High Levels Of Arachidonic Acid Research Articles

Functional coupling between various phospholipase A2s and cyclooxygenases in immediate and delayed prostanoid biosynthetic pathway

Generation of prostaglandins (PGs), which are involved in a wide variety of pathophysiological processes, is regulated by three sequential enzymatic reactions. This pathway is initiated by the release of arachidonic acid (AA) by phospholipase A2s (PLA2s), followed by its conversion to PGH2 by cyclooxygenases (COXs) and then to various biologically active PGs by terminal PG synthases (tPGSs) . PLA2 comprises a growing family of enzymes, among which cytosolic PLA2 (cPLA2) and several secretory PLA2s (sPLA2s) play a crucial role in the release of AA that is supplied to downstream COXs. Activation of cPLA2 is regulated primarily by perinuclear translocation in response to increased cytoplasmic Ca2+ levels and by dual phosphorylation that is under control of the MAP kinase pathway. sPLA2-mediated eicosanoid generation occurs by two distinct (heparan sulfate- or lipid interface dependent) mechanisms. The two COX isozymes, constitutive COX-1 and inducible COX-2, are functionally segregated in different phases of cell activation. COX-1 mediates the immediate PG generation, in which high levels of AA are released in a short time, whereas COX-2 is a prerequisite for the delayed PG generation, in which low levels of AA are gradually supplied. Furthermore, these COXs are differently coupled with tPGSs, which display unique tissue and subcellular distribution. Identification of two PGE2 synthases (PGESs) reveals that the constitutive, cytosolic PGES is functionally linked with only COX-1 and the inducible, perinuclear membrane-bound PGES favors COX-2 over COX-1. Overall, our results suggest that the amounts of AA released by cPLA2 or sPLA2 and subcellular localization of COXs and tPGSs crucially affect the functional coupling among the biosynthetic enzymes in the cascade.

Keloids in rural black South Africans. Part 3: a lipid model for the prevention and treatment of keloid formations

In the third part of this study a basic lipid model (regarding phospholipids, triglycerides, cholesterol esters and free fatty acids) for keloids (n=20), compared with normal skin of keloid prone and non-keloid prone patients (n=20 of each), was constructed according to standard methods, to serve as a sound foundation for essential fatty acid supplementation strategies in the prevention and treatment of keloid formations. Essential fatty acid deficiency (EFAD) of the omega-6 series (linoleic acid (LA), g-linolenic acid (GLA), and dihomo-g-linolenic acid (DGLA)) and the omega-3 series (a-linolenic acid (ALA) and eicosapentaenoic acid (EPA)), but enhanced arachidonic acid (AA) levels, were prevalent in keloid formations. Enhanced AA, but a deficiency of AA precursors (LA, GLA and DGLA) and inflammatory competitors (DGLA and EPA), are inevitably responsible for the overproduction of pro-inflammatory metabolites (prostaglandin E2(PGE2)) participating in the pathogenesis of inflammation. Of particular interest was the extremely high free oleic acid (OA) levels present, apart from the high free AA levels, in the keloid formations. OA stimulates PKC activity which, in turn, activates PLA2activity for the release or further release of AA from membrane pools. Interactions between EFAs, eicosanoids, cytokines, growth factors and free radicals can modulate the immune response and the immune system in undoubtedly involved in keloid formation. The histopathology of keloids can be adequately explained by: persistence of inflammatory- and cytokine-mediated reactions in the keloid/dermal interface and peripheral areas, where fibroblast proliferation and continuous depletion of membrane linoleic acid occur; microvascular regeneration and circulation of sufficient EFAs in the interface and peripheral areas, where maintenance of metabolic active fibroblasts for collagen production occur; microvessel occlusion and hypoxia in the central areas, where deprivation of EFAs and oxygen with consequent fibroblast apoptosis occur, while excessive collagen remain. All these factors contribute to different fibroblast populations present in: the keloid / dermal interface and peripheral areas where increases in fibroblast proliferation and endogenous TGF-b occur, and these metabolic active fibroblast populations are responsible for enhanced collagen production: the central areas where fibroblast populations under hypoxic conditions occur, and these fibroblasts are responsible for excessive collagen production. It was concluded that: fibroblast membrane EFAD of AA precursors and inflammatory competitors, but prevailing enhanced AA levels, can contribute to a chain of reactions eventually responsible for keloid formations.

Lower eicosapentaenoic acid and higher arachidonic acid levels in Sera of young adults in the Netherlands than in Japan

To survey risk factors in coronary heart disease, we compared serum fatty acid composition and lipids for university students in Japan (33 males and 29 females) and in the Netherlands (20 males and 19 females). No significant differences were found between the mean levels of cholesterol (Chol) and triglycerides (TG) between the subjects in the two countries. The mean levels of polyunsaturated fatty acid (PUFA), monounsaturated fatty acid (MUFA) and saturated fatty acid (SFA) of Japanese students were similar to those of the Dutch students. In both countries, the levels of Chol showed a positive correlation with the levels of PUFA, n-6 PUFA, linoleic acid (C18:2n-6), and arachidonic acid (AA, C20:4n-6) but no correlation with the percentages of PUFA and the ratio of PUFA/SFA. On the other hand, the TG levels correlated inversely with the percentage of PUFA and the ratios of PUFA/SFA in both countries. When compared to those of Japanese students, low eicosapentaenoic acid (EPA, C20:5n-3) and high AA were found in the Dutch students (p < 0.001, respectively). The total amounts of n-3 PUFA in the Dutch were significandy lower than those in the Japanese (p < 0.001) but no differences among those of n-6 PUFA. The ratios of EPA/AA and n-3/n-6 PUFA of the Dutch students were lower than those of the Japanese students (p < 0.001, respectively). The ratio of EPA/AA showed a positive correlation with EPA but not with AA in both countries. The levels of Toc which will decrease the risk of coronary vascular disease (CVD) were lower in Japan than those in the Dutch in both sexes (p < 0.01, respectively). These results suggest that the low EPA and high AA levels and the low n-3/n-6 PUFA ratio may lead to greater incidence of CVD.

Arachidonic acid metabolism in inflammatory cells of patients with bronchial asthma.

Over the last few years, the demonstration of beneficial effects of leukotriene receptor antagonists in various forms of asthma has renewed clinical and pharmacologic interest in this class of lipid mediators. Several studies demonstrated an increased biosynthesis of cysteinyl leukotrienes (CysLT) in asthmatic patients. However, the reasons for the dysregulated production of CysLTs in asthmatic patients are not completely defined. An improved method of lipid mediator detection and the availability of cells isolated from human airways (by bronchoalveolar lavage [BAL] and bronchial biopsies) have allowed initial studies to address this issue. Eosinophils retrieved from inflamed airways of asthmatics have a larger arachidonic acid (AA) content than their blood counterpart. The high level of AA in these cells is primarily due to a remodeling of endogenous arachidonate pools with the accumulation of this fatty acid in a triglyceride-associated pool. In addition, elevated levels of a secretory form of phospholipase A2, the key enzyme initiating the cascade of CysLTs, are found in the BAL of asthmatics. Finally, eosinophils isolated from the BAL of asthmatics have an increased expression of LTC4 synthase. The level of expression of this enzyme correlates with the increased amount of CysLTs produced in the airways of these patients. Taken together, these data identify at least two possible mechanisms to explain the excessive CysLT production in asthmatics: 1) an increased content of AA in the glycerolipid pools of inflammatory cells 2) an enhanced activity of key biosynthetic enzymes involved in CysLT synthesis.

Lipid composition of erythrocytes and thrombocytes of a subantarctic seabird, the king penguin.

Phospholipid (PL) compositions and fatty acid (FA) patterns of PL were determined in the erythrocytes and blood thrombocytes of a seabird, the king penguin, living in the subantarctic area and feeding on prey rich in n-3 polyunsaturated FA. Results were compared between birds in three different physiological states (breeding and molting adults, chicks) to those reported for other birds. In erythrocytes, the ratios of cholesterol to PL and of sphingomyelin to phosphatidylcholine (PC) were lower than in other birds. The PL distribution was similar to those previously reported in the hen and pigeon. In contrast to other birds, cardiolipin levels were unexpectedly high (4%). Very long chain n-3 FA were abundant (13-27%) in phosphatidylethanolamine (PE), phosphatidylserine and PC, probably in relation to the natural diet of these birds. Among n-3 FA, 22:6n-3 was the most abundant in all PL (2-20%), whereas the highest levels of arachidonic acid were observed in PE (14%). In thrombocytes, the PL distribution and FA composition of the main PL (PC, PE) differed from those of erythrocytes, and in particular, levels of n-3 FA (9-12%) were 1.5-2 times lower. The highest levels of arachidonic acid were found in phosphatidylinositol (24%). The lipid profile of penguin erythrocytes could contribute to the efficiency of blood circulation and oxygen delivery in microvascular beds, thus favoring diving capacity of these animals. Our observations do not support the hypothesis of a common origin of avian thrombocytes and erythrocytes.

Effect of Culture Temperature on Growth, Survival, and Biochemical Composition of Yellow Perch Perca fiavescens

AbstractJuvenile yellow perch Perca fiavescens were evaluated under controlled conditions in tanks for 13 wk to determine the effect of temperature on growth to advanced sizes under intensive culture conditions. Yellow perch weighing 6.6 ± 1.5 g were stocked into nine 4,755‐L tanks at 131 fish/m3 (625 perch/tank). There were three replicate tanks per temperature (20, 24, and 28 C). Perch were fed to apparent satiation twice daily using a 45% crude protein diet with 16% crude fat. After 93 d the perch in the 24 C treatment were significantly larger (P &lt; 0.05) than those in the 20 C and 28 C treatments, which were not significantly different (P &lt; 0.05) from each other. Yellow perch raised at 28 C had significantly higher (P &lt; 0.05) feed conversion ratios and significantly lower (P &lt; 0.05) survival and net protein utilization than perch raised at 20 C or 24 C. Whole body moisture was significantly higher in (P &lt; 0.05) yellow perch raised at 20 C which also had significantly higher levels of arachidonic acid (20:4 n‐6) and docosohexaenoic acid (22:6 n‐3). The ratio of palmitic acid (16:0) and palmitoleic acid (16:1 n‐6) had a positive correlation (P &lt; 0.05) with culture temperature. These data indicate that 24 C may be an optimum temperature for yellow perch. At 20 C survival and feed conversion are good but growth rates are reduced. Temperatures near 28 C appear sufficient to represent chronic stress conditions.

Cardiac (n-3) Non-Esterified Fatty Acids Are Selectively Increased in Fish Oil-Fed Pigs following Myocardial Ischemia

The effect of fish oil supplementation on the nonesterified fatty acid (NEFA) concentration and composition in the normoxic and hypoxic myocardium of pigs was examined. Two groups of female pigs (n = 7) were fed a diet supplemented with either 5 g beef tallow/kg (as control) or 5 g fish oil/kg (MaxEPA) rich in (n-3) fatty acids. After 6 wk of supplementation, the pigs were anesthetized, hearts exposed by thoracotomy followed by occlusion of the left anterior descending artery. Normoxic and hypoxic regions of the heart were examined for NEFA concentration and composition by using a combination of thin layer and gas chromatography. Nonesterified (n-6) and (n-3) fatty acid concentration and composition differed significantly between the two groups in both the normoxic and hypoxic areas of the heart. Eicosapentaenoic and docosahexaenoic acid concentration in the NEFA fraction of the normoxic myocardium were higher in the fish oil group than in the beef tallow group (P < 0.001). In the fish oil-fed pigs, the (n-3) NEFA concentration was significantly higher in the hypoxic compared to the normoxic region of the heart. The fish oil-fed group had lower levels of arachidonic acid in the NEFA fraction compared to the beef tallow-fed group, whereas the hypoxic myocardium had higher levels of arachidonic acid, regardless of the dietary fat supplementation. Despite large differences in the proportions of saturated fatty acids in the experimental diets, there was little or no difference in the saturated fatty acid content of cardiac phospholipid and NEFA fractions. Following myocardial ischemia, (n-3) fatty acids in the NEFA fractions were selectively increased in the fish oil-fed pigs, implicating the possible role of nonesterified (n-3) polyunsaturated fatty acids in the prevention of arrhythmias.

Identification of a novel delta 6-acyl-group desaturase by targeted gene disruption in Physcomitrella patens.

The moss Physcomitrella patens contains high levels of arachidonic acid. For its synthesis from linoleic acid by desaturation and elongation, novel delta 5- and delta 6-desaturases are required. To isolate one of these, PCR-based cloning was used, and resulted in the isolation of a full-length cDNA coding for a putatively new desaturase. The deduced amino acid sequence has three domains: a N-terminal segment of about 100 amino acids, with no similarity to any sequence in the data banks, followed by a cytochrome b5-related region and a C-terminal sequence with low similarity (27% identify) to acyl-lipid desaturases. To elucidate the function of this protein, we disrupted its gene by transforming P. patens with the corresponding linear genomic sequence, into which a positive selection marker had been inserted. The molecular analysis of five transformed lines showed that the selection cartridge had been inserted into the corresponding genomic locus of all five lines. The gene disruption resulted in a dramatic alteration of the fatty acid pattern in the knockout plants. The large increase in linoleic acid and the concomitant disappearance of gamma-linolenic and arachidonic acid in all knockout lines suggested that the new cDNA coded for a delta 6-desaturase. This was confirmed by expression of the cDNA in yeast and analysis of the resultant fatty acids by GC-MS. Only the transformed yeast cells were able to introduce a further double bond into the delta 6-position of unsaturated fatty acids. To our knowledge, this is the first report of a successful gene disruption in a multicellular plant resulting in a specific biochemical phenotype.

Production of high yields of arachidonic acid in a fed-batch system by Mortierella alpina ATCC 32222

Of six strains of Mortierella tested, Mortierella alpina ATCC 32222 produced the highest yields of arachidonic acid. Supplementation of soy flour (1% w/v) and vegetable oils (1% v/v) significantly increased the biomass, lipid content and arachidonic acid level. Replacement of NaNO3 with corn steep liquor (1% w/v) also improved arachidonic acid production. A fed-batch culture system at 25 °C, producing a high biomass (52.4 g/l) and arachidonic acid content (9.1 g/l) in 8␣days, was developed. A fed-batch system at low temperature (15 °C) gave even higher arachidonic acid levels (11.1 g/l) in 11 days.

14-34 - Trait anxiety is associated with high arachidonic acid levels in plasma — a study of men born in 1933

14-34 - Trait anxiety is associated with high arachidonic acid levels in plasma — a study of men born in 1933

Mechanisms of prostanoid synthesis in human synovial cells: cytokine-peptide synergism.

Bradykinin (BK)2 and interleukin-1 (IL-1) interact synergistically to stimulate prostaglandin synthesis in human synovial fibroblast-like cells. The effect of BK is rapid and correlates with its capacity to elevate cytosolic levels of calcium ([Ca2+]i), while IL-1's effect is slow and s dependent upon de novo protein synthesis. The mechanism of this synergistic interaction was investigated. In the basal state, high levels of arachidonic acid (AA) were spontaneously released from synovial cells but near absent levels of cyclooxygenase activity prevented metabolism of AA to prostanoid. BK was a potent stimulus for elevating AA, but not prostaglandins, above basal levels. IL-1, in contrast, increased prostaglandins but not AA, above basal levels. IL-1 treatment was not associated with a loss or redistribution of AA among phospholipid classes. These results are consistent with high basal phospholipase activity in synovial cells and demonstrate the ability of BK, presumably via its ability to raise [Ca2+]i, to further elevate this activity(ies). Metabolism of AA to prostanoid is minimal in resting and BK-stimulated synovial cells, however, without the concomitant induction of cyclooxygenase activity by IL-1. These studies clarify the different, but synergistic, mechanisms of action of a peptide and cytokine in stimulating prostanoid synthesis in synovial cells. In addition, these data extend the results of previous investigations in demonstrating that basal phospholipase activity provides sufficient AA substrate for IL-1 induced prostanoid synthesis without invoking the concomitant induction of phospholipase activity by IL-1.

The relationship between the fatty acid composition of the lipids of the yolk and the brain of the duck embryo.

Domesticated animals are often reared on formulated diets which differ greatly from the diets of their wild counterparts. In many cases. the formulated diets may be relatively deficient in n-3 polyunsaturated fatty acids, especially in docosahexaenoic acid (22:6). Since this particular fatty acid plays an important role in the embryonidneonatal development of the brain and retina, such deficiencies may result in harmfull consequences. Recent studies in this area from our laboratory have shown that the yolk lipids from eggs of alligators and ostriches currently reared in captivity are markedly deficient in n-3 fatty acids in comparison with the situation in the wild(l,2]. Moreover, this n-3 deficiency is associated with greatly increased rates of embryonic mortality. In the present study. the fatty acid composition of the yolk phospholipids from commercially-reared and free-range ducks were compared. The main difference between the two types was that the proportion of 22:6 (%w/w of total fatty acids) was approx. 3-fold greater in the freerange eggs (P<0.001). The proportion of 22:6 in the commercial duck eggs was very low; in fact yolk lipids from commercially-reared chickens typically contain considerably more 22:6[3]. However, the commercial duck eggs do contain high levels of arachidonic acid (20:4), possibly reflecting an imbalance in the proportions of n-6 to n-3 fatty acids in the formulated diets. Although the free-range ducks were free to select their diet from their environment, they were also supplied with a grain -based feed supplement. Thus it is possible that truly wild-living ducks would exhibit even greater proportions of n-3 fatty acids in their egg yolks. The consequences of the differences in the yolk 22:6 levels on the tissue lipid fatty acid profiles in the embryo were investigated. In general, the fatty acid profiles of the embryonic liver, adipose tissue and heart reflected the yolk compositions; thus the proportions of 22:6 in these tissues from the free-range embryos were approx. 4-fold greater than in the commercial embryos. The fatty acid compositions of the brain phospholipids at day 25 of the 28-day embryonic period are shown in Table I . The proportion of 22:6 in the brains of the free-range embryos was approx. 1.5-fold greater than for the commercial embryos ( P 4 . 0 0 I ) . Thus, although the differences in yolk 22:6 content in the two situations does affect the brain composition, the effects are much less severe in the brain than in the other tissues. Similar rcsults have been obtained for the alligator where a 2-fold difference in the 22:6 level in the yolks of wild versus captive animals was reflected in a 2-fold difference in the levels of this fatty acid in the lipids of the liver, adipose tissue and heart of the embryos, but with no difference observed for the brains[4] Because of the important functions of 22:6 in the lipids of the neural membranes, it is possible that the developing brain strivcs to maintain an appropriate level of this fatty acid, consistent with optimal function. Thus the fatty acid profile of the embryonic brain may be less sensitive to variations in the supply from the yolk compared with other tissues.

Suppression of evoked IPSPs by arachidonic acid and prostaglandin F 2α

Arachidonic acid (AA) and certain prostagladins appear to antagonize GABA A receptors in synaptoneurosomes [18]. We report here that perfusing hippocampal slices with AA or prstaglandin F 2α diminishes evoked IPSP conductance and increases CA1 pyramidal cell input resistance. The effects of the two compounds were similar, though not identical, in time course, magnitude, and response to washout. These findings suggest that high levels of AA and its metabolites may bias neurons towards excitation.

Decreased food efficiency ratio, growth retardation and changes in liver fatty acid composition in rats consuming thermally oxidized and polymerized sunflower oil used for frying

Changes in food intake, body weight, liver weight, hepatosomatic index and hepatic fatty acid composition were studied in growing male Wistar rats fed a diet containing sunflower oil that had been used repeatedly for frying. During a period of 27 days, the animals were fed semi-synthetic diets containing either 15% used oil with 19.1% polar material (group 2) or 15% unused oil with 5.1% polar material (group 1). Although food intake was similar in both experimental groups, final body weight, body weight gain, food efficiency ratio and protein efficiency ratio were significantly lower in group 2. The increase of the hepatosomatic index in rats of group 2 seems related to a higher ingestion of potential toxic components (dimers and polymers of triglycerides and oxidized triglycerides) by this group. The livers of nine out of the 10 animals studied also showed moderate fibrotic degenerative areas with severe vacuolization, together with regenerative areas containing eosinophilic binuclear hepatocytes. In addition, livers of group 2 animals showed a 12% higher content of arachidonic acid. Data suggest that higher arachidonic acid levels would be needed for regeneration to palliate liver injury. These data suggest that frying sunflower oil is potentially toxic; assessment of risk is therefore necessary for frying fats with a high polar content.

Effects of dietary fish oil and corn oil on bile flow and composition in rats

A study was undertaken to compare the effects of n-3 and n-6 fatty acids on bile flow and bile composition in rats. Male Sprague-Dawley rats were fed diets containing either 10% corn oil or 8% fish oil (MaxEPA) and 2% corn oil for a period of 2 weeks. At the end of the feeding period, rats were fitted with exteriorized cannulas in the duodenum and bile duct. While a glucose-saline solution was infused through the duodenal cannula at 3.0 mL/h, bile was collected hourly for 6 hours. Bile secretion was found to be greater in the fish oil fed rats than the corn oil fed animals. As a function of bile flow per hour, the bile acid, cholesterol and phospholipid output appeared to be greater in the group receiving fish oil. However, when concentration was determined, the effect of diet disappeared. Diet had an effect on the fatty acid composition of bile phospholipids. Rats fed fish oil had significantly more eicosapentaenoic and docosahexaenoic acids in the bile phospholipids than those fed corn oil while those fed corn oil had higher levels of arachidonic acid.

Effects of linoleic acid and γ‐linolenic acid on the growth and metastasis of a human breast cancer cell line in nude mice and on its growth and invasive capacityin vitro

It has been reported that gamma-linolenic acid (GLA)-rich diets suppress mammary carcinogenesis and transplanted tumor growth and that GLA inhibits the growth of cultured human cancer cell lines. We compared the effects of dietary GLA and linoleic acid (LA) on the growth of MDA-MB-435 human breast cancer cells and their expression of the metastatic phenotype in vivo and in vitro. Athymic nude mice (30/dietary group) were fed isocaloric diets containing 20% (wt/wt) fat but providing 8% GLA or LA for 7 days, and 10(6) tumor cells were then injected into a thoracic mammary fat pad. The diets were continued for a further 11 weeks. The primary tumor growth rates were similar in mice from the two dietary groups; there was a nonstatistically significant trend for the incidence of macroscopic lung metastases and the total lung metastatic volumes to be higher in the GLA-fed mice (79% and 40.1 +/- 13.9 mm3) than in the LA-fed mice (64% and 15.5 +/- 5.4 mm3). The tumor cell phospholipids from the 8% GLA-fed mice contained significantly lower LA levels but higher arachidonic acid levels (both p < 0.001) than those from 8% LA-fed mice. Also the arachidonate-derived eicosanoids (prostaglandin E, leukotriene B4, and 5-, 12-, and 15-hydroxyeicosatetraenoic acids) were significantly higher in tumors from the 8% GLA group. Zymography showed higher 92-kDa type IV collagenase activity in tumors from 8% GLA-fed mice. In vitro, GLA and LA, at 0.5-2 micrograms/ml, stimulated MDA-MB-435 cell growth; 10 micrograms/ml was mildly inhibitory. Whereas LA stimulated tumor cell invasion and 92-kDa type IV collagenase production in vitro, GLA inhibited invasion and did not induce activity of the proteolytic enzyme. Our results do not support the hypothesis that supplementation with GLA would exert a beneficial effect on the progression of an existing breast cancer, perhaps because it is metabolized in vivo to arachidonate-derived eicosanoids that are known to be involved in the metastatic process.

Genotype effects on the antioxidant enzymes activity and mRNA expression in liver and kidney tissues of autoimmune-prone MRL/McJ-lpr/lpr mice

Congeneic pairs of MKL/lpr and MRL/ + +(+ / +) mice differ in incidence of autoantibodies, lymphoproliferative disease and survival, characteristics that are linked to immunological abnormalities. MRL/lpr mice have a significantly shorter life span compared to +/+ mice. Because a weak antioxidant defense and an increased generation of free radicals are generally implicated in the severity of many autoimmune diseases, the present study was undertaken to compare the influence of genotype on lipid composition, lipid peroxidation and expression of mRNA, and activity of antioxidant enzymes such as catalase (CAT), glutathione peroxidase (GSH-Px) and Superoxide dismutase (SOD) in the livers and kidneys of these mice. The expression of SOD, GSH-Px and CAT mRNAs was significantly higher ( P < 0.05) in the livers of + / + mice, while in the kidneys only SOD expression was found significantly higher in + / + mice when compared to MRL/ lpr mice. Further, the activity of cytosolic SOD and GSH-Px was also found significantly higher ( P < 0.001) in the livers of + / + mice. Both livers and kidneys of MRL/ lpr mice exhibited significantly higher levels of arachidonic acid (20:4( n − 6)), significantly higher generation of thiobarbituric acid reactive substances (TBARS) and higher estimated peroxidation index than the + / + mice. In addition, the MRL/ lpr mice had higher levels of serum anti-cardiolipin antibodies. In summary, the results from the present study indicate that besides several immune-related abnormalities, the MRL/lpr mice may exhibit their inability to cope with oxidative stress due to a poor antioxidant defense system. This weak defense system is revealed by lower mRNA expression of antioxidant enzymes, weak SOD and GSH-Px enzyme activities, and an increased level of 20:4( n − 6) in liver lipids, which in turn may increase generation of free radicals in the livers and kidneys, thus making the MRL/lpr mice more susceptible to autoimmune disease than the + / + mice.

Analysis of lipids in the salivary glands of Amblyomma americanum (L.): detection of a high level of arachidonic acid.

Analysis of lipids in salivary glands of the lone star tick, Amblyomma americanum, demonstrated that arachidonic acid (20:4, n-6) comprises 8% of all fatty acids identified by gas chromatography. The occurrence of arachidonic acid and other C20 polyunsaturated fatty acids in tick salivary glands was confirmed by gas chromatography-mass spectrometry. Arachidonate is located entirely in the phospholipid fraction and is associated exclusively with phosphatidylcholine (PC) and phosphatidylethanolamine (PE). Salivary glands stored and frozen for several months had a similar lipid composition as freshly dissected salivary glands, with the exception of a small amount of free arachidonic acid and an increase in lysophosphatidylcholine. Incubation of salivary gland homogenates with snake venom phospholipase A2 showed that most saturated fatty acids are esterified in the sn-1 position of PC and PE, with the unsaturated fatty acids in the sn-2 position. Approximately 75% of arachidonic acid is in the sn-2 position of PC and PE, adding support to the hypothesis that arachidonic acid is released into the cytoplasm after activation of a phospholipase A2 for subsequent metabolism to prostaglandins and/or other eicosanoids.

Platelet hyperreactivity in hyperlipidaemia with specific reference to platelet lipids and fatty acid composition

Platelet function after thrombin stimulation, the fatty acid composition of individual phospholipids, and levels of lipid components (cholesterol, cholesterol ester, phospholipids and triglycerides) were determined in total membranes of platelets from hyperlipidaemic (HL) and control subjects. Platelet aggregation, thromboxane (TX) B 2 production and serotonin release was significantly greater in HL patients than in controls. Levels of platelet cholesterol, total phospholipids, cholesterol ester and triglycerides, were significantly higher in the HL patients. Small differences between the two groups were observed for the phospholipid fatty acid patterns. However, levels of arachidonic acid (AA) were significantly higher in phosphatidylinositol (PI) of HL patients (40.01 ± 6.59 mol%) as compared to the controls (31.52 ± 9.91 mol%) ( P = 0.002). The higher levels of AA in PI, which is considered a donor pool for eicosanoid synthesis, may be an additional mechanism for the well documented platelet hyperfunction and greater TXB 2 production in hyperlipidaemic subjects.

Insulin binding to liver nuclei from lean and obese mice is altered by dietary fat

Insulin binding to the plasma membrane is known to be altered by modifying the membrane composition through dietary treatment. As insulin binding receptors are also present on neclear membrane, this study was undertaken to investigate if specific bindinf of insulin to the liver nuclei is altered by diet. 8-wk-old female C57 B 6J lean and ob/ob mice were fed semipurified diets containing 20% (w/w) fat of either high or low polyunsaturated-to-saturated (P/S) fatty acid ratio for 4 wl. Liver nuclei weer prepared, insulin binding was measured and nuclear phospholipids were isolated for lipid analysis. Insulin binding was highest in nuclei prepared from lean mice fed a high P/S diet. Specific binding of insulin to nuclei prepared from obese mice was also increased by the high P/S diet, but to a lesser extent compared to lean mice. Feeding a high P/S diet increased polyunsaturated fatty acid content of membrane phospholipids from both lean and ob/ob mice. Obese mice were characterized by higher levels of arachidonic acid and lower levels of linoleic acid in phosphatidylcholine. The present study establishes that insulin binding to liver nuclei is increased by feeding a high P/S diet, and that insulin binding to liver nulcei from obese mice is lower than lean mice.