Hereditary hypophosphataemic rickets: report of a family from the Indian subcontinent.
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Nutritional deficiency continues to be an important cause of rickets in the underdeveloped and developing parts of the world. In the western hemisphere, predominantly non-nutritional forms of rickets and osteomalacia are now seen. In this report we discuss a family with X-linked hypophosphataemic rickets from the Kashmir region of the Indian subcontinent (which is an uncommon entity here). (+info)
Altered diurnal regulation of blood ionized calcium and serum parathyroid hormone concentrations during parenteral nutrition.
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BACKGROUND: Little is known about parathyroid gland function in patients receiving total parenteral nutrition (TPN). OBJECTIVE: Our objective was to determine whether parathyroid gland function is abnormal in TPN recipients. DESIGN: Six patients with a mean (+/-1 SD) age of 45.5 +/- 8.0 y who had been receiving TPN for 18.7 +/- 2. 8 y underwent bone biopsy, bone mass measurements with dual-energy X-ray absorptiometry, and dynamic tests of parathyroid gland function. Diurnal variations in blood ionized calcium (iCa(2+)) and serum parathyroid hormone (PTH) concentrations were also assessed. Results were compared with those of healthy volunteers. RESULTS: Bone mass and bone formation were subnormal in all patients. Basal serum PTH concentrations were moderately higher in the TPN recipients than in healthy volunteers, and values obtained every 30 min over 24 h were significantly higher (P < 0.001) in TPN recipients (5.0 +/- 0.9 pmol/L) than in healthy volunteers (2.6 +/- 0.6 pmol/L). The percentage increase in serum PTH during citrate-induced hypocalcemia was lower in the TPN recipients, consistent with secondary hyperparathyroidism. Evening infusions of calcium-containing TPN eliminated the nocturnal rise in serum PTH, increased the amplitude of change for iCa(2+) and PTH over 24 h, increased the orderliness of change for iCa(2+) and PTH as measured by approximate entropy (ApEn), and enhanced the synchrony of change between iCa(2+) and PTH. Treatment for 10 d with calcium-free TPN restored the nocturnal rise in serum PTH and increased ApEn for PTH. ApEn for iCa(2+) remained low, suggesting that a component of nutrient solutions, but not calcium per se, enhances the regularity of PTH release in TPN recipients. CONCLUSION: Parathyroid gland function is abnormal in long-term TPN recipients, which may contribute to disturbances in bone metabolism. (+info)
Steroid hormone receptor expression and action in bone.
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The skeleton is a complex tissue, and hormonal control of bone remodelling is elaborate. The important role that steroid hormones play in bone cell development and in the maintenance of normal bone architecture is well established, but it is only relatively recently that it has become possible to describe their precise mechanism of action. This review focuses not only on the steroid hormones (oestrogens, corticosteroids, androgens and progesterone), but also on related hormones (vitamin D, thyroid hormone and the retinoids), all of which act via structurally homologous nuclear receptors that form part of the steroid/thyroid receptor superfamily. By examining the actions of all of these hormones in vivo and in vitro, this review gives a general overview of the current understanding of steroid hormone action in bone. In addition, a comprehensive review of steroid hormone receptor expression in bone cells is included. Finally, the role that future developments, such as steroid hormone receptor knockout mice, will play in our understanding of steroid hormone action in bone is considered. (+info)
Warfarin-induced artery calcification is accelerated by growth and vitamin D.
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The present studies demonstrate that growth and vitamin D treatment enhance the extent of artery calcification in rats given sufficient doses of Warfarin to inhibit gamma-carboxylation of matrix Gla protein, a calcification inhibitor known to be expressed by smooth muscle cells and macrophages in the artery wall. The first series of experiments examined the influence of age and growth status on artery calcification in Warfarin-treated rats. Treatment for 2 weeks with Warfarin caused massive focal calcification of the artery media in 20-day-old rats and less extensive focal calcification in 42-day-old rats. In contrast, no artery calcification could be detected in 10-month-old adult rats even after 4 weeks of Warfarin treatment. To directly examine the importance of growth to Warfarin-induced artery calcification in animals of the same age, 20-day-old rats were fed for 2 weeks either an ad libitum diet or a 6-g/d restricted diet that maintains weight but prevents growth. Concurrent treatment of both dietary groups with Warfarin produced massive focal calcification of the artery media in the ad libitum-fed rats but no detectable artery calcification in the restricted-diet, growth-inhibited group. Although the explanation for the association between artery calcification and growth status cannot be determined from the present study, there was a relationship between higher serum phosphate and susceptibility to artery calcification, with 30% higher levels of serum phosphate in young, ad libitum-fed rats compared with either of the groups that was resistant to Warfarin-induced artery calcification, ie, the 10-month-old rats and the restricted-diet, growth-inhibited young rats. This observation suggests that increased susceptibility to Warfarin-induced artery calcification could be related to higher serum phosphate levels. The second set of experiments examined the possible synergy between vitamin D and Warfarin in artery calcification. High doses of vitamin D are known to cause calcification of the artery media in as little as 3 to 4 days. High doses of the vitamin K antagonist Warfarin are also known to cause calcification of the artery media, but at treatment times of 2 weeks or longer yet not at 1 week. In the current study, we investigated the synergy between these 2 treatments and found that concurrent Warfarin administration dramatically increased the extent of calcification in the media of vitamin D-treated rats at 3 and 4 days. There was a close parallel between the effect of vitamin D dose on artery calcification and the effect of vitamin D dose on the elevation of serum calcium, which suggests that vitamin D may induce artery calcification through its effect on serum calcium. Because Warfarin treatment had no effect on the elevation in serum calcium produced by vitamin D, the synergy between Warfarin and vitamin D is probably best explained by the hypothesis that Warfarin inhibits the activity of matrix Gla protein as a calcification inhibitor. High levels of matrix Gla protein are found at sites of artery calcification in rats treated with vitamin D plus Warfarin, and chemical analysis showed that the protein that accumulated was indeed not gamma-carboxylated. These observations indicate that although the gamma-carboxyglutamate residues of matrix Gla protein are apparently required for its function as a calcification inhibitor, they are not required for its accumulation at calcification sites. (+info)
Vitamin D metabolite requirements in dialysed children receiving recombinant human growth hormone.
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BACKGROUND: The aim of the study was to assess the requirement of active vitamin D in dialysed children during treatment with recombinant human growth hormone (rhGH). METHODS: Twenty-six children (aged 5-15 years) were treated with rhGH for 6 months. The serum concentration of parathyroid hormone (PTH), alkaline phosphatase (AP), and calcium and phosphorus were measured in two groups of patients studied in the years 1994-1995 (group I) and 1995-1998 (group II) respectively. Group I received a constant dose of alfacalcidol that was sufficient to keep PTH below 200 pg/ml before rhGH treatment began. The serum PTH level was checked every 3 months. Alfacalcidol was administered to group II according to serum PTH levels checked on a monthly basis. RESULTS: In group I the PTH level increased after 3 and 6 months of rhGH treatment from mean level 73+/-60; 155+/-156 and 344+/-249 pg/ml respectively; P<0.05. AP activity increased after 6 months of treatment from 206+/-99 to 325+/-124 U/l respectively; P<0.01. The calcium level decreased from baseline after 3 months of treatment from 2.36+/-0.21 to 2.17+/-0.12 mmol/l respectively; P<0.05. In group II AP activity increased after 3 and 6 months of treatment from 272+/-169 to 332+/-192 and 404. 9+/-219.8 U/l respectively; P<0.01. The mean level of phosphorus decreased after 6 months from 2.15+/-0.28 to 1.70+/-0.39 mmol/l respectively; P<0.01. In group II the mean dose of alfacalcidol increased by 60.9%. CONCLUSIONS: In children with end-stage renal failure, higher doses of vitamin D are needed during rhGH treatment. During rhGH treatment, frequent control of serum PTH level is necessary. (+info)
Regulation of vitamin D-1alpha-hydroxylase and -24-hydroxylase expression by dexamethasone in mouse kidney.
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We investigated the effects of dexamethasone on vitamin D-1alpha-hydroxylase and -24-hydroxylase expression and on vitamin D receptor (VDR) content in the kidneys of mice fed either a normal (NCD) diet or a calcium- and vitamin D-deficient (LCD) diet for 2 weeks. For the last 5 days mice received either vehicle or dexamethasone (2 mg/kg per day s.c.). Dexamethasone significantly increased plasma calcium concentrations without changing plasma concentrations of 1,25-dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) in both NCD and LCD groups. Northern blot and enzyme activity analyses in NCD mice revealed that dexamethasone increased renal VDR mRNA expression modestly and greatly increased 24-hydroxylase mRNA abundance and enzyme activity, but did not affect 1alpha-hydroxylase mRNA abundance and enzyme activity. In mice fed an LCD diet, dexamethasone increased renal VDR mRNA expression 1.5-fold, decreased 1alpha-hydroxylase mRNA abundance (52%) and activity (34%), and markedly increased 24-hydroxylase mRNA abundance (16-fold) and enzyme activity (9-fold). Dexamethasone treatment did not alter functional VDR number (B(max) 125-141 fmol/mg protein) or ligand affinity (K(d) 0.13-0.10 nM) in LCD mice. Subcutaneous injections of 1,25(OH)(2)D(3) (0.24 nmol/kg per day for 5 days) into NCD mice strongly increased renal 24-hydroxylase mRNA abundance and enzyme activity, while there was no effect of dexamethasone on renal 24-hydroxylase expression in these mice. This may be due to overwhelming induction of 24-hydroxylase by 1,25(OH)(2)D(3). These findings suggest that glucocorticoid-induced osteoporosis is caused by direct action of the steroids on bone, and the regulatory effect of glucocorticoids on renal 25-hydroxyvitamin D(3) metabolism may be less implicated in the initiation and progression of the disease. (+info)
Protective effect of thioredoxin upon NO-mediated cell injury in THP1 monocytic human cells.
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Although NO has been postulated to play important roles in host defences, it is potentially damaging for exposed cells, including for the macrophages producing the NO. Thus a network of radical acceptors and enzymes is thought to play an important redox-buffering role to protect cells against NO-mediated injury. We examined the properties of the redox systems superoxide dismutase (SOD)/catalase, glutathione (GSH) and thioredoxin (Trx), in regulating the viability of two human monocytic cell lines (THP1 and U937) exposed to the NO-generating compound diethylene triamine-nitric oxide (DETA-NO). We observed that NO-induced cytotoxic effects were time- and dose-dependent towards the two cell lines. After vitamin-induced differentiation in vitro with retinoic acid (RA) and 1,25-dihydroxy vitamin D(3) (VD), termed RA/VD, we observed that THP1 RA/VD cells became more resistant to NO-mediated cytotoxicity whereas the susceptibility of U937 cells was not modified. Using Western blotting and reverse-transcriptase PCR methods, we observed that gene transcription and protein expression of Trx and thioredoxin reductase were significantly increased upon RA/VD treatment and differentiation in THP1 cells. By contrast, SOD/catalase and GSH redox state remained unmodified. Finally, a stable transfectant THP1 line overexpressing Trx was found to be more resistant than THP1 control cells that were untransfected or transfected with an empty plasmid, when exposed to DETA-NO in vitro. In conclusion, we observed an inverse correlation between cell susceptibility to NO damaging effects and Trx expression, suggesting that the Trx system may have important preventative capacities towards NO-mediated cellular injury in monocytic macrophage cells. (+info)
25-Hydroxyvitamin D3, the prohormone of 1,25-dihydroxyvitamin D3, inhibits the proliferation of primary prostatic epithelial cells.
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The hormonal metabolite of vitamin D, 1alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3] is known to inhibit the proliferation of prostatic epithelial cells. This has stimulated interest in vitamin D compounds as therapeutic agents for prostate cancer. However, the therapeutic use of 1,25(OH)2D3 is limited because elevations in serum 1,25(OH)2D3 can cause dangerous elevations in serum calcium levels. We wondered whether the prohormone of 1,25(OH)2D3, 25-hydroxyvitamin D3 (25-OH-D3), which is much less calcemic, could also achieve antiproliferative effects in prostatic cells. 25-OH-D3 is converted to 1,25(OH)2D3 by the mitochondrial enzyme 1-alpha-hydroxylase. We have recently shown that human prostatic cells also possess significant 1-alpha-hydroxylase activity (Schwartz et al., Cancer Epidemiol. Biomark. Prev., 7: 391-395, 1998). We studied 1-alpha-hydroxylase gene expression in four strains of primary human prostatic epithelial cells by reverse transcription PCR amplification (RT-PCR) of 1-alpha-hydroxylase. Human prostatic stromal cells were negative for 1-alpha-hydroxylase by RT-PCR. This led us to hypothesize that 25-OH-D3 would inhibit the proliferation of prostatic epithelial cells because 25-OH-D3 would be converted to 1,25(OH)2D3 intracellularly. We studied the effects of 25-OH-D3 and 1,25(OH)2D3 on the proliferation of prostatic epithelial cells using high density growth and clonal growth assays on two different primary cell strains derived from normal human prostatic peripheral zone. 25-OH-D3 and 1,25(OH)2D3 each inhibited growth in a dose- and time-dependent manner. Growth inhibition was evident at 1 nM, and maximal inhibition was observed at 100 nM within 10-12 days of exposure. The potencies of 25-OH-D3 and 1,25(OH)2D3 were not significantly different. These data demonstrate that 25-OH-D3, which previously was thought to have little biological activity, can become a potent antiproliferative hormone for prostatic cells that express 1-alpha-hydroxylase. Because 25-OH-D3 exhibits similar potency to 1,25(OH)2D3 but is less calcemic, 25-OH-D3 may offer a safer option than 1,25(OH)2D3 for prostate cancer therapy. Moreover, because 25-OH-D3 is produced endogenously from vitamin D, these findings support a potential role for vitamin D in the chemoprevention of prostate cancer. (+info)