Biomedical subjects

A Kuksis

Publications and source records attributed to A Kuksis.

At least 55 records · Page 3Linked to original sources

PubMed1995

Comparison of Helicobacter mustelae and Helicobacter pylori adhesion to eukaryotic cells in vitro.

BACKGROUND & AIMS: Bacterial adhesion to mucosal surfaces is an important pathogenic mechanism for Helicobacter-induced gastritis. The aims of this study were to compare binding of selected Helicobacter mustelae and Helicobacter pylori strains to lipids extracted from HEp-2, Chinese hamster ovary, human embryonic lung cells, and ferret gastrointestinal tissues as well as to intact tissue culture cells and to analyze the fatty acids of the receptor. METHODS: Thin-layer chromatography overlay binding and a receptor-based immunoassay detected adhesion of bacteria to commercial lipids and to individual species within the lipid extracts. H. mustelae binding to tissue culture cells was performed by whole cell bacterial adhesion assay. RESULTS: H. mustelae and H. pylori both bound to phosphatidylethanolamine and lysophosphatidylethanolamine. Adhesion of H. mustelae to intact eukaryotic cells correlated with the amount of phosphatidylethanolamine. Binding of helicobacters was greater to lipids derived from ferret antrum compared with colon (P < 0.05). Biochemical analysis suggested that heterogeneity in fatty acid composition of phosphatidylethanolamine could influence the degree of Helicobacter binding. CONCLUSIONS: Adhesion of Helicobacter strains correlates with the quantity of phosphatidylethanolamine present in the epithelial cell and with the differences in the fatty acid profile of the lipid.

Animals↗

PubMed1995

Determination of lipid ester ozonides and core aldehydes by high-performance liquid chromatography with on-line mass spectrometry.

Unsaturated triacylglycerols (TG) and choline (PC) and ethanolamine (PE) phosphatides of known structure were subjected to ozonization and reduction with triphenylphosphine to yield the corresponding lipid ester core aldehydes. Mono- and di-C9 aldehyde palmitoylglycerols were prepared from oleoyldipalmitoyl and oleoyllinoleoylpalmitoyl glycerols, respectively, while egg yolk PC and PE provided the mono-C5 and mono-C9 aldehydes of palmitoyl-and stearoyl glycerophospholipids. The aldehydes were isolated in the free form and as the dinitrophenylhydrazone (DNPH) derivatives by thin-layer chromatography (TLC). The intermediate ozonides, free aldehydes and hydrazones were identified by reversed phase high performance liquid chromatography (HPLC) with on-line negative ion thermospray and normal phase HPLC with on-line positive ion electrospray mass spectrometry (LC-MS). The synthetic aldehydes were used as carriers during isolation from natural sources and as reference compounds in quantitative analyses.

Aldehydes↗

PubMed1995

Apolipoprotein A-I deficiency. Biochemical and metabolic characteristics.

Familial HDL deficiencies are associated with variable susceptibility to premature coronary heart disease, but the mechanism underlying this association remains poorly understood. Three homozygotes with isolated complete apo A-I deficiency caused by an autosomal codominant apo A-I Q[-2]X mutation and one heterozygote developed coronary heart disease before age 40 years. We characterized the effects of this mutation on lipoprotein metabolism. LDL FC, phospholipid, and apo B were all significantly higher in homozygotes than in heterozygotes. The HDLs of the heterozygotes were apo A-I poor relative to apo A-II. Lecithin-cholesterol acyltransferase activity was 59% lower in homozygotes than in normal subjects or heterozygotes. Cholesteryl ester transfer activity was increased in a homozygote compared with a normolipidemic control subject. Postprandial lipid metabolism was studied in one homozygote and one heterozygote. Post-prandial TG response in the homozygote was significantly exaggerated, while residual plasma HDL level remained unaffected. The homozygote also had delayed clearance of retinyl ester, a marker of chylomicron remnant metabolism. Thus, homozygosity and heterozygosity for apo A-I Q[-2]X are associated with qualitative, as well as quantitative, disturbances in plasma HDLs, LDLs, lipid-modifying enzyme activities, and postprandial retinyl ester metabolism. The observed elevation of atherogenic lipoproteins and reduction in antiatherogenic lipoproteins in the affected members of the apo A-I Q[-2]X kindred are consistent with the primary deficiency in apo A-I having pleiotropic effects that markedly enhance susceptibility for coronary heart disease.

Apolipoprotein A-I↗

PubMed1995

Biosynthesis of chylomicron triacylglycerols by rats fed glyceryl or alkyl esters of menhaden oil fatty acids.

We have previously shown great similarity in the distribution of fatty acids in the sn-1 and sn-3 positions of the chylomicron triacylglycerols (TG) from rats fed menhaden oil or its ethyl esters, and have proposed that the acylglycerol products of the phosphatidic acid (PA) pathway (ester feeding) are hydrolyzed to 2-monoacylglycerols (2-MG) prior to reconversion to TG via the 2-MG pathway (oil feeding) and secretion as chylomicrons. As the composition of the sn-2-position would also be retained if the TG were hydrolyzed only to the X-1,2-diacylglycerol (DG) stage before resynthesis, we have now retested the hypothesis by determining the molecular association and reverse isomer content of the sn-1,2- and sn-2,3-DG derived from the chylomicron TG and the PA resulting from the two feedings. The new data demonstrate a better than 90% homology among the molecular species of the PA from the oil and ester feeding, along with the characteristic association of the saturated acids with sn-1- and the unsaturated acids with sn-2-position. Due to increased proportion of unsaturated acids in the sn-1-position of the TG, there was only a 15-20% homology between the PA and the sn-1,2-DG moieties of the chylomicron TG from the oil and ester feeding. A lack of homology was also observed between the PA and free sn-1,2-DG, as well as between the free sn-1,2-DG and the sn-1,2-DG moieties of the chylomicron TG. On the basis of molecular association and the sn-1-/sn-3- reverse isomer content of the chylomicron TG a better than 90% homology was recognized between the chylomicron TG resulting from the oil and ester feeding. It is therefore concluded that hydrolysis to 2-MG followed by reesterification via the 2-MG pathway constitutes the most plausible mechanism for the transfer to chylomicrons of the TG arising from alkyl ester feeding.

Alkylation↗

PubMed1995

Origin of triacylglycerol moiety of plasma very low density lipoproteins in the rat: structural studies.

We have compared the molecular species composition of the glycerolipids of rat liver and rat plasma very low density lipoproteins (VLDL). There were differences in the stereospecific distribution of the fatty acids in the triacylglycerols (TG) of the liver and of VLDL. While chiral and reversed phase chromatography with mass spectrometry (LC/MS) revealed great similarities in positional distribution and molecular association of the fatty acids between the sn-1,2-diacylglycerol (DG) moieties of the VLDL and liver TG, the corresponding sn-2,3-DG were distinctly different. The free hepatic sn-1,2-DG and the sn-1,2-DG moiety contained within hepatic phosphatidic acid showed a maximum 60% homology to the sn-1,2-DG contained within the TG of the liver and of VLDL. By contrast, the smaller pool of hepatic free sn-2,3-DG was nearly identical to the sn-2,3-DG moiety contained in the TG of the liver. These differences between hepatic and VLDL TG indicate that direct transfer of hepatic triacylglycerols is not a major mechanism of VLDL TG formation. On the other hand, the results suggest that stored hepatic TG are largely hydrolyzed to sn-1,2-DG and then reesterified to TG before being secreted as VLDL TG. Although an involvement of 2-monoacylglycerol pathway could not be excluded, it probably plays a minor role in VLDL TG formation. Our data suggest that a minimum of 60% of the VLDL TG could have been derived via hydrolysis to DG and reesterification, and a maximum of 40% could have originated via the conventional phosphatidic acid pathway.

Animals↗

PubMed1995

Plasma fatty acid profiles of Canadian Inuit and Siberian Ganasan.

Cross-sectional data from 86 male and 59 female coastal Inuit of Igloolik (69 degrees 40'N, 81 degrees W) showed a steep age-related increase in the percentage of plasma n-3 fatty acids, with parallel trends in 20:5 and 22:6 but not 18:3 n-3 fatty acid concentrations. Omega-7 + 9 (p < .001) and omega-9 fatty acid concentrations (P < .001 in M, .008 in F) also decreased with age. A tundra-based Siberian indigenous population (30 male and 11 female nGanasan) had similar percentages of n-3 and n-6 fatty acids to the young Inuit, with little age-related change in either measure. Correlation matrices for the Inuit men showed quite strong negative associations of n-3 fatty acid percentages with total triglycerides (r = .34, p < .001) and phosphatidylcholine/free cholesterol ratio (r = -.36, p < .001). In the Inuit women, n-3 percentages were strongly related to phosphatidylcholine/free cholesterol ratio (r = -.60, p < .001), but not to triglyceride readings. The phosphatidylcholine/free cholesterol ratio was also correlated with n-6 percentages (r = -.55, p < .001). In the nGanasan men, triglyceride levels were correlated with n-6 (r = -.35, p < .050), but the size of the female sample was insufficient to establish useful correlations. The present data suggest that as the younger coastal Inuit are abandoning their traditional country foods, plasma levels of n-3 fall. Reasons why n-3 fatty acid levels are negatively related to the plasma phosphatidyl choline/free cholesterol ratio merit further investigation.

Adult↗

PubMed1995

Lipid ester-bound aldehydes among copper-catalyzed peroxidation products of human plasma lipoproteins.

We have isolated the core aldehydes (aldehydes still bound to parent molecules) of phosphatidylcholine (PC) and cholesteryl esters (CE) from copper-catalyzed peroxidation of human plasma low (LDL) and high (HDL) density lipoproteins. The aldehydes were isolated by extraction with acidified chloroform-methanol containing 2,4-dinitrophenylhydrazine. The 2,4-dinitrophenylhydrazone (DNPH) derivatives formed were resolved by reversed phase high performance liquid chromatography (HPLC) and identified by on-line quadrupole mass spectrometry (LC/MS). The major PC core aldehydes from oxidized LDL and HDL were identified as 1-palmitoyl-(1-stearoyl) 2-(9-oxononanoyl)-, 1-palmitoyl-(1-stearoyl) 2-(8-oxooctanoyl)-, and 1-palmitoyl-(1-stearoyl) 2-(5-oxovaleroyl)-sn-glycerols after phospholipase C digestion of the DNPH derivatives of the phospholipids. The major aldehydes from peroxidation of cholesteryl esters were the 9-oxononanoyl, 8-oxooctanoyl, and 5-oxovaleroyl esters of cholesterol and 7-ketocholesterol. The core aldehydes were estimated to account for a minimum of 1-2% of the consumed linoleate and arachidonate esters. A relatively smaller yield of the PC core aldehydes from LDL compared to HDL was attributed to the presence of greater amounts of phospholipases in LDL than in HDL. More comparable yields of PC core aldehydes were obtained in the presence of phenylmethylsulfonylfluoride, which inhibits phospholipases. We conclude that peroxidation of LDL and HDL results in formation of detectable amounts of cholesteryl and glycerophospholipid esters containing aldehyde functions. The yield of PC aldehydes varies with the activity of the platelet activating factor (PAF) acetyl hydrolase.

Aldehydes↗

PubMed1994

Complementary chromatographic analysis of free diacylglycerols and potential glycerophospholipid precursors in human SH-SY5Y neuroblastoma cells following incubation with lithium chloride.

We performed detailed chromatographic analyses on the molecular species of the major glycerophospholipids (GPLs) and free sn-1,2-diacylglycerols (DAGs) from SH-SY5Y human neuroblastoma cells following incubation with or without LiCl. For this comparison the inositol, choline, ethanolamine and serine GPLs were dephosphorylated with phospholipase C and the released sn-1,2-diacylglycerols along with the DAGs were subjected to high-temperature GLC on polar and non-polar capillary columns as their trimethylsilyl and tert.-butyl-dimethylsilyl ethers. A 30-min incubation with 10 mM LiCl increased the total amount of human neuroblastoma DAGs by 32-58% (P < 0.05) to 2.6 pmol/micrograms cell protein. This was accompanied by a limited qualitative shift in the molecular species pattern, the most obvious of which was the increase (13%) in the major saturated-polyunsaturated molecular species and the ca. 46% increase in the minor 18:1-18:1 species over control levels. The DAGs originated mainly from the inositol GPLs (IGPLs), as indicated by the high levels of the characteristic 18:0-20:4n6 (18:0-20:3n9) species in both IGPLs and DAGs, and to a lesser extent from the choline GPLs (CGPLs), as indicated by the high proportion in CGPLs of the oligoenoic species, which were largely absent from IGPLs. Alkenylacylglycerols were not detected in DAGs, although they made up some 60% of the total ethanolamine GPLs (EGPLs). No significant changes in the molecular species composition of the cellular GPLs, including IGPLs, were detected after exposure to LiCl.

Brain Neoplasms↗

PubMed1994

Kinetics of lipolysis of very low density lipoproteins by lipoprotein lipase. Importance of particle number and noncompetitive inhibition by particles with low triglyceride content.

Our objective was to identify the major compositional factor(s) of very low density lipoprotein which determines its properties as a substrate for lipoprotein lipase. Human very low density lipoprotein was fractionated by preparative electrophoresis. The apparent Km was significantly lower for pre-beta very low density lipoprotein compared with beta very low density lipoprotein when calculated on the basis of triglyceride concentration. When the triglyceride concentration was adjusted for the triglyceride/apolipoprotein B ratio, the apparent Km was not different among very low density lipoprotein fractions. This implied that very low density lipoprotein particle number was of primary importance. To test this hypothesis further, rabbit cholesterol-rich very low density lipoprotein and human intermediate density lipoprotein and low density lipoprotein, from a patient with hepatic lipase deficiency, were added to the incubations. Each of these fractions functioned as noncompetitive inhibitors of lipolysis. We speculate that the saturation of lipoprotein lipase by an excess number of particles is a characteristic of human hyperlipoproteinemias that predispose to coronary heart disease and that are commonly classified as familial combined hyperlipoproteinemia or hyperapobetalipoproteinemia.

Animals↗

PubMed1994

A cross-species comparison of neutral lipid composition of milk fat of prosimian primates.

The fatty acid composition of milk fat is known to be affected by dietary and genetic differences, while the milk triacylglycerol structure is believed to be attuned to the needs of the subsequent lipolysis during gastrointestinal passage. The availability of milk samples from eight species of prosimian primates, whose milk triacylglycerol structure had not been analyzed, offered an opportunity to further assess these ideas. The milk samples were collected by manual expression and the lipids extracted with chloroform/methanol (2:1, vol/vol). The lipid classes were resolved by thin-layer chromatography, and the neutral lipids subjected to detailed analyses by capillary gas-liquid chromatography of fatty acids and molecular species of triacylglycerols using nonpolar and polarizable liquid phases. The milk samples were found to differ greatly in total fat content (4-73%) and in the composition of the neutral lipid classes and molecular species. The concentration of triacylglycerols ranged from 88-95%, free fatty acids from 0.5-10%, alkyldiacylglycerols from 0.5-5.0%, and diacylglycerols, monoacylglycerols and free and esterified cholesterol made up the remainder. The fatty acid chain length ranged from C8-C24, with palmitic (16-31%) and oleic (13-40%) acids being the major components in most of the species. In all instances, the molecular association of the fatty acids differed from random distribution by a higher proportion of the monoacid (trioleoyl) and diacid (dipalmitoyloleoyl) glycerols. The phylogenetic influences on neutral milk lipid composition, however, remained unclear, as some of the differences between closely related species were greater than those between more distantly related ones.

Animals↗

PubMed1994

Comparison of the effect of hyperinsulinemia on acyl-CoA:cholesterol acyltransferase activity in the liver and intestine of the rat.

UNLABELLED: Recent studies have suggested that cholesteryl ester synthesis plays a critical role in the assembly of VLDL apo B and triacylglycerol in the liver. Chronic hyperinsulinemia is associated with increased TG production and since cholesteryl ester synthesis depends on acyl CoA:cholesterol acyltransferase (ACAT), we investigated the possibility that chronic hyperinsulinemia might increase ACAT activity. We also measured ACAT activity in the intestinal mucosa, where it has been suggested to play a role in induction of diabetes-associated hypercholesterolemia. Chronically hyperinsulinemic rats were produced by injecting insulin (2 weeks, 6U/day). To prevent profound hypoglycemia, these rats were given 10% sucrose in place of drinking water. Acute hyperinsulinemia was produced by injecting a single dose of 0.5 U insulin ip. Chronic hyperinsulinemia led to a significant increase in free cholesterol, cholesteryl esters, triacylglycerols and phospholipids in the whole liver (27%, P < 0.05; 60%, P < 0.05; 70%, P < 0.01; 37%, P < 0.01, respectively) and an increase in hepatic microsomal triacylglycerol (P < 0.05). In contrast, the microsomal lipids of the intestinal mucosa decreased significantly. In chronically hyperinsulinemic rats there was no change in hepatic ACAT, while ACAT in the intestine actually decreased (26%-50%, P < 0.01). CONCLUSIONS: since the effect of chronic hyperinsulinemia on hepatic ACAT did not parallel that seen previously on VLDL secretion, the effect of chronic hyperinsulinemia on VLDL production cannot be explained by its effect on hepatic ACAT. However, chronic hyperinsulinemia was associated with reduced ACAT activity in the intestine and this might result in decreased lipoprotein production in the hyperinsulinemic intestine.

Animals↗

PubMed1993

Purification of an acyl-CoA hydrolase from rat intestinal microsomes. A candidate acyl-enzyme intermediate in glycerolipid acylation.

We have purified to apparent homogeneity an acyl-CoA hydrolase activity from rat intestinal villus cell microsomes by heparin and anion exchange and affinity chromatography. The purified 54-kDa acyl-CoA hydrolase along with several microsomal proteins form a covalent acyl-protein bond upon incubation with an activated fatty acid (acyl-CoA). The acyl moiety of the acylated acyl-CoA hydrolase is stable to denaturation and extraction with organic solvents, but is displaced by neutral hydroxylamine or mercaptoethanol, indicating a labile high energy (thio)ester linkage. The enzyme activity is inhibited by thiol-directed reagents and activated by the presence of dithiothreitol suggesting the presence of a cysteine residue(s) at or near the active site. Common serine-esterase inhibitors (NaF, phenylmethylsulfonyl fluoride) and activators (Mg2+, Ca2+) had no effect on the hydrolase activity. The enzyme hydrolyzed (transferred to water) 14-20 carbon acyl-CoA with similar efficiencies and did not utilize glycerophospholipids or mono- and diacylglycerols as potential acyl donors/acceptors. Phospholipids and mono- and diradylglycerols at concentrations below 100 microM or polyclonal antibodies raised against the purified hydrolase did not inhibit the enzyme activity. However, the acyl-CoA hydrolase activity could be immunoprecipitated from solubilized microsomes or purified enzyme preparations with corresponding decrease of the hydrolase activity in the supernatant of the immunoprecipitate. Immunoblotting studies show cross-reactivity with a protein of an identical molecular mass in other rat or human tissues. It is concluded that the microsomal acyl-CoA hydrolase deserves consideration as a candidate acyl-enzyme intermediate in glycerolipid synthesis when associated with appropriate acyltransferases.

Acylation↗

PubMed1993

Triacylglycerol synthesis by an sn-1,2(2,3)-diacylglycerol transacylase from rat intestinal microsomes.

A membrane-associated sn-1,2(2,3)-diacylglycerol transacylase activity was purified 550-fold from the microsomes of rat intestinal villus cells. The enzyme was solubilized with the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate and was isolated and purified by sequential chromatography on hydroxylapatite, an anion exchanger, Affi-Gel heparin and Cibacron blue A-agarose. SDS-polyacrylamide gel electrophoresis revealed two major closely migrating polypeptides of apparent molecular mass of 50 and 52 kDa. Incubation of the isolated enzyme with sn-1,2(2,3)dioleoyl-[2-3H]glycerol yielded trioleoyl[2-3H]glycerol and 2-oleoyl[2-3H]glycerol. The synthesis of triacylglycerols was independent of acyl-CoA, as indicated by the absence of incorporation of radioactivity from [1-14C]oleoyl-CoA into mono-, di-, or triacylglycerols under these conditions. The transacylase did not hydrolyze triacylglycerols readily and was not affected by the acyltransferase inhibitors, N-ethylmaleimide and 4,4'-diisothiocyanostilbene-2,2'-disulfonate, while the lipase/hydrolase inhibitors NaF, phenylmethylsulfonyl fluoride, and diethyl p-nitrophenyl phosphate caused partial inactivation. The enzyme was specific toward 1(3)-positions of rac 1,2-diacylglycerols but did not utilize the -1,3-diacylglycerols or other neutral lipid esters effectively and was not capable of removing fatty acids from phosphatidylcholine or of transfer of fatty acids from X (unspecified enantiomer)-1,2-diacylglycerol to lysophosphatidylcholine. Since the diacylglycerol transacylation did not lead to accumulation of either sn-1,2- or sn-2,3-diacylglycerols during incubation with the racemates, it is concluded that both sn-1,2- and sn-2,3-s are utilized at similar rates.

Acyltransferases↗

PubMed1993

Identification of core aldehydes among in vitro peroxidation products of cholesteryl esters.

Synthetic cholesteryl 5-oxovalerate and 9-oxononanoate were used as reference standards for the isolation and identification of cholesteryl ester core aldehydes from tert-butyl hydroperoxide/Fe++ oxidation of synthetic and natural cholesteryl esters. The core aldehydes were recovered from the peroxidation products by thin-layer chromatography as the free aldehydes or the 2,4-dinitrophenylhydrazones and were identified, respectively, by gas-liquid chromatography (GLC) and by GLC combined with mass spectrometry (GC/MS) or by reverse-phase high-performance liquid chromatography (HPLC) and by HPLC with MS (LC/MS). The core aldehydes produced by peroxidation of cholesteryl linoleate were identified as mainly 9-oxononanoates of cholesterol and oxycholesterols, with smaller amounts of the 8-oxooctenoates, 10-oxodecenoates, 11-oxoundecenoates and 12-oxododecenoates. Peroxidation of cholesteryl arachidonate yielded 5-oxovalerates of cholesterol and the oxycholesterols as the main products with smaller amounts of the 4-oxobutyrates, 6-oxohexenoates, 7-oxoheptenoates, 8-oxooctenoates, 9-oxononenoates, 9-oxononadienoates and 10-oxodecadienotes. The oxycholesterols resulting from the peroxidation of the steroid ring were identified as mainly 7-keto-, 7 alpha-hydroxy- and 7 beta-hydroxy-cholesterols and 5 alpha,6 alpha- and 5 beta,6 beta-epoxy-cholestanols. Cholesteryl palmitate and oleate did not yield core aldehydes in the present peroxidation system. In these esters, the sterol and linoleic acid moieties appeared to be oxygenated at about the same rate, while the arachidonic acid moiety reacted more rapidly than did the sterol moiety.

Aldehydes↗

PubMed1993

Stereospecificity of monoacylglycerol and diacylglycerol acyltransferases from rat intestine as determined by chiral phase high-performance liquid chromatography.

Using chiral phase high-performance liquid chromatography of diacylglycerols, we have redetermined the ratios of 1,2-/2,3-diacyl-sn-glycerols resulting from acylation of 2-monoacylglycerols by membrane bound and solubilized triacylglycerol synthetase of rat intestinal mucosa. With 2-oleoyl[-3H]glycerol as the acyl acceptor and oleoyl-CoA as the acyl donor, 97-98% of the diacylglycerol product was 1,2(2,3)-dioleoyl-sn-glycerol, 90% of which was the sn-1,2- and 10% the sn-2,3-enantiomer. The remaining diacylglycerol (less than 3%) was the sn-1,3-isomer. The overall yield of acylation products was 70%, of which 60% were diacylglycerols and 40% triacylglycerols. With 2-oleylglycerol ether as the acyl acceptor and [1-14C]oleoyl-CoA as the acyl donor, 90% of the diradylglycerol was 1-oleoyl-2-oleyl-sn-glycerol and 10% was the 2-oleyl-3-oleoyl-sn-glycerol. The diradylglycerols made up 96% and the triradylglycerols 4% of the radioactive product. With 1-palmitoyl-sn-glycerol as the acyl acceptor and [1-14C]oleoyl-CoA as the acyl donor, the predominant reaction product was 1-palmitoyl-3-oleoyl-sn-glycerol. The 3-palmitoyl-sn-glycerol was not a suitable acyl acceptor. Both 1,2- and 2,3-diacyl-sn-glycerols were substrates for diacylglycerol acyltransferase as neither isomer was favored when 1,2-dioleoyl-rac-[2-3H]glycerol was used as the acyl acceptor. There was a marked decrease in the acylation of the 1(3)-oleoyl-2-oleyl-sn-glycerol to the 1,3-dioleoyl-2-oleyl-sn-glycerol. It is concluded that neither monoacylglycerol nor diacylglycerol acyltransferase exhibit absolute stereospecificity for acylglycerols as fatty acid acceptors.

Acyltransferases↗

PubMed1993

Quantitation of plasma lipids by gas-liquid chromatography on high temperature polarizable capillary columns.

We have previously demonstrated the potential usefulness of capillary columns coated with a high temperature polarizable phenylmethylsilicone liquid phase in plasma lipid profiling (Kuksis, A., J.J. Myher, and P. Sandra. 1990. J. Chromatogr. 500: 427-441). The present study reports improved operating conditions along with a practical application to the analysis of a series of human plasma samples in comparison to capillary gas-liquid chromatography on nonpolar columns. For this purpose the plasma lipids were dephosphorylated with phospholipase C and converted to the trimethylsilyl ethers. The molecular species of the plasma lipids were identified by comparing the relative retention times to reference standards. The species were quantitated using tridecanoylglycerol as internal standard. The recoveries of the lipid classes were determined by summing the molecular species within each carbon number and comparing the proportion of the carbon numbers obtained on polar and nonpolar columns. The relative recoveries varied with the lipid class and sample load and averaged as follows: FA C16, 78%; FA C18, 78%; FC, 99%; tridecanoylglycerol (TD), 100% (by definition); CER 34:1, 92%; DG C34, 103%; DG C36, 98%; CE C16, 73%; CE C18, 61%; TG C50, 93%; TG C52, 60%; TGC54, 32%. We conclude that high temperature polarizable capillary columns are suitable for qualitative and quantitative assessment of plasma lipids and provide more information per man-hour, instrument time, and unit cost than any other analytical method known.

Autoanalysis↗

PubMed1992

Gas chromatographic profiles of plasma total lipids as indicators of dietary history. Correlation with carbohydrate and alcohol intake based on 24-h dietary recall.

Quantitative gas chromatographic estimates of the major lipid classes and molecular species in fasting plasma were correlated with total carbohydrate, starch, fibre, sucrose and alcohol intake based on 24-h dietary recall. Spearman coefficients (rs) and tests of significance (P) were obtained for groups of 775 males and 471 females aged 20-59 years from a Toronto-McMaster Lipid Research Clinics Population Study. The most significant correlations varying from rs 0.1 to 0.2 and P 0.001 to 0.0005 (n = 400-773) were between increased intake of alcohol and increased ratios of C50/C54 triacylglycerols, C34/C36 phosphatidylcholines and phosphatidylcholine/free cholesterol (PC/FC) of plasma. Increase in total dietary carbohydrate, starch and fibre correlated with decreasing C50/C54 triacylglycerol, C34/C36 phosphatidylcholine and PC/FC ratios (rs = -0.1-0.2; P less than 0.002-0.04; n = 400-773). In contrast, consumption of high levels of alcohol was associated with increasing C50/C54 triacylglycerol, C34/C36 phosphatidylcholine and PC/FC ratios. A high intake of alcohol (50-150 ml per day) distinguished itself from other simple carbohydrate-induced lipid profiles by its marked effect on increased C50/C52 triacylglycerol and PC/FC ratio.

Adult↗

PubMed1992

Identification of cholesterol-bound aldehydes in copper-oxidized low density lipoprotein.

Lipid-soluble cholesteryl ester core aldehydes (aldehydes still bound to the cholesterol ring) were identified among the products of copper-catalyzed peroxidation of human low density lipoprotein (LDL). The LDL was exposed to oxygenated buffer and 5 microM CuSO4 for 24 h. The core aldehydes were isolated as the dinitrophenylhydrazones, and were identified by reverse-phase HPLC with mass spectrometry. The major components were the C4-C10 oxoalkanoyl esters of cholesterol and 7-ketocholesterol, and accounted for 1-2% of the cholesteryl linoleate and arachidonate consumed.

Aldehydes↗