Department of Gastroenterology, Human Nutrition and Internal Medicine, Poznan University of Medical Sciences, Poland.
Institute of Human Genetics, Polish Academy of Sciences, Poznań, Poland.
Adv Clin Exp Med. 2019 Jul;28(7):955-960. doi: 10.17219/acem/97376.
A common feature in the etiology of inflammatory bowel disease (IBD) and osteoporosis is a complex genetic background. Moreover, it has been shown that some of the susceptibility loci overlap for both diseases. One of the genes that may be involved in the pathogenesis of IBD as well as decreased bone mass is the vitamin D receptor (VDR) gene.
The aim of this study was to investigate the association of the TaqI polymorphism (rs731236, c.1056T >C) in the VDR gene with serum vitamin D concentration and bone mineral density (BMD) in patients with IBD.
A total of 172 IBD patients (85 with Crohn's disease (CD) and 87 with ulcerative colitis (UC)) and 39 healthy controls were enrolled in the study. Polymorphism was determined with polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP). Bone mineral density was measured at the lumbar spine (L2-L4) and the femoral neck (FN) using dual-energy x-ray absorptiometry (DEXA). Serum concentrations of 25-hydroxyvitamin D were determined using electrochemiluminescence binding assay (ECLIA).
Our studies revealed that serum vitamin D concentration in IBD patients was not lowered in comparison with healthy controls. Patients with CD presented more advanced osteopenia and osteoporosis. Individuals with UC carrying the TaqI tt genotype of VDR gene showed significantly higher FN BMD than carriers of TT and Tt genotypes (p = 0.02). Moreover, tt genotype was present with higher frequency in UC patients than in controls and CD patients (23% vs 7.7% and 16.5%, respectively).
The tt genotype may have a protective effect on BMD in UC patients.
炎症性肠病（IBD）和骨质疏松症的病因有一个共同的特点，就是存在复杂的遗传背景。此外，已经表明这两种疾病的一些易感基因座存在重叠。维生素 D 受体（VDR）基因可能参与 IBD 以及骨量减少的发病机制。
本研究旨在探讨 VDR 基因 TaqI 多态性（rs731236，c.1056T>C）与 IBD 患者血清维生素 D 浓度和骨密度（BMD）的关系。
共纳入 172 例 IBD 患者（85 例克罗恩病（CD）和 87 例溃疡性结肠炎（UC））和 39 名健康对照者。采用聚合酶链反应（PCR）和限制性片段长度多态性（RFLP）方法检测多态性。采用双能 X 线吸收法（DEXA）测定腰椎（L2-L4）和股骨颈（FN）的骨密度。采用电化学发光结合测定法（ECLIA）测定血清 25-羟维生素 D 浓度。
我们的研究表明，与健康对照组相比，IBD 患者的血清维生素 D 浓度并未降低。CD 患者表现出更严重的骨质疏松症和骨质疏松症。携带 VDR 基因 TaqI tt 基因型的 UC 患者的 FN BMD 明显高于 TT 和 Tt 基因型携带者（p=0.02）。此外，UC 患者的 tt 基因型比对照组和 CD 患者更常见（23%比 7.7%和 16.5%）。
tt 基因型可能对 UC 患者的 BMD 有保护作用。
