Genetic lecithin:cholesterol acyltransferase deficiency and cardiovascular disease

Rescue of Familial Lecithin:Cholesterol Acyltranferase Deficiency Mutations with an Allosteric Activator

Lecithin:cholesterol acyltransferase (LCAT) deficiencies represent severe disorders characterized by aberrant cholesterol esterification in plasma, leading to life-threatening conditions. This study investigates the efficacy of Compound 2, a piperidinyl pyrazolopyridine allosteric activator that binds the membrane-binding domain of LCAT, in rescuing the activity of LCAT variants associated with disease. The variants K218N, N228K, and G230R, all located in the cap and lid domains of LCAT, demonstrated notable activity restoration in response to Compound 2. Molecular dynamics simulations and structural modeling indicate that these mutations disrupt the lid and membrane binding domain, with Compound 2 potentially dampening these structural alterations. Conversely, variants such as M252K and F382V in the cap and α/β-hydrolase domain, respectively, exhibited limited or no rescue by Compound 2. Future research should prioritize in vivo investigations that would validate the therapeutic potential of Compound 2 and related activators in familial LCAT deficiency patients with mutations in the cap and lid of the enzyme. SIGNIFICANCE STATEMENT: Lecithin:cholesterol acyltranferase (LCAT) catalyzes the first step of reverse cholesterol transport, namely the esterification of cholesterol in high density lipoprotein particles. Somatic mutations in LCAT lead to excess cholesterol in blood plasma and, in severe cases, kidney failure. In this study, we show that recently discovered small molecule activators can rescue function in LCAT-deficient variants when the mutations occur in the lid and cap domains of the enzyme.

A combined observational and Mendelian randomization investigation reveals NMR-measured analytes to be risk factors of major cardiovascular diseases

Dyslipidaemias is the leading risk factor of several major cardiovascular diseases (CVDs), but there is still a lack of sufficient evidence supporting a causal role of lipoprotein subspecies in CVDs. In this study, we comprehensively investigated several lipoproteins and their subspecies, as well as other metabolites, in relation to coronary heart disease (CHD), heart failure (HF) and ischemic stroke (IS) longitudinally and by Mendelian randomization (MR) leveraging NMR-measured metabolomic data from 118,012 UK Biobank participants. We found that 123, 110 and 36 analytes were longitudinally associated with myocardial infarction, HF and IS (FDR < 0.05), respectively, and 25 of those were associated with all three outcomes. MR analysis suggested that genetically predicted levels of 70, 58 and 7 analytes were associated with CHD, HF and IS (FDR < 0.05), respectively. Two analytes, ApoB/ApoA1 and M-HDL-C were associated with all three CVD outcomes in the MR analyses, and the results for M-HDL-C were concordant in both observational and MR analyses. Our results implied that the apoB/apoA1 ratio and cholesterol in medium size HDL were particularly of importance to understand the shared pathophysiology of CHD, HF and IS and thus should be further investigated for the prevention of all three CVDs.

A High-Throughput NMR Method for Lipoprotein-X Quantification

Lipoprotein X (LP-X) is an abnormal cholesterol-rich lipoprotein particle that accumulates in patients with cholestatic liver disease and familial lecithin-cholesterol acyltransferase deficiency (FLD). Because there are no high-throughput diagnostic tests for its detection, a proton nuclear magnetic resonance (NMR) spectroscopy-based method was developed for use on a clinical NMR analyzer commonly used for the quantification of lipoproteins and other cardiovascular biomarkers. The LP-X assay was linear from 89 to 1615 mg/dL (cholesterol units) and had a functional sensitivity of 44 mg/dL. The intra-assay coefficient of variation (CV) varied between 1.8 and 11.8%, depending on the value of LP-X, whereas the inter-assay CV varied between 1.5 and 15.4%. The assay showed no interference with bilirubin levels up to 317 mg/dL and was also unaffected by hemolysis for hemoglobin values up to 216 mg/dL. Samples were stable when stored for up to 6 days at 4 °C but were not stable when frozen. In a large general population cohort (n = 277,000), LP-X was detected in only 50 subjects. The majority of LP-X positive cases had liver disease (64%), and in seven cases, had genetic FLD (14%). In summary, we describe a new NMR-based assay for LP-X, which can be readily implemented for routine clinical laboratory testing.

Apolipoprotein E isoforms differentially affect LCAT-dependent cholesterol esterification

BACKGROUND AND AIMS

LCAT esterifies cholesterol in both HDL (α-activity) and apoB-containing lipoproteins (β-activity). The main activator of LCAT β-activity is apoE, which in humans exists in 3 main different isoforms (E2, E3 and E4). Here, to gather insights into the potential role of LCAT in apoB-containing lipoprotein metabolism, we investigated the ability of apoE isoforms to promote LCAT-mediated cholesterol esterification.

METHODS

We evaluated the plasma cholesterol esterification rate (CER) in 311 individuals who express functional LCAT and either apoE2, apoE3, or apoE4 and in 28 individuals who also carried LCAT mutations causing selective loss of LCAT α-activity (Fish-Eye Disease (FED)-causing mutations). The association of carrier status with CER was determined using an adjusted linear regression model. The kinetic of LCAT activity towards reconstituted HDLs (rHDLs) containing each apoE isoform was determined using the Michaelis-Menten model.

RESULTS

Plasma CER was ∼20% higher in apoE2 carriers compared to apoE3 carriers, and ∼30% higher in apoE2 carriers compared to apoE4 carriers. After adjusting for age, sex, total cholesterol, HDL-C, apoA-I, apoB, chronic kidney disease diagnosis, zygosity, and LCAT concentration, CER remained significantly different among carriers of the three apoE isoforms. The same trend was observed in carriers of FED-causing mutations. rHDLs containing apoE2 were associated with a lower affinity but higher maximal esterification rate, compared to particles containing apoE3 or apoE4.

CONCLUSION

The present results suggest that the apoE2 isoform is associated with a higher LCAT-mediated cholesterol esterification. This observation may contribute to the characterization of the peculiar functional properties of apoE2.

Molecular Biomarkers for Cardiometabolic Disease: Risk Assessment in Young Individuals

Cardiometabolic diseases, including cardiovascular disease and diabetes, are major causes of morbidity and mortality worldwide. Despite progress in prevention and treatment, recent trends show a stalling in the reduction of cardiovascular disease morbidity and mortality, paralleled by increasing rates of cardiometabolic disease risk factors in young adults, underscoring the importance of risk assessments in this population. This review highlights the evidence for molecular biomarkers for early risk assessment in young individuals. We examine the utility of traditional biomarkers in young individuals and discuss novel, nontraditional biomarkers specific to pathways contributing to early cardiometabolic disease risk. Additionally, we explore emerging omic technologies and analytical approaches that could enhance risk assessment for cardiometabolic disease.

Influence of lecithin cholesterol acyltransferase alteration during different pathophysiologic conditions: A 45 years bibliometrics analysis

Background: Lecithin cholesterol acyltransferase (LCAT) is an important enzyme responsible for free cholesterol (FC) esterification, which is critical for high density lipoprotein (HDL) maturation and the completion of the reverse cholesterol transport (RCT) process. Plasma LCAT activity and concentration showed various patterns under different physiological and pathological conditions. Research on LCAT has grown rapidly over the past 50 years, but there are no bibliometric studies summarizing this field as a whole. This study aimed to use the bibliometric analysis to demonstrate the trends in LCAT publications, thus offering a brief perspective with regard to future developments in this field. Methods: We used the Web of Science Core Collection to retrieve LCAT-related studies published from 1975 to 2020. The data were further analyzed in the number of studies, the journal which published the most LCAT-related studies, co-authorship network, co-country network, co-institute network, co-reference and the keywords burst by CiteSpace V 5.7. Results: 2584 publications contained 55,311 references were used to analyzed. The number of included articles fluctuated in each year. We found that Journal of lipid research published the most LCAT-related studies. Among all the authors who work on LCAT, they tend to collaborate with a relatively stable group of collaborators to generate several major authors clusters which Albers, J. published the most studies (n = 53). The United States of America contributed the greatest proportion (n = 1036) of LCAT-related studies. The LCAT-related studies have been focused on the vascular disease, lecithin-cholesterol acyltransferase reaction, phospholipid, cholesterol efflux, chronic kidney disease, milk fever, nephrotic syndrome, platelet-activating factor acetylhydrolase, reconstituted lpa-i, reverse cholesterol transport. Four main research frontiers in terms of burst strength for LCAT-related studies including "transgenic mice", "oxidative stress", "risk", and "cholesterol metabolism "need more attention. Conclusion: This is the first study that demonstrated the trends and future development in LCAT publications. Further studies should focus on the accurate metabolic process of LCAT dependent or independent of RCT using metabolic marker tracking techniques. It was also well worth to further studying the possibility that LCAT may qualify as a biomarker for risk prediction and clinical treatment.

Plasma FA composition in familial LCAT deficiency indicates SOAT2-derived cholesteryl ester formation in humans

Mutations in the LCAT gene cause familial LCAT deficiency (Online Mendelian Inheritance in Man ID: #245900), a very rare metabolic disorder. LCAT is the only enzyme able to esterify cholesterol in plasma, whereas sterol O-acyltransferases 1 and 2 are the enzymes esterifying cellular cholesterol in cells. Despite the complete lack of LCAT activity, patients with familial LCAT deficiency exhibit circulating cholesteryl esters (CEs) in apoB-containing lipoproteins. To analyze the origin of these CEs, we investigated 24 carriers of LCAT deficiency in this observational study. We found that CE plasma levels were significantly reduced and highly variable among carriers of two mutant LCAT alleles (22.5 [4.0-37.8] mg/dl) and slightly reduced in heterozygotes (218 [153-234] mg/dl). FA distribution in CE (CEFA) was evaluated in whole plasma and VLDL in a subgroup of the enrolled subjects. We found enrichment of C16:0, C18:0, and C18:1 species and a depletion in C18:2 and C20:4 species in the plasma of carriers of two mutant LCAT alleles. No changes were observed in heterozygotes. Furthermore, plasma triglyceride-FA distribution was remarkably similar between carriers of LCAT deficiency and controls. CEFA distribution in VLDL essentially recapitulated that of plasma, being mainly enriched in C16:0 and C18:1, while depleted in C18:2 and C20:4. Finally, after fat loading, chylomicrons of carriers of two mutant LCAT alleles showed CEs containing mainly saturated FAs. This study of CEFA composition in a large cohort of carriers of LCAT deficiency shows that in the absence of LCAT-derived CEs, CEs present in apoB-containing lipoproteins are derived from hepatic and intestinal sterol O-acyltransferase 2.

LCAT- targeted therapies: Progress, failures and future

Lecithin: cholesterol acyltransferase (LCAT) is the only enzyme in plasma which is able to esterify cholesterol and boost cholesterol esterify with phospholipid-derived acyl chains. In order to better understand the progress of LCAT research, it is always inescapable that it is linked to high-density lipoprotein (HDL) metabolism and reverse cholesterol transport (RCT). Because LCAT plays a central role in HDL metabolism and RCT, many animal studies and clinical studies are currently aimed at improving plasma lipid metabolism by increasing LCAT activity in order to find better treatment options for familial LCAT deficiency (FLD), fish eye disease (FED), and cardiovascular disease. Recombinant human LCAT (rhLCAT) injections, cells and gene therapy, and small molecule activators have been carried out with promising results. Recently rhLCAT therapies have entered clinical phase II trials with good prospects. In this review, we discuss the diseases associated with LCAT and therapies that use LCAT as a target hoping to find out whether LCAT can be an effective therapeutic target for coronary heart disease and atherosclerosis. Also, probing the mechanism of action of LCAT may help better understand the heterogeneity of HDL and the action mechanism of dynamic lipoprotein particles.

A novel pathogenic variant in LCAT causing FLD. A case report

BACKGROUND

Fish-eye disease (FED) is due to a partial deficiency in LCAT activity. Nevertheless, Familial lecithin-cholesterol acyltransferase deficiency (FLD), also called Norum disease, appears when the deficiency is complete. They are both rare genetic disorders inherited in an autosomal recessive manner. Clinical signs include decreased circulating HDL cholesterol and dense corneal opacity. Kidney injuries also affect patients suffering from FLD. The diagnosis of FLD is based on the presence of characteristic signs and symptoms and confirmed by genetic testing.

CASE PRESENTATION

We present a case of a 63-year-old man showing an altered lipid profile with low HDL cholesterol, chronic kidney disease (CKD) and corneal disorders. He was referred to genetic counseling in order to discard genetic LCAT deficiency due to decreased visual acuity caused by corneal opacity. A massive DNA sequencing was conducted using a multigene panel associated with lipid metabolism disturbances.Results and genetic findings: Two likely pathogenic variants in LCAT were identified and later confirmed by Sanger sequencing. Both (c.491 G > A and c.496 G > A) were missense variants that originated an amino acid substitution (164Arginine for Histidine and 166Alanine for Threonine, respectively) modifying the protein sequence and its 3D structure.

CONCLUSIONS

FLD and FED sharing common biochemical features, and the existence of other diseases with similar clinical profiles underline the need for a timely differential diagnosis aiming to address patients to preventive programs and future available therapies. This case, added to the reduced number of publications previously reported regarding FLD and FED, contributes to better understanding the genetic characteristics, clinical features, and diagnosis of these syndromes.

Evaluation of lipid metabolizing enzymes: Paraxonase1 (PON1) and lecithin cholesterol acyltransferase (LCAT) activities in children with nephrotic syndrome

Background: The most common glomerular disorder in children is nephrotic syndrome, associated with high morbidity despite notable advances in its treatment. Many of the nephrotic syndrome complications, including the increased risk of atherosclerosis and thromboembolism, can be linked to dysregulated lipid metabolism and dyslipidemia. Paraoxonase enzyme is responsible for the most of the antioxidant properties of HDL, thus preventing the formation of atherogenic ox-LDL molecules, and lecithin cholesterol acyltransferase is intimately involved in HDL maturation and is a key component of the reverse cholesterol transport pathway, which removes excess cholesterol molecules from the peripheral tissues to the liver for excretion. Objectives: The present study aimed to investigate the serum activities of paraoxonase-1 (PON-1) and lecithin cholesterol acyltransferase (LCAT) in children with nephrotic syndrome in an active phase (as newly diagnosed or old cases with acute relapse). Also, to study any correlation exists between paraoxonase-1 activity and lipid profile. Methods: This study consists of group 1 with 40 cases of nephrotic syndrome in the age group of (2-14 years) and group 2 with 40 age and sex-matched healthy controls. Lipid profile and paraoxonase activity, lecithin cholesterol acyltransferase activities were measured in both groups’ serum samples. Results: Statistical analysis of student’s t-test showed that the mean levels of total cholesterol, triglycerides, LDL were significantly increased in group 1 when compared to Group 2 (p <0.001). PON1 and lecithin cholesterol acyltransferase levels were significantly lower in group 1 compared to group 2, and there is no significant difference among nephrotic groups. Conclusions: Both paraoxonase-1 enzyme and lecithin cholesterol acyltransferase are considered good promising predictors for nephrotic syndrome and other parameters such as LDL, HDL, and TG. The significantly decreased paraoxonase-1 enzyme and lecithin cholesterol acyltransferase activities result in increased oxidation of LDL, thus accelerating atherosclerosis.

High Density Lipoprotein Cholesterol Efflux Capacity and Atherosclerosis in Cardiovascular Disease: Pathophysiological Aspects and Pharmacological Perspectives

Over the years, the relationship between high-density lipoprotein (HDL) and atherosclerosis, initially highlighted by the Framingham study, has been revealed to be extremely complex, due to the multiple HDL functions involved in atheroprotection. Among them, HDL cholesterol efflux capacity (CEC), the ability of HDL to promote cell cholesterol efflux from cells, has emerged as a better predictor of cardiovascular (CV) risk compared to merely plasma HDL-cholesterol (HDL-C) levels. HDL CEC is impaired in many genetic and pathological conditions associated to high CV risk such as dyslipidemia, chronic kidney disease, diabetes, inflammatory and autoimmune diseases, endocrine disorders, etc. The present review describes the current knowledge on HDL CEC modifications in these conditions, focusing on the most recent human studies and on genetic and pathophysiologic aspects. In addition, the most relevant strategies possibly modulating HDL CEC, including lifestyle modifications, as well as nutraceutical and pharmacological interventions, will be discussed. The objective of this review is to help understanding whether, from the current evidence, HDL CEC may be considered as a valid biomarker of CV risk and a potential pharmacological target for novel therapeutic approaches.

CER-001 ameliorates lipid profile and kidney disease in a mouse model of familial LCAT deficiency

OBJECTIVE

CER-001 is an HDL mimetic that has been tested in different pathological conditions, but never with LCAT deficiency. This study was designed to investigate whether the absence of LCAT affects the catabolic fate of CER-001, and to evaluate the effects of CER-001 on kidney disease associated with LCAT deficiency.

METHODS

Lcat^-/- and wild-type mice received CER-001 (2.5, 5, 10 mg/kg) intravenously for 2 weeks. The plasma lipid/ lipoprotein profile and HDL subclasses were analyzed. In a second set of experiments, Lcat^-/- mice were injected with LpX to induce renal disease and treated with CER-001 and then the plasma lipid profile, lipid accumulation in the kidney, albuminuria and glomerular podocyte markers were evaluated.

RESULTS

In Lcat^-/- mice a decrease in total cholesterol and triglycerides, and an increase in HDL-c was observed after CER-001 treatment. While in wild-type mice CER-001 entered the classical HDL remodeling pathway, in the absence of LCAT it disappeared from the plasma shortly after injection and ended up in the kidney. In a mouse model of renal disease in LCAT deficiency, treatment with CER-001 at 10 mg/kg for one month had beneficial effects not only on the lipid profile, but also on renal disease, by limiting albuminuria and podocyte dysfunction.

CONCLUSIONS

Treatment with CER-001 ameliorates the dyslipidemia typically associated with LCAT deficiency and more importantly limits renal damage in a mouse model of renal disease in LCAT deficiency. The present results provide a rationale for using CER-001 in FLD patients.

Progression of chronic kidney disease in familial LCAT deficiency: a follow-up of the Italian cohort

Familial LCAT deficiency (FLD) is a rare genetic disorder of HDL metabolism, caused by loss-of-function mutations in the LCAT gene and characterized by a variety of symptoms including corneal opacities and kidney failure. Renal disease represents the leading cause of morbidity and mortality in FLD cases. However, the prognosis is not known and the rate of deterioration of kidney function is variable and unpredictable from patient to patient. In this article, we present data from a follow-up of the large Italian cohort of FLD patients, who have been followed for an average of 12 years. We show that renal failure occurs at the median age of 46 years, with a median time to a second recurrence of 10 years. Additionally, we identify high plasma unesterified cholesterol level as a predicting factor for rapid deterioration of kidney function. In conclusion, this study highlights the severe consequences of FLD, underlines the need of correct early diagnosis and referral of patients to specialized centers, and highlights the urgency for effective treatments to prevent or slow renal disease in patients with LCAT deficiency.

Activation of Naturally Occurring Lecithin:Cholesterol Acyltransferase Mutants by a Novel Activator Compound

Lecithin:cholesterol acyltransferase (LCAT) is a unique plasma enzyme able to esterify cholesterol, and it plays an important role in HDL maturation and promotion of reverse cholesterol transport. Familial LCAT deficiency (FLD; OMIM number 245900) is a rare recessive disease that results from loss-of-function mutations in the LCAT gene and has no cure. In this study, we assessed the in vitro efficacy of a novel small-molecule LCAT activator. Cholesterol esterification rate (CER) and LCAT activity were tested in plasma from six controls and five FLD homozygous carriers of various LCAT mutations at different doses of the compound (0.1, 1, and 10 µg/ml). In control plasma, the compound significantly increased both CER (P < 0.001) and LCAT activity (P = 0.007) in a dose-dependent manner. Both CER and LCAT activity increased by 4- to 5-fold, reaching maximum activation at the dose of 1 µg/ml. Interestingly, Daiichi Sankyo compound produced an increase in CER in two of the five tested LCAT mutants (Leu372--Arg and Val309--Met), while LCAT activity increased in three LCAT mutants (Arg147--Trp, Thr274--Ile and Leu372--Arg); mutant Pro254--Ser was not activated at any of the tested doses. The present findings form the basis for personalized therapeutic interventions in FLD carriers and support the potential LCAT activation in secondary LCAT defects. SIGNIFICANCE STATEMENT: We characterized the pharmacology of a novel small-molecule LCAT activator in vitro on a subset of naturally occurring LCAT mutants. Our findings form the basis for personalized therapeutic interventions for familial LCAT deficiency carriers, who can face severe complications and for whom no cure exists.

Genetic, biochemical, and clinical features of LCAT deficiency: update for 2020

PURPOSE OF REVIEW

Genetic LCAT deficiency is a rare metabolic disorder characterized by low-plasma HDL cholesterol levels. Clinical manifestations of the disease include corneal opacification, anemia, and renal disease, which represents the major cause of morbidity and mortality in carriers.

RECENT FINDINGS

Biochemical and clinical manifestations of the disease are very heterogeneous among carriers. The collection of large series of affected individuals is needed to answer various open questions on this rare disorder of lipid metabolism, such as the cause of renal damage in patients with complete LCAT deficiency and the cardiovascular risk in carriers of different LCAT gene mutations.

SUMMARY

Familial LCAT deficiency is a rare disease, with serious clinical manifestations, which can occur in the first decades of life, and presently with no cure. The timely diagnosis in carriers, together with the identification of disease biomarkers able to predict the evolution of clinical manifestations, would be of great help in the identification of carriers to address to future available therapies.

Low Plasma Lecithin: Cholesterol Acyltransferase (LCAT) Concentration Predicts Chronic Kidney Disease

Low high-density lipoprotein-cholesterol (HDL-c) is the most remarkable lipid trait both in mild-to-moderate chronic kidney disease (CKD) patients as well as in advanced renal disease stages, and we have previously shown that reduced lecithin:cholesterol acyltransferase (LCAT) concentration is a major determinant of the low HDL phenotype. In the present study, we test the hypothesis that reduced LCAT concentration in CKD contributes to the progression of renal damage. The study includes two cohorts of subjects selected from the PLIC study: a cohort of 164 patients with CKD (NefroPLIC cohort) and a cohort of 164 subjects selected from the PLIC participants with a basal estimated glomerular filtration rate (eGFR) > 60 mL/min/1.73 m² (PLIC cohort). When the NefroPLIC patients were categorized according to the LCAT concentration, patients in the 1st tertile showed the highest event rate at follow-up with an event hazard ratio significantly higher compared to the 3rd LCAT tertile. Moreover, in the PLIC cohort, subjects in the 1st LCAT tertile showed a significantly faster impairment of kidney function compared to subjects in the 3rd LCAT tertile. Serum from subjects in the 1st LCAT tertile promoted a higher reactive oxygen species (ROS) production in renal cells compared to serum from subjects in the third LCAT tertile, and this effect was contrasted by pre-incubation with recombinant human LCAT (rhLCAT). The present study shows that reduced plasma LCAT concentration predicts CKD progression over time in patients with renal dysfunction, and, even more striking, it predicts the impairment of kidney function in the general population.

The effects of exercise training on lipid metabolism and coronary heart disease

Blood lipoproteins are formed by various amounts of cholesterol (C), triglycerides (TGs), phospholipids, and apolipoproteins (Apos). ApoA1 is the major structural protein of high-density lipoprotein (HDL), accounting for ~70% of HDL protein, and mediates many of the antiatherogenic functions of HDL. Conversely, ApoB is the predominant low-density lipoprotein (LDL) Apo and is an indicator of circulating LDL, associated with higher coronary heart disease (CHD) risk. Thus, the ratio of ApoB to ApoA1 (ApoB/ApoA1) is used as a surrogate marker of the risk of CHD related to lipoproteins. Elevated or abnormal levels of lipids and/or lipoproteins in the blood are a significant CHD risk factor, and several studies support the idea that aerobic exercise decreases CHD risk by partially lowering serum TG and LDL-cholesterol (LDL-C) levels and increasing HDL-C levels. Exercise also exerts an effect on HDL-C maturation and composition and on reverse C transport from peripheral cells to the liver to favor its catabolism and excretion. This process prevents atherosclerosis, and several studies showed that exercise training increases heart lipid metabolism and protects against cardiovascular disease. In these and other ways, it more and more appears that regular exercise, nutrition, and strategies to modulate lipid profile should be viewed as an integrated whole. The purpose of this review is to assess the effects of endurance training on the nontraditional lipid biomarkers, including ApoB, ApoA1, and ApoB/ApoA1, in CHD risk.

Recombinant LCAT (Lecithin:Cholesterol Acyltransferase) Rescues Defective HDL (High-Density Lipoprotein)-Mediated Endothelial Protection in Acute Coronary Syndrome

Objective- Aim of this study was to evaluate changes in LCAT (lecithin:cholesterol acyltransferase) concentration and activity in patients with an acute coronary syndrome, to investigate if these changes are related to the compromised capacity of HDL (high-density lipoprotein) to promote endothelial nitric oxide (NO) production, and to assess if rhLCAT (recombinant human LCAT) can rescue the defective vasoprotective HDL function. Approach and Results- Thirty ST-segment-elevation myocardial infarction (STEMI) patients were enrolled, and plasma was collected at hospital admission, 48 and 72 hours thereafter, at hospital discharge, and at 30-day follow-up. Plasma LCAT concentration and activity were measured and related to the capacity of HDL to promote NO production in cultured endothelial cells. In vitro studies were performed in which STEMI patients' plasma was added with rhLCAT and HDL vasoprotective activity assessed by measuring NO production in endothelial cells. The plasma concentration of the LCAT enzyme significantly decreases during STEMI with a parallel significant reduction in LCAT activity. HDL isolated from STEMI patients progressively lose the capacity to promote NO production by endothelial cells, and the reduction is related to decreased LCAT concentration. In vitro incubation of STEMI patients' plasma with rhLCAT restores HDL ability to promote endothelial NO production, possibly related to significant modification in HDL phospholipid classes. Conclusions- Impairment of cholesterol esterification may be a major factor in the HDL dysfunction observed during acute coronary syndrome. rhLCAT is able to restore HDL-mediated NO production in vitro, suggesting LCAT as potential therapeutic target for restoring HDL functionality in acute coronary syndrome.

Structural analysis of lecithin:cholesterol acyltransferase bound to high density lipoprotein particles

Lecithin:cholesterol acyltransferase (LCAT) catalyzes a critical step of reverse cholesterol transport by esterifying cholesterol in high density lipoprotein (HDL) particles. LCAT is activated by apolipoprotein A-I (ApoA-I), which forms a double belt around HDL, however the manner in which LCAT engages its lipidic substrates and ApoA-I in HDL is poorly understood. Here, we used negative stain electron microscopy, crosslinking, and hydrogen-deuterium exchange studies to refine the molecular details of the LCAT-HDL complex. Our data are consistent with LCAT preferentially binding to the edge of discoidal HDL near the boundary between helix 5 and 6 of ApoA-I in a manner that creates a path from the lipid bilayer to the active site of LCAT. Our results provide not only an explanation why LCAT activity diminishes as HDL particles mature, but also direct support for the anti-parallel double belt model of HDL, with LCAT binding preferentially to the helix 4/6 region.

Rare dyslipidaemias, from phenotype to genotype to management: a European Atherosclerosis Society task force consensus statement

Genome sequencing and gene-based therapies appear poised to advance the management of rare lipoprotein disorders and associated dyslipidaemias. However, in practice, underdiagnosis and undertreatment of these disorders are common, in large part due to interindividual variability in the genetic causes and phenotypic presentation of these conditions. To address these challenges, the European Atherosclerosis Society formed a task force to provide practical clinical guidance focusing on patients with extreme concentrations (either low or high) of plasma low-density lipoprotein cholesterol, triglycerides, or high-density lipoprotein cholesterol. The task force also recognises the scarcity of quality information regarding the prevalence and outcomes of these conditions. Collaborative registries are needed to improve health policy for the care of patients with rare dyslipidaemias.

Lipid Profile Rather Than the LCAT Mutation Explains Renal Disease in Familial LCAT Deficiency

Renal complications are the major cause of morbidity and mortality in patients with familial lecithin–cholesterol acyltransferase (LCAT) deficiency (FLD). We report three FLD patients, two of them siblings—only one of whom developed renal disease—and the third case being a young man with early renal disease. The aim of this study was to analyze the clinical characteristics and possible mechanisms associated with renal disease in these patients. Plasma lipid levels, LCAT activity, lipoprotein particle profile by NMR and FPLC, free and esterified cholesterol, presence of lipoprotein X (LpX) and DNA sequencing in the three FLD patients have been determined. The three cases presented clinical characteristics of FLD, although only one of the siblings developed renal disease, at 45 years of age, while the other patient developed the disease in his youth. Genetic analysis revealed new missense homozygous mutations, p.(Ile202Thr) in both siblings and p.(Arg171Glu) in the other patient. Lipoprotein particle analysis showed that the two patients with renal disease presented higher numbers of small very low-density lipoprotein (VLDL) and a higher concentration of triglycerides in VLDL. This study reports three new cases of LCAT deficiency, not previously described. Renal disease is not only dependent on LCAT deficiency, and could be due to the presence of VLDL particles, which are rich in triglycerides, free cholesterol and LpX.

Biological Consequences of Dysfunctional HDL

Epidemiological studies have suggested an inverse correlation between high-density lipoprotein (HDL) cholesterol levels and the risk of cardiovascular disease. HDLs promote reverse cholesterol transport (RCT) and possess several putative atheroprotective functions, associated to the anti-inflammatory, anti-thrombotic and anti-oxidant properties as well as to the ability to support endothelial physiology. The assumption that increasing HDL-C levels would be beneficial on cardiovascular disease (CVD), however, has been questioned as, in most clinical trials, HDL-C-raising therapies did not result in improved cardiovascular outcomes. These findings, together with the observations from Mendelian randomization studies showing that polymorphisms mainly or solely associated with increased HDL-C levels did not decrease the risk of myocardial infarction, shift the focus from HDL-C levels toward HDL functional properties. Indeed, HDL from atherosclerotic patients not only exhibit impaired atheroprotective functions but also acquire pro-atherogenic properties and are referred to as "dysfunctional" HDL; this occurs even in the presence of normal or elevated HDL-C levels. Pharmacological approaches aimed at restoring HDL functions may therefore impact more significantly on CVD outcome than drugs used so far to increase HDL-C levels. The aim of this review is to discuss the pathological conditions leading to the formation of dysfunctional HDL and their role in atherosclerosis and beyond.

The P274S Mutation of Lecithin-Cholesterol Acyltransferase (LCAT) and Its Clinical Manifestations in a Large Kindred

RATIONALE & OBJECTIVE

Lecithin-cholesterol acyltransferase (LCAT) catalyzes the maturation of high-density lipoprotein. Homozygosity for loss-of-function mutations causes familial LCAT deficiency (FLD), characterized by corneal opacities, anemia, and renal involvement. This study sought to characterize kidney biopsy findings and clinical outcomes in a family with FLD.

STUDY DESIGN

Prospective observational study.

SETTING & PARTICIPANTS

2 (related) index patients with clinically apparent FLD were initially identified. 110 of 122 family members who consented to genetic analysis were also studied.

PREDICTORS

Demographic and laboratory parameters (including lipid profiles and LCAT activity) and full sequence analysis of the LCAT gene. Kidney histologic examination was performed with samples from 6 participants.

OUTCOMES

Cardiovascular and renal events during a median follow-up of 12 years. Estimation of annual rate of decline in glomerular filtration rate.

ANALYTICAL APPROACH

Analysis of variance, linear regression analysis, and Fine-Gray competing-risk survival analysis.

RESULTS

9 homozygous, 57 heterozygous, and 44 unaffected family members were identified. In all affected individuals, full sequence analysis of the LCAT gene revealed a mutation (c.820C>T) predicted to cause a proline to serine substitution at amino acid 274 (P274S). Homozygosity caused a complete loss of LCAT activity. Kidney biopsy findings demonstrated lipid deposition causing glomerular basement membrane thickening, mesangial expansion, and "foam-cell" infiltration of kidney tissue. Tubular atrophy, glomerular sclerosis, and complement fixation were associated with worse kidney outcomes. Estimated glomerular filtration rate deteriorated among homozygous family members at an average annual rate of 3.56 mL/min/1.73 m². The incidence of cardiovascular and renal complications was higher among homozygous family members compared with heterozygous and unaffected members. Mild thrombocytopenia was a common finding among homozygous participants.

LIMITATIONS

The presence of cardiovascular disease was mainly based on medical history.

CONCLUSIONS

The P274S LCAT mutation was found to cause FLD with renal involvement. Tubular atrophy, glomerular sclerosis, and complement fixation were associated with a worse renal prognosis.

Plasma lipoprotein-X quantification on filipin-stained gels: monitoring recombinant LCAT treatment ex vivo

Familial LCAT deficiency (FLD) patients accumulate lipoprotein-X (LP-X), an abnormal nephrotoxic lipoprotein enriched in free cholesterol (FC). The low neutral lipid content of LP-X limits the ability to detect it after separation by lipoprotein electrophoresis and staining with Sudan Black or other neutral lipid stains. A sensitive and accurate method for quantitating LP-X would be useful to examine the relationship between plasma LP-X and renal disease progression in FLD patients and could also serve as a biomarker for monitoring recombinant human LCAT (rhLCAT) therapy. Plasma lipoproteins were separated by agarose gel electrophoresis and cathodal migrating bands corresponding to LP-X were quantified after staining with filipin, which fluoresces with FC, but not with neutral lipids. rhLCAT was incubated with FLD plasma and lipoproteins and LP-X changes were analyzed by agarose gel electrophoresis. Filipin detects synthetic LP-X quantitatively (linearity 20-200 mg/dl FC; coefficient of variation <20%) and sensitively (lower limit of quantitation <1 mg/ml FC), enabling LP-X detection in FLD, cholestatic, and even fish-eye disease patients. rhLCAT incubation with FLD plasma ex vivo reduced LP-X dose dependently, generated HDL, and decreased lipoprotein FC content. Filipin staining after agarose gel electrophoresis sensitively detects LP-X in human plasma and accurately quantifies LP-X reduction after rhLCAT incubation ex vivo.

An Updated Review of Lysophosphatidylcholine Metabolism in Human Diseases

Lysophosphatidylcholine (LPC) is increasingly recognized as a key marker/factor positively associated with cardiovascular and neurodegenerative diseases. However, findings from recent clinical lipidomic studies of LPC have been controversial. A key issue is the complexity of the enzymatic cascade involved in LPC metabolism. Here, we address the coordination of these enzymes and the derangement that may disrupt LPC homeostasis, leading to metabolic disorders. LPC is mainly derived from the turnover of phosphatidylcholine (PC) in the circulation by phospholipase A₂ (PLA₂). In the presence of Acyl-CoA, lysophosphatidylcholine acyltransferase (LPCAT) converts LPC to PC, which rapidly gets recycled by the Lands cycle. However, overexpression or enhanced activity of PLA₂ increases the LPC content in modified low-density lipoprotein (LDL) and oxidized LDL, which play significant roles in the development of atherosclerotic plaques and endothelial dysfunction. The intracellular enzyme LPCAT cannot directly remove LPC from circulation. Hydrolysis of LPC by autotaxin, an enzyme with lysophospholipase D activity, generates lysophosphatidic acid, which is highly associated with cancers. Although enzymes with lysophospholipase A₁ activity could theoretically degrade LPC into harmless metabolites, they have not been found in the circulation. In conclusion, understanding enzyme kinetics and LPC metabolism may help identify novel therapeutic targets in LPC-associated diseases.

A proteomic approach to identify novel disease biomarkers in LCAT deficiency

Genetic LCAT deficiency is a rare recessive autosomal disease due to loss-of-function mutations in the gene coding for the enzyme lecithin:cholesterol acyltransferase (LCAT). Homozygous carriers are characterized by corneal opacity, haemolytic anaemia and renal disease, which represent the first cause of morbidity and mortality in these subjects. Diagnostic and prognostic markers capable of early detecting declining kidney function in these subjects are not available, and the specific serum or urine proteomic signature of LCAT deficient carriers has never been assessed. Taking advantage of a proteomic approach, we performed 2-DE analysis of carriers' plasma and identified proteins present at different concentration in samples from homozygous carriers. Our data confirm the well-known alterations in the concentration of circulating apolipoproteins, with a statistically significant decrease of both apoA-I and apoA-II and a statistically significant increase of apoC-III. Furthermore, we observed increased level of alpha-1-antitrypsin, zinc-alpha-2-glycoprotein and retinol-binding protein 4, and reduced level of clusterin and haptoglobin. Interestingly, only beta but not alpha subunit of haptoglobin is significant reduced in homozygous subjects. Despite the limited sample size, our findings set the basis for assessing the identified protein in a larger population and for correlating their levels with clinical markers of renal function and anaemia. SIGNIFICANCE: This investigation defines the effects of LCAT deficiency on the level of the major plasma proteins in homozygous and heterozygous carriers. Increase for some proteins, with different function, together with a drop for haptoglobin, and specifically for haptoglobin beta chains, are reported for the first time as part of a coherent signature. We are glad to have the opportunity to report our findings on this subject, which is one of the main interests for our research group, when Journal of Proteomics celebrates its 10th anniversary. With its various sections devoted to different areas of research, this journal is a privileged forum for publishing proteomic investigations without restrictions either in sample type or in technical approach. It is as well a privileged forum for reviewing literature data on various topics related to proteomics investigation, as colleagues in our research group have done over the years; by the way, a good share of the reviewed papers were as well reports published in Journal of Proteomics itself. The journal also offers opportunities for focused surveys through thematic issues devoted to a variety of subjects, timely selected for their current relevance in research; it was an honour for colleagues in our group to recently act as editors of one of those. Out of this diverse experience, we express our appreciation for the endeavour of Journal of Proteomics in its first 10 years of life - and wish identical and possibly greater success for the time to come.

Association of lecithin-cholesterol acyltransferase activity and low-density lipoprotein heterogeneity with atherosclerotic cardiovascular disease risk: a longitudinal pilot study

BACKGROUND

Lecithin-cholesterol acyltransferase (LCAT) is believed to be involved in reverse cholesterol transport, which is known to play a key role in suppression of atherosclerosis. However, recent investigations have demonstrated that higher LCAT activity, measured in terms of the serum cholesterol esterification rate by an endogenous substrate method, is associated with increased formation of triglyceride (TG)-rich lipoproteins (TRLs), leading to a decrease in the low-density lipoprotein (LDL) particle size. The purpose of this hospital-based longitudinal study was to clarify the causal relationship between changes in the LCAT activity and changes in the LDL-particle size.

METHODS

The subjects were a total of 335 patients, derived from our previous study cohort, with one or more risk factors for atherosclerotic cardiovascular disease (ASCVD). For this study, we measured the LDL-particle size (relative LDL migration [LDL-Rm value]) by polyacrylamide gel electrophoresis in the subjects, along with the changes in the LCAT activity, at the end of a follow-up period of at least 1 year.

RESULTS

The results revealed that the absolute change (Δ) in the LDL-particle size increased significantly as the quartile of Δ LCAT activity increased (p = 0.01). A multi-logistic regression adjusted-analysis revealed that Δ LCAT activity in the fourth quartile as compared to that in the first quartile was independently predictive of an increased LDL-particle size (odds ratio [95% confidence interval]: 2.03 [1.02/4.04], p = 0.04). Moreover, the ∆ LCAT activity was also positively correlated with ∆ TRL-related markers (i.e., TG, remnant particle-like cholesterol [RLP-C], apolipoprotein B, apolipoprotein C-2, and apolipoprotein C-3).

CONCLUSIONS

The results lend support to the hypothesis that increased LCAT activity may be associated with increased formation of TRLs, leading to a reduction in the LDL-particle size in patients at a high risk for ASCVD. To reduce the risk of ASCVD, it may be important to focus not only on the quantitative changes in the serum LDL-cholesterol levels, but also on the LCAT activity.

TRIAL REGISTRATION

UMIN ( https://upload.umin.ac.jp/cgi-bin/ctr/ctr_reg_list.cgi ) Study ID: UMIN000033228 retrospectively registered 2 July 2018.

Molecular basis for activation of lecithin:cholesterol acyltransferase by a compound that increases HDL cholesterol

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.

Cholesterol is a fatty substance found throughout the body that is essential to our health. However, if too much cholesterol builds up in our blood vessels, it can cause blockages that lead to heart and kidney problems. The body removes excess cholesterol by sending out high-density lipoproteins (HDL) that capture the fatty molecules and carry them to the liver where they are eliminated. The first step in this process requires an enzyme called LCAT, which converts cholesterol into a form that HDL particles can efficiently pack and transport. The enzyme acts by interacting with HDL particles, and chemically joining cholesterol with another compound.

Finding ways to make LCAT perform better and produce more HDL could improve treatments for heart disease. This could be particularly helpful to people with genetic changes that make LCAT defective. Several small molecules that ‘dial up’ the activity of LCAT have been identified, but how they act on the enzyme is not always well understood.

Manthei et al. therefore set out to determine precisely how one such small activator promotes LCAT function. The experiments involved using a method known as crystallography to look at the structure of LCAT when it is attached to the small molecule. They also evaluated the activity of the enzyme and other aspects of the protein in the presence of the small molecule and HDL particles.

Taken together, the results led Manthei et al. to suggest that the small molecule works by more efficiently bringing into LCAT the materials that this enzyme needs to create the transport-ready form of cholesterol. The small molecule also partially restored the activity of mutant LCAT found in human disease.

This knowledge may help to design more drug-like chemicals to ‘boost’ the activity of LCAT and prevent heart and kidney disease, especially in people who carry a defective version of the enzyme.

Primary genetic disorders affecting high density lipoprotein (HDL)

There is extensive evidence demonstrating that there is a clear inverse correlation between plasma high density lipoprotein cholesterol (HDL-C) concentration and cardiovascular disease (CVD). On the other hand, there is also extensive evidence that HDL functionality plays a very important role in atheroprotection. Thus, genetic disorders altering certain enzymes, lipid transfer proteins, or specific receptors crucial for the metabolism and adequate function of HDL, may positively or negatively affect the HDL-C levels and/or HDL functionality and subsequently either provide protection or predispose to atherosclerotic disease. This review aims to describe certain genetic disorders associated with either low or high plasma HDL-C and discuss their clinical features, associated risk for cardiovascular events, and treatment options.

A retractable lid in lecithin:cholesterol acyltransferase provides a structural mechanism for activation by apolipoprotein A-I

Lecithin:cholesterol acyltransferase (LCAT) plays a key role in reverse cholesterol transport by transferring an acyl group from phosphatidylcholine to cholesterol, promoting the maturation of high-density lipoproteins (HDL) from discoidal to spherical particles. LCAT is activated through an unknown mechanism by apolipoprotein A-I (apoA-I) and other mimetic peptides that form a belt around HDL. Here, we report the crystal structure of LCAT with an extended lid that blocks access to the active site, consistent with an inactive conformation. Residues Thr-123 and Phe-382 in the catalytic domain form a latch-like interaction with hydrophobic residues in the lid. Because these residues are mutated in genetic disease, lid displacement was hypothesized to be an important feature of apoA-I activation. Functional studies of site-directed mutants revealed that loss of latch interactions or the entire lid enhanced activity against soluble ester substrates, and hydrogen-deuterium exchange (HDX) mass spectrometry revealed that the LCAT lid is extremely dynamic in solution. Upon addition of a covalent inhibitor that mimics one of the reaction intermediates, there is an overall decrease in HDX in the lid and adjacent regions of the protein, consistent with ordering. These data suggest a model wherein the active site of LCAT is shielded from soluble substrates by a dynamic lid until it interacts with HDL to allow transesterification to proceed.

Increased prevalence of clinical and subclinical atherosclerosis in patients with damaging mutations in ABCA1 or APOA1

BACKGROUND

A low level of high-density lipoprotein cholesterol (HDL-C) is a common clinical scenario and poses challenges for management. Many patients with low HDL-C harbor a damaging mutation in ABCA1 or APOA1, but the clinical implications of genetic testing for these mutations are unclear.

OBJECTIVE

The purpose of this study was to investigate the prevalence of clinical or subclinical atherosclerosis among patients with low HDL-C due to a mutation in ABCA1 or APOA1, compared with patients with low HDL-C without such a mutation.

METHODS

We performed targeted next-generation sequencing to identify mutations in ABCA1 and APOA1 in 72 patients with HDL-C levels below the 10^th percentile. We examined the prevalence of clinical atherosclerosis and subclinical atherosclerosis in these patients. We also measured cholesterol efflux capacity (CEC) in plasma.

RESULTS

We identified a known disease-causing or likely pathogenic variant in the ABCA1 or APOA1 genes in 22% of patients with low HDL-C. Eighty-three percent of patients with a damaging mutation in ABCA1 or APOA1 had evidence of atherosclerosis compared with 38.6% with low HDL-C without such a mutation (P = .04). Patients with damaging mutations in ABCA1 or APOA1 had lower CEC compared with patients without a mutation (25.9% vs 30.1%).

CONCLUSION

The presence of a damaging mutation in ABCA1 or APOA1 confers an increased risk of atherosclerosis relative to patients without such a mutation at a comparable level of HDL cholesterol, possibly because of a reduction in CEC.

Development of a novel fluorescent activity assay for lecithin:cholesterol acyltransferase

Background Lecithin:cholesterol acyltransferase (LCAT) is a plasma enzyme that esterifies cholesterol. Recombinant human LCAT (rhLCAT) is now being developed as an enzyme replacement therapy for familial LCAT deficiency and as a possible treatment for acute coronary syndrome. The current 'gold standard' assay for LCAT activity involves the use of radioisotopes, thus making it difficult for routine clinical use. Methods We have developed a novel and more convenient LCAT activity assay using fluorescence-labelled cholesterol (BODIPY-cholesterol), which is incorporated into proteoliposomes as a substrate instead of radiolabelled cholesterol. Results The apparent K_m and V_max were 31.5  µmol/L and 55.8 nmol/h/nmoL, rhLCAT, respectively, for the ³H-cholesterol method and 103.1  µmol/L and 13.4 nmol/h/nmol rhLCAT, respectively, for the BODIPY-cholesterol method. Although the two assays differed in their absolute units of LCAT activity, there was a good correlation between the two test assays ( r = 0.849, P < 1.6 × 10^-7, y = 0.1378x + 1.106). The BODIPY-cholesterol assay had an intra-assay CV of 13.7%, which was superior to the intra-assay CV of 20.8% for the radioisotopic assay. The proteoliposome substrate made with BODIPY-cholesterol was stable to storage for at least 10 months. The reference range ( n = 20) for the fluorescent LCAT activity assay was 4.6-24.1 U/mL/h in healthy subjects. Conclusions In summary, a novel fluorescent LCAT activity assay that utilizes BODIPY-cholesterol as a substrate is described that yields comparable results to the radioisotopic method.

The role of paraoxonase 1 in regulating high-density lipoprotein functionality during aging

Pharmacological interventions to increase the concentration of high-density lipoprotein (HDL) have led to disappointing results and have contributed to the emergence of the concept of HDL functionality. The anti-atherogenic activity of HDLs can be explained by their functionality or quality. The capacity of HDLs to maintain cellular cholesterol homeostasis and to transport cholesterol from peripheral cells to the liver for elimination is one of their principal anti-atherogenic activities. However, HDLs possess several other attributes that contribute to their protective effect against cardiovascular diseases. HDL functionality is regulated by various proteins and lipids making up HDL particles. However, several studies investigated the role of paraoxonase 1 (PON1) and suggest a significant role of this protein in the regulation of the functionality of HDLs. Moreover, research on PON1 attracted much interest following several studies indicating that it is involved in cardiovascular protection. However, the mechanisms by which PON1 exerts these effects remain to be elucidated.

HDL as a Causal Factor in Atherosclerosis: Insights from Human Genetics

High-density lipoprotein cholesterol (HDL-C) levels are inversely related to risk of atherosclerotic cardiovascular disease (ASCVD). However, the simplistic assumption that HDL-C levels directly and causally impact atherogenesis has been challenged in recent years. The purpose of this article is to review the current state of knowledge regarding genetically determined HDL-C levels and ASCVD risk and determine what insight these studies provide into the causal relationship between HDL and atherosclerosis.

Atherogenic Impact of Lecithin-Cholesterol Acyltransferase and Its Relation to Cholesterol Esterification Rate in HDL (FERHDL) and AIP [log(TG/HDL-C)] Biomarkers: The Butterfly Effect?

The atherogenic impact and functional capacity of LCAT was studied and discussed over a half century. This review aims to clarify the key points that may affect the final decision on whether LCAT is an anti-atherogenic or atherogenic factor. There are three main processes involving the efflux of free cholesterol from peripheral cells, LCAT action in intravascular pool where cholesterol esterification rate is under the control of HDL, LDL and VLDL subpopulations, and finally the destination of newly produced cholesteryl esters either to the catabolism in liver or to a futile cycle with apoB lipoproteins. The functionality of LCAT substantially depends on its mass together with the composition of the phospholipid bilayer as well as the saturation and the length of fatty acyls and other effectors about which we know yet nothing. Over the years, LCAT puzzle has been significantly supplemented but yet not so satisfactory as to enable how to manipulate LCAT in order to prevent cardiometabolic events. It reminds the butterfly effect when only a moderate change in the process of transformation free cholesterol to cholesteryl esters may cause a crucial turn in the intended target. On the other hand, two biomarkers – FERHDL (fractional esterification rate in HDL) and AIP [log(TG/HDL-C)] can offer a benefit to identify the risk of cardiovascular disease (CVD). They both reflect the rate of cholesterol esterification by LCAT and the composition of lipoprotein subpopulations that controls this rate. In clinical practice, AIP can be calculated from the routine lipid profile with help of AIP calculator www.biomed.cas.cz/fgu/aip/calculator.php.

Association between High-density-lipoprotein-cholesterol Levels and the Prevalence of Asymptomatic Intracranial Arterial Stenosis

Intracranial atherosclerotic stenosis (ICAS) is a common cause of ischemic stroke, and a low level of high-density lipoprotein cholesterol (HDL-C) is also considered to be a predictor for stroke. However, the association between the HDL-C level and asymptomatic ICAS is uncertain. From 2010 to 2011, a random sample of 5,351 participants were enrolled in the Asymptomatic Polyvascular Abnormalities Community (APAC) study. The recruited participants were then separated into 5 roughly uniform-sized factions with varying HDL-C levels. Multivariate logistic regression was implemented to assess the connection of the HDL-C levels and the prevalence of asymptomatic ICAS. The prevalence of asymptomatic ICAS showed no gradual decrease with the increase of HDL-C levels. After adjustment for conventional risk factors, HDL-C levels still showed no significant association with asymptomatic ICAS. The odds ratios (OR) of the prevalence of asymptomatic ICAS between the first group and the other 4 groups were 0.98, 1.00, 0.92, and 0.87 with 95% confidence intervals (CI) being 0.76–1.27, 0.78–1.29, 0.71–1.19, and 0.66–1.13, respectively. The study showed little correlation between HDL-C levels and asymptomatic ICAS. Normal levels of HDL-C are not an independent risk factor for asymptomatic ICAS.

Depletion in LpA-I:A-II particles enhances HDL-mediated endothelial protection in familial LCAT deficiency

The aim of this study was to evaluate the vasoprotective effects of HDL isolated from carriers of LCAT deficiency, which are characterized by a selective depletion of LpA-I:A-II particles and predominance of preβ migrating HDL. HDLs were isolated from LCAT-deficient carriers and tested in vitro for their capacity to promote NO production and to inhibit vascular cell adhesion molecule-1 (VCAM-1) expression in cultured endothelial cells. HDLs from carriers were more effective than control HDLs in promoting eNOS activation with a gene-dose-dependent effect (P_Trend = 0.048). As a consequence, NO production induced by HDL from carriers was significantly higher than that promoted by control HDL (1.63 ± 0.24-fold vs. 1.34 ± 0.07-fold, P = 0.031). HDLs from carriers were also more effective than control HDLs in inhibiting the expression of VCAM-1 (homozygotes, 65.0 ± 8.6%; heterozygotes, 53.1 ± 7.2%; controls, 44.4 ± 4.1%; P_Trend = 0.0003). The increased efficiency of carrier HDL was likely due to the depletion in LpA-I:A-II particles. The in vitro findings might explain why carriers of LCAT deficiency showed flow-mediated vasodilation and plasma-soluble cell adhesion molecule concentrations comparable to controls, despite low HDL-cholesterol levels. These results indicate that selective depletion of apoA-II-containing HDL, as observed in carriers of LCAT deficiency, leads to an increased capacity of HDL to stimulate endothelial NO production, suggesting that changes in HDL apolipoprotein composition may be the target of therapeutic interventions designed to improve HDL functionality.

Quantitative Metabolomic Profiling of Plasma, Urine, and Liver Extracts by 1H NMR Spectroscopy Characterizes Different Stages of Atherosclerosis in Hamsters

Atherosclerosis (AS) is a progressive disease that contributes to cardiovascular disease and shows a complex etiology, including genetic and environmental factors. To understand systemic metabolic changes and to identify potential biomarkers correlated with the occurrence and perpetuation of diet-induced AS, we applied ¹H NMR-based metabolomics to detect the time-related metabolic profiles of plasma, urine, and liver extracts from male hamsters fed a high fat and high cholesterol (HFHC) diet. Conventional biochemical assays and histopathological examinations as well as protein expression analyses were performed to provide complementary information. We found that diet treatment caused obvious aortic lesions, lipid accumulation, and inflammatory infiltration in hamsters. Downregulation of proteins related to cholesterol metabolism, including hepatic SREBP2, LDL-R, CYP7A1, SR-BI, HMGCR, LCAT, and SOAT1 was detected, which elucidated the perturbation of cholesterol homeostasis during the HFHC diet challenge. Using "targeted analysis", we quantified 40 plasma, 80 urine, and 60 liver hydrophilic extract metabolites. Multivariate analyses of the identified metabolites elucidated sophisticated metabolic disturbances in multiple matrices, including energy homeostasis, intestinal microbiota functions, inflammation, and oxidative stress coupled with the metabolisms of cholesterol, fatty acids, saccharides, choline, amino acids, and nucleotides. For the first time, our results demonstrate a time-dependent metabolic progression of multiple biological matrices in hamsters from physiological status to early AS and further to late-stage AS, demonstrating that ¹H NMR-based metabolomics is a reliable tool for early diagnosis and monitoring of the process of AS.

Comparative proteomics of umbilical vein blood plasma from normal and gestational diabetes mellitus patients reveals differentially expressed proteins associated with childhood obesity

PURPOSE

Offspring obesity is one of long-term complications of gestational diabetes mellitus (GDM). The aim of this study is to identify proteins differentially expressed in the umbilical vein blood plasma, which could become markers for early diagnosis of childhood obesity.

EXPERIMENTAL DESIGN

Umbilical vein plasma samples were collected from 30 control and 30 GDM patients in 2007-2008 whose offspring were suffering from obesity at 6-7 years old. Multiplexed isobaric tandem mass tag labeling combined with LC-MS/MS was used to identify differentially expressed proteins. Ingenuity pathway analysis was performed to identify canonical pathways, biological functions, and networks of interacting proteins. Western blotting was used to verify the expression of three selected proteins.

RESULTS

A total of 318 proteins were identified, of which 12 proteins were upregulated in GDM group while 24 downregulated. Lipid metabolism was the top category identified by ingenuity pathway analysis. Three randomly chosen proteins were validated by Western blotting, which were consistent with LC-MS.

CONCLUSION

There are significant differences of protein profile in the umbilical vein blood plasma between normal and GDM patients with obese offspring. The results indicate that a variety of proteins and biological mechanisms may contribute to childhood obesity.

ApoA-I-Directed Therapies for the Management of Atherosclerosis

Several recent reports have raised doubts about the atheroprotective role of high-density lipoprotein cholesterol (HDL-C). Nevertheless, a substantial body of work supports the validity of pharmacological interventions able to enhance HDL function, as opposed to raising HDL-C levels per se. In this article, we briefly review the development of pharmacological interventions that target apoA-I and HDL function as a means of reducing atherosclerotic risk: small molecule pharmaceuticals, small HDL mimetic peptides, and infusion of apoA-I-containing particles.

Targeting high-density lipoproteins: increasing de novo production versus decreasing clearance

Although cardiovascular mortality has been decreasing in industrialized countries, there continues to be a substantial residual risk; thus, novel therapeutic agents and new targets of therapy have been sought. One highly plausible therapeutic target is high-density lipoprotein (HDL). HDL is a key player in reverse cholesterol transport and possesses a slew of other cardioprotective properties; however, recent trials with agents known to increase HDL levels have generally not shown any reduction in cardiovascular events. Further analysis of these trials suggest that fibrates have consistently reduced some cardiovascular outcomes, at least in the subgroup of patients with high serum triglycerides and low HDL cholesterol (HDLc) levels. Since fibrates, unlike niacin or cholesterol ester transfer protein inhibitors, increase HDLc level mostly through the stimulation of apolipoprotein A-I production, it is suggested that the quality and functionality of HDL are enhanced when de novo synthesis rather than inhibition of turnover is the mechanism of increasing HDL level. In this communication, the evidence for and against the cardioprotective properties of HDL is reviewed and the contemporary clinical trials are discussed.

An unusual case of nephrotic syndrome

Nephrotic syndrome can be rarely due to inherited disorders of enzymes. One such variety is lecithin cholesterol acyltransferase deficiency. It leads to accumulation of unesterified cholesterol in the eye and other organs. We report a case of nephrotic syndrome with cloudy cornea and hypocholesterolemia with foam cells and lipid deposits on renal biopsy. Awareness about this rare disease may help in the early institution of specific measures to prevent progression to end-stage renal disease.

Familial lecithin:cholesterol acyltransferase deficiency: First-in-human treatment with enzyme replacement

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.