Bone Disease in Renal Transplantation and Pleotropic Effects of Vitamin D Therapy

Vitamin D Metabolites, Body Composition, and Nutritional Status in Patients in the Long Term After Kidney Transplantation

Background

The aim of the study was to assess the relationship between body composition and nutritional status with the level of vitamin D metabolites 25(OH)D and 1,25(OH)₂D in patients in the long term after kidney transplantation (KTx).

Material/Methods

During 2 routine outpatient visits in summer and winter, the anthropometric and body composition measurements and laboratory data from 105 stable KTx patients were taken and the annual averages were analyzed.

Results

Data of 64 patients (26 F, 38 M) at mean age 49.3±12.2 years and 5.6±2.7 years after KTx with mean BMI 26.9 kg/m² were included for final analysis. Mean annual 25(OH)D concentration was 18.76±6.32 ng/dl and 1,25(OH)₂D 86.65±18.0 pg/ml. A reverse relationship between 25(OH)D level and fat tissue index was observed (r=−0.26; P=0.039). 25(OH)D level increased together with body cell mass (r=0.30, P=0.017) and lean tissue mass values (r=0.30, P=0.015). The body weight and BMI were not associated with 25(OH)D or 1,25(OH)2D level. A reverse relationship was found between: 25(OH)D and total cholesterol (r=−0.31, P=0.012) and LDL level (r=−0.25, P=0.049), and between 1,25(OH)2D and HDL level (r=−0.25, P=0.046). No significant correlations between biochemical nutritional parameters, graft function and 25(OH)D or 1,25(OH)2D were noted.

Conclusions

Body composition is one of the factors affecting the vitamin D status in KTx patients. Fat tissue index is a negative predictor of 25(OH)D level in patients in the long term after KTx. A low level of 25(OH)D predisposes to lipids disturbances in KTx recipients.

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.

Perioperative management of renal transplant patients undergoing total joint arthroplasty

The success of renal transplantation depends on lifelong immunosuppression. This can lead to a high incidence of avascular necrosis of major joints in the body for which arthroplasty is the treatment of choice. The risk of surgical complications is high in these patients, and there is no current set of cohesive perioperative management guidelines. In this review, we discuss the perioperative management of renal transplant patients undergoing elective total joint arthroplasty.

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.

Long-Term Outcome after Rehabilitation of Bilateral Total Hip Arthroplasty in Renal Transplant Recipient - A Case Report

INTRODUCTION:

Total hip replacement is generally proposed for renal transplant patients with avascular osteonecrosis of the femoral head.

PURPOSE:

The purpose of the study is to report the long-term outcome after rehabilitation of bilateral total hip arthroplasty in a patient with renal transplantation suffering from avascular osteonecrosis of the both femoral heads.

MATERIAL AND METHOD:

The patient S.D, 49 years old at follow-up. Few months after renal transplantation, the patient had got avascular osteonecrosis of both femoral head. One year after transplantation the total hip arthroplasty for both hip joints were performed. Three years later repeat total hip arthroplasty surgery for left hip was performed. After any surgery intervention the patient was referred for inpatient rehabilitation. For clinical assessment the clinical findings and Harris Hip Score have been used. The rehabilitation program consisted of exercises, occupational therapy, and patient education.

RESULTS:

After any rehabilitation treatment the patient had improvement of clinical findings. At follow-up assessment outcome for both hip function was good - Harris Hip Score was 81 points.

CONCLUSION:

Rehabilitation is integral part of multidisciplinary treatment of renal transplant recipient after total hip arthroplasty. Regular exercise training of these patients is very important for improving of their long-term outcome.

Is Klotho F352V Polymorphism the Missing Piece of the Bone Loss Puzzle in Renal Transplant Recipients?

BACKGROUND

Bone disorders are next to cardiovascular problems in frequency in renal transplant (RT) recipients. Reduction in 1,25-dihydroxycholecalciferol (1,25D) levels is among the reasons causing bone loss in these patients. Klotho (KL) serves as a co-receptor for fibroblast growth factor 23 (FGF23), and functions in vitamin D metabolism. KL polymorphisms have been identified in several studies, and phenylalanine to valine substitution at amino acid position 352 seemed to be important to KL function. We investigated KL F352V polymorphism and its relation with 1,25D levels in RT recipients.

METHODS

The study included 25 RT recipients (8 female, 17 male) and 26 (14 female, 12 male) healthy control subjects who were wild (FF) phenotypes in terms of KL F352V polymorphism. RT recipients with (FV, n = 11) and without (FF, n = 14) a heterozygote polymorphism were determined with high resolution DNA melting analysis of KL F352V polymorphism. Serum 1,25D levels were measured using the RIA method.

RESULTS

RT recipients with FV phenotype had significantly lower 1,25D levels (17.58 ± 18.38 pg/ml) compared to recipients with FF phenotype (44.91 ± 24.68 pg/ml) and control subjects (28.24 ± 12.13 pg/ml). 1,25D levels in RT recipients with FF phenotype were significantly higher than control subjects.

CONCLUSIONS

KL F352V polymorphism may increase the expression of FGF23 co-receptor, KL protein and thus may decrease renal expression of 1α-hydroxylase, and/or stimulate 24-hydroxylase in RT recipients. The resultant decrease 1,25D levels may participate in bone loss in these patients.

Osteonecrosis requiring total joint arthroplasty is a rare sequel in children and young adults treated for solid tumors

BACKGROUND

Osteonecrosis (ON) is a potential sequel in patients treated for malignancies. The goal of this population-based register study was to determine the incidence of ON requiring total joint arthroplasty (TJA) in patients treated for solid tumors in childhood, adolescence, or early adulthood.

MATERIAL AND METHODS

Patients diagnosed with a solid tumor before the age of 31 years were identified from the Finnish and Danish Cancer Registries. Patients with non-melanoma skin cancers and bone and connective tissue cancers were excluded. The data were combined with data from the National Hospital Discharge Registers and the Finnish Arthroplasty Registry. Data on the orthopedic procedures performed and the diagnosis codes given before the age of 40 years were retrieved.

RESULTS

Twenty-five of 18 542 (0.13%) patients had undergone TJA. The overall 20-year cumulative incidence of ON requiring TJA was 1% in patients treated for kidney cancer, followed by 0.5% in patients with breast cancer and 0.2% in patients with testicular cancer.

CONCLUSION

Severe ON requiring TJA is a rare sequel in children and young adults treated for solid tumors. It was observed most commonly in patients treated for renal, breast, or testicular cancer.

Optimization of Bone Health in Children before and after Renal Transplantation: Current Perspectives and Future Directions

The accrual of healthy bone during the critical period of childhood and adolescence sets the stage for lifelong skeletal health. However, in children with chronic kidney disease (CKD), disturbances in mineral metabolism and endocrine homeostasis begin early on, leading to alterations in bone turnover, mineralization, and volume, and impairing growth. Risk factors for CKD-mineral and bone disorder (CKD-MBD) include nutritional vitamin D deficiency, secondary hyperparathyroidism, increased fibroblast growth factor 23 (FGF-23), altered growth hormone and insulin-like growth factor-1 axis, delayed puberty, malnutrition, and metabolic acidosis. After kidney transplantation, nutritional vitamin D deficiency, persistent hyperparathyroidism, tertiary FGF-23 excess, hypophosphatemia, hypomagnesemia, immunosuppressive therapy, and alteration of sex hormones continue to impair bone health and growth. As function of the renal allograft declines over time, CKD-MBD associated changes are reactivated, further impairing bone health. Strategies to optimize bone health post-transplant include healthy diet, weight-bearing exercise, correction of vitamin D deficiency and acidosis, electrolyte abnormalities, steroid avoidance, and consideration of recombinant human growth hormone therapy. Other drug therapies have been used in adult transplant recipients, but there is insufficient evidence for use in the pediatric population at the present time. Future therapies to be explored include anti-FGF-23 antibodies, FGF-23 receptor blockers, and treatments targeting the colonic microbiota by reduction of generation of bacterial toxins and adsorption of toxic end products that affect bone mineralization.

Low bone mineral density and nutritional vitamin D deficiency in pediatric renal transplant recipients: Assessment of risk factors and response to oral vitamin D therapy

VitD deficiency and bone disease are common after Tx. Prevalence and risk factors for low VitD and BMD and response to VitD therapy were investigated in pediatric renal Tx recipients. 25-hydroxy VitD levels of 71 Tx were compared to 54 healthy AA children. DXA of 44 Tx were compared to 47 AA controls. Of Tx, 59% were AA. Majority (59.1%) of Tx were VitD deficient (23.9%) or insufficient (35.2%). Prevalence of low VitD levels was double in AA (73.9%) vs. non-AA Tx (37.7%), (p = 0.003). Low VitD among Tx was associated with AA ethnicity (p < 0.01), winter (p < 0.05), older age (p < 0.05), males (p < 0.05) and time <6 months post Tx (p < 0.05). Tx with low VitD were treated with oral ergocalciferol or cholecalciferol (23 each); 13% treated with ergocalciferol vs. 82.6% treated with cholecalciferol achieved repletion (p < 0.0001). Of 36 Tx with whole body DXA, 19.5% had BMD (z < -1) after height adjustment. AA Tx had 3.4-fold higher risk of low BMD vs. controls (p < 0.05). Low VitD and BMD are prevalent in children after renal Tx. Better repletion of VitD is achieved with cholecalciferol.