Neutral lipid transfer activities in the plasma of patients with abetalipoproteinemia

Plasma lipid transfer proteins stimulate transfer and molecular exchange of cholesteryl esters, phospholipids and triglycerides between individual plasma lipoproteins. To assess whether transfer protein activities are influenced by the inherent absence of apo B-containing lipoproteins, we determined cholesteryl ester and triglyceride transfer activities in the plasma of patients with abetalipoproteinemia (ABL). Transfer activities were measured in plasma fractions of d > 1.21 g/ml in 2 patients with abetalipoproteinemia and 12 normal volunteers and were expressed as a percent transfer of labeled lipid from donor high density lipoproteins to acceptor very low density lipoproteins. Cholesteryl ester and triglyceride transfer activities were reduced respectively by 50% and 66% in the plasma of patients with ABL. The addition of the plasma fraction d > 1.21 g/ml proteins from abetalipoproteinemic subjects resulted in progressive decreases in cholesteryl ester and triglyceride transfer activities. The reduced activities of these transfer proteins may reflect (at least in part) the presence of an inhibitor(s) which is heat-stable and trypsin-sensitive.