scholarly journals The role of biased calcium-sensing receptor signalling in urinary calcium excretion and kidney stone disease

2021 ◽  
Vol 2 (4) ◽  
Author(s):  
Michelle Goldsworthy
Keyword(s):  
Calcium Concentration ◽  
Urinary Calcium ◽  
Fold Change ◽  
Urinary Calcium Excretion ◽  
Maximal Response ◽  
Calcium Excretion ◽  
Calcium Sensing Receptor ◽  
Serum Calcium Concentration ◽  
University Of Oxford ◽  
Calcium Sensing

Michelle Goldsworthy1,2, Asha Bayliss2, Anna Gluck2, Akira Wiberg3, Benjamin Turney1, DominicFurniss3, Rajesh Thakker2, Sarah Howles1,2 1Nuffield Department of Surgical Sciences, University of Oxford, United Kingdom.2Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, UnitedKingdom.3Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Universityof Oxford, United Kingdom.   Nephrolithiasis is a major health burden with a poorly understood pathogenesis. We conducted a genome-wide association study in British and Japanese populations identifying twenty nephrolithiasis-associated loci. Mutations in the calcium-sensing receptor (CaSR) cause disorders of calcium homeostasis and five identified loci (DGKD, DGKH, WDR72, GPIC1 and BCR) were predicted to influence CaSR-signalling. In a validation population, we demonstrated that genotype at the DGKD-associated locus correlated with urinary calcium excretion but not serum calcium concentration. In vitro studies demonstrated that knockdown and overexpression of DGKD resulted in biased CaSR-signalling. Thus, treatment of CaSR-expressing HEK cells with DGKD-targeted siRNA (DGKD-KD), resulted in decreased MAPK responses to alterations in extracellular calcium concentration [Ca2+]e, as assessed by SRE-reporter and ERK-phosphorylation (pERK) assays, when compared to cells treated with scrambled siRNA (WT) but without alteration in intracellular calcium responses [Ca2+]i as assessed by NFAT-reporter and Fluo-4 calcium assays (SRE maximal response DGKD-KD =5.28 fold change vs. WT=7.20 p=0.0065, pERK maximal response DGKD-KD=24.77, vs. WT= 39.46 fold change, p=0.0056). Conversely, DGKD overexpression (DGKD-OE) increased MAPK responses but suppressed [Ca2+]i responses to alterations in [Ca2+]e (SRE maximal response DGKD-OE =14.13 fold change vs. WT=9.06 fold change, p=0.01; NFAT maximal response DGKD-OE=13.67 fold change vs WT=59.16 fold change, p=0.0001). Our results demonstrate that alterations in DGKD expression cause biased CaSR-signalling. This biased signalling may provide an explanation for the correlation of genotype at the DGKD-associated locus with urinary calcium excretion but not serum calcium concentration. Our findings suggest that biased CaSR-signalling may be a common cause of nephrolithiasis.

scholarly journals The role of biased calcium-sensing receptor signalling in urinary calcium excretion and kidney stone disease

2021 ◽  
Vol 2 (4) ◽  
Author(s):  
Michelle Goldsworthy
Keyword(s):  
Calcium Concentration ◽  
Urinary Calcium ◽  
Fold Change ◽  
Urinary Calcium Excretion ◽  
Maximal Response ◽  
Calcium Excretion ◽  
Calcium Sensing Receptor ◽  
Serum Calcium Concentration ◽  
University Of Oxford ◽  
Calcium Sensing

Michelle Goldsworthy1,2, Asha Bayliss2, Anna Gluck2, Akira Wiberg3, Benjamin Turney1, DominicFurniss3, Rajesh Thakker2, Sarah Howles1,2 1Nuffield Department of Surgical Sciences, University of Oxford, United Kingdom.2Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, UnitedKingdom.3Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, Universityof Oxford, United Kingdom. Nephrolithiasis is a major health burden with a poorly understood pathogenesis. We conducteda genome-wide association study in British and Japanese populations identifying twentynephrolithiasis-associated loci. Mutations in the calcium-sensing receptor (CaSR) causedisorders of calcium homeostasis and five identified loci (DGKD, DGKH, WDR72, GPIC1 and BCR)were predicted to influence CaSR-signalling. In a validation population, we demonstrated that genotype at the DGKD-associated locuscorrelated with urinary calcium excretion but not serum calcium concentration. In vitro studiesdemonstrated that knockdown and overexpression of DGKD resulted in biased CaSR-signalling.Thus, treatment of CaSR-expressing HEK cells with DGKD-targeted siRNA (DGKD-KD), resulted indecreased MAPK responses to alterations in extracellular calcium concentration [Ca2+]e, asassessed by SRE-reporter and ERK-phosphorylation (pERK) assays, when compared to cellstreated with scrambled siRNA (WT) but without alteration in intracellular calcium responses[Ca2+]i as assessed by NFAT-reporter and Fluo-4 calcium assays (SRE maximal response DGKD-KD=5.28 fold change vs. WT=7.20 p=0.0065, pERK maximal response DGKD-KD=24.77, vs. WT=39.46 fold change, p=0.0056). Conversely, DGKD overexpression (DGKD-OE) increased MAPKresponses but suppressed [Ca2+]i responses to alterations in [Ca2+]e (SRE maximal responseDGKD-OE =14.13 fold change vs. WT=9.06 fold change, p=0.01; NFAT maximal response DGKDOE=13.67 fold change vs WT=59.16 fold change, p=0.0001). Our results demonstrate that alterations in DGKD expression cause biased CaSR-signalling. Thisbiased signalling may provide an explanation for the correlation of genotype at the DGKDassociatedlocus with urinary calcium excretion but not serum calcium concentration. Ourfindings suggest that biased CaSR-signalling may be a common cause of nephrolithiasis.  

USE OF TERIPARATIDE IN A FOUR YEAR OLD PATIENT WITH AUTOSOMAL DOMINANT HYPOCALCAEMIA

2016 ◽  
Vol 101 (9) ◽  
pp. e2.63-e2 ◽  
Author(s):  
Andy Fox ◽  
Rodney Gilbert
Keyword(s):  
Calcium Concentration ◽  
Autosomal Dominant ◽  
Urinary Calcium ◽  
Plasma Calcium ◽  
Urinary Calcium Excretion ◽  
Calcium Excretion ◽  
Calcium Sensing Receptor ◽  
Calcium Supplements ◽  
Calcium Sensing ◽  
Plasma Calcium Concentration

AimWe report the effective use of the synthetic parathyroid hormone (PTH) teriparatide to treat a 4 year old boy with autosomal dominant hypocalcaemia.BackgroundAutosomal Dominant hypocalcaemia is characterised by hypocalcaemia with a lack of parathyroid hormone (PTH) response and inappropriately high urinary calcium excretion. It is caused by gain-of-function mutations in the extracellular calcium sensing receptor which then “over-reads” the extracellular fluid concentration of calcium resulting in suppression of PTH secretion. This then reduces PTH-mediated calcium reabsorption in the distal nephron. Treatment of hypocalcaemia with vitamin D analogues and calcium supplements results in further increases in urinary calcium concentrations, frequently causing nephrocalcinosis and progressive renal damage.Our four year old male patient presented in the neonatal period with seizures secondary to hypocalcaemia and low PTH levels. He suffered repeated seizures with associated tetany. Treatment with alfaclacidol and calcium supplements was able to provide seizure control, however episodes of tetany continued. A heterozygous, activating mutation of the extracellular calcium sensing receptor (c.2528C>A; p.Ala843Glu) was confirmed at age 2. The treatment caused significant hypercalciuria and nephrocalcinosis with a reduction in GFR to 73 ml/mim/m.2 Continuing this therapy would have resulted in end stage kidney disease requiring dialysis/transplantation. The decision was made to try treatment with PTH in order to raise the plasma calcium concentration while minimising the increase in urinary calcium excretion.Funding for treatment was approved by specialised commissioning and treatment was commenced at a dose of 0.4 microg/kg BD.AdministrationTeriparatide is only available in a prefilled pen (Forsteo®) delivering 20 microg in 80 microlitre per dose. Following discussions with the pharmacy team at Great Ormond Street Hospital for Sick Children a protocol was developed to allow these set doses to be diluted prior to administration. By diluting the 20 microg dose to 0.5 ml in a 1 ml syringe a solution containing 40 microg/ml was obtained.OutcomeTreatment was started at 3.66 years of age. Pre-treatment adjusted plasma calcium concentration was 1.96 mmol/L and the urinary calcium excretion was 0.11 mmol/kg/day (normal<0.1). After 5 days of treatment the patient felt very much better and had more energy. The adjusted plasma calcium concentration had risen to 2.09 mmol/L and the urinary calcium excretion had fallen to 0.045 mmol/kg/day.Over the following 9 months the dose of alfacalcidol was reduced from 600 nanograms per day to 300 nanograms per day and calcium supplements were reduced from 16 mmol four times per day to zero. The teriparatide dose was increased from an initial dose of 2 microgram twice daily to 6 microgram twice daily. The plasma calcium has remained above 2 mmol/L apart from a period where further weaning of the alfacalcidol dose was attempted.Rather to our surprise, the patient did not experience symptoms of hypercalcaemia with plasma calcium concentrations within the normal range. His muscle power and tone has increased.We conclude that teriparatide is a useful agent for treating patients with gain-of-function mutations of the calcium-sensing receptor/autosomal dominant hypocalcaemia

scholarly journals A Novel Variant in the Calcium-Sensing Receptor Associated with Familial Hypocalciuric Hypercalcemia and Low-to-Normal PTH

2020 ◽  
Vol 2020 ◽  
pp. 1-5
Author(s):  
Sachin K. Majumdar ◽  
Tess Jacob ◽  
Allen Bale ◽  
Allison Bailey ◽  
Jeffrey Kwon ◽  
...  
Keyword(s):  
Serum Calcium ◽  
Urinary Calcium ◽  
Urinary Calcium Excretion ◽  
Calcium Excretion ◽  
Familial Hypocalciuric Hypercalcemia ◽  
Calcium Sensing Receptor ◽  
Benign Condition ◽  
Casr Gene ◽  
Calcium Sensing ◽  
Novel Variant

Familial hypocalciuric hypercalcemia (FHH) is considered a relatively benign condition characterized by mild elevations in serum calcium and relatively low urinary calcium excretion. It results from an elevated set point in serum calcium arising from variants in the calcium-sensing receptor (CaSR) gene but also AP2S1 and GNA11 genes, which encode for adaptor-related protein complex 2 and G11 proteins, respectively. The manifestations of FHH can vary and sometimes overlap with primary hyperparathyroidism making the diagnosis challenging. Case Presentations. We report a mother and daughter with a novel heterozygous variant in the CaSR gene resulting in a serine to leucine substitution at position 147 (S147L) of the CaSR. Both patients had mild hypercalcemia, relatively low urinary calcium excretion, elevated calcitriol, and low-to-normal intact PTH. The proband (daughter) presented with symptoms associated with hypercalcemia and was incidentally found to have a bony lesion suspicious for osteitis fibrosa cystica, and she was also diagnosed with sarcoidosis. Subtotal parathyroidectomy revealed normal-weight parathyroid glands comprised of 50–80% parathyroid epithelial cells, which has been documented as within the spectrum of normal. Her mother had no symptoms, and no intervention was pursued. Conclusion. We report a novel variant in the CaSR associated with FHH in two patients with similar biochemical features yet differing clinical manifestations. While the relationship of the bony findings and parathyroid histology with this variant remains unclear, these cases enrich our knowledge of CaSR physiology and provide further examples of how varied the manifestations of FHH can be.

scholarly journals Hydrochlorothiazide Effectively Reduces Urinary Calcium Excretion in Two Japanese Patients with Gain-of-Function Mutations of the Calcium-Sensing Receptor Gene

2002 ◽  
Vol 87 (7) ◽  
pp. 3068-3073 ◽  
Author(s):  
Kohei Sato ◽  
Yukihiro Hasegawa ◽  
Jun Nakae ◽  
Kenji Nanao ◽  
Ikuko Takahashi ◽  
...  
Keyword(s):  
Serum Calcium ◽  
Japanese Patients ◽  
Urinary Calcium ◽  
Urinary Calcium Excretion ◽  
Calcium Excretion ◽  
Calcium Sensing Receptor ◽  
Gain Of Function ◽  
Dihydroxyvitamin D3 ◽  
Calcium Sensing ◽  
Lower Limit Of Normal

Gain-of-function mutations of the calcium-sensing receptor (CaR) gene cause autosomal dominant and/or sporadic hypocalcemia with hypercalciuria. Because treatment of the hypocalcemia with vitamin D and/or calcium in patients with such mutations results in increased hypercalciuria, nephrocalcinosis, and renal impairment, its use should be limited to alleviating the symptoms of symptomatic patients. Because thiazide diuretics have been successfully used to treat patients with hypercalciuria and hypoparathyroidism, they are theoretically useful in reducing urine calcium excretion and maintaining serum calcium levels in patients with gain-of-function mutations of the CaR gene. In this study, we report on the clinical course, molecular analysis, and effects of hydrochlorothiazide therapy in two Japanese patients with gain-of-function mutations of the CaR gene. Within a few weeks after birth, they developed generalized tonic seizures due to hypocalcemia (serum calcium values: 1.1 mmol/liter and 1.3 mmol/liter, respectively). Despite treatment with the standard dose of 1,25-dihydroxyvitamin D3 in one patient and 1α-hydroxyvitamin D3 in the other, acceptable serum calcium levels near the lower limit of normal were not established, and their urinary calcium excretion inappropriately increased. Addition of hydrochlorothiazide (1 mg/kg) reduced their urinary calcium excretion and maintained their serum calcium concentrations near the lower limit of normal, allowing the 1,25-dihydroxyvitamin D3 and 1α-hydroxyvitamin D3 doses to be reduced, and it alleviated their symptoms. A heterozygous missense mutation was identified in both patients. In one patient, the mutation was A843E in the seventh transmembrane domain of the CaR, and in the other it was L125P in the N-terminal extracellular domain. In vitro transient transfection of their mutant CaR cDNAs into HEK293 cells shifted the concentration-response curve of Ca2+ to the left. In conclusion, two sporadic cases of hypercalciuric hypocalcemia were due to de novo gain-of-function mutations of the CaR gene. Hydrochlorothiazide with vitamin D3 successfully reduced the patients’ urinary calcium excretion and controlled their serum calcium concentrations and symptoms. Thiazide diuretics are effective in patients with gain-of function mutations of the CaR gene.

scholarly journals The Calcilytic Agent NPS 2143 Rectifies Hypocalcemia in a Mouse Model With an Activating Calcium-Sensing Receptor (CaSR) Mutation: Relevance to Autosomal Dominant Hypocalcemia Type 1 (ADH1)

Endocrinology ◽  
2015 ◽  
Vol 156 (9) ◽  
pp. 3114-3121 ◽  
Author(s):  
Fadil M. Hannan ◽  
Gerard V. Walls ◽  
Valerie N. Babinsky ◽  
M. Andrew Nesbit ◽  
Enikö Kallay ◽  
...  
Keyword(s):  
Mouse Model ◽  
Urinary Calcium ◽  
Hek293 Cells ◽  
Calcium Excretion ◽  
Wild Type ◽  
Calcium Sensing Receptor ◽  
Gain Of Function ◽  
Calcium Sensing

Autosomal dominant hypocalcemia type 1 (ADH1) is caused by germline gain-of-function mutations of the calcium-sensing receptor (CaSR) and may lead to symptomatic hypocalcemia, inappropriately low serum PTH concentrations and hypercalciuria. Negative allosteric CaSR modulators, known as calcilytics, have been shown to normalize the gain-of-function associated with ADH-causing CaSR mutations in vitro and represent a potential targeted therapy for ADH1. However, the effectiveness of calcilytic drugs for the treatment of ADH1-associated hypocalcemia remains to be established. We have investigated NPS 2143, a calcilytic compound, for the treatment of ADH1 by in vitro and in vivo studies involving a mouse model, known as Nuf, which harbors a gain-of-function CaSR mutation, Leu723Gln. Wild-type (Leu723) and Nuf mutant (Gln723) CaSRs were expressed in HEK293 cells, and the effect of NPS 2143 on their intracellular calcium responses was determined by flow cytometry. NPS 2143 was also administered as a single ip bolus to wild-type and Nuf mice and plasma concentrations of calcium and PTH, and urinary calcium excretion measured. In vitro administration of NPS 2143 decreased the intracellular calcium responses of HEK293 cells expressing the mutant Gln723 CaSR in a dose-dependent manner, thereby rectifying the gain-of-function associated with the Nuf mouse CaSR mutation. Intraperitoneal injection of NPS 2143 in Nuf mice led to significant increases in plasma calcium and PTH without elevating urinary calcium excretion. These studies of a mouse model with an activating CaSR mutation demonstrate NPS 2143 to normalize the gain-of-function causing ADH1 and improve the hypocalcemia associated with this disorder.

The calcimimetic AMG 641 accelerates regression of extraosseous calcification in uremic rats

2009 ◽  
Vol 296 (6) ◽  
pp. F1376-F1385 ◽  
Author(s):  
Ignacio Lopez ◽  
Francisco J. Mendoza ◽  
Fatima Guerrero ◽  
Yolanda Almaden ◽  
Charles Henley ◽  
...  
Keyword(s):  
Phosphorus Content ◽  
Urinary Calcium ◽  
Calcium Excretion ◽  
Phagocytic Cells ◽  
Calcium Sensing Receptor ◽  
Calcium Sensing ◽  
Dietary Phosphorus ◽  
Tissue Calcium ◽  
Calcium And Phosphorus ◽  
Phosphorus Intake

The purpose of the present study was to test the hypothesis that extraskeletal calcification regresses in uremic rats after reduction in phosphorus intake and treatment with calcimimetics. Extraosseous calcification was induced in five to six nephrectomized rats fed a high-phosphorus (1.2%) diet who received calcitriol (80 ng/kg ip) every other day for a period of 14 days. Next, dietary phosphorus was reduced to 0.6%, and rats were treated with vehicle ( n = 20), calcitriol [80 ng/kg ip/48 h ( n = 20)], or the calcimimetic AMG 641 [1.5 mg/kg sc/48 h ( n = 20)]. Aortic and soft-tissue calcium and phosphorus content was evaluated after 14 and 28 days. At 28 days, reduction of phosphorus intake resulted in a significant decrease in tissue mineral content in vehicle- and AMG 641-treated rats but not in rats receiving calcitriol. Aortic calcium and phosphorus was lower in rats treated with AMG 641 (96.7 ± 26.4 mg/g) than in rats receiving vehicle (178.3 ± 38.6 mg/g). An infiltrate of phagocytic cells expressing the calcium-sensing receptor was identified in areas surrounding foci of calcification. Additional studies in parathyroidectomized rats demonstrated that AMG 641 increased the urinary excretion of calcium (6.2 ± 0.6 vs. 3.1 ± 0.5 mg/day, vehicle) ( P < 0.001). In conclusion, experimentally induced extraosseous calcification in uremic rats can be partially resolved by reducing phosphorus intake; the addition of calcimimetics may accelerate the regression process through mechanisms potentially involving a direct stimulatory effect on mineral phagocytic cells plus an increase in urinary calcium excretion.

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