Discordantly normal ApoB relative to elevated LDL-C in persons with metabolic disorders: A marker of atherogenic heterogeneity

OBJECTIVE: A significant proportion of persons with metabolic syndrome (MetS), prediabetes, or type 2 diabetes (T2D) do not develop atherosclerotic cardiovascular disease (ASCVD). We sought to determine whether discordantly normal apolipoprotein B (ApoB) relative to elevated LDL-C may help to explain heterogeneity in ASCVD risk among persons with metabolic disorders. METHODS: There were 278 Bogalusa Heart Study participants with MetS (n=95), prediabetes (n=233), or T2D (n=31) and LDL-C ≥100 mg/dL who were free of carotid plaque at baseline (2001-02) and underwent carotid ultrasound at follow-up (2013-16). Multivariable modified Poisson regression estimated the long-term absence of carotid plaque for lower ApoB, continuously and categorically. RESULTS: Participants were on average 36.1 years old at baseline, 61.5% were women, and 31.7% were black. A total of 50.7% had discordantly normal ApoB (<90 mg/dL) and the mean ApoB and LDL-C concentrations were 91.6 mg/dL and 137.7 mg/dL, respectively. In addition to having higher HDL-C and lower triglyceride values, individuals with ApoB <90 were more likely to maintain persistent absence of plaque compared to those with ApoB ≥90 (73.1% versus 58.4%, p=0.01). Contrastingly, there was no significant difference in the proportion of individuals who remained free of plaque with increasing LDL-C (p=0.45). Independent of traditional risk factors including LDL-C, each 10 mg/dL lower ApoB (RR=1.11, 95% CI: 1.03-1.19) and ApoB <90 (RR=1.22, 95% CI: 1.00-1.43) were significantly associated with the persistent absence of carotid plaque. CONCLUSIONS: One-half of young persons with metabolic disorders and elevated LDL-C had discordantly normal ApoB and a low burden of carotid atherosclerosis over 13 years, suggesting that ApoB better represents the atherogenic lipid burden compared to LDL-C in this patient population. These results suggest a utility for assessing whether routine ApoB measurement can improve ASCVD risk stratification in young persons with metabolic disorders who have high triglycerides and low HDL-cholesterol.