Lipoprotein lipase prevents the hepatic lipase-induced reduction in particle size of high density lipoproteins during incubation of human plasma.

Human plasma lipoproteins or human whole plasma have been incubated in vitro with canine hepatic lipase (HL) and bovine milk lipoprotein lipase (LPL) to determine the effects of lipases on the particle size distribution of HDL. Confirming previous reports, HL preferentially hydrolysed high density lipoprotein (HDL) triacylglycerol while LPL hydrolysed predominantly very low density lipoprotein (VLDL) triacylglycerol; however, neither lipase altered HDL particle size unless both VLDL and cholesteryl ester transfer protein (CETP) were present. Under these conditions HL promoted marked reduction in HDL particle size in a process dependent on the concentration of VLDL triacylglycerol while LPL was virtually without effect. When both LPL and HL were included in the same incubation, however, LPL prevented the effects of HL. These results are consistent with a proposition that HL has a direct effect on HDL particle size in a process which is dependent on concurrent lipid transfers between HDL and VLDL and that LPL reduces the effect of HL by reducing the concentration of VLDL triacylglycerol.