Slower removal of intestinal apolipoprotein B-48 than of apolipoprotein B-100 in severely hypertriglyceridemic subjects.

Apolipoprotein B, the major structural protein of triacylglycerol-rich lipoprotein, occurs in two immunologically distinct forms, termed apolipoproteins B-100 and B-48. In man, the former is associated with triacylglycerol-rich lipoproteins of hepatic origin and the latter with intestinal triacylglycerol-rich lipoproteins. We have studied the rates of removal of the two proteins when 125I-labelled triacylglycerol-rich lipoproteins were reinjected into six severely hypertriglyceridemic subjects showing hyperchylomicronemia, and into two normal subjects. The specific radioactivities of apolipoproteins B-100 and B-48 were determined over periods of up to 30 h. In all six hyperlipemic subjects the removal of apolipoprotein B-100 was either significantly faster than that of apolipoprotein B-48 (in four) or similar in the two who cleared triacylglycerol-rich lipoproteins very slowly. When triacylglycerol-rich lipoproteins from two hyperlipemic subjects (in whom apolipoprotein B-48 was cleared more slowly) were injected into two normal subjects both B apolipoproteins were cleared at similar rates. Since apolipoprotein B-48 appears to be a marker for remnants of intestinal particles, its slower removal than that of apolipoprotein B-100 in severe hypertriglyceridemia suggests that one metabolic defect associated with the hyperchylomicronemia is defective removal of chylomicron remnants.