Macroscopic domain formation during cooling in the platelet plasma membrane: an issue of low cholesterol content.

There has been ample debate on whether cell membranes can present macroscopic lipid domains as predicted by three-component phase diagrams obtained by fluorescence microscopy. Several groups have argued that membrane proteins and interactions with the cytoskeleton inhibit the formation of large domains. In contrast, some polarizable cells do show large regions with qualitative differences in lipid fluidity. It is important to ask more precisely, based on the current phase diagrams, under what conditions would large domains be expected to form in cells. In this work we study the thermotropic phase behavior of the platelet plasma membrane by FTIR, and compare it to a POPC/Sphingomyelin/Cholesterol model representing the outer leaflet composition. We find that this model closely reflects the platelet phase behavior. Previous work has shown that the platelet plasma membrane presents inhomogeneous distribution of DiI18:0 at 24 degrees C, but not at 37 degrees C, which suggests the formation of macroscopic lipid domains at low temperatures. We show by fluorescence microscopy, and by comparison with published phase diagrams, that the outer leaflet model system enters the macroscopic domain region only at the lower temperature. In addition, the low cholesterol content in platelets ( approximately 15 mol%), appears to be crucial for the formation of large domains during cooling.

High pre-beta1 HDL concentrations and low lecithin: cholesterol acyltransferase activities are strong positive risk markers for ischemic heart disease and independent of HDL-cholesterol.

BACKGROUND: We hypothesized that patients with high HDL-cholesterol (HDL-C) and ischemic heart disease (IHD) may have dysfunctional HDL or unrecognized nonconventional risk factors. METHODS: Individuals with IHD (Copenhagen University Hospital) and either high HDL-C (n = 53; women >or=735 mg/L; men >or=619 mg/L) or low HDL-C (n = 42; women

Physical activity, high-density lipoprotein cholesterol subfractions and lecithin:cholesterol acyltransferase in dialysis patients.

BACKGROUND/AIMS: Although a low level of high-density lipoprotein cholesterol (HDL-C) is an independent risk factor for atherosclerotic heart disease, the mechanism of HDL-C abnormality in hemodialysis (HD) as well as peritoneal dialysis (PD) patients is not fully understood. The purpose of this study was to investigate the relationship of physical activity with HDL-C subfractions and lecithin:cholesterol acyltransferase activity in HD and PD patients. METHODS: Thirty-five HD and 26 PD patients were studied. Physical activity was estimated as the average number of steps taken per day over 7 days (steps/day). RESULTS: When possible confounding factors were included in the stepwise multiple regression analyses, in HD patients, steps/day was significantly positively related to HDL(2)-C and apolipoprotein (Apo) A-I, while it was significantly positively related to HDL(3)-C in PD patients. When subjects were subdivided into 3 groups according to steps/day, in HD patients, the highest category of steps/day had significantly higher HDL(2)-C and Apo A-I than the lowest category, while such results were not observed in PD patients. CONCLUSION: These results suggest that the associations of physical activity with HDL-C subfractions and Apo A-I that are known in the general population are more pronounced in HD patients than PD patients.

[Effect of atorvastatin therapy on the level of secretory phospholipase A2 group IIA and on the modification of low density lipoproteins in patients with ischemic heart disease].

We studied effect of atorvastatin on secretory phospholipase A2 group IIA (sPLA2-IIA) in blood serum of patients with ischemic heart disease (IHD), lipid composition of low density lipoproteins (LDL) and process of modification of LDL induced by sPLA2-IIA in 20 patients taking 20 mg/day of atorvastatin for 3 months. In patients with initially high level of sPLA2-IIA ( > 8 mcg/l) its concentration significantly decreased. Amount of total cholesterol, triglyceride, lecithin, and lysolecithin remained unchanged, however in equimolar relations there occurred decrease of amount of total cholesterol and increase of cholesterol esters. At incubation of LDL, extracted from patient s plasma before initiation of the study, with human sPLA2-IIA from cardiac myxoma, 3.5 nmol of lysolecithin per 1 mg of LDL protein was formed while at incubation of LDL of same patients, extracted after 3 months of atorvastatin administration, amount of lysolecithin was 1.54 nmol/mg LDL protein. Thus atorvastatin therapy causes lowering of sPLA2-IIA in patients with initially high blood level of the enzyme and to a great extent precludes sPLA2-IIA induced LDL modification.

Lecithin and PLGA-based self-assembled nanocomposite, Lecithmer: preparation, characterization, and pharmacokinetic/pharmacodynamic evaluation.

The present study investigates the drug delivery potential of polymer lipid hybrid nanocomposites (Lecithmer®) composed of poly(D,L-lactide-co-glycolide (PLGA) and soya lecithin. Core-shell structure of Lecithmer was evident from cryo-TEM images. Daunorubicin (DNR) and lornoxicam (LNX)-incorporated Lecithmer nanocomposites were evaluated for anticancer and anti-inflammatory activity. DNR- and LNX-loaded Lecithmer had mean particle size of ∼335 and ∼282.7 nm, respectively. Lecithmer formulated with different cationic lipids resulted in lower particle size (∼120 nm) and positive zeta potential. Entrapment efficiency of DNR and LNX was 93.16 and 88.59 %, respectively. In vitro release of DNR from Lecithmer was slower compared to PLGA nanoparticles. DNR release from Lecithmer was significantly higher at pH 5.5 (80.96 %) as compared to pH 7.4 (55.95 %), providing advantage for selective tumor therapy. Similarly, sustained release of LNX (30 % in 10 h) was observed at pH 7.4. DNR in Lecithmer showed superior cytotoxicity on human erythroleukemic K562 cells. Pharmacokinetic study in Wistar rats with i.v. administered DNR-loaded Lecithmer showed higher volume of distribution, lower elimination rate constant, and longer half-life (81.68 L, 0.3535 h(-1), 1.96 h) as compared to DNR solution (57.46 L, 0.4237 h(-1), 1.635 h). Pharmacodynamic evaluation of orally administered LNX-loaded Lecithmer showed superior anti-inflammatory activity with maximum inhibition of 81.2 % vis-à-vis 53.57 % in case of LNX suspension. In light of these results, Lecithmer can be envisaged as a promising nanosystem for parenteral as well as oral drug delivery.

Measurement of lecithin-cholesterol acyltransferase activity with the use of a Peptide-proteoliposome substrate.

Lecithin-cholesterol acyltransferase (LCAT) is the major enzyme responsible for the esterification of free cholesterol on plasma lipoproteins, which is a key step in the reverse cholesterol transport pathway. The measurement of plasma LCAT activity not only is important in the diagnosis of patients with genetic or acquired LCAT deficiency but is also valuable in calculating cardiovascular risk, as well as in research studies of lipoprotein metabolism. In this chapter, we describe a convenient LCAT assay based on the use of an apoA-I mimetic peptide. The proteoliposome substrate used in this assay for LCAT is easily made with the peptide and can be stored by deep freezing without significant loss of activity.

[Fish by-products oil corrects dyslipidemia, improves reverse cholesterol transport and stimulates paraoxonase-1 activity in obese rat]. / L'huile des co-produits de poisson corrige la dyslipidémie, améliore le transport inverse du cholestérol et stimule l'activité de la paraoxonase-1 chez le rat obèse.

AIM OF THE STUDY: To valorize fish by-products oil by investigating its effects on dyslipidemia, hyperglycemia, reverse cholesterol transport and paraoxonase-1 activity in obese rat. METHODS: Sixteen male Wistar rats were fed a high fat diet. At 400 ± 10 g, obese rats were randomly divided into two groups: the first received 20% of sardine by-products oil and the second 20% of the edible portion oil. At d28, glycemia and serum lipids concentrations were estimated. High density lipoproteins (HDL2 and HDL3) were separated and their contents and composition in lipids and apolipoproteins were analyzed. Lecithin: cholesterol acyltransferase and paraoxonase-1 activities were assessed. RESULTS: In group which consumed sardine by-products oil, serum cholesterol and triacylglycerols were reduced (-8% and -36%, respectively). However, glycemia was similar. HDL3-phospholipids, HDL3-unesterified cholesterol and HDL3-apolipoproteins were decreased by 56%, 10% and 12%, respectively. Lecithin: cholesterol acyltransferase activity was increased by 35% and the content of HDL2-cholesteryl esters was elevated by 12%. Serum paraoxonase-1 activity was increased by 25%. CONCLUSION: In obese rat, sardine by-products oil may have a protective effect against cardiovascular risk by improving the anti-atherogenic metabolic pathway of cholesterol and triacylglycerols. This anti-atherogenic action is particularly enhanced by the increase in paraoxonase-1 activity which protects lipoproteins from oxidation.

Effects of metformin on markers of oxidative stress and antioxidant reserve in patients with newly diagnosed type 2 diabetes: a randomized clinical trial.

BACKGROUND & AIMS: Given the long term benefits observed with metformin use in diabetes patients, a role in modulating oxidative stress is imputable. Effects of metformin on markers of oxidative stress, antioxidant reserve, and HDL-c associated antioxidant enzymes were investigated. METHODS: In a clinical trial setting (Registered under Clinical Trials.gov Identifier no. NCT01521624) 99 medication-naïve, newly diagnosed type 2 diabetes patients were randomly assigned to either metformin or lifestyle modification. AOPP, AGE, FRAP, activities of LCAT, and PON were measured at baseline and after 12-weeks. RESULTS: Baseline values of the oxidative stress markers did not differ significantly between the two groups. In cases, after three months treatment, there was a significant reduction in AOPP (137.52 ± 25.59, 118.45 ± 38.42, p < 0.001), and AGE (69.28 ± 4.58, 64.31 ± 8.64, p = 0.002). FRAP and PON increased significantly (1060.67 ± 226.69, 1347.80 ± 251.40, p < 0.001 and 29.85 ± 23.18, 37.86 ± 27.60, p = 0.012 respectively). LCAT levels remained unchanged (45.23 ± 4.95, 46.15 ± 6.28, p = 0.439). Comparing the two groups in a final multivariate model, AOPP, FRAP, and AGE levels changed more significantly in metformin compared with lifestyle modification alone (p = 0.007, p < 0.001 and p < 0.001 respectively). Escalation in LCAT or PON activities did not differ between the two groups (p = 0.199 and 0.843 respectively). CONCLUSIONS: Use of metformin is more effective in reducing oxidative stress compared with lifestyle modification alone.

Ajuga iva aqueous extract improves reverse cholesterol transport in streptozotocin-induced diabetic rat.

OBJECTIVES: The aim of this study was to determine the effects of Ajuga iva aqueous extract on lecithin : cholesterol acyltransferase (LCAT) activity and amount and composition of high-density lipoprotein (HDL)(2) and (HDL)(3), in streptozotocin (STZ)-induced diabetic rats. METHODS: Diabetes was induced in male Wistar rats by intraperitoneal injection of STZ (60 mg/kg body weight). Diabetic rats (n = 12) were divided into two groups. The diabetic control group (D) received a 20% casein diet and the diabetic treated group received the same diet supplemented with A. iva aqueous extract (0.5 g/100 g diet) (DAi), for 4 weeks. KEY FINDINGS: Total cholesterol and HDL(3) -C were respectively decreased by 32% and 55% in the DAi group compared with the D group, whereas HDL(2)-C was increased by 30%. The amounts of HDL(2) and HDL(3), which were the sum of apolipoproteins, unesterified cholesterol (UC), cholesteryl esters (CEs), triacylglycerols (TGs) and phospholipids (PLs), showed no significant difference. A. iva treatment increased LCAT by 33% and its cofactor-activator, apolipoprotein A-I, by 58%. HDL(3)-PL (enzyme substrate) and HDL(3)-UC (acyl group acceptor) were respectively decreased by 70% and 57%, whereas HDL(2)-CE (product of LCAT reaction) was enhanced by 30%. CONCLUSIONS: In STZ-induced diabetic rats, A. iva improves reverse cholesterol transport by enhancing LCAT activity, leading to anti-atherogenic effects.

Linoleic acid is associated with lower long-chain n-6 and n-3 fatty acids in red blood cell lipids of Canadian pregnant women.

BACKGROUND: Arachidonic (ARA), eicosapentaenoic (EPA), and docosahexaenoic (DHA) acids are important in membrane glycerophospholipids. Higher maternal blood ARA, EPA, and DHA concentrations in gestation are associated with higher maternal-to-fetal transfer of ARA, EPA, and DHA, respectively, which emphasizes the importance of maternal fatty acid status in gestation. As in the brain, red blood cell (RBC) ethanolamine phosphoglycerides (EPGs) are high in plasmalogen, ARA, and DHA. OBJECTIVE: We determined the relation between dietary n-6 (omega-6) and n-3 (omega-3) fatty acid intakes and n-6 and n-3 fatty acids in RBC EPGs and phosphatidylcholine in near-term pregnant women. DESIGN: The subjects were 105 healthy Canadian pregnant (36 wk gestation) women. Fatty acid intakes were estimated by food-frequency questionnaire, and fasting venous blood samples were collected. RESULTS: DHA and EPA intakes were positively associated with RBC EPG and phosphatidylcholine concentrations of DHA (rho = 0.309 and 0.369, respectively; P < 0.001) and EPA (rho = 0.391 and 0.228, respectively; P < 0.001) and inversely associated with RBC EPG 22:4n-6 and 22:5n-6 (P < 0.001). In RBCs, concentrations of linoleic acid (LA, 18:2n-6) were inversely associated with DHA, EPA, and ARA, respectively, in EPGs (r = -0.432, P < 0.01; r = -0.201, P < 0.04; and r = -0.303, P < 0.01) and phosphatidylcholine (r = -0.460, -0.490, and -0.604; P < 0.01 for all). CONCLUSIONS: Membrane fatty acids are influenced by the amount and balance of fatty acid substrates. Our results suggest the competitive interaction of LA with ARA, EPA, and DHA, with no evidence that higher LA increases ARA. Biochemical indicators to suggest that DHA is limiting are present in our population. This trial was registered at clinicaltrials.gov as NCT00620672.

Fatty acids in serum phospholipids and carotid intima-media thickness in Spanish subjects with primary dyslipidemia.

BACKGROUND: Low rates of incident ischemic heart disease (IHD) and cardiac death occur in Spain despite a high prevalence of cardiovascular risk factors. High consumption of unsaturated fatty acid-rich foods, such as olive oil, nuts, and seafood, might underlie this paradox. OBJECTIVE: We investigated whether serum phosphatidylcholine enrichment in oleic, linoleic, alpha-linolenic, and n-3 (omega-3) long-chain polyunsaturated fatty acids (as biomarkers of olive oil, seed oil, walnut, and fish intake, respectively) relate to carotid atherosclerosis in Spanish subjects at risk of IHD. DESIGN: In a cross-sectional study, we measured fatty acid concentrations in serum phosphatidylcholine and measured carotid intima-media thickness (IMT) by using ultrasound in 451 asymptomatic subjects (261 men, 190 women; mean age: 45 y) with primary dyslipidemia. Main and secondary outcomes were mean and maximum IMT in the common carotid artery (CCA) and other carotid segments, respectively. RESULTS: Phosphatidylcholine fatty acid composition was similar to that reported for other Spanish populations. Multiple regression analyses showed that proportions of oleic and docosahexaenoic acids were inversely related to mean CCA IMT (P < 0.02, all) after adjustment for several confounders. In similar models, alpha-linolenic acid related inversely to mean and maximum internal carotid artery IMT (P < 0.05 for all). Linoleic and eicosapentaenoic acids were unrelated to IMT. CONCLUSIONS: Higher phospholipid proportions of oleic, alpha-linolenic, and docosahexaenoic acids showed inverse associations with IMT at specific carotid segments in subjects with primary dyslipidemia. High intakes of healthy fats might explain, in part, the Spanish paradox of low IHD rates in the face of a high burden of cardiovascular risk factors.

Relations of lysophosphatidylcholine in low-density lipoprotein with serum lipoprotein-associated phospholipase A2, paraoxonase and homocysteine thiolactonase activities in patients with type 2 diabetes mellitus.

AIMS: We studied the relations of lysophosphatidylcholine (lyso-PC) in LDL with serum lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), paraoxonase and homocysteine thiolactonase (HTLase) activities in patients with type 2 diabetes mellitus. METHODS: Lyso-PC was measured by electrospray ionization-liquid chromatography/mass spectrometry. Paraoxonase and HTLase activities were measured with paraoxon and gamma-thiobutyrolactone as substrates, respectively. RESULTS: Serum HTLase and paraoxonase activities were significantly suppressed in diabetic patients (n=96) compared with control (n=25), whereas serum Lp-PLA(2) did not differ in control and diabetic patients. Lyso-PC contents in LDL correlated with serum Lp-PLA(2) activity positively and with serum HTLase activity negatively. Stepwise regression analysis revealed that serum Lp-PLA(2) and HTLase activities independently contributed to lyso-PC contents in LDL. In patients with diabetic nephropathy, lyso-PC contents in LDL were increased with reduced serum HTLase and paraoxonase activities compared with control, while serum Lp-PLA(2) activity did not differ. On the other hand, 3-month treatment with simvastatin reduced both lyso-PC contents in LDL and serum Lp-PLA(2) activity in hypercholesterolemic diabetic patients, while serum HTLase or paraoxonase activities did not change. CONCLUSIONS: Increased lyso-PC contents in LDL were associated with the suppressed HTLase activity, and serum Lp-PLA(2) and HTLase activities may be related to lyso-PC in type 2 diabetic patients.