Bone mineral disorders in pediatric and adolescent renal transplant recipients

Association of vitamin D status with liver and kidney disease: A systematic review of clinical trials, and cross-sectional and cohort studies

Abstract. Background: Vitamin D deficiency (VDD) is a major public health problem. There are few comprehensive systematic reviews about the relationship between Vitamin D status and liver and renal disease in Iran.

Methods: We systemically searched the following databases: Web of Science; PubMed; Cochrane Library; Scopus; Science Direct; Google Scholar and two Iranian databases (Scientific Information Database (SID) and IranMedex) up until November 2017 to identify all randomized control trials (RCTs), case control, cross-sectional and cohort studies investigating the association between vitamin D and any form of liver or kidney disease.

Results: Vitamin D insufficiency, or deficiency (VDD), is highly prevalent in Iran, reports varying between 44.4% in Isfahan to 98% in Gorgan. There is also a high prevalence of VDD among patients with liver or kidney disease, and the administration of vitamin D supplements may have beneficial effects on lipid profile, blood glucose, liver function and fatty liver disease, and bone health. Low serum vitamin D levels are related with abnormalities in these laboratory and clinical parameters.

Conclusion: VDD is prevalent in patients with chronic liver or renal disease in Iran. There appear to be several beneficial effects of vitamin D supplementation in vitamin D deficient patients with liver or kidney disease.

The evaluation of bone metabolism in children with renal transplantation

This study aims to evaluate BMD and bone biomarkers and to investigate the effects of immunosuppressives on bone disease after RTx. Thirty-three RTR aged 16.7 ± 3.7 yr and healthy controls (n = 32) were enrolled. There was no difference between pre-RTx BMD and BMD at the time of study (45.9 ± 30.9 months after RTx), while both values were lower than controls (p < 0.01 and p < 0.05, respectively). Worst BMD scores were obtained at sixth month after RTx (-0.2 ± 0.9) and best at fourth year (1.4 ± 1.3). 25-hydroxy-(OH) vitamin D and OPG were higher in RTR (p < 0.001). BMD z scores negatively correlated with OPG and cumulative CS doses at the time of study (r = -0.344, p < 0.05 and r = -0.371, p < 0.05, respectively). Regression analysis revealed OPG as the only predictor of BMD (β -0.78, 95% CI -0.004 to -0.013, p < 0.001). The increase in OPG, a significant predictor of BMD, could either be secondary to graft dysfunction or for protection against bone loss. CS doses should be minimized to avoid their untoward effects on bone metabolism.

Mineral metabolism in European children living with a renal transplant: a European society for paediatric nephrology/european renal association-European dialysis and transplant association registry study

BACKGROUND AND OBJECTIVES

Data on mineral metabolism in pediatric renal transplant recipients largely arise from small single-center studies. In adult patients, abnormal mineral levels are related to a higher risk of graft failure. This study used data from the European Society for Paediatric Nephrology/European Renal Association-European Dialysis and Transplant Association Registry to study the prevalence and potential determinants of mineral abnormalities, as well as the predictive value of a disturbed mineral level on graft survival in a large cohort of European pediatric renal transplant recipients.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study included 1237 children (0-17 years) from 10 European countries, who had serum calcium, phosphorus, and parathyroid hormone measurements from 2000 onward. Abnormalities of mineral metabolism were defined according to European guidelines on prevention and treatment of renal osteodystrophy in children on chronic renal failure.

RESULTS

Abnormal serum phosphorus levels were observed in 25% (14% hypophosphatemia and 11% hyperphosphatemia), altered serum calcium in 30% (19% hypocalcemia, 11% hypercalcemia), and hyperparathyroidism in 41% of the patients. A longer time since transplantation was associated with a lower risk of having mineral levels above target range. Serum phosphorus levels were inversely associated with eGFR, and levels above the recommended targets were associated with a higher risk of graft failure independently of eGFR.

CONCLUSIONS

Abnormalities in mineral metabolism are common after pediatric renal transplantation in Europe and are associated with graft dysfunction.

Changes in DXA and quantitative CT measures of musculoskeletal outcomes following pediatric renal transplantation

This prospective study evaluated changes in dual energy X-ray absorptiometry (DXA) whole body bone mineral content (WB-BMC) and spine areal bone mineral density (spine-BMD), and tibia quantitative computed tomography (QCT) trabecular and cortical volumetric BMD and cortical area in 56 children over 12 months following renal transplantation. At transplant, spine-BMD Z-scores were greater in younger recipients (<13 years), versus 898 reference participants (p < 0.001). In multivariate models, greater decreases in spine-BMD Z-scores were associated with greater glucocorticoid dose (p < 0.001) and declines in parathyroid hormone levels (p = 0.008). Changes in DXA spine-BMD and QCT trabecular BMD were correlated (r = 0.47, p < 0.01). At 12 months, spine-BMD Z-scores remained elevated in younger recipients, but did not differ in older recipients (≥ 13) and reference participants. Baseline WB-BMC Z-scores were significantly lower than reference participants (p = 0.02). Greater glucocorticoid doses were associated with declines in WB-BMC Z-scores (p < 0.001) while greater linear growth was associated with gains in WB-BMC Z-scores (p = 0.01). Changes in WB-BMC Z-scores were associated with changes in tibia cortical area Z-scores (r = 0.52, p < 0.001), but not changes in cortical BMD Z-scores. Despite resolution of muscle deficits, WB-BMC Z-scores at 12 months remained significantly reduced. These data suggest that spine and WB DXA provides insight into trabecular and cortical outcomes following pediatric renal transplantation.

Bone density and cortical structure after pediatric renal transplantation

The impact of renal transplantation on trabecular and cortical bone mineral density (BMD) and cortical structure is unknown. We obtained quantitative computed tomography scans of the tibia in pediatric renal transplant recipients at transplantation and 3, 6, and 12 months; 58 recipients completed at least two visits. We used more than 700 reference participants to generate Z-scores for trabecular BMD, cortical BMD, section modulus (a summary measure of cortical dimensions and strength), and muscle and fat area. At baseline, compared with reference participants, renal transplant recipients had significantly lower mean section modulus and muscle area; trabecular BMD was significantly greater than reference participants only in transplant recipients younger than 13 years. After transplantation, trabecular BMD decreased significantly in association with greater glucocorticoid exposure. Cortical BMD increased significantly in association with greater glucocorticoid exposure and greater decreases in parathyroid hormone levels. Muscle and fat area both increased significantly, but section modulus did not improve. At 12 months, transplantation associated with significantly lower section modulus and greater fat area compared with reference participants. Muscle area and cortical BMD did not differ significantly between transplant recipients and reference participants. Trabecular BMD was no longer significantly elevated in younger recipients and was low in older recipients. Pediatric renal transplant associated with persistent deficits in section modulus, despite recovery of muscle, and low trabecular BMD in older recipients. Future studies should determine the implications of these data on fracture risk and identify strategies to improve bone density and structure.