Apoprotein B-48 is a constant finding in very low density lipoproteins of humans.

The results of this study indicate that very low density lipoprotein (VLDL) from the plasma of fasting normolipidemic or slightly hypertriglyceridemic subjects contains two apo B species. In SDS gel electrophoresis, the VLDL shows the presence of a major band corresponding to low density lipoprotein (LDL) apo B (apo B-100) and a minor band with the appropriate mobility of the lymph chylomicron apo B (apo B-48). The reactivity of monoclonal antibodies directed against opportunely selected human apo B suggests that the protein with the lower molecular weight corresponds to apo B-48. This finding was confirmed by using immunoadsorbants and affinity chromatography with monoclonal antibodies that react only with apo B-100. Through this method, VLDL were separated into two fractions: one that had only apo B-100 and one with both apo B-100 and apo B-48. Hepatic and intestinal VLDL may constitute different particles. The ratio of apo B-100 to apo B-48 in VLDL decreased as the mass of fasting plasma VLDL increased. This may improve our understanding of the metabolism of triglyceride-rich lipoproteins. The investigation of the new subspecies of apo B may be relevant in understanding the atherogenetic process and better defining the hyperlipidemic states.