Bone disease in post-transplant patients

Relationship Between Osteoporosis and Serum Sclerostin Levels in Kidney Transplant Recipients

OBJECTIVES

Sclerostin, a peptide secreted primarily by osteocytes, suppresses osteoblast maturation, thus reducing bone formation. Here, we evaluated the relationship between sclerostin levels and osteoporosis in kidney transplant recipients.

MATERIALS AND METHODS

This cross-sectional study included 78 kidney transplantrecipients > 18 years old and at least 6 months posttransplant. In our center, unrelated living-donor kidney transplants are not performed. Patients with parathyroid adenoma or parathyroidectomy history were excluded. Lumbar and femoral neck bone mineral densities andT and Z scores were obtained by dual-energy X-ray absorptiometry; results were used to divide patients into osteoporotic and nonosteoporotic groups. Serum sclerostin was measured by enzyme-linked immunosorbent assay.

RESULTS

Of total patients, 43% had osteoporosis, mean age was 40.8 years, and 70% were male. Groups had similar ages, male-female distribution, time posttransplant, cumulative corticosteroid dose, estimated glomerular filtration rates, and 25-hydroxyvitamin D2 levels (P > .05). The osteoporotic group had lower sclerostin (405.9 ± 234.9 vs 521.7 ± 233.5 ng/dL; P = .035) and higherintact parathyroid hormone levels (110.9 ± 68.0 vs 84.8 ± 41.4 pg/mL; P = .04) than the nonosteoporotic group. Sclerostin levels were not correlated with cumulative corticosteroid dose, intact parathyroid hormone, bone mineral density, and T scores at any site but were weakly negatively correlated with age (P = .04, r = -0.25). In multiple regression analyses, only intact parathyroid hormone had negative effects on lumbar bone mineral density (P = .02) andT scores (P = .036). Serum sclerostin levels, age, and cumulative corticosteroid dose did not affect lumbar or hip bone mineral density and T scores (P > .05).

CONCLUSIONS

Sclerostin levels were low in our osteoporotic patients;therefore, sclerostin may not be a contributing factor to osteoporosis development. Because sclerostin is an osteocyte-derived peptide, its serum levels only reflect total osteocyte number and bone mass.

Bone Mineral Density Changes in Long-Term Kidney Transplant Recipients: A Real-Life Cohort Study of Native Vitamin D Supplementation

Vitamin D insufficiency has been associated with reduced bone mineral density (BMD) in kidney transplant patients (KTRs). However, the efficacy of vitamin D supplementation on BMD remains poorly defined, especially for long-term KTRs. We aimed to investigate the effect of native vitamin D supplementation on the BMD of KTRs during a 2-year follow-up. Demographic, clinical, and laboratory data were collected. BMD was evaluated with standard DEXA that was performed at baseline (before vitamin D supplementation) and at the end of study period. BMD was assessed at lumbar vertebral bodies (LV) and right femoral neck (FN) by a single operator. According to WHO criteria, results were expressed as the T-score (standard deviation (SD) relative to young healthy adults) and Z-score (SD relative to age-matched controls). Osteoporosis and osteopenia were defined as a T-score ≤ -2.5 SD and a T-score < -1 and a > -2.5 SD, respectively. Based on plasma levels, 25-OH-vitamin D (25-OH-D) was supplemented as recommended for the general population. Data from 100 KTRs were analyzed. The mean study period was 27.7 ± 3.4 months. At study inception, 25-OH-D insufficiency and deficiency were recorded in 65 and 35 patients. At the basal DEXA, the percentage of osteopenia and osteoporosis was 43.3% and 18.6% at LV and 54.1% and 12.2% at FN, respectively. At the end of the study, no differences in the Z-score and T-score gains were observed. During linear mixed model analysis, native vitamin D supplementation was found to have a negative nitration with Z-score changes at the right femoral neck in KTRs (p < 0.05). The mean dose of administered cholecalciferol was 13.396 ± 7.537 UI per week; increased 25-OH-D levels were found (p < 0.0001). Either low BMD or 25-OH-vitamin D concentration was observed in long-term KTRs. Prolonged supplementation with 25-OH-D did not modify BMD, Z-score, or T-score.

A Complication Profile of Total Hip and Knee Arthroplasty in Liver Transplantation Patients: A Meta-Analysis

BACKGROUND

There is an increasing demand for total joint arthroplasty in liver transplantation patients. However, significant heterogeneity in existing studies creates difficulty to draw conclusions on the risk profile of arthroplasty in this population.

METHODS

A systematic review of the literature dated from 1980 to 2020 describing the complication rates of liver transplantation patients receiving either total hip or knee arthroplasty was conducted. Multiple outcomes were extracted and a meta-analysis was performed. Four cohorts were created for analysis purposes: liver transplant patients undergoing THA and TKA (1), THA only (2), TKA only (3), and controls (4).

RESULTS

A total of 13 studies were included in this meta-analysis, accounting for 3024 liver transplantation patients. The rate of infection (odds ratio [OR] = 2.14, OR = 1.61, OR = 2.52), myocardial infarction (OR = 1.65, OR = 1.75, OR = 1.57), respiratory failure (OR = 2.19, OR = 2.50, OR = 1.96), acute kidney injury (OR = 5.71, OR = 5.40, OR = 4.35), sepsis (OR = 3.72, OR = 3.30, OR = 4.02), and blood transfusions (OR = 2.09, OR = 3.65, OR = 1.74) were all significantly higher in the 3 cohorts compared to the controls. Revision/reoperation rates were significantly higher in cohorts 1 and 3 (OR = 1.52 and OR = 1.62, respectively). Patient-reported outcomes saw improvements in Harris Hip Score, objective Knee Society Score, and functional Knee Society Score postoperatively (average improvement = 32.4, 37.2, and 15.3, respectively).

CONCLUSION

Liver transplantation patients functionally benefit from total hip and knee arthroplasty, but at the cost of increased risk of infection, revision/reoperation, and medically related complications compared to controls. Mortality may also be a short-term risk.

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.

Cinacalcet in hyperparathyroidism management after pediatric renal transplantation

Secondary hyperparathyroidism is often associated with end stage renal disease; even after renal transplantation, hyperparathyroidism may persist, and is responsible for hypercalcemia, hypophosphatemia and elevated parathyroid hormone (iPTH) levels. Parathyroid hyperplasia is frequently associated with persistent hyperparathyroidism, and may require a surgical treatment. Here, we report hyperparathyroidism along with parathyroid hyperplasia in a 7-year-old child, which persisted after renal transplant. Calcitonin and pamidronate failed to decrease serum calcium levels; clodronate was also inefficient. Cinacalcet therapy normalized serum calcium and phosphorus levels, and decreased iPTH levels in 3 months; a severe parathyroid hyperplasia was also corrected under calcimimetic therapy. In conclusion, we report in a child that hypercalcemia associated with secondary hyperparathyroidism can be corrected with cinacalcet after pediatric renal transplantation. We also show that parathyroid hyperplasia can regress under calcimimetic therapy in a transplanted child, making surgery unnecessary.

Vitamin D Deficiency in Pediatric Hematopoietic Stem Cell Transplantation Patients Despite Both Standard and Aggressive Supplementation

We recently reported that more than 70% of pediatric and young adult patients had a vitamin D (VD) deficiency at the time of their hematopoietic stem cell transplantation (HSCT). Moreover, VD deficiency was associated with inferior survival at 100 days after transplantation. The goal of the present study was to evaluate the VD requirements needed to maintain an optimal VD level (30 to 60 ng/mL) during the first 3 months after transplantation using real-time VD monitoring and personalized VD supplementation. We examined 2 cohorts in this study: cohort 1, the "preintervention" cohort (n = 35), who were treated according to National Kidney Foundation guidelines for VD therapy, and cohort 2, the "intervention" cohort (n = 25) who were treated with high-dose VD with an aggressive dosage increase in those who remained VD-insufficient. Results from cohort 1 showed that despite aggressive monitoring and VD supplementation, therapeutic vitamin D levels were difficult to achieve and maintain in HSCT recipients during the early post-transplantation period. Only 43% of cohort 1 achieved a therapeutic VD level, leading to our intervention in cohort 2. Outcomes improved in cohort 2, but still only 64% of cohort 2 patients achieved a therapeutic VD level despite receiving >200 IU/kg/day of VD enterally. The median VD level in patients who did achieve sufficient levels was 40 ng/mL, with only 1 patient in each cohort achieving a supratherapeutic but nontoxic level. These data indicate that standard guidelines for VD replacement are inadequate in HSCT recipients, and further work is needed to define more appropriate dosing in this clinical setting.