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Background: The functionality of high-density lipoproteins (HDL) is a better cardiovascular risk predictor than HDL concentrations. One of the key elements of HDL functionality is its apolipoprotein composition. Lecithin-cholesterol acyl transferase (LCAT) and cholesterol-ester transfer protein (CETP) are enzymes involved in HDL-mediated reverse cholesterol transport. This study assessed the concentration and activity of LCAT and CETP in HDL subspecies defined by their content of apolipoproteins E (apoE) and C-III (apoC-III) in humans., Methods: Eighteen adults (ten women and eight men, mean age 55.6, BMI 26.9 Kg/m 2 , HbA1c 5.4%) were studied. HDL from each participant were isolated and divided into four subspecies containing respectively: No apoE and no apoC-III (E-C-), apoE but not apoC-III (E + C-), apoC-III but no apoE (E-C+) and both apoE and apoC-III (E + C+). The concentration and enzymatic activity of LCAT and CETP were measured within each HDL subspecies using immunoenzymatic and fluorometric methods. Additionally, the size distribution of HDL in each apolipoprotein-defined fraction was determined using non-denaturing electrophoresis and anti-apoA-I western blotting., Results: HDL without apoE or apoC-III was the predominant HDL subtype. The size distribution of HDL was very similar in all the four apolipoprotein-defined subtypes. LCAT was most abundant in E-C- HDL (3.58 mg/mL, 59.6% of plasma LCAT mass), while HDL with apoE or apoC-III had much less LCAT (19.8, 12.2 and 8.37% of plasma LCAT respectively for E + C-, E-C+ and E + C+). LCAT mass was lower in E + C- HDL relative to E-C- HDL, but LCAT activity was similar in both fractions, signaling a greater activity-to-mass ratio associated with the presence of apoE. Both CETP mass and CETP activity showed only slight variations across HDL subspecies. There was an inverse correlation between plasma LCAT activity and concentrations of both E-C+ pre-beta HDL (r = - 0.55, P = 0.017) and E-C- alpha 1 HDL (r = - 0.49, P = 0.041). Conversely, there was a direct correlation between plasma CETP activity and concentrations of E-C+ alpha 1 HDL (r = 0.52, P = 0.025)., Conclusions: The presence of apoE in small HDL is correlated with increased LCAT activity and esterification of plasma cholesterol. These results favor an interpretation that LCAT and apoE interact to enhance anti-atherogenic pathways of HDL.

Objectives: To identify the association of the rs121912724 polymorphism in the Apolipoprotein A1 gene with diabetic dyslipidemia and its correlation with serum High-density Lipoprotein Cholesterol (HDL), Triglycerides, (TG) and Low-density Lipoprotein Cholesterol (LDL-C) levels. Methods: Two groups were taken, comprising 150 diabetic dyslipidemia (group I) patients and 150 healthy controls (group II). Demographic and biochemical data were analyzed using Statistical Package for Social Sciences 26 by applying the Student independent t-test. DNA samples of both groups were subjected to TETRA-Amplification Refractory System polymerase chain reaction, and allele A and C of the rs121912724 polymorphism were amplified. The association of the rs121912724 polymorphism with the disease was studied using Fisher's exact test and Cochran-Armitage test. The correlation between the polymorphism and levels of lipid levels was determined using Pearson correlation on SPSS version 27. Results: The levels of HDL-C, LDL-C, and TG were significantly higher than in healthy group (p<0.000). The genotypic count of homozygous AA was 137, 12 of heterozygous AC, and 1 of homozygous CC in group I. The genotypic count of homozygous AA was 138, 12 of heterozygous AC in group II, with no homozygous CC. There was no association of rs121912724 observed with the development of diabetic dyslipidemia, and a negative correlation of rs121912724 with deranged levels of HDL-C, LDL-C, and TG was observed. Conclusion: The rs121912724 polymorphism in the APOA1 gene was not associated with diabetic dyslipidemia. There was no correlation found between the polymorphism and deranged levels of HDL-C, TG, and LDL-C. [ABSTRACT FROM AUTHOR]

Background: The etiopathogenesis of abdominal aortic aneurysm (AAA) is still unclarified, but vascular inflammation and matrix metalloproteases activation have a recognized role in AAA development and progression. Circulating lipoproteins are involved in tissue inflammation and repair, particularly through the regulation of intracellular cholesterol, whose excess is associated to cell damage and proinflammatory activation. We analyzed lipoprotein metabolism and function in AAA and in control vasculopathic patients, to highlight possible non-atherosclerosis-related, specific abnormalities. Methods: We measured fluorometrically serum esterified/total cholesterol ratio, as an index of lecithin-cholesterol acyltransferase (LCAT) activity, and cholesteryl ester transfer protein (CETP) activity in patients referred to vascular surgery either for AAA (n=30) or stenotic aortic/peripheral atherosclerosis (n=21) having similar burden of cardiovascular risk factors and disease. We measured high-density lipoprotein (HDL)-cholesterol efflux capacity (CEC), through the ATP-binding cassette G1 (ABCG1) and A1 (ABCA1) pathways and serum cell cholesterol loading capacity (CLC), by radioisotopic and fluorimetric methods, respectively. Results: We found higher LCAT (+23%; p < 0.0001) and CETP (+49%; p < 0.0001) activity in AAA sera. HDL ABCG1-CEC was lower (-16%; p < 0.001) and ABCA1-CEC was higher (+31.7%; p < 0.0001) in AAA. Stratification suggests that smoking may partly contribute to these modifications. CEC and CETP activity correlated with CLC only in AAA. Conclusions: We demonstrated that compared to patients with stenotic atherosclerosis, patients with AAA had altered HDL metabolism and functions involved in their anti-inflammatory and tissue repair activity, particularly through the ABCG1-related intracellular signaling. Clarifying the relevance of this mechanism for AAA evolution might help in developing new diagnostic parameters and therapeutic targets for the early management of this condition. [ABSTRACT FROM AUTHOR]

A coronary artery disease (CAD) is a leading cause of death worldwide that occurs due to deposition of fatty streaks on the artery wall as a plaque. Pivotal role of proteins in heart disease pathogenesis lead the present study to screen proteins having altered expression in CAD patients plasma by proteomic approach. We used two-dimensional gel electrophoresis followed by identification of differential proteins by Matrix Assisted Laser Desorption Ionization-Time of Flight (MALDI-TOF). Apolipoprotein A-I (apoA-I) has been recognized as significantly down regulated protein as compared to healthy control that has been validated by Western blot and enzyme linked immunosorbent assay in 200 North Indian CAD plasma. The in-silico studies of apoA-I was carried out to investigate the effect of single amino acid substitution (A164S) on the function and the stability of apoA-1. Functional analysis indicated that apoA-I helps in reverse cholesterol transportation (RCT) by activating lecithin cholesterol acyltransferase (LCAT) enzyme. Crystallographic structure of apoA-I was taken from protein data bank (PDB), mutation was carried out by Swiss PDB viewer (SPDBV) and its effect was analysed with DUET, I-Mutant2.0, MuPro, Folding Rate Change serevr (RaCe), MuPro, Sorting Intolerant from Tolerant server (SIFT), Site Directed Mutator (SDM) and Tango servers. This analysis indicated that A164S mutation considerably affect the stability and function of apoA-I and may play an important role during its interaction with LCAT. Studied mutation may also lead to the apoA-I aggregation thus present study implicated that this mutation may hamper the apoA-I and LCAT interaction which may lead to CAD progression. [ABSTRACT FROM AUTHOR]

Lecithin:cholesterol acyltransferase (LCAT) and LCAT-activating compounds are being investigated as treatments for coronary heart disease (CHD) and familial LCAT deficiency (FLD). Herein we report the crystal structure of human LCAT in complex with a potent piperidinylpyrazolopyridine activator and an acyl intermediate-like inhibitor, revealing LCAT in an active conformation. Unlike other LCAT activators, the piperidinylpyrazolopyridine activator binds exclusively to the membrane-binding domain (MBD). Functional studies indicate that the compound does not modulate the affinity of LCAT for HDL, but instead stabilizes residues in the MBD and facilitates channeling of substrates into the active site. By demonstrating that these activators increase the activity of an FLD variant, we show that compounds targeting the MBD have therapeutic potential. Our data better define the substrate binding site of LCAT and pave the way for rational design of LCAT agonists and improved biotherapeutics for augmenting or restoring reverse cholesterol transport in CHD and FLD patients.

Aims: To review the formation, catabolism, and the possible atherogenic properties of Lp-X.Data Synthesis: The conversion of cholesterol to bile acids is regulated by several mechanisms including cholesterol 7 alpha hydroxylase, fibroblast growth factor 19, and farnesoid X receptors. During cholestasis these mechanisms are altered and there is an accumulation of bile acids and cholesterol in plasma. The hypercholesterolemia observed in cholestasis is due to the presence of an anomalous lipoprotein called lipoprotein-X (Lp-X). Lp-X is a lipoprotein rich in phospholipid and free cholesterol present in plasma of patients with cholestasis and, with some variations, in patients with lecithin-cholesterol-acyl-transferase deficiency (LCAT), and after lipid infusion. Lp-X is formed from a bile lipoprotein moving to the blood vessels where it incorporates small quantities of triglycerides, apo-C and esterified cholesterol and becomes a "mature" Lp-X. The activity of the phosphatidilcholine canalicular transporter Mdr2 P-glycoprotein (homologous to the human ABCB4) is essential for LpX appearance, since its suppression abolishes Lp-X formation. However, the concentration of Lp-X in plasma is determined also by the degree of the cholestasis, the residual liver function, and the LCAT deficiency. The Lp-X catabolism seems to be mediated by the reticuloendothelial system and possibly the kidney.Conclusions: Lp-X might be considered a defense mechanism against the toxic effect of free cholesterol in cholestasis. The frequency of cardiovascular events in patients affected by primary biliary cholangitis, in whom the Lp-X is present in high concentration, are not increased. Further studies could now clarify the remaining open questions on the role of Lp-X in the dyslipidemia of cholestasis. [ABSTRACT FROM AUTHOR]

Background Humans with familial lecithin:cholesterol acyltransferase (LCAT) deficiency (FLD) have extremely low or undetectable high-density lipoprotein cholesterol (HDL-C) levels and by early adulthood develop many manifestations of the disorder, including corneal opacities, anemia, and renal disease. Objective To determine if infusions of recombinant human LCAT (rhLCAT) could reverse the anemia, halt progression of renal disease, and normalize HDL in FLD. Methods rhLCAT (ACP-501) was infused intravenously over 1 hour on 3 occasions in a dose optimization phase (0.3, 3.0, and 9.0 mg/kg), then 3.0 or 9.0 mg/kg every 1 to 2 weeks for 7 months in a maintenance phase. Plasma lipoproteins, lipids, LCAT levels, and several measures of renal function and other clinical labs were monitored. Results LCAT concentration peaked at the end of each infusion and decreased to near baseline over 7 days. Renal function generally stabilized or improved and the anemia improved. After infusion, HDL-C rapidly increased, peaking near normal in 8 to 12 hours; analysis of HDL particles by various methods all revealed rapid sequential disappearance of preβ-HDL and small α-4 HDL and appearance of normal α-HDL. Low-density lipoprotein cholesterol increased more slowly than HDL-C. Of note, triglyceride routinely decreased after meals after infusion, in contrast to the usual postprandial increase in the absence of rhLCAT infusion. Conclusions rhLCAT infusions were well tolerated in this first-in-human study in FLD; the anemia improved, as did most parameters related to renal function in spite of advanced disease. Plasma lipids transiently normalized, and there was rapid sequential conversion of small preβ-HDL particles to mature spherical α-HDL particles. [ABSTRACT FROM AUTHOR]

Among the most common lipid abnormalities, a low level of high-density lipoprotein-cholesterol (HDL-C) is one of the first risk factors identified for coronary heart disease. Lecithin cholesterol acyltransferase (LCAT) has a pivotal role in the formation and maturation of HDL-C and in reverse cholesterol transport. To identify genetic loci associated with low HDL-C in a population-based cohort in Tehran, the promoter, coding regions and exon/intron boundaries of LCAT were amplified and sequenced in consecutive individuals (n=150) who had extremely low or high HDL-C levels but no other major lipid abnormalities. A total of 14 single-nucleotide polymorphisms (SNPs) were identified, of which 10 were found to be novel; the L393L, S232T and 16:67977696 C>A polymorphisms have been previously reported in the SNP Database (as rs5923, rs4986970 and rs11860115, respectively) and the non-synonymous R47M mutation has been reported in the Catalogue of Somatic Mutations in Cancer (COSM972635). Three of the SNPs identified in the present study (position 6,531 in exon 5, position 6,696 in exon 5 and position 5,151 in exon 1) led to an amino acid substitution. The most common variants were L393L (4886C/T) in exon 6 and Q177E, a novel mutation, in exon 5, and the prevalence of the heterozygous genotype of these two SNPs was significantly higher in the low HDL-C groups. Univariate conditional logistic regression odds ratios (ORs) were nominally significant for Q177E (OR, 5.64; P=0.02; 95% confidence interval, 1.2-26.2). However, this finding was attenuated following adjustment for confounders. Further studies using a larger sample size may enhance the determination of the role of these SNPs. [ABSTRACT FROM AUTHOR]

Apolipoprotein A-I and Apolipoprotein E promote different steps of reverse cholesterol transport, including lecithin-cholesterol acyltransferase stimulation. Our aim was to study the changes in the levels of Apolipoprotein A-I, Apolipoprotein E, and lecithin-cholesterol acyltransferase activity during atherosclerosis progression in rabbits. Quantitative echocardiographic parameters were analyzed in order to evaluate, for the first time, whether atherosclerosis progression in rabbit is associated to apolipoproteins changes and alteration of indices of cardiac function, such as systolic strain and strain rate of the left ventricle. Atherosclerosis was induced by feeding rabbits for 8 weeks with 2 % cholesterol diet. The HDL levels of cholesterol and cholesteryl esters were measured by HPLC. The lecithin-cholesterol acyltransferase activity was evaluated both ex vivo, as cholesteryl esters/cholesterol molar ratio, and in vitro. Apolipoproteins levels were analyzed by ELISA. The HDL levels of cholesterol and cholesteryl esters increased, during treatment, up to 3.7- and 2.5-fold, respectively, compared to control animals. The lecithin-cholesterol acyltransferase activity in vitro was halved after 4 weeks. During cholesterol treatment, Apolipoprotein A-I level significantly decreased, whereas Apolipoprotein E concentration markedly increased. The molar ratio Apolipoprotein E/Apolipoprotein A-I was negatively correlated with the enzyme activity, and positively correlated with both increases in the intima-media thickness of common carotid wall and cardiac dysfunction signs, such as systolic strain and strain rate of the left ventricle. [ABSTRACT FROM AUTHOR]

Lecithin cholesterol acyl transferase (LCAT) is a plasma enzyme that esterifies cholesterol and raises high-density lipoprotein cholesterol, but its role in atherosclerosis is not clearly established. Studies of various animal models have yielded conflicting results, but studies done in rabbits and non-human primates, which more closely simulate human lipoprotein metabolism, indicate that LCAT is likely atheroprotective. Although suggestive, there are also no biomarker studies that mechanistically link LCAT with cardiovascular disease. Imaging studies of patients with LCAT deficiency have also not yielded a clear answer to the role of LCAT in atherosclerosis. Recombinant LCAT, however, is currently being developed as a therapeutic product for enzyme replacement therapy of patients with genetic disorders of LCAT for the prevention and/or treatment of renal disease, but it may also have value for the treatment of acute coronary syndrome. [ABSTRACT FROM AUTHOR]

Abstract: The solvatochromic fluorescent probe 8-anilino-1-naphthalenesulfonate (ANS) has been used to study the hydrophobicity and conformational dynamics of lecithin:cholesterol acyltransferase (LCAT). The ANS to LCAT binding constant was estimated from titrations with ANS, keeping a constant concentration of LCAT (2μM). Apparent binding constant was found to be dependent on the excitation. For the direct excitation of ANS at 375nm the binding constant was 4.7μM−1 and for UV excitation at 295nm was 3.2μM−1. In the later case, not only ANS but also tryptophan (Trp) residues of LCAT is being excited. Fluorescence spectra and intensity decays show an efficient energy transfer from tryptophan residues to ANS. The apparent distance from Trp donor to ANS acceptor, estimated from the changes in donor lifetime was about 3nm and depends on the ANS concentration. Steady-state and time-resolved fluorescence emission and anisotropies have been characterized. The lifetime of ANS bound to LCAT was above 16ns which is characteristic for it being in a hydrophobic environment. The ANS labeled LCAT fluorescence anisotropy decay revealed the correlation time of 42ns with a weak residual motion of 2.8ns. These characteristics of ANS labeled LCAT fluorescence show that ANS is an excellent probe to study conformational changes of LCAT protein and its interactions with other macromolecules. [Copyright &y& Elsevier]

Abstract: In families, well-known monogenic high-density lipoprotein cholesterol (HDL-C) disorders characterized by extreme HDL-C levels on both ends of the continuum occur in multiple HDL pathways and can confer increased risk for atherosclerotic disease. Polygenic HDL-C variants have been more difficult to identify. In many family and twin studies in different populations, HDL-C levels have been shown to be highly heritable, explaining, on average, between 40% and 60% of between-individual variation. This review of abnormal HDL in families addresses known monogenic HDL disorders and HDL-C heritability in the general population, and presents novel data on the heritability of HDL-C in families with a history of premature coronary artery disease. We conclude that levels of HDL-C and HDL abnormalities are largely under genetic control and environmental and behavioral factors alone have only a modest impact. While rare, monogenic disorders offer considerable insight into the genetics of HDL regulation. Moderate to high heritability estimates across different family populations suggest that future genetic studies will be successful in identifying HDL genetic trait loci and that translational studies will ultimately lead to therapies that optimize the cardiovascular protective benefits of HDL. [Copyright &y& Elsevier]