Discordance Between ApoB and LDL-C Predicts Calcification
Is there an association between apolipoprotein B (apoB) and the discordance between apoB and low-density lipoprotein cholesterol (LDL-C) or non–high-density lipoprotein cholesterol (HDL-C) in young adults and measured coronary artery calcium (CAC) in midlife?
Data were derived from CARDIA (Coronary Artery Risk Development in Young Adults), a multicenter cohort study of young adults recruited at ages 18-30 years. All participants with complete baseline cardiovascular disease (CVD) risk factor data, including apoB and year 25 (Y25) CAC score, were entered into this study. Presence of CAC was defined as having a positive, nonzero Agatston score, as determined by computed tomography. Baseline apoB values were divided into tertiles of four mutually exclusive concordant groups, based on median apoB and LDL-C or non–HDL-C.
Analysis included 2,794 participants (mean age, 25 ± 3.6 years; body mass index, 24.5 ± 5 kg/m2; and 44.4% male). Mean lipid values (in mg/dl) were as follows: total cholesterol: 177 ± 33; LDL-C: 110 ± 31; non–HDL-C: 124 ± 33; HDL-C: 53 ± 13; and apoB: 91 ± 24; median triglycerides were 61. Compared with the lowest apoB tertile, higher odds of developing year 25 CAC were seen for the middle (odds ratio [OR], 1.53) and high (OR, 2.28) tertiles based on traditional risk factor-adjusted models. High apoB and low LDL-C or nondiscordance was also associated with Y25 CAC in adjusted models (OR, 1.55 and 1.45, respectively).
These data suggest a dose-response association between apoB in young adults and the presence of midlife CAC independent of baseline traditional CVD risk factors.
The relative value of measuring apo B, the protein on the surface of each of the atherogenic particles (LDL, intermediate-density lipoprotein, lipoprotein a, and very LDL) represents atherogenic particle number, and has been suggested to be as good or better than LDL-C, total C/HDL-C, and non–HDL-C for assessing coronary disease risk and as an on-treatment target for lipid lowering. However, studies have been inconclusive, which may be related to the variability of cholesterol content within the apoB particles.
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