The roles of apo(a) size, phenotype, and dominance pattern in PCSK9-inhibition-induced reduction in Lp(a) with alirocumab

Lipoprotein(a) Response to Dietary Saturated Fat Reduction: Relationship to Apolipoprotein(a) Size Polymorphism in African Americans

BACKGROUND/OBJECTIVES

An elevated lipoprotein(a) [Lp(a)] level, which is a prevalent cardiovascular risk factor, is genetically determined by a size polymorphism of its apolipoprotein(a) [apo(a)] component. Despite its genetic control, Lp(a) level increases in response to dietary saturated fat (SFA) reduction. We tested the roles of apo(a) size and characteristics in modulating Lp(a) response to SFA reduction.

METHODS

We assessed apo(a) characteristics in 165 African Americans experiencing a 24% Lp(a) increase resulting from SFA reduction [16% at an average American Diet diet (AAD) to 6% at a DASH-type diet]. Apo(a) effects were tested based on the following factors: (1) the presence of a small atherogenic size (≤22 kringles), (2) phenotype (single or two isoforms), (3) isoform dominance, and (4) tertiles of combined kringle sizes.

RESULTS

There were no significant differences in Lp(a) increases between carriers vs. non-carriers of a small apo(a), between those with a single vs. two expressed isoforms, or in those with differing isoform dominance patterns (p > 0.05 for all). The extent of Lp(a) increase differed across increasing tertiles of combined kringle sizes (p = 0.006 for trend). In a multivariate model, the AAD Lp(a) level was a significant predictor of Lp(a) changes (p < 0.05). Relative increases in the allele-specific apo(a) level-an Lp(a) level associated with a defined apo(a) size-were similar across the apo(a) size spectrum.

CONCLUSIONS

Reducing dietary SFA intake results in a 24% increase in Lp(a) level in African Americans across apo(a) sizes. Individuals with smaller apo(a) sizes reached an elevated Lp(a) level post-intervention compared to those with larger sizes, in some cases resulting in cardiovascular risk reclassification.

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.

Lipoprotein(a) and Benefit of PCSK9 Inhibition in Emergency Complex Higher-risk and Indicated Patients

OBJECTIVE

There is a large population of patients classified as complex higher-risk and indicated patients (CHIPs) in China with a poor prognosis. The treatment of these patients is complex and challenging, especially when acute cardiac events occur, such as acute coronary syndrome (ACS) or heart failure. Pharmacotherapy and some mechanical circulatory support (MCS) therapeutic devices can provide stable hemodynamic support for CHIPs-percutaneous coronary intervention (PCI). LDL-C is an important pathogenic factor in atherosclerosis, and the target of blood lipid control. Recent studies have revealed that lipoprotein(a) [Lp(a)], which is formed when a covalent bond between apolipoprotein(a) and apolipoprotein B-100 is made, produces an LDL-like particle. This particle is an independent risk factor for the development of atherosclerosis, and is closely correlated to stent thrombosis and restenosis. Furthermore, this requires active intervention. PCSK9 inhibitors have been used in lipid-lowering treatment, and preventing atherosclerosis. The present study explores the efficacy of PCSK9 inhibitors in CHIPs-ACS, and the association between the change in Lp(a) and survival after 2 years of follow-up.

METHODS

The present real-world, prospective control study enrolled 321 CHIPs-ACS who underwent emergency PCI from August 2019 to November 2020, and these patients were followed up for 2 years. These patients were divided into two groups: PCSK9 group (n=161) given the combined PCSK9 inhibitor (140 mg of evolocumab every 2 weeks) and statins-based therapy, and SOC group (n=160) treated with statin-based lipid-lowering therapy alone. Then, the change in lipid index was measured, and the cardiovascular (CV) event recurrence rate was evaluated after one month and 2 years. Afterwards, the contribution of serum lipid parameters, especially the Lp(a) alteration, in patients with earlier initiation of the PCSK9 inhibitor to the CV outcome was analyzed.

RESULTS

The LDL-C level was significantly reduced in both groups: 52.3% in the PCSK9 group and 32.3% (P<0.001) in the SOC group. It is noteworthy that the Lp(a) level decreased by 13.2% in the PCSK9 group, but increased by 30.3% in the SOC group (P<0.001). Furthermore, the number of CV events was not significantly different between the PCSK9 and SOC groups after the 2-year follow-up period. In the PCSK9 group, the Lp(a) reduction was associated with the baseline Lp(a) levels of the patients (r2 =-0.315, P<0.001). Moreover, the decrease in Lp(a) contributed to the decline in CV events in patients who received ACS CHIPs-PCI, and the decrease in Lp(a) level was independent of the LDL-C level reduction.

CONCLUSION

The early initiation of PCSK9 inhibitors can significantly reduce the LDL-C and Lp(a) levels in ACS CHIPs-PCI. However, further studies are needed to confirm whether PCSK9 inhibitors can reduce the incidence of CV disease in CHIPs.

Lipoprotein(a) and the Effect of Alirocumab on Revascularization After Acute Coronary Syndrome

BACKGROUND

Many patients require revascularization after index acute coronary syndrome (ACS). Lipoprotein(a) is thought to play a pathogenic role in atherothrombosis. In ODYSSEY OUTCOMES, alirocumab reduced major adverse cardiovascular events after ACS, with greater reduction among those with higher lipoprotein(a) levels. We explored whether risk of revascularization after ACS was modified by the level of lipoprotein(a) and treatment with alirocumab or placebo.

METHODS

In ODYSSEY OUTCOMES alirocumab was compared with placebo in 18,924 patients with ACS and elevated atherogenic lipoprotein levels despite optimized statin treatment. In this post hoc analysis, treatment effects are summarized using competing risks proportional hazard models.

RESULTS

A total of 1559 (8.2%) patients had coronary, 204 (1.1%) had limb, and 40 (0.2%) had carotid revascularization. Alirocumab reduced coronary revascularization (2.8 vs 3.2 events per 100 patient-years; hazard ratio [HR], 0.88 [95% confidence interval (CI), 0.80-0.97]; P = 0.01) and any revascularization (3.2 vs 3.7 events per 100 patient-years; HR, 0.85 [95% CI, 0.78-0.94]; P = 0.001). Baseline lipoprotein(a) quartile was directly associated with risk of coronary or any revascularization in the placebo arm and inversely related to treatment HRs (all P for trend < 0.01). Alirocumab produced the greatest reduction of coronary revascularization in patients with baseline lipoprotein(a) in the top quartile (≥ 59.6 mg/dL; HR, 0.69 [95% CI, 0.57-0.84]), but no apparent reduction in the bottom quartile (HR, 1.00 [95% CI, 0.82-1.22]). Findings were similar for the effect of alirocumab on any revascularization.

CONCLUSIONS

Alirocumab reduced revascularization rates after ACS. The risk of revascularization and reduction in that risk with alirocumab were greatest in patients with elevated lipoprotein(a) at baseline.

Lp(a)-Associated Oxidized Phospholipids in Healthy Black and White Participants in Relation to apo(a) Size, Age, and Family Structure

Background

Lp(a) (lipoprotein(a)) is the major lipoprotein carrier of oxidized phospholipids (OxPL) and this function mediates Lp(a) atherogenicity. However, the relationship between OxPL, Lp(a), and genetic and biological characteristics remains poorly understood. We assessed the relationship between Lp(a)‐bound OxPL, apolipoprotein(a) (apo(a)) size, age, and family structure in 2 racial groups.

Methods and Results

Healthy Black and White families were recruited from the general population (age: 6–74 years, n=267). OxPL and Lp(a) levels were assayed enzymatically; apo(a) isoform, LPA allele sizes, and allele‐specific Lp(a) levels were determined. Lp(a)‐OxPL levels did not differ significantly by racial and age groups. Lp(a)‐OxPL levels were associated with total plasma Lp(a) in all participants and in race‐specific analyses. Further, OxPL levels were significantly associated with allele‐specific Lp(a) levels carried by the smaller apo(a) size in all participants (β=0.33, P=0.0003) as well as separately for Black (β=0.50, P=0.0032) and White (β=0.26, P=0.0181) participants. A significant association of OxPL with allele‐specific Lp(a) levels for larger apo(a) sizes was seen only in Black participants (β=0.53, P=0.0076). In this group, Lp(a)‐OxPL levels were also heritable (h²=0.29, P=0.0235), resulting in a significant interracial difference in heritability between Black and White people (P=0.0352).

Conclusions

Lp(a)‐OxPL levels were associated with allele‐specific Lp(a) level carried on smaller apo(a) sizes and among Black participants also for larger apo(a) sizes. The heritability estimates for Lp(a)‐bound OxPL differed by race.

The size of apolipoprotein (a) is an independent determinant of the reduction in lipoprotein (a) induced by PCSK9 inhibitors

AIMS

Lipoprotein (a) [Lp(a)] is a lipoprotein species causatively associated with atherosclerosis. Unlike statins, PCSK9 inhibitors (PCSK9i) reduce Lp(a), but this reduction is highly variable. Levels of Lp(a) are chiefly governed by the size of its signature protein, apolipoprotein (a) [apo(a)]. Whether this parameter determines some of the reduction in Lp(a) induced by PCSK9i remains unknown. We aimed to investigate if the Lp(a) lowering efficacy of PCSK9i is modulated by the size of apo(a), which is genetically determined by the variable number of KIV domains present on that protein.

METHODS AND RESULTS

The levels of Lp(a) and the size of apo(a) were assessed in plasma samples from 268 patients before and after treatment with PCSK9i. Patients were recruited at the Outpatient Lipid Clinic of the Charité Hospital (Berlin) between 2015 and 2020. They were hypercholesterolemic at very high CVD risk with LDL-cholesterol levels above therapeutic targets despite maximally tolerated lipid-lowering therapy. Patients received either Alirocumab (75 or 150 mg) or Evolocumab (140 mg) every 2 weeks. Apo(a), apoB100, and apoE concentrations as well as apoE major isoforms were determined by liquid chromatography high-resolution mass spectrometry. Apo(a) isoforms sizes were determined by Western Blot. PCSK9i sharply reduced LDL-cholesterol (-57%), apoB100 (-47%) and Lp(a) (-36%). There was a positive correlation between the size of apo(a) and the relative reduction in Lp(a) induced by PCSK9i (r = 0.363, p = 0.0001). The strength of this association remained unaltered after adjustment for baseline Lp(a) levels and all other potential confounding factors. In patients with two detectable apo(a) isoforms, there was also a positive correlation between the size of apo(a) and the reduction in Lp(a), separately for the smaller (r = 0.350, p = 0.0001) and larger (r = 0.324, p = 0.0003) isoforms. The relative contribution of the larger isoform to the total concentration of apo(a) was reduced from 29% to 15% (p < 0.0001).

CONCLUSIONS

The size of apo(a) is an independent determinant of the response to PCSK9i. Each additional kringle domain is associated with a 3% additional reduction in Lp(a). This explains in part the variable efficacy of PCSK9i and allows to identify patients who will benefit most from these therapies in terms of Lp(a) lowering.

TRANSLATIONAL PERSPECTIVE

Unlike statins, PCSK9 inhibitors reduce the circulating levels of the highly atherogenic Lipoprotein (a). The underlying mechanism remains a matter of considerable debate. The size of apo(a), the signature protein of Lp(a), is extremely variable (300 to more than 800 kDa) and depends on its number of kringle domains. We now show that each increase in apo(a) size by one kringle domain is associated with a 3% additional reduction in Lp(a) following PCSK9i treatment and that apo(a) size polymorphism is an independent predictor of the reduction in Lp(a) induced by these drugs. In an era of personalized medicine, this allows to identify patients who will benefit most from PCSK9i in terms of Lp(a) lowering.

Discordant responses of plasma low-density lipoprotein cholesterol and lipoprotein(a) to alirocumab: A pooled analysis from 10 ODYSSEY Phase 3 studies

AIMS

Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors consistently reduce low-density lipoprotein cholesterol (LDL-C) by 50-60% and lipoprotein(a) (Lp(a)) by 20-30%, but the mechanism of Lp(a) lowering remains unclear. If Lp(a) is cleared by the LDL receptor, similar to LDL-C, then one would expect PCSK9 inhibition to induce a concordant LDL-C/Lp(a) response in an approximately 2:1 ratio. We aim to determine the prevalence of discordant plasma LDL-C/Lp(a) response to the PCSK9 inhibitor alirocumab.

METHODS

This is a post hoc, pooled analysis of 10 randomized controlled trials from the ODYSSEY Phase 3 clinical trial program for alirocumab. Patients enrolled in the trials were high cardiovascular risk and/or with heterozygous familial hypercholesterolemia. The primary end point was prevalence of discordant LDL-C/Lp(a) response to alirocumab at 24 weeks. Discordant response was defined as LDL-C reduction >35% and Lp(a) reduction ≤10%, or LDL-C reduction ≤35% and Lp(a) reduction >10%.

RESULTS

Of the 1709 patients in the pooled study cohort, 62.4% were male, and the mean age was 59.2 (SD: 11.0) years. Baseline mean LDL-C was 126.5 (SD: 46.3) mg/dL and baseline median Lp(a) was 46.9 (interquartile range: 21.8-89.0) mg/dL. Total prevalence of discordant LDL-C/Lp(a) response was 21.5% (12.6% with LDL-C >35% reduction and Lp(a) ≤10% reduction; 8.9% with LDL-C ≤35% reduction and Lp(a) >10% reduction). Baseline Lp(a) and familial hypercholesterolemia status did not affect discordance.

CONCLUSION

A high prevalence of discordant LDL-C/Lp(a) response was observed with alirocumab, further suggesting that PCSK9 inhibitor therapy with alirocumab reduces plasma Lp(a) through alternative pathways to LDL receptor clearance.

Effect of Alirocumab on Lipoprotein(a) and Cardiovascular Risk After Acute Coronary Syndrome

BACKGROUND

Lipoprotein(a) concentration is associated with cardiovascular events. Alirocumab, a proprotein convertase subtilisin/kexin type 9 inhibitor, lowers lipoprotein(a) and low-density lipoprotein cholesterol (LDL-C).

OBJECTIVES

A pre-specified analysis of the placebo-controlled ODYSSEY Outcomes trial in patients with recent acute coronary syndrome (ACS) determined whether alirocumab-induced changes in lipoprotein(a) and LDL-C independently predicted major adverse cardiovascular events (MACE).

METHODS

One to 12 months after ACS, 18,924 patients on high-intensity statin therapy were randomized to alirocumab or placebo and followed for 2.8 years (median). Lipoprotein(a) was measured at randomization and 4 and 12 months thereafter. The primary MACE outcome was coronary heart disease death, nonfatal myocardial infarction, ischemic stroke, or hospitalization for unstable angina.

RESULTS

Baseline lipoprotein(a) levels (median: 21.2 mg/dl; interquartile range [IQR]: 6.7 to 59.6 mg/dl) and LDL-C [corrected for cholesterol content in lipoprotein(a)] predicted MACE. Alirocumab reduced lipoprotein(a) by 5.0 mg/dl (IQR: 0 to 13.5 mg/dl), corrected LDL-C by 51.1 mg/dl (IQR: 33.7 to 67.2 mg/dl), and reduced the risk of MACE (hazard ratio [HR]: 0.85; 95% confidence interval [CI]: 0.78 to 0.93). Alirocumab-induced reductions of lipoprotein(a) and corrected LDL-C independently predicted lower risk of MACE, after adjustment for baseline concentrations of both lipoproteins and demographic and clinical characteristics. A 1-mg/dl reduction in lipoprotein(a) with alirocumab was associated with a HR of 0.994 (95% CI: 0.990 to 0.999; p = 0.0081).

CONCLUSIONS

Baseline lipoprotein(a) and corrected LDL-C levels and their reductions by alirocumab predicted the risk of MACE after recent ACS. Lipoprotein(a) lowering by alirocumab is an independent contributor to MACE reduction, which suggests that lipoprotein(a) should be an independent treatment target after ACS. (ODYSSEY Outcomes: Evaluation of Cardiovascular Outcomes After an Acute Coronary Syndrome During Treatment With Alirocumab; NCT01663402).

Diet and Lp(a): Does Dietary Change Modify Residual Cardiovascular Risk Conferred by Lp(a)?

Lipoprotein(a) [Lp(a)] is an independent, causal, genetically determined risk factor for cardiovascular disease (CVD). We provide an overview of current knowledge on Lp(a) and CVD risk, and the effect of pharmacological agents on Lp(a). Since evidence is accumulating that diet modulates Lp(a), the focus of this paper is on the effect of dietary intervention on Lp(a). We identified seven trials with 15 comparisons of the effect of saturated fat (SFA) replacement on Lp(a). While replacement of SFA with carbohydrate, monounsaturated fat (MUFA), or polyunsaturated fat (PUFA) consistently lowered low-density lipoprotein cholesterol (LDL-C), heterogeneity in the Lp(a) response was observed. In two trials, Lp(a) increased with carbohydrate replacement; one trial showed no effect and another showed Lp(a) lowering. MUFA replacement increased Lp(a) in three trials; three trials showed no effect and one showed lowering. PUFA or PUFA + MUFA inconsistently affected Lp(a) in four trials. Seven trials of diets with differing macronutrient compositions showed similar divergence in the effect on LDL-C and Lp(a). The identified clinical trials show diet modestly affects Lp(a) and often in the opposing direction to LDL-C. Further research is needed to understand how diet affects Lp(a) and its properties, and the lack of concordance between diet-induced LDL-C and Lp(a) changes.

PCSK9 in African Americans and Caucasians in Relation to Lp(a) Level, Apo(a) Size and Heritability

Context

Inhibition of proprotein convertase subtilisin/kexin type 9 (PCSK9) reduces lipoprotein(a) [Lp(a)] levels, but the association of PCSK9 with Lp(a) level and its major determinant, apolipoprotein(a) [apo(a)] size, is not fully understood.

Objective

To assess the relationship between PCSK9, Lp(a) level, apo(a) size, age, and ethnicity/race.

Design

Cross-sectional

Setting

General population

Participants

Healthy African Americans and Caucasians (n = 267); age range: 6 to 74 years.

Interventions

None.

Main outcome measure(s)

PCSK9 levels, apo(a) isoform and LPA allele sizes, and isoform-specific Lp(a) levels.

Results

Plasma PCSK9 levels were significantly higher in African Americans vs Caucasians, in females vs males, and in adults vs children. PCSK9 levels were not associated with total plasma Lp(a) levels either in all participants or in ethnicity-specific analyses. However, PCSK9 levels were significantly positively associated with isoform-specific Lp(a) levels carried by the larger apo(a) size in all participants (r = 0.139, P = 0.0361). In ethnicity/race analyses, a significant association was seen for African Americans (r = 0.268, P = 0.0199), but not for Caucasians. In contrast, there were no significant associations of PCSK9 with isoform-specific Lp(a) levels for the smaller apo(a) sizes in all participants nor in ethnic-specific analyses. Furthermore, heritability (h²) analyses revealed a significant heritability for PCSK9 level in both ethnic groups, with a higher estimate in Caucasians than in African Americans (47% vs 22%, respectively).

Conclusions

Among African Americans, but not Caucasians, PCSK9 levels were associated with isoform-specific Lp(a) levels carried on larger, but not smaller, apo(a) sizes. The findings illustrate a diverging relationship of PCSK9 with isoform-specific Lp(a) levels across ethnicity.

VLDL (Very-Low-Density Lipoprotein)-Apo E (Apolipoprotein E) May Influence Lp(a) (Lipoprotein [a]) Synthesis or Assembly

Objective:

To clarify the association between PCSK9 (proprotein convertase subtilisin/kexin type 9) and Lp(a) (lipoprotein [a]), we studied Lp(a) kinetics in patients with loss-of-function and gain-of-function PCSK9 mutations and in patients in whom extended-release niacin reduced Lp(a) and PCSK9 concentrations.

Approach and Results:

Six healthy controls, 9 heterozygous patients with familial hypercholesterolemia (5 with low-density lipoprotein receptor [ LDLR ] mutations and 4 with PCSK9 gain-of-function mutations) and 3 patients with heterozygous dominant-negative PCSK9 loss-of-function mutations were included in the preliminary study. Eight patients were enrolled in a second study assessing the effects of 2 g/day extended-release niacin. Apolipoprotein kinetics in VLDL (very-low-density lipoprotein), LDL (low-density lipoprotein), and Lp(a) were studied using stable isotope techniques. Plasma Lp(a) concentrations were increased in PCSK9 -gain-of-function and familial hypercholesterolemia- LDLR groups compared with controls and PCSK9 -loss-of-function groups (14±12 versus 5±4 mg/dL; P =0.04), but no change was observed in Lp(a) fractional catabolic rate. Subjects with PCSK9 -loss-of-function mutations displayed reduced apoE (apolipoprotein E) concentrations associated with a VLDL-apoE absolute production rate reduction. Lp(a) and VLDL-apoE absolute production rates were correlated ( r =0.50; P <0.05). ApoE-to-apolipoprotein (a) molar ratios in Lp(a) increased with plasma Lp(a) ( r =0.96; P <0.001) but not with PCSK9 levels. Extended-release niacin-induced reductions in Lp(a) and VLDL-apoE absolute production rate were correlated ( r =0.83; P =0.015). In contrast, PCSK9 reduction (−35%; P =0.008) was only correlated with that of VLDL-apoE absolute production rate ( r =0.79; P =0.028).

Conclusions:

VLDL-apoE production could determine Lp(a) production and/or assembly. As PCSK9 inhibitors reduce plasma apoE and Lp(a) concentrations, apoE could be the link between PCSK9 and Lp(a).

Lipoprotein(a) plasma levels are not associated with survival after acute coronary syndromes: An observational cohort study

Background

Lipoprotein(a) [Lp(a)] is associated with coronary artery disease in population studies, however studies on its predictive value in patients with cardiovascular disease, in particular after acute coronary syndromes (ACS), are conflicting. The aim of this study was to investigate whether Lp(a) is associated with survival after ACS.

Methods and results

We analyzed Lp(a) measurement in 1,245 patients who underwent coronary angiography for ACS. The median follow-up for cardiovascular and all-cause mortality was 5.0 (IQR 3.2–8.0) years. 655 (52.6%) presented with ST-segment elevation myocardial infarction (STEMI), 424 (34.1%) with Non-ST-segment elevation myocardial infarction (NSTEMI) and 166 (13.3%) underwent coronary angiography for unstable angina. Cardiovascular mortality was 9.1% and all-cause mortality was 15.7%. Patients were stratified into four groups to their Lp(a) levels. (≤15mg/dL, >15-30mg/dL, >30-60mg/dL, and >60mg/dL). Multivessel disease was significantly more common in patients with Lp(a)>60mg/dL (p<0.05). Increased levels of Lp(a) were not associated with cardiovascular mortality (HR compared with Lp(a) ≤15mg/dL were 1.2, 1.2, and 1.0, respectively; p = 0.69) and not with all-cause mortality (HR compared with Lp(a) ≤15mg/dL were 1.2, 1.2, and 1.2, respectively; p = 0.46).

Conclusions

Lp(a) levels at time of ACS were neither associated with cardiovascular nor with all-cause mortality. Although Lp(a) has been shown to be associated with incidence of coronary artery disease, this study does not support any role of Lp(a) as a risk factor for mortality after ACS. This should be taken into account for development of outcome studies for agents targeting Lp(a) plasma levels.

A modified algorithm with lipoprotein(a) added for diagnosis of familial hypercholesterolemia

BACKGROUND

Previous studies have observed that high level of lipoprotein (a) [Lp(a)] was common in the phenotypic familial hypercholesterolemia (FH) and may explain part of the clinical diagnosis of FH.

HYPOTHESIS

We aim to develop a modified model including Lp(a) and compare its diagnostic performance with Dutch Lipid Clinic Network (DLCN) criteria.

METHODS

Data of 10 449 individuals were utilized for the model establishment (7806 for derivation and 2643 for validation) from January 2011 to March 2018. The novel score model was modified on the basis of DLCN. Furthermore, 718 patients were screened for LDLR, APOB, and PCSK9 gene mutations.

RESULTS

The novel modified model consisted of untreated low-density lipoprotein cholesterol (LDL-C) level, Lp(a), personal premature coronary heart disease (CHD), tendon xanthomas and family history of CHD and/or hypercholesterolemia. It has shown high discrimination (area under curve [AUC] 0.991, 95% confidence interval [CI[ 0.988-0.994, P < .001) for distinguishing clinical FH from non-FH diagnosed using DLCN. Furthermore, a concordance analysis was performed to compare the modified model with DLCN and it showed a good agreement with DLCN (κ = 0.765). External validation of the novel model also showed good accordance (κ = 0.700). Further genetic analysis showed that the agreements between the new model and mutation improved a little compared to that between DLCN and mutation.

CONCLUSIONS

The novel modified model, including Lp(a), could provide new insights into FH diagnosis in Chinese population with more concerns on the patients with high level of Lp(a).

Heritability of apolipoprotein (a) traits in two-generational African-American and Caucasian families

Heritability of LPA allele, apo(a) isoform sizes, and isoform-associated lipoprotein(a) [Lp(a)] levels was studied in 82 Caucasian and African-American families with two parents and two children (age: 6-74 years). We determined: 1) Lp(a) levels; 2) LPA allele sizes; 3) apo(a) isoform sizes; and 4) isoform-specific apo(a) levels (ISLs), the amount of Lp(a) carried by an individual apo(a) isoform. Trait heritability was estimated by mid-parent-offspring analysis. The ethnicity-adjusted heritability estimate for Lp(a) level was 0.95. Heritability for ISLs corresponding to the smaller LPA allele in a given allele-pair was higher than that corresponding to the larger LPA allele (0.91 vs. 0.59, P = 0.017). Although not statistically different, heritability for both apo(a) isoforms (0.90 vs. 0.70) and LPA alleles (0.98 vs. 0.82) was higher for the smaller versus larger sizes. Heritability was generally lower in African-Americans versus Caucasians with a 4-fold difference for the larger LPA allele (0.25 vs. 0.94, P = 0.001). In Caucasians, an overall higher heritability pattern was noted for the older (≥47 years) versus younger (<47 years) families. In conclusion, Lp(a) level and traits associated with the smaller LPA alleles were strongly determined by genetics, although with a varying ethnic influence. Ethnic differences in heritability of the larger LPA allele warrant further investigations.

A Meta-Analysis of the Effect of PCSK9-Monoclonal Antibodies on Circulating Lipoprotein (a) Levels

BACKGROUND

Lipoprotein (a) [Lp(a)] is an atherogenic lipoprotein. While no effective therapy for Lp(a) is currently available, recently, several pooled analyses with small sample sizes have suggested that proprotein convertase subtilisin/kexin type 9 monoclonal antibodies (PCSK9-mAbs) could reduce circulating Lp(a) levels. This meta-analysis was performed to comprehensively investigate the efficacy of PCSK9-mAbs with respect to serum Lp(a) concentrations.

METHODS

PubMed, MEDLINE, Embase, ClinicalTrials.gov, Cochrane CENTRAL, Web of Science and recent conferences up to July 2018 were searched. Randomized clinical trials evaluating the effect of PCSK9-mAbs and control treatment on plasma Lp(a) concentrations were included. Mean differences and odds ratios with 95% confidence intervals (CIs) were used.

RESULTS

Twenty-seven randomized clinical trials with a total of 11,864 participants were included. PCSK9-mAbs showed a significant efficacy in reducing Lp(a) (- 21.9%, 95% CI - 24.3 to - 19.5), irrespective of PCSK9-mAb types, treatment duration, participant characteristics, treatment methods, differences of control treatment, baseline Lp(a) levels, and test methods. The greatest reduction was achieved with 150 mg alirocumab biweekly (- 24.6%, 95% CI - 28.0 to - 21.2) and  140 mg evolocumab monthly (- 26.8%, 95% CI - 31.6 to - 21.9). Meta-regression analyses found that the more intense low-density lipoprotein cholesterol levels declined during PCSK9-mAb treatment, the greater the reduction in Lp(a) levels. Safety was in accordance with previous reports.

CONCLUSIONS

The results of this analysis suggested that PCSK9-mAbs could significantly reduce circulating Lp(a) levels. Long-term studies may be needed to confirm the effect of PCSK9-mAbs on Lp(a) in the future.

Key aspects of PCSK9 inhibition beyond LDL lowering

PURPOSE OF REVIEW

Our primary objective is to review the most recent findings on the biology of PCSK9 and on two key aspects of PCSK9 inhibition beyond LDL control of great clinical relevance: the regulation of lipoprotein (a) circulating levels by PCSK9 inhibitors and the putative diabetogenic effects of these novel therapies.

RECENT FINDINGS

The reality of two distinct extracellular and intracellular pathways by which PCSK9 decreases the abundance of the LDLR at the surface of many cell types, most importantly hepatocytes, has recently been established. In contrast, the exact mechanisms by which PCSK9 inhibitors lower the circulating levels of lipoprotein (a) remain a point of major dispute. Despite strong indications from genetic studies that PCSK9 inhibition should increase diabetes risk, no such effect has been observed in clinical trials, and in-vitro and in-vivo studies do not clarify this issue.

SUMMARY

The trafficking pathways by which PCSK9 enhance LDLR degradation via the endolysosomal extracellular route or via the Golgi-lysosomal intracellular route remain to be fully elucidated. The mechanisms by which PCSK9 inhibitors reduce lipoprotein (a) also merit additional research efforts. The role of PCSK9 on glucose metabolism should likewise be studied in depth.

Dyslipidemias in clinical practice

Most dyslipidemic conditions have been linked to an increased risk of cardiovascular disease. Over the past few years major advances have been made regarding the genetic and metabolic basis of dyslipidemias. Detailed characterization of the genetic basis of familial lipid disorders and knowledge concerning the effects of environmental factors on the expression of dyslipidemias have increased substantially, contributing to a better diagnosis in individual patients. In addition to these developments, therapeutic options to lower cholesterol levels in clinical practice have expanded even further in patients with familial hypercholesterolemia and in subjects with cardiovascular disease. Finally, promising upcoming therapeutic lipid lowering strategies will be reviewed. All these advances will be discussed in relation to current clinical practice with special focus on common lipid disorders including familial dyslipidemias.

The journey towards understanding lipoprotein(a) and cardiovascular disease risk: are we there yet?

PURPOSE OF REVIEW

Evidence continues to mount for an important role for elevated plasma concentrations of lipoprotein(a) [Lp(a)] in mediating risk of atherothrombotic and calcific aortic valve diseases. However, there continues to be great uncertainty regarding some basic aspects of Lp(a) biology including its biosynthesis and catabolism, its mechanisms of action in health and disease, and the significance of its isoform size heterogeneity. Moreover, the precise utility of Lp(a) in the clinic remains undefined.

RECENT FINDINGS

The contribution of elevated Lp(a) to cardiovascular risk continues to be more precisely defined by larger studies. In particular, the emerging role of Lp(a) as a potent risk factor for calcific aortic valve disease has received much scrutiny. Mechanistic studies have identified commonalities underlying the impact of Lp(a) on atherosclerosis and aortic valve disease, most notably related to Lp(a)-associated oxidized phospholipids. The mechanisms governing Lp(a) concentrations remain a source of considerable dispute.

SUMMARY

This article highlights some key remaining challenges in understanding Lp(a) actions and clinical significance. Most important in this regard is demonstration of a beneficial effect of lowering Lp(a), a development that is on the horizon as effective Lp(a)-lowering therapies are being tested in the clinic.

PCSK9 inhibition with alirocumab reduces lipoprotein(a) levels in nonhuman primates by lowering apolipoprotein(a) production rate

Therapeutic antibodies targeting proprotein convertase subtilisin kexin type 9 (PCSK9) (e.g. alirocumab) lower low-density lipoprotein cholesterol (LDL-C) and lipoprotein (a) [Lp(a)] levels in clinical trials. We recently showed that PCSK9 enhances apolipoprotein(a) [apo(a)] secretion from primary human hepatocytes but does not affect Lp(a) cellular uptake. Here, we aimed to determine how PCSK9 neutralization modulates Lp(a) levels in vivo.

Six nonhuman primates (NHP) were treated with alirocumab or a control antibody (IgG1) in a crossover protocol. After the lowering of lipids reached steady state, NHP received an intravenous injection of [2H3]-leucine, and blood samples were collected sequentially over 48 h. Enrichment of apolipoproteins in [2H3]-leucine was assessed by liquid chromatography–tandem mass spectrometry (LC–MS/MS). Kinetic parameters were calculated using numerical models with the SAAMII software. Compared with IgG1, alirocumab significantly reduced total cholesterol (TC) (−28%), LDL-C (−67%), Lp(a) (−56%), apolipoprotein B100 (apoB100) (−53%), and apo(a) (−53%). Alirocumab significantly increased the fractional catabolic rate of apoB100 (+29%) but not that of apo(a). Conversely, alirocumab sharply and significantly reduced the production rate (PR) of apo(a) (−42%), but not significantly that of apoB100, compared with IgG1, respectively.

In line with the observations made in human hepatocytes, the present kinetic study establishes that PCSK9 neutralization with alirocumab efficiently reduces circulating apoB100 and apo(a) levels by distinct mechanisms: apoB primarily by enhancing its catabolism and apo(a) primarily by lowering its production.

The ever-expanding saga of the proprotein convertases and their roles in body homeostasis: emphasis on novel proprotein convertase subtilisin kexin number 9 functions and regulation

PURPOSE OF REVIEW

The nine members of the proprotein convertase family play major physiological roles during development and in the adult, and their dysregulation leads to various diseases. The primary objective of this article is to review recent findings on the clinical importance of some of these convertases concentrating mostly on PCSK9, the ninth member of the convertase family. This includes the transcriptional and translational regulation of PCSK9, its ability to enhance the degradation of LDL receptor (LDLR), and the implication of PCSK9 in inflammation and sepsis.

RECENT FINDINGS

PCSK9 levels are upregulated by E2F1 and reduced by specific miRNAs and by Annexin A2 that bind the 3' end of its mRNA. The implication of the LDLR in the clearance of pathogenic bacterial debris in mice and human puts in perspective a new role for PCSK9 in the regulation of sepsis. The specific implication of the LDLR in the clearance of Lp(a) is now confirmed by multiple studies of PCSK9 inhibition in human cohorts.

SUMMARY

Emerging data suggest that PCSK9 can be regulated at the transcriptional and translational levels by specific factors and miRNAs. The identification of a novel pocket in the catalytic domain of PCSK9 represents a harbinger for a new class of small inhibitor drugs. The implication of the LDLR in reducing the effects of bacterially induced sepsis has been supported by both human and mouse data. Outcome studies confirmed the clinical importance of reducing PCSK9 levels. The present review puts in perspective new developments in the PCSK9 biology and its regulation of the LDLR. VIDEO ABSTRACT: http://links.lww.com/COL/A17.

Association between lipoprotein (a) and proprotein convertase substilisin/kexin type 9 in patients with heterozygous familial hypercholesterolemia: A case-control study

BACKGROUND

Recent data have suggested an important role of lipoprotein (a) [Lp(a)] and proprotein convertase substilisin/kexin type 9 (PCSK9) in the development of atherosclerotic cardiovascular disease (ASCVD) in both general population and family hypercholesterolemia (FH), while the relation of Lp(a) to PCSK9 has not been examined.

OBJECTIVE

The aim of the present study was to investigate the association between plasma PCSK9 and Lp(a)in patients with heterozygous FH (HeFH).

METHODS

Two hundred and fifty-five molecularly confirmed patients with HeFH were compared to 255 age- and gender-matched non-FH controls. Plasma PCSK9 and Lp(a) concentrations were measured using ELISA and immunoturbidimetric method respectively, and finally their association was assessed.

RESULTS

Both plasma PCSK9 and Lp(a) levels were significantly higher in patients with HeFH compared to control group (p<0.001). Besides, the Lp(a) concentration and percentage of Lp(a)≥300mg/L were increased by PCSK9 tertiles in HeFH group (both p<0.05) while not in control group. In partial correlation analysis, Lp(a) was associated with PCSK9 (r=0.254, p<0.001) in HeFH group but not in control, which were further confirmed by multivariable linear regression analysis. Furthermore, significant associations between Lp(a) and PCSK9 were also found in subgroups of HeFH group irrespective of definite or probable FH, with and without coronary artery disease (CAD), and with statin or not.

CONCLUSIONS

Plasma Lp(a) level was associated with PCSK9 in patients with HeFH alone, suggesting that much about the interaction of PCSK9 with Lp(a) in FH need further explorations.