维生素D分子机制及其与成纤维生长因子23、Klotho 相关性的新进展

维生素D（ VD）的经典作用为调节钙磷和骨代谢,同时还与免疫系统、细胞增殖和分化等有重要联系。1α,25－羟基维生素D（1,25（OH）D）配体结合维生素D受体（VDR）引发VDR与维甲酸X受体（RXR）紧密结合,且配体结合的VDR－RXR异二聚体识别VD调控基因序列中的维生素D应答元件（VDREs）。虽然1,25（OH）D－VDR可通过非基因机制快速发挥作用,但1,25（OH）D－VDR主要通过基因机制实现功能。1,25（OH）D－VDR可控制基因转录,VD配体、VDRE的DNA序列以及招募的共激活因子／共阻遏因子都能影响基因表达。1,25（OH）D－VDR调节基因的VDREs具有重要功能。通过推测RANKL基因染色质成环模型表明DNA成环和染色质的结构在VD调节基因表达的作用中发挥主要作用。1,25（OH）D－VDR调节基因表达可以延缓衰老和老年性疾病,比如癌症、2型糖尿病和心血管疾病。针对VD在磷酸盐代谢与衰老方面的关系已有了新的认识,认为1,25（OH）D－VDR诱导的骨骼中FGF23和肾脏中Klotho蛋白在该代谢途径中发挥重要作用,VD调节磷酸盐稳态可能是延缓衰老及相关慢性疾病的机制。     

Perturbation of Fgf10 signal pathway in mouse embryonic palate by dexamethasone and vitamin B12 in vivo

Background/Purpose

The Fgf10 signaling pathway plays an important role in early stages of mouse embryonic palatal development, which is associated with cell proliferation and differentiation. The objective of this study was to assess whether dexamethasone and vitamin B₁₂ affected the Fgf10 signal pathway of mouse embryonic palate.

Materials and Methods

Immunohistochemical studies were performed for expression of Fgf10, Fgfr2b, and sonic hedgehog and for cell proliferation and apoptosis of mouse embryonic palate.

Results

The expression of Fgf10, Fgfr2b, and sonic hedgehog was changed in mouse embryonic palate after dexamethasone and vitamin B₁₂ treatment, resulting in reduced and restored proliferation of mesenchymal cells.

Conclusions

Dexamethasone and vitamin B₁₂ affected the Fgf10 signaling pathway and cell proliferation of mouse embryonic palate. Cell apoptosis was not altered after dexamethasone and vitamin B₁₂ exposure.     

Persistent high level of fibroblast growth factor 23 as a cause of post-renal transplant hypophosphatemia

Post-transplant hypophosphatemia is a highly prevalent problem, and fibroblast growth factor 23, a newly discovered phosphatonin, has recently been reported to be involved in its pathogenesis. We report a 52-year-old Japanese woman who received a living-related kidney transplant and showed severe hypophosphatemia immediately after transplantation. We suspected that fibroblast growth factor 23 was the main cause of this hypophosphatemia and investigated its levels longitudinally after the transplantation. The patient showed persistently high levels of fibroblast growth factor 23, with suppressed 1,25-dihydroxyvitamin D and parathyroid hormone. She recovered from the hypophosphatemia when fibroblast growth factor returned to its reference level half a year after the transplantation. We conclude that a persistently high level of fibroblast growth factor 23 is an important cause of post-transplant hypophosphatemia, other than hyperparathyroidism, a previously noted cause.     

Vitamin D receptor gene polymorphism,bone mass,body size,and vitamin D receptor density

We determined vitamin D receptor (VDR) gene alleles (based on the BsmI restriction site polymorphism), duodenal mucosal receptor density, bone mass at spine and total body, and body size in 32 healthy premenopausal females. While we found no relationship between allele and receptor density in duodenal mucosa, bone mineral content (BMC) at both spine and total body was significantly associated with VDR gene alleles. BMC was highest for the bb allele, lowest for BB, and intermediate for Bb. A similar association was noted between allele and body size variables, particularly weight. When BMC was adjusted for body weight, the association with VDR polymorphism disappeared. The VDR gene polymorphism may be affecting bone mass not through classical nutritional mechanisms (e.g., intestinal calcium absorption), but through an influence on body size.     

维生素D类药物及其类似物的研发进展

维生素D3对于预防骨骼疾病、肌肉无力、自身免疫性疾病以及某些类型的癌症是必不可少的。维生素D3通过其代谢产物1α,25-二羟基维生素D_3[1,25(OH)_2D_3]充当转录因子维生素D受体(VDR)的有效激动剂。因此维生素D直接影响众多基因组位点及其靶组织的染色质结构和基因调控。近年来单独或组合修饰1,25(OH)_2D_3的侧链、A环、三烯系统或C环以及非甾体模拟物,均获得了多种有效的VDR激动剂和拮抗剂。目前为止,近150个VDR配体与各种维生素D类似物结合体的晶体结构已被逐渐阐明,使得这些化合物的作用机理明确至分子水平。本文综述了过去10年、尤其是近5年提出的重要维生素D类似物以及从有关VDR蛋白的新结构信息中得出的化合物分子水平的作用机理。     

小剂量维生素D受体激活剂(骨化三醇)对血液透析患者血钙及血磷和成纤维细胞生长因子23的影响

目的 探讨小剂量维生素D受体激活剂(骨化三醇)对血液透析患者血钙、血磷和成纤维细胞生长因子23的影响.方法 20例血液透析患者应用骨化三醇(每天0.25μg)治疗,分别于用药前、用药4、8周观察患者血钙、血磷、碱性磷酸酶、全段甲状旁腺激素和成纤维细胞因子23水平.结果 用药4周和8周后患者血钙明显上升(但尚未超过正常范围),与治疗前比较差异有统计学意义(P＜0.01);用药4周和8周后血磷有所下降,但与治疗前比较差异无统计学意义(P＞0.05);用药4周和8周后血碱性磷酸酶明显下降,与治疗前比较差异有统计学意义(P＜0.01);用药4周后血全段甲状旁腺激素有所下降,但与治疗前比较差异无统计学意义(P＞0.05);用药4周和8周后血成纤维细胞因子23明显升高,与治疗前比较差异有统计学意义(P＜0.01).结论 小剂量维生素D受体激活剂(骨化三醇)对维持性血液透析患者具有升高血钙、抑制碱性磷酸酶并升高成纤维细胞生长因子23的作用.     

Conditional Deletion of Murine Fgf23: Interruption of the Normal Skeletal Responses to Phosphate Challenge and Rescue of Genetic Hypophosphatemia

The transgenic and knockout (KO) animals involving Fgf23 have been highly informative in defining novel aspects of mineral metabolism, but are limited by shortened lifespan, inability of spatial/temporal FGF23 control, and infertility of the global KO. To more finely test the role of systemic and genetic influences in FGF23 production, a mouse was developed that carried a floxed (“f”)‐Fgf23 allele (exon 2 floxed) which demonstrated in vivo recombination when bred to global‐Cre transgenic mice (eIIa‐cre). Mice homozygous for the recombined allele (“Δ”) had undetectable serum intact FGF23, elevated serum phosphate (p < 0.05), and increased kidney Cyp27b1 mRNA (p < 0.05), similar to global Fgf23‐KO mice. To isolate cellular FGF23 responses during phosphate challenge, Fgf23^Δ/f mice were mated with early osteoblast type Iα1 collagen 2.3‐kb promoter‐cre mice (Col2.3‐cre) and the late osteoblast/early osteocyte Dentin matrix protein‐1‐cre (Dmp1‐cre). Fgf23^Δ/f/Col2.3‐cre⁺ and Fgf23^Δ/f/Dmp1‐cre⁺ exhibited reduced baseline serum intact FGF23 versus controls. After challenge with high‐phosphate diet Cre^– mice had 2.1‐fold to 2.5‐fold increased serum FGF23 (p < 0.01), but Col2.3‐cre⁺ mice had no significant increase, and Dmp1‐cre⁺ mice had only a 37% increase (p < 0.01) despite prevailing hyperphosphatemia in both models. The Fgf23^Δ/f/Col2.3‐cre was bred onto the Hyp (murine X‐linked hypophosphatemia [XLH] model) genetic background to test the contribution of osteoblasts and osteocytes to elevated FGF23 and Hyp disease phenotypes. Whereas Hyp mice maintained inappropriately elevated FGF23 considering their marked hypophosphatemia, Hyp/Fgf23^Δ/f/Col2.3‐cre⁺ mice had serum FGF23 <4% of Hyp (p < 0.01), and this targeted restriction normalized serum phosphorus and ricketic bone disease. In summary, deleting FGF23 within early osteoblasts and osteocytes demonstrated that both cell types contribute to baseline circulating FGF23 concentrations, and that targeting osteoblasts/osteocytes for FGF23 production can modify systemic responses to changes in serum phosphate concentrations and rescue the Hyp genetic syndrome. © 2016 American Society for Bone and Mineral Research.     

哈尔滨地区部分汉族人群维生素D受体Bsm I基因多态性与骨质疏松性骨折关系的研究

目的旨在了解哈尔滨地区部分汉族人群维生素D受体(VDR)BsmⅠ基因多态性与骨质疏松性骨折患者骨密度(BMD)的相关关系。方法98例研究对象按骨质疏松性骨折诊断标准分2组,骨量正常组:48人;骨质疏松性骨折组:50人。聚合酶链反应限制性片断长度多态性(PCR-RFLP)技术检测98例受试者VDRBsmⅠ基因型。测试受试者腰椎2～4(L2-4),股骨颈(Neck)、大转子(Troch)、Wards三角、桡骨远端(Radius)5个部位骨密度(BMD)。结果骨折组各部位骨密度均显著低于对照组各部位骨密度,差异具有显著性(P<0.01)。受试者VDR基因型未发现BB型,检出Bb型16人,占16.3%,bb型82人,占83.7%。b和B等位基因频率分别为91.8%、8.2%,Bb、bb两基因型在两组之间的分布无差异;VDR两基因型与各部位BMD之间,虽然在腰椎2～4、股骨颈、大转子和桡骨远端等4个部位Bb基因型比bb基因型的BMD高,但结果没有统计学意义。结论这组哈尔滨地区人群VDR基因型分布以bb型、Bb型为主,VDR基因BsmⅠ多态性与骨密度之间没有相关关系。     

Distinct association of gene polymorphisms of estrogen receptor and vitamin D receptor with lumbar spondylosis in post-menopausal women

Contribution of genetic backgrounds to the etiology of lumbar spondylosis has been suggested by epidemiological studies. This study was designed to determine the association of restriction fragment length polymorphisms (RFLPs) of estrogen receptor (ER), vitamin D receptor (VDR), parathyroid hormone (PTH) and interleukin-1β (IL-1β) genes with the radiological severity of lumbar spondylosis at the disk level from L1/2 to L5/S1 in Japanese post-menopausal women. ER and VDR RFLP haplotypes were associated with the severity of spondylosis in the upper levels (L1/2 and L2/3) more than in the lower levels. Association of ER genotype was more pronounced in the group younger than average than in the older group, while that of VDR genotype was more significant in the older group. Neither PTH nor IL1-β RFLP was associated with the severity at any levels in either stratified group. We thus conclude that ER and VDR genes may contribute to lumbar spondylosis in a distinct manner: estrogen sensitivity influences the severity in the early phase after menopause while vitamin D plays an important role at older ages when the contribution of estrogen loss is weaker.     

Susceptibility for Postmenopausal Osteoporosis: Interaction Between Genetic,Hormonal and Lifestyle Factors

Although previous studies have established the importance of genetic, hormonal and lifestyle factors separately, the integral role of these factors on bone mass in postmenopausal women is still controversial. We examined the association of the collagen 1-alpha-1 gene (COLIA1) and vitamin D receptor gene (VDR) polymorphisms, s-IGF-I, s-25OHD and lifestyle factors with bone mineral density (BMD) in postmenopausal women. We determined anthropometric parameters, lifestyle factors, serum levels of IGF-I and 25OHD, the COLIA1 Sp1 (Mscl) and VDR (Bsml, Taql) polymorphisms by PCR and BMD by dual X-ray absorptiometry in 141 ambulatory postmenopausal Spanish women. There were significant linear correlations between S-25OHD and BMD and between s-IGF-I and BMD. BMD was statistically higher in active subjects. Of the three different polymorphisms, only the COLIA1 Sp1 polymorphism was significantly associated with BMD. In the logistic regression model, the COLIA1 Sp1 polymorphism, S-25OHD, s-IGF-I and physical activity variables were independently associated with osteoporosis. Our study shows that COLIA1 Sp1 polymorphism, S-25OHD and s-IGF-I serum levels and physical activity are independently associated with BMD in postmenopausal Spanish women.     

Hormonal regulation of vitamin D receptor levels and osteocalcin synthesis in human osteosarcoma cells

1,25(OH)₂D₃ was found to regulate its own receptor levels via an increase in corresponding mRNA levels in human osteoblast-like osteosarcoma cells (MG-63). In addition, exposure of the cells for 24h to dexamethasone, estradiol, retinoic acid, or triiodothyronine resulted in a dose-dependent accumulation of hVDR mRNA. Combination of 1,25(OH)₂D₃ with any other hormone used in this study did not result in an additive increase in hVDR mRNA levels. Progesterone or dihydrotestosterone did not influence hVDR mRNA levels. Of the studied hormones, only 1,25(OH)₂D₃ was alone able to stimulate the synthesis and secretion of osteocalcin. Compared with 1,25(OH)₂D₃, the combination of 1,25(OH)₂D₃ and retinoic acid resulted an increased synthesis of osteocalcin. In contrast, the combination of 1,25(OH)₂D₃ with dexamethasone, estradiol, or triiodothyronine diminished the stimulatory effect of 1,25(OH)₂D₃. A complex interaction of several different hormone receptors seems to occur within the regulatory regions of hVDR and osteocalcin genes, or at the level of translation, resulting, in each case, a finely adjusted vitamin D receptor and osteocalcin expression.     

Genetic regulation of bone mass: from bone density to bone strength

Osteoporosis is a common disease characterized in adults by diminished bone density. Bone is an organ that evolves and grows throughout life, and establishing optimal bone density in childhood and adolescence serves to buffer bone loss later in life. Bone density, a measurable entity, is the clinical substitute for bone strength, or the ability to defend against fracture. Chronic diseases may adversely affect optimal peak bone density. Bone density is under genetic control, as revealed by three lines of investigations. These include (1) the finding of quantitative trait loci for bone density, (2) the finding that specific mutations in genes that are important in the development of osteoblast or osteoclast lineages alter bone density, and (3) the linkeage of known polymorphisms for genes involved in mineral homeostasis to bone density and/or fracture. Future therapeutics for improving peak bone density or delaying bone loss later in life may take advantage of the genetic nature of bone density development.This work was presented in part at the IPNA Seventh Symposium on Growth and Development in Children with Chronic Kidney Disease: The Molecular Basis of Skeletal Growth, 1–3 April 2004, Heidelberg, Germany     

维生素D受体基因Apa I多态性与骨质疏松症相关性的研究

目的研究维生素D受体（vitamin Dreceptor,VDR）基因ApaⅠ多态性与原发性骨质疏松症的相关性。方法应用聚合酶链反应-限制性片段长度多态性分析技术测定山东半岛地区155例骨质疏松患者和113例对照者维生素D受体基因ApaⅠ多态性,比较两组基因型和等位基因分布频率。结果两组基因型和等位基因差异有显著性（P〈0.05）。男性及〈65岁骨质疏松组同相应对照组相比差异无显著性,女性及≥65岁骨质疏松组同相应对照组相比差异有显著性（P〈0.05）;≥65岁女性骨质疏松组aa基因型与a等位基因频率高于其对照组。结论山东半岛地区汉族人群中,维生素D受体基因ApaⅠ多态性与原发性骨质疏松症存在相关性,65岁及以上女性a等位基因是易感基因,aa基因型个体存在易感性。     

上海地区汉人维生素D受体基因多态性与骨密度关系的初步分析

目的：了解维生素D受体（VDR）基因多态性在中国人群中的分布，并进一步研究其与骨密度的关系。方法：通过聚合酶链反应－限制性片段长度多态性（PCR－RFLP）方法分析了348例无亲缘关系的上海地区男女居民的VDR基因型，并用双能X线吸收仪测定了其中202例骨密度。结果：348例研究对象中bb型占81．9％，Bb型占18．1％，未见到BB型。b等位基因在本组人群中分布 高达90．0％。男女性之间VDR基因型分布频率无明显区别（P＞0．5）。比较这两组各部位的骨密度值，只有女性在华氏三角区部位显示出Bb型比bb型有较高的BMD，在其余部位，不管男性还是女性，两组基因型的BMD均差异无显性（P＞0．05）。结论：VDR基因多态性与骨密度无相关关系。     

Relationship between selection of dosage forms of vitamin D receptor activators and short-term survival of patients on hemodialysis

BackgroundThe benefits of vitamin D receptor activators (VDRAs) for patients with chronic kidney disease are well recognized. However, the optimal criteria for patient selection, dosage forms, and duration providing the highest benefit and the least potential risk remain to be confirmed.Materials and methodsThe study population was derived from the Aichi Cohort Study of Prognosis in Patients Newly Initiated into Dialysis, a multicenter prospective cohort study of 1520 incident dialysis patients. According to the VDRA usage status in March 2015 (interim report), the 967 patients surviving after March 2015 were classified into three groups: without VDRA (NV, n = 177), oral VDRA (OV, n = 447), and intravenous VDRA (IV, n = 343). Mortality rates were compared using the log-rank test, and factors contributing to all-cause mortality were examined using both univariate and multivariate Cox proportional hazard regression analyses.ResultsThere were 104 deaths (NV, n = 27; OV, n = 53; IV, n = 24) during the follow-up period (1360 days, median), and significant differences in cumulative survival rates were observed between the three groups (p = 0.010). Moreover, lower all-cause mortality was associated with IV versus NV (hazard ratio, 0.46 [95% confidence interval 0.24–0.89]; p = 0.020).ConclusionThis study demonstrated the impact of the VDRA dosage form on the short-term survival of incident hemodialysis patients during the introduction period. Our results suggest that relatively early initiation of intravenous VDRA in patients beginning hemodialysis may have some clinical potential.     

广州汉族成年人维生素D受体基因分布及其与骨密度关系的研究

目的　了解中国广州地区人群VDR基因多态性的分布及其与骨密度的关系。方法　选取居住广州地区的汉族成年人 396例。应用PCR RFLP等生物学技术检测VDR基因 ,用双能X线骨密度仪 (DEXA)对入选的大部分对象进行了全身、腰推正侧位 ,股骨近端BMD检测。结果　VDR基因分布频率是BB 6 5 %、Bb 4 8 2 %、bb 4 5 3% ;本组对象峰值骨量出现在 30～ 39岁组 ,并且以Bb基因型的BMD值最高 ;3种基因型按BMD大小排列顺序为 :Bb >BB >bb ,但只有Bb与bb两基因型的BMD存在着差异。结论　①VDR基因多态性与种族、居住地区和人群不同有关。②峰值骨量出现在 30～39岁组 ,以Bb基因型对应较高的BMD ,bb基因型对应较低的BMD。③VDR基因型与BMD间存在着关联 ,但对其骨质疏松相对高危人群的预测价值有待进一步的深入研究。