Elevated lipoprotein (a) levels and risk of peripheral artery disease outcomes: A systematic review

Consensus on lipoprotein(a) of the Spanish Society of Arteriosclerosis. Literature review and recommendations for clinical practice

The irruption of lipoprotein(a) (Lp(a)) in the study of cardiovascular risk factors is perhaps, together with the discovery and use of proprotein convertase subtilisin/kexin type 9 (iPCSK9) inhibitor drugs, the greatest novelty in the field for decades. Lp(a) concentration (especially very high levels) has an undeniable association with certain cardiovascular complications, such as atherosclerotic vascular disease (AVD) and aortic stenosis. However, there are several current limitations to both establishing epidemiological associations and specific pharmacological treatment. Firstly, the measurement of Lp(a) is highly dependent on the test used, mainly because of the characteristics of the molecule. Secondly, Lp(a) concentration is more than 80% genetically determined, so that, unlike other cardiovascular risk factors, it cannot be regulated by lifestyle changes. Finally, although there are many promising clinical trials with specific drugs to reduce Lp(a), currently only iPCSK9 (limited for use because of its cost) significantly reduces Lp(a). However, and in line with other scientific societies, the SEA considers that, with the aim of increasing knowledge about the contribution of Lp(a) to cardiovascular risk, it is relevant to produce a document containing the current status of the subject, recommendations for the control of global cardiovascular risk in people with elevated Lp(a) and recommendations on the therapeutic approach to patients with elevated Lp(a).

Small apolipoprotein(a) isoforms may predict primary patency following peripheral arterial revascularization

Background

High lipoprotein (a) [Lp(a)] is associated with adverse limb events in patients undergoing lower extremity revascularization. Lp(a) levels are genetically pre-determined, with LPA gene encoding for two apolipoprotein (a) [apo(a)] isoforms. Isoform size variations are driven by the number of kringle IV type 2 (KIV-2) repeats. Lp(a) levels are inversely correlated with isoform size. In this study, we examined the role of Lp(a) levels, apo(a) size and inflammatory markers with lower extremity revascularization outcomes.

Methods

25 subjects with chronic peripheral arterial disease (PAD), underwent open or endovascular lower extremity revascularization (mean age of 66.7±9.7 years; F=12, M=13; Black=8, Hispanic=5, and White=12). Pre- and post-operative medical history, self-reported symptoms, ankle brachial indices (ABIs), and lower extremity duplex ultrasounds were obtained. Plasma Lp(a), apoB100, lipid panel, and pro-inflammatory markers (IL-6, IL-18, hs-CRP, TNFα) were assayed preoperatively. Isoform size was estimated using gel electrophoresis and weighted isoform size ( wIS ) calculated based on % isoform expression. Firth logistic regression was used to examine the relationship between Lp(a) levels, and wIS with procedural outcomes: symptoms (better/worse), primary patency at 2-4 weeks, ABIs, and re-intervention within 3-6 months. We controlled for age, sex, history of diabetes, smoking, statin, antiplatelet and anticoagulation use.

Results

Median plasma Lp(a) level was 108 (44, 301) nmol/L. The mean apoB100 level was 168.0 ± 65.8 mg/dL. These values were not statistically different among races. We found no association between Lp(a) levels and w IS with measured plasma pro-inflammatory markers. However, smaller apo(a) wIS was associated with occlusion of the treated lesion(s) in the postoperative period [OR=1.97 (95% CI 1.01 - 3.86, p<0.05)]. The relationship of smaller apo(a) wIS with re-intervention was not as strong [OR=1.57 (95% CI 0.96 - 2.56), p=0.07]. We observed no association between wIS with patient reported symptoms or change in ABIs.

Conclusions

In this small study, subjects with smaller apo(a) isoform size undergoing peripheral arterial revascularization were more likely to experience occlusion in the perioperative period and/or require re-intervention. Larger cohort studies identifying the mechanism and validating these preliminary data are needed to improve understanding of long-term peripheral vascular outcomes.

Key Findings

25 subjects with symptomatic PAD underwent open or endovascular lower extremity revascularization in a small cohort. Smaller apo(a) isoforms were associated with occlusion of the treated lesion(s) within 2-4 weeks [OR=1.97 (95% CI 1.01 - 3.86, p<0.05)], suggesting apo(a) isoform size as a predictor of primary patency in the early period after lower extremity intervention.

Take Home Message

Subjects with high Lp(a) levels, generally have smaller apo(a) isoform sizes. We find that, in this small cohort, patients undergoing peripheral arterial revascularization subjects with small isoforms are at an increased risk of treated vessel occlusion in the perioperative period.

Table of Contents Summary

Subjects with symptomatic PAD requiring lower extremity revascularization have high median Lp(a) levels. Individuals with smaller apo(a) weighted isoform size (wIS) have lower primary patency rates and/or require re-intervention.

Residual cardiovascular risk: When should we treat it?

Cardiovascular disease (CVD) still being the most common cause of death in worldwide. In spite of development of new lipid-lowering therapies which optimize low-density lipoprotein cholesterol (LDL-c) levels, recurrence of CVD events implies addressing factors related with residual cardiovascular (CV) risk. The key determinants of residual CV risk include triglyceride-rich lipoproteins (TRLs) and remnant cholesterol (RC), lipoprotein(a) [Lp(a)] and inflammation including its biochemical markers such as high sensitivity C reactive protein (hs-CRP). On the other hand, unhealthy lifestyle habits, environmental pollution, residual thrombotic risk and the residual metabolic risk determined by obesity and type 2 diabetes (T2D) have a specific weight in the residual CV risk. New pharmacologic therapies and pathways are being explored such as inhibition of apolipoprotein C-III (apoC-III) and angiopoietin-related protein 3 (ANGPTL3) in order to explore if a reduction in TRLs and RC reduce CVD events. Therapeutic target of inflammation plays an attractive way to reduce the atherosclerotic process and to date, approved therapies as colchicine plays a beneficial effect in chronic inflammation and residual CV risk. Lp(a) constitutes one of the most residual CV risk factor due to linkage with CVD and aortic valve stenosis. New and hopeful treatments including antisense oligonucleotides (ASO) and small-interfering ribonucleic acid (siRNA) which interfere in LP(a) codification have been developed to achieve an adequate control in Lp(a) levels. This review points out the paradigms of residual CV risk, discus how we should manage their features and summarize the different therapies targeting each residual CV risk factor.

[Update on lipid lowering therapy in peripheral artery disease]

Despite clear guideline recommendations, only about every second PAD patient is prescribed statins, women less often than men. There is an international consensus that every PAD patient should be treated with statins, as these not only lower lipids but also stabilize plaque, resulting in a prognostic benefit. Limb-related endpoints (MALE) can be reduced by 24% compared to placebo by lowering lipids. The combination of low-dose, high-potency statin with ezetimibe can be equivalent to high-dose statin monotherapy and, with better tolerability, promote therapy adherence. Statin intolerance is observed more frequently in certain risk groups but is very rare overall. Effective alternatives are bempedoic acid and PCSK9 inhibitors. About 20% of the population have severely elevated Lp(a) levels that require risk factor management beyond lipid management. A high Lp(a) concentration is associated with PAD progression as an independent risk factor for all atherosclerosis manifestations. Every adult should have an Lp(a) assessment once in their lifetime.

Lipoprotein(a) Testing Trends in a Large Academic Health System in the United States

Background Despite its high prevalence and clinical significance, clinical measurement of lipoprotein(a) is rare but has not been systematically quantified. We assessed the prevalence of lipoprotein(a) testing overall, in those with various cardiovascular disease (CVD) conditions and in those undergoing cardiac testing across 6 academic medical centers associated with the University of California, in total and by year from 2012 to 2021. Methods and Results In this observational study, data from the University of California Health Data Warehouse on the number of individuals with unique lipoprotein(a) testing, unique CVD diagnoses (using International Classification of Diseases, Tenth Revision [ICD-10], codes), and other unique cardiac testing were collected. The proportion of total individuals, the proportion of individuals with a given CVD diagnosis, and the proportion of individuals with a given cardiac test and lipoprotein(a) testing any time during the study period were calculated. From 2012 to 2021, there were 5 553 654 unique adults evaluated in the University of California health system, of whom 18 972 (0.3%) had lipoprotein(a) testing. In general, those with lipoprotein(a) testing were more likely to be older, men, and White race, with a greater burden of CVD. Lipoprotein(a) testing was performed in 6469 individuals with ischemic heart disease (2.9%), 836 with aortic stenosis (3.1%), 4623 with family history of CVD (3.3%), 1202 with stroke (1.7%), and 612 with coronary artery calcification (6.1%). For most conditions, the prevalence of testing in the same year as the diagnosis of CVD was relatively stable, with a small upward trend over time. Lipoprotein(a) testing was performed in 10 753 individuals (1.8%) who had lipid panels, with higher rates with more specialized testing, including coronary computed tomography angiography (6.8%) and apolipoprotein B (63.0%). Conclusions Lipoprotein(a) testing persists at low rates, even among those with diagnosed CVD, and remained relatively stable over the study period.

Lipoprotein(a) as a Risk Factor for Cardiovascular Diseases: Pathophysiology and Treatment Perspectives

Cardiovascular disease (CVD) is still a leading cause of morbidity and mortality, despite all the progress achieved as regards to both prevention and treatment. Having high levels of lipoprotein(a) [Lp(a)] is a risk factor for cardiovascular disease that operates independently. It can increase the risk of developing cardiovascular disease even when LDL cholesterol (LDL-C) levels are within the recommended range, which is referred to as residual cardiovascular risk. Lp(a) is an LDL-like particle present in human plasma, in which a large plasminogen-like glycoprotein, apolipoprotein(a) [Apo(a)], is covalently bound to Apo B100 via one disulfide bridge. Apo(a) contains one plasminogen-like kringle V structure, a variable number of plasminogen-like kringle IV structures (types 1-10), and one inactive protease region. There is a large inter-individual variation of plasma concentrations of Lp(a), mainly ascribable to genetic variants in the Lp(a) gene: in the general po-pulation, Lp(a) levels can range from <1 mg/dL to >1000 mg/dL. Concentrations also vary between different ethnicities. Lp(a) has been established as one of the risk factors that play an important role in the development of atherosclerotic plaque. Indeed, high concentrations of Lp(a) have been related to a greater risk of ischemic CVD, aortic valve stenosis, and heart failure. The threshold value has been set at 50 mg/dL, but the risk may increase already at levels above 30 mg/dL. Although there is a well-established and strong link between high Lp(a) levels and coronary as well as cerebrovascular disease, the evidence regarding incident peripheral arterial disease and carotid atherosclerosis is not as conclusive. Because lifestyle changes and standard lipid-lowering treatments, such as statins, niacin, and cholesteryl ester transfer protein inhibitors, are not highly effective in reducing Lp(a) levels, there is increased interest in developing new drugs that can address this issue. PCSK9 inhibitors seem to be capable of reducing Lp(a) levels by 25-30%. Mipomersen decreases Lp(a) levels by 25-40%, but its use is burdened with important side effects. At the current time, the most effective and tolerated treatment for patients with a high Lp(a) plasma level is apheresis, while antisense oligonucleotides, small interfering RNAs, and microRNAs, which reduce Lp(a) levels by targeting RNA molecules and regulating gene expression as well as protein production levels, are the most widely explored and promising perspectives. The aim of this review is to provide an update on the current state of the art with regard to Lp(a) pathophysiological mechanisms, focusing on the most effective strategies for lowering Lp(a), including new emerging alternative therapies. The purpose of this manuscript is to improve the management of hyperlipoproteinemia(a) in order to achieve better control of the residual cardiovascular risk, which remains unacceptably high.

Novel Pharmacological Therapies for the Management of Hyperlipoproteinemia(a)

Lipoprotein(a) [Lp(a)] is a well-established risk factor for cardiovascular disease, predisposing to major cardiovascular events, including coronary heart disease, stroke, aortic valve calcification and abdominal aortic aneurysm. Lp(a) is differentiated from other lipoprotein molecules through apolipoprotein(a), which possesses atherogenic and antithrombolytic properties attributed to its structure. Lp(a) levels are mostly genetically predetermined and influenced by the size of LPA gene variants, with smaller isoforms resulting in a greater synthesis rate of apo(a) and, ultimately, elevated Lp(a) levels. As a result, serum Lp(a) levels may highly vary from extremely low to extremely high. Hyperlipoproteinemia(a) is defined as Lp(a) levels > 30 mg/dL in the US and >50 mg/dL in Europe. Because of its association with CVD, Lp(a) levels should be measured at least once a lifetime in adults. The ultimate goal is to identify individuals with increased risk of CVD and intervene accordingly. Traditional pharmacological interventions like niacin, statins, ezetimibe, aspirin, PCSK-9 inhibitors, mipomersen, estrogens and CETP inhibitors have not yet yielded satisfactory results. The mean Lp(a) reduction, if any, is barely 50% for all agents, with statins increasing Lp(a) levels, whereas a reduction of 80-90% appears to be required to achieve a significant decrease in major cardiovascular events. Novel RNA-interfering agents that specifically target hepatocytes are aimed in this direction. Pelacarsen is an antisense oligonucleotide, while olpasiran, LY3819469 and SLN360 are small interfering RNAs, all conjugated with a N-acetylgalactosamine molecule. Their ultimate objective is to genetically silence LPA, reduce apo(a) production and lower serum Lp(a) levels. Evidence thus so far demonstrates that monthly subcutaneous administration of a single dose yields optimal results with persisting substantial reductions in Lp(a) levels, potentially enhancing CVD risk reduction. The Lp(a) reduction achieved with novel RNA agents may exceed 95%. The results of ongoing and future clinical trials are eagerly anticipated, and it is hoped that guidelines for the tailored management of Lp(a) levels with these novel agents may not be far off.

Lipoprotein(a): Evidence for Role as a Causal Risk Factor in Cardiovascular Disease and Emerging Therapies

Lipoprotein(a) (Lp(a)) is an established risk factor for multiple cardiovascular diseases. Several lines of evidence including mechanistic, epidemiologic, and genetic studies support the role of Lp(a) as a causal risk factor for atherosclerotic cardiovascular disease (ASCVD) and aortic stenosis/calcific aortic valve disease (AS/CAVD). Limited therapies currently exist for the management of risk associated with elevated Lp(a), but several targeted therapies are currently in various stages of clinical development. In this review, we detail evidence supporting Lp(a) as a causal risk factor for ASCVD and AS/CAVD, and discuss approaches to managing Lp(a)-associated risk.