Effects of PCSK9 Inhibition With Alirocumab on Lipoprotein Metabolism in Healthy Humans

Effect of alirocumab on postprandial hyperlipidaemia in patients with type 2 diabetes: A randomized, double-blind, placebo-controlled, cross-over trial

AIMS

Postprandial hyperlipidaemia (PPL), characterized by elevated triglyceride (TG) concentrations after a meal, is common in type 2 diabetes (T2D) and is often recognized as an independent cardiovascular risk factor. Here, we aimed to assess the effect of proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition by alirocumab on PPL in patients with T2D.

MATERIALS AND METHODS

EUTERPE is a randomized, double-blind, placebo-controlled cross-over trial conducted in male patients with T2D. Participants received sequentially two sequences of 10-week treatment (alirocumab 75 mg Q2W or placebo s/c) with a wash-out period of 10 weeks. The primary end-point was the percentage reduction in plasma TG response after an oral fat load (incremental area under the curve [iAUC]0-8h TG). Secondary end-points included mass spectrometry-based apolipoprotein measurements and nuclear magnetic resonance (NMR)-based lipoprotein profiling.

RESULTS

Fourteen participants were included: age 59 ± 9 years, BMI 32.8 ± 5.5 kg/m2, HbA1C 6.7 ± 0.5%. Compared to placebo, alirocumab did not reduce PPL (iAUC0-8h TG: -5% [CI 95%: -28, +25], p = 0.68). Alirocumab decreased fasting non-HDL cholesterol (-38.5 ± 5.6%, p = 0.0003), remnant cholesterol (-20.0 ± 13.3%, p = 0.04), apoB100 (-21.2 ± 6.4%, p = 0.004) and apoE (-15.3 ± 6.6%, p = 0.02) concentrations. NMR analyses showed that alirocumab decreased both postprandial VLDL2 cholesterol (-42% [-55, -25], p < 0.001) and IDL cholesterol (-26% [-38, -12], p = 0.0007), without effect on VLDL1 cholesterol or TG concentrations.

CONCLUSIONS

Inhibition of PCSK9 by alirocumab did not reduce PPL in T2D, confirming that PCSK9 controls remnant cholesterol catabolism rather than intestinal chylomicron production.

PCSK9 Targeted Autophagosome-Tethering Compounds: Design, Synthesis, and Antiatherosclerosis Evaluation

Atherosclerosis is a multifaceted disease involving various cell types and complex mechanisms, and it is the main cause of cardiovascular disease. Proprotein convertase subtilisin/kexin type-9 (PCSK9) has been identified as an effective target for treating atherosclerosis; however, most current research focuses on biological drugs. Our work optimized the previously reported autophagosome-tethering compound OY3, and specifically, compound W6 induced PCSK9 degradation with a 5-fold increase in activity and a 6-fold increase in bioavailability. Compared to the currently marketed PCSK9 drug, siRNA, W6 demonstrated comparable antiatherosclerosis effects both in vivo and in vitro. W6 exhibited beneficial effects on hepatocytes, endothelial cells, macrophages, and vascular smooth muscle cells involved in the atherosclerosis process, making it a promising potential antiatherosclerosis drug. This work highlights the feasibility of ATTECs in degrading both intracellular and extracellular proteins, and our novel PCSK9-ATTEC W6 provides a valuable reference for the treatment of atherosclerotic diseases.

Lipoprotein(a) levels and cardiovascular mortality risk in Chinese patients undergoing hemodialysis

PURPOSE

Lipoprotein(a) (Lp(a)) is recognized as an independent risk factor for cardiovascular disease (CVD) in the general population. However, its impact on CVD mortality among Chinese patients undergoing maintenance hemodialysis (MHD) has not been fully established. This study aimed to evaluate the association between Lp(a) levels and both CVD mortality and all-cause mortality in this population.

METHODS

A retrospective cohort study was conducted involving 200 MHD patients from Beijing Tongren Hospital, analyzed from January 1, 2013, to July 1, 2024. The mortality outcomes included CVD-related and all-cause mortality. Kaplan-Meier survival curves were utilized to assess the impact of Lp(a), while Cox regression analysis and restrict cubic spline were performed to explore associations.

RESULTS

The median follow-up duration was 66.5 months, with 121 deaths recorded (60.5%), of which 66 (54.5%) were due to CVD. Kaplan-Meier analysis indicated that patients in the highest tertile of Lp(a) levels had the lowest survival for both CVD mortality and all-cause mortality. In multivariable Cox regression, higher Lp(a) levels were independently associated with an increased risk of both CVD mortality and all-cause mortality. The restricted cubic splines regression model showed that the risk of CVD mortality and all-cause mortality increased with rising Lp(a) levels.

CONCLUSION

Elevated serum Lp(a) levels are independently associated with increased mortality from both CVD and all causes in Chinese MHD patients. These findings indicate that serum Lp(a) may be a significant risk factor for CVD mortality in this population.

The Role of Lipoprotein (a) in the Progression of Aortic Stenosis

Calcific aortic stenosis is a complex process that involves several factors, including genetics, lipid infiltration, inflammation, and hemodynamic stress. This process begins at an early age and progresses throughout one's lifetime. Lipoprotein (a), or Lp(a), has been shown to drive progression of aortic stenosis in several studies. Additionally, analyses have demonstrated that a higher serum level of Lp(a) is associated with earlier onset of aortic stenosis and faster progression of mean pressure across the aortic valve. The current cornerstone medications to lower low-density lipoprotein do not have a meaningful impact on Lp(a) levels. In this article, we will review current therapeutics that are in development to lower serum Lp(a), including several that involve ribonucleic acid modification. Although these novel therapeutics are promising, it is to be determined whether lowering serum Lp(a) correlates to reduced calcific aortic stenosis and improved cardiovascular outcomes.

PCSK9 with a gain of function D374Y mutation aggravates atherosclerosis by inhibiting PPARα expression

The preprotein convertase, Bacillus subtilis protease/kexin type 9 serine protease (PCSK9), has garnered significant attention as a potential lipid lowering and therapeutic drug target for atherosclerosis (AS). Peroxisome proliferator-activated receptor alpha (PPARα) is expressed in various tissues and has crucial roles in lipid metabolism and the inflammatory response; however, the precise impact of PCSK9 on AS progression through its regulation of PPARα remains uncertain. The present study aimed to examine the impact of introducing stable liver transduction of human derived PCSK9 with a gain of function D374Y mutation (PCSK9DY) into systemic PPARα knockout mice (PPARα-/-) on plasma lipid levels and AS. Enzymatic assays were employed to evaluate plasma lipid concentrations at various time points, and aortic plaque formation and the degree of inflammatory infiltration quantified. Subsequently, we validated our in vivo results using mouse primary peritoneal macrophages (MPMs). Furthermore, AAV8.2-PPARα virus vector was transduced into transgenic mice of human PCSK9(hPCSK9DY-Tg) by tail vein, and the changes of plasma lipid level and AS were detected. PCSK9DY expression exacerbated symptoms of hypercholesterolemia in PPARα-/- mice. En face analysis and quantification of aortic root sections demonstrated a significant increase in aortic plaque area and inflammatory infiltration in PCSK9DY transduced PPARα-/- mice. Secretion of inflammatory cytokines was elevated in PCSK9DY transduced PPARα-/- mice. In vitro, recombinant hPCSK9 protein promotes the foam cell formation and inflammatory cytokines secretion of PPARα-/- MPMs by increasing the expression of SR-A and TLR4/NF-κB pathway proteins. AAV8.2-PPARα virus vector can reduce the plasma lipid level and AS formation in hPCSK9DY-Tg mice. These finding demonstrate that PCSK9DY expression notably facilitated AS progression in PPARα-/- mice by increasing plasma lipid concentrations and inflammation. However, overexpression of PPARα can reduce AS formation in hPCSK9DY-Tg mice.

Treatment with PCSK9 inhibitors influences microRNAs expression and changes of arterial wall properties: a randomized controlled trial

BACKGROUND

MicroRNAs (miRNAs) are involved in the synthesis of proprotein convertase subtilisin-kexin type 9 (PCSK9), one of the regulators of low-density lipoprotein cholesterol (LDL-C) metabolism, and are directly involved in the atherosclerotic process. The aim of this study was to verify whether treatment with PCSK9 inhibitors (PCSK9i) and changes in the expression of miRNAs involved in PCSK9 metabolism are associated with arterial wall properties in stable post-myocardial infarction (MI) patients with insufficiently regulated LDL-C levels and significantly increased Lp(a) levels.

METHODS

Ninety-five patients after MI were enrolled and randomized to a placebo (N = 31) or PCSK9i group (N = 64). The treatment group received subcutaneous alirocumab 150 mg or evolocumab 140 mg, every 2 weeks. Blood for biochemical and epigenetic analysis was taken and ultrasound measurements of flow-mediated dilation of brachial artery (FMD), carotid intima-media thickness (c-IMT) and pulse wave velocity (PWV) were performed initially and after 6 months of treatment. The expression of the selected 5 miRNAs (miR-191-5p, miR-224-5p, miR-337-3p, miR-483-5p, and miR-552-3p) was quantified using quantitative polymerase chain reaction.

RESULTS

A decrease in c-IMT was associated with a decrease in the expression of miR-337-3p (ρ = 0.329; p = 0.010) and miR-483-5p (ρ = 0.324; p = 0.012). We did not detect any associations between miRNA changes and FMD or PWV.

CONCLUSIONS

Our results suggest that changes in the selected miRNAs are associated with changes in the morphological properties of the arterial wall. We have shown that the decrease in miR-483-5p expression present a good indicator of the regression of morphological atherosclerotic change. The trial registration: The study is registered with CinicalTrials under the number NCT04613167, date of registration November 2nd, 2020. Approval for this study was obtained from the National Medical Ethics Committee of the Republic of Slovenia (reference number: KME 0120-357/2018/8).

Impact of Proprotein Convertase Subtilisin/Kexin Type 9 Inhibitors on Lipoprotein(a): A Meta-Analysis and Meta-Regression of Randomized Controlled Trials

Background

Lipoprotein(a) [Lp(a)] has been independently associated with increased cardiovascular risk.

Objectives

The authors examined the effect of monoclonal antibody proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9is) on plasma Lp(a) levels across multiple trials.

Methods

Studies were retrieved comparing the effect of PCSK9i vs placebo on Lp(a) levels. The primary outcome was percent change in Lp(a) levels. Factors associated with the treatment effect were determined by meta-regression analysis. Subgroup analyses were done to explore potential treatment effect differences.

Results

PCSK9i reduced Lp(a) levels on average of -27% (95% CI: -29.8% to -24.1%, P < 0.001). Factors associated with the treatment effect included mean percent change in low-density lipoprotein cholesterol (P = 0.003, beta coefficient 0.34, 95% CI: 0.11-0.57, tau2 = 94.8, R2 = 11.82) and apolipoprotein B (P < 0.002, beta coefficient 0.4, 95% CI: 0.14-0.64, tau2 = 93.68, R2 = 11.86). Subgroup analyses revealed consistent treatment effect amongst comparators vs placebo: -27.69% (95% CI: -30.85% to -24.54%, P < 0.001), vs ezetimibe: -24.0% (95% CI: -29.95% to -18.01%, P < 0.001), type of PCSK9i, evolocumab: -29.35% (95% CI: -33.56% to -25.14%, P < 0.001) vs alirocumab: -24.50% (95% CI: -27.96% to -21.04%, P < 0.001), and presence of familial hypercholesterolemia: -25.63% (95% CI: -31.96% to -19.30%, P < 0.001 vs no familial hypercholesterolemia: -27.22%; 95% CI: -30.34% to -24.09%, P < 0.001). Varying treatment effects were noted in the duration of treatment (12 weeks or shorter: -32.43% [95% CI: -36.63% to -28.23% vs >12 weeks: -22.31%] [95% CI: -25.13% to -19.49%, P < 0.001]), P interaction < 0.01.

Conclusions

PCSK9is reduce Lp(a) levels by an average of 27%. Mean percent change in low-density lipoprotein cholesterol and apolipoprotein B were associated with treatment effect.

Lipoprotein(a) in atherosclerotic cardiovascular disease and proprotein convertase subtilisin/kexin-type 9 inhibitors

High plasma lipoprotein(a) (Lp(a)) levels increase the cardiovascular risk in populations with atherosclerotic cardiovascular disease (ASCVD). Apolipoprotein (a) [apo(a)], a unique protein component of Lp(a), plays an important role in the pathogenesis of atherosclerosis. Statins, the primary medication in managing ASCVD, lower low-density lipoprotein cholesterol (LDL-C) but concurrently elevate plasma Lp(a) levels, contributing to an increased residual cardiovascular risk. In turn, proprotein convertase subtilisin/kexin-type 9 (PCSK9) inhibitors, a novel class of LDL-C lowering drugs, effectively reduce plasma Lp(a) levels, which is believed to decrease residual cardiovascular risk. However, the mechanism by which PCSK9 inhibitors reduce Lp(a) levels remains unknown. In addition, there are some clinical limitations of PCSK9 inhibitors. Here, we systematically review the past, present, and prospects of studies pertaining to Lp(a), PCSK9 inhibitors, and ASCVD.

Variation in lipoprotein(a) response to potent lipid lowering: The role of apolipoprotein (a) isoform size

BACKGROUND

Lipoprotein(a) [Lp(a)] is a driver of residual cardiovascular risk. Proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i) decrease Lp(a) with significant heterogeneity in response. We investigated contributors to the heterogeneous response.

METHODS

Cholesterol Reduction and Residual Risk in Diabetes (CHORD) was a prospective study examining lipid lowering in participants with a low-density lipoprotein cholesterol (LDL-C) > 100 mg/dL with and without diabetes (DM) on lipid lowering therapy (LLT) for 30-days with evolocumab 140 mg every 14 days combined with either atorvastatin 80 mg or ezetimibe 10 mg daily. Lp(a) level was measured by immunoturbidometry, and the apolipoprotein(a) [apo(a)] isoform size was measured by denaturing agarose gel electrophoresis and Western blotting. We examined the change in Lp(a) levels from baseline to 30 days.

RESULTS

Among 150 participants (mean age 50 years, 58% female, 50% non-White, 17% Hispanic, 50% DM), median (interquartile range) Lp(a) was 27.5 (8-75) mg/dL at baseline and 23 (3-68) mg/dL at 30 days, leading to a 10% (0-36) median reduction (P < .001). Among 73 (49%) participants with Lp(a) ≥ 30 mg/dL at baseline, there was a 15% (3-25) median reduction in Lp(a) (P < .001). While baseline Lp(a) level was not correlated with change in Lp(a) (r = 0.04, P = .59), apo(a) size directly correlated with Lp(a) reduction (P < .001). After adjustment for age, sex, race/ethnicity, DM, and type of LLT, apo(a) size remained positively associated with a reduction in Lp(a) (Beta 0.95, 95% confidence interval, 0.93-0.97, P < .001).

CONCLUSION

Our data demonstrate variation in Lp(a) reduction with potent LLT. Change in Lp(a) was strongly associated with apo(a) isoform size.

Molecular Regulation and Therapeutic Targeting of VLDL Production in Cardiometabolic Disease

There exists a complex relationship between steatotic liver disease (SLD) and atherosclerotic cardiovascular disease (CVD). CVD is a leading cause of morbidity and mortality among individuals with SLD, particularly those with metabolic dysfunction-associated SLD (MASLD), a significant proportion of whom also exhibit features of insulin resistance. Recent evidence supports an expanded role of very low-density lipoprotein (VLDL) in the pathogenesis of CVD in patients, both with and without associated metabolic dysfunction. VLDL represents the major vehicle for exporting neutral lipid from hepatocytes, with each particle containing one molecule of apolipoproteinB100 (APOB100). VLDL production becomes dysregulated under conditions characteristic of MASLD including steatosis and insulin resistance. Insulin resistance not only affects VLDL production but also mediates the pathogenesis of atherosclerotic CVD. VLDL assembly and secretion therefore represents an important pathway in the setting of cardiometabolic disease and offers several candidates for therapeutic targeting, particularly in metabolically complex patients with MASLD at increased risk of atherosclerotic CVD. Here we review the clinical significance as well as the translational and therapeutic potential of key regulatory steps impacting VLDL initiation, maturation, secretion, catabolism, and clearance.

Safety of Inclisiran: A Disproportionality Analysis from the EudraVigilance Database

Introduction: The discovery of serine protease proprotein convertase subtilisin-kexin type 9 (PCSK9) has revolutionized pharmacological lipid-lowering treatments. The first PCSK9 antagonists (PCSK9-A), evolocumab and alirocumab, were approved in 2015. Targeting PCSK9 synthesis marked a major advancement in this field, leading to the development of inclisiran, a long-acting siRNA targeting PCSK9 mRNA. However, real-world safety data on this drug are still limited. Therefore, this study aims to provide a real-world safety evaluation of inclisiran, comparing its characteristics to those of PCSK9-As. Methods: A retrospective pharmacovigilance study was conducted using EudraVigilance (EV). Inclisiran-related individual case safety reports (I-ICSRs) from 01/01/2021 to 06/30/2023 were retrieved. ICSRs for evolocumab or alirocumab from 01/01/2015 to 06/30/2023 were collected as a reference group (RG). ADRs were classified using the MedDRA dictionary. Data were evaluated using descriptive and disproportionality analyses. Crude reporting odds ratio (ROR) with 95% confidence intervals (CI) were used as disproportionality measures. Results: Of the 15,236 ICSRs, 3.7% (n = 563) involved inclisiran, with the rest in the RG. Most I-ICSRs involved female patients (51.7%) aged 18 to 64 (52.8%). The most-reported ADRs for inclisiran were "general disorders and administration site conditions" (n = 347) and "investigations" (n = 277). Significant disproportionality was found in I-ICSRs compared to the RG for "Myalgia" (ROR: 2.43; 95% CI: 1.94-3.04), "Low-density lipoprotein increased" (ROR: 11.95; 95% CI: 9.10-15.52), and "Drug ineffective" (ROR: 6.37; 95% CI: 4.64-8.74). Conclusions: The inclisiran safety profile aligns with the existing literature and pre-commercial data. However, further studies are needed to fully understand the observed differences with PCSK9-As.

Emerging clinical role of proprotein convertase subtilisin/kexin type 9 inhibition-Part one: Pleiotropic pro-atherosclerotic effects of PCSK9

BACKGROUND

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is primarily recognized for its role in lipid metabolism, but recent evidence suggests that it may have broader implications due to its diverse tissue expression.

OBJECTIVE

This review aims to explore the multifaceted functions of PCSK9, highlighting its pro-atherosclerotic effects, including its impact on circulating lipoprotein variables, non-low-density lipoprotein receptors, and various cell types involved in atherosclerotic plaque development.

CONCLUSIONS

PCSK9 exhibits diverse roles beyond lipid metabolism, potentially contributing to atherosclerosis through multiple pathways. Understanding these mechanisms could offer new insights into therapeutic strategies targeting PCSK9 for cardiovascular disease management.

Inhibition of PCSK9: A Promising Enhancer for Anti-PD-1/PD-L1 Immunotherapy

Immune checkpoint therapy, such as programmed cell death protein 1/programmed death-ligand 1 (PD-1/PD-L1) blockade, has achieved remarkable results in treating various tumors. However, most cancer patients show a low response rate to PD-1/PD-L1 blockade, especially those with microsatellite stable/mismatch repair-proficient colorectal cancer subtypes, which indicates an urgent need for new approaches to augment the efficacy of PD-1/PD-L1 blockade. Cholesterol metabolism, which involves generating multifunctional metabolites and essential membrane components, is also instrumental in tumor development. In recent years, inhibiting proprotein convertase subtilisin/kexin type 9 (PCSK9), a serine proteinase that regulates cholesterol metabolism, has been demonstrated to be a method enhancing the antitumor effect of PD-1/PD-L1 blockade to some extent. Mechanistically, PCSK9 inhibition can maintain the recycling of major histocompatibility protein class I, promote low-density lipoprotein receptor-mediated T-cell receptor recycling and signaling, and modulate the tumor microenvironment (TME) by affecting the infiltration and exclusion of immune cells. These mechanisms increase the quantity and enhance the antineoplastic effect of cytotoxic T lymphocyte, the main functional immune cells involved in anti-PD-1/PD-L1 immunotherapy, in the TME. Therefore, combining PCSK9 inhibition therapy with anti-PD-1/PD-L1 immunotherapy may provide a novel option for improving antitumor effects and may constitute a promising research direction. This review concentrates on the relationship between PCSK9 and cholesterol metabolism, systematically discusses how PCSK9 inhibition potentiates PD-1/PD-L1 blockade for cancer treatment, and highlights the research directions in this field.

The role of natural products as PCSK9 modulators: A review

A variety of mechanisms and drugs have been shown to attenuate cardiovascular disease (CVD) onset and/or progression. Recent researchers have identified a potential role of proprotein convertase subtilisin/kexin type 9 (PCSK9) in modulating lipid metabolism and reducing plasma low density lipoprotein (LDL) levels. PCSK9 is the central protein in the metabolism of LDL cholesterol (LDL-C) owing to its major function in LDL receptor (LDLR) degradation. Due to the close correlation of cardiovascular disease with lipid levels, many in vivo and in vitro investigations are currently underway studying the physiological role of PCSK9. Furthermore, many studies are actively investigating the mechanisms of various compounds that influence lipid associated-disorders and their associated cardiovascular diseases. PCSK9 inhibitors have been shown to have significant impact in the prevention of emerging cardiovascular diseases. Natural products can effectively be used as PCSK9 inhibitors to control lipid levels through various mechanisms. In this review, we evaluate the role of phytochemicals and natural products in the regulation of PCSK9, and their ability to prevent cardiovascular diseases. Moreover, we describe their mechanisms of action, which have not to date been delineated.

Early administration of proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors in patients with acute coronary syndrome: a systematic review and meta-analysis

BACKGROUND

High-intensity statin therapy is currently recommended initial guideline therapy in ACS treatment. However, only a minority of patients are achieving LDL-C attainment goal at 6 months. Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors are on recommended guideline therapy post-ACS if LDL-C goal attainment is not achieved after high-intensity statin (4-6 weeks) and after the addition of ezetimibe if guideline goal attainment is not achieved after an additional 4-6 weeks. Thus, it has been recommended that PCSK9 inhibitors be considered earlier post-ACS. However, the efficacy of early PCSK9 inhibitors initiation in ACS patients remains uncertain.

METHODS

This systematic review and meta-analysis was conducted following PRISMA guidelines. Randomized controlled trials (RCTs) and observational studies involving ACS patients who received PCSK9 inhibitors within 48 h of hospitalization were included. Common and random effects models were used to evaluate the pooled effect of early PCSK9 inhibitor administration. Nine RCTs and three cohort studies were included.

RESULTS

Early PCSK9 inhibitor administration reduced the incidence of MI, ACS hospitalization, and revascularization at 6-18 months post-ACS. Although there was a drift towards reduced stroke, all-cause mortality, and cardiovascular death, no statistically significant reduction was observed. Additionally, PCSK9 inhibitors significantly enhanced lipid control at 4-12 weeks after index hospitalization.

CONCLUSION

Early PCSK9 inhibitors initiation in ACS patients reduces MACE and improves lipid profiles. While the results propose promising benefits in terms of stroke and mortality, further research with longer follow-up is required for more decisive evidence.

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.

Lipoprotein(a): Emerging insights and therapeutics

The strong association between lipoprotein (a) [Lp(a)] and atherosclerotic cardiovascular disease has led to considerations of Lp(a) being a potential target for mitigating residual cardiovascular risk. While approximately 20 % of the population has an Lp(a) level greater than 50 mg/dL, there are no currently available pharmacological lipid-lowering therapies that have demonstrated substantial reduction in Lp(a). Novel therapies to lower Lp(a) include antisense oligonucleotides and small-interfering ribonucleic acid molecules and have shown promising results in phase 2 trials. Phase 3 trials are currently underway and will test the causal relationship between Lp(a) and ASCVD and whether lowering Lp(a) reduces cardiovascular outcomes. In this review, we summarize emerging insights related to Lp(a)'s role as a risk-enhancing factor for ASCVD, association with calcific aortic stenosis, effects of existing therapies on Lp(a) levels, and variations amongst patient populations. The evolving therapeutic landscape of emerging therapeutics is further discussed.

Directly Measuring Atherogenic Lipoprotein Kinetics in Zebrafish with the Photoconvertible LipoTimer Reporter

Lipoprotein kinetics are a crucial factor in understanding lipoprotein metabolism since a prolonged time in circulation can contribute to the atherogenic character of apolipoprotein-B (ApoB)-containing lipoproteins (B-lps). Here, we report a method to directly measure lipoprotein kinetics in live developing animals. We developed a zebrafish geneticly encoded reporter, LipoTimer, in which endogenous ApoBb.1 is fused to the photoconvertible fluorophore Dendra2 which shift its emission profile from green to red upon UV exposure. By quantifying the red population of ApoB-Dendra2 over time, we found that B-lp turnover in wild-type larvae becomes faster as development proceeds. Mutants with impaired B-lp uptake or lipolysis present with increased B-lp levels and half-life. In contrast, mutants with impaired B-lp triglyceride loading display slightly fewer and smaller-B-lps, which have a significantly shorter B-lp half-life. Further, we showed that chronic high-cholesterol feeding is associated with a longer B-lp half-life in wild-type juveniles but does not lead to changes in B-lp half-life in lipolysis deficient apoC2 mutants. These data support the hypothesis that B-lp lipolysis is suppressed by the flood of intestinal-derived B-lps that follow a high-fat meal.

Apolipoprotein(a) production and clearance are associated with plasma IL-6 and IL-18 levels, dependent on ethnicity

BACKGROUND AND AIMS

High plasma lipoprotein (a) [Lp(a)] levels are associated with increased atherosclerotic cardiovascular disease (ASCVD), in part attributed to elevated inflammation. High plasma Lp(a) levels inversely correlate with apolipoprotein (a) [(APO(a)] isoform size. APO(a) isoform size is negatively associated with APO(a) production rate (PR) and positively associated with APO(a) fractional catabolic rate (FCR). We asked whether APO(a) PR and FCR (kinetics) are associated with plasma levels of interleukin (IL)-6 and IL-18, pro-inflammatory interleukins that promote ASCVD.

METHODS

We used samples from existing data of APO(a) kinetic studies from an ethnically diverse cohort (n = 25: 10 Black, 9 Hispanic, and 6 White subjects) and assessed IL-6 and IL-18 plasma levels. We performed multivariate linear regression analyses to examine the relationships between predictors APO(a) PR or APO(a) FCR, and outcome variables IL-6 or IL-18. In these analyses, we adjusted for parameters known to affect Lp(a) levels and APO(a) PR and FCR, including race/ethnicity and APO(a) isoform size.

RESULTS

APO(a) PR and FCR were positively associated with plasma IL-6, independent of isoform size, and dependent on race/ethnicity. APO(a) PR was positively associated with plasma IL-18, independent of isoform size and race/ethnicity. APO(a) FCR was not associated with plasma IL-18.

CONCLUSIONS

Our studies demonstrate a relationship between APO(a) PR and FCR and plasma IL-6 or IL-18, interleukins that promote ASCVD. These studies provide new insights into Lp(a) pro-inflammatory properties and are especially relevant in view of therapies targeting APO(a) to decrease cardiovascular risk.

Elevated High-Sensitivity C-Reactive Protein Level Enhances the Impact of Lipoprotein(a) on Platelet Reactivity in PCI Patients Treated with Clopidogrel

BACKGROUND

Recently, the effect of Lipoprotein(a) [Lp(a)] on thrombogenesis has aroused great interest, while inflammation has been reported to modify the Lp(a)-associated risks through an unidentified mechanism.

PURPOSE

This study aimed to evaluate the association between platelet reactivity with Lp(a) and high-sensitivity C-reactive protein (hs-CRP) levels in percutaneous intervention (PCI) patients treated with clopidogrel.

METHODS

Data were collected from 10,724 consecutive PCI patients throughout the year 2013 in Fuwai Hospital. High on-treatment platelet reactivity (HTPR) and low on-treatment platelet reactivity (LTPR) were defined as thrombelastography (TEG) maximum amplitude of adenosine diphosphate-induced platelet (MAADP) > 47 mm and < 31 mm, respectively.

RESULTS

6615 patients with TEG results were finally enrolled. The mean age was 58.24 ± 10.28 years and 5131 (77.6%) were male. Multivariable logistic regression showed that taking Lp(a) < 30 mg/dL and hs-CRP < 2 mg/L as the reference, isolated Lp(a) elevation [Lp(a) ≥ 30 mg/dL and hs-CRP < 2 mg/L] was not significantly associated with HTPR (P = 0.153) or LTPR (P = 0.312). However, the joint elevation of Lp(a) and hs-CRP [Lp(a) ≥ 30 mg/dL and hs-CRP ≥ 2 mg/L] exhibited enhanced association with both HTPR (OR:1.976, 95% CI 1.677-2.329) and LTPR (OR:0.533, 95% CI 0.454-0.627).

CONCLUSIONS

The isolated elevation of Lp(a) level was not an independent indicator for platelet reactivity, yet the concomitant elevation of Lp(a) and hs-CRP levels was significantly associated with increased platelet reactivity. Whether intensified antiplatelet therapy or anti-inflammatory strategies could mitigate the risks in patients presenting combined Lp(a) and hs-CRP elevation requires future investigation.

Lp(a) and risk of cardiovascular disease - A review of existing evidence and emerging concepts

Cardiovascular disease (CVD) remains the leading cause of death among adults in the United States. There has been significant advancement in the diagnosis and treatment of atherosclerotic cardiovascular disease (ASCVD) and its underlying risk factors. In certain populations, there remains a significant residual risk despite adequate lowering of low-density lipoprotein cholesterol (LDL-C) and control of traditional risk factors. This has led to an interest in research to identify additional risk factors that contribute to atherosclerotic cardiovascular disease. Elevated lipoprotein (a) [Lp(a)] has been identified as an independent risk factor contributing to an increased risk for CVD. There are also ethnic and racial disparities in Lp(a) inheritance that need to be understood. This paper reviews the current literature on lipoprotein a, proposed mechanisms of actions for cardiovascular disease, recommendations for testing, and the current and emerging therapies for lowering Lp(a).

The Promise of PCSK9 and Lipoprotein(a) as Targets for Gene Silencing Therapies

PURPOSE

High plasma concentrations of LDL and lipoprotein(a) (Lp[a]) are independent and causal risk factors for atherosclerotic cardiovascular disease (ASCVD). There is an unmet therapeutic need for high-risk patients with elevated levels of LDL-C and/or Lp(a). Recent advances in the development of nucleic acids for gene silencing (ie, triantennary N-acetylgalactosamine conjugated antisense-oligonucleotides [ASOs] and small interfering RNA [siRNA]) targeting proprotein convertase subtilisin/kexin type 9 (PCSK9) and Lp(a) offer effective and sustainable therapies.

METHODS

Related articles in the English language were identified through a search for original and review articles in the PubMed database using the following key terms: cardiovascular disease, dyslipidemia, PCSK9 inhibitors, Lp(a), LDL-cholesterol, familial hypercholesterolemia, siRNA, and antisense oligonucleotide and clinical trials (either alone or in combination).

FINDINGS

Inclisiran, the most advanced siRNA-treatment targeting hepatic PCSK9, is well tolerated, producing a >30% reduction on LDL-C levels in randomized controlled trials. Pelacarsen is the most clinical advanced ASO, whereas olpasiran and SLN360 are the 2 siRNAs directed against the mRNA of the LPA gene. Evidence suggests that all Lp(a)-targeting agents are safe and well tolerated, with robust and sustained reduction in plasma Lp(a) concentration up to 70% to 90% in individuals with elevated Lp(a) levels.

IMPLICATIONS

Cumulative evidence from clinical trials supports the value of ASO and siRNA therapies targeting the synthesis of PCSK9 and Lp(a) for lowering LDL-C and Lp(a) in patients with established ASCVD or high risk of ASCVD. Further research is needed to examine whether gene silencing therapy could improve clinical outcomes in patients with elevated LDL and/or Lp(a) levels. Confirmation of the tolerability and cost-effectiveness of long-term inhibition of PCSK9 and Lp(a) with this approach is essential.

Inclisiran: a new generation of lipid-lowering siRNA therapeutic

Atherosclerotic heart disease (AHD) is a major cause of morbidity and mortality worldwide. Lowering low-density lipoprotein cholesterol (LDL-C) levels is a key strategy to prevent and treat AHD. Inclisiran is a novel siRNA drug that targets proprotein convertase subtilisin/kexin type 9 (PCSK9) gene expression and reduces LDL-C levels with only two or three injections per year. This review summarizes the mechanism, efficacy, safety, and applications of Inclisiran in various populations and settings, based on recent literature. It also compares Inclisiran with other lipid-lowering drugs, especially other PCSK9 inhibitors. We conclude that Inclisiran is a promising lipid-lowering agent that can provide convenience and effectiveness for patients with high cardiovascular risk. However, some challenges and limitations remain for Inclisiran, such as its long-term safety and efficacy, its cost-effectiveness and accessibility, and its interactions and synergies with other drugs. These issues need further investigation and evaluation in future studies.

Plasminogen Receptors Promote Lipoprotein(a) Uptake by Enhancing Surface Binding and Facilitating Macropinocytosis

BACKGROUND

High levels of Lp(a) (lipoprotein(a)) are associated with multiple forms of cardiovascular disease. Lp(a) consists of an apoB100-containing particle attached to the plasminogen homologue apo(a). The pathways for Lp(a) clearance are not well understood. We previously discovered that the plasminogen receptor PlgRKT (plasminogen receptor with a C-terminal lysine) promoted Lp(a) uptake in liver cells. Here, we aimed to further define the role of PlgRKT and to investigate the role of 2 other plasminogen receptors, annexin A2 and S100A10 (S100 calcium-binding protein A10) in the endocytosis of Lp(a).

METHODS

Human hepatocellular carcinoma (HepG2) cells and haploid human fibroblast-like (HAP1) cells were used for overexpression and knockout of plasminogen receptors. The uptake of Lp(a), LDL (low-density lipoprotein), apo(a), and endocytic cargos was visualized and quantified by confocal microscopy and Western blotting.

RESULTS

The uptake of both Lp(a) and apo(a), but not LDL, was significantly increased in HepG2 and HAP1 cells overexpressing PlgRKT, annexin A2, or S100A10. Conversely, Lp(a) and apo(a), but not LDL, uptake was significantly reduced in HAP1 cells in which PlgRKT and S100A10 were knocked out. Surface binding studies in HepG2 cells showed that overexpression of PlgRKT, but not annexin A2 or S100A10, increased Lp(a) and apo(a) plasma membrane binding. Annexin A2 and S100A10, on the other hand, appeared to regulate macropinocytosis with both proteins significantly increasing the uptake of the macropinocytosis marker dextran when overexpressed in HepG2 and HAP1 cells and knockout of S100A10 significantly reducing dextran uptake. Bringing these observations together, we tested the effect of a PI3K (phosphoinositide-3-kinase) inhibitor, known to inhibit macropinocytosis, on Lp(a) uptake. Results showed a concentration-dependent reduction confirming that Lp(a) uptake was indeed mediated by macropinocytosis.

CONCLUSIONS

These findings uncover a novel pathway for Lp(a) endocytosis involving multiple plasminogen receptors that enhance surface binding and stimulate macropinocytosis of Lp(a). Although the findings were produced in cell culture models that have limitations, they could have clinical relevance since drugs that inhibit macropinocytosis are in clinical use, that is, the PI3K inhibitors for cancer therapy and some antidepressant compounds.

Use of Apolipoprotein B in the Era of Precision Medicine: Time for a Paradigm Change?

Atherosclerotic cardiovascular disease (ASCVD) remains the leading cause of death worldwide and the risk of a major cardiovascular event is highest among those with established disease. Ongoing management of these patients relies on the accurate assessment of their response to any prescribed therapy, and their residual risk, in order to optimize treatment. Recent international guidelines and position statements concur that the plasma concentration of apolipoprotein B (apoB) is the most accurate measure of lipoprotein associated ASCVD risk. This is especially true for the growing number of individuals with diabetes, obesity, or the metabolic syndrome, and those on statin therapy. Most guidelines, however, continue to promote LDL-C as the primary risk marker due to uncertainty as to whether the greater accuracy of apoB is sufficient to warrant a paradigm shift. Recommendations regarding apoB measurement vary, and the information provided on how to interpret apoB results is sometimes insufficient, particularly for non-lipid specialists. Misinformation regarding the reliability of the assays is also frequently repeated despite its equivalent or better standardization than many other diagnostic assays. Thus, demand for apoB testing is relatively low, which means there is little incentive to increase its availability or reduce its cost. In this review, we examine the results of recent clinical outcomes studies and meta-analyses on the relative values of apoB, LDL-C, and non-HDL-C as markers of ASCVD risk. Although there is seemingly minimal difference among these markers when only population-based metrics are considered, it is evident from our analysis that, from a personalized or precision medicine standpoint, many individuals would benefit, at a negligible total cost, if apoB measurement were better integrated into the diagnosis and treatment of ASCVD.

Composition and distribution of lipoproteins after evolocumab in familial dysbetalipoproteinemia: A randomized controlled trial

BACKGROUND

Proprotein convertase subtilisin kexin type 9 (PCSK9) monoclonal antibodies (mAbs) reduce fasting and post fat load cholesterol in non-HDL and intermediate density lipoprotein (IDL) in familial dysbetalipoproteinemia (FD). However, the effect of PCSK9 mAbs on the distribution and composition of atherogenic lipoproteins in patients with FD is unknown.

OBJECTIVE

To evaluate the effect of the PCSK9 mAb evolocumab added to standard lipid-lowering therapy in patients with FD on fasting and post fat load lipoprotein distribution and composition.

METHODS

Randomized placebo-controlled double-blind crossover trial comparing evolocumab (140 mg subcutaneous every 2 weeks) with placebo during two 12-week treatment periods. Patients received an oral fat load at the start and end of each treatment period. Apolipoproteins (apo) were measured with ultracentrifugation, gradient gel electrophoresis, retinyl palmitate and SDS-PAGE.

RESULTS

PCSK9 mAbs significantly reduced particle number of all atherogenic lipoproteins, with a stronger effect on smaller lipoproteins than on larger lipoproteins (e.g. IDL-apoB 49%, 95%confidence interval (CI) 41-59 and very low-density lipoprotein (VLDL)-apoB 33%, 95%CI 16-50). Furthermore, PCSK9 mAbs lowered cholesterol more than triglyceride (TG) in VLDL, IDL and low-density lipoprotein (LDL) (e.g. VLDL-C 48%, 95%CI 29-63%; and VLDL-TG 20%, 95%CI 6.3-41%). PCSK9 mAbs did not affect the post fat load response of chylomicrons.

CONCLUSION

PCSK9 mAbs added to standard lipid-lowering therapy in FD patients significantly reduced lipoprotein particle number, in particular the smaller and more cholesterol-rich lipoproteins (i.e. IDL and LDL). PCSK9 mAbs did not affect chylomicron metabolism. It seems likely that the observed effects are achieved by increased hepatic lipoprotein clearance, but the specific working mechanism of PCSK9 mAbs in FD patients remains to be elucidated.

Daring to dream: Targeting lipoprotein(a) as a causal and risk-enhancing factor

Lipoprotein(a) [Lp(a)], a distinct lipoprotein class, has become a major focus for cardiovascular research. This review is written in light of the recent guideline and consensus statements on Lp(a) and focuses on 1) the causal association between Lp(a) and cardiovascular outcomes, 2) the potential mechanisms by which elevated Lp(a) contributes to cardiovascular diseases, 3) the metabolic insights on the production and clearance of Lp(a) and 4) the current and future therapeutic approaches to lower Lp(a) concentrations. The concentrations of Lp(a) are under strict genetic control. There exists a continuous relationship between the Lp(a) concentrations and risk for various endpoints of atherosclerotic cardiovascular disease (ASCVD). One in five people in the Caucasian population is considered to have increased Lp(a) concentrations; the prevalence of elevated Lp(a) is even higher in black populations. This makes Lp(a) a cardiovascular risk factor of major public health relevance. Besides the association between Lp(a) and myocardial infarction, the relationship with aortic valve stenosis has become a major focus of research during the last decade. Genetic studies provided strong support for a causal association between Lp(a) and cardiovascular outcomes: carriers of genetic variants associated with lifelong increased Lp(a) concentration are significantly more frequent in patients with ASCVD. This has triggered the development of drugs that can specifically lower Lp(a) concentrations: mRNA-targeting therapies such as anti-sense oligonucleotide (ASO) therapies and short interfering RNA (siRNA) therapies have opened new avenues to lower Lp(a) concentrations more than 95%. Ongoing Phase II and III clinical trials of these compounds are discussed in this review.

Protein structural insights into a rare PCSK9 gain-of-function variant (R496W) causing familial hypercholesterolemia in a Saudi family: whole exome sequencing and computational analysis

Familial hypercholesterolemia (FH) is a globally underdiagnosed genetic condition associated with premature cardiovascular death. The genetic etiology data on Arab FH patients is scarce. Therefore, this study aimed to identify the genetic basis of FH in a Saudi family using whole exome sequencing (WES) and multidimensional bioinformatic analysis. Our WES findings revealed a rare heterozygous gain-of-function variant (R496W) in the exon 9 of the PCSK9 gene as a causal factor for FH in this family. This variant was absent in healthy relatives of the proband and 200 healthy normolipidemic controls from Saudi Arabia. Furthermore, this variant has not been previously reported in various regional and global population genomic variant databases. Interestingly, this variant is classified as "likely pathogenic" (PP5) based on the variant interpretation guidelines of the American College of Medical Genetics (ACMG). Computational functional characterization suggested that this variant could destabilize the native PCSK9 protein and alter its secondary and tertiary structural features. In addition, this variant was predicted to negatively influence its ligand-binding ability with LDLR and Alirocumab antibody molecules. This rare PCSK9 (R496W) variant is likely to expand our understanding of the genetic basis of FH in Saudi Arabia. This study also provides computational structural insights into the genotype-protein phenotype relationship of PCSK9 pathogenic variants and contributes to the development of personalized medicine for FH patients in the future.

Proteomic studies on apoB-containing lipoprotein in cardiovascular research: A comprehensive review

The complexity of cardiovascular diseases (CVDs), which remains the leading cause of death worldwide, makes the current clinical pathway for cardiovascular risk assessment unsatisfactory, as there remains a substantial unexplained residual risk. Simultaneous assessment of a large number of plasma proteins may be a promising tool to further refine risk assessment, and lipoprotein-associated proteins have the potential to fill this gap. Technical advances now allow for high-throughput proteomic analysis in a reproducible and cost-effective manner. Proteomics has great potential to identify and quantify hundreds of candidate marker proteins in a sample and allows the translation from isolated lipoproteins to whole plasma, thus providing an individual multiplexed proteomic fingerprint. This narrative review describes the pathophysiological roles of atherogenic apoB-containing lipoproteins and the recent advances in their mass spectrometry-based proteomic characterization and quantitation for better refinement of CVD risk assessment.

Supporting evidence for lipoprotein(a) measurements in clinical practice

High levels of lipoprotein(a) [Lp(a)] are causal for development of atherosclerotic cardiovascular disease and highly regulated by genetics. Levels are higher in Blacks compared to Whites, and in women compared to men. Lp(a)'s main protein components are apolipoprotein (apo) (a) and apoB100, the latter being the main component of Low-Density Lipoprotein (LDL) particles. Studies have identified Lp(a) to be associated with inflammatory, coagulation and wound healing pathways. Lack of validated and accepted assays to measure Lp(a), risk cutoff values, guidelines for diagnosis, and targeted therapies have added challenges to the field. Scientific efforts are ongoing to address these, including studies evaluating the cardiovascular benefits of decreasing Lp(a) levels with targeted apo(a) lowering treatments. This review will provide a synopsis of evidence-based effects of high Lp(a) on disease presentation, highlight available guidelines and discuss promising therapies in development. We will conclude with current clinical information and future research needs in the field.

Emerging Therapies for the Treatment of Atherosclerotic Cardiovascular Disease: From Bench to Bedside

Primarily a consequence of sedentary lifestyle, atherosclerosis has already reached pandemic proportions, and with every year the burden of it is only increasing. As low-density lipoprotein cholesterol (LDL-C) represents a crucial factor in atherosclerosis formation and progression, stringent lipid-lowering therapy could conceivably be the key to preventing the unfavorable outcomes that arise as a consequence of atherosclerosis. The use of statins in lipid-lowering is often burdened by adverse events or is insufficient to prevent cardiovascular events as a monotherapy. Therefore, in the present review, the authors aimed to discuss the underlying mechanisms of dyslipidemia and associated atherosclerotic cardiovascular disease (ASCVD) and preclinical and clinical trials of novel therapeutic approaches to its treatment, some of which are still in the early stages of development. Apart from novel therapies, a novel change in perspective is needed. Specifically, the critical objective in the future management of ASCVD is to embrace emerging evidence in the field of atherosclerosis, because clinicians are often burden by common practice and personal experience, both of which have so far been shown to be futile in the setting of atherosclerosis.

Genetics, Safety, Cost-Effectiveness, and Accessibility of Injectable Lipid-Lowering Agents: A Narrative Review

Cardiovascular disease causes significant personal, financial, and societal burden and is a major cause of mortality and morbidity globally. Dyslipidemia has proven to be a major factor that contributes to its increased incidence; thus, since a long time, low-density lipoprotein cholesterol-lowering therapies have been employed to reduce coronary artery disease-associated mortality. The first-line therapy for hyperlipidemia and dyslipidemia is statins. Evidence showed that statins decrease the level of LDL-C resulting in a lower risk of CVD (20-25% for every decrease of 1 mmol/L). However, due to statin intolerance in some patients and despite using maximal doses, they have not been successful in lowering cardiovascular-associated mortality. Moreover, bococizumab was recently suspended due to its higher immunogenicity with time, resulting in less efficacy with long-term use. Alternatives to statins are PCSK9 inhibitors which are administered subcutaneously every two or four weeks. They are injectables with considerable lipid-lowering properties. This narrative review discusses their genetics, safety, tolerability, and cost-effectiveness. It also quantifies their benefit in certain subgroups by analyzing the findings from recent randomized clinical trials. Current data from phase 2 and 3 trials (ORION, ODYSSEY, and FOURIER) suggest a favorable profile for evolocumab, alirocumab, and inclisiran with minimal tolerable side effects and superior efficacy in statin-intolerant patients. Their cost-effectiveness has not yet been established clearly, but future outcomes seem promising.

Relationship of apolipoprotein(a) isoform size with clearance and production of lipoprotein(a) in a diverse cohort

Lipoprotein(a) [Lp(a)] has two main proteins, apoB100 and apo(a). High levels of Lp(a) confer an increased risk for atherosclerotic cardiovascular disease. Most people have two circulating isoforms of apo(a) differing in their molecular mass, determined by the number of Kringle IV Type 2 repeats. Previous studies report a strong inverse relationship between Lp(a) levels and apo(a) isoform sizes. The roles of Lp(a) production and fractional clearance and how ancestry affects this relationship remain incompletely defined. We therefore examined the relationships of apo(a) size with Lp(a) levels and both apo(a) fractional clearance rates (FCR) and production rates (PR) in 32 individuals not on lipid-lowering treatment. We determined plasma Lp(a) levels and apo(a) isoform sizes, and used the relative expression of the two isoforms to calculate a "weighted isoform size" (wIS). Stable isotope studies were performed, using D3-leucine, to determine the apo(a) FCR and PR. As expected, plasma Lp(a) concentrations were inversely correlated with wIS (R2 = 0.27; P = 0.002). The wIS had a modest positive correlation with apo(a) FCR (R2 = 0.10, P = 0.08), and a negative correlation with apo(a) PR (R2 = 0.11; P = 0.06). The relationship between wIS and PR became significant when we controlled for self-reported race and ethnicity (SRRE) (R2 = 0.24, P = 0.03); controlling for SRRE did not affect the relationship between wIS and FCR. Apo(a) wIS plays a role in both FCR and PR; however, adjusting for SRRE strengthens the correlation between wIS and PR, suggesting an effect of ancestry.

Structure-activity relationship and biological evaluation of xanthine derivatives as PCSK9 inhibitors for the treatment of atherosclerosis

Developing non-statin small molecules for the treatment of hypercholesterolemia remains challenging. The proprotein convertase subtilisin/kexin type 9 (PCSK9)-targeted therapies have attracted considerable attentions. Forty-five 7030B-C5 derivatives were synthesized and evaluated for the PCSK9 repression activity, taking the PCSK9 transcriptional inhibitor 7030B-C5 as the lead. Structure-activity relationship (SAR) analysis at C8 and N7-position was carried out, and compound 3s and 5r exhibited comparable PCSK9 transcriptional inhibitory activity but much lower cytotoxicity with the therapeutic index (TI) values doubled of that of 7030B-C5. In the in vitro assay, both compounds significantly reduced the level of PCSK9 protein and increased LDL receptor (LDLR) protein level. What's more, both compounds promoted LDL cholesterol (LDL-C) clearance more efficiently than 7030B-C5 in HepG2 cells. Most importantly, compound 3s reduced the atherosclerotic plaque areas with promising lipid-lowing effects in ApoE KO mice with a higher in vivo activity and lower toxicity. The regulatory mechanism of 3s was explored that it might target the transcription factor HNF1α and/or HINFP upstream of PCSK9 transcription, similar to that of 7030B-C5. Thus, 3s was considered as a potential anti-atherosclerosis drug candidate as a novel PCSK9 down-regulatory agent, worthy of further investigations.

Effect of Triglyceride-Glucose Indices and Circulating PCSK9-Associated Cardiovascular Risk in STEMI Patients with Primary Percutaneous Coronary Artery Disease: A Prospective Cohort Study

Background and Aims

This study aimed to determine whether convertase subtilisin/kexin type 9 (PCSK9)-associated cardiovascular risk is modulated by triglyceride-glucose (TyG) in ST-segment elevation myocardial infarction (STEMI) patients with primary percutaneous coronary disease (PCI).

Methods

A total of 1541 patients with STEMI (aged ≥18 years) undergoing primary PCI were consecutively enrolled between March 2017 and March 2019.

Outcomes

When stratifying the overall population according to TyG indices less than or greater than the median (TyG median = 9.07) as well as according to quartiles of PCSK9 levels, higher TyG index levels were significantly associated with all-cause mortality only when TyG levels were 9.07 or higher (ie, relative to quartile 1 [Q1], the adjusted HR for all-cause mortality was 3.20 [95% CI, 0.54-18.80] for Q2, p = 0.199; 7.89 [95% CI, 1.56-40.89] for Q3, p = 0.013; and 5.61 [95% CI, 1.04-30.30] for Q4, p = 0.045. During a median follow-up period of 1.96 years, the HR for all-cause mortality was higher in the subset of patients with TyG ≥median and PCSK9 ≥median (p for trend = 0.023) among those with type 2 diabetes mellitus (T2DM). However, there were no statistically significant differences among the subgroups. Among T2DM patients with a TyG index greater than the median, the Kaplan-Meier curve showed that patients with the highest PCSK9 levels had an increased risk of all-cause mortality (log-rank p = 0.017) and cardiac-cause mortality (log-rank p = 0.037) compared with lower PCSK9 quartile levels.

Conclusion

Elevated PCSK9 levels are related to all-cause mortality and cardiac-related mortality when TyG levels are greater than the median, but not when levels are less than the median. This suggests a potential benefit of lowering circulating PCSK9 levels in STEMI patients with insulin resistance.

Lipoprotein(a) in Atherosclerotic Diseases: From Pathophysiology to Diagnosis and Treatment

Lipoprotein(a) (Lp(a)) is a low-density lipoprotein (LDL) cholesterol-like particle bound to apolipoprotein(a). Increased Lp(a) levels are an independent, heritable causal risk factor for atherosclerotic cardiovascular disease (ASCVD) as they are largely determined by variations in the Lp(a) gene (LPA) locus encoding apo(a). Lp(a) is the preferential lipoprotein carrier for oxidized phospholipids (OxPL), and its role adversely affects vascular inflammation, atherosclerotic lesions, endothelial function and thrombogenicity, which pathophysiologically leads to cardiovascular (CV) events. Despite this crucial role of Lp(a), its measurement lacks a globally unified method, and, between different laboratories, results need standardization. Standard antilipidemic therapies, such as statins, fibrates and ezetimibe, have a mediocre effect on Lp(a) levels, although it is not yet clear whether such treatments can affect CV events and prognosis. This narrative review aims to summarize knowledge regarding the mechanisms mediating the effect of Lp(a) on inflammation, atherosclerosis and thrombosis and discuss current diagnostic and therapeutic potentials.

Inclisiran-Safety and Effectiveness of Small Interfering RNA in Inhibition of PCSK-9

Dyslipidemia is listed among important cardiovascular disease risk factors. Treating lipid disorders is difficult, and achieving desirable levels of LDL-cholesterol (LDL-C) is essential in both the secondary and primary prevention of cardiovascular disease. For many years, statins became the basis of lipid-lowering therapy. Nevertheless, these drugs are often insufficient due to their side effects and restrictive criteria for achieving the recommended LDL-C values. Even the addition of other drugs, i.e., ezetimibe, does not help one achieve the target LDL-C. The discovery of proprotein convertase subtilisin/kexin type 9 (PCSK9) discovery has triggered intensive research on a new class of protein-based drugs. The protein PCSK9 is located mainly in hepatocytes and is involved in the metabolism of LDL-C. In the beginning, antibodies against the PCSK9 protein, such as evolocumab, were invented. The next step was inclisiran. Inclisiran is a small interfering RNA (siRNA) that inhibits the expression of PCSK9 by binding specifically to the mRNA precursor of PCSK9 protein and causing its degradation. It has been noticed in recent years that siRNA is a powerful tool for biomedical research and drug discovery. The purpose of this work is to summarize the molecular mechanisms, pharmacokinetics, pharmacodynamics of inclisiran and to review the latest research.

Can proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors regress coronary atherosclerotic plaque? A systematic review and meta-analysis

OBJECTIVE

Whether inhibition of proprotein convertase subtilisin/kexin type 9 (PCSK9) promotes the regression of coronary atherosclerotic plaque in statin-treated individuals remains unclear. This study examined whether PCSK9 inhibitors combined with statin therapy could increase atherosclerotic plaque regression compared with statin therapy alone.

METHODS

PubMed, the Cochrane Central Register of Controlled Trials (CENTRAL), the database Clinical trials, and the Web of Science were searched to report the coronary atherosclerotic plaque of PCSK9 inhibitors using intravascular ultrasonography (IVUS) or optical coherence tomography (OCT) in statin patients. The weighted mean difference (WMD) of the random-effects/fixed-effects model was used to pool data that satisfied our inclusion criteria obtained from the included studies.

RESULTS

When compared with statin therapy alone, pooled studies revealed that PCSK9 inhibitors combined with statin therapy significantly decreased percent atheroma volume (PAV) (WMD: -1.06%, 95% confidence interval [CI]: -1.39 to -0.73; P<0.001) and total atheroma volume (TAV) (WMD: -6.38 mm³, 95% CI: -10.12 to -2.64; P=0.001). Moreover, the fibrous cap thickness (FCT) of the coronary atherosclerotic plaque increases to 21.31 um (WMD: 21.31, 95% CI: 7.08 to 35.53, P<0.001), and the maximum lipid arc decreases 10.9° (WMD: -10.9, 95% CI: -15.24 to -5.34, P<0.001).

CONCLUSION

In our systematic review and meta-analysis, PCSK9 inhibitors combined with statin therapy were found to be more effective than statin therapy alone for slowing coronary plaque progression by decreasing PAV, TAV, and increasing FCT, maximum lipid arc.

Effect of evolocumab on the progression of intraplaque neovascularization of the carotid based on contrast-enhanced ultrasonography (EPIC study): A prospective single-arm, open-label study

Background and Purpose: The aim of this study was to explore the effect of half a year of evolocumab plus moderate-intensity statin treatment on carotid intraplaque neovascularization (IPN) and blood lipid levels. Methods: A total of 31 patients with 33 carotid plaques who received evolocumab plus statin treatment were included. Blood lipid levels, B-mode ultrasound and contrast-enhanced ultrasonography (CEUS) at baseline and after half a year of evolocumab plus statin therapy were collected. The area under the curve (AUC) reflected the total amount of acoustic developer entering the plaque or lumen within the 180 s measurement period. The enhanced intensity reflected the peak blood flow intensity during the monitoring period, and the contrast agent area reflected the area of vessels in the plaques. Results: Except for high-density lipoprotein cholesterol (HDL-c), all other lipid indices decreased. Compared with baseline, low-density lipoprotein cholesterol (LDL-c) decreased by approximately 57% (p < 0.001); total cholesterol (TC) decreased by approximately 34% (p < 0.001); small dense low-density lipoprotein (sd-LDL) decreased by approximately 52% (p < 0.001); and HDL-c increased by approximately 20% (p < 0.001). B-mode ultrasonography showed that the length and thickness of the plaque and the hypoechoic area ratio were reduced (p < 0.05). The plaque area, calcified area ratio, and lumen cross-sectional area changed little (p > 0.05). CEUS revealed that the area under the curve of plaque/lumen [AUC (P/L)] decreased from 0.27 ± 0.13 to 0.19 ± 0.11 (p < 0.001). The enhanced intensity ratio of plaque/lumen [intensity ratio (P/L)] decreased from 0.37 ± 0.16 to 0.31 ± 0.14 (p = 0.009). The contrast agent area in plaque/area of plaque decreased from 19.20 ± 13.23 to 12.66 ± 9.59 (p = 0.003). The neovascularization score decreased from 2.64 ± 0.54 to 2.06 ± 0.86 (p < 0.001). Subgroup analysis based on statin duration (<6 months and ≥6 months) showed that there was no significant difference in the AUC (P/L) or intensity ratio (P/L) at baseline or after half a year of evolocumab treatment. Conclusion: This study found that evolocumab combined with moderate-intensity statins significantly improved the blood lipid profile and reduced carotid IPN. Clinical Trial Registration: https://www.clinicaltrials.gov; identifier: NCT04423406.

Pathogenic gain-of-function mutations in the prodomain and C-terminal domain of PCSK9 inhibit LDL binding

Proprotein convertase subtilisin/kexin type-9 (PCSK9) is a secreted protein that binds and mediates endo-lysosomal degradation of low-density lipoprotein receptor (LDLR), limiting plasma clearance of cholesterol-rich LDL particles in liver. Gain-of-function (GOF) point mutations in PCSK9 are associated with familial hypercholesterolemia (FH). Approximately 30%–40% of PCSK9 in normolipidemic human plasma is bound to LDL particles. We previously reported that an R496W GOF mutation in a region of PCSK9 known as cysteine-histidine–rich domain module 1 (CM1) prevents LDL binding in vitro [Sarkar et al., J. Biol. Chem. 295 (8), 2285–2298 (2020)]. Herein, we identify additional GOF mutations that inhibit LDL association, localized either within CM1 or a surface-exposed region in the PCSK9 prodomain. Notably, LDL binding was nearly abolished by a prodomain S127R GOF mutation, one of the first PCSK9 mutations identified in FH patients. PCSK9 containing alanine or proline substitutions at amino acid position 127 were also defective for LDL binding. LDL inhibited cell surface LDLR binding and degradation induced by exogenous PCSK9-D374Y but had no effect on an S127R-D374Y double mutant form of PCSK9. These studies reveal that multiple FH-associated GOF mutations in two distinct regions of PCSK9 inhibit LDL binding, and that the Ser-127 residue in PCSK9 plays a critical role.

An Updated Perspective on the Dual-Track Model of Enterocyte Fat Metabolism

The small intestinal epithelium has classically been envisioned as a conduit for nutrient absorption, but appreciation is growing for a larger and more dynamic role for enterocytes in lipid metabolism. Considerable gaps remain in our knowledge of this physiology, but it appears that the enterocyte's structural polarization dictates its behavior in fat partitioning, treating fat differently based on its absorption across the apical versus the basolateral membrane. In this review, we synthesize existing data and thought on this dual-track model of enterocyte fat metabolism through the lens of human integrative physiology. The apical track includes the canonical pathway of dietary lipid absorption across the apical brush-border membrane, leading to packaging and secretion of those lipids as chylomicrons. However, this track also reserves a portion of dietary lipid within cytoplasmic lipid droplets for later uses, including the "second-meal effect," which remains poorly understood. At the same time, the enterocyte takes up circulating fats across the basolateral membrane by mechanisms that may include receptor-mediated import of triglyceride-rich lipoproteins or their remnants, local hydrolysis and internalization of free fatty acids, or enterocyte de novo lipogenesis using basolaterally absorbed substrates. The ultimate destinations of basolateral-track fat may include fatty acid oxidation, structural lipid synthesis, storage in cytoplasmic lipid droplets, or ultimate resecretion, although the regulation and purposes of this basolateral track remain mysterious. We propose that the enterocyte integrates lipid flux along both of these tracks in order to calibrate its overall program of lipid metabolism.

New Strategies for Lowering Low Density Lipoprotein Cholesterol for Cardiovascular Disease Prevention

Purpose of review

The primary and secondary prevention of atherosclerotic cardiovascular disease (ASCVD) relies on optimizing cardiovascular health and appropriate pharmacotherapy, a mainstay of which is low-density lipoprotein-cholesterol (LDL-C) lowering. Typically, statin therapy remains the first line approach. Advances in technology and understanding of lipid metabolism have facilitated the development of several novel therapeutic targets and medications within the last decade. This review focuses on medications recently approved by the U.S. Food and Drug Administration (FDA) for the reduction of LDL-C and ASCVD risk, as well as new therapies in the pipeline.

Recent findings

Novel lipid therapies aim to lower risk of ASCVD by targeting reduction of atherogenic compounds, such as LDL, lipoprotein(a) (Lp(a)), and triglyceride-rich lipoproteins. Evolocumab and alirocumab, monoclonal antibody proprotein convertase subtilisin-kexin type 9 (PCSK9) inhibitors which lower LDL-C by approximately 60%, have emerged as important therapies for use in patients with ASCVD as well as familial hypercholesterolemia (FH). Bempedoic acid, an ATP citrate lyase inhibitor, is an oral medication recently approved that can lower LDL-C by approximately 18% alone and 38% when combined with ezetimibe. Inclisiran, a small-interfering RNA (siRNA) molecule which inhibits the translation of PCSK9, is the most recently FDA-approved LDL-C lowering medication, and can reduce LDL-C by approximately 50% with twice yearly subcutaneous dosing. The cardiovascular outcome trials for bempedoic acid and inclisiran are still on-going. Evinacumab, a monoclonal antibody which targets angiopoietin-like protein 3 (ANGPTL3), has been approved for use in patients with homozygous FH. SiRNAs and anti-sense oligonucleotides (ASO) facilitating selective inhibition of the production of targeted proteins including Lp(a) and ANGLPTL3 are active areas of clinical investigation.

Summary

Recently several novel LDL-C lowering medications have been approved. New therapeutic targets have been identified and present additional means of lowering LDL-C and other atherogenic compounds for patients who remain at high ASCVD risk.

Lipoprotein(a) in atherosclerotic cardiovascular disease and aortic stenosis: a European Atherosclerosis Society consensus statement

This 2022 European Atherosclerosis Society lipoprotein(a) [Lp(a)] consensus statement updates evidence for the role of Lp(a) in atherosclerotic cardiovascular disease (ASCVD) and aortic valve stenosis, provides clinical guidance for testing and treating elevated Lp(a) levels, and considers its inclusion in global risk estimation. Epidemiologic and genetic studies involving hundreds of thousands of individuals strongly support a causal and continuous association between Lp(a) concentration and cardiovascular outcomes in different ethnicities; elevated Lp(a) is a risk factor even at very low levels of low-density lipoprotein cholesterol. High Lp(a) is associated with both microcalcification and macrocalcification of the aortic valve. Current findings do not support Lp(a) as a risk factor for venous thrombotic events and impaired fibrinolysis. Very low Lp(a) levels may associate with increased risk of diabetes mellitus meriting further study. Lp(a) has pro-inflammatory and pro-atherosclerotic properties, which may partly relate to the oxidized phospholipids carried by Lp(a). This panel recommends testing Lp(a) concentration at least once in adults; cascade testing has potential value in familial hypercholesterolaemia, or with family or personal history of (very) high Lp(a) or premature ASCVD. Without specific Lp(a)-lowering therapies, early intensive risk factor management is recommended, targeted according to global cardiovascular risk and Lp(a) level. Lipoprotein apheresis is an option for very high Lp(a) with progressive cardiovascular disease despite optimal management of risk factors. In conclusion, this statement reinforces evidence for Lp(a) as a causal risk factor for cardiovascular outcomes. Trials of specific Lp(a)-lowering treatments are critical to confirm clinical benefit for cardiovascular disease and aortic valve stenosis.

Effect of a PCSK9 inhibitor and a statin on cholesterol efflux capacity: A limitation of current cholesterol-lowering treatments?

BACKGROUND

Cellular cholesterol efflux is a key step in reverse cholesterol transport that may impact on atherosclerotic cardiovascular risk. The process may be reliant on the availability of apolipoprotein (apo) B-100-containing lipoproteins to accept cholesterol from high-density lipoprotein. Evolocumab and atorvastatin are known to lower plasma apoB-100-containing lipoproteins that could impact on cholesterol efflux capacity (CEC).

METHODS

We conducted a 2-by-2 factorial trial of the effects of subcutaneous evolocumab (420 mg every 2 weeks) and atorvastatin (80 mg daily) for 8 weeks on CEC in 81 healthy, normolipidaemic men. The capacity of whole plasma and apoB-depleted plasma, including ATP-binding cassette transporter A1 (ABCA1)-mediated and passive diffusion, to efflux cholesterol, was measured.

RESULTS

Evolocumab and atorvastatin independently decreased whole plasma CEC (main effect p < .01 for both). However, there were no significant effects of evolocumab and atorvastatin on apoB-depleted plasma, ABCA1-mediated and passive diffusion-mediated CEC (p > .05 in all). In the three intervention groups combined, the reduction in whole plasma CEC was significantly correlated with the corresponding reduction in plasma apoB-100 concentration (r = .339, p < .01). In the evolocumab monotherapy group, the reduction in whole plasma CEC was also significantly correlated with the corresponding reduction in plasma lipoprotein(a) concentration (r = .487, p < .05).

CONCLUSIONS

In normolipidaemic men, evolocumab and atorvastatin decrease the capacity of whole plasma to efflux cellular cholesterol. These effects may be chiefly owing to a fall in the availability of apoB-100-containing lipoproteins. Reduction in circulating lipoprotein(a) may also contribute to the decrease in whole plasma cholesterol efflux with evolocumab monotherapy.

[Inclisiran - a new era in lipid-lowering therapy]

Inclisiran is a novel hypolipidemic drug that inhibits synthesis of the PCSK9 protein through the process called RNA interference. Inclisiran is a double-stranded, modified RNA bound to the N-acetylgalactosamine (GalNAc) carbohydrate molecule, a ligand of the acialoglycoprotein receptor, that is expressed by hepatocytes. After entering hepatocytes, inclisiran cleaves matrix RNA and, thereby, reduces the PCSK9 protein synthesis. This, in turn, enhances the uptake of circulating low-density lipoproteins (LDL) by specific receptors on hepatocytes, thereby lowering LDL levels in circulation. Efficacy and safety of inclisiran for lowering LDL cholesterol (C) in blood and its effect on the risk of clinical complications of atherosclerosis have been studied in the ORION program that includes multiple clinical trials. According to results of this program, inclisiran effectively reduces both LDL-C levels and the incidence of cardiovascular complications in the absence of clinically significant adverse reactions. An important advantage of inclisiran compared with other lipid-lowering drugs is the administration schedule (twice a year), which allows a considerable improvement of patients' compliance with the treatment and also of the effectiveness of the hypolipidemic treatment.

PCSK9 inhibitors for secondary prevention in patients with cardiovascular diseases: a bayesian network meta-analysis

BACKGROUND

The Food and Drug Administration has approved Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) inhibitors for the treatment of dyslipidemia. However, evidence of the optimal PCSK9 agents targeting PCSK9 for secondary prevention in patients with high-risk of cardiovascular events is lacking. Therefore, this study was conducted to evaluate the benefit and safety of different types of PCSK9 inhibitors.

METHODS

Several databases including Cochrane Central, Ovid Medline, and Ovid Embase were searched from inception until March 30, 2022 without language restriction. Randomized controlled trials (RCTs) comparing administration of PCSK9 inhibitors with placebo or ezetimibe for secondary prevention of cardiovascular events in patients with statin-background therapy were identified. The primary efficacy outcome was all-cause mortality. The primary safety outcome was serious adverse events.

RESULTS

Overall, nine trials totaling 54,311 patients were identified. Three types of PCSK9 inhibitors were evaluated. The use of alirocumab was associated with reductions in all-cause mortality compared with control (RR 0.83, 95% CrI 0.72-0.95). Moreover, evolocumab was associated with increased all-cause mortality compared with alirocumab (RR 1.26, 95% CrI 1.04-1.52). We also found alirocumab was associated with decreased risk of serious adverse events (RR 0.94, 95% CrI 0.90-0.99).

CONCLUSIONS

In consideration of the fact that both PCSK9 monoclonal antibody and inclisiran enable patients to achieve recommended LDL-C target, the findings in this meta-analysis suggest that alirocumab might provide the optimal benefits regarding all-cause mortality with relatively lower SAE risks, and evolocumab might provide the optimal benefits regarding myocardial infarction for secondary prevention in patients with high-risk of cardiovascular events. Further head-to-head trials with longer follow-up and high methodologic quality are warranted to help inform subsequent guidelines for the management of these patients.

PCSK9 inhibition with alirocumab decreases plasma lipoprotein(a) concentration by a dual mechanism of action in statin-treated patients with very high apolipoprotein(a) concentration

BACKGROUND

Inhibition of proprotein convertase subtilisin/kexin type 9 with alirocumab decreases plasma lipoprotein(a) [Lp(a)] levels. The kinetic mechanism for lowering Lp(a) by alirocumab may differ according to pre-treatment apolipoprotein(a) [apo(a)] levels.

METHODS

The effect of 12-week alirocumab (150 mg subcutaneously fortnightly) on the kinetics of apo(a) was compared in statin-treated patients with high (n = 10) and very high Lp(a) concentrations (n = 11).

RESULTS

In patients with high apo(a) concentrations, alirocumab lowered plasma apo(a) pool size (-17%, p < 0.01) chiefly by increasing the fractional catabolic rate (FCR) of apo(a) (+27%, p < 0.001). By contrast in patients with very high apo(a) concentrations, alirocumab significantly lowered plasma apo(a) pool size (-32%, p < 0.001) by both increasing apo(a) FCR (+30%, p < 0.001) and lowering production rate (-11%, p < 0.05).

CONCLUSIONS

In statin-treated patients with very high apo(a) concentrations, alirocumab lowers plasma Lp(a) concentration by a dual mode of action that increases the clearance and decreases the production of Lp(a) particles.