Effect of a fish oil diet on the composition of rat neutrophil lipids and the molecular species of choline and ethanolamine glycerophospholipids

Dynamics of Docosahexaenoic Acid Utilization by Mouse Peritoneal Macrophages

In this work, the incorporation of docosahexaenoic acid (DHA) in mouse resident peritoneal macrophages and its redistribution within the various phospholipid classes were investigated. Choline glycerophospholipids (PC) behaved as the major initial acceptors of DHA. Prolonged incubation with the fatty acid resulted in the transfer of DHA from PC to ethanolamine glycerophospholipids (PE), reflecting phospholipid remodeling. This process resulted in the cells containing similar amounts of DHA in PC and PE in the resting state. Mass spectrometry-based lipidomic analyses of phospholipid molecular species indicated a marked abundance of DHA in ether phospholipids. Stimulation of the macrophages with yeast-derived zymosan resulted in significant decreases in the levels of all DHA-containing PC and PI species; however, no PE or PS molecular species were found to decrease. In contrast, the levels of an unusual DHA-containing species, namely PI(20:4/22:6), which was barely present in resting cells, were found to markedly increase under zymosan stimulation. The levels of this phospholipid also significantly increased when the calcium-ionophore A23187 or platelet-activating factor were used instead of zymosan to stimulate the macrophages. The study of the route involved in the synthesis of PI(20:4/22:6) suggested that this species is produced through deacylation/reacylation reactions. These results define the increases in PI(20:4/22:6) as a novel lipid metabolic marker of mouse macrophage activation, and provide novel information to understand the regulation of phospholipid fatty acid turnover in activated macrophages.

Role of EPA in Inflammation: Mechanisms, Effects, and Clinical Relevance

Many chronic inflammatory processes are linked with the continuous release of inflammatory mediators and the activation of harmful signal-transduction pathways that are able to facilitate disease progression. In this context atherosclerosis represents the most common pathological substrate of coronary heart disease, and the characterization of the disease as a chronic low-grade inflammatory condition is now validated. The biomarkers of inflammation associated with clinical cardiovascular risk support the theory that targeted anti-inflammatory treatment appears to be a promising strategy in reducing residual cardiovascular risk. Several literature data highlight cardioprotective effects of the long-chain omega-3 polyunsaturated fatty acids (PUFAs), such as eicosapentaenoic acid (EPA). This PUFA lowers plasma triglyceride levels and has potential beneficial effects on atherosclerotic plaques. Preclinical studies reported that EPA reduces both pro-inflammatory cytokines and chemokines levels. Clinical studies in patients with coronary artery disease that receive pharmacological statin therapy suggest that EPA may decrease plaque vulnerability preventing plaque progression. This review aims to provide an overview of the links between inflammation and cardiovascular risk factors, importantly focusing on the role of diet, in particular examining the proposed role of EPA as well as the success or failure of standard pharmacological therapy for cardiovascular diseases.

Insight on Polyunsaturated Fatty Acids in Endometrial Receptivity

Endometrial receptivity plays a crucial role in fertilization as well as pregnancy outcome in patients faced with fertility challenges. The optimization of endometrial receptivity may help with normal implantation of the embryo, and endometrial receptivity may be affected by numerous factors. Recently, the role of lipids in pregnancy has been increasingly recognized. Fatty acids and their metabolites may be involved in all stages of pregnancy and play a role in supporting cell proliferation and development, participating in cell signaling and regulating cell function. Polyunsaturated fatty acids, in particular, are essential fatty acids for the human body that can affect the receptivity of the endometrium through in a variety of methods, such as producing prostaglandins, estrogen and progesterone, among others. Additionally, polyunsaturated fatty acids are also involved in immunity and the regulation of endometrial decidualization. Fatty acids are essential for fetal placental growth and development. The interrelationship of polyunsaturated fatty acids with these substances and how they may affect endometrial receptivity will be reviewed in this article.

Determinants of the urinary and serum metabolome in children from six European populations

BACKGROUND

Environment and diet in early life can affect development and health throughout the life course. Metabolic phenotyping of urine and serum represents a complementary systems-wide approach to elucidate environment-health interactions. However, large-scale metabolome studies in children combining analyses of these biological fluids are lacking. Here, we sought to characterise the major determinants of the child metabolome and to define metabolite associations with age, sex, BMI and dietary habits in European children, by exploiting a unique biobank established as part of the Human Early-Life Exposome project ( http://www.projecthelix.eu ).

METHODS

Metabolic phenotypes of matched urine and serum samples from 1192 children (aged 6-11) recruited from birth cohorts in six European countries were measured using high-throughput ¹H nuclear magnetic resonance (NMR) spectroscopy and a targeted LC-MS/MS metabolomic assay (Biocrates AbsoluteIDQ p180 kit).

RESULTS

We identified both urinary and serum creatinine to be positively associated with age. Metabolic associations to BMI z-score included a novel association with urinary 4-deoxyerythreonic acid in addition to valine, serum carnitine, short-chain acylcarnitines (C3, C5), glutamate, BCAAs, lysophosphatidylcholines (lysoPC a C14:0, lysoPC a C16:1, lysoPC a C18:1, lysoPC a C18:2) and sphingolipids (SM C16:0, SM C16:1, SM C18:1). Dietary-metabolite associations included urinary creatine and serum phosphatidylcholines (4) with meat intake, serum phosphatidylcholines (12) with fish, urinary hippurate with vegetables, and urinary proline betaine and hippurate with fruit intake. Population-specific variance (age, sex, BMI, ethnicity, dietary and country of origin) was better captured in the serum than in the urine profile; these factors explained a median of 9.0% variance amongst serum metabolites versus a median of 5.1% amongst urinary metabolites. Metabolic pathway correlations were identified, and concentrations of corresponding metabolites were significantly correlated (r > 0.18) between urine and serum.

CONCLUSIONS

We have established a pan-European reference metabolome for urine and serum of healthy children and gathered critical resources not previously available for future investigations into the influence of the metabolome on child health. The six European cohort populations studied share common metabolic associations with age, sex, BMI z-score and main dietary habits. Furthermore, we have identified a novel metabolic association between threonine catabolism and BMI of children.

Long-chain fatty acids and inflammation

Inflammation plays a key role in many common conditions and diseases. Fatty acids can influence inflammation through a variety of mechanisms acting from the membrane to the nucleus. They act through cell surface and intracellular receptors that control inflammatory cell signalling and gene expression patterns. Modifications of inflammatory cell membrane fatty acid composition can modify membrane fluidity, lipid raft formation and cell signalling leading to altered gene expression and can alter the pattern of lipid and peptide mediator production. Cells involved in the inflammatory response usually contain a relatively high proportion of the n-6 fatty acid arachidonic acid in their membrane phospholipids. Eicosanoids produced from arachidonic acid have well-recognised roles in inflammation. Oral administration of the marine n-3 fatty acids EPA and DHA increases the contents of EPA and DHA in the membranes of cells involved in inflammation. This is accompanied by a decrease in the amount of arachidonic acid present. EPA is a substrate for eicosanoid synthesis and these are often less potent than those produced from arachidonic acid. EPA gives rise to E-series resolvins and DHA gives rise to D-series resolvins and protectins. Resolvins and protectins are anti-inflammatory and inflammation resolving. Thus, the exposure of inflammatory cells to different types of fatty acids can influence their function and so has the potential to modify inflammatory processes.

Omega-3 fatty acids and inflammatory processes

Long chain fatty acids influence inflammation through a variety of mechanisms; many of these are mediated by, or at least associated with, changes in fatty acid composition of cell membranes. Changes in these compositions can modify membrane fluidity, cell signaling leading to altered gene expression, and the pattern of lipid mediator production. Cell involved in the inflammatory response are typically rich in the n-6 fatty acid arachidonic acid, but the contents of arachidonic acid and of the n-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) can be altered through oral administration of EPA and DHA. Eicosanoids produced from arachidonic acid have roles in inflammation. EPA also gives rise to eicosanoids and these often have differing properties from those of arachidonic acid-derived eicosanoids. EPA and DHA give rise to newly discovered resolvins which are anti-inflammatory and inflammation resolving. Increased membrane content of EPA and DHA (and decreased arachidonic acid content) results in a changed pattern of production of eicosanoids and resolvins. Changing the fatty acid composition of cells involved in the inflammatory response also affects production of peptide mediators of inflammation (adhesion molecules, cytokines etc.). Thus, the fatty acid composition of cells involved in the inflammatory response influences their function; the contents of arachidonic acid, EPA and DHA appear to be especially important. The anti-inflammatory effects of marine n-3 PUFAs suggest that they may be useful as therapeutic agents in disorders with an inflammatory component.

Molecular species analysis of phospholipids

The elucidation of phospholipid molecular species composition provides detailed structural information concerning various lipids and thus offers descriptions of crucial determinants of membrane physical and biological properties. Various methods differing in labor intensity, mode of separation and detection, type of calibration, as well as other factors, have been published. Thus precision and accuracy are expected to vary considerably between methods. Qualitative and quantitative aspects of different procedures for molecular species analysis of individual phospholipid classes are discussed in this review. Special emphasis has been given to the characterization of biological tissue samples.

Molecular species of ethanolamine plasmalogens and transacylase activity in rat tissues are altered by fish oil diets

Effects of dietary fish oil ethyl esters and alkyldiacetylglycerols (an ether-linked lipid) on the distribution of subclasses of choline- and ethanolamine-glycerophospholipids as well as effects on highly unsaturated molecular species of ethanolamine plasmalogens from brain, spleen, kidney, lung, and testis of rats were examined. Supplementation of ethyl ester concentrates of n-3 fatty acids had no effect on the distribution of subclasses in any of the tissues. However, the supplements of 1-O-octadec-9'-enyl-2,3-diacetyl-sn-glycerol (diacetates of selachyl alcohol) caused significant increases in the alkylacylglycerophosphocholine and alkylacylglycerophosphoethanolamine subclasses from spleen and lung and in the alkylacylglycerophosphoethanolamine subclass from kidney. Dietary supplements of fish oil ethyl esters reduced the arachidonate-containing species of ethanolamine plasmalogens whereas molecular species having 20:5(n-3), 22:6(n-3), and/or 22:5(n-3) acyl groups were increased in the spleen, lung, and kidneys, but not brain. In testicular tissue from rats fed the fish oil diets, the molecular species of ethanolamine plasmalogens containing 22:5(n-6) acyl groups were reduced. An increase of ethanolamine plasmalogens with 18:1 alk-1-enyl moieties paired with highly unsaturated sn-2 acyl groups were found in the tissues of rats fed the fish oil plus selachyl alcohol diacetate supplements. Rats on the diet containing fish oil ethyl esters had significantly lower [3H]alkyllysoglycerophosphocholine CoA-independent transacylase activity in spleen microsomes than controls. This suggests that supplements of n-3 fatty acids interferes with the transacylation of arachidonate, an event that could seriously impair the release of arachidonate and lysophospholipids (e.g., lyso-PAF) that are precursors of potent bioactive lipid derivatives.

Differences in the interconversion between 20- and 22-carbon (n - 3) and (n - 6) polyunsaturated fatty acids in rat liver

When male weanling rats were fed diets containing either 5% corn oil or a diet in which half of the corn oil was replaced by fish oil, the 20:5(n - 3) in liver choline and ethanolamine phosphoglycerides, not only partially replaced arachidonate but also paired with palmitic and stearic acids in the same molar ratio as did arachidonate. The 22:5(n - 3)/22:6(n - 3) ratio in the liver phospholipids of corn oil fed rats was similar to that found when the esterified levels of these two acids were increased 5-fold by feeding fish oil. Moreover, the pairing of both 22:5(n - 3) and 22:6(n - 3) with palmitic and stearic acids, on a molar ratio basis, was relatively independent of the total amount of esterified 22:5(n - 3) and 22:6(n - 3). When (3-14C)-labeled 22:4(n - 6) was injected into rats raised on a chow diet or incubated with hepatocytes from these animals, its primary metabolic fate was retroconversion to arachidonate followed by esterification. Conversely, [3-14C]22:5(n - 3) was a poorer substrate for retroconversion with a larger amount being esterified directly into phospholipids and, in addition, this acid served as a precursor for 22:6(n - 3). The enhanced metabolism of both [3-14C]22:4(n - 6) to 22:5(n - 6) and of [3-14C]22:5(n - 3) to 22:6(n - 3) in animals raised on a diet devoid of fat or in their hepatocytes may possibly be due to elevated 6-desaturase activity and/or the level of this enzyme or enzymes. This hypothesis is based on studies showing that the synthesis of 22:6(n - 3) proceeds via a pathway independent of a 4-desaturase but requires the use of a 6-desaturase at two steps (Voss, A., Reinhart, M., Sankarappa, S. and Sprecher, H. (1991) J. Biol. Chem. 266, 19995-20000).

Alteration in mouse splenic phospholipid fatty acid composition and lymphoid cell populations by dietary fat

The fatty acid composition of diacyl- and alkylacylglycerophosphocholine (PC), phosphatidylinositol (PI), phosphatidylserine (PS), alkenylacyl-glycerophosphoethanolamine (aPE), and diacyl- and alkylacyl-glycerophosphoethanolamine (dPE) was assessed in isolated splenocytes from C3H/Hen mice fed one of four purified isocaloric diets for six weeks. Diets contained 20% by weight of either a high-linoleate sunflower oil (Hi 18:2), a high-oleate sunflower oil (Hi 18:1), a mixture of 17% menhaden fish oil and 3% high-linoleate sunflower oil (Hi n-3), or a mixture of 17% coconut oil and 3% high-linoleate sunflower oil (Hi SFA). Spleen weight and immune cell yield were significantly higher (P less than 0.05) in mice fed the Hi 18:1 or the Hi n-3 diets compared with those fed the Hi 18:2 and Hi SFA diets. Distinctive patterns of fatty acids were observed for each phospholipid in response to dietary fatty acids. Dietary fat significantly affected (P less than 0.05) total polyunsaturated fatty acids (PUFA) in PC and dPE, total saturated fatty acids (SFA) in PC, total monounsaturated fatty acids (MUFA), and n-3 PUFA in all phospholipid classes examined. In mice fed the Hi n-3 diet, n-3 PUFA were significantly elevated, whereas n-6 PUFA decreased in all of the phospholipids. In these mice, eicosapentaenoic acid (EPA) was the predominant n-3 PUFA in PC and PI, whereas docosahexaenoic acid (DHA) was the major n-3 PUFA in aPE and PS.(ABSTRACT TRUNCATED AT 250 WORDS)

C20 polyunsaturated fatty acids and phorbol myristate acetate enhance agonist-stimulated synthesis of 1-radyl-2-acetyl-sn-glycero-3-phosphocholine in vascular endothelial cells

This study has investigated the effect of supplementation of vascular endothelial cells with arachidonate and other polyunsaturated fatty acids on the agonist-stimulated synthesis of platelet activating factor (PAF; 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine; 1-alkyl-2-acetyl-GPC). Incubation of calf pulmonary artery endothelial cells for 48 h in medium containing 40 microM arachidonate resulted in a 2-3-fold enhancement of [3H]acetate incorporation into 1-radyl-2[3H]acetyl-GPC in response to either bradykinin or calcium ionophore A23187. The effects of arachidonate supplementation were both dose- and time-dependent, requiring a minimum exogenous arachidonate concentration of 2.5 microM and an incubation time of 4-6 h. Eicosapentaenoate and docosahexaenoate also enhanced the synthesis of 1-radyl-2-[3H]acetyl-GPC, but were less potent than arachidonate; alpha-linolenate, linoleate and oleate were without effect. Although not effective as an agonist, phorbol myristate acetate potentiated A23187- and bradykinin-stimulated synthesis of 1-radyl-2-[3H]acetyl-GPC. The effects of arachidonate supplementation were synergistic with potentiation by phorbol myristate acetate. Sphingosine inhibited agonist-stimulated incorporation of [3H]acetate into 1-radyl-2-[3H]acetyl-GPC both in the presence and absence of PMA. Characterization of the radiolabeled material indicated that the primary product was the acyl analogue of PAF (1-acyl-2-acetyl-GPC) rather than PAF. The results from this study suggest that agonist-stimulated synthesis of 1-radyl-2-acetyl-GPC in vascular endothelial cells is modulated both by cellular fatty acyl composition and activation of protein kinase C. Enrichment of vascular endothelial cells with fatty acids, which are mobilized by agonist-stimulated phospholipase A2, may enhance subsequent deacylation of choline phospholipids and, thus, increase synthesis of both 1-acyl-2-acetyl-GPC and PAF.

The metabolism of 20- and 22-carbon unsaturated acids in rat heart and myocytes as mediated by feeding fish oil

When rats were fed 5% corn oil, the heart phospholipids contained large amounts of 22-carbon (n-6) acids. When half of the corn oil was replaced with fish oil, the reduced level of arachidonate and 22-carbon (n-6) acids in phospholipids was accompanied by increases in the levels of 22-carbon (n-3) acids while only small amounts of 20:5(n-3) were acylated. Heart myocytes readily took up and acylated [1-14C]-labeled 20:4(n-6), 20:5(n-3) and 22:6(n-3) into phospholipids. The uptake and acylation of 20:4(n-6) was greater than for 20:5(n-3) but the intracellular labeling profiles were similar. Uptake and acylation of 22:6(n-3) was somewhat lower. In addition the intracellular labeling profile differed in that more 22:6(n-3) was incorporated into the ethanolamine-containing phospholipids than when 20:4(n-6) or 20:5(n-3) were the substrates. Neither 20:4(n-6) nor 20:5(n-3) was chain elongated. When [3-14C]-labeled 22:4(n-6) and 22:5(n-3) were the substrates, it was not possible to detect radioactive 22:5(n-6) or 22:6(n-3). Both [3-14]-labeled substrates were acylated into phospholipids and retroconverted with the subsequent esterification of radioactive 20:4(n-6) and 20:5(n-3) into triglycerides and phospholipids. These studies show that cardiomyocytes lack the ability to make 22-carbon acids from 20-carbon precursors but they retroconvert 22-carbon acids to 20-carbon acids. The high levels of 22-carbon polyunsaturated acids in total heart lipids thus cannot be attributed to the synthetic capacities of cardiomyocytes.

Effects of a fish oil diet on the metabolism of endogenous (n-6) and (n-3) fatty acids in rat neutrophils

The present study was carried out to define more precisely how dietary (n-3) fatty acids mediate leukotriene and phospholipid metabolism in neutrophils. Neutrophils from chow-fed rats did not synthesize detectable levels of LTB5 or 5-hydroxyeicosapentanenoic acid. The ratio of esterified 20:4(n-6)/20:5(n-3) in the phospholipids of neutrophils from rats fed a corn oil/fish oil diet was 4.6. The ratio of LTB4/LTB5 made by these cells was 2.6, thus suggesting that 20:5(n-3) release and/or subsequent metabolism was somewhat more efficient than for 20:4(n-6). When tritiated lyso-platelet activating factor was added to neutrophils from chow-fed rats, it was deactivated primarily by acylation with arachidonic acid. With the fish oil-fed animals both arachidonic acid and 20:5(n-3) were transferred to deactivate lyso-platelet activating factor. Molecular species analysis of the resulting radioactive 1-O-alkyl-2-acyl-sn-glycerol-3-phosphocholine showed that 20:5(n-3) pairs with the same 1-O-alkyl groups and in approximately the same ratio as does arachidonate. Collectively, these studies show that once 20:5(n-3) is incorporated into neutrophil lipids it is metabolized in a similar way as is arachidonate.

Effects of dietary n-3 fatty acids on the phospholipid molecular species of monkey brain

We examined the changes in the molecular species of brain ethanolamine glycerophospholipids of monkeys fed diets containing widely ranging amounts of n-3 fatty acids. Two groups of rhesus monkeys were fed pre- and postnatally either a control diet (soy oil; containing 8% of fatty acids as 18:3n-3) or a deficient diet (safflower oil; containing less than 0.3% 18:3n-3). The brains of these animals were analyzed at 22 months of age. A third group of monkeys was fed the safflower oil diet to 22 months of age and then switched to a fish oil diet (28% long-chain n-3 fatty acids) for 1-2 years before autopsy. The molecular species of the diacyl, alkylacyl, and alkenylacyl ethanolamine glycerophospholipids from frontal cortex were separated by HPLC. A total of 24 molecular species were identified. Fatty acids in the sn-2 position differed markedly among the diet groups, but the sn-1 position always contained only 16:0, 18:0, or 18:1. In the diacyl subclass of the control brain, the n-3 molecular species represented 41% of total and the n-6 species 45%, whereas in the deficient brain the n-3 molecular species decreased to 9% and n-6 molecular species increased to 77%. The fatty acid 22:5n-6 did not replace 22:6n-3 in a symmetrical fashion in the molecular species of the deficient brain. In the brains of the fish oil-fed monkeys, the n-3 molecular species amounted to 61% and n-6 molecular species were reduced to 25%. The species 18:1-22:6, 16:0-22:6, and 18:0-22:6 generally changed proportionally in response to diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Composition of mouse peritoneal macrophage phospholipid molecular species

The individual molecular species composition of diacyl, alkylacyl and alkenylacyl glycerophospholipids was determined in mouse peritoneal macrophages. A marked heterogeneity in the relative composition (mol%) of macrophage ether and ester phospholipid individual species was noted. High concentrations of 16:0-20:4 were found in ether phospholipids such as alkenylacyl glycerophosphoethanolamine (GPE; 27.5 mol%) and alkylacyl glycerophosphocholine (GPC; 16.6%) as compared to mol% levels of 16:0-20:4 in diacyl GPE (5.7%) and diacyl GPC (8.1%), respectively. Interestingly, alkenylacyl GPE was highly enriched in 1-ether (16:0) relative to alkylacyl GPC. The predominant diacyl molecular species in glycerophosphoinositol (GPI) and glycerophosphoserine (GPS) were 18:0-20:4 (59.1%) and 16:0-18:1 (41.1%), respectively. It is noteworthy that the level of 18:0-20:4 was several times higher in diacyl GPI (59.1%) than in diacyl GPS (11.1%), diacyl GPE (25.7%), and diacyl GPC (3.7%). The most abundant molecular species in diacyl GPC and diacyl GPE were 16:0-18:1 (29.9%) and 18:0-20:4 (25.7%), respectively. The abundance of 20:4 in ether phospholipids, specifically 16:0-20:4 and 18:0-20:4, in alkylacyl GPC is significant in view of the role these antecedents play in the biosynthesis of platelet-activating factor (PAF) and 20:4-derived eicosanoids in stimulated macrophages. The unique molecular species composition of the peritoneal macrophage distinguishes this cell type from others.

Lipids, membrane receptors, and enzymes: effects of dietary fatty acids

Dietary polyunsaturated fatty acids can significantly affect many biochemical and physiologic functions that are related to inflammatory, immune, and protective reactions. The different types of fatty acids can impact on energy metabolism, determine the lipid composition of membranes, and influence eicosanoid synthesis, all of which are relevant to prevention of and recovery from illness. In this paper, the effects of dietary polyunsaturated fatty acids on membrane composition, membrane-associated enzyme and receptor functions, signal transduction, second messenger, and eicosanoid generation are summarized. The differential effects of the polyunsaturated fatty acids of the n-6 and n-3 families are reviewed in the context of optimizing levels in diets.

Incorporation of polyunsaturated fatty acids into plasmalogens, compared to other phospholipids of cultured glioma cells, is more dependent on chain length than on selectivity between (n - 3) and (n - 6) families

In several tissues and cells, polyunsaturated fatty acids (PUFA) are esterified to plasmalogens (1-O-alk-1'-enyl-2-acyl-sn-glycero-3 phosphoethanolamine). Some studies have implicated selectivity for (n - 3) fatty acids, particularly of 20- and 22-carbons, over the (n - 6) family of fatty acids. We have investigated selectivity for esterification of both families of PUFA to plasmalogens in cultured C6 glioma cells. By 24 h, approx. 40% of cell-associated label from [1-14C]18:3(n - 3) was incorporated into plasmalogens and that label consisted almost exclusively of desaturation and chain elongation products [80% 20:5(n - 3) and 15% 22:5(n - 3)]. Relative incorporation of label from PUFA into plasmalogens was 20:5(n - 3) greater than 20:4(n - 6) greater than 18:3(n - 3) much greater than 18:2(n - 6); incorporation of unaltered 18-carbon chains was highly restricted. Cells incubated with [1-14C]18:3(n - 3) and 20-150 microM competing unlabeled fatty acids showed 20:5(n - 3) greater than 20:4(n - 6) greater than or equal to 22:4(n - 6) greater than 18:3(n - 3) as inhibitors of plasmalogen labeling. Chase experiments in cells prelabeled with [1-14C]18:3(n - 3) for 2 h showed limited reduction of label in plasmalogen. Reduction of plasmalogen label did occur when (n - 3) or (n - 6) fatty acids were added to cells prelabeled for 48 h, accounting for losses of 20-35% compared to controls. Accordingly, little selectivity occurs in esterification of plasmalogens from mixtures of (n - 3) and (n - 6) fatty acyl chains. Subsequent remodeling of (n - 3) acyl chains occurs, but is more dependent on acyl chain length than on selectivity between (n - 3) and (n - 6) families. Our data are consistent with a stable plasmalogen pool enriched in PUFA, but not specifically with (n - 3) fatty acids.

Studies on the incorporation and transacylation of various fatty acids in choline and ethanolamine-containing phosphoacylglycerol subclasses in human neutrophils

The incorporation of eight 14C-labeled fatty acids into human neutrophil phospholipids was investigated and the results were expressed as percent of the total phospholipid associated 14C-labeled substrate incorporated after an initial 15 min labeling and a subsequent 2 h reincubation in fatty acid-free buffer. In all cases, the PC fraction accounted for more than 40% of the total phospholipid radioactivity. The inositol-containing phosphoacylglycerols were also labeled well by all the fatty acids except 22:6(n - 3) and 16:0; however, a greater percentage of [14C]22:6(n - 3) was found in PE than that of any other labeled fatty acid substrate. In all cases, most of the radioactivity in PC after 15 min was in the diacyl subclass. After 2 h, there was a shift of [14C]20:4(n - 6), [14C]20:5(n - 3), [14C]22:6(n - 3) and [14C]18:4(n - 4) into the ether-linked subclass. No such shift was observed for [14C]16:0 or [14C]18:2(n - 6) and, although there was an increase in the percent radioactive 20:3(n - 6) and 20:3(n - 9) in ether-linked PC after 2 h, the total radioactivity in this fraction remained low by comparison. A similar shift in label occurred in the plasmalogenic-linked PE subspecies in cells labeled with [14C]20:4(n - 6), [14C]20:5(n - 3) and [14C]22:6(n - 3).

The effect of a fish oil diet on the fatty acid composition of individual phospholipids and eicosanoid production by rat platelets

When rats were fed a diet containing chow or fish oil for six weeks, the platelet phospholipid content and percent distribution were similar. In the fish oil fed animals there was a 54, 40, 41, and 24% reduction, respectively, in the levels of 20:4(n-6) in the choline-, ethanolamine-, inositol- and serine-containing glycerophospholipids. Dietary fish oil increased the total (n-3) polyunsaturated fatty acid content in all lipids. This effect was most pronounced in the ethanolamine glycerophospholipids which now contained 26, 11, and 4 nmols of 20:5(n-3), 22:5(n-3), and 22:6(n-3) in 10(9) cells. Ionophore A23187 stimulation of platelets from the chow fed rats resulted in the synthesis of 7, 64, and 3.5 nmols of 12-hydroxy-5,8,10-heptadecatrienoic acid, 12-hydroxy-5,8,10,14-eicosatetraenoic acid and 12-hydroxy-5,8,10,14,17-eicosapentaenoic acid, respectively, from 1 X 10(9) cells. The values from animals fed fish oil were 4, 18, and 27 nmol/10(9) platelets. It was not possible to detect any lipoxygenase products from 22:5(n-3) or 22:6(n-3), even though both acids are readily metabolized by lipoxygenase when added directly to platelets. These findings suggest that 22-carbon (n-3) fatty acids are not liberated when phospholipases are activated by calcium mobilization.