TY - JOUR
T1 - Isolation and characterization of human apolipoprotein M-containing lipoproteins
AU - Christoffersen, Christina
AU - Nielsen, Lars Bo
AU - Axler, Olof
AU - Andersson, Astra
AU - Johnsen, Anders H
AU - Dahlbäck, Björn
PY - 2006/8
Y1 - 2006/8
N2 - 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.
AB - 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.
KW - Apolipoproteins/blood
KW - Apolipoproteins M
KW - Cell Line
KW - Cholesterol/metabolism
KW - Electrophoresis, Polyacrylamide Gel/methods
KW - Foam Cells/cytology
KW - Humans
KW - Lipocalins
KW - Lipoproteins, HDL/chemistry
KW - Lipoproteins, LDL/chemistry
KW - Molecular Weight
KW - Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization/methods
U2 - 10.1194/jlr.M600055-JLR200
DO - 10.1194/jlr.M600055-JLR200
M3 - Journal article
C2 - 16682745
SN - 0022-2275
VL - 47
SP - 1833
EP - 1843
JO - Journal of Lipid Research
JF - Journal of Lipid Research
IS - 8
ER -