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PubMed1997

Fatty alcohol synthesis accompanied with chain elongation in liver peroxisomes.

We have reported that the fatty alcohol destined to form the 1-alkenyl group of plasmalogen is synthesized as a nascent fatty alcohol within peroxisomes, from acetyl-CoA supplied by beta-oxidation. The present experiment was designed to confirm this peroxisomal fatty alcohol synthesis by using [1-14C]acetyl-CoA. Rats were fed for 2 weeks on chow containing 0.25% clofibrate, as a peroxisome proliferator. Peroxisomes were prepared from the rat liver to more than 85% purity, and incubated with [1-14C]acetyl-CoA in order to investigate suitable conditions for fatty alcohol biosynthesis. Dodecanoyl-CoA was the most suitable primer, and the reaction required NADH and/or NADPH as a reducing factor; NAD+ or NADP+ greatly inhibited the reaction, even if a significant amount of the reduced form still remained. The reaction proceeded linearly with respect to peroxisomal protein concentration and incubation time. Under the optimum conditions for fatty alcohol synthesis, 1 mg of peroxisomal protein could produce approx. 0.7 nmol of fatty alcohol per hour, and the main product was hexadecanol.

Acetyl Coenzyme A↗
PubMed1988

1-O-hexadec-1'-enyl-2-acetyl-sn-glycero-3-phosphocholine and its biological activity.

1-O-Alk-1'-enyl analog of platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine, alkylacetyl-GPC) was prepared semi-synthetically from choline plasmalogens of beef heart muscle. The main compound was identified mass spectrometrically as 1-hexadec-1'-enyl-2-acetyl-sn-glycero-3-phosphocholine (16:O alk-1'-enylacetyl-GPC, 16:O vinyl form of PAF) and its platelet aggregation activity was about one-fifth of that of the corresponding 16:O alkylacetyl-GPC. The irreversible platelet aggregation activity induced by 5X10(-10) M 16:O alk-1'-enylacetyl-GPC was completely inhibited by 5X10(-7) M CV-3988 and 1X10(-7) M L-652, 731, specific PAF antagonists, and more than 99% of the activity was also lost by acid treatment. The hydrogenated product, alkylacetyl analog, showed quite same activity as that of authentic 16:O alkylacetyl-GPC. The platelets desensitized with 16:O alkylacetyl-GPC and with 16:O alk-1'-enylacetyl-GPC were not aggregated with 5X10(-10) M 16:O alk-1'-enylacetyl-GPC, suggesting that alk-1'-enylacetyl-GPC occupied the same receptor site of alkylacetyl-GPC.

Animals↗
PubMed2000

Phospholipid composition and levels are altered in Down syndrome brain.

Phospholipid composition (mol %) and levels (nmol/mg protein) were determined in postmortem frontal cortical and cerebellar gray matter from older Down Syndrome (DS) patients (age range 38-68 years) and from control subjects. Neither DS nor control tissue exhibited any age-dependent alteration in phospholipid composition or levels. Total phospholipid content was significantly reduced approximately 20% in DS frontal cortex and cerebellum relative to these regions in control tissue. Individual phospholipid levels were also reduced in DS frontal cortex and cerebellum, including a specific 37% decrease in phosphatidylinositol (PtdIns) and a nearly 35% decrease in ethanolamine plasmalogen. Because of the large decrease in phospholipid content in DS brain, the cholesterol/phospholipid ratio was calculated for each group. There was no significant difference in this ratio between groups, indicative of compensatory changes to keep the cholesterol/phospholipid ratio constant. Despite the large changes in DS brain phospholipid levels, significant changes in composition were limited to a 18% decrease in PtdIns mol % and a 22% increase in the mol % of sphingomyelin. These results suggest either a decrease in membrane phospholipids due to a loss of dendrites and dendritic spines, or a general defect in brain lipid metabolism in older DS subjects. The proportionally greater alterations in PtdIns and PlsEtn levels, indicate that the metabolism of these two phospholipids was affected to a greater extent than the other phospholipids. Further, because these changes are found in both the frontal cortical and cerebellar gray matter, they likely are related to the Down syndrome condition rather than to Alzheimer neuropathology.

Adult↗
PubMed1978

Myelin lipids in the brain after transplacental intoxication with ethylnitrosourea.

At day 15 of gestation pregnant mice were injected with a single intravenous dose of ethylnitrosourea (ENU) (80 mg/kg of body weight). The lipid composition of the myelin fraction isolated by means of differential centrifugation from brains of their offsprings was studied. The transplacentally intoxicated mice developed severe changes in the lipid composition of their central myelin sheaths, such as a markedly decreased galactolipid (both cerebroside and sulfatide) as well as plasmalogen contents. The results show, that besides being a well known carcinogenic agent, ENU is capable of affecting the lipid metabolism of the developing central nervous system. The resultant effect is the formation of a chemically defective myelin sheath.

Animals↗
PubMed1997

Mg2+ modulates membrane lipids in vascular smooth muscle: a link to atherogenesis.

Epidemiological studies associate low dietary magnesium intake with an increased incidence of ischemic heart disease and sudden cardiac death. We have used proton-magnetic resonance (1H-NMR) techniques and Mg2+-selective electrodes to monitor changes in lipid extracts of aortic and cerebrovascular smooth muscle as extracellular ionized magnesium ion concentration ([Mg2+]o) is lowered. We have found that, within the pathophysiological range of Mg2+ concentrations, fatty acid chain length and double bond content are progressively reduced as [Mg2+]o is lowered. In contrast, the plasmalogen content is progressively increased. A concomitant decrease in fatty acid chain length and double bonds indicates oxidation of double bonds resulting in truncation of the fatty acids. A decrease in lipid oxidation in the presence of elevated Mg2+ could contribute to the apparent protective role of increased Mg2+ intake on vascular function in humans.

Animals↗
PubMed1986

Peroxisomal dysfunction in a boy with neurologic symptoms and amaurosis (Leber disease): clinical and biochemical findings similar to those observed in Zellweger syndrome.

A boy with psychomotor retardation and Leber congenital amaurosis, sensory hearing loss, and hepatomegaly is reported. Accumulation of bile acid precursors and very long chain fatty acids together with impaired biosynthesis of plasmalogens in cultured fibroblasts (similar to those in the cerebrohepatorenal syndrome of Zellweger) were detected, but the clinical picture was distinctly different. Defective oxidation of phytanic acid was measured in fibroblasts. The virtual lack of peroxisomes in a liver biopsy specimen lends further support to the contention that at least some patients with Leber congenital amaurosis may have one of the recently defined "peroxisomal disorders." The biochemical findings indicate the possibility of prenatal diagnosis.

Adrenoleukodystrophy↗
PubMed1988

Biochemical abnormalities in rhizomelic chondrodysplasia punctata.

Biochemical studies with emphasis on peroxisomal functions were conducted in six patients with well-documented rhizomelic chondrodysplasia punctata (RCDP) and compared with findings in patients with Zellweger syndrome and neonatal adrenoleukodystrophy (ALD). Patients with RCDP had three characteristic biochemical abnormalities: (1) profound defect in plasmalogen (ether lipid) synthesis, which is significantly greater than the analogous defect in Zellweger syndrome or neonatal ALD; (2) reduction of phytanic acid oxidation activity to 1% to 5% of control, similar to that observed in Refsum disease, Zellweger syndrome, and neonatal ALD; (3) presence of the unprocessed form of peroxisomal 3-oxoacyl-coenzyme A thiolase in the postmortem liver of two patients. Other peroxisomal functions were normal, including levels of very long chain fatty acids, pipecolic acid, and bile acid intermediates, and immunoblot studies of peroxisomal acyl-CoA oxidase and bifunctional enzyme in postmortem liver. Unlike what is observed in Zellweger syndrome and neonatal ALD, catalase activity in cultured skin fibroblasts was sedimentable, indicating that peroxisome structure is not grossly deficient in RCDP. The biochemical abnormalities in RCDP were consistent and set it apart from all the other known peroxisomal disorders.

Acetyl-CoA C-Acyltransferase↗
PubMedDate not supplied

Age-related changes in ethanolamine glycerophospholipid fatty acid levels in rat frontal cortex and hippocampus.

Morphological and biochemical alterations are associated with a progressive age-related cognitive deficit. Plasmenylethanolamine, the major brain plasmalogen, may be modified during aging because of a possible antioxidant role and involvement in synaptic transmission. Two- and 18-month-old rats were used to study the effect of aging on the levels and acyl composition of plasmenylethanolamine (PmE), phosphatidylethanolamine (PE), and phosphatidylserine (PS) in the frontal cortex and hippocampus. Aging only reduced significantly the PE levels in the frontal cortex. In 18-month-old rats, the fatty acid composition of the three phospholipid classes studied showed an increase of monounsaturated fatty acid (18:1 n-9 and 20:1 n-9) and a decrease in polyunsaturated fatty acid (PUFAs), essentially docosahexaenoic acid (DHA). DHA was markedly decreased in hippocampus PE. DHA, but also arachidonic acid, were considerably lower in frontal cortex PmE. PS modifications were similar in both regions. Hippocampus and frontal cortex underwent specific age-induced modifications in PmE and PE acyl composition. This could produce different effects on the functional ability of these two structures involved in the processes of specific memorization.

Aging↗
PubMed2000

Phospholipid composition and levels are not altered in fibroblasts bearing presenilin-1 mutations.

Lipid alterations have been reported in brain regions affected by Alzheimer disease (AD). The mechanisms causing these changes are poorly understood because it is difficult to study dynamic, biochemical processes in post-mortem brain. Fibroblasts derived from AD patients offer an alternative model to study disease-related alterations in lipid metabolism. Therefore, we measured the phospholipid levels and composition of fibroblasts from individuals bearing two different presenilin-1 mutations and compared these values to appropriate control fibroblasts. There were no differences between groups in phospholipid composition or in individual phospholipid levels, including the plasmalogens. Cholesterol levels and the cholesterol/phospholipid ratio were not different between presenilin-1 mutation bearing and control fibroblasts. Although these presenilin-1 mutation bearing fibroblasts have a number of biochemical changes related to AD, the absence of a change in phospholipid levels suggests that under these conditions, these cells are not useful in studying the mechanisms underlying the alterations in brain phospholipid levels associated with AD. However, these results do not preclude the possible use of other fibroblasts bearing AD-related mutations, e.g., APP mutations, to examine AD-related changes in brain lipid metabolism, or of these fibroblasts under different conditions.

Alzheimer Disease↗
PubMed2001

Dual regulation of glutathione peroxidase by docosahexaenoic acid in endothelial cells depending on concentration and vascular bed origin.

Docosahexaenoic acid (DHA) has been reported to elicit oxidative stress, which in turn can induce antioxidant enzymes. Glutathione peroxidase (GPx) has received particular attention in this respect, as this enzyme is specifically required for the degradation of lipid hydroperoxides. Because we previously found that DHA could protect against oxidative stress when used in low amounts, we have compared the effect of a low (10 microM) versus high (100 microM) concentration of DHA on oxidant/antioxidant balance in bovine retinal and bovine aortic endothelial cells (BREC and BAEC). At 100 microM, DHA elicited a marked oxidative stress, as evidenced by high malondialdehyde levels and decreased plasmalogen phosphatidylethanolamine in both cells, and for BAEC only, a decrease of alpha-tocopherol. At 10 microM, DHA induced a slight increase of malondialdehyde in both cells, but did not affect alpha-tocopherol levels, which is indicative of a mild oxidative stress. In BREC, 10 microM DHA slightly but significantly decreased cytosolic GPx (cGPx) activity whereas 100 microM had no effect. In contrast, in BAEC, DHA 10 microM did not affect cGPx activity, whereas 100 microM increased it. The decreased cGPx activity in BREC was associated with a lower level of protein, suggesting a transcriptional and/or posttranscriptional effect. Phospholipid hydroperoxide GPx (PHGPx) activity was not modified by DHA at either concentration in BREC, whereas it was increased in BAEC when using 100 microM. Our results confirm that large amounts of DHA lead to oxidative stress, but do no support an antioxidant action of DHA at low concentration, in endothelium. Nevertheless, we showed that DHA can exert opposite effects on GPx regulation in endothelial cells, with regard to its concentration and to vascular bed origin.

Animals↗
PubMed2002

Lipid rafts are enriched in arachidonic acid and plasmenylethanolamine and their composition is independent of caveolin-1 expression: a quantitative electrospray ionization/mass spectrometric analysis.

Lipid rafts are specialized cholesterol-enriched membrane domains that participate in cellular signaling processes. Caveolae are related domains that become invaginated due to the presence of the structural protein, caveolin-1. In this paper, we use electrospray ionization mass spectrometry (ESI/MS) to quantitatively compare the phospholipids present in plasma membranes and nondetergent lipid rafts from caveolin-1-expressing and nonexpressing cells. Lipid rafts are enriched in cholesterol and sphingomyelin as compared to the plasma membrane fraction. Expression of caveolin-1 increases the amount of cholesterol recovered in the lipid raft fraction but does not affect the relative proportions of the various phospholipid classes. Surprisingly, ESI/MS demonstrated that lipid rafts are enriched in plasmenylethanolamines, particularly those containing arachidonic acid. While the total content of anionic phospholipids was similar in plasma membranes and nondetergent lipid rafts, the latter were highly enriched in phosphatidylserine but relatively depleted in phosphatidylinositol. Detergent-resistant membranes made from the same cells showed a higher cholesterol content than nondetergent lipid rafts but were depleted in anionic phospholipids. In addition, these detergent-resistant membranes were not enriched in arachidonic acid-containing ethanolamine plasmalogens. These data provide insight into the structure of lipid rafts and identify potential new roles for these domains in signal transduction.

Arachidonic Acid↗
PubMed2003

Direct synthesis of plasmenylcholine from allyl-substituted glycerols.

We report a new method for the facile preparation of plasmenylcholine via reaction of lithioalkoxy allyl intermediates with 1-iodoalkanes as the key step in the stereoselective formation of 1'-(Z)-alkenyl glyceryl ethers. The allyl anion intermediate is prepared by treating mono- or disiloxy-protected 1-allylglycerol precursors with s-BuLi at -65 to -80 degrees C. Subsequent addition of 1-iodoalkane solutions at low temperature gives moderate yields of gamma-coupled, Z-vinyl ethers as the major product and alpha-coupled product as the minor component. Several different preparative strategies for the total synthesis of plasmalogens are enabled by this simple transformation.

Glycerol↗
PubMed1997

Biochemistry of peroxisomes in health and disease.

The ubiquitous distribution of peroxisomes and the identification of a number of inherited diseases associated with peroxisomal dysfunction indicate that peroxisomes play an essential part in cellular metabolism. Some of the most important metabolic functions of peroxisomes include the synthesis of plasmalogens, bile acids, cholesterol and dolichol, and the oxidation of fatty acids (very long chain fatty acids > C22, branched chain fatty acids (e.g. phytanic acid), dicarboxylic acids, unsaturated fatty acids, prostaglandins, pipecolic acid and glutaric acid). Peroxisomes are also responsible for the metabolism of purines, polyamines, amino acids, glyoxylate and reactive oxygen species (e.g. O-2 and H2O2). Peroxisomal diseases result from the dysfunction of one or more peroxisomal metabolic functions, the majority of which manifest as neurological abnormalities. The quantitation of peroxisomal metabolic functions (e.g. levels of specific metabolites and/or enzyme activity) has become the basis of clinical diagnosis of diseases associated with the organelle. The study of peroxisomal diseases has also contributed towards the further elucidation of a number of metabolic functions of peroxisomes.

Animals↗
PubMed2001

Effect of retinoic acid on the Ca2+-independent phospholipase A2 in nuclei of LA-N-1 neuroblastoma cells.

LA-N-1 neuroblastoma cell cultures contain Ca2+-independent phospholipases A2 hydrolyzing phosphatidylethanolamine and ethanolamine plasmalogens. These enzymes differ from each other in their molecular mass, substrate specificity, and kinetic properties. Subcellular distribution studies have indicated that the activity of these phospholipases is not only localized in the cytosol but also in non-nuclear membranes and in nuclei. The treatment of LA-N-1 neuroblastoma cell cultures with retinoic acid results in a marked stimulation of Ca2+-independent phospholipases A2 hydrolyzing phosphatidylethanolamine and plasmenylethanolamine. The increase of the activities of both enzymes was first observed in nuclei followed by those present in the cytosol. No effect of retinoic acid on either phospholipase activity could be observed in non-nuclear membranes. The stimulation of these enzymes may be involved in the generation and regulation of arachidonic acid and its metabolites during differentiation.

Calcium↗
PubMed1997

Effects of maturation on the phospholipid and phospholipid fatty acid compositions in primary rat cortical astrocyte cell cultures.

Phospholipid and phospholipid fatty acid compositional changes were studied in rat cortical astrocytes during dibutyryl cyclic adenosine monophosphate (dBcAMP, 0.25 mM) treatment starting after 14 days in culture (DIC). After 15 DIC, ethanolamine- and choline glycerophospholipid levels were increased 1.2- and 1.3-fold, respectively in treated compared to control cells. However, after 21 and 28 DIC, these levels were not significantly different between groups. Both groups had an increase in phosphatidylserine levels with increasing time in culture. Similarly, ethanolamine plasmalogen levels were transiently elevated after 21 DIC, but returned to previous levels after 28 DIC. The phospholipid fatty acid compositions for the acid stable and labile ethanolamine- and choline glycerophospholipids indicated that in dBcAMP treated cells, 20:4 n-6 and 22:6 n-3 proportions were elevated with increasing time in culture relative to control cells. As 20:4 n-6 proportions increased, there was a concomitant decrease in 20:3 n-9 proportions, suggesting an up regulation of n-6 series elongation and desaturation. In contrast, in control cells, the 20:4 n-6 proportions decreased with a corresponding increase in the 20:3 n-9 proportions. Thus, in treated cells, the cellular phospholipid fatty acid composition was dramatically different than control cells, suggesting that dBcAMP treatment may act to increase fatty acid elongation and desaturation.

Animals↗
PubMed1967

The aminoethylphosphonate-containing lipids of rumen protozoa.

1. A method is presented for identifying and estimating the aminoethylphosphonate (ciliatine)-containing phospholipids in a complex mixture. 2. Evidence was obtained that the phospholipids of a pure culture of Entodinium caudatum and a mixed rumen protozoa sample contain diglyceride ciliatine, and a plasmalogen ciliatine was detected in the latter. 3. A ninhydrin-positive sphingolipid was isolated from rumen protozoa. Although chromatographically homogeneous on silica gel it contains two components, which were provisionally identified as ceramide ciliatine and ceramide phosphorylethanolamine. 4. A detailed phospholipid analysis of E. caudatum and rumen protozoa is presented. They contain no phosphatidylserine or cardiolipin, but an unidentified phosphoglyceride containing a zwitterionic amino acid is present.

Animals↗
PubMed1968

Metabolism of phospholipids and the characterization of fatty acids in bovine corpus luteum.

1. Phosphatidylcholine was the predominant phospholipid in bovine corpora lutea; it accounted for about 50% of the total phospholipid phosphorus. Phosphatidylethanolamine (13%) and ethanolamine plasmalogen (8-9%) were the next two major components. 2. After incubation of the tissue with [(32)P]orthophosphate the total radioactivity and specific radioactivity of phosphatidylinositol were higher than those of any other lipid. 3. Luteinizing hormone failed to increase significantly the incorporation of [(32)P]orthophosphate into total phospholipids from luteal tissue slices, but did stimulate progesterone synthesis and lactate production. 4. The proportion of oleate (18:1) in the neutral lipids and phospholipids was higher than that of any other fatty acid. 5. The proportion of unsaturated fatty acid in the tissue lipids exceeded 60%, and almost half of this was polyunsaturated. Arachidonate (20:4), docosatetraenoate (22:4) and docosapentaenoate (22:5) were the principal polyunsaturated fatty acids. 6. After incubation of luteal tissue with [1-(14)C]acetate, the greatest proportion of radioactivity in the fatty acids isolated from the total lipid fraction was in palmitate (16:0) and docosatetraenoate (22:4). Polyunsaturated fatty acids accounted for almost 50% of the (14)C radioactivity incorporated and this pattern was observed in phospholipids, triglycerides and free fatty acids.

Acetates↗
PubMed1969

The metabolism of polyphosphoinositides in hen brain and sciatic nerve.

1. The distribution of individual phospholipids was determined in hen brain and compared with that in sciatic nerve obtained in a previous investigation. Sciatic nerve is more enriched in the myelinic phospholipids ethanolamine plasmalogen, phosphatidylserine and sphingomyelin, but it contains relatively less triphosphoinositide, and much less diphosphoinositide, than the brain. 2. The course of incorporation of intraperitoneally injected (32)P into the acid-soluble phosphorus, phosphoinositides and total phospholipids of hen brain and sciatic nerve was followed. Although the maximum specific radioactivity in sciatic nerve of acid-soluble phosphorus is 4.5 times, and that of triphosphoinositide six times, that in the brain, the relative rate of triphosphoinositide phosphorus synthesis per gram of brain is three times that in sciatic nerve. 3. Administration of the demyelinating agent tri-o-cresyl phosphate to hens has no significant effect on the amounts or the rate of (32)P incorporation into the total phospholipids of the sciatic nerve. However, the rate of incorporation of (32)P into triphosphoinositide, although not its concentration, is raised from the first day after administration of the drug and remains thus 13 and 23 days later. 4. The incorporation of (32)P into polyphosphoinositides of hen brain slices in vitro was studied. The recovery of triphosphoinositide from the slices is markedly increased in the presence of EDTA, although the rate of incorporation of (32)P is unaffected. The incorporation of (32)P is dependent on the presence of Mg(2+) and Ca(2+) in the medium, and is decreased when Na(+) is replaced with K(+) or cholinium ions.

Animals↗