Distribution and metabolism of arachidonic and docosahexaenoic acids in rat pineal cells. Effect of norepinephrine

The time-course incorporation of 10 μM [¹⁴C]arachidonic (AA) and docosahexaenoic (DHA) acids into glycerolipids was studied in rat pineal cells. The incorporation of both labeled fatty acids into total lipids was approximately equal, but their distribution profiles among the various cell lipids showed marked differences. The esterification of [¹⁴C]DHA in the neutral lipids, triacylglycerols (TAG) and cholesterol esters (CE), was 2-fold higher than that of [¹⁴C]AA whereas the opposite could be observed in total phospholipids (PL). The order of incorporation into PL was phosphatidylcholine (PC) > phosphatidylinositol (PI) = phosphatidylethanolamine (PE) for [¹⁴C]AA and PC = PE for [¹⁴C]DHA, the incorporation of both fatty acids being not detected in phosphatidylserine (PS) and that of DHA not in PI. When using 0.5 μM [³H] fatty acids, the respective distribution patterns resembled that of fatty acids at 10 μM, except for a lower proportion in TAG. The stimulation of ³H-labeled cells by 100 μM norepinephrine induced a 170% increase of basal release of [³H]AA into the medium, while [³H]DHA was virtually not released. However, the analysis of cell labeling revealed that both [³H] fatty acid levels were decreased in PL and increased in TAG. These findings suggest different involvement for AA and DHA in the pineal function. The preferential incorporation of DHA in TAG suggests that TAG might play an important role in the pineal enrichment with DHA. The absence of DHA release after NE stimulation, which however cannot be ascertained, may raise the question of the role of DHA in NE transduction.     

Effects of docosahexaenoic and arachidonic acids on the synthesis and distribution of aminophospholipids during neuronal differentiation of PC12 cells

We have shown previously that docosahexaenoic acid (DHA) promotes and arachidonic acid (AA) suppresses neurite outgrowth of PC12 cells induced by nerve growth factor (NGF) and that incorporation of [3H]ethanolamine into phosphatidylethanolamine (PE) is suppressed in PC12 cells by AA while DHA has no effect. In the present study, the effects of these fatty acids on PE synthesis via decarboxylation of phosphatidylserine (PS), another pathway of PE synthesis, and distribution of aminophospholipids were examined. Incorporation of [3H]serine into PS and PE was elevated in the course of NGF-induced differentiation and was further stimulated significantly by DHA, but not by AA. [3H]Ethanolamine uptake by PC12 cells was significantly suppressed by AA but not by DHA while these fatty acids did not affect [3H]serine uptake, indicating that the suppression by AA of [3H]ethanolamine incorporation into phosphatidylethanolamine is attributable, at least in part, to a reduction in [3H]ethanolamine uptake. The distribution of PE in the outer leaflet of plasma membrane decreased during differentiation, which is known to be accompanied by an increase in the surface area of plasma membrane. Supplementation of PC12 cells with DHA or AA did not affect the distribution of aminophospholipids. Thus, DHA and AA affected aminophospholipid synthesis and neurite outgrowth differently, but not the transport and distribution of aminophospholipids, while the PE concentration in the outer leaflet of the plasma membrane decreased in association with morphological changes in PC12 cells induced by NGF.     

Preferential distribution of long chain polyunsaturated fatty acids in phospatidyl ethanolamine fraction of guinea pig alveolar apical membranes

We investigated the fatty acid distribution in guinea pig alveolar apical membranes at different developmental stages. Fatty acid composition of the purified membranes isolated from guinea pig fetuses (at 65 day, term=68 day), neonates (day 1) and adult males was determined. The levels of arachidonic acid (AA) and docosahexaenoic acid (DHA) were higher in the adult guinea pig alveolar apical membrane phosphatidylethanolamine (PE) fraction (9. 3+/-2.2 and 2.9+/-1.0%, respectively) while in other phospholipids (PL) fractions their levels were low or absent (P<0.01). Furthermore, levels of AA and DHA in the PE fraction of apical membrane increased significantly from fetal (6.6+/-3.0 and 0.8+/-0.4%, respectively) to neonatal life (10.3+/-1.5 and 3.0+/-0.8%, respectively). Increase in the level of DHA (almost four-fold) was much more pronounced than that of AA (P<0.05). As for guinea pig alveolar membranes, EPA and AA were mostly present in the PE fraction in pulmonary adenocarcinoma derived cells (A549 cells), a parallel model of type II pneumocytes, with the levels of AA around three-fold greater than that of EPA, Binding of radiolabelled fatty acids to A549 cells showed no significant differences between the maximum uptake achieved for different fatty acids (AA, 1.7+/-0.2, EPA, 2.3+/-0.3, LA, 1.7+/-0.2, OA, 2.0+/-0.2nmol/mg protein, P>0.5). Once the fatty acids were taken up by these cells AA was mostly identifiable in the monoacylglycerol (MAG) fraction, whereas EPA was equally distributed between the MAG and PL fractions. Oleic acid was mainly present in the triglyceride (TAG) fraction whereas LA was evenly distributed between the TAG, MAG, and PL fractions. Our data demonstrate a preferential distribution of AA and DHA in PE fractions of alveolar apical membranes during development.     

Incorporation of exogenous fatty acids into phospholipids by cultured hamster fibroblasts. Effect of SV40 transformation

In situ incorporation of two saturated (palmitic, 16:0; stearic, 18:0) and three unsaturated fatty acids (oleic, 18:1; linoleic, 18:2; arachidonic, 20:4) into the four major phospholipids, sphingomyelin, PC, PI and PE, was followed. Transformed cells incorporated unsaturated fatty acids more rapidly, whereas no significant differences were found concerning saturated fatty acids. In vitro determination of phospholipid acylation showed that incorporation of coenzyme A-activated forms of two saturated fatty acids (16:0 and 18:0) and one unsaturated fatty acid (18:1) into phospholipids was increased in transformed cells. Comparison of results obtained in situ and in vitro strongly suggests that incorporation of fatty acids into phospholipids in cultured cells is not limited by acyltransferase activities.     

Maternal dietary fat alters amniotic fluid and fetal intestinal membrane essential n-6 and n-3 fatty acids in the rat

We investigated whether maternal fat intake alters amniotic fluid and fetal intestine phospholipid n-6 and n-3 fatty acids. Female rats were fed a 20% by weight diet from fat with 20% linoleic acid (LA; 18:2n-6) and 8% alpha-linolenic acid (ALA; 18:3n-3) (control diet, n = 8) or 72% LA and 0.2% ALA (n-3 deficient diet, n = 7) from 2 wk before and then throughout gestation. Amniotic fluid and fetal intestine phospholipid fatty acids were analyzed at day 19 gestation using HPLC and gas-liquid chromotography. Amniotic fluid had significantly lower docosahexaenoic acid (DHA; 22:6n-3) and higher docosapentaenoic acid (DPA; 22:5n-6) levels in the n-3-deficient group than in the control group (DHA: 1.29 +/- 0.10 and 6.29 +/- 0.33 g/100 g fatty acid; DPA: 4.01 +/- 0.35 and 0.73 +/- 0.15 g/100 g fatty acid, respectively); these differences in DHA and DPA were present in amniotic fluid cholesterol esters and phosphatidylcholine (PC). Fetal intestines in the n-3-deficient group had significantly higher LA, arachidonic acid (20:4n-6), and DPA levels; lower eicosapentaenoic acid (EPA; 20:5n-3) and DHA levels in PC; and significantly higher DPA and lower EPA and DHA levels in phosphatidylethanolamine (PE) than in the control group; the n-6-to-n-3 fatty acid ratio was 4.9 +/- 0.2 and 32.2 +/- 2.1 in PC and 2.4 +/- 0.03 and 17.1 +/- 0.21 in PE in n-3-deficient and control group intestines, respectively. We demonstrate that maternal dietary fat influences amniotic fluid and fetal intestinal membrane structural lipid essential fatty acids. Maternal dietary fat can influence tissue composition by manipulation of amniotic fluid that is swallowed by the fetus or by transport across the placenta.     

Polyunsaturated fatty acids stimulate phosphatidylcholine synthesis in PC12 cells

The synthesis of phospholipids in mammalian cells is regulated by the availability of three critical precursor pools: those of choline, cytidine triphosphate and diacylglycerol. Diacylglycerols containing polyunsaturated fatty acids (PUFAs) apparently are preferentially utilized for phosphatide synthesis. PUFAs are known to play an important role in the development and function of mammalian brains. We therefore studied the effects of unsaturated, monounsaturated and polyunsaturated fatty acids on the overall rates of phospholipid biosynthesis in PC12 rat pheochromocytoma cells. Docosahexaenoic acid (DHA, 22:6n-3), eicosapentaenoic acid (EPA, 20:5n-3) and arachidonic acid (AA, 20:4n-6) all significantly stimulated the incorporation of (14)C-choline into total cellular phospholipids. In contrast, monounsaturated oleic acid (OA) and the saturated palmitic (PA) and stearic (SA) acids did not have this effect. The action of DHA was concentration-dependent between 5 and 50 microM; it became statistically significant by 3 h after DHA treatment and then increased over the ensuing 3 h. DHA was preferentially incorporated into phosphatidylethanolamine (PE) and phosphatidylserine (PS), while AA predominated in phosphatidylcholine (PC).     

Composition and metabolism of phospholipids of human leukocytes

Human mononuclear (MN) and polymorphonuclear (PMN) leukocytes were analyzed for their phospholipid, triglyceride, cholesterol and fatty acid content. The phospholipid/cholesterol ratio was 1.24 for both cels. MN cells contain more phosphatidylcholine (PC), but less phosphatidylserine (PS), phosphatidylethanolamine (PE) and sphingomyelin (SPH) than PMN cells when expressed as percent of total phospholipid. When expressed on the basis of lipid content per cell, MN cells contain less PS, PE and SPH but more triglyceride than PMN cells. PMN cells incorporate palmitic, stearic, linoleic and linolenic acids into their phospholipids, triglycerides or cholesterol esters. The incorporation into triglycerides was highest for all fatty acids. Of the phospholipids, the incorporation was highest into PC. Labeled fatty acids also were found in proteins which had been delipidized by exhaustive extraction with organic solvents. These represent tightly or covalently bound fatty acids. The incorporation of [³H]palmitic acid into this protein fraction is stimulated by insulin.     

Fatty acid composition and incorporation of arachidonic acid into phospholipids of hemocytes from the tobacco hornworm Manduca sexta

The fatty acid compositions were determined for total lipids, triacylglycerols, phospholipids and four phospholipid fractions, including phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylserine/phosphatidylinositol (PS/PI) and cardiolipin (CA) obtained from hemocytes and cell-free serum from second day, fifth instar larvae of the tobacco hornworm Manduca sexta and the standard Manduca rearing medium. The hemocyte fatty acid profiles were considerably different from the profiles of the medium the insects were reared on and from the profiles of the cell-free serum. Hemocyte neutral lipids had lower proportions of polyunsaturated fatty acids than phospholipids. The fatty acid profiles of PC, PE, PS/PI and CA differ from each other and from the total lipid profiles, indicating selective fatty acid incorporation into hemocyte phospholipid species. Studies with radioactive arachidonic acid similarly indicated selective incorporation of polyunsaturated fatty acids into hemocyte lipids. Under our in vitro conditions, >40% of the total radioactivity was incorporated into hemocyte lipids. About 93% of the incorporated radioactivity was found in phospholipids. Within phospholipids. most of the radioactivity was associated with PC (46%), and less with PE (28%) and PS/PI (21%). Very little radioactivity was recovered in CA (0.9%).     

Regional Membrane Phospholipid Alterations in Alzheimer's Disease

Regional levels of membrane phospholipids [phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylcholine (PC)] were measured in the brain of Alzheimer's disease (AD) and control subjects. The levels of PE-derived and PI-derived total fatty acids were significantly decreased in the hippocampus of AD subjects. Here significant decreases were found in PE-derived stearic, oleic and arachidonic and docosahexaenoic acids, and in PI-derived oleic and arachidonic acids. In the inferior parietal lobule of AD subjects, significant decreases were found only in PE and those decreases were contributed by stearic, oleic and arachidonic acids. In the superior and middle temporal gyri and cerebellum of AD subjects, no significant decreases were found in PC-, PE- and PI-derived fatty acids. The decrease of PE and PI, which are rich in oxidizable arachidonic and docosahexaenoic acids, but not of PC, which contains lesser amounts of these fatty acids, suggests a role for oxidative stress in the increased degradation of brain phospholipids in AD.     

Preferential incorporation of eicosanoid precursor fatty acids into human umbilical vein endothelial cell phospholipids

We have examined the preferential incorporation of specific fatty acids into phospholipid classes of cultured human umbilical vein endothelial cells. Pulse-labeling of human umbilical vein endothelial cell phospholipids with radiolabeled fatty acids and inhibition of radiolabeled fatty acid incorporation by competition with excess, unlabeled fatty acids in pair-wise combinations revealed two distinct classes of esterification systems into human umbilical vein endothelial cell phospholipids. The eicosanoid precursor fatty acids, including arachidonate, 8,11,14-eicosatrienoate (ETA) and 5,8,11,14,17-eicosapentaenoate (EPA), exhibited high affinity incorporation into total phospholipids, whereas other fatty acids, including docosahexaenoate and monohydroxy eicosatetraenoates, showed low affinity incorporation. The relative degree of incorporation of eicosanoid precursor fatty acids into phospholipid classes was phosphatidylcholine (PC) greater than phosphatidylethanolamine (PE) greater than phosphatidylinositol (PI) greater than phosphatidylserine (PS). The specific activity of [14C]arachidonic acid-labeled PI was two times higher than that of any other radiolabeled phospholipids. When competitive incorporation of eicosanoid precursor fatty acids into phospholipid classes was studied, they were found to be acylated into different phospholipid classes at different rates. Although eicosanoid precursor fatty acids were not preferentially incorporated into PC, arachidonic acid was preferentially incorporated into the other phospholipids and exhibited particular selectivity in comparison with the other eicosanoid precursor fatty acids for incorporation into PI. These results demonstrate that human umbilical vein endothelial cells possess selective incorporation mechanisms for specific fatty acids into various phospholipids via the deacylation-reacylation pathway.     

Fatty acid exchange of phospholipids in membranes of rat heart

Incorporation of ¹⁴C fatty acids in phospholipids of plasma membranes and sarcoplasmic reticulum of rat heart was studied. Mainly phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were labelled. Our studies showed that the incorporation of unsaturated fatty acids (oleic and linoleic acid) was higher than for saturated fatty acids (palmitic and stearic acid). The range of uptake was between 0.2 and 2.2 nmol·mg⁻¹ protein·h⁻¹ and 0.5–7.4 nmol·μgatom⁻¹ P₁·h⁻¹, respectively. Uptake of activity in individual phospholipids (measured after separation on TLC) was calculated as percentage of total activity. Incorporation in phosphatidylcholine was higher than in phosphatidylethanolamine. Phosphatidylcholine showed an increasing sequence for the following fatty acids: C_18:0 < C_16:0 < C_18:0 < C_18:2. However, phosphatidylethanolamine showed a decreasing sequence for the incorporation of the same fatty acids. Labelling of PC was always greater than for PE, except for stearic acid which was better incorporated into phosphatidylethanolamine. Uptake of the same fatty acid into phospholipids of sarcoplasmic reticulum was always higher than uptake into plasma membranes. As incorporation of fatty acids bound to albumin was studied in isolated membranes of rat heart, the addition of ATP and CoASH was an absolute requirement.     

Long-chain fatty acids and ethanol affect the properties of membranes inDrosophila melanogaster larvae

The larval fatty acid composition of neutral lipids and membrane lipids was determined in three ethanol-tolerant strains ofDrosophila melanogaster. Dietary ethanol promoted a decrease in long-chain fatty acids in neutral lipids along with enhanced alcohol dehydrogenase (EC 1.1.1.1) activity in all of the strains. Dietary ethanol also increased the incorporation of¹⁴C-ethanol into fatty acid ethyl esters (FAEE) by two- to threefold and decreased the incorporation of¹⁴C-ethanol into free fatty acids (FFA). When cultured on sterile, defined media with stearic acid at 0 to 5 mM, stearic acid decreased ADH activity up to 33%. In strains not selected for superior tolerance to ethanol, dietary ethanol promoted a loss of long-chain fatty acids in membrane lipids. The loss of long-chain fatty acids in membranes was strongly correlated with increased fluidity in hydrophobic domains of mitochondrial membranes as determined by electron spin resonance and correlated with a loss of ethanol tolerance. In the ethanol-tolerant E2 strain, which had been exposed to ethanol for many generations, dietary ethanol failed to promote a loss of long-chain fatty acids in membrane lipids. We are grateful for the support of National Institutes of Health Grant AA06702 (B.W.G.) and National Science Foundation Grant CHE-891987 (R.G.K.).     

Mitochondrial lipids in Bufo arenarum full-grown oocytes

Both the content and composition of polar and neutral lipids from the mitochondrial fraction of ovarian full-grown Bufo arenarum oocytes were analysed in the present study. Triacylglycerols (TAG) represent 33% of the total lipids, followed by phosphatidylcholine (PC), free fatty acids (FFA) and phosphatidylethanolamine (PE). Diphosphatidylglycerol (DPG) or cardiolipin, a specific component of the inner mitochondrial membrane, represents about 4% of the total lipid content. Palmitic (16:0) and arachidonic (20:4n6) acids are the most abundant fatty acids in PC and PE, respectively. DPG is enriched in fatty acids with carbon chain lengths of 18, the principal component being linoleic acid. In phosphatidylinositol (PI), 20:4n6 and stearic acid (18:0) represent about 72 mol% of the total acyl group level. The main fatty acids in TAG are linoleic (18:2), oleic (18:1), and palmitic acids. The fatty acid composition of FFA and diacylglycerols (DAG) is similar, 16:0 being the most abundant acyl group. PE is the most unsaturated lipid and sphingomyelin (SM) has the lowest unsaturation index.     

Effects of fatty acid unsaturation numbers on membrane fluidity and α-secretase-dependent amyloid precursor protein processing

Fatty acids may integrate into cell membranes to change physical properties of cell membranes, and subsequently alter cell functions in an unsaturation number-dependent manner. To address the roles of fatty acid unsaturation numbers in cellular pathways of Alzheimer's disease (AD), we systematically investigated the effects of fatty acids on cell membrane fluidity and α-secretase-cleaved soluble amyloid precursor protein (sAPP(α)) secretion in relation to unsaturation numbers using stearic acid (SA, 18:0), oleic acid (OA, 18:1), linoleic acid (LA, 18:2), α-linolenic acid (ALA, 18:3), arachidonic acid (AA, 20:4), eicosapentaenoic acid (EPA, 20:5), and docosahexaenoic acid (DHA, 22:6). Treatments of differentiated human neuroblastoma (SH-SY5Y cells) with AA, EPA and DHA for 24h increased sAPP(α) secretion and membrane fluidity, whereas those treatments with SA, OA, LA and ALA did not. Treatments with AA and DHA did not alter the total expressions of amyloid precursor protein (APP) and α-secretases in SH-SY5Y cells. These results suggested that not all unsaturated fatty acids but only those with 4 or more double bonds, such as AA, EPA and DHA, are able to increase membrane fluidity and lead to increase in sAPP(α) secretion. This study provides insights into dietary strategies for the prevention of AD.     

Effect of hormones on phospholipid metabolism in human cultured fibroblasts

The effect of hormones on phospholipid metabolism, pool size, 32P labeling and changes in fatty acid of human adult fibroblasts was determined. Simultaneously the change in membrane fluidity of single cells was recorded via fluorescence recovery after photobleaching under the influence of hormones. From all substances tested (isoproterenol, phenylephrine, adrenalin, histamine, angiotensin II, dansylcadaverine, propranolol) only isoproterenol and adrenalin slightly decreased total amount of phosphatidylcholine (PC). The amount of the other phospholipids analyzed remained unchanged. The 32P incorporation rate into phospholipids (PC, phosphatidylinositol (PI), phosphatidylethanolamine (PE)) was affected basicly different analyzing either PC, PI or PE. Histamine and propranolol provoked the highest incorporation of 32P (240% increase in PI labeling). Isoproterenol and adrenalin decreased PC labeling (45% and 18%) whereas isoproterenol decreased 32P incorporation into PI (18%), and adrenalin led to an increase (37%). PE labeling showed no or a slight increase in 32P incorporation applying the other agonists or antagonists. The fatty acid pattern of the respective phospholipids changed only to a minor extend. A decrease in hexadecanoic acid content of PI was found after administration of either isoproterenol, adrenalin or histamine. Parallel determination of membrane fluidity of single cells by fluorescence recovery after photobleaching showed an increase in the diffusion coefficient of a fluorescent lipid probe sticking in the membrane, following administration of isoproterenol and adrenalin, other substances tested exerted no effect. A relationship to changes in phospholipid metabolism became obvious. These results are discussed considering known mechanisms of receptor coupling and change in phospholipid metabolism and fluidity.     

A comparison of the effects of linolenic (18:3 omega 3) and docosahexaenoic (22:6 omega 3) acids on phospholipid bilayers

The class of long chain polyunsaturated fatty acids known as omega-3 are believed to be involved in prevention of a number of human afflictions. The mode of action for two of the most common omega-3 fatty acids, linolenic 18:3 delta 9,12,15 and docosahexaenoic 22:6 delta 4,7,10,13,16,19 (DHA), is not known. One suggestion is that they may be incorporated into membranes and there provide some specific function. Here we compare the effects of DHA and its metabolic precursor linolenic acid on the membrane properties of fluidity, fusion and permeability. The fatty acids were investigated as both free fatty acids and mixed chain 18:0, 18:3 and 18:0, 22:6 phosphatidylcholines (PCs). Fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene (DPH) and a series of anthracene stearic acid probes indicates 20 mol% incorporation of either fatty acid into dipalmitoylphosphatidylcholine bilayers broadens and depresses the temperature of the phase transition, but has almost no effect on fluidity in the liquid crystalline state. Similar fluidity was also observed in the liquid crystalline bilayers of the mixed chain PCs using the same set of fluorescent fatty acid probes. In contrast, DHA as a free fatty acid or as part of a mixed chain PC, causes a much greater enhancement than linolenic acid of the rates of fusion and permeability as monitored by fluorescence resonance energy transfer and aqueous compartment mixing (fusion) and by lipid vesicle swelling in isotonic erythritol, (permeability). These experiments establish a clear distinction between the effects of linolenic acid and DHA in membranes.     

Aluminum mediates compositional alterations of polar lipid classes in maize seedlings

Changes in lipid composition were investigated on maize roots and shoots under aluminum stress. After 4d exposure to 100 microM Al, root growth was inhibited while shoot growth was not affected. In roots, the decrease of the DBI (double bond index) of total fatty acids may signal a decrease in membrane fluidity. The total lipids (TL) decreased by 49%, but phospholipids (PL), phosphatidylcholine (PC) and phosphatidylinositol (PI) increased to approximately 3-fold. The MGDG increased to 2-fold but no significant change was found in the DGDG. The steryl lipids (SL) increased by 69%. The SL/PL ratio decreased from 2.64 to 1.52 and the MGDG/DGDG ratio increased from 0.45 to 1.06 in roots of Al-stressed plants. Al leads to oxidative stress in roots of treated plants as indicated by the increase of malondialdehyde (MDA) concentrations. In shoots, changes in fatty acid composition were associated with an increase of the DBI in all lipid classes except that of the DGDG decreased. The PG was the lipid class which shows the large variation of fatty acid composition. No significant changes were found either for TL, PL, SL or MDA concentrations in shoots of Al-treated plants. While PE levels did not show significant change, PI and PG increased and PC decreased. However, the Al caused 87% decrease in the GL levels. The MGDG and DGDG decreased to 19- and 8-fold, respectively. The deleterious effects of Al on polar lipids could be caused by a direct intervention of Al on plasma membrane and/or alteration of cell metabolism.     

Fatty Acid Distribution in Glycolipids and Phospholipids in Cotyledons of Germinating Soybeans

This investigation was conducted to observe changes in the fatty acid distributions of glycolipids (GL) and phospholipids (PL) in cotyledons of soybean seeds which were germinated either in the dark or the light at 28°C for 8 days. The GL isolated from the total lipids of cotyledons at different germinating stages were : acyl sterylglycoside (ASG), monogalactosyl diglyceride (MGD), digalactosyl diglyceride (DGD) and sulfolipid (SL). The PL isolated from the same total lipids as described above were : diphosphatidyl glycerol (DPG), phosphatidic acid (PA), phosphatidyl ethanolamine (PE), phosphatidyl glycerol (PG), phosphatidyl choline (PC) and phosphatidyl inositol (PI).

During germination of soybean seeds, the content of linoleic and linolenic acids in MGD or DGD was markedly higher than that of the other GL. The positional distribution of fatty acids in PE, PC and PI was shown in all PL, in which saturated fatty acids, especially palmitic acid, were highly concentrated in position 1 and unsaturated fatty acids, especially linoleic acid, mainly occupied position 2. A remarkable difference in the changing patterns of fatty acid composition, which depended on the germinating conditions tested, was observed between GL and PL. The changes in fatty acid composition of GL were more marked in the light-grown seedlings than in the dark-grown, whereas those of PL were more remarkable in the latter than in the former. Therefore, the positional distribution of fatty acids in PL was more evident in the light-grown seedlings than in the dark-grown ones.

These results suggest the metabolic fate of GL and PL in cotyledons of soybean seeds, probably owing to the differences in the two germinating conditions tested.     

Effect of phospholipids containing omega-3 fatty acids on structural changes of microsomal lipids in cell membranes of functionally different cells

As a result of the experimental researches conducted it has been shown that administration of some normal animal marine phospholipids (PL) including in their structure omega-3 polyunsaturated fatty acids (PUFA) provides for quantitative changes of individual PL, fatty acids (FA) content and quantity in general and individual PL of liver, heart, brain and gonads microsomes. While estimating general microsomal PL fraction FA content under the action of PL omega-3 PUFA FA concentration change, unsaturation index (omega 6/omega 3) and relation of arachidonic acid to docosahexenic (AA/DHA) decrease have been identified. The decrease of AA/DHA relationship occurs due to AA and DHA quantitative changes. In the case of AA increase in some tissues there is observed the decrease of docosapentaenic acid and increase of DHA and eucosapentaenic (EPA) acidds. As a result of studying FA content in the individual PL composition it has been identified that certain PL classes characteristic for some tissues respond by changes of some certain FA. The relationship omega 6/omega 3 has been shown as decreasing in phosphatidilcholine (PC) all tissues microsomes (liver, gonads, heart, brain), in phosphatidilethanolamine (PEA) of liver and cardiac microsomes, in phosphatidilserine (PS) this relationship relationship decreases in the liver, brain and heart, for phosphatidilinositole (PI) the changes take place in liver, gonads, brain. Simultaneously, the decrease of AA/DHA relationship in the individual PL decrease of AA and increase of EPA and DHA depend on the tested tissues. The marine phospholipids might be supposed to render their effect on AA metabolism resulting in AA/DHA relationship in PEA and PS relationship displays itself as specific and depends on the tissues functions. The preference of PEA and PS use by certain tissues microsomes could be explained by their membrane protective capability.     

Group VIA phospholipase A2 deficiency in mice chronically fed with high-fat-diet attenuates hepatic steatosis by correcting a defect of phospholipid remodeling

A defect of hepatic remodeling of phospholipids (PL) is seen in non-alcoholic fatty liver disease and steatohepatitis (NASH) indicating pivotal role of PL metabolism in this disease. The deletion of group VIA calcium-independent phospholipase A2 (iPla2β) protects ob/ob mice from hepatic steatosis (BBAlip 1861, 2016, 440–461), however its role in high-fat diet (HFD)-induced NASH is still elusive. Here, wild-type and iPla2β-null mice were subjected to chronic feeding with HFD for 6 months. We showed that protection was observed in iPla2β-null mice with an attenuation of diet-induced body and liver-weight gains, liver enzymes, serum free fatty acids as well as hepatic TG and steatosis scores. iPla2β deficiency under HFD attenuated the levels of 1-stearoyl lysophosphatidylcholine (LPC), lysophosphatidylethanolamine (LPE), and lysophosphatidylinositol (LPI) as well as elevation of hepatic arachidonate, arachidonate-containing cholesterol esters and prostaglandin E₂. More importantly, this deficiency rescued a defect in PL remodeling and attenuated the ratio of saturated and unsaturated PL. The protection by iPla2β deficiency was not observed during short-term HFD feeding of 3 or 5 weeks which showed no PL remodeling defect. In addition to PC/PE, this deficiency reversed the suppression of PC/PI and PE/PI among monounsaturated PL. However, this deficiency did not modulate hepatic PL contents and PL ratios in ER fractions, ER stress, fibrosis, and inflammation markers. Hence, iPla2β inactivation protected mice against hepatic steatosis and obesity during chronic dietary NASH by correcting PL remodeling defect and PI composition relative to PC and PE.