Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0020438 (hypercalciuria)
 2,502 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Inorganic phosphate (Pi) is fundamental to cellular metabolism and skeletal mineralization. Ingested Pi is absorbed by the small intestine, deposited in bone, and filtered by the kidney where it is reabsorbed and excreted in amounts determined by the specific needs of the organism. Two distinct renal Na-dependent Pi transporters, type IIa (NPT2a, SLC34A1) and type IIc (NPT2c, SLC34A3), are expressed in brush border membrane of proximal tubular cells where the bulk of filtered Pi is reabsorbed. Both are regulated by dietary Pi intake and parathyroid hormone. Regulation is achieved by changes in transporter protein abundance in the brush border membrane and requires the interaction of the transporter with scaffolding and signaling proteins. The demonstration of hypophosphatemia secondary to decreased renal Pi reabsorption in mice homozygous for the disrupted type IIa gene underscores its crucial role in the maintenance of Pi homeostasis. Moreover, the recent identification of mutations in the type IIc gene in patients with hereditary hypophosphatemic rickets with hypercalciuria attests to the importance of this transporter in Pi conservation and subsequent skeletal mineralization. Two novel Pi regulating genes, PHEX and FGF23, play a role in the pathophysiology of inherited and acquired hypophosphatemic skeletal disorders and studies are underway to define their mechanism of action on renal Pi handling in health and disease.
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PMID:Phosphate transport: molecular basis, regulation and pathophysiology. 1727 Apr 30

Sotos syndrome is characterized by overgrowth, a typical facial appearance, and learning difficulties. It is caused by heterozygous mutations, including deletions, of NSD1 located at chromosome 5q35. Here we report two unrelated cases of Sotos syndrome associated with nephrocalcinosis. One patient also had idiopathic infantile hypercalcemia. Genetic investigations revealed heterozygous deletions at 5q35 in both patients, encompassing NSD1 and SLC34A1 (NaPi2a). Mutations in SLC34A1 have previously been associated with hypercalciuria/nephrolithiasis. Our cases suggest a contiguous gene deletion syndrome including NSD1 and SLC34A1 and provide a potential genetic basis for idiopathic infantile hypercalcemia.
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PMID:Sotos syndrome, infantile hypercalcemia, and nephrocalcinosis: a contiguous gene syndrome. 2159 70

The proximal renal epithelia express three different Na-dependent inorganic phosphate (Pi) cotransporters: NaPi-IIa/SLC34A1, NaPi-IIc/SLC34A3, and PiT2/SLC20A2. Constitutive mouse knockout models of NaPi-IIa and NaPi-IIc suggested that NaPi-IIa mediates the bulk of renal reabsorption of Pi whereas the contribution of NaPi-IIc to this process is minor and probably restricted to young mice. However, many reports indicate that mutations of NaPi-IIc in humans lead to hereditary hypophosphatemic rickets with hypercalciuria (HHRH). Here, we report the generation of a kidney-specific and inducible NaPi-IIc-deficient mouse model based on the loxP-Cre system. We found that the specific removal of the cotransporter from the kidneys of young mice does not impair the capacity of the renal epithelia to transport Pi. Moreover, the levels of Pi in plasma and urine as well as the circulating levels of parathyroid hormone, FGF-23, and vitamin D3 remained unchanged. These findings are in agreement with the data obtained with the constitutive knockout model and suggest that, under steady-state conditions of normal dietary Pi, NaPi-IIc is not an essential Na-Pi cotransporter in murine kidneys. However, and unlike the constitutive mutants, the kidney-specific depletion of NaPi-IIc does not result in alteration of the homeostasis of calcium. This suggests that the calcium-related phenotype observed in constitutive knockout mice may not be related to inactivation of the cotransporter in kidney.
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PMID:Renal-specific and inducible depletion of NaPi-IIc/Slc34a3, the cotransporter mutated in HHRH, does not affect phosphate or calcium homeostasis in mice. 2455 30

Serum phosphate levels are regulated in both calcium-dependent and -independent fashions. Active vitamin D increases while PTH decreases serum phosphate levels in association with the elevation of serum calcium. On the other hand, a calcium-independent phosphaturic factor, historically called phosphatonin is believed to exert a physiological function based on findings in hereditary and tumor-induced diseases characterized by hypophosphatemia with normocalcemia. Among them, autosomal dominant hypophosphatemic rickets (ADHR) has contributed greatly to its elucidation because the gene responsible for ADHR encodes fibroblast growth factor 23 (FGF23) that has been found to have a phosphaturic effect. In addition, FGF23 has been proved to be involved in most cases of oncogenic osteomalacia and X-linked hypophosphatemic rickets that are also characterized by hypophosphatemia and normocalcemia. Moreover, familial tumoral calcinosis, which represents the metabolic mirror image of hypophosphatemic conditions, is caused by a loss-of-function mutation in the FGF23 gene in some patients. Very recently, hereditary hypophosphatemic rickets with hypercalciuria has been found to be caused by mutations in the SLC34A1 gene which encodes a type of sodium phosphate cotransporter. These findings may provide new strategies for treating patients with abnormal phosphate metabolism.
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PMID:Molecular bases of diseases characterized by hypophosphatemia and phosphaturia: new understanding. 2479 Mar 33

Inorganic phosphate (Pi) is an essential compound for several biologic functions. Pi levels outside the normal range, however, contribute to several pathological processes. Hypophosphatemia leads to bone abnormalities, such as rickets/osteomalacia. Hyperphosphatemia contributes to vascular calcification in patients with chronic kidney disease and hemodialysis patients and is independently associated with cardiac mortality.Pi homeostasis is regulated by the coordinated function of renal and intestinal sodium-dependent phosphate (NaPi) transporters with dietary Pi, parathyroid hormone, 1,25-dihydroxyvitamin D3, and fibroblast growth factor 23. The type II NaPi transporter/SLC34 family, with three members identified to date, is mainly responsible for Pi homeostasis in the body. SLC34A1 and SCL34A3 are predominantly expressed in the kidney, whereas SLC34A2 is expressed in the small intestine. The role of each SLC34 in the body was recently established by studies of gene-targeted mice. Mutation of SLC34A1 causes Fanconi syndrome and mutation of SLC34A3 causes autosomal recessive hereditary hypophosphatemic rickets with hypercalciuria. SLC34A2 is thought to be a major intestinal NaPi transporter and mutation of SLC34A2 causes pulmonary alveolar microlithiasis. A detailed understanding of Pi regulation in the body is important toward maintaining health.
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PMID:The Role of Sodium-Dependent Phosphate Transporter in Phosphate Homeostasis. 2659 21

The calcium-sensing receptor (CaSR) plays a pivotal role in systemic calcium metabolism by regulating parathyroid hormone secretion and urinary calcium excretion. The diseases caused by an abnormality of the CaSR are genetically determined or are more rarely acquired. The genetic diseases consist of hyper- or hypocalcemia disorders. Hypercalcaemia disorders are related to inactivating mutations of the CASR gene either heterozygous (autosomal dominant familial benign hypercalcaemia, still named hypocalciuric hypercalcaemia syndrome type 1) or homozygous (severe neonatal hyperparathyroidism). The A986S, R990G and Q1011E variants of the CASR gene are associated with higher serum calcium levels than in the general population, hypercalciuria being also associated with the R990G variant. The differential diagnosis consists in the hypocalciuric hypercalcaemia syndrome, types 2 (involving GNA11 gene) and 3 (involving AP2S1 gene); hyperparathyroidism; abnormalities of vitamin D metabolism, involving CYP24A1 and SLC34A1 genes; and reduced GFR. Hypocalcemia disorders, which are more rare, are related to heterozygous activating mutations of the CASR gene (type 1), consisting of autosomal dominant hypocalcemia disorders, sometimes with a presentation of pseudo-Bartter's syndrome. The differential diagnosis consists of the hypercalciuric hypocalcaemia syndrome type 2, involving GNA11 gene and other hypoparathyroidism aetiologies. The acquired diseases are related to the presence of anti-CaSR antibodies, which can cause hyper- or especially hypocalcemia disorders (for instance in APECED syndromes), determined by their functionality. Finally, the role of CaSR in digestive, respiratory, cardiovascular and neoplastic diseases is gradually coming to light, providing new therapeutic possibilities. Two types of CaSR modulators are known: CaSR agonists (or activators, still named calcimimetics) and calcilytic antagonists (or inhibitors of the CasR). CaSR agonists, such as cinacalcet, are indicated in secondary and primary hyperparathyroidism. Calcilytics have no efficacy in osteoporosis, but could be useful in the treatment of hypercalciuric hypocalcaemia syndromes.
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PMID:Diseases associated with calcium-sensing receptor. 2812 87

Idiopathic infantile hypercalcemia (IIH) is a mineral metabolism disorder characterized by severe hypercalcemia, failure to thrive, vomiting, dehydration, and nephrocalcinosis. The periodical increase in incidence of IIH, which occurred in the twentieth century in the United Kingdom, Poland, and West Germany, turned out to be a side effect of rickets over-prophylaxis. It was recently discovered that the condition is linked to two genes, CYP24A1 and SLC34A1. The aim of the study was to search for pathogenic variants of the genes in adult persons who were shortlisted in infancy as IIH caused by "hypersensitivity to vit. D". All persons were found to carry mutations in CYP24A1 or SLC34A1, nine and two persons respectively. The changes were biallelic, with one exception. Incidence of IIH in Polish population estimated on the basis of allele frequency of recurrent p.R396W CYP24A1 variant, is 1:32,465 births. It indicates that at least a thousand homozygotes and compound heterozygotes with risk of IIH live in the country. Differences in mechanism of developing hypercalcemia indicate that its prevention may vary in both IIH defects. Theoretically, vit. D restriction is a first indication for CYP24A1 defect (which disturbs 1,25(OH)2D degradation) and phosphate supplementation for SLC34A1 defect (which impairs renal phosphate transport). In conclusion, we suggest that molecular testing for CYP24A1 and SLC34A1 mutations should be performed in each case of idiopathic hypercalcemia/hypercalciuria, both in children and adults, to determine the proper way for acute treatment and complications prevention.
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PMID:Biallelic mutations in CYP24A1 or SLC34A1 as a cause of infantile idiopathic hypercalcemia (IIH) with vitamin D hypersensitivity: molecular study of 11 historical IIH cases. 2847 Mar 90

Renal phosphate handling critically determines plasma phosphate and whole body phosphate levels. Filtered phosphate is mostly reabsorbed by Na+-dependent phosphate transporters located in the brush border membrane of the proximal tubule: NaPi-IIa (SLC34A1), NaPi-IIc (SLC34A3), and Pit-2 (SLC20A2). Here we review new evidence for the role and relevance of these transporters in inherited disorders of renal phosphate handling. The importance of NaPi-IIa and NaPi-IIc for renal phosphate reabsorption and mineral homeostasis has been highlighted by the identification of mutations in these transporters in a subset of patients with infantile idiopathic hypercalcemia and patients with hereditary hypophosphatemic rickets with hypercalciuria. Both diseases are characterized by disturbed calcium homeostasis secondary to elevated 1,25-(OH)2 vitamin D3 as a consequence of hypophosphatemia. In vitro analysis of mutated NaPi-IIa or NaPi-IIc transporters suggests defective trafficking underlying disease in most cases. Monoallelic pathogenic mutations in both SLC34A1 and SLC34A3 appear to be very frequent in the general population and have been associated with kidney stones. Consistent with these findings, results from genome-wide association studies indicate that variants in SLC34A1 are associated with a higher risk to develop kidney stones and chronic kidney disease, but underlying mechanisms have not been addressed to date.
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PMID:Renal phosphate handling and inherited disorders of phosphate reabsorption: an update. 2927 31

The Na+-dependent phosphate transporter NaPi-IIa (SLC34A1) is mostly expressed in kidney, whereas NaPi-IIb (SLC34A2) has a wider tissue distribution with prominent expression in the lung and small intestine. NaPi-IIa is involved in renal reabsorption of inorganic phosphate (Pi) from urine, and patients with biallelic inactivating mutations in SLC34A1 develop hypophosphatemia, hypercalcemia, hypercalciuria and nephrocalcinosis, and nephrolithiasis in early childhood. Monoallelic mutations are frequent in the general population and may impact on the risk to develop kidney stones in adulthood. SNPs in close vicinity to the SLC34A1 locus associate with the risk to develop CKD. NaPi-IIb mediates high-affinity transport of Pi from the diet and appears to be mostly important during low Pi availability. Biallelic inactivating SLC34A2 mutations are found in patients with pulmonary alveolar microlithiasis, a lung disease characterized by the deposition of microcrystals. In contrast, no evidence for disturbed systemic Pi homeostasis has been reported in these patients to date. Nevertheless, NaPi-IIb-mediated intestinal Pi absorption may be a target for pharmaceutical interventions in patients with chronic kidney disease and Pi overload.
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PMID:Clinical aspects of the phosphate transporters NaPi-IIa and NaPi-IIb: mutations and disease associations. 3093 52

Idiopathic infantile hypercalcemia is characterized by hypercalcemia, dehydration, vomiting, and failure to thrive, and it is due to mutations in 24-hydroxylase (CYP24A1). Recently, mutations in sodium-phosphate cotransporter (SLC34A1) expressed in the kidney were discovered as an additional cause of idiopathic infantile hypercalcemia. This report describes a female infant admitted for evaluation of nephrocalcinosis. She presented with hypercalcemia, hypercalciuria, low intact parathyroid hormone level, and high 1,25-dihydroxyvitamin D3 level. Exome sequencing identified novel compound heterozygous mutations in SLC34A1 (c.1337G>A, c.1483C>T). The patient was treated with fluids for hydration, furosemide, a corticosteroid, and restriction of calcium/vitamin D intake. At the age of 7 months, the patient's calcium level was within the normal range, and hypercalciuria waxed and waned. Renal echogenicity improved on the follow-up ultrasonogram, and developmental delay was not noted. In cases of hypercalcemia with subsequent hypercalciuria, DNA analysis for SLC34A1 gene mutations and CYP24A1 gene mutations should be performed. Further studies are required to obtain long-term data on hypercalciuria and nephrocalcinosis.
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PMID:Infantile hypercalcemia with novel compound heterozygous mutation in SLC34A1 encoding renal sodium-phosphate cotransporter 2a: a case report. 3094 83


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