Serum vitamin D metabolites in younger and elderly postmenopausal women

Summary Previous investigations have suggested that a lower-than-normal serum 1,25(OH)₂D is found in elderly women with postmenopausal osteoporosis. We examined the fundamental aspects of this theory by investigating serum vitamin D metabolites infour representative samples of Caucasian women. These included 44 early postmenopausal women divided intotwo subgroups: fast bone losers, that is, bone loss>3%/year (n=20), and “physiological” bone loss (n=24); and 28 70-year-old women divided intotwo subgroups: with and without osteoporotic fractures. Serum 1,25(OH)₂D concentrations were virtually the same in all groups thus contradicting the previous reports of low 1,25(OH)₂D in elderly women. Furthermore, mean 25OHD and 24,25(OH)₂D did not differ between the groups. We conclude that 1,25(OH)₂D is unlikely to be significant in the development or treatment of a majority of women with postmenopausal osteoporosis.     

Effect of the administration of 1,25-dihydroxyvitamin D3 on serum levels of 25-hydroxyvitamin D in postmenopausal osteoporosis

Summary Serum concentrations of 25-hydroxyvitamin D were measured in a group of women with symptomatic postmenopausal osteoporosis, before and after long-term treatment with physiological doses of 1,25-dihydroxyvitamin D₃. A competitive protein binding assay was used, which included a chromatographic step. The treatment resulted in a significant decrease in serum 25-hydroxyvitamin D levels that were higher than normal in basal conditions, the mean values before and after therapy being 27.7 ng/ml (±17.1 SD) and 19.7 ng/ml (±12.7), respectively. These findings seem to confirm the hypothesis that an inadequate product-inhibition of liver 25-hydroxylase is responsible for the increased basal levels of 25-hydroxyvitamin D found in postmenopausal osteoporosis.     

Serum 1,25-dihydroxyvitamin D concentration in hypophosphatemic vitamin D-resistant rickets

Summary Fasting serum 1α,25-dihydroxyvitamin D (1,25-(OH)₂D) levels were measured in 3 groups of hypophosphatemic vitamin D-resistant rickets (VDRR) patients: those untreated; those treated with vitamin D and phosphate; and those treated with 1,25-(OH)₂D₃ and phosphate. In the untreated patients, the mean 1,25-(OH)₂D level was higher than in our age-matched control group. Except for one at 66 pg/ml, individual values were however within normal limits. Long term vitamin D₂ therapy was accompanied by a slight but significant decrease in 1,25-(OH)₂D concentrations; nonetheless the levels remained within the normal range. In the third group of patients, the concentration of 1,25-(OH)₂D rose to supranormal levels when sampling was done 1–3 hours after administration of the hormone, decreasing rapidly to levels below that of normal subjects when the specimens were collected 12–24 hours later. Our data show that an alteration of the vitamin D activation pathway is unlikely to be part of the pathogenic mechanism underlying the VDRR condition. Calcitriol (1α,25-(OH)₂D₃) as Rocaltrol^R in capsules of 0.25 and 0.50 μg was kindly supplied by Dr. Patrick Le Morvan (Hoffmann-La Roche Ltd, Vaudreuil, Que., Canada).     

Decrease in bone levels of 1,25-dihydroxyvitamin D in women with subcapital fracture of the femur

Summary In a previous study we were able to show that in women over the age of 45 the level of 1,25-dihydroxyvitamin D (1,25(OH)₂D) in bone, but not in serum, is significantly reduced when compared with younger women. In the present study we measured the concentration of 1,25(OH)₂D in sera and bones of 19 female patients with subcapital fractures of the femur, mean age 78±2 years. We were able to show that serum levels of 1,25(OH)₂D were within the normal range, while bone levels were markedly reduced compared to levels in femoral bone obtained from young female cadavers or to the previously reported levels in non-osteoporotic elderly women. Thus, reduced levels of 1,25(OH)₂D in bones of elderly women may lead, together with other factors, to subcapital fractures.Holder of Prof. T. Reichstein Professorial Chair     

IGF-Binding proteins in human prostate tumor cells: Expression and regulation by 1,25-dihydroxyvitamin D3

The expression of the six known insulin-like growth factor binding proteins (IGFBPs) and their corresponding messenger RNAs has been examined in three cell lines established from surgical and biopsy specimens of human prostate carcinoma. All three cell lines produced both IGFBP-4 and IGFBP-6 and the respective mRNAs; expression of IGFBP-6 has not been previously demonstrated in human prostate tumor cells. No other binding proteins were detected. The levels of IGFBP mRNAs were not regulated by androgens or IGF-1, but the level of IGFBP-6 mRNA was sharply increased by 1,25-dihydroxyvitamin D₃ (1,25(OH)D₃). The stimulation was dose-dependent with a maximum effect at 10 nM 1,25(OH)D₃ and a clearly discernible effect at 0.1 nM. The results support a role for vitamin D in the control of prostate tumor growth, mediated at least in part by interaction with IGFs and specific IGFBPs.     

The effect of 1,25-dihydroxyvitamin D3 on the growth of soft-tissue sarcoma cells as mediated by the vitamin D receptor

Background: Soft-tissue sarcomas, malignant neoplasms originating from mesenchymal tissue, are rare but highly aggressive tumors. Present modes of therapy are associated with high rates of recurrence. 1,25-Dihydroxyvitamin D₃, the active metabolite of vitamin D, serves as a potent antiproliferative agent in human cancer cells. Methods: In this study, six soft-tissue sarcoma cell lines were analyzed for vitamin D receptor (VDR) expression, which was then correlated with the degree of growth inhibition in response to 1,25-dihydroxyvitamin D₃. These cell lines included rhabdomyosarcoma (HS729, A204), fibrosarcoma (HS913t). synovial sarcoma (SW982), liposarcoma (SW872), and leiomyosarcoma (SKLMS-1). The level of VDR messenger RNA (mRNA) expression was determined using a ribonuclease protection assay, and functional receptor content was determined by using a ligand-binding assay. Growth studies, including [³H]thymidine up-take and growth curves, were performed on two of the six cell lines that expressed the highest and lowest receptor levels. Results: Ribonuclease protection and ligand-binding assays demonstrated variable levels of VDR, with HS729 showing high expression and A204 showing no expression. In HS729, [³H]thymidine uptake was significantly decreased at 10^–7 M (33%) and 10^–6 M (40%) 1,25-dihydroxyvitamin D₃. Growth curve studies showed significant growth inhibition of 55% at 10^–6 M. A204 cells showed no growth inhibition upon treatment with 1,25-dihydroxyvitamin D₃. Conclusion: This study demonstrates the existence of VDR in soft-tissue sarcoma cells and suggests a correlation between the level of VDR in cells and the degree of growth inhibition caused by 1,25-dihydroxyvitamin D₃ which may potentially serve as an alternative form of therapy for soft-tissue sarcomas.Presented at the 48th Annual Cancer Symposium of The Society of Surgical Oncology, Boston, Massachusetts, March 23–26, 1995.     

Effect of a long-term treatment with 1,25-dihydroxyvitamin D3 on osteocalcin in postmenopausal osteoporosis

Summary Serum bone Gla-protein (BGP or osteocalcin) was measured in 25 women with histologically confirmed postmenopausal osteoporosis before and during long-term treatment with 1 μg/day of 1,25-dihydroxyvitamin D₃(1,25(OH)₂D₃). Basal serum BGP was significantly lower in osteoporotic women (3.8±1.4 ng/ml) than in agematched controls (6.8±2.0 ng/ml). During 1,25(OH)₂D₃ therapy serum BGP increased so that the mean of the values observed on treatment (4.8±1.5) was significantly higher than the mean basal value. It is known that BGP synthesis is stimulated by 1,25 (OH)₂D₃ and that serum BGP is a specific marker of bone formation; therefore, it is possible that the low basal levels of osteocalcin we observed were related to the low serum 1,25(OH)₂D concentrations reported in osteoporotic women and that the increase in BGP levels observed under 1,25(OH)₂D₃ treatment was a consequence of osteoblast stimulation.     

Serum 1,25-dihydroxyvitamin D concentrations in premature infants: Preliminary results

Summary Serum 1,25(OH)₂D concentrations were measured in serial serum samples from 19 premature infants of 29.6±1.3 weeks gestation and 1,129±159 g birthweight. 1,25(OH)₂D was always normal or elevated and mean concentrations increased with age (adult, 55.2±13; infants, 1–2 weeks, 81.5±37.7 pg/mg; 3 weeks, 65±21; 6 weeks, 90.0±17.3; 9 weeks, 99.0±25.1; 12 weeks, 103.3±26.6 pg/ml). No correlation was seen with 25-OHD. Infants given 800 IU D₂ supplements had lower 1,25(OH)₂D levels than infants given 400 IU D₂. Breast fed infants had initially higher 1,25(OH)₂D levels; however, this was not sustained. These preliminary data suggest that premature infants regulate 1,25(OH)₂D production similar to more mature infants and children. Whether the premature infant has a normal gastrointestinal and/or bone responsiveness to 1,25(OH)₂D and whether these elevated 1,25(OH)₂D concentrations are “adequately elevated” requires further study. NIH Grant 2R01HD-09998-06.     

1,25-dihydroxyvitamin D synthesis after renal transplantation: the role of fibroblast growth factor 23 and cyclosporine

Abstract:  1,25-dihydroxyvitamin D₃ (1,25D) is tightly regulated by circulating factors, containing fibroblast growth factor 23 (FGF23). However, this control is disturbed in chronic kidney disease. Renal transplantation (RTX) alters 1,25D homeostasis. To examine the clinical relevance of 1,25D in RTX, we drew blood samples from 27 renal transplant recipients (20 cyclosporine-based, seven non-cyclosporine-based) and examined serum concentrations of 25-hydroxyvitamin D₃ (25D), 1,25D, and FGF23. Our protocol for cyclosporine was as follows, an initial dose of 8 mg/kg two d before RTX, and subsequently adjusted on the basis of the pharmacokinetic profile. No baseline differences were observed between cyclosporine-based and non-cyclosporine-based regimens before RTX. All variables except 1,25D levels changed similarly between the two groups. In the cyclosporine-based regimen, 1,25D levels increased steeply on day 2 and re-increased from days 7 to 21. Post-transplant FGF23 levels sharply decreased until day 14. Interestingly, the cyclosporine-treated group revealed an unexpected tendency between circulating 1,25D and FGF23 on day 21. Multiple regression analyses indicated the cyclosporine pharmacokinetic profile as a significant predictor for 1,25D levels. Post-transplant 1,25D production is induced by a steep fall in serum FGF23 and prompt graft function on day 2; 1,25D levels thereafter may be stimulated by circulating abundant cyclosporine.     

Influence of age on effects of endogenous 1,25-dihydroxyvitamin D on calcium absorption in normal women

Recent reports of increases in serum 1,25-dihydroxyvitamin D [1,25(OH₂)D] concentration with aging despite no changes or decreases in calcium absorption suggest that elderly women have intestinal resistance to vitamin D action. Thus, in 15 young adult (30±1 year) and 15 elderly (74±1 year) women (mean±SE), we assessed the responsiveness of intestinal calcium absorption to increases in circulating 1,25(OH)₂D induced by 4 days of an experimental diet (150 mg calcium and 1600 mg phosphorus daily). True fractional calcium absorption (FCA) (⁴⁴Ca mixed with food and ⁴²Ca given intravenously, then their ratio in urine measured by mass spectrometry) was determined. Baseline serum intact parathyroid hormone (PTH) concentration was higher in the older women (P=0.01) whereas serum 1,25(OH)₂D concentration and true FCA were similar. In both groups, serum 1,25(OH)₂D concentrations increased (P<0.002) on the experimental diet. After 4 days on the diet, serum 1,25(OH)₂D increased over baseline by 30.5 and 35.6% and, despite these increases, true FCA was 40±3 versus 40±4%/24 hours (NS between groups) in the young and elderly women, respectively. These data suggest that either elderly women have normal intestinal responsiveness to vitamin D or that the resistance to it is too mild to be detected by these methods.     

1,25-DIHYDROXYVITAMIN D3 AND BREAST CANCER*

Studies by this laboratory have demonstrated the presence of specific, high affinity 1,25-dihydroxyvitamin D3 (1,25-(OH)2, D3) receptors both in surgical specimens of human breast cancer and in breast cancer cells in culture. We report here that 1,25-(OH)2D3 receptors were found in 54% of 230 human primary breast cancers. Although receptor levels are lower than those of oestrogen receptors, using a modified and more sensitive assay method, the apparent receptor concentration is increased without altering the receptor positivity rate. Also in preliminary studies on lymph node metastases and their primary tumours, the receptor positivity rate is higher in the lymph nodes. These findings suggest that metastatic cells may be selected for the presence of 1,25-(OH)2D3 receptors. These data, taken with the evidence that 1,25-(OH)2D3 and several of its metabolites inhibit the growth of human breast cancer cells in culture, exactly analogously with the effects of oestrogens on cancer cell growth in vitro and in vivo, indicate that 1,25-(OH)2D3 or its metabolites could have a role in the ‘hormonal’ therapy of metastatic human breast cancer.     

Autoradiographic localization of target cells for 1α, 25-dihydroxyvitamin D3 in bones from fetal rats

Summary Thaw-mount autoradiographic studies after injection of³H-1,25-D₃ were conducted on 18-and 20-day-old rat fetuses. In maxillary bones, ribs, and tibia, nuclear concentration of radioactivity was found in osteoprogenitor cells and osteoblasts. Osteocytes and chondrocytes in epiphyseal plates were either unlabeled or weakly labeled. In competition experiments, nuclear concentration of radioactivity was blocked by the injection of a high dose of nonradioactive 1,25-D₃ prior to the administration of the labeled hormone, but not by a similar dose of nonradioactive 25-D₃. The results are interpreted as indicating that osteoprogenitor cells and osteoblasts are target cells for the direct action of 1,25-D₃ on fetal bone.     

Vitamin D metabolites in childhood nephrotic syndrome

We measured serum levels of total and ionised calcium, phosphate, intact parathyroid hormone, 25-hydroxyvitamin D [25(OH)D], 1,25-dihydroxyvitamin D [1,25(OH)₂D] and the vitamin D binding protein (DBP) in 14 children with idiopathic nephrotic syndrome and 10 healthy, age-matched controls. In all nephrotics serum DBP levels were below the normal range. Serum 25(OH)D was below 7 ng/ml in 10 of 14 nephrotic children and in the low normal range in the remaining 4 patients. The average serum 1,25(OH)₂D levels were lower in the nephrotic patients than in the controls. However, free 1,25(OH)₂D levels were normal in the nephrotic patients. Both serum 25(OH)D and 1,25(OH)₂D correlated positively with the concentration of DBP There was a significant negative correlation between serum DBP levels and the urinary protein excretion and a significant positive correlation between the urinary excretions of DBP and albumin. From this study it can be concluded that the nephrotic child is capable of maintaining appropriate serum concentrations of free calcitriol despite important urinary losses of both substrate and bound calcitriol.     

岳阳地区50岁以上人群25经维生素D水平及其与骨密度的关系

目的 通过测定269名岳阳地区50岁以上人群血清25经维生素D(25(OH)D)和骨密度(BMD)水平,分析岳阳地区50岁以上人群的维生素D ( VitD)状况,并探讨其与BMD的关系。方法 采集受试者的血清后,用电化学发光法测定血清25(OH)D水平,并同时应用双能X线吸收仪测定腰椎及髓部BMD。结果 所有受试者中,VitD严重缺乏者占24. 2 %,缺乏者占45. 0%,不足者占24. 5 %,充足者占6. 3。男、女性受试者的25(OH)D水平、腰椎及髓部的BMD间有统计学差异(P<0.001),男性高于女性。男性各年龄段间25(OH)D水平及各部位BMD无统计学差异(P=0. 101 ,P = 0. 261 ,0. 055 ,0. 170 ,0. 108 ,0. 051 ) ;女性各年龄段之间25(OH)D水平及腰椎BMD无统计学差异(P = 0. 364 , 0. 063 ) ;髓部BMD有统计学差异(P < 0. 001 ),随着年龄的增长而逐步减低。男性受试者中,不同25(OH)D水平组间股骨颈、转子间区及整髓BMD无统计学差异(P = 0. 076 , 0. 425 , 0. 122 );腰椎、大转子区BMD水平间有统计学差异(P=0. 027 , 0. 017 ) , VitD充足组腰椎BMD高于其他各组(P = 0. 005 , 0. 025 , 0. 009 );不足组、严重缺乏组大转子区BMD高于缺乏组(P = 0. 021, 0. 005 )。女性受试者中,不同25(OH)D水平组各部位BMD均无统计学差异(P = 0. 616 , 0. 739 , 0. 559 ; 0. 608 , 0. 641)。结论 在湖南岳阳地区50岁以上人群存在严重的维生素D缺乏及不足;对于维生素D状况与骨密度之间可能无直接关联,需加大样本量进一步观察。     

Serum 1,25-dihydroxyvitamin D levels in subjects with X-linked hypophosphatemic rickets and osteomalacia

Summary In order to determine whether a defect in vitamin D metabolism might play a role in the pathogenesis of X-linked hypophosphatemic rickets and osteomalacia (XLH), we compared the serum 1,25-dihydroxyvitamin D [1,25(OH)₂D] level in 52 normal subjects and 37 patients with XLH. In untreated patients, adults were found to have values similar to age-matched controls, while youths had values similar to growth-rate-matched controls but significantly lower than the levels of age-matched controls who were growing at a normal rate. In contrast, treated XLH patients of all ages had serum levels significantly lower than both controls and untreated XLH patients. Further, the serum levels of 1,25(OH)₂D in these treated patients had a significant inverse linear correlation with serum 25-(OH)D concentrations. We propose that subjects with XLH have serum 1,25(OH)₂D levels within appropriate age- and growth-rate-matched normal ranges. However, in the presence of hypophosphatemia, we would have anticipated elevated levels of 1,25(OH)₂D; viewed in this light the serum 1,25(OH)₂D levels are inadequate, suggesting the presence of a relative deficiency of this active vitamin D metabolite.     

Importance of 1,25-dihydroxyvitamin D3 and the nonadherent cells of marrow for osteoblast differentiation from rat marrow stromal cells

Although steroid hormones regulate mature osteoblast function, much less is known about their actions on osteoprogenitor cells. The possibility of steroid hormone regulation of early stages in osteoblast differentiation was investigated by measuring the growth and induction of the osteoblast marker enzyme alkaline phosphatase (AP) in rat bone marrow stromal cell cultures. Experiments were performed in charcoalstripped serum; conditions which markedly impaired stromal cell growth. However, growth could be stimulated by nonadherent marrow cell-derived conditioned medium. 1,25(OH)₂D₃, but not dexamethasone, 17β-estradiol, or retinoic acid, increased both stromal cell proliferation and AP activity. The increased proliferation with 1,25(OH)₂D₃ was nonadherent cell-dependent. BMP-2 also increased AP levels and acted in synergy with 1,25(OH)₂D₃. These results suggest that (i) nonadherent marrow cells may support stromal cell development, and (ii) 1,25(OH)₂D₃ as well as glucocorticoids may regulate osteogenesis from the bone marrow but a similar role for estrogen is not supported.     

Relationship between serum 1,25-dihydroxyvitamin D and mortality in patients with pre-dialysis chronic kidney disease

Background It is known that vitamin D has many functions besides involvement in calcium metabolism. It has recently been recognized that vitamin D deficiency is associated with mortality, especially in cardiovascular disease (CVD). Vitamin D deficiency is common in end-stage renal disease, but develops from the early stage of chronic kidney disease (CKD). So we investigated whether the serum level of the activated form of vitamin D (1,25-dihydroxyvitamin D) affected mortality in patients with CKD stages 3 and 4. Methods Between January 1, 1995, and June 30, 2006 we measured serum 1,25-dihydroxyvitamin D In 226 patients with CKD stages 3 and 4 and classified the results into two groups depending on whether the level was below (group I) or above (group II) 20 pg/ml. We ended the follow-up period on December 31, 2006. We compared all-cause and cardiovascular mortality between the two groups. We also examined predictors of mortality by using Cox proportional regression analysis. Results Two-hundred and twenty-six patients (67 men and 159 women, mean age 67.0) were registered in this study, and groups 1 and 2 comprised 84 and 142 patients, respectively. During the follow-up period 43 patients died. CVD was the major cause of death, followed by infectious disease. The Kaplan–Meier survival curve revealed that all-cause mortality was significantly higher in group I, but a significant difference between CVD mortality in the two groups was not demonstrated. By Cox proportional regression analysis, group I was related to all-cause mortality, but this was not proved to be an independent predictor. Conclusion The results suggested that serum level of 1,25-dihydroxyvitamin D was associated with all-cause mortality in patients with CKD stages 3 and 4.     

131例40岁以上绝经前女性的骨密度及骨代谢指标特点分析

目的了解广州地区40岁以上绝经前女性的骨密度及骨代谢指标的临床特点。方法在2017年3月至2017年4月份纳入广州市社区骨质疏松症流行病学调查的1170名女性人群中,选取资料齐全、符合入选标准的131名绝经前女性(43～59岁)作为研究对象。记录并分析患者身高、体重、体质量指数、腰围、臀围等一般资料,检测血清钙、磷、碱性磷酸酶、甲状旁腺素、骨钙素、Ⅰ型前胶原氨基端前肽、Ⅰ型胶原羧基端肽、25羟维生素D等骨代谢指标,应用双能X线吸收法测量腰椎1-4及左股骨近端的骨密度,并分别应用T值及Z值进行诊断。结果应用T值诊断:骨量正常组55例(42.0%),骨量减少组67例(51.1%),骨质疏松组9例(6.9%)。应用Z值诊断:骨量正常组128例(97.7%),低骨量组3例(2.3%)。与骨量正常组相比,骨质疏松组的身高、体重、体质量指数、腰围、臀围差异均无统计意义。3组之间的Ca、P、25(OH) D、PTH的水平差异无统计学意义。与骨量正常或骨量减少组相比,骨质疏松组的破骨指标β-CTX有上升的趋势,而成骨指标ALP、OC、PINP水平则显著上升,且差异均具有统计学意义。结论应用T值诊断骨质疏松症的敏感性高于Z值,本研究人群发生的骨质疏松症为绝经前特发性骨质疏松症,绝经前特发性骨质疏松症的发病与Ca、P、25(OH) D、PTH无显著关联性,骨代谢的高转换状态可能是发病的主要机制,遗传性因素可能是发病的主要原因。     

Higher 1,25-dihydroxyvitamin D3 concentrations associated with lower fall rates in older community-dwelling women

Introduction The purpose of this study was to examine the relationships of vitamin D supplementation and serum concentrations of vitamin D metabolites and parathyroid hormone (PTH) with neuromuscular function and falls in older community-dwelling women.Methods We examined these relationships using a 4-year prospective multi-center study among 9,526 community-dwelling women enrolled in the Study of Osteoporotic Fractures (median age: 70 years; interquartile range: 67–75) and a subset of 389 women (97%) out of 400 who were randomly selected from the entire cohort for serum measures. Measurements included: vitamin D supplementation, serum 25-hydroxyvitamin D₃ [25(OH)D₃], serum 1,25-dihydroxyvitamin D₃ [1,25(OH) ₂D₃], and serum intact parathyroid hormone (iPTH); grip and quadriceps strength, chair-stand time, walking speed, reaction time, and balance-walk time (including changes in grip strength, chair-stand time, walking speed and balance-walk time over approximately 3.7 years); and incident fall rates (number of falls/woman-years).Results In 9,526 women, vitamin D supplementation was not associated with any measures of neuromuscular function, change in neuromuscular function, or fall rates (p>0.01 for all). In a subgroup of 389 women, there was a trend of higher 25(OH)D₃ concentration with slightly weaker grip strength (p=0.007), and women in the fourth quartile of 1,25(OH)₂D₃ had a faster chair-stand time (p=0.017) than women in the first quartile; still, in general, concentrations of 25(OH)D₃, 1,25(OH)₂D₃, and iPTH were not associated with either neuromuscular function or changes in neuromuscular function (p>0.05 for all). However, higher 1,25(OH)₂D₃ concentration was associated with lower fall rates (p=0.039).Conclusions Higher 1,25(OH)₂D₃ concentration is associated with a lower fall risk in older community-dwelling women, but vitamin D supplementation, and 25(OH)D₃ and iPTH concentrations are not associated with either neuromuscular function or falls.