Abstract
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 language | English |
|---|---|
| Journal | Journal of Lipid Research |
| Volume | 47 |
| Issue number | 8 |
| Pages (from-to) | 1833-43 |
| Number of pages | 11 |
| ISSN | 0022-2275 |
| DOIs | |
| Publication status | Published - Aug 2006 |
Keywords
- 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