Vitamin D metabolites in diabetic patients: Decreased serum concentration of 24,25-dihydroxyvitamin D

AbstractHypercalcemia occurs in up to 4% of the population in association with malignancy, primary hyperparathyroidism, ingestion of excessive calcium and/or vitamin D, ectopic production of 1,25-dihydroxyvitamin D [1,25(OH)2D], and impaired degradation of 1,25(OH)2D. The ingestion of excessive amounts of vitamin D3 (or vitamin D2) results in hypercalcemia and hypercalciuria due to the formation of supraphysiological amounts of 25-hydroxyvitamin D [25(OH)D] that bind to the vitamin D receptor, albeit with lower affinity than the active form of the vitamin, 1,25(OH)2D, and the formation of 5,6-trans 25(OH)D, which binds to the vitamin D receptor more tightly than 25(OH)D. In patients with granulomatous disease such as sarcoidosis or tuberculosis and tumors such as lymphomas, hypercalcemia occurs as a result of the activity of ectopic 25(OH)D-1-hydroxylase (CYP27B1) expressed in macrophages or tumor cells and the formation of excessive amounts of 1,25(OH)2D. Recent work has identified a novel cause of non-PTH-mediated hypercalcemia that occurs when the degradation of 1,25(OH)2D is impaired as a result of mutations of the 1,25(OH)2D-24-hydroxylase cytochrome P450 (CYP24A1). Patients with biallelic and, in some instances, monoallelic mutations of the CYP24A1 gene have elevated serum calcium concentrations associated with elevated serum 1,25(OH)2D, suppressed PTH concentrations, hypercalciuria, nephrocalcinosis, nephrolithiasis, and on occasion, reduced bone density. Of interest, first-time calcium renal stone formers have elevated 1,25(OH)2D and evidence of impaired 24-hydroxylase-mediated 1,25(OH)2D degradation. We will describe the biochemical processes associated with the synthesis and degradation of various vitamin D metabolites, the clinical features of the vitamin D-mediated hypercalcemia, their biochemical diagnosis, and treatment.

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Measurement of Plasma 1,25 Dihydroxyvitamin D Using a Novel Immunoextraction Technique and Immunoassay with Iodine Labelled Vitamin D Tracer

Annals of Clinical Biochemistry International Journal of Laboratory Medicine ◽

10.1177/000456329703400606 ◽

1997 ◽

Vol 34 (6) ◽

pp. 632-637 ◽

Cited By ~ 52

Author(s):

W D Fraser ◽

B H Durham ◽

J L Berry ◽

E B Mawer

Keyword(s):

Vitamin D ◽

Solid Phase ◽

Plasma Concentrations ◽

Sample Volume ◽

Cross Reactivity ◽

Regression Equations ◽

Vitamin D Metabolites ◽

Dihydroxyvitamin D ◽

1,25 Dihydroxyvitamin D ◽

High Concentrations

We evaluated a novel assay for the measurement of 1,25 dihydroxyvitamin D (1,25 (OH)2D). Immunoextraction of 1,25 (OH)2D is performed using a mini column containing a solid-phase monoclonal antibody followed by radioimmunoassay (RIA) using an 125I-labelled 1,25 (OH)2D derivative tracer and Sac-cell separation. The mean recovery of 1,25(OH)2D3 was 101%, linearity was excellent, inter- and intra-assay coefficients of variation were 9, 8 and 13% and 11, 10 and 14% at low, medium and high concentrations of 1,25(OH)2D3, respectively. The cross-reactivity of vitamin D metabolites was <0·0015% for 25-hydroxyvitamin D3, 24, 25 dihydroxyvitamin D3 and dihydrotachysterol and 0·54% for lα calcidol. 1,25 dihydroxyvitamin D2 cross-reactivity was 79%. The detection limit of the assay was 5pmol/L. Comparison with a commercial radio receptor assay (RRA) and an in-house RIA gave regression equations of y = 0·94x+11·8 ( r = 0·98) and y = 0·91x-1·7 ( r = 0.95), respectively, with no major discrepancies between the methods in all patient groups studied. Plasma concentrations of 1,25 (OH)2D obtained with the assay were as follows: normal, unsupplemented subjects: mean 88, range 48–155 pmol/L, n = 68, patients with chronic renal failure: mean 11, range 3–36 pmol/L, n = 27, primary hyperparathyroidism: mean 198, range 130–299 pmol/L, n = 23, Paget's disease: mean 92, range 42–149 pmol/L, n = 24, osteomalacia: mean 43, range 27–61 pmol/L, n = 9. A minimum sample volume of 300 μL is required, the hands-on time is significantly less than other commercial assays and the measuring procedure is gamma counting rather than scintillation counting. The assay offers several advantages over previous methods and should allow more laboratories to offer measurement of 1,25 (OH)2D as part of their repertoire.

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Thyroid and parathyroid-independent increase in plasma 1,25-dihydroxyvitamin D during late pregnancy in the rat

Journal of Endocrinology ◽

10.1677/joe.0.1160381 ◽

1988 ◽

Vol 116 (3) ◽

pp. 381-385 ◽

Cited By ~ 9

Author(s):

T. M. Nguyen ◽

A. Halhali ◽

H. Guillozo ◽

M. Garabedian ◽

S. Balsan

Keyword(s):

Vitamin D ◽

Placental Transfer ◽

Plasma Concentrations ◽

Late Pregnancy ◽

Maternal Plasma ◽

Vitamin D Metabolites ◽

Pregnant Rats ◽

Dihydroxyvitamin D ◽

Fetal Plasma ◽

And Control

ABSTRACT The effect of thyroparathyroidectomy (TPTX) on the plasma concentrations of the vitamin D metabolites (25-(OH)D, 24,25-(OH)2D and 1,25-(OH)2D) has been studied in pregnant rats and their fetuses during the last quarter of gestation. Maternal and fetal vitamin D metabolites were not significantly affected by TPTX. A significant increase in plasma 1,25-(OH)2D concentrations was observed in both TPTX and control mothers and fetuses from days 19 to 21. Fetal and maternal plasma 25-(OH)D were positively correlated in both control and TPTX groups. Such a correlation was also found for 24,25-(OH)2D in the two groups. In contrast, a positive correlation between maternal and fetal plasma concentrations of 1,25-(OH)2D was found in TPTX but not in control rats. These data suggest that major alterations in calcium metabolism, such as that produced by maternal TPTX, are insufficient to affect the changes in maternal and fetal plasma 1,25-(OH)2D during late pregnancy significantly. They also suggest that parathyroid hormone, thyroxine, and/or calcitonin may control a possible placental transfer of 1,25-(OH)2D in the rat. J. Endocr. (1988) 116, 381–385

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1,25(OH)2D3 blunts hormone-elevated cytosolic Ca2+ in osteoblast-like cells

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1992.263.6.e1070 ◽

1992 ◽

Vol 263 (6) ◽

pp. E1070-E1076

Author(s):

J. Green ◽

C. R. Kleeman ◽

S. Schotland ◽

L. H. Ye

Keyword(s):

Vitamin D ◽

Plasma Membrane ◽

Bone Cell ◽

Free Calcium ◽

Osteoblastic Cell ◽

Cell Physiology ◽

Vitamin D Metabolites ◽

Osteoblastic Cell Line ◽

Calciotropic Hormones ◽

Dihydroxyvitamin D

Cytosolic free calcium ([Ca2+]i) is an important regulator of bone cell physiology. We studied the interaction of vitamin D metabolites on the hormonal-activated Ca message system in the osteoblastic cell line UMR-106. The acute rise in [Ca2+]i induced by different calciotropic hormones [parathyroid hormone, prostaglandin E2 (PGE2)] was dose dependently blunted by 1,25-dihydroxyvitamin D [1,25(OH)2D3; half-maximal inhibitory concn approximately 5 x 10(-11) M] and was initially observed after 8 h of preincubation. The 1,25(OH)2D3 metabolite of vitamin D was two orders of magnitude more potent than 24,25(OH)2D3 and 25(OH)D3. To discern between an effect of 1,25(OH)2D3 on hormonal-induced Ca2+ entry through the plasma membrane channel vs. release of Ca2+ from internal stores, we suspended fura-2-loaded cells in Mn2+ rather than Ca2+ buffers. In cells preincubated with 1,25(OH)2D3, [Ca2+]i release (indicated by [Ca2+]i transient) was significantly blunted, whereas Mn2+ influx (indicating Ca2+ flux across the plasma membrane) was unaltered, suggesting a selective effect of 1,25(OH)2D3 on hormonal-activated release of Ca2+ from intracellular stores. 1,25(OH)2D3 also inhibited the PGE2-induced production of inositol 1,4,5-trisphosphate. We conclude that, in osteoblasts, chronic (hours) incubation with 1,25(OH)2D3 leads to attenuated stimulation of the [Ca2+]i transduction pathway by calciotropic hormones. This effect of 1,25(OH)2D3 may provide a cellular basis for the synergism between the effects of vitamin D and calciotropic hormones at the bone level.

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Calcium Malabsorption in Elderly Women with Vertebral Fractures: Evidence for Resistance to the Action of Vitamin D Metabolites on the Bowel

Clinical Science ◽

10.1042/cs0660103 ◽

1984 ◽

Vol 66 (1) ◽

pp. 103-107 ◽

Cited By ~ 102

Author(s):

R. M. Francis ◽

M. Peacock ◽

G. A. Taylor ◽

J. H. Storer ◽

B. E. C. Nordin

Keyword(s):

Vitamin D ◽

Vertebral Fractures ◽

Calcium Absorption ◽

Elderly Women ◽

Vitamin D Metabolites ◽

Hydroxyvitamin D ◽

Dihydroxyvitamin D ◽

Significant Difference ◽

Before And After ◽

Calcium Malabsorption

1. Radio-calcium absorption, plasma 25-hydroxyvitamin D [25-(OH)D] and 1,25-dihydroxyvitamin D [1,25-(OH)2D] concentrations were measured in 19 elderly women with, and 21 without, vertebral fractures, before and after treatment with 25-hydroxyvitamin D3 [25-(OH)D3], to establish whether malabsorption of calcium in elderly women with vertebral fractures has a cause different from that in elderly women without vertebral fractures. 2. Malabsorption of calcium and low plasma 25-(OH)D and 1,25-(OH)2D concentrations were common in both groups of women but there was no significant difference in these variables between the two groups. 3. After treatment with 40 μg of 25-(OH)D3 daily for 7 days, there was a significant increase in plasma 25-(OH)D and 1,25-(OH)2D in both groups of women, but radio-calcium absorption increased significantly only in the group without vertebral fractures. 4. Elderly women with vertebral fractures have malabsorption of calcium which is resistant to the action of vitamin D metabolites at concentrations which correct calcium malabsorption in elderly women without vertebral fractures.

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Vitamin D metabolites regulate osteocalcin synthesis and proliferation of human bone cells in vitro

Journal of Endocrinology ◽

10.1677/joe.0.1050391 ◽

1985 ◽

Vol 105 (3) ◽

pp. 391-396 ◽

Cited By ~ 89

Author(s):

H. Skjødt ◽

J. A. Gallagher ◽

J. N. Beresford ◽

M. Couch ◽

J. W. Poser ◽

...

Keyword(s):

Vitamin D ◽

Cell Proliferation ◽

Bone Cells ◽

Rank Order ◽

Human Bone ◽

Dependent Manner ◽

Vitamin D Metabolites ◽

Hydroxyvitamin D ◽

Dihydroxyvitamin D

ABSTRACT The effects of six natural vitamin D metabolites of potential biological and therapeutic interest, 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3), 25-hydroxyvitamin D3 (25-OH-D3), 24R,25-dihydroxyvitamin D3 (24R,25-(OH)2D3), 1,24R,25-trihydroxyvitamin D3 (1,24R,25-(OH)3D3), 25S,26-dihydroxyvitamin D3 (25S,26-(OH)2D3) and 1,25S,26-trihydroxyvitamin D3 (1,25S,26-(OH)3D3) on cell replication and expression of the osteoblastic phenotype in terms of osteocalcin production were examined in cultured human bone cells. At a dose of 5 × 10−12 mol/l, 1,25-(OH)2D3 stimulated cell proliferation, whereas at higher doses (5 × 10−9−5 × 10 −6 mol/l) cell growth was inhibited in a dose-dependent manner. The same pattern of effects was seen for the other metabolites in a rank order of potency: 1,25-(OH)2D3> 1,25S,26-(OH)3D3 = 1,24R,25-(OH)3D3>25S,26-(OH)2D3 = 24R,25-(OH)2D3 = 25-OH-D3. Synthesis of osteocalcin was induced by 1,25-(OH)2D3 in doses similar to those required to inhibit cell proliferation. Biphasic responses were observed for some of the metabolites in terms of osteocalcin synthesis, inhibitory effects becoming apparent at 5 × 10−6 mol/l. The cells did not secrete osteocalcin spontaneously. These results indicate that vitamin D metabolites may regulate growth and expression of differentiated functions of normal human osteoblasts. J. Endocr. (1985) 105, 391–396

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Evidence for an interaction of insulin and sex steroids in the regulation of vitamin D metabolism in the rat

Journal of Endocrinology ◽

10.1677/joe.0.1150295 ◽

1987 ◽

Vol 115 (2) ◽

pp. 295-301 ◽

Cited By ~ 16

Author(s):

B. L. Nyomba ◽

R. Bouillon ◽

P. De Moor

Keyword(s):

Vitamin D ◽

Diabetic Rats ◽

Vitamin D Metabolites ◽

Serum Concentrations ◽

Insulin Deficiency ◽

Intact Male ◽

Vitamin D Metabolism ◽

Dihydroxyvitamin D ◽

Androgen Withdrawal ◽

Intact Rats

ABSTRACT Vitamin D metabolites and vitamin D-binding protein (DBP) were measured in non-diabetic rats and in rats made diabetic with streptozotocin. The animals were studied in the intact state, after gonadectomy and during pregnancy. In male non-diabetic rats the serum concentrations of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) and DBP decreased after orchidectomy and were restored by treatment with testosterone. In female non-diabetic rats, these parameters increased after ovariectomy. Increased 1,25-(OH)2D3 and decreased DBP concentrations were found during pregnancy in non-diabetic rats. After the induction of diabetes in intact rats of both sexes, the concentration of DBP decreased, but a significant decrease in the concentration of 1,25-(OH)2D3 was found in male animals only. After ovariectomy, however, 1,25-(OH)2D3 decreased also in female diabetic rats. Both orchidectomy and insulin deficiency depressed serum concentrations of 1,25-(OH)2D3 (−22 and −45% respectively) and DBP (−14 and −29% respectively), but the effects of insulin deficiency were greater than those of androgen withdrawal. Moreover, the testosterone concentration was twofold lower in intact male diabetic rats than in non-diabetic animals. Insulin, but not testosterone treatment, however, restored DBP and 1,25-(OH)2D3 concentrations in diabetic rats, and insulin was effective in intact as well as in gonadectomized animals. This study shows that insulin deficiency decreases the concentrations of DBP and 1,25-(OH)2D3 in the rat, and that these decreases are facilitated by androgens, but counteracted by oestrogens. J. Endocr. (1987) 115, 295–301

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The influence of vitamin D metabolites on collagen synthesis by chick cartilage in organ culture

Journal of Endocrinology ◽

10.1677/joe.0.1050079 ◽

1985 ◽

Vol 105 (1) ◽

pp. 79-85 ◽

Cited By ~ 16

Author(s):

I. R. Dickson ◽

P. M. Maher

Keyword(s):

Vitamin D ◽

Collagen Synthesis ◽

Bone Cells ◽

Endochondral Bone Formation ◽

Primary Role ◽

Vitamin D Metabolites ◽

Minimum Concentration ◽

Dihydroxyvitamin D ◽

Growth Cartilage ◽

1,25 Dihydroxyvitamin D

ABSTRACT When growth cartilage from rachitic chicks was cultured in the presence of the calcium-regulating hormone 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3), collagen resorption was increased and collagen synthesis decreased compared to control cultures containing no hormone. The minimum concentration of the hormone that caused a statistically significant inhibition of collagen synthesis was 10 −8 mol/l. Collagen synthesis by growth cartilage from normal chicks was also reduced by 1,25-(OH)2D3, showing that it was not an abnormal response of vitamin D-depleted tissue. 25-Hydroxyvitamin D3 and 24,25-dihydroxyvitamin D3 also inhibited collagen synthesis by cultures of growth cartilage but only at higher metabolite concentrations. 1,25-Dihydroxyvitamin D3 (10−7 mol/l) did not significantly inhibit collagen synthesis by cultures of articular fibrocartilage and of sternal cartilage, tissues that do not calcify physiologically. The minimum concentration of 1,25-(OH)2D3 (10−9 mol/l) necessary to cause decreased collagen synthesis by embryonic chick calvaria was lower than the value obtained with growth cartilage; this suggests that bone cells may be more sensitive to the hormone in this respect than are growth cartilage chondrocytes. These findings provide evidence of a direct role of 1,25-(OH)2D3 in the control of endochondral bone formation which is consistent with its primary role in the maintenance of plasma calcium homeostasis. J. Endocr. (1985) 105, 79–85

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Perinatal parathyroid hormone, vitamin D metabolites, and calcitonin in man

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1980.239.5.e385 ◽

1980 ◽

Vol 239 (5) ◽

pp. E385-E390 ◽

Cited By ~ 9

Author(s):

P. Wieland ◽

J. A. Fischer ◽

U. Trechsel ◽

H. R. Roth ◽

K. Vetter ◽

...

Keyword(s):

Vitamin D ◽

Parathyroid Hormone ◽

Plasma Levels ◽

Maternal Blood ◽

Sign Test ◽

Blood Levels ◽

Vitamin D Metabolites ◽

Dihydroxyvitamin D ◽

Umbilical Blood ◽

Arteriovenous Difference

Plasma levels of calcium and of parathyroid hormone (PTH) were comparable in the mothers at delivery and in nonpregnant controls; magnesium was decreased (P < 0.001) in maternal blood; and phosphate (P < 0.001), 1,25-dihydroxyvitamin D (1,25(OH)2D) (P < 0.001), and calcitonin (CT) (P < 0.01) were raised. Cord levels of calcium (P < 0.01), magnesium (P < 0.05), and CT (P < 0.01) were higher, and PTH (P < 0.01) was lower than in the maternal blood. Levels of 25(OH)D, 1,25(OH)2D, and 24,25(OH)2D lower in fetal than in maternal blood (P < 0.01) and significant linear correlations between the vitamin D metabolites examined in mothers and neonates (P < 0.001) are consistent with a diffusion barrier across the placenta and/or different affinities of binding proteins. Plasma levels of 25(OH)D and 24,25(OH)2D were significantly related (P < 0.01), suggesting precursor product type, relationships. Levels of 1,25(OH)2D higher in arterial than in venous umbilical blood (P = 0.06, sign test; P < 0.005, paired t test) suggest that the fetus participates in the synthesis of 1,25(OH)2D. Maternal PTH was significantly related to the arteriovenous difference of 1,25(OH)2D levels (P < 0.01) in cord blood, and it possibly enhances the synthesis of 1,25(OH)2D during the final stage of fetal development.

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