Elevated Lipoprotein(a): Background, Current Insights and Future Potential Therapies

Attitudes and barriers to lipoprotein(a) testing: A survey of providers at the University of Pennsylvania Health System

Guidelines recommend checking lipoprotein(a) [Lp(a)] levels in patients at high-risk for cardiovascular disease, with more recent recommendations advocating for universal screening in all adults. A brief electronic survey was distributed to select groups of University of Pennsylvania Health System (UPHS) providers, including Internal Medicine and Cardiology physicians and advance practice providers, to understand the current attitudes and barriers to testing for Lp(a). Of the 126 survey respondents, only 31 % answered that they test for Lp(a) regularly in their practice. Presence of ASCVD and a family history of ASCVD were the most common reasons for testing. Most survey respondents (69 %) replied that they do not currently check Lp(a) levels in patients. The most common reasons provided included lack of familiarity with Lp(a), insurance/ billing concerns, lack of clinical trial outcomes data, and lack of available pharmaceutical interventions. Results from ongoing clinical trials of novel Lp(a)-lowering therapies, if successful, may address provider hesitation toward Lp(a)-testing, but there remains a large gap to fill in awareness of Lp(a).

Genetics and Pathophysiological Mechanisms of Lipoprotein(a)-Associated Cardiovascular Risk

Elevated lipoprotein(a) is a genetically transmitted codominant trait that is an independent risk driver for cardiovascular disease. Lipoprotein(a) concentration is heavily influenced by genetic factors, including LPA kringle IV-2 domain size, single-nucleotide polymorphisms, and interleukin-1 genotypes. Apolipoprotein(a) is encoded by the LPA gene and contains 10 subtypes with a variable number of copies of kringle -2, resulting in >40 different apolipoprotein(a) isoform sizes. Genetic loci beyond LPA, such as APOE and APOH, have been shown to impact lipoprotein(a) levels. Lipoprotein(a) concentrations are generally 5% to 10% higher in women than men, and there is up to a 3-fold difference in median lipoprotein(a) concentrations between racial and ethnic populations. Nongenetic factors, including menopause, diet, and renal function, may also impact lipoprotein(a) concentration. Lipoprotein(a) levels are also influenced by inflammation since the LPA promoter contains an interleukin-6 response element; interleukin-6 released during the inflammatory response results in transient increases in plasma lipoprotein(a) levels. Screening can identify elevated lipoprotein(a) levels and facilitate intensive risk factor management. Several investigational, RNA-targeted agents have shown promising lipoprotein(a)-lowering effects in clinical studies, and large-scale lipoprotein(a) testing will be fundamental to identifying eligible patients should these agents become available. Lipoprotein(a) testing requires routine, nonfasting blood draws, making it convenient for patients. Herein, we discuss the genetic determinants of lipoprotein(a) levels, explore the pathophysiological mechanisms underlying the association between lipoprotein(a) and cardiovascular disease, and provide practical guidance for lipoprotein(a) testing.

Obesity: An Impact with Cardiovascular and Cerebrovascular Diseases

The authors sought to correlate the complex sequel of obesity with various parameters known to develop metabolic syndrome viz. insulin resistance, dyslipidemia, hypertension etc., as these anomalies are linked to vascular atherosclerosis and outbreak of cardiovascular and cerebrovascular diseases.  A comprehensive online survey using MEDLINE, Scopus, PubMed and Google Scholar was conducted for relevant journals from 1970 till present time (2023) with key search terms like: 'obesity', 'leptin', type-2 diabetes', 'atherosclerosis', 'cardiovascular and cerebrovascular diseases'. The findings of the reports were compared and correlated. The information was then collated for developing this review. Reports showed that in human obesity, hyper-leptinemia could induce hyperglycemia, which in turn templates hypercholesterolemia. Persisting hypercholesterolemia over a period of time may en-route atherosclerosis in blood vessels. Thus obesity has been considered as a template for originating hyperglycemia, hypercholesterolemia and outbreak of vascular atherogenesis or in other words, obesity in long run can trigger atherosclerosis and its related disorders e.g. heart attack and stroke. Literature survey shows that primarily, co-morbidities of human obesity start with leptin and insulin resistance and then multiplies with metabolic irregularities to an extreme that results in pathogenesis of heart attack and stroke. Atherosclerosis associated cardiovascular and cerebrovascular events are independent risks of obese subjects and particularly in the cases of persisting obesity.

Lipoprotein(a): An important piece of the ASCVD risk factor puzzle across diverse populations

Elevated lipoprotein(a) (Lp[a]) is an independent, genetic risk factor for atherosclerotic cardiovascular disease (ASCVD) that impacts ~1.4 billion people globally. Generally, Lp(a) levels remain stable over time; thus, most individuals need only undergo Lp(a) testing through a non-fasting blood draw once in their lifetime, unless elevated Lp(a) is identified. Despite the convenience of the test for clinicians and patients, routine Lp(a) testing has not been widely adopted. This review provides a guide to the benefits of Lp(a) testing and solutions for overcoming common barriers in practice, including access to testing and lack of awareness. Lp(a) testing provides the opportunity to reclassify ASCVD risk and drive intensive cardiovascular risk factor management in individuals with elevated Lp(a), and to identify patients potentially less likely to respond to statins. Moreover, cascade screening can help to identify elevated Lp(a) in relatives of individuals with a personal or family history of premature ASCVD. Overall, given the profound impact of elevated Lp(a) on cardiovascular risk, Lp(a) testing should be an essential component of risk assessment by primary and specialty care providers.

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).

Lipoprotein(a)-60 Years Later-What Do We Know?

Lipoprotein(a) (Lp(a)) molecule includes two protein components: apolipoprotein(a) and apoB100. The molecule is the main transporter of oxidized phospholipids (OxPL) in plasma. The concentration of this strongly atherogenic lipoprotein is predominantly regulated by the LPA gene expression. Lp(a) is regarded as a risk factor for several cardiovascular diseases. Numerous epidemiological, clinical and in vitro studies showed a strong association between increased Lp(a) and atherosclerotic cardiovascular disease (ASCVD), calcific aortic valve disease/aortic stenosis (CAVD/AS), stroke, heart failure or peripheral arterial disease (PAD). Although there are acknowledged contributions of Lp(a) to the mentioned diseases, clinicians struggle with many inconveniences such as a lack of well-established treatment lowering Lp(a), and common guidelines for diagnosing or assessing cardiovascular risk among both adult and pediatric patients. Lp(a) levels are different with regard to a particular race or ethnicity and might fluctuate during childhood. Furthermore, the lack of standardization of assays is an additional impediment. The review presents the recent knowledge on Lp(a) based on clinical and scientific research, but also highlights relevant aspects of future study directions that would approach more suitable and effective managing risk associated with increased Lp(a), as well as control the Lp(a) levels.

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.

Lipoprotein(a) and the risk of recurrent coronary heart disease: the Dubbo Study

OBJECTIVE

Elevated Lipoprotein(a) [Lp(a)] has not been firmly established as a risk factor for recurrent coronary heart disease (CHD). The present analysis explored this relationship in senior citizens.

METHODS

This was a longitudinal study in 607 subjects, all with prevalent CHD, mean age 71 years, followed for 16 years. Baseline examinations of lipids and other CHD risk factors were conducted in 1988-89 in Dubbo, Australia. The independent contribution of Lp(a) to a further CHD event was examined in proportional hazards regression models.

RESULTS

There were 399 incident CHD cases. Median Lp(a) in CHD cases was 130 mg/L (Interquartile range 60-315) and in non-cases 105 mg/L (45-250) (p < .07, U-Test). 26% of CHD cases and 19% of non-cases had Lp(a) 300 + mg/L; 18% of CHD cases and 8% of non-cases had Lp(a) 500 + mg/L. Lp(a) in Quintile 5 of its distribution (355 + mg/L), using Lp(a) Quintile 1 (<50mg/L) as reference, significantly predicted recurrent CHD with Hazard Ratio 1.53 (95% CI 1.11-2.11, p = .01). Prediction was independent of other risk factors. Lp(a) 500 + mg/L versus lower, significantly predicted recurrent CHD with Hazard Ratio 1.59 (1.16-2.17, p < .01). Prediction was similarly significant for Lp(a) 300 + mg/L versus lower, with Hazard Ratio 1.37 (1.09-1.73, p < .01).

CONCLUSION

Elevated Lp(a) is an independent and significant predictor of recurrent CHD in senior citizens. Upper reference Lp(a) levels of 500 mg/L (≈125nmol/L) or 300 mg/L (≈75nmol/L) both appear to be appropriate. The clinical benefit of therapy to reduce elevated Lp(a) remains to be confirmed.

The association between circulating lipoprotein subfractions and lipid content in coronary atheromatous plaques assessed by near-infrared spectroscopy

Background

Lipid content in coronary atheromatous plaques, measured by near-infrared spectroscopy (NIRS), can predict the risk of future coronary events. Biomarkers that reflect lipid content in coronary plaques may therefore improve coronary artery disease (CAD) risk assessment.

Purpose

We aimed to investigate the association between circulating lipoprotein subfractions and lipid content in coronary atheromatous plaques in statin-treated patients with stable CAD undergoing percutaneous coronary intervention.

Methods

56 patients with stable CAD underwent three-vessel imaging with NIRS when feasible. The coronary artery segment with the highest lipid content, defined as the maximum lipid core burden index within any 4 mm length across the entire lesion (maxLCBI_4mm), was defined as target segment. Lipoprotein subfractions and Lipoprotein a (Lp(a)) were analyzed in fasting serum samples by nuclear magnetic resonance spectroscopy and by standard in-hospital procedures, respectively. Penalized linear regression analyses were used to identify the best predictors of maxLCBI_4mm. The uncertainty of the lasso estimates was assessed as the percentage presence of a variable in resampled datasets by bootstrapping.

Results

Only modest evidence was found for an association between lipoprotein subfractions and maxLCBI_4mm. The lipoprotein subfractions with strongest potential as predictors according to the percentage presence in resampled datasets were Lp(a) (78.1 % presence) and free cholesterol in the smallest high-density lipoprotein (HDL) subfractions (74.3 % presence). When including established cardiovascular disease (CVD) risk factors in the regression model, none of the lipoprotein subfractions were considered potential predictors of maxLCBI_4mm.

Conclusion

In this study, serum levels of Lp(a) and free cholesterol in the smallest HDL subfractions showed the strongest potential as predictors for lipid content in coronary atheromatous plaques. Although the evidence is modest, our study suggests that measurement of lipoprotein subfractions may provide additional information with respect to coronary plaque composition compared to traditional lipid measurements, but not in addition to established risk factors. Further and larger studies are needed to assess the potential of circulating lipoprotein subfractions as meaningful biomarkers both for lipid content in coronary atheromatous plaques and as CVD risk markers.

The associations between exercise and lipid biomarkers

Cardiovascular diseases (CVD) remain the leading cause of death globally, and further efforts are being undertaken to understand and modify CVD risk factors, such as dyslipidemia (DLD), hypertension, and diabetes. The sedentary lifestyle of most individuals today contributes to the prevalence of these conditions. Uncontrolled dyslipidemia serves as a fertile ground for atherosclerotic plaque formation, while lipoproteins (Lp) act as cofactors for inflammatory processes that cause plaque destabilization leading to subsequent CVD events. As such, many health experts and institutions continue to emphasize the importance of cardiorespiratory fitness (CRF) and muscular strength (MusS) with the intent to reduce atherogenic lipoproteins and proprotein convertase subtilisin kexin type 9 (PCSK-9) expression. Concordantly, the two modes of exercise training (ET), such as aerobic ET (aET) and resistance ET (rET) have both demonstrated to improve CRF and MusS, respectively. Although both modes of ET were shown to independently reduce mortality, participation in both forms resulted in a more pronounced improvement in cholesterol levels and CVD-related mortality. Though reduction of adiposity is not a pre-requisite to achieve better control of DLD through increased CRF and MusS, the beneficial effects of physical activity on the inflammatory processes linked to atherosclerosis are almost always associated with a simultaneous decrease in overall adiposity. It is therefore essential to promote both aET and rET, including weight loss in order to attenuate the risks stemming from atherosclerosis and its proinflammatory components.

Cholesteryl Ester Transfer Protein Inhibition Reduces Major Adverse Cardiovascular Events by Lowering Apolipoprotein B Levels

Cholesteryl ester transfer protein (CETP) facilitates the exchange of cholesteryl esters and triglycerides (TG) between high-density lipoprotein (HDL) particles and TG-rich, apolipoprotein (apo) B-containing particles. Initially, these compounds were developed to raise plasma HDL cholesterol (HDL-C) levels, a mechanism that was previously thought to lower the risk of atherosclerotic cardiovascular disease (ASCVD). More recently, the focus changed and the use of pharmacologic CETP inhibitors to reduce low-density lipoprotein cholesterol (LDL-C), non-HDL-C and apoB concentrations became supported by several lines of evidence from animal models, observational investigations, randomized controlled trials and Mendelian randomization studies. Furthermore, a cardiovascular outcome trial of anacetrapib demonstrated that CETP inhibition significantly reduced the risk of major coronary events in patients with ASCVD in a manner directly proportional to the substantial reduction in LDL-C and apoB. These data have dramatically shifted the attention on CETP away from raising HDL-C instead to lowering apoB-containing lipoproteins, which is relevant since the newest CETP inhibitor, obicetrapib, reduces LDL-C by up to 51% and apoB by up to 30% when taken in combination with a high-intensity statin. An ongoing cardiovascular outcome trial of obicetrapib in patients with ASCVD is expected to provide further evidence of the ability of CETP inhibitors to reduce major adverse cardiovascular events by lowering apoB. The purpose of the present review is to provide an up-to-date understanding of CETP inhibition and its relationship to ASCVD risk reduction.

The mechanistic pathways of oxidative stress in aortic stenosis and clinical implications

Despite the elucidation of the pathways behind the development of aortic stenosis (AS), there remains no effective medical treatment to slow or reverse its progress. Instead, the gold standard of care in severe or symptomatic AS is replacement of the aortic valve. Oxidative stress is implicated, both directly as well as indirectly, in lipid infiltration, inflammation and fibro-calcification, all of which are key processes underlying the pathophysiology of degenerative AS. This culminates in the breakdown of the extracellular matrix, differentiation of the valvular interstitial cells into an osteogenic phenotype, and finally, calcium deposition as well as thickening of the aortic valve. Oxidative stress is thus a promising and potential therapeutic target for the treatment of AS. Several studies focusing on the mitigation of oxidative stress in the context of AS have shown some success in animal and in vitro models, however similar benefits have yet to be seen in clinical trials. Statin therapy, once thought to be the key to the treatment of AS, has yielded disappointing results, however newer lipid lowering therapies may hold some promise. Other potential therapies, such as manipulation of microRNAs, blockade of the renin-angiotensin-aldosterone system and the use of dipeptidylpeptidase-4 inhibitors will also be reviewed.

Lipoprotein(a): Insights for the Practicing Clinician

Following the discovery of the Lipoprotein(a) (Lp(a)) molecule by Kare Berg in 1963, many physiological and pathological properties of this particle remain to be fully understood. Multiple population-based studies have demonstrated a correlation between elevated Lp(a) levels and the incidence of cardiovascular disease. Data extrapolated from the Copenhagen City Heart and ASTRONOMER studies also demonstrated the link between Lp(a) levels and the incidence and rate of progression of calcific aortic stenosis. Interest in Lp(a) has increased in recent years, partly due to new emerging therapies that can specifically reduce serum Lp(a) concentrations. Given the strong correlation between Lp(a) and CV disease from epidemiological studies, several international guidelines have also been updated to advocate Lp(a) testing in specific population groups. This review aims to highlight the importance of the role of Lp(a) in cardiovascular disease and discusses the potential of novel therapies in patients with elevated Lp(a) levels.

NLA scientific statement on statin intolerance: a new definition and key considerations for ASCVD risk reduction in the statin intolerant patient

Although statins are generally well tolerated, statin intolerance is reported in 5-30% of patients and contributes to reduced statin adherence and persistence, as well as higher risk for adverse cardiovascular outcomes. This Scientific Statement from the National Lipid Association was developed to provide an updated definition of statin intolerance and to inform clinicians and researchers about its identification and management. Statin intolerance is defined as one or more adverse effects associated with statin therapy which resolves or improves with dose reduction or discontinuation and can be classified as a complete inability to tolerate any dose of a statin or partial intolerance with inability to tolerate the dose necessary to achieve the patient-specific therapeutic objective. To classify a patient as having statin intolerance, a minimum of two statins should have been attempted, including at least one at the lowest approved daily dosage. This Statement acknowledges the importance of identifying modifiable risk factors for statin intolerance and recognizes the possibility of a "nocebo" effect (patient expectation of harm resulting in perceived side effects). To identify a tolerable statin regimen it is recommended that clinicians consider using several different strategies (e.g., different statin, dose, and/or dosing frequency). Non-statin therapy may be required for patients who cannot reach therapeutic objectives with lifestyle and maximal tolerated statin therapy. If so, therapies with outcomes data from randomized trials showing reduced cardiovascular events are favored. In high and very high risk patients who are statin intolerant, clinicians should consider initiating non-statin therapy while additional attempts are made to identify a tolerable statin in order to limit the time of exposure to elevated levels of atherogenic lipoproteins.

New targets for treating hypertriglyceridemia

PURPOSE OF REVIEW

Elevated fasting and postprandial plasma triglyceride concentrations are associated with an increased risk for atherosclerotic cardiovascular disease in patients on and off low-density lipoprotein (LDL) lowering therapy.

RECENT FINDINGS

This association is not mediated by triglycerides directly. Other components of triglyceride rich lipoproteins, such as cholesterol and apolipoproteins B and -CIII can directly induce and enhance atherosclerosis. In addition, an elevated concentration of triglyceride rich lipoproteins affects the concentration, composition, function, and metabolism of LDL and high-density lipoprotein (HDL), which contributes to the risk. Especially in patients with hypertriglyceridemia, apolipoprotein B and non-HDL-cholesterol (encompassing cholesterol of all atherogenic lipoproteins) predict risk better than LDL-cholesterol and/or triglycerides. Therefore, current guidelines have stated secondary goals relating to non-HDL-cholesterol and apolipoprotein B (in addition to the primary goal relating to LDL-cholesterol). These secondary goals can be achieved by further reducing LDL-cholesterol or by decreasing triglyceride rich lipoproteins. However, only further LDL reduction has so far proven to be beneficial in outcome trials. In addition, high dose eicosapentaenoic acid (EPA) can reduce atherosclerotic cardio-vascular disease risk in patients with hypertriglyceridemia, although benefit is not (or not only) related to apolipoprotein B or non-HDL-cholesterol reduction.

SUMMARY

Non-HDL-cholesterol and apoB represent novel targets for patients with hypertriglyceridemia, but achieving LDL-cholesterol targets remains the first step for cardio-vascular risk reduction.

Value of repeated measurements of lipoprotein (a) to assess cardiovascular risk: a retrospective study

Background: High plasma concentrations of lipoprotein (a) [Lp(a)] are associated with an increased cardiovascular risk. Current guidelines recommend measurement of only a single Lp(a) in an individual's lifetime under specific circumstances to improve cardiovascular risk prediction. Accordingly, the question raised is the number of false positives and negatives missed through only a single measurement.Methods: All Lp(a) measurements between 2004 and March 2021 were retrieved from the laboratory database of the Erasme hospital. Only patients with repeated measurement were included. The first and subsequent Lp(a) measurement were compared. Two different cohorts were studied as a result of a change in Lp(a) determination methodology (n = 2049 and n = 309, respectively). The effects of a third Lp(a) measurement were assessed through binary analyses (n = 678). The 180 mg/dl (430 nmol/L) threshold recommended in the ESC guidelines was assessed first. Analysis was repeated for 100, 70 and 50 mg/dl thresholds of raised Lp(a) levels.Results: A low rate of false negatives (0.8%-1%) and false positives (0.6-0.3%) were revealed with two Lp(a) measurements. There was no difference in regards to the divergent Lp(a) thresholds nor the measurement of Lp(a) on two or three occasions.Conclusion: The present study showed Lp(a) determination to be reproducible. A single measurement is sufficient to assess if a patient exceeds various cut-off values of elevated Lp(a) levels.