Lipoprotein(a): an elusive cardiovascular risk factor

Causal effect of lipoprotein(a) level on chronic kidney disease of European ancestry: a two-sample Mendelian randomization study

INTRODUCTION

Chronic kidney disease is a growing health issue, and the options of prevention and therapy remain limited. Although a number of observational studies have linked higher Lp(a) [lipoprotein(a)] levels to the kidney impairment, the causal relationship remains to be determined. The purpose of this study was to assess the causal association between Lp(a) levels and CKD.

METHODS

We selected eight single-nucleotide polymorphisms (SNPs) significantly associated with Lp(a) levels as instrumental variables. Genome-wide association study (GWAS) from CKDGen consortium yielded the summary data information for CKD. We designed the bidirectional two-sample Mendelian randomization (MR) analyses. The estimates were computed using inverse-variance weighted (IVW), simple median, weighted median, and maximum likelihood. MR-Egger regression was used to detect pleiotropy.

RESULTS

Fixed-effect IVW analysis indicated that genetically predicted Lp(a) levels were associated with CKD significantly (odds ratio, 1.039; 95% CI, 1.009-1.069; p = 0.010). The SNPs showed no pleiotropy according to result of MR-Egger test. Results from sensitivity analyses were consistent. In the inverse MR analysis, random-effect IVW method showed CKD had no causal effect on the elevated Lp(a) (odds ratio, 1.154; 95% CI, 0.845-1.576; p = 0.367).

CONCLUSION

In this bidirectional two-sample MR analysis, the causal deteriorating effects of genetically predicted plasma Lp(a) levels on the risk of CKD were identified. On the contrary, there is no evidence to support a causal effect of CKD on Lp(a) levels.

Association between lipoprotein(a) plasma levels and diabetic nephropathy in Han Chinese patients with type 2 diabetes mellitus

The goal of this study was to evaluate the relationship between serum lipoprotein(a) [Lp(a)] levels and diabetic nephropathy (DN) among Han Chinese individuals with type 2 diabetes mellitus (T2DM). This retrospective analysis comprised a consecutive case series of 767 grown-up patients with T2DM (199 among them with DN) hospitalized in the Department of Endocrinology at the The First Affiliated Hospital of Anhui Medical University from February 20220 to February 2021. Clinical data and other laboratory measurements, such as glycated hemoglobin (HbA1c), were extracted from medical records and compared among groups. Clinical characteristics according to Lp(a) quartiles were also studied. Univariate and multivariate regression analysis were used to examine the relationship between serum Lp(a) and DN. Patients with DN had a longer disease duration, higher HbA1c, higher level of Lp(a), and were more likely to have diabetic retinopathy (DR) than those without DN (P < 0.005 for each). With regard to the Lp(a) quartile group, patients with a higher Lp(a) concentration were more likely to have DN and have higher level of HbA1c during the study (P for trend < 0.005 for each). After adjusting for several confounding factors, the development of DN was significantly associated with the serum Lp(a) level (P = 0.026, comparing the 4th vs 1st quartile of Lp(a)) according to multivariate regression analysis. The receiver operating characteristic (ROC) curves for DN development using serum Lp(a) showed that the area under the receiver operating characteristic curves (AUC) was 0.590 (P < 0.001). Findings from this study demonstrated that the DN was independently associated with the serum Lp(a) level in patients with T2DM in this retrospective study.

Haplotype of the Lipoprotein(a) Gene Variants rs10455872 and rs3798220 Is Associated with Parameters of Coagulation, Fibrinolysis, and Inflammation in Patients after Myocardial Infarction and Highly Elevated Lipoprotein(a) Values

Lipoprotein(a) (Lp(a)) is an independent risk factor for future coronary events. Variants rs10455872 and rs3798220 in the gene encoding Lp(a) are associated with an increased Lp(a) concentration and risk of coronary artery disease. We aimed to determine whether in high-risk coronary artery disease patients these two genetic variants and the kringle IV type 2 (KIV-2) repeats are associated with impairment of inflammatory and hemostatic parameters. Patients after myocardial infarction with elevated Lp(a) levels were included. Blood samples underwent biochemical and genetic analyses. In carriers of the AC haplotype, the concentrations of tumor necrosis factor (TNF)-α (4.46 vs. 3.91 ng/L, p = 0.046) and plasminogen activator inhibitor-1 (PAI-1) (p = 0.026) were significantly higher compared to non-carriers. The number of KIV-2 repeats was significantly associated with the concentration of high-sensitivity C-reactive protein (ρ = 0.251, p = 0.038) and overall fibrinolytic potential (r = -0.253, p = 0.038). In our patients, a direct association between the AC haplotype and both TNF-α and PAI-1 levels was observed. Our study shows that the number of KIV-2 repeats not only affects proatherosclerotic and proinflammatory effects of Lp(a) but is also associated with its antifibrinolytic properties.

Novel and future lipid-modulating therapies for the prevention of cardiovascular disease

Lowering the levels of LDL cholesterol in the plasma has been shown to reduce the risk of atherosclerotic cardiovascular disease (ASCVD). Several other lipoproteins, such as triglyceride-rich lipoproteins, HDL and lipoprotein(a) are associated with atherosclerosis and ASCVD, with strong evidence supporting causality for some. In this Review, we discuss novel and upcoming therapeutic strategies targeting different pathways in lipid metabolism to potentially attenuate the risk of cardiovascular events. Key proteins involved in lipoprotein metabolism, such as PCSK9, angiopoietin-related protein 3, cholesteryl ester transfer protein and apolipoprotein(a), have been identified as viable targets for therapeutic intervention through observational and genetic studies. These proteins can be targeted using a variety of approaches, such as protein inhibition or interference, inhibition of translation at the mRNA level (with the use of antisense oligonucleotides or small interfering RNA), and the introduction of loss-of-function mutations through base editing. These novel and upcoming strategies are complementary to and could work synergistically with existing therapies, or in some cases could potentially replace therapies, offering unprecedented opportunities to prevent ASCVD. Moreover, a major challenge in the prevention and treatment of non-communicable diseases is how to achieve safe, long-lasting reductions in causal exposures. This challenge might be overcome with approaches such as small interfering RNAs or genome editing, which shows how far the field has advanced from when the burden of achieving this goal was placed upon patients through rigorous adherence to daily small-molecule drug regimens.

Identification of allele-specific KIV-2 repeats and impact on Lp(a) measurements for cardiovascular disease risk

The abundance of Lp(a) protein holds significant implications for the risk of cardiovascular disease (CVD), which is directly impacted by the copy number (CN) of KIV-2, a 5.5 kbp sub-region. KIV-2 is highly polymorphic in the population and accurate analysis is challenging. In this study, we present the DRAGEN KIV-2 CN caller, which utilizes short reads. Data across 166 WGS show that the caller has high accuracy, compared to optical mapping and can further phase ~50% of the samples. We compared KIV-2 CN numbers to 24 previously postulated KIV-2 relevant SNVs, revealing that many are ineffective predictors of KIV-2 copy number. Population studies, including USA-based cohorts, showed distinct KIV-2 CN, distributions for European-, African-, and Hispanic-American populations and further underscored the limitations of SNV predictors. We demonstrate that the CN estimates correlate significantly with the available Lp(a) protein levels and that phasing is highly important.

Identification of biomarkers for vascular dementia: a literature review

Alzheimer's disease and vascular dementia are the two most common types of dementia. It becomes difficult to distinguish between the two, especially when there are no specific genetic causes or vascular changes apparent. The aim of this review was to identify specific biomarkers supporting the diagnosis of vascular dementia by conducting a literature search for systematic reviews and observational studies. We found seven studies meeting our inclusion/exclusion criteria, and from these we identified four specific biomarkers supporting the diagnosis of vascular dementia: high levels of thyroid-stimulating hormone, lipoprotein(a), homocysteine and N-terminal prosomatostatin. However, the studies were small and a well-conducted study with larger populations is recommended to strengthen the evidence base.

Lipid Biomarkers and Atherosclerosis-Old and New in Cardiovascular Risk in Childhood

Lipids are a complex group of molecules in the body, essential as structural, functional and metabolic components. When disbalanced, they are regarded as a cardiovascular risk factor, traditionally in cholesterol level evaluation. However, due to their complex nature, much research is still needed for a comprehensive understanding of their role in atherosclerosis, especially in the young. Several new lipid biomarkers are emerging, some already researched to a point, such as lipoproteins and apolipoproteins. Other lipid molecules are also being increasingly researched, including oxidized forms due to oxidative inflammation in atherosclerosis, and sphingolipids. For many, even those less new, the atherogenic potential is not clear and no clinical recommendations are in place to aid the clinician in using them in everyday clinical practice. Moreover, lipids' involvement in atherogenesis in children has yet to be elucidated. This review summarizes the current knowledge on lipids as biomarkers of cardiovascular risk in the paediatric population.

Relationship between lipoprotein(a) and colorectal cancer among inpatients: a retrospective study

The present study was to explore the association between lipoprotein(a) [Lp(a)] and colorectal cancer (CRC) among inpatients. This study included 2822 participants (393 cases vs. 2429 controls) between April 2015 and June 2022. Logistic regression models, smooth curve fitting, and sensitivity analyses were performed to investigate the relationship between Lp(a) and CRC. Compared with the lower Lp(a) quantile 1 (<79.6 mg/L), the adjusted odds ratios (ORs) in quantile 2 (79.6-145.0 mg/L), quantile 3 (146.0-299.0 mg/L), and quantile 4 (≥300.0 mg/L) were 1.41 (95% confidence interval [CI]: 0.95-2.09), 1.54 (95% CI: 1.04-2.27), 1.84 (95% CI: 1.25-2.7), respectively. A linear relationship between lipoprotein(a) and CRC was observed. The finding that Lp(a) has a positive association with CRC supports the "common soil" hypothesis of cardiovascular disease (CVD) and CRC.

Association of Lipoprotein (a) With Coronary-Computed Tomography Angiography-Assessed High-Risk Coronary Disease Attributes and Cardiovascular Outcomes

BACKGROUND

Lipoprotein(a) [Lp(a)] is a risk factor for cardiovascular events. This study evaluated the relationship between Lp(a) and high-risk attributes by coronary computed tomography angiography as well as their prognostic value.

METHODS

Lp(a) and coronary computed tomography angiography from 377 consecutive patients at Zhongshan Hospital (Shanghai, China) were evaluated. High-risk attributes were defined as high-risk morphological attributes (low attenuation plaque, positive remodeling, napkin-ring sign, spotty calcification, minimum lumen area <4 mm², or plaque burden [ratio between cross-sectional plaque area at the site of maximum stenosis and cross-sectional vessel area] ≥70%); inflammatory attribute represented by fat attenuation index; high-risk physiological attributes [lesion-specific ischemia defined by fractional flow reserve by coronary computed tomography angiography ≤0.8, physiologic diffuseness defined by fractional flow reserve by coronary computed tomography angiography pullback pressure gradient]. Total plaque volume in mm³ was also quantified. Quintiles or binary classification of Lp(a) levels were used to evaluate its relationships with plaque features and clinical outcomes with ANOVA, Cox models, and log-rank tests, as appropriate. The major adverse cardiovascular event included cardiovascular death, nonfatal myocardial infarction, and target vessel revascularization.

RESULTS

Lp(a) was significantly associated with total plaque volume (P=0.004), fat attenuation index (P=0.031), and fractional flow reserve by coronary computed tomography angiography pullback pressure gradient (P=0.038). Patients with a high Lp(a) level had a higher total plaque volume (393.3 mm³ versus 293.9 mm³, P<0.001), lower pullback pressure gradient (0.62 versus 0.69, P=0.023), higher fat attenuation index (-70.5HU versus -73.9HU, P=0.004), and higher incidence of major adverse cardiovascular event (14.5% versus 6.3%, adjusted hazard ratio: 2.52, 95% CI: 1.12-5.63, P=0.025). In a 4-group classification according to Lp(a) and high-risk attributes, patients with high Lp(a) and ≥3 high-risk attributes had the highest risk of major adverse cardiovascular event (25.9%; overall P<0.001). Causal mediation analysis revealed that around 40% of the prognostic effect of Lp(a) was mediated by high-risk attributes.

CONCLUSIONS

Lp(a) level is associated with coronary computed tomography angiography high-risk characteristics, including morphologic, physiologic, and inflammatory attributes as well as major adverse cardiovascular event. This effect is partly mediated by inflammation and vulnerable plaque.

REGISTRATION

URL: https://www.

CLINICALTRIALS

gov; Unique identifier: NCT05323227.

Correlations Between Coronary Artery Disease, Coronary Artery Calcium Score, and Lipoprotein(a) Level in Korea

Background

Methods

Results

Conclusion

Animal Models of Atherosclerosis-Supportive Notes and Tricks of the Trade

Atherosclerotic cardiovascular disease is a major cause of death among humans. Animal models have shown that cholesterol and inflammation are causatively involved in the disease process. Apolipoprotein B-containing lipoproteins elicit immune reactions and instigate inflammation in the vessel wall. Still, a treatment that is specific to vascular inflammation is lacking, which motivates continued in vivo investigations of the immune-vascular interactions that drive the disease. In this review, we distill old notions with emerging concepts into a contemporary understanding of vascular disease models. Pros and cons of different models are listed and the complex integrative interplay between cholesterol homeostasis, immune activation, and adaptations of the vascular system is discussed. Key limitations with atherosclerosis models are highlighted, and we suggest improvements that could accelerate progress in the field. However, excessively rigid experimental guidelines or limiting usage to certain animal models can be counterproductive. Continued work in improved models, as well as the development of new models, should be of great value in research and could aid the development of cardiovascular disease diagnostics and therapeutics of the future.

A method for lipoprotein (a) Isolation from a small volume of plasma with applications for clinical research

High levels of circulating Lipoprotein (a) [Lp(a)] are an independent risk factor for CVD. One of the major limitations to investigating Lp(a) biology is the need for large volumes of plasma (4-10 mL) for its isolation. We developed an isolation technique requiring only 0.4 mL of plasma yielding an enriched Lp(a) fraction suitable for compositional and functional studies. We collected plasma from patients (n = 9) in EDTA presenting to our Center for Preventive Cardiology for CVD risk management and with circulating Lp(a) > 66 mg/dL. 0.4 mL of plasma was added to 90 µL of potassium bromide (1.33 g/mL) and subjected to our two-step density-gradient ultracentrifugation method. The first step separates VLDL and LDL from the Lp(a) and HDL fractions and the second step further separates VLDL from LDL and Lp(a) from HDL. Lp(a) is then dialyzed for up to 24 h in potassium phosphate buffer. We performed cholesterol gel electrophoresis, immunoblotting and LC-MS/MS proteomics on isolated lipoprotein fractions to confirm fraction enrichment. Functional studies including Lp(a)-dependent induction of macrophage gene expression and cholesterol efflux inhibition were performed on isolated Lp(a) to confirm its preserved bioactivity. Lp(a) yields (264 ± 82.3 µg/mL on average) correlated with Lp(a) plasma concentrations (r2 = 0.75; p < 0.01) and represented the relative distribution of circulating apo(a) isoforms. Proteomic analyses confirm lipoprotein fraction separation. Functional integrity was confirmed by the findings that isolated Lp(a) inhibited plasminogen-dependent cholesterol efflux in HEK293T cells expressing ABCA1 and increased expressions of Il1b, Nos2 and Ccl2. We developed a small-volume isolation technique for Lp(a) suited for a range of applications used in biomedical research. The use of this technique circumvents volume-dependent limitations and expands our ability to investigate the mysteries of this deleterious lipoprotein.

Apolipoproteins in vascular biology and atherosclerotic disease

Apolipoproteins are important structural components of plasma lipoproteins that influence vascular biology and atherosclerotic disease pathophysiology by regulating lipoprotein metabolism. Clinically important apolipoproteins related to lipid metabolism and atherogenesis include apolipoprotein B-100, apolipoprotein B-48, apolipoprotein A-I, apolipoprotein C-II, apolipoprotein C-III, apolipoprotein E and apolipoprotein(a). Apolipoprotein B-100 is the major structural component of VLDL, IDL, LDL and lipoprotein(a). Apolipoprotein B-48 is a truncated isoform of apolipoprotein B-100 that forms the backbone of chylomicrons. Apolipoprotein A-I provides the scaffolding for lipidation of HDL and has an important role in reverse cholesterol transport. Apolipoproteins C-II, apolipoprotein C-III and apolipoprotein E are involved in triglyceride-rich lipoprotein metabolism. Apolipoprotein(a) covalently binds to apolipoprotein B-100 to form lipoprotein(a). In this Review, we discuss the mechanisms by which these apolipoproteins regulate lipoprotein metabolism and thereby influence vascular biology and atherosclerotic disease. Advances in the understanding of apolipoprotein biology and their translation into therapeutic agents to reduce the risk of cardiovascular disease are also highlighted.

Lipoprotein(a) is a Promising Residual Risk Factor for Long-Term Clinical Prognosis in Peripheral Arterial Disease

Objectives: We investigated the relationship between plasma lipoprotein(a) [Lp(a)] level and long-term prognosis, cardiovascular events, or pure leg events (LE) in patients with peripheral arterial disease (PAD).

Materials and Methods: We prospectively enrolled 1104 PAD patients. The endpoints were LE, cerebrovascular- or cardiovascular-related death (CVRD), all-cause death (ACD), and major adverse cardiovascular events (MACE).

Results: The incidences of LE, CVRD, ACD, and MACE were correlated with Lp(a) level (P<0.05). Lp(a) was positively correlated with low-density lipoprotein cholesterol and C-reactive protein (CRP) and negatively correlated with estimated glomerular filtration rate (eGFR). In the Cox multivariate regression analysis, high Lp(a), CRP, age, low ankle-brachial pressure index (ABI), eGFR, albumin, critical limb ischemia (CLI), cerebrovascular disease (CVD), and diabetes were associated with LE; high Lp(a), age, CRP, low ABI, body mass index, eGFR, albumin, CLI, coronary heart disease (CHD), CVD, and diabetes were associated with CVRD; high Lp(a), CRP, age, low ABI, eGFR, albumin, CLI, and CVD were associated with ACD; and high Lp(a), CRP, age, low eGFR, albumin, CLI, CHD, and diabetes were associated with MACE (P<0.05). Statins improved all endpoints (P<0.01).

Conclusion: Lp(a) was a significant residual risk factor for LE, CVRD, ACD, and MACE in PAD patients.

Lipoprotein(a): Pathophysiology, measurement, indication and treatment in cardiovascular disease. A consensus statement from the Nouvelle Société Francophone d'Athérosclérose (NSFA)

Lipoprotein(a) is an apolipoprotein B100-containing low-density lipoprotein-like particle that is rich in cholesterol, and is associated with a second major protein, apolipoprotein(a). Apolipoprotein(a) possesses structural similarity to plasminogen but lacks fibrinolytic activity. As a consequence of its composite structure, lipoprotein(a) may: (1) elicit a prothrombotic/antifibrinolytic action favouring clot stability; and (2) enhance atherosclerosis progression via its propensity for retention in the arterial intima, with deposition of its cholesterol load at sites of plaque formation. Equally, lipoprotein(a) may induce inflammation and calcification in the aortic leaflet valve interstitium, leading to calcific aortic valve stenosis. Experimental, epidemiological and genetic evidence support the contention that elevated concentrations of lipoprotein(a) are causally related to atherothrombotic risk and equally to calcific aortic valve stenosis. The plasma concentration of lipoprotein(a) is principally determined by genetic factors, is not influenced by dietary habits, remains essentially constant over the lifetime of a given individual and is the most powerful variable for prediction of lipoprotein(a)-associated cardiovascular risk. However, major interindividual variations (up to 1000-fold) are characteristic of lipoprotein(a) concentrations. In this context, lipoprotein(a) assays, although currently insufficiently standardized, are of considerable interest, not only in stratifying cardiovascular risk, but equally in the clinical follow-up of patients treated with novel lipid-lowering therapies targeted at lipoprotein(a) (e.g. antiapolipoprotein(a) antisense oligonucleotides and small interfering ribonucleic acids) that markedly reduce circulating lipoprotein(a) concentrations. We recommend that lipoprotein(a) be measured once in subjects at high cardiovascular risk with premature coronary heart disease, in familial hypercholesterolaemia, in those with a family history of coronary heart disease and in those with recurrent coronary heart disease despite lipid-lowering treatment. Because of its clinical relevance, the cost of lipoprotein(a) testing should be covered by social security and health authorities.

The effects of eight serum lipid biomarkers on age-related macular degeneration risk: a Mendelian randomization study

BACKGROUND

Age-related macular degeneration (AMD) is a leading cause of vision loss. Whereas lipids have been studied extensively to understand their effects on cardiovascular diseases, their relationship with AMD remains unclear.

METHODS

Two-sample Mendelian randomization (MR) analyses were performed to systematically evaluate the causal relationships between eight serum lipid biomarkers, consisting of apolipoprotein A1 (ApoA1), apolipoprotein B (ApoB), total cholesterol (CHOL), high-density lipoprotein cholesterol (HDL-C), direct low-density lipoprotein cholesterol (LDL-C), lipoprotein A [Lp(a)], triglycerides (TG) and non-HDL cholesterol (non-HDL-C), and the risk of different AMD stages and subtypes. We derived 64-407 genetic instruments for eight serum lipid biomarkers in 419 649 participants of European descent from the UK Biobank cohort. We conducted genome-wide association studies (GWAS) for 12 711 advanced AMD cases [8544 choroidal neovascularization (CNV) and 2656 geographic atrophy (GA) specific AMD subtypes] and 5336 intermediate AMD cases with 14 590 controls of European descent from the International AMD Genomics Consortium.

RESULTS

Higher genetically predicted HDL-C and ApoA1 levels increased the risk of all AMD subtypes. LDL-C, ApoB, CHOL and non-HDL-C levels were associated with decreased risk of intermediate and GA AMD but not with CNV. Genetically predicted TG levels were associated with decreased risk of different AMD subtypes. Sensitivity analyses revealed no evidence for directional pleiotropy effects. In our multivariable MR analyses, adjusting for the effects of correlated lipid biomarkers yielded similar results.

CONCLUSION

These results suggest the role of lipid metabolism in drusen formation and particularly in AMD development at the early and intermediate stages. Mechanistic studies are warranted to investigate the utility of lipid pathways for therapeutic treatment in preventing AMD.

Lipoprotein (a) and risk for calcification of the coronary arteries, mitral valve, and thoracic aorta: The Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Lipoprotein (a) [Lp(a)] is a risk factor for coronary heart disease and calcific aortic valve disease. We determined the relationships of Lp(a) with prevalence and progression of coronary artery calcification (CAC), mitral annular calcification (MAC), and thoracic aortic calcification (TAC) in a multi-ethnic cohort of middle to older-aged adults.

METHODS

This analysis included 6705 Multi-Ethnic Study of Atherosclerosis participants. Lp(a) was measured with a turbidimetric immunoassay. CAC, MAC, and TAC were assessed by cardiac computed tomography both at baseline and once during follow-up.

RESULTS

In adjusted relative risk regression cross-sectional analysis, a Lp(a) level ≥50 ​mg/dL was associated with a 22% higher prevalence of MAC (relative risk (RR) ​= ​1.22, 95% confidence interval (CI) 1.00, 1.49). No significant associations were observed for prevalent CAC or TAC. In adjusted prospective analyses, participants with Lp(a) ≥50 ​mg/dL were at significantly higher risk for rapid CAC progression (median follow-up ​= ​8.9 years), defined as ≥100 units/year, compared to those with lower Lp(a) levels (RR ​= ​1.67, 95% CI ​= ​1.23, 2.27). The association between higher Lp(a) levels and incident CHD was no longer significant after adjusting for CAC progression. No significant associations were observed for MAC or TAC progression (median follow-up ​= ​2.6 years).

CONCLUSIONS

Higher Lp(a) levels are associated with more rapid CAC progression. Additional study is needed to better understand how this relationship can further improve the ability of Lp(a) to enhance cardiovascular disease risk prediction.

Lipoprotein (a) and aortic valve calcium in South Asians compared to other race/ethnic groups

BACKGROUND AND AIMS

South Asians are at increased risk for cardiovascular disease (CVD). Aortic valve calcium (AVC) is associated with CVD risk and aortic stenosis. Elevated Lp(a) is a heritable risk factor for CVD and AVC. AVC prevalence and its association with Lp(a) have not been studied in South Asians.

METHODS

Among participants in the Mediators of Atherosclerosis in South Asians Living in America (MASALA) study (n = 695), AVC prevalence and extent were compared to four race/ethnic groups in the Multi-Ethnic Study of Atherosclerosis (MESA) (n = 4671). Multivariable regression was performed to evaluate associations between Lp(a) and AVC stratified by race/ethnic groups, adjusting for cardiovascular risk factors.

RESULTS

After age and sex adjustment, South Asians had higher median Lp(a) (17.0 mg/dL) compared to Whites (12.9 mg/dL), Hispanics (13.1 mg/dL) and Chinese Americans (12.9 mg/dL), and Blacks had highest Lp(a) levels (35.1 mg/dL). There were no differences in the odds of AVC in South Asians compared with Whites or Hispanics, after age and sex adjustment (p = 0.64 and 0.63, respectively). Odds of AVC was lower in Chinese (OR 0.35; 95%CI 0.23-0.54) and somewhat lower in Blacks compared with South Asians (OR 0.76; 0.56-1.04). There were no associations between Lp(a) and AVC presence or extent in South Asians. Lp(a) was associated with AVC only among Blacks and Whites.

CONCLUSIONS

Although present in Whites and Blacks, there were no associations between Lp(a) and AVC in South Asians. These differences may be due to statistic power or race specific modifying factors that influences the effect of Lp(a) particles on AVC pathogenesis.

Lipoprotein(a) in atherosclerosis: from pathophysiology to clinical relevance and treatment options

Lipoprotein(a) (Lp(a)) was discovered more than 50 years ago, and a decade later, it was recognized as a risk factor for coronary artery disease. However, it has gained importance only in the past 10 years, with emergence of drugs that can effectively decrease its levels. Lp(a) is a low-density lipoprotein (LDL) with an added apolipoprotein(a) attached to the apolipoprotein B component via a disulphide bond. Circulating levels of Lp(a) are mainly genetically determined. Lp(a) has many functions, which include proatherosclerotic, prothrombotic and pro-inflammatory roles. Here, we review recent data on the role of Lp(a) in the atherosclerotic process, and treatment options for patients with cardiovascular diseases. Currently 'Proprotein convertase subtilisin/kexin type 9' (PCSK9) inhibitors that act through non-specific reduction of Lp(a) are the only drugs that have shown effectiveness in clinical trials, to provide reductions in cardiovascular morbidity and mortality. The effects of PCSK9 inhibitors are not purely through Lp(a) reduction, but also through LDL cholesterol reduction. Finally, we discuss new drugs on the horizon, and gene-based therapies that affect transcription and translation of apolipoprotein(a) mRNA. Clinical trials in patients with high Lp(a) and low LDL cholesterol might tell us whether Lp(a) lowering per se decreases cardiovascular morbidity and mortality.KEY MESSAGESLipoprotein(a) is an important risk factor in patients with cardiovascular diseases.Lipoprotein(a) has many functions, which include proatherosclerotic, prothrombotic and pro-inflammatory roles.Treatment options to lower lipoprotein(a) levels are currently scarce, but new drugs are on the horizon.

Lipoprotein(a) and Atherosclerotic Cardiovascular Disease: Current Understanding and Future Perspectives

PURPOSE

To review current knowledge of elevated lipoprotein(a) [Lp(a)] levels in relation to atherosclerotic cardiovascular disease (ASCVD) and discuss their potential use as biomarkers and therapeutic approaches in clinical practice.

METHODS

We summarized the current understanding and recent advances in the structure, metabolism, atherogenic mechanisms, standardized laboratory measurement, recommended screening populations, and prognostic value of Lp(a), with a special focus on the current potential treatment approaches for hyperlipoprotein(a)emia in patients with ASCVD.

RESULTS

Lp(a) is composed of LDL-like particle and characteristic apolipoprotein(a) [apo(a)] connected by a disulfide bond. Substantial evidence shows that elevated plasma Lp(a) level is a heritable, independent, and possibly causal risk factor for ASCVD through its proatherogenic, proinflammatory, and potentially prothrombotic properties. Current guidelines recommend Lp(a) measurement for patients with an intermediate-high risk of ASCVD, familial hypercholesterolemia, a family history of early ASCVD or elevated Lp(a), and progressive ASCVD despite receiving optimal therapy. Traditional Lp(a)-lowering approaches such as niacin, PCSK9 inhibitors, mipomersen, lomitapide, and lipoprotein apheresis were associated with a non-specific and limited reduction of Lp(a), intolerable side effects, invasive procedure, and high expense. The phase 2 randomized controlled trial of antisense oligonucleotide against the apo(a) encoding gene LPA mRNA showed that IONIS-APO(a)-L_RX could specifically reduce the level of Lp(a) by 90% with good tolerance, which may become a promising candidate for the prevention and treatment of ASCVD in the future.

CONCLUSIONS

It is reasonable to measure Lp(a) levels to reclassify ASCVD risk and manage individuals with elevated Lp(a) to further reduce the residual risk of ASCVD, especially with IONIS-APO(a)-L_RX.

Elevated Lipoprotein A in South Asians and the Associated Risk of Cardiovascular Disease: A Systematic Review

BACKGROUND

South Asians have a premature risk of cardiovascular disease and increased lipoprotein A which enhances their risk.

METHODS

This systematic review evaluates the role of elevated lipoprotein A in cardiovascular disease risk for South Asians. It discusses the pathophysiology, clinical studies, and treatment of elevated lipoprotein A using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses method.

RESULTS

A total of 72 articles was incorporated which consisted of clinical studies, case-control and cohort studies, meta-analysis, reviews, and editorials. Cardiovascular disease and myocardial infarction occurs prematurely in South Asians, which is further enhanced with an elevated lipoprotein A.

CONCLUSIONS

South Asians with an elevated lipoprotein A have an increased risk of coronary artery disease so they should have early enactment of lifestyle modification and aggressive medical management.

High Lipoprotein(a) Level Is Independently Associated with Adverse Clinicopathological Features in Patients with Prostate Cancer

Background

The effect of lipoprotein(a) (Lp(a)) on prostate cancer (PCa) is unclear. The aim of this study was to investigate the association between serum Lp(a) levels and clinicopathological features in patients with PCa.

Methods

A total of 376 consecutive pathologically diagnosed PCa patients were enrolled and were classified as a low-intermediate-risk group or a high-risk group. The association of Lp(a) and the other lipid parameters including total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglycerides (TG), TC/HDL-C, LDL-C/HDL-C, and remnant cholesterol (RC) with clinicopathological parameters was tested by univariate and multivariate logistic regression analyses.

Results

The high-risk PCa patients tended to have higher Lp(a) levels (p = 0.022) while there was no significant difference regarding the other lipid parameters (p > 0.05) compared to low-intermediate-risk counterparts. Patients with PSA ≥ 100 ng/ml had significantly higher Lp(a) levels than subjects with PSA < 100 ng/ml (p = 0.002). Univariate logistic regression analyses revealed that high Lp(a) levels were correlated with high-risk PCa (Q4 vs. Q1, HR = 2.687, 95% CI: 1.113-6.491, p = 0.028), while the other lipid parameters were not correlated with high-risk PCa. In the stepwise multivariate regression analysis, the association between Lp(a) levels and high-risk PCa remained significant (Q4 vs. Q1, HR = 2.890, 95% CI: 1.148-7.274, p = 0.024) after adjusting for confounding factors including age, body mass index, hypertension, diabetes, coronary artery disease, and lipid-lowering drugs.

Conclusions

This is the first study showing the positive association between high Lp(a) and adverse clinicopathological features of PCa. PCa patients with high Lp(a) tends to be more aggressive and should receive more attention in clinical practice.

Association study of TAAAA polymorphism in the first intron of p53 gene with risk of colorectal cancer in Iranian population

Background

Colorectal cancer is the most common gastrointestinal cancer and the third most common cancer over the world. Genetic mutations in the p53 gene are associated with tumorigenesis of most cancers. So far, no study has been conducted on the association between TAAAA repeats in the first intron of the p53 gene and risk of colorectal cancer. In this study, we investigated the association of the TAAAA polymorphism in the first intron of p53 gene with colorectal cancer. We evaluated p53 gene polymorphism in 151 patients with colorectal cancer and a control group of 180 healthy individuals. For TAAAA repeat polymorphism evaluation, we used conventional polymerase chain reaction (PCR) to amplify the desired sequence and the number of TAAAA repeats was specified by polyacrylamide gel electrophoresis and direct sequencing.

Results

In the present study, 5 different alleles of TAAAA repeat with 6–10 repeats and 13 allele genotypes were determined between cases and controls. The most frequent allele in both controls (59.8%) and cases (57.6%) was the 8 repeats of TAAAA. Results of homozygous genotypes equal or lower than 8 repeats are higher among the healthy individuals than among the cases. In contrast, the number of genotypes equal or higher than 9 (9.10, 9.9) was higher among the colorectal cancer patients. Because of the small size of the studied population, the statistical analysis did not demonstrate a significant relationship. Also, there is no significant association between genotype, metastasis, and age.

Conclusion

Our observations did not show a significant association between the TAAAA repeat polymorphism in the first intron of the p53 gene and the colorectal cancer risk.

Prognostic impact of lipoprotein(a) levels during lipid management with statins after ST-elevation acute myocardial infarction

The causal relationship of lipoprotein(a) with cardiovascular disease has been established. However, clinical impacts of lipoprotein(a) levels on adverse vascular events in patients with established coronary artery disease who are undergoing statin treatment have not been fully elucidated. We measured lipoprotein(a) levels of 668 consecutive patients with ST-elevated myocardial infarction upon admission and reevaluated lipoprotein(a) of 189 of these patients during statin treatment at least 6 months later than the date of index ST-elevated myocardial infarction. Changes in lipoprotein(a) and associations between lipoprotein(a) levels and the incidence of major adverse cardiac and cerebrovascular event for 3 years were examined. Lipoprotein(a) at baseline was an independent predictor of 3-year major adverse cardiac and cerebrovascular event after ST-elevated myocardial infarction. Levels of lipoprotein(a) at follow-up were slightly but significantly elevated despite improvements in other lipid parameters due to statin treatment. Furthermore, higher levels of lipoprotein(a) achieved with statin treatment were also associated with the subsequent incidence of major adverse cardiac and cerebrovascular event over 3 years, regardless of whether or not the LDL-cholesterol levels were below 100 mg/dl. In conclusion, lipoprotein(a) levels during lipid management by statin are also predictive of adverse vascular events in Japanese patients with ST-elevated myocardial infarction.

Systemic Factors Related to Intraocular Levels of Interleukin-6 and Vascular Endothelial Growth Factor in Diabetic Retinopathy

This study is for identifying systemic factors correlating with intraocular levels of interleukin-6 (IL-6) and vascular endothelial growth factor (VEGF) in diabetic retinopathy. Forty-two consecutive patients undergoing pars plana vitrectomy (PPV) for PDR were included in this cross-sectional study. The aqueous humor was sampled just prior to PPV for assay of IL-6 and VEGF. One day before PPV, patient characteristics were recorded and a number of systemic markers were amassed, including fasting and postprandial glucose, homeostasis model assessment- (HOMA-) IR, HOMA-beta, C-peptide, insulin, total cholesterol, triglycerides, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, apolipoprotein- (Apo-) A, Apo-B, and lipoprotein A (Lp-A). Relationships between systemic determinants and intraocular cytokine levels were analyzed by regression analysis. Mean levels of IL-6 and VEGF were 15.3 pg/mL (range, 2.4–10124.5 pg/mL) and 21.1 pg/mL (range, 3.2–766.1 pg/mL), respectively. After adjustment for age, gender, duration of diabetes, and BMI, multivariate analysis showed significant association of smoking (p=0.002) and HOMA-IR (p=0.003) with intraocular IL-6 levels, while intraocular VEGF and systemic Lp-A levels correlated significantly (p=0.032). Insulin resistance and smoking status impacted intraocular levels of IL-6, while intraocular VEGF levels were influenced by Lp-A. An appreciation for the relationship between systemic factors and intraocular cytokines may help elucidate the complex pathophysiology of diabetic retinopathy.

High Level of Lipoprotein(a) as Predictor for Recurrent Heart Failure in Patients with Chronic Heart Failure: a Cohort Study

BACKGROUND

Elevated plasma levels of Lipoprotein(a) [Lp(a)] are recognized as a significant risk factor for atherosclerotic vascular disease. However, there are limited data regarding association between Lp(a) and recurrent heart failure (HF) in patients with chronic HF caused by coronary heart disease (CHD).

OBJECTIVE

Elevated levels of Lp(a) might have a prognostic impact on recurrent HF in patients with chronic HF caused by CHD.

METHODS

A total of 309 patients with chronic HF caused by CHD were consecutively enrolled in this study. The patients were divided into 2 groups according to whether Lp(a) levels were above or below the median level for the entire cohort (20.6 mg/dL): the high Lp(a) group (n = 155) and the low Lp(a) group (n = 154). A 2-sided p < 0.05 was statistically considered significant.

RESULTS

During the median follow-up period of 186 days, 31 cases out of a total of 309 patients (10.03%) could not be reached during follow-up. A Kaplan-Meier analysis demonstrated that patients with higher Lp(a) levels had a higher incidence of recurrent HF than those with lower Lp(a) levels (log-rank < 0.0001). A multivariate Cox regression analysis revealed that Lp(a) levels were independently correlated with the incidence of recurrent HF after adjustment of potential confounders (hazard ratio: 2.720, 95 % confidence interval: 1.730-4.277, p < 0.0001).

CONCLUSIONS

In Chinese patients with chronic HF caused by CHD, elevated levels of Lp(a) are independently associated with recurrent HF.

Relationship between LPA SNPs and inflammatory burden in patients with preeclampsia to address future cardiovascular risk

OBJECTIVE

The study tested whether cardiovascular corresponding LPA risk genotypes improve pre-eclampsia and coronary heart disease (CHD) risk prediction beyond conventional risk factors.

BACKGROUND

Studies have shown that women specific risk factors for cardiovascular disease (CVD) have taken an attention recently. It might be possible to identify women who have the highest risk in developing CVD in their further lives. It is well-known that Lp(a) levels have an impact on increased risk of CVD which is affected by LPA gene. Further, LPA risk genotypes are not considered in cardiovascular risk prediction.

METHODS

We have included 200 pregnant Turkish women into the study. We stratified the preeclamptic (PE) group: early (EOP) (28.7 ± 3.0 weeks) and late onset (LOP) (36.0 ± 1.4 weeks). 14 LPA SNPs were evaluated in the study. Rs9355296 and rs3798220 were found as independent risk factors for preeclampsia by logistic regression analysis. A positive correlation was found between rs9355296 and the diagnostic criteria of preeclampsia. Further rs9355296 G/* carriers have higher vascular inflammation rather than AA carriers.

CONCLUSIONS

The findings reveal that LPA genetic variability with high inflammatory response might be an indication of future cardiovascular events.

Nucleic Acid Therapies for Ischemic Stroke

Stroke remains a leading cause of disability and death worldwide despite significant scientific and therapeutic advances. Therefore, there is a critical need to improve stroke prevention and treatment. In this review, we describe several examples that leverage nucleic acid therapeutics to improve stroke care through prevention, acute treatment, and recovery. Aptamer systems are under development to increase the safety and efficacy of antithrombotic and thrombolytic treatment, which represent the mainstay of medical stroke therapy. Antisense oligonucleotide therapy has shown some promise in treating stroke causes that are genetically determined and resistant to classic prevention approaches such as elevated lipoprotein (a) and cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL). Targeting microRNAs may be attractive because they regulate factors involved in neuronal cell death and reperfusion-associated injury, as well as neurorestorative pathways. Lastly, microRNAs may aid reliable etiologic classification of stroke subtypes, which is important for effective secondary stroke prevention.

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.

Using topic modeling via non-negative matrix factorization to identify relationships between genetic variants and disease phenotypes: A case study of Lipoprotein(a) (LPA)

Genome-wide and phenome-wide association studies are commonly used to identify important relationships between genetic variants and phenotypes. Most studies have treated diseases as independent variables and suffered from the burden of multiple adjustment due to the large number of genetic variants and disease phenotypes. In this study, we used topic modeling via non-negative matrix factorization (NMF) for identifying associations between disease phenotypes and genetic variants. Topic modeling is an unsupervised machine learning approach that can be used to learn patterns from electronic health record data. We chose the single nucleotide polymorphism (SNP) rs10455872 in LPA as the predictor since it has been shown to be associated with increased risk of hyperlipidemia and cardiovascular diseases (CVD). Using data of 12,759 individuals with electronic health records (EHR) and linked DNA samples at Vanderbilt University Medical Center, we trained a topic model using NMF from 1,853 distinct phenotypes and identified six topics. We tested their associations with rs10455872 in LPA. Topics enriched for CVD and hyperlipidemia had positive correlations with rs10455872 (P < 0.001), replicating a previous finding. We also identified a negative correlation between LPA and a topic enriched for lung cancer (P < 0.001) which was not previously identified via phenome-wide scanning. We were able to replicate the top finding in a separate dataset. Our results demonstrate the applicability of topic modeling in exploring the relationship between genetic variants and clinical diseases.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Dietary natural products as emerging lipoprotein(a)-lowering agents

Elevated plasma lipoprotein(a) (Lp(a)) levels are associated with an increased risk of cardiovascular disease (CVD). Hitherto, niacin has been the drug of choice to reduce elevated Lp(a) levels in hyperlipidemic patients but its efficacy in reducing CVD outcomes has been seriously questioned by recent clinical trials. Additional drugs may reduce to some extent plasma Lp(a) levels but the lack of a specific therapeutic indication for Lp(a)-lowering limits profoundly reduce their use. An attractive therapeutic option is natural products. In several preclinical and clinical studies as well as meta-analyses, natural products, including l-carnitine, coenzyme Q ₁₀ , and xuezhikang were shown to significantly decrease Lp(a) levels in patients with Lp(a) hyperlipoproteinemia. Other natural products, such as pectin, Ginkgo biloba, flaxseed, red wine, resveratrol and curcuminoids can also reduce elevated Lp(a) concentrations but to a lesser degree. In conclusion, aforementioned natural products may represent promising therapeutic agents for Lp(a) lowering.

LPA Variants Are Associated With Residual Cardiovascular Risk in Patients Receiving Statins

BACKGROUND

Coronary heart disease (CHD) is a leading cause of death globally. Although therapy with statins decreases circulating levels of low-density lipoprotein cholesterol and the incidence of CHD, additional events occur despite statin therapy in some individuals. The genetic determinants of this residual cardiovascular risk remain unknown.

METHODS

We performed a 2-stage genome-wide association study of CHD events during statin therapy. We first identified 3099 cases who experienced CHD events (defined as acute myocardial infarction or the need for coronary revascularization) during statin therapy and 7681 controls without CHD events during comparable intensity and duration of statin therapy from 4 sites in the Electronic Medical Records and Genomics Network. We then sought replication of candidate variants in another 160 cases and 1112 controls from a fifth Electronic Medical Records and Genomics site, which joined the network after the initial genome-wide association study. Finally, we performed a phenome-wide association study for other traits linked to the most significant locus.

RESULTS

The meta-analysis identified 7 single nucleotide polymorphisms at a genome-wide level of significance within the LPA/PLG locus associated with CHD events on statin treatment. The most significant association was for an intronic single nucleotide polymorphism within LPA/PLG (rs10455872; minor allele frequency, 0.069; odds ratio, 1.58; 95% confidence interval, 1.35-1.86; P=2.6×10-10). In the replication cohort, rs10455872 was also associated with CHD events (odds ratio, 1.71; 95% confidence interval, 1.14-2.57; P=0.009). The association of this single nucleotide polymorphism with CHD events was independent of statin-induced change in low-density lipoprotein cholesterol (odds ratio, 1.62; 95% confidence interval, 1.17-2.24; P=0.004) and persisted in individuals with low-density lipoprotein cholesterol ≤70 mg/dL (odds ratio, 2.43; 95% confidence interval, 1.18-4.75; P=0.015). A phenome-wide association study supported the effect of this region on coronary heart disease and did not identify noncardiovascular phenotypes.

CONCLUSIONS

Genetic variations at the LPA locus are associated with CHD events during statin therapy independently of the extent of low-density lipoprotein cholesterol lowering. This finding provides support for exploring strategies targeting circulating concentrations of lipoprotein(a) to reduce CHD events in patients receiving statins.

Deep coverage whole genome sequences and plasma lipoprotein(a) in individuals of European and African ancestries

Lipoprotein(a), Lp(a), is a modified low-density lipoprotein particle that contains apolipoprotein(a), encoded by LPA, and is a highly heritable, causal risk factor for cardiovascular diseases that varies in concentrations across ancestries. Here, we use deep-coverage whole genome sequencing in 8392 individuals of European and African ancestry to discover and interpret both single-nucleotide variants and copy number (CN) variation associated with Lp(a). We observe that genetic determinants between Europeans and Africans have several unique determinants. The common variant rs12740374 associated with Lp(a) cholesterol is an eQTL for SORT1 and independent of LDL cholesterol. Observed associations of aggregates of rare non-coding variants are largely explained by LPA structural variation, namely the LPA kringle IV 2 (KIV2)-CN. Finally, we find that LPA risk genotypes confer greater relative risk for incident atherosclerotic cardiovascular diseases compared to directly measured Lp(a), and are significantly associated with measures of subclinical atherosclerosis in African Americans.

Is Lp(a) ready for prime time use in the clinic? A pros-and-cons debate

Lipoprotein (a) (Lp(a)) is a cholesterol-rich lipoprotein known since 1963. In spite of extensive research on Lp(a), there are still numerous gaps in our knowledge relating to its function, biosynthesis and catabolism. One reason for this might be that apo(a), the characteristic glycoprotein of Lp(a), is expressed only in primates. Results from experiments using transgenic animals therefore may need verification in humans. Studies on Lp(a) are also handicapped by the great number of isoforms of apo(a) and the heterogeneity of apo(a)-containing fractions in plasma. Quantification of Lp(a) in the clinical laboratory for a long time has not been standardized. Starting from its discovery, reports accumulated that Lp(a) contributed to the risk of cardiovascular disease (CVD), myocardial infarction (MI) and stroke. Early reports were based on case control studies but in the last decades a great deal of prospective studies have been published that highlight the increased risk for CVD and MI in patients with elevated Lp(a). Final answers to the question of whether Lp(a) is ready for wider clinical use will come from intervention studies with novel selective Lp(a) lowering medications that are currently underway. This article expounds arguments for and against this proposition from currently available data.

The role of lipoprotein (a) in chronic kidney disease

Lipoprotein (a) [Lp(a)] and its measurement, structure and function, the impact of ethnicity and environmental factors, epidemiological and genetic associations with vascular disease, and new prospects in drug development have been extensively examined throughout this Thematic Review Series on Lp(a). Studies suggest that the kidney has a role in Lp(a) catabolism, and that Lp(a) levels are increased in association with kidney disease only for people with large apo(a) isoforms. By contrast, in those patients with large protein losses, as in the nephrotic syndrome and continuous ambulatory peritoneal dialysis, Lp(a) is increased irrespective of apo(a) isoform size. Such acquired abnormalities can be reversed by kidney transplantation or remission of nephrosis. In this Thematic Review, we focus on the relationship between Lp(a), chronic kidney disease, and risk of cardiovascular events.

Oxidized phospholipids and lipoprotein-associated phospholipase A2 as important determinants of Lp(a) functionality and pathophysiological role

Lipoprotein(a) [Lp(a)] is composed of a low density lipoprotein (LDL)-like particle to which apolipoprotein (a) [apo(a)] is linked by a single disulfide bridge. Lp(a) is considered a causal risk factor for ischemic cardiovascular disease (CVD) and calcific aortic valve stenosis (CAVS). The evidence for a causal role of Lp(a) in CVD and CAVS is based on data from large epidemiological databases, mendelian randomization studies, and genome-wide association studies. Despite the well-established role of Lp(a) as a causal risk factor for CVD and CAVS, the underlying mechanisms are not well understood. A key role in the Lp(a) functionality may be played by its oxidized phospholipids (OxPL) content. Importantly, most of circulating OxPL are associated with Lp(a); however, the underlying mechanisms leading to this preferential sequestration of OxPL on Lp(a) over the other lipoproteins, are mostly unknown. Several studies support the hypothesis that the risk of Lp(a) is primarily driven by its OxPL content. An important role in Lp(a) functionality may be played by the lipoprotein-associated phospholipase A₂ (Lp-PLA₂), an enzyme that catalyzes the degradation of OxPL and is bound to plasma lipoproteins including Lp(a). The present review article discusses new data on the pathophysiological role of Lp(a) and particularly focuses on the functional role of OxPL and Lp-PLA₂ associated with Lp(a).

Lipoprotein(a) in clinical practice: New perspectives from basic and translational science

Elevated plasma concentrations of lipoprotein(a) (Lp(a)) are a causal risk factor for coronary heart disease (CHD) and calcific aortic valve stenosis (CAVS). Genetic, epidemiological and in vitro data provide strong evidence for a pathogenic role for Lp(a) in the progression of atherothrombotic disease. Despite these advancements and a race to develop new Lp(a) lowering therapies, there are still many unanswered and emerging questions about the metabolism and pathophysiology of Lp(a). New studies have drawn attention to Lp(a) as a contributor to novel pathogenic processes, yet the mechanisms underlying the contribution of Lp(a) to CVD remain enigmatic. New therapeutics show promise in lowering plasma Lp(a) levels, although the complete mechanisms of Lp(a) lowering are not fully understood. Specific agents targeted to apolipoprotein(a) (apo(a)), namely antisense oligonucleotide therapy, demonstrate potential to decrease Lp(a) to levels below the 30-50 mg/dL (75-150 nmol/L) CVD risk threshold. This therapeutic approach should aid in assessing the benefit of lowering Lp(a) in a clinical setting.

The mixed benefit of low lipoprotein(a) in type 2 diabetes

Background

Lipoprotein(a) (Lp(a)), a variant low-density lipoprotein (LDL), is a major genetic risk factor for cardiovascular disease. It is unknown whether an inverse relationship exists between Lp(a) and β-cell function (BCF), as for LDL-cholesterol (LDL-C) lowering by statins.

We therefore assessedthe cardiometabolic phenotype of 340 men with type 2 diabetes mellitus (T2DM) in relation to Lp(a), focusing on BCF and hyperbolic product [BxS], which adjusts BCF to insulin sensitivity and secretion.

Methods

Two groups were analyzed according to Lp(a) quartiles (Q): a (very-)low Lp(a) (Q1;n = 85) vs a normal-to-high Lp(a) group (Q2-Q4;n = 255).

Results

In the overall cohort, mean Lp(a) was 52 nmol.L⁻¹. Median Lp(a) was 6 nmol.L⁻¹ (Q1) vs 38 nmol.L⁻¹ (Q2-Q4). There were no differences between groups regarding age; education; diabetes duration; body mass index; body composition and smoking. Q1 had significantly worse glycemic control, higher systolic blood pressure, more severe metabolic syndrome, and more frequent hepatic steatosis. Insulin sensitivity was significantly lower (− 37%) in Q1, who also had lesser hyperbolic product (− 27%), and higher [BxS] loss rate (+ 15%). Q1 also had higher frequency (+31%) and severity (+20%) of atherogenic dyslipidemia. Microangiopathy and neuropathy were higher in Q1 (+ 34% and + 48%, respectively), whereas Q2-Q4 patients had increased macroangiopathy (+ 51%) and coronary artery disease (CAD; + 94%).

Conclusions

Low Lp(a) appears both beneficial and unhealthy in T2DM. It is associated with unfavourable cardiometabolic phenotype, lesser BCF, poorer glycemic control, and increased microvascular damage despite being linked to markedly reduced CAD, suggesting that Lp(a)-related vascular risk) follows a J-shaped curve.

Usefulness of Lipoprotein(a) for Predicting Clinical Outcomes After Endovascular Therapy for Aortoiliac Atherosclerotic Lesions

PURPOSE

To evaluate the usefulness of serum lipoprotein(a) as a biomarker of clinical outcomes after endovascular therapy (EVT) for atherosclerotic aortoiliac lesions.

METHODS

Serum lipoprotein(a) concentrations were measured at admission in 189 consecutive patients (median age 72 years; 160 men) with peripheral artery disease who underwent EVT for aortoiliac occlusive disease. The patients were dichotomized into 2 groups based on serum lipoprotein(a) levels ≤40 mg/dL (LOW; n=135) or >40 mg/dL (HIGH; n=54). After EVT, the incidences of major adverse limb events (MALE) were analyzed. Predictors of MALE were sought with a Cox proportional hazards analysis; results are presented as the hazard ratio (HR) and 95% confidence interval.

RESULTS

At the median follow-up of 33 months (interquartile range 11, 54), MALE occurred in 44 (23.3%) patients. The MALE-free survival estimate was significantly lower in patients in the HIGH group (55.6% vs 85.2%, p<0.001). Independent predictors of MALE after EVT were hemodialysis (HR 2.23, 95% CI 1.04 to 4.78, p=0.039) and high lipoprotein(a) levels (HR 2.80, 95% CI 1.44 to 5.45, p=0.003).

CONCLUSION

High lipoprotein(a) levels were associated with a higher incidence of MALE after EVT for patients with aortoiliac lesions.

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

An elevated level of lipoprotein (a) [Lp(a)] is a risk factor for CVD. Alirocumab, a monoclonal antibody to proprotein convertase subtilisin/kexin type 9, is reported to reduce Lp(a) levels. The relationship of Lp(a) reduction with apo(a) size polymorphism, phenotype, and dominance pattern and LDL cholesterol (LDL-C) reduction was evaluated in a pooled analysis of 155 hypercholesterolemic patients (75 with heterozygous familial hypercholesterolemia) from two clinical trials. Alirocumab significantly reduced total Lp(a) (pooled median: -21%, P = 0.0001) and allele-specific apo(a), an Lp(a) level carried by the smaller (median: -18%, P = 0.002) or the larger (median: -37%, P = 0.0005) apo(a) isoform, at week 8 versus baseline. The percent reduction in Lp(a) level with alirocumab was similar across apo(a) phenotypes (single vs. double bands) and carriers and noncarriers of a small size apo(a) (≤22 kringles). The percent reduction in LDL-C correlated significantly with the percent reduction in Lp(a) level (r = 0.407, P < 0.0001) and allele-specific apo(a) level associated with the smaller (r = 0.390, P < 0.0001) or larger (r = 0.270, P = 0.0183) apo(a) sizes. In conclusion, alirocumab-induced Lp(a) reduction was independent of apo(a) phenotypes and the presence or absence of a small size apo(a).

A Comparative Analysis of Serum Lipids in Patients with Chronic Hepatitis C, Nonalcoholic Fatty Liver Disease and Healthy Controls

Serum lipids abnormalities are widespread among patients with chronic hepatitis C (CHC), but the impact of concomitant hepatic steatosis [steatosis, nonalcoholic steatosis (NAS)], as well as distinctions between it and nonalcoholic fatty liver disease (NAFLD) are not well established yet. The aim of the study was to assess and compare the serum lipids in patients with genotype 1 CHC with and without steatosis, those with NAFLD, and healthy controls (HC). A total of 1010 subjects were included in this study: 366 CHC genotype 1 patients with steatosis (n = 227) and without steatosis (n = 139), 403 NAFLD patients, and 241 HC without fatty liver or other disease, matched for age and gender. Serum lipids, body mass index (BMI), components of metabolic syndrome (MS), and serum insulin levels were evaluated. In addition serum lipoprotein (a) [Lp(a)] levels were studied in 112 CHC and 80 NAFLD patients. The mean levels of total cholesterol, LDL-cholesterol and triglycerides (Tg) were higher and the mean levels of HDL-cholesterol were lower in all patients with steatosis (CHC and NAFLD) than in CHC cases without steatosis (p < 0.05 and p = 0.001, resp.). Higher prevalence and severity of lipid abnormalities, including Lp(a), were observed in patients with NAFLD than in those with CHC (p < 0.001). No difference was found between CHC patients without steatosis and HC. Higher prevalence and grade of glucose metabolic abnormalities were also observed in patients with NAFLD and CHC with steatosis than in cases without steatosis (p < 0.05 and p = 0.001, resp.). Lipid and glucose metabolic abnormalities in patients with CHC were dependent on steatosis. CHC with steatosis and NAFLD were associated with insulin resistant type dyslipidemia, with total cholesterol and LDL-cholesterol being generally lower in CHC.

Association of lipoprotein(a) with long-term mortality following coronary angiography or percutaneous coronary intervention

BACKGROUND

There is no consistent evidence to suggest the association of plasma lipoprotein(a) (Lp[a]) with long-term mortality in patients undergoing coronary angiography (CAG) or percutaneous coronary intervention (PCI).

HYPOTHESIS

Level of Lp(a) is associated with long-term mortality following CAG or PCI.

METHODS

We enrolled 1684 patients with plasma Lp(a) data undergoing CAG or PCI between April 2009 and December 2013. The patients were divided into 2 groups: a low-Lp(a) group (Lp[a] <16.0 mg/dL; n = 842) and a high-Lp(a) group (Lp[a] ≥16.0 mg/dL; n = 842).

RESULTS

In-hospital mortality was not significantly different between the high and low Lp(a) groups (0.8% vs 0.5%, respectively; P = 0.364). During the median follow-up period of 1.95 years, the high-Lp(a) group had a higher long-term mortality than did the low-Lp(a) group (5.8% vs 2.5%, respectively; P = 0.003). After adjustment of confounders, multivariate Cox regression analysis revealed that a higher Lp(a) level was an independent predictor of long-term mortality (hazard ratio: 1.96, 95% confidence interval: 1.07-3.59, P = 0.029).

CONCLUSIONS

Our data suggested that an elevated Lp(a) level was significantly associated with long-term mortality following CAG or PCI. However, additional larger multicenter studies will be required to investigate the predictive value of Lp(a) levels and evaluate the benefit of controlling Lp(a) levels for patients undergoing CAG or PCI.

Cholesterol Levels of Six Fractionated Serum Lipoproteins and its Relevance to Coronary Heart Disease Risk Scores

Aim: Evaluation of serum lipoprotein profiles including triglyceride (TG)-rich lipoprotein, that is, intermediate-density lipoprotein (IDL), very low-density lipoprotein (VLDL), and chylomicron (CM) remnant is important to manage coronary heart disease (CHD) risk. The purpose of this study was to investigate CHD or cardiovascular disease (CVD) risk scores with cholesterol levels of six fractionated lipoprotein classes {high-density lipoprotein [HDL], low-density lipoprotein [LDL], IDL, VLDL, CM including CM remnant, and lipoprotein (a) [Lp (a)]} in Japanese healthy men.

Methods: The present study enrolled 161 healthy men without any medications. Lipoprotein profiles (fractionated lipoprotein cholesterol levels) were measured by anion-exchange high-performance liquid chromatography (AEX-HPLC) method and were compared with age, estimated glomerular filtration rate (eGFR), and three risk scores, that is, NIPPON DATA, Hisayama risk predicting model, and Suita score.

Results: Levels of LDL-cholesterol (C), VLDL-C, and CM-C significantly differed with age, while values of HDL-C, IDL-C, and Lp(a)-C were not different. The eGFR inversely correlated with LDL-C, IDL-C, VLDL-C, and CM-C. In a stepwise multiple logistic regression analysis, VLDL-C only correlated independently with eGFR. Three risk scores significantly correlated with CM-C.

Conclusions: These results suggested that VLDL-C concentration contributes to an increased risk at early stages of renal dysfunction, and CM-C may serve as a marker for estimating CHD risk in Japanese healthy men.

Effect of Two Lipoprotein (a)-Associated Genetic Variants on Plasminogen Levels and Fibrinolysis

Two genetic variants (rs3798220 and rs10455872) in the apolipoprotein (a) gene (LPA) have been implicated in cardiovascular disease (CVD), presumably through their association with lipoprotein (a) [Lp(a)] levels. While Lp(a) is recognized as a lipoprotein with atherogenic and thrombogenic characteristics, it is unclear whether or not the two Lp(a)-associated genetic variants are also associated with markers of thrombosis (i.e., plasminogen levels and fibrinolysis). In the present study, we genotyped the two genetic variants in 2919 subjects of the Old Order Amish (OOA) and recruited 146 subjects according to the carrier and noncarrier status for rs3798220 and rs10455872, and also matched for gender and age. We measured plasma Lp(a) and plasminogen levels in these subjects, and found that the concentrations of plasma Lp(a) were 2.62- and 1.73-fold higher in minor allele carriers of rs3798220 and rs10455872, respectively, compared with noncarriers (P = 2.04 × 10⁻¹⁷ and P = 1.64 × 10⁻⁶, respectively). By contrast, there was no difference in plasminogen concentrations between carriers and noncarriers of rs3798220 and rs10455872. Furthermore, we observed no association between carrier status of rs3798220 or rs10455872 with clot lysis time. Finally, plasminogen mRNA expression in liver samples derived from 76 Caucasian subjects was not significantly different between carriers and noncarriers of these two genetic variants. Our results provide further insight into the mechanism of action behind two genetic variants previously implicated in CVD risk and show that these polymorphisms are not major modulating factors for plasma plasminogen levels and fibrinolysis.

Lipoprotein (a) level, apolipoprotein (a) size, and risk of unexplained ischemic stroke in young and middle-aged adults

BACKGROUND AND AIMS

Circulating lipoprotein (a) [Lp(a)] level relates inversely to apolipoprotein (a) [apo(a)] size. Both smaller apo(a) isoforms and higher Lp(a) levels have been linked to coronary heart disease and stroke, but their independent contributions are less well defined. We examined the role of Lp(a) in younger adults with cryptogenic stroke.

METHODS

Lp(a) and apo(a) isoforms were evaluated in a prospectively designed case-control study of patients with unexplained ischemic stroke and stroke-free controls, ages 18 to 64. Serum Lp(a) was measured among 255 cases and 390 controls with both apo(a)-size independent and dependent assays. Apo(a) size was determined by agarose gel electrophoresis.

RESULTS

Cases and controls were similar in socio-demographic characteristics, but cases had more hypertension, diabetes, smoking, and migraine with aura. In race-specific analyses, Lp(a) levels showed positive associations with cryptogenic stroke in whites, but not in the smaller subgroups of blacks and Hispanics. After full adjustment, comparison of the highest versus lowest quartile in whites was significant for apo(a)-size-independent (OR = 2.10 [95% CI = 1.04, 4.27], p = 0.040), and near-significant for apo(a)-size-dependent Lp(a) (OR = 1.81 [95% CI = 0.95, 3.47], p = 0.073). Apo(a) size was not associated with cryptogenic stroke in any race-ethnic subgroup.

CONCLUSIONS

This study underscores the importance of Lp(a) level, but not apo(a) size, as an independent risk factor for unexplained ischemic stroke in young and middle-aged white adults. Given the emergence of effective Lp(a)-lowering therapies, these findings support routine testing for Lp(a) in this setting, along with further research to assess the extent to which such therapies improve outcomes in this population.

SCARB1 Gene Variants Are Associated With the Phenotype of Combined High High-Density Lipoprotein Cholesterol and High Lipoprotein (a)

BACKGROUND

SR-B1 (scavenger receptor class B type 1), encoded by the gene SCARB1, is a lipoprotein receptor that binds both high-density lipoprotein (HDL) and low-density lipoprotein. We reported that SR-B1 is also a receptor for lipoprotein (a) (Lp(a)), mediating cellular uptake of Lp(a) in vitro and promoting clearance of Lp(a) in vivo. Although genetic variants in SCARB1 are associated with variations in HDL level, no SCARB1 variants affecting Lp(a) have been reported.

METHODS AND RESULTS

In an index subject with high levels of HDL cholesterol and Lp(a), SCARB1 was sequenced and demonstrated a missense mutation resulting in an S129L substitution in exon 3. To follow up, 2 cohorts (GeneSTAR, the family-based Genetic Study of Atherosclerosis Risk [n=543], and CCHS, the population-based Copenhagen City Heart Study [n=5835]) were screened for combined HDL cholesterol and Lp(a) elevations. Subjects with the extreme phenotype (HDL >80 mg/dL and Lp(a) >100 nmol/L in GeneSTAR, n=8, and >100 mg/dL in CCHS, n=9) underwent sequencing of SCARB1 exons; 15 of 18 from the combined population demonstrated genetic variants, including rare or uncommon missense or splice site mutations in 9 and homozygous synonymous variants in 6. Functional studies with 4 of the SCARB1 variants (c.386C>T, c.631-14T>G, c.4G>A, and c.631-53^mC>T & c.726+55^mCG>CA) showed decreased receptor function in vitro.

CONCLUSIONS

Human SCARB1 gene variants are associated with a new lipid phenotype, characterized by high levels of both HDL cholesterol and Lp(a). SCARB1 exonic variants often result in diminished function of translated SR-B1 via reduced binding/intracellular transport of Lp(a).

Elevated lipoprotein (a) levels predict deep vein thrombosis in acute ischemic stroke patients

Lipoprotein (a) [Lp(a)] plays a crucial role in the pathogenesis of deep vein thrombosis (DVT). The purpose of this study was to investigate whether Lp(a) serum levels at admission could be a risk factor for DVT in Chinese patients with acute ischemic stroke (AIS). A total of 232 patients with AIS were included in the study. The patients were assessed for DVT using colour Doppler ultrasonography. We performed colour Doppler ultrasonography 15 days after the stroke and whenever clinically requested. The value of Lp(a) to predict the DVT was analyzed using logistic regression analysis after adjusting for the possible confounders. In our study, 44 out of the 232 patients (19.0%) were diagnosed with DVT at 15-day follow-up. Serum Lp(a) levels were higher in AIS with DVT than in those patients without DVT [656 (interquartile range, 521-898) mg/l vs. 253 (interquartile range, 143-440) mg/l; P<0.0001]. Increased risk of DVT associated with Lp(a) levels greater than or equal to 300 mg/l was found in the multivariate analysis [odds ratio 12.14, 95% confidence interval (CI): 3.08-42.09; P<0.0001]. Visible by the receiver operating characteristic, the optimal cutoff value of serum Lp(a) levels for predicting DVT was projected to be 420 mg/l, yielding a sensitivity of 88.5% and a specificity of 75.4%. With an area under the curve (AUC) of 0.89 (95% CI, 0.84-0.94), Lp(a) exhibited greater discrimination in predicting DVT compared with Hs-CRP (AUC, 0.77; 95% CI, 0.69-0.85; P<0.01), HCY (AUC, 0.76; 95% CI, 0.68-0.84; P<0.01), and NIHSS score (AUC, 0.74; 95% CI, 0.66-0.82; P<0.001). Elevated serum Lp(a) levels were independent predictors of DVT in AIS patients in China, revealing the critical role played by Lp(a) in the pathogenesis of DVT.