Institute for Laboratory Medicine, IFLB, Berlin, Germany.
Fifth Department of Medicine (Nephrology/Endocrinology/Rheumatology), University Medical Centre Mannheim, University of Heidelberg, Heidelberg, Germany.
Sci Rep. 2021 Jan 21;11(1):1923. doi: 10.1038/s41598-021-81452-9.
25-Hydroxyvitamin D (25OHD) and 1,25-dihydroxyvitamin D (1,25(OH)D) need to be bound to carrier proteins to be transported to their target cells. The majority of either 25OHD or 1,25(OH)D is bound to vitamin D-binding protein (DBP), a smaller fraction is bound to albumin and only very small amounts of 25OHD or 1,25(OH)D are free. Albumin-bound 25OHD or 1,25(OH)D is relatively easily available after dissociation from albumin. Thus, the sum of free and albumin-bound forms is called bioavailable 25OHD and bioavailable 1,25(OH)D. Total 25OHD and 1,25(OH)D are defined as the sum of free, albumin-bound and DBP-bound 25OHD and 1,25(OH)D, respectively. This cross-sectional study in 427 pregnant women compared the correlation of the six vitamin D compounds with biomarkers of bone health, lipid metabolism, kidney function, endocrine parameters, and group B water-soluble vitamins. Among the 25OHD metabolites analysed, total 1,25(OH)D showed clearly the best correlation with calcium, bone-specific alkaline phosphatase, adiponectin, LDL, HDL, urea, thyroxine, and group B water-soluble vitamins. When comparing the three 25OHD metabolites, both free 25OHD and bioavailable 25OHD showed overall good correlations with calcium, bone-specific alkaline phosphatase, adiponectin, LDL, HDL, urea, thyroxine, triiodothyronine, and group B water-soluble vitamins, The correlations of 1,25(OH)D and 25OHD metabolites went always in opposite directions. Only PTH correlates always inversely with all six vitamin D compounds. In conclusion, free 25(OH)D and bioavailable 25(OH)D are more precise determinants of the vitamin D status than total 25(OH)D in normal pregnancy, whereas total 1,25(OH)D is superior to free and bioavailable 1,25(OH)D. Except for PTH, correlations of 25(OH)D and 1,25(OH)D metabolites with typical clinical chemistry readouts go in opposite directions.
25-羟维生素 D（25OHD）和 1,25-二羟维生素 D（1,25（OH）2D）需要与载体蛋白结合才能被运输到靶细胞。25OHD 或 1,25（OH）2D 的大部分与维生素 D 结合蛋白（DBP）结合，较小部分与白蛋白结合，只有很少量的 25OHD 或 1,25（OH）2D 是游离的。与白蛋白解离后，白蛋白结合的 25OHD 或 1,25（OH）2D 相对容易获得。因此，游离和白蛋白结合形式的总和称为生物可利用的 25OHD 和生物可利用的 1,25（OH）2D。总 25OHD 和 1,25（OH）2D 分别定义为游离、白蛋白结合和 DBP 结合的 25OHD 和 1,25（OH）2D 的总和。这项在 427 名孕妇中的横断面研究比较了六种维生素 D 化合物与骨健康、脂质代谢、肾功能、内分泌参数和 B 族水溶性维生素生物标志物的相关性。在分析的 25OHD 代谢物中，总 1,25（OH）2D 与钙、骨特异性碱性磷酸酶、脂联素、LDL、HDL、尿素、甲状腺素和 B 族水溶性维生素的相关性最为明显。在比较三种 25OHD 代谢物时，游离 25OHD 和生物可利用的 25OHD 与钙、骨特异性碱性磷酸酶、脂联素、LDL、HDL、尿素、甲状腺素、三碘甲状腺原氨酸和 B 族水溶性维生素的相关性总体较好。1,25（OH）2D 和 25OHD 代谢物的相关性总是相反的。只有甲状旁腺激素总是与所有六种维生素 D 化合物呈负相关。总之，在正常妊娠中，游离 25（OH）D 和生物可利用的 25（OH）D 比总 25（OH）D 更能精确地反映维生素 D 状态，而总 1,25（OH）2D 优于游离和生物可利用的 1,25（OH）2D。除甲状旁腺激素外，25OHD 和 1,25（OH）2D 代谢物与典型临床化学检测结果的相关性呈相反方向。
