Oral alendronate can suppress bone turnover but not fracture in kidney transplantation recipients with hyperparathyroidism and chronic kidney disease

Effect of neridronate in osteopenic patients after heart, liver or lung transplant: a multicenter, randomized, double-blind, placebo-controlled study

BACKGROUND

Transplantation (Tx) is an effective therapeutic option in patients with end-stage organ failure and osteoporosis and related fractures are a recognized complication in these patients. Aim of this study was to evaluate the efficacy of neridronate in patients with reduced bone mass after Tx of the heart, liver or lung.

METHODS

In this multicenter randomized double-blind controlled trial (RCT), 22 patients were treated with neridronate (25 mg i.m./month) and 17 received placebo. All patients received daily oral calcium (500 mg) and vitamin D (400 IU). Dual-energy X-ray absorptiometry (DXA) was evaluated at 0, 6 and 12 months and markers of bone turnover at 0, 3, 6, 9 and 12 months.

RESULTS

Thirty-nine patients (11 heart Tx, 21 liver Tx, 7 lung Tx), aged 49.3±9.1 years, with a T-score <-2.0 SD at lumbar spine or femoral level were included. In neridronate-treated patients, a significant increase in lumbar bone mineral density (BMD) was observed after 12 months vs. placebo control (0.92±0.13 g/cm² vs. 0.84±0.08 g/cm²; P=0.005). Femur and hip BMD remained unchanged between groups. Total alkaline phosphatase, bone alkaline phosphatase and beta-cross-laps significantly decreased over the 12 months in neridronate-treated patients vs. placebo, respectively (107.4±74 U/L vs. 157.6±107.1 U/L, P=0.002; 5.7±3.3 µg/L vs. 11.7±4.3 µg/L, P<0.001 and 0.25±0.13 ng/mL vs. 0.73±0.57 ng/mL, P<0.001). No difference was observed between neridronate and placebo groups regarding safety profile.

CONCLUSIONS

This is the first RCT that demonstrates the efficacy of neridronate in increasing bone density and reducing bone turnover in organ Tx recipients with significant skeletal morbidity.

Effect of Bisphosphonates on Bone Health in Adult Renal Transplant Patients: Beyond the First Year Posttransplant-A Systematic Review and Meta-Analysis

Background:

Bone mineral density (BMD) decreases postrenal transplantation. Evidence demonstrating the effects of bisphosphonates on BMD and fracture risk beyond 1-year posttransplant is sparse in existing literature, but remains essential to enhance clinical outcomes in this population.

Objective:

Our study aimed to systematically review and meta-analyze the current literature on the use of any bisphosphonate in the adult renal transplant population beyond the first year of renal transplant to determine its effect on BMD and fracture incidence.

Design:

We conducted a systematic review and meta-analysis of primary research literature that included full-text, English-language, original randomized clinical trials (RCTs) and observational studies.

Setting:

Patient data were primarily captured in an outpatient setting across various studies.

Patients:

Our population of interest was patients older than 18 years who received deceased/living donor kidney transplantation and any bisphosphonate with a follow-up greater than 12 months posttransplantation.

Measurements:

The primary outcome was change in BMD from baseline. Secondary outcomes were the incidence of fractures and effects of other confounders on bone health.

Methods:

We included RCTs and observational studies that satisfied our inclusion criteria. Each study was analyzed for risk of bias and data were extrapolated to analyze for overall statistical significance accounting for heterogeneity of studies.

Results:

Sixteen studies (N = 1762) were analyzed. The follow-up ranged from 12 to 98 months. There was a nonsignificant improvement in BMD with bisphosphonate treatment persisting into the second and third years posttransplant at the lumbar spine. The calculated standardized mean BMD difference was −0.29 (−0.75 to 0.17), P = .22. Only 5 studies reported a total of 43 new fractures. Prednisone (P < .01), low body weight (P < .001), low body mass index (P < .01), and male gender (P < .05) correlated with reduced lumbar and femoral BMD.

Limitations:

Limitations of this review include the use of BMD as a surrogate outcome, the bias of the included studies, and the incomplete reporting data in numerous analyzed studies.

Conclusions:

We demonstrate no statistically significant benefit of bisphosphonate treatment on BMD beyond the first year postrenal transplantation. Despite heterogeneity of treatment, a differential nonsignificant improvement in lumbar spine BMD was consistent and may be clinically relevant.

Trial Registration:

PROSPERO CRD42019125593

Effects of denosumab on bone metabolism and bone mineral density in kidney transplant patients: a systematic review and meta-analysis

OBJECTIVE

The use of immunosuppressive agents, especially glucocorticoids, are associated with increased risks of bone loss in kidney transplant patients. Denosumab, a potent antiresorptive agent, has been shown to increase bone mineral density (BMD) in patients with CKD. However, its effects on bone metabolism and BMD in kidney transplant patients remain unclear.

METHODS

A literature search was conducted using MEDLINE, EMBASE, and Cochrane Database from inception through April 2018 to identify studies evaluating denosumab's effect on changes in bone metabolism and BMD from baseline to post-treatment course in kidney transplant patients. Study results were pooled and analyzed utilizing random-effects model. The protocol for this systematic review is registered with PROSPERO (International Prospective Register of Systematic Reviews; no. CRD42018095055).

RESULTS

Five studies (a clinical trial and four cohort studies) with a total of 162 kidney transplant patients were identified. The majority of patients had a baseline eGFR ≥ 30 mL/min/1.73 m². After treatment (≥ 6 to 12 months), there were significant increases in BMD with standardized mean differences (SMDs) of 3.26 (95% CI 0.88-5.64) and 1.83 (95% CI 0.43 to 3.22) for lumbar spine and femoral neck, respectively. There were also significant increases in T scores with SMDs of 0.92 (95% CI 0.58 to 1.25) and 1.14 (95% CI 0.17 to 2.10) for lumbar spine and femoral neck, respectively. After treatment, there were no significant changes in serum calcium (Ca) or parathyroid hormone (PTH) from baseline to post-treatment course (≥ 6 months) with mean differences (MDs) of 0.52 (95% CI, - 0.13 to 1.16) mmol/L and - 13.24 (95% CI, - 43.85 to 17.37) ng/L, respectively. The clinical trial data demonstrated more asymptomatic hypocalcemia in the denosumab (12 episodes in 39 patients) than in the control (1 episode in 42 patients) group. From the cohort studies, the pooled incidence of hypocalcemia following denosumab treatment was 1.7% (95% CI 0.4 to 6.6%). All reported hypocalcemic episodes were mild and asymptomatic, but the majority of patients required Ca and vitamin D supplements.

CONCLUSION

Among kidney transplant patients with good allograft function, denosumab effectively increases BMD and T scores in the lumbar spine and femur neck. From baseline to post-treatment, there are no differences in serum Ca and PTH. However, mild hypocalcemia can occur following denosumab treatment, requiring monitoring and titration of Ca and vitamin D supplements.

The effect of vitamin D and zoledronic acid in bone marrow adiposity in kidney transplant patients: A post hoc analysis

PURPOSE

Osteoblasts and adipocytes are derived from mesenchymal stem cells. An imbalance in the differentiation of these lineages could affect the preservation of bone integrity. Several studies have suggested the importance of this imbalance in the pathogenesis of osteoporosis after kidney transplant (KT), but the role of bone marrow adiposity in this process is not well known, and if the treatment with the anti-absorptive (zoledronic acid-ZA) drugs could attenuate bone loss. Thus, our objective was compare bone marrow adiposity, osteoblasts and osteocytes before and after KT, verify an association between bone remodeling process (Turnover, Volume, and Mineralization-TMV classification), the osteocyte sclerostin expression to evaluate if there is a role of Wnt pathway, as well as the effect of ZA on these cells.

METHODS

We studied 29 new living-donor KT patients. One group received ZA at the time of KT plus cholecalciferol for twelve months, and the other group received only cholecalciferol. Bone biopsies were performed at baseline and after 12 months of treatment. Histomorphometric evaluation was performed in bone and bone marrow adipocytes. Sclerostin (Scl) expression in osteocytes was evaluated by immunohistochemistry.

RESULTS

Some bone marrow adiposity parameters were increased before KT. After KT, some of them remained increased and they worsened with the use of ZA. In the baseline, lower bone Volume and Turnover, were associated with increased bone marrow adiposity parameters (some of them). After KT, both groups showed the same associations. Osteocyte Scl expression after KT decreased with the use of ZA. We observed also an inverse association between bone adiposity parameters and lower osteocyte sclerostin expression 12 months after KT.

CONCLUSION

In conclusion, the present study suggests that KT fails to normalize bone marrow adiposity, and it even gets worse with the use of ZA. Moreover, bone marrow adiposity is inversely associated with bone Volume and Turnover, which seems to be accentuated by the antiresorptive therapy.

Osteoporosis in patients with diabetes after kidney transplantation

Preexisting diabetes increases risk of fractures after kidney transplantation (KT). However, little is known about mechanisms and prevention of increased fragility in these patients. Pathophysiology of osteoporosis after KT is complex and characterized by high prevalence of adynamic bone disease. Despite high prevalence of preexisting diabetes in KT recipients, diabetes patients were underrepresented in the studies that explored mechanisms and treatments of osteoporosis after KT. Therefore, caution should be exercised before considering conventional fracture prevention strategies in this unique group of patients. Many traditional osteoporosis medications reduce bone turnover and, hence, can be ineffective or even harmful in diabetic patients after KT. Contrary to predictions, evidence from the studies conducted in mostly non-diabetic subjects demonstrated that bisphosphonates failed to reduce fracture rates after KT. Therefore, bisphosphonates use should be limited in diabetic patients until more evidence supporting their post-transplant efficacy is available. We recommend the following strategies that may help reduce fracture risk in diabetes subjects after KT such as adequate management of calcium, parathyroid hormone, and vitamin D levels, optimization of glycemic control, use of steroid-sparing immunosuppressive regimens, and fall prevention.

[INITIAL EXPERIENCE OF DENOSUMAB TREATMENT FOR OSTEOPOROSIS AFTER KIDNEY TRANSPLANTATION]

(Purpose) Denosumab is a fully human monoclonal antibody against RANKL, which was developed for treatment of osteoporosis and prevention of fractures. However, its efficacy in patients after kidney transplantation remains unclear. Treatment cases of denosumab for osteoporosis after kidney transplantation in our department were examined. (Methods) We retrospectively reviewed four patients with osteoporosis after kidney transplantation who were treated with denosmab in our hospital. Osteoporosis was diagnosed using the dual energy X-ray absorptiometry. (Results) After 12 months, bone mineral density of total lumbar spine and femoral neck increased by 5.5% and 3.0%, respectively. Biomarkers of bone turnover (Tartrate-resistant acid phosphatase-5b and Intact-procollagen type 1 N-terminal propeptide) markedly decreased in the first one month and remained at the low level thereafter. Obvious adverse event was not recognized and graft function was stable in all cases. (Conclusion) Denosumab was considered to be safe and effective in patients who underwent kidney transplantation.

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.

Current Status of Research on Osteoporosis after Solid Organ Transplantation: Pathogenesis and Management

Improved survival following organ transplantation has brought to the forefront some long-term complications, among which osteoporosis and associated fractures are the major ones that adversely affect the quality of life in recipients. The pathogenesis of osteoporosis in transplant recipients is complex and multifactorial which may be related to increased bone resorption, decreased bone formation, or both. Studies have shown that the preexisting underlying metabolic bone disorders and the use of immunosuppressive agents are the major risk factors for osteoporosis and fractures after organ transplantation. And rapid bone loss usually occurs in the first 6–12 months with a significant increase in fracture risk. This paper will provide an updated review on the possible pathogenesis of posttransplant osteoporosis and fractures, the natural history, and the current prevention and treatment strategies concerning different types of organ transplantation.

[Mineral and bone disorders in renal transplantation]

The deregulation of bone and mineral metabolism during chronic kidney disease (CKD) is a daily challenge for physicians, its management aiming at decreasing the risk of both fractures and vascular calcifications. Renal transplantation in the context of CKD, with pre-existing renal osteodystrophy as well as nutritional impairment, chronic inflammation, hypogonadism and corticosteroids exposure, represents a major risk factor for bone impairment in the post-transplant period. The aim of this review is therefore to provide an update on the pathophysiology of mineral and bone disorders after renal transplantation.