and DGLA significantly increased in BSO-treated dogs, but not in the CLA+BSO group. CLA at the dosage used in this study was not efficacious in treating canine AD, whereas BSO may help some dogs with AD, although further studies are necessary before this can be recommended as a treatment.

Co-expression of the borage Delta 6 desaturase and the Arabidopsis Delta 15 desaturase results in high accumulation of stearidonic acid in the seeds of transgenic soybean

Two relatively rare fatty acids, gamma-linolenic acid (GLA) and stearidonic acid (STA), have attracted much interest due to their nutraceutical and pharmaceutical potential. STA, in particular, has been considered a valuable alternative source for omega-3 fatty acids due to its enhanced conversion efficiency in animals to eicosapentaenoic acid when compared with the more widely consumed omega-3 fatty acid, alpha-linolenic acid (ALA), present in most vegetable oils. Exploiting the wealth of information currently available on in planta oil biosynthesis and coupling this information with the tool of genetic engineering it is now feasible to deliberately perturb fatty acid pools to generate unique oils in commodity crops. In an attempt to maximize the STA content of soybean oil, a borage Delta(6) desaturase and an Arabidopsis Delta(15) desaturase were pyramided by either sexual crossing of transgenic events, re-transformation of a Delta(6) desaturase event with the Delta(15) desaturase or co-transformation of both desaturases. Expression of both desaturases in this study was under the control of the seed-specific soybean beta-conglycinin promoter. Soybean events that carried only the Delta(15 )desaturase possessed a significant elevation of ALA content, while events with both desaturases displayed a relative STA abundance greater than 29%, creating a soybean with omega-3 fatty acids representing over 60% of the fatty acid profile. Analyses of the membrane lipids in a subset of the transgenic events suggest that soybean seeds compensate for enhanced production of polyunsaturated fatty acids by increasing the relative content of palmitic acid in phosphatidylcholine and other phospholipids.

Lipids of Cunninghamella echinulata with emphasis to γ-linolenic acid distribution among lipid classes

Changes in lipid composition of the oleaginous fungus Cunninghamella echinulata were monitored during growth. Lipid fractions and individual lipid classes varied in amount, relative proportions, and fatty acid profile depending on the developmental stage. Neutral lipids (N), comprised mainly of triacylglycerol, were accumulated in the fungal mycelium during both the late exponential and the stationary growth phases with a concomitant decrease in the amount of polar lipids. While fatty acid composition of N fraction remained almost constant, individual N classes showed a noticeable alteration in gamma-linolenic acid (GLA) concentration. The glycolipid plus sphingolipid (G+S) fraction consisted mainly of monoglycosylglycerol and diglycosylglycerol. The sugar composition of G+S fraction was analyzed and showed a partial replacement of galactose for glucose as growth proceeded. Phospholipid (P) major classes were phosphatidylcholine (PC) and phosphatidylethanolamine, followed by phosphatidylinositol, phosphatidylserine, and diphosphatidylglycerol. P fatty acid composition showed significant changes with time, resulting in a considerable drop in the unsaturation index of this fraction. While in mid exponential growth phase, all P classes contained more than 20% w/w GLA of total fatty acids, and their concentration decreased to 12-17% w/w, except for the PC class where GLA concentration remained at high levels (e.g., more than 20% w/w). The constant level of GLA in PC at all growth phases suggests that PC was the major source of GLA. Sterol analysis showed that their concentration increased during growth, whereas ergosterol was the major component.

Comparative fatty acid profiling ofMucor rouxiiunder different stress conditions

To understand the relationship between fatty acid metabolism and the growth morphology of Mucor rouxii, fatty acid profiling was studied comparatively in cells grown under conditions which included different atmospheric conditions or the addition of phenethyl alcohol (PEA). The significant difference in fatty acid profiles from M. rouxii grown under aerobic or anaerobic conditions was not found to be directly related to morphological growth. Oxygen limitation, which induced the formation of pure multipolar budding yeasts, led to a decrease in long-chain fatty acids-- particularly unsaturated fatty acids-- and an increase in medium-chain saturated fatty acids, a finding which contrasted with the aerobic cultures, including mycelia and PEA-induced bipolar budding cells. High levels of C18 : 1Delta(9) were found in aerobic yeast cultures with additional PEA when compared to that in the aerobically grown mycelia. The identification of unusual fatty acids in Mucor in response to alcoholic and hypoxic stresses - including odd-numbered fatty acids and 7-hydroxy dodecanoic acid (7-OH C12 : 0) in addition to the more common fatty acids - implied that an important role existed for these unusual fatty acids.

Identification and functional characterization of the moss Physcomitrella patens delta5-desaturase gene involved in arachidonic and eicosapentaenoic acid biosynthesis

The moss Physcomitrella patens contains high levels of arachidonic acid and lesser amounts of eicosapentaenoic acid. Here we report the identification and characterization of a delta5-desaturase from P. patens that is associated with the synthesis of these fatty acids. A full-length cDNA for this desaturase was identified by data base searches based on homology to sequences of known delta5-desaturase cDNAs from fungal and algal species. The resulting P. patens cDNA encodes a 480-amino acid polypeptide that contains a predicted N-terminal cytochrome b5-like domain as well as three histidine-rich domains. Expression of the enzyme in Saccharomyces cerevisiae resulted in the production of the delta5-containing fatty acid arachidonic acid in cells that were provided di-homo-gamma-linolenic acid. In addition, the expressed enzyme generated delta5-desaturation products with the C20 substrates omega-6 eicosadienoic and omega-3 eicosatrienoic acids, but no products were detected with the C18 fatty acid linoleic and alpha-linolenic acids or with the C22 fatty acid adrenic and docosapentaenoic acids. When the corresponding P. patens genomic sequence was disrupted by replacement through homologous recombination, a dramatic alteration in the fatty acid composition was observed, i.e. an increase in di-homo-gamma-linolenic and eicosatetraenoic acids accompanied by a concomitant disappearance of the delta5-fatty acid arachidonic and eicosapentaenoic acids. In addition, overexpression of the P. patens cDNA in protoplasts isolated from a disrupted line resulted in the restoration of arachidonic acid synthesis.

The keloid phenomenon: Progress toward a solution

For centuries, keloids have been an enigma and despite considerable research to unravel this phenomenon no universally accepted treatment protocol currently exists. Historically, the etiology of keloids has been hypothesized by multiple different theories; however, a more contemporary view postulates a multifactoral basis for this disorder involving nutritional, biochemical, immunological, and genetic factors that play a role in this abnormal wound healing. Critical to the process of preventing or managing keloids is the need to locally control fibroblasts and their activities at the wound site. In recent years, considerable evidence has accumulated demonstrating the importance of fatty acids and bioactive lipids in health and disease, especially those involving inflammatory disorders or immune dysfunction. If hypertrophic scarring and keloid formation can be argued to have significant inflammatory histories, then it is possible to postulate a role for lipids in their etiology and potentially in their treatment. This report briefly visits past views and theories on keloid formation and treatment, and offers a theoretical rationale for considering adjuvant fatty acid therapy for keloid management. Sufficient scientific evidence in support of fatty acid strategies for the prevention and treatment of keloids currently exists, which offer opportunities to bridge the gap between the laboratory and the clinic. The intent of this paper is to serve as a basic guideline for researchers, nutritionists, and clinicians interested in keloids and to propose new directions for keloid management.

Gamma-linolenic acid from Cape Verdian Boraginaceae

The distribution of gamma-linolenic acid (GLA) was studied in the seed oil of six Cape Verdian Boraginaceae. The GLA ranges from trace levels in the three Heliotropum surveyed to 22.2% on saponifiable oil in Echium stenosiphon. All Echium species had GLA percentages in their seed oil around 20%. Echium seeds yield saponifiable oil from 15.8% (E. stenosiphon) to 17.3% (E. hypertropicum).

Targeted mutagenesis of a fatty acid Delta6-desaturase from Mucor rouxii: role of amino acid residues adjacent to histidine-rich motif II

The amino acid residues serine at position 213 (S213) and lysine at position 218 (K218), which are present in close proximity to the histidine-rich motif II of Mucor rouxii fatty acid Delta(6)-desaturase isoform II, were targeted for studying structure-function relationships using site-directed mutagenesis. The mutants were functionally characterized in a heterologous host, Saccharomyces cerevisiae. Substrate specificity and preference studies revealed that S213 and K218 are involved in substrate recognition. K218 plays a role in substrate preference by involvement in the binding of substrates, particularly C15-C18 monoene fatty acids. Modification of the M. rouxii Delta(6)-desaturase therefore has potential in specifically altering substrate utilization for production of desired fatty acids.

Effect of dietary lipids on plasma fatty acid profiles and prostaglandin and leptin production in gilthead seabream (Sparus aurata)

The aim of this study was to investigate the effects of different levels of substitution of fish oil by vegetable oils rich in oleic, linoleic and linolenic acids on gilthead seabream plasma and leukocyte fatty acid compositions and prostaglandin (PG) and leptin production. Juvenile seabream of 24 g initial body mass were fed four iso-energetic and iso-proteic experimental diets for 281 days. Fatty acid composition of plasma lipids was markedly affected by the inclusion of vegetable oils (VO). ARA (arachidonate), EPA (eicosapentaenoate) and DHA (docosahexaenoate) were preferentially incorporated into polar lipids of plasma, and DHGLA (di-homogammalinoleate) accumulated with increased vegetable oil inclusion. Dietary treatments resulted in alterations of DHGLA/ARA ratios, but not ARA/EPA. ARA-derived PGE(2) production in plasma was not affected by vegetable oils, in agreement with similar eicosanoid precursor ratio (ARA/EPA) in leukocytes total lipids and plasma phospholipids among fish fed with the different dietary treatments. Feeding vegetable oils leads to a decrease in plasma EPA which in turn reduced plasma PGE(3) concentration. Moreover, PGE(3) was the major prostaglandin produced in plasma of fish fed fish oil based diet. Such findings point out the importance of EPA as a precursor of prostaglandins in marine fish, at least for the correct function of the blood cells, and correlates well with the predominant role of this fatty acid in immune regulation in this species. A negative correlation was found between plasma PGE(2) and leptin plasma concentration, suggesting that circulating levels of leptin may act as a metabolic signal modulating PGE(2) release. The present study has shown that increased inclusion of vegetable oils in diet for gilthead seabream may profoundly affect the fatty acid composition of plasma and leukocytes, specially HUFA (highly unsaturated fatty acids), and consequently the production of PGE(3), which can be a major PG in plasma. Alteration in the amount and type of PG produced can be at least partially responsible for the changes in the immune system and health parameters of fish fed diets with high inclusion of VO.

Expression of thromboxane synthase, TBXAS1 and the thromboxane A2 receptor, TBXA2R, in human breast cancer

Background

Thromboxane synthase (TxS) metabolizes the cyclooxygenase product, prostaglandin H(2), into thromboxanes. Some of the thromboxanes are known to be biologically active on cancer cells. The aim of the study was to investigate the expression of thromboxane synthases, TBXAS1 and the thromboxane A2 receptor, TBXA2R in a cohort of human breast cancer patients and also to assess their potential clinical relevance.

Methods

Human breast tumour tissues (n = 120) and non-neoplastic mammary tissues (n = 32) were studied. Levels of TBXA2R and TBXAS1 transcripts were quantified using quantitative real-time RT-PCR analysis and correlated with clinical/pathological information including nodal status, grade, prognosis and long term survival (median follow-up period 120 months).

Results

Breast tumour tissue expressed higher levels of TBXA2R compared with normal mammary tissues, although the difference was not statistically significant (p = 0.09). There was no difference between tumour and normal tissues for TBXAS1. However, TBXA2R expression was significantly increased in grade 3 tumours(p = 0.006 vs grade 1), while TBXAS1 was significantly reduced in grade 3 tumours (p = 0.026 vs grade 1 tumours). A similar differential expression pattern was seen in tumours from patients with different prognosis, in that patients with predicted poor prognosis had higher, but not statistically different, levels of TBXA2R, and significantly lower levels of TBXAS1 (p = 0.008). Finally, Kaplan-Meier survival analysis has shown that patients with high levels of TBXA2R had significantly shorter disease free survival (103.8 (79.1–128.5) months) compared with those with low levels (123.7 (112.0–135.3)) months, p = 0.043.

Conclusion

Thromboxane synthases are differentially expressed in human breast cancer. While TBXA2R is highly expressed in aggressive tumours and linked with poor prognosis, TBXAS1 is expressed at significantly low levels in high grade tumours and tumour patients with poor prognosis. TBXA2R thus has a significant prognostic value in clinical breast cancer.

Improvement of the fatty acid composition of an oil-producing filamentous fungus, Mortierella alpina 1S-4, through RNA interference with delta12-desaturase gene expression

An oleaginous fungus, Mortierella alpina 1S-4, is used commercially for arachidonic acid production. Delta12-Desaturase, which desaturates oleic acid (18:1n-9) to linoleic acid (18:2n-6), is a key enzyme in the arachidonic acid biosynthetic pathway. To determine if RNA interference (RNAi) by double-stranded RNA occurs in M. alpina 1S-4, we silenced the Delta12-desaturase gene. The silenced strains accumulate 18:2n-9, 20:2n-9, and Mead acid (20:3n-9), which are not detected in either the control strain or wild type strain 1S-4. The fatty acid composition of stable transformants was similar to that of Delta12-desaturation-defective mutants previously identified. Thus, RNAi occurs in M. alpina and could be used to alter the types and relative amounts of fatty acids produced by commercial strains of this fungus without mutagenesis or other permanent changes in the genetic background of the producing strains.