Transformation Of Polyunsaturated Fatty Acids Research Articles

Phyto-oxylipin mediated plant immune response to colonization and infection in the soybean-Phytophthora sojae pathosystem.

Food security is a major challenge to sustainably supply food to meet the demands of the ever-growing global population. Crop loss due to pathogens is a major concern to overcoming this global food security challenge. Soybean root and stem rot caused by Phytophthora sojae results in approximately 20B $US crop loss annually. Phyto-oxylipins are metabolites biosynthesized in the plants by oxidative transformation of polyunsaturated fatty acids through an array of diverging metabolic pathways and play an important role in plant development and defense against pathogen colonization and infection. Lipid mediated plant immunity is a very attractive target for developing long term resistance in many plants' disease pathosystem. However, little is known about the phyto-oxylipin's role in the successful strategies used by tolerant soybean cultivar to mitigate Phytophthora sojae infection. We used scanning electron microscopy to observe the alterations in root morphology and a targeted lipidomics approach using high resolution accurate mass tandem mass spectrometry to assess phyto-oxylipin anabolism at 48h, 72h and 96h post infection. We observed the presence of biogenic crystals and reinforced epidermal walls in the tolerant cultivar suggesting a mechanism for disease tolerance when compared with susceptible cultivar. Similarly, the unequivocally unique biomarkers implicated in oxylipin mediated plant immunity [10(E),12(Z)-13S-hydroxy-9(Z),11(E),15(Z)-octadecatrienoic acid, (Z)-12,13-dihydroxyoctadec-9-enoic acid, (9Z,11E)-13-Oxo-9,11-octadecadienoic acid, 15(Z)-9-oxo-octadecatrienoic acid, 10(E),12(E)-9-hydroperoxyoctadeca-10,12-dienoic acid, 12-oxophytodienoic acid and (12Z,15Z)-9, 10-dihydroxyoctadeca-12,15-dienoic acid] generated from intact oxidized lipid precursors were upregulated in tolerant soybean cultivar while downregulated in infected susceptible cultivar relative to non-inoculated controls at 48h, 72h and 96h post infection by Phytophthora sojae, suggesting that these molecules may be a critical component of the defense strategies used in tolerant cultivar against Phytophthora sojae infection. Interestingly, microbial originated oxylipins, 12S-hydroperoxy-5(Z),8(Z),10(E),14(Z)-eicosatetraenoic acid and (4Z,7Z,10Z,13Z)-15-[3-[(Z)-pent-2-enyl]oxiran-2-yl]pentadeca-4,7,10,13-tetraenoic acid were upregulated only in infected susceptible cultivar but downregulated in infected tolerant cultivar. These microbial originated oxylipins are capable of modulating plant immune response to enhance virulence. This study demonstrated novel evidence for phyto-oxylipin metabolism in soybean cultivars during pathogen colonization and infection using the Phytophthora sojae-soybean pathosystem. This evidence may have potential applications in further elucidation and resolution of the role of phyto-oxylipin anabolism in soybean tolerance to Phytophthora sojae colonization and infection.

Effect of Natural Antioxidants from Fruit Leaves on the Oxidative Stability of Soybean Oil during Accelerated Storage.

Plant by-products are safe, sustainable, and abundant natural antioxidant sources. Here we investigated the antioxidant activity of a mixture of lyophilized pomegranate, guava, and grape (PGG) leaves water extract (1:1:1) and examined its ability to retard the rancidity of soybean oil during accelerated storage at 65 °C for 30 days. To achieve this, we evaluated the oxidative stability of soybean oil enriched with PGG extract at 200, 400, and 800 ppm. We also compared the effect of PGG extract with butylated hydroxytoluene (BHT) (400/100 ppm) with that of only BHT (200 ppm). We observed that 8.19 and 1.78 µg/mL of the extract could scavenge 50% of DPPH• and ABTS•, respectively, indicating its enhanced antioxidant activity. Enriching soyabean oil with the extract at 800 ppm improved its oxidative stability by reducing the acid value to 1.71 mg/g and the total oxidation to 99.87 compared to 2.27 mg/g and 150.32 in the raw oil, respectively. Moreover, PGG-800 ppm inhibited oxidation by 46.07%. Similarly, PGG-400 ppm reinforced BHT (100 ppm) to provide oxidative stability as BHT (p > 0.05), with TOTOX values of 87.93 and 79.23, respectively. PGG-800 ppm and PGG/BHT mix potently inhibited the transformation of polyunsaturated fatty acids into saturated ones. Therefore, the PGG extract might be an efficient substitute for BHT (partially or totally) during industrial processes.

Yağ Asitlerinin İnflamasyonla İlişkili Süreçlere Etkisinin Değerlendirilmesi

Metabolik süreçlerin devamında ve pek çok hastalığın ortaya çıkışında inflamasyonun önemli bir rol oynadığı bilinmektedir. Konağın enfeksiyona karşı verdiği inflamatuvar yanıtlar; immün hücreler, çeşitli inflamatuvar aracılar, transkripsiyon faktörleri ve nükleer reseptörler aracılığı ile olmaktadır. Yağ asitleri konağın inflamatuvar yanıtının düzenlenmesi ve homeostazın sağlanmasında işlev gören aracılardan biridir. Güncel çalışmalar ile yağ asitlerinin inflamasyon üzerine etkilerini gösteren sonuçlar ortaya konulmuştur. Özellikle çoklu doymamış yağ asitlerinin eikozanoidlere dönüşümü ile yağ asitleri inflamatuvar yanıt sürecine katılmaktadır. Omega-6 yağ asidi kaynaklı araşidonik asidin proinflamatuvar, omega-3 yağ asidi kaynaklı EPA ve DHA’nın ise antiinflamatuvar özellikleri bilinmektedir. Bu derlemede, yağ asitlerinin inflamatuvar süreçlere etkisinin değerlendirilmesi amaçlanmıştır.

LC-MS3 method for the analysis of Lipid Peroxidation Products (LPPs) positional isomers

Lipid peroxidation is an enzymatic or non-enzymatic transformation of polyunsaturated fatty acids (PUFAs) leading to the formation of various lipid peroxidation products (LPPs) including low molecular weight aldehydes (i.e. 4-hydroxy-trans-2- nonenal, acrolein), truncated lipids (i.e. alkanals, alkenals), and hydroxy-alka(e)nals), isoprostanes, hydroperoxy-, hydroxy-, keto- and epoxy-derivatives. Numerous studies shown the involvement of lipid peroxidation in the onset and progression of inflammatory based diseases such as diabetes, Alzheimer, Parkinson diseas and cardiovascular diseases [1]. LPPs are known to modulate different cellular signaling pathways by inducing changes in the biological membranes [2], protein lipoxidation, and interaction with cell surface (e.g. scavenger receptors and TLRs) [3] and intracellular (e.g. PPARs) receptors [4]. Various biological activities of LPPs are mainly determined by their chemical diversity. In order to understand LPPs structure-functional relationships, specific and sensitive analytical tools allowing separation and identification of structural isomers are required. Liquid chromatography coupled on-line to mass spectrometry (LC-MS) allows high-throughput characterization of LPPs in biological samples. However, majority of the methods are not capable to distinguish LPP structural isomers. Here a novel LC-MS method for analysis of isomeric LPPs was developed. MS and tandem MS analysis was performed in negative ion mode. Anions of oxidized PUFAs, produced by collision induced dissociation of LPP precursors, were further used for data-driven MS3 analysis yielding structure specific fragment ions necessary to assign type and position of oxidation within PUFA alkyl chain. Method was validated using in vitro oxidized standard PLs and further translated for analysis of complex biological samples. Thus, using novel LC-MS3 based approach it was possible to reveal structural diversity of LPPs in a high-throughput manner.

Survey of the C20 and C22 oxylipin family in marine diatoms

Diatoms are highly abundant microalgae that are prolific sources for bioactive oxylipins, which are generated by the oxidative transformation of polyunsaturated fatty acids and contribute to the chemical defense of algae. We introduce herein a targeted survey of oxylipins from four diatom species with a focus on metabolites that also occur in mammalians. Analytical data from LC–MS/MS measurements indicate that diatoms produce a surprising variety of oxylipins, including several hydroxylated and dihydroxylated C18-, C20-, and C22-polyunsaturated fatty acids. It was also found that diatoms represent the first non-mammalian source for the resolvins (Rv)E2 and RvE3, which have recently been identified as modulators of inflammation in humans and rodents. The oxylipins are produced in response to mechanical disruption of the cells, suggesting their potential involvement in the wound-activated chemical defense of these diatoms.

Linoleic acid peroxidation vs. isomerization: a biomimetic model of free radical reactivity in the presence of thiols

Biomimetic models of free radical-induced transformation of polyunsaturated fatty acids, such as micelles and liposomes, have been used for the study of lipid peroxidation and lipid isomerization. Free radical reactivity of thiol compounds is the common link between the two processes, since lipid peroxidation is inhibited by thiols, due to their H-donation ability, whereas lipid isomerization is catalysed by S-centered radicals. In this paper the two processes are compared for the first time, in solution and under biomimetic conditions, demonstrating that hydroperoxides and trans lipids are formed to comparable extents as a result of oxidative free radical conditions. The biomimetic model of micelles of linoleic acid, prepared by addition of a non-ionic surfactant (TWEEN(®)-20) and 2-mercaptoethanol as the amphiphilic thiol, was irradiated by ionizing radiation up to 400 Gy under various conditions. In air-equilibrated solutions, the cis-trans isomerization process was observed with a catalytic cycle of 370 together with a substantial amount of hydroperoxides (LOOH). The effect of micelle size was also studied in order to envisage the effect of the supramolecular organization on the outcome of the two processes, and in particular, for the positional preference of the double bond isomerization.

TransFatty Acids, Insulin Resistance, and Type 2 Diabetes

Type 2 diabetes, a growing global health problem, has a complex etiology involving many interactions between genetic and environmental factors. Essential to the development of the disease is insulin resistance of the peripheral tissues. Insulin resistance may be partly modified by the specific types of dietary fatty acids. Trans fatty acids (TFAs), created through the transformation of polyunsaturated fatty acids from their natural cis form to the trans form, are abundant in the Western diet. TFAs take on similar properties as saturated fats, and appear to be more atherogenic. High intakes of saturated fats may promote insulin resistance. It is therefore reasonable to hypothesize that high intakes of TFAs would have similar, or stronger, effects. In this review, all current evidence on the topic of TFAs, insulin resistance, and type 2 diabetes is summarized and interpreted. Although there is some support from observational and experimental studies for the hypothesis that high intakes of TFAs may increase the risk for type 2 diabetes, inconsistencies across studies and methodological problems make it premature to draw definitive conclusions at this time. More experimental research in humans is needed to further address this question.

Are lipid peroxidation processes induced by changes in the cell wall structure and how are these processes connected with diseases?

Apparently nature uses the unique sensitivity of polyunsaturated fatty acids (PUFAs) versus oxygen to generate chemical signals if the surface of a cell is influenced by an outside or inside event; for instance the attack of microorganisms, proliferation, aging or by treatment of isolated cells with surfactants. It seems that mammalian and plant cells respond equally to such changes in their structures by transformation of polyunsaturated fatty acids localized in the phospholipid layer of the cell wall to lipidhydroperoxides (LOOHs). These lipid peroxidation (LPO) processes involve all PUFAs, not only arachidonic acid. Slight physiological changes of the cell wall for instance by proliferation seem to activate enzymes, e.g., phospholipases and lipoxygenases (LOX). When an outside impact (for instance by attack of microorganisms) exceeds a certain level LOX commit suicide and liberate iron ions. These start a nonenzymatic LPO. Enzymatic and nonenzymatic LPO distinguish fundamantally which has not been recognized in the past. In the enzymatic LPO processes peroxyl radicals generated as intermediates cannot leave the enzyme complex. In contrast in a nonenzymatic LPO process peroxyl radicals are not trapped. They attack nearly any kind of biological molecules, for instance proteins. Thus only the amount of an outside impact decides if proliferation, apoptosis, or necrosis is started. Some evidence indicates that cancer might be the consequence of a low response of cells to induce apoptotic LPO processes. In contrast to high level of LPO processes induces diseases combined with inflammation, for instance rheumatic arthritis. After consumption of food rich in linoleic acid its LPO products become increased in low density lipoprotein (LDL). This LDL is able to enter endothelial cells and damage cells from inside, long before an inflammatory response is detectable.

The transfer of fatty acids in a freshwater planktonic foodweb of the Kuibyshevskoe reservoir (middle reaches of the Volga)

The fatty acid composition of seston (small-size fraction, < 50 μm) and of Daphnia galeata, Bythotrephes longimanus and adult individuals of Leptodora kindtii was analysed in the summer of 1997. When comparing the eicosapentaenoic acid (EPA) content of seston with Daphnia, Daphnia with Bythotrephes; Daphnia with Leptodora, we found similarities in the dynamics of EPA accumulation, in most cases. The content of EPA in seston was found to be significantly correlated with numerical abundance of small diatoms (r =0.662). ). Maximally the % EPA increased from seston (traces - 4% of total fatty acids) to Daphnia (traces - 12.2%). ). Both the lower and upper relative EPA contents were higher in Bythotrephes (10.8-16%), whereas the maximum value was lower in Leptodora (0.4-6.3%) compared to Daphnia. Correlation coefficients between the EPA content of the organisms at different trophic levels were not significant. The existence of species-specific differences in accumulation and /or transformation of polyunsaturated fatty acids in freshwater crustaceans is proposed.

The discovery of the leukotrienes.

In a study of the transformation of polyunsaturated fatty acids in rabbit polymorphonuclear leukocytes in 1976 it was discovered that arachidonic acid is oxygenated at C-5 (1). Subsequently a number of derivatives, including leukotriene B 4 (LTB 4 ), were identified (2-4). Extension of these studies led in 1979 to the discovery of the pivot epoxide intermediate, LTA 4 (5), and the elucidation of the structure of SRS-A (slow-reacting substance of anaphylaxis) as a group of cysteinyl-leukotrienes, namely LTC 4 , LTD 4 , and LTE 4 (6-10). Earlier work had shown that the prostaglandins are formed by oxygenation and further transformation of arachidonic acid and other polyunsaturated fatty acids (11). The first intermediate in the formation of prostaglandins, the endoperoxide PGG 2 , was isolated and identified in 1974 (12). At the same time we introduced the name cyclooxygenase for the enzyme catalyzing the transformation of arachidonic acid into PGG 2 (12). However, the endoperoxides, PGG 2 and PGH 2 , had some biological effects that could not be explained by their conversion to the known prostaglandins (12). This finding eventually led to the discovery of thromboxane A 2 , an unstable platelet-aggregating and vasoconstrictor substance (13). Subsequent work showed that the endoperoxide can also be converted into a derivative, prostacyclin (PGI 2 ), with opposite biological effects (14). Prostaglandins E 2 and I 2 have strong proinflammatory effects. Aspirin and other nonsteroidal antiinflammatory drugs (NSAIDs) inhibit the enzyme (cyclooxygenase) responsible for conversion of arachidonic acid into prostaglandins and thromboxanes (15). An induced form of the cyclooxygenase (COX-2) seems to play an important role in inflammation, thus opening the possibility of developing antiinflammatory NSAIDs that lack the side effects of the previous generation of such drugs (16, 17). In 1975 antiinflammatory steroids were proposed to inhibit prostaglandin formation by blocking of the release of the precursor acid from phospholipid stores (18). Since steroids and NSAIDs have significantly different antiinflammatory effects it seemed conceivable that some of these differences might be explained by the formation of proinflammatory derivatives of arachidonic acid by cyclooxygenase-independent reactions. Our studies of the metabolism of arachidonic acid in leukocytes unraveled a new metabolic pathway and led to the discovery of the leukotrienes (8). These compounds play a role in allergy and asthma and have pronounced proinflammatory effects (19, 20).

Nonenzymic browning. X. Kinetics of the oxidative browning of phosphatidylethanolamine

The formation of brown pigments produced by autoxidation of egg phosphatidylethanolamine in thin films in the temperature range of 20-100°C proceeds in three steps: (a) very rapid transformation of polyunsaturated fatty acids into conjugated hydroperoxides (a first order reaction); (b) reaction of hydroperoxide decomposition products (various aldehydic cleavage products) with the primary amino group of phosphatidylethanolamine resulting in the formation of nearly colourless Schiff bases (a zeroth-order reaction, slow at 30-60°C., fast at higher temperatures); (c) transformation of intermediary Schiff bases into brown pigments by further polycondensation reactions (a first order reaction). The activation energies of the three reactions were calculated.