👤 Calvin Yeang

Lipoprotein (a) [Lp(a)] is viewed as a cholesterol-rich, LDL-like particle, yet potential heterogeneity in its lipid composition is not well understood. We developed and validated a novel immune-isolation assay to directly quantify triglycerides (TGs) associated with Lp(a) [Lp(a)-TGs]. Lp(a) was selectively isolated from plasma using magnetic beads conjugated with monoclonal antibody LPA4 targeting apolipoprotein(a), followed by enzymatic quantification of TGs. Assay specificity was ensured using washing buffers to prevent nonspecific lipoprotein interactions. Spike-in experiments with purified VLDL/intermediate density lipoprotein lacking Lp(a) demonstrated no measurable interference. Lp(a)-cholesterol [Lp(a)-C] was measured using an established immune-isolation method. The ratio of Lp(a)-TG to Lp(a)-C was calculated to distinguish TG-enriched Lp(a) particles from the typical cholesterol-rich, LDL-like phenotype. Lp(a)-TG, Lp(a)-C, Lp(a) molar concentration, and estimated compositional ratios were quantified in 36 normotriglyceridemic individuals and 114 individuals with moderate hypertriglyceridemia (150-500 mg/dl). In normotriglyceridemic individuals, mean (SD) TGs were 98.4 (31.9) mg/dl, Lp(a)-TG 1.42 (2.83) mg/dl, Lp(a)-C 4.03 (4.01) mg/dl, and the Lp(a)-TG/Lp(a)-C ratio was 0.59 (1.27). Lp(a)-TG and Lp(a)-C accounted for mean (SD) 1.22% (0.10) of total plasma TGs and 2.62% (2.01) of total plasma cholesterol. In individuals with hypertriglyceridemia, mean (SD) TGs were 284 (85) mg/dl, Lp(a)-TG 53.7 (25.3) mg/dl, Lp(a)-C 14.4 (6.9) mg/dl, and the Lp(a)-TG/Lp(a)-C ratio was 3.99 (1.20). Lp(a)-TG and Lp(a)-C accounted for mean (SD) 19.9% (6.53) of total plasma TGs and 9.68% (4.41) of total plasma cholesterol. This immune-isolation assay is the first validated, high-throughput method for direct quantification of Lp(a)-TG. This study demonstrates that Lp(a) lipid composition is variable and enriched in triglycerides and cholesterol in hypertriglyceridemic states. It provides a platform for future mechanistic, epidemiologic, and pharmacologic studies of Lp(a)-triglyceride interactions. This immune-isolation assay is the first validated, high-throughput method for direct quantitation of Lp(a)-TG. Show less

There is a need for effective tools to stratify and modify cardiovascular risk associated with elevated lipoprotein(a) [Lp(a)] and oxidized phospholipids (OxPL). The objective of this analysis was to explore the modifying effects of low-grade inflammation on Lp(a)- and OxPL-associated risk in a secondary prevention cohort. Levels of Lp(a), OxPL associated with apolipoprotein(a) (OxPL-apo[a]) and apolipoprotein B (OxPL-apoB) were determined in the placebo-arm of the low-dose colchicine 2 trial. Patients were between 35 and 82 years, had established chronic coronary syndrome (CCS), and were clinically stable for at least six months prior to randomization. The outcome was the incidence of the composite endpoint of spontaneous myocardial infarction, ischemic stroke, or ischemia-driven coronary revascularization stratified by biomarker levels using a Cox regression model. There was a significant interaction between Lp(a) and IL-6 <3.2 ng/L (median) and IL-6 ≥3.2 ng/L for the composite endpoint (HR 0.90; 95 %CI 0.78-1.03 vs HR 1.18; 95 %CI 1.01-1.39, P In patients with CCS, Lp(a), OxPL-apo(a) and OxPL-apoB associated cardiovascular risk was only pertinent in those with elevated IL-6 but not hsCRP levels. Show less

Inflammatory lipoprotein(a) [Lp(a)] and oxidized phospholipids (OxPLs) on lipoproteins convey residual cardiovascular disease risk. The low-dose colchicine 2 (LoDoCo2) trial showed that colchicine reduced the risk of cardiovascular events occurring on standard therapies in patients with chronic coronary syndrome (CCS). We explored the effects of colchicine on Lp(a)- and oxidized lipoprotein-associated risk in a LoDoCo2 biomarker subpopulation. Lipoprotein(a) and OxPLs on apolipoprotein(a) [OxPL-apo(a)] and apolipoprotein B-100 (OxPL-apoB) levels were determined in the biomarker population of the LoDoCo2 trial (n = 1777). The Cox regression analysis was used to compare the risk of the primary endpoint, consisting of myocardial infarction, ischaemic stroke, or ischaemia-driven revascularization by biomarker levels. Interactions between treatment, Lp(a), and OxPL levels were evaluated. Lipoprotein(a), OxPL-apo(a), and OxPL-apoB levels were similar between the colchicine and placebo groups. Consistent risk reduction by colchicine was observed in those with Lp(a) < 125 nmol/L and ≥125 nmol/L and the highest OxPL-apo(a) tertile compared with the lowest (Pinteraction = 0.92 and 0.66). The absolute risk reduction for those with Lp(a) ≥ 125 nmol/L appeared higher compared with those with Lp(a) < 125 nmol/L (4.4% vs. 2.4%). A treatment interaction for colchicine was found in those with the highest OxPL-apoB tertile vs. the lowest (Pinteraction = 0.04). In patients with CCS, colchicine reduces cardiovascular disease risk in those with and without elevated Lp(a) but absolute benefits appeared higher in those with Lp(a) ≥ 125 nmol/L. Patients with higher levels of OxPL-apoB experienced greater benefit of colchicine, suggesting that colchicine may be more effective in subjects with heightened oxidation-driven inflammation. Show less

Elevated lipoprotein(a) [Lp(a)] is associated with atherosclerotic cardiovascular disease (ASCVD) risk, and vascular inflammation is one mechanism through which Lp(a) causes ASCVD. The authors aimed to evaluate whether interleukin-6 (IL-6), a biomarker associated with inflammation and cardiovascular disease, helps risk-stratify individuals with elevated Lp(a). Data from participants in the MESA (Multi-Ethnic Study of Atherosclerosis) (n = 6,514) and the UK Biobank (UKB) (n = 26,574) were used for this analysis. The associations between Lp(a) and IL-6 with coronary heart disease (CHD) (defined as myocardial infarction or resuscitated cardiac arrest), ASCVD (CHD and ischemic stroke), and peripheral vascular disease (PVD) were evaluated separately and with mutual adjustment in Cox proportional hazard models adjusted for traditional cardiovascular risk factors and high-sensitivity C-reactive protein (hsCRP). HRs were presented per standard deviation. Participants were also grouped by Lp(a) level (≤50 or >50 mg/dL [125 nmol/L]) and IL-6 level (≤ median or > median) in similar models. Participants with higher IL-6 levels were more likely to have higher body mass index, systolic blood pressure, triglycerides, and hsCRP with lower high-density lipoprotein cholesterol. Lp(a) (HR: 1.13; 95% CI: 1.04-1.23 in MESA; HR: 1.11; 95% CI: 1.09-1.13 in UKB) and IL-6 (HR: 1.22; 95% CI: 1.10-1.35 in MESA; HR: 1.19; 95% CI: 1.15-1.24 in UKB) were both independently associated with CHD events when evaluated separately. When evaluated together, no significant change was noted, and interaction testing was not significant. Similar results were seen for ASCVD and PVD. When participants were categorized by both Lp(a) and IL-6 levels, the strongest association for each outcome was noted when both levels were high (for CHD: HR: 1.72; 95% CI: 1.25-2.36 in MESA; HR: 1.39; 95% CI: 1.12-1.72 in UKB). In 2 independent primary prevention cohorts, Lp(a) and IL-6 were independent predictors of ASCVD risk, and their combination identified individuals at highest risk. Show less