Bone disease after kidney transplantation

Evaluation of the Relationship Between Homocysteine, Parathormone, Vitamin D3, and Bone Mineral Densitometry in Recipients of Kidney Transplant

PURPOSE

In this study, we evaluated the relationship between serum homocysteine level and proteinuria, parathyroid hormone, vitamin D, and bone mineral density in kidney transplant recipients (KTR).

MATERIALS AND METHODS

A total of 117 stable KTR older than 18 years was followed in our outpatient clinic. Demographic data were recorded. Simultaneously biochemical parameters, including glucose, blood urea nitrogenous, creatinine, calcium, phosphorus, sodium, potassium, albumin, parathormone, vitamin D₃, homocysteine, vitamin B₁₂, folate, and 24-hour urine protein, and bone mineral density of the femoral neck and spine by dual-energy x-ray absorptiometry (DEXA) were measured.

RESULTS

DEXA measurements were normal, osteoporotic, and osteopenic (12.3%, 36.3%, and 51.3%, respectively). There was a relationship between the serum homocysteine and usage of rapamycin (P = .05), statins (P = .057), and beta blockers (P = .01), DEXA measurements were not related with serum homocysteine levels and immunosuppressive drugs used. Serum homocysteine levels correlated negatively with blood urea nitrogen (P = .002), creatinine (P = .001), vitamin B₁₂ (P < .001), and a positively daily proteinuria (rho = 0.203, P = .031). There was a negative relationship between proteinuria and serum level of vitamin D.

CONCLUSIONS

The bone mineral density decreased in more than 87% of our KTR. We did not find any relationship between DEXA measurements and levels of homocysteine, vitamin D, parathormone, and immunosuppressive drugs. It should be noted that some drugs used may affect serum homocysteine levels. Interestingly, there was a relationship between proteinuria and serum levels of homocysteine and vitamin D. Therefore, serum levels of homocysteine and vitamin D should be evaluated for preventing renal damage in KTR.

Outcomes of bisphosphonate and its supplements for bone loss in kidney transplant recipients: a systematic review and network meta-analysis

BACKGROUND

Mineral bone disease constitutes a common complication of post-kidney transplantation, leading to great disability. As there is no consensus on the optimal treatment for post-kidney transplant recipients (KTRs), we aimed to evaluate the efficacy and safety of bisphosphonate and its combined therapies.

METHODS

We incorporated relevant trials to perform a network meta-analysis from direct and indirect comparisons. We searched PubMed, Embase and the CENTRAL and the reference lists of relevant articles up to August 1, 2017, for randomized controlled trials. The primary outcome was bone mineral density (BMD) change at the femoral neck and the lumbar spine.

RESULTS

From a total of 864 citations, 18 randomized controlled trials with a total of 1200 participants were included. Five different regimens were considered. Bisphosphonate plus calcium revealed a significant gain in percent BMD change than calcium alone at the femoral neck (mean difference (MD), 5.83; 95% credible interval (CrI), 1.61 to 9.27). No significant difference was detected when restricting to absolute terms. At the lumbar spine, bisphosphonate and calcium with or without vitamin D analogs outperformed calcium solely (MD, 0.07; 95% CrI, 0.00 to 0.13; MD, 0.06; 95% CrI, 0.02 to 0.09). Compared to calcium with vitamin D analogs, adding bisphosphonate was associated with marked improvement (MD, 0.03; 95% CrI, 0.00 to 0.05). Considering percent terms, combination of bisphosphonate with calcium and vitamin D analogs showed greater beneficial effects than calcium alone or with either vitamin D analogs or calcitonin (MD, 10.51; 95% CrI, 5.92 to 15.34; MD, 5.48; 95% CrI, 2.57 to 8.42; MD, 6.39; 95% CrI, 0.55 to 12.89). Both bisphosphonate and vitamin D analogs combined with calcium displayed a notable improvement compared to calcium alone (MD, 7.24; 95% CrI, 3.73 to 10.69; MD, 5.02; 95% CrI, 1.20 to 8.84).

CONCLUSIONS

Our study suggested that additional use of bisphosphonate was well-tolerated and more favorable in KTRs to improve BMD.

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.

Osteoporosis in the adult solid organ transplant population: underlying mechanisms and available treatment options

The prevention and treatment of osteoporosis is an increasingly important topic in the solid organ transplant (SOT) population. Compared to the general population, these patients are at an elevated risk of developing osteoporosis due to progressive disease, lifelong immunosuppressant therapy, and malnutrition. As patients live longer after transplant, chronic disease management is increasingly more important. Supplementation with calcium and vitamin D is often necessary in the SOT population due to a high incidence of vitamin D deficiency. Bisphosphonate therapy is most commonly used for prevention and treatment of osteoporosis, but therapy can be limited by renal dysfunction which is common in transplant recipients. Alternative agents such as teriparatide and calcitonin have not been shown to provide a significant impact on the rate of fractures in this population. Additionally, denosumab may be a promising treatment option due to its novel mechanism of action, and is currently being studied in renal transplant patients. Timely initiation of supplementation and treatment, and minimizing glucocorticoid exposure prior to and after transplantation will aid in the prevention and proper management of osteoporosis in these patients.

Alendronate as an effective treatment for bone loss and vascular calcification in kidney transplant recipients

Kidney transplant recipients develop secondary osteoporosis induced by immunosuppressive medication, with a high risk of fracture, and abdominal aortic calcification (AC) is a known predictor of cardiovascular mortality. In this study of 12 stable kidney recipients, we estimated the preventive effect of bisphosphonate treatment on bone loss and progression of AC. We randomly divided the subjects into a treatment group with alendronate (group A: 5 subjects) and a control group (group C: 7 subjects). Group A patients received 35 mg/week of alendronate over 24 months, while group C patients were not administered with any bisphosphonates. Two major endpoints were established: (1) the time-dependent change in bone mineral density (BMD) estimated with DEXA and (2) progression of abdominal AC, calculated twice as an index (ACI) using computed tomography data. Over the 2-year study period, group A patients showed significantly increased BMD of 1.86 ± 0.85% (P = 0.015 versus baseline), and almost complete inhibition of ACI progression (38.2 ± 24.2% to 39.6 ± 24.3%), but group C patients showed a decrease in BMD decline with bone loss and progression of ACI (32.8 ± 25.0% to 37.8 ± 29.2%, P = 0.061). In conclusion, alendronate therapy was an effective treatment in kidney transplant recipients for secondary osteoporosis and vascular calcification as ectopic calcification. This clinical trial is registered with number JMA-IIA00155 of JMACCT CTR.

What is the impact of immunosuppressive treatment on the post-transplant renal osteopathy?

Although glucocorticoid therapy is considered to be the main pathogenic factor, a consistent body of evidence suggests that other immunosuppressants might also play an important role in the development of the post-transplant renal osteopathy (PRO) through their pleiotropic pharmacological effects. Glucocorticoids seem to induce osteoclasts' activity suppressing the osteoblasts while data regarding other immunosuppressive drugs are still controversial. Mycophenolate mofetil and azathioprine appear to be neutral regarding the bone metabolism. However, the study analyzing any independent effect of antimetabolites on bone turnover has not been conducted yet. Calcineurin inhibitors (CNIs) induce trabecular bone loss in rodent, with contradictory results in renal transplant recipients. Suppression of vitamin D receptor is probably the underlying mechanism of renal calcium wasting in renal transplant recipients receiving CNI. In spite of an increased 1,25(OH)2 vitamin D level, the kidney is not able to reserve calcium, suggesting a role of vitamin D resistance that may be related to bone loss. More efforts should be invested to determine the role of CNI in PRO. In particular, data regarding the role of mammalian target of rapamycin inhibitors (mTORi), such as sirolimus and everolimus, in the PRO development are still controversial. Rapamycin markedly decreases bone longitudinal growth as well as callus formation in experimental models, but also lowers the rate of bone resorption markers and glomerular filtration in clinical studies. Everolimus potently inhibits primary mouse and human osteoclast activity as well as the osteoclast differentiation. It also prevents the ovariectomy-induced loss of cancellous bone by 60 %, an effect predominantly associated with a decreased osteoclast-mediated bone resorption, resulting in a partial preservation of the cancellous bone. At present, there is no clinical study analyzing the effect of everolimus on bone turnover in renal transplant recipients or comparing sirolimus versus everolimus impact on bone, so only general conclusions could be drawn. Hence, the use of mTORi might be useful in patients with PRO due to their possible potential to inhibit osteoclast activity which might lead to a decreased rate of bone resorption. In addition, it should be also emphasized that they might inhibit osteoblast activity which may lead to a decreased bone formation and adynamic bone disease. Further studies are urgently needed to solve these important clinical dilemmas.

Oral alendronate can suppress bone turnover but not fracture in kidney transplantation recipients with hyperparathyroidism and chronic kidney disease

Post-transplantation bone diseases negatively affect the quality of life of solid organ recipients. Secondary or tertiary hyperparathyroidism is a frequent complication in kidney transplantation (KTx) recipients. Treatment with immunosuppressive agents including glucocorticoids can lead to deterioration in bone metabolism in these patients. In the present study, we explored the effects of a three-year treatment period with oral alendronate (ALN) in long-term KTx recipients. Post-KTx recipients were recruited (n = 24, M/F = 12/12, mean age 52.0 ± 7.8 years) into this study. All patients were prescribed methylprednisolone (4.07 ± 0.86 mg/day) with various immunosuppressive agents. Before treatment with oral ALN (35 mg/week), the mean concentrations of intact parathyroid hormone (iPTH) and 25-hydroxyvitamin D were 139.2 ± 71.4 pg/mL and 20.8 ± 4.1 ng/mL, respectively. After 36 months of ALN treatment, mean iPTH levels increased slightly (+20.9 %). Treatment with ALN reduced bone-specific alkaline phosphatase (-35.4 %), serum type I collagen N-terminal telopeptide (-31.2 %) and osteocalcin (-55.6 %) levels. ALN did not increase bone mass after 24 months. Four patients with the highest baseline iPTH levels suffered a clinical osteoporotic fracture during the 36-month ALN treatment period. Higher iPTH levels with chronic kidney disease (CKD) at baseline were associated with the incidence of new clinical fractures during ALN treatment. In conclusion, anti-resorptive therapy with ALN can suppress bone turnover even when iPTH concentration is elevated in long-term KTx recipients. However, hyperparathyroidism with CKD seems to be associated with new clinical fractures during ALN treatment.

Fibroblast growth factor 23 and calcium phosphate homeostasis after pediatric renal transplantation

FGF23 is a circulating factor regulating TPR and is increased in CKD. After RT, it seems to induce phosphorus wasting in adults. Data on FGF23 after PRT are scarce. Parameters of bone metabolism including calcium, phosphate, 25-(OH) vitamin D, 1,25-(OH)(2) vitamin D, alkaline phosphatase, PTH, and FGF23 were analyzed in 57 children after PRT and 11 controls. Median time after PRT was 25.9 (range 2-135) months. eGFR after PRT ranged from 15 to 175 mL/min/1.73 qm. Mean (±s.e.) FGF23 and PTH levels were significantly elevated compared with controls (146 ± 30 vs. 43 ± 3 ng/L, p = 0.001 and 182 ± 42 vs. 74 ± 18 ng/L, p = 0.004, respectively). Highest FGF23 levels were found in children with an eGFR below 60 mL/min*1.73 sqm (280 ± 69 vs. 62 ± 5 ng/L, p = 0.001), but significantly elevated values were already present in CKD2T. In a multivariate analysis, eGFR, PTH, calcium, and phosphate were significantly associated with FGF23. In a subgroup of 17 patients (29.8%) with persistent hypophosphatemia, phosphate levels were significantly associated with FGF23 and not with PTH. FGF23 is increased in children after PRT, especially in patients with chronic allograft dysfunction, and seems to be a more sensitive marker of dysregulated calcium phosphate homeostasis than PTH.

Immunosuppressive agents and bone disease in renal transplant patients with hypercalcemia

Renal transplantation is the definitive treatment for many metabolic abnormalities of uremic patients, although it is only partially effective for renal osteodystrophy, which may interact with posttransplant renal osteopathy. Osteopenic-osteoporotic syndrome represents, together with fractures secondary to osteoporosis and osteonecrosis, the bone complication most related to renal transplantation. Several factors contribute to the pathogenesis of posttransplantation osteoporosis, particularly immunosuppressive treatment. In this study, we evaluated the prevalence of factors related to posttransplant renal osteopathy and the clinical impact of immunosuppressive protocols. We studied 24 renal transplant recipients with hypercalcemia. Glomerular filtration rate was >50 mL/min. Mean age, time on dialysis, and time from transplantation were 49.6, 5.4, and 6.9 years, respectively. We evaluated serum and urine calcium and phosphorus, calcitonin, parathormone, bone-specific alkaline phosphatase, osteocalcin, urine deoxypyridinoline, telopeptide of type 1 procollagen, 1,25-(OH)(2) and 25-OH vitamin D, parathyroid ultrasound, and computerized bone mineralometry. The combination of sirolimus and steroids resulted in the most disadvantageous outcomes regarding alkaline phosphatase and mineralometry. Calcineurin inhibitors did not significantly influence bone metabolism markers; mycophenolate mofetil evidenced no effect on bone. According to the literature, steroids account for the abnormalities found in our patients and in severe osteopenia. Several factors may contribute to the development of osteoporosis and fractures in transplantation patients, although they are overcome by the prominent effect of steroids. In patients at high risk of osteoporosis, steroid-free therapy should be considered. Everolimus is indicated for diseases with bone loss. Combined therapy with everolimus and mycophenolic acid without cyclosporine and steroids, seemed to be particularly indicated. Prophylactic treatments should be commenced early. No single marker was useful to diagnose posttransplant renal osteopathy. The definitive diagnosis should be made by bone biopsy during transplantation, and noninvasive procedures, such as densitometry and evaluation of biologic markers, may be useful during follow-up.

Intermittent therapy with 1,25 vitamin D and calcitonin prevents cyclosporin-induced alveolar bone loss in rats

Bone loss associated with cyclosporin A (CsA) therapy can result in serious morbidity to patients. Intermittent administration of 1,25 Vitamin D and calcitonin reduces osteopenia in a murine model of postmenopausal osteoporosis. The purpose of this study was to evaluate the effects of this therapeutic approach on CsA-induced alveolar bone loss in rats. Forty male Wistar rats were allocated to four experimental groups according to the treatment received during 8 weeks: (1) CsA (10 mg/kg/day, s.c.); (2) 1,25 Vitamin D (2 microg/kg, p.o.; in weeks 1, 3, 5, and 7) plus calcitonin (2 microg/kg, i.p.; in weeks 2, 4, 6, and 8); (3) CsA concurrently with intermittent 1,25 Vitamin D and calcitonin administration; and (4) the control treatment group (vehicle). At the end of the 8-week treatment period, serum concentrations of bone-specific alkaline phosphatase, tartrate-resistant acid phosphatase (TRAP-5b), osteocalcin, interleukin (IL)-1 beta, IL-6, and tumor necrosis factor alpha (TNF-alpha) were measured and an analysis of bone volume, bone surface, number of osteoblasts, and osteoclasts was performed. CsA administration resulted in significant alveolar bone resorption, as assessed by a lower bone volume and an increased number of osteoclasts, and increased serum bone-specific alkaline phosphatase, TRAP-5b, IL-1 beta, IL-6, and TNF-alpha concentrations. The intermittent administration of calcitriol and calcitonin prevented the CsA-induced osteopenic changes and the increased serum concentrations of TRAP-5b and inflammatory cytokines. Intermittent calcitriol/calcitonin therapy prevents CsA-induced alveolar bone loss in rats and normalizes the production of associated inflammatory mediators.

Open-label trial: effect of weekly risedronate immediately after transplantation in kidney recipients

BACKGROUND

Treatment with oral risedronate to prevent bone mineral density (BMD) loss in renal transplant recipients has been shown to be effective. There is no agreement on the optimum moment of introduction or how long it should be continued. The aim was to evaluate the effectiveness of risedronate at doses of 35 mg/week in renal transplant recipients who underwent treatment immediately after transplant.

METHODS

A randomized clinical trial was performed on 101 renal transplant patients. The study group (52 patients) received 35 mg risedronate weekly, vitamin D, and calcium, whereas the control group (49 patients) received only vitamin D and calcium. At baseline, 3, 6, and 12 months, basic biochemistry and mineral bone metabolic parameters were determined. Vertebra and hip fracture assessment was performed by means of x-ray and DEXA; an intention-to-treat analysis was performed.

RESULTS

Patients in control group showed a significant worsening of BMD (P<0.05) 12 months into the study. At all follow-up points, lumbar BMD of the study group was significantly greater (P<0.05), whereas femoral BMD of those treated with risedronate was only significant at 6-month follow-up (P<0.05). There was a trend of more vascular calcifications and fractures in the control group, but this was not statistically significant.

CONCLUSION

Weekly oral administration of risedronate immediately after renal transplantation contributes to an improved BMD, particularly in the femoral neck at 6-month follow-up, without major side effects. Long-term follow-up is needed to establish whether oral risedronate has an influence on vascular calcifications and bone fractures.

Renal transplantation in patients with HIV

HIV infection has been a major global health problem for almost three decades. With the introduction of highly active antiretroviral therapy in 1996, and the advent of effective prophylaxis and management of opportunistic infections, AIDS mortality has decreased markedly. In developed countries, this once fatal infection is now being treated as a chronic condition. As a result, rates of morbidity and mortality from other medical conditions leading to end-stage liver, kidney and heart disease are steadily increasing in individuals with HIV. Presence of HIV infection used to be viewed as a contraindication to transplantation for multiple reasons: concerns for exacerbation of an already immunocompromised state by administration of additional immunosuppressants; the use of a limited supply of donor organs with unknown long-term outcomes; and, the risk of viral transmission to the surgical and medical staff. This Review examines open questions on kidney transplantation in patients infected with HIV-1 and clinical strategies that have resulted in good outcomes. It also describes the clinical concerns associated with the treatment of renal transplant recipients with HIV.

Evolution of coronary artery calcifications following kidney transplantation: relationship with osteoprotegerin levels

We prospectively assessed the evolution of coronary artery calcification (CAC) and osteoprotegerin (OPG) levels after renal transplantation (RT). Eighty-three recipients were followed-up prospectively during 1 year. Blood was collected before (baseline) and after RT for determination of mineral metabolism parameters including OPG. CAC was measured by multidetector computed tomography at transplantation (baseline) and 1 year later. Progression of CAC was defined as a difference between the follow-up square-root transformed volume (SRV) and the baseline SRV >or= 2.5. By multivariate analysis, baseline OPG level, age and low LDL levels were significantly associated with baseline CAC. RT was accompanied by mineral metabolism improvement with a decrease of OPG from 955 [395-5652] to 527 [217-1818] pg/mL and parathyroid hormone from 94 [1-550] to 62 [16-410] pg/mL. Thirty-one percent of patients did not exhibit CAC at baseline. CAC diminished in 14.5%, stabilized in 59.2% and progressed in 26.3% of patients. Baseline CAC was associated with progression (OR 2.92 [1.02-8.36]). No significant association was found between OPG and CAC progression despite a higher baseline OPG level in progressors (1046 [456-3285]) vs. non-progressors (899 [396-5952] pg/mL). CAC at baseline, but not 1 year after RT, is independently associated with baseline OPG; posttransplant CAC progression is predicted by baseline CAC score.