Metabolic characterization of sciadonic acid (5c,11c,14c-eicosatrienoic acid) as an effective substitute for arachidonate of phosphatidylinositol

Unusual polyunsaturated fatty acids in edible marine worms identified by covalent adduct chemical ionization mass spectrometry

Non-traditional seafood, such as spoon worms (Urechis unicinctus) and peanut worms (Sipunculus nudus), serves as both delicacies and potential solutions to the global food insecurity crisis. Despite being consumed primarily in parts of China, Korea, and Japan, the nutritional values especially the complex fatty acid compositions of these marine worms are difficult to characterize. To overcome this obstacle, we employed covalent adduct chemical ionization (CACI) tandem mass spectrometry for the de novo identification of their unusual polyunsaturated fatty acids (PUFA). Through this method, we identified several PUFA with polymethylene-interrupted (PMI) double bond configurations, including 22:3(7Z,13Z,16Z), a novel PUFA derived from sciadonic acid. U. unicinctus exhibits an exceptionally low n-6/n-3 PUFA ratio of 0.15, making it a potential functional food to counterbalance the n-6/n-3 imbalance in modern diets. S. nudus boasts notably high concentrations (∼3 %, wt/wt) of branched chain fatty acids (BCFA), exceeding typical levels found in dairy products.

Sciadonic acid attenuates high-fat diet-induced bone metabolism disorders in mice

High-fat diet (HFD) has been associated with certain negative bone-related outcomes, such as bone metabolism disruption and bone loss. Sciadonic acid (SC), one of the main nutritional and functional components of Torreya grandis seed oil, is a unique Δ5-unsaturated-polymethylene-interrupted fatty acid (Δ5-UPIFA) that has been claimed to counteract such disorders owing to some of its physiological effects. However, the role of SC in ameliorating bone metabolism disorders due to HFD remains unclear. In the present investigation, we observed that SC modulates the OPG/RANKL/RANK signaling pathway by modifying the lipid metabolic state and decreasing inflammation in mice. In turn, it could balance bone resorption and formation as well as calcium and phosphorus levels, enhance bone strength and bone mineral density (BMD), and improve its microstructure. In addition, SC could inhibit fat vacuoles in bone, reverse the phenomenon of reduced numbers and poor continuity of bone trabeculae, and promote orderly arrangement of collagen fibers and cartilage repair. This study provides some theoretical basis for SC as a dietary intervention agent to enhance bone nutrition.

Paternò-Büchi Reaction Mass Spectrometry Enables Positional Assignment of Polymethylene-Interrupted Double Bonds in Food-Derived Lipids

Fatty acids (FAs) containing polymethylene-interrupted (PMI) double bonds are a component of human foods; however, they present a significant analytical challenge for de novo identification. Covalent adduct chemical ionization and ozone-induced dissociation mass spectrometry (MS) methods enable unambiguous assignment of PMI-FA double bond positions, however, no method has been reported with electrospray ionization (ESI) platform using off-the-shelf systems. In the current work, we studied the Paternò-Büchi (PB) fragmentation patterns of PMI-FA and triacylglycerol (TG) by analyzing several known food sources. PB-MS/MS and MS3 enabled complete double bond location assignments, including the isolated double bond in PMI-FA and triacylglycerols. Sea urchin ("uni"), oyster, pine nut, and ginkgo nut were characterized for their signature PMI-FA, 20:2(5Z,11Z), 22:2(7Z, 15Z), 18:3(5Z,9Z,12Z), and 20:3(5Z,11Z,14Z), respectively. Quantitative analyses of the relative abundance of these PMI-FA led to results similar to reference methods. 18:3(5Z,9Z,12Z) was enriched at the sn-1/sn-3 position in pine nut major TG.

Fatty acid isomerism: analysis and selected biological functions

The biological functions of fatty acids and the lipids in which they are esterified are determined by their chain length, double bond position and geometry and other structural motifs such as the presence of methyl branches. Unusual isomeric features in fatty acids of human foods such as conjugated double bonds or chain branching found in dairy products, some seeds and nuts, and marine foods potentially have important effects on human health. Recent advancements in identifying fatty acids with unusual double bond positions and pinpointing the position of methyl branches have empowered the study of their biological functions. We present recent advances in fatty acid structural elucidation by mass spectrometry in comparison with the more traditional methods. The double bond position can be determined by purely instrumental methods, specifically solvent-mediated covalent adduct chemical ionization (SM-CACI) and ozone induced dissociation (OzID), with charge inversion methods showing promise. Prior derivatization using the Paternò-Büchi (PB) reaction to yield stable structures that, upon collisional activation, yield the double bond position has emerged. The chemical ionization (CI) based three ion monitoring (MRM) method has been developed to simultaneously identify and quantify low-level branched chain fatty acids (BCFAs), unattainable by electron ionization (EI) based methods. Accurate identification and quantification of unusual fatty acid isomers has led to research progress in the discovery of biomarkers for cancer, diabetes, nonalcoholic fatty liver disease (NAFLD) and atherosclerosis. Modulation of eicosanoids, weight loss and the health significance of BCFAs are also presented. This review clearly shows that the improvement of analytical capacity is critical in the study of fatty acid biological functions, and stronger coupling of the methods discussed here with fatty acid mechanistic research is promising in generating more refined outcomes.

FADS2 function at the major cancer hotspot 11q13 locus alters fatty acid metabolism in cancer

Dysregulation of fatty acid metabolism and de novo lipogenesis is a key driver of several cancer types through highly unsaturated fatty acid (HUFA) signaling precursors such as arachidonic acid. The human chromosome 11q13 locus has long been established as the most frequently amplified in a variety of human cancers. The fatty acid desaturase genes (FADS1, FADS2 and FADS3) responsible for HUFA biosynthesis localize to the 11q12-13.1 region. FADS2 activity is promiscuous, catalyzing biosynthesis of several unsaturated fatty acids by Δ6, Δ8, and Δ4 desaturation. Our main aim here is to review known and putative consequences of FADS2 dysregulation due to effects on the 11q13 locus potentially driving various cancer types. FADS2 silencing causes synthesis of sciadonic acid (5Z,11Z,14Z-20:3) in MCF7 cells and breast cancer in vivo. 5Z,11Z,14Z-20:3 is structurally identical to arachidonic acid (5Z,8Z,11Z,14Z-20:4) except it lacks the internal Δ8 double bond required for prostaglandin and leukotriene synthesis, among other eicosanoids. Palmitic acid has substrate specificity for both SCD and FADS2. Melanoma, prostate, liver and lung cancer cells insensitive to SCD inhibition show increased FADS2 activity and sapienic acid biosynthesis. Elevated serum mead acid levels found in hepatocellular carcinoma patients suggest an unsatisfied demand for arachidonic acid. FADS2 circular RNAs are at high levels in colorectal and lung cancer tissues. FADS2 circular RNAs are associated with shorter overall survival in colorectal cancer patients. The evidence thusfar supports an effort for future research on the role of FADS2 as a tumor suppressor in a range of neoplastic disorders.

Sciadonic acid attenuates high-fat diet-induced obesity in mice with alterations in the gut microbiota

Obesity has been reported to be associated with dysbiosis of gut microbiota. Sciadonic acid (SC) is one of the main functional components of Torreya grandis "Merrillii" seed oil. However, the effect of SC on high-fat diet (HFD)-induced obesity has not been elucidated. In this study, we evaluated the effects of SC on lipid metabolism and the gut flora in mice fed with a high-fat diet. The results revealed that SC activates the PPARα/SREBP-1C/FAS signaling pathway and reduces the levels of total cholesterol (TC), triacylglycerols (TG), and low-density lipoprotein cholesterol (LDL-C), but increases the level of high-density lipoprotein cholesterol (HDL-C) and inhibits weight gain. Among them, high-dose SC was the most effective; the TC, TG and LDL-C levels were reduced by 20.03%, 28.40% and 22.07%, respectively; the HDL-C level was increased by 8.55%. In addition, SC significantly increased glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) levels by 98.21% and 35.17%, respectively, decreased oxidative stress, and ameliorated the pathological damage to the liver caused by a high-fat diet. Furthermore, SC treatment altered the composition of the intestinal flora, promoting the relative abundance of beneficial bacteria such as Lactobacillus and Bifidobacterium, while simultaneously decreasing the relative abundance of potentially harmful bacteria such as Faecalibaculum, norank_f_Desulfovibrionaceae, and Romboutsia. Spearman's correlation analysis indicated that the gut microbiota was associated with SCFAs and biochemical indicators. In summary, our results suggested that SC can improve lipid metabolism disorders and regulate the gut microbial structure.

Comparative de novo Transcriptome Analysis of Two Cultivars With Contrasting Content of Oil and Fatty Acids During Kernel Development in Torreya grandis

Vegetable oil is an indispensable nutritional resource for human health and mainly characterized by the composition and content of fatty acids (FAs). As a commercial species of gymnosperm, Torreya grandis produces oil-rich nuts with high unsaturated fatty acids content in the mature kernels. In this study, two cultivars, T. grandis 'Xifei' and T. grandis 'Dielsii,' with distinct oil content were employed to compare the profiles of FAs accumulation during kernel development. The accumulation rate of oil content was significantly different between 'Xifei' and 'Dielsii.' Besides, the final oil content of 'Xifei' (52.87%) was significantly higher than that of 'Dielsii' (41.62%) at maturity. The significant differences in main FAs were observed at almost each kernel development stages between the two cultivars. C16:0, C18:1, and C20:3 FA exhibited different accumulation patterns between cultivars. The content and the initiation of accumulation of C20:3 FA were different between the two cultivars. To explore the molecular mechanism associated with different content of oil and FAs between two cultivars, de novo transcriptome of kernels was compared between 'Xifei' (high oil) and 'Dielsii' (low oil) at three stages of oil accumulation, respectively. Totally 142,213 unigenes were assembled and 16,379 unigenes with a length of over 1,000 nt were successfully annotated, including 139 unigenes related to FA biosynthesis, elongation, and metabolism. Compared with 'Dielsii,' totally 1,476, 2,140, and 1,145 differentially expressed genes (DEGs) were upregulated in 'Xifei' at the stage of the initiative, the rapid rise, and the stationary oil accumulation, respectively; the number of downregulated DEGs reached 913, 1,245, and 904, respectively. Relative expressions of 11 DEGs involved in FAs biosynthesis and metabolism were confirmed by RT-qPCR. Abundant differentially expressed transcription factors and pathway DEGs were correlated to oil and FAs according to Pearson's correlation analysis between transcriptome and metabolites (oil and FAs), suggesting their contributions to the differential oil and FAs between the two cultivars during kernel development of T. grandis. To conclude, our findings can provide novel insights into the developmental differences in metabolites and de novo transcriptome correlated to lipid accumulation and FA synthesis of kernels between cultivars with contrasting oil deposits and demystify the regulatory mechanism of high oil accumulation in T. grandis.

Unusual polymethylene-interrupted, Δ5 monounsaturated and omega-3 fatty acids in sea urchin (Arbacia punctulata) from the Gulf of Mexico identified by solvent mediated covalent adduct chemical ionization mass spectrometry

Sea urchin (class Echinoidea) gonads are a prized delicacy in Japan and many other world cultures. The complexity of its fatty acid (FA) profile, particularly minor FA, presents a formidable analytical challenge. We applied solvent mediated (SM) covalent adduct chemical ionization (CACI) tandem mass spectrometry to comprehensive de novo structural and quantitative characterization of the FA profile of Gulf of Mexico Atlantic sea urchin (Arbacia punctulata). >100 FA were detected including many with unusual double bond structure. Gulf sea urchin gonad lipids are rich in Δ5 monounsaturated FA 20:1(5Z) at 2.7% and the polymethylene-interrupted (PMI) diene 20:2(5Z,11Z) at 4.9%, as well as common omega-3 eicosapentaenoic acid (EPA; 5Z, 8Z, 11Z, 14Z, 17Z) at 9.8%±3.1% and arachidonic acid (AA; 5Z, 8Z, 11Z, 14Z) at 6.1%±2.1%. We propose plausible desaturation/elongation-based biochemical pathways for the endogenous production of unusual unsaturates. Unusual unsaturates may modify mammalian signaling and present novel bioactivities.

Rotavirus-Mediated Prostaglandin E2 Production in MA104 Cells Promotes Virus Attachment and Internalisation, Resulting in an Increased Viral Load

Rotaviruses are one of the leading causes of severe dehydrating diarrhoea in infants and children under the age of five. Despite the introduction of vaccines, disease burden remains high in sub-Saharan Africa, with no known anti-viral treatments available. During early infection rotavirus attaches to several cellular receptors and enters the cells by either clathrin-dependent or -independent endocytosis. Prostaglandin E_2, an abundant eicosanoid, is produced from arachidonic acid during rotavirus infection and inhibition of prostaglandin E₂ formation have a deleterious effect on rotavirus infection. In this study, MA104 cells were supplemented with γ-linolenic acid (GLA), a precursor of arachidonic acid. Infection of supplemented cells with rotavirus SA11 led to a depletion in the relative percentages of GLA and arachidonic acid which coincided with an increased production of prostaglandin E₂ as monitored by ELISA. Confocal microscopy demonstrated that prostaglandin E₂ co-localises with the viroplasm-forming proteins, NSP5 and NSP2. Due to the known association of viroplasms with lipid droplets and the fact that lipid droplets are sites for prostaglandin E₂ production, our results indicate a possible role for viroplasms in the production of rotavirus-induced prostaglandin E₂. Replication kinetics showed that inhibitors, targeting the biosynthesis of prostaglandin E₂, had negative effects on rotavirus yield, especially during the early stages of infection. Using flow cytometry and prostaglandin E₂ addback experiments, we show that prostaglandin E₂ enhances the attachment and internalisation of rotavirus in MA104 cells indicating a possible role for prostaglandin E₂ during clathrin-mediated rotavirus entry. The production of prostaglandin E₂ during rotavirus infection could serve as a possible target for anti-viral treatment.

Advances on delta 5-unsaturated-polymethylene-interrupted fatty acids: Resources, biosynthesis, and benefits

Though the knowledge on delta 5-unsaturated-polymethylene-interrupted fatty acids (Δ5-UPIFAs) is being updated, the issue of their integration still exists within the field. Thus, this review systematically summarizes the sources, biosynthesis and metabolism, analytical methods, preparation, and health-promoting roles of Δ5-UPIFAs. In plants, the content of Δ5-UPIFAs is higher, which is an ideal source. In animals, although the content of Δ5-UPIFAs is not high, there are many species, which is the possible source of some special Δ5-UPIFAs. At present, although the extraction of Δ5-UPIFAs is mainly from plants, the fermentation by organisms, especially for genetically modified microorganisms engineering maybe be a substitue of pepration of Δ5-UPIFAs. Δ5-UPIFAs have been proved to possess multi-beneficial effects, such as lipid lowering, anti-inflammation and so on, so it has a certain potential application value. However, related knowledge of the underlying molecular mechanisms regarding Δ5-UPIFAs limited, and how Δ5-UPIFAs work is not clear. Further clinical and human studies about Δ5-UPIFAs are also needed. Studies on tapping new resources, developing structured lipide rich in Δ5-UPIFA and enhancing delivery were quite deficient. This review emphasizes the further directions on Δ5-UPIFAs with scientific suggestions to pay more attention to the applications of Δ5-UPIFAs in food, pharmaceutical and cosmetic industries.

A review of the functional effects of pine nut oil, pinolenic acid and its derivative eicosatrienoic acid and their potential health benefits

Pine nut oil (PNO) is rich in a variety of unusual delta-5-non-methylene-interrupted fatty acids (NMIFAs), including pinolenic acid (PLA; all cis-5,-9,-12 18:3) which typically comprises 14 to 19% of total fatty acids. PLA has been shown to be metabolised to eicosatrienoic acid (ETA; all cis-7,-11,-14 20:3) in various cells and tissues. Here we review the literature on PNO, PLA and its metabolite ETA in the context of human health applications. PNO and PLA have a range of favourable effects on body weight as well as fat deposition through increased energy expenditure (fatty acid oxidation) and decreased food energy intake (reduced appetite). PNO and PLA improve blood and hepatic lipids in animal models and insulin sensitivity in vitro and reduce inflammation and modulate immune function in vitro and in animal models. The few studies which have examined effects of ETA indicate it has anti-inflammatory properties. Another NMIFA from PNO, sciadonic acid (all cis-5,-11,-14 20:3), has generally similar properties to PLA where these have been investigated. There is potential for human health benefits from PNO, its constituent NMIFA PLA and the PLA derivative ETA. However further studies are needed to explore the effects in humans.

Sciadonic acid derived from pine nuts as a food component to reduce plasma triglycerides by inhibiting the rat hepatic Δ9-desaturase

Sciadonic acid (Scia) is a Δ5-olefinic fatty acid that is particularly abundant in edible pine seeds and that exhibits an unusual polymethylene-interrupted structure. Earlier studies suggested that Scia inhibited the in vitro expression and activity of the Stearoyl-CoA Desaturase 1 (SCD1), the hepatic Δ9-desaturase involved in the formation of mono-unsaturated fatty acids. To confirm this hypothesis, rats were given 10% Scia in diets balanced out with n-6 and n-3 fatty acids. In those animals receiving the Scia supplement, monoene synthesis in the liver was reduced, which was partly attributed to the inhibition of SCD1 expression. As a consequence, the presence of Scia induced a 50% decrease in triglycerides in blood plasma due to a reduced level of VLDL-secreted triglycerides from the liver. In non-fasting conditions, results showed that Scia-induced inhibition of SCD1 led to a decrease in the proportions of 16:1n-7 and 18:1n-7 in the liver without impacting on the level of 18:1n-9, suggesting that only triglycerides with neosynthesized monoenes are marked out for release. In conclusion, this in vivo study confirms that Scia highly inhibits SCD1 expression and activity. The work was performed on normo-triglyceride rats over six weeks, suggesting promising effects on hyper-triglyceridemic models.

A rare eicosanoid precursor analogue, sciadonic acid (5Z,11Z,14Z-20:3), detected in vivo in hormone positive breast cancer tissue

Numerous genetic alterations of HSA 11q13 are found frequently in several cancer types, including breast cancer (BC). The 11q13 locus harbors FADS2 encoding Δ6 desaturation which is not functional in several cancer cell lines, including hormone positive MCF7 BC cells. In vitro, the non-functional FADS2 activity unmasks 18:2n-6 elongation to 20:2n-6 and Δ5 desaturation by FADS1 to yield 5Z,11Z,14Z-20:3 (sciadonic acid) rather than 5Z,8Z,11Z,14Z-20:4 (arachidonic acid). In this pilot study we aimed to determine whether 5,11,14-20:3 appears in vivo in hormone positive human BC tissue. Fatty acids were profiled in surgically removed human breast tumor and adjacent normal tissue (n = 9). Sciadonic acid was detected in three of nine breast tumor samples and was below detect limits in normal breast tissue. The internal Δ8 double bond of arachidonic acid is required for normal eicosanoid synthesis but is missing in sciadonic acid. This pilot study demonstrates for the first time in vivo sciadonic acid in hormone positive BC tissue, warranting a larger survey study to further evaluate its appearance and the functional implications.

Non-methylene-interrupted fatty acids from marine invertebrates: Occurrence, characterization and biological properties

Marine organisms, in particular invertebrates, have proved to be a major source of unique fatty acid (FA) structures originating from unusual biosynthetic pathways. Among them, non-methylene-interrupted (NMI) FA occur in various molluscs in the wide ranges of concentrations (up to 20%), such as the most often encountered 20:2 Delta5,11, 20:2 Delta5,13, 22:2 Delta7,13 or 22:2 Delta7,15. Such NMI FA have also been reported from algae, echinoderms, sponges, tropical rays, and many other invertebrates. The most intriguing marine invertebrates seem to be sponges that commonly contain very long-chain Delta5,9 FA. A third double bond can occur in the NMI FA as reported in some marine organisms, such as 20:3 Delta7,13,16 or 30:3 Delta5,9,23. Lipids of invertebrates from deep-sea hydrothermal and cold-seep vents gave rise to an intense research activity including reports on unprecedented NMI polyunsaturated FA. The bivalve molluscs are able to synthesize de novo the NMI FA but their precise biological interest is presently not well-known, although structural and functional roles in biological membranes have been suggested, in particular a higher resistance to oxidative processes and microbial lipases. Biosynthetic pathways of Delta5,9 FA in sponges were demonstrated up to C(26) FA structures and include particular elongation and desaturation steps. Recently, intense research effort has been conducted to investigate the biomedical potential of these unusual FA. Thus, Delta5,9 FA displayed interesting antiplasmodial activity. The most promising FA topoisomerase I inhibitors to date seem to be the long-chain Delta5,9 FA. This inhibitory activity is probably partially responsible for the toxicity displayed by some of the Delta5,9 FA towards cancer cell lines.

Cloning and characterization of unusual fatty acid desaturases from Anemone leveillei: identification of an acyl-coenzyme A C20 Delta5-desaturase responsible for the synthesis of sciadonic acid

The seed oil of Anemone leveillei contains significant amounts of sciadonic acid (20:3Delta(5,11,14); SA), an unusual non-methylene-interrupted fatty acid with pharmaceutical potential similar to arachidonic acid. Two candidate cDNAs (AL10 and AL21) for the C(20) Delta(5cis)-desaturase from developing seeds of A. leveillei were functionally characterized in transgenic Arabidopsis (Arabidopsis thaliana) plants. The open reading frames of both Delta(5)-desaturases showed some similarity to presumptive acyl-coenzyme A (CoA) desaturases found in animals and plants. When expressed in transgenic Arabidopsis, AL21 showed a broad range of substrate specificity, utilizing both saturated (16:0 and 18:0) and unsaturated (18:2, n-6 and 18:3, n-3) substrates. In contrast, AL10 did not show any activity in wild-type Arabidopsis. Coexpression of AL10 or AL21 with a C(18) Delta(9)-elongase in transgenic Arabidopsis plants resulted in the production of SA and juniperonic fatty acid (20:4Delta(5,11,14,17)). Thus, AL10 acted only on C(20) polyunsaturated fatty acids in a manner analogous to "front-end" desaturases. However, neither AL10 nor AL21 contain the cytochrome b(5) domain normally present in this class of enzymes. Acyl-CoA profiling of transgenic Arabidopsis plants and developing A. leveillei seeds revealed significant accumulation of Delta(5)-unsaturated fatty acids as acyl-CoAs compared to the accumulation of these fatty acids in total lipids. Positional analysis of triacylglycerols of A. leveillei seeds showed that Delta(5)-desaturated fatty acids were present in both sn-2 and sn-1 + sn-3 positions, although the majority of 16:1Delta(5), 18:1Delta(5), and SA was present at the sn-2 position. Our data provide biochemical evidence for the A. leveillei Delta(5)-desaturases using acyl-CoA substrates.

Metabolic pathway that produces essential fatty acids from polymethylene-interrupted polyunsaturated fatty acids in animal cells

Sciadonic acid (20:3 Delta-5,11,14) and juniperonic acid (20:4 Delta-5,11,14,17) are polyunsaturated fatty acids (PUFAs) that lack the Delta-8 double bond of arachidonic acid (20:4 Delta-5,8,11,14) and eicosapentaenoic acid (20:5 Delta-5,8,11,14,17), respectively. Here, we demonstrate that these conifer oil-derived PUFAs are metabolized to essential fatty acids in animal cells. When Swiss 3T3 cells were cultured with sciadonic acid, linoleic acid (18:2 Delta-9,12) accumulated in the cells to an extent dependent on the concentration of sciadonic acid. At the same time, a small amount of 16:2 Delta-7,10 appeared in the cellular lipids. Both 16:2 Delta-7,10 and linoleic acid accumulated in sciadonic acid-supplemented CHO cells, but not in peroxisome-deficient CHO cells. We confirmed that 16:2 Delta-7,10 was effectively elongated to linoleic acid in rat liver microsomes. These results indicate that sciadonic acid was partially degraded to 16:2 Delta-7,10 by two cycles of beta-oxidation in peroxisomes, then elongated to linoleic acid in microsomes. Supplementation of Swiss 3T3 cells with juniperonic acid, an n-3 analogue of sciadonic acid, induced accumulation of alpha-linolenic acid (18:3 Delta-9,12,15) in cellular lipids, suggesting that juniperonic acid was metabolized in a similar manner to sciadonic acid. This PUFA remodeling is thought to be a process that converts unsuitable fatty acids into essential fatty acids required by animals.

Regulation of de novo phosphatidylinositol synthesis

Mechanisms that function to regulate the rate of de novo phosphatidylinositol (PtdIns) synthesis in mammalian cells have not been elucidated. In this study, we characterize the effect of phorbol ester treatment on de novo PtdIns synthesis in C3A human hepatoma cells. Incubation of cells with 12-O-tetradecanoyl phorbol 13-acetate (TPA) initially (1-6 h) results in a decrease in precursor incorporation into PtdIns; however, at later times (18-24 h), a marked increase is observed. TPA-induced glucose uptake from the medium is not required for observation of the stimulation of PtdIns synthesis, because the effect is apparent in glucose-free medium. Inhibition of the activation of arachidonic acid substantially blocks the synthesis of PtdIns but has no effect on the synthesis of phosphatidylcholine (PtdCho). Increasing the concentration of cellular phosphatidic acid by blocking its conversion to diacylglycerol, on the other hand, enhances the synthesis of PtdIns and inhibits the synthesis of PtdCho. The TPA-induced stimulation of PtdIns synthesis is not the result of the concomitant TPA-induced G1 arrest, because G1 arrest induced by mevastatin has no effect on PtdIns synthesis. Inhibition of protein kinase C activity blocks the stimulatory action of TPA on de novo synthesis of PtdIns but has no effect on TPA-induced inhibition. Potential sites of enzymatic regulation are discussed.

Production and protein kinase C activation of diacylglycerols containing polymethylene-interrupted PUFA

Sciadonic acid (20:3, delta-5c,11 c,14c) is a polymethylene-interrupted PUFA (PMI-PUFA) that is present in conifer seeds and known to be incorporated into animal cells and to accumulate in membrane PI as a substitute for arachidonate. In this study, we investigated whether PI having sciadonate could serve as source of DAG that could activate protein kinase C (PKC). When Swiss 3T3 cells cultured with sciadonic acid were stimulated with 100 nM of bombesin, 1-stearoyl-2-sciadonoyl-glycerol (G) and 1-stearoyl-2-arachidonoyl-G were produced. The net increments of these two molecular species of DAG reflected the levels of the two molecular species in the PI in the cells. When cells cultured with juniperonic acid (20:4, delta-5c,11c,14c,17c) were stimulated, 1-stearoyl-2-juniperonoyl-G was produced in proportion to the level of this molecular species in PI in the cells. We also examined PKC activation by synthetic DAG using a partially purified PKC fraction from rat brain and found that both 1-stearoyl-2-sciadonoyl-G and 1-stearoyl-2-juniperonoyl-G could activate PKC comparably to 1 -stearoyl-2-arachidonoyl-G. These results indicate that 1-stearoyl-PI having these C20 PMI-PUFA residues can serve as sources of potential signaling molecules.

Mechanisms of accumulation of arachidonate in phosphatidylinositol in yellowtail. A comparative study of acylation systems of phospholipids in rat and the fish species Seriola quinqueradiata

It is known that phosphatidylinositol (PtdIns) contains abundant arachidonate and is composed mainly of 1-stearoyl-2-arachidonoyl species in mammals. We investigated if this characteristic of PtdIns applies to the PtdIns from yellowtail (Seriola quinqueradiata), a marine fish. In common with phosphatidylcholine (PtdCho), phosphatidylethanolamine (PtdEtn) and phosphatidylserine (PtdSer) from brain, heart, liver, spleen, kidney and ovary, the predominant polyunsaturated fatty acid was docosahexaenoic acid, and levels of arachidonic acid were less than 4.5% (PtdCho), 7.5% (PtdEtn) and 3.0% (PtdSer) in these tissues. In striking contrast, arachidonic acid made up 17.6%, 31.8%, 27.8%, 26.1%, 25.4% and 33.5% of the fatty acid composition of PtdIns from brain, heart, liver, spleen, kidney and ovary, respectively. The most abundant molecular species of PtdIns in all these tissues was 1-stearoyl-2-arachidonoyl. Assay of acyltransferase in liver microsomes of yellowtail showed that arachidonic acid was incorporated into PtdIns more effectively than docosahexaenoic acid and that the latter inhibited incorporation of arachidonic acid into PtdCho without inhibiting the utilization of arachidonic acid for PtdIns. This effect of docosahexaenoic acid was not observed in similar experiments using rat liver microsomes and is thought to contribute to the exclusive utilization of arachidonic acid for acylation to PtdIns in yellowtail. Inositolphospholipids and their hydrolysates are known to act as signaling molecules in cells. The conserved hydrophobic structure of PtdIns (the 1-stearoyl-2-arachidonoyl moiety) may have physiological significance not only in mammals but also in fish.

Epidermal anti-Inflammatory properties of 5,11,14 20:3: effects on mouse ear edema, PGE2 levels in cultured keratinocytes, and PPAR activation

BACKGROUND

5,11,14 20:3 is similar to 20:4n-6 but lacks the internal Delta8 double bond essential for prostaglandin and eicosanoid synthesis. When previously fed to laboratory animals as a gymnosperm seed oil component it has shown anti-inflammatory properties.

RESULTS

Herein, topically applied Podocarpus nagi methyl esters (containing 26% 5,11,14 20:3) were incorporated into mouse ear phospholipids, reduced 20:4n-6, and reduced 20:4n-6- and TPA-induced mouse ear edema. Purified 5,11,14 20:3 was taken up by cultured human skin keratinocytes, reduced 20:4n-6, and reduced PGE2 levels dramatically. Purified 5,11,14 20:3 did not affect PPARalpha, PPARgamma, or PPARdelta transactivation.

CONCLUSIONS

Topical application of 5,11,14 20:3 to skin surfaces can thus reduce inflammatory processes, most likely by displacing 20:4n-6 from phospholipid pools and reducing downstream inflammatory products derived from 20:4n-6 such as PGE2 and leukotrienes. It could have potential use in treating clinical skin disorders resulting from overproduction of 20:4n-6-derived eicosanoid products.