Treatment of secondary hyperparathyroidism in CKD patients with cinacalcet and/or vitamin D derivatives

“Ideal” parathyroid hormone in erythropoietin‐stimulating agents‐resistant anemia

Erythropoietin‐stimulating agents (ESAs) have revolutionized anemia treatment in end‐stage renal disease (ESRD), but ESA resistance is increasingly identified. Secondary hyperparathyroidism (SHP) is one cause of ESA resistance. We describe a patient with ESA‐resistant, transfusion‐dependent anemia and mild SHP with remodeling and reticulin fibrosis on bone marrow biopsy, all of which resolved with stricter SHP management. We identified 64 patients with anemia, ESRD, and bone marrow biopsy. The parathyroid hormone (PTH) range for bony remodeling was 183–16,161.9 pg/ml versus 90.8–3283 pg/ml. The PTH range for fibrotic changes was 183–2487 pg/ml versus 90.8–16,161.9 pg/ml. We found no clear PTH range predictive for bone marrow changes.

Management of endocrine surgical disorders during COVID-19 pandemic: expert opinion for non-surgical options

Purpose

The COVID-19 pandemic brought unprecedented conditions for overall health care systems by restricting resources for non-COVID-19 patients. As the burden of the disease escalates, routine elective surgeries are being cancelled. The aim of this paper was to provide a guideline for management of endocrine surgical disorders during a pandemic.

Methods

We used Delphi method with a nine-scale Likert scale on two rounds of voting involving 64 experienced eminent surgeons and endocrinologists who had the necessary experience to provide insight on endocrine disorder management. All voting was done by email using a standard questionnaire.

Results

Overall, 37 recommendations were voted on. In two rounds, all recommendations reached an agreement and were either endorsed or rejected. Endorsed statements include dietary change in primary hyperparathyroidism, Cinacalcet treatment in secondary hyperparathyroidism, alpha-blocker administration for pheochromocytoma, methimazole ± β-blocker combination for Graves’ disease, and follow-up for fine-needle aspiration results of thyroid nodules indicated as Bethesda 3–4 cytological results and papillary microcarcinoma.

Conclusion

This survey summarizes expert opinion for the management of endocrine surgical conditions during unprecedented times when access to surgical treatment is severely disrupted. The statements are not applicable in circumstances in which surgical treatment is possible.

Parathyroidectomy in the Management of Secondary Hyperparathyroidism

Secondary hyperparathyroidism develops in CKD due to a combination of vitamin D deficiency, hypocalcemia, and hyperphosphatemia, and it exists in nearly all patients at the time of dialysis initiation. There is insufficient data on whether to prefer vitamin D analogs compared with calcimimetics, but the available evidence suggests advantages with combination therapy. Calcium derangements, patient adherence, side effects, and cost limit the use of these agents. When parathyroid hormone level persists >800 pg/ml for >6 months, despite exhaustive medical interventions, monoclonal proliferation with nodular hyperplasia is likely present along with decreased expression of vitamin D and calcium-sensing receptors. Hence, surgical parathyroidectomy should be considered, especially if concomitant disorders exist, such as persistent hypercalcemia or hyperphosphatemia, tissue or vascular calcification including calciphylaxis, and/or worsening osteodystrophy. Parathyroidectomy is associated with 15%-57% greater survival in patients on dialysis, and it also improves hypercalcemia, hyperphosphatemia, tissue calcification, bone mineral density, and health-related quality of life. The parathyroidectomy rate in the United States declined to approximately seven per 1000 dialysis patient-years between 2002 and 2011 despite an increase in average parathyroid hormone levels, reflecting calcimimetics introduction and uncertainty regarding optimal parathyroid hormone targets. Hospitalization rates are 39% higher in the first postoperative year. Hungry bone syndrome occurs in approximately 25% of patients on dialysis, and profound hypocalcemia requires high doses of oral and intravenous calcium along with calcitriol supplementation. Total parathyroidectomy with autotransplantation carries a higher risk of permanent hypocalcemia, whereas risk of hyperparathyroidism recurrence is higher with subtotal parathyroidectomy. Given favorable long-term outcomes from observational parathyroidectomy cohorts, despite surgical risk and postoperative challenges, it is reasonable to consider parathyroidectomy in more patients with medically refractory secondary hyperparathyroidism.

The Determinants of Hemoglobin Variability in Hemodialysis Patients

Introduction. Factors that have been reported to affect erythropoietin (EPO) responsiveness in hemodialysis (HD) patients include iron deficiency, chronic inflammation, secondary hyperparathyroidism, malnutrition and inadequate HD dose. The aim of the study was to analyze the deteminants of hemoglobin variability in HD patients. Methods. The study encompassed 526 patients (197 F and 329 M). According to HD vintage at the beginning of the study the patients were divided into two groups: group-1 encompassed 153 patients with HD vintage bellow 24 months, and group-2 encompassed 329 patients with HD vintage over 24 months. Over a period of 21 months after admission the following parameters were analyzed: hemoglobin (Hb), EPO dose, iron dose, HD dose (eKT/V), transferrin saturation (TSAT), C-reactive protein (CRP), ferritin and serum albumin at 3 months and parathyroid hormone (PTH) at 6 months. Results. The percentage of patients with Hb>=105g/L significantly improved, and the average Hb level significantly increased in both groups over a period of 21 months. The average EPO and iron dose significantly decreased, but TSAT and ferritin levels significantly increased over a period of 21 months. The average eKT/V and s-albumin values significantly increased, but the average CRP and PTH levels significantly decresead over a period of 21 months. In group-1 EPO dose and CRP, but in group-2 EPO dose, ferritin, HD vintage, and iron dose were statistically significant predictors of the Hb level 9 months after admission. Conclusions. Insufficient EPO therapy, iron deficiency and chronic inflammation were the main factors of inadequate correction of anemia in HD patients before admission.

Aerobic biosynthesis of hydrocinnamic acids in Escherichia coli with a strictly oxygen-sensitive enoate reductase

3-Phenylpropionic acid (3PPA) and 3-(4-hydroxyphenyl) propionic acid (HPPA) are important commodity aromatic acids widely used in food, pharmaceutical and chemical industries. Currently, 3PPA and HPPA are mainly manufactured through chemical synthesis, which contains multiple steps involving toxic solvents and catalysts harmful to environment. Therefore, replacement of such existing petroleum-derived approaches with simple and environmentally friendly biological processes is highly desirable for manufacture of these chemicals. Here, for the first time we demonstrated the de novo biosynthesis of 3PPA and HPPA using simple carbon sources in E. coli by extending the cinnamic acids biosynthesis pathways through biological hydrogenation. We first screened 11 2-enoate reductases (ER) from nine microorganisms, leading to efficient conversion of cinnamic acid and p-coumaric acid to 3PPA and HPPA, respectively. Surprisingly, we found a strictly oxygen-sensitive Clostridia ER capable of functioning efficiently in E. coli even under aerobic conditions. On this basis, reconstitution of the full pathways led to the de novo production of 3PPA and HPPA and the accumulation of the intermediates (cinnamic acid and p-coumaric acid) with cell toxicity. To address this problem, different expression strategies were attempted to optimize individual enzyme׳s expression level and minimize intermediates accumulation. Finally, the titers of 3PPA and HPPA reached 366.77mg/L and 225.10mg/L in shake flasks, respectively. This study not only demonstrated the potential of microbial approach as an alternative to chemical process, but also proved the possibility of using oxygen-sensitive enzymes under aerobic conditions.

Assessment of resource use and costs associated with parathyroidectomy for secondary hyperparathyroidism in end stage renal disease in the UK

INTRODUCTION

Secondary hyperparathyroidism (SHPT) is a major complication of end stage renal disease (ESRD). For the National Health Service (NHS) to make appropriate choices between medical and surgical management, it needs to understand the cost implications of each. A recent pilot study suggested that the current NHS healthcare resource group tariff for parathyroidectomy (PTX) (£2071 and £1859 in patients with and without complications, respectively) is not representative of the true costs of surgery in patients with SHPT.

OBJECTIVE

This study aims to provide an estimate of healthcare resources used to manage patients and estimate the cost of PTX in a UK tertiary care centre.

METHODS

Resource use was identified by combining data from the Proton renal database and routine hospital data for adults undergoing PTX for SHPT at the University Hospital of Wales, Cardiff, from 2000-2008. Data were supplemented by a questionnaire, completed by clinicians in six centres across the UK. Costs were obtained from NHS reference costs, British National Formulary and published literature. Costs were applied for the pre-surgical, surgical, peri-surgical, and post-surgical periods so as to calculate the total cost associated with PTX.

RESULTS

One hundred and twenty-four patients (mean age=51.0 years) were identified in the database and 79 from the questionnaires. The main costs identified in the database were the surgical stay (mean=£4066, SD=£,130), the first month post-discharge (£465, SD=£176), and 3 months prior to surgery (£399, SD=£188); the average total cost was £4932 (SD=£4129). From the questionnaires the total cost was £5459 (SD=£943). It is possible that the study was limited due to missing data within the database, as well as the possibility of recall bias associated with the clinicians completing the questionnaires.

CONCLUSION

This analysis suggests that the costs associated with PTX in SHPT exceed the current NHS tariffs for PTX. The cost implications associated with PTX need to be considered in the context of clinical assessment and decision-making, but healthcare policy and planning may warrant review in the light of these results.

Outcomes of Total Parathyroidectomy with Autotransplantation versus Subtotal Parathyroidectomy with Routine Addition of Thymectomy to both Groups: Single Center Experience of Secondary Hyperparathyroidism

BACKGROUND

Secondary hyperparathyroidism is a common acquired disorder seen in chronic renal failure. It may result in potentially serious complications including metabolic bone diseases, severe atherosclerosis and undesirable cardiovascular events. Parathyroidectomy is required in about 20% of patients after 3-10 years of dialysis and in up to 40% after 20 years.

AIMS

The aim of the current study was to evaluate the short-term and long-term outcomes of patients with secondary hyperparathyroidism who had undergone total parathyroidectomy with autotransplantation and thymectomy or subtotal parathyroidectomy with thymectomy by the same surgical team during the study period.

STUDY DESIGN

Retrospective comparative study.

METHODS

Clinical data of 50 patients who underwent parathyroid surgery for secondary hyperparathyroidism between 2003 and 2011 were reviewed retrospectively. Patients were divided into two subgroups of total parathyroidectomy with autotransplantation or subtotal parathyroidectomy. Thymectomy was routinely performed for both groups. Short term outcome parameters included intact parathyroid hormone, ionized calcium and alkaline phosphatase levels. Bone pain, bone fractures, persistent or recurrent disease were included in long term outcome parameters.

RESULTS

The mean duration of dialysis was eight years. The mean ionized calcium levels dropped significantly in the total parathyroidectomy with autotransplantation group (p=0.016). No serious postoperative complications were observed. Postoperative intravenous calcium supplementation was required in four patients in the total parathyroidectomy with autotransplantation group (total PTX+AT) and in three patients in the subtotal parathyroidectomy group (subtotal PTX). Postoperatively, all patients received oral calcium carbonate and calcitriol. The length of average hospital stay was 5 (3-10) days. Including nine patients who underwent successful renal transplantation pre-operative bone symptoms, hypercalcemia, hyperphosphatemia, and an increased alkaline phosphatase levels were improved or resolved in all patients. After a mean follow-up of 65 months, three patients (6%) had persistent and one (2%) had recurrent disease.

CONCLUSION

Total parathroidectomy with autotransplantation is a beneficial and safe surgical procedure for patients on chronic dialysis with otherwise uncontrollable secondary hyperparathroidism and even in patients who have undergone renal transplantation after parathyroidectomy. Careful cervical exploration and routine thymectomy should be considered as a routine part of the surgical approach regardless of the preferred technique.

Paricalcitol- or cinacalcet-centred therapy affects markers of bone mineral disease in patients with secondary hyperparathyroidism receiving haemodialysis: results of the IMPACT-SHPT study

BACKGROUND

In this Phase 4 international study, efficacy and safety of paricalcitol-centred therapy were compared with that of cinacalcet-centred therapy for the treatment of chronic kidney disease (CKD)-associated secondary hyperparathyroidism (SHPT) in patients undergoing haemodialysis (ClinicalTrials.gov identifier NCT00977080).

METHODS

Patients ≥ 18 years of age with Stage 5 CKD and SHPT [intact parathyroid hormone (iPTH) level of 300-800 pg/mL, calcium level of 8.4-10.0 mg/dL and phosphate concentration of ≤ 6.5 mg/dL] who were undergoing haemodialysis were included. Patients were randomized by mode of paricalcitol administration [i.e. intravenous (IV) or oral strata] to receive paricalcitol- or cinacalcet-centred therapy for ≤ 28 weeks. Changes in metabolic markers [total alkaline phosphatase (AP), bone-specific AP and fibroblast growth factor-23 (FGF-23)] and the proportion of patients in each treatment group who achieved an iPTH level of 150-300 pg/mL during Weeks 8, 16 and 21-28 as a composite value were evaluated.

RESULTS

Compared with cinacalcet-centred therapy, levels of both bone turnover markers were significantly reduced from baseline with IV and oral paricalcitol-centred treatment (P < 0.05 for both dosing strata) at Weeks 8, 16 and 28. Levels of FGF-23 were increased with paricalcitol versus cinacalcet-centred treatment. A greater proportion of patients receiving paricalcitol-centred therapy achieved target iPTH levels (i.e. 150-300 pg/mL) throughout the study in the IV and oral dosing strata compared with patients receiving cinacalcet-centred treatment.

CONCLUSIONS

In patients with CKD and SHPT undergoing haemodialysis, paricalcitol-centred therapy reduced circulating bone turnover markers and iPTH levels and increased FGF-23 levels compared with cinacalcet-centred treatment.

TRIAL REGISTRATION

ClinicalTrials.gov identifier NCT00977080.

Calcium sensing receptor expression in ovine amniotic fluid mesenchymal stem cells and the potential role of R-568 during osteogenic differentiation

Amniotic fluid-derived stem (AFS) cells have been identified as a promising source for cell therapy applications in bone traumatic and degenerative damage. Calcium Sensing Receptor (CaSR), a G protein-coupled receptor able to bind calcium ions, plays a physiological role in regulating bone metabolism. It is expressed in different kinds of cells, as well as in some stem cells. The bone CaSR could potentially be targeted by allosteric modulators, in particular by agonists such as calcimimetic R-568, which may potentially be helpful for the treatment of bone disease. The aim of our study was first to investigate the presence of CaSR in ovine Amniotic Fluid Mesenchymal Stem Cells (oAFMSCs) and then the potential role of calcimimetics in in vitro osteogenesis. oAFMSCs were isolated, characterized and analyzed to examine the possible presence of CaSR by western blotting and flow cytometry analysis. Once we had demonstrated CaSR expression, we worked out that 1 µM R-568 was the optimal and effective concentration by cell viability test (MTT), cell number, Alkaline Phosphatase (ALP) and Alizarin Red S (ARS) assays. Interestingly, we observed that basal diffuse CaSR expression in oAFMSCs increased at the membrane when cells were treated with R-568 (1 µM), potentially resulting in activation of the receptor. This was associated with significantly increased cell mineralization (ALP and ARS staining) and augmented intracellular calcium and Inositol trisphosphate (IP3) levels, thus demonstrating a potential role for calcimimetics during osteogenic differentiation. Calhex-231, a CaSR allosteric inhibitor, totally reversed R-568 induced mineralization. Taken together, our results demonstrate for the first time that CaSR is expressed in oAFMSCs and that calcimimetic R-568, possibly through CaSR activation, can significantly improve the osteogenic process. Hence, our study may provide useful information on the mechanisms regulating osteogenesis in oAFMSCs, perhaps prompting the use of calcimimetics in bone regenerative medicine.

Rapid decrease of intact parathyroid hormone could be a predictor of better response to cinacalcet in hemodialysis patients

PURPOSE

Cinacalcet is effective for treating refractory secondary hyperparathyroidism (SHPT), but little is known about the response rates and clinical factors influencing the response.

MATERIALS AND METHODS

A prospective, single-arm, multi-center study was performed for 24 weeks. Cinacalcet was administered to patients with intact parathyroid hormone (iPTH) level greater than 300 pg/mL. Cinacalcet was started at a dose of 25 mg daily and titrated until 100 mg to achieve a serum iPTH level<300 pg/mL (primary end point). Early response to cinacalcet was defined as a decrease of iPTH more than 50% within one month.

RESULTS

Fifty-seven patients were examined. Based on the magnitude of iPTH decrease, patients were divided into responder (n=47, 82.5%) and non-responder (n=10, 17.5%) groups. Among the responders, 38 achieved the primary end point, whereas 9 patients showed a reduction in serum iPTH of 30% or more, but did not reach the primary end point. Compared to non-responders, responders were significantly older (p=0.026), female (p=0.041), and diabetics (p<0.001). Additionally, early response was observed more frequently in the responders (30/47, 63.8%), of whom the majority (27/30, 90.0%) achieved the primary end point. Multivariate analysis showed that lower baseline iPTH levels [odds ratio (OR) 0.96, 95% confidence interval (CI) 0.93-0.99], the presence of diabetes (OR 46.45, CI 1.92-1125.6) and early response (OR 21.54, CI 2.94-157.7) were significant clinical factors affecting achievement of iPTH target.

CONCLUSION

Cinacalcet was effective in most hemodialysis patients with refractory SHPT. The presence of an early response was closely associated with the achievement of target levels of iPTH.

Fibroblast growth factor 23 and Klotho: physiology and pathophysiology of an endocrine network of mineral metabolism

The metabolically active and perpetually remodeling calcium phosphate-based endoskeleton in terrestrial vertebrates sets the demands on whole-organism calcium and phosphate homeostasis that involves multiple organs in terms of mineral flux and endocrine cross talk. The fibroblast growth factor (FGF)-Klotho endocrine networks epitomize the complexity of systems biology, and specifically, the FGF23-αKlotho axis highlights the concept of the skeleton holding the master switch of homeostasis rather than a passive target organ as hitherto conceived. Other than serving as a coreceptor for FGF23, αKlotho circulates as an endocrine substance with a multitude of effects. This review covers recent data on the physiological regulation and function of the complex FGF23-αKlotho network. Chronic kidney disease is a common pathophysiological state in which FGF23-αKlotho, a multiorgan endocrine network, is deranged in a self-amplifying vortex resulting in organ dysfunction of the utmost severity that contributes to its morbidity and mortality.

Prescription patterns and mineral metabolism abnormalities in the cinacalcet era: results from the MBD-5D study

BACKGROUND AND OBJECTIVES

Prescription patterns for hemodialysis patients with secondary hyperparathyroidism have varied widely since market introduction of cinacalcet. This study examined associations between prescription patterns and subsequent laboratory values.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Using a Mineral and Bone Disorder Outcomes Study for Japanese CKD Stage 5D Patients subcohort, 1716 prevalent hemodialysis patients (4048 sets for repeated measures between January 2008 and July 2009) with an intact parathyroid hormone (iPTH) level >180 pg/ml who used intravenous vitamin D receptor activator (VDRA) without cinacalcet were selected. Prescription patterns were defined based on cinacalcet administration (starting or not) and VDRA dosage change (decreased [<-25%], stable [-25% to 25%], or increased [>25%]). Proportion differences (PDs) were determined for decreasing iPTH levels by at least one category (<180, 180-299, 300-499, and ≥500 pg/ml) and for achieving target phosphorus (3.5-6.0 mg/dl) and calcium (8.4-10.0 mg/dl) levels, adjusting for potential confounders.

RESULTS

The starting cinacalcet and increased VDRA patterns were associated with decreasing iPTH levels (PD, 0.25 and 0.13; 95% confidence intervals [95% CIs], 0.19-0.31 and 0.09-0.17, respectively); combination use had an additive association (PD, 0.34; 95% CI, 0.20-0.42). The starting cinacalcet and decreased VDRA combination was associated with simultaneously achieving target phosphorus (PD, 0.12; 95% CI: 0.04-0.20) and calcium (PD, 0.09; 95% CI, 0.01-0.17) levels.

CONCLUSIONS

Certain combinations of cinacalcet and VDRA were associated with decreasing iPTH and achieving targets for phosphorus and calcium. Combinations may prove advantageous versus VDRA alone in managing secondary hyperparathyroidism.

Left ventricular diastolic dysfunction in dialysis patients assessed by novel speckle tracking strain rate analysis: prevalence and determinants

Background. Diastolic dysfunction is common among dialysis patients and is associated with increased morbidity and mortality. Novel echocardiographic speckle tracking strain analysis permits accurate assessment of left ventricular diastolic function, independent of loading conditions and taking all myocardial segments into account. The aim of the study was to evaluate the prevalence of diastolic dysfunction in chronic dialysis patients using this novel technique, and to identify its determinants among clinical and echocardiographic variables. Methods. Patients currently enrolled in the ICD2 study protocol were included for this analysis. Next to conventional echo measurements diastolic function was also assessed by global diastolic strain rate during isovolumic relaxation (SRIVR). Results. A total of 77 patients were included (age 67 ± 8 years, 74% male). When defined as E/SRIVR ≥236, the prevalence of diastolic dysfunction was higher compared to more conventional measurements (48% versus 39%). Left ventricular mass (OR 1.02, 95% CI 1.00–1.04, P = 0.014) and pulse wave velocity (OR 1.34, 95% CI 1.07–1.68, P = 0.01) were independent determinants of diastolic dysfunction. Conclusion. Diastolic dysfunction is highly prevalent among dialysis patients and might be underestimated using conventional measurements. Left ventricular mass and pulse wave velocity were the only determinants of diastolic dysfunction in these patients.

Efficacy and safety of cinacalcet for the treatment of secondary hyperparathyroidism in patients with advanced chronic kidney disease before initiation of regular dialysis

AIM

To evaluate the compassionate use of cinacalcet for the management of secondary hyperparathyroidism in patients who are not on dialysis.

METHODS

Patients with stage 4-5 chronic kidney disease (CKD) who were not on dialysis, had an intact parathyroid hormone (iPTH) level greater than 300 pg/mL, and had not responded satisfactorily to treatment with phosphate binders and vitamin D were prospectively studied. Patients received 6 months of compassionate treatment with cinacalcet, which was initiated at a dose of 30 mg/day orally and flexibly dosed thereafter based on iPTH levels.

RESULTS

Twenty-six patients with a mean age±standard deviation (SD) of 58.8±16.1 years were enrolled in the study and included in the statistical analysis. The mean percentage change in iPTH levels from baseline after 6 months of treatment was -67.9±17.0%, with 92.3% (95% confidence interval (CI), 75.9-97.9) of patients showing an iPTH level within the limits recommended by Kidney Disease Outcomes Quality Initiative (K/DOQI) guidelines. The mean serum calcium concentrations had decreased significantly at the end of the study (-8.0±6.9%), while the mean serum phosphorus concentration had significantly increased (+8.3±17.0%).

CONCLUSION

Our results suggest that cinacalcet may be a useful alternative for the treatment of secondary hyperparathyroidism in pre-dialysis patients who are unresponsive to other treatments. The hypocalcemia and hyperphosphatemia reported in previous studies may not occur if a moderate dose of calcimimetics is used in patients with marginal glomerular filtration rates, especially if combined with vitamin D analogues and calcium-based phosphate binders.

A mathematical model of calcium and phosphorus metabolism in two forms of hyperparathyroidism

Parathyroid hormone (PTH) plays a critical role in calcium and phosphorus metabolism. Interestingly, in two forms of hyperparathyroidism (excessive amount of PTH in the serum), the metabolic disturbances in patients with chronic kidney disease (CKD) significantly differ from those with primary hyperparathyroidism (PHP). Since an intuitive understanding of these PTH-linked regulatory mechanisms are hardly possible, we developed a mathematical model using clinical data (1586 CKD and 40 PHP patients). The model was composed of a set of ordinary differential equations, in which the regulatory mechanism of PTH together with other key factors such as 1,25-Dihydroxyvitamin D (1,25(OH)₂D) and calcium was described in the tissues including bone, the kidney, the serum, and the parathyroid glands. In this model, an increase in PTH was induced by its autonomous production in PHP, while PTH in CKD was elevated by a decrease in feedback inhibition of 1,25(OH)₂D in the serum, as well as an increase in stimulation by phosphorus in the serum. The model-based analysis revealed characteristic differences in the outcomes of hyperparathyroidism in CKD and PHP. The calcium exchange in bone, for instance, was predicted significantly higher in PHP than CKD. Furthermore, we evaluated the observed and predicted responses to the administration of calcimimetics, a recently developed synthetic drug that modulated efficacy of calcium-sensing receptors. The results herein support the notion that the described model would enable us to pose testable hypotheses about the actions of PTH, providing a quantitative analytical tool for evaluating treatment strategies of PHP and CKD.

Calcimimetic R-568 and its enantiomer S-568 increase nitric oxide release in human endothelial cells

Background

Calcimimetics, such as R-568, are thought to activate G protein-linked Ca²⁺-sensing receptor (CaSR) by allosterically increasing the affinity of the receptor for Ca²⁺ allowing for efficient control of uremic hyperparathyroidism. Several recent studies suggest they possess additional vascular actions. Although it has been postulated that calcimimetics may have a direct effect on CaSR in the blood vessels, further studies are needed to elucidate their vascular CaSR-dependent versus CaSR-independent effects.

Methodology/Principal Findings

Focusing on human umbilical vein endothelial cells (HUVECs), we studied the CaSR expression and distribution by Immunofluorescence and Western Blot analysis. CaSR function was evaluated by measuring the potential effect of calcimimetic R-568 and its enantiomer S-568 upon the modulation of intracellular Ca²⁺ levels (using a single cell approach and FURA-2AM), in the presence or absence of Calhex-231, a negative modulator of CaSR. To address their potential vascular functions, we also evaluated R- and S-568-stimulated enzymatic release of Nitric Oxide (NO) by DAF-2DA, by Nitric Oxide Synthase (NOS) radiometric assay (both in HUVECs and in Human Aortic Endothelial Cells) and by measuring eNOS-ser1177 phosphorylation levels (Immunoblotting). We show that, although the CaSR protein was expressed in HUVECs, it was mainly distributed in cytoplasm while the functional CaSR dimers, usually localized on the plasma membrane, were absent. In addition, regardless of the presence or absence of Calhex-231, both R- and S-568 significantly increased intracellular Ca²⁺ levels by mobilization of Ca²⁺ from intracellular stores, which in turn augmented NO release by a time- and Ca²⁺-dependent increase in eNOS-ser1177 phosphorylation levels.

Conclusions/Significance

Taken together, these data indicate that in human endothelium there is no stereoselectivity in the responses to calcimimetics and that CaSR is probably not involved in the action of R- and S-568. This suggests an additional mechanism in support of the CaSR-independent role of calcimimetics as vasculotrope agents.

High-intensity focussed ultrasound (HIFU) treatment in uraemic secondary hyperparathyroidism

BACKGROUND

The recently developed non-invasive high-intensity focussed ultrasound (HIFU) technique for the destruction of parathyroid adenomas could also be of interest for the treatment of secondary hyperparathyroidism (SHP) in patients with chronic kidney disease (CKD). We conducted a pilot study using this method.

METHODS

Five chronic haemodialysis patients with severe SHP underwent one to three HIFU treatments, respectively. They had at least one or two enlarged parathyroid glands, which were accessible to this technique.

RESULTS

In Patients 1-I and 5-V, serum intact parathyroid hormone (iPTH) could be successfully reduced in the long run. In Patient 3-N, serum iPTH decreased dramatically down to the normal range but increased again subsequently. In Patients 2-E and 4-D, transient reductions in serum iPTH were also obtained but HIFU failed to correct SHP during follow-up. Serum total calcium and phosphorus decreased in four among the five patients, either transiently or permanently. Serum total alkaline phosphatases were reduced in four of five patients. Side effects included local oedema, transient impairment of vocal cord mobility and bitonal voice.

CONCLUSIONS

HIFU treatment may be of help in controlling SHP in selected patients with CKD. Further experience is clearly needed.

Modulation of vitamin D signaling is a potential therapeutic target to lower cardiovascular risk in chronic kidney disease

While it is true that many traditional cardiovascular risk factors are amenable to intervention in chronic kidney disease (CKD), the results of intervention may not be as efficacious as those obtained in the general population. Thus, there may also be a unique milieu established in CKD, which causes excess cardiovascular disease (CVD) burden by mechanisms that are as yet not fully recognized. Recently, vitamin D has sparked widespread interest because of its potential favorable benefits on CVD. However, the mechanisms for how vitamin D may improve CVD risk markers and outcomes have not been fully elucidated. Furthermore, hypovitaminosis D is highly prevalent in the CKD cohort. Given this background, we hypothesize that low vitamin D status may act as a new CVD risk marker, and modulation of vitamin D signaling may be a potential therapeutic target to lower cardiovascular risk in CKD. The data presented in this review support that the low vitamin D status may be linked with the high cardiovascular risk in CKD, based on both the biological effects of vitamin D itself on the cardiovascular system, and the cross-actions between vitamin D signaling and the multiple metabolic pathways. Considering the high prevalence of hypovitaminosis D, limited natural vitamin D food sources, and reduced sun exposure in CKD patients, recommendations for treatment of hypovitaminosis D mainly focus on exogenous supplementation with vitamin D and its analogues. Although promising, when to start therapy, the route of administration, the dose, and the duration remain need to be discussed.

Paricalcitol versus cinacalcet plus low-dose vitamin D for the treatment of secondary hyperparathyroidism in patients receiving haemodialysis: study design and baseline characteristics of the IMPACT SHPT study

Background. Paricalcitol and cinacalcet are common therapies for patients on haemodialysis with secondary hyperparathyroidism (SHPT). We conducted a multi-centre study in 12 countries to compare the safety and efficacy of paricalcitol and cinacalcet for the treatment of SHPT.

Methods. Patients aged ≥18 years with Stage 5 chronic kidney disease receiving maintenance haemodialysis and with intact parathyroid hormone (iPTH) 300–800 pg/mL, calcium 8.4–10.0 mg/dL (2.09–2.49 mmol/L) and phosphorus ≤6.5 mg/dL (2.09 mmol/L) were randomized within two strata defined by the mode of paricalcitol administration to treatment with paricalcitol- (intra-venous, US and Russian sites, IV stratum; oral, non-US and non-Russian sites, oral stratum) or cinacalcet-centred therapy. The primary endpoint is the proportion of patients in each treatment group who achieve a mean iPTH value of 150–300 pg/mL during Weeks 21–28 of treatment. Assuming efficacy response rates of 36 and 66% for cinacalcet and paricalcitol, respectively, and a 20% discontinuation rate, 124 subjects in each stratum were estimated to provide 81% power to detect a 30% absolute difference in the primary endpoint.

Results. Of 746 patients screened, 272 (mean age, 63 years; mean iPTH, 509 pg/mL) were randomized. Mean duration of haemodialysis at baseline was 3.7 years. Comorbidities included hypertension (90.4%), Type 2 diabetes (40.4%), congestive heart failure (17.3%), coronary artery disease (34.6%) and gastrointestinal disorders (75%).

Conclusions. The study participants are representative of a multinational cohort of patients on haemodialysis with elevated iPTH. The study results will provide valuable information on the best available treatment of SHPT in patients on haemodialysis.

Cinacalcet: a pharmacoeconomic review of its use in secondary hyperparathyroidism in end-stage renal disease

This article provides an overview of the clinical profile of the calcimimetic agent cinacalcet (Mimpara®, Sensipar®) in the treatment of patients with secondary hyperparathyroidism (SHPT) undergoing dialysis for end-stage renal disease (ESRD), followed by a comprehensive review of pharmacoeconomic analyses with cinacalcet in this patient population. Most patients with ESRD undergoing dialysis develop SHPT, which is associated with disturbances in bone mineral metabolism and the development of fractures, cardiovascular disease and other clinical events. Standard treatment of SHPT includes phosphate binders and active vitamin D derivatives. However, standard treatment alone seldom achieves recommended target plasma or serum levels of parathyroid hormone (PTH), calcium and phosphorous. The addition of cinacalcet to standard therapy in patients with SHPT undergoing dialysis for ESRD improves the likelihood of achieving target biochemical levels compared with standard therapy alone. On the basis of association studies, improvements in these intermediate endpoints are likely to reduce the risk of clinical events, such as fractures and cardiovascular disease. Therefore, part of the acquisition cost of cinacalcet is likely to be offset by reductions in other healthcare resource use, such as reductions in costs associated with a lower likelihood of clinical events, as well as potential reductions in dosages of standard treatment. A number of pharmacoeconomic analyses across various country settings indicate that cinacalcet plus standard therapy is cost effective relative to standard therapy alone if dialysis costs are excluded, or that early initiation of cinacalcet is cost effective compared with delaying cinacalcet treatment until PTH levels become very uncontrolled. However, across analyses with cinacalcet, results were variable and not always favourable. This wide range of results stems from differences in selection of data sources used to populate the models, regional differences in healthcare resource use and costs, as well as other factors. Future cost-effectiveness analyses with cinacalcet should incorporate data on hard clinical outcomes from the EVOLVE study once this information becomes available.

Prevention of secondary hyperparathyroidism in hemodialysis patients: the key role of native vitamin D supplementation

Secondary hyperparathyroidism (SHPT) is a frequent complication in chronic kidney disease, especially in hemodialysis (HD) patients. Treatments for SHPT include calcitriol analogues (CA), phosphate binders, cinacalcet (CC), and surgical parathyroidectomy (PTX). This study aimed to assess the incidence and prevalence of SHPT in a single center during the period when native vitamin D (N-VitD) supplementation and CC treatment became available. All incident and prevalent HD patients were prospectively recorded and compared using 3 periods from 2004 to 2005 (period 1), 2006 to 2007 (period 2), and 2008 to 2009 (period 3). SHPT was diagnosed with serum parathyroid hormone (PTH) levels >300 pg/mL or the need for CA, CC, or PTX. Between periods 1 and 3, in incident patients (n=120 and 101), N-VitD prescription increased from 11% to 68% (P<0.0001), CA prescription remained stable (40%), and patients with PTH>300 pg/mL decreased from 40% to 12% (P<0.0001). In prevalent HD patients (n=235), N-VitD treatment increased from 55% to 91% (P<0.0001), whereas treatment with CA decreased from 67% to 17% (P<0.0001). Patients with serum PTH>300 pg/mL decreased from 38% to 13% (P<0.001), whereas patients with PTH<150 pg/mL remained stable (<30%). New CC prescriptions decreased from 45 to 3 (P<0.0001). Since 2004, SHPT has decreased drastically in incident and prevalent HD patients. The preventive role of N-VitD supplementation appears to be obvious and represents one more argument for its general recommendation in CKD patients.

Allosteric modulation of family C G-protein-coupled receptors: from molecular insights to therapeutic perspectives

Allosteric receptor modulation is an attractive concept in drug targeting because it offers important potential advantages over conventional orthosteric agonism or antagonism. Allosteric ligands modulate receptor function by binding to a site distinct from the recognition site for the endogenous agonist. They often have no effect on their own and therefore act only in conjunction with physiological receptor activation. This article reviews the current status of allosteric modulation at family C G-protein coupled receptors in the light of their specific structural features on the one hand and current concepts in receptor theory on the other hand. Family C G-protein-coupled receptors are characterized by a large extracellular domain containing the orthosteric agonist binding site known as the "venus flytrap module" because of its bilobal structure and the dynamics of its activation mechanism. Mutational analysis and chimeric constructs have revealed that allosteric modulators of the calcium-sensing, metabotropic glutamate and GABA(B) receptors bind to the seven transmembrane domain, through which they modify signal transduction after receptor activation. This is in contrast to taste-enhancing molecules, which bind to different parts of sweet and umami receptors. The complexity of interactions between orthosteric and allosteric ligands is revealed by a number of adequate biochemical and electrophysiological assay systems. Many allosteric family C GPCR modulators show in vivo efficacy in behavioral models for a variety of clinical indications. The positive allosteric calcium sensing receptor modulator cinacalcet is the first drug of this type to enter the market and therefore provides proof of principle in humans.

Effects of calcimimetic combined with an angiotensin-converting enzyme inhibitor on uremic cardiomyopathy progression

BACKGROUND/AIMS

Angiotensin-converting enzyme (ACE) inhibitors have cardioprotective properties and functional calcium-sensing receptors express in cardiac myocytes.

METHODS

Rats were made uremic by 5/6 nephrectomy and treated as follows: uremic rats were fed on a regular diet (UC), uremic + enalapril (E), uremic + calcimimetic agent R-568 (R-568), and uremic + enalapril + R-568 (E+R-568). A group of normal rats served as controls (NC).

RESULTS

Blood pressure (BP) and left ventricle mass were elevated significantly in the UC and R-568 groups compared with those in the NC group, but were indistinguishable from normal controls in the E and E+R-568 groups. Cardiac fibrosis was significantly increased in the UC group compared with that in the NC group. This increase was significantly attenuated in the R-568 and E groups, and the attenuation was further enhanced in the E+R-568 group. Factors associated with cardiac hypertrophy such as proliferating cell nuclear antigen, cyclin D1, and cyclin D2, as well as factors associated with cardiac fibrosis such as type I collagen, fibronectin, and transforming growth factor-β1 were significantly increased in the UC group compared with those in the NC group. Monotherapy with R-568 or E attenuated this increase and the combination further attenuated these measures.

CONCLUSIONS

Calcimimetics can suppress the progression of uremic cardiomyopathy and this effect is amplified when BP is controlled via renin-angiotensin system blockade.

The ADVANCE study: a randomized study to evaluate the effects of cinacalcet plus low-dose vitamin D on vascular calcification in patients on hemodialysis

BACKGROUND

This prospective, randomized, controlled trial compared the progression of vascular and cardiac valve calcification in 360 prevalent adult hemodialysis patients with secondary hyperparathyroidism treated with either cinacalcet plus low-dose vitamin D sterols or flexible doses of vitamin D sterols alone.

METHODS

Eligible subjects were on hemodialysis for ≥ 3 months with parathyroid hormone (PTH) > 300 pg/mL or PTH 150-300 pg/mL with calcium-phosphorus product > 50 mg(2)/dL(2) while receiving vitamin D. All subjects received calcium-based phosphate binders. Coronary artery calcification (CAC) and aorta and cardiac valve calcium scores were determined both by Agatston and volume scoring using multi-detector computed tomography. Subjects with Agatston CAC scores ≥ 30 were randomized to cinacalcet (30- 180 mg/day) plus low-dose calcitriol or vitamin D analog (≤ 2 μg paricalcitol equivalent/dialysis), or flexible vitamin D therapy. The primary end point was percentage change in Agatston CAC score from baseline to Week 52.

RESULTS

Median (P10, P90) Agatston CAC scores increased 24% (-22%, 119%) in the cinacalcet group and 31% (-9%, 179%) in the flexible vitamin D group (P = 0.073). Corresponding changes in volume CAC scores were 22% (-12%, 105%) and 30% (-6%, 133%; P = 0.009). Increases in calcification scores were consistently less in the aorta, aortic valve and mitral valve among subjects treated with cinacalcet plus low-dose vitamin D sterols, and the differences between groups were significant at the aortic valve.

CONCLUSIONS

In hemodialysis patients with moderate to severe secondary hyperparathyroidism, cinacalcet plus low-dose vitamin D sterols may attenuate vascular and cardiac valve calcification.

Endorsement of the Kidney Disease Improving Global Outcomes (KDIGO) Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD) Guidelines: a European Renal Best Practice (ERBP) commentary statement

Under the auspices of the European Renal Best Practice, a group of European nephrologists, not serving on the Kidney Disease Improving Global Outcomes (KDIGO) working group, but with significant clinical and research interests and expertise in these areas, was invited to examine and critique the Chronic Kidney Disease-Mineral and Bone Disorder KDIGO document published in August 2009. The final form of this paper in Nephrology Dialysis Transplantation, as a commentary, not as a position statement, reflects the fact that we have had no more evidence to review, discuss and debate available to us than was available to the KDIGO working group. However, we have felt that we were able to comment on specific areas where we feel that further clinical guidance would be helpful, thereby going beyond the KDIGO position as reflected in their document. This present paper, we hope, will be of most use to the practising kidney specialist and those allied to the clinical team.

Pharmacotherapy of end-stage renal disease

IMPORTANCE OF THE FIELD

The incidence and prevalence of end-stage renal disease (ESRD) requiring renal replacement therapy (RRT) continues to grow worldwide. ESRD causes significant morbidity and mortality and has enormous financial and personal costs.

AREAS COVERED IN THIS REVIEW

Major electronic databases (including the Cochrane Library, MEDLINE and EMBASE) were searched from 1989 to September 2009 to summarize current pharmacotherapy of ESRD-associated complications in adults receiving maintenance dialysis (hemodialysis or continuous ambulatory peritoneal dialysis). Current guidelines for the treatment of ESRD (e.g., NKF-K/DOQI, KDIGO, and the ERA-EDTA's European Renal Best Practice Guidelines) were included.

WHAT THE READER WILL GAIN

Commonly used pharmacological treatment strategies for chronic arterial hypertension, anemia, iron management, dyslipidemia, hyperglycemia, and for disturbances of bone and mineral metabolism, including hyperphosphatemia and secondary hyperparathyroidism in ESRD, are presented. In addition, the reader will learn that nonadherence to oral medication in ESRD can contribute significantly to excess morbidity and mortality of the dialysis population.

TAKE HOME MESSAGE

Improvements in pharmacotherapy of ESRD may be at least in part counteracted by continuously increasing age and comorbid disease of the dialysis population. Individualized and tailor-made pharmacological management of the ESRD patient remains a challenge for the future.

Clinical utility of calcimimetics targeting the extracellular calcium-sensing receptor (CaSR)

Calcimimetics, which activate the extracellular calcium (Ca(o)(2+))-sensing receptor in the parathyroid and other tissues participating in Ca(o)(2+) homeostasis, were the first described allosteric activators of a G-protein-coupled receptor. Cinacalcet, the only calcimimetic currently approved for human use, is used clinically for treating secondary hyperparathyroidism (e.g., overactivity of parathyroid glands) in patients being dialyzed for chronic kidney disease. By sensitizing the parathyroids to Ca(o)(2+), cinacalcet lowers the circulating parathyroid hormone (PTH) level. It also reduces serum calcium and phosphate, changes increasing the percentage of patients achieving the guidelines recommended by the National Kidney Foundation (NKF) for these minerals. Studies are underway addressing whether better adherence to these guidelines in patients receiving cinacalcet reduces cardiovascular disease and related mortality, which are both common is the dialysis population. The second approved use of cinacalcet is for treating hypercalcemia in patients with inoperable parathyroid carcinoma. In this setting, it provides the first medical therapy chronically lowering serum calcium concentration in this condition, albeit not to normal in most patients. Its effect on the long-term prognosis of these patients, if any, is presently unclear. "Off-label" administration of cinacalcet [i.e., not yet approved by the US Food and Drug Administration (FDA)] effectively lowers serum calcium and/or PTH in various other forms of hyperparathyroidism and increases serum phosphate in renal phosphate-wasting syndromes by reducing PTH-induced phosphaturia. In the future, the drug could conceivably be utilized to modulate the activity of the CaSR in other tissues (i.e., kidney, colon) in therapeutically desirable ways.

Vasculotropic effects of calcimimetics

PURPOSE OF REVIEW

At all stages of chronic kidney disease (CKD) cardiovascular death is the most prominent cause of mortality. Current treatment options are still not completely satisfactory in this group of high cardiovascular risk patients. Experimental data and clinical observations suggest a role of secondary hyperparathyroidism, hyperphosphatemia, and hypercalcemia in the genesis of cardiovascular complications of CKD. The ubiquitous expression of the calcium-sensing receptor, which is targeted by calcimimetics and the pleiotropic effects of calcimimetics, make this class of drugs potential candidates for cardiovascular intervention.

RECENT FINDINGS

Recent experimental studies suggest that calcimimetics interfere with the development of vascular abnormalities in CKD and to some extent even reverse them. The effects of calcimimetics on the vasculature are, at least partially, independent of their effects on calcemia, phosphatemia, and parathyroid hormone concentration. The beneficial effects of calcimimetics on vascular calcification, arteriolar thickening, atherogenesis, and myocardial capillarization are well documented. In addition they have hypotensive and renoprotective actions.

SUMMARY

Experimental models suggest beneficial effects of calcimimetics on cardiovascular disease. Although prospective clinical data are still lacking, retrospective data suggest cardiovascular benefit of calcimimetics even in humans. Clinical trials with calcimimetics evaluating hard cardiovascular end-points would be desirable.

Physiology and pathophysiology of the calcium-sensing receptor in the kidney

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.

[Treatment of secondary hyperparathyroidism resistant to conventional therapy and tertiary hyperparathyroidism with Cinacalcet: an efficiency strategy]

INTRODUCTION

The treatment of secondary hyperparathyroidism (SHPT) in dialysis patients has changed with the introduction of cinacalcet (CC), which represents a medical alternative to surgical parathyroidectomy (PTX). The aim of our study is to prospectively assess the tolerance and efficacy of CC in patients, treated in one centre using long haemodialysis, with SHPT who do not respond to conventional therapy.

PATIENTS AND METHODS

We prospectively observed all patients treated with CC between September 2004 and 2009. The characteristics of the patients were compared with that recorded for the patients non treated with CC. Biological factors and the efficacy of the treatment in the patients were compared before (T-0) and after (T-End) CC therapy. The haemodialysis (HD) schedule was 3 x 5 to 3 x 8 h per week. The biological criteria for CC prescription were a serum PTH level greater than 300 pg/ml, calcium level greater than 2.45 mmol/l and bone alkaline phosphatase level greater than 20 microg/l or, in cases of tertiary hyperparathyroidism (THPT), a calcium level greater than 2.55 mmol/l.

RESULTS

Eighty-one (14.7%) among the 550 HD patients were treated with CC. As compared to the untreated population, these patients were younger and had higher body mass index (BMI) and higher protein-catabolic rate (nPCR). The treatment failed in 6.1% of the treated patients; 12.3% had severe gastrointestinal side effects and 10% underwent PTX. The treatment was successful in 81.4% patients who were prescribed a mean final CC dosage of 51+/-30 mg/day. Between T-0 and T-End (18+/-15) months), the serum PTH levels decreased by 77%, calcaemia levels decreased by 10% and phosphataemia levels decreased by 14%. Therefore, the percentage of patients with normal biological parameters increased significantly : serum PTH (150-300 pg/ml: 0 to 50%), calcaemia (2.1-2.37 mmol/l: 6 to 77%) and phosphataemia (1.15-1.78 mol/l: 58 to 84%). After 12 months, eight patients (10%) successfully weaned from CC therapy. No episodes of hypocalcaemia (<2.0 mmol/l) occurred. Treatments with alfacalcidol (68 to 40%) and sevelamer (72 to 50%) decreased, treatments with CaCO(3) remained stable (20%), those with native vitamin D increased (55 to 95%).

CONCLUSION

The treatment of HD patients having SHPT and THPT with CC and vitamin D derivatives was efficacious and well tolerated in a majority of cases after the failure of conventional therapies. These treatments improved mineral metabolism significantly.

Parathyroid hyperplasia of auto-transplanted tissue in forearm skin

Currently, the treatment of choice for refractory tertiary hyperparathyroidism is a total parathyroidectomy with autotransplantation of the parathyroid tissue into the forearm. Recurrent hyperparathyroidism after autotransplantation requiring surgical excision of the autograft is uncommon. We describe a female patient with recurrent hyperplasia who underwent an excision of her parathyroid autograft. The excisional specimen was submitted to pathology with the only provided history of a 'left arm mass'. The lack of clinical history led to a preliminary impression of an adnexal neoplasm by the primary pathologist.