IMMUNOMAGNETIC SEPARATION OF SUBPOPULATIONS OF APOLIPOPROTEIN-A-I

Objective: This study was undertaken to measure the subfractions of high-density lipoprotein (HDL) in patients with diabetes or coronary artery disease and in normal control subjects. Design: A new immunomagnetic separation technique was used to characterize the lipid profile in four groups: (1) control subjects, (2) patients with diabetes but no coronary artery disease (CAD), (3) those with CAD only, and (4) those with both diabetes and CAD. Material and Methods: To study the individual roles of the two discrete HDL subpopulations of particles-LpAI/AII (apolipoprotein [apo] A-I associated with A-II) and LpAI (ape A-I without A-II)-in lipoprotein metabolism, we developed an immunomagnetic separation technique using magnetic beads coated with antibodies to human apo A-II. The beads bind particles that contain both apo A-II and apo A-I and are precipitated by a magnetic field. LpAI levels were measured in the supernatant by performing an apo A-I radioimmunoassay. LpAI/AII levels were determined by subtracting the LpAI levels from total plasma apo A-I. Results: In comparison with control subjects, patients with diabetes, CAD, or both had significantly decreased levels of LpAI/AII. LpAI levels were normal in patients with diabetes without CAD but significantly lower, than control values in those with diabetes and CAD. Conclusion: Our findings suggest that both sub populations of HDL particles have implications in the development of atherosclerosis in patients with and without diabetes.