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

Gliflozins, sucrose and flavonoids are allosteric activators of lecithin-cholesterol acyltransferase

Lecithin-cholesterol acyltransferase (LCAT) serves as a pivotal enzyme in preserving cholesterol homeostasis via reverse cholesterol transport, a process closely associated with the onset of atherosclerosis. Impaired LCAT function can lead to severe LCAT deficiency disorders for which no pharmacological treatment exists. LCAT-based therapies, such as small molecule positive allosteric modulators (PAMs), against LCAT deficiencies and atherosclerosis hold promise, although their efficacy against atherosclerosis remains challenging. Herein we utilized a quantitative in silico metric to predict the activity of novel PAMs and tested their potencies with in vitro enzymatic assays. As predicted, sodium-glucose cotransporter 2 (SGLT2) inhibitors (gliflozins), sucrose and flavonoids activate LCAT. This has intriguing implications for the mechanism of action of gliflozins, which are commonly used in the treatment of type 2 diabetes, and for the endogenous activation of LCAT. Our results underscore the potential of molecular dynamics simulations in rational drug design.

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.

Longitudinal analysis of clinical and laboratory biomarkers in a patient with familial lecithin: cholesterol acyltransferase deficiency (FLD) and accelerated eGFR decline: A case study

Familial lecithin:cholesterol acyltransferase (LCAT) deficiency (FLD) is an ultra-rare autosomal recessive disease characterized by very low high-density lipoprotein cholesterol (HDL-C) levels, corneal opacity, anemia, and progressive renal disease. The rate and severity of renal disease are variable across FLD patients and the biomarkers and risk factors for disease progression are poorly understood. Here we report a 30 year-long comparative analysis of the clinical and laboratory biomarkers in an FLD patient with accelerated renal decline, who underwent two kidney and one liver transplantations. Results show that elevated triglyceride and non-HDL-C levels may promote the formation of LpX and accelerate renal function decline, whereas markers of anemia may be early predictors. Conversely, corneal opacity progresses at a steady rate and does not correlate with lipid, hematologic, or renal biomarkers. Our study suggests that monitoring of markers of anemia may aid the early detection and timely management of kidney disease with conservative therapies. Furthermore, it suggests that controlling hypercholesterolemia and hypertriglyceridemia may help improve renal disease prognosis.

Mechanisms modulating foam cell formation in the arterial intima: exploring new therapeutic opportunities in atherosclerosis

In recent years, the role of macrophages as the primary cell type contributing to foam cell formation and atheroma plaque development has been widely acknowledged. However, it has been long recognized that diffuse intimal thickening (DIM), which precedes the formation of early fatty streaks in humans, primarily consists of lipid-loaded smooth muscle cells (SMCs) and their secreted proteoglycans. Recent studies have further supported the notion that SMCs constitute the majority of foam cells in advanced atherosclerotic plaques. Given that SMCs are a major component of the vascular wall, they serve as a significant source of microvesicles and exosomes, which have the potential to regulate the physiology of other vascular cells. Notably, more than half of the foam cells present in atherosclerotic lesions are of SMC origin. In this review, we describe several mechanisms underlying the formation of intimal foam-like cells in atherosclerotic plaques. Based on these mechanisms, we discuss novel therapeutic approaches that have been developed to regulate the generation of intimal foam-like cells. These innovative strategies hold promise for improving the management of atherosclerosis in the near future.

Effects of Recombinant Human Lecithin Cholesterol Acyltransferase on Lipoprotein Metabolism in Humans

BACKGROUND

LCAT (lecithin cholesterol acyl transferase) catalyzes the conversion of unesterified, or free cholesterol, to cholesteryl ester, which moves from the surface of HDL (high-density lipoprotein) into the neutral lipid core. As this iterative process continues, nascent lipid-poor HDL is converted to a series of larger, spherical cholesteryl ester-enriched HDL particles that can be cleared by the liver in a process that has been termed reverse cholesterol transport.

METHODS

We conducted a randomized, placebocontrolled, crossover study in 5 volunteers with atherosclerotic cardiovascular disease, to examine the effects of an acute increase of recombinant human (rh) LCAT via intravenous administration (300-mg loading dose followed by 150 mg at 48 hours) on the in vivo metabolism of HDL APO (apolipoprotein)A1 and APOA2, and the APOB100-lipoproteins, very low density, intermediate density, and low-density lipoproteins.

RESULTS

As expected, recombinant human LCAT treatment significantly increased HDL-cholesterol (34.9 mg/dL; P≤0.001), and this was mostly due to the increase in cholesteryl ester content (33.0 mg/dL; P=0.014). This change did not affect the fractional clearance or production rates of HDL-APOA1 and HDL-APOA2. There were also no significant changes in the metabolism of APOB100-lipoproteins.

CONCLUSIONS

Our results suggest that an acute increase in LCAT activity drives greater flux of cholesteryl ester through the reverse cholesterol transport pathway without significantly altering the clearance and production of the main HDL proteins and without affecting the metabolism of APOB100-lipoproteins. Long-term elevations of LCAT might, therefore, have beneficial effects on total body cholesterol balance and atherogenesis.

Targeting host-specific metabolic pathways-opportunities and challenges for anti-infective therapy

Microorganisms can takeover critical metabolic pathways in host cells to fuel their replication. This interaction provides an opportunity to target host metabolic pathways, in addition to the pathogen-specific ones, in the development of antimicrobials. Host-directed therapy (HDT) is an emerging strategy of anti-infective therapy, which targets host cell metabolism utilized by facultative and obligate intracellular pathogens for entry, replication, egress or persistence of infected host cells. This review provides an overview of the host lipid metabolism and links it to the challenges in the development of HDTs for viral and bacterial infections, where pathogens are using important for the host lipid enzymes, or producing their own analogous of lecithin-cholesterol acyltransferase (LCAT) and lipoprotein lipase (LPL) thus interfering with the human host's lipid metabolism.

Understanding HDL Metabolism and Biology Through In Vivo Tracer Kinetics

HDL (high-density lipoprotein), owing to its high protein content and small size, is the densest circulating lipoprotein. In contrast to lipid-laden VLDL (very-low-density lipoprotein) and LDL (low-density lipoprotein) that promote atherosclerosis, HDL is hypothesized to mitigate atherosclerosis via reverse cholesterol transport, a process that entails the uptake and clearance of excess cholesterol from peripheral tissues. This process is mediated by APOA1 (apolipoprotein A-I), the primary structural protein of HDL, as well as by the activities of additional HDL proteins. Tracer-dependent kinetic studies are an invaluable tool to study HDL-mediated reverse cholesterol transport and overall HDL metabolism in humans when a cardiovascular disease therapy is investigated. Unfortunately, HDL cholesterol-raising therapies have not been successful at reducing cardiovascular events suggesting an incomplete picture of HDL biology. However, as HDL tracer studies have evolved from radioactive isotope- to stable isotope-based strategies that in turn are reliant on mass spectrometry technologies, the complexity of the HDL proteome and its metabolism can be more readily addressed. In this review, we outline the motivations, timelines, advantages, and disadvantages of the various tracer kinetics strategies. We also feature the metabolic properties of select HDL proteins known to regulate reverse cholesterol transport, which in turn underscore that HDL lipoproteins comprise a heterogeneous particle population whose distinct protein constituents and kinetics likely determine its function and potential contribution to cholesterol clearance.

Kidney lipid dysmetabolism and lipid droplet accumulation in chronic kidney disease

Chronic kidney disease (CKD) is a global health problem with rising incidence and prevalence. Among several pathogenetic mechanisms responsible for disease progression, lipid accumulation in the kidney parenchyma might drive inflammation and fibrosis, as has been described in fatty liver diseases. Lipids and their metabolites have several important structural and functional roles, as they are constituents of cell and organelle membranes, serve as signalling molecules and are used for energy production. However, although lipids can be stored in lipid droplets to maintain lipid homeostasis, lipid accumulation can become pathogenic. Understanding the mechanisms linking kidney parenchymal lipid accumulation to CKD of metabolic or non-metabolic origin is challenging, owing to the tremendous variety of lipid species and their functional diversity across different parenchymal cells. Nonetheless, multiple research reports have begun to emphasize the effect of dysregulated kidney lipid metabolism in CKD progression. For example, altered cholesterol and fatty acid metabolism contribute to glomerular and tubular cell injury. Newly developed lipid-targeting agents are being tested in clinical trials in CKD, raising expectations for further therapeutic development in this field.

Abnormal Lipoproteins Trigger Oxidative Stress-Mediated Apoptosis of Renal Cells in LCAT Deficiency

Familial lecithin:cholesterol acyltransferase (LCAT) deficiency (FLD) is a rare genetic disease caused by the loss of function mutations in the LCAT gene. LCAT deficiency is characterized by an abnormal lipoprotein profile with severe reduction in plasma levels of high-density lipoprotein (HDL) cholesterol and the accumulation of lipoprotein X (LpX). Renal failure is the major cause of morbidity and mortality in FLD patients; the pathogenesis of renal disease is only partly understood, but abnormalities in the lipoprotein profile could play a role in disease onset and progression. Serum and lipoprotein fractions from LCAT deficient carriers and controls were tested for renal toxicity on podocytes and tubular cells, and the underlying mechanisms were investigated at the cellular level. Both LpX and HDL from LCAT-deficient carriers triggered oxidative stress in renal cells, which culminated in cell apoptosis. These effects are partly explained by lipoprotein enrichment in unesterified cholesterol and ceramides, especially in the HDL fraction. Thus, alterations in lipoprotein composition could explain some of the nephrotoxic effects of LCAT deficient lipoproteins on podocytes and tubular cells.

HDL and chronic kidney disease

Low HDL-cholesterol (HDL-C) concentrations are a typical trait of the dyslipidemia associated with chronic kidney disease (CKD). In this condition, plasma HDLs are characterized by alterations in structure and function, and these particles can lose their atheroprotective functions, e.g., the ability to promote cholesterol efflux from peripheral cells, anti-oxidant and anti-inflammatory proprieties and they can even become dysfunctional, i.e., exactly damaging. The reduction in plasma HDL-C levels appears to be the only lipid alteration clearly linked to the progression of renal disease in CKD patients. The association between the HDL system and CKD development and progression is also supported by the presence of genetic kidney alterations linked to HDL metabolism, including mutations in the APOA1, APOE, APOL and LCAT genes. Among these, renal disease associated with LCAT deficiency is well characterized and lipid abnormalities detected in LCAT deficiency carriers mirror the ones observed in CKD patients, being present also in acquired LCAT deficiency. This review summarizes the major alterations in HDL structure and function in CKD and how genetic alterations in HDL metabolism can be linked to kidney dysfunction. Finally, the possibility of targeting the HDL system as possible strategy to slow CKD progression is reviewed.

Novel therapeutic opportunities for familial lecithin:cholesterol acyltransferase deficiency: promises and challenges

PURPOSE OF REVIEW

Genetic lecithin:cholesterol acyltransferase (LCAT) deficiency is a rare, inherited, recessive disease, which manifests as two different syndromes: Familial LCAT deficiency (FLD) and Fish-eye disease (FED), characterized by low HDL-C and corneal opacity. FLD patients also develop anaemia and renal disease. There is currently no therapy for FLD, but novel therapeutics are at different stages of development. Here, we summarize the most recent advances and the opportunities for and barriers to the further development of such therapies.

RECENT FINDINGS

Recent publications highlight the heterogeneous phenotype of FLD and the uncertainty over the natural history of disease and the factors contributing to disease progression. Therapies that restore LCAT function (protein and gene replacement therapies and LCAT activators) showed promising effects on markers of LCAT activity. Although they do not restore LCAT function, HDL mimetics may slow renal disease progression.

SUMMARY

The further development of novel therapeutics requires the identification of efficacy endpoints, which include quantitative biomarkers of disease progression. Because of the heterogeneity of renal disease progression among FLD individuals, future treatments for FLD will have to be tailored based on the specific clinical characteristics of the patient. Extensive studies of the natural history and biomarkers of the disease will be required to achieve this goal.

Sphingolipidomic profile and HDL subfractions in obese dyslipidemic type 2 diabetic patients

PURPOSE

The aim of the study was to investigate changes in serum sphingolipid levels and high density lipoprotein (HDL) subtypes with relation to low-density lipoprotein cholesterol (LDL-C), non-HDL-C and triglyceride (TG) levels in type 2 diabetes mellitus (T2DM) patients.

METHODS

Blood was obtained from 60 patients with T2DM. Levels of sphingosine-1-phosphate (S1P), C16-C24 sphingomyelins (SMs), C16-C24 ceramides (CERs), and C16 CER-1 P were determined by LC-MS/MS. Serum concentrations of cholesterol ester transfer protein (CETP), lecithin-cholesterol acyltransferase (LCAT) and apolipoprotein A-1 (apoA-I) were analyzed by enzyme-linked immunosorbent assay (ELISA). HDL subfraction analysis was performed by Disc polyacrylamide gel electrophoresis.

RESULTS

C16 SM, C24 SM, C24-C16 CER and C16 CER-1 P levels were significantly increased in T2DM patients with LDL-C above 160 mg/dL, compared to those with LDL-C below 100 mg/dL. A significant correlation was observed between C24:C16 SM, C24:C16 CER ratios and LDL-C, non HDL-C levels. Higher serum levels of C24 SM, C24-C18 CER and C24:C16 SM ratio was seen in obese T2DM patients (BMI>30) compared to those with BMI 27-30. Patients with fasting TG levels below 150 mg/dL had significantly increased HDL-large and significantly decreased HDL-small fractions compared to those with fasting TG levels above 150 mg/dL.

CONCLUSION

Obese dyslipidemic T2DM patients had increased levels of serum sphingomyelins, ceramides and HDL-small fractions. The ratio of serum C24:C16 SM, C24:C16 CER and long chain CER levels may be used as diagnostic and prognostic indicators of dyslipidemia in T2DM.

Very low HDL levels: clinical assessment and management

In individuals with very low high-density lipoprotein (HDL-C) cholesterol, such as Tangier disease, LCAT deficiency, and familial hypoalphalipoproteinemia, there is an increased risk of premature atherosclerosis. However, analyzes based on comparisons of populations with small variations in HDL-C mediated by polygenic alterations do not confirm these findings, suggesting that there is an indirect association or heterogeneity in the pathophysiological mechanisms related to the reduction of HDL-C. Trials that evaluated some of the HDL functions demonstrate a more robust degree of association between the HDL system and atherosclerotic risk, but as they were not designed to modify lipoprotein functionality, there is insufficient data to establish a causal relationship. We currently have randomized clinical trials of therapies that increase HDL-C concentration by various mechanisms, and this HDL-C elevation has not independently demonstrated a reduction in the risk of cardiovascular events. Therefore, this evidence shows that (a) measuring HDL-C as a way of estimating HDL-related atheroprotective system function is insufficient and (b) we still do not know how to increase cardiovascular protection with therapies aimed at modifying HDL metabolism. This leads us to a greater effort to understand the mechanisms of molecular action and cellular interaction of HDL, completely abandoning the traditional view focused on the plasma concentration of HDL-C. In this review, we will detail this new understanding and the new horizon for using the HDL system to mitigate residual atherosclerotic risk.

Red Blood Cell Membrane Cholesterol May Be a Key Regulator of Sickle Cell Disease Microvascular Complications

Cell membrane lipid composition, especially cholesterol, affects many functions of embedded enzymes, transporters and receptors in red blood cells (RBC). High membrane cholesterol content affects the RBCs' main vital function, O₂ and CO₂ transport and delivery, with consequences on peripheral tissue physiology and pathology. A high degree of deformability of RBCs is required to accommodate the size of micro-vessels with diameters significantly lower than RBCs. The potential therapeutic role of high-density lipoproteins (HDL) in the removal of cholesterol and its activity regarding maintenance of an optimal concentration of RBC membrane cholesterol have not been well investigated. On the contrary, the focus for HDL research has mainly been on the clearance of cholesterol accumulated in atherosclerotic macrophages and plaques. Since all interventions aiming at decreasing cardiovascular diseases by increasing the plasma level of HDL cholesterol have failed so far in large outcome studies, we reviewed the potential role of HDL to remove excess membrane cholesterol from RBC, especially in sickle cell disease (SCD). Indeed, abundant literature supports a consistent decrease in cholesterol transported by all plasma lipoproteins in SCD, in addition to HDL, low- (LDL) and very low-density lipoproteins (VLDL). Unexpectedly, these decreases in plasma were associated with an increase in RBC membrane cholesterol. The concentration and activity of the main enzyme involved in the removal of cholesterol and generation of large HDL particles-lecithin cholesterol ester transferase (LCAT)-are also significantly decreased in SCD. These observations might partially explain the decrease in RBC deformability, diminished gas exchange and tendency of RBCs to aggregate in SCD. We showed that incubation of RBC from SCD patients with human HDL or the HDL-mimetic peptide Fx5A improves the impaired RBC deformability and decreases intracellular reactive oxygen species levels. We propose that the main physiological role of HDL is to regulate the cholesterol/phospholipid ratio (C/PL), which is fundamental to the transport of oxygen and its delivery to peripheral tissues.

First-in-human autologous implantation of genetically modified adipocytes expressing LCAT for the treatment of familial LCAT deficiency

Background

Familial lecithin: cholesterol acyltransferase (LCAT) deficiency (FLD) is a severe inherited disease without effective treatment. Patients with FLD develop severe low HDL, corneal opacity, hemolytic anemia, and renal injury.

Objective

We developed genetically modified adipocytes (GMAC) secreting LCAT (LCAT-GMAC) for ex vivo gene therapy. GMACs were prepared from the patient’s adipocytes to express LCAT by retroviral gene transduction to secrete functional enzymes. This study aimed to evaluate the safety and efficacy of LCAT-GMAC implantation in an FLD patient.

Methods

Proliferative preadipocytes were obtained from a patient using a ceiling culture and retrovirally transduced with LCAT. After obtaining enough cells by expansion culture of the transduced cells, the resulting LCAT-GMACs were implanted into a patient with FLD. To evaluate the safety and efficacy, we analyzed the outcome of the autologous implantation for 24 weeks of observation and subsequent 240 weeks of the follow-up periods.

Results

This first-in-human autologous implantation of LCAT-GMACs was shown to be safe by evaluating adverse events. The LCAT-GMAC implantation increased serum LCAT activity by approximately 50% of the baseline and sustained over three years. Consistent with increased LCAT activity, intermediate-density lipoprotein (IDL) and free cholesterol levels of the small and very small HDL fractions decreased. We found the hemoglobin/haptoglobin complex in the hemolyzed pre-implantation sera of the patient. After one week of the implantation, the hemoglobin/haptoglobin complex almost disappeared. Immediately after the implantation, the patient's proteinuria decreased temporarily to mild levels and gradually increased to the baseline. At 48 weeks after implantation, the patient's proteinuria deteriorated with the development of mild hypertension. By the treatment with antihypertensives, the patient's blood pressure normalized. With the normalization of blood pressure, the proteinuria rapidly decreased to mild proteinuria levels.

Conclusions

LCAT-GMAC implantation in a patient with FLD is shown to be safe and appears to be effective, in part, for treating anemia and proteinuria in FLD.

The pleiotropic effects of high-density lipoproteins and apolipoprotein A-I

The high density lipoprotein (HDL) fraction of human plasma consists of multiple subpopulations of spherical particles that are structurally uniform, but heterogeneous in terms of size, composition and function. Numerous epidemiological studies have established that an elevated high density lipoprotein cholesterol (HDL-C) level is associated with decreased cardiovascular risk. However, with several recent randomised clinical trials of HDL-C raising agents failing to reduce cardiovascular events, contemporary research is transitioning towards clinical development of the cardioprotective functions of HDLs and the identification of functions that can be exploited for treatment of other diseases. This review describes the origins of HDLs and the causes of their compositional and functional heterogeneity. It then summarises current knowledge of how cardioprotective and other functions of HDLs are regulated. The final section of the review summarises recent advances in the clinical development of HDL-targeted therapies.

LCAT-trial-24 weeks: Protocol for a clinical study to evaluate the safety of regenerative medicine and gene therapy by the autologous transplantation of human lecithin:cholesterol acyltransferase gene-transduced human pre-adipocytes

Backgrounds

Despite the absolute need for life-long treatment of inherited and genetic diseases, there has been little effort to develop such treatments for most of these conditions due to their rarity. Familial lecithin:cholesterol acyltransferase (LCAT) deficiency is recognized as one such orphan disease. We have been developing an adipocyte-based ex vivo gene therapy/regenerative medicine, a novel methodology that differs from the adeno-associated virus-mediated in vivo gene therapy or ex vivo gene-transduced hematopoietic cell therapy, to treat familial LCAT deficiency. Recently, a first-in-human (FIH) clinical study was conducted under the Act on Securement of Safety of Regenerative Medicine, wherein a patient with familial LCAT deficiency was treated. To obtain approval to put this treatment into practical use, a clinical trial has been designed with reference to the FIH clinical study.

Methods

An interventional, open-label, unblinded dose-escalation trial was planned, referring to previous FIH clinical study. The trial aims to evaluate the safety of the investigational product in relation to the characteristics of the investigational product (ex vivo gene/cell therapy product by retroviral vector-mediated LCAT gene transduction) using two doses, and the efficacy of the treatment will be evaluated exploratively. A total of three patients will be enrolled sequentially and followed for 24 weeks after administration. This study is designed as a multicenter trial, with Chiba University Hospital administering and evaluating the safety/efficacy of the investigational products at the prescribed visit.

Conclusion

This clinical trial is expected to facilitate the provision of lifelong treatment to many patients with LCAT deficiency.

Trial registration number

Japan Registry of Clinical Trials (jRCT2033200096).

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Familial LCAT deficiency is an orphan disease without any effective treatment.

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We have been developing a novel adipocyte-based ex vivo gene therapy that enables life-long enzyme replacement.

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This clinical study was designed to assess the dose-response and the safety in a limited number of orphan disease patients.

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The protocol includes a preclinical tumorigenicity test in immunodeficient (NSG) mice as one of the primary endpoints.

Two novel variants in the lecithin:cholesterol acyltransferase gene resulted in classic LCAT deficiency

Background and aims

We report the first two cases of familial lecithin:cholesterol acyltransferase (LCAT) deficiency in Croatia with classical clinical and biochemical features.

Patients and methods

A 30-year-old man with nephrotic syndrome, corneal opacities, hepatosplenomegaly, anemia, low high-density lipoprotein (HDL)-cholesterol levels and arterial hypertension (blood pressure >200/100 mmHg) was admitted to our department. At admission, he had an elevated creatinine serum level (233 μmol/L), proteinuria of 12 g in 24-h urine (g/24 h), 3-7 erythrocytes in urine sediment and notable anemia (hemoglobin level 90 g/l). His HDL-cholesterol was significantly low (0.42 mmol/L). Besides chronic kidney disease (CKD), other secondary causes of hypertension were ruled out. The patient was previously diagnosed with membranous nephropathy and treated unsuccessfully with immunosuppressive agents (steroids, cyclosporine, cyclophosphamide). Re-evaluation of histopathological findings of kidney biopsy revealed massive deposition of lipid material in the glomerular basal membrane and in the mesangial region. His 4-year younger brother was also evaluated due to corneal opacities and new-onset arterial hypertension. Nephrotic range proteinuria with preserved global renal function was determined. He also had very low HDL-cholesterol levels.

Results

Kidney biopsies from both patients were consistent with LCAT deficiency. The disease was confirmed by measurement of LCAT enzyme activity, plasma cholesterol esterification rate, and genetic testing. Two novel missense variants in the LCAT gene (c.496G > A and c.1138T  >  C) were found.

Conclusions

To our knowledge, the presented cases are the first reported cases of genetic LCAT deficiency in Croatia. Given the clinical presentation, the complete lack of LCAT activity and cholesterol esterification rate, diagnosis of familial LCAT deficiency was made.

Inflammation and atherosclerosis: signaling pathways and therapeutic intervention

Atherosclerosis is a chronic inflammatory vascular disease driven by traditional and nontraditional risk factors. Genome-wide association combined with clonal lineage tracing and clinical trials have demonstrated that innate and adaptive immune responses can promote or quell atherosclerosis. Several signaling pathways, that are associated with the inflammatory response, have been implicated within atherosclerosis such as NLRP3 inflammasome, toll-like receptors, proprotein convertase subtilisin/kexin type 9, Notch and Wnt signaling pathways, which are of importance for atherosclerosis development and regression. Targeting inflammatory pathways, especially the NLRP3 inflammasome pathway and its regulated inflammatory cytokine interleukin-1β, could represent an attractive new route for the treatment of atherosclerotic diseases. Herein, we summarize the knowledge on cellular participants and key inflammatory signaling pathways in atherosclerosis, and discuss the preclinical studies targeting these key pathways for atherosclerosis, the clinical trials that are going to target some of these processes, and the effects of quelling inflammation and atherosclerosis in the clinic.

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.

The HDL mimetic CER-001 remodels plasma lipoproteins and reduces kidney lipid deposits in inherited lecithin:cholesterol acyltransferase deficiency

BACKGROUND

Kidney failure is the major cause of morbidity and mortality in familial lecithin:cholesterol acyltransferase deficiency (FLD), a rare inherited lipid disorder with no cure. Lipoprotein X (LpX), an abnormal lipoprotein, is primarily accountable for nephrotoxicity.

METHODS

CER-001 was tested in an FLD patient with dramatic kidney disease for 12 weeks.

RESULTS

Infusions of CER-001 normalized the lipoprotein profile, with a disappearance of the abnormal LpX in favour of normal-sized LDL. The worsening of kidney function was slowed by the treatment, and kidney biopsy showed a slight reduction of lipid deposits and a stabilization of the disease. In vitro experiments demonstrate that CER-001 progressively reverts lipid accumulation in podocytes by a dual effect: remodelling plasma lipoproteins and removing LpX-induced lipid deposit.

CONCLUSION

This study demonstrates that CER-001 may represent a therapeutic option in FLD patients. It also has the potential to be beneficial in other renal diseases characterized by kidney lipid deposits.

A systematic review of the natural history and biomarkers of primary lecithin:cholesterol acyltransferase deficiency

Syndromes associated with LCAT deficiency, a rare autosomal recessive condition, include fish-eye disease (FED) and familial LCAT deficiency (FLD). FLD is more severe and characterized by early and progressive chronic kidney disease (CKD). No treatment is currently available for FLD, but novel therapeutics are under development. Furthermore, although biomarkers of LCAT deficiency have been identified, their suitability to monitor disease progression and therapeutic efficacy is unclear, as little data exist on the rate of progression of renal disease. Here, we systematically review observational studies of FLD, FED, and heterozygous subjects, which summarize available evidence on the natural history and biomarkers of LCAT deficiency, in order to guide the development of novel therapeutics. We identified 146 FLD and 53 FED patients from 219 publications, showing that both syndromes are characterized by early corneal opacity and markedly reduced HDL-C levels. Proteinuria/hematuria were the first signs of renal impairment in FLD, followed by rapid decline of renal function. Furthermore, LCAT activity toward endogenous substrates and the percentage of circulating esterified cholesterol (EC%) were the best discriminators between these two syndromes. In FLD, higher levels of total, non-HDL, and unesterified cholesterol were associated with severe CKD. We reveal a nonlinear association between LCAT activity and EC% levels, in which subnormal levels of LCAT activity were associated with normal EC%. This review provides the first step toward the identification of disease biomarkers to be used in clinical trials and suggests that restoring LCAT activity to subnormal levels may be sufficient to prevent renal disease progression.

HDL maturation and remodelling

Cholesterol in the circulation is mostly transported in an esterified form as a component of lipoproteins. The majority of these cholesteryl esters are produced in nascent, discoidal high density lipoproteins (HDLs) by the enzyme, lecithin:cholesterol acyltransferase (LCAT). Discoidal HDLs are discrete populations of particles that consist of a phospholipid bilayer, the hydrophobic acyl chains of which are shielded from the aqueous environment by apolipoproteins that also confer water solubility on the particles. The progressive LCAT-mediated accumulation of cholesteryl esters in discoidal HDLs generates the spherical HDLs that predominate in normal human plasma. Spherical HDLs contain a core of water insoluble, neutral lipids (cholesteryl esters and triglycerides) that is surrounded by a surface monolayer of phospholipids with which apolipoproteins associate. Although spherical HDLs all have the same basic structure, they are extremely diverse in size, composition, and function. This review is concerned with how the biogenesis of discoidal and spherical HDLs is regulated and the mechanistic basis of their size and compositional heterogeneity. Current understanding of the impact of this heterogeneity on the therapeutic potential of HDLs of varying size and composition is also addressed in the context of several disease states.

Impact of Sepsis on High-Density Lipoprotein Metabolism

Background: High-density lipoproteins (HDL) are thought to play a protective role in sepsis through several mechanisms, such as promotion of steroid synthesis, clearing bacterial toxins, protection of the endothelial barrier, and antioxidant/inflammatory activities. However, HDL levels decline rapidly during sepsis, but the contributing mechanisms are poorly understood.

Methods/Aim: In the present study, we investigated enzymes involved in lipoprotein metabolism in sepsis and non-sepsis patients admitted to the intensive care unit (ICU).

Results: In 53 ICU sepsis and 25 ICU non-sepsis patients, we observed significant differences in several enzymes involved in lipoprotein metabolism. Lecithin-cholesterol acyl transferase (LCAT) activity, LCAT concentration, and cholesteryl transfer protein (CETP) activity were significantly lower, whereas phospholipid transfer activity protein (PLTP) and endothelial lipase (EL) were significantly higher in sepsis patients compared to non-sepsis patients. In addition, serum amyloid A (SAA) levels were increased 10-fold in sepsis patients compared with non-sepsis patients. Furthermore, we found that LCAT activity was significantly associated with ICU and 28-day mortality whereas SAA levels, representing a strong inflammatory marker, did not associate with mortality outcomes.

Conclusion: We provide novel data on the rapid and robust changes in HDL metabolism during sepsis. Our results clearly highlight the critical role of specific metabolic pathways and enzymes in sepsis pathophysiology that may lead to novel therapeutics.

MEDI6012: Recombinant Human Lecithin Cholesterol Acyltransferase, High-Density Lipoprotein, and Low-Density Lipoprotein Receptor-Mediated Reverse Cholesterol Transport

Background MEDI6012 is recombinant human lecithin cholesterol acyltransferase, the rate-limiting enzyme in reverse cholesterol transport. Infusions of lecithin cholesterol acyltransferase have the potential to enhance reverse cholesterol transport and benefit patients with coronary heart disease. The purpose of this study was to test the safety, pharmacokinetic, and pharmacodynamic profile of MEDI6012. Methods and Results This phase 2a double-blind study randomized 48 subjects with stable coronary heart disease on a statin to a single dose of MEDI6012 or placebo (6:2) (NCT02601560) with ascending doses administered intravenously (24, 80, 240, and 800 mg) and subcutaneously (80 and 600 mg). MEDI6012 demonstrated rates of treatment-emergent adverse events that were similar to those of placebo. Dose-dependent increases in high-density lipoprotein cholesterol were observed with area under the concentration-time curves from 0 to 96 hours of 728, 1640, 3035, and 5318 should be: mg·h/mL in the intravenous dose groups and 422 and 2845 mg·h/mL in the subcutaneous dose groups. Peak mean high-density lipoprotein cholesterol percent change was 31.4%, 71.4%, 125%, and 177.8% in the intravenous dose groups and 18.3% and 111.2% in the subcutaneous dose groups, and was accompanied by increases in endogenous apoA1 (apolipoprotein A1) and non-ATP-binding cassette transporter A1 cholesterol efflux capacity. Decreases in apoB (apolipoprotein B) were observed across all dose levels and decreases in atherogenic small low-density lipoprotein particles by 41%, 88%, and 79% at the 80-, 240-, and 800-mg IV doses, respectively. Conclusions MEDI6012 demonstrated an acceptable safety profile and increased high-density lipoprotein cholesterol, endogenous apoA1, and non-ATP-binding cassette transporter A1 cholesterol efflux capacity while reducing the number of atherogenic low-density lipoprotein particles. These findings are supportive of enhanced reverse cholesterol transport and a functional high-density lipoprotein phenotype. Registration URL: https://www.clinicaltrials.gov; Unique identifier: NCT02601560.

HDL in the 21st Century: A Multifunctional Roadmap for Future HDL Research

Low high-density lipoprotein cholesterol (HDL-C) characterizes an atherogenic dyslipidemia that reflects adverse lifestyle choices, impaired metabolism, and increased cardiovascular risk. Low HDL-C is also associated with increased risk of inflammatory disorders, malignancy, diabetes, and other diseases. This epidemiologic evidence has not translated to raising HDL-C as a viable therapeutic target, partly because HDL-C does not reflect high-density lipoprotein (HDL) function. Mendelian randomization analyses that have found no evidence of a causal relationship between HDL-C levels and cardiovascular risk have decreased interest in increasing HDL-C levels as a therapeutic target. HDLs comprise distinct subpopulations of particles of varying size, charge, and composition that have several dynamic and context-dependent functions, especially with respect to acute and chronic inflammatory states. These functions include reverse cholesterol transport, inhibition of inflammation and oxidation, and antidiabetic properties. HDLs can be anti-inflammatory (which may protect against atherosclerosis and diabetes) and proinflammatory (which may help clear pathogens in sepsis). The molecular regulation of HDLs is complex, as evidenced by their association with multiple proteins, as well as bioactive lipids and noncoding RNAs. Clinical investigations of HDL biomarkers (HDL-C, HDL particle number, and apolipoprotein A through I) have revealed nonlinear relationships with cardiovascular outcomes, differential relationships by sex and ethnicity, and differential patterns with coronary versus noncoronary events. Novel HDL markers may also have relevance for heart failure, cancer, and diabetes. HDL function markers (namely, cholesterol efflux capacity) are associated with coronary disease, but they remain research tools. Therapeutics that manipulate aspects of HDL metabolism remain the holy grail. None has proven to be successful, but most have targeted HDL-C, not metrics of HDL function. Future therapeutic strategies should focus on optimizing HDL function in the right patients at the optimal time in their disease course. We provide a framework to help the research and clinical communities, as well as funding agencies and stakeholders, obtain insights into current thinking on these topics, and what we predict will be an exciting future for research and development on HDLs.

Proatherogenic Sialidases and Desialylated Lipoproteins: 35 Years of Research and Current State from Bench to Bedside

This review summarizes the main achievements in basic and clinical research of atherosclerosis. Focusing on desialylation as the first and the most important reaction of proatherogenic pathological cascade, we speak of how desialylation increases the atherogenic properties of low density lipoproteins and decreases the anti-atherogenic properties of high density lipoproteins. The separate sections of this paper are devoted to immunogenicity of lipoproteins, the enzymes contributing to their desialylation and animal models of atherosclerosis. In addition, we evaluate the available experimental and diagnostic protocols that can be used to develop new therapeutic approaches for atherosclerosis.

Correction of Familial LCAT Deficiency by AAV-hLCAT Prevents Renal Injury and Atherosclerosis in Hamsters-Brief Report

[Figure: see text].

Current Status of Familial LCAT Deficiency in Japan

Lecithin cholesterol acyltransferase (LCAT) is a lipid-modification enzyme that catalyzes the transfer of the acyl chain from the second position of lecithin to the hydroxyl group of cholesterol (FC) on plasma lipoproteins to form cholesteryl acylester and lysolecithin. Familial LCAT deficiency is an intractable autosomal recessive disorder caused by inherited dysfunction of the LCAT enzyme. The disease appears in two different phenotypes depending on the position of the gene mutation: familial LCAT deficiency (FLD, OMIM 245900) that lacks esterification activity on both HDL and ApoB-containing lipoproteins, and fish-eye disease (FED, OMIM 136120) that lacks activity only on HDL. Impaired metabolism of cholesterol and phospholipids due to LCAT dysfunction results in abnormal concentrations, composition and morphology of plasma lipoproteins and further causes ectopic lipid accumulation and/or abnormal lipid composition in certain tissues/cells, and serious dysfunction and complications in certain organs. Marked reduction of plasma HDL-cholesterol (HDL-C) and corneal opacity are common clinical manifestations of FLD and FED. FLD is also accompanied by anemia, proteinuria and progressive renal failure that eventually requires hemodialysis. Replacement therapy with the LCAT enzyme should prevent progression of serious complications, particularly renal dysfunction and corneal opacity. A clinical research project aiming at gene/cell therapy is currently underway.

High-Density Lipoproteins and the Kidney

Dyslipidemia is a typical trait of patients with chronic kidney disease (CKD) and it is typically characterized by reduced high-density lipoprotein (HDL)-cholesterol(c) levels. The low HDL-c concentration is the only lipid alteration associated with the progression of renal disease in mild-to-moderate CKD patients. Plasma HDL levels are not only reduced but also characterized by alterations in composition and structure, which are responsible for the loss of atheroprotective functions, like the ability to promote cholesterol efflux from peripheral cells and antioxidant and anti-inflammatory proprieties. The interconnection between HDL and renal function is confirmed by the fact that genetic HDL defects can lead to kidney disease; in fact, mutations in apoA-I, apoE, apoL, and lecithin–cholesterol acyltransferase (LCAT) are associated with the development of renal damage. Genetic LCAT deficiency is the most emblematic case and represents a unique tool to evaluate the impact of alterations in the HDL system on the progression of renal disease. Lipid abnormalities detected in LCAT-deficient carriers mirror the ones observed in CKD patients, which indeed present an acquired LCAT deficiency. In this context, circulating LCAT levels predict CKD progression in individuals at early stages of renal dysfunction and in the general population. This review summarizes the main alterations of HDL in CKD, focusing on the latest update of acquired and genetic LCAT defects associated with the progression of renal disease.

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.

Metabolism of PLTP, CETP, and LCAT on multiple HDL sizes using the Orbitrap Fusion Lumos

Recent in vivo tracer studies demonstrated that targeted mass spectrometry (MS) on the Q Exactive Orbitrap could determine the metabolism of HDL proteins 100s-fold less abundant than apolipoprotein A1 (APOA1). In this study, we demonstrate that the Orbitrap Lumos can measure tracer in proteins whose abundances are 1000s-fold less than APOA1, specifically the lipid transfer proteins phospholipid transfer protein (PLTP), cholesterol ester transfer protein (CETP), and lecithin-cholesterol acyl transferase (LCAT). Relative to the Q Exactive, the Lumos improved tracer detection by reducing tracer enrichment compression, thereby providing consistent enrichment data across multiple HDL sizes from 6 participants. We determined by compartmental modeling that PLTP is secreted in medium and large HDL (alpha2, alpha1, and alpha0) and is transferred from medium to larger sizes during circulation from where it is catabolized. CETP is secreted mainly in alpha1 and alpha2 and remains in these sizes during circulation. LCAT is secreted mainly in medium and small HDL (alpha2, alpha3, prebeta). Unlike PLTP and CETP, LCAT’s appearance on HDL is markedly delayed, indicating that LCAT may reside for a time outside of systemic circulation before attaching to HDL in plasma. The determination of these lipid transfer proteins’ unique metabolic structures was possible due to advances in MS technologies.

Novel LCAT (Lecithin:Cholesterol Acyltransferase) Activator DS-8190a Prevents the Progression of Plaque Accumulation in Atherosclerosis Models

OBJECTIVE

Enhancement of LCAT (lecithin:cholesterol acyltransferase) activity has possibility to be beneficial for atherosclerosis. To evaluate this concept, we characterized our novel, orally administered, small-molecule LCAT activator DS-8190a, which was created from high-throughput screening and subsequent derivatization. We also focused on its mechanism of LCAT activation and the therapeutic activity with improvement of HDL (high-density lipoprotein) functionality. Approach and Results: DS-8190a activated human and cynomolgus monkey but not mouse LCAT enzymes in vitro. DS-8190a was orally administered to cynomolgus monkeys and dose dependently increased LCAT activity (2.0-fold in 3 mg/kg group on day 7), resulting in HDL cholesterol elevation without drastic changes of non-HDL cholesterol. Atheroprotective effects were then evaluated using Ldl-r KO×hLcat Tg mice fed a Western diet for 8 weeks. DS-8190a treatment achieved significant reduction of atherosclerotic lesion area (48.3% reduction in 10 mg/kg treatment group). Furthermore, we conducted reverse cholesterol transport study using Ldl-r KO×hLcat Tg mice intraperitoneally injected with J774A.1 cells loaded with [3H]-cholesterol and confirmed significant increases of [3H] count in plasma (1.4-fold) and feces (1.4-fold on day 2 and 1.5-fold on day3) in the DS-8190a-treated group. With regard to the molecular mechanism involved, direct binding of DS-8190a to human LCAT protein was confirmed by 2 different approaches: affinity purification by DS-8190a-immobilized beads and thermal shift assay. In addition, the candidate binding site of DS-8190a in human LCAT protein was identified by photoaffinity labeling.

CONCLUSIONS

This study demonstrates the potential of DS-8190a as a novel therapeutic for atherosclerosis. In addition, this compound proves that a small-molecule direct LCAT activator can achieve HDL-C elevation in monkey and reduction of atherosclerotic lesion area with enhanced HDL function in rodent.

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.

Spontaneous Atherosclerosis in Aged LCAT-Deficient Hamsters With Enhanced Oxidative Stress-Brief Report

OBJECTIVE

LCAT (lecithin cholesterol acyltransferase) deficiency results in severe low HDL (high-density lipoprotein). Although whether LCAT is pro- or antiatherosclerosis was in debate in mouse studies, our previous study clearly shows that LCAT deficiency (LCAT^-/-) in hamster accelerates atherosclerotic development on high-fat diet. However, unlike in hypercholesterolemia and hypertriglyceridemia, whether LCAT deficiency could lead to spontaneous atherosclerosis has not been studied yet in animal models. We, therefore, sought to investigate the atherosclerosis in LCAT^-/- hamsters on standard laboratory diet and explore the potential underlying mechanisms. Approach and Results: Young (<8 months) and aged (>16 months) male and female wild-type and LCAT^-/- hamsters on standard laboratory diet were used. Compared with age- and sex-matched wild-type hamsters, LCAT^-/- hamsters showed a complete loss of plasma HDL and an increase in triglyceride by 2- to 8-fold at different stages of age. In aged LCAT^-/- hamsters, the lesion areas at the aortic roots were ≈40×10⁴ μm³ in males and 18×10⁴ μm³ in females, respectively, which were consistent with the en face plaques observed in male (1.2%) and (1.5%) female groups, respectively. The results of plasma malondialdehyde measurement showed that malondialdehyde concentrations were markedly elevated to 54.4 μmol/L in males and 30 μmol/L in females, which are significantly associated with the atherosclerotic lesions.

CONCLUSIONS

Our study demonstrates the development of spontaneous atherosclerotic lesions in aged male and female LCAT^-/- hamsters with higher plasma oxidative lipid levels independent of plasma total cholesterol levels, further confirming the antiatherosclerotic role of LCAT.

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.

Efficacy and safety of add on therapies in patients with hypercholesterolemia undergoing statin therapy

INTRODUCTION

Statins are the first-line treatment to reduce cardiovascular (CV) events, mainly by reducing low-density-lipoprotein cholesterol (LDL-C), but many patients need additional treatments to reach the current lipid goals.

AREAS COVERED

Herein, the authors review the published literature on the efficacy and safety of the therapies that are most often added to statins to achieve lipid targets.

EXPERT OPINION

Ezetimibe is usually the first additional treatment to achieve LDL-C targets. It reduces LDL-C by about a further 20% and has an excellent safety and tolerability profile. The monoclonal antibody proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors, evolocumab, and alirocumab, can reduce LDL-C by ≥50% when added to statins and they also have a well-established safety and tolerability record. The recently approved bempedoic acid is well tolerated and appears to be free of skeletal muscle-related problems, but the CV outcome study with this drug has not been completed. Inclisiran, a small-interfering RNA targeting PCSK9 is at an advanced stage of development and the available data indicate a satisfactory safety profile and LDL-C lowering efficacy similar to the PCSK9 monoclonal antibodies with the advantage of less frequent administration.

Novel emerging therapies in atherosclerosis targeting lipid metabolism

INTRODUCTION

Recent years have brought significant developments in lipid and atherosclerosis research. Although statins are a cornerstone in hyperlipidemia management, new non-statin therapies have had an impact. The reduction of low-density lipoprotein cholesterol (LDL-C) further translates into the lowering of cardiovascular mortality. Additionally, lipid research has progressed beyond LDL-C reduction and this has brought triglyceride (TG) and other apoprotein-B containing lipids into focus.

AREAS COVERED

Inclisiran and pemafibrate, with expected approval soon, come under the spotlight. We discuss other therapeutics such as lomitapide, mipomersen, volanesorsen, and evinacumab and newly approved non-statin-based therapies such as ezetimibe, icosapent ethyl (IPE), and bempedoic acid.

EXPERT OPINION

New options now exist for the prevention of atherosclerosis in patients that are not optimized on statin therapy. Multiple guidelines endorse ezetimibe, PCSK9 inhibitors, bempedoic, and IPE as add-on therapy. Recently approved bempedoic acid/ezetimibe combination might gain popularity among clinicians. Inclisiran and pemafibrate show promise in the reduction of LDL-C and TG, respectively, and results are pending in cardiovascular outcome trials. Combination strategies could improve outcomes, but the challenge will be balancing cost and selecting the correct patient population for each treatment modality to maximize benefit with the fewest medications.

Novel lecithin: cholesterol acyltransferase-based therapeutic approaches

PURPOSE OF REVIEW

To review recent lecithin:cholesterol acyltransferas (LCAT)-based therapeutic approaches for atherosclerosis, acute coronary syndrome, and LCAT deficiency disorders.

RECENT FINDINGS

A wide variety of approaches to using LCAT as a novel therapeutic target have been proposed. Enzyme replacement therapy with recombinant human LCAT is the most clinically advanced therapy for atherosclerosis and familial LCAT deficiency (FLD), with Phase I and Phase 2A clinical trials recently completed. Liver-directed LCAT gene therapy and engineered cell therapies are also another promising approach. Peptide and small molecule activators have shown efficacy in early-stage preclinical studies. Finally, lifestyle modifications, such as fat-restricted diets, cessation of cigarette smoking, and a diet rich in antioxidants may potentially suppress lipoprotein abnormalities in FLD patients and help preserve LCAT activity and renal function but have not been adequately tested.

SUMMARY

Preclinical and early-stage clinical trials demonstrate the promise of novel LCAT therapies as HDL-raising agents that may be used to treat not only FLD but potentially also atherosclerosis and other disorders with low or dysfunctional HDL.

LCAT protects against Lipoprotein-X formation in a murine model of drug-induced intrahepatic cholestasis

Familial lecithin:cholesterol acyltransferase (LCAT) deficiency (FLD) is a rare genetic disease characterized by low HDL-C levels, low plasma cholesterol esterification, and the formation of Lipoprotein-X (Lp-X), an abnormal cholesterol-rich lipoprotein particle. LCAT deficiency causes corneal opacities, normochromic normocytic anemia, and progressive renal disease due to Lp-X deposition in the glomeruli. Recombinant LCAT is being investigated as a potential therapy for this disorder. Several hepatic disorders, namely primary biliary cirrhosis, primary sclerosing cholangitis, cholestatic liver disease, and chronic alcoholism also develop Lp-X, which may contribute to the complications of these disorders. We aimed to test the hypothesis that an increase in plasma LCAT could prevent the formation of Lp-X in other diseases besides FLD. We generated a murine model of intrahepatic cholestasis in LCAT-deficient (KO), wild type (WT), and LCAT-transgenic (Tg) mice by gavaging mice with alpha-naphthylisothiocyanate (ANIT), a drug well known to induce intrahepatic cholestasis. Three days after the treatment, all mice developed hyperbilirubinemia and elevated liver function markers (ALT, AST, Alkaline Phosphatase). The presence of high levels of LCAT in the LCAT-Tg mice, however, prevented the formation of Lp-X and other plasma lipid abnormalities in WT and LCAT-KO mice. In addition, we demonstrated that multiple injections of recombinant human LCAT can prevent significant accumulation of Lp-X after ANIT treatment in WT mice. In summary, LCAT can protect against the formation of Lp-X in a murine model of cholestasis and thus recombinant LCAT could be a potential therapy to prevent the formation of Lp-X in other diseases besides FLD.

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.

Rare Diseases Related with Lipoprotein Metabolism

Rare diseases are gathering increasing attention in last few years, not only for its effects on innovation scientific research, but also for its propounding influence on common diseases. One of the most famous milestones made by Michael Brown and Joseph Goldstein in metabolism field is the discovery of the defective gene in familial hypercholesterolemia, a rare human genetic disease manifested with extreme high level of serum cholesterol (Goldstein JL, Brown MS, Proc Natl Acad Sci USA 70:2804-2808, 1973; Brown MS, Dana SE, Goldstein JL, J Biol Chem 249:789-796, 1974). Follow-up work including decoding the gene function, mapping-related pathways, and screening therapeutic targets are all based on the primary finding (Goldstein JL, Brown MS Arterioscler Thromb Vasc Biol 29:431-438, 2009). A series of succession win the two brilliant scientists the 1985 Nobel Prize, and bring about statins widely used for lipid management and decreasing cardiovascular disease risks. Translating the clinical extreme phenotypes into laboratory bench work has turned out to be the first important step in the paradigm conducting translational and precise medical research. Here we review the main categories of rare disorders related with lipoprotein metabolism, aiming to strengthen the notion that human rare inheritable genetic diseases would be the window to know ourselves better, to treat someone more efficiently, and to lead a healthy life longer. Few rare diseases related with lipoprotein metabolism were clustered into six sections based on changes in lipid profile, namely, hyper- or hypocholesterolemia, hypo- or hyperalphalipoproteinemia, abetalipoproteinemia, hypobetalipoproteinemia, and sphingolipid metabolism diseases. Each section consists of a brief introduction, followed by a summary of well-known disease-causing genes in one table, and supplemented with one or two diseases as example for detailed description. Here we aimed to raise more attention on rare lipoprotein metabolism diseases, calling for more work from basic research and clinical trials.

Novel lipid-modifying therapies addressing unmet needs in cardiovascular disease

Cardiovascular disease (CVD) remains a major cause of morbidity and mortality worldwide. Currently, it is well established that dyslipidemia is one of the major risk factors leading to the development of atherosclerosis and CVD. Statins remain the standard-of-care in the treatment of hypercholesterolemia and their use has significantly reduced cardiovascular morbidity and mortality. In addition, recent advances in lipid-modifying therapies, such as the development of proprotein convertase subtilisin/kexin type 9 inhibitors, have further improved cardiovascular outcomes in patients with hypercholesterolemia. However, despite significant progress in the treatment of dyslipidemia, there is still considerable residual risk of recurring cardiovascular events. Furthermore, in some cases, an effective therapy for the identified primary cause of a specific dyslipidemia has not been found up to date. Thus, a number of novel pharmacological interventions are under early human trials, targeting different molecular pathways of lipid formation, regulation and metabolism. This editorial aims to discuss the current clinical and scientific data on new promising lipid-modifying therapies addressing unmet needs in CVD, which may prove beneficial in the near future.

Inherited metabolic disorders and dyslipidaemia

Monogenic dyslipidaemia is a diverse group of multisystem disorders. Patients may present to various specialities from early childhood to late in adult life, and it usually takes longer before the diagnosis is established. Increased awareness of these disorders among clinicians is imperative for early diagnosis. This best practice review provides an overview of primary dyslipidaemias, highlighting their clinical presentation, relevant biochemical and molecular tests. It also addresses the emerging role of genetics in the early diagnosis and prevention of these disorders.

Lipid-Lowering Agents

Several new or emerging drugs for dyslipidemia owe their existence, in part, to human genetic evidence, such as observations in families with rare genetic disorders or in Mendelian randomization studies. Much effort has been directed to agents that reduce LDL (low-density lipoprotein) cholesterol, triglyceride, and Lp[a] (lipoprotein[a]), with some sustained programs on agents to raise HDL (high-density lipoprotein) cholesterol. Lomitapide, mipomersen, AAV8.TBG.hLDLR, inclisiran, bempedoic acid, and gemcabene primarily target LDL cholesterol. Alipogene tiparvovec, pradigastat, and volanesorsen primarily target elevated triglycerides, whereas evinacumab and IONIS-ANGPTL3-L_Rx target both LDL cholesterol and triglyceride. IONIS-APO(a)-L_Rx targets Lp(a).

Effects of Replacing Dietary Monounsaturated Fat With Carbohydrate on HDL (High-Density Lipoprotein) Protein Metabolism and Proteome Composition in Humans

OBJECTIVE

Clinical evidence has linked low HDL (high-density lipoprotein) cholesterol levels with high cardiovascular disease risk; however, its significance as a therapeutic target remains unestablished. We hypothesize that HDLs functional heterogeneity is comprised of metabolically distinct proteins, each on distinct HDL sizes and that are affected by diet. Approach and Results: Twelve participants were placed on 2 healthful diets high in monounsaturated fat or carbohydrate. After 4 weeks on each diet, participants completed a metabolic tracer study. HDL was isolated by Apo (apolipoprotein) A1 immunopurification and separated into 5 sizes. Tracer enrichment and metabolic rates for 8 HDL proteins-ApoA1, ApoA2, ApoC3, ApoE, ApoJ, ApoL1, ApoM, and LCAT (lecithin-cholesterol acyltransferase)-were determined by parallel reaction monitoring and compartmental modeling, respectively. Each protein had a unique, size-specific distribution that was not altered by diet. However, carbohydrate, when replacing fat, increased the fractional catabolic rate of ApoA1 and ApoA2 on alpha3 HDL; ApoE on alpha3 and alpha1 HDL; and ApoM on alpha2 HDL. Additionally, carbohydrate increased the production of ApoC3 on alpha3 HDL and ApoJ and ApoL1 on the largest alpha0 HDL. LCAT was the only protein studied that diet did not affect. Finally, global proteomics showed that diet did not alter the distribution of the HDL proteome across HDL sizes.

CONCLUSIONS

This study demonstrates that HDL in humans is composed of a complex system of proteins, each with its own unique size distribution, metabolism, and diet regulation. The carbohydrate-induced hypercatabolic state of HDL proteins may represent mechanisms by which carbohydrate alters the cardioprotective properties of HDL.

Inheritance of high and low HDL: mechanisms and management

PURPOSE OF REVIEW

The inverse association between plasma high-density lipoprotein cholesterol (HDL-C) concentration and the incidence of cardiovascular disease (CVD) has been unequivocally proven by many epidemiological studies. There are several genetic disorders affecting HDL-C plasma levels, either providing atheroprotection or predisposing to premature atherosclerosis. However, up to date, there has not been any pharmacological intervention modulating HDL-C levels, which has been clearly shown to prevent the progression of CVD. Thus, clarifying the exact underlying mechanisms of inheritance of these genetic disorders that affect HDL is a current goal of the research, as key roles of molecular components of HDL metabolism and function can be revealed and become targets for the discovery of novel medications for the prevention and treatment of CVD.

RECENT FINDINGS

Primary genetic disorders of HDL can be either associated with longevity or, in contrast, may lead to premature CVD, causing high morbidity and mortality to their carriers. A large body of recent research has closely examined the genetic disorders of HDL and new promising therapeutic strategies have been developed, which may be proven beneficial in patients predisposed to CVD in the near future.

SUMMARY

We have reviewed recent findings on the inheritance of genetic disorders associated with high and low HDL-C plasma levels and we have discussed their clinical features, as well as information about new promising HDL-C-targeted therapies that are under clinical trials.