Detection of apolipoproteins B-48 and B-100 carrying particles in lipoprotein fractions extracted from human aortic atherosclerotic plaques in sudden cardiac death cases.

BACKGROUND: ApoB-48 is a major apolipoprotein secreted by the small intestine and is the main constitutive apolipoprotein in chylomicrons (CM). In the past, presence of apoB-48 in human aortic atherosclerotic plaques has not been detected.
METHODS: A newly developed apoB-48 ELISA together with an HPLC fractionation technique, were applied to investigate the presence of apoB-48 (CM) in aortic atherosclerotic plaques. The atherosclerotic plaques were obtained from aortae of sudden cardiac death cases. Total cholesterol, triglycerides (TG), apoB-100 and apoB-48 were measured in the aortic plaques extracts.
RESULTS: HPLC analysis of plaques extracts monitored by cholesterol revealed mainly particle sizes of CM and very low density lipoproteins (VLDL) in the d>1.006 fractions. The plaques extracts were monitored by apoB-48 and apoB-100 ELISA. There were no TG peaks in any lipoprotein fraction extracted from the plaques except as free glycerol. ApoB-100 was detected in VLDL particles and in LDL sizes. In contrast, apoB-48 was detected in particles of CM, VLDL and LDL sizes. Further, in postmortem plasma, apo B-48 was detected in particles sizes of HDL or smaller and the Western blot analysis could not show any 250 kDa molecular weight (MW) protein in the plaque extracts, but smaller and broader MW staining were observed at 20-150 kDa.
CONCLUSION: Hitherto there has been lack of an appropriate assay to measure apoB-48 in plaques. Our investigations show that apoB-48 is present in atherosclerotic plaques with denatured or degraded structure. This is the first report describing presence of apoB-48 in human atherosclerotic plaques.