Effect of alendronate on vascular calcification in CKD stages 3 and 4: a pilot randomized controlled trial

Does the OPG/RANKL system contribute to the bone-vascular axis in chronic kidney disease? A systematic review

Vascular calcification (VC) is highly prevalent in patients with chronic kidney disease (CKD) and is strongly associated with cardiovascular mortality and morbidity. Accumulating evidence over the past decade has challenged the hypothesis of close interaction between bone and VC what raises the possibility of a common underlying pathophysiological mechanism. Lately, bone regulatory proteins such as: osteoprotegerin (OPG) and Receptor Activator for Nuclear Factor κB Ligand (RANKL) has attracted attention of researchers as a possible key mediators of bone-vascular calcification imbalance. The literature search was carried out using the MEDLINE/PubMed database and a combination of keywords and MeSH terms, and only papers published since January 2005 to July 2016 were selected. The search resulted in 562 potential articles. After selection according to the eligibility criteria, 107 studies fulfilled were included (102 full texts and 5 was case reports). OPG and RANKL plays essential role in the regulation of bone metabolism and may be regarded as a possible link between VC, bone and mineral metabolism in CKD patients. Further studies are required to determine the diagnostic significance of these proteins in evaluation of progression and severity of VC process in CKD patients. Finally, the efficacy and safety, especially in regard to VC, of anti-RANKL therapy in CKD patients requires well-designed prospective, randomized trials.

Arterial Calcification in Diabetes Mellitus: Preclinical Models and Translational Implications

Diabetes mellitus increasingly afflicts our aging and dysmetabolic population. Type 2 diabetes mellitus and the antecedent metabolic syndrome represent the vast majority of the disease burden-increasingly prevalent in children and older adults. However, type 1 diabetes mellitus is also advancing in preadolescent children. As such, a crushing wave of cardiometabolic disease burden now faces our society. Arteriosclerotic calcification is increased in metabolic syndrome, type 2 diabetes mellitus, and type 1 diabetes mellitus-impairing conduit vessel compliance and function, thereby increasing the risk for dementia, stroke, heart attack, limb ischemia, renal insufficiency, and lower extremity amputation. Preclinical models of these dysmetabolic settings have provided insights into the pathobiology of arterial calcification. Osteochondrogenic morphogens in the BMP-Wnt signaling relay and transcriptional regulatory programs driven by Msx and Runx gene families are entrained to innate immune responses-responses activated by the dysmetabolic state-to direct arterial matrix deposition and mineralization. Recent studies implicate the endothelial-mesenchymal transition in contributing to the phenotypic drift of mineralizing vascular progenitors. In this brief overview, we discuss preclinical disease models that provide mechanistic insights-and point to challenges and opportunities to translate these insights into new therapeutic strategies for our patients afflicted with diabetes mellitus and its arteriosclerotic complications.

Vascular calcification: When should we interfere in chronic kidney disease patients and how?

Chronic kidney disease (CKD) patients are endangered with the highest mortality rate compared to other chronic diseases. Cardiovascular events account for up to 60% of the fatalities. Cardiovascular calcifications affect most of the CKD patients. Most of this calcification is related to disturbed renal phosphate handling. Fibroblast growth factor 23 and klotho deficiency were incriminated in the pathogenesis of vascular calcification through different mechanisms including their effects on endothelium and arterial wall smooth muscle cells. In addition, deficient klotho gene expression, a constant feature of CKD, promotes vascular pathology and shares in progression of the CKD. The role of gut in the etio-pathogenesis of systemic inflammation and vascular calcification is a newly discovered mechanism. This review will cover the medical history, prevalence, pathogenesis, clinical relevance, different tools used to diagnose, the ideal timing to prevent or to withhold the progression of vascular calcification and the different medications and medical procedures that can help to prolong the survival of CKD patients.

Cardiovascular calcifications in chronic kidney disease: Potential therapeutic implications

Cardiovascular (CV) calcification is a highly prevalent condition at all stages of chronic kidney disease (CKD) and is directly associated with increased CV and global morbidity and mortality. In the first part of this review, we have shown that CV calcifications represent an important part of the CKD-MBD complex and are a superior predictor of clinical outcomes in our patients. However, it is also necessary to demonstrate that CV calcification is a modifiable risk factor including the possibility of decreasing (or at least not aggravating) its progression with iatrogenic manoeuvres. Although, strictly speaking, only circumstantial evidence is available, it is known that certain drugs may modify the progression of CV calcifications, even though a direct causal link with improved survival has not been demonstrated. For example, non-calcium-based phosphate binders demonstrated the ability to attenuate the progression of CV calcification compared with the liberal use of calcium-based phosphate binders in several randomised clinical trials. Moreover, although only in experimental conditions, selective activators of the vitamin D receptor seem to have a wider therapeutic margin against CV calcification. Finally, calcimimetics seem to attenuate the progression of CV calcification in dialysis patients. While new therapeutic strategies are being developed (i.e. vitamin K, SNF472, etc.), we suggest that the evaluation of CV calcifications could be a diagnostic tool used by nephrologists to personalise their therapeutic decisions.

Vascular Calcification in Uremia: New-Age Concepts about an Old-Age Problem

A hallmark of aging, and major contributor to the increased prevalence of cardiovascular disease in patients with chronic kidney disease (CKD), is the progressive structural and functional deterioration of the arteries and concomitant accrual of mineral. Vascular calcification (VC) was long viewed as a degenerative age-related pathology that resulted from the passive deposition of mineral in the extracellular matrix; however, since the discovery of "bone-related" protein expression in calcified atherosclerotic plaques over 20 years ago, a plethora of studies have evoked the now widely accepted view that VC is a highly regulated and principally cell-mediated phenomenon that recapitulates many features of physiologic ossification. Central to this theory are changes in vascular smooth muscle cell (VSMC) phenotype and viability, thought to be driven by chronic exposure to a number of dystrophic stimuli characteristics of the uremic state. Here, dedifferentiated synthetic VSMCs are seen to spawn calcifying matrix vesicles that actively seed mineralization of the arterial matrix. This review provides an overview of the major epidemiological, histological, and molecular aspects of VC in the context of CKD, and a counterpoint to the prevailing paradigm that emphasizes the primacy of VSMC-mediated mechanisms. Particular focus is given to the import of protein and small molecule inhibitors in regulating physiologic and pathological mineralization and the emerging role of mineral nanoparticles and their interplay with proinflammatory processes.

Arteriosclerosis and vascular calcification: causes, clinical assessment and therapy

BACKGROUND

Arteriosclerosis is a pathological, structural (media vascular calcification) and physiological (modified vascular smooth vessel cells; increased arterial stiffness) alteration of the vessel wall. Through improved assessment methods (functional and imaging), it has become a well-known phenomenon in recent decades. However, its clinical importance was underestimated until recently.

MATERIALS AND METHODS

Currently available English-speaking data about conditions/diseases associated with arteriosclerosis, its clinical sequels, available diagnostic procedures and therapeutic modalities were reviewed and summarized.

RESULTS

In recent decades, emerging data have brought about a better understanding of causes and consequences of arteriosclerosis and highlight its growing clinical impact.

CONCLUSION

Although arteriosclerosis showed an independent clinical impact on cardiovascular morbidity and mortality, especially in patients with chronic kidney disease/end-stage renal disease (CKD/ESRD) and diabetes mellitus, convincing clinical therapy concepts are not available until now. The establishment of novel therapeutic strategies derived from basic research is strongly needed.

Molecular Mechanisms of Vascular Calcification in Chronic Kidney Disease: The Link between Bone and the Vasculature

Vascular calcification is highly prevalent in patients with chronic kidney disease (CKD) and increases mortality in those patients. Impaired calcium and phosphate homeostasis, increased oxidative stress, and loss of calcification inhibitors have been linked to vascular calcification in CKD. Additionally, impaired bone may perturb serum calcium/phosphate and their key regulator, parathyroid hormone, thus contributing to increased vascular calcification in CKD. Therapeutic approaches for CKD, such as phosphate binders and bisphosphonates, have been shown to ameliorate bone loss as well as vascular calcification. The precise mechanisms responsible for vascular calcification in CKD and the contribution of bone metabolism to vascular calcification have not been elucidated. This review discusses the role of systemic uremic factors and impaired bone metabolism in the pathogenesis of vascular calcification in CKD. The regulation of the key osteogenic transcription factor Runt-related transcription factor 2 (Runx2) and the emerging role of Runx2-dependent receptor activator of nuclear factor kappa-B ligand (RANKL) in vascular calcification of CKD are emphasized.

Pharmacology of Bisphosphonates in Patients with Chronic Kidney Disease

Bisphosphonates are medications which bind strongly to mineral. They are ingested by osteoclasts and inhibit an enzyme necessary for bone resorption. The gastrointestinal absorption is poor and the only method of excretion is renal. Therefore, in patients with CKD the body accumulates a higher percentage of a dose of bisphosphonate. These medications remain attached to bone mineral for many years. Although the primary action is to inhibit bone resorption, secondarily bone formation is also inhibited, and in patients with CKD bisphosphonate use often leads to adynamic bone. In some experimental models in animals, the bisphosphonates can inhibit vascular calcification but this effect has not been seen in humans. Intravenous bisphosphonates may cause renal damage but oral doses do not reduce creatinine clearance. In stage 3 CKD, in patients who still have normal PTH, calcium, and alkaline phosphatase, randomized trials show similar benefits as in patients without CKD. Data from stage 4 and 5 CKD are very limited and no clear benefit has been shown.

Vascular calcification in chronic kidney disease: an update

Cardiovascular calcification is both a risk factor and contributor to morbidity and mortality. Patients with chronic kidney disease (and/or diabetes) exhibit accelerated calcification of the intima, media, heart valves and likely the myocardium as well as the rare condition of calcific uraemic arteriolopathy (calciphylaxis). Pathomechanistically, an imbalance of promoters (e.g. calcium and phosphate) and inhibitors (e.g. fetuin-A and matrix Gla protein) is central in the development of calcification. Next to biochemical and proteinacous alterations, cellular processes are also involved in the pathogenesis. Vascular smooth muscle cells undergo osteochondrogenesis, excrete vesicles and show signs of senescence. Therapeutically, measures to prevent the initiation of calcification by correcting the imbalance of promoters and inhibitors appear to be essential. In contrast to prevention, therapeutic regression of cardiovascular calcification in humans has been rarely reported. Measures to enhance secondary prevention in patients with established cardiovascular calcifications are currently being tested in clinical trials.

Bisphosphonates and risk of cardiovascular events: a meta-analysis

Background and Objectives

Some evidence suggests that bisphosphonates may reduce atherosclerosis, while concerns have been raised about atrial fibrillation. We conducted a meta-analysis to determine the effects of bisphosphonates on total adverse cardiovascular (CV) events, atrial fibrillation, myocardial infarction (MI), stroke, and CV death in adults with or at risk for low bone mass.

Methods

A systematic search of MEDLINE and EMBASE through July 2014 identified 58 randomized controlled trials with longer than 6 months in duration that reported CV events. Absolute risks and the Mantel-Haenszel fixed-effects odds ratios (ORs) and 95% confidence intervals (CIs) of total CV events, atrial fibrillation, MI, stroke, and CV death were estimated. Subgroup analyses by follow-up duration, population characteristics, bisphosphonate types, and route were performed.

Results

Absolute risks over 25–36 months in bisphosphonate-treated versus control patients were 6.5% versus 6.2% for total CV events; 1.4% versus 1.5% for atrial fibrillation; 1.0% versus 1.2% for MI; 1.6% versus 1.9% for stroke; and 1.5% versus 1.4% for CV death. Bisphosphonate treatment up to 36 months did not have any significant effects on total CV events (14 trials; ORs [95% CI]: 0.98 [0.84–1.14]; I² = 0.0%), atrial fibrillation (41 trials; 1.08 [0.92–1.25]; I² = 0.0%), MI (10 trials; 0.96 [0.69–1.34]; I² = 0.0%), stroke (10 trials; 0.99 [0.82–1.19]; I² = 5.8%), and CV death (14 trials; 0.88 [0.72–1.07]; I² = 0.0%) with little between-study heterogeneity. The risk of atrial fibrillation appears to be modestly elevated for zoledronic acid (6 trials; 1.24 [0.96–1.61]; I² = 0.0%), not for oral bisphosphonates (26 trials; 1.02 [0.83–1.24]; I² = 0.0%). The CV effects did not vary by subgroups or study quality.

Conclusions

Bisphosphonates do not have beneficial or harmful effects on atherosclerotic CV events, but zoledronic acid may modestly increase the risk of atrial fibrillation. Given the large reduction in fractures with bisphosphonates, changes in osteoporosis treatment decision due to CV risk are not justified.

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.

Are there ways to attenuate arterial calcification and improve cardiovascular outcomes in chronic kidney disease?

The risk of cardiovascular mortality among patients with end-stage renal disease is several times higher than general population. Arterial calcification, a marker of atherosclerosis and a predictor of cardiovascular mortality, is common in chronic kidney disease (CKD). The presence of traditional cardiovascular risk factors such as diabetes, hypertension, hyperlipidemia, and advanced age cannot fully explain the high prevalence of atherosclerosis and arterial calcification. Other factors specific to CKD such as hyperphosphatemia, excess of calcium, high dose active vitamin D and prolonged dialysis vintage play important roles in the development of arterial calcification. Due to the significant health risk, it is prudent to attempt to lower arterial calcification burden in CKD. Treatment of hyperlipidemia with statin has failed to lower atherosclerotic and arterial calcification burden. Data on diabetes and blood pressure controls as well as smoking cessation on cardiovascular outcomes in CKD population are limited. Currently available treatment options include non-calcium containing phosphate binders, low dose active vitamin D, calcimimetic agent and perhaps bisphosphonates, vitamin K and sodium thiosulfate. Preliminary data on bisphosphonates, vitamin K and sodium thiosulfate are encouraging but larger studies on efficacy and outcomes are needed.

A comparison of calcium to zoledronic acid for improvement of cortical bone in an animal model of CKD

Patients with chronic kidney disease (CKD) have increased risk of fractures, yet the optimal treatment is unknown. In secondary analyses of large randomized trials, bisphosphonates have been shown to improve bone mineral density and reduce fractures. However, bisphosphonates are currently not recommended in patients with advanced kidney disease due to concern about oversuppressing bone remodeling, which may increase the risk of developing arterial calcification. In the present study we used a naturally occurring rat model of CKD with secondary hyperparathyroidism, the Cy/+ rat, and compared the efficacy of treatment with zoledronic acid, calcium given in water to simulate a phosphate binder, and the combination of calcium and zoledronic acid. Animals were treated beginning at 25 weeks of age (approximately 30% of normal renal function) and followed for 10 weeks. The results demonstrate that both zoledronic acid and calcium improved bone volume by micro-computed tomography (µCT) and both equally suppressed the mineral apposition rate, bone formation rate, and mineralizing surface of trabecular bone. In contrast, only calcium treatment with or without zoledronic acid improved cortical porosity and cortical biomechanical properties (ultimate load and stiffness) and lowered parathyroid hormone (PTH). However, only calcium treatment led to the adverse effects of increased arterial calcification and fibroblast growth factor 23 (FGF23). These results suggest zoledronic acid may improve trabecular bone volume in CKD in the presence of secondary hyperparathyroidism, but does not benefit extraskeletal calcification or cortical biomechanical properties. Calcium effectively reduces PTH and benefits both cortical and trabecular bone yet increases the degree of extra skeletal calcification. © 2014 American Society for Bone and Mineral Research.

Bisphosphonates and mortality in women with CKD and the presence or absence of cardiovascular disease

BACKGROUND AND OBJECTIVES

A modest protective association between bisphosphonate prescription and mortality among women with CKD but without clinically manifest cardiovascular disease has been shown. Whether a prior cardiovascular event (myocardial infarction, stroke, or heart failure) modifies this association is unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

A cohort of adult women with stages 3 and 4 CKD receiving primary care in a rural integrated health care system during the period 2004-2011 without history of advanced malignancy or organ transplantation (n=6756, median age=74 years, median follow-up=4.3 years) was retrospectively assembled. The primary analysis compared those patients prescribed bisphosphonates (both prevalent and incident use during follow-up) with those patients not prescribed. Additional approaches were taken to account for survival and indication biases. The primary outcome was time to death by Cox multivariable regression.

RESULTS

In the primary analysis, compared with women not prescribed a bisphosphonate, the hazard ratio (95% confidence interval) for death among women prescribed a bisphosphonate was 0.90 (0.78 to 1.04) if there was no history of cardiovascular event but 1.22 (1.04 to 1.42) if there was history of cardiovascular event (P for interaction=0.004). In the additional approaches, associations between bisphosphonate prescription and mortality among those patients with a prior cardiovascular history varied: hazard ratios (95% confidence intervals) were 1.25 (1.01 to 1.57), 1.48 (1.16 to 1.88), and 0.94 (0.66 to 1.34). Interaction by prior cardiovascular event history varied across these three approaches (P=0.07, P=0.22, and P=0.05).

CONCLUSION

In this study of women with CKD, the association between bisphosphonate treatment and mortality risk was inconclusive across a series of analyses designed to account for various types of selection and indication bias.

Bisphophonates in CKD patients with low bone mineral density

Patients with chronic kidney disease-mineral and bone disorder (CKD-MBD) have a high risk of bone fracture because of low bone mineral density and poor bone quality. Osteoporosis also features low bone mass, disarranged microarchitecture, and skeletal fragility, and differentiating between osteoporosis and CKD-MBD in low bone mineral density is a challenge and usually achieved by bone biopsy. Bisphosphonates can be safe and beneficial for patients with a glomerular filtration rate of 30 mL/min or higher, but prescribing bisphosphonates in advanced CKD requires caution because of the increased possibility of low bone turnover disorders such as osteomalacia, mixed uremic osteodystrophy, and adynamic bone, even aggravating hyperparathyroidism. Therefore, bone biopsy in advanced CKD is an important consideration before prescribing bisphosphonates. Treatment also may induce hypocalcemia in CKD patients with secondary hyperparathyroidism, but vitamin D supplementation may ameliorate this effect. Bisphosphonate treatment can improve both bone mineral density and vascular calcification, but the latter becomes more unlikely in patients with stage 3-4 CKD with vascular calcification but no decreased bone mineral density. Using bisphosphonates requires considerable caution in advanced CKD, and the lack of adequate clinical investigation necessitates more studies regarding its effects on these patients.

Anti-osteoporotic drugs and vascular calcification: the bidirectional calcium traffic

During the last years, numerous epidemiological studies have demonstrated a direct relationship between vascular calcification and low bone mineral density. This observation is in line with experimental data demonstrating the osteogenic characteristics of calcified arteries. Various common risk factors have been suggested to link vascular calcification and bone loss, including aging, estrogen deficiency, vitamin D and K deficiency, diabetes mellitus, renal failure, smoking, chronic inflammation and oxidative stress. Although the underlying pathogenetic mechanisms are not yet clear, current research is focusing on anti-osteoporotic agents that could potentially affect the deposition of calcium in the arterial wall and thus provide an additional therapeutic strategy in elderly osteoporotic women prone to calcific cardiovascular disease.

Vascular calcification: an update on mechanisms and challenges in treatment

Vascular calcification is highly associated with cardiovascular disease mortality, particularly in high-risk patients with diabetes and chronic kidney diseases (CKD). In blood vessels, intimal calcification is associated with atherosclerosis, whereas medial calcification is a nonocclusive process which leads to increased vascular stiffness and reduced vascular compliance. In the valves, calcification of the leaflets can change the mechanical properties of the tissue and result in stenosis. For many decades, vascular calcification has been noted as a consequence of aging. Studies now confirm that vascular calcification is an actively regulated process and shares many features with bone development and metabolism. This review provides an update on the mechanisms of vascular calcification including the emerging roles of the RANK/RANKL/OPG triad, osteoclasts, and microRNAs. Potential treatments adapted from osteoporosis and CKD treatments that are under investigation for preventing and/or regressing vascular calcification are also reviewed.

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.

Lowering vascular calcification burden in chronic kidney disease: Is it possible?

High prevalence of atherosclerosis and arterial calcification in chronic kidney disease is far beyond the explanation by common cardiovascular risk factors such as aging diabetes, hypertension and dyslipidemia. The magnitude of coronary artery calcification is independently and inversely associated with renal function. In addition to cardiovascular risk factors, other chronic kidney disease-related risks such as phosphate retention, excess of calcium and prolonged dialysis vintage also contribute to the development of vascular calcification. Strategies to lower vascular calcification burden in chronic kidney disease population should include minimizing chronic kidney disease and atherosclerotic risk factors. Current therapies available are non-calcium containing phosphate binders, low dose active vitamin D and calcimimetic agent. The role of bisphosphonates in vascular calcification in chronic kidney disease population remains unclear. Preliminary data on sodium thiosulfate are promising, however, larger studies on efficacy and patient outcomes are necessary. Several large randomized controlled trials have confirmed the lack of benefit of statin in attenuating the progression of vascular calcification.

Bisphosphonate safety and efficacy in chronic kidney disease

A new population-based study of elderly patients hospitalized for a fracture and treated with an oral bisphosphonate finds no increased risk of acute kidney injury. The safety and efficacy of bisphosphonates may be different in patients with chronic kidney disease (CKD). The effects on vascular calcifications need further study, because low bone turnover might exacerbate vascular calcifications in patients with CKD. Even if bisphosphonates prove safe, their efficacy in this population is uncertain.

Skeletal effects of zoledronic acid in an animal model of chronic kidney disease

Bisphosphonates reduce skeletal loss and fracture risk, but their use has been limited in patients with chronic kidney disease. This study shows skeletal benefits of zoledronic acid in an animal model of chronic kidney disease.

INTRODUCTION

Bisphosphonates are routinely used to reduce fractures but limited data exists concerning their efficacy in non-dialysis chronic kidney disease. The goal of this study was to test the hypothesis that zoledronic acid produces similar skeletal effects in normal animals and those with kidney disease.

METHODS

At 25 weeks of age, normal rats were treated with a single dose of saline vehicle or 100 μg/kg of zoledronic acid while animals with kidney disease (approximately 30% of normal kidney function) were treated with vehicle, low dose (20 μg/kg), or high dose (100 μg/kg) zoledronic acid, or calcium gluconate (3% in the drinking water). Skeletal properties were assessed 5 weeks later using micro-computed tomography, dynamic histomorphometry, and mechanical testing.

RESULTS

Animals with kidney disease had significantly higher trabecular bone remodeling compared to normal animals. Zoledronic acid significantly suppressed remodeling in both normal and diseased animals yet the remodeling response to zoledronic acid was no different in normal and animals with kidney disease. Animals with kidney disease had significantly lower cortical bone biomechanical properties; these were partially normalized by treatment.

CONCLUSIONS

Based on these results, we conclude that zoledronic acid produces similar amounts of remodeling suppression in animals with high turnover kidney disease as it does in normal animals, and has positive effects on select biomechanical properties that are similar in normal animals and those with chronic kidney disease.

Vascular calcification in chronic kidney disease: Pathogenesis and clinical implication

Cardiovascular disease is the leading cause of death among patients with chronic kidney disease (CKD). Vascular calcification (VC) is one of the independent risk factors associated with cardiovascular disease and cardiovascular mortality in both the general population and CKD patients. Earlier evidence revealed substantially higher prevalence of VC in young adults on chronic hemodialysis compared to the general population in the same age range, indicating the influence of CKD-related risk factors on the development of VC. Pathogenesis of VC involves an active, highly organized cellular transformation of vascular smooth muscle cells to bone forming cells evidenced by the presence of bone matrix proteins in the calcified arterial wall. VC occurs in both the intima and the media of arterial wall with medial calcification being more prevalent in CKD. In addition to traditional cardiovascular risks, risk factors specific to CKD such as phosphate retention, excess of calcium, history of dialysis, active vitamin D therapy in high doses and deficiency of calcification inhibitors play important roles in promoting the development of VC. Non-contrast multi-slice computed tomography has often been used to detect coronary artery calcification. Simple plain radiographs of the lateral lumbar spine and pelvis can also detect VC in the abdominal aorta and femoral and iliac arteries. Currently, there is no specific therapy to reverse VC. Reduction of calcium load, lowering phosphate retention using non-calcium containing phosphate binders, and moderate doses of active vitamin D may attenuate progression. Parenteral sodium thiosulfate has also been shown to delay VC progression.

Bisphosphonate therapy, death, and cardiovascular events among female patients with CKD: a retrospective cohort study

BACKGROUND

Accelerated vascular calcification contributes to cardiovascular disease burden in patients with chronic kidney disease (CKD). We hypothesized that bisphosphonate therapy would reduce the risk of mortality and cardiovascular events in this population.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

Adult women with stage 3 or 4 CKD receiving primary care in a large rural integrated health care system in 2004-2010.

EXPOSURE

Time-dependent exposure status based on outpatient prescription for any medication within the bisphosphonate class, obtained from electronic health records.

OUTCOMES

Time to death and first cardiovascular event (composite of myocardial infarction, heart failure, or stroke).

RESULTS

Data from 9,604 eligible female patients with CKD were analyzed; 3,234 were treated with bisphosphonate therapy. During a median follow-up of 3.9 (25th-75th percentile, 2.3-5.4) years, there were 286 versus 881 deaths and 206 versus 571 cardiovascular events (treated vs not-treated groups, respectively). In a multivariate Cox proportional hazard model, the adjusted HR for death (treated vs not treated) was 0.78 (95% CI, 0.67-0.91; P = 0.003). In Cox modeling adjusted for similar baseline covariates, treatment with bisphosphonates was not associated with a lower risk of the composite cardiovascular outcome (adjusted HR, 1.14; 95% CI, 0.94-1.39; P = 0.2).

LIMITATIONS

Residual confounding by unidentified factors, exclusion of male patients, and lack of information about longitudinal drug adherence.

CONCLUSIONS

For female patients with CKD, treatment with bisphosphonates is associated with a lower risk of death, but not cardiovascular events. Confirmatory studies and investigations of potential causal mechanisms are warranted.

Can bisphosphonates play a role in the treatment of children with chronic kidney disease?

In patients with chronic kidney disease (CKD) renal osteodystrophy, in the form of either low- or high-turnover bone disease, is quite common. While renal transplantation is expected to reverse renal osteodystrophy, long-term treatment with glucocorticoids before and/or after transplantation may lead to osteoporosis instead. Osteoporosis is defined as a skeletal disease with low bone mineral density, microarchitectural deterioration, and concomitant fragility. In adults, bisphosphonates are widely used to treat osteoporosis and other diseases associated with excessive bone resorption. In pediatric CKD patients the efficacy and safety of these drugs have not yet been addressed adequately and thus no evidence-based recommendations regarding the optimal type of bisphosphonate, dosage, or duration of therapy are available. Furthermore, while in adults the determination of areal bone mineral density is sufficient to diagnose osteoporosis, this is not the case in children. Instead, in pediatric patients, careful morphological assessment of bone structure and formation is required. Indeed, data from studies with uremic rats indicated that bisphosphonates, via a deceleration of bone turnover, have the potential not only to aggravate pre-existing adynamic bone disease, but also to impair longitudinal growth. Thus, the widespread use of bisphosphonates in children with CKD should be discouraged until the risks and benefits have been carefully elucidated in clinical trials.

Association of warfarin use with valvular and vascular calcification: a review

Vitamin K is required for the activity of various biologically active proteins in our body. Apart from clotting factors, vitamin K-dependent proteins include regulatory proteins like protein C, protein S, protein Z, osteocalcin, growth arrest-specific gene 6 protein, and matrix Gla protein. Glutamic acid residues in matrix Gla protein are γ-carboxylated by vitamin K-dependent γ-carboxylase, which enables it to inhibit calcification. Warfarin, being a vitamin K antagonist, inhibits this process, and has been associated with calcification in various animal and human studies. Though no specific guidelines are currently available to prevent or treat this less-recognized side effect, discontinuing warfarin and using an alternative anticoagulant seems to be a reasonable option. Newer anticoagulants such as dabigatran and rivaroxaban offer promise as future therapeutic options in such cases. Drugs including statins, alendronate, osteoprotegerin, and vitamin K are currently under study as therapies to prevent or treat warfarin-associated calcification. Copyright © 2011 Wiley Periodicals, Inc. The authors have no funding, financial relationships, or conflicts of interest to disclose.

Recent progress in the treatment of vascular calcification

Vascular calcification is common in patients with advanced chronic kidney disease and is associated with poorer outcomes. Although the pathophysiology is not completely understood, it is clear that it is a multifactorial process involving altered mineral metabolism, as well as changes in systemic and local factors that can promote or inhibit vascular calcification, and all of these are potential therapeutic targets. Current therapy is closely linked to strategies for preventing disordered bone and mineral metabolism in advanced kidney disease and involves lowering the circulating levels of both phosphate and calcium. The efficacy of compounds that specifically target calcification, such as bisphosphonates and thiosulfate, has been shown in animals but only in small numbers of humans, and safety remains an issue. Additional therapies, such as pyrophosphate, vitamin K, and lowering of pH, are supported by animal studies, but are yet to be investigated clinically. As the mineral composition of vascular calcifications is the same as in bone, potential effects on bone must be addressed with any therapy for vascular calcification.