Oral paricalcitol reduces the prevalence of posttransplant hyperparathyroidism: results of an open label randomized trial

Vitamin D3 Improves Adipose Stromal Cell Survival and Human Fat Graft Retention in Xenograft Model

Adipose stem cells are considered one of the primary drivers of autologous fat graft biologic activity and survival. We have previously demonstrated that hormonally active VD3 improved adipose stem cell viability in ex vivo and in vivo fat grafting models. In this study, we evaluated the inactive form of VD3 (cholecalciferol) on adipose stromal cell (ASC) phenotype during hypoxia and the subsequent effect on human fat graft retention in the xenograft model. Lipoaspirate collected from six human donors was used for ex-vivo particle culture studies and isolated ASC studies. Adipose particles were treated with increasing doses of VD3 to determine impact on ASC survival. Expanded stromal cells were treated with VD3 during hypoxic culture and assessed for viability, apoptosis, mitochondrial activity, and nitric oxide release via caspase, DAF-FM, or TMRM. Finally, forty Nu/J mice receiving bilateral dorsal human lipoaspirate were treated thrice weekly with 1) Vehicle control, 2) 50ng calcitriol, 3) 50ng VD3, 4) 500ng VD3, and 5) 5000ng VD3 for 12 weeks, n=8 per group. Graft weight, volume, and architecture were analyzed. Adipose particles treated with dose escalating VD3 had significantly increased ASC viability compared to control (p<0.01). Under hypoxia, ASCs treated with 1nM VD3 had significantly greater viability than untreated and pre-treated cells (p<0.01, p<0.01) and significantly lower apoptosis-to-viability ratio (p<0.01). ASCs pre-treated with 1nM VD3 had significantly lower nitric oxide release (p<0.05) and lower mitochondrial polarization (p<0.05) compared to controls. In vivo results showed mice receiving 5000ng VD3 had significantly greater graft weight (p<0.05) and volume (p<0.05) after 12 weeks of treatment compared to controls. Grafts had enhanced neovascularization, intact adipocyte architecture, and absence of oil cysts. VD3 is an over-the-counter nutritional supplement with a known safety profile in humans. Our xenograft model suggests administering VD3 at the time of surgery may significantly improve fat graft retention.

Post-Transplant Bone Disease in Kidney Transplant Recipients: Diagnosis and Management

Kidney transplantation is the preferred gold standard modality of treatment for kidney failure. Bone disease after kidney transplantation is highly prevalent in patients living with a kidney transplant and is associated with high rates of hip fractures. Fractures are associated with increased healthcare costs, morbidity and mortality. Post-transplant bone disease (PTBD) includes renal osteodystrophy, osteoporosis, osteonecrosis and bone fractures. PTBD is complex as it encompasses pre-existing chronic kidney disease-mineral bone disease and compounding factors after transplantation, including the use of immunosuppression and the development of de novo bone disease. After transplantation, the persistence of secondary and tertiary hyperparathyroidism, renal osteodystrophy, relative vitamin D deficiency and high levels of fibroblast growth factor-23 contribute to post-transplant bone disease. Risk assessment includes identifying both general risk factors and kidney-specific risk factors. Diagnosis is complex as the gold standard bone biopsy with double-tetracycline labelling to diagnose the PTBD subtype is not always readily available. Therefore, alternative diagnostic tools may be used to aid its diagnosis. Both non-pharmacological and pharmacological therapy can be employed to treat PTBD. In this review, we will discuss pathophysiology, risk assessment, diagnosis and management strategies to manage PTBD after kidney transplantation.

Parathyroidectomy and Cinacalcet Use in Medicare-Insured Kidney Transplant Recipients

RATIONALE & OBJECTIVE

Posttransplant hyperparathyroidism is common, and treatment practices are poorly characterized. The goal of this study was to examine the incidence, associations, and outcomes of posttransplant parathyroidectomy and calcimimetic use in a cohort of Medicare-insured US kidney transplant recipients.

STUDY DESIGN

Retrospective observational cohort study.

SETTING & PARTICIPANTS

We used the US Renal Data System to extract demographic, clinical, and prescription data from Medicare Parts A, B, and D-insured patients who received their first kidney transplant in 2007-2013. We excluded patients with pretransplant parathyroidectomy.

PREDICTORS

Calendar year of transplantation and pretransplant patient characteristics.

OUTCOME

(1) Incidence of and secular trends in parathyroidectomy and cinacalcet use in the 3 years after transplant; (2) 90-day outcomes after posttransplant parathyroidectomy and cinacalcet initiation.

ANALYTICAL APPROACH

Temporal trends and pretransplant correlates of parathyroidectomy and cinacalcet use were assessed using proportional hazards models and multivariable Poisson regression, respectively.

RESULTS

The inclusion criteria were met by 30,127 patients, of whom 10,707 used cinacalcet before transplant, 551 underwent posttransplant parathyroidectomy, and 5,413 filled≥1 prescription for cinacalcet. The rate of posttransplant parathyroidectomy was stable over time. By contrast, cinacalcet use increased during the period studied. Long dialysis vintage and pretransplant cinacalcet use were strongly associated with posttransplant parathyroidectomy and cinacalcet use. Roughly 1 in 4 patients were hospitalized within 90 days of posttransplant parathyroidectomy, with hypocalcemia-related diagnoses being the most common complication. Parathyroidectomy (vs cinacalcet initiation) was not associated with an increase in acute kidney injury.

LIMITATIONS

We lacked access to laboratory data to help assess the severity of secondary/tertiary hyperparathyroidism. The cohort was limited to Medicare beneficiaries.

CONCLUSIONS

Almost one-fifth of our study cohort was treated with parathyroidectomy and/or cinacalcet. Further studies are needed to establish the optimal treatment for posttransplant hyperparathyroidism.

Persistent hyperparathyroidism in long-term kidney transplantation: time to consider a less aggressive approach

PURPOSE OF REVIEW

Persistent hyperparathyroidism affects 50% of long-term kidney transplants with preserved allograft function. Timing, options and the optimal target for treatment remain unclear. Clinical practice guidelines recommend the same therapeutic approach as patients with chronic kidney disease.

RECENT FINDINGS

Mild to moderate elevation of parathyroid hormone (PTH) levels in long-term kidney transplants may not be associated with bone loss and fracture. Recent findings on bone biopsy revealed the lack of association between hypercalcaemic hyperparathyroidism with pathology of high bone turnover. Elevated PTH levels may be required to maintain normal bone volume. Nevertheless, several large observational studies have revealed the association between hypercalcemia and the elevation of PTH levels with unfavourable allograft and patient outcomes. Both calcimimetics and parathyroidectomy are effective in lowering serum calcium and PTH. A recent meta-analysis suggested parathyroidectomy may be performed safely after kidney transplantation without deterioration of allograft function.

SUMMARY

Treatment of persistent hyperparathyroidism is warranted in kidney transplants with hypercalcemia and markedly elevated PTH levels. A less aggressive approach should be applied to those with mild to moderate elevation. Whether treatments improve outcomes remain to be elucidated.

Systematic Review of the Treatment of Persistent Hyperparathyroidism Following Kidney Transplantation

Chronic kidney disease-mineral and bone disorder is one of the complications associated with chronic kidney disease. About 10-50% of patients following kidney transplantation have persistent hyperparathyroidism. Hypercalcaemic hyperparathyroidism has a negative impact on the kidney transplant outcome; therefore, it requires treatment. The data regarding the treatment of persistent hyperparathyroidism provided in scientific publications are divergent and contradictory. Therefore, the aim of our systematic review was to evaluate the efficacy of persistent hyperparathyroidism treatment in patients following kidney transplantation. The Cochrane, PubMed, and Scopus databases were browsed independently by two authors. The search strategy included controlled vocabulary and keywords. The effectiveness of calcitriol, paricalcitol, cinacalcet, and parathyroidectomy was compared and analysed. The mean calcium and parathormone (PTH) concentrations per patient in the group of paricalcitol increased by 1.27% and decreased by 35.14% (n = 248); in the group of cinacalcet decreased by 12.09% and 32.16% (n = 368); and in the group of parathyroidectomy decreased by 19.06% and 86.49% (n = 15) at the end of the study compared to the baseline (n = 244, n = 342 and n = 15), respectively. Paricalcitol, cinacalcet, and parathyroidectomy decreased the intact PTH level. Cinacalcet and parathyroidectomy lowered calcium levels in renal transplant patients with hypercalcaemia. Conversely, paricalcitol increased the serum calcium concentration. Cinacalcet seems to be a good candidate in the treatment of post-transplant hyperparathyroidism.

Bone and Mineral Disorder in Renal Transplant Patients: Overview of Pathology, Clinical, and Therapeutic Aspects

Renal transplantation (RTx) allows us to obtain the resolution of the uremic status but is not frequently able to solve all the metabolic complications present during end-stage renal disease. Mineral and bone disorders (MBDs) are frequent since the early stages of chronic kidney disease (CKD) and strongly influence the morbidity and mortality of patients with CKD. Some mineral metabolism (MM) alterations can persist in patients with RTx (RTx-p), as well as in the presence of complete renal function recovery. In those patients, anomalies of calcium, phosphorus, parathormone, fibroblast growth factor 23, and vitamin D such as bone and vessels are frequent and related to both pre-RTx and post-RTx specific factors. Many treatments are present for the management of post-RTx MBD. Despite that, the guidelines that can give clear directives in MBD treatment of RTx-p are still missed. For the future, to obtain an ever-greater individualisation of therapy, an increase of the evidence, the specificity of international guidelines, and more uniform management of these anomalies worldwide should be expected. In this review, the major factors related to post-renal transplant MBD (post-RTx-MBD), the main mineral metabolism biochemical anomalies, and the principal treatment for post-RTx MBD will be reported.

Bone and Mineral Disease in Kidney Transplant Recipients

After kidney transplantation, mineral and bone disorders are associated with higher risk of fractures and consequent morbidity and mortality. Disorders of calcium and phosphorus, vitamin D deficiency, and hyperparathyroidism are also common. The epidemiology of bone disease has evolved over the past several decades due to changes in immunosuppressive regimens, mainly glucocorticoid minimization or avoidance. The assessment of bone disease in kidney transplant recipients relies on risk factor recognition and bone mineral density assessment. Several drugs have been trialed for the treatment of post-transplant mineral and bone disorders. This review will focus on the epidemiology, effect, and treatment of metabolic and skeletal derangements in the transplant recipient.

The effect of cholecalciferol supplementation on allograft function in incident kidney transplant recipients: A randomized controlled study

It is unknown whether cholecalciferol supplementation improves allograft outcomes in kidney transplant recipients (KTRs). We conducted a single-center randomized, double-blind, placebo-controlled trial of daily 4000 IU cholecalciferol supplementation in KTRs at 1-month posttransplant. The primary endpoint was the change in eGFR from baseline to 12-month posttransplant. Secondary endpoints included severity of interstitial fibrosis and tubular atrophy (IFTA) at 12-month posttransplant and changes in urinary biomarkers. Of 193 randomized patients, 180 participants completed the study. Changes in eGFR were 1.2 mL/min/1.73 m² (95% CI; -0.7 to 3.1) in the cholecalciferol group and 1.8 mL/min/1.73 m² (95% CI, -0.02 to 3.7) in the placebo group, with no significant between-group difference (-0.7 mL/min/1.73 m² [95% CI; -3.3 to 2.0], p = 0.63). Subgroup analyses showed detrimental effects of cholecalciferol in patients with eGFR <45 mL/min/1.73 m² (P_interaction <0.05, between-group difference; -4.3 mL/min/1.73 m² [95% CI; -7.3 to -1.3]). The degree of IFTA, changes in urine albumin-to-creatinine ratio, or adverse events including hypercalcemia and infections requiring hospitalization did not differ between groups. In conclusion, cholecalciferol supplementation did not affect eGFR change compared to placebo among incident KTRs. These findings do not support cholecalciferol supplementation for improving allograft function in incident KTRs. Clinical trial registry: This study was registered in the University Hospital Medical Information Network Clinical Trials Registry (UMIN-CTR) as UMIN000020597 (please refer to the links below). UMIN-CTR: https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000023776.

Exploring the potential effect of paricalcitol on markers of inflammation in de novo renal transplant recipients

Following a successful renal transplantation circulating markers of inflammation may remain elevated, and systemic inflammation is associated with worse clinical outcome in renal transplant recipients (RTRs). Vitamin D-receptor (VDR) activation is postulated to modulate inflammation and endothelial function. We aimed to explore if a synthetic vitamin D, paricalcitol, could influence systemic inflammation and immune activation in RTRs. Newly transplanted RTRs were included in an open-label randomized controlled trial on the effect of paricalcitol on top of standard care over the first post-transplant year. Fourteen pre-defined circulating biomarkers reflecting leukocyte activation, endothelial activation, fibrosis and general inflammatory burden were analyzed in 74 RTRs at 8 weeks (baseline) and 1 year post-engraftment. Mean changes in plasma biomarker concentrations were compared by t-test. The expression of genes coding for the same biomarkers were investigated in 1-year surveillance graft biopsies (n = 60). In patients treated with paricalcitol circulating osteoprotegerin levels increased by 0.19 ng/ml, compared with a 0.05 ng/ml increase in controls (p = 0.030). In graft tissue, a 21% higher median gene expression level of TNFRSF11B coding for osteoprotegerin was found in paricalcitol-treated patients compared with controls (p = 0.026). Paricalcitol treatment did not significantly affect the blood- or tissue levels of any other investigated inflammatory marker. In RTRs, paricalcitol treatment might increase both circulating and tissue levels of osteoprotegerin, a modulator of calcification, but potential anti-inflammatory treatment effects in RTRs are likely very modest. [NCT01694160 (2012/107D)]; [www.clinicaltrials.gov].

Risk Factors and Management of Osteoporosis Post-Transplant

Bone and mineral disorders are common after organ transplantation. Osteoporosis post transplantation is associated with increased morbidity and mortality. Pathogenesis of bone disorders in this particular sub set of the population is complicated by multiple co-existing factors like preexisting bone disease, Vitamin D deficiency and parathyroid dysfunction. Risk factors include post-transplant immobilization, steroid usage, diabetes mellitus, low body mass index, older age, female sex, smoking, alcohol consumption and a sedentary lifestyle. Immunosuppressive medications post-transplant have a negative impact on outcomes, and further aggravate osteoporotic risk. Management is complex and challenging due to the sub-optimal sensitivity and specificity of non-invasive diagnostic tests, and the underutilization of bone biopsy. In this review, we summarize the prevalence, pathophysiology, diagnostic tests and management of osteoporosis in solid organ and hematopoietic stem cell transplant recipients.

Interventions for preventing bone disease in kidney transplant recipients

BACKGROUND

People who have chronic kidney disease (CKD) have important changes to bone structure, strength, and metabolism. Children experience bone deformity, pain, and delayed or impaired growth. Adults experience limb and vertebral fractures, avascular necrosis, and pain. The fracture risk after kidney transplantation is four times that of the general population and is related to Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD) occurring with end-stage kidney failure, steroid-induced bone loss, and persistent hyperparathyroidism after transplantation. Fractures may reduce quality of life and lead to being unable to work or contribute to community roles and responsibilities. Earlier versions of this review have found low certainty evidence for effects of treatment. This is an update of a review first published in 2005 and updated in 2007.

OBJECTIVES

This review update evaluates the benefits and harms of interventions for preventing bone disease following kidney transplantation.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 16 May 2019 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

RCTs and quasi-RCTs evaluating treatments for bone disease among kidney transplant recipients of any age were eligible.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial risks of bias and extracted data. Statistical analyses were performed using random effects meta-analysis. The risk estimates were expressed as a risk ratio (RR) for dichotomous variables and mean difference (MD) for continuous outcomes together with the corresponding 95% confidence interval (CI). The primary efficacy outcome was bone fracture. The primary safety outcome was acute graft rejection. Secondary outcomes included death (all cause and cardiovascular), myocardial infarction, stroke, musculoskeletal disorders (e.g. skeletal deformity, bone pain), graft loss, nausea, hyper- or hypocalcaemia, kidney function, serum parathyroid hormone (PTH), and bone mineral density (BMD).

MAIN RESULTS

In this 2019 update, 65 studies (involving 3598 participants) were eligible; 45 studies contributed data to our meta-analyses (2698 participants). Treatments included bisphosphonates, vitamin D compounds, teriparatide, denosumab, cinacalcet, parathyroidectomy, and calcitonin. Median duration of follow-up was 12 months. Forty-three studies evaluated bone density or bone-related biomarkers, with more recent studies evaluating proteinuria and hyperparathyroidism. Bisphosphonate therapy was usually commenced in the perioperative transplantation period (within 3 weeks) and regardless of BMD. Risks of bias were generally high or unclear leading to lower certainty in the results. A single study reported outcomes among 60 children and adolescents. Studies were not designed to measure treatment effects on fracture, death or cardiovascular outcomes, or graft loss.Compared to placebo, bisphosphonate therapy administered over 12 months in transplant recipients may prevent fracture (RR 0.62, 95% CI 0.38 to 1.01; low certainty evidence) although the 95% CI included the possibility that bisphosphonate therapy might make little or no difference. Fracture events were principally vertebral fractures identified during routine radiographic surveillance. It was uncertain whether any other drug class decreased fracture (low or very low certainty evidence). It was uncertain whether interventions for bone disease in kidney transplantation reduce all-cause or cardiovascular death, myocardial infarction or stroke, or graft loss in very low certainty evidence. Bisphosphonate therapy may decrease acute graft rejection (RR 0.70, 95% CI 0.55 to 0.89; low certainty evidence), while it is uncertain whether any other treatment impacts graft rejection (very low certainty evidence). Bisphosphonate therapy may reduce bone pain (RR 0.20, 95% CI 0.04 to 0.93; very low certainty evidence), while it was very uncertain whether bisphosphonates prevent spinal deformity or avascular bone necrosis (very low certainty evidence). Bisphosphonates may increase to risk of hypocalcaemia (RR 5.59, 95% CI 1.00 to 31.06; low certainty evidence). It was uncertain whether vitamin D compounds had any effect on skeletal, cardiovascular, death, or transplant function outcomes (very low certainty or absence of evidence). Evidence for the benefits and harms of all other treatments was of very low certainty. Evidence for children and young adolescents was sparse.

AUTHORS' CONCLUSIONS

Bisphosphonate therapy may reduce fracture and bone pain after kidney transplantation, however low certainty in the evidence indicates it is possible that treatment may make little or no difference. It is uncertain whether bisphosphonate therapy or other bone treatments prevent other skeletal complications after kidney transplantation, including spinal deformity or avascular bone necrosis. The effects of bone treatment for children and adolescents after kidney transplantation are very uncertain.

Management of Post-transplant Hyperparathyroidism and Bone Disease

Significant advances in immunosuppressive therapies have been made in renal transplantation, leading to increased allograft and patient survival. Despite improvement in overall patient survival, patients continue to require management of persistent post-transplant hyperparathyroidism. Medications that treat persistent hyperparathyroidism include vitamin D, vitamin D analogues, and calcimimetics. Medication side effects such as hypocalcemia or hypercalcemia, and adynamic bone disease, may lead to a decrease in the drugs. When medical management fails to control persistent post-transplant hyperparathyroidism, treatment is a parathyroidectomy. Surgical techniques are not uniform between centers and surgeons. Undergoing the surgery may include a subtotal technique or a technique including total parathyroid gland resection with partial heterotopic gland reimplantation. In addition, there are possible post-surgical complications. The ideal treatment for persistent post-transplant hyperparathyroidism is the treatment and prevention of the condition while patients are being managed for their late-stage chronic kidney disease and end-stage renal disease.

Mineral and Bone Disease in Kidney Transplant Recipients

PURPOSE OF REVIEW

Despite metabolic improvements following kidney transplantation, transplant recipients still often suffer from complex mineral and bone disease after transplantation.

RECENT FINDINGS

The pathophysiology of post-transplant disease is unique, secondary to underlying pre-transplant mineral and bone disease, immunosuppression, and changing kidney function. Changes in modern immunosuppression regimens continue to alter the clinical picture. Modern management includes reducing cumulative steroid exposure and correcting the biochemical abnormalities in mineral metabolism. While bone mineral density screening appears to help predict fracture risk and anti-osteoporotic therapy appears to have a positive effect on bone mineral density, more data regarding specific treatment is necessary. Patients with mineral and bone disease after kidney transplantation require special care in order to properly manage and mitigate their mineral and bone disease. Recent changes in clinical management of transplant patients may also be changing the implications on patients' mineral and bone disease.

Paricalcitol supplementation during the first year after kidney transplantation does not affect calcification propensity score

Background

Cardiovascular complications are common in kidney transplant patients and calcification propensity of blood, measured as T₅₀, is associated with cardiovascular outcomes. Paricalcitol supplementation affects calcium/phosphate homeostasis and may affect calcification propensity. To assess this hypothesis we measured T₅₀ in kidney transplant recipients participating in a randomized study comparing paricalcitol versus no treatment during the first year after kidney transplantation.

Methods

Stored serum samples from 76 kidney transplant recipients (paricalcitol n = 37, no treatment n = 39) were analyzed. Analyses were performed at inclusion (8 weeks after transplantation) and repeated one year after transplantation.

Results

There were no statistically significant differences in T₅₀ between the paricalcitol and placebo groups, neither at baseline (p = 0.56) nor at 1 year (p = 0.61). Also, there were no significant changes in T₅₀ over time in either group or when pooling all data (p <  0.20). In multivariate regression analysis, out of 16 potentially relevant covariates, comprising clinical and biochemical parameters, only plasma PTH and T₅₀ at baseline were significantly correlated to T₅₀ after one year. (p <  0.03 and p < 0.01, respectively).

Conclusions

Calcium propensity measured as T₅₀ score remained unchanged with paricalcitol treatment in kidney transplant recipients, and was not changed over time during the study period of one year.

Trial registration

ClinicalTrials.gov, NCT01694160, registered 23 September 2012.

Paricalcitol versus placebo for reduction of proteinuria in kidney transplant recipients: a double-blind, randomized controlled trial

Proteinuria after kidney transplantation is accompanied by an increased risk of graft failure. In this single-center, placebo-controlled, double-blind trial we studied whether vitamin D receptor activator paricalcitol might reduce proteinuria. Patients with urinary protein-to-creatinine ratio (UPCR) ≥20 mg/mmol despite optimization of the renin angiotensin aldosterone system (RAAS) blockade were randomly assigned to receive 24 weeks' treatment with 2 μg/day paricalcitol or placebo. Primary endpoint was change in UPCR, and main secondary endpoints were change in urinary albumin-to-creatinine ratio (UACR) and 24-h proteinuria. Analysis was by intention to treat. One hundred and sixty-eight patients undergo randomization, and 83 were allocated to paricalcitol, and 85 to placebo. Compared with baseline, UPCR declined in the paricalcitol group (-39%, 95% CI -45 to -31) but not in the placebo group (21%, 95% CI 9 to 35), with a between group difference of -49% (95% CI -57 to -41; P < 0.001). UACR and 24-h proteinuria decreased only on paricalcitol therapy and significantly differed between groups at end-of-treatment (P < 0.001). Paricalcitol was well tolerated but incidence of mild hypercalcemia was higher than in placebo. In conclusion, addition of 2 μg/day paricalcitol lowers residual proteinuria in kidney transplant recipients. Long-term studies are needed to determine if the reduction in proteinuria improves transplant outcomes (ClinicalTrials.gov, number NCT01436747).

Paricalcitol Versus Calcifediol for Treating Hyperparathyroidism in Kidney Transplant Recipients

INTRODUCTION

Secondary hyperparathyroidism (SHPT) and vitamin D deficiency are common at kidney transplantation and are associated with some early and late complications. This study was designed to evaluate whether paricalcitol was more effective than nutritional vitamin D for controlling SHPT in de novo kidney allograft recipients.

METHODS

This was a 6-month, investigator-initiated, multicenter, open-label, randomized clinical trial. Patients with pretransplantation iPTH between 250 and 600 pg/ml and calcium <10 mg/dl were randomized to paricalcitol (PAR) or calcifediol (CAL). The intention-to-treat population (PAR: n = 46; CAL: n = 47) was used for the analysis. The primary endpoint was the percentage of patients with serum iPTH >110 pg/ml at 6 months. Secondary endpoints were bone mineral metabolism, renal function, and allograft protocol biopsies.

RESULTS

The primary outcome occurred in 19.6% of patients in the PAR group and 36.2% of patients in the CAL group (P = 0.07). However, there was a higher percentage of patients with iPTH <70 pg/ml in the PAR group than in the CAL group (63.4% vs. 37.2%; P = 0.03). No differences were observed in bone turnover biomarkers and bone mineral density. The estimated glomerular filtration rate was significantly higher in the CAL group than in the PAR group without differences in albuminuria. In protocol biopsies, interstitial fibrosis and tubular atrophy tended to be higher in the PAR group than in the CAL group (48% vs. 23.8%; P = 0.09). Both medications were well tolerated.

CONCLUSION

Both PAR and CAL reduced iPTH, but PAR was associated with a higher proportion of patients with iPTH <70 pg/ml. These results do not support the use of PAR to treat posttransplantation hyperparathyroidism.

Current evidence on vitamin D deficiency and kidney transplant: What's new?

Kidney transplant is the treatment of choice for end-stage chronic kidney disease. Kidneys generate 1,25-dihydroxyvitamin D (calcitriol) from 25-hydroxyvitamin D (calcidiol) for circulation in the blood to regulate calcium levels. Transplant patients with low calcidiol levels have an increased risk of metabolic and endocrine problems, cardiovascular disease, type 2 diabetes mellitus, poor graft survival, bone disorders, cancer, and mortality rate. The recommended calcidiol level after transplant is at least 30 ng/mL (75 nmol/L), which could require 1000-3000 IU/d vitamin D3 to achieve. Vitamin D3 supplementation studies have found improved endothelial function and acute rejection episodes. However, since kidney function may still be impaired, raising calcidiol levels may not lead to normal calcitriol levels. Thus, supplementation with calcitriol or an analog, alfacalcidiol, is often employed. Some beneficial effects found include possible improved bone health and reduced risk of chronic allograft nephropathy and cancer.

Effects of paricalcitol on cardiovascular outcomes and renal function in patients with chronic kidney disease : A meta-analysis

BACKGROUND

Paricalcitol, a selective activator of the vitamin D receptor (VDR), influences calcium and phosphorus homeostasis and bone metabolism. Whether paricalcitol reduces cardiovascular risk and protects renal function remains unclear. To systematically evaluate this in patients with chronic kidney disease (CKD), we conducted a meta-analysis of published randomized controlled trials (RCTs).

METHODS

We searched MEDLINE, Embase, the Cochrane Library, and reference lists for RCTs comparing paricalcitol with placebo in stage 2-5 CKD (including pre-dialysis and renal replacement patients). The Cochrane quality assessment method was used to evaluate study quality. Results were summarized as risk ratios (RRs) for dichotomous outcomes or mean differences (MD) for continuous outcomes.

RESULTS

We included 21 studies comprising 1894 patients. Compared to placebo, paricalcitol reduced the risk of cardiovascular events (RR 0.55; 95% CI 0.35-0.87; p = 0.01), but the RR of hypercalcemia associated with paricalcitol was 6.50 (95% CI 3.21-13.15; p < 0.00001). Paricalcitol cannot significantly change systolic blood pressure and cardiac structure. Although proteinuria reduction was achieved more frequently with paricalcitol (RR 1.51; 95% CI 1.25-1.82; p < 0.0001), it did not significantly reduce proteinuria level compared to placebo. Paricalcitol could not protect renal function to delay CKD progression, since it reduced the glomerular filtration rate (MD -3.15; 95% CI -4.35--1.96; p < 0.0001) and elevated serum creatinine (MD 0.93; 95% CI 0.10-0.68; p = 0.008).

CONCLUSION

Paricalcitol reduces the risk of cardiovascular events in CKD patients but increases the risk of hypercalcemia and cannot improve cardiac structure. Meanwhile, it cannot significantly reduce proteinuria level or protect renal function.

Anti-inflammatory profile of paricalcitol in kidney transplant recipients

BACKGROUND AND OBJECTIVES

Paricalcitol, a selective vitamin D receptor activator, is used to treat secondary hyperparathyroidism in kidney transplant patients. Experimental and clinical studies in non-transplant kidney disease patients have found this molecule to have anti-inflammatory properties. In this exploratory study, we evaluated the anti-inflammatory profile of paricalcitol in kidney-transplant recipients.

METHODS

Thirty one kidney transplant recipients with secondary hyperparathyroidism completed 3 months of treatment with oral paricalcitol (1μg/day). Serum concentrations and gene expression levels of inflammatory cytokines in peripheral blood mononuclear cells were analysed at the beginning and end of the study.

RESULTS

Paricalcitol significantly decreased parathyroid hormone levels with no changes in calcium and phosphorous. It also reduced serum concentrations of interleukin (IL)-6 and tumour necrosis factor-alpha (TNF-α) by 29% (P<0.05) and 9.5% (P<0.05) compared to baseline, respectively. Furthermore, gene expression levels of IL-6 and TNF-α in peripheral blood mononuclear cells decreased by 14.1% (P<0.001) and 34.1% (P<0.001), respectively. The ratios between pro-inflammatory cytokines (TNF-α and IL-6) and anti-inflammatory cytokines (IL-10), both regarding serum concentrations and gene expression, also experienced a significant reduction.

CONCLUSIONS

Paricalcitol administration to kidney transplant recipients has been found to have beneficial effects on inflammation, which may be associated with potential clinical benefits.

Early introduction of oral paricalcitol in renal transplant recipients. An open-label randomized study

In stable renal transplant recipients with hyperparathyroidism, previous studies have indicated that vitamin D agonist treatment might have anti-proteinuric effects. Animal studies indicate possible anti-fibrotic and anti-inflammatory effects. Early introduction of paricalcitol in de novo renal transplant recipients might reduce proteinuria and prevent progressive allograft fibrosis. We performed a single-center, prospective, randomized, open-label trial investigating effects of paricalcitol 2 μg/day added to standard care. Participants were included 8 weeks after engraftment and followed for 44 weeks. Primary end point was change in spot urine albumin/creatinine ratio. Exploratory microarray analyses of kidney biopsies at study end investigated potential effects on gene expression. Secondary end points included change in glomerular filtration rate (GFR), pulse wave velocity (PWV), and endothelial function measured by peripheral arterial tonometry as reactive hyperemia index (RHI). Seventy-seven de novo transplanted kidney allograft recipients were included, 37 receiving paricalcitol. Paricalcitol treatment lowered PTH levels (P = 0.01) but did not significantly reduce albuminuria (P = 0.76), change vascular parameters (PWV; P = 0.98, RHI; P = 0.33), or influence GFR (P = 0.57). Allograft gene expression was not influenced. To summarize, in newly transplanted renal allograft recipients, paricalcitol reduced PTH and was well tolerated without negatively affecting kidney function. Paricalcitol did not significantly reduce/prevent albuminuria, improve parameters of vascular health, or influence allograft gene expression.

Effect of Paricalcitol on FGF-23 and Klotho in Kidney Transplant Recipients

BACKGROUND

Paricalcitol decreases intact parathyroid hormone and the frequency of secondary hyperparathyroidism after kidney transplantation. This proof-of-concept study aimed to assess the effect of paricalcitol on fibroblast growth factor-23/KLOTHO axis in renal transplants.

METHODS

Twenty-nine subjects with secondary hyperparathyroidism received oral paricalcitol 1 μg/d for 3 months, and 8 patients matched by age, sex, and creatinine clearance, but with intact parathyroid hormone less than 100 pg/mL, were included as controls.

RESULTS

Intact parathyroid hormone decreased in paricalcitol-treated patients (P < 0.0001). Serum fibroblast growth factor-23 enhanced (P < 0.01), whereas KLOTHO concentrations showed a trend to increase (P = 0.067). KLOTHO gene expression in peripheral blood mononuclear cells increased by 45.7% in paricalcitol-treated patients (P < 0.01), without change in controls. Paricalcitol administration resulted in a median percent decrease of 56% in methylated DNA levels of KLOTHO promoter (P < 0.001). The ratio of the unmethylated/methylated KLOTHO promoter DNA did not change in controls, but it increased by 177% in paricalcitol-treated subjects (P < 0.0001). The increase in this ratio was independently associated with the change in serum KLOTHO (r = 0.55, P < 0.01) and messenger RNA expression levels (r = 0.40, P < 0.05).

CONCLUSIONS

Paricalcitol administration to renal transplant patients significantly reduced intact parathyroid hormone and increased fibroblast growth factor-23, with a trend to increase in serum KLOTHO. Paricalcitol-treated patients showed a decrease in the methylation of the KLOTHO promoter with an increment in the ratio of un-methyated/methylated DNA, which was associated with an increase of KLOTHO gene expression levels and serum KLOTHO concentrations. Long-term studies are needed to assess whether paricalcitol-induced increase in KLOTHO gene expression and serum concentrations may translate into beneficial clinical effects.

CYP3A4 is a crosslink between vitamin D and calcineurin inhibitors in solid organ transplant recipients: implications for bone health

The use of calcineurin inhibitors (CNIs) and vitamin D deficiency may contribute to the pathogenesis of post-transplant bone disease. CNIs and 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) are substrates of the drug-metabolizing enzyme CYP3A4. This review summarizes the indications for the use of activated vitamin D analogs in post-transplant care and the current knowledge on the impact of CNIs on bone. We searched for clinical evidence of the interaction between CNIs and 1,25(OH)₂D₃. We also provide an overview of the literature on the interplay between vitamin D metabolism and CYP3A4 in experimental and clinical settings and discuss its possible implications for solid organ transplant recipients. In conclusion, there is a body of evidence on the interplay between vitamin D and the drug-metabolizing enzyme CYP3A4, which may have therapeutic implications.

Secondary Hyperparthyroidism: Pathogenesis, Diagnosis, Preventive and Therapeutic Strategies

Uremic secondary hyperparathyroidism is a multifactorial and complex disease often present in advanced stages of chronic kidney disease. The accumulation of phosphate, the increased FGF23 levels, the reduction in active vitamin D production, and the tendency to hypocalcemia are persistent stimuli for the development and progression of parathyroid hyperplasia with increased secretion of PTH. Parathyroid proliferation may become nodular mainly in cases of advanced hyperparathyroidism. The alterations in the regulation of mineral metabolism, the development of bone disease and extraosseous calcifications are essential components of chronic kidney disease-mineral and bone disorder and have been associated with negative outcomes. The management of hyperparathyroidism includes the correction of vitamin D deficiency and control of serum phosphorus and PTH without inducing hypercalcemia. An update of the leading therapeutic tools available for the prevention and clinical management of secondary hyperparathyroidism, its diagnosis, and the main mechanisms and factors involved in the pathogenesis of the disease will be described in this review.

Impact of seasonality on the dynamics of native Vitamin D repletion in long-term renal transplant patients

Background: Renal transplant recipients (RTRs) are often Vitamin D (VitD) depleted as a result of both chronic kidney disease and mandated sun avoidance behaviours. Repleting VitD may be warranted, but how, and for how long, is unknown, as is the impact of seasonality on the success of repletion. We investigated the impact of seasonality on VitD status following VitD repletion in a large cohort of stable, long-term RTRs.

Methods: Serum 25-hydroxyvitamin D [25(OH)D] concentrations and bone biochemistry parameters were analysed from 102 VitD repletion courses in 98 RTRs that had undergone VitD repletion. Repletion was delivered over 6 months with either 240 000 IU colecalciferol if pre-repletion serum VitD was between 20 and 50 nmol/L, or with 360 000 IU if VitD was <20 nmol/L. Twelve months post-repletion 25(OH)D and parathyroid hormone (PTH) were available for 75 patients.

Results: At baseline, 25(OH)D was 20.1 ± 1.0 nmol/L, increasing to 65.4 ± 1.8 nmol/L following repletion (+7.55 nmol/L/month, P < 0.0001). Twelve months post-repletion and after no further VitD administration, 25(OH)D fell to 35.4 ± 1.8 nmol/L (14.2 ± 0.7 ng/mL; −2.50 nmol/L/month, P < 0.0001). PTH followed the opposite trend with baseline, repletion-end and post-repletion values being 144.2 ± 12.0, 109.6 ± 7.5 and 129.2 ± 11.4 ng/L, respectively. VitD repletion during the summer was associated with significantly higher at repletion-end 25(OH)D compared with any other time of year [summer 80.9 ± 4.0, autumn 64.1 ± 3.0 (P = 0.002), winter 48.9 ± 3.0 (P <0.001), spring 63.8 ± 2.5 nmol/L (P <0.001)]. There was no hypercalcaemia during repletion and renal transplant function remained stable without any evidence of allograft rejection.

Conclusions: VitD repletion can safely and effectively be achieved in the majority of chronic stable RTRs using a 6-month bolus intermediate-dose schedule. Winter repletion is associated with an inadequate response in 25(OH)D; however, all patients experience a post-repletion fall towards deficiency in the absence of maintenance supplementation, irrespective of the season of repletion.

Bone Disease after Kidney Transplantation

Bone and mineral disorders occur frequently in kidney transplant recipients and are associated with a high risk of fracture, morbidity, and mortality. There is a broad spectrum of often overlapping bone diseases seen after transplantation, including osteoporosis as well as persisting high- or low-turnover bone disease. The pathophysiology underlying bone disorders after transplantation results from a complex interplay of factors, including preexisting renal osteodystrophy and bone loss related to a variety of causes, such as immunosuppression and alterations in the parathyroid hormone-vitamin D-fibroblast growth factor 23 axis as well as changes in mineral metabolism. Management is complex, because noninvasive tools, such as imaging and bone biomarkers, do not have sufficient sensitivity and specificity to detect these abnormalities in bone structure and function, whereas bone biopsy is not a widely available diagnostic tool. In this review, we focus on recent data that highlight improvements in our understanding of the prevalence, pathophysiology, and diagnostic and therapeutic strategies of mineral and bone disorders in kidney transplant recipients.

Effect of Twice-Yearly Denosumab on Prevention of Bone Mineral Density Loss in De Novo Kidney Transplant Recipients: A Randomized Controlled Trial

We conducted an open-label, prospective, randomized trial to assess the efficacy and safety of RANKL inhibition with denosumab to prevent the loss of bone mineral density (BMD) in the first year after kidney transplantation. Ninety kidney transplant recipients were randomized 1:1 2 weeks after surgery to receive denosumab (60 mg at baseline and 6 months) or no treatment. After 12 months, total lumbar spine areal BMD (aBMD) increased by 4.6% (95% confidence interval [CI] 3.3-5.9%) in 46 patients in the denosumab group and decreased by -0.5% (95% CI -1.8% to 0.9%) in 44 patients in the control group (between-group difference 5.1% [95% CI 3.1-7.0%], p < 0.0001). Denosumab also increased aBMD at the total hip by 1.9% (95% CI, 0.1-3.7%; p = 0.035) over that in the control group at 12 months. High-resolution peripheral quantitative computed tomography in a subgroup of 24 patients showed that denosumab increased volumetric BMD at the distal tibia and radius (all p < 0.05). Biomarkers of bone turnover (C-terminal telopeptide of type I collagen, procollagen type I N-terminal propeptide) markedly decreased with denosumab (all p < 0.0001). Episodes of cystitis and asymptomatic hypocalcemia occurred more often with denosumab, whereas graft function, rate of rejections, and incidence of opportunistic infections were similar. In conclusion, denosumab increased BMD in the first year after kidney transplantation but was associated with more frequent episodes of urinary tract infection.

Mineral metabolism disorders, vertebral fractures and aortic calcifications in stable kidney transplant recipients: The role of gender (EMITRAL study)

BACKGROUND AND OBJECTIVES

The relationship between mineral metabolism disorders, bone fractures and vascular calcifications in kidney transplant recipients has not been established.

METHOD

We performed a cross-sectional study in 727 stable recipients from 28 Spanish transplant clinics. Mineral metabolism parameters, the semi-quantification of vertebral fractures and abdominal aortic calcifications were determined centrally.

RESULTS

Vitamin D deficiency (25OHD3<15ng/ml) was more common in female recipients at CKD-T stages I-III (29.6% vs 44.4%; p=0.003). The inverse and significant correlation between 25OHD3 and PTH was gender-specific and women exhibited a steeper slope than men (p=0.01). Vertebral fractures (VFx) with deformity grade ≥2 were observed in 15% of recipients. Factors related to VFx differed by gender; in males, age (OR 1.04; 95% CI 1.01-1.06) and CsA treatment (OR: 3.2; 95% CI: 1.6-6.3); in females, age (OR 1.07; 95% CI: 1.03-1.12) and PTH levels (OR per 100pg/ml increase: 1.27; 95% CI: 1.043-1.542). Abdominal aortic calcifications were common (67.2%) and related to classical risk factors but not to mineral metabolism parameters.

CONCLUSIONS

Vitamin D deficiency is more common among female kidney transplant recipients at earlier CKD-T stages, and it contributes to secondary hyperparathyroidism. Prevalent vertebral fractures are only related to high serum PTH levels in female recipients.

Vitamin D in patients with chronic kidney disease: a position statement of the Working Group "Trace Elements and Mineral Metabolism" of the Italian Society of Nephrology

In the late 1970s, calcitriol was introduced into clinical practice for the management of secondary renal hyperparathyroidism in chronic kidney disease (CKD). Since then, the use of calcifediol or other native forms of vitamin D was largely ignored until the publication of the 2009 Kidney Disease Improving Global Outcomes (KDIGO) recommendations. The guidelines suggested that measurement of circulating levels of 25(OH)D (calcifediol) and its supplementation were to be performed on the same basis as for the general population. This indication was based on the fact that the precursors of active vitamin D had provided to CKD patients considerable benefits in survival, mainly due to their pleiotropic effects on the cardiovascular system. However, despite the long-term use of various classes of vitamin D in CKD, a clear definition is still lacking concerning the most appropriate time for initiation of therapy, the best compound to prescribe (active metabolites or analogs), the proper dosage, and the most suitable duration of therapy. The aim of this position statement is to provide and critically appraise the current plentiful evidence on vitamin D in different clinical settings related to CKD, particularly focusing on outcomes, monitoring and treatment-associated risks. However, it should be taken in account that position statements are meant to provide guidance; therefore, they are not to be considered prescriptive for all patients and, importantly, they cannot replace the judgment of clinicians.

Effect of Vitamin D Receptor Activators on Glomerular Filtration Rate: A Meta-Analysis and Systematic Review

Background

Vitamin D receptor activators (VDRAs) can protect against mineral bone disease, but they are reported to elevate serum creatinine (SCr) and may also reduce glomerular filtration rate (GFR).

Methods

We conducted a systematic review and meta-analysis of randomized clinical trials (RCTs) to evaluate the effect of VDRAs on kidney function and adverse events. MEDLINE, EMBASE, the Cochrane Controlled Trials Register were searched for RCTs that evaluate vitamin D receptor activators (alfacalcidol, calcitriol, doxercalciferol, falecalcitriol, maxacalcitol and paricalcitol) up to March 2015.

Results

We included 31 studies, all of which were performed between 1976 and 2015, which enrolled 2621 patients. Patients receiving VDRAs had lower eGFR (weighted mean difference WMD -1.29 mL/min /1.73 m², 95% CI -2.42 to -0.17) and elevated serum creatinine (WMD 7.03 μmol/L, 95% CI 0.61 to 13.46) in sensitivity analysis excluding studies with dropout rate more than 30%. Subgroup analysis of the 5 studies that not use SCr-based measures did not indicated lower GFR in the VDRAs group(WMD -0.97 mL/min/1.73 m2, 95% CI -4.85 to 2.92). Compared with control groups, there was no difference in all-cause mortality (relative risk RR 1.41, 95% CI 0.58 to 3.80), cardiovascular disease (RR 0.84, 95% CI 0.42 to 1.71), and severe adverse events (RR 1.15, 95% CI 0.75 to 1.77) for the VDRAs groups. Episodes of hypercalcemia (RR 3.29, 95% CI 2.02 to 5.38) were more common in the VDRAs group than in the control group.

Conclusions

Administration of VDRAs increased serum creatinine levels. Subgroup analysis of studies that did not use SCr-based measures did not indicate a lower GFR in the VDRA group. Future studies with non-SCr-based measures are needed to assess whether the mild elevations of serum creatinine are of clinical significance.

Comparison between paricalcitol and active non-selective vitamin D receptor activator for secondary hyperparathyroidism in chronic kidney disease: a systematic review and meta-analysis of randomized controlled trials

PURPOSE

The goal of this systematic review is to evaluate the efficacy and safety of paricalcitol versus active non-selective vitamin D receptor activators (VDRAs) for secondary hyperparathyroidism (SHPT) management in chronic kidney disease (CKD) patients.

METHODS

PubMed, EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), clinicaltrials.gov (inception to September 2015), and ASN Web site were searched for relevant studies. A meta-analysis of randomized controlled trials (RCTs) and quasi-RCTs that assessed the effects and adverse events of paricalcitol and active non-selective VDRA in adult CKD patients with SHPT was performed using Review Manager 5.2.

RESULTS

A total of 10 trials involving 734 patients were identified for this review. The quality of included trials was limited, and very few trials reported all-cause mortality or cardiovascular calcification without any differences between two groups. Compared with active non-selective VDRAs, paricalcitol showed no significant difference in both PTH reduction (MD -7.78, 95% CI -28.59-13.03, P = 0.46) and the proportion of patients who achieved the target reduction of PTH (OR 1.27, 95% CI 0.87-1.85, P = 0.22). In addition, no statistical differences were found in terms of serum calcium, episodes of hypercalcemia, serum phosphorus, calcium × phosphorus products, and bone metabolism index.

CONCLUSIONS

Current evidence is insufficient, showing paricalcitol is superior to active non-selective VDRAs in lowering PTH or reducing the burden of mineral loading. Further trials are required to prove the tissue-selective effect of paricalcitol and to overcome the limitation of current research.

Mineral and bone disorder after kidney transplantation

After successful kidney transplantation, accumulated waste products and electrolytes are excreted and regulatory hormones return to normal levels. Despite the improvement in mineral metabolites and mineral regulating hormones after kidney transplantation, abnormal bone and mineral metabolism continues to present in most patients. During the first 3 mo, fibroblast growth factor-23 (FGF-23) and parathyroid hormone levels decrease rapidly in association with an increase in 1,25-dihydroxyvitamin D production. Renal phosphate excretion resumes and serum calcium, if elevated before, returns toward normal levels. FGF-23 excess during the first 3-12 mo results in exaggerated renal phosphate loss and hypophosphatemia occurs in some patients. After 1 year, FGF-23 and serum phosphate return to normal levels but persistent hyperparathyroidism remains in some patients. The progression of vascular calcification also attenuates. High dose corticosteroid and persistent hyperparathyroidism are the most important factors influencing abnormal bone and mineral metabolism in long-term kidney transplant (KT) recipients. Bone loss occurs at a highest rate during the first 6-12 mo after transplantation. Measurement of bone mineral density is recommended in patients with estimated glomerular filtration rate > 30 mL/min. The use of active vitamin D with or without bisphosphonate is effective in preventing early post-transplant bone loss. Steroid withdrawal regimen is also beneficial in preservation of bone mass in long-term. Calcimimetic is an alternative therapy to parathyroidectomy in KT recipients with persistent hyperparathyroidism. If parathyroidectomy is required, subtotal to near total parathyroidectomy is recommended. Performing parathyroidectomy during the waiting period prior to transplantation is also preferred in patients with severe hyperparathyroidism associated with hypercalcemia.

A Randomized Study Comparing Parathyroidectomy with Cinacalcet for Treating Hypercalcemia in Kidney Allograft Recipients with Hyperparathyroidism

Tertiary hyperparathyroidism is a common cause of hypercalcemia after kidney transplant. We designed this 12-month, prospective, multicenter, open-label, randomized study to evaluate whether subtotal parathyroidectomy is more effective than cinacalcet for controlling hypercalcemia caused by persistent hyperparathyroidism after kidney transplant. Kidney allograft recipients with hypercalcemia and elevated intact parathyroid hormone (iPTH) concentration were eligible if they had received a transplant ≥6 months before the study and had an eGFR>30 ml/min per 1.73 m(2) The primary end point was the proportion of patients with normocalcemia at 12 months. Secondary end points were serum iPTH concentration, serum phosphate concentration, bone mineral density, vascular calcification, renal function, patient and graft survival, and economic cost. In total, 30 patients were randomized to receive cinacalcet (n=15) or subtotal parathyroidectomy (n=15). At 12 months, ten of 15 patients in the cinacalcet group and 15 of 15 patients in the parathyroidectomy group (P=0.04) achieved normocalcemia. Normalization of serum phosphate concentration occurred in almost all patients. Subtotal parathyroidectomy induced greater reduction of iPTH and associated with a significant increase in femoral neck bone mineral density; vascular calcification remained unchanged in both groups. The most frequent adverse events were digestive intolerance in the cinacalcet group and hypocalcemia in the parathyroidectomy group. Surgery would be more cost effective than cinacalcet if cinacalcet duration reached 14 months. All patients were alive with a functioning graft at the end of follow-up. In conclusion, subtotal parathyroidectomy was superior to cinacalcet in controlling hypercalcemia in these patients with kidney transplants and persistent hyperparathyroidism.

Phosphate and FGF-23 homeostasis after kidney transplantation

Dysregulated phosphate metabolism is a common consequence of chronic kidney disease, and is characterized by a high circulating level of fibroblast growth factor (FGF)-23, hyperparathyroidism, and hyperphosphataemia. Kidney transplantation can elicit specific alterations to phosphate metabolism that evolve over time, ranging from severe hypophosphataemia (<0.5 mmol/l) to hyperphosphataemia (>1.50 mmol/l) and high FGF-23 levels. The majority of renal transplant recipients develop hypophosphataemia during the first 3 months after transplantation as a consequence of relatively slow adaptation of FGF-23 and parathyroid hormone levels to restored renal function, and the influence of immunosuppressive drugs. By 3-12 months after transplantation, phosphate homeostasis is at least partially restored in the majority of recipients, which is paralleled by a substantially reduced risk of cardiovascular-associated morbidity and mortality compared with the pre-transplantation setting. Many renal transplant recipients, however, exhibit persistent abnormalities in phosphate homeostasis, which is often due to multifactorial causes, and may contribute to adverse outcomes on the cardiovascular system, kidney, and bone. Dietary and pharmacologic interventions might improve phosphate homeostasis in renal transplant recipients, but additional insight into the pathophysiology of transplantation-associated abnormalities in phosphate homeostasis is needed to further optimize disease management and improve prognosis for renal transplant recipients.

Paricalcitol for secondary hyperparathyroidism in renal transplantation

Secondary hyperparathyroidism contributes to post-transplant CKD mineral and bone disorder. Paricalcitol, a selective vitamin D receptor activator, decreased serum parathyroid hormone levels and proteinuria in patients with secondary hyperparathyroidism. This single-center, prospective, randomized, crossover, open-label study compared the effect of 6-month treatment with paricalcitol (1 μg/d for 3 months and then uptitrated to 2 µg/d if tolerated) or nonparicalcitol therapy on serum parathyroid hormone levels (primary outcome), mineral metabolism, and proteinuria in 43 consenting recipients of renal transplants with secondary hyperparathyroidism. Participants were randomized 1:1 according to a computer-generated sequence. Compared with baseline, median (interquartile range) serum parathyroid hormone levels significantly declined on paricalcitol from 115.6 (94.8-152.0) to 63.3 (52.0-79.7) pg/ml (P<0.001) but not on nonparicalcitol therapy. At 6 months, levels significantly differed between treatments (P<0.001 by analysis of covariance). Serum bone-specific alkaline phosphatase and osteocalcin decreased on paricalcitol therapy only and significantly differed between treatments at 6 months (P<0.001 for all comparisons). At 6 months, urinary deoxypyridinoline-to-creatinine ratio and 24-hour proteinuria level decreased only on paricalcitol (P<0.05). L3 and L4 vertebral mineral bone density, assessed by dual-energy x-ray absorption, significantly improved with paricalcitol at 6 months (P<0.05 for both densities). Paricalcitol was well tolerated. Overall, 6-month paricalcitol supplementation reduced parathyroid hormone levels and proteinuria, attenuated bone remodeling and mineral loss, and reduced eGFR in renal transplant recipients with secondary hyperparathyroidism. Long-term studies are needed to monitor directly measured GFR, ensure that the bone remodeling and mineral effects are sustained, and determine if the reduction in proteinuria improves renal and cardiovascular outcomes.