Characteristics of Lipoprotein(a)-Containing Circulating Immune Complexes as Markers of Coronary Heart Disease

The Association of Lipoprotein(a) and Circulating Monocyte Subsets with Severe Coronary Atherosclerosis

Background and aims: Chronic inflammation associated with the uncontrolled activation of innate and acquired immunity plays a fundamental role in all stages of atherogenesis. Monocytes are a heterogeneous population and each subset contributes differently to the inflammatory process. A high level of lipoprotein(a) (Lp(a)) is a proven cardiovascular risk factor. The aim of the study was to investigate the association between the increased concentration of Lp(a) and monocyte subpopulations in patients with a different severity of coronary atherosclerosis. Methods: 150 patients (124 males) with a median age of 60 years undergoing a coronary angiography were enrolled. Lipids, Lp(a), autoantibodies, blood cell counts and monocyte subpopulations (classical, intermediate, non-classical) were analyzed. Results: The patients were divided into two groups depending on the Lp(a) concentration: normal Lp(a) < 30 mg/dL (n = 82) and hyperLp(a) ≥ 30 mg/dL (n = 68). Patients of both groups were comparable by risk factors, autoantibody levels and blood cell counts. In patients with hyperlipoproteinemia(a) the content (absolute and relative) of non-classical monocytes was higher (71.0 (56.6; 105.7) vs. 62.2 (45.7; 82.4) 10³/mL and 17.7 (13.0; 23.3) vs. 15.1 (11.4; 19.4) %, respectively, p < 0.05). The association of the relative content of non-classical monocytes with the Lp(a) concentration retained a statistical significance when adjusted for gender and age (r = 0.18, p = 0.03). The severity of coronary atherosclerosis was associated with the Lp(a) concentration as well as the relative and absolute (p < 0.05) content of classical monocytes. The high content of non-classical monocytes (OR = 3.5, 95% CI 1.2–10.8) as well as intermediate monocytes (OR = 8.7, 2.5–30.6) in patients with hyperlipoproteinemia(a) were associated with triple-vessel coronary disease compared with patients with a normal Lp(a) level and a low content of monocytes. Conclusion: Hyperlipoproteinemia(a) and a decreased quantity of classical monocytes were associated with the severity of coronary atherosclerosis. The expansion of CD16+ monocytes (intermediate and non-classical) in the presence of hyperlipoproteinemia(a) significantly increased the risk of triple-vessel coronary disease.

Interaction between lipoprotein (a) levels and body mass index in first incident acute myocardial infarction

BACKGROUND

Possible interaction between Lipoprotein (a) (Lp(a)) and body mass index (BMI) was investigated with regard to the risk of first incident acute myocardial infarction (AMI).

METHODS

Cross-sectional study of 1522 cases with initial AMI and 1691 controls without coronary artery disease (CAD) were retrospectively analyzed using logistic regression model. Subjects were categorized based on Lp(a) and BMI and compared with regard to occurrence of AMI by calculating odds ratios (ORs) with 95% confidence intervals (CIs). A potential interaction between Lp(a) and BMI was evaluated by the measures of effect modification on both additive (Relative excess risk due to interaction, RERI) and multiplicative scales.

RESULTS

Compared with reference group (BMI < 24 kg/m² and in the first quintile of Lp(a)), multivariable-adjusted analysis revealed that ORs(95%CI) of AMI were 2.27(1.46-3.52) for higher BMI alone; 1.79(1.11-2.90), 1.65(1.05-2.60), 1.96(1.20-3.20) and 2.34(1.47-3.71) for higher Lp(a) alone across its quintiles; and 2.86(1.85-4.40), 3.30(2.14-5.11), 4.43(2.76-7.09) and 5.98(3.72-9.60) for both higher BMI and higher Lp(a), greater than the sum of the both risks each. Prominent interaction was found between Lp(a) and BMI on additive scale (RERI = 2.45 (0.36-4.54) at the fifth quintile of Lp(a)) but not on multiplicative scale.

CONCLUSIONS

This study demonstrates that BMI and Lp(a) levels are important factors affecting the risk of AMI. Significant interaction is found between Lp(a) and BMI in initial AMI on additive scale, indicating that Lp(a) confers greater risk for initial AMI when BMI is elevated. For those whose BMIs are inadequately controlled, Lp(a) lowering may be an option.

TRIAL REGISTRATION

This clinical study was not registered in a publicly available registry because this study was a retrospective study first started in 2015. Data are available via the correspondent.

A Low-Molecular-Weight Phenotype of Apolipoprotein(a) as a Factor Provoking Accumulation of Cholesterol by THP-1 Monocyte-Like Cells

Increased concentration of lipoprotein(a) is a risk factor of coronary heart disease. lipoprotein(a) consists of LDL-like and highly polymorphic apolipoprotein(a). Here we studied the effect of lipoprotein(a)-containing sera with different apolipoprotein(a) phenotypes on lipid accumulation by THP-1 monocyte-like cells. Cholesterol concentration in lysates of THP-1 cells was significantly higher after their incubation with lipoprotein(a)-containing serum samples with low-molecular-weight phenotype of apolipoprotein(a) in comparison with samples with a high-molecular-weight apolipoprotein(a) phenotype irrespective of initial cholesterol level as well as serum concentrations of apoB-100, oxidized LDL, and circulating immune complexes. The presence of the most atherogenic small dense LDL subfractions in examined sera in addition to a low-molecular-weight apolipoprotein(a) phenotype resulted in significant elevation of cholesterol accumulation by THP-1 cells. The data obtained explain greater atherogenicity of lipoprotein(a) with low-molecular-weight apolipoprotein(a) phenotype.