Effect of calcium-based versus non-calcium-based phosphate binders on mortality in patients with chronic kidney disease: an updated systematic review and meta-analysis

Cardiovascular mortality in chronic kidney disease patients: potential mechanisms and possibilities of inhibition by resin-based phosphate binders

Cardiovascular mortality has been considered as the most important risk associated with chronic kidney disease. The mechanisms underlying this include inflammation, poor control of serum phosphate, high serum calcium, increased calcification of the arteries and cardiac valves, hyperlipidemia, diabetes, severe anemia, uric acid accumulation and others. Elevated phosphate levels have been strongly associated with increased mortality, thus phosphate-binding drugs have long been used to control the increase serum phosphate levels. However, phosphate-binding drugs differ considerably and recently numerous publications suggest differences between agents in the effects on overall mortality. The resin-based phosphate binders, comprising sevelamer and colestilan, not only reduce serum phosphate but also do not raise serum calcium. In addition, they reduce serum LDL-C, inflammation, uric acid and high Hba1c values. These differences suggest that not all phosphate binders may be equal in the context of cardiovascular mortality in this patient population.

Calcium acetate or calcium carbonate for hyperphosphatemia of hemodialysis patients: a meta-analysis

BACKGROUND

High levels of serum phosphorus both at baseline and during follow-up are associated with increased mortality in dialysis patients, and administration of phosphate binders was independently associated with improved survival among hemodialysis population. Calcium-based phosphate binders are the most commonly used phosphate binders in developing countries for their relatively low costs.

OBJECTIVES

To compare the efficacy and safety between calcium carbonate and calcium acetate in the treatment of hyperphosphatemia in hemodialysis patients.

METHODS

PubMed, EMBASE, Cochrane Library, Google scholar and Chinese databases (Wanfang, Weipu, National Knowledge Infrastructure of China) were searched for relevant studies published before March 2014. Reference lists of nephrology textbooks and review articles were checked. A meta-analysis of randomized controlled trials (RCTs) and quasi-RCTs that assessed the effects and adverse events of calcium acetate and calcium carbonate in adult patients with MHD was performed using Review Manager 5.0.

RESULTS

A total of ten studies (625 participants) were included in this meta-analysis. There was insufficient data in all-cause mortality and cardiovascular events for meta-analysis. Compared with calcium carbonate group, the serum phosphorus was significantly lower in calcium acetate group after4 weeks' administration (MD -0.15 mmol/L, 95% CI -0.28 to -0.01) and after 8 weeks' administration (MD -0.25 mmol/L, 95% CI -0.40 to -0.11). There was no difference in serum calcium levels or the incidence of hypercalcemia between two groups at 4 weeks and 8 weeks. No statistical difference was found in parathyroid hormone (PTH) levels or serum calcium by phosphorus (Ca x P) product. There was significantly higher risk of intolerance with calcium acetate treatment (RR 3.46, 95% CI 1.48 to 8.26).

CONCLUSIONS

For hyperphosphatemia treatment, calcium acetate showed better efficacy and with a higher incidence of intolerance compared with calcium carbonate. There are insufficient data to establish the comparative superiority of the two calcium-based phosphate binders on all-cause mortality and cardiovascular end-points in hemodialysis patients.

The challenge of controlling phosphorus in chronic kidney disease

The pathogenesis and management of chronic kidney disease-mineral bone disorders (CKD-MBD) has experienced major changes, but the control of serum phosphorus at all stages of CKD still seems to be a key factor to improve clinical outcomes. High serum phosphorus is the most important uremia-related, non-traditional risk factor associated with vascular calcification in CKD patients and in the general population. Phosphorus may also be one of the key elements linking vascular calcification with low bone turnover. The main hormones and factors that contribute to the kidney regulation of phosphorus and calcium include parathyroid hormone, FGF-23, klotho and 1,25-dihydroxyvitamin D (1,25(OH)2D). Serum phosphorus did not start rising until CKD 3b in contrast with the earlier changes observed with fibroblast growth factor-23 (FGF-23), Klotho, calcitriol and parathyroid hormone (PTH). Despite FGF-23 and PTH having synergic effects regarding phosphorus removal, they have opposite effects on 1,25(OH)2D3. At the same stages of CKD in which phosphorus retention appears to occur, calcium retention also occurs. As phosphorus accumulation is associated with poor outcomes, an important question without a clear answer is at which level-range should serum phosphorus be maintained at different stages of CKD to improve clinical outcomes. There are four main strategies to manage phosphate homeostasis; phosphorus dietary intake, administration of phosphate binder agents, effective control of hyperparathyroidism and to ensure in the CKD 5D setting, an adequate scheme of dialysis. Despite all the available strategies, and the introduction of new phosphate binder agents in the market, controlling serum phosphorus remains challenging, and hyperphosphatemia continues to be extremely common in CKD 5 patients. Furthermore, despite phosphate binding agents having proved to be effective in reducing serum phosphorus, their ultimate effects on clinical outcomes remain controversial. Thus, we still need well-designed, large-scale, placebo-controlled studies to definitively prove that the reduction of serum phosphorus by phosphate binders improves clinical outcomes.

Colestilan for the treatment of hyperphosphatemia in chronic kidney disease patients on dialysis

Chronic kidney disease in the later stages poses many treatment challenges. Hyperphosphatemia is one that is well-known and is often linked to increased cardiovascular morbidity/mortality. Currently, a number of phosphate binders are available that act to conserve serum phosphate at normal or near normal levels. However, it is the overall profile of all binders that needs to be taken into account and the risks and the potential benefits associated with each agent must be balanced when selecting a particular phosphate binder. It is known that calcium-based binders, although effective phosphate binders, may lead to hypercalcemia and/or positive calcium balance and cardiovascular calcification. One, new non-calcium phosphate binder, recently approved in Europe, is colestilan. Colestilan possesses a range of properties that may afford further advantages over simply reducing serum phosphate. This review assesses the pharmacology and clinical data of colestilan used to treat hyperphosphatemia in chronic kidney disease stage 5 patients on dialysis. The article was written based on literature searches using PubMed to find articles published on phosphate binders or colestilan over the last 10 years.

Revisiting KDIGO clinical practice guideline on chronic kidney disease-mineral and bone disorder: a commentary from a Kidney Disease: Improving Global Outcomes controversies conference

A new definition and classification of chronic kidney disease-mineral and bone disorder (CKD-MBD) was proposed in 2005 and it was later followed by a guideline publication on this topic from Kidney Disease: Improving Global Outcomes (KDIGO) in 2009. This work recognized that CKD-MBD is a syndrome of bone abnormalities, laboratory abnormalities, and vascular calcification linked to fractures, cardiovascular disease, and mortality. Because of limited data at the time of the original guideline systematic review, many of the recommendations were cautiously vague. KDIGO convened a Controversies Conference in October 2013 to review the CKD-MBD literature published since the 2009 guideline. Specifically, the objective of this conference was to determine whether sufficient new data had emerged to support a reassessment of the CKD-MBD guideline and if so to determine the scope of these potential revisions. This report summarizes the results of these proceedings, highlighting important new studies conducted in the interval since the original KDIGO CKD-MBD guideline.

Translational nephrology: what translational research is and a bird's-eye view on translational research in nephrology

The ultimate aim of biomedical research is to preserve health and improve patient outcomes. However, by a variety of measures, preservation of kidney health and patient outcomes in kidney disease are suboptimal. Severe acute kidney injury has been treated solely by renal replacement therapy for over 50 years and mortality still hovers at around 50%. Worldwide deaths from chronic kidney disease (CKD) increased by 80% in 20 years--one of the greatest increases among major causes of death. This dramatic data concur with huge advances in the cellular and molecular pathophysiology of kidney disease and its consequences. The gap appears to be the result of sequential roadblocks that impede an adequate flow from basic research to clinical development [translational research type 1 (T1), bench-to-bed and back] and from clinical development to clinical practice and widespread implementation (translational research T2) that supported by healthcare policy-making reaches all levels of society throughout the globe (sometimes called translational research T3). Thus, it is more than 10 years since the introduction of the last new-concept drug for CKD patients, cinacalcet; and 30 years since the introduction of reninangiotensin system (RAS) blockade, the current mainstay to prevent progression of CKD, illustrating the basic science-clinical practice disconnect. Roadblocks from clinical advances to widespread implementation, together with lag time-to-benefit may underlie the 20 years since the description of the antiproteinuric effect of RAS blockade to the observation of decreased age-adjusted incidence of endstage renal disease due to diabetic kidney disease. Only a correct understanding of the roadblocks in translational medicine and a full embracement of a translational research culture will spread the benefits of the biomedical revolution to its ultimate destinatary, the society.

The demise of calcium-based phosphate binders-is this appropriate for children?

In children with chronic kidney disease (CKD) optimal control of mineral and bone disorder (MBD) is essential not only for the prevention of debilitating skeletal complications and for achieving adequate growth, but also for preserving long-term cardiovascular health. The growing skeleton is particularly vulnerable to the effects of CKD, and bone pain, fractures and deformities are common in children on dialysis. Defective bone mineralisation has been linked with ectopic calcification, which in turn leads to significant morbidity and mortality. Despite national and international guidelines for the management of CKD-MBD, the management of mineral dysregulation in CKD can be extremely challenging, and a significant proportion of patients have calcium, phosphate or parathyroid hormone levels outside the normal ranges. Clinical and experimental studies have shown that, in the setting of CKD, low serum calcium levels are associated with poor bone mineralisation, whereas high serum calcium levels can lead to arterial calcification, even in children. The role of calcium in CKD-MBD is the focus of this review.

Iron-based phosphate binders: do they offer advantages over currently available phosphate binders?

Increased cardiovascular morbidity and mortality has been associated with the hyperphosphatemia seen in patients with end-stage chronic kidney disease (CKD). Oral phosphate binders are prescribed in these patients to prevent intestinal absorption of dietary phosphate and reduce serum phosphate. In prospective observational cohorts they have shown to decrease all-cause and cardiovascular mortality risk. Different problems have been associated with currently available phosphate binders as positive calcium balance and impaired outcomes with calcium-based phosphate binders or increased costs with non-calcium-based phosphate binders. Iron-based phosphate binders represent a new class of phosphate binders. Several iron-based phosphate binders have undergone testing in clinical trials. Ferric citrate (JTT-751) and sucroferric oxyhydroxide (PA21) are the two iron-based binders that have passed to the clinical field after being found safe and effective in decreasing serum phosphate. Iron from ferric citrate is partially absorbed compared to sucroferric oxyhydroxide. Ferric citrate usage could result in an important reduction in erythropoiesis-stimulating agent (ESA) and IV iron usage, resulting in significant cost savings. Sucroferric oxyhydroxide was effective in lowering serum phosphorus in dialysis patients with similar efficacy to sevelamer carbonate, but with lower pill burden, and better adherence. Ferric citrate may be more suited for the treatment of chronic hyperphosphatemia in CKD patients requiring iron supplements but its use may have been hampered by potential aluminum overload, as citrate facilitates its absorption; sucroferric oxyhydroxide may be more suited for hyperphosphatemic CKD patients not requiring iron supplementation, with low pill burden.

Use of vitamin D receptor activator, incident cardiovascular disease and death in a cohort of hemodialysis patients

The use of vitamin D receptor activators (VDRAs) is an independent predictor of a lower risk of death from cardiovascular disease (CVD) in patients with chronic kidney disease (CKD). We examined whether the use of VDRAs and other CKD-mineral bone disorder (MBD)-related factors are associated with incident CVD or death after CVD in hemodialysis patients. This is a historical cohort study of 37 690 prevalent hemodialysis patients without previous history of CVD at the end of 2004 extracted from a nationwide registry in Japan. The key exposure was the use of VDRAs, and the outcomes were incident CVD (myocardial infarction, cerebral infarction, cerebral hemorrhage, and sudden death) and death after CVD during the 1-year follow-up. VDRAs were used in 57% of the subjects at baseline. We identified 2433 patients with incident CVD and 397 deaths after the events. In multivariate logistic regression models, independent predictors of incident CVD were non-use of VDRA, higher intact PTH, non-use of calcium-based phosphate-binder, and non-use of non-calcium-based phosphate binder. Risk of death after CVD was not significantly associated with VDRA, whereas it was lower in those with lower corrected calcium, and the risk was higher in those with higher phosphate and in non-users of calcium-based phosphate binders. The use of VDRAs was associated with a lower risk of incident CVD but not with death after CVD in this large cohort of hemodialysis patients. The CKD-MBD-related predictors of poor outcomes are associated with the risk of incident CVD, the risk of death after CVD, or both.

Cardiovascular endocrinology: controversy--cardiovascular effects of calcium supplementation

Of late, clinical trial data, meta-analyses and observational studies have caused concern that the use of calcium supplements might increase the risk of myocardial infarction and stroke. A new meta-analysis suggests that there is no problem with calcium supplements, but as the analysis includes controversial data omitted from previous analyses, the debate will continue.

Optimal management of hyperphosphatemia in end-stage renal disease: an Indian perspective

There has been an exponential increase in the incidence of diabetes and hypertension in India in the last few decades, with a proportional increase in chronic kidney disease (CKD). Preventive health care and maintenance of asymptomatic chronic disease such as CKD are often neglected by patients until they become symptomatic with fluid retention and uremia. Management of hyperphosphatemia in CKD remains one of the challenges of nephrology in India for this reason, as it is almost completely asymptomatic but contributes to renal osteodystrophy, metastatic vascular calcification, and acceleration of cardiovascular disease. Lack of understanding of the dangers of asymptomatic hyperphosphatemia, the huge pill burden of phosphate binders, difficulty with dietary and dialysis compliance, and most importantly, the added expense of the drugs places additional road blocks in the treatment of hyperphosphatemia at a population level in developing countries like India. In this review we seek to address the contribution of hyperphosphatemia to adverse outcomes and discuss economic, cultural, and societal factors unique to the management of phosphate levels in Indian patients with advanced CKD.

Phosphate management in chronic kidney disease

PURPOSE OF REVIEW

The review focuses on the rationale and evidence behind management strategies for hyperphosphatemia in patients with chronic kidney disease (CKD).

RECENT FINDINGS

Optimal management of phosphate in CKD remains an area of uncertainty, but multiple studies now point to a clinical benefit from the use of phosphate binders. Evidence of improved survival is particularly strong with sevelamer, though it remains unclear whether the absence of calcium or other properties of sevelamer are responsible for this relationship. Newer agents, such as iron-based binders or niacin compounds to inhibit phosphorus absorption, may have additional benefits which will be better defined with additional experience. A reduced pill count may be a particularly beneficial characteristic of newer agents, and has been associated with improved response to therapy. Increased use of frequent, nocturnal hemodialysis is an additional tool to help ameliorate phosphate control. Data on the reduction of fibroblast growth factor 23 through use of phosphate binders remain weak.

SUMMARY

An improved understanding of phosphate regulation and the development of new therapeutic agents have reinvigorated a once stagnant field, but significant changes to practice cannot yet be justified. There is increasing support for using sevelamer in place of calcium-based binders, though economic practicability remains challenging.

Phosphate balance in ESRD: diet, dialysis and binders against the low evident masked pool

Phosphate metabolism is crucial in the pathophysiology of secondary hyperparathyroidism and vascular calcification. High phosphate levels have been consistently associated with unfavorable outcomes in dialysis patients, but several limitations are still hampering a resolutive definition of the optimal targets of phosphate serum levels to be achieved in this cohort. Nonetheless, hyperphosphatemia is a late marker of phosphate overload in humans. Clinical nephrologists routinely counteract the positive phosphate balance in dialysis patients through nutritional counseling, stronger phosphate removal by dialysis and prescription of phosphate binders. However, the superiority against placebo of phosphate control by diet, dialysis or binders in terms of survival has never been tested in dedicated randomized controlled trials. The present review discusses this conundrum with particular emphasis on the rationale supporting the value of a simultaneous intervention against phosphate overload in dialysis patients via the improvement of dietary intakes, dialysis efficiency and an individualized choice of phosphate binders.

Medication beliefs are associated with phosphate binder non-adherence in hyperphosphatemic haemodialysis patients

OBJECTIVES

Patients with end-stage kidney disease receiving haemodialysis (HD) are at risk of cardiovascular disease and bone disorders related to high levels of serum phosphate. We studied the association between medication beliefs and depressive symptoms, with non-adherence to phosphate binding medication in a group of HD patients at risk of complications due to hyperphosphatemia.

DESIGN

Cross-sectional design.

METHODS

Baseline data from 112 patients participating in a randomized controlled trial, evaluating an adherence intervention, are presented. All patients had serum phosphate levels >1.6 mmol/l at baseline. Adherence was measured by (1) serum phosphate and (2) Medication Adherence Report Scales (MARS). Beliefs about Medicines (BMQ) and depressive symptoms (PHQ-9) were also evaluated.

RESULTS

Beliefs about Medicines Questionnaire necessity, but not concerns, beliefs were found to correlate with serum phosphate (r = -.23, p < .05) and self-reported adherence (r = .35, p < .01). In regression models, controlling for demographic, clinical and psychological variables, necessity beliefs explained the variance of serum phosphate (β = -.22, p = .01) and self-reported adherence (β = .30, p ≤ .01). Both BMQ concerns and depressive symptoms were not related to non-adherence.

CONCLUSION

Patients' beliefs about the necessity of their prescribed phosphate binding medications explain variation in non-adherence levels, measured both subjective and objectively. Dialysis patient's medication beliefs are potentially modifiable targets for future interventions.

Educational intervention for metabolic bone disease in patients with chronic kidney disease: a systematic review and meta-analysis

Metabolic bone disease (MBD) is a common complication of chronic kidney disease (CKD). The currently accepted international guidelines for treatment of CKD-MBD has been published, unfortunately adequate control of serum markers of disorder, especially hyperphosphatemia, is poorly achieved. Whether educational intervention is an effective way for improving CKD-MBD remains controversial. A systematic review of educational intervention versus routine care to improve patients with CKD-MBD was conducted. All randomized controlled trials (RCTs) and quasi-RCTs examining the efficacy of educational intervention to improve patients with CKD-MBD were included. We performed a comprehensive search of several databases and sources to identify eligible trials. In addition, we searched unpublished studies by tracking the SIGLE (System for Information on Grey Literature) database. Finally, 8 RCTs and 2 quasi-RCTs containing 775 participants were included in our systematic review. The result of our study revealed that the educational intervention to patients with CKD-MBD led to an improvement of the serum phosphorus and calcium by phosphate product. Educational intervention is a beneficial supplement method in improving CKD-MBD and putting off deterioration of the disease.

Recent advances in the management of hemodialysis patients: a focus on cardiovascular disease

The number of patients requiring chronic hemodialysis is rapidly growing worldwide. Hemodialysis both greatly reduces quality of life and is associated with extremely high mortality rates. Management of care of patients requiring chronic hemodialysis is complex, and randomized controlled trials aimed at reducing primary outcomes of cardiovascular disease events, mortality, or both in this population have largely been unsuccessful. Topics of major concern in the management of maintenance hemodialysis patients as related to these outcomes include the overall cardiovascular disease burden, blood pressure control, anemia, abnormalities in mineral metabolism, and inflammation. The focus of this review is a discussion of these topics on the basis of current recommendations from major organizations, expert opinion, and the available randomized controlled trials to date. These issues are further complicated by sometimes conflicting observational and randomized controlled trial data. Overall, treatment options for reducing these endpoints in maintenance hemodialysis patients are limited, and future randomized controlled trials are essential to continuing to advance care in this population, with the goal of ultimately improving hard outcomes. Such trials should consider new therapies to better target these factors, additional risk factors that have not been well tested to date, and therapies with new targets, including inflammation.

[Pleiotropic effects of sevelamer: a model of intestinal tract chelating agent]

The number of patients with chronic kidney disease (CKD) with its associated complications has increased dramatically worldwide in recent years. Therefore, many experimental and clinical studies have examined over the last decade the mechanisms involved, in order to explain the sharp increase in cardiovascular mortality. Hyperphosphatemia is a major problem in these patients especially at advanced stages of CKD, and it is associated with cardiovascular and mineral complications in these patients. Sevelamer is a phosphate binder that allows a better control of hyperphosphatemia, like other phosphate binder agents, but it has additional pleiotropic effects such as correcting certain abnormalities of lipid metabolism and clearance of several uremic toxins. These effects of sevelamer, restricted to the intestinal lumen, underline the importance of intestinal pathway in CKD and open the way to new therapeutic strategies for the management of the CKD and its complications.

Is there a need for new phosphate binders to treat phosphate imbalance associated with chronic kidney disease?

INTRODUCTION

Mineral and bone disorder (MBD) begins early in the course of chronic kidney disease (CKD). Phosphate imbalance in CKD-MBD can lead to various pathologies of clinical importance such as further deterioration of kidney function, cardiovascular complications, renal osteodystrophy and increased mortality.

AREAS COVERED

The authors conducted a systematic review of the biomedical literature to evaluate currently available drugs and new phosphate binder therapeutics in development.

EXPERT OPINION

There is a need to continue searching for novel phosphate binders that better match an 'ideal' product profile. This profile should have: i) a product that is highly efficient in binding phosphate; ii) low patient compliance issues; iii) minimal interaction with other drugs; and iv) reduced side effects and safety concerns. Targeting alternative mechanisms, such as developing inhibitors for intestinal type II sodium-dependent phosphate co-transporter, may also improve the limitations of phosphate binder therapeutics. Current medical practice focuses on using serum phosphorus levels as the only marker for detecting, monitoring and treating phosphate imbalance in CKD. However, the consequences of phosphate imbalance are evident in non-dialysis patients before serum phosphate levels rise above the normal range. There is a need to search for other markers to guide detection and treatment of clinically significant alterations in phosphate metabolism of non-dialysis CKD.

Preventing the progression of chronic kidney disease: two case reports and review of the literature

A variety of therapeutic modalities are available to alter the abnormalities seen in patients with chronic kidney disease (CKD). A comprehensive plan can now be developed to slow the progression of CKD. Two clinical cases of delay in the need for renal replacement therapy are described. This delay was achieved by using recognized recommendations for optimal diabetes therapy (HbA1c target 7 %), goals for blood pressure levels, reduction of proteinuria, and the proper use of ACEI/ARB therapies. Recent recommendations include BP <140/90 mmHg for patients <60 years old and <150/90 mmHg for older patients unless they have CKD or diabetes. Limits on dietary sodium and protein intake and body weight reduction will decrease proteinuria. Proper treatment for elevated serum phosphorous and parathyroid hormone levels is now appreciated as well as the benefits of therapy for dyslipidemias and anemia. Concerns regarding unfavorable outcomes with excess ESA therapy have led to hemoglobin goals in the 10-12 g/dL range. Finally, new therapeutic considerations for the treatment of acidosis and hyperuricemia are presented with data available to suggest that increasing serum bicarbonate to >22 mmol/L is beneficial, while serum uric acid therapeutic goals are still uncertain. Also, two as yet insufficiently understood approaches to altering the course of CKD (FGF-23 level reduction and balancing gut microbiota) are noted.

Sling exercise for chronic low back pain: a systematic review and meta-analysis

Background

Trials on sling exercise (SE), commonly performed to manage chronic low back pain (LBP), yield conflicting results. This study aimed to review the effects of SE on chronic LBP.

Methods

The randomized controlled trials comparing SE with other treatments or no treatment, published up to August 2013, were identified by electronic searches. Primary outcomes were pain, function, and return to work. The weighted mean difference (WMD) and 95% confidence interval (CI) were calculated, using a random-effects model.

Results

Risk of bias was rated as high in 9 included trials, where some important quality components such as blinding were absent and sample sizes were generally small. We found no clinically relevant differences in pain or function between SE and other forms of exercise, traditional Chinese medical therapy, or in addition to acupuncture. Based on two trials, SE was more effective than thermomagnetic therapy at reducing pain (short-term: WMD –13.90, 95% CI –22.19 to –5.62; long-term: WMD –26.20, 95% CI –31.32 to –21.08) and improving function (short-term: WMD –10.54, 95% CI –14.32 to –6.75; long-term: WMD –25.75, 95% CI –30.79 to –20.71). In one trial we found statistically significant differences between SE and physical agents combined with drug therapy (meloxicam combined with eperisone hydrochloride) but of borderline clinical relevance for pain (short-term: WMD –15.00, 95% CI –19.64 to −10.36) and function (short-term: WMD −10.00; 95% CI −13.70 to −6.30). There was substantial heterogeneity among the two trials comparing SE and thermomagnetic therapy; both these trials and the trial comparing SE with physical agents combined with drug therapy had serious methodological limitations.

Interpretation

Based on limited evidence from 2 trials, SE was more effective for LBP than thermomagnetic therapy. Clinically relevant differences in effects between SE and other forms of exercise, physical agents combined with drug therapy, traditional Chinese medical therapy, or in addition to acupuncture could not be found. More high-quality randomized trials on the topic are warranted.

Epidemiology, contributors to, and clinical trials of mortality risk in chronic kidney failure

Patients with chronic kidney failure--defined as a glomerular filtration rate persistently below 15 mL/min per 1·73 m(2)--have an unacceptably high mortality rate. In developing countries, mortality results primarily from an absence of access to renal replacement therapy. Additionally, cardiovascular and non-cardiovascular mortality are several times higher in patients on dialysis or post-renal transplantation than in the general population. Mortality of patients on renal replacement therapy is affected by a combination of socioeconomic factors, pre-existing medical disorders, renal replacement treatment modalities, and kidney failure itself. Characterisation of the key pathophysiological contributors to increased mortality and cardiorenal risk staging systems are needed for the rational design of clinical trials aimed at decreasing mortality. Policy changes to improve access to renal replacement therapy should be combined with research into low-cost renal replacement therapy and optimum clinical care, which should include multifaceted approaches simultaneously targeting several of the putative contributors to increased mortality.

Lipid, blood pressure and kidney update 2013

The year 2013 proved to be very exciting as far as landmark trials and new guidelines in the field of lipid disorders, blood pressure and kidney diseases. Among these are the International Atherosclerosis Society Global Recommendations for the Management of Dyslipidemia, European Society of Cardiology (ESC)/European Society of Hypertension Guidelines for the Management of Arterial Hypertension, American Diabetes Association Clinical Practice Recommendations, the Kidney Disease: Improving Global Outcomes Clinical Practice Guidelines for Managing Dyslipidemias in Chronic Kidney Disease (CKD) Patients, the American College of Cardiology/American Heart Association Guideline on the Treatment of Blood Cholesterol to Reduce Atherosclerotic Cardiovascular Risk in Adults, the Joint National Committee Expert Panel (JNC 8) Evidence-Based Guideline for the Management of High Blood Pressure in Adults, the American Society of Hypertension/International Society of Hypertension Clinical Practice Guidelines for the Management of Hypertension in the Community, the American College of Physicians Clinical Practice Guideline on Screening, Monitoring, and Treatment of Stage 1-3 CKD and many important trials presented among others during the ESC Annual Congress in Amsterdam and the American Society of Nephrology Annual Meeting--Kidney Week in Atlanta, GA. The paper is an attempt to summarize the most important events and reports in the mentioned areas in the passing year.

Osteoprotegerin and kidney disease

Vascular calcification in chronic kidney disease (CKD) patients is associated to increased mortality. Osteoprotegerin (OPG) is a soluble tumor necrosis factor (TNF) superfamily receptor that inhibits the actions of the cytokines receptor activator of nuclear factor kappa-B ligand (RANKL) and TNF-related apoptosis-inducing ligand (TRAIL) by preventing their binding to signaling receptors in the cell membrane. OPG-deficient mice display vascular calcification while OPG prevented calcification of cultured vascular smooth muscle cells and protected kidney cells from TRAIL-induced death. OPG may be a biomarker in patients with kidney disease. Circulating OPG is increased in predialysis, dialysis and transplant CKD patients and may predict vascular calcification progression and patient survival. By contrast, circulating OPG is decreased in nephrotic syndrome. In addition, free and exosome-bound urinary OPG is increased in human kidney disease. Increased urinary OPG has been associated with lupus nephritis activity. Despite the association of high OPG levels with disease, experimental functional information available suggests that OPG might be protective in kidney disease and in vascular injury in the context of uremia. Thus, tissue injury results in increased OPG, while OPG may protect from tissue injury. Recombinant OPG was safe in phase I randomized controlled trials. Further research is needed to fully define the therapeutic and biomarker potential of OPG in patients with kidney disease.

Phosphate binders for the treatment of hyperphosphatemia in chronic kidney disease patients on dialysis: a comparison of safety profiles

INTRODUCTION

Hyperphosphatemia is common in the late stages of chronic kidney disease (CKD) and is associated with elevated parathormone levels, abnormal bone mineralization, extraosseous calcification and increased risk of cardiovascular events and death. Several classes of oral phosphate binders are available to help control phosphorus levels. Although effective at lowering serum phosphorus, they all have safety issues that need to be considered when selecting which one to use.

AREAS COVERED

This paper reviews the use of phosphate binders in patients with CKD on dialysis, with a focus on safety and tolerability. In addition to the more established agents, a new resin-based phosphate binder, colestilan, is discussed.

EXPERT OPINION

Optimal phosphate control is still an unmet need in CKD. Nonetheless, we now have an extending range of phosphate binders available. Aluminium has potentially serious toxic risks. Calcium-based binders are still very useful but can lead to hypercalcemia and/or positive calcium balance and cardiovascular calcification. No long-term data are available for the new calcium acetate/magnesium combination product. Lanthanum is an effective phosphate binder, but there is insufficient evidence about possible long-term effects of tissue deposition. The resin-based binders, colestilan and sevelamer, appear to have profiles that would lead to less vascular calcification, and the main adverse events seen with these agents are gastrointestinal effects.

Renal osteodystrophy in children: pathogenesis, diagnosis and treatment

PURPOSE OF REVIEW

Disturbances in calcium-phosphate homeostasis play an important role in children with chronic kidney disease, and not only cause renal osteodystrophy but also result in increased cardiovascular morbidity and mortality. This review outlines the current aspects in the pathogenesis, diagnostic approach and treatment of renal osteodystrophy.

RECENT FINDINGS

The pathogenesis of renal osteodystrophy is under strong influence of the fibroblast growth factor 23/Klotho system, which is able to enhance phosphate excretion and reduce calcitriol synthesis in the kidney. Fibroblast growth factor 23 increases tissue calcinosis and is cardiotoxic, and is independently associated with mortality. Despite improvement in diagnostic imaging (bone density measurements), determination of biomarkers, mainly parathyroid hormone, still plays a central role. New treatment options resulted in improved bone health and also a reduction in mortality was achieved in adults with calcium-free phosphate binders. Substitution of active and inactive vitamin D is important and also has a beneficial effect on proteinuria.

SUMMARY

Knowledge about the biochemical and molecular mechanisms of renal osteodystrophy is increasing dramatically and has an impact not only to bone health but also overall morbidity and mortality. This will ultimately translate into further improved diagnostic approaches and novel treatment options.

Balancing nutrition and serum phosphorus in maintenance dialysis

Elevated serum phosphorus levels are common in patients with chronic kidney disease and are associated with heart and vascular disease, conditions that in turn are associated with increased mortality. Accurately managing phosphorus intake by restricting dietary protein alone can prove challenging because protein from different sources can contain varying amounts of available phosphorus. Additives used in processed foods frequently are high in inorganic phosphorus, which is readily absorbed, compounding this difficulty. Recent evidence suggests that dietary protein restriction in some cases may do more harm than good in some patients treated with maintenance hemodialysis because protein restriction can lead to protein-energy wasting, which is associated with increased mortality. Accordingly, phosphorus binders are important for managing hyperphosphatemia in dialysis patients. Managing hyperphosphatemia in patients with late-stage chronic kidney disease requires an individualized approach, involving a combination of adequate dietary advice, phosphate-binder use, and adjustments to dialysis prescription. We speculate that increased use of phosphate binders could allow patients to eat more protein-rich foods and that communicating this to patients might increase their perception of their need for phosphate binders, providing an incentive to improve adherence. The aim of this review is to discuss the challenges involved in maintaining adequate nutrition while controlling phosphorus levels in patients on maintenance hemodialysis therapy.

Treatment of phosphate retention: The earlier the better?

Over the last 15 years, our knowledge and understanding of the underlying mechanisms involved in the regulation of calcium and phosphate homeostasis in chronic kidney disease have advanced dramatically. Contrary to general opinion in the 20(th) century that moderate hypercalcemia and hyperphosphatemia were acceptable in treating secondary hyperparathyroidism, the calcium and phosphate load is increasingly perceived to be a major trigger of vascular and soft tissue calcification. The current treatment options are discussed in view of historical developments and the expectations of the foreseeable future, focusing on the early treatment of hyperphosphatemia. At present, we lack indisputable evidence that active intervention using currently available drugs is of benefit to patients in chronic kidney disease stages 3 and 4.

Should we prescribe calcium supplements for osteoporosis prevention?

Advocacy for the use of calcium supplements arose at a time when there were no other effective interventions for the prevention of osteoporosis. Their promotion was based on the belief that increasing calcium intake would increase bone formation. Our current understandings of the biology of bone suggest that this does not occur, though calcium does act as a weak antiresorptive. Thus, it slows postmenopausal bone loss but, despite this, recent meta-analyses suggest no significant prevention of fractures. In sum, there is little substantive evidence of benefit to bone health from the use of calcium supplements. Against this needs to be balanced the likelihood that calcium supplement use increases cardiovascular events, kidney stones, gastrointestinal symptoms, and admissions to hospital with acute gastrointestinal problems. Thus, the balance of risk and benefit seems to be consistently negative. As a result, current recommendations are to obtain calcium from the diet in preference to supplements. Dietary calcium intake has not been associated with the adverse effects associated with supplements, probably because calcium is provided in smaller boluses, which are absorbed more slowly since they come together with quantities of protein and fat, resulting in a slower gastric transit time. These findings suggest that calcium supplements have little role to play in the modern therapeutics of osteoporosis, which is based around the targeting of safe and effective anti-resorptive drugs to individuals demonstrated to be at increased risk of future fractures.

Laboratory abnormalities in CKD-MBD: markers, predictors, or mediators of disease?

Chronic kidney disease-mineral and bone disorder (CKD-MBD) is characterized by bone abnormalities, vascular calcification, and an array of laboratory abnormalities. The latter classically include disturbances in the parathyroid hormone/vitamin D axis. More recently, fibroblast growth factor 23 (FGF23) and klotho also have been identified as important regulators of mineral metabolism. Klotho deficiency and high circulating FGF23 levels precede secondary hyperparathyroidism in CKD patients. Levels of FGF23 and parathyroid hormone increase along the progression of CKD to maintain mineral homeostasis and to overcome end-organ resistance. It is hard to define when the increase of both hormones becomes maladaptive. CKD-MBD is associated with adverse outcomes including cardiovascular disease and mortality. This review summarizes the complex pathophysiology of CKD-MBD and outlines which laboratory abnormalities represent biomarkers of disease severity, which laboratory abnormalities are predictors of cardiovascular disease, and which laboratory abnormalities should be considered (direct) uremic toxins exerting organ damage. This information may help to streamline current and future therapeutic efforts.