Therapy for patients with CKD and low bone mineral density

Serum calcification propensity and its association with biochemical parameters and bone mineral density in hemodialysis patients

BACKGROUND

T50 is a novel serum-based marker that assesses the propensity for calcification in serum. A shorter T50 indicates a greater propensity to calcify and has been associated with cardiovascular disease and mortality among patients with chronic kidney disease. The factors associated with T50 and the correlation between T50 and bone mineral density (BMD) are unknown in hemodialysis (HD) patients.

METHODS

This cross-sectional study included 184 patients undergoing HD. Individuals were grouped into tertiles of T50 to compare the demographic and disease indicators of the tertiles. Linear regression was used to evaluate the association between T50 and hip and spinal BMD in a multivariate model.

RESULTS

Mineral and inflammatory parameters, including serum phosphate (r = -0.156, p = 0.04), albumin (r = 0.289, p < 0.001), and high-sensitivity C-reactive protein (r = -0.224, p = 0.003) levels, were associated with T50. We found a weak association between T50 and BMD in the total hip area in the unadjusted model (β = 0.030, p = 0.04) but did not find a statistically significant association with the total hip (β = 0.017, p = 0.12), femoral neck (β = -0.001, p = 0.96), or spinal BMD (β = 0.019, p = 0.33) in multivariable-adjusted models.

CONCLUSION

T50 was moderately associated with mineral and inflammatory parameters but did not conclusively establish an association with BMD in HD patients. Broad-scale future studies should determine whether T50 can provide insights into BMD beyond traditional risk factors in this population.

Mitochondria and vascular calcification in chronic kidney disease: Lessons learned from the past to improve future therapy

Chronic kidney disease-mineral and bone disorders (CKD-MBD) is a common complication of CKD Stages 3-5. Hyperphosphatemia is one of the major metabolic components of CKD-MBD, frequently resulting in vascular calcification (VC) in advanced-stage patients. Also, a long duration of renal replacement therapy can cause the worsening of VC, leading to increased cardiovascular morbidity and mortality. Vascular smooth muscle cells play an important role in the development of VC through osteochondrogenic transformation and the apoptotic process. It has been shown that mitochondrial dysfunction is involved with CKD progression, and excessive oxidative stress can aggravate osteoblastic transformation and VC. Currently, novel interventions targeting mitochondrial function and dynamics, in addition to mitochondrial antioxidants, have been studied with the aim of attenuating VC. This review aims to comprehensively summarize and discuss the experimental and clinical reports concerning mitochondrial studies, along with the purpose of interventions that can improve the outcomes of VC among CKD patients.

Bisphosphonates and bone mineral density in patients with end-stage kidney disease and renal transplants: A 15-year single-centre experience

Chronic Kidney Disease Stage 5 (CKD-5) imparts a 4-fold increase in minimal trauma fracture with a substantial increase in mortality following hip fracture. Bone disease in CKD is complex, characterised by abnormal levels of PTH, calcium, phosphate, ALP, and vitamin D, manifesting as a condition known as CKD-Mineral and Bone Disorder (CKD-MBD). While bisphosphonates (BPs) are widely used in the management of osteoporosis, their therapeutic role when end-stage renal function and bone disease co-exist remains unclear. This 15-year retrospective cohort study examines the long-term use of BPs in CKD-4 and -5 patients receiving no renal replacement therapy, haemodialysis and renal transplant in a tertiary centre in Sydney, Australia. In multivariate regression adjusting for age, baseline bone mineral density (BMD) and history of fracture, BP use was associated with net gain in lumbar spine bone density in renal transplant recipients over a mean treatment period of 3.5 years (net annual BMD gain of 0.039 g/cm², p = 0.005). No such benefit was seen in hip BMD in CKD subjects. Regardless of transplant status, CKD patients treated with BPs had no improvement in hip BMD with a general decline in hip BMD across both groups during the study period (hip BMD: transplant recipients decline 0.024 ± 0.81 g/cm², non-transplant CKD patients decline 0.055 ± 0.84 g/cm²). BP therapy did not result in significant changes in biochemical parameters (ALP, PTH, and phosphate) and no serious adverse effects were detected in association with BP use. In particular, kidney function was not affected by BPs post-transplant (eGFR = 43 ± 29 ml/min/1.73 m², p = 0.80). BPs preserved lumbar spine bone density in kidney transplant recipients but did not prevent declines in hip bone mineral density in either transplant patients or those with CKD-4 and -5.

Summary

There remains a lack of clarity of the risks vs. benefits of bone-sparing pharmacotherapy in chronic kidney disease Stages 4 and 5. This single-centre 15-year retrospective data analysis showed that bisphosphonates are not associated with any detectable serious adverse effects in CKD-4 and -5 and effective at mitigating lumbar spine bone loss in kidney transplant patients.

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In patients with CKD stages 4 and 5, effects of Bisphosphonates on bone mineral density over time were assessed.

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Hip bone mineral density declined in CKD and transplant recipients, regardless of bisphosphonate use.

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Bone density at the lumbar spine improved, but only in transplant recipients treated with bisphosphonates.

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Kidney function in CKD stages 4 and 5 was not impacted by the use of bisphosphonates.

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Biochemical parameters of CKD-MBD (Chronic Kidney Disease-Mineral Bone Disorder) were not influenced by bisphosphonates.

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Our study demonstrated that bisphosphonates were generally not effective in improving bone density, particularly at the hip.

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Specific strategies to promote cortical bone in CKD patients require further evaluation.

Renal Rehabilitation: Exercise Intervention and Nutritional Support in Dialysis Patients

With the growing number of dialysis patients with frailty, the concept of renal rehabilitation, including exercise intervention and nutrition programs for patients with chronic kidney disease (CKD), has become popular recently. Renal rehabilitation is a comprehensive multidisciplinary program for CKD patients that is led by doctors, rehabilitation therapists, diet nutritionists, nursing specialists, social workers, pharmacists, and therapists. Many observational studies have observed better outcomes in CKD patients with more physical activity. Furthermore, recent systematic reviews have shown the beneficial effects of exercise intervention on exercise tolerance, physical ability, and quality of life in dialysis patients, though the beneficial effect on overall mortality remains unclear. Nutritional support is also fundamental to renal rehabilitation. There are various causes of skeletal muscle loss in CKD patients. To prevent muscle protein catabolism, in addition to exercise, a sufficient supply of energy, including carbohydrates, protein, iron, and vitamins, is needed. Because of decreased digestive function and energy loss due to dialysis treatment, dialysis patients are recommended to ingest 1.2-fold more protein than the regular population. Motivating patients to join in activities is also an important part of renal rehabilitation. It is essential for us to recognize the importance of renal rehabilitation to maximize patient satisfaction.

Nephrectomy Does not Exacerbate Cancellous Bone loss in Thalassemic Mice

Patients with β-thalassemia have an increased risk of developing chronic kidney disease which is associated with osteoporosis and periodontitis. The purpose of this study was to evaluate mandibular and femoral bone change in heterozygous β-globin knockout (BKO) mice following 5/6 nephrectomy (Nx). Female and male BKO mouse blood smears demonstrated microcytic hypochromic anemia. Serum urea nitrogen, creatinine, calcium, and phosphorus levels were not changed in BKO mice. Nx increased the serum levels of urea nitrogen in both wild type (WT) and BKO mice and the level was much higher in BKO males. Serum level of creatinine was increased in Nx WT but not BKO mice. However, serum calcium and phosphorus levels were not altered. Nx induced comparable renal fibrosis in BKO mice and WT controls. Bone loss was observed in mandibular cancellous bone but not cortical bone of both male and female BKO mice. Nx decreased cancellous bone volume and cortical thickness in WT. Interestingly, BKO mice were resistant to Nx-induced cancellous bone loss. However, cortical thickness and cortical bone mineral density were reduced in Nx male BKO mice. Nx increased mRNA levels of type I collagen, Osx and Trap in WT but not BKO mice. Similarly, Nx reduced cancellous bone volume in femurs and increased osteoblast number and osteoclast number in WT not BKO mice. Serum FGF23 and erythropoietin levels were markedly increased in BKO mice. Nx decreased serum erythropoietin but not FGF23 levels. Since WT treated with erythropoietin exhibited a significant reduction in cancellous bone volume, it was possible that lower level of erythropoietin in Nx BKO mice prevented the Nx-induced cancellous bone loss.

Denosumab for dialysis patients with osteoporosis: A cohort study

Evidence for the efficacy of denosumab in HD patients is limited. Accordingly, here we report a study on the safety and efficacy of denosumab in these patients. We prospectively followed 324 patients (121 HD and 203 non-HD patients) receiving denosumab between June 2013 and May 2018, assessing changes in bone mineral density (BMD) and bone metabolic markers, and noting side-effects. Annual changes in BMD at the lumbar spine in HD and non-HD patients from baseline were, respectively, 6.7 ± 11.1% and 7.5 ± 10.2% (p = 0.60), those at the femoral neck were 4.3 ± 7.9% and 3.1 ± 9.5% (p = 0.32), and those at the distal radius were −0.5 ± 6.4% and 0.2 ± 13.0% (p = 0.66). The prevalence of hypocalcemia (<8.5 mg/dL) was significantly higher in HD than in non-HD patients (35.6% vs 5.4%, p < 0.001). The median elapsed time between the first injection of denosumab and the occurrence of hypocalcemia was 7 days in HD patients. The decrease of serum calcium was greater in patients with higher TRACP5b, corticosteroid use, and those without CaCO₃ supplementation. Our study suggests that denosumab was equally as effective in HD as non-HD patients. However, careful hypocalcemia monitoring, for at least 4 weeks, is recommended for HD patients.

Effects of denosumab on bone metabolism and bone mineral density in kidney transplant patients: a systematic review and meta-analysis

OBJECTIVE

The use of immunosuppressive agents, especially glucocorticoids, are associated with increased risks of bone loss in kidney transplant patients. Denosumab, a potent antiresorptive agent, has been shown to increase bone mineral density (BMD) in patients with CKD. However, its effects on bone metabolism and BMD in kidney transplant patients remain unclear.

METHODS

A literature search was conducted using MEDLINE, EMBASE, and Cochrane Database from inception through April 2018 to identify studies evaluating denosumab's effect on changes in bone metabolism and BMD from baseline to post-treatment course in kidney transplant patients. Study results were pooled and analyzed utilizing random-effects model. The protocol for this systematic review is registered with PROSPERO (International Prospective Register of Systematic Reviews; no. CRD42018095055).

RESULTS

Five studies (a clinical trial and four cohort studies) with a total of 162 kidney transplant patients were identified. The majority of patients had a baseline eGFR ≥ 30 mL/min/1.73 m². After treatment (≥ 6 to 12 months), there were significant increases in BMD with standardized mean differences (SMDs) of 3.26 (95% CI 0.88-5.64) and 1.83 (95% CI 0.43 to 3.22) for lumbar spine and femoral neck, respectively. There were also significant increases in T scores with SMDs of 0.92 (95% CI 0.58 to 1.25) and 1.14 (95% CI 0.17 to 2.10) for lumbar spine and femoral neck, respectively. After treatment, there were no significant changes in serum calcium (Ca) or parathyroid hormone (PTH) from baseline to post-treatment course (≥ 6 months) with mean differences (MDs) of 0.52 (95% CI, - 0.13 to 1.16) mmol/L and - 13.24 (95% CI, - 43.85 to 17.37) ng/L, respectively. The clinical trial data demonstrated more asymptomatic hypocalcemia in the denosumab (12 episodes in 39 patients) than in the control (1 episode in 42 patients) group. From the cohort studies, the pooled incidence of hypocalcemia following denosumab treatment was 1.7% (95% CI 0.4 to 6.6%). All reported hypocalcemic episodes were mild and asymptomatic, but the majority of patients required Ca and vitamin D supplements.

CONCLUSION

Among kidney transplant patients with good allograft function, denosumab effectively increases BMD and T scores in the lumbar spine and femur neck. From baseline to post-treatment, there are no differences in serum Ca and PTH. However, mild hypocalcemia can occur following denosumab treatment, requiring monitoring and titration of Ca and vitamin D supplements.

Correlations between plasma strontium concentration, components of calcium and phosphate metabolism and renal function in type 2 diabetes mellitus

BACKGROUND

Renal function decline in diabetic kidney disease is accompanied by calcium and phosphate metabolism alterations. Whereas strontium (Sr²⁺ ) has many similarities with calcium, little is known about Sr²⁺ in this respect. We studied the association of plasma Sr²⁺ concentration and parameters associated with an altered calcium and phosphate metabolism in diabetic kidney disease.

MATERIALS AND METHODS

Plasma Sr²⁺ concentration was measured in 450 patients included in the DIAbetes and LifEstyle Cohort Twente-1. Patients were classified based on chronic kidney disease (CKD) stages: stages 1-2, stage 3 and stages 4-5 (estimated glomerular filtration rate of ≥60 mL·min^-1 ·1.73 m^-2 , 30-59 mL·min^-1 ·1.73 m^-2 and ≤29 mL·min^-1 ·1.73 m^-2 , respectively). The associations between log-transformed plasma Sr²⁺ concentration and parameters of calcium and phosphate metabolism were studied using multivariate linear regression analysis.

RESULTS

Overall, median plasma Sr²⁺ concentration was in normal range, 269 nmol/L, but was progressively higher in patients with lower renal function, that is 246 nmol/L (CKD 1-2), 347 nmol/L (CKD 3) and 419 nmol/L (CKD 4-5). In multivariate analysis, independent associations were found between plasma Sr²⁺ concentration and both eGFR (β = -0.401, P < 0.001) and plasma fibroblast growth factor 23 (FGF23) concentration (β = 0.087, P = 0.04).

CONCLUSIONS

We found an independent inverse association between eGFR and plasma Sr²⁺ concentration and an independent association between plasma Sr²⁺ concentration and plasma FGF23 concentration, a marker of deranged calcium and phosphate metabolism. Further research is needed to determine the mechanisms behind these associations and the impact of an elevation in plasma Sr²⁺ concentration on bone mineralization and calcification.

Hypocalcemia and bone mineral density changes following denosumab treatment in end-stage renal disease patients: a meta-analysis of observational studies

The incidence of hypocalcemia and bone mineral density (BMD) changes in end-stage renal disease (ESRD) patients on denosumab remains unclear. We performed this meta-analysis to assess the incidence of denosumab-associated hypocalcemia and effects of denosumab on BMD in ESRD patients. A literature search was conducted using MEDLINE, EMBASE, and Cochrane Database from inception through November 2017 to identify studies evaluating incidence of denosumab-associated hypocalcemia and changes in serum calcium, phosphate, alkaline phosphatase (ALP), parathyroid hormone (PTH), and BMD from baseline to post-treatment course of denosumab in ESRD patients. Study results were pooled and analyzed using a random-effect model. The protocol for this meta-analysis is registered with PROSPERO (International Prospective Register of Systematic Reviews; no. CRD42017081074). Six observational studies with a total of 84 ESRD patients were enrolled. The pooled estimated incidence of hypocalcemia during denosumab treatment was 42% (95% CI 29-55%, I² = 0%). Hypocalcemia occurred approximately 7 to 20 days after the first dose and reached nadir of low calcium levels in the first 2 weeks up to 2 months. However, there were no significant changes in serum calcium or phosphate from baseline to post-treatment course (≥ 3 months after treatment) with mean differences [MDs] of 0.20 mg/dL (95% CI, - 0.30 to 0.69 mg/dL) and - 0.10 mg/dL (95% CI, - 0.70 to 0.49 mg/dL). There were significant reductions in ALP and PTH levels with standardized mean differences (SMDs) of - 0.65 (95% CI - 1.13 to - 0.16) and - 1.89 (95% CI - 3.44 to - 0.34), respectively. There were significant increases in T-scores with MDs of 0.39 (95% CI 0.10 to 0.69) and 0.79 (95% CI 0.60 to 0.98) for lumbar spine and femoral neck, respectively. Our study demonstrates the estimated incidence of denosumab-associated hypocalcemia in dialysis patients of 42%. From baseline to post-treatment course, although there are no differences in serum calcium and phosphate, our findings suggest significant reductions in ALP and PTH and a significant increase in BMD. Currently, denosumab should not be considered as the treatment of choice in ESRD patients until more safety and efficacy data are available.

Discrepancies in Clinic and Ambulatory Blood Pressure in Korean Chronic Kidney Disease Patients

Blood pressure (BP) control is considered the most important treatment for preventing chronic kidney disease (CKD) progression and associated cardiovascular complications. However, clinic BP is insufficient to diagnose hypertension (HT) and to monitor overall BP control because it does not correlate well with ambulatory blood pressure monitoring (ABPM). We enrolled 387 hypertensive CKD patients (stages G1-G4, 58.4% male with median age 61 years) from 3 hospitals in Korea. HT of clinic BP and ABPM was classified as ≥ 140/90 and ≥ 130/80 mmHg, respectively. Clinic BP control rate was 60.2%. The median 24-hour systolic blood pressures (SBPs) of CKD G3b and CKD G4 were significantly higher than those of CKD G1-2 and CKD G3a. However, the median 24-hour SBPs were not different between CKD G1-2 and CKD G3a or between CKD G3b and CKD G4. Of all patients, 5.7%, 38.0%. 42.3%, and 14.0% were extreme-dippers, dippers, non-dippers, and reverse-dippers, respectively. Non-/reverse-dippers independently correlated with higher Ca × P product, higher intact parathyroid hormone (iPTH), and lower albumin. Normal BP was 33.3%, and sustained, masked, and white-coat HT were 29.7%, 26.9%, and 10.1%, respectively. White-coat HT independently correlated with age ≥ 61 years and masked HT independently correlated with CKD G3b/G4. In conclusion, ABPM revealed a high prevalence of non-/reverse-dippers and sustained/masked HT in Korean CKD patients. Clinicians should try to obtain a CKD patient's ABPM, especially among those who are older or who have advanced CKD as well as those with abnormal Ca × P product, iPTH, and albumin.

Chronic Kidney Disease-Mineral Bone Disorder in Korean Patients: a Report from the KoreaN Cohort Study for Outcomes in Patients With Chronic Kidney Disease (KNOW-CKD)

This study examined the characteristics of biochemical parameters, bone diseases, and vascular calcification in Korean patients with chronic kidney disease (CKD) not yet on dialysis. Serum levels of fibroblast growth factor 23 (FGF23), intact parathyroid hormone (iPTH), 25-hydroxyvitamin D3 (25D), and 1,25-dihydroxyvitamin D3 (1,25D); lumbar spine, total hip, and femur neck bone mineral densities; and brachial-to-ankle pulse wave velocity (baPWV) representing vascular calcification were measured at baseline for 2,238 CKD patients in the KoreaN Cohort Study for Outcomes in Patients With CKD (KNOW-CKD). Increases in serum FGF23 and iPTH preceded changes in serum calcium and phosphate, similar to Western populations. However, the 25D and 1,25D levels decreased earlier than serum FGF23 or iPTH increased, with a decreased estimated glomerular filtration rate (eGFR) in Korean CKD patients. Vitamin D deficiency occurred in 76.7% of patients with CKD stage 1. Bone mineral densities were lowest in CKD stage 5 (lumbar spine, -0.64 ± 1.67; total hip, -0.49 ± 1.21; femur neck, -1.02 ± 1.25). Osteoporosis was more prevalent in patients with higher CKD stages. The mean baPWV, abdominal aortic calcification (AAC), and coronary calcium score also increased, with declined eGFR. In conclusion, a decline in serum vitamin D levels was observed in early CKD stages before significant increases of FGF23 and iPTH in the Korean CKD population compared with that in Western populations. Increased bone disease and vascular calcification occurred in early-stage CKD.

Safety and effectiveness of daily teriparatide for osteoporosis in patients with severe stages of chronic kidney disease: post hoc analysis of a postmarketing observational study

Teriparatide (recombinant 1-34 N-terminal sequence of human parathyroid hormone) for the treatment of osteoporosis should be prescribed with caution in patients with severe stages of chronic kidney disease (CKD). However, in clinical settings, physicians and surgeons who treat such patients have few available options. We sought to further explore the safety and effectiveness of teriparatide for the treatment of osteoporosis in Japanese patients with severe stages of CKD. This was a post hoc analysis of a postmarketing surveillance study that included patients with osteoporosis at high risk of fracture and stage 4 or 5 CKD. Patients received subcutaneous teriparatide 20 μg daily for up to 24 months. Safety profiles were assessed by physician-reported adverse drug reactions (ADRs). Effectiveness was assessed by measuring bone formation (via procollagen type 1 N-terminal propeptide [P1NP]), bone mineral density (BMD), and the incidence of clinical vertebral or nonvertebral fragility fractures. A total of 33 patients with severe stages of CKD (stage 4, n=30; stage 5, n=3) were included. All patients were female, and 81.8% had a history of previous fracture. No serious ADRs were recorded; a total of 4 ADRs were recorded for 4 of 33 patients. Increases in BMD and P1NP levels were observed both overall and in most individual patients. New fractures occurred in 1 patient with stage 5 CKD, but not in patients with stage 4 CKD. In this post hoc analysis conducted in Japan, teriparatide appeared to be effective for the treatment of osteoporosis in elderly female patients with severe stages of CKD, and no new safety concerns were observed.

Relationship between Fetuin A, Vascular Calcification and Fracture Risk in Dialysis Patients

Background

Fractures are a common morbidity that lead to worse outcomes in dialysis patients. Fetuin A inhibits vascular calcification (VC), potentially promotes bone mineralization and its level positively correlates with bone mineral density in the general population. On the other hand, the presence of VC is associated with low bone volume in dialysis patients. Whether the fetuin A level and VC can predict the occurrence of fractures in dialysis patients remains unknown.

Methods

We performed this prospective, observational cohort study including 685 dialysis patients (629 hemodialysis and 56 peritoneal dialysis) from a single center in Taiwan for a median follow-up period of 3.4 years. The baseline fetuin A level and status of presence of aortic arch calcification (VC) and incidence of major fractures (hip, pelvis, humerus, proximal forearm, lower leg or vertebrae) were assessed using adjusted Cox proportional hazards models, recursive partitioning analysis and competing risk models.

Results

Overall, 177 of the patients had major fractures. The incidence rate of major fractures was 3.29 per 100 person-years. In adjusted analyses, the patients with higher baseline fetuin A levels had a lower incidence of fractures (adjusted hazard ratio (HR), 0.3; 95% CI, 0.18‒0.5, fetuin A tertile 3 vs. tertile 1 and HR, 0.52; 95% CI, 0.34‒0.78, tertile 2 vs. tertile 1). The presence of aortic arch calcification (VC) independently predicted the occurrence of fractures (adjusted HR, 1.95; 95% CI, 1.34‒2.84) as well. When accounting for death as an event in competing risk models, the patients with higher baseline fetuin A levels remained to have a lower incidence of fractures (SHR, 0.31; 95% CI, 0.17‒0.56, fetuin A tertile 3 vs. tertile 1 and 0.51; 95% CI, 0.32‒0.81, tertile 2 vs. tertile 1).

Interpretations

Lower baseline fetuin A levels and the presence of VC were independently linked to higher risk of incident fractures in prevalent dialysis patients.

Fractures in chronic kidney disease: pursuing the best screening and management

PURPOSE OF REVIEW

Osteoporotic fractures are common and cause increased sickness and death. Men and women with chronic kidney disease (CKD) are at particularly high risk of osteoporotic fractures. Currently, however, there are no guidelines concerning noninvasive methods to assess fracture risk in CKD. Further, approved treatments to prevent fractures in otherwise healthy men and women are only recommended for use with caution in those with CKD. This review focuses on the recent data that support the use of noninvasive methods to assess fracture risk in CKD and highlights new therapies that could be used in fracture prevention in CKD.

RECENT FINDINGS

Data from prospective studies demonstrate that low bone mineral density predicts fracture in CKD patients. Post-hoc analyses demonstrate that agents approved for the treatment of postmenopausal osteoporosis (bisphosphonates, denosumab and teriparatide) when given to those with CKD are well tolerated and potentially efficacious with respect to fracture risk reduction.

SUMMARY

To date, patients, and nephrologists taking care of them, have largely ignored fracture risk assessment and treatment in CKD. This should change given recent data. Further studies are needed, specifically bone histomorphometric studies, which will increase our understanding of CKD-mineral bone disease (MBD) pathophysiology, and randomized clinical trials of therapy in patients with CKD.

Calcitriol Suppression of Parathyroid Hormone Fails to Improve Skeletal Properties in an Animal Model of Chronic Kidney Disease

BACKGROUND

Chronic kidney disease (CKD) leads to complex metabolic changes and an increased risk of fracture. Currently, calcitriol is the standard of care as it effectively suppresses parathyroid hormone (PTH) levels in CKD patients. While calcitriol and its analogs improve BMD and reduce fractures in the general population, the extension of these benefits to patients with advanced kidney disease is unclear. Here, the impact of calcitriol on the skeleton was examined in the setting of reduction in PTH.

METHODS

Male Cy/+ rats, a PKD-like CKD model, were treated with either vehicle or calcitriol for 5 weeks. Their normal littermates served as controls. Animals were assessed for changes in mineral metabolism and skeletal parameters (microCT, histology, whole bone mechanics and bone quality).

RESULTS

PTH levels were significantly higher (12-fold) in animals with CKD compared to normal controls. CKD animals also exhibited negative changes in bone structural and mechanical properties. Calcitriol treatment resulted in a 60% suppression of PTH levels in animals with CKD. Despite these changes, it had no impact on bone volume (cortical or cancellous), bone turnover, osteoclast number or whole bone mechanical properties.

CONCLUSIONS

These data indicate that while calcitriol effectively lowered PTH in rats with CKD, it did little to prevent the negative effects of secondary hyperparathyroidism on the skeleton.

Raloxifene improves skeletal properties in an animal model of cystic chronic kidney disease

Patients with chronic kidney disease (CKD) have an increased risk of fracture. Raloxifene is a mild antiresorptive agent that reduces fracture risk in the general population. Here we assessed the impact of raloxifene on the skeletal properties of animals with progressive CKD. Male Cy/+ rats that develop autosomal dominant cystic kidney disease were treated with either vehicle or raloxifene for five weeks. They were assessed for changes in mineral metabolism and skeletal parameters (microCT, histology, whole-bone mechanics, and material properties). Their normal littermates served as controls. Animals with CKD had significantly higher parathyroid hormone levels compared with normal controls, as well as inferior structural and mechanical skeletal properties. Raloxifene treatment resulted in lower bone remodeling rates and higher cancellous bone volume in the rats with CKD. Although it had little effect on cortical bone geometry, it resulted in higher energy to fracture and modulus of toughness values than vehicle-treated rats with CKD, achieving levels equivalent to normal controls. Animals treated with raloxifene had superior tissue-level mechanical properties as assessed by nanoindentation, and higher collagen D-periodic spacing as assessed by atomic force microscopy. Thus, raloxifene can positively impact whole-bone mechanical properties in CKD through its impact on skeletal material properties.

Adynamic bone disease: from bone to vessels in chronic kidney disease

Adynamic bone disease (ABD) is a well-recognized clinical entity in the complex chronic kidney disease (CKD)-mineral and bone disorder. Although the combination of low intact parathyroid hormone (PTH) and low bone alkaline phosphatase levels may be suggestive of ABD, the gold standard for precise diagnosis is histomorphometric analysis of tetracycline double-labeled bone biopsies. ABD essentially is characterized by low bone turnover, low bone volume, normal mineralization, and markedly decreased cellularity with minimal or no fibrosis. ABD is increasing in prevalence relative to other forms of renal osteodystrophy, and is becoming the most frequent type of bone lesion in some series. ABD develops in situations with reduced osteoanabolic stimulation caused by oversuppression of PTH, multifactorial skeletal resistance to PTH actions in uremia, and/or dysregulation of Wnt signaling. All may contribute not only to bone disease but also to the early vascular calcification processes observed in CKD. Various risk factors have been linked to ABD, including calcium loading, ageing, diabetes, hypogonadism, parathyroidectomy, peritoneal dialysis, and antiresorptive therapies, among others. The relationship between low PTH level, ABD, increased risk fracture, and vascular calcifications may at least partially explain the association of ABD with increased mortality rates. To achieve optimal bone and cardiovascular health, attention should be focused not only on classic control of secondary hyperparathyroidism but also on prevention of ABD, especially in the steadily growing proportions of diabetic, white, and elderly patients. Overcoming the insufficient osteoanabolic stimulation in ABD is the ultimate treatment goal.

Treatment of adynamic bone disease in a haemodialysis patient with teriparatide

Prevalence of adynamic bone disease (ABD), characterized by low bone turnover and absence or a reduced number of osteoblasts and osteoclasts, is increasing steadily over the last years. We present a dialysis patient, with recurrent bone fractures and biopsy-proven ABD, who was treated with teriparatide. Nine months after initiation of treatment, iPTH plasma levels increased to 520 pg/mL and a second bone biopsy revealed high bone turnover, normal mineralization and normal bone volume. Two years later, iPTH was 250-350 pg/dL and bone metabolism parameters within normal range. The probable utility of teriparatide in the treatment of ABD in dialysis patients is discussed.

Treatment of osteoporosis in renal insufficiency

Patients with osteoporosis often have chronic kidney disease (CKD). CKD is associated with bone and mineral disturbances, renal osteodystrophy, which like osteoporosis leads to a higher risk of fractures. Bisphosphonates are first-line therapy for osteoporosis; however, these are contra-indicated in patients with a GFR <30 ml/min. In this article, we have reviewed the diagnosis and treatment of osteoporosis in moderate to severe renal failure from data of clinical trials. Results have shown that osteoporosis patients and severe CKD with no signs of renal osteodystrophy, oral bisphosphonates (risedronate) seem to be a safe choice. Renal function and PTH should subsequently be monitored strictly. Denosumab, with regularly monitoring of calcium and adequate vitamin D levels or raloxifene are a possible second choice. In any case, one should be certain that there is no adynamic bone before treatment can be started. If there is any doubt, bone biopsies should be taken.

Current and future treatments of secondary osteoporosis

Osteoporosis is commonly associated with menopause and ageing. It can, however, also be caused by diseases, lifestyle, genetic diseases, drug therapies and other therapeutic interventions. In cases of secondary osteoporosis, a common rule is the management of the underlying condition. Healthy habits and calcium and vitamin D supplementation are also generally advised. In cases of high risk of fracture, specific antiosteoporosis medications should be prescribed. For most conditions, the available evidence is limited. Special attention should be paid to possible contraindications of drugs used for the treatment of postmenopausal or senile osteoporosis. Bisphosphonates are the most widely used drugs in secondary osteoporosis, and denosumab or teriparatide have been also assessed in some cases. Important research is needed to develop more tailored strategies, specific to the peculiarities of the different types of secondary osteoporosis.

Vascular calcification and renal bone disorders

At the early stage of chronic kidney disease (CKD), the systemic mineral metabolism and bone composition start to change. This alteration is known as chronic kidney disease-mineral bone disorder (CKD-MBD). It is well known that the bone turnover disorder is the most common complication of CKD-MBD. Besides, CKD patients usually suffer from vascular calcification (VC), which is highly associated with mortality. Many factors regulate the VC mechanism, which include imbalances in serum calcium and phosphate, systemic inflammation, RANK/RANKL/OPG triad, aldosterone, microRNAs, osteogenic transdifferentiation, and effects of vitamins. These factors have roles in both promoting and inhibiting VC. Patients with CKD usually have bone turnover problems. Patients with high bone turnover have increase of calcium and phosphate release from the bone. By contrast, when bone turnover is low, serum calcium and phosphate levels are frequently maintained at high levels because the reservoir functions of bone decrease. Both of these conditions will increase the possibility of VC. In addition, the calcified vessel may secrete FGF23 and Wnt inhibitors such as sclerostin, DKK-1, and secreted frizzled-related protein to prevent further VC. However, all of them may fight back the inhibition of bone formation resulting in fragile bone. There are several ways to treat VC depending on the bone turnover status of the individual. The main goals of therapy are to maintain normal bone turnover and protect against VC.

Osteoporosis management in patient with renal function impairment

Aging is associated with decreases in bone quality and in glomerular filtration. Consequently, osteoporosis and chronic kidney disease (CKD) are common comorbid conditions in the elderly, and often coexist. Biochemical abnormalities in the homeostasis of calcium and phosphorus begin early in CKD, leading to an increase in fracture risk and cardiovascular complications since early stages of the disease. The ability of DXA (dual energy X-ray absorptiometry) to diagnose osteoporosis and to predict fractures in this population remains unclear. The management of the disease is also controversial: calcium and vitamin D, although recommended, must be prescribed with caution, considering vascular calcification risk and the development of adynamic bone disease. Furthermore, safety and effectiveness of osteoporosis drugs are not established in patients with CKD. Thus, risks and benefits of antiosteoporosis treatment must be considered individually.