Postprandial lipemia. A key for the conversion of high density lipoprotein2 into high density lipoprotein3 by hepatic lipase.

Abstract

In this study, we have investigated the effects of alimentary lipemia in 15 normotriglycerid- emic individuals on high density lipoproteins2 (HDL2) with respect to structure, composition, and substrate efficacy for hepatic lipase in vitro. In the study subjects, HDL2 levels ranged widely from 4.7 to 151.7 mg/dl plasma. HDL2 were isolated in the postabsorptive (pa) state and in the postprandial (pp) state, i.e., 7 h after ingestion of a standard fatty meal. In going from the pa state to the pp state, HDL2 exhibited higher flotation rates and lower densities due to a decreased proportion of protein (38.7 -a 36.2%) and a higher abundance in phospholipid (32.5 -4 34.9%). There was a variable increase in triglyceride at the expense of cholesteryl esters; this increase was correlated positively with the magnitude of pp lipemia (r = 0.69, P < 0.01) and inversely with HDL2 levels (r = -0.72, P < 0.01). HDL2 fractions were incubated with human hepatic lipase in vitro. Product lipoproteins formed from lipolysis of pa-HDL2 and triglyceride-poorer pp-HDL2 were reduced in phos- pholipid content (by 25 and 50%, respectively) but remained in the size and density range of native HDL2. By contrast, a major fraction of triglyceride-richer pp- HDL2 was converted to particles with density, size, and