Department of Clinical Chemistry, Ghent University Hospital, Gent, Belgium.
Ann Clin Biochem. 2010 Mar;47(Pt 2):143-50. doi: 10.1258/acb.2009.009018. Epub 2010 Feb 9.
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.
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.
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.
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.
维生素 D 结合蛋白（DBP）作为维生素 D 的载体和肌动蛋白清除剂。我们之前曾报道过囊性纤维化人群中血清 DBP 与脂质参数之间的相关性。在本研究中，研究了血清 DBP、脂蛋白分数和维生素 D 之间的关系。
使用沉淀、凝胶渗透色谱法和超速离心法检查脂蛋白分数中 DBP 的存在。在 211 名男性的队列研究中研究了 DBP 与脂质之间的关系。通过免疫比浊法和酶联免疫吸附试验评估总 DBP 和无肌动蛋白 DBP 浓度。通过放射免疫法测定血清 25(OH)-和 1.25(OH)(2)-维生素 D(3)。使用常规方法测量总胆固醇、高密度脂蛋白胆固醇（HDL）、甘油三酯和胰岛素。根据 Friedewald 公式计算低密度脂蛋白胆固醇（LDL）。
发现 DBP 存在于极低密度脂蛋白（VLDL）中。凝胶渗透色谱法显示 DBP 存在双峰分布，除了已知的游离部分外，还有脂质结合部分。超速离心证实 DBP 和 25(OH)-维生素 D(3)存在于 VLDL 颗粒中。总血清 DBP 浓度和肌动蛋白结合 DBP/DBP 比值与总胆固醇、LDL 胆固醇、甘油三酯和白蛋白显著相关。25(OH)-维生素 D(3)/DBP 比值与血清甘油三酯浓度和体重指数（BMI）呈负相关。肌动蛋白结合的 DBP 复合物通过 Western blot 鉴定。
脂质结合的 DBP 部分可能比最初认为的更为重要。鉴于 DBP 的重要生理作用，目前的发现可能具有临床意义。
