CONTRIBUTION OF APO-B-48 AND APO-B-100 TRIGLYCERIDE-RICH LIPOPROTEINS(TRL) TO POSTPRANDIAL INCREASES IN THE PLASMA-CONCENTRATION OF TRL TRIGLYCERIDES AND RETINYL ESTERS

After the ingestion of a fat-rich meal, there is a postprandial increa se in the plasma concentration of both apolipoprotein B-48- and apoB-1 00-containing triglyceride-rich lipoproteins (apoB-48 and apoB-100 TRL ). In order to determine the contribution of these lipoproteins to pos tprandial lipemia, the concentration of triglycerides (TG) and retinyl esters (RE) was measured in apoB-48 and apoB-100 TRL after an oral fa t load. Six normolipidemic male subjects were fed heavy cream (1 g fat per kg body weight) containing vitamin A (3000 retinol equivalents). TRL were isolated by ultracentrifugation from plasma samples obtained at regular intervals after the meal, and apoB-100 TRL were separated f rom apoB-48 TRL by affinity chromatography using monoclonal antibodies . Postprandial increase in plasma TG concentration was due to an incre ase in TG in the TRL fraction, which in turn was predominantly (82 +/- 4%) due to an increase in TG in apoB-48 TRL. Contribution of apoB-100 TRL to postprandial increase in TRL TG was 3-27% in individual subjec ts. ApoB-100 TRL remained a significant carrier of total plasma trigly ceride in the fed state, as reflected by similar apoB-100 and apoB-48 TRL TG concentrations at 2, 4, and 6 h after the fat meal. Retinyl est ers were regularly detected in apoB-100 TRL. Seventy-five (+/- 9) perc ent of the increase in TRL-RE was due to RE in apoB-48 TRL and 25 +/- 9% was due to RE in apoB-100. These data suggest that RE in plasma arc not always associated with apoB-48-containing lipoproteins. Furthermo re, we conclude that apoB-100 TRL, as well as apoB-48 TRL, make a sign ificant contribution to postprandial triglyceridemia.