Abstract P192: Lipoprotein(a) is Significantly Associated with ApoB-containing Atherogenic Lipoproteins in African Americans

Background: Lipoprotein(a), Lp(a), is a genetically regulated independent cardiovascular risk factor, where levels differ across ethnicity. The relationship between Lp(a) and apolipoprotein B (apoB)-containing atherogenic lipoproteins across ethnicity is not well understood. Objective: To investigate the associations of Lp(a) levels with other apoB-containing lipoproteins with a focus on ethnicity. Methods: Plasma lipid and lipoproteins were measured in 336 Caucasians and 224 African Americans undergoing coronary angiography. Lp(a) levels were determined using an apo(a) size insensitive sandwich ELISA. Values for Lp(a) and triglyceride (TG) were square root or logarithmically transformed before analyses. Total and low density lipoprotein (LDL) cholesterol, and apoB levels were corrected for contribution of Lp(a) using previously published algorithms. Values are given mean ± standard deviation or median (interquartile range) for normally or non-normally distributed variables, respectively. Results: Levels of total and LDL cholesterol and apoB-100 did not differ between Caucasians and African Americans. As expected, African Americans had significantly higher levels of Lp(a) [110 (60-180) nmol/l vs. 24 (7-79) nmol/l, p<0.001] and high density lipoprotein (HDL) cholesterol (49±17 mg/dl vs. 41±12 mg/dl, p<0.001), as well as significantly lower levels of TG [106 (80-144) mg/dl vs. 153 (114-222) mg/dl, p<0.001] compared to Caucasians. For both ethnic groups, Lp(a) levels were significantly and positively correlated with total cholesterol (p<0.005 for Caucasians and p<0.001 for African Americans), LDL cholesterol (p<0.001 for both groups), apoB100 (p<0.05 for Caucasians and p<0.001 for African Americans) and apoB/apoA-1 ratio (p<0.05 for Caucasians and p<0.001 for African Americans). However, when adjusted for the corresponding contribution of Lp(a) to the levels of these parameters, the associations remained significant in African Americans (p<0.05 for total cholesterol; p<0.05 for LDL cholesterol; p<0.001 for apoB100, respectively), but not in Caucasians. Conclusion: Although total and LDL cholesterol, and apoB100 levels were comparable in African Americans and Caucasians, the associations of these parameters with Lp(a) levels differed across ethnicity. For African Americans, but not for Caucasians, associations of all three parameters with Lp(a) remained significant after appropriate adjustments. The findings suggest an interethnic difference in the relation between Lp(a) and other plasma apoB-containing lipoprotein levels, with a closer relationship among African Americans.