Global Consensus Recommendations on Prevention and Management of Nutritional Rickets

"BACKGROUND: Vitamin D and calcium deficiencies are common worldwide, causing nutritional rickets and osteomalacia, which have a major impact on health, growth, and development of infants, children, and adolescents; the consequences can be lethal or can last into adulthood. The goals of this evidence-based consensus document are to provide health care professionals with guidance for prevention, diagnosis, and management of nutritional rickets and to provide policy makers with a framework to work toward its eradication. EVIDENCE: A systematic literature search examining the definition, diagnosis, treatment, and prevention of nutritional rickets in children was conducted. Evidence-based recommendations were developed using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) system that describes the strength of the recommendation and the quality of supporting evidence. PROCESS: Thirty-three nominated experts in pediatric endocrinology, pediatrics, nutrition, epidemiology, public health, and health economics evaluated the evidence on specific questions within five working groups. The consensus group, representing 11 international scientific organizations, participated in a multiday conference in May 2014 to reach a global evidence-based consensus. RESULTS: This consensus document defines nutritional rickets and its diagnostic criteria and describes the clinical management of rickets and osteomalacia. Risk factors, particularly in mothers and infants, are ranked, and specific prevention recommendations including food fortification and supplementation are offered for both the clinical and public health contexts. CONCLUSION: Rickets, osteomalacia, and vitamin D and calcium deficiencies are preventable global public health problems in infants, children, and adolescents. Implementation of international rickets prevention programs, including supplementation and food fortification, is urgently required."

Antagonistic action of novel 1alpha,25-dihydroxyvitamin D(3)-26, 23-lactone analogs on 25-hydroxyvitamin-D(3)-24-hydroxylase gene expression induced by 1alpha,25-dihydroxy-vitamin D(3) in human promyelocytic leukemia (HL-60) cells.

We have demonstrated that 1alpha,25-dihydroxyvitamin D(3)-26, 23-lactone analogs, (23S)- and (23R)-25-dehydro-1alpha-hydroxyvitamin D(3)-26,23-lactone (TEI-9647, TEI-9648, respectively), inhibit HL-60 cell differentiation induced by 1alpha,25-dihydroxyvitamin D(3) [1alpha,25(OH)(2)D(3)], but not differentiation caused by all-trans retinoic acid (D. Miura et al., 1999, J. Biol. Chem. 274, 16392). To assess whether the antagonistic actions of TEI-9647 and TEI-9648 in HL-60 cells are related to 1alpha,25(OH)(2)D(3) breakdown, we investigated their effects on catabolism of 1alpha,25(OH)(2)D(3). In HL-60 cells, the C-24 but not the C-23 side-chain oxidation pathway of 1alpha,25(OH)(2)D(3) has been reported. Here we demonstrate that 1alpha,25(OH)(2)D(3) was metabolized both to 24,25,26,27-tetranor-1alpha,23-(OH)(2)D(3) and 1alpha,25(OH)(2)D(3)-26,23-lactone; thus HL-60 cells constitutively possess both the 24- and the 23-hydroxylases. Metabolism of 1alpha, 25(OH)(2)D(3) was strongly suppressed by 10(-7) M TEI-9647 or 10(-6) M TEI-9648. 1alpha,25(OH)(2)D(3) alone slightly induced 24-hydroxylase gene expression by 8 h with full enhancement by 24-48 h; this induction was inhibited by 10(-6) M TEI-9647 and 10(-6) M TEI-9648 (86.2 and 31.9%, respectively) 24 h after treatment. However, analogs of TEI-9647 and TEI-9648 without the 25-dehydro functionality induced 24-hydroxylase gene expression. These results indicate that TEI-9647 and TEI-9648 clearly mediate their stereoselective antagonistic actions independent of their actions to block the catabolism of 1alpha,25(OH)(2)D(3). Therefore, TEI-9647 and TEI-9648 appear to be the first antagonists specific for the nuclear 1alpha,25(OH)(2)D(3) receptor-mediated genomic actions of 1alpha,25(OH)(2)D(3) in HL-60 cells.

Analysis of localization of mutated tissue-nonspecific alkaline phosphatase proteins associated with neonatal hypophosphatasia using green fluorescent protein chimeras.

Hypophosphatasia is associated with a defect of the tissue-nonspecific alkaline phosphatase (TNSALP) gene. The onset and clinical severity are usually correlated in hypophosphatasia; patients with perinatal hypophosphatasia die approximately at the time of birth. In contrast, we describe a male neonatal patient with hypophosphatasia who had no respiratory problems and survived. He was compound heterozygous for the conversion of Phe to Leu at codon 310 (F310L) and the deletion of a nucleotide T at 1735 (delT1735), causing the frame shift with the result of the addition of 80 amino acids at the C-terminal of the protein. Because the C-terminal portion of TNSALP is known to be important for TNSALP to bind to the plasma membrane, the localization of wild-type and mutated TNSALP proteins was analyzed using green fluorescent protein chimeras. The expression vectors containing the complementary DNA of fusion proteins consisting of signal peptide, green fluorescent protein, and wild-type or mutated TNSALP, caused by delT1735 or F310L mutation, were introduced transiently or stably in Saos-2 cells. The delT1735 mutant failed to localize at the cell surface membrane, whereas the wild-type and the F310L mutants were located in the plasma membrane and cytoplasm. The assay for enzymatic activity of TNSALP revealed that the delT1735 mutant lost the activity and that the F310L mutant exhibited an enzymatic activity level that was 72% of the normal level. The F310L mutation was also detected in another neonatal patient with relatively mild (nonlethal) hypophosphatasia (reported in J Clin Endocrinol Metab, 81:4458-4461, 1996), suggesting that residual ALP activity of the F310L mutant contributes to the less severe phenotype. The patient is unique, with respect to a discrepancy between onset and clinical severity in hypophosphatasia.

Human galactocerebrosidase gene: promoter analysis of the 5'-flanking region and structural organization.

Galactocerebrosidase (GALC; EC 3.2.1.46) is a lysosomal enzyme which hydrolyzes several galactolipids and the deficiency of GALC is responsible for Krabbe disease. Recently, we cloned cDNAs for human and murine GALC. In this study we characterized the genomic organization and the promoter of the human gene. The gene was about 60 kb in length and consisted of 17 exons as reported by Luzi et al. DNA sequence analysis showed that the 5'-flanking region of the first exon was GC-rich and had not typical TATA-box but ten GC-box-like sequences within a 200 bp sequence upstream from the initiation codon. Another inframe ATG, which has better Kozak consensus sequence, was found at 48 bp upstream to the first ATG reported]. Promoter analysis using a luciferase assay in COS 7 cells showed that the -149 to -112 nucleotide (from the initiation codon A) region has dominant promoter activity. In this region three GC-box-like sequence and one YY1 binding site were detected. Primer extension revealed several transcription start sites within the region of -146 to -103 nucleotide. In this study we firstly demonstrated that the YY1 binding site and subsequent GC-box-like sequences could be a promoter in a housekeeping gene.

Monoallelic expression of normal mRNA in the PIT1 mutation heterozygotes with normal phenotype and biallelic expression in the abnormal phenotype.

The combined deficiency of thyrotropin, growth hormone and prolactin, caused by PIT1 abnormality manifests in the homozygous or heterozygous state. We studied a patient having an allele with Arg271Trp mutation, which produces clinical symptoms in heterozygotes by a dominant-negative effect. However, in the family, her father, grandmother and aunts had the same mutation without clinical symptoms, although the proband had typical phenotypic expression. We analyzed the PIT1 transcript in peripheral lymphocytes by reverse transcription-polymerase chain reaction and found monoallelic expression of normal allele in the father and grandmother and skewed pattern of biallelic expression in the proband. The phenotypic expression of PIT1 abnormality may depend on different transcription of the PIT1 gene.

A new point mutation in the deoxyribonucleic acid-binding domain of the vitamin D receptor in a kindred with hereditary 1,25-dihydroxyvitamin D-resistant rickets.

Hereditary 1,25-dihydroxyvitamin D [1,25-(OH)2D]-resistant rickets (HVDRR) is a rare disorder characterized by rickets, alopecia, hypocalcemia, secondary hyperparathyroidism, and normal or elevated serum 1,25-dihydroxyvitamin D levels. We describe a patient with typical clinical characteristics of HVDRR, except that elevated levels of serum phosphorus were present coincident with increased levels of serum intact PTH. The patient was treated with high dose calcium infusion after an ineffective treatment with 1 alpha-hydroxyvitamin D3; serum calcium and phosphorus as well as intact PTH and alkaline phosphatase levels were normalized. Evaluation of phytohemagglutinin-activated lymphocytes derived from this patient revealed that 1,25-(OH)2D3 was unable to inhibit thymidine incooperation, a result that contrasts with the capacity of 1,25-(OH)2D3 to inhibit uptake into normal activated lymphocytes. 1,25-(OH)2D3 did not induce human osteocalcin promoter activity after transfection of this DNA linked to a reporter gene into patient cells. Cointroduction of a human vitamin D receptor (VDR) cDNA expression vector with the reporter plasmid, however, restored the hormone response. Evaluation of extracts from the patient cells for VDR DNA binding revealed a defect in DNA binding. Analysis of genomic DNA from the patient's cells by PCR confirmed the presence of a point mutation in exon 2 of the VDR. This exon directs synthesis of a portion of the DNA-binding domain of the receptor. We conclude that the genetic basis for 1,25-(OH)2D3 resistance in this kindred with VDR-positive HVDRR is due to a single base mutation in the VDR that leads to production of a receptor unable to interact appropriately with DNA.

1,25-Dihydroxyvitamin D3 enhances the effect of refeeding on steady state preproinsulin messenger ribonucleic acid levels in rats.

To elucidate the regulatory mechanism of vitamin D action on insulin biosynthesis and secretion, we examined preproinsulin (ppI) mRNA levels in the pancreas of normal rats, vitamin D-deficient rats, and rats supplemented with 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] or calcium (Ca) for 3 days. The ppI mRNA levels determined by dot blot analysis in vitamin D-deficient, 1,25-(OH)2D3-replete, and Ca-replete rats were 39.1%, 68.7%, and 66.7%, respectively, of values in normal rats. These results concur with previously reported levels of insulin secretion in the perfused rat pancreas. The reduced level of ppI mRNA should lead to a decrease in insulin biosynthesis and, thus, impair insulin secretion in vitamin D-deficient rats. The observed partial recovery of ppI mRNA levels through supplementation of 1,25-(OH)2D3 or Ca may be one mechanism by which insulin secretion is restored in rats after 1,25-(OH)2D3 or Ca repletion. We examined further the time course of ppI mRNA accumulation in rats after a single administration of 1,25-(OH)2D3. When fasting was continued for an additional 24-h period after an overnight fast, ppI mRNA levels were not changed significantly in either vitamin D-deficient or replete rats. However, in the rats that were pair-fed after overnight fasting, ppI mRNA levels in 1,25-(OH)2D3-replete rats increased at 8 and 24 h, whereas ppI mRNA in vitamin D-deficient rats increased only at 24 h. Moreover, the increment at 24 h was significantly larger in 1,25-(OH)2D3-replete rats than in vitamin D-deficient rats. We conclude that 1,25-(OH)2D3 enhances steady state levels of ppI mRNA only under conditions of refeeding and during feeding.

Effect of single oral phosphate loading on vitamin D metabolites in normal subjects and in X-linked hypophosphatemic rickets.

There have been several reports that document abnormal vitamin D metabolism in X-linked hypophosphatemic rickets (XLH). Those reports indicate a blunted renal 25-hydroxyvitamin D-1 alpha-hydroxylase response to a potent stimulator, phosphorus restriction. We examined here its response to phosphate supplementation. Seven normal volunteers and 12 patients with XLH were submitted to single oral phosphate loading. This treatment produced a marked elevation of the serum phosphorus level, with a mild reduction in the serum calcium level. In normal subjects, although the concentrations of intact parathyroid hormone and mid-region parathyroid hormone were increased, with two peaks at 2 and 8 h after treatment, there were no significant changes in vitamin D metabolites including 25-hydroxyvitamin D (25(OH)D), 24,25-dihydroxyvitamin D (24,25(OH)2D) and 1,25-dihydroxyvitamin D (1,25(OH)2D). On the other hand, in the patients with XLH, the serum 1,25(OH)2D level increased from 23.4 +/- 12.0 (mean +/- SD) pg/ml to 44.3 +/- 33.6 pg/ml 6 h after ingestion without any significant change in 25(OH)D or 24,25(OH)2D.