Association of apolipoprotein A phenotypes and oxidized low-density lipoprotein immune complexes in children

Background: Small apolipoprotein A. (apo[A]) phenotypes and oxidized low-de nsity lipoprotein immune complexes (oxLDL-ICs) are known to be associated w ith the development of atherosclerosis in adults. Presence of these factors in children and their relationships with other known cardiovascular risk f actors have not been well documented. Objective: To examine the relationship of oxLDL-ICs with apo(A) phenotypes and other known cardiovascular risk factors in children. Design: A survey of asymptomatic 9- to 11-year-old children, randomly selec ted from a cohort of children stratified based on family history of prematu re coronary artery disease. Setting: A preventive medicine research institute. Participants: Thirty-five children with or without a family history of prem ature coronary artery disease who are participating in a longitudinal cardi ovascular health study. Main Outcome Measures: The influence of apo(A) phenotypes on plasma levels of oxLDL-ICs after controlling for lipid/lipoprotein levels, percentage of body fat, and physical fitness. Results: Oxidized low-density lipoprotein immune complexes were significant ly correlated with the levels of total cholesterol (r - = 0.56, P less than or equal to.05), low-density lipoprotein cholesterol (r = 0.64, P less tha n or equal to.01), and low-density lipoprotein cholesterol/high-density lip oprotein cholesterol (r=0.54, P<.05). Oxidized low-density lipoprotein immu ne complexes were also correlated with total cholesterol high-density lipop rotein cholesterol (r = 0.49, P less than or equal to.06) and percentage of body fat (r = 0.48, P less than or equal to.06). However, they achieved on ly a borderline level of statistical significance after adjustment for mult iple comparisons. Multiple regression analysis demonstrated that small apo( A) phenotypes, levels of low-density lipoprotein cholesterol, and family hi story of premature coronary artery disease explained 54% of the variation o f oxLDL-ICs using a parsimonious model (P =.001). Conclusions: Significant correlations exist between oxLDL-ICs and known car diovascular risk factors in children. The association of oxLDL-ICs with the genetically controlled small apo(A) phenotype suggests that the genetic pr edisposition to immune complex formation may be an important determinant of future coronary artery disease.