Abstract 13534: Plasma Apolipoprotein C3 is Negatively Associated With High Lipoprotein(a) Plasma Levels in Healthy Volunteers

Abstract

Introduction: ApoliproteinC3 (apoC3) is a small (~8.8kDa) protein, made in the liver. It is an inhibitor of lipoprotein lipase as well as the uptake of triglyceride (TG) rich lipoproteins and remnants by the liver. Overexpression contributes to atherosclerosis by increasing plasma concentration of TG-rich lipoproteins. A recent study reported the presence of apoC3 on lipoprotein(a) [Lp(a)] particles in subjects with mild to moderate aortic stenosis. Lp(a) is an apoB100 containing lipoprotein with apo(a) covalently bound and is a causal factor of ASCVD. Our goal was to investigate relationships between apoC3 and Lp(a) in a healthy population. Methods: We analyzed data from 39 healthy subjects who completed studies of lipoprotein metabolism at the Columbia University Irving Medical Center. Subjects were 18 - 75 years old, and 44% were female. Twenty were Black, 9 Hispanic, 8 White, and 2 mixed race. Lipids (total Cholesterol (C), TG, HDLC, LDLC) were measured by an automatic analyzer. Plasma apoC3, apoB100 and Lp(a) levels were measured via validated ELISA assays. Lp(a) particles were isolated from plasma by immunoprecipitation (IP) with a monoclonal antibody and Western blots were performed. Results: We did not find an association between plasma Lp(a) and apoC3 levels. In a sub-group analysis of participants (N=15), with Lp(a) levels >100nmol/L, we found a significant negative association between apoC3 and Lp(a) plasma concentrations (R = -0.58, p=0.018). Based on the Western blots and ELISA analysis, we see an interaction between Lp(a) (apo(a) and apoB100 intact) and apoC3. There seem to be some differences in the Lp(a) and apoC3 interaction based on Lp(a) plasma concentration. Conclusion and Future Direction: In healthy subjects, there is no association of apoC3 with Lp(a) plasma levels. In a subset of subjects (high Lp(a)), we observed an association with apoC3 plasma levels. Our small data set suggests possible distinct roles for apoC3 in healthy individuals with high Lp(a) level. ApoC3 may be associated with specific circulating isoform sizes of Lp(a). Future studies will focus on analysis of larger cohorts and examining lipid composition in the isolated particles.