Is Lipoprotein(a) Ready for Prime-Time Use in the Clinic?

The ins and outs of lipoprotein(a) assay methods

Pathophysiological, epidemiological and genetic studies convincingly showed lipoprotein(a) (Lp(a)) to be a causal mediator of atherosclerotic cardiovascular disease (ASCVD). This happens through a myriad of mechanisms including activation of innate immune cells, endothelial cells as well as platelets. Although these certainties whether or not Lp(a) is ready for prime-time clinical use remain debated. Thus, remit of the present review is to provide an overview of different methods that have been employed for the measurement of Lp(a). The methods include dynamic light scattering, multi-angle light scattering analysis, near-field imaging, sedimentation, gel filtration, and electron microscopy. The development of multiple Lp(a) detection methods is vital for improved prediction of ASCVD risk.

Lipid Parameters and Proprotein Convertase Subtilisin/Kexin Type 9 in Healthy Lebanese Adults

Background: High levels of non-HDL cholesterol (non-HDL-C), triglycerides (TG), lipoprotein (a) (Lp(a)), and Proprotein convertase subtilisin/kexin type 9 (PCSK9) as well as low levels of HDL-C are strongly associated with cardiovascular disease (CVD). Our study aims to estimate the prevalence of dyslipidemia and high Lp(a) in the Lebanese population and to study the relationship of these variables with gender, age, body mass index (BMI), and PCSK9. Methods: This cross-sectional study was carried out on a sample of healthy volunteers aged 18 to 65. Blood samples were drawn from volunteers for total cholesterol (TC), HDL-C, TG, PCSK9, and Lp(a) measurements. Non-HDL-C was calculated by subtracting HDL-C from TC. Results: In total, 303 volunteer subjects with an average age of 38.9 years were included in the study. Respectively, 44%, 29.8%, and 44% of men had high non-HDL-C and TG with low HDL-C versus 23.5%, 8%, and 37% in women. Non-HDL-C and TG were significantly higher in men than in women, while the reverse was observed for HDL-C (p < 0.0001 for the three comparisons). Non-HDL-C and TG were significantly correlated with age and BMI (p< 0.0001 for all correlations), while HDL-C was inversely correlated with BMI (p < 0.0001) but not with age. Abnormal Lp(a) levels (≥75 nmol/L) were found in 19.1% of the population, predominantly in women (24.1% versus 13.4% in men, p = 0.004). The median PCSK9 and its interquartile was 300 (254−382) ng/L with no gender difference (p = 0.18). None of the following factors: gender, age, BMI, non-HDL-C, HDL-C, or TG, were independently associated with Lp(a), while PCSK9 was significantly correlated with age, non-HDL-C, and TG in both men and women and inversely correlated with HDL-C in men. Dyslipidemia is very common in the Lebanese population and is associated with age, high BMI, and male sex. Lp(a) is higher in women without any correlation with the lipid profile, whereas PCSK9 is associated with non-HDL-C and TG. Further studies are needed to evaluate the potential role of Lp(a) and PCSK9 in predicting CVD in healthy populations.

Circulating PCSK9 Linked to Dyslipidemia in Lebanese Schoolchildren

In adults, elevated levels of circulating Proprotein Convertase Subtilisin/Kexin type 9 (PCSK9) have been associated with increased Low-density lipoprotein cholesterol (LDL-C), triglycerides (TG), and worse cardiovascular outcomes. However, few studies analyzed the relation between PCSK9 and lipid parameters in pediatric populations. The aim of our study is to evaluate the distribution and the correlation of serum PCSK9 levels with lipid parameters in a sample of Lebanese school children. Using an immunofluorescence assay, we measured serum PCSK9 levels in 681 school children recruited from ten public and private Lebanese schools. We analyzed the association between PCSK9 and age, sex, Body Mass Index (BMI), and lipid parameters (total cholesterol (TC), LDL-C, TG, High-density lipoprotein cholesterol (HDL-C), non-HDL-C, and lipoprotein (a) (Lp(a)). Serum PCSK9 levels were significantly correlated with TC, LDL-C, and non-HDL-C (p value < 0.0001) but not with TG, HDL-C, and Lp(a). PCSK9 levels were also significantly higher in children with high TC, LDL-C, and non-HDL-C (p values = 0.0012, 0.0002, 0.001, respectively). No significant gender differences in PCSK9 were found. In addition, no significant associations between PCSK9 and both age and BMI percentiles were observed. In girls, no difference in PCSK9 values was observed according to menarche while in boys, testosterone levels were not significantly associated with PCSK9. Serum PCSK9 levels were significantly correlated with TC, LDL-C, and non-HDL-C levels. Further studies are needed to find if PCSK9 measurements have an additional value to predict future cardiovascular outcomes in pediatric populations.

Unbiased plasma proteomics discovery of biomarkers for improved detection of subclinical atherosclerosis

Background

Imaging of subclinical atherosclerosis improves cardiovascular risk prediction on top of traditional risk factors. However, cardiovascular imaging is not universally available. This work aims to identify circulating proteins that could predict subclinical atherosclerosis.

Methods

Hypothesis-free proteomics was used to analyze plasma from 444 subjects from PESA cohort study (222 with extensive atherosclerosis on imaging, and 222 matched controls) at two timepoints (three years apart) for discovery, and from 350 subjects from AWHS cohort study (175 subjects with extensive atherosclerosis on imaging and 175 matched controls) for external validation. A selected three-protein panel was further validated by immunoturbidimetry in the AWHS population and in 2999 subjects from ILERVAS cohort study.

Findings

PIGR, IGHA2, APOA, HPT and HEP2 were associated with subclinical atherosclerosis independently from traditional risk factors at both timepoints in the discovery and validation cohorts. Multivariate analysis rendered a potential three-protein biomarker panel, including IGHA2, APOA and HPT. Immunoturbidimetry confirmed the independent associations of these three proteins with subclinical atherosclerosis in AWHS and ILERVAS. A machine-learning model with these three proteins was able to predict subclinical atherosclerosis in ILERVAS (AUC [95%CI]:0.73 [0.70–0.74], p < 1 × 10⁻⁹⁹), and also in the subpopulation of individuals with low cardiovascular risk according to FHS 10-year score (0.71 [0.69–0.73], p < 1 × 10⁻⁶⁹).

Interpretation

Plasma levels of IGHA2, APOA and HPT are associated with subclinical atherosclerosis independently of traditional risk factors and offers potential to predict this disease. The panel could improve primary prevention strategies in areas where imaging is not available.

Lipoprotein(a) as a unique primary risk factor for early atherosclerotic peripheral arterial disease

Elevated plasma lipoprotein(a) is a relatively common condition that contributes to many cardiovascular diseases. However, the awareness and testing for this condition remain low. Herein, we present a case of an otherwise healthy and active man who developed symptoms of peripheral arterial disease starting at age 49, and was found to have hyper-lipoprotein(a) as his only notable risk factor. Diagnosis was not made until years later, after an extensive workup. Upon further screening, he was also found to have subclinical coronary and carotid artery atherosclerotic disease. The patient was treated with aspirin, statin, niacin and angioplasty to bilateral superficial femoral arteries with good symptom resolution. Early screening of his son also revealed a similarly elevated lipoprotein(a) level. It is important to raise awareness of this condition and its relationship to early-onset peripheral arterial disease so patients and their families can be appropriately identified, counselled and treated.

Use of cardiovascular imaging in risk restratification of the diabetic patient

PURPOSE OF REVIEW

Diabetes mellitus is no longer considered a cardiovascular disease (CVD) risk equivalent, but the optimal methods of risk stratification are a matter of debate. The coronary calcium score (CCS) is a measure of the burden of atherosclerosis and is widely used for CVD risk stratification in the general population. We review recently published data to describe the role of the CCS in people with diabetes mellitus.

RECENT FINDINGS

People with diabetes mellitus have 10-year event rates for CVD and CVD mortality that are considered high, at a much lower level of CCS than the general population. Different categories of CCS are pertinent to men and women with diabetes mellitus. CCS may be particularly useful in clinical settings when CVD risk is known to be increased but difficult to quantify, for example peri-menopausal women, young persons with diabetes, type 1 diabetic individuals and others. With modern techniques, the radiation dose of a CSS has fallen to levels wherein screening and surveillance could be considered.

SUMMARY

The CCS is able to quantify CVD risk in people with diabetes mellitus when there is clinical uncertainty and identifies those with very high event rates. Future research should aim to identify effective risk reduction strategies in this important group.

Lipoprotein (a) and diabetes mellitus: causes and consequences

PURPOSE OF REVIEW

This review provides an update on the role of lipoprotein (a) [Lp(a)] in diabetes, including its impact as a risk factor as well as its contribution to the development of cardiovascular disease.

RECENT FINDINGS

Although a specific role for Lp(a) has not yet been conclusively established, it appears to have an inverse association with risk of diabetes. Several population-based studies have demonstrated associations between low levels of Lp(a) and increased risk of type 2 diabetes, but Mendelian randomization studies do not consistently support causality. Conversely, in patients with type 2 diabetes, elevated Lp(a) levels are associated with an increased risk of cardiovascular events.

SUMMARY

Although Lp(a) contributes to the development of cardiovascular disease in patients with diabetes, few trials have investigated the benefits of reducing Lp(a) within this patient population. Furthermore, guidelines do not specifically address the risk associated with elevated Lp(a) levels. Despite this, Lp(a) should be measured in patients with diabetes and considered when evaluating their overall risk burden.

Prevalence and status of Lipoprotein (a) among Lebanese school children

Lipoprotein a (Lp(a) is an independent risk factor for atherosclerotic cardiovascular disease. The prevalence of high Lipoprotein (a) (Lp(a)) in the Lebanese pediatric population is unknown. Our study aims to assess this prevalence and to study the relationship of Lp(a) with the lipid profile, age, body mass index (BMI) and socio-economic status (SES) in Lebanese schoolchildren. A total of 961 children aged 8–18 years (497 boys and 464 girls) were recruited from ten private and public schools in 2013–2014 using a stratified random sample. Schools were selected from the Greater Beirut and Mount Lebanon areas, and were categorized into three subgroups according to the schools’ SES status (high, medium, low). Lp(a) was assayed in 2018 on samples previously frozen at − 80 °C. Abnormal Lp(a) levels (≥ 75 nmol/L) were observed in 14.4% of the overall sample (13.5% for boys,15.3% of girls p = 0.56). The median of Lp(a) was 20(10–50) in the whole sample with no significant gender difference. No significant relationship was found between Lp(a) and age. However, Lp(a) was significantly correlated with BMI in whole sample, as well as in boys and girls (p = 0.02, p = 0.03, p = 0.03, respectively). A significant correlation was found between Lp(a) and non-HDL-C in the whole sample as well as in boys and girls (respectively p < 0.001,p = 0.024 and p = 0.03), but not with triglycerides and HDL-C. In a multivariate linear regression analysis, Lp(a) was only independently associated with BMI and non-HDL-C in boys and girls. Lp(a) was independently associated with BMI and non-HDL-C while no significant relationship was observed with age and sex confirming the strong genetic determination of Lp(a).

Genetic and nutritional factors determining circulating levels of lipoprotein(a): results of the "Montignoso Study"

Increasing evidence shows an association between high lipoprotein(a) [Lp(a)] levels and atherothrombotic diseases. Lp(a) trait is largely controlled by kringle-IV type 2 (KIV-2) size polymorphism in LPA gene, encoding for apo(a). Environmental factors are considered to determinate minor phenotypic variability in Lp(a) levels. In the present study, we investigated the possible gene-environment interaction between KIV-2 polymorphism and Mediterranean diet adherence or fish weekly intake in determining Lp(a) levels. We evaluated Lp(a), KIV-2 polymorphism, fish intake and Mediterranean diet adherence in 452 subjects [median age (range) 66 (46-80)years] from Montignoso Heart and Lung Project (MEHLP) population. In subjects with high KIV-2 repeats number, influence of Mediterranean diet adherence in reducing Lp(a) levels was observed (p = 0.049). No significant difference in subjects with low KIV-2 repeats according to diet was found. Moreover, in high-KIV-2-repeat subjects, we observed a trend towards influence of fish intake on reducing Lp(a) levels (p = 0.186). At multivariate linear regression analysis, high adherence to Mediterranean diet remains a significant and independent determinant of lower Lp(a) levels (β = - 64.97, standard error = 26.55, p = 0.015). In conclusion, this study showed that only subjects with high KIV-2 repeats can take advantage to lower Lp(a) levels from correct nutritional habits and, in particular, from Mediterranean diet.

Lipoprotein(a) the Insurgent: A New Insight into the Structure, Function, Metabolism, Pathogenicity, and Medications Affecting Lipoprotein(a) Molecule

Lipoprotein(a) [Lp(a)], aka "Lp little a", was discovered in the 1960s in the lab of the Norwegian physician Kåre Berg. Since then, we have greatly improved our knowledge of lipids and cardiovascular disease (CVD). Lp(a) is an enigmatic class of lipoprotein that is exclusively formed in the liver and comprises two main components, a single copy of apolipoprotein (apo) B-100 (apo-B100) tethered to a single copy of a protein denoted as apolipoprotein(a) apo(a). Plasma levels of Lp(a) increase soon after birth to a steady concentration within a few months of life. In adults, Lp(a) levels range widely from <2 to 2500 mg/L. Evidence that elevated Lp(a) levels >300 mg/L contribute to CVD is significant. The improvement of isoform-independent assays, together with the insight from epidemiologic studies, meta-analyses, genome-wide association studies, and Mendelian randomization studies, has established Lp(a) as the single most common independent genetically inherited causal risk factor for CVD. This breakthrough elevated Lp(a) from a biomarker of atherosclerotic risk to a target of therapy. With the emergence of promising second-generation antisense therapy, we hope that we can answer the question of whether Lp(a) is ready for prime-time clinic use. In this review, we present an update on the metabolism, pathophysiology, and current/future medical interventions for high levels of Lp(a).

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.

A genome-wide association study on lipoprotein (a) levels and coronary artery disease severity in a Chinese population

Lipoprotein (a) [Lp(a)] is a genetically determined risk factor of coronary artery disease (CAD). Previous genome-wide association studies (GWASs), which were mostly carried out in Caucasians, have identified many Lp(a)-associated SNPs. Here, we performed a GWAS on Lp(a) levels and further explored the relationships between Lp(a)-associated SNPs and CAD severity in 1,403 Han Chinese subjects. We observed that elevated Lp(a) levels were significantly associated with the increased synergy between percutaneous coronary intervention with TAXUS and cardiac surgery (SYNTAX) score and the counts of heavily calcified lesions and long-range lesions (LRLs; P < 0.05), which are defined as lesions spanning >20 mm. Moreover, we identified four independent SNPs, namely, rs7770628, rs73596816, and rs6926458 in LPA, and rs144217738 in SLC22A2, that were significantly associated with Lp(a) levels. We also found that rs7770628 was associated with high SYNTAX scores [odds ratio (OR) (95% CI): 1.37 (1.05-1.80), P = 0.0213, false discovery rate (FDR) = 0.0852], and that rs7770628 and rs73596816 were associated with high risk of harboring LRLs [OR (95% CI): 1.53 (1.17-2.01), P = 0.0018, FDR = 0.0072 and 1.72 (1.19-2.49), P = 0.0040, FDR = 0.0080, respectively]. Our study was a large-scale GWAS to identify Lp(a)-associated variants in the Han Chinese population. Our findings highlight the importance and potential of Lp(a) intervention and expand our understanding of CAD prevention and treatment.