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Tang OW, Tang J. Idiopathic Hypercalciuria - A Major Metabolic Risk for Calcium Kidney Stone Disease. R I Med J (2013) 2023; 106:9-13. [PMID: 38015778] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/30/2023]
Abstract
Idiopathic hypercalciuria is defined as excessive urine calcium excretion in the absence of an identifiable cause. It has been strongly associated with the risk of calcium kidney stone formation. Animal and human studies have suggested excessive bone mineral loss or increased gastrointestinal calcium absorption with abnormal renal calcium excretion may contribute to this process. In this article we will review the complex pathophysiology of idiopathic hypercalciuria and discuss clinical management and challenges.
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Affiliation(s)
- Olive W Tang
- Department of Medicine,The Johns Hopkins University School of Medicine, Baltimore, MD
| | - Jie Tang
- Division of Kidney Diseases and Hypertension, Alpert Medical School of Brown University, Providence, RI
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Kriuchkova N, Breiderhoff T, Müller D, Yilmaz DE, Demirci H, Drewell H, Günzel D, Himmerkus N, Bleich M, Persson PB, Mutig K. Furosemide rescues hypercalciuria in familial hypomagnesaemia with hypercalciuria and nephrocalcinosis model. Acta Physiol (Oxf) 2023; 237:e13927. [PMID: 36606514 DOI: 10.1111/apha.13927] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 11/10/2022] [Accepted: 01/02/2023] [Indexed: 01/07/2023]
Abstract
AIM Perturbed calcium homeostasis limits life expectancy in familial hypomagnesaemia with hypercalciuria and nephrocalcinosis (FHHNC). This rare disease occurs by loss-of-function mutations in CLDN16 or CLDN19 genes, causing impaired paracellular reabsorption of divalent cations along the cortical thick ascending limb (cTAL). Only partial compensation takes place in the ensuing late distal convoluted tubule, connecting tubule, and collecting duct, where the luminal transient receptor potential channel V5 (TRPV5), as well as basolateral plasma membrane calcium ATPase (PMCA) and sodium-potassium exchanger (NCX1) mediate transcellular Ca2+ reabsorption. The loop diuretic furosemide induces compensatory activation in these distal segments. Normally, furosemide enhances urinary calcium excretion via inhibition of the aforementioned cTAL. As Ca2+ reabsorption in the cTAL is already severely impaired in FHHNC patients, furosemide may alleviate hypercalciuria in this disease by activation of the distal transcellular Ca2+ transport proteins. METHODS Cldn16-deficient mice (Cldn16-/- ) served as a FHHNC model. Wild-type (WT) and Cldn16-/- mice were treated with furosemide (7 days of 40 mg/kg bw) or vehicle. We assessed renal electrolyte handling (metabolic cages) and key divalent transport proteins. RESULTS Cldn16-/- mice show higher Ca2+ excretion than WT and compensatory stimulation of Cldn2, TRPV5, and NCX1 at baseline. Furosemide reduced hypercalciuria in Cldn16-/- mice and enhanced TRPV5 and PMCA levels in Cldn16-/- but not in WT mice. CONCLUSIONS Furosemide significantly reduces hypercalciuria, likely via upregulation of luminal and basolateral Ca2+ transport systems in the distal nephron and collecting duct in this model for FHHNC.
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Affiliation(s)
- Natalia Kriuchkova
- Department of Translational Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Tilman Breiderhoff
- Division of Gastroenterology, Nephrology and Metabolic Diseases, Department of Pediatrics, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Dominik Müller
- Division of Gastroenterology, Nephrology and Metabolic Diseases, Department of Pediatrics, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Duygu Elif Yilmaz
- Department of Functional Anatomy, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Hasan Demirci
- Department of Functional Anatomy, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Hoora Drewell
- Department of Translational Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Dorothee Günzel
- Clinical Physiology/Division of Nutritional Medicine, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | | | - Markus Bleich
- Institute of Physiology, Kiel University, Kiel, Germany
| | - Pontus B Persson
- Department of Translational Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
| | - Kerim Mutig
- Department of Translational Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany
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Kwon EJ, Kim MS, Noh ES, Kim CW, Jang J, Choi JH, Cho SY, Jin DK. The Youngest Infant to Be Diagnosed with Autosomal Dominant Hypocalcemia Type 2 Harboring a Novel Variant of GNA11: A Case Study and Literature Review. Ann Clin Lab Sci 2022; 52:494-498. [PMID: 35777808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Autosomal dominant hypocalcemia (ADH) is characterized by hypocalcemia and inappropriately low PTH concentrations. ADH type 2 (ADH2) is caused by a heterozygous gain-of-function mutation in GNA11 that encodes the subunit of G11, the principal G protein that transduces calcium-sensing receptor signaling in the parathyroid. Clinical features related to hypocalcemia in ADH2 range from asymptomatic to tetany and seizures. We report the clinical and molecular analysis of an infant with ADH2. Exome sequencing identified a de novo heterozygous missense variant, c. G548C (p. Arg183Pro) in GNA11. This is the youngest Korean case to be diagnosed with ADH 2. In addition, we summarized the literature related to eight mutations in GNA11 from 10 families.
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Affiliation(s)
- Eun-Jung Kwon
- Departments of Pediatrics and Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
| | - Min-Sun Kim
- Departments of Pediatrics and Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
| | - Eu-Seon Noh
- Departments of Pediatrics and Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
| | - Chi-Woo Kim
- Departments of Pediatrics and Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
| | - Jahyun Jang
- Laboratory Medicine and Genetics, Samsung Medical Center, Sungkyunkwan University School of Medicine, and Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
| | - Jin-Ho Choi
- Department of Pediatrics, Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
| | - Sung Yoon Cho
- Departments of Pediatrics and Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
| | - Dong-Kyu Jin
- Departments of Pediatrics and Asan Medical Center Children's Hospital, University of Ulsan College of Medicine, Seoul, Korea
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Liu CJ, Cheng CW, Tsai YS, Huang HS. Crosstalk between Renal and Vascular Calcium Signaling: The Link between Nephrolithiasis and Vascular Calcification. Int J Mol Sci 2021; 22:ijms22073590. [PMID: 33808324 PMCID: PMC8036726 DOI: 10.3390/ijms22073590] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2021] [Revised: 03/18/2021] [Accepted: 03/26/2021] [Indexed: 12/11/2022] Open
Abstract
Calcium (Ca2+) is an important mediator of multicellular homeostasis and is involved in several diseases. The interplay among the kidney, bone, intestine, and parathyroid gland in Ca2+ homeostasis is strictly modulated by numerous hormones and signaling pathways. The calcium-sensing receptor (CaSR) is a G protein–coupled receptor, that is expressed in calcitropic tissues such as the parathyroid gland and the kidney, plays a pivotal role in Ca2+ regulation. CaSR is important for renal Ca2+, as a mutation in this receptor leads to hypercalciuria and calcium nephrolithiasis. In addition, CaSR is also widely expressed in the vascular system, including vascular endothelial cells (VECs) and vascular smooth muscle cells (VSMCs) and participates in the process of vascular calcification. Aberrant Ca2+ sensing by the kidney and VSMCs, owing to altered CaSR expression or function, is associated with the formation of nephrolithiasis and vascular calcification. Based on emerging epidemiological evidence, patients with nephrolithiasis have a higher risk of vascular calcification, but the exact mechanism linking the two conditions is unclear. However, a dysregulation in Ca2+ homeostasis and dysfunction in CaSR might be the connection between the two. This review summarizes renal calcium handling and calcium signaling in the vascular system, with a special focus on the link between nephrolithiasis and vascular calcification.
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Affiliation(s)
- Chan-Jung Liu
- Department of Urology, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan 704302, Taiwan; (C.-J.L.); (C.-W.C.)
| | - Chia-Wei Cheng
- Department of Urology, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan 704302, Taiwan; (C.-J.L.); (C.-W.C.)
| | - Yau-Sheng Tsai
- Institute of Clinical Medicine, College of Medicine, National Cheng Kung University, Tainan 704302, Taiwan;
- Center for Clinical Medicine Research, National Cheng Kung University Hospital, Tainan 704302, Taiwan
| | - Ho-Shiang Huang
- Department of Urology, National Cheng Kung University Hospital, College of Medicine, National Cheng Kung University, Tainan 704302, Taiwan; (C.-J.L.); (C.-W.C.)
- Correspondence: ; Tel.: +886-6-2353535 (ext. 5251); Fax: +886-6-2766179
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Boisen IM, Rehfeld A, Mos I, Poulsen NN, Nielsen JE, Schwarz P, Rejnmark L, Dissing S, Bach-Mortensen P, Juul A, Bräuner-Osborne H, Lanske B, Blomberg Jensen M. The Calcium-Sensing Receptor Is Essential for Calcium and Bicarbonate Sensitivity in Human Spermatozoa. J Clin Endocrinol Metab 2021; 106:e1775-e1792. [PMID: 33340048 DOI: 10.1210/clinem/dgaa937] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Indexed: 11/19/2022]
Abstract
CONTEXT The calcium-sensing receptor (CaSR) is essential to maintain a stable calcium concentration in serum. Spermatozoa are exposed to immense changes in concentrations of CaSR ligands such as calcium, magnesium, and spermine during epididymal maturation, in the ejaculate, and in the female reproductive environment. However, the role of CaSR in human spermatozoa is unknown. OBJECTIVE This work aimed to investigate the role of CaSR in human spermatozoa. METHODS We identified CaSR in human spermatozoa and characterized the response to CaSR agonists on intracellular calcium, acrosome reaction, and 3',5'-cyclic adenosine 5'-monophosphate (cAMP) in spermatozoa from men with either loss-of-function or gain-of-function mutations in CASR and healthy donors. RESULTS CaSR is expressed in human spermatozoa and is essential for sensing extracellular free ionized calcium (Ca2+) and Mg2+. Activators of CaSR augmented the effect of sperm-activating signals such as the response to HCO3- and the acrosome reaction, whereas spermatozoa from men with a loss-of-function mutation in CASR had a diminished response to HCO3-, lower progesterone-mediated calcium influx, and were less likely to undergo the acrosome reaction in response to progesterone or Ca2+. CaSR activation increased cAMP through soluble adenylyl cyclase (sAC) activity and increased calcium influx through CatSper. Moreover, external Ca2+ or Mg2+ was indispensable for HCO3- activation of sAC. Two male patients with a CASR loss-of-function mutation in exon 3 presented with normal sperm counts and motility, whereas a patient with a loss-of-function mutation in exon 7 had low sperm count, motility, and morphology. CONCLUSION CaSR is important for the sensing of Ca2+, Mg2+, and HCO3- in spermatozoa, and loss-of-function may impair male sperm function.
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Affiliation(s)
- Ida Marie Boisen
- Group of Skeletal, Mineral, and Gonadal Endocrinology, Department of Growth and Reproduction, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
- Division of Bone and Mineral Research, Harvard School of Dental Medicine/Harvard Medical School, Harvard University, Boston, MA, USA
| | - Anders Rehfeld
- Department of Growth and Reproduction, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Iris Mos
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Nadia Nicholine Poulsen
- Group of Skeletal, Mineral, and Gonadal Endocrinology, Department of Growth and Reproduction, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - John Erik Nielsen
- Department of Growth and Reproduction, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Peter Schwarz
- Department of Endocrinology, Rigshospitalet, Copenhagen, Denmark
- Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Lars Rejnmark
- Department of Endocrinology, Aarhus University Hospital, Aarhus, Denmark
| | - Steen Dissing
- Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | | | - Anders Juul
- Department of Growth and Reproduction, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
- Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Hans Bräuner-Osborne
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Beate Lanske
- Division of Bone and Mineral Research, Harvard School of Dental Medicine/Harvard Medical School, Harvard University, Boston, MA, USA
| | - Martin Blomberg Jensen
- Group of Skeletal, Mineral, and Gonadal Endocrinology, Department of Growth and Reproduction, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
- Division of Bone and Mineral Research, Harvard School of Dental Medicine/Harvard Medical School, Harvard University, Boston, MA, USA
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Oh IH, Jo CH, Kim S, Jo S, Chung S, Kim GH. Thick ascending limb claudins are altered to increase calciuria and magnesiuria in metabolic acidosis. Am J Physiol Renal Physiol 2021; 320:F418-F428. [PMID: 33522409 DOI: 10.1152/ajprenal.00282.2020] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Accepted: 01/21/2021] [Indexed: 12/14/2022] Open
Abstract
Urinary calcium and magnesium wasting is a characteristic feature of metabolic acidosis, and this study focused on the role of the thick ascending limb of Henle's loop in metabolic acidosis-induced hypercalciuria and hypermagnesiuria because thick ascending limb is an important site of paracellular calcium and magnesium reabsorption. Male Sprague-Dawley rats were used to determine the effects of acid loading (by adding NH4Cl, 7.2 mmol/220 g body wt/day to food slurry for 7 days) on renal expression of claudins and then to evaluate whether the results were reversed by antagonizing calcium-sensing receptor (using NPS-2143). At the end of each animal experiment, the kidneys were harvested for immunoblotting, immunofluorescence microscopy, and quantitative PCR (qPCR) analysis of claudins and the calcium-sensing receptor. As expected, NH4Cl loading lowered urinary pH and increased excretion of urinary calcium and magnesium. In NH4Cl-loaded rats, renal protein and mRNA expression of claudin-16, and claudin-19, were decreased compared with controls. However, claudin-14 protein and mRNA increased in NH4Cl-loaded rats. Consistently, the calcium-sensing receptor protein and mRNA were up-regulated in NH4Cl-loaded rats. All these changes were reversed by NPS-2143 coadministration and were confirmed using immunofluorescence microscopy. Hypercalciuria and hypermagnesiuria in NH4Cl-loaded rats were significantly ameliorated by NPS-2143 coadministration as well. We conclude that in metabolic acidosis, claudin-16 and claudin-19 in the thick ascending limb are down-regulated to produce hypercalciuria and hypermagnesiuria via the calcium-sensing receptor.NEW & NOTEWORTHY This study found that the thick ascending limb of Henle's loop is involved in the mechanisms of hypercalciuria and hypermagnesiuria in metabolic acidosis. Specifically, expression of claudin-16/19 and claudin-14 was altered via up-regulation of calcium-sensing receptor in NH4Cl-induced metabolic acidosis. Our novel findings contribute to understanding the regulatory role of paracellular tight junction proteins in the thick ascending limb.
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Affiliation(s)
- Il Hwan Oh
- Department of Internal Medicine, Hanyang University College of Medicine, Seoul, Republic of Korea
| | - Chor Ho Jo
- Institute of Biomedical Science, Hanyang University College of Medicine, Seoul, Republic of Korea
| | - Sua Kim
- Institute of Biomedical Science, Hanyang University College of Medicine, Seoul, Republic of Korea
| | - Sungsin Jo
- Hanyang University Institute for Rheumatology Research, Seoul, Republic of Korea
| | - Sungjin Chung
- Department of Internal Medicine, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea
| | - Gheun-Ho Kim
- Department of Internal Medicine, Hanyang University College of Medicine, Seoul, Republic of Korea
- Institute of Biomedical Science, Hanyang University College of Medicine, Seoul, Republic of Korea
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Gratreak BDK, Swanson EA, Lazelle RA, Jelen SK, Hoenderop J, Bindels RJ, Yang C, Ellison DH. Tacrolimus-induced hypomagnesemia and hypercalciuria requires FKBP12 suggesting a role for calcineurin. Physiol Rep 2020; 8:e14316. [PMID: 31908154 PMCID: PMC6944708 DOI: 10.14814/phy2.14316] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Calcineurin inhibitors (CNIs) are immunosuppressive drugs used to prevent graft rejection after organ transplant. Common side effects include renal magnesium wasting and hypomagnesemia, which may contribute to new-onset diabetes mellitus, and hypercalciuria, which may contribute to post-transplant osteoporosis. Previous work suggested that CNIs reduce the abundance of key divalent cation transport proteins, expressed along the distal convoluted tubule, causing renal magnesium and calcium wasting. It has not been clear, however, whether these effects are specific for the distal convoluted tubule, and whether these represent off-target toxic drug effects, or result from inhibition of calcineurin. The CNI tacrolimus can inhibit calcineurin only when it binds with the immunophilin, FKBP12; we previously generated mice in which FKBP12 could be deleted along the nephron, to test whether calcineurin inhibition is involved, these mice are normal at baseline. Here, we confirmed that tacrolimus-treated control mice developed hypomagnesemia and urinary calcium wasting, with decreased protein and mRNA abundance of key magnesium and calcium transport proteins (NCX-1 and Calbindin-D28k ). However, qPCR also showed decreased mRNA expression of NCX-1 and Calbindin-D28k , and TRPM6. In contrast, KS-FKBP12-/- mice treated with tacrolimus were completely protected from these effects. These results indicate that tacrolimus affects calcium and magnesium transport along the distal convoluted tubule and strongly suggests that inhibition of the phosphatase, calcineurin, is directly involved.
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Affiliation(s)
- Brittany D. K. Gratreak
- Division of Nephrology and HypertensionDepartment of MedicineOregon Health and Science UniversityPortlandORUSA
| | - Elizabeth A. Swanson
- Division of Nephrology and HypertensionDepartment of MedicineOregon Health and Science UniversityPortlandORUSA
| | - Rebecca A. Lazelle
- Division of Nephrology and HypertensionDepartment of MedicineOregon Health and Science UniversityPortlandORUSA
| | - Sabina K. Jelen
- Radboud Institute for Molecular Life SciencesRadboud University Medical CenterNijmegenNetherlands
| | - Joost Hoenderop
- Radboud Institute for Molecular Life SciencesRadboud University Medical CenterNijmegenNetherlands
| | - René J. Bindels
- Radboud Institute for Molecular Life SciencesRadboud University Medical CenterNijmegenNetherlands
| | - Chao‐Ling Yang
- Division of Nephrology and HypertensionDepartment of MedicineOregon Health and Science UniversityPortlandORUSA
| | - David H. Ellison
- Division of Nephrology and HypertensionDepartment of MedicineOregon Health and Science UniversityPortlandORUSA
- Renal SectionVeterans Affairs Portland Health Care SystemPortlandORUSA
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Gorvin CM, Frost M, Malinauskas T, Cranston T, Boon H, Siebold C, Jones EY, Hannan FM, Thakker RV. Calcium-sensing receptor residues with loss- and gain-of-function mutations are located in regions of conformational change and cause signalling bias. Hum Mol Genet 2018; 27:3720-3733. [PMID: 30052933 PMCID: PMC6196656 DOI: 10.1093/hmg/ddy263] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Revised: 07/06/2018] [Accepted: 07/09/2018] [Indexed: 12/20/2022] Open
Abstract
The calcium-sensing receptor (CaSR) is a homodimeric G-protein-coupled receptor that signals via intracellular calcium (Ca2+i) mobilisation and phosphorylation of extracellular signal-regulated kinase 1/2 (ERK) to regulate extracellular calcium (Ca2+e) homeostasis. The central importance of the CaSR in Ca2+e homeostasis has been demonstrated by the identification of loss- or gain-of-function CaSR mutations that lead to familial hypocalciuric hypercalcaemia (FHH) or autosomal dominant hypocalcaemia (ADH), respectively. However, the mechanisms determining whether the CaSR signals via Ca2+i or ERK have not been established, and we hypothesised that some CaSR residues, which are the site of both loss- and gain-of-function mutations, may act as molecular switches to direct signalling through these pathways. An analysis of CaSR mutations identified in >300 hypercalcaemic and hypocalcaemic probands revealed five 'disease-switch' residues (Gln27, Asn178, Ser657, Ser820 and Thr828) that are affected by FHH and ADH mutations. Functional expression studies using HEK293 cells showed disease-switch residue mutations to commonly display signalling bias. For example, two FHH-associated mutations (p.Asn178Asp and p.Ser820Ala) impaired Ca2+i signalling without altering ERK phosphorylation. In contrast, an ADH-associated p.Ser657Cys mutation uncoupled signalling by leading to increased Ca2+i mobilization while decreasing ERK phosphorylation. Structural analysis of these five CaSR disease-switch residues together with four reported disease-switch residues revealed these residues to be located at conformationally active regions of the CaSR such as the extracellular dimer interface and transmembrane domain. Thus, our findings indicate that disease-switch residues are located at sites critical for CaSR activation and play a role in mediating signalling bias.
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Affiliation(s)
- Caroline M Gorvin
- Academic Endocrine Unit, Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), University of Oxford, Oxford OX3 7LJ, UK
| | - Morten Frost
- Academic Endocrine Unit, Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), University of Oxford, Oxford OX3 7LJ, UK
- University of Southern Denmark, Odense C, Denmark
| | - Tomas Malinauskas
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Treena Cranston
- Oxford Molecular Genetics Laboratory, Churchill Hospital, Oxford OX3 7LJ, UK
| | - Hannah Boon
- Oxford Molecular Genetics Laboratory, Churchill Hospital, Oxford OX3 7LJ, UK
| | - Christian Siebold
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - E Yvonne Jones
- Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Fadil M Hannan
- Academic Endocrine Unit, Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), University of Oxford, Oxford OX3 7LJ, UK
- Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, UK
| | - Rajesh V Thakker
- Academic Endocrine Unit, Radcliffe Department of Medicine, Oxford Centre for Diabetes, Endocrinology and Metabolism (OCDEM), University of Oxford, Oxford OX3 7LJ, UK
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Gorvin CM. Insights into calcium-sensing receptor trafficking and biased signalling by studies of calcium homeostasis. J Mol Endocrinol 2018; 61:R1-R12. [PMID: 29599414 DOI: 10.1530/jme-18-0049] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2018] [Accepted: 03/29/2018] [Indexed: 12/18/2022]
Abstract
The calcium-sensing receptor (CASR) is a class C G-protein-coupled receptor (GPCR) that detects extracellular calcium concentrations, and modulates parathyroid hormone secretion and urinary calcium excretion to maintain calcium homeostasis. The CASR utilises multiple heterotrimeric G-proteins to mediate signalling effects including activation of intracellular calcium release; mitogen-activated protein kinase (MAPK) pathways; membrane ruffling; and inhibition of cAMP production. By studying germline mutations in the CASR and proteins within its signalling pathway that cause hyper- and hypocalcaemic disorders, novel mechanisms governing GPCR signalling and trafficking have been elucidated. This review focusses on two recently described pathways that provide novel insights into CASR signalling and trafficking mechanisms. The first, identified by studying a CASR gain-of-function mutation that causes autosomal dominant hypocalcaemia (ADH), demonstrated a structural motif located between the third transmembrane domain and the second extracellular loop of the CASR that mediates biased signalling by activating a novel β-arrestin-mediated G-protein-independent pathway. The second, in which the mechanism by which adaptor protein-2 σ-subunit (AP2σ) mutations cause familial hypocalciuric hypercalcaemia (FHH) was investigated, demonstrated that AP2σ mutations impair CASR internalisation and reduce multiple CASR-mediated signalling pathways. Furthermore, these studies showed that the CASR can signal from the cell surface using multiple G-protein pathways, whilst sustained signalling is mediated only by the Gq/11 pathway. Thus, studies of FHH- and ADH-associated mutations have revealed novel steps by which CASR mediates signalling and compartmental bias, and these pathways could provide new targets for therapies for patients with calcaemic disorders.
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Affiliation(s)
- Caroline M Gorvin
- Institute of Metabolism and Systems Research (IMSR), University of Birmingham, Birmingham, UK
- Centre for Endocrinology, Diabetes and Metabolism (CEDAM), Birmingham Health Partners, Birmingham, UK
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10
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Olefir YV, Yavorskii AN, Butnaru DV, Shatalova OV, Gorbatenko VS, Gerasimenko AS. [Idiopathic hypercalciuria. Diagnosis and treatment]. Urologiia 2017:112-119. [PMID: 29376607] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Most patients with idiopathic hypercalciuria and calcium nephrolithiasis have a family history of the disease. Idiopathic hypercalciuria is a metabolic abnormality with various causes and developmental pathways. The systematic review describes specific mutations associated with idiopathic hypercalciuria and nephrolithiasis. Detection of these mutations may provide a better understanding of the pathogenesis of this heterogeneous disease and personalize patient management depending on the detected polymorphisms. A promising treatment option for a mutation in the vitamin D receptor gene is thiazide diuretics in combination with bisphosphonates. Among bisphosphonates, the drug of choice which has been most strongly supported by research evidence is alendronate.
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Affiliation(s)
- Yu V Olefir
- I.M. Sechenov First MSMU, Moscow, Russia
- Scientific Centre for Expert Evaluation of Medicinal Products, Moscow, Russia
- Volgograd State Medical University of the Ministry of Health of Russia, Volgograd, Russia
| | - A N Yavorskii
- I.M. Sechenov First MSMU, Moscow, Russia
- Scientific Centre for Expert Evaluation of Medicinal Products, Moscow, Russia
- Volgograd State Medical University of the Ministry of Health of Russia, Volgograd, Russia
| | - D V Butnaru
- I.M. Sechenov First MSMU, Moscow, Russia
- Scientific Centre for Expert Evaluation of Medicinal Products, Moscow, Russia
- Volgograd State Medical University of the Ministry of Health of Russia, Volgograd, Russia
| | - O V Shatalova
- I.M. Sechenov First MSMU, Moscow, Russia
- Scientific Centre for Expert Evaluation of Medicinal Products, Moscow, Russia
- Volgograd State Medical University of the Ministry of Health of Russia, Volgograd, Russia
| | - V S Gorbatenko
- I.M. Sechenov First MSMU, Moscow, Russia
- Scientific Centre for Expert Evaluation of Medicinal Products, Moscow, Russia
- Volgograd State Medical University of the Ministry of Health of Russia, Volgograd, Russia
| | - A S Gerasimenko
- I.M. Sechenov First MSMU, Moscow, Russia
- Scientific Centre for Expert Evaluation of Medicinal Products, Moscow, Russia
- Volgograd State Medical University of the Ministry of Health of Russia, Volgograd, Russia
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Grellier J, Jaafar A, Martin A, El Alaoui M, Lebely C, Tack I, Vallet M. Syndrome of inappropriate anti-diuresis induces volume-dependent hypercalciuria. Osteoporos Int 2017; 28:3161-3168. [PMID: 28812111 DOI: 10.1007/s00198-017-4186-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Accepted: 08/01/2017] [Indexed: 01/30/2023]
Abstract
UNLABELLED Hyponatremia is associated with bone demineralization. We hypothesized that, during hyponatremia, calciuria and calcium balance depend on volemic status. We evaluated calciuria in patients with hyponatremia, secondary to SIAD or hypovolemia. Patients with SIAD exhibited a volemic expansion that was associated with hypercalciuria. Calciuria was proportional to markers of volemia. INTRODUCTION Chronic mild hyponatremia has been associated with bone demineralization of unknown mechanisms. During chronic hyponatremia, arginine-vasopressin secretion can result from hypovolemia or from syndrome of inappropriate anti-diuresis (SIAD) that leads to a slightly volemic expansion. Since volemia determines renal calcium excretion and balance, we evaluated calcium homeostasis in patients with chronic hyponatremia, related to SIAD or to hypovolemia. METHODS We retrospectively included all patients referred to our Department between May 2006 and May 2014 for hyponatremia, resulting from SIAD or chronic hypovolemia. None had edema, cirrhosis, cardiac, or renal insufficiency. Exploration included estimation of volemia, extracellular fluid volume (ECFV) measurement with inulin, and calcium homeostasis. RESULTS In total, the SIAD and hypovolemic groups included 22 and 7 patients, respectively. The SIAD group exhibited signs of increased volemia: higher glomerular filtration rate, higher fractional excretion of uric acid, and lower plasma renin. ECFV exceeded that of the hypovolemic group and was above usual values. There was no difference between the two groups regarding plasma calcium, PTH, and vitamin D. However, in the SIAD group, calciuria was higher than in the hypovolemic group, reaching levels of hypercalciuria. Furthermore, there was a positive correlation between calciuria and markers of volemia. CONCLUSIONS Our results show that SIAD results in a volemic expansion tendency that is associated with a decrease in renal calcium reabsorption and thus hypercalciuria, whereas in the hypovolemic group, calciuria was not increased. Therefore, renal loss of calcium and bone demineralization in SIAD patients could be partly induced by volemic expansion.
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Affiliation(s)
- J Grellier
- CHU de Rangueil, Service des Explorations Fonctionnelles Physiologiques, 1, Avenue du Professeur Jean Poulhès-TSA 50032, 310599, Toulouse Cedex, France
| | - A Jaafar
- CHU de Rangueil, Service des Explorations Fonctionnelles Physiologiques, 1, Avenue du Professeur Jean Poulhès-TSA 50032, 310599, Toulouse Cedex, France
| | - A Martin
- CHU de Rangueil, Service des Explorations Fonctionnelles Physiologiques, 1, Avenue du Professeur Jean Poulhès-TSA 50032, 310599, Toulouse Cedex, France
| | - M El Alaoui
- CHU de Rangueil, Service des Explorations Fonctionnelles Physiologiques, 1, Avenue du Professeur Jean Poulhès-TSA 50032, 310599, Toulouse Cedex, France
| | - C Lebely
- CHU de Rangueil, Service des Explorations Fonctionnelles Physiologiques, 1, Avenue du Professeur Jean Poulhès-TSA 50032, 310599, Toulouse Cedex, France
| | - I Tack
- CHU de Rangueil, Service des Explorations Fonctionnelles Physiologiques, 1, Avenue du Professeur Jean Poulhès-TSA 50032, 310599, Toulouse Cedex, France
| | - M Vallet
- CHU de Rangueil, Service des Explorations Fonctionnelles Physiologiques, 1, Avenue du Professeur Jean Poulhès-TSA 50032, 310599, Toulouse Cedex, France.
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Carpenter TO. CYP24A1 loss of function: Clinical phenotype of monoallelic and biallelic mutations. J Steroid Biochem Mol Biol 2017; 173:337-340. [PMID: 28093352 DOI: 10.1016/j.jsbmb.2017.01.006] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Revised: 01/06/2017] [Accepted: 01/10/2017] [Indexed: 02/02/2023]
Abstract
CYP24A1, encoding the vitamin D-24-hydroxylase, is of major clinical and physiologic importance, serving to regulate the catabolism of 1,25-(OH)2D, the physiologically active vitamin D metabolite. In addition to facilitating catabolism of 1,25-(OH)2D, CYP24A1 also enhances the turnover and elimination of 25-OHD, the abundant precursor metabolite and storage form of the vitamin. CYP24A1 can be stimulated hormonally by 1,25-(OH)2D and by FGF23, whereas CYP27B1, encoding the vitamin D-1α-hydroxylase, is stimulated hormonally by parathyroid hormone (PTH) and downregulated by FGF23. Thus CYP24A1 and CYP27B1, together, provide for alternate and regulated fates of 25-OHD, and control the availability of the active metabolite, 1,25-(OH)2D, depending upon physiologic needs. These two enzymes, are therefore central to the homeostatic control of vitamin D metabolism, and as a result affect calcium metabolism in critical ways. Disruption of CYP24A1 in mice results in elevated circulating 1,25-(OH)2D, substantiating the importance of the enzyme in the maintenance of vitamin D metabolism. The consequential skeletal phenotype in these mice further demonstrates the biologic sequelae of the disruption of the vitamin D pathway, and illustrates a specific developmental pathology mediated largely by oversupply of 1,25-(OH)2D. More recent evidence has identified loss of function mutations in CYP24A1 in association with hypercalcemia, hypercalciuria and nephrolithiasis in humans. Initial reports described certain variant mutations in CYP24A1 as an unrecognized cause of "Idiopathic Infantile Hypercalcemia," and more recently older children and adults have been identified with a similar phenotype. Over 25 likely disease-causing variants are described. Homozygous and compound heterozygote mutations account for the overwhelming majority of cases, however the heterozygous loss-of-function mutations of CYP24A1 do not appear to consistently result in symptomatic hypercalcemia. Considerations ripe for exploration include the potential role for such mutations in the tolerance to challenges to the calcium homeostatic system, such as changes in dietary calcium intake, vitamin D supplementation, sunlight exposure or pregnancy.
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Affiliation(s)
- Thomas O Carpenter
- Yale University, School of Medicine, New Haven, CT 06520-8064, United States.
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Gorvin CM, Hannan FM, Howles SA, Babinsky VN, Piret SE, Rogers A, Freidin AJ, Stewart M, Paudyal A, Hough TA, Nesbit MA, Wells S, Vincent TL, Brown SD, Cox RD, Thakker RV. G α11 mutation in mice causes hypocalcemia rectifiable by calcilytic therapy. JCI Insight 2017; 2:e91103. [PMID: 28194447 PMCID: PMC5291742 DOI: 10.1172/jci.insight.91103] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Accepted: 01/03/2017] [Indexed: 12/11/2022] Open
Abstract
Heterozygous germline gain-of-function mutations of G-protein subunit α11 (Gα11), a signaling partner for the calcium-sensing receptor (CaSR), result in autosomal dominant hypocalcemia type 2 (ADH2). ADH2 may cause symptomatic hypocalcemia with low circulating parathyroid hormone (PTH) concentrations. Effective therapies for ADH2 are currently not available, and a mouse model for ADH2 would help in assessment of potential therapies. We hypothesized that a previously reported dark skin mouse mutant (Dsk7) - which has a germline hypermorphic Gα11 mutation, Ile62Val - may be a model for ADH2 and allow evaluation of calcilytics, which are CaSR negative allosteric modulators, as a targeted therapy for this disorder. Mutant Dsk7/+ and Dsk7/Dsk7 mice were shown to have hypocalcemia and reduced plasma PTH concentrations, similar to ADH2 patients. In vitro studies showed the mutant Val62 Gα11 to upregulate CaSR-mediated intracellular calcium and MAPK signaling, consistent with a gain of function. Treatment with NPS-2143, a calcilytic compound, normalized these signaling responses. In vivo, NPS-2143 induced a rapid and marked rise in plasma PTH and calcium concentrations in Dsk7/Dsk7 and Dsk7/+ mice, which became normocalcemic. Thus, these studies have established Dsk7 mice, which harbor a germline gain-of-function Gα11 mutation, as a model for ADH2 and have demonstrated calcilytics as a potential targeted therapy.
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Affiliation(s)
- Caroline M. Gorvin
- Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Fadil M. Hannan
- Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
- Department of Musculoskeletal Biology, Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool, United Kingdom
| | - Sarah A. Howles
- Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Valerie N. Babinsky
- Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Sian E. Piret
- Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Angela Rogers
- Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Andrew J. Freidin
- ARUK Centre for Osteoarthritis Pathogenesis, The Kennedy Institute of Rheumatology, University of Oxford, Oxford, United Kingdom
| | - Michelle Stewart
- Medical Research Council (MRC) Mammalian Genetics Unit and Mary Lyon Centre, MRC Harwell Institute, Harwell Science and Innovation Campus, United Kingdom
| | - Anju Paudyal
- Medical Research Council (MRC) Mammalian Genetics Unit and Mary Lyon Centre, MRC Harwell Institute, Harwell Science and Innovation Campus, United Kingdom
| | - Tertius A. Hough
- Medical Research Council (MRC) Mammalian Genetics Unit and Mary Lyon Centre, MRC Harwell Institute, Harwell Science and Innovation Campus, United Kingdom
| | - M. Andrew Nesbit
- Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
- Biomedical Sciences Research Institute, Ulster University, Coleraine, United Kingdom
| | - Sara Wells
- Medical Research Council (MRC) Mammalian Genetics Unit and Mary Lyon Centre, MRC Harwell Institute, Harwell Science and Innovation Campus, United Kingdom
| | - Tonia L. Vincent
- ARUK Centre for Osteoarthritis Pathogenesis, The Kennedy Institute of Rheumatology, University of Oxford, Oxford, United Kingdom
| | - Stephen D.M. Brown
- Medical Research Council (MRC) Mammalian Genetics Unit and Mary Lyon Centre, MRC Harwell Institute, Harwell Science and Innovation Campus, United Kingdom
| | - Roger D. Cox
- Medical Research Council (MRC) Mammalian Genetics Unit and Mary Lyon Centre, MRC Harwell Institute, Harwell Science and Innovation Campus, United Kingdom
| | - Rajesh V. Thakker
- Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
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Roszko KL, Bi R, Gorvin CM, Bräuner-Osborne H, Xiong XF, Inoue A, Thakker RV, Strømgaard K, Gardella T, Mannstadt M. Knockin mouse with mutant G α11 mimics human inherited hypocalcemia and is rescued by pharmacologic inhibitors. JCI Insight 2017; 2:e91079. [PMID: 28194446 PMCID: PMC5291736 DOI: 10.1172/jci.insight.91079] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Heterotrimeric G proteins play critical roles in transducing extracellular signals generated by 7-transmembrane domain receptors. Somatic gain-of-function mutations in G protein α subunits are associated with a variety of diseases. Recently, we identified gain-of-function mutations in Gα11 in patients with autosomal-dominant hypocalcemia type 2 (ADH2), an inherited disorder of hypocalcemia, low parathyroid hormone (PTH), and hyperphosphatemia. We have generated knockin mice harboring the point mutation GNA11 c.C178T (p.Arg60Cys) identified in ADH2 patients. The mutant mice faithfully replicated human ADH2. They also exhibited low bone mineral density and increased skin pigmentation. Treatment with NPS 2143, a negative allosteric modulator of the calcium-sensing receptor (CASR), increased PTH and calcium concentrations in WT and mutant mice, suggesting that the gain-of-function effect of GNA11R6OC is partly dependent on coupling to the CASR. Treatment with the Gα11/q-specific inhibitor YM-254890 increased blood calcium in heterozygous but not in homozygous GNA11R60C mice, consistent with published crystal structure data showing that Arg60 forms a critical contact with YM-254890. This animal model of ADH2 provides insights into molecular mechanism of this G protein-related disease and potential paths toward new lines of therapy.
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Affiliation(s)
- Kelly L Roszko
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Ruiye Bi
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
- West China School of Stomatology, Sichuan University, Chengdu, Sichuan, China
| | - Caroline M Gorvin
- Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Churchill Hospital, Oxford, England, United Kingdom
| | - Hans Bräuner-Osborne
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Xiao-Feng Xiong
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Asuka Inoue
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
- Japan Science and Technology Agency (JST), Precursory Research for Embryonic Science and Technology (PRESTO), Kawaguchi, Saitama, Japan
| | - Rajesh V Thakker
- Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Churchill Hospital, Oxford, England, United Kingdom
| | - Kristian Strømgaard
- Department of Drug Design and Pharmacology, University of Copenhagen, Copenhagen, Denmark
| | - Thomas Gardella
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
| | - Michael Mannstadt
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
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Mayr B, Glaudo M, Schöfl C. Activating Calcium-Sensing Receptor Mutations: Prospects for Future Treatment with Calcilytics. Trends Endocrinol Metab 2016; 27:643-652. [PMID: 27339034 DOI: 10.1016/j.tem.2016.05.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 05/17/2016] [Accepted: 05/20/2016] [Indexed: 12/20/2022]
Abstract
Activating mutations of the G protein-coupled receptor, calcium-sensing receptor (CaSR), cause autosomal dominant hypocalcemia and Bartter syndrome type 5. These mutations lower the set-point for extracellular calcium sensing, thereby causing decreased parathyroid hormone secretion and disturbed renal calcium handling with hypercalciuria. Available therapies increase serum calcium levels but raise the risk of complications in affected patients. Symptom relief and the prevention of adverse outcome is currently very difficult to achieve. Calcilytics act as CaSR antagonists that attenuate its activity, thereby correcting the molecular defect of activating CaSR proteins in vitro and elevating serum calcium in mice and humans in vivo, and have emerged as the most promising therapeutics for the treatment of these rare and difficult to treat diseases.
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Affiliation(s)
- Bernhard Mayr
- Division of Endocrinology and Diabetes, Department of Medicine I, Universitätsklinikum Erlangen, Friedrich-Alexander University Erlangen-Nuremberg, Germany.
| | - Markus Glaudo
- Division of Endocrinology and Diabetes, Department of Medicine I, Universitätsklinikum Erlangen, Friedrich-Alexander University Erlangen-Nuremberg, Germany
| | - Christof Schöfl
- Division of Endocrinology and Diabetes, Department of Medicine I, Universitätsklinikum Erlangen, Friedrich-Alexander University Erlangen-Nuremberg, Germany
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Vezzoli G, Macrina L, Rubinacci A, Spotti D, Arcidiacono T. Intestinal Calcium Absorption among Hypercalciuric Patients with or without Calcium Kidney Stones. Clin J Am Soc Nephrol 2016; 11:1450-1455. [PMID: 27284011 PMCID: PMC4974885 DOI: 10.2215/cjn.10360915] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2015] [Accepted: 04/06/2016] [Indexed: 12/31/2022]
Abstract
BACKGROUND AND OBJECTIVES Idiopathic hypercalciuria is a frequent defect in calcium kidney stone formers that is associated with high intestinal calcium absorption and osteopenia. Characteristics distinguishing hypercalciuric stone formers from hypercalciuric patients without kidney stone history (HNSFs) are unknown and were explored in our study. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS We compared 172 hypercalciuric stone formers with 36 HNSFs retrospectively selected from patients referred to outpatient clinics of the San Raffaele Hospital in Milan from 1998 to 2003. Calcium metabolism and lumbar bone mineral density were analyzed in these patients. A strontium oral load test was performed: strontium was measured in 240-minute urine and serum 30, 60, and 240 minutes after strontium ingestion; serum strontium concentration-time curve and renal strontium clearance were evaluated to estimate absorption and excretion of divalent cations. RESULTS Serum strontium concentration-time curve (P<0.001) and strontium clearance (4.9±1.3 versus 3.5±2.7 ml/min; P<0.001) were higher in hypercalciuric stone formers than HNSFs, respectively. The serum strontium-time curve was also higher in hypercalciuric stone formers with low bone mineral density (n=42) than in hypercalciuric stone formers with normal bone mineral density (n=130; P=0.03) and HNSFs with low (n=22; P=0.01) or normal bone mineral density (n=14; P=0.02). Strontium clearance was greater in hypercalciuric stone formers with normal bone mineral density (5.3±3.4 ml/min) than in hypercalciuric stone formers and HNSFs with low bone mineral density (3.6±2.5 and 3.1±2.5 ml/min, respectively; P=0.03). Multivariate regression analyses displayed that strontium absorption at 30 minutes was positively associated calcium excretion (P=0.03) and negatively associated with lumbar bone mineral density z score (P=0.001) in hypercalciuric stone formers; furthermore, hypercalciuric patients in the highest quartile of strontium absorption had increased stone production risk (odds ratio, 5.06; 95% confidence interval, 1.2 to 20.9; P=0.03). CONCLUSIONS High calcium absorption in duodenum and jejunum may expose hypercalciuric patients to the risk of stones because of increased postprandial calcium concentrations in urine and tubular fluid. High calcium absorption may identify patients at risk of bone loss among stone formers.
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Affiliation(s)
- Giuseppe Vezzoli
- Nephrology and Dialysis Unit, San Raffaele Scientific Institute and Postgraduate School of Nephrology, Vita Salute University, Milan, Italy; and
| | - Lorenza Macrina
- Nephrology and Dialysis Unit, San Raffaele Scientific Institute and Postgraduate School of Nephrology, Vita Salute University, Milan, Italy; and
| | | | - Donatella Spotti
- Nephrology and Dialysis Unit, San Raffaele Scientific Institute and Postgraduate School of Nephrology, Vita Salute University, Milan, Italy; and
| | - Teresa Arcidiacono
- Nephrology and Dialysis Unit, San Raffaele Scientific Institute and Postgraduate School of Nephrology, Vita Salute University, Milan, Italy; and
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Soleimani M, Barone S, Xu J, Alshahrani S, Brooks M, McCormack FX, Smith RD, Zahedi K. Prostaglandin-E2 Mediated Increase in Calcium and Phosphate Excretion in a Mouse Model of Distal Nephron Salt Wasting. PLoS One 2016; 11:e0159804. [PMID: 27442254 PMCID: PMC4956050 DOI: 10.1371/journal.pone.0159804] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Accepted: 07/10/2016] [Indexed: 01/29/2023] Open
Abstract
Contribution of salt wasting and volume depletion to the pathogenesis of hypercalciuria and hyperphosphaturia is poorly understood. Pendrin/NCC double KO (pendrin/NCC-dKO) mice display severe salt wasting under basal conditions and develop profound volume depletion, prerenal renal failure, and metabolic alkalosis and are growth retarded. Microscopic examination of the kidneys of pendrin/NCC-dKO mice revealed the presence of calcium phosphate deposits in the medullary collecting ducts, along with increased urinary calcium and phosphate excretion. Confirmatory studies revealed decreases in the expression levels of sodium phosphate transporter-2 isoforms a and c, increases in the expression of cytochrome p450 family 4a isotypes 12 a and b, as well as prostaglandin E synthase 1, and cyclooxygenases 1 and 2. Pendrin/NCC-dKO animals also had a significant increase in urinary prostaglandin E2 (PGE-2) and renal content of 20-hydroxyeicosatetraenoic acid (20-HETE) levels. Pendrin/NCC-dKO animals exhibit reduced expression levels of the sodium/potassium/2chloride co-transporter 2 (NKCC2) in their medullary thick ascending limb. Further assessment of the renal expression of NKCC2 isoforms by quantitative real time PCR (qRT-PCR) reveled that compared to WT mice, the expression of NKCC2 isotype F was significantly reduced in pendrin/NCC-dKO mice. Provision of a high salt diet to rectify volume depletion or inhibition of PGE-2 synthesis by indomethacin, but not inhibition of 20-HETE generation by HET0016, significantly improved hypercalciuria and salt wasting in pendrin/NCC dKO mice. Both high salt diet and indomethacin treatment also corrected the alterations in NKCC2 isotype expression in pendrin/NCC-dKO mice. We propose that severe salt wasting and volume depletion, irrespective of the primary originating nephron segment, can secondarily impair the reabsorption of salt and calcium in the thick ascending limb of Henle and/or proximal tubule, and reabsorption of sodium and phosphate in the proximal tubule via processes that are mediated by PGE-2.
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Affiliation(s)
- Manoocher Soleimani
- Center on Genetics of Transport, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Departments of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Research Services, Veterans Affairs Medical Center, Cincinnati, OH, United States of America
- * E-mail:
| | - Sharon Barone
- Center on Genetics of Transport, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Departments of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Research Services, Veterans Affairs Medical Center, Cincinnati, OH, United States of America
| | - Jie Xu
- Center on Genetics of Transport, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Departments of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
| | - Saeed Alshahrani
- Department of Pharmacology and Cell Biophysics and, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
| | - Marybeth Brooks
- Center on Genetics of Transport, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Departments of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
| | - Francis X. McCormack
- Departments of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
| | - Roger D. Smith
- Department of Pathology and Laboratory Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
| | - Kamyar Zahedi
- Center on Genetics of Transport, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Departments of Internal Medicine, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Research Services, Veterans Affairs Medical Center, Cincinnati, OH, United States of America
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Pointer MA, Eley S, Anderson L, Waters B, Royall B, Nichols S, Wells C. Differential Effect of Renal Cortical and Medullary Interstitial Fluid Calcium on Blood Pressure Regulation in Salt-Sensitive Hypertension. Am J Hypertens 2015; 28:1049-55. [PMID: 25552516 DOI: 10.1093/ajh/hpu255] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Accepted: 11/24/2014] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Hypercalciuria is a frequent characteristic of hypertension. In this report we extend our earlier studies investigating the role of renal interstitial fluid calcium (ISF(Ca))(2+) as a link between urinary calcium excretion and blood pressure in the Dahl salt-sensitive (DS) hypertensive model. METHODS Dahl salt-sensitive and salt-resistant (DR) rats were placed on control (0.45%) and high (8%) salt diets to determine if changes in renal cortical and medullary ISF(Ca)(2+)correlated with changes in urinary calcium excretion and blood pressure. RESULTS We observed that renal ISFCa(2+) was predicted by urinary calcium excretion (P < 0.05) in DS rats but not DR rats. Renal cortical ISF(Ca)(2+) was negatively associated with blood pressure (P < 0.03) while renal medullary ISF(Ca)(2+) was positively associated with blood pressure in DS rats (P < 0.04). In contrast, neither urinary calcium excretion nor renal ISF(Ca)(2+) was associated with blood pressure in the DR rats under the conditions of this study. CONCLUSION We interpret these findings to suggest that decreased renal cortical ISF(Ca)(2+) plays a role in the increase in blood pressure following a high salt diet in salt hypertension perhaps by mediating renal vasoconstriction; the role of medullary calcium remains to be fully understood. Further studies are needed to determine the mechanism of the altered renal ISF(Ca)(2+) and its role in blood pressure regulation.
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Affiliation(s)
- Mildred A Pointer
- Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, North Carolina, USA; Department of Biology; North Carolina Central University, Durham, North Carolina, USA.
| | - Shaleka Eley
- Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, North Carolina, USA; Department of Biology; North Carolina Central University, Durham, North Carolina, USA
| | - Lauren Anderson
- Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, North Carolina, USA; Department of Biology; North Carolina Central University, Durham, North Carolina, USA
| | - Brittany Waters
- Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, North Carolina, USA; Department of Biology; North Carolina Central University, Durham, North Carolina, USA
| | - Brittany Royall
- Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, North Carolina, USA; Department of Biology; North Carolina Central University, Durham, North Carolina, USA
| | - Sheena Nichols
- Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, North Carolina, USA; Department of Biology; North Carolina Central University, Durham, North Carolina, USA
| | - Candace Wells
- Julius L. Chambers Biomedical/Biotechnology Research Institute, North Carolina Central University, Durham, North Carolina, USA; Department of Biology; North Carolina Central University, Durham, North Carolina, USA
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Abstract
PURPOSE OF REVIEW In this review, we discuss how the genetic hypercalciuric stone-forming (GHS) rats, which closely model idiopathic hypercalciuria and stone formation in humans, provide insights into the pathophysiology and consequences of clinical hypercalciuria. RECENT FINDINGS Hypercalciuria in the GHS rats is due to a systemic dysregulation of calcium transport, as manifest by increased intestinal calcium absorption, increased bone resorption and decreased renal tubule calcium reabsorption. Increased levels of vitamin D receptor in intestine, bone and kidney appear to mediate these changes. The excess receptors are biologically active and increase tissue sensitivity to exogenous vitamin D. Bones of GHS rats have decreased bone mineral density (BMD) as compared with Sprague-Dawley rats, and exogenous 1,25(OH)2D3 exacerbates the loss of BMD. Thiazide diuretics improve the BMD in GHS rats. SUMMARY Studying GHS rats allows direct investigation of the effects of alterations in diet and utilization of pharmacologic therapy on hypercalciuria, urine supersaturation, stone formation and bone quality in ways that are not possible in humans.
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Affiliation(s)
- Kevin K Frick
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, New York, USA
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Baran N, ter Braak M, Saffrich R, Woelfle J, Schmitz U. Novel activating mutation of human calcium-sensing receptor in a family with autosomal dominant hypocalcaemia. Mol Cell Endocrinol 2015; 407:18-25. [PMID: 25766501 DOI: 10.1016/j.mce.2015.02.021] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 01/13/2015] [Accepted: 02/19/2015] [Indexed: 12/24/2022]
Abstract
INTRODUCTION Autosomal dominant hypocalcaemia (ADH) is caused by activating mutations in the calcium sensing receptor gene (CaR) and characterised by mostly asymptomatic mild to moderate hypocalcaemia with low, inappropriately serum concentration of PTH. OBJECTIVE The purpose of the present study was to biochemically and functionally characterise a novel mutation of CaR. PATIENTS A female proband presenting with hypocalcaemia was diagnosed to have "idiopathic hypoparathyroidism" at the age of 10 with a history of muscle pain and cramps. Further examinations demonstrated hypocalcaemia in nine additional family members, affecting three generations. MAIN OUTCOME MEASURE P136L CaR mutation was predicted to cause gain of function of CaR. RESULTS Affected family members showed relevant hypocalcaemia (mean ± SD; 1.9 ± 0.1 mmol/l). Patient history included mild seizures and recurrent nephrolithiasis. Genetic analysis confirmed that hypocalcaemia cosegregated with a heterozygous mutation at codon 136 (CCC → CTC/Pro → Leu) in exon 3 of CaR confirming the diagnosis of ADH. For in vitro studies P136L mutant CaR was generated by site-directed mutagenesis and examined in transiently transfected HEK293 cells. Extracellular calcium stimulation of transiently transfected HEK293 cells showed significantly increased intracellular Ca(2+) mobilisation and MAPK activity for mutant P136L CaR compared to wild type CaR. CONCLUSIONS The present study gives insight about a novel activating mutation of CaR and confirms that the novel P136L-CaR mutation is responsible for ADH in this family.
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Affiliation(s)
- Natalia Baran
- Department of Endocrinology and Diabetology, University of Bonn, Sigmund-Freud-Str. 25, 53127 Bonn, Germany; Department of Medicine V, University of Heidelberg, INF 410, 69120 Heidelberg, Germany.
| | - Michael ter Braak
- Institut of Pharmacology, University of Essen, Hufelandstr. 55, 45122 Essen, Germany
| | - Rainer Saffrich
- Department of Medicine V, University of Heidelberg, INF 410, 69120 Heidelberg, Germany
| | - Joachim Woelfle
- Pediatric Endocrinology Division, University of Bonn, Adenauerallee 119, 53113 Bonn, Germany
| | - Udo Schmitz
- Department of Endocrinology and Diabetology, University of Bonn, Sigmund-Freud-Str. 25, 53127 Bonn, Germany
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Ng AH, Frick KK, Krieger NS, Asplin JR, Cohen-McFarlane M, Culbertson CD, Kyker-Snowman K, Grynpas MD, Bushinsky DA. 1,25(OH)₂D₃ induces a mineralization defect and loss of bone mineral density in genetic hypercalciuric stone-forming rats. Calcif Tissue Int 2014; 94:531-43. [PMID: 24481706 PMCID: PMC4276134 DOI: 10.1007/s00223-014-9838-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2013] [Accepted: 01/07/2014] [Indexed: 11/29/2022]
Abstract
Genetic hypercalciuric stone-forming (GHS) rats, bred to maximize urine (u) calcium (Ca) excretion, demonstrate increased intestinal Ca absorption, increased bone Ca resorption, and reduced renal Ca reabsorption, all leading to elevated uCa compared to the parental Sprague-Dawley (SD) rats. GHS rats have increased numbers of vitamin D receptors (VDRs) at each site, with normal levels of 1,25(OH)₂D₃ (1,25D), suggesting their VDR is undersaturated with 1,25D. We have shown that 1,25D induces a greater increase in uCa in GHS than SD rats. To examine the effect of the increased VDR on the osseous response to 1,25D, we fed GHS and SD rats an ample Ca diet and injected either 1,25D [low dose (LD) 12.5 or high dose (HD) 25 ng/100 g body weight/day] or vehicle (veh) daily for 16 days. Femoral areal bone mineral density (aBMD, by DEXA) was decreased in GHS+LD and GHS+HD relative to GHS+veh, while there was no effect on SD. Vertebral aBMD was lower in GHS compared to SD and further decreased in GHS+HD. Both femoral and L6 vertebral volumetric BMD (by μCT) were lower in GHS and further reduced by HD. Histomorphometry indicated a decreased osteoclast number in GHS+HD compared to GHS+veh or SD+HD. In tibiae, GHS+HD trabecular thickness and number increased, with a 12-fold increase in osteoid volume but only a threefold increase in bone volume. Bone formation rate was decreased in GHS+HD relative to GHS+veh, confirming the mineralization defect. The loss of BMD and the mineralization defect in GHS rats contribute to increased hypercalciuria; if these effects persist, they would result in decreased bone strength, making these bones more fracture-prone. The enhanced effect of 1,25D in GHS rats indicates that the increased VDRs are biologically active.
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Affiliation(s)
- Adeline H. Ng
- Samuel Lunenfeld Research Institute, Toronto, Ontario, Canada
| | - Kevin K. Frick
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - Nancy S. Krieger
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | | | | | - Christopher D. Culbertson
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - Kelly Kyker-Snowman
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
| | - Marc D. Grynpas
- Samuel Lunenfeld Research Institute, Toronto, Ontario, Canada
| | - David A. Bushinsky
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine and Dentistry, Rochester, NY, USA
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Kinoshita Y, Hori M, Taguchi M, Watanabe S, Fukumoto S. Functional activities of mutant calcium-sensing receptors determine clinical presentations in patients with autosomal dominant hypocalcemia. J Clin Endocrinol Metab 2014; 99:E363-8. [PMID: 24297799 DOI: 10.1210/jc.2013-3430] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
OBJECTIVE Autosomal dominant hypocalcemia (ADH) is a congenital isolated hypoparathyroidism caused by activating mutations in the calcium-sensing receptor (CASR) gene. The clinical features of ADH are heterogeneous; some patients are asymptomatic, and others show severe hypocalcemia with Bartter's syndrome. We therefore recruited 12 patients with ADH to clarify the determinants of their clinical presentation. DESIGN AND METHODS We studied two sporadic and 10 familial cases of ADH. Serum concentrations of calcium, intact PTH, and magnesium (Mg(2+)) were measured in each patient. Fractional excretion of Mg (FE(Mg)) was calculated in spot urine samples. A nuclear factor of activated T cells luciferase assay was used to analyze the responsiveness of each mutant CaSR to extracellular Ca(2+). RESULTS Genomic analysis revealed five known activating mutations and a novel mutation, E481K, in the CASR. Patients with the A843E, C131W, or F788C mutation showed hypomagnesemia with elevated FE(Mg). Intact PTH in these patients was consistently near the detection limit. In contrast, patients with the P221L, K47N, or E481K mutation exhibited normal Mg(2+) levels. In these patients, intact PTH increased in response to low calcium, and their maximum intact PTH exceeded the lower limit of the reference range. Functional analysis showed an association between the disease severity and the in vitro activity of the mutant CaSR. CONCLUSIONS The functional activity of mutant CaSR determines the serum Mg(2+) level, renal Mg(2+) handling, and intact PTH in patients with ADH. The presence of hypomagnesemia with elevated FE(Mg) may indicate the diagnosis of ADH among patients with PTH-deficient hypoparathyroidism.
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Affiliation(s)
- Yuka Kinoshita
- Division of Nephrology and Endocrinology, Department of Medicine, University of Tokyo Hospital, Tokyo 113-8655, Japan
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Abstract
Hypercalciuria is the most common metabolic abnormality found in patients with calcium-containing kidney stones. Patients with hypercalciuria often excrete more calcium than they absorb, indicating a net loss of total-body calcium. The source of this additional urinary calcium is almost certainly the skeleton, the largest repository of calcium in the body. Hypercalciuric stone formers exhibit decreased bone mineral density (BMD), which is correlated with the increase in urine calcium excretion. The decreased BMD also correlates with an increase in markers of bone turnover as well as increased fractures. In humans, it is difficult to determine the cause of the decreased BMD in hypercalciuric stone formers. To study the effect of hypercalciuria on bone, we utilized our genetic hypercalciuric stone-forming (GHS) rats, which were developed through successive inbreeding of the most hypercalciuric Sprague-Dawley rats. GHS rats excrete significantly more urinary calcium than similarly fed controls, and all the GHS rats form kidney stones while control rats do not. The hypercalciuria is due to a systemic dysregulation of calcium homeostasis, with increased intestinal calcium absorption, enhanced bone mineral resorption, and decreased renal tubule calcium reabsorption associated with an increase in vitamin D receptors in all these target tissues. We recently found that GHS rats fed an ample calcium diet have reduced BMD and that their bones are more fracture-prone, indicating an intrinsic disorder of bone not secondary to diet. Using this model, we should better understand the pathogenesis of hypercalciuria and stone formation in humans to ultimately improve the bone health of patients with kidney stones.
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Affiliation(s)
- Nancy S Krieger
- Division of Nephrology, Department of Medicine, University of Rochester School of Medicine, 601 Elmwood Ave., Box 675, Rochester, NY, 14642, USA,
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Vezzoli G, Terranegra A, Aloia A, Arcidiacono T, Milanesi L, Mosca E, Mingione A, Spotti D, Cusi D, Hou J, Hendy GN, Soldati L, Paloschi V, Dogliotti E, Brasacchio C, Dell'Antonio G, Montorsi F, Bertini R, Bellinzoni P, Guazzoni G, Borghi L, Guerra A, Allegri F, Ticinesi A, Meschi T, Nouvenne A, Lupo A, Fabris A, Gambaro G, Strazzullo P, Rendina D, De Filippo G, Brandi ML, Croppi E, Cianferotti L, Trinchieri A, Caudarella R, Cupisti A, Anglani F, Del Prete D. Decreased transcriptional activity of calcium-sensing receptor gene promoter 1 is associated with calcium nephrolithiasis. J Clin Endocrinol Metab 2013; 98:3839-47. [PMID: 23864702 PMCID: PMC3763974 DOI: 10.1210/jc.2013-1834] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
BACKGROUND CaSR gene is a candidate for calcium nephrolithiasis. Single-nucleotide polymorphisms (SNPs) encompassing its regulatory region were associated with calcium nephrolithiasis. AIMS We tested SNPs in the CaSR gene regulatory region associated with calcium nephrolithiasis and their effects in kidney. SUBJECTS AND METHODS One hundred sixty-seven idiopathic calcium stone formers and 214 healthy controls were genotyped for four CaSR gene SNPs identified by bioinformatics analysis as modifying transcription factor binding sites. Strontium excretion after an oral load was tested in 55 stone formers. Transcriptional activity induced by variant alleles at CaSR gene promoters was compared by luciferase reporter gene assay in HEK-293 and HKC-8 cells. CaSR and claudin-14 mRNA levels were measured by real-time PCR in 107 normal kidney medulla samples and compared in patients with different CaSR genotype. RESULTS Only rs6776158 (A>G), located in the promoter 1, was associated with nephrolithiasis. Its minor G allele was more frequent in stone formers than controls (37.8% vs 26.4%, P = .001). A reduced strontium excretion was observed in GG homozygous stone formers. Luciferase fluorescent activity was lower in cells transfected with the promoter 1 including G allele at rs6776158 than cells transfected with the A allele. CaSR mRNA levels were lower in kidney medulla samples from homozygous carriers for the G allele at rs6776158 than carriers for the A allele. Claudin-14 mRNA levels were also lower in GG homozygous subjects. CONCLUSIONS Minor allele at rs6776158 may predispose to calcium stones by decreasing transcriptional activity of the CaSR gene promoter 1 and CaSR expression in kidney tubules.
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Affiliation(s)
- Giuseppe Vezzoli
- Nephrology and Dialysis Unit, San Raffaele Hospital Instituto di Ricovero e Cura a Carattere Scientifico, 20132 Milan, Italy.
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Abstract
Calcium nephrolithiasis is a common condition. Family-based genetic linkage studies and genome-wide association studies (GWASs) have uncovered a run of important candidate genes involved in renal Ca(++) disorders and kidney stone diseases. The susceptible genes include NKCC2, ROMK and ClCkb/Barttin that underlie renal salt excretion; claudin-14, -16 and -19 that underlie renal Ca(++) excretion; and CaSR that provides a sensing mechanism for the kidney to regulate salt, water and Ca(++) homeostasis. Biological and physiological analyses have revealed the cellular mechanism for transepithelial Ca(++) transport in the kidney that depends on the concerted action of these gene products. Although the individual pathogenic weight of the susceptible genes in nephrolithiasis remains unclear, perturbation of their expression or function compromises the different steps within the integrated pathway for Ca(++) reabsorption, providing a physiological basis for diagnosing and managing kidney stone diseases.
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Affiliation(s)
- Jianghui Hou
- Washington University Renal Division, St. Louis, MO 63110, USA.
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Arrabal-Polo MA, Arrabal-Martin M, Arias-Santiago S, Garrido-Gomez J, De Haro-Muñoz TD, Zuluaga-Gomez A. Metabolic-mineral study in patients with renal calcium lithiasis, severe lithogenic activity and loss of bone mineral density. Singapore Med J 2012; 53:808-813. [PMID: 23268154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
INTRODUCTION This study assessed the presence of osteoporosis/osteopenia in patients with severe lithogenic activity and compared their metabolisms with those in patients without lithiasis or with mild lithogenic activity. METHODS From a sample of 182 patients, those with osteopenia/osteoporosis at the hip and lumbar spine were studied separately in a two-pronged study. 66 patients with bone mineral densities (BMDs) < -1 standard deviation (SD) on a T-score scale at the hip were divided into three groups: group A1 without lithiasis (n = 15); group A2 with lithiasis and mild lithogenic activity (n = 22); and group A3 with lithiasis and severe lithogenic activity (n = 29). Similarly, 86 patients with BMDs < -1 SD on a T-score scale at the lumbar spine were divided into three groups: group B1 without lithiasis (n = 15); group B2 with lithiasis and mild lithogenic activity (n = 29); and group B3 with lithiasis and severe lithogenic activity (n = 42). RESULTS Patients from group A3 exhibited significantly higher levels of bone remodelling markers as compared to groups A1 and A2. Urinalysis also revealed higher excretion of calcium in 24-hour assessments in this group. Patients from group B3 differed from groups B1 and B2 mainly in bone remodelling markers and 24-hour urinary calcium excretion, which were significantly elevated in patients from group B3. CONCLUSION Patients with calcium lithiasis and severe lithogenic activity in addition to osteopenia/osteoporosis present with higher levels of hypercalciuria and negative osseous balance, which possibly perpetuate and favour lithiasic activity.
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Abstract
Calcium is an important participant in many physiologic processes including coagulation, cell membrane transfer, hormone release, neuromuscular activation, and myocardial contraction. The body cooperates in a sophisticated web of hormonally mediated interactions to maintain stable extracellular calcium levels. Calcium is vital for skeletal mineralization, and perturbations in extracellular calcium may be corrected at the expense of bone strength and integrity. The aim of this review is to delineate our current understanding of idiopathic hypercalciuria in the context of bone health, specifically its definition, etiology, epidemiology, laboratory evaluation, and potential therapeutic management.
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Affiliation(s)
- Laura E Ryan
- Center for Women's Health, Division of Endocrinology, Diabetes and Metabolism, The Ohio State University, Columbus, 43210, USA.
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Guarnieri V, Valentina D'Elia A, Baorda F, Pazienza V, Benegiamo G, Stanziale P, Copetti M, Battista C, Grimaldi F, Damante G, Pellegrini F, D'Agruma L, Zelante L, Carella M, Scillitani A. CASR gene activating mutations in two families with autosomal dominant hypocalcemia. Mol Genet Metab 2012; 107:548-52. [PMID: 22789683 DOI: 10.1016/j.ymgme.2012.06.012] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Accepted: 06/19/2012] [Indexed: 12/19/2022]
Abstract
BACKGROUND Autosomal dominant hypocalcemia (ADH) is an endocrine disorder caused by activating mutations of the calcium-sensing receptor (CASR) gene which plays a major role in maintaining calcium homeostasis. Biochemical features of ADH are hypocalcemia and hypercalciuria with inappropriately low levels of parathyroid hormone (PTH). We report on two four-generation families affected by ADH. AIM To identify mutations of CASR gene in subjects affected by familial idiopathic hypoparathyroidism. To perform functional assays of identified CASR variants by transient transfection on HEK293 cells. RESULTS We identified two CASR variants (Q681R and P221L): the Q681R variant was novel while the P221L had been previously published. Functional assays on the Q681R variant showed that it did not alter the whole expression nor the correct plasmamembrane localization, but enhanced the signaling function, increasing the sensitivity of the receptor as compared to the WT. CONCLUSIONS We report two activating CASR mutations in two families affected by ADH and the functional assays performed on the novel variant Q681R. Our work enlarged the spectrum of mutations of the CASR and contributed to a better elucidation of the protein function.
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Affiliation(s)
- Vito Guarnieri
- Medical Genetics, IRCCS Casa Sollievo della Sofferenza Hospital, viale Padre Pio, 71013 San Giovanni Rotondo, FG, Italy.
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Mannstadt M, Magen D, Segawa H, Stanley T, Sharma A, Sasaki S, Bergwitz C, Mounien L, Boepple P, Thorens B, Zelikovic I, Jüppner H. Fanconi-Bickel syndrome and autosomal recessive proximal tubulopathy with hypercalciuria (ARPTH) are allelic variants caused by GLUT2 mutations. J Clin Endocrinol Metab 2012; 97:E1978-86. [PMID: 22865906 PMCID: PMC3462928 DOI: 10.1210/jc.2012-1279] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
CONTEXT Many inherited disorders of calcium and phosphate homeostasis are unexplained at the molecular level. OBJECTIVE The objective of the study was to identify the molecular basis of phosphate and calcium abnormalities in two unrelated, consanguineous families. PATIENTS The affected members in family 1 presented with rickets due to profound urinary phosphate-wasting and hypophosphatemic rickets. In the previously reported family 2, patients presented with proximal renal tubulopathy and hypercalciuria yet normal or only mildly increased urinary phosphate excretion. METHODS Genome-wide linkage scans and direct nucleotide sequence analyses of candidate genes were performed. Transport of glucose and phosphate by glucose transporter 2 (GLUT2) was assessed using Xenopus oocytes. Renal sodium-phosphate cotransporter 2a and 2c (Npt2a and Npt2c) expressions were evaluated in transgenically rescued Glut2-null mice (tgGlut2-/-). RESULTS In both families, genetic mapping and sequence analysis of candidate genes led to the identification of two novel homozygous mutations (IVS4-2A>G and R124S, respectively) in GLUT2, the gene mutated in Fanconi-Bickel syndrome, a rare disease usually characterized by renal tubulopathy, impaired glucose homeostasis, and hepatomegaly. Xenopus oocytes expressing the [R124S]GLUT2 mutant showed a significant reduction in glucose transport, but neither wild-type nor mutant GLUT2 facilitated phosphate import or export; tgGlut2-/- mice demonstrated a profound reduction of Npt2c expression in the proximal renal tubules. CONCLUSIONS Homozygous mutations in the facilitative glucose transporter GLUT2, which cause Fanconi-Bickel syndrome, can lead to very different clinical and biochemical findings that are not limited to mild proximal renal tubulopathy but can include significant hypercalciuria and highly variable degrees of urinary phosphate-wasting and hypophosphatemia, possibly because of the impaired proximal tubular expression of Npt2c.
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Affiliation(s)
- Michael Mannstadt
- Massachusetts General Hospital, Endocrine Unit, Harvard Medical School, Thier 1051, 55 Fruit Street, Boston Massachusetts 02114, USA.
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Kawamura Y. [Drugs affecting serum magnesium concentration]. Clin Calcium 2012; 22:1211-1216. [PMID: 22846357] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Several oral or intravenous drug administrations can cause abnormalities in serum magnesium concentration. Most of drug-induced hypomagnesemia derives from a loss of the mineral in the urine by facilitating renal secretion. Hypermagnesemia can occur by a direct intake of drugs including magnesium, especially in patients with renal insufficiency. Frequent check of serum magnesium concentration will be needed to monitor these abnormalities.
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Kamenický P, Blanchard A, Gauci C, Salenave S, Letierce A, Lombès M, Brailly-Tabard S, Azizi M, Prié D, Souberbielle JC, Chanson P. Pathophysiology of renal calcium handling in acromegaly: what lies behind hypercalciuria? J Clin Endocrinol Metab 2012; 97:2124-33. [PMID: 22496496 DOI: 10.1210/jc.2011-3188] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
BACKGROUND Hypercalciuria is frequent in patients with acromegaly, but it is unclear how GH/IGF-I regulate renal calcium handling. Elevated fasting plasma calcium levels despite increased glomerular filtration suggest enhanced renal calcium reabsorption. OBJECTIVE The aim of this study was to investigate the impact of acromegaly on phosphocalcium metabolism. DESIGN AND SETTING We conducted a prospective sequential study at a tertiary referral medical center and clinical investigation center (www.ClinicalTrials.gov Identifier: NCT00531908). INTERVENTION Sixteen consecutive patients (five females/11 males) with acromegaly received a single iv infusion of 25 mg of furosemide to induce an acute increase in calcium and magnesium delivery to distal tubular segments during a high-sodium diet with stable dietary calcium, magnesium, and phosphate intake. MEASUREMENTS Baseline plasma and urine electrolytes, plasma calciotropic hormones, and furosemide-induced changes in the fractional excretion and tubular reabsorption of Na, Ca, and Mg were measured before and 6 months (range, 1-12) after effective treatment of acromegaly. RESULTS Serum IGF-I concentrations normalized in all the patients after acromegaly treatment. Compared with controlled acromegaly, active acromegaly was associated with higher fasting plasma (P = 0.0002) and urinary calcium (P = 0.0003) levels, lower PTH levels (P = 0.0075), higher calcitriol levels (P = 0.0137), higher phosphatemia (P<0.0001) and tubular phosphate reabsorption (P = 0.0002), and a lower calciuric (P = 0.0327) but not magnesiuric response to furosemide related to higher baseline and postfurosemide tubular calcium (P = 0.0034 and P = 0.0081, respectively), but not magnesium reabsorption. CONCLUSION The IGF-I-mediated and PTH-independent increase in calcitriol synthesis in acromegaly is responsible for both absorptive hypercalciuria and increased fasting plasma calcium linked to enhanced distal tubular calcium reabsorption, as shown by the selectively diminished calciuric response to furosemide.
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Affiliation(s)
- Peter Kamenický
- Service d'Endocrinologie et des Maladies de la Reproduction, Hôpital de Bicêtre, 78 rue du Général Leclerc, F-94275 Le Kremlin-Bicêtre, France
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Procino G, Mastrofrancesco L, Tamma G, Lasorsa DR, Ranieri M, Stringini G, Emma F, Svelto M, Valenti G. Calcium-sensing receptor and aquaporin 2 interplay in hypercalciuria-associated renal concentrating defect in humans. An in vivo and in vitro study. PLoS One 2012; 7:e33145. [PMID: 22403735 PMCID: PMC3293925 DOI: 10.1371/journal.pone.0033145] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2011] [Accepted: 02/10/2012] [Indexed: 01/08/2023] Open
Abstract
One mechanism proposed for reducing the risk of calcium renal stones is activation of the calcium-sensing receptor (CaR) on the apical membranes of collecting duct principal cells by high luminal calcium. This would reduce the abundance of aquaporin-2 (AQP2) and in turn the rate of water reabsorption. While evidence in cells and in hypercalciuric animal models supports this hypothesis, the relevance of the interplay between the CaR and AQP2 in humans is not clear. This paper reports for the first time a detailed correlation between urinary AQP2 excretion under acute vasopressin action (DDAVP treatment) in hypercalciuric subjects and in parallel analyzes AQP2-CaR crosstalk in a mouse collecting duct cell line (MCD4) expressing endogenous and functional CaR. In normocalciurics, DDAVP administration resulted in a significant increase in AQP2 excretion paralleled by an increase in urinary osmolality indicating a physiological response to DDAVP. In contrast, in hypercalciurics, baseline AQP2 excretion was high and did not significantly increase after DDAVP. Moreover DDAVP treatment was accompanied by a less pronounced increase in urinary osmolality. These data indicate reduced urinary concentrating ability in response to vasopressin in hypercalciurics. Consistent with these results, biotinylation experiments in MCD4 cells revealed that membrane AQP2 expression in unstimulated cells exposed to CaR agonists was higher than in control cells and did not increase significantly in response to short term exposure to forskolin (FK). Interestingly, we found that CaR activation by specific agonists reduced the increase in cAMP and prevented any reduction in Rho activity in response to FK, two crucial pathways for AQP2 translocation. These data support the hypothesis that CaR–AQP2 interplay represents an internal renal defense to mitigate the effects of hypercalciuria on the risk of calcium precipitation during antidiuresis. This mechanism and possibly reduced medulla tonicity may explain the lower concentrating ability observed in hypercalciuric patients.
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Affiliation(s)
- Giuseppe Procino
- Department of Biosciences, Biotechnologies and Pharmacological Sciences and Center of Excellence in Comparative Genomics, University of Bari, Bari, Italy
| | - Lisa Mastrofrancesco
- Department of Biosciences, Biotechnologies and Pharmacological Sciences and Center of Excellence in Comparative Genomics, University of Bari, Bari, Italy
| | - Grazia Tamma
- Department of Biosciences, Biotechnologies and Pharmacological Sciences and Center of Excellence in Comparative Genomics, University of Bari, Bari, Italy
| | - Domenica Rita Lasorsa
- Department of Biosciences, Biotechnologies and Pharmacological Sciences and Center of Excellence in Comparative Genomics, University of Bari, Bari, Italy
| | - Marianna Ranieri
- Department of Biosciences, Biotechnologies and Pharmacological Sciences and Center of Excellence in Comparative Genomics, University of Bari, Bari, Italy
| | | | | | - Maria Svelto
- Department of Biosciences, Biotechnologies and Pharmacological Sciences and Center of Excellence in Comparative Genomics, University of Bari, Bari, Italy
| | - Giovanna Valenti
- Department of Biosciences, Biotechnologies and Pharmacological Sciences and Center of Excellence in Comparative Genomics, University of Bari, Bari, Italy
- * E-mail:
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Abstract
The physiology of paracellular permeation of ions and solutes in the kidney is pivotally important but poorly understood. Claudins are the key components of the paracellular pathway. Defects in claudin function result in a broad range of renal diseases, including hypomagnesemia, hypercalciuria and nephrolithiasis. This review describes recent findings on the physiological function of claudins underlying paracellular transport mechanisms with a focus on renal Ca(2+) handling. We have uncovered a molecular mechanism underlying paracellular Ca(2+) transport in the thick ascending limb of Henle (TAL) that involves the functional interplay of three important claudin genes: claudin-14, -16 and -19, all of which are associated with human kidney diseases with hypercalciuria, nephrolithiasis and bone mineral loss. The Ca(2+) sensing receptor (CaSR) signaling in the kidney has long been a mystery. By analyzing small non-coding RNA molecules in the kidney, we have uncovered a novel microRNA based signaling pathway downstream of CaSR that directly regulates claudin-14 gene expression and establishes the claudin-14 molecule as a key regulator for renal Ca(2+) homeostasis. The molecular cascade of CaSR-microRNAs-claudins forms a regulatory loop to maintain proper Ca(2+) homeostasis in the kidney.
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Affiliation(s)
- Jianghui Hou
- Renal Division, Washington University, St. Louis, MO, USA.
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Sato Y, Yonekura Y, Tsukamoto T, Kakita H, Tateishi Y, Komiya T, Yonemoto S, Muso E. [A case of hypomagnesemia linked to refractory hypokalemia and hypocalcemia with short bowel syndrome]. Nihon Jinzo Gakkai Shi 2012; 54:1197-1202. [PMID: 23387283] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
We report a case of a 59-year old Japanese woman with short bowel syndrome, whose hypokalemia and hypocalcemia were successfully treated with magnesium (Mg) supplementation. Two years previously, she underwent Mile's operation for advanced rectal cancer, which could have been the cause of subsequent extensive resection of the small intestine by strangulation. After serial resection, she gradually developed chronic diarrhea and anorexia. Three weeks before admission, she developed general fatigue and tetany, and was hospitalized at another hospital. On admission, her serum K and Ca were 2.5 mEq/L and 4.3 mg/dL, respectively, hence regular fluid therapy containing potassium (K) and calcium (Ca) was provided following admission. However, her hypokalemia and hypocalcemia persisted, and she also displayed renal dysfunction and thereafter was transferred to our department for further evaluation and treatment. Since the laboratory tests revealed severe hypomagnesemia (0.4 mg/dL), we started intravenous Mg supplementation together with fluid therapy containing K and Ca. After the combination therapy, her clinical symptoms and electrolyte disorders were remarkably improved within a week. As Mg is essential for PTH secretion in response to hypocalcemia and to inhibit the K channel activity that controls urinary K excretion, hypomagnesemia can cause hypocalcemia and hypokalemia, which is refractory to repletion therapy unless Mg is administered. Therefore, for patients who present with signs of Mg deficiency, early and accurate diagnosis of Mg deficiency should be made and corrected.
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Affiliation(s)
- Yuki Sato
- Division of Nephrology and Dialysis, Kitano Hospital, The Tazuke Kofukai Medical Research Institute, Osaka, Japan
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Abstract
CONTEXT AND OBJECTIVE Dietary intake of animal proteins is associated with an increase in urinary calcium and nephrolithiasis risk. We tested the hypothesis that the acid load imposed by dietary proteins causes this hypercalciuria. DESIGN AND SETTING In a short-term crossover metabolic study, an alkali salt was provided with a high-protein diet (HPD) to neutralize the acid load imparted by dietary proteins. PARTICIPANTS AND INTERVENTIONS Eleven healthy volunteers were evaluated at the end of each of four phases while consuming metabolic diets with fixed calcium and sodium content. Phases 1 and 3 consisted of a control diet (CD). Phases 2 and 4 consisted of a eucaloric HPD (60 g/d animal proteins added to CD). Along with HPD in phases 2 and 4, subjects ingested 30 mEq twice daily of either potassium citrate (KCitrate, alkaline salt) or potassium chloride (KCl, control neutral salt). RESULTS KCitrate completely neutralized the acid load imparted by HPD (based on changes in urine pH and net acid excretion) and increased urinary citrate. Urinary calcium increased during both HPD phases compared with CD but was not significantly different between the HPD + KCl and HPD + KCitrate phases (182 ± 85 vs. 170 ± 85 mg/d; P = 0.28). Increased urinary saturation with respect to calcium oxalate and uric acid with HPD was abrogated by KCitrate. CONCLUSIONS This study suggests that, at least in the short-term, mechanism(s) other than acid load account for hypercalciuria induced by HPD. The beneficial effect of KCitrate on nephrolithiasis risk with HPD is through correction of declines in urine pH and citrate.
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Affiliation(s)
- Naim M Maalouf
- Department of Internal Medicine and Charles, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, Texas 75390-8885, USA.
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Wróblewski T, Wystrychowski A. [Hypercalciuria]. Przegl Lek 2011; 68:107-113. [PMID: 21751520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Hypercalciuria is the most common metabolic abnormality that causes urolithiasis. The pathogenetic mechanisms responsible for hypercalciuria include enhanced gastrointestinal absorption of calcium, increased bone resorption and/or decreased renal reabsorption of calcium; the main dietary factors promoting hypercalciuria are high dietary sodium intake and protein-rich diet. The authors discuss pathophysiology of hypercalciuria and genetic factors behind 'idiopathic hypercalciuria'. The simplified diagnostic approach to hypercalciuria is outlined herein, and available therapeutic interventions of proven efficacy in idiopathic hypercalciuria are presented as well. Dietary intervention for hypercalciuria should include reduced sodium, protein and oxalate intake. Thiazide diuretics, in conjunction with a low-sodium diet, tend to reduce urinary calcium excretion and ameliorate idiopathic hypercalciuria. Potassium citrate acts as an inhibitor of calcium stone formation in the urinary tract. A low-calcium diet should generally be avoided, as it may increase urinary oxalate excretion and actually promote stone formation. In addition, a low-calcium diet may lead to negative calcium balance in subjects with hypercalciuria, and therefore increases the risk of osteopenia.
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Affiliation(s)
- Tomasz Wróblewski
- Oddział Nefrologiczny i Chorób Wewnetrznych, Szpital Powiatowy w Chrzanowie.
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Bai S, Wang H, Shen J, Zhou R, Bushinsky DA, Favus MJ. Elevated vitamin D receptor levels in genetic hypercalciuric stone-forming rats are associated with downregulation of Snail. J Bone Miner Res 2010; 25:830-40. [PMID: 19929616 PMCID: PMC3153334 DOI: 10.1359/jbmr.091010] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2009] [Revised: 09/21/2009] [Accepted: 10/09/2009] [Indexed: 11/18/2022]
Abstract
Patients with idiopathic hypercalciuria (IH) and genetic hypercalciuric stone-forming (GHS) rats, an animal model of IH, are both characterized by normal serum Ca, hypercalciuria, Ca nephrolithiasis, reduced renal Ca reabsorption, and increased bone resorption. Serum 1,25-dihydroxyvitamin D [1,25(OH)(2)D] levels are elevated or normal in IH and are normal in GHS rats. In GHS rats, vitamin D receptor (VDR) protein levels are elevated in intestinal, kidney, and bone cells, and in IH, peripheral blood monocyte VDR levels are high. The high VDR is thought to amplify the target-tissue actions of normal circulating 1,25(OH)(2)D levels to increase Ca transport. The aim of this study was to elucidate the molecular mechanisms whereby Snail may contribute to the high VDR levels in GHS rats. In the study, Snail gene expression and protein levels were lower in GHS rat tissues and inversely correlated with VDR gene expression and protein levels in intestine and kidney cells. In human kidney and colon cell lines, ChIP assays revealed endogenous Snail binding close to specific E-box sequences within the human VDR promoter region, whereas only one E-box specifically bound Snail in the rat promoter. Snail binding to rat VDR promoter E-box regions was reduced in GHS compared with normal control intestine and was accompanied by hyperacetylation of histone H(3). These results provide evidence that elevated VDR in GHS rats likely occurs because of derepression resulting from reduced Snail binding to the VDR promoter and hyperacetylation of histone H(3).
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Affiliation(s)
- Shaochun Bai
- Section of Endocrinology and Metabolism, The University of Chicago Pritzker School of MedicineChicago, IL, USA
| | - Hongwei Wang
- Section of Endocrinology and Metabolism, The University of Chicago Pritzker School of MedicineChicago, IL, USA
| | - Jikun Shen
- Section of Endocrinology and Metabolism, The University of Chicago Pritzker School of MedicineChicago, IL, USA
| | - Randal Zhou
- Section of Endocrinology and Metabolism, The University of Chicago Pritzker School of MedicineChicago, IL, USA
| | - David A Bushinsky
- Department of Medicine, University of Rochester School of MedicineRochester, New York, USA
| | - Murray J Favus
- Section of Endocrinology and Metabolism, The University of Chicago Pritzker School of MedicineChicago, IL, USA
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Abstract
The mechanisms underlying hypercalciuria in pseudohypoaldosteronism type II (PHAII) caused by WNK4 mutations remain unclear. In this study, we used Wnk4(D561A/+) knock-in mice as a model of human PHAII for investigating the pathogenesis of hypercalciuria in PHAII. Serum and urine biochemistries were obtained from Wnk4(+/+) and Wnk4(D561A/+) littermates. Expression of the epithelial Ca(2+) channels [transient receptor potential channel vanilloid subtype 5 (TRPV5) and TRPV6] and calbindin-D28k (CBP-D28k) in the distal nephron and two upstream Na(+) transporters, Na(+)/H(+) exchanger 3 and Na(+)-K(+)-2Cl(-) cotransporter 2 involved in paracellular Ca(2+) reabsorption, were examined by real-time PCR, immunofluorescent staining, and immunoblotting. Compared with Wnk4(+/+) littermate controls, Wnk4(D561A/+) mice manifested hypercalciuria despite no significant differences in serum creatinine, ionized Ca(2+), PTH, and 1,25 hydroxylvitamin D(3) levels. There was no significant difference in TRPV5 expression, but a significant increase in TRPV6 and CBP-D28k was observed in Wnk4(D561A/+) mice. Despite no significant change in Na(+)/H(+) exchanger 3 expression, Na(+)-K(+)-2Cl(-) cotransporter 2 expression was significantly attenuated and urine Ca(2+) excretion rate in response to furosemide was blunted in Wnk4(D561A/+) mice. Decreased Ca(2+) reabsorption in the upstream nephron, especially in the thick ascending loops of Henle, with a secondary adaptive increase in TRPV6 and CBP-D28k expression in the distal tubules might be involved in the hypercalciuria of PHAII.
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Affiliation(s)
- Sung-Sen Yang
- Division of Nephrology, Department of Medicine, Tri-Service General Hospital, and School of Medicine, National Defense Medical Center, Neihu 114, Taipei, Taiwan
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Riccardi D, Brown EM. Physiology and pathophysiology of the calcium-sensing receptor in the kidney. Am J Physiol Renal Physiol 2010; 298:F485-99. [PMID: 19923405 PMCID: PMC2838589 DOI: 10.1152/ajprenal.00608.2009] [Citation(s) in RCA: 264] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2009] [Accepted: 11/13/2009] [Indexed: 12/21/2022] Open
Abstract
The extracellular calcium-sensing receptor (CaSR) plays a major role in the maintenance of a physiological serum ionized calcium (Ca2+) concentration by regulating the circulating levels of parathyroid hormone. It was molecularly identified in 1993 by Brown et al. in the laboratory of Dr. Steven Hebert with an expression cloning strategy. Subsequent studies have demonstrated that the CaSR is highly expressed in the kidney, where it is capable of integrating signals deriving from the tubular fluid and/or the interstitial plasma. Additional studies elucidating inherited and acquired mutations in the CaSR gene, the existence of activating and inactivating autoantibodies, and genetic polymorphisms of the CaSR have greatly enhanced our understanding of the role of the CaSR in mineral ion metabolism. Allosteric modulators of the CaSR are the first drugs in their class to become available for clinical use and have been shown to treat successfully hyperparathyroidism secondary to advanced renal failure. In addition, preclinical and clinical studies suggest the possibility of using such compounds in various forms of hypercalcemic hyperparathyroidism, such as primary and lithium-induced hyperparathyroidism and that occurring after renal transplantation. This review addresses the role of the CaSR in kidney physiology and pathophysiology as well as current and in-the-pipeline treatments utilizing CaSR-based therapeutics.
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Affiliation(s)
- Daniela Riccardi
- School of Biosciences, Cardiff University, Cardiff, United Kingdom.
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40
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Naseri M, Varasteh AR, Alamdaran SA. Metabolic factors associated with urinary calculi in children. Iran J Kidney Dis 2010; 4:32-38. [PMID: 20081302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
INTRODUCTION We aimed to identify metabolic and anatomical abnormalities present in children with urinary calculi. MATERIALS AND METHODS Metabolic evaluation was done in 142 pediatric calculus formers. Evaluation included serum biochemistry; measurement of daily excretion of urinary calcium, uric acid, oxalate, citrate, and magnesium (in older children); and measurement of calcium, uric acid, oxalate, and creatinine in random urine samples in nontoilet-trained patients. Urinary tests for cystinuria were also performed. All of the patients underwent renal ultrasonography. RESULTS Sixty-one patients (42.7%) had metabolic abnormalities. Anatomical abnormalities were found in 12 patients (8.4%). Three children (2.1%) had infectious calculi, and 3(2.1%) had a combination of metabolic and anatomic abnormalities. In 66 children (46.2 %) we did not find any reasons for calculus formation (idiopathic). Urinalysis revealed hypercalciuria in 25 (17.6%), hyperuricosuria in 23 (16.1%), hyperoxaluria in 17 (11.9%), cystinuria in 9 (6.3%), hypocitraturia in 3 (2.1%), and low urinary magnesium level in 1 (0.7%) patients. Sixteen patients (11.2%) had mixed metabolic abnormalities. CONCLUSIONS Metabolic abnormalities are common in pediatric patients with urinary calculi. In our study, calcium and uric acid abnormalities were the most common, and vesicoureteral reflux seemed to be the most common urological abnormality which led to urinary stasis and calculus formation.
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Affiliation(s)
- Mitra Naseri
- Department of Pediatrics, Dr Sheikh Children Hospital, Mashhad University of Medical Sciences, Mashhad, Iran.
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Piemonte S, Romagnoli E, Cipriani C, Fassino V, Del Fiacco R, Carnevale V, Scillitani A, D'Erasmo E, Tancredi A, Minisola S. The effect of recombinant PTH(1-34) and PTH(1-84) on serum ionized calcium, 1,25-dihydroxyvitamin D, and urinary calcium excretion: a pilot study. Calcif Tissue Int 2009; 85:287-92. [PMID: 19756348 DOI: 10.1007/s00223-009-9280-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/01/2009] [Accepted: 07/09/2009] [Indexed: 10/20/2022]
Abstract
We investigated the frequency of hypercalcemia and/or hypercalciuria following parathyroid hormone (PTH) 1-34 and 1-84 administration in a crossover trial. Ten postmenopausal osteoporotic women previously treated with bisphosphonates were subdivided into two groups of five patients each. A 24-h urine collection to determine baseline calcium (Ca) and creatinine (Cr) the day before administration of PTH was followed by determination of serum ionized Ca (Ca(2+)), Cr, 25(OH)D, and 1,25(OH)(2)D at baseline. Thereafter, 100 mcg of PTH(1-84) or 20 mcg of PTH(1-34) was administered. A 24-h urinary collection and blood samples 2, 4, and 24-h after each PTH administration were again taken. One week after the first PTH administration patients were rechallenged with the second PTH. The PTH peptides did not differ with respect to changes in Ca(2+) at 2, 4, and 24 h postinjection; at the last time point the values were virtually identical to the initial values. There was no difference in urinary Ca on the day following PTH injection compared to baseline, in terms both of Ca/Cr and of Ca excretion. The two PTH peptides did not differ with respect to changes in 1,25(OH)(2)D at 2, 4, and 24 h considering both the absolute values and the percent changes with respect to baseline (24-h 1-84 = 125.6 + or - 58.6 pg/ml, 153% increase; 1-34 = 124.1 + or - 64.7, 130%). Our results indicate no difference in postinjection serum Ca(2+), 1,25(OH)(2)D, or urinary Ca excretion after a single dose of either PTH(1-84) or PTH(1-34) in patients previously treated with bisphosphonates.
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Affiliation(s)
- Sara Piemonte
- Department of Clinical Sciences, University of Rome "Sapienza", Viale del Policlinico 155, 00161 Rome, Italy
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Segawa H, Aranami F, Kaneko I, Tomoe Y, Miyamoto KI. The roles of Na/Pi-II transporters in phosphate metabolism. Bone 2009; 45 Suppl 1:S2-7. [PMID: 19232403 DOI: 10.1016/j.bone.2009.02.003] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2008] [Revised: 01/23/2009] [Accepted: 02/04/2009] [Indexed: 12/25/2022]
Abstract
The renal type II Na/Pi cotransporters, Na/Pi-IIa and Na/Pi-IIc, are expressed in the brush border membrane (BBM) of the renal proximal tubule cells. Because it has long been thought that Na/Pi-IIa alone can regulate the reabsorption of phosphate in the proximal renal tubules, Na/Pi-IIc has not been paid much attention by the renal research community. Recent studies, however, have identified Na/Pi-IIc mutations as the defective cause of hereditary hypophosphatemic rickets with hypercalciuria (HHRH). This finding indicates that Na/Pi-IIc has a rather important role in renal Pi reabsorption and bone mineralization, and that it may be a key determinant of plasma Pi concentrations in humans. Studies of Na/Pi-IIc mice indicate that Na/Pi-IIc is necessary for normal calcium homeostasis, but its role in the regulation of Pi metabolism and bone physiology may be different from that in HHRH patients. Of note, Na/Pi-IIc KO mice display abnormal vitamin D regulation without hypophosphatemia or hyperphosphaturia. Thus, Na/Pi-IIc may be involved in regulating renal vitamin D synthesis in the proximal tubular cells. The identification of proteins that interact with Na/Pi-IIc is an important area of future research. The physiologic roles of Na/Pi-IIa and Na/Pi-IIc require future elucidation.
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Affiliation(s)
- Hiroko Segawa
- Department of Molecular Nutrition, Institution of Health Biosciences, University of Tokushima Graduate School, Kuramoto-Cho 3, Tokushima 770-8503, Japan.
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Stoermann Chopard C, Jaeger P. [Is kidney stone a bone disease?]. Rev Med Suisse 2009; 5:1314-1317. [PMID: 19626931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
Idiopathic calcium stone formation affects 10% of the adult western population in a lifetime and is, consequently, a real public health problem in these countries. Abnormalities of bone metabolism with osteopenia have been found in patients with idiopathic hypercalciuria. The type of diet (high protein intake, calcium restriction) and some mediators (cytokines, calcitriol) are involved in the pathophysiology of bone alterations. The purpose of this article is to discuss the link between calcium nephrolithiasis and bone density, factors implicated in bone loss and how to treat this pathology.
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Affiliation(s)
- C Stoermann Chopard
- Département de médecine interne, Service de néphrologie, HUG et Faculté de médecine, Genève.
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Bevilacqua M, Dominguez LJ, Gandolini G, Valdes V, Vago T, Righini V, Barrella M, Barbagallo M. Vitamin D substrate-product relationship in idiopathic hypercalciuria. J Steroid Biochem Mol Biol 2009; 113:3-8. [PMID: 19013526 DOI: 10.1016/j.jsbmb.2008.08.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/30/2007] [Accepted: 08/06/2008] [Indexed: 11/16/2022]
Abstract
Absorptive hypercalciuria (AH) is associated with elevated levels of 1,25-dihydroxyvitamin D (1,25(OH)(2)D). While no increase of 1,25(OH)(2)D after oral administration of 25-hydroxyvitamin D (25OHD) at high doses has been claimed in normal subjects, a substrate-product relationship has been reported in normal children, young people after UV irradiation, older persons, postmenopausal women, primary hyperparathyroidism, renal failure, osteomalacia, and sarcoidosis. No data of this relationship in AH is available. To investigate 25OHD-1,25(OH)(2)D substrate-product relationship in AH, 161 AH patients (mean age 60.9+/-11.7 years) and 110 age- and sex-matched controls (mean age 61.5+/-12.4 years) were studied. In 57 controls and 52 AH subjects 25OHD-1,25(OH)(2)D relationship in basal conditions and after 2-week oral 25OHD (25 microg/day) administration were evaluated. In basal conditions 25OHD and 1,25(OH)(2)D were correlated in both, controls and AH; 25OHD treatment was followed by an increase in serum 25OHD and 1,25(OH)(2)D in both groups. However, delta responses of 25OHD and 1,25(OH)(2)D to 25OHD were higher in AH suggesting an enhanced activity of 1 alpha-hydroxylase. In conclusion, the higher response of 1,25(OH)(2)D after oral 25OHD in AH patients suggests a differential capacity between both groups in handling the increases in 1,25(OH)(2)D.
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Affiliation(s)
- Maurizio Bevilacqua
- Endocrinology and Diabetes Unit, Department of Medicine, Luigi Sacco Hospital (Vialba), University of Milan, Italy
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Wang S, Hu D, Xi Q, Su S, Bai J, Liu J, Ye Z. The expression and implication of TRPV5, Calbindin-D28k and NCX1 in idiopathic hypercalciuria. ACTA ACUST UNITED AC 2008; 28:580-3. [PMID: 18846343 DOI: 10.1007/s11596-008-0520-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2008] [Indexed: 11/26/2022]
Abstract
The expression of calcium epithelium TRPV5, alcium binding protein Calbindin-D28k and Na(+)/Ca(2+) exchanger NCX1 was detected in renal distal convoluted tubule, and their effects on urine calcium reabsorption and the possible pathogenic mechanism in idiopathic hypercalciuria (IH) were investigated. Genetic hypercalciuric stone-forming (GHS) rats were chosen as animal models to study urine calcium reabsorption and IH. The cognate female and male rats that had maximal urine calcium were matched to breed next generation. Twelve GHS rats and 12 normal control (NC) SD rats were selected. Western blot and real time quantitative PCR were used to detect the protein and gene expression of TRPV5, Calbindin-D28k and NCX1 respectively. The expression levels of TRPV5 protein and mRNA in GHS rats were significantly lower than in NC rats (P<0.05). Western blot revealed that the expression levels of Calbindin-D28k in GHS rats and NC rats were 0.49+/-0.02 and 0.20+/-0.01 respectively, with the difference being significant between them (P<0.05). By using real time quantitative PCR, it was found that there was no significant difference in Calbindin-28k mRNA expression levels between GHS rats and NC rats (P>0.05). There was no significant difference in the NCX1 expression between GHS rats and NC rats (P>0.05). It was suggested that TRPV5 and Calbindin-D28k might play an important role in urine calcium reabsorption and IH, but they differently contributed to the pathogenesis: The down-regulation of TRPV5 decreases urine calcium reabsorption, directly leading to loss of the urine calcium and resulting in hypercalciuria, and the increased Calbindin-D28k expression could relieve, neutralize and decrease intracellular Ca(2+) concentration to maintain calcium balance. NCX1 is not the key protein in urine calcium reabsorption.
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Affiliation(s)
- Shaogang Wang
- Department of Urology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
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Wang SG, Hu DL, Xi QL, Bai J, Su SQ, Yu X, Liu JH, Ye ZQ. [Expression of calbindin-D28k in genetic hypercalciuric stone-forming rats kidney and its role in pathogenesis of idiopathic hypercalciuria]. Zhonghua Yi Xue Za Zhi 2008; 88:1422-1424. [PMID: 18953885] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
OBJECTIVE To study the expression level of calbindin-D28k, a kind of calcium binding protein, in the kidneys of genetic hypercalciuric stone-forming (GHS) rats and to investigate its role in idiopathic hypercalciuria (IH). METHODS Kidneys were taken out from 16 GHS rats and 6 normal control (NC) rats. Western blotting and real time quantitative PCR were used to detect the protein and mRNA expression levels of calbindin-D28k respectively. RESULTS Western blotting showed that the A value of calbindin-D28k of the GHS rats was 0.49 +/- 0.02, significantly higher than that of the NC rats (0.20 +/- 0.01, P < 0.05). The 2(-(delta delta CT)) value of mRNA of calbindin-D28k of the GHS rats was 1.21, remarkably higher than that of the NC rats [with the of 2(-(delta delta CT)) value of 1.0]. There was not significant difference in the delta CT value between the two groups (P > 0.05). CONCLUSION The up-regulation of calbindin-D28k in the GHS rats is possibly caused by hyperexpression of VDR and hypercalcinuria, and plays an important role in urine calcium reabsorption; however, it is not the key protein that results in IH.
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Affiliation(s)
- Shao-gang Wang
- Department of Urology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.
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Abstract
Ca2+ is essential for numerous physiological functions in our bodies. Therefore, its homeostasis is finely maintained through the coordination of intestinal absorption, renal reabsorption, and bone resorption. The Ca2+-selective epithelial channels TRPV5 and TRPV6 have been identified, and their physiological roles have been revealed: TRPV5 is important in final renal Ca2+ reabsorption, and TRPV6 has a key role in intestinal Ca2+ absorption. The TRPV5 knockout mice exhibit renal leak hypercalciuria and accordingly upregulate their intestinal TRPV6 expression to compensate for their negative Ca2+ balance. In contrast, despite their severe negative Ca2+ balance, TRPV6-null mice do not display any compensatory mechanism, thus resulting in secondary hyperparathyroidism. These results indicate that the genes for TRPV5 and TRPV6 are differentially regulated in human diseases associated with disturbed Ca2+ balance such as hypercalciuria, osteoporosis, and vitamin D-resistant rickets.
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Affiliation(s)
- Yoshiro Suzuki
- Institute of Biochemistry and Molecular Medicine, University of Bern, CH-3012 Berne, Switzerland
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Oz OK, Hajibeigi A, Howard K, Cummins CL, van Abel M, Bindels RJ, Word RA, Kuro-o M, Pak CYC, Zerwekh JE. Aromatase deficiency causes altered expression of molecules critical for calcium reabsorption in the kidneys of female mice *. J Bone Miner Res 2007; 22:1893-902. [PMID: 17708714 DOI: 10.1359/jbmr.070808] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
UNLABELLED Kidney stones increase after menopause, suggesting a role for estrogen deficiency. ArKO mice have hypercalciuria and lower levels of calcium transport proteins, whereas levels of the klotho protein are elevated. Thus, estrogen deficiency is sufficient to cause altered renal calcium handling. INTRODUCTION The incidence of renal stones increases in women after menopause, implicating a possible role for estrogen deficiency. We used the aromatase deficient (ArKO) mouse, a model of estrogen deficiency, to test the hypothesis that estrogen deficiency would increase urinary calcium excretion and alter the expression of molecular regulators of renal calcium reabsorption. MATERIALS AND METHODS Adult female wildtype (WT), ArKO, and estradiol-treated ArKO mice (n = 5-12/group) were used to measure urinary calcium in the fed and fasting states, relative expression level of some genes involved in calcium reabsorption in the distal convoluted tubule by real-time PCR, and protein expression by Western blotting or immunohistochemistry. Plasma membrane calcium ATPase (PMCA) activity was measured in kidney membrane preparations. ANOVA was used to test for differences between groups followed by posthoc analysis with Dunnett's test. RESULTS Compared with WT, urinary Ca:Cr ratios were elevated in ArKO mice, renal mRNA levels of transient receptor potential cation channel vallinoid subfamily member 5 (TRPV5), TRPV6, calbindin-D28k, the Na+/Ca+ exchanger (NCX1), and the PMCA1b were significantly decreased, and klotho mRNA and protein levels were elevated. Estradiol treatment of ArKO mice normalized urinary calcium excretion, renal mRNA levels of TRPV5, calbindin-D(28k), PMCA1b, and klotho, as well as protein levels of calbindin-D28k and Klotho. ArKO mice treated with estradiol had significantly greater PMCA activity than either untreated ArKO mice or WT mice. CONCLUSIONS Estrogen deficiency caused by aromatase inactivation is sufficient for renal calcium loss. Changes in estradiol levels are associated with coordinated changes in expression of many proteins involved in distal tubule calcium reabsorption. Estradiol seems to act at the genomic level by increasing or decreasing (klotho) protein expression and nongenomically by increasing PMCA activity. PMCA, not NCX1, is likely responsible for extruding calcium in response to in vivo estradiol hormonal challenge. These data provide potential mechanisms for regulation of renal calcium handling in response to changes in serum estrogen levels.
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Affiliation(s)
- Orhan K Oz
- Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9153, USA.
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Guggino SE. Mechanisms of Disease: what can mouse models tell us about the molecular processes underlying Dent disease? ACTA ACUST UNITED AC 2007; 3:449-55. [PMID: 17653124 DOI: 10.1038/ncpneph0541] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2007] [Accepted: 05/15/2007] [Indexed: 11/09/2022]
Abstract
Two knockout mouse models of Dent disease are similar with regard to the characteristics of Fanconi syndrome, but differ markedly with respect to vitamin D and renal calcium handling. One model exhibits hypercalciuria, renal calcifications and renal failure; the other does not. Data from such experimental models have greatly advanced our understanding of the molecular mechanisms underlying Dent disease. This Review summarizes some of the important phenotypic characteristics shared by mouse models and people with Dent disease. Experimental data are used to predict the molecular mechanisms underlying this disease. Receptor-mediated endocytosis and the mistargeting of megalin, cubilin, the sodium/proton exchanger Nhe3 and the sodium/phosphate transporter Napi-2a will be reviewed, and the causes of mistargeting will be discussed. Kidney stones and renal failure are prominent features of Dent disease. Investigations using a mouse model with nephrocalcinosis and renal failure indicate that citrate therapy delays the onset of these processes in Dent disease. Throughout this Review, questions that might underpin new areas of investigation are proposed.
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Affiliation(s)
- Sandra E Guggino
- Johns Hopkins University Medical School, Baltimore, MD 21205, USA.
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Ashton N, Al-Wasil SH, Bond H, Berry JL, Denton J, Freemont AJ. The effect of a low-protein diet in pregnancy on offspring renal calcium handling. Am J Physiol Regul Integr Comp Physiol 2007; 293:R759-65. [PMID: 17567711 DOI: 10.1152/ajpregu.00523.2006] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Low birth weight humans and rats exposed to a low-protein diet in utero have reduced bone mineral content. Renal calcium loss during the period of rapid skeletal growth is associated with bone loss. Because young rats exposed to low protein display altered renal function, we tested the hypothesis that renal calcium excretion is perturbed in this model. Pregnant Wistar rats were fed isocalorific diets containing either 18% (control) or 9% (low) protein throughout gestation. Using standard renal clearance techniques, Western blotting for renal calcium transport proteins, and assays for Na+-K+-ATPase activity and serum calcitropic hormones, we characterized calcium handling in 4-wk-old male offspring. Histomorphometric analyses of femurs revealed a reduction in trabecular bone mass in low-protein rats. Renal calcium (control vs. low protein: 10.4 ± 2.1 vs. 27.6 ± 4.5 nmol·min−1·100 g body wt−1; P < 0.01) and sodium excretion were increased, but glomerular filtration rate was reduced in low-protein animals. Total plasma calcium was reduced in low-protein rats ( P < 0.01), but ionized calcium, serum calcitropic hormone concentrations, and total body calcium did not differ. There was no significant change in plasma membrane Ca2+-ATPase pump, epithelial calcium channel, or calbindin-D28K expression in low-protein rat kidneys. However, Na+-K+-ATPase activity was 36% lower ( P < 0.05) in low-protein rats. These data suggest that the hypercalciuria of low-protein rats arises through a reduction in passive calcium reabsorption in the proximal tubule rather than active distal tubule uptake. This may contribute to the reduction in bone mass observed in this model.
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Affiliation(s)
- Nick Ashton
- Faculty of Life Sciences, University of Manchester, 1.124 Stopford Bldg., Oxford Road, Manchester M13 9PT, UK.
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