Isolation of remnant particles by immunoseparation: a new approach for investigation of postprandial lipoprotein metabolism in normolipidemic subjects

Abnormal postprandial lipoproteins are associated with an increased risk for cardiovascular disease. Postprandial remnant lipoproteins were usually analyzed indirectly using retinyl esters (RE) as a chylomicron core label during an oral fat loading test. Apo B-100 containing VLDL remnants in addition to apo B-48 containing chylomicron remnants can also be directly quantified using the RLP-Cholesterol Immunoseparation Assay. This recently available method uses monoclonal antibodies to apo A-I and apo B-100 to remove non-remnant lipoproteins and quantifies cholesterol in the remaining apo E-rich remnant fraction. In the present study we compared the analysis of retinyl ester with the immuno-based RLP-Cholesterol (RLP-C) analysis in measuring postprandial remnant lipoproteins in healthy normolipidemic subjects. Sixteen healthy normolipidemic subjects were selected for this study. Postprandial plasma retinyl esters peaked at 5.0+/-1.2 h, whereas plasma RLP-C showed a peak significantly earlier (P <0.001) at 3.5+/-0.6 h. In comparison, postprandial plasma TG and FFA peaked at 3.3+/-1.1 h (P <0.005 compared to retinyl esters). In conclusion, levels of RLP-C changed, during the postprandial phase, in parallel with plasma TG and FFA concentrations and peaked significantly earlier than retinyl esters. Postprandial measurements of RLP-C can be considered as a fast alternative method for the more laborious retinyl-ester analysis in clinical studies