Fatty Acid Composition Of Diacylglycerol Research Articles

Suppression of visceral adipose tissue by palm kernel and soy‐canola diacylglycerol in C57BL/6N mice

The present study investigated the health effect of two types of diacylglycerol (DG) produced from (i) palm kernel (PK) oil of medium‐chain saturated fatty acids and (ii) soy‐canola oil (SC) blend of long‐chain unsaturated fatty acids in C57BL/6N mice. As compared to diet containing 30% PK triacylglycerol (TG), 16 wk feeding trial on C57BL/6N mice with a diet consisting of 30% PKDG and 30% SCDG significantly (p<0.05) reduced the fat accumulation in epididymal and retroperitoneal regions. Serum glucose, cholesterol, leptin and insulin levels were significantly (p<0.05) suppressed in PKDG‐ and SCDG‐fed mice. In terms of gene expression, PKDG diet induced expression of acyl‐CoA synthase long chain (ACSL) and acyl‐CoA synthase medium chain mRNA in the small intestine of the mice while SCDG fed mice upregulated ACSL in liver and small intestine. This suggests that the difference in fatty acid composition of DG may potentially induce β‐oxidation in different organs in mice. Besides, expression of apolipoprotein B mRNA were reduced in mice fed with PKDG and SCDG, indicating the ability of PKDG and SCDG to reduce LDL levels. In conclusion, structural differences between DG and TG markedly influenced the metabolism of lipids in the body while fatty acid composition has only showed a minor effect.Practical applications: Medium chain type of DG oil, if proven to have similar effects to long chain type DG in this study, can be incorporated into food for health purposes and can replace conventional cooking oil as healthy functional cooking oil.

Dietary long-chainn-3 fatty acids modify blood and cardiac phospholipids and reduce protein kinase-C-δ and protein kinase-C-ε translocation

The effects of an n-3 PUFA-enriched diet on cardiac cell membrane phospholipid fraction compositions and associated protein kinase-C (PKC) translocation modification have never been studied in higher mammals. This is of importance since membrane fatty acid composition has been shown to influence PKC signalling pathways. In the present study, we have tested whether the incorporation of n-3 PUFA in cardiac membrane phospholipids correlated with changes in the fatty acid composition of diacylglycerols (DAG) and led to a differential translocation of PKC isoforms. Two groups of five dogs were fed the standard diet supplemented with palm oil or fish oil for 8 weeks. Dogs fed a fish oil-enriched diet showed a preferential incorporation of EPA and, to a lesser extent, of DHA, at the expense of arachidonic acid, in the circulating TAG, plasma phospholipids, erythrocyte phospholipids and cardiomyocyte phospholipid fractions. Analysis of 1,2-DAG fatty acid composition also indicated a preferential enrichment of EPA compared with DHA. Associated with these results, a reduction in the expression of PKC-delta and PKC-epsilon isoforms in the particulate fractions was observed whereas no effect was seen for PKC-alpha and PKC-zeta. We conclude that a fish oil-enriched diet induces a modification in fatty acid composition of cardiac membrane phospholipids, associated with a differential translocation of PKC isoforms. These results can be explained by the production of structurally different DAG that may participate in some of the protective effects of n-3 PUFA against various chronic diseases.

Lipid and fatty acid composition of the fat body during the female reproductive cycle of Labidura riparia (Insecta Dermaptera)

During the reproductive cycle of the female Labidura riparia, cytological observations show cyclical modifications of lipid droplets in the periovarian adipocyte. Fat body lipids and their constitutive fatty acids are analyzed. The lipids are predominantly triacylglycerols, which increase after adult ecdysis during vitellogenic and non-vitellogenic periods. Small amounts of diacylglycerols and phospholipids are found. Diacylglycerols increase during vitellogenesis and decrease during the non-vitellogenic period. Cytological modifications of lipid droplets are probably related to diacylglycerol fluctuations. Gas-liquid chromatography of fatty acid methyl esters shows oleic acid to be the predominant fatty acid in total lipids and triacylglycerols; unsaturated acids are approximately twice as abundant as saturated acids all along the reproductive cycle. Fatty acid composition of diacylglycerols and phospholipids differs from triacylglycerols and total lipids composition. Palmitic, stearic, oleic and linoleic acids represent the major fatty acids; their relative amounts vary during the different periods of the reproductive cycle. The correlations between fat body lipid changes and ovarian development were discussed and compared with observations made on other insect species.

Partial characterization of a glycosylphosphatidyl-inositol (GPI) in porcine thyroid cultured cells

The aim of this study was to provide information on the structure of glycosylphosphatidylinositol (GPI) and to characterize this novel phospholipid isolated from pig thyroid. We investigated the incorporation of different radioactive precursors: [ 3H]glucosamine, [ 3H]inositol, [ 3H]oleic acid, [ 32P]orthophosphate and demonstrated the presence of these moieties in the structure of GPI. After labelling and hydrochloric acid hydrolysis, the major part of radioactivity comigrated with glucosamine used as marker. Cleavage of GPI by nitrous acid deamination indicated the presence of a glycosidic bond between the lipid moiety and glucosamine. The fatty acid composition of diacylglycerol was also studied by gas chromatography. Oleic acid was found preferentially to other fatty acids. In a previous paper we reported that a chronic treatment with 0.1 mU/ml thyrotropin (TSH) of thyroid cultured cells for 3 days produced a large increase in the turnover rate of GPI and concomitantly the release of a water-soluble product of GPI hydrolysis: an inositolphosphateglycan (IPG). These findings confirm that GPI may play a role in membrane signalling systems and thyroid cell regulation.

Effect of exogenous gangliosides on the lipid composition of chick neurons in culture

When exogenous gangliosides are added to the growth medium of neuronal cell cultures they are inserted into their plasma membranes and are afterwards metabolized in the cytoplasmic interior. The action of exogenous gangliosides brings important morphological and biochemical changes to neurons in culture. The present report shows that the treatment with exogenous gangliosides of a primary culture of chick neurons modified the distribution of fatty acids in phosphatidylinositol (PI), mainly that of arachidonic acid and the fatty acids of the ( n − 3) series without affecting the other phospholipids. The composition of neutral lipids did not change but their content was increased up to 2–3-fold depending upon the concentration of gangliosides. The change of the growth medium from one containing fetal calf serum to a chemically defined one reduced dramatically the content of free fatty acids while the addition of gangliosides raised this content to normal levels. The increase in the amount of diacylglycerol (DG) confirmed the finding that gangliosides stimulate phosphoinositide degradation. Finally the fatty acid composition of DG suggests indirectly that this compound might be produced also by degradation of phosphatidylcholine and not only of PI.

Glucose and carbachol generate 1,2-diacylglycerols by different mechanisms in pancreatic islets.

Diacylglycerols (DAG) modulate secretory responses by the activation of protein kinase C. Early changes in DAG formation induced by the muscarinic receptor agonist carbachol were compared to those caused by the nutrient secretagogue glucose in pancreatic islets. Turnover rates of DAG were investigated in radiolabeling experiments, whereas changes in total mass and fatty acid composition of DAG were assessed by gas-liquid chromatography. When islet lipids were labeled to steady state in tissue culture with [3H]glycerol, carbachol induced a rapid (10 s) and sustained increase of [3H]DAG generation. In contrast, glucose stimulation failed to increase [3H]glycerol containing DAG, and this was probably due to the isotopic dilution of the label secondary to enhanced glycolysis. This was substantiated by following the transfer of 14C from glucose into DAG. Within 1 min of acute exposure of islets to D-[U-14C]-glucose at stimulatory concentrations, DAG labeling increased fivefold representing up to 2% of total glucose usage. Similar stimulation of 14C incorporation into other neutral lipids and inositol phospholipids was observed, suggesting the enhanced de novo synthesis of phosphatidic acid, the common precursor for DAG, and inositol phospholipids from glycolytic intermediates. Transfer of 14C from glucose was not stimulated by agents such as carbachol and exogenous phospholipase C that act primarily on inositol phospholipid breakdown. The total mass of islet DAG was increased by 60% after both carbachol and glucose stimulation. However, analysis of the fatty acid composition of carbachol-generated DAG revealed at the early time point (10 s) a prevalent stearoyl-arachidonoyl configuration similar to that reported for inositol phospholipids. This pattern shifted to a DAG enriched in palmitic acid at a later time point. Glucose-stimulated islets displayed a predominance of palmitic acid containing DAG, indicating increased de novo synthesis of the putative second messenger rather than its formation by inositol phospholipid hydrolysis. Indeed, steady-state labeling of these phospholipids with [3H]inositol confirmed this idea since only carbachol caused detectable inositol phospholipid hydrolysis. Thus, although protein kinase C may be activated by both carbachol and glucose, the two secretagogues generate diacylglycerols through different mechanisms.

Diacylglycerols interfere in normal phase HPLC analysis of lipoxygenase products of docosahexaenoic or arachidonic acids

A methodological problem with the normal phase high performance liquid chromatography (HPLC) of hydroxylated products of docosahexaenoic and arachidonic acids is described. Diacylglycerols present in lipid extracts of rat retina co-elute with monohydroxy derivatives of docosahexaenoic or arachidonic acid, when samples are applied to uPorosil columns and eluted with hexane/isopropanol/acetic acid. Analysis of fatty acid composition of diacylglycerols which were acetone-extracted from the incubation medium showed a profile similar to diacylglycerols extracted from the tissue by hexane/isopropanol, although acetone extraction resulted in extremely variable recovery of diacylglycerols. This co-elution of diacylglycerols with monohydroxy polyunsaturated fatty acids can lead to a significant error in estimation of lipoxygenation activity by conversion of radiolabeled precursors, because the incorporation of fatty acids into diacylglycerols is very active in many tissues. An alternative extraction method and reverse phase HPLC procedures that result in the complete separation of hydroxy fatty acids and diacylglycerols are described.

Effects of cholinergic stimulation on levels and fatty acid composition of diacylglycerols in mouse pancreas

1. 1. During 15 min after intraperitoneal injection of 1 mg pilocarpine in vivo in the mouse, the level of diacylglycerol in the pancreas rose from 0.47 to 0.80 μmol per g wet weight. There were increases in the levels of all of the individual fatty acids which were measured in the diacylglycerol pool. The major increases were in palmitic and linoleic acids. These accounted for 65% of the total increase. 2. 2. After in vitro incubation of mouse pancreas for 80 min, the levels of diacylglycerol (expressed in μmol/g wet weight) in unstimulated tissue and in tissue incubated with 10 μM or 100 μM acetylcholine (plus 100 μM eserine) were, respectively, 0.51, 1.30 and 3.73. Increases in palmitic, oleic and linoleic acids in the diacylglycerol pool accounted for 75% of the total increase. With 100 μM acetylcholine, the proportions of individual fatty acids in diacylglycerol showed a significant enrichment of stearic and arachidonic acid at 40 min and of linoleic and arachidonic acids at 80 min. With the exception of an enrichment of stearic and arachidonic acids, the fatty acid composition of the new diacylglycerol resembled that of the triacylglycerol pool more closely than that of other classes of lipid in the pancreas. 3. 3. After addition of atropine to acetylcholine-stimulated tissue, the level of diacylglycerol fell so that, after 40 min, the levels and proportions of all individual fatty acids in the diacylglycerol were not significantly different from those in unstimulated tissue. 4. 4. In both the in vivo and in vitro experiments, the changes in levels of stearic and arachidonic acids in diacylglycerol indicated that only a small proportion of the total increase in diacylglycerol level could have been derived from the breakdown of stearoyl, arachidonoyl phosphatidylinositol which occurs in response to cholinergic stimulation in the pancreas. The major effect of acetylcholine in diacylglycerol metabolism in mouse pancreas is separate, therefore, from the effect on phosphatidylinositol metabolism.

The effect of fasting and refeeding on the composition and synthesis of triacylglycerols, phosphatidylcholines, and phosphatidylethanolamines in rat liver

Refeeding a high-sucrose, fat-free diet to fasted rats caused drastic alterations in the fatty acid composition of hepatic diacylglycerols, triacylglycerols, and phosphatidylcholines. However, the fatty acid profile of phosphatidylethanolamines did not change significantly. These results suggest that the fatty acid composition of diacylglycerols may influence the distribution of diacylglycerols among triacylglycerols, phosphatidylcholines, and phosphatidylethanolamines. Fasting and refeeding also affected the activities in vitro of a number of enzymes responsible for the formation of triacylglycerols, phosphatidylcholines, and phosphatidylethanolamines. The activity of hepatic phosphatidate phosphatase increased fourfold upon refeeding. However, fasting the rats did not affect the activity of this enzyme despite the reduced triacylglycerol synthesis in the fasted liver in vivo. Fasting and refeeding induced alterations in the activities of diacylglycerol acyltransferase, cholinephosphotransferase, and ethanolaminephosphotransferase which correlated reasonably well with the changes observed in the synthesis of triacylglycerols, phosphatidylcholines, and phosphatidylethanolamines in vivo, although the changes in diacylglycerol acyltransferase were too moderate. The changes in the activity of cholinephosphate cytidylyltransferase, which is suggested to catalyze the rate-limiting step in the formation of CDP-choline, ran parallel with the alterations in the synthesis of phosphatidylcholines in vivo. No such correlation was found between the activity of ethanolaminephosphate cytidylyltransferase and the rate of phosphatidylethanolamine synthesis. The present results indicate that the synthesis of triacylglycerols, phosphatidylcholines, and phosphatidylethanolamines is controlled by the availability of the various substrates as well as by the activities of several enzymes involved in these processes.

The cytidine mechanism and methylation pathway in the formation of N-methylated ethanolamine phosphoglycerides in Neurospora crassa.

InNeurospora crassa, phospholipids containing ethanolamine, monomethylaminoethanol, dimethylaminoethanol and choline are formed by a pathway involving cytidine nucleotides. The rate of formation of these phospholipids does not appear to be dependent on the fatty acid composition of diacylglycerols acting as acceptors of phosphorylated aminoethanols. The presence of choline in the growth medium represses the activity of enzymes of the methylation pathway for the biosynthesis of 1,2-diacyl-sn-glycero-3-phosphorylcholine (diacyl-GPCh) and induces the activity of enzymes of the cytidine mechanism.

Fatty acid composition and level of diacylglycerols and phosphoglycerides in brain and retina

The fatty acid composition of diacylglycerols of toad brain and retina is reported. In addition, the fatty acid composition of brain and retina phospholipids and of diacylglycerols and phospholipids from choroid is also presented. Retina diacylglycerol content is 7-fold that of the brain; fatty acid acyl groups are also more unsaturated in the former tissue. The diacylglycerols of the retina contain an unusually high amount of docosahexaenoate (42%), while arachidonate represents about 7%. Other major fatty acids are palmitate (19%) and stearate (20%). Brain diacylglycerols contain only 3% docosahexaenoate, while arachidonate represents about 27%. Other components are stearate (24%), palmitate (17%) and oleate (14%). In the retina, the fatty acid composition of phospholipids resembled that of diacylglycerols, and the total unsaturated components were greater than in diacylglycerols. The ratio docosahexaenoate to arachidonate in retina phospholipids and diacylglycerols was similar. On the contrary, the fatty acid composition in the phospholipids from brain and choroid was unlike that observed in their diacylglycerols. It is concluded that the unique characteristics of retina diacylglycerols may be related to a lipid metabolic differentiation developed to sustain the polar lipids of the photoreceptor cell membranes during their renewal process.