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Immunomagnetic separation of subpopulations of apolipoprotein A-I
A Rastogi1, N D Bren, B J Hallaway
1Atherosclerosis Research Unit, Mayo Clinic Rochester, Minnesota 55905.
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 (apo 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 subpopulations of HDL particles have implications in the development of atherosclerosis in patients with and without diabetes.