Abstract 13787: Postprandial Increases of Circulating Mass of Endothelial Lipase Impact Plasma High-Density Lipoprotein-Cholesterol Concentrations

Abstract

Purpose: Hypertriglyceridemia is the most common cause of low plasma concentrations of high-density lipoprotein cholesterol (HDL-C). Endothelial lipase (EL) has been implicated in the regulation of plasma HDL-C levels. However, the detailed role of EL in HDL metabolism has not been completely investigated in humans. This study was undertaken to better characterize the association between plasma EL mass and HDL-C level in the fasting and postprandial states.

Methods: A total of 71 overweight and obese volunteer subjects resided in the UC,Davis Clinical and Translational Science Center’s Clinical Research Center for 2 weeks and consumed an energy-balanced, high-complex carbohydrate diet. Pre- and post-heparin plasma samples were collected and characterized in the subjects in both the fasting and postprandial states. Plasma levels of EL and angiopoietin-like 3 (Angptl3), an inhibitor of EL, were determined with novel and specific ELISA systems that we have recently developed.

Results: Remnant like particles-triglyceride (RLP-TG) concentrations were 116% higher in the postprandial state compared with the fasting state (p<0.001). The plasma EL mass in the human subjects in the fasting state was 306.8±14.2 pg/mL (mean±SE), which ranged from 141.0 to 716.8 pg/mL, and did not fit a normal distribution model. Unexpectedly, plasma EL mass was not affected by administration of heparin both under fasting and postprandial conditions. However, postprandial EL mass was 12% higher than fasting EL mass (p<0.001), which was concomitant with a 19% decrease of plasma Angptl3 level (p<0.001). Plasma HDL-C levels were significantly decreased by 6% in the postprandial compared with the fasting state (p<0.001). Consequently, the diet-induced increase of EL mass was inversely proportional to the decrease of plasma HDL-C level (R=0.24, p<0.05), although the correlation was not evident in the fasting state.

Conclusions: Plasma EL mass is increased during postprandial conditions and this is associated with a decrease of circulating angtptl3 levels. The postprandial increase of EL mass was significantly correlated with the decrease of plasma HDL-C levels. Thus, EL action may contribute to the low HDL-C levels in patients with postprandial hyperlipidemia.