Abstract

The preheparin and postheparin lipoprotein lipids (cholesterol C and triacylglycerols TAG) were related to the serum insulin and to the postheparin plasma activities of lipoprotein lipase (LPL) and hepatic lipase (HL) in normolipemic human. The positive correlation, although not statistically significant, of insulin level of the LPL activity was found, while no correlation to the HL activity was seen. Under preheparin conditions: 1) both insulin level and LPL activity were negatively related to the VLDL-C/TAG ratio indicating an enrichment of VLDL with TAG, 2) moreover, the LPL activity was positively related to the HDL-C and HDL3-C, 3) the HL activity predominated in relation to the HDL, and particularly to the HDL3, as indicated by negative correlations to the both lipids and to the lipid/apoA-I ratios of HDL and HDL3. This lipid depletion of HDL3 was more expressive due to the TAG, while HDL2 appeared to be relatively enriched with TAG, as suggested by correlations of C/TAG ratios with HL activity. The in vivo acceleration of lipoprotein metabolism by heparin resulted in: 1) the reduction of VLDL-TAG and HDL2-TAG, and in the increase of HDL3-TAG, 2) the appearance of positive relation of HDL2-C to the LPL activity and of opposite relation to the HL activity, 3) the lack of HL correlation to the TAG of HDL and HDL3. Even under these conditions no relation of insulin level to any HDL lipid was revealed. The results suggest that in normal human the HL affects more considerably than LPL the lipid metabolism of HDL subfractions and it does not seem to be under insulin control.