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

25-hydroxyvitamin D sufficiency is associated with lower de novo anti-HLA donor specific antibody and better kidney transplant outcomes

T-cell mediated rejection (TCMR), de novo anti-HLA donor-specific antibodies (dnDSAs) and ensuing antibody-mediated rejection (ABMR) reduce kidney transplantation (KT) survival. The immunomodulatory effects of 25-hydroxyvitamin D [25(OH)D] could be beneficial for KT outcomes. We aimed to evaluating the association between 25(OH)D levels, the development of dnDSAs, clinical TCMR and ABMR, and graft survival. This single center retrospective study included 253 KT recipients (KTRs) transplanted without preformed DSA between 2010 and 2013. We measured 25(OH)D in successive serum samples: at KT (M0) and M12 for the entire cohort, and additionally at M24 and/or M36 when sera were available. We assessed graft outcomes up to 5 years post-KT. The proportion of KTRs having sufficient 25(OH)D at KT (M0) was high (81.4%) and then dropped at M12 (71.1%). KTRs with sufficient 25(OH)D at M0 experienced less clinical TCMR (HR, 0.41; 95% CI, 0.19-0.88 in multivariate analysis). A sufficient 25(OH)D at M12 was independently associated with a longer dnDSA-free survival (HR, 0.34; 95% CI, 0.17-0.69). There was no association between 25(OH)D and clinical AMBR. Studying the KTRs with 25(OH)D measurements at M12, M24 and M36 (n = 203), we showed that 25(OH)D sufficiency over the 3 first-years post-KT was associated with a longer graft survival in multivariate analyses (HR, 0.39; 95% CI, 0.22-0.70). To our knowledge, this study is the first showing an association between 25(OH)D sufficiency post-KT and dnDSA occurrence in KTRs. Moreover, we reinforce previously published data showing an association between 25(OH)D, TCMR and graft survival in KT.

[Vitamin D and its positive effect on the PTH/vitamin D/calcium-FGF23/klotho/phosphorus axis in kidney transplant recipients]

BACKGROUND

hypovitaminosis D is frequent in kidney transplant recipient (KTR) patients and is associated with deleterious effects both at the bone and extraosseous levels. Treatment with cholecalciferol is effective for the normalization of 25(OH)D, demonstrating a beneficial effect on the calcium-tropic axis in other populations; however, its effect on the PTH/vitamin D/calcium and FGF23/klotho/phosphorus axis in RTR has not been reported. The aim of this study was to evaluate the effect of normalization of serum 25(OH)D concentrations on the PTH/vitamin D/calcium-FGF23/klotho/phosphorus axis in KTR treated with cholecalciferol, as well as the association between the components of this axis.

METHODS

a prospective study in 23 KTR with hypovitaminosis D, with evolution from 1 to 12 months post-transplantation, an estimated glomerular filtration rate > 60 mL/min/1.73 m2 and a history of primary nephropathy treated with cholecalciferol, in whom the PTH/vitamin D/calcium and FGF23/klotho/phosphorus axis was evaluated during the state of hypovitaminosis D and at normalization of 25(OH)D.

RESULTS

at the normalization of 25(OH)D, a reduction in PTH [103 (58.5-123.9) vs 45.6 (30.1-65.1) pg/mL; p = 0.002] and an increase in serum phosphorus [3.1 (2.3-3.5) vs 3.3 (3-3.6) mg/dL; p = 0.01] were evident, with no differences in calcium, klotho and FGF23 concentrations. The time to achieve normalization of 25(OH)D was 12 weeks (RIC, 4-12), with a dose of 5000 IU/day (RIC, 4000-6000). A positive association between klotho and PTH was corroborated (r = 0.54; p = 0.008; linear regression, b = 0.421; B = 0.004; 95 % CI, 0.003-0.007; p = 0.045).

CONCLUSIONS

treatment with cholecalciferol is effective for the normalization of 25(OH)D, with a beneficial effect on calcium-phosphotropic metabolism characterized by a reduction in PTH concentration, without significant changes in calcemia or calciuria, as well as an increase in phosphatemia, without modifications in FGF23 or klotho concentrations.

Long-term supplementation with 3200 to 4000 IU of vitamin D daily and adverse events: a systematic review and meta-analysis of randomized controlled trials

PURPOSE

The upper tolerable intake level for vitamin D in the general population has been set at 4000 international units (IU) daily, but considerable uncertainty remains. We summarized reported harmful effects of a daily vitamin D supplement of 3200-4000 IU in trials lasting ≥ 6 months.

METHODS

We performed a systematic review and meta-analysis of randomized controlled trials in several databases and identified 22 trials reporting safety data. Parameters of calcium metabolism, falls, hospitalization, and mortality were assessed.

RESULTS

The selected trials comprised a total number of 12,952 participants. All trials used supplemental vitamin D₃. The relative risk (RR) of hypercalcemia in the vitamin D vs. control arm was 2.21 (95%CI: 1.26-3.87; 10 studies), with a vitamin D-induced frequency of hypercalcemia of 4 cases per 1000 individuals. Subgroup analysis in trials with > 100 and ≤ 100 study participants revealed an RR of 2.63 (95%CI: 1.30-5.30; 7 studies) and 0.80 (95%CI: 0.24-2.62; 3 studies), respectively (P_interaction = 0.06). Risks of falls and hospitalization were also significantly increased in the vitamin D arm with an RR of 1.25 (95%CI: 1.01-1.55; 4 studies) and 1.16 (95%CI: 1.01-1.33; 7 studies), respectively. Risks of hypercalciuria, kidney stones, and mortality did not differ significantly between study arms. Quality assessment revealed high risk of incomplete reporting of safety-related outcome data.

CONCLUSION

Supplemental vitamin D doses of 3200-4000 IU/d appear to increase the risk of hypercalcemia and some other adverse events in a small proportion of individuals, indicating that this dose is not completely safe. In future studies, rigorous reporting of safety-related outcomes is needed when using moderately high doses of vitamin D.

Hyperparathyroidism Is an Independent Risk Factor for Allograft Dysfunction in Pediatric Kidney Transplantation

Introduction

Little is known about the consequences of deranged chronic kidney disease-mineral and bone disorder (CKD-MBD) parameters on kidney allograft function in children. We examined a relationship between these parameters over time and allograft outcome.

Methods

This registry study from the Cooperative European Paediatric Renal Transplant Initiative (CERTAIN) collected data at baseline, months 1, 3, 6, 9, and 12 after transplant; and every 6 months thereafter up to 5 years. Survival analysis for a composite end point of graft loss or estimated glomerular filtration rate (eGFR) ≤30 ml/min per 1.73 m² or a ≥50% decline from eGFR at month 1 posttransplant was performed. Associations of parathyroid hormone (PTH), calcium, phosphate, and 25-hydroxyvitamin D (25(OH)D) with allograft outcome were investigated using conventional stratified Cox proportional hazards models and further verified with marginal structural models with time-varying covariates.

Results

We report on 1210 patients (61% boys) from 16 European countries. The composite end point was reached in 250 grafts (21%), of which 11 (4%) were allograft losses. In the conventional Cox proportional hazards models adjusted for potential confounders, only hyperparathyroidism (hazard ratio [HR], 2.94; 95% confidence interval [CI], 1.82-4.74) and hyperphosphatemia (HR, 1.94; 95% CI, 1.28-2.92) were associated with the composite end point. Marginal structural models showed similar results for hyperparathyroidism (HR, 2.74; 95% CI, 1.71-4.38), whereas hyperphosphatemia was no longer significant (HR, 1.35; 95% CI, 0.87-2.09), suggesting that its association with graft dysfunction can be ascribed to a decline in eGFR.

Conclusion

Hyperparathyroidism is a potential independent risk factor for allograft dysfunction in children.

Cholecalciferol supplementation effectively improved tertiary hyperparathyroidism, FGF23 resistance and lowered coronary calcification score: a prospective study

Introduction

Tertiary hyperparathyroidism (THPT) and vitamin D deficiency are commonly seen in kidney transplant recipients, which may result in persistently elevated fibroblast growth factor 23 (FGF23) level after transplantation and decreased graft survival. The aim of this study is to evaluate the effect of vitamin D supplementation on THPT, FGF23-alpha Klotho (KLA) axis and cardiovascular complications after transplantation.

Materials and methods

Two hundred nine kidney transplant recipients were included and further divided into treated and untreated groups depending on whether they received vitamin D supplementation. We tracked the state of THPT, bone metabolism and FGF23-KLA axis within 12 months posttransplant and explored the predictors and risk factors for intact FGF23 levels, KLA levels, THPT and cardiovascular complications in recipients.

Results

Vitamin D supplementation significantly improved FGF23 resistance, THPT and high bone turnover status, preserved better graft function and prevented coronary calcification in the treated group compared to the untreated group at month 12. The absence of vitamin D supplementation was an independent risk factor for THPT and a predictor for intact FGF23 and KLA levels at month 12. Age and vitamin D deficiency were independent risk factors for coronary calcification in recipients at month 12.

Conclusion

Vitamin D supplementation effectively improved THPT, FGF23 resistance and bone metabolism, preserved graft function and prevented coronary calcification after transplantation.

Cholecalciferol Supplementation Attenuates Bone Loss in Incident Kidney Transplant Recipients: A Prespecified Secondary Endpoint Analysis of a Randomized Controlled Trial

Vitamin D deficiency, persistent hyperparathyroidism, and bone loss are common after kidney transplantation (KTx). However, limited evidence exists regarding the effects of cholecalciferol supplementation on parathyroid hormone (PTH) and bone loss after KTx. In this prespecified secondary endpoint analysis of a randomized controlled trial, we evaluated changes in PTH, bone metabolic markers, and bone mineral density (BMD). At 1 month post-transplant, we randomized 193 patients to an 11-month intervention with cholecalciferol (4000 IU/d) or placebo. The median baseline 25-hydroxyvitamin D (25[OH]D) level was 10 ng/mL and 44% of participants had osteopenia or osteoporosis. At the end of the study, the median 25(OH)D level was increased to 40 ng/mL in the cholecalciferol group and substantially unchanged in the placebo group. Compared with placebo, cholecalciferol significantly reduced whole PTH concentrations (between-group difference of -15%; 95% confidence interval [CI] -25 to -3), with greater treatment effects in subgroups with lower 25(OH)D, lower serum calcium, or higher estimated glomerular filtration rate (p_int  < 0.05). The percent change in lumbar spine (LS) BMD from before KTx to 12 months post-transplant was -0.2% (95% CI -1.4 to 0.9) in the cholecalciferol group and -1.9% (95% CI -3.0 to -0.8) in the placebo group, with a significant between-group difference (1.7%; 95% CI 0.1 to 3.3). The beneficial effect of cholecalciferol on LS BMD was prominent in patients with low bone mass p_int  < 0.05). Changes in serum calcium, phosphate, bone metabolic markers, and BMD at the distal radius were not different between groups. In mediation analyses, change in whole PTH levels explained 39% of treatment effects on BMD change. In conclusion, 4000 IU/d cholecalciferol significantly reduced PTH levels and attenuated LS BMD loss after KTx. This regimen has the potential to eliminate vitamin D deficiency and provides beneficial effects on bone health even under glucocorticoid treatment. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).