Vitamin D status in kidney transplant patients: need for intensified routine supplementation

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.

Vitamin D and parathyroid hormone status in community-dwelling elderly patients with mild-to-moderate kidney impairment

INTRODUCTION

Evidence on vitamin D and parathyroid hormone (PTH) status in patients with early kidney impairment is limited. We aimed to determine the associations among kidney function, vitamin D, and PTH status in community-dwelling elderly patients with mild-to-moderate kidney impairment.

METHODS

Community-dwelling elderly patients were enrolled in this Institutional Review Board approved cross-sectional study. The eligibility criteria were as follows: age > 60 years, no recent hospitalization within the past 12 months, no conditions that affect vitamin D status including vitamin D supplementation, and eGFR > 30 mL/min/1.73 m². Serum 25-hydroxyvitamin D [25(OH)D] and parathyroid hormone (PTH) levels were assessed.

RESULTS

A total of 226 patients were enrolled. Data were expressed as mean ± SD. The mean serum 25(OH)D was 26.61 ± 10.44 ng/mL and the mean serum PTH was 50.67 ± 22.67 pg/mL. The prevalence of vitamin D deficiency [25(OH)D < 20 ng/mL] and secondary hyperparathyroidism [PTH > 65 pg/mL] were 25.3% and 18.1%, respectively. Patients with eGFR 30- < 60 mL/min/1.73m² had significantly higher prevalence of 25(OH)D < 20 ng/mL (33.7% versus 19.4%, p < 0.05) than patients with eGFR ≥ 60 mL/min/1.73 m². Multiple regression analysis showed independent negative association of serum PTH level with eGFR (mL/min/1.73 m², β: - 0.261, 95% CI [- 0.408, - 0.114]) and serum 25(OH)D (ng/mL, β: - 0.499, 95% CI [- 0.775, - 0.223], adjusted for possible confounders).

CONCLUSIONS

The prevalence of vitamin D deficiency was higher in patients with eGFR 30 - < 60 mL/min/1.73 m² than those with eGFR ≥ 60 mL/min/1.73 m². Both decreased serum 25(OH)D levels and decreased eGFR were independently associated with increased serum PTH levels among these patients.

Efficacy of weekly administration of cholecalciferol on parathyroid hormone in stable kidney-transplanted patients with CKD stage 1-3

Objectives

Kidney transplant (KTx) recipients frequently have deficient or insufficient levels of serum vitamin D. Few studies have investigated the effect of cholecalciferol in these patients. We evaluated the efficacy of weekly cholecalciferol administration on parathyroid hormone (PTH) levels in stable KTx patients with chronic kidney disease stage 1-3.

Methods

In this retrospective cohort study, 48 stable KTx recipients (37 males, 11 females, aged 52 ± 11 years and 26 months post-transplantation) were treated weekly with oral cholecalciferol (7500-8750 IU) for 12 months and compared to 44 untreated age- and gender-matched recipients. Changes in levels of PTH, 25(OH) vitamin D (25[OH]D), serum calcium, phosphate, creatinine and estimated glomerular filtration rate (eGFR) were measured at baseline, 6 and 12 months.

Results

At baseline, clinical characteristics were similar between treated and untreated patients. Considering the entire cohort, 87 (94.6%) were deficient in vitamin D and 64 (69.6%) had PTH ≥130 pg/mL. Serum calcium, phosphate, creatinine and eGFR did not differ between groups over the follow-up period. However, 25(OH)D levels were significantly higher at both 6 (63.5 vs. 30.3 nmol/L, p < 0.001) and 12 months (69.4 vs. 30 nmol/L, p < 0.001) in treated vs. untreated patients, corresponding with a significant reduction in PTH at both 6 (112 vs. 161 pg/mL) and 12 months (109 vs. 154 pg/mL) in treated vs. untreated patients, respectively (p < 0.001 for both).

Conclusions

Weekly administration of cholecalciferol can significantly and stably reduce PTH levels, without any adverse effects on serum calcium and renal function.

The Role of Vitamin D and Omega-3 PUFAs in Islet Transplantation

Recurrence of autoimmunity and allograft rejection represent major challenges that impact the success of islet transplantation. Despite the remarkable improvements achieved in immunosuppression strategies after the publication of the Edmonton protocol, long-term data of intra-hepatic islet transplantation show a gradual decline in beta-cell function. Therefore, there is a growing interest in the investigation of novel, safe and effective anti-inflammatory and immunomodulatory strategies able to promote long-term islet graft survival and notable improvements in clinical outcomes of islet transplant recipients. Vitamin D has been shown to exert anti-inflammatory and immunomodulatory effects. Pre-clinical studies investigating the use of vitamin D and its analogs (alone or in combination with immunosuppressive agents and/or other anti-inflammatory agents, such as omega-3 polyunsaturated fatty acids) showed beneficial results in terms of islet graft survival and prevention of recurrence of autoimmunity/allograft rejection in animal models of syngeneic and allogeneic islet transplantation. Moreover, epidemiologic studies demonstrated that vitamin D deficiency is highly prevalent after solid organ transplantation (e.g., heart, liver or kidney transplantation). However, studies that critically assess the prevalence of vitamin D deficiency among islet transplant recipients have yet to be conducted. In addition, prospective studies aimed to address the safety and efficacy of vitamin D supplementation as an adjuvant immunomodulatory strategy in islet transplant recipients are lacking and are therefore awaited in the future.

Bone Metabolism Parameters in Hemodialysis Patients With Chronic Kidney Disease and in Patients After Kidney Transplantation

Chronic kidney disease adversely affects the structure and metabolism of bone tissue, which may be a result of disturbed biochemical processes in adipose tissue. Renal replacement therapy is a life-saving therapy but it does not restore all metabolic functions and sometimes even escalates some disturbances. The study included 126 subjects: 47 hemodialysis patients (HD), 56 patients after renal transplantation (Tx) and 23 healthy controls (K). Bone density at the femoral neck (FN) and lumbar spine (LS), as well as body composition (adipose tissue content and lean body mass) were measured in each patient using the DXA method. In addition, serum concentrations of glucose, calcium, phosphorus, parathormone, FGF23, Klotho, osteocalcin, leptin, adiponectin and 1,25-dihydroxyvitamin D3 were measured. We observed significantly higher concentrations of leptin, FGF23 and Klotho proteins in the HD patients (77.2±48.1 ng/ml, 54.7±12.4 pg/ml, 420.6±303.8 ng/ml, respectively) and the Tx group (33.2±26.5 ng/ml; 179.8±383.9 pg/ml; 585.4±565.7, respectively) compared to the control group (24.4±24.6 ng/ml, 43.3±37.3 pg/ml, 280.5±376.0 ng/ml). Significantly lower bone density at FN was observed in the HD and Tx patients in comparison to the controls and in the HD patients compared to the Tx group. There were no significant differences in body mass composition between the studied groups. The results of this study indicate that both hemodialysis and transplantation are associated with increased serum concentrations of leptin, FGF23 and Klotho proteins, as well as lower bone density at femoral neck.

Joint association of vitamins D and K status with long-term outcomes in stable kidney transplant recipients

Background

Kidney transplant recipients (KTRs) experience substantial survival benefit compared with dialysis patients. However, their mortality and graft failure risk remain high. KTRs are often low in micronutrient status, including vitamins D and K. We investigated the association of both vitamins D and K status, and vitamin D treatment with all-cause mortality and death-censored graft failure.

Methods

We studied 461 KTRs from a single-centre study at median 6.1 years after transplantation. At baseline, vitamins D and K concentrations were measured by 25-hydroxyvitamin D [25(OH)D] and dephosphorylated uncarboxylated matrix gla protein (dp-ucMGP) and patients were categorized into: 25(OH)D &lt;50/≥50 nmol/L and median dp-ucMGP &lt;1057/≥1057 pmol/L.

Results

Mean age was 52 ± 12 years, and 122 KTRs (26%) had low vitamins D and K status. During median 9.8 years follow-up, 128 patients (28%) died and 48 (10%) developed death-censored graft failure. Low vitamins D and K status was associated with 2.33 (1.26–4.30) [hazard ratio (95% confidence interval)] increased mortality risk and 3.25 (1.17–9.08) increased graft failure risk compared with KTR with 25(OH)D ≥50 nmol/L and dp-ucMGP &lt;1057 pmol/L. Dp-ucMGP was strongly associated with mortality (per 500 pmol/L increase): 1.41 (1.08–1.41) for vitamin D treatment versus no treatment 1.07 (0.97–1.18), and graft failure 1.71 (1.17–2.49) for vitamin D treatment versus 1.19 (1.05–1.36) no treatment, P-interaction &lt;0.07 for vitamin D treatment (n = 44).

Conclusions

Combined vitamins D and K deficiency are highly prevalent and are associated with increased mortality and graft failure risk compared with high vitamins D and K status. Low vitamin K status was strongly associated with an increased risk of premature mortality and graft failure for patients treated with vitamin D versus no vitamin D treatment.

Vitamin D deficiency in solid-organ transplant recipients from a Spanish Mediterranean population

BACKGROUND

Solid-organ transplant recipients (SOTRs) are at risk of developing vitamin D deficiency, mainly caused by reduced sunlight exposure with subsequent low vitamin D synthesis in the skin.

AIM

To analyse whether SOTRs from a Spanish Mediterranean region were vitamin D-deficient.

METHODS

This was a cross-sectional, descriptive and observational study in a transplantation-specialized Dermatological Unit from a Mediterranean area to determine the calcidiol levels of a cohort of 78 consecutively attending patients not receiving vitamin D supplements. Serum 25(OH)D₃ levels were determined and clinical characteristics were collected. Logistic regression analysis was used to analyse variables associated with dichotomized 25(OH)D₃ levels (≤ or > 10 ng/mL).

RESULTS

The cohort comprised 30 lung, 29 kidney and 19 liver transplant recipients. Mean calcidiol was 18 ± 9 ng/mL. Deficiency of 25(OH)D₃ was present in 19% of patients, while 68% had insufficient levels and 13% had sufficient levels. Following multivariate logistic regression analysis, the season of blood sampling remained the only predictor of deficient 25(OH)D₃ levels.

CONCLUSION

Despite living in a mid-latitude country with sunny weather, our SOTR population was at high risk of developing hypovitaminosis D, especially in autumn/winter. Avoiding sun exposure is important to prevent skin cancer, but careful monitoring of vitamin D status is recommended, with supplementation if hypovitaminosis D is detected.

Status of vitamin D and parameters of calcium homeostasis in renal transplant recipients in Nepal: a cross sectional study

BACKGROUND

Vitamin D, apart from being an important part of the "calcium-vitamin D-parathyroid hormone" endocrine axis, has diverse range of "non-calcemic" biological actions. A high prevalence of vitamin D deficiency has been observed in renal transplant recipients (RTRs) worldwide. This study aimed to determine the prevalence of hypovitaminosis D in Nepalese RTRs and interrelations between serum 25-hydroxyvitamin D [25(OH) D] and other biochemical parameters.

METHODS

A total of 80 adult RTRs visiting a university hospital were enrolled in this cross sectional study. Serum 25(OH) D and intact parathyroid hormone (iPTH) were measured using Enhanced Chemiluminiscent Immunoassay. The RTR population was categorized into recent transplant recipients (≤1 year) and long term recipients (> 1 year). The vitamin D status was defined as per NKF/KDOQI guidelines. SPSS version 20.0 was used to analyze the data. Appropriate statistical tests were applied to compare variables between groups and establish correlation. P < 0.05 was considered to be statistically significant.

RESULTS

The mean age of the recipients was 38.11 ± 11.47 years (68 males, 85.0%). Chronic glomerulonephritis was the leading cause of CKD. The two RTR groups (recent and long term) didn't differ in demographic and biochemical characteristics. 83.75% of the recipients had PTH levels above the upper limit of the recommended range for their stage of CKD. 57.5% had hypocalcemia and none of the recipients had hypercalcemia. The median serum 25(OH) D was 24.15 ng/ml (8.00-51.50 ng/ml). Only 27.5% had sufficient vitamin D status whereas 53.8% were vitamin D insufficient and 18.8% were vitamin D deficient, the distribution almost comparable in the 2 transplant group. The serum 25(OH) D was not significantly affected by the time post-transplant, gender and sunlight avoidance. There was a significant negative correlation between serum 25(OH) D and iPTH (Pearson's r = - 0.35, P = 0.001), but not so with the graft function.

CONCLUSION

There is a high prevalence of vitamin D insufficiency in RTRs. The deficiency status is not corrected despite of nutritional improvement and normalization of GFR post-transplantation and likely exacerbates secondary hyperparathyroidism. Vitamin D supplementation coupled with sensible sun exposure could be important strategies in optimization of the vitamin D status in this population.

Vitamin D Concentration in Patients After Heart and Kidney Transplantation

BACKGROUND

One of the main actions of vitamin D is bone mineralization regulation. Vitamin D is linked also to hypertension, diabetes, and cardiovascular disease. Vitamin D deficiency may result in osteomalacia, but its excess may result in bone calcium mobilization. Kidney transplant recipients are also at risk of hypovitaminosis D because of impaired graft function. The aim of the study was to assess vitamin D concentration in patients after heart and kidney transplantation.

MATERIAL AND METHODS

Ninety-eight stable heart transplant recipients were enrolled in the study; 80 kidney transplant recipients and 22 healthy volunteers served as controls. The laboratory tests, including parameters of 25-hydroxyvitamin D (calcidiol), were assayed using commercially available kits.

RESULTS

Calcidiol deficiency (level below 10 ng/mL) was observed in 10% of the transplant group and in 55 % of the orthotopic heart transplant recipients (OHT). There was positive correlation between calcidiol concentration, hemoglobin, kidney function, and serum glucose in kidney transplant recipients. In OHT, vitamin D correlated with age, kidney function, hemoglobin, cholesterol, low-density lipoprotein cholesterol, and glucose. Both groups had similar kidney function. In both groups of patients with estimated glomerular filtration rate above 60 mL/min/1.72 m², vitamin D was significantly higher. In OHT, vitamin D was higher in nondiabetic patients. In OHT in multivariate analysis, vitamin D was predicted in 24% by kidney function (beta = -0.30; P = .02) and hemoglobin concentration (beta = 0.25; P = .03).

CONCLUSIONS

Vitamin D deficiency is more common in patients after heart transplantation than in kidney allograft recipients despite similar kidney function. The possible associations between the cardiovascular system and vitamin D merit further studies.

Mineral and Bone Disorders After Kidney Transplantation

The risk of mineral and bone disorders among patients with chronic kidney disease is substantially elevated, owing largely to alterations in calcium, phosphorus, vitamin D, parathyroid hormone, and fibroblast growth factor 23. The interwoven relationship among these minerals and hormones results in maladaptive responses that are differentially affected by the process of kidney transplantation. Interpretation of conventional labs, imaging, and other fracture risk assessment tools are not standardized in the post-transplant setting. Post-transplant bone disease is not uniformly improved and considerable variation exists in monitoring and treatment practices. A spectrum of abnormalities such as hypophosphatemia, hypercalcemia, hyperparathyroidism, osteomalacia, osteopenia, and osteoporosis are commonly encountered in the post-transplant period. Thus, reducing fracture risk and other bone-related complications requires recognition of these abnormalities along with the risk incurred by concomitant immunosuppression use. As kidney transplant recipients continue to age, the drivers of bone disease vary throughout the post-transplant period among persistent hyperparathyroidism, de novo hyperparathyroidism, and osteoporosis. The use of anti-resorptive therapies require understanding of different options and the clinical scenarios that warrant their use. With limited studies underscoring clinical events such as fractures, expert understanding of MBD physiology, and surrogate marker interpretation is needed to determine ideal and individualized therapy.

Seasonal Variation of Vitamin D Status in Long-Term Kidney Transplant Recipients

BACKGROUND

There is little information about circannual rhythm of vitamin D level in kidney transplantation (KTx) patients.

MATERIAL AND METHODS

In 71 patients (27 females; 44 males) in the long term after KTx (5.5 ± 2.6 years) during the winter and summer months plasma concentration of 25-hydroxyvitamin D (25(OH)D), 1,25-hydroxyvitamin D, parathormone (PTH), fibroblast growth factor 23 (FGF-23), calcium, and phosphorus were assessed. Vitamin D status was classified according to 25(OH)D level (ie, insufficiency, ≤30 ng/mL; deficiency, <15 ng/mL).

RESULTS

In this study, 96% of KTx patients had vitamin D insufficiency including 37% deficiency during winter and 89% of KTx patients had vitamin D insufficiency and 24% had vitamin D deficiency, respectively, during summer. Mean 25(OH)D level during winter was lower than in summer (17.4 ± 7.1 vs 20.2 ± 7.2 ng/mL; P = .02), similar to calcitriol (163.6 ± 37.4 vs 284.5 ± 77.8 pmol/L; P = .001). There were no significant differences in winter and summer levels of calcium, phosphorus, and PTH. The 25(OH)D level was significantly higher in patients with estimated glomerular filtration rate (eGFR) ≥45 mL/min/1.73 m² compared with those with lower eGFR (21.6 ± 7.5 vs 17.6 ± 6.0; P = .02) only in the summer time.

CONCLUSIONS

Most of the KTx patients have vitamin D insufficiency during both winter and summer with higher concentration of vitamin D metabolites in summer. Other factors than graft function may have an impact on vitamin D levels in KTx patients.

Underrecognition and Underestimation of Disturbances in Calcium-Phosphate Balance in Kidney Transplant Recipients

Disturbances in mineral metabolism, namely chronic kidney disease-metabolic bone disease, became more profound with impairment of renal function. The aim of the study was to assess how often calcium, phosphate, alkaline phosphatase, and parathyroid hormone (PTH) were measured in kidney transplant recipients relative to hemodialyzed patients. In addition, prevalence of hypercalcemia defined as calcium concentration over 10.5 mg/dL was assessed.

PATIENTS AND METHODS

We studied 200 kidney allograft recipients and 100 hemodialyzed patients. Calcium, phosphate, alkaline phosphatase, 25-hydroxy vitamin D, and PTH were obtained from outpatient charts.

RESULTS

All the studied parameters were available in 100% of the hemodialyzed patients. In kidney allograft recipients, calcium and phosphate levels were available in 80%, alkaline phosphatase activity was available in 40%, PTH was available in less than 10%, and vitamin D was available in 1%. Hypercalcemia was present in 10% of hemodialyzed patients and in 5% of kidney allograft recipients. Vitamin D analogue was administered to 98% of hemodialyzed patients, whereas vitamin D was administered to 28% of kidney allograft recipients, particularly those with impaired kidney function. In conclusion, calcium and phosphate are seldom assessed on an outpatient basis in kidney allograft recipients, making the diagnosis and treatment of secondary hyperparathyroidism in this population difficult. Care of kidney transplant recipients could be substantially improved, particularly in regard to chronic kidney disease-metabolic bone disease, when regular check-ups for calcium-phosphate balance are implemented and proper treatment could be introduced to prevent further chronic kidney disease-metabolic bone disease.

Raising awareness on the therapeutic role of cholecalciferol in CKD: a multidisciplinary-based opinion

Vitamin D is recognized to play an essential role in health and disease. In kidney disease, vitamin D analogs have gained recognition for their involvement and potential therapeutic importance. Nephrologists are aware of the use of oral native vitamin D supplementation, however, uncertainty still exists with regard to the use of this treatment option in chronic kidney disease as well as clinical settings related to chronic kidney disease, where vitamin D supplementation may be an appropriate therapeutic choice. Two consecutive meetings were held in Florence in July and November 2016 comprising six experts in kidney disease (N = 3) and bone mineral metabolism (N = 3) to discuss a range of unresolved issues related to the use of cholecalciferol in chronic kidney disease. The panel focused on the following six key areas where issues relating to the use of oral vitamin D remain controversial: (1) vitamin D and parathyroid hormone levels in the general population, (2) cholecalciferol in chronic kidney disease, (3) vitamin D in cardiovascular disease, (4) vitamin D and renal bone disease, (5) vitamin D in rheumatological diseases affecting the kidney, (6) vitamin D and kidney transplantation.

Pre-sarcopenia and bone mineral density in adults submitted to hematopoietic stem cell transplantation

BACKGROUND

The aim of this study was to evaluate the prevalence of pre-sarcopenia and bone mineral density after hematopoietic stem cell transplantation.

METHODS

The study group consisted of over 18-year-old patients who had been submitted to allogeneic transplantation at least one year previously. Patients and healthy controls were matched by sex, ethnic background, age, and body mass index. Body composition and bone mineral density were measured by dual-energy X-ray absorptiometry. A 24-h food recall and food frequency survey were performed. The biochemical evaluation included calcium, parathormone and vitamin D. Eighty-seven patients (52 men; age: 37.2±12.7 years; body mass index: 25±4.5kg/m2) were compared to 68 controls [31 men; age 35.4±15.5 years (p=0.467); body mass index 25.05±3.7kg/m2 (p=0.927)].

RESULTS

There was no significant difference in the dietary intake between patients and controls. The mean levels of vitamin D were 23.5±10.3ng/mL; 29 patients (41.0%) had insufficient and 26 (37.14%) deficient levels. A higher prevalence of reduced bone mineral density was observed in 24 patients (25%) compared to 12 controls (19.1% - p<0.001). Pre-sarcopenia was diagnosed in 14 (14.4%) patients and none of the controls (p=0.05). There was a higher prevalence of pre-sarcopenia (66%) in patients with grades III and IV compared to those with grades 0-II graft-versus-host disease (10.9%) (p=0.004).

CONCLUSION

patients submitted to transplantation had a higher prevalence of pre-sarcopenia and greater changes in bone mineral density compared to controls; the severity of graft-versus-host disease had an impact on the prevalence of pre-sarcopenia.

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.

Vitamin D status in renal transplant recipients living in a low-latitude city: association with body fat, cardiovascular risk factors, estimated glomerular filtration rate and proteinuria

Recent evidence suggests that vitamin D deficiency is associated with CVD, impaired kidney function and proteinuria. To date, no study has evaluated these associations in renal transplant recipients (RTR) adjusting for body adiposity assessed by a ‘gold standard’ method. This study aimed to evaluate the vitamin D status and its association with body adiposity, CVD risk factors, estimated glomerular filtration rate (eGFR) and proteinuria in RTR, living in Rio de Janeiro, Brazil (a low-latitude city (22°54'10"S)), taking into account body adiposity evaluated by dual-energy X-ray absorptiometry (DXA). This cross-sectional study included 195 RTR (114 men) aged 47·6 (sd11·2) years. Nutritional evaluation included anthropometry and DXA. Risk factors for CVD were hypertension, diabetes mellitus, dyslipidaemia and the metabolic syndrome. eGFR was evaluated using the Chronic Kidney Disease Epidemiology Collaboration equation. Serum 25-hydroxyvitamin D (25(OH)D) concentration was used to define vitamin D status as follows: 10 % (n19) had vitamin D deficiency (<16 ng/ml), 43 % (n85) had insufficiency (16–30 ng/ml) and 47 % (n91) had sufficiency (>30 ng/ml). Percentage of body fat (DXA) was significantly associated with vitamin D deficiency independently of age, sex and eGFR. Lower 25(OH)D was associated with higher odds of the metabolic syndrome and dyslipidaemia after adjustment for age, sex and eGFR, but not after additional adjustment for body fat. Hypertension and diabetes were not related to 25(OH)D. Lower serum 25(OH)D was associated with increasing proteinuria and decreasing eGFR even after adjustments for age, sex and percentage of body fat. This study suggests that in RTR of a low-latitude city hypovitaminosis D is common, and is associated with excessive body fat, decreased eGFR and increased proteinuria.

Nutritional Vitamin D in Renal Transplant Patients: Speculations and Reality

Reduced levels of nutritional vitamin D are commonly observed in most chronic kidney disease (CKD) patients and particularly in patients who have received a kidney transplant (KTx). In the complex clinical scenario characterizing the recipients of a renal graft, nutritional vitamin D deficiency has been put in relation not only to the changes of mineral and bone metabolism (MBM) after KTx, but also to most of the medical complications which burden KTx patients. In fact, referring to its alleged pleiotropic (non-MBM related) activities, vitamin D has been claimed to play some role in the occurrence of cardiovascular, metabolic, immunologic, neoplastic and infectious complications commonly observed in KTx recipients. Furthermore, low nutritional vitamin D levels have also been connected with graft dysfunction occurrence and progression. In this review, we will discuss the purported and the demonstrated effects of native vitamin D deficiency/insufficiency in most of the above mentioned fields, dealing separately with the MBM-related and the pleiotropic effects.

Bone fractures and lumbar mineral density after renal transplantation. A long-term cross-sectional study

BACKGROUND

The purpose of this work was to investigate the association of vertebral and peripheral fractures 10 yr after grafting with bone metabolic markers and body mass density (BMD).

PATIENTS AND METHODS

One hundred thirty-eight recipients with stable graft function were included in a cross-sectional study. Graft function, biochemical mineral metabolism markers and body mass density (DEXA) were measured. Vertebral fractures were assessed by a semiquantitative analysis of lateral spine X-ray exam.

RESULTS

At the time of the study, intact parathyroid hormone levels were 127.5 ± 78.4 pg/mL and serum calcidiol 20.4 ± 9.3 ng/mL. DEXA showed osteopenia in 47% and osteoporosis in 23% at lumbar spine, 51% and 14% at femoral neck, and 53% and 8% at trochanter. Eighty-five recipients presented vertebral fractures, 69 mild and 16 moderate/severe fractures. In the multivariate analysis, vertebral fractures were associated with older age (p = 0.010), length of follow-up (p = 0.022) and trochanter T-score (p = 0.038). Twenty-three patients presented peripheral fractures and 19 of them also had vertebral fractures. Patients with peripheral fractures were younger, mostly women and had lower BMD.

CONCLUSIONS

Vertebral fractures were associated with lower BMD at trochanter. Most fractures were mild and were several times more frequent than in general population. Their clinical significance needs to be determined.

Vitamin D Treatment Effect on Serum Endocan and High-Sensitivity C-Reactive Protein Levels in Renal Transplant Patients

Context:

Endocan is a marker showing endothelial dysfunction and inflammation. Significantly increased endocan levels have been observed in serum of patients with sepsis and cancer.

Objective:

Our aim was to investigate the relationship between vitamin D treatment and serum endocan and high-sensitivity C-reactive protein (hs-CRP) levels as inflammatory markers in transplant patients.

Design:

Prospective.

Setting:

Nephrology clinic.

Patients:

Thirty-eight renal transplant patients with serum 25-hydroxy-vitamin D (25-OH-vitamin D) levels below 20 ng/mL and transplanted at least 12 months.

Intervention:

One-time oral dose of 300 000 IU vitamin D3.

Main Outcome Measures:

Before and after vitamin D treatment, serum endocan, hs-CRP, calcium, phosphorus, and parathyroid hormone (PTH) levels were measured.

Results:

Median serum endocan and PTH values before vitamin D were significantly higher than those of after treatment values ( P = .001 and P < .001, respectively). On the other hand, serum total calcium and phosphorus levels before vitamin D treatment were lower than the values obtained after vitamin D treatment ( P = .0013 and P < .001, respectively). Serum hs-CRP was lower after vitamin D therapy than before, but the difference was not statistically significant ( P = .06). A moderate negative correlation was determined between endocan and 25-OH-vitamin D levels after treatment with vitamin D ( r = −.36, P = .02).

Conclusion:

This study has revealed that vitamin D treatment reduced markers of endothelial dysfunction in patients with renal transplantation and vitamin D deficiency.

Low-dose oral cholecalciferol is associated with higher numbers of Helios(+) and total Tregs than oral calcitriol in renal allograft recipients: an observational study

Background

Regulatory T cells (Tregs) are a cornerstone of graft acceptance. High numbers of Tregs are associated with better long-term graft survival. Recently, Vitamin D was suggested as an immunomodulator, in addition to its classical role in calcium metabolism. Vitamin D modulates Tregs and might, thereby, promote graft acceptance and long-term graft survival.

Methods

One hundred twenty-three renal allograft recipients attending either Heidelberg nephrology or Giessen internal medicine clinic were enrolled in this cross- sectional study. Sixteen healthy controls were studied in addition. Sixty-nine patients were receiving no vitamin D, 38 calcitriol, and 16 cholecalciferol supplementations. We evaluated whether there was a difference in the absolute numbers of Helios⁺, Helios⁻, CTLA-4⁺, IFNg⁺, and total Tregs among the patient groups.

Results

Cholecalciferol supplementation was associated with higher absolute numbers of Helios⁺, CTLA-4⁺, and total Tregs than calcitriol (p < 0.001, p = 0.004, p = 0.001 respectively). Helios⁺ Tregs were also higher in cholecalciferol than no vitamin D supplementation patients (p = 0.001), whereas CTLA-4⁺ and total Tregs were similar in both groups (p = NS). Helios⁺, Helios⁻, CTLA-4⁺, IFNg⁺, and total Tregs were similar in the cholecalciferol and healthy control groups (p = NS).

Conclusion

Our findings indicate that cholecalciferol, even when administered at low dosages, has a stabilizing effect on Tregs (particularly the Helios + subset), in contrast to calcitriol which showed neither a stabilizing nor a proliferation-inducing effect on the same cell population.

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.

The consequences of pediatric renal transplantation on bone metabolism and growth

PURPOSE OF REVIEW

During childhood, growth retardation, decreased final height and renal osteodystrophy are common complications of chronic kidney disease (CKD). These problems remain present in patients undergoing renal transplantation, even though steroid-sparing strategies are more widely used. In this context, achieving normal height and growth in children after transplantation is a crucial issue for both quality of life and self-esteem. The aim of this review is to provide an overview of pathophysiology of CKD-mineral bone disorder (MBD) in children undergoing renal transplantation and to propose keypoints for its daily management.

RECENT FINDINGS

In adults, calcimimetics are effective for posttransplant hyperparathyroidism, but data are missing in the pediatric population. Fibroblast growth factor 23 levels are associated with increased risk of rejection, but the underlying mechanisms remain unclear. A recent meta-analysis also demonstrated the effectiveness of rhGH therapy in short transplanted children.

SUMMARY

In 2013, the daily clinical management of CKD-MBD in transplanted children should still focus on simple objectives: to optimize renal function, to develop and promote steroid-sparing strategies, to provide optimal nutritional support to maximize final height and avoid bone deformations, to equilibrate calcium/phosphate metabolism so as to provide acceptable bone quality and cardiovascular status, to correct all metabolic and clinical abnormalities that can worsen both bone and growth (mainly metabolic acidosis, anemia and malnutrition), promote good lifestyle habits (adequate calcium intake, regular physical activity, no sodas consumption, no tobacco exposure) and eventually to correct native vitamin D deficiency (target of 25-vitamin D >75 nmol/l).

Overweight and body fat are predictors of hypovitaminosis D in renal transplant patients

Background

Hypovitaminosis D has been frequently reported after renal transplantation, but the impact of obesity and other factors in the reduction of vitamin D levels is not well established. We aimed to evaluate risk factors contributing to hypovitaminosis D among nondiabetic renal transplant recipients (RTR) with serum creatinine <2.0 mg/dL, at least 6 months after transplantation.

Methods

One hundred RTR were subjected to anthropometric evaluation and body composition assessment through bioelectrical impedance analysis; blood samples were drawn for biochemical and hormonal determinations and clinical data were retrieved from the medical records.

Results

Hypovitaminosis D was observed in 65% and overweight (body mass index, BMI >25 kg/m²) in 59% of cases with a significant median weight gain after transplantation of 5.1 kg. An inadequate distribution of body fat was evidenced in 50% of males and in 58% of females. Patients with either vitamin D deficiency or insufficiency presented significantly higher median values of body fat and weight gain since transplantation, as well as lower lean mass compared with patients with normal vitamin D levels (P < 0.001). Moreover, median values of waist circumference, BMI, serum leptin and parathyroid hormone levels were significantly higher in the group with vitamin D deficiency. A multivariate linear regression analysis then revealed that body fat and leptin levels, but not skin color, gender, age, glucocorticoid use, renal function, microalbuminuria and other confounding factors, were independently associated with low levels of 25 hydroxyvitamin D3 even after adjustments for seasonal variations.

Conclusion

In conclusion, the present study showed body fat and serum leptin levels to be the only independent risk factors for hypovitaminosis D among RTR.

Vitamin D: a new player in kidney transplantation?

Vitamin D is a hormone with pleiotropic effects. It mainly regulates calcium and phosphate metabolism through interactions with FGF23 and its receptor klotho. In addition, it has been shown that Vitamin D also regulates the immune response and has protective effects from cardiovascular disease, cancer and infections. Most renal transplant recipients have overt Vitamin D deficiency, a condition that may be associated with a decline in graft function and other complications. After kidney transplantation, elevated levels of FGF23 may predict increased risks of death and allograft loss. Theoretically, an optimal Vitamin D supplementation might favor operational tolerance and protect transplant recipients from the triad cardiovascular disease-cancer-infection. However, more solid data are needed to confirm this and to set the optimal level of serum Vitamin D supplementation in order to attain the best clinical outcome.

Serum 25-hydroxy vitamin D concentrations are more deficient/insufficient in peritoneal dialysis than haemodialysis patients in a sunny climate

BACKGROUND

Research has identified associations between serum 25(OH)D and a range of clinical outcomes in chronic kidney disease and wider populations. The present study aimed to investigate vitamin D deficiency/insufficiency in dialysis patients and the relationship with vitamin D intake and sun exposure.

METHODS

A cross-sectional study was used. Participants included 30 peritoneal dialysis (PD) (43.3% male; 56.87 ± 16.16 years) and 26 haemodialysis (HD) (80.8% male; 63.58 ± 15.09 years) patients attending a department of renal medicine. Explanatory variables were usual vitamin D intake from diet/supplements (IU day(-1) ) and sun exposure (min day(-1) ). Vitamin D intake, sun exposure and ethnic background were assessed by questionnaire. Weight, malnutrition status and routine biochemistry were also assessed. Data were collected during usual department visits. The main outcome measure was serum 25(OH)D (nm).

RESULTS

Prevalence of inadequate/insufficient vitamin D intake differed between dialysis modality, with 31% and 43% found to be insufficient (<50 nm) and 4% and 33% found to be deficient (<25 nm) in HD and PD patients, respectively (P < 0.001). In HD patients, there was a correlation between diet and supplemental vitamin D intake and 25(OH)D (ρ = 0.84, P < 0.001) and average sun exposure and 25(OH)D (ρ = 0.50, P < 0.02). There were no associations in PD patients. The results remained significant for vitamin D intake after multiple regression, adjusting for age, gender and sun exposure.

CONCLUSIONS

The results highlight a strong association between vitamin D intake and 25(OH)D in HD but not PD patients, with implications for replacement recommendations. The findings indicate that, even in a sunny climate, many dialysis patients are vitamin D deficient, highlighting the need for exploration of determinants and consequences.

Metabolic bone disease after renal transplantation

PURPOSE OF THE REVIEW

Posttransplantation mineral and bone disorder (MBD) is an important issue in the care of children after kidney transplantation (KTx) resulting in increased comorbidity, for example, bone pain, fractures, growth failure, and vascular calcifications. It is distinctly different from common forms of osteoporosis and mainly due to preexisting renal osteodystrophy at the time of KTx, glucocorticoid treatment, and reduced graft function. The purpose of this review is to give an overview of the pathogenesis and treatment of posttransplant MBD in children.

RECENT FINDINGS

Recent studies underline the impact of elevated levels of the phosphaturic hormone fibroblast growth factor-23 on posttransplant MBD. Glucocorticoid treatment results in impairment of bone strength, increased fracture risk, and lack of significant catch up, whereas steroid-sparing protocols allow for a normal adult height in the majority of patients. Whether the latter also improves bone strength remains to be elucidated.

SUMMARY

Therapeutic efforts to reduce MBD after KTx should focus on steroid-sparing immunosuppressive protocols, adequate treatment of alterations of calcium, phosphate and vitamin D metabolism, maintenance of regular physical activity, and preservation of transplant function. Preemptive KTx, that is with no prior dialysis, can prevent progressive vascular calcifications.

Growth in children with chronic kidney disease: role of nutrition, growth hormone, dialysis, and steroids

PURPOSE OF REVIEW

Children with chronic kidney disease (CKD) have impaired growth that leads to short stature in adulthood. The problem persists even with successful transplantation and steroid withdrawal protocols. The aim of this review is to provide an overview of the pressing issues related to growth failure in children with CKD both before and after transplantation.

RECENT FINDINGS

Although great strides have been made in dialysis and transplantation, the incidence of abnormal adult height in children growing up with CKD remains as high as 45-60%. The lack of catch-up growth and resultant short stature is a critical issue for self-esteem and quality of life in many children with CKD. Aggressive daily dialysis, improved nutrition, treatment of metabolic bone disease, and the use of recombinant human growth hormone provide some hope for catch-up growth in select patients.

SUMMARY

The causes of growth failure in the setting of CKD are multifactorial. Attention to all the details by optimizing nutritional, bone and mineral metabolism, correcting metabolic acidosis and anemia, achieving excellent blood pressure control, reversing cardiovascular complications such as left ventricular hypertrophy, and minimizing the use of corticosteroids is the current standard of care. Aggressive daily dialysis can reverse many of the uremic derangements. For patients not yet on dialysis or for those after renal transplant, early institution of recombinant human growth hormone can promote growth. Improved understanding of the mechanisms of hormone resistance may offer novel targets or measurements of treatment effectiveness.

Vitamin D deficiency predicts decline in kidney allograft function: a prospective cohort study

CONTEXT

Vitamin D, often deficient in kidney transplant (KTx) recipients, has potential immunomodulatory effects.

OBJECTIVE

This study aimed to evaluate whether vitamin D status affects the rate of decline in kidney allograft function.

DESIGN, SETTING, AND PATIENTS

The study included a prospective cohort of 264 ambulatory KTx recipients at a single Japanese center.

MAIN OUTCOME MEASURES

We measured the baseline 25-hydroxyvitamin D (25D) concentration and examined its association with annual decline in estimated glomerular filtration rate (eGFR). Secondary outcome was rescue treatment with iv methylprednisolone (IV-MP) as an index of rejection episodes.

RESULTS

The mean serum 25D concentration was 17.1 (SD 6.5) ng/mL, and 68.4% patients had vitamin D inadequacy or deficiency. Time after KTx was a significant effect modifier for the association of serum 25D concentration with annual eGFR change and need for IV-MP (P for interaction < .1). We divided patients according to the median time after KTx (10 y) and found that low vitamin D was significantly associated with a rapid eGFR decline at less than 10 years after KTx but not at 10 or more years after KTx. The same was true for rescue treatment with IV-MP. Overall, propensity score matching showed independent associations of low vitamin D with both outcomes. Stratified matching confirmed pronounced associations at less than 10 years after KTx.

CONCLUSIONS

Vitamin D deficiency predicts a rapid decline in eGFR and need for IV-MP at less than 10 years after KTx. Future studies are warranted to evaluate the clinical efficacy of vitamin D supplementation.

Immune, metabolic and epidemiological aspects of vitamin D in chronic kidney disease and transplant patients

Chronic kidney disease strongly impacts on mineral and bone metabolism. Despite numerous medications, the biological targets recommended by international guidelines are often unmet. Among the treatment armamentarium, native or nutritional vitamin D (25OHD3) has been rediscovered in the early 2000s, and its general and specific actions further studied. Effects on bone, immunity, infection prevention, muscle function and phosphocalcic metabolism have been reviewed. Assessment of nutritional vitamin D status showed very low serum 25OHD3 levels and increase in nutritional vitamin D prescription led to improvement in these levels. However, about 45% of adult CKD patients still have insufficient serum 25OHD3 levels. Epidemiological studies should be enforced to describe further the mineral and bone disease management in CKD.

[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.

Predicting deficiency of vitamin D in renal transplant recipients in northern climates

BACKGROUND

Renal transplant patients have been shown to have a higher risk of bone disease than the general population. The aim of this study was to examine vitamin D status, a modifiable risk factor in bone disease, in the renal transplant population in a northern climate.

METHODS

This retrospective observational study included 331 subjects and analyzed demographic, biochemical, and medication information for associations with vitamin D.

RESULTS

Of the study population, 45.3% were vitamin D deficient. The percentage of deficient subjects increases to 76.5% if those receiving supplementation are excluded. The mean daily dose of vitamin D was 1275 IU for sufficient patients. For every 1000 IU of vitamin D daily, the risk of deficiency is decreased by 40.3%. Time from transplantation had a significant positive association (P<0.001) in which every year out of transplantation decreased the risk of deficiency by 9.1%. Body mass index had a significant negative association (P=0.012) with vitamin D in which the risk of deficiency increased by 6% for each kilogram per meter squared. Ethnicity was found to be statistically significant on univariate analysis (P=0.034), with white patients having 9.1% decreased risk of deficiency.

CONCLUSION

Despite a high rate of supplementation of vitamin D, close to half of the renal transplant population was still deficient. Those who were receiving over 1000 IU daily were more likely to be vitamin D sufficient. Early supplementation after transplantation along with higher doses for non-white patients or patients with a high body mass index may be warranted for normalization of vitamin D status.

Recovery versus persistence of disordered mineral metabolism in kidney transplant recipients

In patients with end-stage renal disease, successful renal transplantation improves the quality of life and increases survival, as compared with long-term dialysis treatment. Although it long has been believed that successful kidney transplantation to a large extent solves the problem of chronic kidney disease-mineral and bone disorders (CKD-MBD), increasing evidence indicates that it only changes the phenotype of CKD-MBD. Posttransplant CKD-MBD reflects the effects of immunosuppression, previous CKD-MBD persisting after transplantation, and de novo CKD-MBD. A major and often-underestimated problem after successful renal transplantation is persistent hyperparathyroidism. Besides contributing to posttransplant hypercalcemia and hypophosphatemia, persistent hyperparathyroidism may be involved in the pathogenesis of allograft dysfunction (nephrocalcinosis), progression of vascular calcification, and bone disease (uncoupling of bone formation and bone resorption and bone mineral density loss) in renal transplant recipients. Similar to nontransplanted patients, CKD-MBD has a detrimental impact on (cardiovascular) mortality and morbidity. Additional studies urgently are needed to get more insights into the pathophysiology of posttransplant CKD-MBD. These new insights will allow for a more targeted and causal therapeutic approach.

Are low levels of 25-hydroxyvitamin D a risk factor for cardiovascular diseases or malignancies in renal transplantation?

BACKGROUND

Observational studies in healthy people suggest an inverse relationship between 25-hydroxy-vitamin D (25(OH)D levels) and cardiovascular diseases and malignancies. We performed an observational prospective study in renal transplant recipients to investigate the effects of vitamin D deficiency on cardiovascular and malignancy risks.

METHODS

From 389 renal transplant recipients, 331 with a functioning graft at 12 months were included in the study. Mineral metabolism parameters were measured at 1, 3, 4 and 12 months. Information regarding the cardiovascular events and malignancies were collected from an electronic database.

RESULTS

According to the 1-year mean of 25(OH)D levels, 75 recipients (22.7%) had a normal vitamin D status, 161 (48.6%) had insufficiency and 95 (28.7%) had deficiency in vitamin D levels. During the follow-up, 80 recipients presented at least one cardiovascular event. The total cardiovascular diseases included: 27 patients with coronary diseases, 25 with cardiac failure, 18 with arrhythmia, 11 with acute cerebrovascular events and 19 with peripheral vascular disease. Cardiovascular events were not associated with 25(OH)D levels or vitamin D status, and the 10-year cumulative incidence was 29.3% for normal vitamin D status and 31.6% for insufficiency and 51.9% for deficiency (P = 0.216). Furthermore, Cox univariate analysis showed no association between cardiovascular events and vitamin D levels or vitamin D status. In addition, 53 recipients presented at least one malignancy: 33 non-melanoma skin malignancies and 20 non-skin malignancies (5 prostate, 3 kidney and urinary tract, 2 colon, 2 lung, 2 lymphoma, 2 breast and 4 from other locations). The cumulative incidence of malignancies was 21.3% for normal vitamin D status, 22.7% for insufficiency and 16.7% for deficiency (P = 0.818).

CONCLUSIONS

Our data suggested that low vitamin D levels were not associated with an increased risk of cardiovascular diseases or malignancies. However, due to the small number of patients and events, the results should not be considered as definitive. Additional studies with a higher number of patients are required to elucidate the true impact of vitamin D status on cardiovascular and malignancy risks.

Calcidiol deficiency in end-stage organ failure and after solid organ transplantation: status quo

Among patients with organ failure, vitamin D deficiency is extremely common and frequently does not resolve after transplantation. This review crystallizes and summarizes existing data on the status quo of vitamin D deficiency in patients with organ failure and in solid organ transplant recipients. Interventional studies evaluating different treatment strategies, as well as current clinical practice guidelines and recommendations on the management of low vitamin D status in these patients are also discussed.

Longitudinal analysis of vascular function and biomarkers of metabolic bone disorders before and after renal transplantation

BACKGROUND/AIMS

The role of chronic kidney disease-mineral bone disorder (CKD-MBD) reversibility in the amelioration of vascular function and in the reduction of the risk for cardiovascular events after renal transplantation is still unknown.

METHODS

We investigated the longitudinal relationship between the main biomarkers of CKD-MBD and the evolution of vascular function [flow-mediated dilatation (FMD)] after transplantation in a series of 161 patients with kidney failure maintained on chronic dialysis (5D-CKD).

RESULTS

Before transplantation, FMD in patients was markedly lower (-40%, p < 0.001) than in well-matched healthy subjects and increased by 27% after transplantation (p = 0.001). Fibroblast growth factor 23 (FGF23), 25-hydroxy-vitamin D (25OHVD) and serum phosphate (p < 0.01) were independently associated with simultaneous changes in FMD. Changes in classical risk factors and in risk factors related to CKD like the glomerular filtration rate, serum albumin, C-reactive protein and insulin resistance failed to independently explain the variability in FMD changes after transplantation.

CONCLUSION

Endothelium-dependent vasodilatation improves after kidney transplantation, which is parallel to the dramatic fall in FGF23, the reduction in serum phosphorus and the increase in 25OHVD levels. If these associations are causal, a part of decline in cardiovascular risk after transplantation is related to partial resolution of CKD-MBD.

Determinants of vitamin D status in long-term renal transplant patients

In this study, we explored the determinants of vitamin D status in a large cohort of stable, Long-term renal transplant (RTx) patients. Serum 25(OH)D concentrations, and bone biochemistry parameters, were retrospectively analyzed from 266 RTx patients (>10 yr post-engraftment) presenting to clinic over the course of a year. Forty-five percent of the cohort were vitamin D deficient (<37.5 nM), 38% insufficient (37.5 75-nM), and 17% sufficient (>75 nM). Serum 25(OH)D concentrations were higher in patients presenting in summer (p<0.001) and in more active patients (p<0.05). RTx patients with non-melanoma skin cancer (NMSC) (n=45) had higher 25(OH)D concentrations than patients without NMSC (n=221; p<0.05) despite these patients being older, having worse eGFR, transplanted for longer, and less active physically (p<0.05). Lower 25(OH)D concentrations were associated with higher PTH concentrations (p<0.05) which, in the setting of widespread hypovitaminosis, suggests that secondary hyperparathyroidism was common in this cohort. In conclusion, season and activity status are important determinants of vitamin D status. We report, for the first time, that NMSC is associated with higher 25(OH)D, probably through increased UV radiation exposure. Long-term RTx patients may benefit from oral vitamin D supplementation, but this requires a randomized controlled trial to confirm.

Orally active vitamin d for potential chemoprevention of posttransplant malignancy

Posttransplant malignancy (PTM) is a limiting factor both for patient and allograft survival in kidney transplant recipients (KTRs). We hypothesized that active vitamin D compounds (AVD) could reduce PTM development in KTRs. Ambulatory KTRs in a Japanese prospective cohort were followed from August 2007 to November 2010. The outcome of interest was newly diagnosed PTM. A propensity score (PS) of having received AVDs was estimated using 26 clinically relevant factors. We used the Cox proportional hazards model with stratification by PS tertiles on the assumption that baseline hazard functions differ among tertiles. As sensitivity analyses, we used inverse probability weighting and PS matching. Among 218 participants, the median age was 50 (interquartile range [IQR], 40 to 59) years, 63.3% were male, median time since transplantation was 11.2 (IQR, 5.2 to 17.1) years, and mean estimated GFR was 41.3 (SD, 15.6) mL/min per 1.73 m(2). At baseline, 42.2% had been treated with AVDs mainly for glucocorticoid-induced osteoporosis. AVDs used were calcitriol (58.7%) and alfacalcidol (41.3%). During follow-up, PTM developed in 5.4% of 92 AVD users and 8.7% of 126 nonusers. Poor vitamin D status was common in the participants, but the serum 25-hydroxyvitamin D level was not significantly associated with PTM in Cox regression analysis. After stratifying patients by PS tertiles, we found that AVDs were significantly associated with a lower risk of PTM (HR 0.25 [0.07 to 0.82]). Sensitivity analyses yielded similar results. AVDs are potential chemopreventive agents against PTM in KTRs.

Randomized controlled trial of cholecalciferol supplementation in chronic kidney disease patients with hypovitaminosis D

BACKGROUND

Hypovitaminosis D is common in chronic kidney disease (CKD). Effects of 25-hydroxyvitamin D replenishment in CKD are not well described.

METHODS

An 8-week randomized, placebo-controlled, double-blind parallel intervention study was conducted in haemodialysis (HD) and non-HD CKD patients. Treatment consisted of 40,000 IU of cholecalciferol orally per week. Plasma 25-hydroxyvitamin D (25-OHD), plasma 1,25-dihydroxyvitamin D (1,25-diOHD), plasma parathyroid hormone (PTH), serum phosphate, ionized serum calcium and serum fibroblast growth factor 23 (FGF-23) were analysed. We also investigated biomarkers related to cardiovascular disease (plasma D-dimer, plasma fibrinogen, plasma von Willebrand factor antigen and activity, plasma interleukin 6, plasma C-reactive protein, blood pressure, aortic augmentation index, aortic pulse wave velocity and 24-h urinary protein loss). Objective and subjective health variables were assessed (muscle function tests, visual analogue scores and Health Assessment Questionnaire).

RESULTS

Fifty-two CKD patients with 25-OHD <50 nmol/L at screening were included. Cholecalciferol supplementation led to a significant increase to a median of 155 nmol/L 25-OHD (interquartile range 137-173 nmol/L) in treated patients (n = 25, P < 0.001). In non-HD patients, we saw a significant increase in 1,25-diOHD (n = 13, P < 0.01) and a lowering of PTH (n = 13, P < 0.001). This was not observed in HD patients. Cholecalciferol supplementation caused a significant increase in serum calcium and FGF-23.

CONCLUSIONS

25-OHD replenishment was effectively obtained with the employed cholecalciferol dosing. In non-HD patients, it had favourable effects on 1,25-diOHD and PTH. Vitamin D-supplemented patients must be monitored for hypercalcaemia. The present study could not identify significant pleiotropic effects of 25-OHD replenishment.

Prevalence of vitamin D deficiency in post renal transplant patients

AIM

Deficiency of Vitamin D is prevalent in the general population, especially in Chronic Kidney Disease (CKD) patients. The exact prevalence of Vitamin D deficiency is unknown in post renal transplant recipients. The classical and non-classical effects of vitamin D deficiency are complicated by the use of steroids and calcineurin inhibitors (CNIs) in the renal transplant population. The aim of this study is to document the prevalence of Vitamin D deficiency in the post renal transplant population.

MATERIALS AND METHODS

A total of 51 renal transplant recipients under follow-up at Indraprastha Apollo Hospital, between June 2009 and March 2011, were enrolled in this study. Parathormone (PTH), 25(OH)-vitaminD3, calcium, and phosphate levels were determined in all the patients. The patients were then classified into different groups based on the severity of the Vitamin D deficiency, time since transplantation, and level of graft function.

RESULTS

Overall, four patients (8%) were vitamin D sufficient, 17 patients (33%) insufficient, 26 patients (51%) mildly deficient, and four (8%) severely deficient. The degree of deficiency did not differ with reference to the time since transplant or level of graft function. Sixty-nine percent had high PTH level, 22% were normal, and 9% had a low parathyroid hormone level. There was an inverse correlation between Vitamin D deficiency and serum PTH level.

CONCLUSION

In this study, there was a high prevalence of vitamin D deficiency in renal transplant recipients. This did not get corrected, despite nutritional improvement or normalization of the glomerular filtration rate (GFR) post transplantation. Therefore, the study emphasizes routine evaluation and proper supplementation of Vitamin D in all post renal transplant patients.

Renal phosphate loss in long-term kidney transplantation

BACKGROUND AND OBJECTIVES

Renal phosphate wasting occurs early postkidney transplantation as a result of an accumulation of parathyroid hormone and fibroblast growth factor 23 from the CKD period. Serum phosphate, parathyroid hormone, and fibroblast growth factor 23 return to baseline 1 year postkidney transplantation. What happens beyond this period is unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Mineral parameters were obtained from 229 kidney transplant recipients at least 1 year posttransplantation; 46 normal subjects and 202 CKD patients with similar GFR served as controls. Factors associated with phosphate metabolism were analyzed.

RESULTS

Despite the reduced graft function, most kidney transplant recipients had lower serum phosphate than normal subjects accompanied by renal phosphate loss. Fibroblast growth factor 23 was mostly lower or comparable with normal subjects, whereas parathyroid hormone was elevated in most patients. Hyperparathyroidism is also more common among kidney transplant recipients compared with CKD patients. Both parathyroid hormone and fibroblast growth factor 23 showed relationships with renal phosphate excretion, but only parathyroid hormone displayed an independent association. Parathyroid hormone showed the highest area under the curve in predicting renal phosphate leak. When patients were categorized according to parathyroid hormone and fibroblast growth factor 23 levels, only subset of patients with high parathyroid hormone had an increased renal phosphate excretion.

CONCLUSIONS

Relatively low serum phosphate from renal phosphate leak continued to present in long-term kidney transplantation. Both parathyroid hormone and fibroblast growth factor 23 participated in renal tubular phosphate handling, but persistent hyperparathyroidism seemed to have a greater influence in this setting.

Vitamin D in organ transplantation

Vitamin D deficiency is prevalent among patients with end-stage organ failure awaiting transplant. Low serum 25-hydroxyvitamin D (25-OHD) levels in these patients may be related to many disease-specific factors, as well as decreased sunlight exposure and limited intake of foods containing vitamin D. Low serum 25-OHD levels are also extremely common following solid organ transplantation, both during the immediate postoperative period and in long-term graft recipients. Demographic and lifestyle factors are important in determining D status in transplant recipients. Worse vitamin D status is associated with poorer general health, lower albumin, and even decreased survival among these patients. Although several studies have demonstrated that active forms of vitamin D and its analogues prevent bone loss following transplantation, the data do not show consistent benefit. These therapies may have particular utility after renal transplantation. However, given the narrow therapeutic window with respect to hypercalcemia and hypercalciuria, and the demonstrated efficacy of bisphosphonates to prevent post-transplantation bone loss, we regard these agents as adjunctive rather than primary therapy for transplantation osteoporosis. The effects of 1,25(OH)(2)D on the immune system, which are still being elucidated, may have potential for reducing infections and preventing allograft rejection after transplantation.

Therapeutic management of post-kidney transplant hyperparathyroidism

Left uncontrolled, persistent post-kidney transplant hyperparathyroidism (HPT) may lead to or exacerbate pre-existing bone and cardiovascular disease. Parathyroidectomy has long been the primary treatment option for long-term uncontrolled HPT in post-kidney transplant patients. However, patients with contraindications for surgery and parathyroidectomy-associated complications, including graft loss, highlight the need for other approaches. Conventional medical therapies have limited impact on serum calcium (Ca) and parathyroid hormone (PTH) levels. Bisphosphonates and calcitonin, used to spare bone loss, and phosphorus supplementation, to correct hypophosphatemia, do not directly regulate PTH or Ca. Although vitamin D supplementation can reduce PTH, it is often contraindicated because of hypercalcemia. Studies of the calcimimetic cinacalcet in patients with post-kidney transplant HPT suggest that it can rapidly reduce serum PTH and Ca concentrations while increasing serum phosphorus concentrations toward the normal range. Although the clearest application for cinacalcet is the non-surgical treatment of hypercalcemic patients with persistent HPT, current indications for other transplant patients are as yet uncertain. Further studies are needed to determine the utility of cinacalcet in patients with spontaneous resolution of HPT or low bone turnover. This review discusses the pathophysiology of post-kidney transplant HPT, associated complications, and current options for clinical management.

Vitamin D status in children and adolescents with kidney transplants

Hypovitaminosis D is highly prevalent in adult kidney-transplanted patients. The knowledge of vitamin D status in kidney-transplanted children and adolescents is sparse. The present study investigated the vitamin D status of a cohort of kidney-transplanted children and adolescents, and the association between vitamin D status and plasma concentrations of PTH, ionized calcium, and phosphate. The study included 35 patients with a functioning graft. Their mean age was 12.0 yr, and the mean graft age was 2.8 yr. Forty percent of the patients were vitamin D insufficient (P-25-hydroxyvitamin D 40-75 nm), and 14% were deficient (P-25-hydroxyvitamin D < 40 nm). S-25-hydroxyvitamin D was inversely associated with PTH (p = 0.02) and positively associated with S-1,25-dihydroxyvitamin D (p = 0.02). There was no significant association between S-1,25-dihydroxyvitamin D and PTH. In conclusion, we found hypovitaminosis D in 54% of the study population despite the fact that samples were collected in spring and summer months. Hypovitaminosis D was associated with adverse effects on PTH and 1,25-dihydroxyvitamin D. Our data suggest that it is warranted to monitor vitamin D status of kidney-transplanted children and adolescents and indicate that correction of hypovitaminosis D might have favorable effects on calcium-phosphate metabolism.

Vitamin D deficiency in a renal transplant population: safe repletion with moderate doses of calcidiol

BACKGROUND

Deficits of vitamin D are a common finding in the general population, especially among patients with chronic kidney disease. However, there are not much data about its prevalence after renal transplantation. Our aim was to analyze the calcidiol status among a cohort of kidney transplant recipients, in a region of Spain with a high number of annual sunshine hours, as well as the effects of supplementation with oral calcidiol.

PATIENTS AND METHODS

We included 110 kidney transplant recipients in a retrospective observational study. Measurements of 25-hydroxyvitamin D (25OHD), calcium, phosphate, intact parathyroid hormone (iPTH), serum creatinine and albumin, 24-hour microalbuminuria, and proteinuria were performed at the same time. Patients were classified based on their serum 25OHD levels: normal (>30 ng/mL); insufficiency (16-30 ng/mL); and deficiency (<16 ng/mL). In a second analysis, we included 63 patients with 25OHD<30 ng/mL with adjusted calcium levels below 10.2 mg/dL for treatment with oral calcidiol to approach target levels of 30 to 40 ng/mL. Mineral metabolism parameters were monitored at baseline as well as 6 and 12 months after beginning treatment.

RESULTS

Insufficient or deficient 25OHD levels were present in 106/110 patients (96.3%); they were normal in just four patients (3.6%). Patients with calcidiol deficiency were older. We observed no differences in sex, posttransplant follow up, serum calcium, phosphate, iPTH, glomerular filtration rate, or 24- hour albuminuria or proteinuria. The 63 patients treated with oral calcidiol received a mean dose of 8044±4087 IU/wk at baseline. The 61.3% of them with deficient 25OHD levels at baseline decreased to 2.1% at 6 months and 7.5% at 12 months after treatment. No significant changes in calcium, phosphate or iPTH were observed during the treatment.

CONCLUSIONS

Deficits of 25 OHD was frequent after renal transplantation but improved safely with moderate doses of oral calcidiol without negative secondary effects.

Mineral abnormalities and long-term graft function in pediatric renal transplant recipients: a role for FGF-23?

BACKGROUND

Although current guidelines recommend the evaluation of mineral and bone metabolism in patients with all stages of chronic kidney disease (CKD), the prevalence of altered mineral ion homeostasis in the pediatric posttransplant population is unknown. Moreover, the contribution of abnormal mineral ion metabolism to graft outcomes in this population has not been evaluated.

METHODS

Serum calcium, phosphorus, 25(OH)vitamin D, 1,25(OH)(2)vitamin D, parathyroid hormone (PTH) and fibroblast growth factor 23 (FGF-23) levels were evaluated 4.9 ± 0.5 years after transplantation in 68 stable pediatric renal allograft recipients. Patients were subsequently followed for 2 years.

RESULTS

At baseline, mean estimated glomerular filtration rate (GFR) was 60 ± 2 mL/min/1.73 m(2). Serum calcium and phosphorus values were within the reference interval. PTH values were elevated but did not differ by CKD stage. 25(OH)vitamin D levels were low in nearly half of all subjects. Tubular reabsorption of phosphate and 1,25(OH)(2)vitamin D values were lower, while FGF-23 and PTH values were higher in more advanced stages of CKD. Thirty percent of patients with FGF-23 values >110 RU/mL had a decrease in GFR of >50% (P < 0.05) and FGF-23 values predicted future episodes of rejection.

CONCLUSIONS

Despite normal serum calcium and phosphorus levels in the majority of prevalent pediatric renal transplant recipients, abnormalities in PTH, 25(OH)vitamin D and FGF-23 are common. FGF-23 levels may be associated with increased risk for deterioration of kidney function and episodes of rejection.

Tertiary excess of fibroblast growth factor 23 and hypophosphatemia following kidney transplantation

Hypophosphatemia caused by inappropriate urinary phosphate wasting is a frequent metabolic complication of the early period following kidney transplantation. Although previously considered to be caused by tertiary hyperparathyroidism, recent evidence suggests a primary role for persistently elevated circulating levels of the phosphorus-regulating hormone, FGF23. In the setting of a healthy renal allograft, markedly increased FGF23 levels from the dialysis period induce renal phosphate wasting and inhibition of calcitriol production, which contribute to hypophosphatemia. While such tertiary FGF23 excess and resultant hypophosphatemia typically abates within the first few weeks to months post-transplant, some recipients manifest persistent renal phosphate wasting. Furthermore, increased FGF23 levels have been associated with increased risk of kidney disease progression, cardiovascular disease, and death outside of the transplant setting. Whether tertiary FGF23 excess is associated with adverse transplant outcomes is unknown. In this article, we review the physiology of FGF23, summarize its relationship with hypophosphatemia after kidney transplantation, and speculate on its potential impact on long-term outcomes of renal allograft recipients.

1,25-dihydroxyvitamin D deficiency predicts poorer outcome after renal transplantation

OBJECTIVE

To assess 1,25-dihydroxyvitamin D status and the effect of vitamin concentration on transplantation outcome in renal allograft recipients.

PATIENTS AND METHODS

Ninety patients underwent renal transplantation between 2002 and 2005. All received alfacalcidol supplementation before surgery. 1,25-Dihydroxyvitamin D concentration was determined on day 3 posttransplantation and at 1-, 6-, 12-, 18-, and 24-month follow-up.

RESULTS

Severe 1,25-dihydroxyvitamin D deficiency was noted in 83% of patients immediately posttransplantation. From 1 to 12 months thereafter, concentrations increased almost 3-fold, and remained constant to 24 months. In 50% of patients, the 1,25-dihydroxyvitamin D concentration reached a concentration of more than 30 pg/mL, similar to that in healthy volunteers; in the other 50%, the concentration reached 17.2 pg/mL. A high incidence of delayed graft function was observed in patients with 1,25-dihydroxyvitamin D deficiency (44% vs 6%). There was a negative correlation between the initial 1,25-dihydroxyvitamin D and serum creatinine concentrations at day 3 and month 6 (P < .03). Similarly, the 1,25-dihydroxyvitamin D concentration at 1 month was negatively correlated with creatinine concentration at months 1 through 24 (P < .01). Poor outcome was observed primarily in patients with 1,25-dihydroxyvitamin D deficiency; 2 patients developed cancer, 5 grafts were lost, and 4 patients died of cardiovascular events.

CONCLUSIONS

1,25-Dihydroxyvitamin D deficiency is highly prevalent in renal allograft recipients. Patients with 1,25-dihydroxyvitamin D deficiency are at greater risk of delayed graft function, and the graft is more likely to be lost. These findings suggest the necessity of adequate vitamin D supplementation both before and after transplantation.

Severe vitamin D deficiency among heart and liver transplant recipients

INTRODUCTION

Although patients with end-stage organ failure are at high risk for vitamin D deficiency because of limited sunlight exposure and hepatic dysfunction, few studies have measured 25-hydroxy vitamin D (25OHD) at the time of transplantation.

METHODS

We measured serum 25OHD immediately after transplantation in 69 heart and liver transplant recipients.

RESULTS

Forty-six heart and 23 liver transplant recipients were evaluated (mean age 53 yr). Mean 25OHD was well below the lower limit of the normal range (43.2 +/- 21.2 nmol/L). Ninety-one percent had levels below 75 nmol/L, the threshold commonly used to denote sufficiency, and 71% had levels below 50 nmol/L. Severe deficiency (25OHD <25 nmol/L) was found in 16%. Vitamin D levels did not differ by race, age, gender, or season. Mean 25OHD was lower among liver than heart transplant recipients (34.4 +/- 17.5 vs. 47.7 +/- 20.7 nmol/L; p < 0.03). Among liver transplant recipients, 22% had undetectable levels (<17 nmol/L).

CONCLUSIONS

Vitamin D deficiency is highly prevalent among heart and liver transplant recipients; those with liver failure are at greatest risk. As vitamin D deficiency has many serious skeletal and extra-skeletal sequelae, physicians who treat transplant patients should maintain a high degree of vigilance for this problem.