[Apolipoprotein E mobility between plasma lipoproteins in intravenous administration of fat emulsions (MCT, LCT)]

Apolipoprotein (apo) E plays a key role in chylomicron metabolism as a ligand for their uptake via the apo B/E- and apo E receptor into the liver. Apo E is not primarily synthesized with chylomicrons but is postprandially transferred to chylomicrons during lipolysis in plasma from high density lipoproteins (HDL). As triglyceride-/phospholipid emulsions given intravenously acquire apolipoproteins in plasma, we set out to investigate a possible transfer of apo E to these artificial lipoproteins and its role during their further metabolism. To this end healthy normolipemic volunteers and carriers of the frequent apo E3/3 phenotype were infused lipid emulsions. The lipoprotein-distribution of apo E during MCT and LCT infusions was monitored over four hours. Infusion of MCT and LCT resulted in a substantial transfer of apo E from HDL to triglyceride rich lipoproteins. During MCT infusion the transfer of apo E seemed to occur more rapidly than during LCT infusion. This could be one of the reasons for the faster metabolism of MCT over LCT. Plasma levels of apo E also decreased significantly during infusion of triglyceride/phospholipid emulsions in accordance with the role of apo E as a ligand for the uptake of the artificial particles into the liver.