Different reactivities of high density lipoprotein2 subfractions with hepatic lipase

J Lipid Res. 1992 Sep;33(9):1269-79.

Abstract

Human high density lipoproteins2 (HDL2) consist of particles that contain both apolipoprotein (apo) A-I and apoA-II (A-I/A-II-HDL2) and others that contain apoA-I but are devoid of apoA-II (A-I-HDL2). When postprandial lipemia is pronounced, a fraction of HDL2 is converted into HDL2-like particles. These HDL3 exhibit lower apoA-I/apoA-II ratios than the parent HDL2, suggesting preferential conversion of A-I/A-II-HDL2 into HDL3 (J. Clin. Invest. 1984. 74: 2017-2023). Triglyceride transfer from triglyceride-rich lipoproteins to HDL2 and subsequent lipolysis by hepatic lipase are thought to mediate the conversion of HDL2 into HDL3. To understand why A-I/A-II-HDL2 are preferentially converted into HDL3, we separated postprandial HDL2 into A-I-HDL2 and A-I/A-II-HDL2 species by immunoaffinity chromatography using a monoclonal antibody for apoA-II, and determined the ability of HDL2 species i) to participate in protein-mediated lipid transfer; and ii) to interact with hepatic lipase in vitro. Triglyceride transfer from/to triglyceride-rich lipoproteins was similar for the two HDL2 species. In contrast, A-I/A-II-HDL2 were twice as effective as A-I-HDL2 in liberating hepatic lipase immobilized on HDL3-Sepharose. Lipolysis of triglycerides by hepatic lipase was 60% higher in postprandial A-I/A-II-HDL2 than in postprandial A-I-HDL2. Hydrolysis of phosphatidylcholine by hepatic lipase was threefold higher in A-II-containing HDL2 when compared with HDL2 devoid of apoA-II. The different lipolytic rates in HDL2 subspecies correlated with the size reduction of substrate lipoproteins. Reconstitution of postprandial A-I-HDL2 with apoA-II enhanced the rate of lipolysis by hepatic lipase to that observed in A-I/A-II-HDL2. We conclude that it is the interaction with hepatic lipase rather than the rate of triglyceride transfer that results in the preferred conversion of postprandial A-II-containing HDL2 into HDL3, and that apoA-II exerts a crucial role in this process.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Apolipoprotein A-I / analysis
  • Apolipoprotein A-II / analysis
  • Humans
  • Kinetics
  • Lipase / metabolism*
  • Lipolysis
  • Lipoproteins, HDL / analysis
  • Lipoproteins, HDL / metabolism*
  • Lipoproteins, HDL2
  • Lipoproteins, HDL3
  • Liver / enzymology*
  • Triglycerides / analysis
  • Triglycerides / metabolism

Substances

  • Apolipoprotein A-I
  • Apolipoprotein A-II
  • Lipoproteins, HDL
  • Lipoproteins, HDL2
  • Lipoproteins, HDL3
  • Triglycerides
  • Lipase