Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “LECITHINS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,531 records · Page 85Linked to original sources
PubMed1977

The lecithin-cholesterol acyl transferase activity of rat intestinal lymph.

The lecithin-cholesterol acyl transferase (LCAT) activity in rat mesenteric lymph was examined as a possible source of chylomicron cholesteryl ester. Lymph activity was only 2-3% of rat serum activity. Removal of d less than 1.006 lipoproteins increased lymph LCAT activity, but only to 6-8% of that of serum. Relative to total cholesterol in the d greater than 1.08 g/ml fractions, lymph LCAT activity in lymph from fasting rats was less than serum, but in lymph from nonfasting rats the ratio LCAT/HDL-cholesterol reached levels greater than serum, suggesting a contribution of enzyme from the gut. Both LCAT activity and HDL concentration in mesenteric lymph increased during feeding. Subfractions of lymph that inhibited serum LCAT were: chylomicrons, VLDL, chylomicron lipid, VLDL apoprotein, and HDL apoprotein. In the rat, the low LCAT activity of mesenteric lymph was in part due to the low enzyme concentration present, and the activity was apparently lowered further by lipid-rich lipoproteins that inhibited the reaction. Enzyme inhibition due to the apoprotein fractions of lipoproteins is probably minor in the rat in vivo.

Acyltransferases↗
PubMed1991

Lecithin cholesterol acyltransferase activity in acute lymphoblastic leukemia.

Lecithin cholesterol acyltransferase (LCAT) activity and free cholesterol and cholesterol ester concentrations were determined in serum samples from 28 patients with acute lymphoblastic leukemia (ALL) and in an equal number of healthy controls. No significant alterations in LCAT activity, free cholesterol, or esterified cholesterol levels were observed in the ALL patients compared with the controls.

Adolescent↗
PubMed1990

[The characteristics of the lecithin-cholesterol-acyltransferase reaction in the blood serum during liver regeneration].

The rate of cholesterin ether formation in blood serum during the periods of rapid recovery of liver mass decreases after partial hepatectomy in rats. This effect is connected with the changes in quantity and composition of lecithin cholesterin acyltransferase (LCAT) as well the kinetic characteristics of lipoprotein of high density. This ferment was isolated from blood serum and purified in 28,500 times at different periods of liver regeneration. A conclusion concerning the presence of reverse dependence between the pronounced regeneration processes in liver and LCAT activity at high level of nonetherificated cholesterin in substrate has been drawn. Some recommendations for LCAT activity reducing processes in liver are given.

Animals↗
PubMed1978

The integrative role of lecithin:cholesterol acyl transferase in triglyceride clearance.

There is evidence that not only lipoprotein lipase (LPL) but also lecithin:cholesterol acyl transferase (LCAT) are involved in the directional flow of triglyceride (TG) from endogenous very low density lipoproteins (VLDL) and chylomicrons as part of a general energy storage pathway. Evidence is given to suggest that LCAT plays an integrative role in this process.

Animals↗
PubMed1978

Plasma lecithin:cholesterol acyltransferase activity in hypophysectomized rats.

Hypophysectomy in rats induces a decrease in VLDL and HDL and an increase in LDL. To investigate the importance of lecithin:cholesterol acyltransferase (LCAT) for these changes, plasma LCAT activity was determined, both according to the methods of Stokke-Norum and Glomset-Wright. Plasma LCAT activity as assessed by both these methods decreased significantly after hypophysectomy, indicating a reduction in plasma enzyme concentration. Plasma total and free cholesterol increased slightly, while the concentration of cholesteryl esters and triglycerides remained unchanged. Blood sugar and FFA decreased. The osmotic resistance of the red cells was increased, and target cells were seen. There was a decrease in blood haemoglobin and haematocrit. Serum total protein concentration, electrophoresis, and plasma ALAT activity did not change. The observed changes in lipoproteins and LCAT following hypophysectomy can be partly explained by decreased liver secretion of both LCAT and VLDL. Because of the complex relationship between lipoproteins and LCAT, no clear-cut conclusions about the association between decreased HDL and LCAT can be drawn. The precise hormonal mechanisms controlling LCAT activity and lipoprotein metabolism remain to be solved.

Animals↗
PubMed1978

The role of high density lipoproteins in lecithin:cholesterol acyltransferase activity: perspectives from Tangier disease.

Lecithin:cholesterol acyltransferase activity and the lipid composition of VLDL and LDL were examined in five patients homozygous for Tangier disease. The following results were obtained: I. The percentage of cholesterol that was esterified was similar in Taniger and control lipoproteins. II. Linoleic acid was the predominant fatty acid constituent of cholesteryl esters in Tangier plasma. III. Molar cholesterol esterification rates in Tangier plasma were reduced; however, fractional rates of cholesterol esterification were equal to or exceeded those of control plasma. IV. In vitro addition of apoprotein A-I and isolated lipoproteins led to a concentration-dependent increase in the initial rates of cholesterol esterification in Tangier plasma. It is concluded that HDL is not an exclusive substrate for the LCAT reaction, and that cholesterol esterification is not impaired in Tangier plasma.

Apolipoproteins↗
PubMed1979

[Choice of a spin label probe in order to study the recombination of beta-hydroxybutyrate dehydrogenase of a rat liver inner mitochondrial membrane with lecithin vesicles].

We find from studying the inhibitory effect of N-ethylmaleimide (NEM) on the enzymatic activity of beta-hydroxybutyrate dehydrogenase, that approximately one molecule of NEM is bound for one molecule of protein when the enzymatic activity is completely inhibited. Since the protein is a dimer this implies that each molecule of protein possesses only one thiol group in its catalytic center. Two long chain maleimide derivates: (10.3) NEM and (1.14) NEM conform, if a reasonable assumption is accepted to the conditions required for the study of the recombination of beta-hydroxybutyrate dehydrogenase with lecithin vesicles by spin label technique.

Animals↗
PubMed1990

Affinity of lipid transfer protein for lipid and lipoprotein particles as influenced by lecithin-cholesterol acyltransferase.

The effects of lecithin-cholesterol acyltransferase (LCAT) on the transfer of cholesterol esters mediated by lipid transfer protein (LTP) and its affinity for lipid and lipoprotein particles were investigated. When the single bilayer vesicle preparations (containing phosphatidylcholine, cholesterol, cholesteryl ester, and apolipoprotein- (apo) A-I at the molar ratio of 90:30:1.2:0.18) or high density lipoprotein 3 (HDL3) were used as the cholesteryl ester donor and low density lipoproteins (LDL) as the acceptor, the transfer activity of LTP was enhanced by the addition of low concentrations of LCAT. In contrast, no enhancement of cholesteryl ester transfer was observed upon addition of LCAT to either the discoidal bilayer particle preparations (containing phosphatidylcholine, cholesterol, cholesteryl ester, and apo-A-I at the molar ratio of 90:30:1.2:1.0) or high density lipoprotein 2 (HDL2). Although both apo-A-I and apo-A-II promoted the transfer of cholesteryl ester from vesicles to LDL, the additional enhancement of the transfer by LCAT was observed only with the vesicles containing apo-A-I. Gel permeation chromatography of LTP/vesicle and LTP/HDL3 mixtures in the presence and absence of LCAT showed that the affinity of LTP for both the vesicles and HDL3 increased upon addition of LCAT. In contrast, neither HDL2 nor discoidal bilayer particles showed any significant enhancement of LTP binding upon addition of LCAT. By using LCAT covalently bound to Sepharose 4B, a maximal interaction between LTP and bound LCAT was shown to occur at the ionic strength of 0.16. Deviation from this ionic strength reduced the extent of the interaction. At the ionic strength of 0.01 and 0.5, the elution volume of LTP was identical to that of bovine serum albumin.

Apolipoproteins↗
PubMed1990

Cellular localization of apolipoprotein D and lecithin:cholesterol acyltransferase mRNA in rhesus monkey tissues by in situ hybridization.

Apolipoprotein D (apoD) and lecithin:cholesterol acyl transferase (LCAT) are found on high density lipoprotein particles (HDLs) and have been postulated to form part of a complex involved in the transport of cholesterol from peripheral tissues to the liver for excretion. We have examined the sites of synthesis of the mRNAs for these two proteins in the rhesus monkey by in situ hybridization. ApoD mRNA-containing cells were widely distributed throughout peripheral tissues in interstitial and connective tissue fibroblasts often associated with blood vessels or capillaries. ApoD mRNA was also found localized in cells associated with peripheral nerves, neuroglial cells, cells in the subarachnoid space on the surface of the brain including the pial cells, perivascular cells, and scattered neurons in the brain. LCAT demonstrated a much more restricted pattern of synthesis and was found to be synthesized by hepatocytes, the basal cell layer of the epidermis, and in brain cell populations distinct from those that synthesize apoD. In the brain LCAT was synthesized by scattered neurons, neuroglial cells, ependymal cells, as well as a discrete cell layer in the cerebellum. ApoD has been shown to possess extensive homology to retinol binding protein, which has a binding pocket for vitamin A. We propose that apoD may also function to bind cholesterol or its derivatives in compartments not in direct contact with the blood. The findings of both apoD and LCAT synthesis in the brain suggest that they play a significant role in lipid transport in the brain.

Animals↗
PubMed1990

Increase of plasma nonesterified fatty acid concentration and decrease of albumin binding affinity after intravenous injection of glycocholate-lecithin mixed micelles.

Lipophilic drugs intended for intravenous use can be solubilized by mixed-micellar systems containing glycoholic acid and lecithin (MM). Our present studies determined the influence of such MM preparations on albumin binding of monoacetyldiaminodiphenyl sulfone (MADDS), a deputy ligand for bilirubin. After intravenous administration of MMs to healthy male and female adult volunteers, concentration-time profiles of bile acid and nonesterified (NEFA) and esterified fatty acids were obtained as well. In vitro experiments with blood from adults and from neonatal cords indicated a modest reduction in reserve albumin for binding of MADDS after addition of MMs, resulting from glycocholic acid in the micellar preparation. After injection of MM preparations with up to 530 mg glycocholic acid, a rapid decrease of the reserve albumin was observed. The effect was more pronounced in men than in women and resulted in different areas under the time curve for the decrease (p = 0.049). At their maximum (3 to 10 minutes after MM doses) the decreases averaged (+/- SD) 68% +/- 14% in men and 45% +/- 8.5% in women. Low reserve albumin concentrations were maintained over 20 minutes despite rapidly declining bile acid concentrations. Injection of MM caused a drastic increase of NEFA in the serum samples with a more pronounced effect in men (average +/- SD increase: 473% +/- 93%) than in women (148% +/- 91%) (p = 0.01). The changes in NEFA concentrations ran reciprocal to the changes of reserve albumin for binding MADDS. In all subjects the increase in NEFA was accompanied by a decrease in reserve albumin for palmitate. Fatty acid binding to albumin was well restored within 1 hour. Thus, before drugs incorporated in MM can be prescribed to neonates who are at risk for having kernicterus, the impact of intravenous MM on bilirubin binding and NEFA levels must be investigated in that patient population.

Adult↗
PubMed1989

Oral lecithin improves ultrafiltration in patients on peritoneal dialysis.

Three patients on peritoneal dialysis (two on continuous ambulatory and one on intermittent) with severe ultrafiltration failure were treated with 2 capsules of Lecithin three times a day (containing of 1.08 g of phosphatidylcholine). Their ultrafiltration improved significantly to the point that their edema improved and were able to continue on peritoneal dialysis with fewer daily hypertonic exchange.

Administration, Oral↗
PubMed1989

In vitro transformation of apoA-I-containing lipoprotein subpopulations: role of lecithin:cholesterol acyltransferase and apoB-containing lipoproteins.

Two populations of apoA-I-containing lipoproteins are found in plasma: particles with apoA-II [Lp(AI w AII)] and particles without apoA-II [Lp(AI w/o AII)]. Both are heterogeneous in size. However, their size subpopulation distributions differ considerably between healthy subjects and patients with coronary artery diseases. The metabolic basis for such alterations was studied by determining the role of lecithin:cholesterol acyltransferase (LCAT) and apoB-containing lipoproteins (LpB) in the size subpopulation distributions of Lp(AI w AII) and Lp(AI w/o AII). ApoB-free and LCAT-free plasmas, prepared by affinity chromatography, and whole plasma were incubated at 4 degrees C and 37 degrees C for 24 hr. After incubation, Lp(AI w AII) and Lp(AI w/o AII) were isolated by anti-A-II and anti-A-I immunosorbents. Their size subpopulation distributions were studied by nondenaturing gradient polyacrylamide gel electrophoresis. At 4 degrees C most Lp(AI w AII) particles were in the range of 7.0-9.2 nm Stokes diameter. Incubation of plasma at 37 degrees C resulted in an overall enlargement of particles up to 11.2 nm and larger. These particles were enriched with cholesteryl ester and triglyceride and depleted of phospholipids and free cholesterol. Removal of LpB or LCAT from plasma prior to incubation greatly reduced their enlargement. At 4 degrees C, Lp(AI w/o AII) contained mostly particles of 8.5 and 10.1 nm. Incubation at 37 degrees C abolished both subpopulations with the formation of a new subpopulation of 9.2 nm. This transformation was identical in apoB-free plasma but was not seen in LCAT-free plasma. Our study shows that transformation of Lp(AI w AII) requires both LCAT and LpB. However, LpB is not necessary for the transformation of Lp(AI w/o AII) in vitro. The relevance of these in vitro studies to in vivo lipoprotein metabolism was demonstrated in a subject with hepatic triglyceride lipase deficiency.

Adult↗
PubMed1989

Tissue-specific expression, developmental regulation, and chromosomal mapping of the lecithin: cholesterol acyltransferase gene. Evidence for expression in brain and testes as well as liver.

Lecithin:cholesterol acyltransferase (LCAT) catalyzes the esterification of cholesterol in high density lipoproteins, thereby facilitating transport of excess cholesterol from peripheral tissues to liver. We report here studies of the developmental, dietary, and genetic control of LCAT gene expression. In adult male Sprague-Dawley rats fed a standard chow diet LCAT mRNA was most abundant in liver, a major source of the plasma enzyme, but appreciable levels were also present in brain and testes. Since both brain and testes are isolated from blood by tight cellular barriers, undoubtedly greatly reducing the level of plasma-derived LCAT in cerebrospinal fluid and testes, the production of LCAT in these tissues may be important for removal of excess cholesterol. Noteworthy changes in the expression of LCAT mRNA were observed during development of both rodents and humans. On the other hand, LCAT mRNA levels were relatively resistant to dietary challenge or to drugs affecting cholesterol metabolism. Since human epidemiological studies have suggested an association between LCAT levels and variations of high density lipoprotein cholesterol, we examined LCAT gene polymorphisms in a mouse animal model. Mapping of the LCAT gene (Lcat) to mouse Chromosome 8 within 2 centimorgans of the Es-2 locus indicates that it does not correspond to any previously mapped loci affecting high density lipoprotein phenotypes in the mouse.

Aging↗
PubMed1989

Molecular species of phosphatidylcholine in abetalipoproteinemia: effect of lecithin:cholesterol acyltransferase and lysolecithin acyltransferase.

In order to study the role of very low density lipoproteins (VLDL) and low density lipoproteins (LDL) in determining the molecular species composition of phosphatidylcholine (PC) and the specificity of lecithin:cholesterol acyltransferase (LCAT) in human plasma, we studied the PC species composition in plasma from abetalipoproteinemic (ABL) and control subjects before and after incubation at 37 degrees C. The ABL plasma contained significantly higher percentages of sn-2-18:1 species (16:0-18:1, 18:0-18:1, and 18:1-18:1) and lower percentages of sn-2-18:2 species (16:0-18:2, 18:0-18:2, and 18:1-18:2) as well as sn-2-20:4 species (16:0-20:4, 18:0-20:4, and 18:1-20:4). Similar abnormalities were found in the PC of ABL erythrocytes, while the PE of the erythrocytes was less affected. The relative contribution of various PC species towards LCAT reaction in ABL plasma was significantly different from that found in normal plasma. Thus, while 16:0-18:2 and 16:0-18:1 contributed, respectively, 43.8% and 15.9% of the total acyl groups used for cholesterol esterification in normal plasma, they contributed, respectively, 21.5% and 37.9% in ABL plasma. The relative contribution of 16:0-20:4 was also significantly lower in ABL plasma (4.7% vs. 9.0% in normal), while that of 16:0-16:0 was higher (6.4% vs. 0.5%). However, the selectivity factors of various species (percent contribution/percent concentration) were not significantly different between ABL and normal plasma, indicating that the substrate specificity of LCAT is not altered in the absence of VLDL and LDL. Incubation of ABL plasma in the presence of normal VLDL or LDL resulted in normalization of its molecular species composition and in the stimulation of its LCAT activity. Addition of LDL, but not VLDL, also resulted in the activation of lysolecithin acyltransferase (LAT) activity. The incorporation of [1-14C]palmitoyl lysoPC into various PC species in the presence of LDL was similar to that observed in normal plasma, with the 16:0-16:0 species having the highest specific activity. These results indicate that the absence of apoB-containing lipoproteins significantly affects the molecular species composition of plasma PC as well as its metabolism by LCAT and LAT reactions.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1989

Inhibition of human lecithin: cholesterol acyltransferase activity by catecholamines in vitro.

The effects of L-adrenaline and L-noradrenaline on human lecithin: cholesterol acyltransferase (LCAT) activity were investigated in vitro. Both catecholamines are shown to be inhibitors of this enzyme. Despite inter-individual variations in the dose-response relationships calculated for both hormones, significant effects can be expected in the upper physiological range of concentration. Since diminished LCAT activity is known to be followed by a low level of HDL cholesterol and an increased concentration of triglycerides, it is supposed that catecholamine mediated inhibition of LCAT activity may contribute to the development of stress mediated fluctuations in plasma lipoprotein concentrations.

Epinephrine↗
PubMed1989

[Protective effect of high density lipoproteins, their subfractions and lecithin-cholesterol-acyltransferases on the peroxidation modification of low density lipoproteins].

The role of high density lipoproteins (HDL), their subfractions (HDL2 and HDL3) and lecithin: cholesterol acyltransferase (LCAT) on peroxidative modification of low density lipoproteins (LDL) in vitro was studied. Peroxidative modification was estimated by the formation of malonic dialdehyde (MDA) and LDL aggregates during LDL incubation at 37 degrees C for several days without Fe2+ or for 2 hours in the presence of Fe2+ in EDTA-free media. It was shown that the addition of HDL3 (but not HDL2) markedly decreases the formation of both MDA and LDL aggregates. Since LCAT is bound to HDL3, its effect was examined. An addition of LCAT isolated from human plasma (650-fold purification) at a concentration of 450 micrograms/ml resulted in a complete inhibition of LDL peroxidation and LDL aggregate formation. Heat-inactivated LCAT had no effect. Possible mechanisms of the protective effect of LCAT on LDL peroxidative modification are discussed.

Humans↗
PubMed1989

Lecithin:retinol acyltransferase in retinal pigment epithelial microsomes.

Microsomal preparations from retinal pigment epithelium carry out phosphatidylcholine synthesis upon incubation with 1-palmitoyllysophosphatidylcholine and fatty acyl-CoA. Phosphatidylcholine synthesized in situ in this manner is an acyl donor for retinyl ester synthesis, demonstrating the existence of lecithin:retinol acyltransferase. Although acyl transfer to retinol is from the 1-position of phosphatidylcholine, the fatty acid in the 2-position is important in substrate recognition. The finding of this novel enzyme activity in retinal pigment epithelial microsomes suggests that phosphatidylcholine is the endogenous acyl donor in CoA-independent retinol esterification observed in these preparations.

Acyltransferases↗
PubMed1989

Lecithin:sphingomyelin ratio in the amniotic fluid of male and female fetuses.

The effect of fetal sex on the amniotic fluid lecithin:sphingomyelin (L:S) ratio was determined with a prospective, randomized, double-blind study designed to evaluate the effect of antenatal steroid administration on the incidence of neonatal respiratory distress syndrome. The immature L:S ratios of 183 single births to nondiabetic women were analyzed. L:S ratios increased with increasing gestational age. Regression lines of L:S versus gestational age suggested that male infants' L:S ratios were lower than females', although the differences were not statistically significant.

Amniotic Fluid↗