Isolation and characterization of human apolipoprotein M-containing lipoproteins

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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.

Original languageEnglish
JournalJournal of Lipid Research
Issue number8
Pages (from-to)1833-43
Number of pages11
Publication statusPublished - Aug 2006

    Research areas

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

ID: 195963544