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Höppner J, Jüppner H. Rare genetic disorders that impair parathyroid hormone synthesis, secretion, or bioactivity provide insights into the diagnostic utility of different parathyroid hormone assays. Curr Opin Nephrol Hypertens 2024; 33:375-382. [PMID: 38701324 DOI: 10.1097/mnh.0000000000000999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/05/2024]
Abstract
PURPOSE OF REVIEW Parathyroid hormone (PTH) is the major peptide hormone regulator of blood calcium homeostasis. Abnormal PTH levels can be observed in patients with various congenital and acquired disorders, including chronic kidney disease (CKD). This review will focus on rare human diseases caused by PTH mutations that have provided insights into the regulation of PTH synthesis and secretion as well as the diagnostic utility of different PTH assays. RECENT FINDINGS Over the past years, numerous diseases affecting calcium and phosphate homeostasis have been defined at the molecular level that are responsible for reduced or increased serum PTH levels. The underlying genetic mutations impair parathyroid gland development, involve the PTH gene itself, or alter function of the calcium-sensing receptor (CaSR) or its downstream signaling partners that contribute to regulation of PTH synthesis or secretion. Mutations in the pre sequence of the mature PTH peptide can, for instance, impair hormone synthesis or intracellular processing, while amino acid substitutions affecting the secreted PTH(1-84) impair PTH receptor (PTH1R) activation, or cause defective cleavage of the pro-sequence and thus secretion of a pro- PTH with much reduced biological activity. Mutations affecting the secreted hormone can alter detection by different PTH assays, thus requiring detailed knowledge of the utilized diagnostic test. SUMMARY Rare diseases affecting PTH synthesis and secretion have offered helpful insights into parathyroid biology and the diagnostic utility of commonly used PTH assays, which may have implications for the interpretation of PTH measurements in more common disorders such as CKD.
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Affiliation(s)
| | - Harald Jüppner
- Endocrine Unit
- Pediatric Nephrology Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, USA
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Portales-Castillo I, Simic P. PTH, FGF-23, Klotho and Vitamin D as regulators of calcium and phosphorus: Genetics, epigenetics and beyond. Front Endocrinol (Lausanne) 2022; 13:992666. [PMID: 36246903 PMCID: PMC9558279 DOI: 10.3389/fendo.2022.992666] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2022] [Accepted: 09/12/2022] [Indexed: 11/30/2022] Open
Abstract
The actions of several bone-mineral ion regulators, namely PTH, FGF23, Klotho and 1,25(OH)2 vitamin D (1,25(OH)2D), control calcium and phosphate metabolism, and each of these molecules has additional biological effects related to cell signaling, metabolism and ultimately survival. Therefore, these factors are tightly regulated at various levels - genetic, epigenetic, protein secretion and cleavage. We review the main determinants of mineral homeostasis including well-established genetic and post-translational regulators and bring attention to the epigenetic mechanisms that affect the function of PTH, FGF23/Klotho and 1,25(OH)2D. Clinically relevant epigenetic mechanisms include methylation of cytosine at CpG-rich islands, histone deacetylation and micro-RNA interference. For example, sporadic pseudohypoparathyroidism type 1B (PHP1B), a disease characterized by resistance to PTH actions due to blunted intracellular cAMP signaling at the PTH/PTHrP receptor, is associated with abnormal methylation at the GNAS locus, thereby leading to reduced expression of the stimulatory G protein α-subunit (Gsα). Post-translational regulation is critical for the function of FGF-23 and such modifications include glycosylation and phosphorylation, which regulate the cleavage of FGF-23 and hence the proportion of available FGF-23 that is biologically active. While there is extensive data on how 1,25(OH)2D and the vitamin D receptor (VDR) regulate other genes, much more needs to be learned about their regulation. Reduced VDR expression or VDR mutations are the cause of rickets and are thought to contribute to different disorders. Epigenetic changes, such as increased methylation of the VDR resulting in decreased expression are associated with several cancers and infections. Genetic and epigenetic determinants play crucial roles in the function of mineral factors and their disorders lead to different diseases related to bone and beyond.
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Affiliation(s)
- Ignacio Portales-Castillo
- Department of Medicine, Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States
| | - Petra Simic
- Department of Medicine, Division of Nephrology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States
- Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA, United States
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Goto S, Komaba H, Fukagawa M. Pathophysiology of parathyroid hyperplasia in chronic kidney disease: preclinical and clinical basis for parathyroid intervention. NDT Plus 2015; 1:iii2-iii8. [PMID: 25983967 PMCID: PMC4421132 DOI: 10.1093/ndtplus/sfn079] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2008] [Accepted: 03/14/2008] [Indexed: 01/15/2023] Open
Abstract
Secondary hyperparathyroidism is characterised by excessive secretion of parathyroid hormone and parathyroid hyperplasia, resulting in both skeletal and extraskeletal consequences. Recent basic and clinical studies have brought considerable advances in our understanding of the pathophysiology of parathyroid hyperplasia and have also provided practical therapeutic approaches, especially with regard to indications for parathyroid intervention. In this context, it is quite important to recognize the development of nodular hyperplasia, because the cells in nodular hyperplasia are usually resistant to calcitriol treatment. Patients with nodular hyperplasia should undergo parathyroid intervention including percutaneous ethanol injection therapy (PEIT). Selective PEIT of the parathyroid gland is an effective approach in which the enlarged parathyroid gland with nodular hyperplasia is 'selectively' destroyed by ethanol injection, and other glands with diffuse hyperplasia are then managed by medical therapy. With a more focused attention to applying parathyroid intervention, we can expect significant improvement in the management of secondary hyperparathyroidism in dialysis patients.
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Affiliation(s)
- Shunsuke Goto
- Division of Nephrology and Kidney Center , Kobe University School of Medicine , Kobe 650-0017 , Japan
| | - Hirotaka Komaba
- Division of Nephrology and Kidney Center , Kobe University School of Medicine , Kobe 650-0017 , Japan
| | - Masafumi Fukagawa
- Division of Nephrology and Kidney Center , Kobe University School of Medicine , Kobe 650-0017 , Japan
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Sallée M, Fontès M, Louis L, Cérini C, Brunet P, Burtey S. Alternative splicing events is not a key event for gene expression regulation in uremia. PLoS One 2013; 8:e82702. [PMID: 24358217 PMCID: PMC3865105 DOI: 10.1371/journal.pone.0082702] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Accepted: 10/26/2013] [Indexed: 11/29/2022] Open
Abstract
Background The control of gene expression in the course of chronic kidney disease (CKD) is not well addressed. Alternative splicing is a common way to increase complexity of proteins. More than 90% of human transcripts are alternatively spliced. We hypothesised that CKD can induce modification of the alternative splicing machinery. Methods During mutation screening in autosomal dominant polycystic kidney disease, we identified in mononuclear cells (PBMC), an alternative splicing event on the exon 30 of PKD1 gene, the gene implicated in this disease. This alternative splice variant was not correlated with the cystic disease but with CKD. To confirm the association between this variant and CKD, a monocentric clinical study was performed with 3 different groups according to their kidney function (CKD5D, CKD3-5 and normal kidney function). An exon microarray approach was used to highlight splicing events in whole human genome in a normal cell model (fibroblasts) incubated with uremic serum. Alternative splicing variants identified were confirmed by RT-PCR. Results The splicing variant of the exon 30 of PKD1 was more frequent in PBMCs from patients with CKD compared to control. With the microarray approach, despite the analysis of more than 230 000 probes, we identified 36 genes with an abnormal splicing index evocating splicing event in fibroblasts exposed to uremic serum. Only one abnormal splicing event in one gene, ADH1B, was confirmed by RT-PCR. Conclusion We observed two alternative spliced genes in two different cell types associated with CKD. Alternative splicing could play a role in the control of gene expression during CKD but it does not seem to be a major mechanism.
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Affiliation(s)
- Marion Sallée
- Aix-Marseille Université, INSERM UMR_S 1076, UFR Pharmacie, Marseille, France ; Centre de Néphrologie et Transplantation Rénale, Assistance Publique-Hôpitaux de Marseille, Hôpital de La Conception, Marseille, France
| | - Michel Fontès
- Aix-Marseille Université, INSERM UMR_S 1062 UFR Médecine, Marseille, France
| | - Laurence Louis
- Aix-Marseille Université, Plate-forme génomique et transcriptomique, UMR_S 910, UFR médecine, Marseille, France
| | - Claire Cérini
- Aix-Marseille Université, INSERM UMR_S 1076, UFR Pharmacie, Marseille, France
| | - Philippe Brunet
- Aix-Marseille Université, INSERM UMR_S 1076, UFR Pharmacie, Marseille, France ; Centre de Néphrologie et Transplantation Rénale, Assistance Publique-Hôpitaux de Marseille, Hôpital de La Conception, Marseille, France
| | - Stéphane Burtey
- Aix-Marseille Université, INSERM UMR_S 1076, UFR Pharmacie, Marseille, France ; Centre de Néphrologie et Transplantation Rénale, Assistance Publique-Hôpitaux de Marseille, Hôpital de La Conception, Marseille, France
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Naveh-Many T. Minireview: the play of proteins on the parathyroid hormone messenger ribonucleic Acid regulates its expression. Endocrinology 2010; 151:1398-402. [PMID: 20032048 DOI: 10.1210/en.2009-1160] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
PTH regulates serum calcium and phosphate levels and bone strength. The parathyroid is unique in that the trigger for PTH secretion is a low extracellular calcium rather than high calcium as for other hormones. The parathyroid senses small changes in serum calcium through the seven-trans-membrane G protein-coupled calcium receptor to alter PTH secretion. PTH then acts on bone and kidney to correct serum calcium. Parathyroid cells have few secretory granules as compared with other endocrine cells, and therefore PTH production is regulated largely at the levels of PTH gene expression and parathyroid cell proliferation. The regulation of PTH gene expression by changes in calcium and phosphate and in chronic kidney failure is posttranscriptional involving the binding of trans-acting proteins to a defined cis element in the PTH mRNA 3'-untranslated region. These protein-PTH mRNA interactions are orchestrated by the peptidyl-prolyl isomerase Pin1. This review discusses the mechanisms of regulation of PTH mRNA stability determining serum PTH levels and mineral metabolism.
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Affiliation(s)
- Tally Naveh-Many
- Minerva Center for Calcium and Bone Metabolism, Nephrology Services, Hadassah Hebrew University Medical Center, POB 12000, Jerusalem 91120, Israel.
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Kanai G, Kakuta T, Sawada K, Yokoyama TA, Tanaka R, Saito A. Suppression of parathyroid hormone production in vitro and in vivo by RNA interference. Kidney Int 2009; 75:490-8. [DOI: 10.1038/ki.2008.568] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Muscher A, Hattendorf J, Pfeffer E, Breves G, Huber K. Hormonal regulation of phosphate homeostasis in goats during transition to rumination. J Comp Physiol B 2008; 178:585-96. [PMID: 18210130 DOI: 10.1007/s00360-007-0248-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2007] [Revised: 12/21/2007] [Accepted: 12/21/2007] [Indexed: 12/01/2022]
Abstract
Regulatory processes in phosphorus (P) homeostasis in small ruminants are quite different compared to monogastric animals. Adaptive responses of modulating hormones [parathyroid hormone (PTH) and calcitriol] to feeding variable amounts of P are lacking. Therefore, the aim of this study was to examine the influence of high dietary P intake (control diet: 4 g kg(-1) dry matter; high-P diet: 8 g kg(-1) dry matter) on the expression levels of PTH receptor (PTHR), vitamin D receptor (VDR) and Na+-dependent Pi transporters (NaPi II) in kidney and jejunum of goats starting rumination. After 3 months of feeding, plasma phosphate (Pi) and PTH concentrations were increased in the high-P diet group, whereas calcium and calcitriol were not changed. The intestinal Na+-dependent Pi transport capacity was not influenced by a high-P diet and the expression of jejunal VDR, PTHR and NaPi IIb was not modified. Interestingly, renal Na+-dependent Pi transport capacity was significantly reduced and concomitantly the expression of PTHR and NaPi IIa was decreased. In conclusion, the adaptive response of renal Pi reabsorption in goats, which were in transition from non-ruminant to ruminant stage was comparable to that of monogastric animals. In contrast, the modulation of the intestinal Pi absorption was like in adult ruminants.
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Affiliation(s)
- Alexandra Muscher
- Department of Physiology, School of Veterinary Medicine Hannover, Bischofsholer Damm 15/102, 30173, Hannover, Germany.
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8
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Martin KJ, González EA. Pathophysiology of renal osteodystrophy. Clin Rev Bone Miner Metab 2007. [DOI: 10.1007/bf02736667] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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9
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Abstract
Metabolic bone disease is a common complication of chronic kidney disease (CKD) and is part of a broad spectrum of disorders of mineral metabolism that occur in this clinical setting and result in both skeletal and extraskeletal consequences. Detailed research in that past 4 decades has uncovered many of the mechanisms that are involved in the initiation and maintenance of the disturbances of bone and mineral metabolism and has been translated successfully from "bench to bedside" so that efficient therapeutic strategies now are available to control the complications of disturbed mineral metabolism. Recent emphasis is on the need to begin therapy early in the course of CKD. Central to the assessment of disturbances in bone and mineral metabolism is the ability to make an accurate assessment of the bone disease by noninvasive means. This remains somewhat problematic, and although measurements of parathyroid hormone are essential, recently recognized difficulties with these assays make it difficult to provide precise clinical practice guidelines for the various stages of CKD at the present time. Further research and progress in this area continue to evaluate the appropriate interventions to integrate therapies for both the skeletal and extraskeletal consequences with a view toward improving patient outcomes.
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Affiliation(s)
- Kevin J Martin
- Division of Nephrology, Saint Louis University and Medical Center, 3635 Vista Avenue, St. Louis, MO 63110l, USA.
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10
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Hostutler RA, DiBartola SP, Chew DJ, Nagode LA, Schenck PA, Rajala-Schultz PJ, Drost WT. Comparison of the Effects of Daily and Intermittent-Dose Calcitriol on Serum Parathyroid Hormone and Ionized Calcium Concentrations in Normal Cats and Cats with Chronic Renal Failure. J Vet Intern Med 2006. [DOI: 10.1111/j.1939-1676.2006.tb00743.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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11
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Lewin E, Huan J, Olgaard K. Basic Science and Dialysis: Parathyroid Growth and Suppression in Renal Failure. Semin Dial 2006; 19:238-45. [PMID: 16689976 DOI: 10.1111/j.1525-139x.2006.00161.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
In advanced uremia, parathyroid hormone (PTH) levels should be controlled at a moderately elevated level in order to promote normal bone turnover. As such, a certain degree of parathyroid hyperplasia has to be accepted. Uremia is associated with parathyroid growth. In experimental studies, proliferation of the parathyroid cells is induced by uremia and further promoted by hypocalcemia, phosphorus retention, and vitamin D deficiency. On the other hand, parathyroid cell proliferation might be arrested by treatment with a low-phosphate diet, vitamin D analogs, or calcimimetics. When established, parathyroid hyperplasia is poorly reversible. There exists no convincing evidence of programmed parathyroid cell death or apoptosis in hyperplastic parathyroid tissue or of involution of parathyroid hyperplasia. However, even considerable parathyroid hyperplasia can be controlled when the functional demand for increased PTH levels is removed by normalization of kidney function. Today, secondary hyperparathyroidism can be controlled in patients with long-term uremia in whom considerable parathyroid hyperplasia is to be expected. PTH levels can be suppressed in most uremic patients and this suppression can be maintained by continuous treatment with phosphate binders, vitamin D analogs, or calcimimetics. Thus modern therapy permits controlled development of parathyroid growth. When nonsuppressible secondary hyperparathyroidism is present, nodular hyperplasia with suppressed expression of the calcium-sensing receptor (CaR) and vitamin D receptor (VDR) has been found in most cases. An altered expression of some autocrine/paracrine factors has been demonstrated in the nodules. The altered quality of the parathyroid mass, and not only the increased parathyroid mass per se, might be responsible for uncontrollable hyperparathyroidism in uremia and after kidney transplantation.
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Affiliation(s)
- Ewa Lewin
- Nephrological Department P, Rigshospitalet, Copenhagen, Denmark.
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12
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Levi R, Ben-Dov IZ, Lavi-Moshayoff V, Dinur M, Martin D, Naveh-Many T, Silver J. Increased Parathyroid Hormone Gene Expression in Secondary Hyperparathyroidism of Experimental Uremia Is Reversed by Calcimimetics: Correlation with Posttranslational Modification of theTransActing Factor AUF1. J Am Soc Nephrol 2005; 17:107-12. [PMID: 16291838 DOI: 10.1681/asn.2005070679] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Most patients with chronic kidney disease develop secondary hyperparathyroidism with disabling systemic complications. Calcimimetic agents are effective tools in the management of secondary hyperparathyroidism, acting through allosteric modification of the calcium-sensing receptor (CaR) on the parathyroid gland (PT) to decrease parathyroid hormone (PTH) secretion and PT cell proliferation. This study showed that rats that were fed an adenine high-phosphorus diet had increased serum PTH and PTH mRNA levels at 7 and 21 d. For studying the effect of activation of the CaR by the calcimimetics R-568 on PTH gene expression, R-568 was given by gavage to uremic rats for the last 4 d of a 7-d adenine high-phosphorus diet. R-568 decreased both PTH mRNA and serum PTH levels. The effect of the calcimimetic on PTH gene expression was posttranscriptional and correlated with differences in protein-RNA binding and posttranslational modifications of the trans acting factor AUF1 in the PT. The AUF1 modifications as a result of uremia were reversed by treatment with R-568 to those of normal rats. Therefore, uremia and activation of the CaR mediated by calcimimetics modify AUF1 posttranslationally. These modifications in AUF1 correlate with changes in protein-PTH mRNA binding and PTH mRNA levels.
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Affiliation(s)
- Ronen Levi
- Minerva Center for Calcium and Bone Metabolism, Nephrology Services, Hebrew University Hadassah Hospital, P.O. Box 12000, Jerusalem, Israel 91120
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13
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Silver J, Levi R. Regulation of PTH synthesis and secretion relevant to the management of secondary hyperparathyroidism in chronic kidney disease. Kidney Int 2005:S8-12. [PMID: 15882315 DOI: 10.1111/j.1523-1755.2005.09501.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Regulation of PTH synthesis and secretion relevant to the management of secondary hyperparathyroidism in chronic kidney disease. Small decreases in serum Ca(++) and more prolonged increases in serum phosphate (P) stimulate the parathyroid (PT) to secrete parathyroid hormone (PTH), while 1,25(OH)(2)-vitamin D(3) decreases PTH synthesis and secretion. A prolonged decrease in serum Ca(++) and 1,25(OH)(2)D(3), or increase in serum P, such as in patients with chronic renal failure, leads to the appropriate secondary increase in serum PTH. This secondary hyperparathyroidism involves increases in PTH gene expression, synthesis, and secretion, and, if chronic, to proliferation of the parathyroid cells. A low serum Ca(++) leads to an increase in PTH secretion, PTH mRNA stability, and parathyroid cell proliferation. Pi also regulates the parathyroid in a similar manner. The effect of Ca(++) on the parathyroid is mediated by a membrane Ca(2+) receptor (CaR). 1,25(OH)(2)D(3) decreases PTH gene transcription. Ca(2+) and P regulate the PTH gene post-transcriptionally by regulating the binding of parathyroid cytosolic proteins, trans factors, to a defined cis sequence in the PTH mRNA 3'-untranslated region (UTR), thereby determining the stability of the transcript. The parathyroid trans factors and cis elements have been defined.
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Affiliation(s)
- Justin Silver
- Minerva Center for Calcium and Bone Metabolism, Nephrology and Hypertension Services, Hadassah Hebrew University Medical Center, Jerusalem, Israel 91120.
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Levi R, Silver J. Pathogenesis of parathyroid dysfunction in end-stage kidney disease. Pediatr Nephrol 2005; 20:342-5. [PMID: 15549412 DOI: 10.1007/s00467-004-1628-4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2004] [Revised: 07/16/2004] [Accepted: 07/20/2004] [Indexed: 11/29/2022]
Abstract
Small decreases in serum calcium (Ca(2+)) and more-prolonged increases in serum phosphate (Pi) stimulate the parathyroid (PT) to secrete parathyroid hormone (PTH). 1,25-Dihydroxyvitamin D(3) [1,25(OH)(2) D(3)] decreases PTH synthesis and secretion. The prolonged decrease in serum Ca(2+) and 1,25(OH)(2) D(3), or increase in serum Pi, observed in patients with chronic renal failure leads to a secondary increase in serum PTH. This secondary hyperparathyroidism involves increases in PTH gene expression, synthesis, and secretion and, if chronic, to proliferation of the PT cells. A low serum Ca(2+) leads to an increase in PTH secretion, PTH mRNA stability, and PT cell proliferation. Pi also regulates the PT in a similar manner. The effect of Ca(2+) on the PT is mediated by a membrane Ca(2+) receptor. 1,25(OH)(2) D(3) decreases PTH gene transcription. Ca(2+) and Pi regulate the PTH gene post transcriptionally by regulating the binding of PT cytosolic proteins, trans factors, to a defined cis sequence in the PTH mRNA 3'-untranslated region, thereby determining the stability of the transcript. The PT trans factors and cis elements have been defined.
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Affiliation(s)
- Ronen Levi
- Nephrology and Hypertension Services, Minerva Center for Calcium and Bone Metabolism, Hebrew University Hadassah Medical Center, 91120, Jerusalem, Israel
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15
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Abstract
It is now known that variations in extracellular calcium concentration exert diverse physiologic effects in a variety of tissues that are mediated by a calcium-sensing receptor (CaSRs). In parathyroid tissue, the CaSR represents the molecular mechanism by which parathyroid cells detect changes in blood ionized calcium concentration, modulate parathyroid hormone (PTH) secretion accordingly, and thus maintain serum calcium levels within a narrow physiologic range. In the kidney, the CaSR regulates renal calcium excretion and influences the transepithelial movement of water and other electrolytes. More generally, activation of the CaSR represents an important signal transduction pathway in intestine, placenta, brain, and perhaps bone. Some of these actions involve cell cycle regulation, changes that may be relevant to understanding the pathogenesis of parathyroid gland hyperplasia in secondary hyperparathyroidism caused by chronic kidney disease. The CaSR represents an appealing target for therapeutic agents designed to modify parathyroid gland function in vivo, offering the prospect of novel therapies for selected disorders of bone and mineral metabolism. Other receptors capable of responding to extracellular calcium ions also have been identified, but the functional importance of these interactions remains to be determined.
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Affiliation(s)
- William G Goodman
- Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
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16
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Block GA. The impact of calcimimetics on mineral metabolism and secondary hyperparathyroidism in end-stage renal disease. Kidney Int 2003:S131-6. [PMID: 14531786 DOI: 10.1046/j.1523-1755.64.s87.20.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The impact of calcimimetics on mineral metabolism and secondary hyperparathyroidism in end-stage renal disease. Secondary hyperparathyroidism is often complicated by elevations in calcium and phosphorus either as a result of the disease per se or due to toxicity from current therapeutic options. These disturbances in mineral metabolism limit the successfulness of therapy and have been implicated as contributing to the development and progression of vascular calcification, an important and often overlooked component of cardiovascular disease in patients on dialysis. Phosphorus, active vitamin D, and calcium all play important roles in the pathogenesis of secondary hyperparathyroidism; however, serum calcium is the primary regulator of minute-to-minute parathyroid hormone secretion. Small changes in serum calcium are detected by a cell surface calcium sensing receptor that has recently been cloned. Calcimimetic agents modulate the activity of the calcium-sensing receptor and result in profound reductions in levels of circulating parathyroid hormone. Additionally, these agents result in decreases in serum calcium, phosphorus, and calcium-phosphorus product. Recently completed phase 2 clinical trials with the second-generation calcimimetic agent cinacalcet HCl confirm that this agent represents a safe and effective novel therapeutic agent which has the potential to dramatically alter the treatment and complications associated with secondary hyperparathyroidism in patients on dialysis.
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Abstract
Small decreases in serum Ca(2+) and more prolonged increases in serum phosphate (P(i)) stimulate the parathyroid (PT) to secrete parathyroid hormone (PTH), and 1,25(OH)(2)D(3) decreases PTH synthesis and secretion. A prolonged decrease in serum Ca(2+) and 1,25(OH)(2)D(3), or increase in serum P(i), such as in patients with chronic renal failure, leads to the appropriate secondary increase in serum PTH. This secondary hyperparathyroidism involves increases in PTH gene expression, synthesis, and secretion, and if chronic, to proliferation of the PT cells. Low serum Ca(2+) leads to an increase in PTH secretion, PTH mRNA stability, and PT cell proliferation. P(i) also regulates the PT in a similar manner. The effect of Ca(2+) on the PT is mediated by a membrane Ca(2+) receptor. 1,25(OH)(2)D(3) decreases PTH gene transcription. Ca(2+) and P(i) regulate the PTH gene posttranscriptionally by regulating the binding of PT cytosolic proteins, trans factors, to a defined cis sequence in the PTH mRNA 3'-untranslated region, thereby determining the stability of the transcript. PT trans factors and cis elements have been defined.
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Affiliation(s)
- Justin Silver
- Minerva Center for Calcium and Bone Metabolism, Nephrology and Hypertension Services, Hadassah University Hospital, Jerusalem, Israel 91120.
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18
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Silver J. Pathogenesis of parathyroid dysfunction in end-stage renal disease. ADVANCES IN RENAL REPLACEMENT THERAPY 2002; 9:159-67. [PMID: 12203197 DOI: 10.1053/jarr.2002.34846] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The parathyroid functions to maintain normal calcium and phosphate homeostasis and is central to normal bone physiology. In end-stage renal disease (ESRD), there is a failure of these normal homeostatic mechanisms with the frequent development of secondary hyperparathyroidism, which contributes to the pathogenesis of renal bone disease. The phosphate retention of ESRD, together with the reduced serum calcium and 1,25-dihydroxycholecalciferol vitamin D(3) (1,25[OH](2)D(3)) concentrations are the known factors that determine the progression to secondary hyperparathyroidism. 1,25(OH)(2)D(3) markedly decreases parathyroid hormone (PTH) gene transcription, whereas the effects of calcium and phosphate are on PTH mRNA stability, PTH secretion, and parathyroid cell proliferation. The mechanisms of these effects are discussed in this review.
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Affiliation(s)
- Justin Silver
- Minerva Center for Calcium and Bone Metabolism, Nephrology Services, Hadassah University Hospital, Jerusalem, Israel.
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Välimäki S, Farnebo F, Forsberg L, Larsson C, Farnebo LO. Heterogeneous expression of receptor mRNAs in parathyroid glands of secondary hyperparathyroidism. Kidney Int 2001; 60:1666-75. [PMID: 11703583 DOI: 10.1046/j.1523-1755.2001.00986.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Secondary hyperparathyroidism (HPT) is characterized by inappropriate control of parathyroid hormone (PTH) secretion and asymmetric hyperplasia of the parathyroid glands. Receptors for calcium and vitamin D are involved in the control of secretion, as well as parathyroid cell proliferation. Defective receptor mechanisms therefore may play a role in the pathogenensis of secondary HPT. Previous studies have shown that the expression of calcium receptor (CaR), calcium-sensing receptor (CAS) and vitamin D receptor (VDR) protein, and mRNA is decreased in hyperplastic parathyroid glands of secondary HPT when compared with normal parathyroid glands. METHODS Thirty-six hyperplastic glands from 18 patients with secondary hyperparathyroidism were analyzed with in situ hybridization in order to investigate the expression of CaR, CAS, VDR, and PTH mRNAs in the same specimens. In nine nodular parathyroid glands, it was possible to make a comparison between the expression of these mRNAs in nodular and internodular areas. RESULTS The level of CaR was in the same order of magnitude in the hyperplastic glands and in the biopsies of normal parathyroid, whereas the levels of CAS, VDR and PTH were clearly reduced in the hyperplastic glands. There was a positive correlation between the expression of CaR and CAS (P = 0.02). Otherwise, no correlations between CaR, CAS, VDR, and PTH mRNAs were found. The expression of all four genes was highly variable as well between different glands as within individual glands. CONCLUSION The expression of mRNAs for receptors of importance in the control of PTH secretion and parathyroid cell proliferation is heterogeneously decreased in parathyroid glands of secondary HPT. The expression pattern corroborates earlier studies in which it has been assumed that each nodule in secondary HPT is of monoclonal origin, but that the monoclonal origin of each nodule is independent.
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Affiliation(s)
- S Välimäki
- Department of Molecular Medicine, Endocrine Tumor Unit, CMM L8:01, Karolinska Hospital, S-171 76 Stockholm, Sweden.
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Abstract
The discovery, characterization, and cloning of the calcium-sensing receptor (CaR) in 1993 was soon followed by the creation of a new type of drug, the calcimimetics-NPS R-568 and NPS R-467-which are small phenylalkylamine derivative compounds that act as CaR agonists and increase the sensitivity of the CaR to activation by extracellular calcium (Ca2+). As expected, these compounds turned out to have a significant effect on the Ca2+/parathyroid hormone (PTH) relationship, resulting in a dramatically greater suppression of the PTH level than would otherwise occur at the actual extracellular Ca2+ levels. Renal osteodystrophy (RO) due to secondary hyperparathyroidism (HPT) in chronic renal failure was an obvious target for studying the effects of NPS R-568. In a study on experimental animals, the results clearly showed that this first generation of calcimimetics, NPS R-568, had an acute dose-dependent and short-lived suppressive effect on PTH secretion from the parathyroid glands. A similar effect was found in patients with chronic renal failure and secondary HPT. At the same time, the calcimimetics induced a slight degree of hypocalcemia. Such a significant suppressive effect on PTH secretion would be expected to result in therapeutic potential for a preventive or therapeutic effect on the RO accompanying chronic uremia. Administration would probably be in close concert with present strategies, phosphate binders and vitamin D analogs. A wide distribution of CaRs have now been demonstrated in the body, and an important question is how calcimimetics will affect the function of different tissues and organs when used for long-term treatment or prevention of secondary HPT and RO. Although relatively few experimental and clinical investigations have been completed, they clearly confirm the suppressive effect of calcimimetics on PTH secretion. In rats with experimental chronic renal failure, a significant and beneficial effect on the prevention of RO has been demonstrated. The effect of calcimimetic compounds is presently being evaluated in humans. Besides induction of hypocalcemia, the adverse effects in these mainly short-term studies have been few. Future studies with calcimimetics will further define the physiology and pathophysiology of the CaR and the long-term benefit of calcimimetic compounds in patients with chronic renal failure.
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Affiliation(s)
- K Olgaard
- Nephrological Department P, Rigshospitalet, University of Copenhagen, 9 Blegdamsvej, Copenhagen, DK-2100 Denmark.
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Affiliation(s)
- J Silver
- Minerva Center for Calcium and Bone Metabolism, Nephrology Services, Hadassah Hospital and Hebrew University Hadassah Medical School, Jerusalem, Israel
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Affiliation(s)
- W G Goodman
- UCLA School of Medicine, Los Angeles, California, USA.
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Drüeke TB. Cell biology of parathyroid gland hyperplasia in chronic renal failure. J Am Soc Nephrol 2000; 11:1141-1152. [PMID: 10820180 DOI: 10.1681/asn.v1161141] [Citation(s) in RCA: 121] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Affiliation(s)
- Tilman B Drüeke
- Institut National de la Santé et de la Recherche Médicale U507 and Division of Nephrology, Necker Hospital, Paris, France
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