Department of Woman, Child and of General and Specialized Surgery, Seconda Università degli Studi di Napoli, 80138 Napoli, Italy.
J Clin Endocrinol Metab. 2015 Oct;100(10):3949-55. doi: 10.1210/jc.2015-2973. Epub 2015 Aug 28.
Studies examining vitamin D levels in association with childhood obesity usually do not consider the effect of insulin on vitamin D-binding protein and do not calculate the unbound, bioavailable vitamin D.
This study aimed to evaluate in a group of children 1) the concentrations of both total 25-hydroxyvitamin D and bioavailable fraction, and 2) the potential role of insulin resistance in modulating the concentrations of bioavailable vitamin D. Design, Setting, and Patients or Other Participants: This was a cross-sectional study at a University Pediatric Department in which 63 obese children and 21 lean controls were enrolled.
Total 25-hydroxyvitamin D and vitamin D-binding protein were measured, two single-nucleotide polymorphisms in the coding region of the vitamin D-binding protein (rs4588 and rs7041) were studied, and the vitamin D bioavailable fraction was calculated.
Obese children showed total 25-hydroxyvitamin D levels lower compared with nonobese children (21.3 ± 6.7 ng/mL vs 29.6 ± 11.7 ng/mL; P = .0004). Bioavailable 25-hydroxyvitamin D levels were not different among the two groups (3.1 ± 1.6 ng/mL vs 2.6 ± 1.2 ng/mL; P > .05). Insulin-resistant children showed higher bioavailable levels of 25-hydroxyvitamin D compared with noninsulin-resistant children (3.4 ± 1.4 ng/mL vs 2.0 ± 0.9 ng/mL; P = .013) and an inverse correlation between insulin resistance and vitamin D-binding protein was found (r:= -0.40; P = .024).
Obese children present levels of bioavailable 25-hydroxyvitamin D similar to those of normal-weight children due to reduced concentration of vitamin D-binding protein. The insulin resistance could play a role in this reduced concentration.
研究维生素 D 水平与儿童肥胖的关系时，通常不考虑胰岛素对维生素 D 结合蛋白的影响，也不计算未结合的、有生物活性的维生素 D。
本研究旨在评估一组儿童 1）总 25-羟维生素 D 和生物可利用部分的浓度，2）胰岛素抵抗在调节生物可利用维生素 D 浓度中的潜在作用。设计、设置和患者或其他参与者：这是在大学儿科系进行的一项横断面研究，其中纳入了 63 名肥胖儿童和 21 名瘦对照。
测量总 25-羟维生素 D 和维生素 D 结合蛋白，研究维生素 D 结合蛋白编码区的两个单核苷酸多态性（rs4588 和 rs7041），并计算维生素 D 的生物可利用部分。
肥胖儿童的总 25-羟维生素 D 水平低于非肥胖儿童（21.3±6.7 ng/mL 比 29.6±11.7 ng/mL；P=0.0004）。两组间生物可利用的 25-羟维生素 D 水平无差异（3.1±1.6 ng/mL 比 2.6±1.2 ng/mL；P>0.05）。胰岛素抵抗儿童的生物可利用 25-羟维生素 D 水平高于非胰岛素抵抗儿童（3.4±1.4 ng/mL 比 2.0±0.9 ng/mL；P=0.013），并且发现胰岛素抵抗与维生素 D 结合蛋白呈负相关（r=-0.40；P=0.024）。
肥胖儿童的生物可利用 25-羟维生素 D 水平与正常体重儿童相似，这是由于维生素 D 结合蛋白浓度降低所致。胰岛素抵抗可能在这种浓度降低中起作用。
