Effect of 24,25-dihydroxyvitamin D3 on 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] metabolism in vitamin D-deficient rats infused with 1,25-(OH)2D3

Previous studies revealed that administration of 24,25-dihydroxyvitamin D3 [24,25-(OH)2D3] to calcium (Ca)-deficient rats causes a dose-dependent reduction in markedly elevated serum 1,25-(OH)2D3 level. Although the results suggested that the metabolism of 1,25-(OH)2D3 was accelerated by 24,25-(OH)2D3, those experiments could not define whether the enhanced metabolism of 1,25-(OH)2D3 played a role in the reduction in the serum 1,25-(OH)2D3 level. In the present study, in order to address this issue more specifically, serum 1,25-(OH)2D3 was maintained solely by exogenous administration through miniosmotic pumps of 1,25-(OH)2D3 into vitamin D-deficient rats. Thus, by measuring the serum 1,25-(OH)2D3 concentration, the effect of 24,25-(OH)2D3 on the MCR of 1,25-(OH)2D3 could be examined. Administration of 24,25-(OH)2D3 caused a dose-dependent enhancement in the MCR of 1,25-(OH)2D3, and 1 microgram/100 g rat.day 24,25-(OH)2D3, which elevated serum 24,25-(OH)2D3 to 8.6 +/- 1.3 ng/ml, significantly increased MCR and suppressed serum levels of 1,25-(OH)2D3. The effect of 24,25-(OH)2D3 on 1,25-(OH)2D3 metabolism developed with a rapid time course, and the recovery of iv injected [1 beta-3H]1,25-(OH)2D3 in blood was significantly reduced within 1 h. In addition, there was an increase in radioactivity in the water-soluble fraction of serum as well as in urine, suggesting that 1,25-(OH)2D3 is rapidly degraded to a water-soluble metabolite(s). Furthermore, the reduction in serum 1,25-(OH)2D3 was associated with a reduction in both serum and urinary Ca levels. Because the conversion of [3H]24,25-(OH)2D3 to [3H]1,24,25-(OH)2D3 or other metabolites was minimal in these rats, 24,25-(OH)2D3 appears to act without being converted into other metabolites. These results demonstrate that 24,25-(OH)2D3 rapidly stimulates the metabolism of 1,25-(OH)2D3 and reduces its serum level. It is suggested that 24,25-(OH)2D3 plays a role in modifying serum 1,25-(OH)2D3 concentrations by affecting the metabolism of 1,25-(OH)2D3 and may have a therapeutic values in the treatment of hypercalcemia or hypercalciuria caused by 1,25-(OH)2D3 excess.     

Effect of vitamin D2 and vitamin D3 on the serum concentrations of 1,25(OH)2D2, and 1,25(OH)2D3 in normal subjects

Serum concentrations of vitamin D2 and vitamin D3 metabolites were measured in 19 normal subjects before and during treatment with either vitamin D2 or vitamin D3, 4000 IU per day for 8 weeks. Vitamin D2 treatment increased the serum concentration of 1,25(OH)2D2, but a corresponding decrease in 1,25(OH)2D3 resulted in an unchanged serum concentration of total 1,25(OH)2D. During treatment with vitamin D3, the serum concentration of 1,25(OH)2D metabolites was unchanged. We conclude that the production of 1,25(OH)2D is tightly regulated and that 1 alpha-hydroxylase does not discriminate between D2 and D3 metabolites in normal subjects.     

1,25(OH)2-Vitamin D3Das Vitamin D-Hormon

Im Jahr 1650 wurde die seit dem Altertum bekannte Krankheit der Rachitis, die „Englische Krankheit”unter dem Namen „rickets” (englisch: H?cker) von Glisson als Entit?t beschrieben, ohne da? man ihre Ursache kannte. In den 20er Jahren wurde „Vitamin” D als fettl?sliche Substanz entdeckt, die Rachitis heilt, und es wurde beschrieben, da? Vitamin D in der Haut durch Sonneneinstrahlung gebildet wird. Die chemische Struktur wurde in den Jahren 1931/32 aufgekl?rt. Erst in 1969 und 1971 wurden zwei wichtige Hydroxylierungsschritte in Position 25 und 1 α beschrieben, die offensichtlich zur Aktivierung dieser Substanz n?tig waren. Schlie?lich wurde in den 70er Jahren ein Rezeptorprotein für Vitamin D biochemisch charakterisiert und 1987 wurde die Sequenz des Vitamin D-Rezeptors aufgekl?rt. Es handelt sich um ein Protein, das ganz eindeutig in die Familie der Steroidhormon-Rezeptoren einzugliedern ist. Aktuell wird zudem ein membranst?ndiger Rezeptor charakterisiert, der vermutlich die schnellen Effekte des Vitamin D-Hormons vermittelt. M?glicherweise handelt es sich dabei um das Annexin II. Insgesamt kennen wir somit drei spezifische Bindungsproteine für von Vitamin D ₃ abgeleitete Secosteroide: Das Vitamin D-bindende Protein im Serum, den membranst?ndigen Rezeptor und den klassischen intrazellul?ren Rezeptor (VDR). Sp?testens nach diesen Erkenntnissen wurde klar, da? es sich bei dem Secosteroid 1,25-Dihydroxy-Cholecalciferol nicht um ein Vitamin sondern um ein Hormon handelt und da? die vorher charakterisierten Vorstufen weitgehend inerte Vorl?ufer-Substanzen sind.      

Hypercalcaemia and elevated 1,25(OH)(2)D(3) levels associated with disseminated Mycobacterium avium infection in AIDS

Hypercalcaemia may complicate granulomatous diseases, such as tuberculosis and sarcoidosis, and various AIDS-related opportunistic infections and malignancies. We report here two patients with AIDS and disseminated Mycobacterium avium infection who developed symptomatic hypercalcaemia several weeks after commencing antimycobacterial chemotherapy, and in whom inappropriately elevated 1,25(OH)(2)D(3)levels were documented. Although vitamin D supplementation may have contributed, no other cause for the hypercalcaemia was found. The biochemical and clinical similarities between these cases and other hypercalcaemic granulomatous diseases suggest a common mechanism related to macrophage activation and dysregulated vitamin D production.     

Levels of 1,25(OH)2D3 for patients with pulmonary tuberculosis and correlations of 1,25(OH)2D3 with the clinical features of TB

Background

To determine the 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] concentrations to patients with tuberculosis (TB) and whether it influenced the patient’s clinical features.

Methods

For the first part, a total of 153 healthy adults and 74 patients with pulmonary TB (PTB) were enrolled. Serum concentrations of 1,25(OH)2D3 were determined by liquid chromatography-tandem mass spectroscopy to examine the 1,25(OH)2D3 concentrations of the two groups from the peripheral blood. If there are differences between the two groups, what follow will increase the experimental group numbers to examine the relationship among the 1,25(OH)2D3 concentrations with the numbers of the lesion area, the tubercule bacilli in sputum and the CD4/CD8 ratio of T lymphocytes in the peripheral blood.

Results

In the first part, the 1,25(OH)2D3 concentrations was lower in patients with TB than in those healthy adults [365.9 (SD 235.7) vs. 464.3 (SD 335.6), P<0.05]. In the second part, we increased the sample size to 134 (male 91 cases, female 43 cases). we found that the plasma levels of 1,25(OH)2D3 are not correlated with the numbers of the lesion area and the tubercule bacilli in sputum, but the 1,25(OH)2D3 levels can interact the ratio of CD4/CD8 T lymphocytes, it shows a positive correlation with the ratio of CD4/CD8 T lymphocytes.

Conclusions

The 1,25(OH)2D3 concentrations in TB patients lower than the healthy adults, it might exist as a risk factor during the development of TB or TB might affect the levels of 1,25(OH)2D3. But the different status vitamin D concentration might not affect the numbers of the lesion area, the tubercule bacilli in sputum. It shows a positive correlation with the ratio of CD4/CD8 T lymphocytes. The study will have a significance value to clinical medicine, but further study will need to study the levels of 1,25(OH)2D3 with the TB.     

1,25-Dihydroxyvitamin D3 [1,25-(OH)2D3] increases insulin-like growth factor I (IGF-I) receptors in clonal osteoblastic cells. Study on interaction of IGF-I and 1,25-(OH)2D3

We previously reported a cooperative effect between insulin-like growth factor I (IGF-I) and 1,25-dihydroxy-vitamin D3 [1,25-(OH)2D3] in murine clonal osteoblastic cells, MCT3T3-E1. In the present study, the possible mechanism of interaction between these hormones was investigated. The effect of IGF-I on 1,25-(OH)2D3 receptors in MC3T3-E1 cells was examined. The affinity and hormone binding capacity of 1,25-(OH)2D3 receptors were not altered by IGF-I. Immunoblot analysis showed about 54 kilodaltons (kDa) 1,25-(OH)2D3 receptors, similar to that observed for mouse fibroblasts. The synthesis of IGF-I by the cells under a serum-free condition was determined by RIA. The assay revealed immunoreactive IGF-I secreted by MC3T3-E1 cells (1.79 +/- 0.04 x 10(-9) M, mean +/- SE, n = 5). Rat GH significantly increased the concentration of IGF-I, but 1,25-(OH)2D3 did not. IGF-I radioligand-receptor assay revealed specific binding of IGF-I to MC3T3-E1 cells. The relative potency of IGF-I-related peptides to bind with the cells was in the order of IGF-I much greater than multiplication-stimulating activity (the rat homologue of IGF-II) greater than insulin, and the receptor protein migrated as a 130-kDa band in autoradiography. Scatchard analysis showed a significant increase in IGF-I binding sites by 50% after 3-day treatment with 5 x 10(-11) M 1,25-(OH)2D3, without any change in affinity. These results indicate that the interaction of IGF-I and 1,25-(OH)2D3 in the culture of MC3T3-E1 cells may be mediated by the effect of 1,25-(OH)2D3 on IGF-I receptors.     

Regulation of rat ileal NHE3 by 1,25(OH)2-vitamin D3

We have previously demonstrated a modulation of Na⁺/H⁺ exchange (NHE) activity by vitamin D₃ in the rat ileum and Caco-2 cells. However, the molecular mechanism(s) of action of vitamin D₃ on NHE are still not understood. The current studies were undertaken to understand the regulation of individual NHE isoforms on mRNA levels in two distinct models of vitamin D₃ deficiency. Acute D₃ deficiency was induced secondary to streptozotocin-induced diabetes mellitus, while chronic D₃ deficiency was induced by feeding a D₃-deficient diet in an environment devoid of fluorescent light. Vitamin D₃ deficiency in both models increased the initial rates of rat ileal brush-border membrane (BBM) Na⁺/H⁺ exchange by 2.5-fold compared to D-repleted controls. In parallel to the increased exchanger activity, NHE3 mRNA abundance was increased about twofold in both acute and chronic D deficiency compared to control. There was no change in NHE1 or NHE2 abundance in vitamin D₃-deficient rat ileum. These findings indicate that vitamin D₃ regulates Na⁺/H⁺ exchange activity in rat ileum by influencing the mRNA levels of NHE3, the predominant luminal membrane isoform involved in vectorial Na⁺ transport.     

血清25羟维生素D3或1,25二羟维生素D3水平与慢性阻塞性肺疾病关系的Meta分析

目的：系统评价血清25(OH)D3或1,25(OH)2 D3与 COPD 相关病例对照研究,进一步明确血清维生素 D 水平与 COPD 之间的关系。方法计算机检索 PubMed、EMBASE、The Cochrane Library、中国生物医学文献数据库(CBM)、中国知网(CNKI)数据库、万方数据库、维普数据库,并辅以文献追溯的方法,收集国内外发表的相关病例对照研究,检索时间均从建库至2015年11月。2位研究者按纳入排除标准筛选文献并评价纳入研究质量,应用 RevMan 5.2软件进行 Meta 分析。结果共纳入15篇病例对照研究,包含1948例 COPD患者及1549例健康对照者。25(OH)D3浓度水平结果：Meta分析结果表明无论是急性加重期 COPD还是稳定期 COPD,与健康对照组相比,其25(OH)D3浓度水平差异均有统计学意义,COPD组25(OH)D3浓度低于健康对照组。急性加重期组vs对照组,WMD=-14.28,95%CI =(-23.82~-4.73),Z=2.93,P <0.01;稳定期组vs对照组 WMD=-4.46,95%CI =(-7.36~-1.57),Z=3.02,P <0.01;急性加重期与稳定期相比,25(OH)D3浓度水平差异亦有统计学意义[WMD=-2.66,95%CI =(-4.19~-1.12), Z=3.38,P<0.01,见图2];1,25(OH)2 D3浓度水平结果：Meta分析结果表明无论是急性加重期COPD还是稳定期 COPD,与健康对照组相比,其1,25(OH)2 D3浓度水平差异均有统计学意义, COPD组1,25(OH)2 D3浓度低于健康对照组。急性加重期组vs对照组,WMD=-15.09,95%CI =(-17.97~-12.22),Z =10.3,P <0.01;稳定期组 vs 对照组,WMD=-9.62,95%CI =(-12.55~-6.70),Z=3.02,P<0.01。结论 COPD患者体内25(OH)D3与1,25(OH)2 D3浓度水平均显著降低,维生素D缺乏可能参与COPD的发生、发展,并影响COPD患者的预后。     

Systemic cardiovascular disease in uremic rats induced by 1,25(OH)2D3

OBJECTIVE: Vitamin D may contribute to cardiovascular disease in the absence of hypercalcemia in patients with chronic kidney disease. METHODS: We investigated the effects of long-term (6-week) treatment with 1,25(OH)2D3, at a non-hypercalcemic dosage (0.25 microg/kg per day per orally) in 5/6 nephrectomized rats: (i) vehicle-treated, sham-operated rats; (ii) 1,25(OH)2D3-treated, sham-operated rats; (iii) vehicle-treated, 5/6 nephrectomized rats; and (iv) 1,25(OH)2D3-treated, 5/6 nephrectomized rats. RESULTS: Creatinine clearance after 6 weeks was significantly lower and parathyroid hormone levels were significantly higher in 1,25(OH)2D3-treated uremic rats, compared with uremic controls (P < 0.01). Serum calcium levels, as well as the calcium-phosphorus product, did not differ between both groups. Mean systolic blood pressure in 1,25(OH)2D3-treated animals was significantly increased, compared with vehicle (each P < 0.01). In addition, 1,25(OH)2D3-treated uremic animals showed left ventricular hypertrophy. Diffuse aortic calcification involving the intima and media layer occurred in 1,25(OH)2D3-treated uremic animals, but not in other groups. The mean aortic wall area and lumen area were increased two-fold in 1,25(OH)2D3-treated uremic animals compared with vehicle (P < 0.01), whereas the wall/lumen ratio remained unchanged, indicating fusiform aneurysm formation. CONCLUSIONS: Hypertension, left ventricular hypertrophy, aortic calcification, and aneurysm, without hypercalcemia, occurred in 1,25(OH)2D3-treated, 5/6 nephrectomized rats. These data indicate a permissive effect of uremia for cardiovascular damage induced by non-hypercalcemic doses of 1,25(OH)2D3.     

Pivotal role of peroxisome proliferator-activated receptor gamma (PPARgamma) in regulation of erythroid progenitor cell proliferation and differentiation

OBJECTIVE: The aim of this study was to reveal the role of peroxisome proliferator-activated receptor gamma (PPARgamma) in erythropoiesis. METHODS: The effects of PPARgamma ligands on cellular proliferation and differentiation were investigated in erythroid colony-forming cells (ECFCs) purified from human peripheral blood. RESULTS: RT-PCR analysis revealed that PPARgamma mRNA is expressed in ECFCs. Synthetic PPARgamma ligands, troglitazone or pioglitazone, suppressed cellular proliferation without inducing apoptosis and delayed maturation of ECFCs, as determined by flow cytometry. The delay in erythroid maturation by troglitazone was confirmed by the down-regulation of gamma-globin, beta-globin and GATA-1 mRNA, and the maintenance of GATA-2 mRNA. CONCLUSIONS: Our results suggest that PPARgamma modulates the differentiation process of erythroid progenitor cells, and plays a crucial role in regulating the balance of hematopoiesis.     

1,25-二羟基维生素D3对小鼠成骨细胞增殖的影响

目的 检测1,25-二羟基维生素D3[1,25(OH)2D3]对小鼠成骨细胞增殖及细胞周期的影响及其意义.方法 取出生24 h内的小鼠30只,无菌条件下取出颅骨,应用酶消化法进行成骨细胞培养,在培养液中加入不同浓度的1,25(OH)2Ds(10-8、10-9、10-11 mol/L),应用四唑蓝比色法(MTT)法检测其对成骨细胞增殖的影响,应用流式细胞仪检测其对成骨细胞细胞周期的影响.结果 小鼠成骨细胞在1,25(OH)2D3处理的24、48、72 h,10-8、10-9mol/L组与对照组吸光度(A)相比较,差异有统计学意义(P＜0.01),10-11mol/L组与对照组A比较,差异无统计学意义(P＞0.05);1,25(OH)2D3作用下小鼠成骨细胞S期(8.00±1.42)、G2-M期(7.70±0.67)的细胞减少,G1期(84.30±1.90)细胞增加. 结论 1,25(OH)2D3可以抑制体外培养的小鼠成骨细胞的增殖,并呈现一定的浓度依赖性.     

Ribozyme knockdown functionally links a 1,25(OH)2D3 membrane binding protein (1,25D3-MARRS) and phosphate uptake in intestinal cells

We used a ribozyme loss-of-function approach to demonstrate that the protein product of a cDNA encoding a multifunctional membrane-associated protein binds the seco-steroid 1,25(OH)(2)D(3) and transduces its stimulatory effects on phosphate uptake. These results are paralleled by studies in which the ability of the hormone to stimulate phosphate uptake in isolated chick intestinal epithelial cells is abolished by preincubation with Ab099 directed against the amino terminus of the protein. We now report the complete sequence of the cloned chicken cDNA for the 1,25D(3)-MARRS (membrane-associated, rapid-response steroid-binding) protein and reveal it to be identical to the multifunctional protein ERp57. Functional studies showed that active ribozyme, but not a scrambled control, decreased specific membrane-associated 1,25(OH)(2)D(3) binding, but did not affect binding to the nuclear receptor for 1,25(OH)(2)D(3). Seco-steroid-dependent stimulation of protein kinase C activity was diminished as 1,25D(3)-MARRS protein levels were reduced in the presence of the ribozyme, as judged by Western blot analyses. Phosphate uptake in isolated cells is an index of intestinal phosphate transport that occurs during growth and maturation. Whereas cells and perfused duodena robustly responded to 1,25(OH)(2)D(3) in preparations from young birds, older animals no longer responded with stimulated phosphate uptake or transport. The age-related decline was accompanied by a decrease in 1,25D(3)-MARRS mRNA that was apparent up to 1 year of age. Together, these studies functionally link phosphate transport in the chick duodenum with the 1,25D(3)-MARRS protein and point to a previously uncharacterized role for this multifunctional protein class.     

Action of 1,25-(OH)2D3 in nude mice bearing transplantable human myelogenous leukemic cell lines

After cyclophosphamide priming, subcutaneously (s.c.) transplanted cells from established human leukemia cell lines U937, K562, or HL-60 consistently yielded single, nonmetastatic tumors. Tumorigenesis with KG-1 cells was inconstant. Within each cell line, cytologic, electron-microscopic, cytogenetic, isoenzyme, immunochemical, and enzyme cytochemical studies confirmed identity of cultured and tumor cells. Adenosine triphosphatase reactivity was limited to leukemic cells in vivo. Isoenzyme electrophoretic patterns, distinct for each cell line, provided a reliable criterion to establish clonality and to verify tumor cell origin. Antitumor activity of the active vitamin-D3 metabolite 1,25-(OH)2D3 was assessed in vivo against U937, K562, and HL-60 cells by cell transplantation and concurrent s.c. contralateral implantation of miniosmotic pumps containing the 1,25-(OH)2D3 in a propylene glycol vehicle. Tumors developed in all treated U937 mice, 50% with K562 and 25% bearing HL-60 transplants. All transplants proliferated in mice either with pumps containing only vehicle or no pumps. Coincidence of tumor and vehicle decreased survival time. No differences in cytoreactivities or morphology were apparent between cultured cells and tumor cells in treated or untreated mice. This nude mouse system is useful for in vivo studies of human myelogenous leukemia cells. Implanted miniosmotic pumps provide controlled delivery of antineoplastic agents and their vehicles for in vivo studies. 1,25-(OH)2D3 may be a valuable adjunctive therapeutic for control of human myelogenous leukemias.     

乙肝后肝硬化患者血清1,25(OH)2D3检测及其临床意义

采用竞争性放射受体法测定３２例乙肝后肝硬化患者血清１Ｍ２５（ＯＨ）２Ｄ３水平,并与３２例性乙型肝炎、３１例健康者对照。发现：肝硬化组血清１,２５（ＯＨ）２Ｄ３水平较肝炎组和对照组明显下降（Ｐ〈０．０１,Ｐ〈０．００１）,且与血清骨钙素、尺桡密度呈正相关（Ｐ〈０．０１,Ｐ〈０．０５）。提示：测定乙肝后肝硬化患者血清１,２５（ＯＨ）２Ｄ３水平有利于肝性骨病的早期发现。