Investigation of the potential association of vitamin D binding protein with lipoproteins.
BACKGROUND
Vitamin D binding protein (DBP) acts as a vitamin D carrier and an actin scavenger. We have previously reported a correlation between serum DBP and lipid parameters in a cystic fibrosis population. In the present study, the relationship between serum DBP, lipoprotein fractions and vitamin D is investigated.


METHODS
The presence of DBP in lipoprotein fractions was examined using precipitation, gel permeation chromatography and ultracentrifugation. The association between DBP and lipids was investigated in a cohort study of 211 men. Total and actin-free DBP concentrations were assessed by immunonephelometry and enzyme-linked immunosorbent assay. Serum 25(OH)- and 1.25(OH)(2)-vitamin D(3) were assayed by radioimmunoassay. Total cholesterol, high-density lipoprotein cholesterol (HDL), triglycerides and insulin were measured using routine methods. Low-density lipoprotein-cholesterol (LDL) was calculated according to Friedewald's formula.


RESULTS
DBP was found to be present in very-low-density lipoprotein (VLDL). Gel permeation chromatography revealed a bimodal DBP distribution with a lipid-bound fraction besides the known free fraction. Ultracentrifugation confirmed the presence of DBP and 25(OH)-vitamin D(3) in the VLDL particle. Total serum DBP concentration and the actin-bound DBP/DBP ratio correlated significantly with total cholesterol, LDL-cholesterol, triglycerides and albumin. The 25(OH)-vitamin D(3)/DBP ratio correlated negatively with serum triglyceride concentration and body mass index (BMI). The actin-bound DBP complex was identified with Western blot.


CONCLUSIONS
The lipid-bound DBP fraction may be of greater importance than initially thought. The present findings may have clinical consequences in view of the important physiological role of DBP.
Department of Clinical Chemistry, Ghent University Hospital, Gent, Belgium. joris.delanghe@ugent.be
Marijn M
MM
Speeckaert
Youri E
YE
Taes
Marc L
ML
De Buyzere
Armand B
AB
Christophe
Jean-Marc
JM
Kaufman
Joris R
JR
Delanghe
D000368:Aged; D000369:Aged, 80 and over; D002352:Carrier Proteins / Q000097:blood*; D002784:Cholesterol / Q000097:blood; D002788:Cholesterol Esters; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood; D015243:Cholesterol, VLDL / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D006801:Humans; D008055:Lipids / Q000097:blood; D008074:Lipoproteins / Q000097:blood*; D008077:Lipoproteins, LDL / Q000097:blood; D008079:Lipoproteins, VLDL / Q000097:blood; D008297:Male; D011506:Proteins / Q000378:metabolism; D014280:Triglycerides / Q000097:blood; D014461:Ultracentrifugation / Q000379:methods; D014807:Vitamin D / Q000097:blood* / Q000378:metabolism*; D014809:Vitamin D-Binding Protein / Q000097:blood*
D002352:Carrier Proteins; D002788:Cholesterol Esters; D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D015243:Cholesterol, VLDL; D008055:Lipids; D008074:Lipoproteins; D008077:Lipoproteins, LDL; D008079:Lipoproteins, VLDL; D011506:Proteins; D014280:Triglycerides; D014809:Vitamin D-Binding Protein; C019455:low density lipoprotein inhibitor; D014807:Vitamin D; D002784:Cholesterol