Institute of Nutritional Sciences, University of Potsdam, Potsdam, Germany; Institute for Laboratory Medicine, IFLB, Berlin, Germany.
Institute for Laboratory Medicine, IFLB, Berlin, Germany.
J Steroid Biochem Mol Biol. 2018 Jul;181:80-87. doi: 10.1016/j.jsbmb.2018.03.005. Epub 2018 Mar 19.
The determination of free 25-hydroxyvitamin D (25(OH)D) as compared to the analysis of total 25-hydroxyvitamin D might reflect better the vitamin D status during pregnancy, since vitamin D-binding protein (DBP) concentrations increase throughout pregnancy and the vast majority of 25(OH)D is tightly bound to DBP thus strongly influencing total 25(OH)D. The concentration of the biologically active free 25(OH)D - on the other hand - is much less dependent on the DBP concentrations. The study was conducted in May-June 2016 in 368 Caucasian pregnant healthy women - residents of Northeastern Germany. Free 25(OH)D was either measured directly by commercial ELISA kit or assessed by calculation via total 25(OH)D, DBP, and albumin serum concentrations. Regardless of the detection method, free 25(OH)D lowers in the 3rd trimester comparing to the 1st trimester (by 12% and 21%, p < 0.05 and p < 0.001, for measured and calculated free 25(OH)D, respectively), whereas total 25(OH)D was not decreased in late pregnancy. DBP rises with gestational age. Total 25(OH)D was not correlated with serum calcium (p = 0.251), whereas free 25(OH)D was significantly (p = 0.007 for measured free 25(OH)D and p < 0.001 for calculated free 25(OH)D) positively correlated with calcium. All 25(OH)D isoforms were significantly negatively correlated with bone-specific alkaline phosphatase (BSAP), however the correlation strength was the lowest with total 25(OH)D (rho = -0.108, p = 0.038), whereas both measured and calculated free 25(OH)D revealed better associations with BSAP (rho = -0.203 and rho = -0.211 for measured and calculated free 25(OH)D, respectively, p < 0.001 for both). We established pregnancy trimester-specific reference intervals for free measured and calculated 25(OH)D and DBP. Both measured and calculated free 25(OH)D showed better correlations with parameters of the endocrine vitamin D system (calcium and BSAP). Both ways of measuring free 25(OH)D in pregnant women are suitable as novel laboratory parameter for vitamin D status monitoring during human pregnancy and might replace in the future the routine total 25(OH)D assessment.
与分析总 25-羟维生素 D 相比，测定游离 25-羟维生素 D（25（OH）D）可能更能反映妊娠期间维生素 D 状况，因为维生素 D 结合蛋白（DBP）浓度在整个怀孕期间增加，而绝大多数 25（OH）D 与 DBP 紧密结合，因此强烈影响总 25（OH）D。另一方面，生物活性游离 25（OH）D 的浓度受 DBP 浓度的影响要小得多。该研究于 2016 年 5 月至 6 月在德国东北部的 368 名白种人健康孕妇中进行。游离 25（OH）D 要么通过商业 ELISA 试剂盒直接测量，要么通过总 25（OH）D、DBP 和白蛋白血清浓度计算评估。无论采用哪种检测方法，与妊娠早期相比，妊娠晚期游离 25（OH）D 均降低（通过测量和计算游离 25（OH）D，分别降低 12%和 21%，p<0.05 和 p<0.001），而总 25（OH）D 在妊娠晚期没有降低。DBP 随妊娠周数增加而升高。总 25（OH）D 与血清钙无相关性（p=0.251），而游离 25（OH）D 与钙呈显著正相关（p=0.007 用于测量游离 25（OH）D，p<0.001 用于计算游离 25（OH）D）。所有 25（OH）D 同工型与骨特异性碱性磷酸酶（BSAP）均呈显著负相关，但与总 25（OH）D 的相关性最低（rho=-0.108，p=0.038），而游离 25（OH）D 的测量和计算均与 BSAP 具有更好的相关性（rho=-0.203 和 rho=-0.211 分别用于测量和计算游离 25（OH）D，两者均为 p<0.001）。我们建立了游离测量和计算 25（OH）D 和 DBP 的妊娠特定参考区间。游离 25（OH）D 的测量值和计算值均与内分泌维生素 D 系统的参数（钙和 BSAP）具有更好的相关性。在孕妇中测量游离 25（OH）D 的这两种方法都适合作为人类妊娠期间维生素 D 状态监测的新型实验室参数，并且可能在未来取代常规的总 25（OH）D 评估。
