REDUCED CHOLESTERYL ESTER TRANSFER IN PLASMA OF PATIENTS WITH LIPOPROTEIN-LIPASE DEFICIENCY

The net mass transfer of cholesteryl ester (CE) from high density lipo protein (HDL) to the apolipoprotein (apo) B-containing lipoproteins, v ery low density lipoprotein (VLDL) and low density lipoprotein (LDL) i n plasma (cholesteryl ester transfer (CET)) from three patients lackin g lipoprotein lipase (LpL) activity was significantly lower (P < 0.001 ) than in plasma from fasting control subjects with comparable triglyc eride levels. Chylomicrons isolated from LpL-deficient fasting plasma showed the same low level of CET activity as observed in the intact pl asma when combined with HDL and cholesteryl ester transfer protein (CE TP)-containing d 1.063 g/ml bottom fractions from control subjects. Pr eincubation of chylomicrons and large triglyceride-rich lipoproteins ( S-f > 400) from LpL-deficient plasma with milk LpL, however, stimulate d the capacity to engage in CET 4- to 5-fold to the same level as chyl omicrons and VLDL from control subjects after a fat load. Consistent w ith these measurements of CET activity in plasma, chylomicrons obtaine d from the LpL-deficient subjects after a 14-h fast had higher TG/CE r atios than chylomicrons from controls 3 h after ingesting a fat load ( LpL-deficient 26.3 +/- 9.0 vs. controls 6.9 +/- 2.1; mean +/- SD). The mass of CETP did not differ in LpL-deficient and control subjects (Lp L-deficient 1.03 +/- 0.22 mu g/ml vs. controls 1.58 +/- 0.58 mu g/ml). These studies are consistent with earlier in vitro studies showing th at the actions of lipoprotein lipase and its lipolytic products are es sential for maximal cholesteryl ester transfer protein activity.