Lecithin and cardiovascular health: a comprehensive review

BACKGROUND

Cardiovascular diseases are one of the prime causes of mortality globally. Therefore, concerted efforts are made to prevent or manage disruptions from normal functioning of the cardiovascular system. Disruption in lipid metabolism is a major contributor to cardiovascular dysfunction. This review examines how lecithin impacts lipid metabolism and cardiovascular health. It emphasizes lecithin's ability to reduce excess low-density lipoproteins (LDL) while specifically promoting the synthesis of high-density lipoprotein (HDL) particles, thus contributing to clearer understanding of its role in cardiovascular well-being. Emphasizing the importance of lecithin cholesterol acyltransferase (LCAT) in the reverse cholesterol transport (RCT) process, the article delves into its contribution in removing surplus cholesterol from cells. This review aims to clarify existing literature on lipid metabolism, providing insights for targeted strategies in the prevention and management of atherosclerotic cardiovascular disease (ASCVD). This review summarizes the potential of lecithin in cardiovascular health and the role of LCAT in cholesterol metabolism modulation, based on articles from 2000 to 2023 sourced from databases like MEDLINE, PubMed and the Scientific Electronic Library Online.

MAIN BODY

While studies suggest a positive correlation between increased LCAT activities, reduced LDL particle size and elevated serum levels of triglyceride-rich lipoprotein (TRL) markers in individuals at risk of ASCVD, the review acknowledges existing controversies. The precise nature of LCAT's potential adverse effects remains uncertain, with varying reports in the literature. Notably, gastrointestinal symptoms such as diarrhea and nausea have been sporadically documented.

CONCLUSIONS

The review calls for a comprehensive investigation into the complexities of LCAT's impact on cardiovascular health, recognizing the need for a nuanced understanding of its potential drawbacks. Despite indications of potential benefits, conflicting findings warrant further research to clarify LCAT's role in atherosclerosis.

Flipped C-Terminal Ends of APOA1 Promote ABCA1-Dependent Cholesterol Efflux by Small HDLs

BACKGROUND

Cholesterol efflux capacity (CEC) predicts cardiovascular disease independently of high-density lipoprotein (HDL) cholesterol levels. Isolated small HDL particles are potent promoters of macrophage CEC by the ABCA1 (ATP-binding cassette transporter A1) pathway, but the underlying mechanisms are unclear.

METHODS

We used model system studies of reconstituted HDL and plasma from control and lecithin-cholesterol acyltransferase (LCAT)-deficient subjects to investigate the relationships among the sizes of HDL particles, the structure of APOA1 (apolipoprotein A1) in the different particles, and the CECs of plasma and isolated HDLs.

RESULTS

We quantified macrophage and ABCA1 CEC of 4 distinct sizes of reconstituted HDL. CEC increased as particle size decreased. Tandem mass spectrometric analysis of chemically cross-linked peptides and molecular dynamics simulations of APOA1, the major protein of HDL, indicated that the mobility of C-terminus of that protein was markedly higher and flipped off the surface in the smallest particles. To explore the physiological relevance of the model system studies, we isolated HDL from LCAT-deficient subjects, whose small HDLs (like reconstituted HDLs) are discoidal and composed of APOA1, cholesterol, and phospholipid. Despite their very low plasma levels of HDL particles, these subjects had normal CEC. In both the LCAT-deficient subjects and control subjects, the CEC of isolated extra-small HDL (a mixture of extra-small and small HDL by calibrated ion mobility analysis) was 3- to 5-fold greater than that of the larger sizes of isolated HDL. Incubating LCAT-deficient plasma and control plasma with human LCAT converted extra-small and small HDL particles into larger particles, and it markedly inhibited CEC.

CONCLUSIONS

We present a mechanism for the enhanced CEC of small HDLs. In smaller particles, the C-termini of the 2 antiparallel molecules of APOA1 are "flipped" off the lipid surface of HDL. This extended conformation allows them to engage with ABCA1. In contrast, the C-termini of larger HDLs are unable to interact productively with ABCA1 because they form a helical bundle that strongly adheres to the lipid on the particle. Enhanced CEC, as seen with the smaller particles, predicts decreased cardiovascular disease risk. Thus, extra-small and small HDLs may be key mediators and indicators of the cardioprotective effects of HDL.

Flipped C-Terminal Ends of APOA1 Promote ABCA1-dependent Cholesterol Efflux by Small HDLs

Background

Cholesterol efflux capacity (CEC) predicts cardiovascular disease (CVD) independently of HDL cholesterol (HDL-C) levels. Isolated small HDL particles are potent promoters of macrophage CEC by the ABCA1 pathway, but the underlying mechanisms are unclear.

Methods

We used model system studies of reconstituted HDL and plasma from control and lecithin-cholesterol acyltransferase (LCAT)-deficient subjects to investigate the relationships among the sizes of HDL particles, the structure of APOA1 in the different particles, and the CECs of plasma and isolated HDLs.

Results

We quantified macrophage and ABCA1 CEC of four distinct sizes of reconstituted HDL (r-HDL). CEC increased as particle size decreased. MS/MS analysis of chemically crosslinked peptides and molecular dynamics simulations of APOA1 (HDL's major protein) indicated that the mobility of that protein's C-terminus was markedly higher and flipped off the surface in the smallest particles. To explore the physiological relevance of the model system studies, we isolated HDL from LCAT-deficient subjects, whose small HDLs-like r-HDLs-are discoidal and composed of APOA1, cholesterol, and phospholipid. Despite their very low plasma levels of HDL particles, these subjects had normal CEC. In both the LCAT-deficient subjects and control subjects, the CEC of isolated extra-small HDL (a mixture of extra-small and small HDL by calibrated ion mobility analysis) was 3-5-fold greater than that of the larger sizes of isolated HDL. Incubating LCAT-deficient plasma and control plasma with human LCAT converted extra-small and small HDL particles into larger particles, and it markedly inhibited CEC.

Conclusions

We present a mechanism for the enhanced CEC of small HDLs. In smaller particles, the C-termini of the two antiparallel molecules of APOA1 are flipped off the lipid surface of HDL. This extended conformation allows them to engage with ABCA1. In contrast, the C-termini of larger HDLs are unable to interact productively with ABCA1 because they form a helical bundle that strongly adheres to the lipid on the particle. Enhanced CEC, as seen with the smaller particles, predicts decreased CVD risk. Thus, extra-small and small HDLs may be key mediators and indicators of HDL's cardioprotective effects.

Crosstalk between high-density lipoproteins and endothelial cells in health and disease: Insights into sex-dependent modulation

Atherosclerotic cardiovascular disease is the leading cause of death worldwide. Intense research in vascular biology has advanced our knowledge of molecular mechanisms of its onset and progression until complications; however, several aspects of the patho-physiology of atherosclerosis remain to be further elucidated. Endothelial cell homeostasis is fundamental to prevent atherosclerosis as the appearance of endothelial cell dysfunction is considered the first pro-atherosclerotic vascular modification. Physiologically, high density lipoproteins (HDLs) exert protective actions for vessels and in particular for ECs. Indeed, HDLs promote endothelial-dependent vasorelaxation, contribute to the regulation of vascular lipid metabolism, and have immune-modulatory, anti-inflammatory and anti-oxidative properties. Sex- and gender-dependent differences are increasingly recognized as important, although not fully elucidated, factors in cardiovascular health and disease patho-physiology. In this review, we highlight the importance of sex hormones and sex-specific gene expression in the regulation of HDL and EC cross-talk and their contribution to cardiovascular disease.

Lipoprotein Proteomics and Aortic Valve Transcriptomics Identify Biological Pathways Linking Lipoprotein(a) Levels to Aortic Stenosis

Lipoprotein(a) (Lp(a)) is one of the most important risk factors for the development of calcific aortic valve stenosis (CAVS). However, the mechanisms through which Lp(a) causes CAVS are currently unknown. Our objectives were to characterize the Lp(a) proteome and to identify proteins that may be differentially associated with Lp(a) in patients with versus without CAVS. Our second objective was to identify genes that may be differentially regulated by exposure to high versus low Lp(a) levels in explanted aortic valves from patients with CAVS. We isolated Lp(a) from the blood of 21 patients with CAVS and 22 volunteers and performed untargeted label-free analysis of the Lp(a) proteome. We also investigated the transcriptomic signature of calcified aortic valves from patients who underwent aortic valve replacement with high versus low Lp(a) levels (n = 118). Proteins involved in the protein activation cascade, platelet degranulation, leukocyte migration, and response to wounding may be associated with Lp(a) depending on CAVS status. The transcriptomic analysis identified genes involved in cardiac aging, chondrocyte development, and inflammation as potentially influenced by Lp(a). Our multi-omic analyses identified biological pathways through which Lp(a) may cause CAVS, as well as key molecular events that could be triggered by Lp(a) in CAVS development.

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.

Effects of 9,10-phenanthrenequione on antioxidant indices and metabolite profiles in Takifugu obscurus plasma

Derived from polycyclic aromatic hydrocarbons (PAHs), oxygenated-PAHs (oxy-PAHs) may pose hazards to aquatic organisms, which remain largely unknown. Takifugu obscurus is an important anadromous fish species of high economic and ecological values. In the present study, T. obscurus was acutely exposed to 44.29 µg l-1 9,10-phenanthrenequione (9,10-PQ) for 96 h. Changes of antioxidant indices and metabolite profiles in plasma were compared between 9,10-PQ treatment and the control. The results showed that 9,10-PQ treatment significantly increased malondialdehyde (MDA) content during 6 to 96 h, increased superoxide dismutase (SOD) and catalase (CAT) activities at 6 h, but decreased them at 96 h. These results indicated that 9,10-PQ induced oxidative stress to fish. Ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) analysis revealed that four metabolic pathways were influenced in response to treatment with 9,10-PQ, including glycerophospholipid metabolism, phenylalanine, tyrosine and tryptophan biosynthesis, purine metabolism and sulfur metabolism. These pathways are associated with antioxidant mechanisms, biosynthesis of neurotransmitters and innate immune functions. Thus, the as-obtained results confirmed that 9,10-PQ induced oxidative stress and raised concerns of neurotoxicity and immunotoxicity to fish. Overall, the present study posed a high environmental risk of oxy-PAHs to aquatic ecosystems.

The association between lecithin-cholesterol acyltransferase activity and fatty liver index

Background

Non-alcoholic fatty liver disease is a frequent ailment with known complications, including those within the cardiovascular system. Associations between several indicators of high-density lipoprotein metabolism and function with clinical and laboratory parameters for the assessment of fatty liver index, a surrogate marker of non-alcoholic fatty liver disease, were evaluated.

Methods

The study comprised 130 patients classified according to fatty liver index values: fatty liver index < 30, fatty liver index 30–59 (the intermediate group) and fatty liver index ⩾ 60. Lecithin–cholesterol acyltransferase and cholesteryl ester transfer protein activities were determined. Paraoxonase 1 concentration and its activity, paraoxonase 3 concentration and high-density lipoprotein subclass distribution were assessed.

Results

Increased lecithin–cholesterol acyltransferase activity correlated with increased fatty liver index ( P < 0.001). Paraoxonase 3 concentration was lower in the fatty liver index ⩾ 60 group compared with the fatty liver index < 30 group ( P < 0.05). Cholesteryl ester transfer protein activity, paraoxonase 1 concentration and its activity did not significantly differ across the fatty liver index groups. The relative proportion of small-sized high-density lipoprotein 3 subclass was higher in the fatty liver index ⩾ 60 group compared with the other two fatty liver index groups ( P < 0.01). Lecithin–cholesterol acyltransferase activity positively associated with the fatty liver index ⩾ 60 group and remained significant after adjustment for other potential confounders. Only the triglyceride concentration remained significantly associated with lecithin–cholesterol acyltransferase activity when the parameters that constitute the fatty liver index equation were examined.

Conclusions

Higher lecithin–cholesterol acyltransferase activity is associated with elevated fatty liver index values. Significant independent association between triglycerides and lecithin–cholesterol acyltransferase activity might indicate a role of hypertriglyceridaemia in alterations of lecithin–cholesterol acyltransferase activity in individuals with elevated fatty liver index.

Lipid trafficking in cardiovascular disease

The reduction of plasma apolipoprotein B (apoB) containing lipoproteins has long been pursued as the main modifiable risk factor for the development of cardiovascular disease (CVD). This has led to an intense search for strategies aiming at reducing plasma apoB-lipoproteins, culminating in reduction of overall CV risk. Despite 3 decades of progress, CVD remains the leading cause of morbidity and mortality worldwide and, as such, new therapeutic targets are still warranted. Clinical and preclinical research has moved forward from the original concept, under which some lipids must be accumulated and other removed to achieve the ideal condition in disease prevention, into the concept that mechanisms that orchestrate lipid movement between lipoproteins, cells and organelles is equally involved in CVD. As such, this review scrutinizes potentially atherogenic changes in lipid trafficking and assesses the molecular mechanisms behind it. New developments in risk assessment and new targets for the mitigation of residual CVD risk are also addressed.

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.

Allele-specific enhancers mediate associations between LCAT and ABCA1 polymorphisms and HDL metabolism

For most complex traits, the majority of SNPs identified through genome-wide association studies (GWAS) reside within noncoding regions that have no known function. However, these regions are enriched for the regulatory enhancers specific to the cells relevant to the specific trait. Indeed, many of the GWAS loci that have been functionally characterized lie within enhancers that regulate expression levels of key genes. In order to identify polymorphisms with potential allele-specific regulatory effects, we developed a bioinformatics pipeline that harnesses epigenetic signatures as well as transcription factor (TF) binding motifs to identify putative enhancers containing a SNP with potential allele-specific TF binding in linkage disequilibrium (LD) with a GWAS-identified SNP. We applied the approach to GWAS findings for blood lipids, revealing 7 putative enhancers harboring associated SNPs, 3 of which lie within the introns of LCAT and ABCA1, genes that play crucial roles in cholesterol biogenesis and lipoprotein metabolism. All 3 enhancers demonstrated allele-specific in vitro regulatory activity in liver-derived cell lines. We demonstrated that these putative enhancers are in close physical proximity to the promoters of their respective genes, in situ, likely through chromatin looping. In addition, the associated alleles altered the likelihood of transcription activator STAT3 binding. Our results demonstrate that through our approach, the LD blocks that contain GWAS signals, often hundreds of kilobases in size with multiple SNPs serving as statistical proxies to the true functional site, can provide an experimentally testable hypothesis for the underlying regulatory mechanism linking genetic variants to complex traits.

Association between vegetarian diets and cardiovascular risk factors in non-Hispanic white participants of the Adventist Health Study-2

The association between dietary patterns and CVD risk factors among non-Hispanic whites has not been fully studied. Data from 650 non-Hispanic white adults who participated in one of two clinical sub-studies (about 2 years after the baseline) of the Adventist Health Study-2 (AHS-2) were analysed. Four dietary patters were identified using a validated 204-item semi-quantitative FFQ completed at enrolment into AHS-2: vegans (8·3 %), lacto-ovo-vegetarians (44·3 %), pesco-vegetarians (10·6 %) and non-vegetarians (NV) (37·3 %). Dietary pattern-specific prevalence ratios (PR) of CVD risk factors were assessed adjusting for confounders with or without BMI as an additional covariable. The adjusted PR for hypertension, high total cholesterol and high LDL-cholesterol were lower in all three vegetarian groups. Among the lacto-ovo-vegetarians the PR were 0·57 (95 % CI 0·45, 0·73), 0·72 (95 % CI 0·59, 0·88) and 0·72 (95 % CI 0·58, 0·89), respectively, which remained significant after additionally adjusting for BMI. The vegans and the pesco-vegetarians had similar PR for hypertension at 0·46 (95 % CI 0·25, 0·83) and 0·62 (95 % CI 0·42, 0·91), respectively, but estimates were attenuated and marginally significant after adjustment for BMI. Compared with NV, the PR of obesity and abdominal adiposity, as well as other CVD risk factors, were significantly lower among the vegetarian groups. Similar results were found when limiting analyses to participants not being treated for CVD risk factors, with the vegans having the lowest mean BMI and waist circumference. Thus, compared with the diet of NV, vegetarian diets were associated with significantly lower levels of CVD risk factors among the non-Hispanic whites.

Metabonomics Study on the Hepatoprotective Effect of Panax notoginseng Leaf Saponins Using UPLC/Q-TOF-MS Analysis

Alcohol liver disease is a major public health problem associated with lifestyle. Our recent study demonstrated that the roots of Panax notoginseng saponins (PNS) exert hepatoprotective effects against alcohol consumption. Considering that the leaves of Panax notoginseng saponins (LPNS) have similar chemical ingredients with PNS, increased attention should be given to the hepatoprotective effects of LPNS. In this study, a metabonomic approach based on ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-QTOF/MS) was developed to evaluate the hepatoprotective effect of LPNS on alcoholic fatty liver and elucidate the interaction mechanisms. Results showed that the ethanol-induced metabolic perturbations were restored after treatment with LPNS. Furthermore, 12 potential biomarkers (11 upregulated and 1 downregulated) were identified by V-plot and orthogonal partial least square discriminant analysis. Changes in the levels of these metabolites indicated that glycerophospholipid and fatty acid metabolism were disturbed in alcoholic fatty liver mouse. Our findings demonstrated that the UHPLC–QTOF/MS-based metabonomic method may provide a useful means for exploring biomarkers involved in alcoholic fatty liver and elucidating the therapeutic effects of LPNS. This work also showed that the metabonomic approach is a powerful and promising tool for the evaluation of the efficacy of traditional Chinese medicine and elucidation of related mechanisms.

Cholesterol is Inefficiently Converted to Cholesteryl Esters in the Blood of Cardiovascular Disease Patients

Shotgun lipidomic analysis of 203 lipids in 13 lipid classes performed on blood plasma of donors who had just suffered an acute coronary syndrome (ACS, n = 74), or an ischemic stroke (IS, n = 21), or who suffer from stable angina pectoris (SAP, n = 78), and an age-matched control cohort (n = 52), showed some of the highest inter-lipid class correlations between cholesteryl esters (CE) and phosphatidylcholines (PC) sharing a common fatty acid. The concentration of lysophospatidylcholine (LPC) and ratios of concentrations of CE to free cholesterol (Chol) were also lower in the CVD cohorts than in the control cohort, indicating a deficient conversion of Chol to CE in the blood plasma in the CVD subjects. A non-equilibrium reaction quotient, Q′, describing the global homeostasis of cholesterol as manifested in the blood plasma was shown to have a value in the CVD cohorts (Q′_ACS = 0.217 ± 0.084; Q′_IS = 0.201 ± 0.084; Q′_SAP = 0.220 ± 0.071) that was about one third less than in the control cohort (Q′_Control = 0.320 ± 0.095, p < 1 × 10⁻⁴), suggesting its potential use as a rapid predictive/diagnostic measure of CVD-related irregularities in cholesterol homeostasis.

Plasma lecithin:cholesterol acyltransferase and phospholipid transfer protein activity independently associate with nonalcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a highly prevalent condition which contributes to atherogenic apolipoprotein B dyslipoproteinemias. Lecithin:cholesterol acyltransferase (LCAT) and phospholipid transfer protein (PLTP) are both synthesized by the liver and are important in lipid metabolism. Here, we interrogated the impact of NAFLD on plasma LCAT and PLTP activities.

METHODS

Plasma LCAT activity (exogenous substrate assay) and PLTP activity (phospholipid vesicles-HDL assay) were determined in 348 subjects (279 men; 81 subjects with type 2 diabetes (T2DM); 123 with metabolic syndrome (MetS)). A Fatty Liver Index (FLI) ≥60 was used as a proxy of NAFLD. Insulin resistance was determined by homoeostasis model assessment (HOMA-IR).

RESULTS

A total of 147 participants had an FLI ≥60 coinciding with T2DM and MetS (P < 0.001 for each). Plasma LCAT activity and PLTP activity were on average 12% and 5% higher, respectively, in subjects with an FLI ≥ 60 (P < 0.001 for each). In age- and sex-adjusted partial linear regression analysis, LCAT activity and PLTP activity were positively related to various obesity measures and HOMA-IR (P < 0.001 for each). In multivariable linear regression analyses adjusted for age and sex, LCAT activity was associated with an FLI ≥ 60 independent of T2DM and MetS, the waist/hip ratio, or HOMA-IR (β = 0.307 to 0.366, P < 0001 for all models). PLTP activity was also associated with an FLI ≥ 60 independent of these variables (β = 0.151 to 0223, P = 0.013 to 0.001).

CONCLUSION

NAFLD, as inferred from an FLI≥60, confers higher plasma LCAT and to a lesser extent PLTP activity, even when taking account of T2DM, MetS, central obesity and insulin resistance.

Lipidomic signature of serum from the rats exposed to alcohol for one year

Alcohol abuse and its related diseases are the major risk factors for human health. Although the mechanism of alcohol-related disorders has been widely investigated, serum metabolites associated with long-term alcohol intake have not been well explored. In this study, we aimed to investigate the profiles of serum metabolites and lipid species of rats chronically exposed to alcohol, which may be involved in the pathogenesis of alcohol-associated disease. An ¹H NMR-based metabolomics and Q-TOF/MS-based lipidomics approach were applied to investigate the profile of serum metabolites and lipid species of rats administrated daily with alcohol (12% vol/vol, 10 ml/kg per day, i.g.) for one year continuously. The rats administered with sterile water (10 ml/kg per day, i.g.) were used as control. We found that alcohol affected mostly the lipid species rather than small molecule metabolites in the serum of both female and male rats. Among the modified lipids, glycerophospholipid, sphingolipid and glycerolipids metabolism pathways were profoundly altered. The prominent changes in lipid profiles included diacylglycerol (DG), lysophosphatidylcholine (LysoPC), phosphatidic acid (PA), phosphatidylcholine (PC), phosphatidylethanolamine (PE) and triacylglycerol (TG). Moreover, fatty-acyl profile of lipids and total degree of unsaturation of fatty acid were also significantly altered by alcohol. The modified lipidomic profile may help to understand the pathogenesis of alcohol-associated diseases and also be of value for clinical evaluation of alcohol abuse, alcohol-associated disease diagnosis.

HDL Cholesterol Metabolism and the Risk of CHD: New Insights from Human Genetics

PURPOSE OF REVIEW

Elevated high-density lipoprotein cholesterol levels in the blood (HDL-C) represent one of the strongest epidemiological surrogates for protection against coronary heart disease (CHD), but recent human genetic and pharmacological intervention studies have raised controversy about the causality of this relationship. Here, we review recent discoveries from human genome studies using new analytic tools as well as relevant animal studies that have both addressed, and in some cases, fueled this controversy.

RECENT FINDINGS

Methodologic developments in genotyping and sequencing, such as genome-wide association studies (GWAS), exome sequencing, and exome array genotyping, have been applied to the study of HDL-C and risk of CHD in large, multi-ethnic populations. Some of these efforts focused on population-wide variation in common variants have uncovered new polymorphisms at novel loci associated with HDL-C and, in some cases, CHD risk. Other efforts have discovered loss-of-function variants for the first time in genes previously implicated in HDL metabolism through common variant studies or animal models. These studies have allowed the genetic relationship between these pathways, HDL-C and CHD to be explored in humans for the first time through analysis tools such as Mendelian randomization. We explore these discoveries for selected key HDL-C genes CETP, LCAT, LIPG, SCARB1, and novel loci implicated from GWAS including GALNT2, KLF14, and TTC39B. Recent human genetics findings have identified new nodes regulating HDL metabolism while reshaping our current understanding of known candidate genes to HDL and CHD risk through the study of critical variants across model systems. Despite their effect on HDL-C, variants in many of the reviewed genes were found to lack any association with CHD. These data collectively indicate that HDL-C concentration, which represents a static picture of a very dynamic and heterogeneous metabolic milieu, is unlikely to be itself causally protective against CHD. In this context, human genetics represent an extremely valuable tool to further explore the biological mechanisms regulating HDL metabolism and investigate what role, if any, HDL plays in the pathogenesis of CHD.

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.

HDL Cholesterol Efflux Capacity: Cardiovascular Risk Factor and Potential Therapeutic Target

Low high-density lipoprotein cholesterol (HDL-C) levels are associated with incident cardiovascular events; however, many therapies targeting increases in HDL-C have failed to show consistent clinical benefit. Thus, focus has recently shifted toward measuring high-density lipoprotein (HDL) function. HDL is the key mediator of reverse cholesterol transport, the process of cholesterol extraction from foam cells, and eventual excretion into the biliary system. Cholesterol efflux from peripheral macrophages to HDL particles has been associated with atherosclerosis in both animals and humans. We review the mechanism of cholesterol efflux and the emerging evidence on the association between cholesterol efflux capacity and cardiovascular disease in human studies. We also focus on the completed and ongoing trials of novel therapies targeting different aspects of HDL cholesterol efflux.

High-Density Lipoprotein, Lecithin: Cholesterol Acyltransferase, and Atherosclerosis

Epidemiological data clearly show the existence of a strong inverse correlation between plasma high-density lipoprotein cholesterol (HDL-C) concentrations and the incidence of coronary heart disease. This relation is explained by a number of atheroprotective properties of HDL, first of all the ability to promote macrophage cholesterol transport. HDL are highly heterogeneous and are continuously remodeled in plasma thanks to the action of a number of proteins and enzymes. Among them, lecithin:cholesterol acyltransferase (LCAT) plays a crucial role, being the only enzyme able to esterify cholesterol within lipoproteins. LCAT is synthetized by the liver and it has been thought to play a major role in reverse cholesterol transport and in atheroprotection. However, data from animal studies, as well as human studies, have shown contradictory results. Increased LCAT concentrations are associated with increased HDL-C levels but not necessarily with atheroprotection. On the other side, decreased LCAT concentration and activity are associated with decreased HDL-C levels but not with increased atherosclerosis. These contradictory results confirm that HDL-C levels per se do not represent the functionality of the HDL system.

Serum- and HDL3-serum amyloid A and HDL3-LCAT activity are influenced by increased CVD-burden

BACKGROUND

High density lipoproteins (HDL) protect against cardiovascular disease (CVD). However, increased serum amyloid-A (SAA) related inflammation may negate this property. This study investigated if SAA was related to CVD-burden.

METHODS

Subjects referred to the rapid chest pain clinic (n = 240) had atherosclerotic burden assessed by cardiac computerised tomography angiography. Subjects were classified as: no-CVD (n = 106), non-obstructive-CVD, stenosis<50% (n = 58) or moderate/significant-CVD, stenosis ≥50% (n = 76). HDL was subfractionated into HDL2 and HDL3 by rapid-ultracentrifugation. SAA-concentration was measured by ELISA and lecithin cholesterol acyltransferase (LCAT) activity measured by a fluorimetric assay.

RESULTS

We illustrated that serum-SAA and HDL3-SAA-concentration were higher and HDL3-LCAT-activity lower in the moderate/significant-CVD-group, compared to the no-CVD and non-obstructive-CVD-groups (percent differences: serum-SAA, +33% & +30%: HDL3-SAA, +65% and +39%: HDL3-LCAT, -6% & -3%; p < 0.05 for all comparisons). We also identified a positive correlation between serum-SAA and HDL3-SAA (r = 0.698; p < 0.001) and a negative correlation between HDL3-SAA and HDL3-LCAT-activity (r = -0.295; p = 0.003), while CVD-burden positively correlated with serum-SAA (r = 0.150; p < 0.05) and HDL3-SAA (r = 0.252; p < 0.001) and negatively correlated with HDL3-LCAT-activity (r = -0.182; p = 0.006). Additionally, multivariate regression analysis adjusted for age, gender, CRP and serum-SAA illustrated that HDL3-SAA was significantly associated with modifying CVD-risk of moderate/significant CVD-risk (p < 0.05).

CONCLUSION

This study has demonstrated increased SAA-related inflammation in subjects with moderate/significant CVD-burden, which appeared to impact on the antiatherogenic potential of HDL. We suggest that SAA may be a useful biomarker to illustrate increased CVD-burden, although this requires further investigation.

Agonistic Human Antibodies Binding to Lecithin-Cholesterol Acyltransferase Modulate High Density Lipoprotein Metabolism

Drug discovery opportunities where loss-of-function alleles of a target gene link to a disease-relevant phenotype often require an agonism approach to up-regulate or re-establish the activity of the target gene. Antibody therapy is increasingly recognized as a favored drug modality due to multiple desirable pharmacological properties. However, agonistic antibodies that enhance the activities of the target enzymes are rarely developed because the discovery of agonistic antibodies remains elusive. Here we report an innovative scheme of discovery and characterization of human antibodies capable of binding to and agonizing a circulating enzyme lecithin cholesterol acyltransferase (LCAT). Utilizing a modified human LCAT protein with enhanced enzymatic activity as an immunogen, we generated fully human monoclonal antibodies using the XenoMouse^TM platform. One of the resultant agonistic antibodies, 27C3, binds to and substantially enhances the activity of LCAT from humans and cynomolgus macaques. X-ray crystallographic analysis of the 2.45 Å LCAT-27C3 complex shows that 27C3 binding does not induce notable structural changes in LCAT. A single administration of 27C3 to cynomolgus monkeys led to a rapid increase of plasma LCAT enzymatic activity and a 35% increase of the high density lipoprotein cholesterol that was observed up to 32 days after 27C3 administration. Thus, this novel scheme of immunization in conjunction with high throughput screening may represent an effective strategy for discovering agonistic antibodies against other enzyme targets. 27C3 and other agonistic human anti-human LCAT monoclonal antibodies described herein hold potential for therapeutic development for the treatment of dyslipidemia and cardiovascular disease.

A novel protein glycan biomarker and LCAT activity in metabolic syndrome

BACKGROUND

The cholesterol-esterifying enzyme, lecithin:cholesterol acyltransferase (LCAT), is instrumental in high-density lipoprotein (HDL) remodelling. LCAT may also modify oxidative and inflammatory processes, as supported by an inverse relationship with HDL antioxidative functionality and a positive relationship with high-sensitivity C-reactive protein (hsCRP). GlycA is a recently developed proton nuclear magnetic resonance (NMR) spectroscopy-measured biomarker of inflammation whose signal originates from a subset of N-acetylglucosamine residues on the most abundant glycosylated acute-phase proteins. Plasma GlycA correlates positively with hsCRP and may predict cardiovascular disease even independent of hsCRP. Here, we tested the extent to which plasma GlycA is elevated in metabolic syndrome (MetS), and determined its relationship with LCAT activity.

MATERIALS AND METHODS

Plasma GlycA, hsCRP, serum amyloid A (SAA), tumour necrosis factor-α (TNF-α) and LCAT activity were measured in 58 subjects with MetS (including 46 subjects with type 2 diabetes mellitus (T2DM)) and in 45 nondiabetic subjects without MetS.

RESULTS

Plasma GlycA was higher in MetS coinciding with higher hsCRP and LCAT activity (P < 0.01 for each). In all subjects combined, GlycA was correlated positively with hsCRP, SAA and LCAT activity (P < 0.001 for each), but not with TNF-α. Age- and sex-adjusted multivariable linear regression analysis revealed that GlycA was positively associated with LCAT activity (P = 0.029), independent of the presence of MetS, T2DM, hsCRP and SAA. GlycA was unrelated to diabetes status.

CONCLUSION

A pro-inflammatory glycoprotein biomarker, GlycA, is higher in MetS. Higher plasma levels of this glycoprotein biomarker relate to increased LCAT activity in the setting of MetS.

Association of lecithin-cholesterol acyltransferase activity measured as a serum cholesterol esterification rate and low-density lipoprotein heterogeneity with cardiovascular risk: a cross-sectional study

The cholesterol-esterifying enzyme, lecithin-cholesterol acyltransferase (LCAT), is believed to play a key role in reverse cholesterol transport. However, recent investigations have demonstrated that higher LCAT activity levels increase the formation of triglyceride (TG)-rich lipoproteins (TRLs) and atherogenesis. We hypothesized that higher LCAT activity measured as a serum cholesterol esterification rate by the endogenous substrate method might increase the formation of TRLs and thereby alter low-density lipoprotein (LDL) heterogeneity. The estimated LDL particle size [relative LDL migration (LDL-Rm)] was measured by polyacrylamide gel electrophoresis with the LipoPhor system (Joko, Tokyo, Japan) in 538 consecutive patients with at least risk factor for atherosclerosis. Multivariate regression analysis after adjustments for traditional risk factors identified elevated TRL-related marker (TG, remnant-like particle cholesterol, apolipoprotein C-II, and apolipoprotein C-III) levels as independent predictors of smaller-sized LDL particle size, both in the overall subject population and in the subset of patients with serum LDL cholesterol levels of <100 mg/dL. Area under the receiver operating characteristic curve of the LCAT activity (0.79; sensitivity 60 %; specificity 84.8 %) was observed for the evaluation of the indicators of an LDL-Rm value of ≥0.40, which suggests the presence of large amounts of small-dense LDL. The results lend support to the hypothesis that increased LCAT activity may be associated with increased formation of TRLs, leading to a reduction in LDL particle size. Therefore, to reduce the risk of atherosclerotic cardiovascular disease, it may be of importance to pay attention not only to a quantitative change in the serum LDL-C, but also to the LCAT activity which is possibly associated with LDL heterogeneity.

Effects of Pu-erh tea aqueous extract (PTAE) on blood lipid metabolism enzymes

Effects of Pu-erh tea aqueous extract (PTAE) on blood lipid metabolism enzymes (e.g.HMGR) are assayedin vitro.

Adrenal Function in females with low plasma HDL-C due to mutations in ABCA1 and LCAT

INTRODUCTION

Adrenal steroidogenesis is essential for human survival and depends on the availability of the precursor cholesterol. Male subjects with low plasma levels of high density lipoprotein (HDL) cholesterol are characterized by decreased adrenal function. Whether this is also the case in female subjects with low plasma HDL-C levels is unresolved to date.

FINDINGS

15 female ATP binding cassette transporter AI (ABCAI) and 14 female lecithin-cholesterol acyltransferase (LCAT) were included in the study. HDL-C levels were 38% and 41% lower in ABCA1 and LCAT mutation carriers compared to controls, respectively. Urinary steroid excretion of 17-ketogenic steroids or 17-hydroxy corticosteroids did not differ between 15 female ABCA1 mutation carriers (p = 0.27 vs 0.30 respectively) and 30 matched normolipidemic controls or between 14 female LCAT mutation carriers and 28 matched normolipidemic controls (p = 0.10 and 0.14, respectively). Cosyntropin testing in an unselected subgroup of 8 ABCA1 mutation carriers and 3 LCAT mutation carriers did not reveal differences between carriers and controls.

CONCLUSION

Adrenal function in females with molecularly defined low HDL-C levels is not different from controls. The discrepancy with the finding of impaired steroidogenesis in males with molecularly defined low HDL-C levels underscores the importance of gender specific analyses in cholesterol-related research.

Alterations in plasma lecithin:cholesterol acyltransferase and myeloperoxidase in acute myocardial infarction: implications for cardiac outcome

BACKGROUND

The cholesterol esterifying enzyme, lecithin:cholesterol acyltransferase (LCAT), plays a key role in HDL maturation and remodeling. Myeloperoxidase (MPO) may compromise LCAT enzymatic activity. We tested the extent to which plasma LCAT activity is altered in acute myocardial infarction (MI) in conjunction with abnormal MPO levels. We also assessed the impact of LCAT and MPO on newly developed major adverse cardiovascular events (MACE).

METHODS

Two-hundred one consecutive patients referred for acute chest pain of whom 134 had MI (95 with ST-elevation) participated. Forty-five new MACE were ascertained during 1203 (range 13-1745) days of follow-up among 185 patients. Plasma LCAT activity was measured using an exogenous substrate assay. MPO mass was assayed by chemiluminescent microparticle immunoassay.

RESULTS

Plasma LCAT activity was decreased by 15%, coinciding with 7-fold increased MPO levels in acute MI patients vs. patients with non-cardiac chest pain (p < 0.001 for both; correlation: r = -0.343, p < 0.001). MI at admission was associated independently with both lower plasma LCAT activity and higher MPO (age- and sex-adjusted odds ratio per 1 SD increment: 0.46 (95% CI, 0.31-0.68), p < 0.001 and 7.58 (95% CI, 3.34-17.11), p < 0.001, respectively). In an analysis with LCAT and MPO together these associations were modestly attenuated. MPO mass (hazard ratio: 1.59 (95% CI, 1.15-2.19), p = 0.004), but not LCAT activity (hazard ratio: 0.87 (95% CI, 0.65-1.19), p = 0.39), predicted newly manifest MACE.

CONCLUSION

In acute MI patients, plasma LCAT activity is decreased coinciding with increased MPO levels. Higher MPO but not lower LCAT activity prospectively predicts adverse cardiac outcome.

Alcohol-induced metabolomic differences in humans

Alcohol consumption is one of the world's major risk factors for disease development. But underlying mechanisms by which moderate-to-heavy alcohol intake causes damage are poorly understood and biomarkers are sub-optimal. Here, we investigated metabolite concentration differences in relation to alcohol intake in 2090 individuals of the KORA F4 and replicated results in 261 KORA F3 and up to 629 females of the TwinsUK adult bioresource. Using logistic regression analysis adjusted for age, body mass index, smoking, high-density lipoproteins and triglycerides, we identified 40/18 significant metabolites in males/females with P-values <3.8E-04 (Bonferroni corrected) that differed in concentrations between moderate-to-heavy drinkers (MHD) and light drinkers (LD) in the KORA F4 study. We further identified specific profiles of the 10/5 metabolites in males/females that clearly separated LD from MHD in the KORA F4 cohort. For those metabolites, the respective area under the receiver operating characteristic curves were 0.812/0.679, respectively, thus providing moderate-to-high sensitivity and specificity for the discrimination of LD to MHD. A number of alcohol-related metabolites could be replicated in the KORA F3 and TwinsUK studies. Our data suggests that metabolomic profiles based on diacylphosphatidylcholines, lysophosphatidylcholines, ether lipids and sphingolipids form a new class of biomarkers for excess alcohol intake and have potential for future epidemiological and clinical studies.

Lecithin:cholesterol acyltransferase: old friend or foe in atherosclerosis?

Lecithin:cholesterol acyltransferase (LCAT) is a key enzyme that catalyzes the esterification of free cholesterol in plasma lipoproteins and plays a critical role in high-density lipoprotein (HDL) metabolism. Deficiency leads to accumulation of nascent preβ-HDL due to impaired maturation of HDL particles, whereas enhanced expression is associated with the formation of large, apoE-rich HDL(1) particles. In addition to its function in HDL metabolism, LCAT was believed to be an important driving force behind macrophage reverse cholesterol transport (RCT) and, therefore, has been a subject of great interest in cardiovascular research since its discovery in 1962. Although half a century has passed, the importance of LCAT for atheroprotection is still under intense debate. This review provides a comprehensive overview of the insights that have been gained in the past 50 years on the biochemistry of LCAT, the role of LCAT in lipoprotein metabolism and the pathogenesis of atherosclerosis in animal models, and its impact on cardiovascular disease in humans.

HDL dysfunction in diabetes: causes and possible treatments

HDL is known to be inversely correlated with cardiovascular disease due to its diverse antiatherogenic functions. These functions include cholesterol efflux and reverse cholesterol transport, antioxidative and anti-inflammatory activities. However, HDL has been shown to undergo a loss of function in several pathophysiological states, as in the acute phase response, obesity and chronic inflammatory diseases. Some of these diseases were also shown to be associated with increased risk for cardiovascular disease. One such disease that is associated with HDL dysfunction and accelerated atherosclerosis is diabetes mellitus, a disease in which the HDL particle undergoes diverse structural modifications that result in significant changes in its function. This review will summarize the changes that occur in HDL in diabetes mellitus and how these changes lead to HDL dysfunction. Possible treatments for HDL dysfunction are also briefly described.

Increased LCAT activity and hyperglycaemia decrease the antioxidative functionality of HDL

BACKGROUND

Type 2 diabetes mellitus increases the risk of atherosclerotic cardiovascular disease. Antioxidative properties of high density lipoprotein (HDL) are important for atheroprotection. This study investigated whether the antioxidative functionality of HDL is altered in type 2 diabetes mellitus and aimed to identify potential determinants of this parameter.

MATERIALS AND METHODS

In a cross-sectional study, we investigated 74 patients with type 2 diabetes and 75 control subjects. Antioxidative properties of HDL were measured and expressed as either (i) HDL antioxidative capacity or (ii) HDL antioxidation index after multiplying HDL antioxidative capacity results with individual plasma HDL cholesterol concentrations. Lecithin:cholesterol acyltransferase (LCAT) and paraoxonase-1 (PON-1) activities were determined.

RESULTS

HDL antioxidative capacity was similar in patients with diabetes and controls, while the HDL antioxidation index was decreased in patients with diabetes (P = 0.005) owing to lower plasma HDL cholesterol (P < 0.001). LCAT activity was higher and PON-1 activity lower in type 2 diabetes mellitus (each P < 0.001). In the combined subjects, HDL antioxidative capacity was inversely related to LCAT activity (P < 0.01). The HDL antioxidation index correlated negatively with blood glucose (P < 0.001), HbA1c and LCAT activity (each P < 0.01), and positively with PON-1 activity (P < 0.01). Multiple linear regression analysis demonstrated that high LCAT activity was associated with both decreased HDL antioxidation capacity (P < 0.05) and index (P < 0.001) independent of diabetes status, glycaemic control and PON-1.

CONCLUSIONS

Overall, the antioxidative functionality of HDL is impaired in type 2 diabetes mellitus mostly because of lower HDL cholesterol. Hyperglycaemia, increased LCAT activity and lower PON-1 activity likely contribute to impaired antioxidative functionality of HDL.

Hypolipidaemic effects and mechanisms of the main component of Opuntia dillenii Haw. polysaccharides in high-fat emulsion-induced hyperlipidaemic rats

The antihyperlipidaemic effects of ODP-Ia, one of the main components of Opuntia dillenii Haw. polysaccharides, were studied. Gavage administration of ODP-Ia was observed to significantly decrease serum lipid levels and to increase serum high-density lipoprotein cholesterol level in hyperlipidaemic rats. Similar suppressive patterns were also seen in hepatic total cholesterol and triglyceride levels. Moreover, the ODP-Ia administration significantly increased serum lecithin:cholesterol acyltransferase activity, increased the production of serum NO, inhibited hepatic HMG-CoA reductase activity, augmented serum and hepatic superoxide dismutase activities and decreased the serum and hepatic malondialdehyde contents in hyperlipidaemic rats. In addition, a histopathological examination revealed that ODP-Ia administration significantly suppressed inflammatory cell infiltration and the expression of VCAM-1. Together, these results indicate that ODP-Ia is a potential natural product for the treatment of hyperlipidaemia-related diseases by improving antioxidant levels, modulating the activities of enzymes involved in cholesterol metabolism, promoting the production of NO and suppressing the expression of VCAM-1, thereby suppressing lipid accumulation and inflammatory cell infiltration.

Carriers of lecithin cholesterol acyltransferase gene mutations have accelerated atherogenesis as assessed by carotid 3.0-T magnetic resonance imaging [corrected]

OBJECTIVES

The aim of this study was to investigate the role of reduced lecithin: cholesterol acyltransferase (LCAT) function on atherogenesis using 3.0-T carotid magnetic resonance imaging (MRI) and B-mode ultrasound.

BACKGROUND

The role of low high-density lipoprotein cholesterol as a causal factor in atherogenesis has recently been questioned. LCAT plays a key role in high-density lipoprotein cholesterol metabolism.

METHODS

Carotid 3.0-T MRI and B-mode ultrasound measurements were performed in 40 carriers of LCAT gene mutations and 40 controls, matched for age. Patients with cardiovascular disease were excluded.

RESULTS

Carriers had 31% lower LCAT activity levels and 38% decreased high-density lipoprotein cholesterol levels (both p < 0.001 vs. controls). Carriers presented with a 10% higher normalized wall index (0.34 ± 0.07 vs. 0.31 ± 0.04, p = 0.002), a 22% higher mean wall area (17.3 ± 8.5 mm(2) vs. 14.2 ± 4.1 mm(2), p = 0.01), and a 22% higher total wall volume (1,039 ± 508 mm(3) vs. 851 ± 247 mm(3), p = 0.01 vs. controls) as measured by MRI. The prevalence (20 vs. 5, p = 0.002) and the total volume (102 mm(3) vs. 3 mm(3)) of atherosclerotic plaque components on MRI relating to lipid-rich tissue or calcification were also higher in carriers than in controls. All differences retained significance after adjustment for age, sex, blood pressure, low-density lipoprotein cholesterol, body mass index, smoking, and family history of cardiovascular disease. Common carotid intima-media thickness measured with ultrasound was increased in carriers by 12.5% (0.72 ± 0.33 mm vs. 0.64 ± 0.15 mm, p = 0.14).

CONCLUSIONS

Carriers of LCAT gene mutations exhibit increased carotid atherosclerosis, indicating an increased risk of cardiovascular disease. The present findings imply that increasing LCAT activity may be an attractive target in cardiovascular prevention strategies.

The role of lecithin:cholesterol acyltransferase in the modulation of cardiometabolic risks - a clinical update and emerging insights from animal models

Lecithin cholesterol acyltransferase (LCAT) is the key enzyme in mediating the esterification of cholesterol on circulating lipoproteins. It has long been suggested that LCAT plays a crucial role in reverse cholesterol transport, a process depicting the removal of cellular cholesterol through efflux to high density lipoproteins (HDL) and its delivery to the liver for eventual excretion from the body. Although loss-of-function LCAT mutations invariably result in profound HDL deficiency, the role of LCAT in atherogenesis continues to be clouded with controversy. Increasing number of large scale, population-based studies failed to detect an elevated cardiac risk with reduced blood levels of LCAT, suggesting that reduced LCAT activity may not be a risk factor nor a therapeutic target. More recent studies in human LCAT gene mutation carriers tend to suggest that atherogenicity in LCAT deficiency may be dependent on the nature of the mutations, providing plausible explanations for the otherwise contradictory findings. Genetic models of LCAT excess or deficiency yielded mixed findings. Despite its known profound effects on HDL and triglyceride metabolism, the role of LCAT in metabolic disorders, including obesity and diabetes, has not received much attention. Recent studies in LCAT deficient mouse models suggest that absence of LCAT may protect against insulin resistance, diabetes and obesity. Coordinated modulation of a number of anti-obesity and insulin sensitizing pathways has been implicated. Further studies to explore the role of LCAT in the modulation of cardiometabolic disorders and the underlying mechanisms are warranted.

Plasma lecithin:cholesterol acyltransferase and carotid intima-media thickness in European individuals at high cardiovascular risk

Lecithin:cholesterol acyltransferase (LCAT) is the enzyme responsible for cholesterol esterification in plasma. LCAT is a major factor in HDL remodeling and metabolism, and it has long been believed to play a critical role in macrophage reverse cholesterol transport (RCT). The effect of LCAT on human atherogenesis is still controversial. In the present study, the plasma LCAT concentration was measured in all subjects (n = 540) not on drug treatment at the time of enrollment in the multicenter, longitudinal, observational IMPROVE study. Mean and maximum intima-media thickness (IMT) of the whole carotid tree was measured by B-mode ultrasonography in all subjects. In the entire cohort, LCAT quartiles were not associated with carotid mean and maximum IMT (P for trend 0.95 and 0.18, respectively), also after adjustment for age, gender, HDL-cholesterol (HDL-C), and triglycerides. No association between carotid IMT and LCAT quartiles was observed in men (P=0.30 and P=0.99 for mean and maximum IMT, respectively), whereas carotid IMT increased with LCAT quartiles in women (P for trend 0.14 and 0.019 for mean and maximum IMT, respectively). The present findings support the concept that LCAT is not required for an efficient reverse cholesterol transport and that a low plasma LCAT concentration and activity is not associated with increased atherosclerosis.

Novel HDL-directed pharmacotherapeutic strategies

The burden of atherothrombotic cardiovascular disease remains high despite currently available optimum medical therapy. To address this substantial residual risk, the development of novel therapies that attempt to harness the atheroprotective functions of HDL is a major goal. These functions include the critical role of HDL in reverse cholesterol transport, and its anti-inflammatory, antithrombotic, and antioxidant activities. Discoveries in the past decade have shed light on the complex metabolic and antiatherosclerotic pathways of HDL. These insights have fueled the development of HDL-targeted drugs, which can be classified among four different therapeutic approaches: directly augmenting apolipoprotein A-I (apo A-I) levels, such as with apo A-I infusions and upregulators of endogenous apo A-I production; indirectly augmenting apo A-I and HDL-cholesterol levels, such as through inhibition of cholesteryl ester transfer protein or endothelial lipase, or through activation of the high-affinity niacin receptor GPR109A; mimicking the functionality of apo A-I with apo A-I mimetic peptides; and enhancing steps in the reverse cholesterol transport pathway, such as via activation of the liver X receptor or of lecithin-cholesterol acyltransferase.