[Role of hepatic lipases, cholesterol ester transfer proteins and LCAT in the postprandial phase]

Abstract

Hepatic, heparin-releaseable lipase is a multifunctional enzyme that may act on all lipoprotein classes present in plasma from fasted subjects. Recent evidence suggests that the enzyme also plays a role in the metabolism of chylomicronremnants. Its activity is impaired in normolipidemic patients with coronary heart disease, which also have a delayed removal of chylomicronremnants from plasma. Therefore hepatic lipase, in addition to lipoprotein lipase, plays an important role in postprandial lipoprotein metabolism. The activity levels of lecithin: cholesterol acyltransferase (LCAT) and cholesterylester transfer protein (CETP) are virtually unchanged after the ingestion of an oral fat load by normolipidemic subjects. However, the net mass transfer of cholesterylesters out of HDL into apo B-containing lipoproteins (chylomicronremnants, VLDL/IDL/LDL) is strongly increased. All triglyceride-rich lipoprotein fractions accumulate postprandially and, as a result of CETP action, become enriched in cholesterylesters. Defects in hepatic remnant removal may result in influx of remnants into the arterial wall. In patients with hyperlipidemia (and increased risk for atherosclerosis) the CETP-mediated formation of cholesterylester-rich remnants may operate, not only during the postprandial phase, but continuously.