Capacity of high-density lipoprotein for donating apolipoproteins to fat particles in hypertriglyceridemia induced by fat infusion.

Acquisition of apolipoproteins C-II (apoCII) and C-III (apoCIII) is essential for the regulation of intravascular metabolism of fat particles (exoTG). This study was undertaken to investigate whether the capacity of high-density lipoprotein (HDL) for donating apoCII and apoCIII is influenced by the concentration of triglycerides (TGs) in plasma. A fat emulsion was infused into six male volunteers at a rate of 0.5 g TG.kg-1.h-1 (priming dose) for 30 min. For the following 160 min, fat was infused a fat emulsion was infused into the same subjects at a rate of 0.3 g.kg-1.h-1 for 160 min after the administration of the priming dose of fat emulsion for 30 min (experiment 2). The plasma TG concentrations and the amounts of apoCII and apoCIII in exo TG and HDL were monitored. The concentration of TG in the plasma stabilized at approximately 500 mg/dl in experiment 1, whereas it continued to increase to 815 +/- 42 mg/dl at 160 min after the start of the infusion of the fat emulsion in experiment 2. In experiment 1, the amount of both apoCII and apoCIII began to increase in exoTG and to decrease in HDL after the initiation of fat infusion. These changes in the distribution of apoC stabilized while the TG concentration remained at a plateau value. However, in experiment 2, the amount of apoC in exoTG did not increase further in response to the additional rise in plasma TG level. These results suggest that there is a relative lack of apoC that can be donated by HDL, depending on the quantitative balance between exoTG and HDL.(ABSTRACT TRUNCATED AT 250 WORDS)