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.
Speeckaert
Marijn M
MM
Department of Clinical Chemistry, Ghent University Hospital, Gent, Belgium. joris.delanghe@ugent.be
Taes
Youri E
YE
De Buyzere
Marc L
ML
Christophe
Armand B
AB
Kaufman
Jean-Marc
JM
Delanghe
Joris R
JR
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