Apolipoprotein(a) size and lipoprotein(a) concentration and future risk of angina pectoris with evidence of severe coronary atherosclerosis in men: The Physicians' Health Study

The levels of serum lipoprotein(a) on clinical outcomes in Chinese hospitalized patients with cardiovascular diseases

OBJECTIVE

Serum lipoprotein(a) [Lp(a)] is a risk factor of cardiovascular diseases. However, the relationship between the serum Lp(a) and clinical outcomes has been seldom studied in Chinese hospitalized patients with cardiovascular diseases.

METHODS

We retrospectively collected the clinical data of hospitalized patients with cardiovascular diseases in the Cardiovascular Department of Dongguan People's Hospital from 2016 to 2021 through the electronic case system. Patients were divided into 4 groups based on Lp(a) quartiles: Quartile1 (≤ 80.00 mg/L), Quartile 2 (80.01 ~ 160.90 mg/L), Quartile 3 (160.91 ~ 336.41 mg/L), Quartile 4 (> 336.41 mg/L). Cox proportional hazard regression models were constructed to examine the relationship between Lp(a) and cardiovascular events.

RESULTS

A total of 8382 patients were included in this study. After an average follow-up of 619 (320 to 1061) days, 1361 (16.2%) patients developed major adverse cardiovascular events, and 125 (1.5%) all-cause death were collected. The incidence of MACEs was 7.65, 8.24, 9.73 and 10.75 per 100 person-years in each Lp(a) quartile, respectively; the all-cause mortality was 0.48, 0.69, 0.64 and 1.18 per 100 person-years in each Lp(a) quartile, respectively. The multivariate Cox regression analysis suggested that high Lp(a) level was an independent risk factor for MACEs (HR: 1.189, [95% CI: 1.045 to 1.353], P = 0.030) and all-cause death (HR: 1.573, [95% CI: 1.009 to 2.452], P = 0.046).

CONCLUSION

In addition to traditional lipid indicators, higher Lp(a) exhibited higher risks of adverse cardiovascular events and death, indicated worse prognosis. Lp(a) may be a new target for the prevention of atherosclerotic diseases.

The current status of lipoprotein (a) measurement in clinical biochemistry laboratories in the UK: Results of a 2021 national survey

BACKGROUND

Lipoprotein(a) (Lp(a)) is now established as a causal risk factor for cardiovascular disease (CVD) and accurate laboratory measurement is of pivotal importance in reducing Lp(a) associated risk. The consensus statement by HEART UK in 2019 included recommendations to improve standardisation of clinical laboratory measurement and reporting of Lp(a).

METHODS

A 16 question, electronic audit survey was circulated to 190 accredited clinical biochemistry laboratories to assess the adoption of these recommendations in the UK.

RESULTS

Responses were received from 65 of 190 laboratories (34%). Only 5 (8%) did not offer Lp(a) measurement. Of those providing the test, 23% (n = 14) offered an in-house service (IHS), the remaining laboratories (77%; n = 46) used an external referral service (ERS). The majority (10 of 14 or 71%) of IHS laboratories responded with details of their method, stating whether it minimised sensitivity to the effect of Lp(a) isoform size and used calibrators certified for traceability to the WHO/IFCC reference material, however, only a minority ERS laboratories (13 of the 46 or 28%) were able to specify the method used by their referral laboratory. Of the laboratories who specified their reporting units, 6 of 10 IHS and 7 of 23 ERS laboratories reported in nmol/L. Among the 60 laboratories who responded, the HEART UK recommendations appear to have been adopted in full by only 3 IHS laboratories.

CONCLUSIONS

Further efforts are needed to standardise the measurement and reporting of Lp(a) so that results and interpretation are comparable across clinical biochemistry laboratories in the UK.

Lipoprotein(a): A Review of Risk Factors, Measurements, and Novel Treatment Modalities

The study of lipoprotein(a) [Lp(a)] has long been a source of interest as a possible independent risk factor for atherosclerotic cardiovascular disease (ASCVD). The results of large sample observational studies, genome-wide association studies, and Mendelian randomization studies have been strong indicators supporting the link between ASCVD and Lp(a) despite early studies, with less sensitive assays, failing to show a connection. The recommendations for the indications and frequency of testing Lp(a) levels vary between US, Canadian, and European organizations due to the uncertain role of Lp(a) in ASCVD. The innovation of recent therapies, such as antisense oligonucleotides and small interfering RNA, designed to specifically target and reduce Lp(a) levels by targeting mRNA translation have once more thrust LP(a) into the spotlight of inquiry. These emerging modalities serve the dual purpose of definitively elucidating the connection between elevated Lp(a) levels and atherosclerotic cardiovascular risk, as well as the possibility of providing clinicians with the tools necessary to manage elevated Lp(a) levels in vulnerable populations. This review seeks to examine the mechanisms of atherogenicity of Lp(a) and explore the most current pharmacologic therapies currently in development.

Lipoprotein(a): a genetically determined risk factor for Cardiovascular disease

Lipoprotein(a) is a complex lipoprotein with unique characteristics distinguishing it from all the other apolipoprotein B-containing lipoprotein particles. Its lipid composition and the presence of a single molecule of apolipoprotein B per particle, render lipoprotein(a) similar to low-density lipoproteins. However, the presence of a unique, carbohydrate-rich protein termed apolipoprotein(a), linked by a covalent bond to apolipoprotein B imparts unique characteristics to lipoprotein(a) distinguishing it from all the other lipoproteins. Apolipoprotein(a) is highly polymorphic in size ranging in molecular weight from <300 KDa to >800 kDa. Both the size polymorphism and the concentration of lipoprotein(a) in plasma are genetically determined and unlike other lipoproteins, plasma concentration is minimally impacted by lifestyle modifications or lipid-lowering drugs. Many studies involving hundreds of thousands of individuals have provided strong evidence that elevated lipoprotein(a) is genetically determined and a causal risk factor for atherosclerotic cardiovascular disease. The concentration attained in adulthood is already present in children at around 5 years of age and therefore, those with elevated lipoprotein(a) are prematurely exposed to a high risk of cardiovascular disease. Despite the large number of guidelines and consensus statements on the management of lipoprotein(a) in atherosclerotic cardiovascular disease published in the last decade, lipoprotein(a) is still seldom measured in clinical settings. In this review, we provide an overview of the most important features that characterize lipoprotein(a), its role in cardiovascular disease, and the importance of adding the measurement of lipoprotein(a) for screening adults and youths to identify those at increased risk of atherosclerotic cardiovascular disease due to their elevated plasma concentration of lipoprotein(a).

Developing an SI-traceable Lp(a) reference measurement system: a pilgrimage to selective and accurate apo(a) quantification

In the past decade a remarkable rebirth of serum/plasma lipoprotein(a) (Lp(a)) as an independent risk factor of cardiovascular disease (CVD) occurred. Updated evidence for a causal continuous association in different ethnic groups between Lp(a) concentrations and cardiovascular outcomes has been published in the latest European Atherosclerosis Society (EAS) Lp(a) consensus statement. Interest in measuring Lp(a) at least once in a person's lifetime moreover originates from the development of promising new Lp(a) lowering drugs. Accurate and clinically effective Lp(a) tests are of key importance for the timely detection of high-risk individuals and for future evaluation of the therapeutic effects of Lp(a) lowering medication. To this end, it is necessary to improve the performance and standardization of existing Lp(a) tests, as is also noted in the Lp(a) consensus statement. Consequently, a state-of-the-art internationally endorsed reference measurement system (RMS) must be in place that allows for performance evaluation of Lp(a) field tests in order to certify their validity and accuracy. An ELISA-based RMS from Northwest Lipid Research Laboratory (University of Washington, Seattle, USA) has been available since the 1990s. A next-generation apo(a)/Lp(a) RMS is now being developed by a working group from the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). The envisioned apo(a) RMS is based on the direct measurement of selected proteotypic fragments generated after proteolytic digestion using quantitative protein mass spectrometry (MS). The choice for an MS-based RMS enables selective measurement of the proteotypic peptides and is by design apo(a) isoform insensitive. Clearly, the equimolar conversion of apo(a) into the surrogate peptide measurands is required to obtain accurate Lp(a) results. The completeness of proteolysis under reaction conditions from the candidate reference measurement procedure (RMP) has been demonstrated for the quantifying apo(a) peptides. Currently, the candidate apo(a) RMP is endorsed by the IFCC and recommendations for suitable secondary reference materials have been made in a recent commutability study paper. Ongoing efforts toward a complete apo(a) RMS that is listed by the Joint Committee on Traceability in Laboratory Medicine (JCTLM) are focused on the peptide-based calibration and the establishment of a network of calibration laboratories running the apo(a) RMS in a harmonized way. Once completed, it will be the holy grail for evaluation and certification of Lp(a) field methods.

Circulating lipoprotein (a) and all-cause and cause-specific mortality: a systematic review and dose-response meta-analysis

AIMS

To investigate the association between circulating lipoprotein(a) (Lp(a)) and risk of all-cause and cause-specific mortality in the general population and in patients with chronic diseases, and to elucidate the dose-response relations.

METHODS AND RESULTS

We searched literature to find prospective studies reporting adjusted risk estimates on the association of Lp(a) and mortality outcomes. Forty-three publications, reporting on 75 studies (957,253 participants), were included. The hazard ratios (HRs) and 95% confidence intervals (95%CI ) for the top versus bottom tertile of Lp(a) levels and risk of all-cause mortality were 1.09 (95%CI: 1.01-1.18, I²: 75.34%, n = 19) in the general population and 1.18 (95%CI: 1.04-1.34, I²: 52.5%, n = 12) in patients with cardiovascular diseases (CVD). The HRs for CVD mortality were 1.33 (95%CI: 1.11-1.58, I²: 82.8%, n = 31) in the general population, 1.25 (95%CI: 1.10-1.43, I²: 54.3%, n = 17) in patients with CVD and 2.53 (95%CI: 1.13-5.64, I²: 66%, n = 4) in patients with diabetes mellitus. Linear dose-response analyses revealed that each 50 mg/dL increase in Lp(a) levels was associated with 31% and 15% greater risk of CVD death in the general population and in patients with CVD. No non-linear dose-response association was observed between Lp(a) levels and risk of all-cause or CVD mortality in the general population or in patients with CVD (P_nonlinearity > 0.05).

CONCLUSION

This study provides further evidence that higher Lp(a) levels are associated with higher risk of all-cause mortality and CVD-death in the general population and in patients with CVD. These findings support the ESC/EAS Guidelines that recommend Lp(a) should be measured at least once in each adult person's lifetime, since our study suggests those with higher Lp(a) might also have higher risk of mortality.

Lipoprotein(a) and Atherosclerotic Cardiovascular Disease, the Impact of Available Lipid-Lowering Medications on Lipoprotein(a): An Update on New Therapies

OBJECTIVE

To review evidence of existing and new pharmacological therapies for lowering lipoprotein(a) (Lp[a]) concentrations and their impact on clinically relevant outcomes.

METHODS

We searched for literature pertaining to Lp(a) and pharmacological treatments in PubMed. We reviewed articles published between 1963 and 2020.

RESULTS

We found that statins significantly increased Lp(a) concentrations. Therapies that demonstrated varying degrees of Lp(a) reduction included ezetimibe, niacin, proprotein convertase subtilisin/kexin type 9 inhibitors, lipoprotein apheresis, fibrates, aspirin, hormone replacement therapy, antisense oligonucleotide therapy, and small interfering RNA therapy. There was limited data from large observational studies and post hoc analyses showing the potential benefits of these therapies in improving cardiovascular outcomes.

CONCLUSION

There are multiple lipid-lowering agents currently being used to treat hyperlipidemia that also have a Lp(a)-lowering effect. Two RNA therapies specifically targeted to lower Lp(a) are being investigated in phase 3 clinical trials and, thus far, have shown promising results. However, evidence is lacking to determine the clinical relevance of reducing Lp(a). At present, there is a need for large-scale, randomized, controlled trials to evaluate cardiovascular outcomes associated with lowering Lp(a).

Lipoprotein (a) and long-term outcome in patients with peripheral artery disease undergoing revascularization

BACKGROUND AND AIMS

Despite low LDL-C goals, the residual risk for further cardiovascular (CV) events in patients with peripheral artery disease (PAD) remains high. Lipoprotein (a) (Lp(a)) is a known risk factor for PAD incidence, but little is known regarding the outcome in patients with symptomatic PAD. Thus, this study investigates Lp(a) and CV mortality in PAD after endovascular repair.

METHODS

A total of 1222 patients with PAD in two cohorts according to Lp(a) assay in nmol/L (n = 964, Lip-LEAD-A) or mg/dl (n = 258, Lip-LEAD-B) were followed up for 4.3 (IQR 3.0-5.6) or 7.6 (IQR 3.2-8.1) years. Lp(a) was measured before endovascular repair for either intermittent claudication (IC) or critical limb ischemia (CLI). Outcome information was obtained from the federal death registry.

RESULTS

In Lip-LEAD-A, 141 CV-deaths occurred (annual calculated CV-death rate 3.4%), whereas 64 CV-deaths were registered in Lip-LEAD-B (annual calculated CV-death rate 3.3%). After adjustment for traditional CV risk factors Lp(a) was neither associated with outcome in Lip-LEAD-A (highest tertile HR 1.47, 95%CI [0.96-2.24]) nor in Lip-LEAD-B (highest tertile HR 1.34 [0.70-2.58]). Subanalyses for IC (HR 1.37 [0.74-2.55]; HR 1.10 [0.44-2.80], CLI (HR 1.55 [0.86-2.80], HR 3.01 [0.99-9.10]), or concomitant coronary artery disease (CAD; HR 1.34 [0.71-2.54]; HR 1.21 [0.46-3.17]) failed to show a significant association between Lp(a) and CV-mortality.

CONCLUSIONS

In this large-scale cohort of symptomatic PAD no association of elevated Lp(a) with CV mortality was found over a median observation period of 5 years. Thus, an even longer study including asymptomatic patients is warranted.

Lipoprotein(a) levels and risk of adverse events after myocardial infarction in patients with and without diabetes

Introduction: The aim of this study was to evaluate the association of lipoprotein(a) [Lp(a)] levels with long-term outcome in patients with recent history of myocardial infarction (MI), and to investigate if diabetes may influence this association.

Methods: Consecutive MI patients who underwent urgent/emergent coronary angiography from February 2013 to June 2019 were prospectively collected. The primary outcome was the composite of MI recurrence and all-cause death. The propensity score weighting technique was used to account for covariates potentially influencing the relationship between Lp(a) levels and the study outcomes.

Results: The study population consisted of 1018 post-MI patients (median age 63 years). Diabetes was reported in 280 patients (27.5%), who showed lower Lp(a) levels than patients without diabetes (p = 0.026). At a median follow-up of 1121 days, the primary outcome was reported in 182 patients (17.9%). At univariable Cox regression analysis, Lp(a) was associated with the risk of the primary outcome in the overall population and in non-diabetic patients, but not in diabetics. The adjusted Cox regression analysis confirmed the independent association between Lp(a) values and the primary outcome in non-diabetic patients, but not in diabetics.

Lp(a) levels > 70 mg/dL were independently associated with the risk of the primary outcome in non-diabetic patients (adjusted HR: 2.839; 95% CI, 1.382–5.832), but not in diabetics.

Conclusions: In this real-world post-MI population, increasing Lp(a) levels were significantly associated with the risk of recurrent MI and all-cause death, and very high Lp(a) serum concentration independently predicted long-term outcome in non-diabetic patients, but not in diabetics.

Elevated Lipoprotein(a) Linked to Recurrent Cardiovascular Events – A Case Report

The role of lipoprotein(a) [Lp(a)] in the development of atherosclerosis has been recently recognized, and the current recommendation is to measure Lp(a) once in a lifetime in all individuals, in order to identify those at risk for developing an acute coronary syndrome or recurrent events, even in the absence of other cardiovascular risk factors. We present the case of a middle-aged patient with recurrent cardiovascular events, in whom we identified high levels of Lp(a) as a possible explanation of the recurrent events.

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.

Lipoprotein(a) and Cardiovascular Disease

BACKGROUND

High lipoprotein(a) concentrations present in 10%-20% of the population have long been linked to increased risk of ischemic cardiovascular disease. It is unclear whether high concentrations represent an unmet medical need. Lipoprotein(a) is currently not a target for treatment to prevent cardiovascular disease.

CONTENT

The present review summarizes evidence of causality for high lipoprotein(a) concentrations gained from large genetic epidemiologic studies and discusses measurements of lipoprotein(a) and future treatment options for high values found in an estimated >1 billion individuals worldwide.

SUMMARY

Evidence from mechanistic, observational, and genetic studies support a causal role of lipoprotein(a) in the development of cardiovascular disease, including coronary heart disease and peripheral arterial disease, as well as aortic valve stenosis, and likely also ischemic stroke. Effect sizes are most pronounced for myocardial infarction, peripheral arterial disease, and aortic valve stenosis where high lipoprotein(a) concentrations predict 2- to 3-fold increases in risk. Lipoprotein(a) measurements should be performed using well-validated assays with traceability to a recognized calibrator to ensure common cut-offs for high concentrations and risk assessment. Randomized cardiovascular outcome trials are needed to provide final evidence of causality and to assess the potential clinical benefit of novel, potent lipoprotein(a) lowering therapies.

Lp(a): When and how to measure it

Lipoprotein(a) has long been regarded as a risk factor for cardiovascular disease; however, its routine use in clinical practice has been hampered by difficulties inherent in the measurement of this complex lipoprotein. The major challenges relate to its size heterogeneity and related issues including (1) use of appropriate calibrators (2) standardization of calibration protocols (3) traceability and (4) reporting units. In the UK, results from the current EQA schemes for lipoprotein(a) suggest that there is considerable work required to standardize lipoprotein(a) measurement. This is becoming increasingly pertinent with the increasing recognition of lipoprotein(a) as an independent risk factor for cardiovascular disease in international guidelines and the emergence of novel antisense therapies to effectively reduce lipoprotein(a). This article raises awareness of the importance of measurement of lipoprotein(a) for the assessment of cardiovascular disease risk and gives guidance to clinical laboratories regarding choice of appropriate assays.

Lipoprotein(a) - Marker for cardiovascular risk and target for lipoprotein apheresis

Lipoprotein(a) (Lp(a)) consists of an LDL particle whose apolipoprotein B (apoB) is covalently bound to apolipoprotein(a) (apo[a]). An increased Lp(a) concentration is a causal, independent risk factor for atherosclerotic cardiovascular disease (ASCVD) and a predictor of incident or recurrent cardiovascular events. Although Lp(a) was first described as early as 1963, only the more recent results of epidemiological, molecular, and genetic studies have led to this unequivocal conclusion. More than 20% of Western populations have elevated Lp(a) values. Lp(a) concentrations should be always part of the lipid profile when ASCVD risk is assessed. However, presence of other risk factors, laboratory findings, medical history and family history must be considered to conclude on its clinical relevance in an individual patient. Early or progressive ASCVD or a familial predisposition are key findings which can be associated with elevated Lp(a). The cholesterol portion contained in Lp(a) is also included in the various methods of LDL-C measurement. To assess proximity to the cardiovascular risk related target value for LDL-C, appropriate correction should be applied when high Lp(a) values are obtained to estimate the LDL-C that can actually be treated by lipid lowering drugs. Initial study data show that antisense oligonucleotides, which selectively decrease apolipoprotein(a), are promising as future treatment options. Currently, lipoprotein apheresis, which has a reimbursement guideline in Germany, is the therapy of choice for patients with Lp(a)-associated progressive ASCVD, with the aim of sustained prevention of further cardiovascular events.

Lipoprotein(a) concentration, genetic variants, apo(a) isoform size, and cellular cholesterol efflux in patients with elevated Lp(a) and coronary heart disease submitted or not to lipoprotein apheresis: An Italian case-control multicenter study on Lp(a)

BACKGROUND

Coronary artery disease (CAD) risk is greater with higher plasma lipoprotein(a)[Lp(a)] concentrations or smaller apoisoform size and putatively with increased cellular cholesterol loading capacity (CLC). The relationship between Lp(a) and CLC is not known. Information on Lp(a) polymorphisms in Italian patients is lacking.

OBJECTIVE

The objective of this study was to determine relationships between Lp(a) and CLC, the impact of lipoprotein apheresis (LA), and describe the genetic profile of Lp(a).

METHODS

We conducted a multicenter, observational study in Italian patients with hyperLp(a) and premature CAD with (n = 18)/without (n = 16) LA in which blood samples were analyzed for Lp(a) parameter and CLC. Genetic profiling of LPA was conducted in patient receiving LA.

RESULTS

Mean macrophage CLC of the pre-LA serum was significantly higher than that of normolipidemic controls (19.7 ± 0.9 μg/mg vs 16.01 ± 0.98 μg/mg of protein, respectively). After LA, serum macrophage CLC was markedly lower relative to preapheresis (16.1 ± 0.8 μg/mg protein; P = .003) and comparable with CLC of the normolipidemic serum. LA did not significantly affect average apo(a) isoform size distribution. No anthropometric or lipid parameters studied were related to serum CLC, but there was a relationship between CLC and the Lp(a) plasma concentration (P = .035). DNA analysis revealed a range of common genetic variants. Two rare, new variants were identified: LPA exon 21, c.3269C>G, p.Pro1090Arg, and rs41259144 p.Arg990Gln, c.2969G>A CONCLUSIONS: LA reduces serum Lp(a) and also reduces macrophage CLC. Novel genetic variants of the LPA gene were identified, and geographic variations were noted. The complexity of these polymorphisms means that genetic assessment is not a predictor of CAD risk in hyperLp(a).

Lipoprotein(a) Levels and the Risk of Myocardial Infarction Among 7 Ethnic Groups

BACKGROUND

Lipoprotein(a) [Lp(a)] levels predict the risk of myocardial infarction (MI) in populations of European ancestry; however, few data are available for other ethnic groups. Furthermore, differences in isoform size distribution and the associated Lp(a) concentrations have not fully been characterized between ethnic groups.

METHODS

We studied 6086 cases of first MI and 6857 controls from the INTERHEART study that were stratified by ethnicity and adjusted for age and sex. A total of 775 Africans, 4443 Chinese, 1352 Arabs, 1856 Europeans, 1469 Latin Americans, 1829 South Asians, and 1221 Southeast Asians were included in the study. Lp(a) concentration was measured in each participant using an assay that was insensitive to isoform size, with isoform size being assessed by Western blot in a subset of 4219 participants.

RESULTS

Variations in Lp(a) concentrations and isoform size distributions were observed between populations, with Africans having the highest Lp(a) concentration (median=27.2 mg/dL) and smallest isoform size (median=24 kringle IV repeats). Chinese samples had the lowest concentration (median=7.8 mg/dL) and largest isoform sizes (median=28). Overall, high Lp(a) concentrations (>50 mg/dL) were associated with an increased risk of MI (odds ratio, 1.48; 95% CI, 1.32-1.67; P<0.001). The association was independent of established MI risk factors, including diabetes mellitus, smoking, high blood pressure, and apolipoprotein B and A ratio. An inverse association was observed between isoform size and Lp(a) concentration, which was consistent across ethnic groups. Larger isoforms tended to be associated with a lower risk of MI, but this relationship was not present after adjustment for concentration. Consistent with variations in Lp(a) concentration across populations, the population-attributable risk of high Lp(a) for MI varied from 0% in Africans to 9.5% in South Asians.

CONCLUSIONS

Lp(a) concentration and isoform size varied markedly between ethnic groups. Higher Lp(a) concentrations were associated with an increased risk of MI and carried an especially high population burden in South Asians and Latin Americans. Isoform size was inversely associated with Lp(a) concentration, but did not significantly contribute to risk.

Molecular, Population, and Clinical Aspects of Lipoprotein(a): A Bridge Too Far?

There is now significant evidence to support an independent causal role for lipoprotein(a) (Lp(a)) as a risk factor for atherosclerotic cardiovascular disease. Plasma Lp(a) concentrations are predominantly determined by genetic factors. However, research into Lp(a) has been hampered by incomplete understanding of its metabolism and proatherogeneic properties and by a lack of suitable animal models. Furthermore, a lack of standardized assays to measure Lp(a) and no universal consensus on optimal plasma levels remain significant obstacles. In addition, there are currently no approved specific therapies that target and lower elevated plasma Lp(a), although there are recent but limited clinical outcome data suggesting benefits of such reduction. Despite this, international guidelines now recognize elevated Lp(a) as a risk enhancing factor for risk reclassification. This review summarises the current literature on Lp(a), including its discovery and recognition as an atherosclerotic cardiovascular disease risk factor, attempts to standardise analytical measurement, interpopulation studies, and emerging therapies for lowering elevated Lp(a) levels.

Lipoprotein(a) – Link between Atherogenesis and Thrombosis

Lipoprotein(a) – Lp(a) – is an independent risk factor for cardiovascular disease (CVD). Indeed, individuals with plasma concentrations of Lp(a) > 200 mg/l carry an increased risk of developing CVD. Circulating levels of Lp(a) are remarkably resistant to common lipid lowering therapies, currently available treatment for reduction of Lp(a) is plasma apheresis, which is costly and labour intensive. The Lp(a) molecule is composed of two parts: LDL/apoB-100 core and glycoprotein, apolipoprotein(a) – Apo(a), both of them can interact with components of the coagulation cascade, inflammatory pathways and blood vessel cells (smooth muscle cells and endothelial cells). Therefore, it is very important to determine the molecular pathways by which Lp(a) affect the vascular system in order to design therapeutics for targeting the Lp(a) cellular effects. This paper summarises the cellular effects and molecular mechanisms by which Lp(a) participate in atherogenesis, thrombogenesis, inflammation and development of cardiovascular diseases.

To test, or not to test: that is the question for the future of lipoprotein(a)

INTRODUCTION

Lipoprotein(a) [Lp(a)] is a potent, highly heritable and common risk factor for atherosclerotic cardiovascular disease (ASCVD). Evidence for a causal association between elevated Lp(a) and ASCVD has been provided by large epidemiological investigations that have demonstrated a curvilinear association with increased risk, as well as from genetic examinations and cellular and transgenic animal studies. Although there are several therapies available for lowering Lp(a), none are selective for Lp(a) and there is no clinical trial data that has specifically shown that lowering Lp(a) reduces the risk of ASCVD. Hence, screening for elevated Lp(a) is not routinely incorporated into clinical practice. Areas covered: This paper reviews the current evidence supporting the causal role of Lp(a) in the primary and secondary prevention of ASCVD, screening approaches for high Lp(a), current guidelines on testing Lp(a), and barriers to the routine screening of elevated Lp(a) in clinical practice. Expert opinion: At present, there is a moderate level of evidence supporting the routine screening of elevated Lp(a). Current guidelines recommend testing for elevated Lp(a) in individuals at intermediate or high risk of ASCVD.

Lipoprotein(a) Particle Production as a Determinant of Plasma Lipoprotein(a) Concentration Across Varying Apolipoprotein(a) Isoform Sizes and Background Cholesterol-Lowering Therapy

Background Elevated lipoprotein(a) (Lp(a)), a low-density lipoprotein-like particle bound to the polymorphic apolipoprotein(a) (apo(a)), may be causal for cardiovascular disease. However, the metabolism of Lp(a) in humans is poorly understood. Methods and Results We investigated the kinetics of Lp(a)-apo(a) and low-density lipoprotein-apoB-100 in 63 normolipidemic men. The fractional catabolic rate ( FCR ) and production rate PR ) were studied. Plasma apo(a) concentration was significantly and inversely associated with apo(a) isoform size ( r=-0.536, P<0.001) and apo(a) FCR ( r=-0.363, P<0.01), and positively with apo(a) PR ( r=0.877, P<0.001). There were no significant associations between the FCR s of apo(a) and low-density lipoprotein-apoB-100. Subjects with smaller apo(a) isoform sizes (≤22 kringle IV repeats) had significantly higher apo(a) PR ( P<0.05) and lower apo(a) FCR ( P<0.01) than those with larger sizes. Plasma apo(a) concentration was significantly associated with apo(a) PR ( r=0.930, P<0.001), but not with FCR ( r=-0.012, P>0.05) in subjects with smaller apo(a) isoform size. In contrast, both apo(a) PR and FCR were significantly associated with plasma apo(a) concentrations ( r=0.744 and -0.389, respectively, P<0.05) in subjects with larger isoforms. In multiple regression analysis, apo(a) PR and apo(a) isoform size were significant predictors of plasma apo(a) concentration independent of low-density lipoprotein-apoB-100 FCR and background therapy with atorvastatin and evolocumab. Conclusions In normolipidemic men, the plasma Lp(a) concentration is predominantly determined by the rate of production of Lp(a) particles, irrespective of apo(a) isoform size and background therapy with a statin and a proprotein convertase subtilisin-kexin type 9 inhibitor. Our findings underscore the importance of therapeutic targeting of the hepatic synthesis and secretion of Lp(a) particles. Lp(a) particle catabolism may only play a modest role in determining Lp(a) concentration in subjects with larger apo(a) isoform size. Clinical Trial Registration URL : http://www.clinicaltrials.gov . Unique identifier: NCT 02189837.

Lipoprotein(a): An independent, genetic, and causal factor for cardiovascular disease and acute myocardial infarction

Lipoprotein(a) [Lp(a)] is a circulating lipoprotein, and its level is largely determined by variation in the Lp(a) gene (LPA) locus encoding apo(a). Genetic variation in the LPA gene that increases Lp(a) level also increases coronary artery disease (CAD) risk, suggesting that Lp(a) is a causal factor for CAD risk. Lp(a) is the preferential lipoprotein carrier for oxidized phospholipids (OxPL), a proatherogenic and proinflammatory biomarker. Lp(a) adversely affects endothelial function, inflammation, oxidative stress, fibrinolysis, and plaque stability, leading to accelerated atherothrombosis and premature CAD. The INTER-HEART Study has established the usefulness of Lp(a) in assessing the risk of acute myocardial infarction in ethnically diverse populations with South Asians having the highest risk and population attributable risk. The 2018 Cholesterol Clinical Practice Guideline have recognized elevated Lp(a) as an atherosclerotic cardiovascular disease risk enhancer for initiating or intensifying statin therapy.

South Asian Cardiovascular Disease & Cancer Risk: Genetics & Pathophysiology

South Asians (SAs) are at heightened risk for cardiovascular disease as compared to other ethnic groups, facing premature and more severe coronary artery disease, and decreased insulin sensitivity. This disease burden can only be partially explained by conventional risk factors, suggesting the need for a specific cardiovascular risk profile for SAs. Current research, as explored through a comprehensive literature review, suggests the existence of population specific genetic risk factors such as lipoprotein(a), as well as population specific gene modulating factors. This review catalogues the available research on cardiovascular disease and genetics, anthropometry, and pathophysiology, and cancer genetics among SAs, with a geographical focus on the U.S. A tailored risk profile will hinge upon population customized classification and treatment guidelines, informed by continued research.

Lipoprotein (a): a historical appraisal

Initially, lipoprotein (a) [Lp(a)] was believed to be a genetic variant of lipoprotein (Lp)-B. Because its lipid moiety is almost identical to LDL, Lp(a) has been deliberately considered to be highly atherogenic. Lp(a) was detected in 1963 by Kare Berg, and individuals who were positive for this factor were called Lpa⁺ Lpa⁺ individuals were found more frequently in patients with coronary heart disease than in controls. After the introduction of quantitative methods for monitoring of Lp(a), it became apparent that Lp(a), in fact, is present in all individuals, yet to a greatly variable extent. The genetics of Lp(a) had been a mystery for a long time until Gerd Utermann discovered that apo(a) is expressed by a variety of alleles, giving rise to a unique size heterogeneity. This size heterogeneity, as well as countless mutations, is responsible for the great variability in plasma Lp(a) concentrations. Initially, we proposed to evaluate the risk of myocardial infarction at a cut-off for Lp(a) of 30-50 mg/dl, a value that still is adopted in numerous epidemiological studies. Due to new therapies that lower Lp(a) levels, there is renewed interest and still rising research activity in Lp(a). Despite all these activities, numerous gaps exist in our knowledge, especially as far as the function and metabolism of this fascinating Lp are concerned.

Lipoprotein (a) as a cause of cardiovascular disease: insights from epidemiology, genetics, and biology

Human epidemiologic and genetic evidence using the Mendelian randomization approach in large-scale studies now strongly supports that elevated lipoprotein (a) [Lp(a)] is a causal risk factor for cardiovascular disease, that is, for myocardial infarction, atherosclerotic stenosis, and aortic valve stenosis. The Mendelian randomization approach used to infer causality is generally not affected by confounding and reverse causation, the major problems of observational epidemiology. This approach is particularly valuable to study causality of Lp(a), as single genetic variants exist that explain 27-28% of all variation in plasma Lp(a). The most important genetic variant likely is the kringle IV type 2 (KIV-2) copy number variant, as the apo(a) product of this variant influences fibrinolysis and thereby thrombosis, as opposed to the Lp(a) particle per se. We speculate that the physiological role of KIV-2 in Lp(a) could be through wound healing during childbirth, infections, and injury, a role that, in addition, could lead to more blood clots promoting stenosis of arteries and the aortic valve, and myocardial infarction. Randomized placebo-controlled trials of Lp(a) reduction in individuals with very high concentrations to reduce cardiovascular disease are awaited. Recent genetic evidence documents elevated Lp(a) as a cause of myocardial infarction, atherosclerotic stenosis, and aortic valve stenosis.

Dyslipidaemia among Indo-Asians strategies for identification and management

ndo-Asians have the highest rates of coronary artery disease (CAD) despite the fact that nearly half are lifelong vegetarians. The incidence, prevalence, and mortality from CAD among overseas Indo-Asians have been 50% to 300% higher than the Europeans, Americans, and other Asians with a higher risk at younger ages. Approximately 10% of the adults in urban India have CAD, a rate similar to overseas Indians. Traditional risk factors do not fully explain the excess burden of CAD in Indo-Asians. Therefore, conventional approaches to testing and treatment of risk factors are not sufficient in this population. Indo-Asians have a higher prevalence of glucose intolerance, metabolic syndrome, diabetes, elevated concentrations of lipoprotein(a) (LP[a]), and homocysteine, and low concentrations of high density lipoprotein (HDL). HDL particles are also smaller in Indo-Asians than Whites. A more aggressive approach to all risk factors, including HDL, LP(a), triglycerides and homocysteine is warranted. The current evidence of established safety and broad spectrum lipoprotein benefits of niacin and statins would make these invaluable agents in the armamentarium against dyslipidaemia, especially in Indo-Asians. This is particularly true for those with metabolic syndrome, diabetic dyslipidaemia and Lp(a) excess.

The relationship between Lp(a) and CVD outcomes: a systematic review

Robust associations between lipoprotein(a) [Lp(a)] and CVD outcomes among general populations have been published in previous studies. However, associations in high risk primary prevention and secondary prevention populations are less well defined. In order to investigate this further, a systematic review was performed including prospective studies, which assessed the relationship between Lp(a) and CVD outcomes using multivariable analyses. Additional information was gathered on Lp(a) assays, multivariable modelling and population characteristics. Literature searches from inception up to December 2015 retrieved 2850 records. From these 60 studies were included. Across 39 primary prevention studies in the general population (hazard ratios ranged from 1.16 to 2.97) and seven high risk primary prevention studies (hazard ratios ranged from 1.01 to 3.7), there was evidence of a statistically significant relationship between increased Lp(a) and an increased risk of future CVD. Results in 14 studies of secondary prevention populations were also suggestive of a modest statistically significant relationship (hazard ratios ranged from 0.75 to 3.7).Therefore current evidence would suggest that increased Lp(a) levels are associated with modest increases in the risk of future CVD events in both general and higher risk populations. However, further studies are required to confirm these findings.

Lipoprotein(a) Interactions With Low-Density Lipoprotein Cholesterol and Other Cardiovascular Risk Factors in Premature Acute Coronary Syndrome (ACS)

Background

Current recommendations for lipoprotein(a) (Lp[a]) focus on the control of other risk factors, including lowering low‐density lipoprotein cholesterol (LDL‐C), with little evidence to support this approach. Identifying interactions between Lp(a) and other risk factors could identify individuals at increased risk for Lp(a)‐mediated disease.

Methods and Results

We used a case‐only study design and included 939 participants (median age=49 years, interquartile range 46–53, women=33.1%) from the GENdEr and Sex determInantS of cardiovascular disease: from bench to beyond‐Premature Acute Coronary Syndrome (GENESIS‐PRAXY) study, a multicenter prospective cohort study of premature acute coronary syndrome. There was a higher prevalence of elevated Lp(a) levels (>50 mg/dL; 80th percentile) in PRAXY participants as compared to the general population (31% versus 20%; P<0.001). Lp(a) was strongly associated with LDL‐C (adjusted β 0.17; P<0.001). Individuals with high Lp(a) were more likely to have LDL‐C >2.5 mmol/L, indicating a synergistic interaction (adjusted odds ratio 1.51; 95% CI 1.08–2.09; P=0.015). The interaction with high Lp(a) was stronger at increasing LDL‐C levels (LDL‐C >3.5, adjusted odds ratio 1.87; LDL‐C >4.5, adjusted odds ratio 2.72). In a polytomous logistic model comparing mutually exclusive LDL‐C categories, the interaction with high Lp(a) became attenuated at LDL‐C ≤3.5 mmol/L (odds ratio 1.16; 95% CI 0.80–1.68, P=0.447). Other risk factors were not associated with high Lp(a).

Conclusions

In young acute coronary syndrome patients, high Lp(a) is more prevalent than in the general population and is strongly associated with high LDL‐C, suggesting that Lp(a) confers greater risk for acute coronary syndrome when LDL‐C is elevated. Individuals with high Lp(a) and LDL‐C >3.5 mmol/L may warrant aggressive LDL‐C lowering.

Structure, function, and genetics of lipoprotein (a)

Lipoprotein (a) [Lp(a)] has attracted the interest of researchers and physicians due to its intriguing properties, including an intragenic multiallelic copy number variation in the LPA gene and the strong association with coronary heart disease (CHD). This review summarizes present knowledge of the structure, function, and genetics of Lp(a) with emphasis on the molecular and population genetics of the Lp(a)/LPA trait, as well as aspects of genetic epidemiology. It highlights the role of genetics in establishing Lp(a) as a risk factor for CHD, but also discusses uncertainties, controversies, and lack of knowledge on several aspects of the genetic Lp(a) trait, not least its function.

Lipoprotein apheresis results in plaque stabilization and prevention of cardiovascular events: comments on the prospective Pro(a)LiFe study

Elevated lipoprotein(a) (Lp(a)) has emerged as an important independent cardiovascular risk factor, and causal association has been accepted with adverse outcome in atherosclerotic disease. Lipoprotein apheresis (LA) can lower low-density lipoprotein (LDL)-cholesterol and Lp(a) by 60–70 % and is the final escalating therapeutic option in patients with hyperlipoproteinemias (HLP) involving LDL or Lp(a) particles. Major therapeutic effect of LA is preventing cardiovascular events. Stabilizing plaque morphology might be an important underlying mechanism of action. In Germany, since 2008, a reimbursement guideline has been implemented to establish the indication for LA not only for familial or severe forms of hypercholesterolemia but also for Lp(a)-HLP associated with a progressive course of cardiovascular disease, that persists despite effective treatment of other concomitant cardiovascular risk factors, i.e. isolated Lp(a)-HLP. The Pro(a)LiFe-study confirmed with a prospective multicenter design that LA can effectively reduce Lp(a) plasma levels and prevent cardiovascular events.

Lipoprotein (a) measurements for clinical application

The high degree of size heterogeneity of apo(a), the distinct protein component of lipoprotein (a) [Lp(a)], renders the development and selection of specific antibodies directed to apo(a) more difficult and poses significant challenges to the development of immunoassays to measure its concentration in plasma or serum samples. Apo(a) is extremely variable in size not only between but also within individuals because of the presence of two different, genetically determined apo(a) isoform sizes. Therefore, the antigenic determinants per particle available to interact with the antibodies will vary in the samples and the calibrators, thus contributing to apo(a) size-dependent inaccuracy of different methods. The lack of rigorous validation of the immunoassays and common means of expressing Lp(a) concentrations hinder the harmonization of results obtained by different studies and contribute to the lack of common cut points for identification of individuals at risk for coronary artery disease or for interventions aimed at reducing Lp(a) levels. The aim of our review is to present and critically evaluate the issues surrounding the measurements of Lp(a), their impact on the clinical interpretation of the data, and the obstacles we need to overcome to achieve the standardization of Lp(a) measurements.

[Extracardiac manifestation of elevated lipoprotein(a) levels--cumulative incidence of peripheral arterial disease and stenosis of the carotid artery]

BACKGROUND

Elevated lipoprotein(a) (Lp(a)) levels are an accepted risk factor for coronary heart disease. The role of Lp(a) in the development of extracardiac arteriosclerosis like peripheral arterial disease (PAD) and stenosis of the arteria carotis (ACIS) has hardly been documented so far. We aimed to investigate the incidence of extracardiac arteriosclerosis in individuals with elevated Lp(a) values.

METHODIK

In our center, we measured Lp(a) levels in 31,734 consecutive patients over 5 years. Of these, 1411 patients were selected retrospectively for the presented analysis. Patients were matched according to age, sex, and other accepted cardiovascular risk factors and were assigned to 6 groups according to their Lp(a) values. Retrospectively, we analysed the incidence of PAD and ACIS.

RESULTS

In the group with Lp(a) values < 2 mg/dl the incidence of PAD was 1.9 % (ACIS 2.8 %), in the group with Lp(a) 23-29 mg/dl 7.3 % (6.1 %), 30-60 mg/dl 9.0 % (8.3 %), 60-91 mg/dl 11.4 % (7.9 %), 91-110 mg/dl 8.6 % (6.0 %) and > 110 mg/dl 12.7 % (10.9 %). None of the patients had LDL levels > 130 mg/dl or HbA1c 6.1 %.

CONCLUSION

Elevated Lp(a) levels seem to be associated with an increased incidence of PAD and ACIS. Even Lp(a) concentrations between 23 and 29 mg/dl show a threefold increased risk of PAD when compared to patients with Lp(a) < 2 mg/dl. However, these findings have to be verified in large prospective studies. In this context cut-off values have to be reevaluated as well.

Discrimination and net reclassification of cardiovascular risk with lipoprotein(a): prospective 15-year outcomes in the Bruneck Study

BACKGROUND

Recent studies showed that lipoprotein(a) [Lp(a)] is a causal risk factor for cardiovascular disease (CVD). However, whether Lp(a) modifies clinical risk assessment was not established.

OBJECTIVES

This study was conducted to determine whether Lp(a) improves CVD risk prediction.

METHODS

In 1995, Lp(a) was measured in 826 men and women (age range, 45 to 84 years) from the general community. Incidence of CVD was recorded over 15 years of follow-up.

RESULTS

In models adjusted for Framingham Risk Score (FRS) and Reynolds Risk Score (RRS) variables, the hazard ratio (HR) for incident CVD was 1.37 per 1-SD higher Lp(a) level (SD = 32 mg/dl) and 2.37 when comparing the top fifth quintile with other quintiles. The addition of Lp(a) to the RRS increased the C-index by 0.016. Of the 502 subjects who remained free of CVD, 82 were correctly reclassified to a lower risk category and 49 were reclassified to a higher risk category (predicted 15-year categories: <7.5%, 7.5% to <15%, 15% to <30%, ≥30%) (p < 0.001). Of the 148 subjects who developed CVD, 18 were correctly reclassified to a higher risk category and 17 were reclassified to a lower risk category. In subjects at intermediate risk (15% to <30%), the net reclassification improvement afforded by Lp(a) was 22.5% for noncases, 17.1% for cases, and 39.6% overall. Allele-specific Lp(a) levels did not add to the predictive ability of the FRS or RRS or to Lp(a).

CONCLUSIONS

Elevated Lp(a) predicts 15-year CVD outcomes and improves CVD risk prediction. These findings suggest that Lp(a) levels may be used in risk assessment of subjects in the general community, particularly in intermediate-risk groups.

Association between the polymorphisms in intercellular adhesion molecule-1 and the risk of coronary atherosclerosis: a case-controlled study

Intercellular adhesion molecule-1 (ICAM-1), an important immune adhesion molecule, is related to the atherosclerosis. We explored the association between the polymorphisms of the ICAM-1 gene and coronary atherosclerotic stenosis to determine whether any risk factors correlate with genetic polymorphisms in Chinese patients with coronary atherosclerosis. Using the SNaPshot assay, we examined six SNPs of rs5491, rs281428, rs281432, rs5496, rs5498 and rs281437 in 604 patients diagnosed with coronary atherosclerotic stenosis by angiography and in 468 controls. We found that AG genotype of rs5498 had higher frequency in the coronary atherosclerotic stenosis patients (41.56% to 34.19%, P = 0.017, OR = 1.368,95%CI 1.057–1.770) and that the haplotype A_rs5491C_rs281428G_rs281432 had higher frequency in patients (13.8% to 12.1%, P = 0.048). When analyzing the clinical risk factors for coronary atherosclerosis, we found that the rs5498 locus was associated with the levels of apolipoprotein A (APOA) (P = 0.0002) and triglycerides (TG) (P = 0.002). Furthermore, the levels of triglycerides (TG) were also associated with rs281432 (P = 0.040). Additionally, the TT genotype of rs281437 was associated with a higher level of apolipoprotein A (APOA) (P = 0.039) and apolipoprotein B (APOB) (P = 0.003). Finally, among those with coronary atherosclerosis, we found no differences in the haplotype analysis of polymorphisms of the ICAM-1 gene from individuals with hypertension or those who smoked. According to our results, the ICAM-1 polymorphisms were associated with risk of coronary atherosclerotic stenosis in Chinese individuals.

Impact of lipoprotein(a) levels and apolipoprotein(a) isoform size on risk of coronary heart disease

OBJECTIVES

Observational and genetic studies have shown that lipoprotein(a) [Lp(a)] levels and apolipoprotein(a) [apo(a)] isoform size are both associated with coronary heart disease (CHD) risk, but the relative independence of these risk factors remains unclear. Clarification of this uncertainty is relevant to the potential of future Lp(a)-lowering therapies for the prevention of CHD.

METHODS

Plasma Lp(a) levels and apo(a) isoform size, estimated by the number of kringle IV (KIV) repeats, were measured in 995 patients with CHD and 998 control subjects. The associations between CHD risk and fifths of Lp(a) levels were assessed before and after adjustment for KIV repeats and, conversely, the associations between CHD risk and fifths of KIV repeats were assessed before and after adjustment for Lp(a) levels.

RESULTS

Individuals in the top fifth of Lp(a) levels had more than a twofold higher risk of CHD compared with those in the bottom fifth, and this association was materially unaltered after adjustment for KIV repeats [odds ratio (OR) 2.05, 95% confidence interval (CI) 1.38-3.04, P < 0.001]. Furthermore, almost all of the excess risk was restricted to the two-fifths of the population with the highest Lp(a) levels. Individuals in the bottom fifth of KIV repeats had about a twofold higher risk of CHD compared with those in the top fifth, but this association was no longer significant after adjustment for Lp(a) levels (OR 1.13, 95% CI 0.77-1.66, P = 0.94).

CONCLUSIONS

The effect of KIV repeats on CHD risk is mediated through their impact on Lp(a) levels, suggesting that absolute levels of Lp(a), rather than apo(a) isoform size, are the main determinant of CHD risk.

Screening for and management of elevated Lp(a)

While lipoprotein(a) (Lp(a)) has long been an intriguing subject for basic researchers and clinicians alike, it is only recently that this unique cardiovascular risk factor has begun to be broadly utilized as part of risk prediction. This has dovetailed with the recognition, from genetic studies, that Lp(a) is indeed causal for atherothrombotic disease rather than being merely a marker. Yet, significant questions remain the subject of ongoing study including: what patients groups benefit the most from determination of plasma Lp(a) concentrations; how can elevated plasma Lp(a) concentrations be most effectively managed; does reduction in plasma Lp(a) concentrations reduce risk for atherothrombotic events; and what is the molecular mechanism or mechanisms underlying the risk attributed to elevated Lp(a)? This review summarizes recent progress in genetic studies, basic laboratory research, and epidemiology with a focus on how Lp(a) might be incorporated into clinical practice.

Relook at lipoprotein (A): independent risk factor of coronary artery disease in north Indian population

AIMS

Lipoprotein (a) [Lp(a)] levels have shown wide ethnic variations. Sparse data on mean Lp(a) levels, its link with clinical variables and severity of coronary artery disease (CAD) in North Indian population needed further studies.

METHODS

150 patients, each of single vessel disease (SVD), double vessel disease (DVD) and triple vessel disease (TVD) with 150 healthy controls were drawn for the study. Serum Lp(a) estimation was performed by immunoturbidimetric method.

RESULTS

Lp(a) had a skewed distribution. Median Lp(a) level was significantly raised in cases as compared to controls (median 30.30 vs. 20 mg/dl, p < 0.001). Cases with acute coronary syndrome (ACS, 55.8%) had significantly higher median Lp(a) levels as compared to those with chronic stable angina (35.4 mg/dl vs. 23 mg/dl, p < 0.001). Significant difference in median Lp(a) levels were observed in patients with DVD or TVD versus control (30, 39.05 vs 20 mg/dl, p < 0.008). Lp(a) level was found to be an independent risk factor for CAD (AOR{adjusted odds ratio} 1.018, 95% CI 1.010-1.027; p < 0.001). Analysis using Lp(a) as categorical variable showed that progressive increase in Lp(a) concentration was associated with increased risk of CAD [AOR from lowest to highest quartile (1, 1.04, 1.43 and 2.65, p value for trend = 0.00026)]. Multivariably AOR of CAD for subjects with Lp(a) in the highest quartile (above 40 mg/dl) compared to those with Lp(a) ≤40 mg/dl was 2.308 (95% CI 1.465-3.636, p < 0.001).

CONCLUSION

Lp(a) above 40 mg/dl (corresponding to 75th percentile)assessed by an isoform insensitive assay is an independent risk factor for CAD. Raised Lp(a) level is also associated with increased risk of ACS and multivessel CAD.

Lipoprotein(a) for risk assessment in patients with established coronary artery disease

OBJECTIVES

The purpose of this study was to assess the prognostic utility of lipoprotein(a) [Lp(a)] in individuals with coronary artery disease (CAD).

BACKGROUND

Data regarding an association between Lp(a) and cardiovascular (CV) risk in secondary prevention populations are sparse.

METHODS

Plasma Lp(a) was measured in 6,708 subjects with CAD from 3 studies; data were then combined with 8 previously published studies for a total of 18,978 subjects.

RESULTS

Across the 3 studies, increasing levels of Lp(a) were not associated with the risk of CV events when modeled as a continuous variable (odds ratio [OR]: 1.03 per log-transformed SD, 95% confidence interval [CI]: 0.96 to 1.11) or by quintile (Q5:Q1 OR: 1.05, 95% CI: 0.83 to 1.34). When data were combined with previously published studies of Lp(a) in secondary prevention, subjects with Lp(a) levels in the highest quantile were at increased risk of CV events (OR: 1.40, 95% CI: 1.15 to 1.71), but with significant between-study heterogeneity (p = 0.001). When stratified on the basis of low-density lipoprotein (LDL) cholesterol, the association between Lp(a) and CV events was significant in studies in which average LDL cholesterol was ≥130 mg/dl (OR: 1.46, 95% CI: 1.23 to 1.73, p < 0.001), whereas this relationship did not achieve statistical significance for studies with an average LDL cholesterol <130 mg/dl (OR: 1.20, 95% CI: 0.90 to 1.60, p = 0.21).

CONCLUSIONS

Lp(a) is significantly associated with the risk of CV events in patients with established CAD; however, there exists marked heterogeneity across trials. In particular, the prognostic value of Lp(a) in patients with low cholesterol levels remains unclear.

Lipoprotein(a): a promising marker for residual cardiovascular risk assessment

Atherosclerotic cardiovascular diseases (CVD) are still the leading cause of morbidity and mortality worldwide, although optimal medical therapy has been prescribed for primary and secondary preventions. Residual cardiovascular risk for some population groups is still considerably high although target low density lipoprotein-cholesterol (LDL-C) level has been achieved. During the past few decades, compelling pieces of evidence from clinical trials and meta-analyses consistently illustrate that lipoprotein(a) (Lp(a)) is a significant risk factor for atherosclerosis and CVD due to its proatherogenic and prothrombotic features. However, the lack of effective medication for Lp(a) reduction significantly hampers randomized, prospective, and controlled trials conducting. Based on previous findings, for patients with LDL-C in normal range, Lp(a) may be a useful marker for identifying and evaluating the residual cardiovascular risk, and aggressively lowering LDL-C level than current guidelines' recommendation may be reasonable for patients with particularly high Lp(a) level.

Lipoprotein(a) and risk of coronary, cerebrovascular, and peripheral artery disease: the EPIC-Norfolk prospective population study

OBJECTIVE

Although the association between circulating levels of lipoprotein(a) [Lp(a)] and risk of coronary artery disease (CAD) and stroke is well established, its role in risk of peripheral arterial disease (PAD) remains unclear. Here, we examine the association between Lp(a) levels and PAD in a large prospective cohort. To contextualize these findings, we also examined the association between Lp(a) levels and risk of stroke and CAD and studied the role of low-density lipoprotein as an effect modifier of Lp(a)-associated cardiovascular risk.

METHODS AND RESULTS

Lp(a) levels were measured in apparently healthy participants in the European Prospective Investigation of Cancer (EPIC)-Norfolk cohort. Cox regression was used to quantify the association between Lp(a) levels and risk of PAD, stroke, and CAD outcomes. During 212 981 person-years at risk, a total of 2365 CAD, 284 ischemic stroke, and 596 PAD events occurred in 18 720 participants. Lp(a) was associated with PAD and CAD outcomes but not with ischemic stroke (hazard ratio per 2.7-fold increase in Lp(a) of 1.37, 95% CI 1.25-1.50, 1.13, 95% CI 1.04-1.22 and 0.91, 95% CI 0.79-1.03, respectively). Low-density lipoprotein cholesterol levels did not modify these associations.

CONCLUSIONS

Lp(a) levels were associated with future PAD and CAD events. The association between Lp(a) and cardiovascular disease was not modified by low-density lipoprotein cholesterol levels.

The current status of lipoprotein (a) in pregnancy: a literature review

BACKGROUND AND PURPOSE

Lipoprotein (Lp) (a) is a neglected element of the blood lipid profile. It is now recognized as a determinant of coronary heart disease progression and its role in atherosclerosis and its ability to induce thrombosis make it potentially important in the course of normal and complicated pregnancies. Pregnancy involves a major transformation of metabolism to sustain fetal growth. Multiple studies have been conducted on Lp(a) in pregnancy, and it is timely to synthesize and evaluate this evidence.

METHODS AND SUBJECTS

We reviewed the MEDLINE database for all articles published concerning "lipoprotein a" and "pregnancy" from May 2003 to May 2012. A previous comprehensive review assessed the literature up to May 2003.

RESULTS

We critically analyzed 14 studies detailing the effect of complications in pregnancy on Lp(a) profile, and subsequent pregnancy outcomes where available. Studies evaluating the normal metabolic response to pregnancy, pregnancies complicated by pre-eclampsia and intra-uterine growth restriction were reviewed.

CONCLUSIONS

A substantial mass of data has accumulated describing Lp(a) changes in pregnancy. The diversity of study design limits the ability to draw broad-ranging conclusions, but brings into focus the important questions remaining, which we discuss.