Role of 1,25-Dihydroxy Vitamin D3 and Parathyroid Hormone in Urinary Calcium Excretion in Calcium Stone Formers

Purpose

To find out the possible role of 1,25(OH)₂ vitamin D₃ [1,25(OH)₂D₃] and parathyroid hormone (PTH) as intrinsic factors in urinary calcium stone formers (SFs), we investigated their relationship with serum and urinary biochemical parameters.

Materials and Methods

A total of 326 calcium SFs (male: 204, female: 122) were enrolled and underwent outpatient metabolic evaluations including 1,25(OH)₂D₃ and PTH as well as serum and 24-hour urinary biochemical parameters. As control, 163 age- and sex-matched (2:1) individuals (non-SFs) who have never urinary stone episode were included.

Results

1,25(OH)₂D₃ level was positively correlated with urinary calcium excretion (r=0.347, p<0.001). The hypercalciuric group and recurrent SFs had higher serum 1,25(OH)₂D₃ levels than the normocalciuric group (p<0.001) and first SFs (p=0.050). In the adjusted multiple linear regression analysis, serum 1,25(OH)₂D₃ level (β=0.259, p<0.001) and serum PTH level (β=-0.160, p<0.001) were significantly correlated with urinary calcium excretion. The patients in highest tertile of 1,25(OH)₂D₃ had a more than 3.1 fold risk of hypercalciuria than those in the lowest tertile (odds ratio=3.14, 95% confidence interval: 1.431-6.888, p=0.004). No correlation was observed between PTH and 1,25(OH)₂D₃ (R=0.005, p=0.929) in calcium SFs, while a negative correlation was found in controls (R=-0.269, p=0.001).

Conclusion

1,25(OH)₂D₃ was closely correlated with urinary calcium excretion, and high 1,25(OH)₂D₃ levels were detected in the hypercalciuric group and in recurrent SFs. However, 1,25(OH)₂D₃ was not correlated with PTH in calcium SFs. These findings suggest that 1,25(OH)₂D₃ might be important intrinsic factor for altered calcium regulation in SFs.     

Parathyroid hormone, 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D concentration in elderly patients

Summary In 50 patients of a geriatric hospital (33 women, aged 65–96 years, mean age 80 years, and 17 men, aged 68–91, mean age 78.3 years) calcium, albumin, phosphate, urea, creatinine, parathyroid hormone, 25-hydroxyvitamin D, and 1,25-dihydroxyvitamin D were determined. Forty patients with serum creatinine levels up to 1.4 mg/dl (124 mol/l) and 10 patients with creatinine concentrations 1.5 mg/dl (132mol/l) were evaluated. In patients with normal creatinine, a positive correlation was found between parathyroid hormone and age (r=0.41;P<0.01). In patients with elevated creatinine, negative correlations were found in 1,25-dihydroxyvitamin D and calcium (r=–0.724;P<0.05), 1,25dihydroxyvitamin D and creatinine (r=–0.79;P<0.01) and 1,25-dihydroxyvitamin D and phosphate (r=–0.87;P< 0.002). The best correlation was observed in patients with elevated serum creatinine for 1,25-dihydroxyvitamin D and phosphate (r=–0.91;P< 0.001). The results suggest that low levels of calcium and phosphate stimulate the 1-hydroxylation of 25-hydroxyvitamin D even in advanced age and that the calcium metabolism of these patients is frequently disturbed. Nineteen patients had low levels of 25-hydroxyvitamin D, indicating an insufficient supply of vitamin D or rare exposure to sunlight. In 49 of 50 patients, one ore more of the parameters of calcium metabolism were outside the normal range.Abbreviations 25-OH-D 25-hydroxyvitamin D - 1,25(OH)₂D 1,25-dihydroxyvitamin D - PTH parathyroid hormone Supported by the Deutsche Forschungsgemeinschaft (Schm 405–407)     

1α,25‐dihydroxyvitamin D3 acts via transforming growth factor‐β to up‐regulate expression of immunosuppressive CD73 on human CD4+ Foxp3– T cells

Vitamin D deficiency is associated with increased incidence and severity of various immune‐mediated diseases. Active vitamin D (1α,25‐dihydroxyvitamin D3; 1,25(OH)₂D3) up‐regulates CD4⁺ T‐cell expression of the purine ectonucleotidase CD39, a molecule that is associated with the generation of anti‐inflammatory adenosine. Here we aimed to investigate the direct impact of 1,25(OH)₂D3 on expression of the downstream ecto‐5′‐nucleotidase CD73 by human CD4 T cells, and components of the transforming growth factor‐β (TGF‐β) pathway, which have been implicated in the modulation of CD73 by murine T cells. At 10^?8 to 10^?7 m , 1,25(OH)₂D3 significantly increased expression of CD73 on peripheral human CD4⁺ T cells. Although 1,25(OH)₂D3 did not affect the mRNA expression of latent TGF‐β₁, 1,25(OH)₂D3 did up‐regulate expression of TGF‐β‐associated molecules [latency‐associated peptide (LAP), glycophorin A repetitions predominant (GARP), GP96, neuropilin‐1, thrombospondin‐1 and α_v integrin] which is likely to have contributed to the observed enhancement in TGF‐β bioactivity. CD73 was highly co‐expressed with LAP and GARP following 1,25(OH)₂D3 treatment, but unexpectedly, each of these cell surface molecules was expressed primarily on CD4⁺ Foxp3^– T cells, rather than CD4⁺ Foxp3⁺ T cells. Notably, neutralization of TGF‐β significantly impaired 1,25(OH)₂D3‐mediated induction of CD73. Collectively, we show that 1,25(OH)₂D3 enhances expression of CD73 on CD4⁺ Foxp3^– T cells in a process that is at least partially TGF‐β‐dependent. These data reveal an additional contributing mechanism by which vitamin D may be protective in immune‐mediated disease.     

Effect of seasonal ultraviolet radiation fluctuations on vitamin D homeostasis during an Antarctic expedition

Antarctica is a unique and challenging environment where members of expeditions face a range of conditions not normally experienced. Ultraviolet (uv) radiation levels show marked variation during the year. The 25-hydroxy metabolite of vitamin D [25(OH)D] is largely produced by sunlight and shows a yearly variation in concentration that corresponds to uv radiation levels. The active metabolite 1,25-dihydroxyvitamin D [1,25(OH)2D] does not generally show any such variation provided 25(OH)D concentrations are sufficient. Previous studies have shown a seasonal variation in 25(OH)D with a significant winter drop. No other study of 1,25(OH)2D has been reported on members of Antarctic expeditions. A group of 19 men wintering at Davis Station (68° 34 S) had four blood samples taken at 3-monthly intervals beginning in the Antarctic summer. Analysis for 25(OH)D showed a drop in concentration for each of the latter three sampling periods (P < 0.005). This correlated with uv radiation levels and would suggest that endogenous production of 25(OH)D ceases for at least the duration of the Antarctic winter. There were no significant alterations in 1,25(OH)2D or calcium concentrations over the same period. Providing that individuals with pre-existing vitamin D deficiencies are detected before departure for Antarctica and missions are limited in duration, clinical deficiency is unlikely to occur.     

Plasma 1,25 Dihydroxy Vitamin D<Subscript>3</Subscript> Level and Expression of Vitamin D Receptor and Cathelicidin in Pulmonary Tuberculosis

Introduction  Vitamin D₃, which exerts its effect through vitamin D receptor (VDR), is known for its potent immunomodulatory activities. Associations between low serum vitamin D₃ levels and increased risk of tuberculosis have been reported. Study Subjects and Methods  Plasma 1,25 dihydroxy vitamin D₃ levels (1,25(OH)₂ D₃) and ex vivo levels of VDR protein from peripheral blood mononuclear cells were studied in 65 pulmonary tuberculosis (PTB) patients and 60 normal healthy subjects (NHS) using enzyme-linked immunosorbent assay-based methods. Using real-time polymerase chain reaction (PCR), induction of VDR, cathelicidin, and CYP27B1 mRNA were studied in live Mycobacterium tuberculosis-stimulated macrophage cultures treated with or without 1,25 dihydroxy vitamin D₃. VDR and CYP27B1 (-1077 A/T) gene polymorphisms were studied using PCR-based methods. Results  1,25(OH)₂ D₃ were significantly increased (p = 0.0004), while ex vivo levels of VDR protein were significantly decreased in PTB patients (p = 0.017) as compared to NHS. 1,25(OH)₂ D₃ levels were not different between variant genotypes of CYP27B1. A trend towards decreased levels of VDR protein was observed among NHS with BsmI BB and TaqI tt genotypes compared to NHS with other genotypes. Relative quantification of mRNA using real-time PCR revealed increased VDR mRNA expression in live M. tuberculosis-stimulated culture in PTB patients (p < 0.01) than normal healthy subjects. Cathelicidin mRNA expression was significantly increased in vitamin D₃-treated cultures compared to unstimulated and M. tuberculosis-stimulated culture in both patients (p < 0.001) and NHS (p < 0.05). Conclusions  The present study suggests that PTB patients may have increased 1,25(OH)₂ D₃ levels, and this might lead to downregulation of VDR expression. Decreased VDR levels could result in defective VDR signaling. Moreover, addition of 1,25(OH)₂ D₃ might lead to increased expression of cathelicidin which could enhance the immunity against tuberculosis.     

Blockade of the renal tubular effects of vitamin D by cycloheximide in the rat

To further characterize the mechanisms by which 25(OH)vitamin D₃ (25(OH)D₃) and 1.25(OH)₂ vitamin D₃ (1,25(OH)₂D₃) suppress the phosphaturic action of parathyroid hormone (PTH) we have studied the effects of cycloheximide (cyclohex), a protein synthesis inhibitor, on the interaction between PTH and vitamin D metabolites in parathyroidectomized (PTX) rats, both in vivo and in vitro experiments. In clearance studies PTX PTH-infused rats were pretreated with cyclohex 2 h before the administration of vitamin D. In control, PTX PTH-infused rats not pretreated with cyclohex, the administration of 25(OH)D₃ and 1,25(OH)₂D₃ was associated with a fall in fractional excretion of phosphate (CP/CIN) from 0.30±0.05 to 0.16±0.02 and from 0.31±0.05 to 0.13±0.01 (P<0.005) respectively. Cyclohex-pretreated PTX PTH-infused rats failed to respond to both 25(OH)D₃ and 1,25(OH)₂D₃, and CP/CIN, which rose after PTH, remained 0.32±0.05 and 0.29±0.03 respectively. In vitro, both 25(OH)D₃ and 1,25(OH)₂D₃ inhibited the PTH-induced activation of adenylate cyclase in the renal isolated membrane fractions. Pretreatment with cyclohex abolished this effect of vitamin D metabolites. These results show that cyclohex blocks the antiphosphaturic effects of both 25(OH)D₃ and 1,25(OH)₂D₃ but does not alter the response to PTH. These findings are consistent with the possibility that the acute renal action of vitamin D depends on de novo synthesis of protein.An abstract of this work appeared in Clinical Research, 28 (2) A 387, 1980.     

Effects of 1,25-(OH)2D3 administered in vivo on phosphate uptake by isolated chick renal cells

Renal cells from Vitamin D-deficient and 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3]-repleted chicks were isolated by a collagenase-hyaluronidase procedure. Exclusion of trypan blue and respiratory measurements indicate that the cells were functionally intact and metabolically active. The uptakes of phosphate and alpha-methylglucoside were stimulated markedly by Na+ in the extracellular medium. Phosphate uptake in the presence of Na+ was saturable with respect to phosphate concentration; half-maximal activity was obtained with approximately 0.2 mM. Three hours after 1,25-(OH)2D3 was injected into vitamin D-deficient chicks the Na+-dependent phosphate uptake by the isolated cells had increased about 40%, i.e., 2.00 compared with 1.44 nmol.min-1.mg protein-1. Phosphate uptake in the presence of K+ in the extracellular medium and alpha-methylglucoside uptake in the presence or absence of Na+ were unchanged. In a secondary response found 17 h after 1,25-(OH)2D3 injection, Na+-dependent phosphate uptake decreased. Serum concentrations of phosphorus and calcium were not measurably changed in the 3-h repleted bird, but both levels were increased 17 h after treatment. Administration of phosphate into vitamin D-deficient chicks, so that the serum concentration of phosphorus was raised to that of the 17-h 1,25-(OH)2D3 repleted animal, effected a comparable decrease in phosphate uptake. Serum calcium levels were not altered by this treatment. The actions of parathyroid hormone in stimulating adenylate cyclase and in inhibiting phosphate uptake were notably blunted in the vitamin D-deficient chick. Sensitivity to parathyroid hormone was not restored until several days after 1,25-(OH)2D3 repletion. These findings suggest that the initial response to 1,25-(OH)2D3, to increase renal phosphate uptake, and the secondary response, to decrease phosphate uptake, were by parathyroid hormone-independent processes. The results also indicate that the isolated renal cell represents an excellent model for studying the mechanism by which 1,25-(OH)2D3 regulates phosphate transport in the kidney.     

EHDP-induced rachitic syndrome in rats is not reversed by vitamin D metabolites

To examine whether either of the two known active vitamin D metabolites 1,25(OH)2D3 or 24,25(OH)2D3 could reverse the mineralization defect induced by 1-hydroxyethylidene-1,1-bis phosphonate (EHDP), a model of EHDP-induced rickets was used. Rats at the age of 31 days were injected for 10 consecutive days with EHDP (10 mg/kg). Other littermates were treated with a combination of EHDP and either 1,25(OH)2D3 or 24,25(OH)2D3 or were treated following 10 days of EHDP, with either of the vitamin D metabolites for an additional 72 hr. Samples of cartilage fluid (Cfl) and of blood were removed prior to sacrifice for biochemical studies of some parameters of calcification. These parameters were correlated with the results of light and electron microscope studies of growth plate cartilage and bone. EHDP-treated rats revealed signs of typical rickets, manifested by widened growth plates and impaired bone mineralization. Transmission electron microscope (TEM) examination revealed matrix vesicles distributed throughout the growth plate; however, there appeared to be an arrest of the spread of the crystals at the provisional zone of calcification. Treatment with either 1,25(OH)2D3 or 24,25(OH)2D3 failed to reverse the rachitic condition of the animals. Serum calcium blood levels were elevated in the 1,25(OH)2D3 and EHDP-treated group. 1,25(OH)2D3 and 24,25(OH)2/D3 further increased the already elevated serum alkaline phosphatase levels observed in EHDP rats, although the increase observed with 1,25(OH)2D3 was not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)     

Vitamin D status is not associated with inflammatory cytokine levels during experimental human endotoxaemia

Vitamin D has been shown to modulate innate immune responses in vitro and ex vivo; however, human in‐vivo data are lacking. At high latitudes, seasonal vitamin D deficiency is common due to alternating ultraviolet (UV)‐B radiation exposure. In the present study, we investigated whether levels of 25 hydroxyvitamin D₃ [25(OH)D₃] and its active metabolite 1,25 dihydroxyvitamin D₃ [1,25(OH)₂D₃] are subject to seasonal variation and whether plasma levels of these vitamin D metabolites correlate with the in‐vivo cytokine response during experimental human endotoxaemia [administration of lipopolysaccharide (LPS) in healthy volunteers]. Plasma levels of 25(OH)D₃ and 1,25(OH)₂D₃ were determined in samples obtained just prior to administration of an intravenous bolus of 2 ng/kg LPS (derived from Escherichia coli O:113) in 112 healthy male volunteers. In the same subjects, plasma levels of the inflammatory cytokines tumour necrosis factor (TNF)‐α, interleukin (IL)‐6 and IL‐10 were analysed serially after endotoxin administration. Plasma levels of 1,25(OH)₂D₃, but not 25(OH)D₃, were subject to significant seasonal variation, with lower levels in autumn and winter. 25(OH)D₃ and 1,25(OH)₂D₃ levels did not correlate with plasma cytokine responses. Furthermore, 25(OH)D₃ deficient subjects (< 50 nmol/l) displayed an identical cytokine response compared with sufficient subjects. In conclusion, plasma levels of vitamin D are not correlated with the LPS‐induced TNF, IL‐6 and IL‐10 cytokine response in humans in vivo. These findings question the direct role of vitamin D in modulation of the innate immune response.     

Long-term therapy with cyclosporin A does not influence serum concentrations of vitamin D metabolites in patients with multiple sclerosis

Summary Animal studies have shown that cyclosporin A (CyA) stimulates renal 25-hydroxyvitamin D₃ [25(OH)D₃]-1-hydroxylase activity; in contrast, studies in renal transplant recipients indirectly suggest that CyA reduces 1,25-dihydroxyvitamin D₃ [1,25 (OH)₂D₃] production. To clarify the effect of CyA on vitamin D metabolite concentrations, we measured parameters of calcium metabolism in 37 CyA-treated patients (median trough whole blood levels 171–222 ng/ml) with multiple sclerosis and initially normal kidney function. The patients participated in a randomized double-blind study to assess the efficacy of CyA in multiple sclerosis. An age- and sex-matched control group (n = 39) received azathioprine (Aza). Measurements were made at the end of a 2-year treatment period. The 1,25(OH)₂D₃ serum concentrations were not significantly different between the two groups, although they were numerically lower in CyA-treated patients [median (range), 28.4 pg/ml (7.8–85.9) vs 41.0 pg/ml (9.2–105.1) in Aza-treated patients]. The 25(OH)D₃ levels were comparable in both groups. There was no correlation between the 25(OH)D₃ and 1,25(OH)₂D₃ concentrations. The renal function in both groups was stable in the last 6 months of the study. At the end of the study period, the endogenous creatinine clearance was significantly lower in the CyA-treated group (85 ± 17 ml/min versus 99 ± 22 in the Aza-treated group, P < 0.05). The carboxyterminal parathyroid hormone (C-PTH) was within the normal range in both groups, although CyA-treated patients had significantly higher concentrations (P<0.01). The urinary excretion of mineral ions, cations and protein was similar in both groups. Our data suggest that long-term treatment with CyA does not cause clinically important alterations of vitamin D metabolism in humans. Subtle differences in the concentrations of 1,25(OH)₂D₃ and C-PTH between CyA- and Aza-treated patients result presumably from a slight impairment of renal function through CyA.Abbreviations CyA cyclosporin A - Aza azathioprine - 25(OH)D₃ 25-hydroxyvitamin D₃ - 1,25(OH)₂D₃ 1,25-dihydroxyvitamin D₃ - PTH parathyroid hormone - C-PTH carboxyterminal-PTH - AP alkaline phosphatase - Ccr endogenous creatinine clearance - gamma-GT gamma-glutamyltransferase     

1,25‐Dihydroxy‐vitamin D3 regulates NK‐cell cytotoxicity,cytokine secretion,and degranulation in women with recurrent pregnancy losses

Vitamin D has a pivotal role in regulating immune responses by promoting Th2 immune responses and suppressing Th1 responses. Propensities to a Th1 immune response and increased NK‐cell levels and cytotoxicity have been reported in women with recurrent pregnancy losses (RPL). In women with RPL, vitamin D deficiency is prevalent; however, the effect of vitamin D on NK cells is largely unknown. In this study, we demonstrated that CD69⁺ activating receptor expression on NK cells was significantly decreased by incubation with 1,25(OH)₂D₃ in a dose‐dependent manner, while CD158a and CD158b inhibitory receptor expression was upregulated. The degranulation marker CD107a was significantly downregulated on NK cells following incubation with 1,25(OH)₂D₃. NK‐cell conjugation with K562 target cells was not affected by 1,25(OH)₂D₃; however, depolarization of perforin granules in conjugated NK cells was significantly increased. TLR4 expression on NK cells was significantly decreased and TNF‐α and IFN‐γ production was significantly reduced by 1,25(OH)₂D₃ through interference with NF‐κB. Our results suggest 1,25(OH)₂D₃ has immune regulatory effects on NK cell cytotoxicity, cytokine secretion and degranulation process as well as TLR4 expression. Potential therapeutic application of 1,25(OH)₂D₃ for dysregulated NK‐cell immunity should be explored in the future.     

Effect of 1α-25-dihydroxyvitamin D3 on intimal hyperplasia developing in vascular anastomoses: a rabbit model

Introduction

A common problem encountered in routine daily practice of cardiovascular surgery is migration of smooth muscle cells leading to intimal hyperplasia developing at vascular anastomosis sites which then causes luminal narrowing. The aim of this study was to investigate the antiproliferative effect of 1,25 (OH)₂D₃ on intimal hyperplasia.

Material and methods

Twenty-one male white New Zealand rabbits weighing 2-3 kg were selected. There were 3 groups of animals each consisting of 7 rabbits. Group 1 was the control group. Group 2 was the sham group and group 3 consisted of rabbits receiving 1,25 (OH)₂D₃. The right carotid arteries of the subjects in groups 2 and 3 were transected and re-anastomosed. A daily dose of 25 ng 1,25 (OH)₂D₃ per 100 g body weight was administered for 14 days to rabbits in group 3. Rabbits in group 2 were not subject to any pharmaceutical agent. All the subjects were sacrificed at the end of the 28^th postoperative day. Their right carotid arteries were resected and then investigated histopathologically.

Results

Intimal thickness and intimal area were measured as significantly lower in group 1 when compared with the other groups (p = 0.004). In group 3, the ratios of thickness of tunica intima/thickness of tunica media and area of tunica intima/area of tunica media were significantly lower than those of group 2 (p = 0.015, p = 0.003).

Conclusions

1,25 (OH)₂D₃, the active metabolite of vitamin D, reduces the intimal hyperplasia developing after vascular anastomoses.     

Phosphate fluxes in isolated enterocytes from vitamin D replete and vitamin D deficient rats — early effects of calcitriol

In the present work we studied rapid in vitro effects of calcitriol (1,25(OH)₂ vitamin D₃) on the intestinal transport of inorganic phosphate (P_i). Enterocytes from vitamin D replete (D⁺) as well as vitamin D depleted (D^–) rats were isolated mechanically from the duodeno-jejunum. In this model, P_i uptake was a temperature and Na⁺-dependent phenomenon. The in vitro-addition of calcitriol (1 pM) resulted in a significant enhancement of initial P_i uptake rate by enterocytes from D⁺ (P<0.01) and D^– (P<0.05) rats. This effect which was Na⁺-dependent, was observed within the time of 20 min, but not before. A similar effect on P_i uptake rates of D⁺ or D^– enterocytes could be elicited by the in vitro addition of the methyl ester of cis-vaccinic acid (MCVA) which is thought to increase membrane fluidity by modifying the lipid composition of the cell membrane. The stimulatory effect of calcitriol on P_i uptake rate was blunted in the presence of the methyl ester of transvaccinic acid (MTVA) thought to decrease membrane fluidity. Enterocyte P_i efflux rate constant (^o KP_i) remained unchanged in the presence of calcitriol (1 pM). In conclusion, the study demonstrates a rapid in vitro effect of calcitriol on P_i uptake by isolated enterocytes from D⁺ and D^– rats. It suggests, but does not prove, that the hormone may act via an action independent of genomic nuclear activation.     

Partial prevention of active Heymann nephritis by 1 alpha, 25 dihydroxyvitamin D3.

The hormone 1 alpha, 25 dihydroxyvitamin D3 (1,25(OH)2D3) has potent immunosuppressive effects in vitro. Recent publications also described a protective effect of the hormone in various animal models of immune-mediated diseases. To test its in vivo activity we induced active Heymann nephritis in Lewis rats that were either untreated or treated with 1,25(OH)2D3 or its synthetic 20-epi analogue, KH1060. Treatment with cyclosporine A (CsA) was used as an immunosuppressive control. In this nephrotic model the administration of 1,25(OH)2D3 (0.5 microgram/kg body weight) given on alternate days during the first 13 days after active immunization significantly reduced the proteinuria as measured by weeks 7-9. This reduction was comparable to the reduction observed in rats treated with CsA (20 mg/kg) on alternate days. A second series of experiments with 1,25(OH)2D3 confirmed these findings. The level of autoantibodies was found to be significantly suppressed during the treatment time in the CsA (20 mg/kg) group, whereas the limit of significance (P = 0.06) was reached in the 1,25(OH)2D3 (0.5 microgram/kg) group. The size of the immune deposits also was found to be substantially smaller in the groups that developed less proteinuria. The administration of 1,25(OH)2D3 transiently increased the mean serum calcium concentration with 2.5 mg/dl above the pretreatment values, and the urinary calcium excretion by a factor of 3-5 during the short treatment time. Treatment with the analogue KH1060 did not reduce the proteinuria significantly. Our experiments add evidence to the hypothesis that 1,25(OH)2D3 in pharmacological doses has immunosuppressive potency.     

25-hydroxyvitamin D, 24, 25-dihydroxyvitamin D and 1,25-dihydroxyvitamin D in human cerebrospinal fluid

Summary Samples of CSF and plasma were obtained simultaneously from 46 adult patients who had no endocrine disorders and were undergoing routine diagnostic lumbar puncture because of suspected or proved prolapse of a disc. Concentrations of 25-OHD, 24,25(OH)₂D and 1,25(OH)₂D were measured. The samples were purified by column chromatography and fractionated by HPLC. In the appropriate fractions the vitamin D metabolites were measured by PBA, and cytoreceptor assay. The results were as follows (median, range in brackets): 25-OHD in CSF 8.3 ng/ml (2.0–24.8), in plasma 14.5 ng/ml (7.0–36.0). 24,25(OH)₂D in CSF 1.8 ng/ml (0.3–4.6) and 2.5 ng/ml (0.4–4.7) in plasma. 1.25(OH)₂ D in CSF 25.0 pg/ml (2.2–39.0) and 31.0 pg/ml (10.1–55.0) in plasma. The correlations between plasma and CSF concentrations were as follows: 25-OHDr=0.479 (P<0.001); 24,25(OH)₂Dr=0.815 (P<0.001) and for 1.25(OH)₂Dr=0.497 (P<0.001).Our findings showed vitamin D metabolites to be present in human CSF.Abbreviations Ca Calcium - CSF Cerebrospinal fluid - Vitamin D₃ Cholecalciferol - CPM Counts per min - 24, 25 (OH)₂D 24, 25-dihydroxyvitamin D₃ - 1,25(OH)₂D 1,25-dihydroxyvitamin D₃ - Vitamin D₂ Ergocalciferol - HPLC High-pressure liquid chromatography - 25OHD 25-hydroxyvitamin D₃ - PTH Parathyroid hormone - PBA Protein binding assay - RIA Radioimmunoassay - D-CaBP Vitamin D dependent calcium-binding protein     

Disturbed calcium metabolism in subjects with elevated diastolic blood pressure

Summary Essential hypertension has been associated with disturbed calcium metabolism, but the available data are controversial. We measured parameters of calcium metabolism in groups of untreated male subjects (n = 78) with elevated diastolic blood pressure (101 ± 6 mmHg, mean ± SD) and age-matched male subjects (n=79) with low diastolic blood pressure (62 ± 4 mmHg). The participants of the study were drawn from a random population sample. Subjects with high diastolic blood pressure had significantly higher carboxy-terminal parathyroid hormone (PTH) plasma concentrations than controls with low diastolic blood pressure (median 114 vs. 43 pmol/l, P < 0.01). The 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D concentrations were comparable in both groups. Individuals with high diastolic blood pressure had significantly lower total serum calcium (2.41 ± 0.10 vs. 2.47 ± 0.10 mmol/l, mean ± SD; P < 0.01). PTH concentrations were correlated with diastolic pressure (r = –0.39, P < 0.001). The data are compatible with increased parathyroid activity despite unchanged concentrations of vitamin D metabolites in human hypertension.Abbreviations PTH parathyroid hormone - C-PTH carboxy-terminal parathyroid hormone - 1,25(OH)₂D 1,25-di-hydroxyvitamin D - 25(OH)D 25-hydroxyvitamin D     

1,25-Dihydroxyvitamin D3 restores sensitivity to cyclophosphamide-induced apoptosis in non-obese diabetic (NOD) mice and protects against diabetes

The activated form of vitamin D, 1,25(OH)₂D₃, and its analogues can prevent type I diabetes in NOD mice. Protection is achieved without signs of systemic immunosuppression and is associated with a restoration of the defective immune regulator system of the NOD mice. The aim of the present study was to investigate whether this restoration of regulator cell function is the only mechanism in the prevention of diabetes by 1,25(OH)₂D₃. We tested therefore if 1,25(OH)₂D₃ could prevent cyclophosphamide-induced diabetes, since diabetes occurring after cyclophosphamide injection is believed to be due to an elimination of suppresser cells. NOD mice treated with 1,25(OH)₂D₃ (5 μg/kg every 2 days) from the time of weaning were clearly protected against diabetes induced by cyclophosphamide (200 mg/kg body wt at 70 days old) (2/12 (17%) versus 36/53 (68%) in control mice, P < 0.005). By co-transfer experiments it was demonstrated that cyclophosphamide had indeed eliminated the suppresser cells present in 1,25(OH)₂D₃-treated mice. Since cyclophosphamide injection did not break the protection offered by 1,25(OH)₂D₃, it was clear that diabetogenic effector cells were affected by 1,25(OH)₂D₃ treatment as well. This was confirmed by the finding that splenocytes from 1,25(OH)₂D₃-treated mice were less capable of transferring diabetes in young, irradiated NOD mice, and by the demonstration of lower Th1 cytokine levels in the pancreases of 1,25(OH)₂D₃-treated, cyclophosphamide-injected mice. This better elimination of effector cells in 1,25(OH)₂D₃-treated mice could be explained by a restoration of the sensitivity to cyclophosphamide-induced apoptosis in both thymocytes and splenocytes, in normally apoptosis-resistant NOD mice. Altogether, these data indicate that the protection against diabetes offered by 1,25(OH)₂D₃ may be independent of the presence of suppresser cells, and may involve increased apoptosis of Th1 autoimmune effector cells.     

Vitamin D Deficiency in Adult Sickle Cell Patients

Introduction

Vitamin D levels in adult black Americans with sickle cell disease (SCD) are comparatively lower than those found in the general population of black Americans. The objectives of this study were to examine the prevalence of Vitamin D deficiency (VDD) in adults with various subtypes of sickle cell disease and identify risk factors for vitamin D deficiency.

1, 25-dihydroxyvitamin D3 decreases adriamycin-induced podocyte apoptosis and loss

Background: Selective proteinuria is frequently observed in glomerular diseases characterized by podocyte injury. Although, 1,25-dihydroxyvitamin D3 [1,25(OH)₂D₃] has potential therapeutic effects on chronic kidney diseases through decreasing podocyte loss, the mechanism underlying the beneficial effects of 1,25(OH)₂D₃ on podocytes remains still unknown. The present study tested the hypothesis that 1,25(OH)₂D₃ directly reduced podocyte apoptosis and loss.Methods: Sprague-Dawley (SD) rats were randomly assigned into three groups: Adriamycin (ADR) group (n=15), ADR+1,25-(OH)₂D₃ group (n=16), and control group (n=16). Rats in ADR+1,25-(OH)₂D₃ group were treated with 1,25(OH)₂D₃ for 8 weeks. The number of podocytes and foot process width (FPW) were detected by transmission electron microscopy. The number of apoptotic podocytes per glomerulus and that of apoptotic nuclei and caspase-3 activity in cultured podocytes were determined by TUNEL staining. The average number of podocytes per glomerulus was quantified by immunohistochemistry. Expressions of p-Smad2/3, p-Smad1/5/8, Fas, Fas-Associated protein with Death Domain (FADD), Bax, and Bcl-2 proteins were examined by Western blot assay.Results: Compared with control group, proteinuria, FPW, apoptotic podocytes, caspase-3 activity, the protein expressions of p-Smad2/3, Fas, FADD, and Bax were significantly increased, podocyte density, p-Smad1/5/8 and Bcl-2 expression were decreased in ADR group. 1,25(OH)₂D₃ significantly reduced proteinuria, FPW, caspase-3 activity, expressions of p-Smad2/3, Fas, FADD, and Bax and apoptosis of podocytes, but increased serum albumin, number of viable podocytes , p-Smad1/5/8 and Bcl-2 expression in ADR treated rats.Conclusion: ADR-induced podocyte apoptosis was associated with the imbalance of p-Smad2/3, p-Smad1/5/8 the activity of caspase-3 and aberrant expressions of, Fas, FADD, Bax and Bcl-2. The beneficial effects of 1,25(OH)₂D₃ on podocytes may be attributable to inhibit podocyte apoptosis and the amelioration of podocytopenia.