Targeting lipoprotein (a): an evolving therapeutic landscape

Lipoprotein(a) and risk of cognitive impairment in Black and White Americans: the Reasons for Geographic and Racial Differences in Stroke cohort

Background

Cognitive impairment has a substantial vascular etiology. Higher lipoprotein(a) [Lp(a)] is associated with cardiovascular disease risk, but its association with cognitive function is uncertain. We hypothesized that Lp(a) is a risk factor for cognitive impairment, a relationship that would be modified by race and sex.

Objectives

To study the association of Lp(a) with cognitive impairment in a biracial cohort.

Methods

The Reasons for Geographic and Racial Differences in Stroke (REGARDS) study recruited 30,239 Black and White Americans aged >45 years from 2003 to 2007. After 3.4 years, among participants with normal baseline cognition, baseline Lp(a) was measured in 434 cases of incident cognitive impairment and 557 controls. Cognitive impairment was defined as scores below the sixth percentile based on age, sex, race, and education norms on 2 or 3 components of a 3-test battery administered every 2 years.

Results

Median Lp(a) was higher in Black than in White individuals. Among Black participants, the adjusted odds ratio (OR) of cognitive impairment per SD higher increment Lp(a) was 1.39 (95% CI: 1.05, 1.84). The OR in White participants was 1.03 (95% CI: 0.87, 1.21; P for race difference = .03). The relationship of Lp(a) with cognitive trajectory differed by sex and race. Elevated Lp(a) was associated with worse baseline memory in Black men and a steeper trajectory of verbal fluency decline in Black men than in White men and women.

Conclusion

Higher Lp(a) was associated with increased risk of cognitive impairment in Black but not White individuals. Future studies should evaluate the biological and social mechanisms through which race and Lp(a) interact to increase risk of cognitive impairment.

Recent Updates of Lipoprotein(a) and Cardiovascular Disease

In recent years, epidemiological studies, genome-wide association studies, and Mendelian randomization studies have shown a strong association between increased levels of lipoproteins and increased risks of coronary heart disease and cardiovascular disease (CVD). Although lipoprotein(a) [Lp(a)] was an independent risk factor for ASCVD, the latest international clinical guidelines do not recommend direct reduction of plasma Lp(a) concentrations. The main reason was that there is no effective clinical medicine that directly lowers plasma Lp(a) concentrations. However, recent clinical trials have shown that proprotein convertase subtilisin/kexin-type 9 inhibitors (PCSK9) and second-generation antisense oligonucleotides can effectively reduce plasma Lp(a) levels. This review will present the structure, pathogenicity, prognostic evidences, and recent advances in therapeutic drugs for Lp(a).

Lipoprotein (a): An Update on a Marker of Residual Risk and Associated Clinical Manifestations

Lipoprotein (a) [Lp(a)] is a low-density, cholesterol-containing lipoprotein that differs from other low-density lipoproteins due to the presence of apolipoprotein(a) bound to its surface apolipoprotein B100. Multiple epidemiologic studies, including Mendelian Randomization studies, have demonstrated that increasing Lp(a) levels are associated with increased risk of heart disease, including atherosclerotic cardiovascular disease and calcific aortic stenosis. The risk associated with elevations in Lp(a) appears to be independent of other lipid markers. While the current treatment options for elevated Lp(a) are limited, promising new therapies are under development, leading to renewed interest in Lp(a). This review provides an overview of the biology and epidemiology of Lp(a), available outcome studies, and insights into future therapies.

Lipoprotein(a) and Risk of Ischemic Stroke in the REGARDS Study

Objective- Increased Lp(a) [lipoprotein(a)] is associated with coronary heart disease risk, but links with stroke are less consistent. Blacks have higher Lp(a) levels and stroke incidence than whites but have been underrepresented in studies. We hypothesized that Lp(a) is a risk factor for ischemic stroke and that risk differs by race. Approach and Results- REGARDS (Reasons for Geographic and Racial Differences in Stroke) recruited 30 239 black and white US adults aged ≥45 in 2003-2007 to study regional and racial differences in stroke mortality. We measured baseline Lp(a) by immunonephelometric assay in 572 cases of incident ischemic stroke and a 967-person cohort random sample. The hazard ratio of stroke by baseline Lp(a) was calculated using Cox proportional hazards models, stratified by race. Lp(a) was modeled in sex- and race-specific quartiles, given known differences in distributions by race and sex. Interactions were tested by including interaction terms in the proportional hazards models, with P<0.10 considered statistically significant. After adjustment for age, sex, and stroke risk factors, being in the fourth versus the first Lp(a) quartile was weakly associated with ischemic stroke overall, hazard ratio, 1.45 (95% CI, 0.96-2.19). In blacks, the hazard ratio was 1.96 (95% CI, 1.10-3.46), whereas in whites HR was 1.14 (95% CI, 0.64-2.04); P interaction=0.12. Lp(a) was lower in men than women, but associations with stroke in men and women were similar. Conclusions- We confirm that Lp(a) is a risk factor for ischemic stroke. Further research is needed to confirm the role of racial differences of the Lp(a) risk multiplier in ischemic stroke.

The Effects of Tamoxifen on Plasma Lipoprotein(a) Concentrations: Systematic Review and Meta-Analysis

Introduction

Tamoxifen is a selective estrogen receptor modulator widely used in the treatment of breast cancer. Tamoxifen therapy is associated with lower circulating low-density lipoprotein cholesterol and increased triglycerides, but its effects on other lipids are less well studied.

Aims

We aimed to investigate the effect of tamoxifen on circulating concentrations of lipoprotein(a) [Lp(a)] through a meta-analysis of available randomized controlled trials (RCTs) and observational studies.

Methods

This study was registered in the PROSPERO database (CRD42016036890). Scopus, MEDLINE and EMBASE were searched from inception until 22 March 2016 to identify studies investigating the effect of tamoxifen on Lp(a) values in humans. Meta-analysis was performed using an inverse variance-weighted, random-effects model with standardized mean difference (SMD) as the effect size estimate.

Results

Meta-analysis of five studies with 215 participants suggested a statistically significant reduction of Lp(a) levels following tamoxifen treatment (SMD −0.41, 95% confidence interval −0.68 to −0.14, p = 0.003). This effect was robust in the sensitivity analysis.

Conclusions

Meta-analysis suggested a statistically significant reduction of Lp(a) levels following tamoxifen treatment. Further well-designed trials are required to validate these results.

Inflammation and beyond: new directions and emerging drugs for treating atherosclerosis

INTRODUCTION

Cardiovascular (CV) atherosclerotic disease remains the leading cause of morbidity and mortality worldwide, despite the advances in contemporary therapies. Inflammation is an important process in atherosclerosis, leading to plaque rupture and acute coronary syndrome. Although statin therapy has substantially reduced CV events in primary and secondary prevention, many treated patients will have recurrent adverse CV events despite the standard of care. Thus, drug development aiming to target inflammatory pathways seems a promising avenue for novel therapies in atherosclerosis. Areas covered: Statins have been extensively studied and are the most effective lipid-lowering drugs available for CV prevention. Novel anti-inflammatory drugs are being tested in Phase II and III trials, targeting pathways like interleukin-1, leukotrienes, TNF-α, P-selectin, CCL2-CCR2 and MAP Kinase. Expert opinion: Novel anti-inflammatory therapies seem promising additions to address the residual CV risk present despite the current standard of care, but large clinical trials have not yet shown beneficial effects on clinical events. PCSK9 inhibitors have been shown to substantially reduce LDL-C, however their long-term safety and effects on CV risk are currently being investigated. Pharmacogenomics holds great potential in future lipid trials, enabling the identification of patients who will respond with greater benefits and smaller risk to therapies and to decrease failure rates in drug development, as genotype-dependent effects of the CETP inhibitor dalcetrapib were shown in the dal-OUTCOMES and dal-PLAQUE-2 trials.

Lipoprotein (a), an independent cardiovascular risk marker

Epidemiological and genetic studies have identified elevated levels of lipoprotein (a) ((Lp(a)) as a causal and independent risk factor for cardiovascular diseases (CVD). The Lp(a)-induced increased risk of CVD may be mediated by both its proatherogenic and prothrombotic mechanisms. Several guidelines recommend screening of Lp(a) level; however, there are few treatment options for the management of patients with elevated Lp(a). Several new medications for Lp(a) are under development. PCSK9 inhibitors, apolipoprotein (a)-antisense, and apolipoprotein(B-100)-antisense mipomersen have shown promising results. Lp(a) reduction will continue to be an active area of investigation.