Value of Ascitic Lipids in the Differentiation between Cirrhotic and Malignant Ascites

Ascitic fluid concentrations of cholesterol, triglycerides and phospholipids, were compared with ascitic fluid total protein in 40 patients with chronic liver disease, 51patients with various neoplasms and 1 patient with cardiac failure. Seven patients withboth chronic liver disease and malignancy were considered separately. The first 54 patients (23 cirrhotic and 31 with malignancy) were used to determine median values and ranges and to define the most suitable cutoff concentrations between both groups. Median values for cholesterol (75 mg per dl), phospholipids (0.79 mmole per liter), triglycerides (75 mg per dl) and protein (3.8 gm per dl)were higher in malignant ascites compared to ascitic fluid concentrations of cholesterol (20 mg per dl), phospholipids (0.33 mmole per liter), triglycerides (51 mg per dl) and protein (1.9 gm per dl) in patients withcirrhosis. The best discrimination values were 48 mg per dl for cholesterol, 0.6 mmole per liter for phospholipids, 65 mg per dl for triglycerides and 2.5 gm per dl for protein. Application of these cutoff points to 38 subsequent patients (17 cirrhotic, 1 with cardiac failure and 20 with malignancy) revealed an efficiency of 86.8% for cholesterol, 86.8% for phospholipids, 68.4% for triglycerides and 79.0% for protein. From the data of all 92 patients, an efficiency of 92.3% forcholesterol, 79.4% for phospholipids, 72.8% for triglycerides and 79.4% for protein was calculated. We conclude that ascitic fluid cholesterol determination offers an excellent, cost-effective discrimination of ascites due to cirrhosis vs. ascites caused by malignancies

Detailed study of Brazil nut (Bertholletia excelsa) oil micro-compounds : Phospholipids, tocopherols and sterols

The oil of the Brazil nut (Bertholletia excelsa) was studied for its composition in fatty acids, tocopherols, sterols and phospholipids. The fatty acids composition of phospholipids was also studied. These results were compared to those of sunflower, walnut, almond, soya and olive oils. Its high content of unsaturated fatty acids, of [bêta]-tocopherol and of [bêta]-sitosterol gave to the Brazil nut interesting antioxidant and anti-cholesterol properties. The composition of fatty acids in phospholipid is very different from the composition of the oil. Linolenic acid, which is not present in the oil, is present at a high level in phosphatidylethanolamine. (Résumé d'auteur

Influence of pretreatments for extraction of lipids from yeast by using supercritical carbon dioxide and ethanol as cosolvent

Saccharomyces cerevisiae is one of the most studied and industrially exploited yeast. It is a non-oleaginous yeast whose lipids are mainly phospholipids. In this work, the extraction of yeast lipids by supercritical carbon dioxide (SCCO2) and ethanol as a co-solvent was studied. In particular our attention was focused on the selectivity toward triglycerides, and in a subsequent extraction of the phospholipids present in the yeast. Indeed CO2 is a non-polar solvent and is not an efficient solvent for the extraction of phospholipids. However, SCCO2 can be used to extract neutral lipids, as triglycerides, and the addition of polar co-solvents like ethanol, at different compositions, allows a more efficient extraction of triglycerides, and also an extraction–fractionation of phospholipids. In this work SCCO2extractions of a specific membrane complex of S. cerevisiae, obtained from an industrial provider, were carried out at 20 MPa and 40 °C, using ethanol as a co-solvent (9%, w/w). It was shown that different pretreatments are necessary to obtain good extraction yields and have a great impact on the extraction. The kinetic of the extractions were successfully modeled using Sovova's model. From the fitting of the main parameters of the model it was possible to compare the effects of the pretreatments over the yeast material, and to better understand the extraction process. Among the seven tested pretreatments the more appropriate was found to be an acid hydrolysis followed by a methanol maceration

General model of phospholipid bilayers in fluid phase within the single chain mean field theory

Coarse-grained model for saturated (DCPC, DLPC, DMPC, DPPC, DSPC) and unsaturated (POPC, DOPC) phospholipids is introduced within the Single Chain Mean Field theory. A single set of parameters adjusted for DMPC bilayers gives an adequate description of equilibrium and mechanical properties of a range of saturated lipid molecules that differ only in length of their hydrophobic tails and unsaturated (POPC, DOPC) phospholipids which have double bonds in the tails. A double bond is modeled with a fixed angle of 120 degrees, while the rest of the parameters are kept the same as saturated lipids. The thickness of the bilayer and its hydrophobic core, the compressibility and the equilibrium area per lipid correspond to experimentally measured values for each lipid, changing linearly with the length of the tail. The model for unsaturated phospholipids also fetches main thermodynamical properties of the bilayers. This model is used for an accurate estimation of the free energies of the compressed or stretched bilayers in stacks or multilayers and gives reasonable estimates for free energies. The proposed model may further be used for studies of mixtures of lipids, small molecule inclusions, interactions of bilayers with embedded proteins

Do anionic phospholipids serve as cofactors or second messengers for the regulation of activity of cloned ATP-sensitive K+ channels?

The regulation of ion channels by anionic phospholipids is currently very topical. An outstanding issue is whether phosphatidylinositol 4,5-diphosphate and related species act as true second messengers in signaling or behave in a manner analogous to an enzymatic cofactor. This question is especially pertinent regarding ATP-sensitive K+ channels in smooth muscle, for which there is substantial literature supporting inhibitory regulation by hormones. In this study, we have examined regulation of the potential cloned equivalents of the smooth muscle ATP-sensitive K+ channel (SUR2B/Kir6.1 and SUR2B/Kir6.2). We find that both can be inhibited via the G(q/11)-coupled muscarinic M3 receptor but that the pathways by which this occurs are different. Our data show that SUR2B/Kir6.1 is inhibited by protein kinase C and binds anionic phospholipids with high affinity, such that potential physiological fluctuations in their levels do not influence channel activity. In contrast, Kir6.2 is not regulated by protein kinase C but binds anionic phospholipids with low affinity. In this case, phosphatidylinositol 4,5-diphosphate and related species have the potential to act as second messengers in signaling. Thus, Kir6.1 and Kir6.2 are regulated by distinct inhibitory mechanisms

Dietary N-3 polyunsaturated fatty acids decrease biliary cholesterol saturation in gallstone disease

Because fatty acid composition of biliary phospholipids influences cholesterol secretion into bile, we investigated whether replacement of n-1 monounsaturated or n-6 polyunsaturated fatty acids with n-3 polyunsaturated fatty acids in biliary phosphatidylcholines reduces supersaturation with cholesterol and prevents precipitation of cholesterol crystals in bile of gallstone patients. Seven patients with radiolucent gallstones in functioning gallbladders were studied before (control) and after 5 wk of dietary supplementation with marine fish oil (11.3 gm/day = 3.75 gm n-3 polyunsaturated fatty acids/day). Duodenal bile was collected for analysis during intravenous infusion of cholecystokinin. Gallbladder emptying in response to cholecystokinin was comparable before and during intake of n-3 polyunsaturated fatty acids. Intake of n-3 polyunsaturated fatty acids increased (p < 0.001) the fractions of eicosapentaenoic and docosahexaenoic acids and decreased the fractions of linoleic (p < 0.001) and arachidonic acids (p < 0.02) in biliary phospholipids. Concomitantly, the molar ratio of cholesterol to phospholipids decreased (-19%; p < 0.05). As a consequence, the cholesterol saturation index was reduced by -25% (p = 0.01), from 1.60 ± 0.44 to 1.24 ± 0.38. However, in vitro nucleation time of duodenal bile was not prolonged. The decrease in cholesterol saturation was not sufficient to prevent nucleation of cholesterol crystals in bile of gallstone patients. In conclusion, our data suggest that cholesterol saturation can be influenced by the fatty acid composition of the phosphatidylcholines secreted in bile

Direct binding of phosphatidylglycerol at specific sites modulates desensitization of a ligand-gated ion channel

Pentameric ligand-gated ion channels (pLGICs) are essential determinants of synaptic transmission, and are modulated by specific lipids including anionic phospholipids. The exact modulatory effect of anionic phospholipids in pLGICs and the mechanism of this effect are not well understood. Using native mass spectrometry, coarse-grained molecular dynamics simulations and functional assays, we show that the anionic phospholipid, 1-palmitoyl-2-oleoyl phosphatidylglycerol (POPG), preferentially binds to and stabilizes the pLGIC, Erwinia ligand-gated ion channel (ELIC), and decreases ELIC desensitization. Mutations of five arginines located in the interfacial regions of the transmembrane domain (TMD) reduce POPG binding, and a subset of these mutations increase ELIC desensitization. In contrast, a mutation that decreases ELIC desensitization, increases POPG binding. The results support a mechanism by which POPG stabilizes the open state of ELIC relative to the desensitized state by direct binding at specific sites

Substrate-Specific Inhibition Constants for Phospholipase A2 Acting on Unique Phospholipid Substrates in Mixed Micelles and Membranes Using Lipidomics.

Assaying lipolytic enzymes is extremely challenging because they act on water-insoluble lipid substrates, which are normally components of micelles, vesicles, and cellular membranes. We extended a new lipidomics-based liquid chromatographic-mass spectrometric assay for phospholipases A2 to perform inhibition analysis using a variety of commercially available synthetic and natural phospholipids as substrates. Potent and selective inhibitors of three recombinant human enzymes, including cytosolic, calcium-independent, and secreted phospholipases A2 were used to establish and validate this assay. This is a novel use of dose-response curves with a mixture of phospholipid substrates, not previously feasible using traditional radioactive assays. The new application of lipidomics to developing assays for lipolytic enzymes revolutionizes in vitro testing for the discovery of potent and selective inhibitors using mixtures of membranelike substrates