FRACTIONAL REMOVAL RATE OF FAT EMULSION (K-2) REMAINS TO BE LOW IN APOE3 3 PHENOTYPE SUBJECTS WITH SERUM TRIGLYCERIDE LEVEL ABOVE 180MG/DL/

The relation between fractional catabolic rate (IG) Of an intravenousl y injected fat emulsion, Intralipid(R), and the level of serum triglyc eride (TG) was evaluated to cast light on TG-rich lipoprotein metaboli sm in 182 subjects who were homozygotes for the most common form of ap oE3/3. Both normolipidemic individuals and primary hyperlipidemic pati ents were included. To assess the influence of variation in the apoE p henotype on fat emulsion metabolism, 25 subjects with the apoE 4/3 phe notype and 21 with apoE 3/2 phenotype were also evaluated. In the apoE 3/3 subjects, K2 decreased with increasing TG level up to 180mg/dl, b ut above 180mg/dl, K2 remained at a constant level. This TG value was therefore concluded to be a cut off beyond which the TG-dependent decr ease in K2 disappeared. No aparent correlation between K2 and serum TG was observed in subjects with apoE 4/3 or 3/2 phenotypes. In subjects with TG above 180mg/dl, presumably both accelerated synthesis and lim ited removal are involved in the development of their hypertriglycerid emia. Since K2 demonstrated little change with increase of TG over 180 mg/dl in apoE 3/3 subjects, we concluded that the capacity to cataboli ze fat emulsion reaches a kinetic saturation. The TG value of 180mg/dl may be a physiological significance. The relation between K2 and TG w as specific in apoE 3/3, as it was not observed in subjects having apo E 4/3 or 3/2 phenotypes.