Isolation and characterization of human apolipoprotein M-containing lipoproteins

J Lipid Res. 2006 Aug;47(8):1833-43. doi: 10.1194/jlr.M600055-JLR200. Epub 2006 May 8.


Apolipoprotein M (apoM) is a novel apolipoprotein with unknown function. In this study, we established a method for isolating apoM-containing lipoproteins and studied their composition and the effect of apoM on HDL function. ApoM-containing lipoproteins were isolated from human plasma with immunoaffinity chromatography and compared with lipoproteins lacking apoM. The apoM-containing lipoproteins were predominantly of HDL size; approximately 5% of the total HDL population contained apoM. Mass spectrometry showed that the apoM-containing lipoproteins also contained apoJ, apoA-I, apoA-II, apoC-I, apoC-II, apoC-III, paraoxonase 1, and apoB. ApoM-containing HDL (HDL(apoM+)) contained significantly more free cholesterol than HDL lacking apoM (HDL(apoM-)) (5.9 +/- 0.7% vs. 3.2 +/- 0.5%; P < 0.005) and was heterogeneous in size with both small and large particles. HDL(apoM+) inhibited Cu(2+)-induced oxidation of LDL and stimulated cholesterol efflux from THP-1 foam cells more efficiently than HDL(apoM-). In conclusion, our results suggest that apoM is associated with a small heterogeneous subpopulation of HDL particles. Nevertheless, apoM designates a subpopulation of HDL that protects LDL against oxidation and stimulates cholesterol efflux more efficiently than HDL lacking apoM.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apolipoproteins / blood
  • Apolipoproteins / chemistry*
  • Apolipoproteins / isolation & purification*
  • Apolipoproteins / metabolism
  • Apolipoproteins M
  • Cell Line
  • Cholesterol / metabolism
  • Electrophoresis, Polyacrylamide Gel / methods
  • Foam Cells / cytology
  • Foam Cells / metabolism
  • Humans
  • Lipocalins
  • Lipoproteins, HDL / chemistry
  • Lipoproteins, HDL / isolation & purification
  • Lipoproteins, HDL / metabolism
  • Lipoproteins, LDL / chemistry
  • Lipoproteins, LDL / isolation & purification
  • Lipoproteins, LDL / metabolism
  • Molecular Weight
  • Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / methods


  • APOM protein, human
  • Apolipoproteins
  • Apolipoproteins M
  • Lipocalins
  • Lipoproteins, HDL
  • Lipoproteins, LDL
  • Cholesterol