Evaluation of calcium acetate/magnesium carbonate as a phosphate binder compared with sevelamer hydrochloride in haemodialysis patients: a controlled randomized study (CALMAG study) assessing efficacy and tolerability

Comparative Efficacy and Acceptability of 12 Phosphorus-Lowering Drugs in Adults with Hyperphosphatemia and Chronic Kidney Disease: A Systematic Review and Network Meta-Analysis

BACKGROUND

Hyperphosphatemia is associated with cardiovascular morbidity and mortality in adults with chronic kidney disease (CKD). Drug therapy has an irreplaceable role in the management of hyperphosphatemia.

OBJECTIVES

We aimed to compare and rank phosphorus-lowering drugs, including phosphate binder and nonphosphate binder, in hyperphosphatemia adults with CKD.

METHODS

We did a systematic review and frequentist random-effect network meta-analysis. We searched in PubMed, Cochrane Library, Web of Science, and Embase from inception to February 1, 2023, for randomized controlled trials of 12 phosphorus-lowering drugs in adults with hyperphosphatemia and CKD. Primary outcomes were efficacy (changes in serum phosphorus) and acceptability (treatment withdrawals due to any cause). We ranked each drug according to the value of surface under the cumulative ranking curve. We applied the Confidence in Network Meta-Analysis frameworks to rate the certainty of evidence. This study was registered with PROSPERO, number CRD42022322270.

RESULTS

We identified 2,174 citations, and of these, we included 94 trials comprising 14,459 participants and comparing 13 drugs or placebo. In terms of efficacy, except for niacinamide, all drugs lowered the level of serum phosphorus compared with placebo, with mean difference ranging between -1.61 (95% credible interval [CrI], -2.60 to -0.62) mg/dL for magnesium carbonate and -0.85 (-1.66 to -0.05) mg/dL for bixalomer. Only ferric citrate with odds ratios 0.56 (95% CrI: 0.36-0.89) was significantly associated with fewer dropouts for acceptability. Of the 94 trials, 43 (46%), 7 (7%), and 44 (47%) trials were rated as high, moderate, and low risk of bias, respectively, the certainty of the evidence was moderate to very low.

CONCLUSIONS

Magnesium carbonate has the best phosphorus-lowering effect in hyperphosphatemia adults with CKD; considering efficacy and acceptability, ferric citrate shows evidence to be the most appropriate drug with or without dialysis.

Recommendations of the Spanish Society of Nephrology for the management of mineral and bone metabolism disorders in patients with chronic kidney disease: 2021 (SEN-MM)

As in 2011, when the Spanish Society of Nephrology (SEN) published the Spanish adaptation to the Kidney Disease: Improving Global Outcomes (KDIGO) universal Guideline on Chronic Kidney Disease-Mineral and Bone Disorder (CKD-MBD), this document contains an update and an adaptation of the 2017 KDIGO guidelines to our setting. In this field, as in many other areas of nephrology, it has been impossible to irrefutably answer many questions, which remain pending. However, there is no doubt that the close relationship between the CKD-MBD/cardiovascular disease/morbidity and mortality complex and new randomised clinical trials in some areas and the development of new drugs have yielded significant advances in this field and created the need for this update. We would therefore highlight the slight divergences that we propose in the ideal objectives for biochemical abnormalities in the CKD-MBD complex compared to the KDIGO suggestions (for example, in relation to parathyroid hormone or phosphate), the role of native vitamin D and analogues in the control of secondary hyperparathyroidism and the contribution of new phosphate binders and calcimimetics. Attention should also be drawn to the adoption of important new developments in the diagnosis of bone abnormalities in patients with kidney disease and to the need to be more proactive in treating them. In any event, the current speed at which innovations are taking place, while perhaps slower than we might like, globally drives the need for more frequent updates (for example, through Nefrología al día).

Magnesium Administration in Chronic Kidney Disease

Awareness of the clinical relevance of magnesium in medicine has increased over the last years, especially for people with chronic kidney disease (CKD), due to magnesium's role in vascular calcification and mineral metabolism. The inverse association between serum magnesium and clinically relevant, adverse outcomes is well-established in people with CKD. Subsequent intervention studies have focused on the effect of magnesium administration, mainly in relation to cardiovascular diseases, mineral bone metabolism, and other metabolic parameters. The most commonly used routes of magnesium administration are orally and by increasing dialysate magnesium. Several oral magnesium formulations are available and the daily dosage of elemental magnesium varies highly between studies, causing considerable heterogeneity. Although data are still limited, several clinical studies demonstrated that magnesium administration could improve parameters of vascular function and calcification and mineral metabolism in people with CKD. Current clinical research has shown that magnesium administration in people with CKD is safe, without concerns for severe hypermagnesemia or negative interference with bone metabolism. It should be noted that there are several ongoing magnesium intervention studies that will contribute to the increasing knowledge on the potential of magnesium administration in people with CKD.

Mineral Bone Disorders in Kidney Disease Patients: The Ever-Current Topic

Chronic kidney disease (CKD) is a complex and multifactorial disease, and one of the most prevalent worldwide. Chronic kidney disease-mineral bone disorders (CKD-MBD) with biochemical and hormonal alterations are part of the complications associated with the progression of CKD. Pathophysiology of CKD-MBD focused on abnormalities in serum levels of several biomarkers (such as FGF-23, klotho, phosphate, calcium, vitamin D, and PTH) which are discussed in this review. We therefore examine the prognostic association between CKD-MBD and the increased risk for cardiovascular events, mortality, and CKD progression to end-stage kidney disease (ESKD). Lastly, we present specific treatments acting on CKD to prevent and treat the complications associated with secondary hyperparathyroidism (SHPT): control of hyperphosphatemia (with dietary restriction, intestinal phosphate binders, and adequate dialysis), the use of calcimimetic agents, vitamin D, and analogues, and the use of bisphosphonates or denosumab in patients with osteoporosis.

Past, Present, and Future of Phosphate Management

Cardiovascular (CV) disease (CVD) accounts for >50% of deaths with known causes in patients on dialysis. Elevated serum phosphorus levels are an important nontraditional risk factor for bone mineral disease and CVD in patients with chronic kidney disease (CKD). Given that phosphorus concentrations drive other disorders associated with increased CV risk (e.g., endothelial dysfunction, vascular calcification, fibroblast growth factor-23, parathyroid hormone), phosphate is a logical target to improve CV health. Phosphate binders are the only pharmacologic treatment approved for hyperphosphatemia. Although their safety has improved since inception, the mechanism of action leads to characteristics that make ingestion difficult and unpleasant; large pill size, objectionable taste, and multiple pills required for each meal and snack make phosphate binders a burden. Side effects, especially those affecting the gastrointestinal (GI) system, are common with binders, often leading to treatment discontinuation. The presence of “hidden” phosphates in processed foods and certain medications makes phosphate management even more challenging. Owing to these significant issues, most patients on dialysis are not consistently achieving and maintaining target phosphorus concentrations of <5.5 mg/dl, let alone more normal levels of <4.5 mg/dl, indicating novel approaches to improve phosphate management and CV health are needed. Several new nonbinder therapies that target intestinal phosphate absorption pathways have been developed. These include EOS789, which acts on the transcellular pathway, and tenapanor, which targets the dominant paracellular pathway. As observational evidence has established a strong association between phosphorus concentration and clinical outcomes, such as mortality, phosphate is an important target for improving the health of patients with CKD and end-stage kidney disease (ESKD).

Systematic review and meta-analysis of potential pleiotropic effects of sevelamer in chronic kidney disease: Beyond phosphate control

Sevelamer, has been shown to have many pleiotropic actions on lipid panel, various inflammatory markers, and blood glucose levels in chronic kidney disease patients. We conducted a systematic review and meta-analysis to compare these pleiotropic effects of sevelamer to other phosphate binders used in chronic kidney disease patients. The relevant randomized controlled trials published from 1 January 2001 to 31 November 2019 on the following databases: Cochrane Central Register of Controlled Trials published in The Cochrane Library, PubMed, Scopus and Google Scholar were identified. All the included studies were independently assessed for eligibility and risk of bias. The modified data extraction form of Cochrane was used. This review included 44 studies for qualitative analysis and 28 reports for quantitative analysis. A meta-analysis of three studies (n = 180) showed that glycated haemoglobin had significantly decreased in sevelamer-treated patients (MD: 0.5%; p = <.001). Compared with calcium-based phosphate binders, sevelamer showed a significant reduction in low-density lipoprotein (MD: -19.43 mg/dL; p = <.001) and total cholesterol (MD: -19.98 mg/dL; p < .001). A significant increase in high-density lipoprotein (MD: 1.29 mg/dL; p = .05) was also prominent in sevelamer treated patients. However, we were not able to observe a significant change in other biochemical parameters such as TG, CRP, hs-CRP, FGF-23, IL-6 and albumin as, no statistically significant difference was observed.

Comparison of Sevelamer and Calcium Carbonate in Prevention of Hypomagnesemia in Hemodialysis Patients

BACKGROUND

Chronic kidney disease (CKD) is a life-threatening disease with numerous complications. Hemodialysis (HD) patients are prone to magnesium deficiency due to malnutrition, which can cause cardiovascular complications and increase mortality. The present study aimed to investigate the effects of sevelamer and calcium carbonate, as phosphate binders, on serum levels of magnesium, calcium, and phosphorus in HD patients.

METHODS

A parallel clinical trial was conducted on 54 patients undergoing HD at Kosar Hospital of Semnan. The inclusion criteria were end-stage renal disease (ESRD), alternative HD treatment for at least 3 months 3 times a week, and serum phosphate levels greater than 4.5 mg/dL. The participants were randomly assigned to two groups of sevelamer (n = 27) and calcium carbonate (n = 27). If the participants were taking a phosphate binder, they were asked to stop it for 3 weeks. Participants in the sevelamer group received 800 mg of sevelamer at most three times a day and those in the calcium carbonate group were treated with 500 mg of calcium carbonate at most 3 times a day. Before and 3 months after the intervention, the serum levels of calcium, magnesium, and phosphorus were measured through the Arsenazo method using the Pars Azmun kit in the Selectra auto-analyzer. Twenty-one patients in the sevelamer group and 22 patients in the calcium carbonate group finished the study.

RESULTS

The results showed that calcium carbonate and sevelamer increased serum magnesium level by 0.20 (P = 0.028) and 0.26 (P = 0.002), on average, which were statistically significant. The administration of calcium carbonate did not significantly change serum calcium levels (P = 0.53), whereas sevelamer reduced serum calcium levels by 0.23 (P = 0.017), on average. This reduction was statistically significant. The results also indicated that none of the calcium carbonate (P = 0.099) and sevelamer (P = 0.543) caused significant changes in serum phosphorus levels. The study findings showed no significant difference between the two groups in terms of changes in the serum levels of magnesium (0.590), calcium (0.116), and phosphorus (0.113).

CONCLUSIONS

Both drugs (Sevelamer and calcium carbonate) prevented hypomagnesemia and increased serum magnesium levels, but no significant differences were found in blood levels of calcium, phosphorus, and magnesium compared to the two drugs. Considering the effect of magnesium on cardiovascular diseases, increasing the serum magnesium levels through the administration of calcium carbonate and sevelamer can prevent the likelihood of cardiovascular diseases. However, none of the studied drugs was superior to the other in this regard.

Multidisciplinary Perspectives of Current Approaches and Clinical Gaps in the Management of Hyperphosphatemia

Population-based studies have shown that most patients with advanced chronic kidney disease (CKD) do not have optimal phosphate levels. Meta-analyses suggest that there is a morbidity and mortality benefit associated with the lowering of serum phosphate levels. However, to date there is no conclusive evidence from randomized controlled trials (RCTs) that lowering serum phosphate levels reduces the risk of morbidity and mortality. However, hyperphosphatemia may pose a risk to patients and treatment should be considered. We therefore sought to conduct a multidisciplinary review to help guide clinical decision-making pending results of ongoing RCTs. Restricting dietary phosphate intake is frequently the first step in the management of hyperphosphatemia. Important considerations when proposing dietary restriction include the patient's socioeconomic status, lifestyle, dietary preferences, comorbidities, and nutritional status. While dietary phosphate restriction may be a valid strategy in certain patients, serum phosphate reductions achieved solely by limiting dietary intake are modest and should be considered in conjunction with other interventions. Conventional dialysis is also typically insufficient; however phosphate removal may be augmented by increased frequency or duration of dialysis, or through enhanced methods such as hemodiafiltration. Phosphate binders have been shown to reduce absorption of dietary phosphate and lower serum phosphate levels. There are several phosphate binders available, and while they all lower phosphate levels to variable degrees, they differ with respect to their pill burden, potential to induce or exacerbate vascular calcification or ectopic calcification, tissue accumulation, safety, and tolerability. The widespread treatment of hyperphosphatemia requires convincing data from RCTs to ascertain whether lowering serum phosphate levels improves patient-important outcomes, as well as the optimal method and degree of phosphate control. In the interim, the decision and approach used to treat hyperphosphatemia should be based on the best available data, as well as patient needs and clinical judgment.

Magnesium supplementation reduces inflammation in rats with induced chronic kidney disease

BACKGROUND

Inflammation is a common feature in chronic kidney disease (CKD) that appears specifically associated with cardiovascular derangements in CKD patients. Observational studies have revealed a link between low Mg levels and inflammation. In this study, we hypothesize that Mg might have a modulatory effect on the inflammation induced under the uraemic milieu.

METHODS

In vivo studies were performed in a 5/6 nephrectomized rat model of CKD. Furthermore, a possible direct effect of Mg was addressed through in vitro studies with vascular smooth muscle cells (VSMCs).

RESULTS

Uraemic rats fed a normal (0.1%) Mg diet showed a systemic inflammatory response evidenced by the elevation in plasma of the pro-inflammatory cytokines TNF-α, IL-1β and IL-6, and GPx activity, a marker of oxidative stress. Importantly, an increased expression of these cytokines in the aortic tissue was also observed. In contrast, a dietary Mg supplementation (0.6%) greatly prevented the oxidative stress and the pro-inflammatory response. In vitro, in VSMCs cultured in a pro-inflammatory high phosphate medium, incubation with Mg 1.6 mM inhibited the increase in the production of ROS, the rise in the expression of TNF-α, IL-1β, IL-6 and IL-8 and the activation of NF-κB signalling that was observed in cells incubated with a normal (0.8 mM) Mg.

CONCLUSION

Mg supplementation reduced inflammation associated with CKD, exerting a direct effect on vascular cells. These findings support a possible beneficial effect of Mg supplementation along the clinical management of CKD patients.

Intestinal Chelators, Sorbants, and Gut-Derived Uremic Toxins

Chronic kidney disease (CKD) is a highly prevalent condition and is associated with a high comorbidity burden, polymedication, and a high mortality rate. A number of conventional and nonconventional risk factors for comorbidities and mortality in CKD have been identified. Among the nonconventional risk factors, uremic toxins are valuable therapeutic targets. The fact that some uremic toxins are gut-derived suggests that intestinal chelators might have a therapeutic effect. The phosphate binders used to prevent hyperphosphatemia in hemodialysis patients act by complexing inorganic phosphate in the gastrointestinal tract but might conceivably have a nonspecific action on gut-derived uremic toxins. Since phosphorous is a major nutrient for the survival and reproduction of bacteria, changes in its intestinal concentration may impact the gut microbiota’s activity and composition. Furthermore, AST-120 is an orally administered activated charcoal adsorbent that is widely used in Asian countries to specifically decrease uremic toxin levels. In this narrative review, we examine the latest data on the use of oral nonspecific and specific intestinal chelators to reduce levels of gut-derived uremic toxins.

Randomized Trial of Acute Changes in Plasma Phosphate After Phosphorus-Standardized Meals in Peritoneal Dialysis

Introduction

Hyperphosphatemia is associated with increased morbidity and mortality in patients with chronic kidney disease. The aim of this study was to assess whether a meal with high phosphorus content would affect plasma phosphate in the hours that follow among subjects with end-stage kidney disease on peritoneal dialysis.

Methods

This was a single-blinded randomized cross-over trial of 12 subjects on maintenance peritoneal dialysis, in which subjects were randomized to consume a meal with either high or low phosphorus content on 2 separate trial days. On each trial day, plasma phosphate was measured immediately before consumption of the standardized meal and after 1, 2, 3, and 5 hours.

Results

The mean fasting plasma phosphate at baseline was 1.69 ± 0.22 mmol/l. Plasma phosphate was similar between the 2 meals at baseline, as well as at 1, 2, 3, and 5 hours after consumption. The largest observed difference in plasma phosphate between the 2 meals was 0.15 mmol/l, which occurred 5 hours after consumption (high-phosphorus meal 1.75 ± 0.32 mmol/l vs. low-phosphorus meal 1.60 ± 0.14 mmol/l (P = 0.06)). Using summary analyses for repeated measures, we observed a significant difference in the plasma phosphate between the 2 meals (P = 0.03).

Conclusion

Our results show that in subjects with end-stage kidney disease, a meal with high phosphorus content has only a negligible effect on plasma phosphate compared to a meal with low phosphorus content. Thus, large increases in plasma phosphate cannot be accounted for by a high intake of phosphorus in the hours before blood sampling.

Adsorptivity of cationic cellulose nanocrystals for phosphate and its application in hyperphosphatemia therapy

Nanocellulose has gained much attention because of its excellent properties. Cationic cellulose nanocrystals (cCNC) shows good adsorptivity toward negative ions and molecules. Phosphate binders are most used to treat hyperphosphatemia and it is significant to develop its alternatives with high specific and low cost in the clinic. Herein, we prepared cCNC and characterized it by FTIR, TEM, dynamic light scattering, and viscosity method. We simulated the binding process of cationic cellulose for phosphate and used it as phosphate binder for hyperphosphatemia therapy to study the phosphate binding effect and evaluate the oral toxicity. Cationic cellulose improved the conditions of mice models and efficiently decreased the level of phosphate in the serum. cCNC had a better binding effect than cationic microcrystalline cellulose both in vitro and in vivo. cCNC could be used as alternatives to phosphate binder for therapy of chronic renal failure and hyperphosphatemia.

A Higher Concentration of Dialysate Magnesium to Reduce the Frequency of Muscle Cramps: A Narrative Review

Purpose of review:

Strategies to mitigate muscle cramps are a top research priority for patients receiving hemodialysis. As hypomagnesemia is a possible risk factor for cramping, we reviewed the literature to better understand the physiology of cramping as well as the epidemiology of hypomagnesemia and muscle cramps. We also sought to review the evidence from interventional studies on the effect of oral and dialysate magnesium-based therapies on muscle cramps.

Sources of information:

Peer-reviewed articles.

Methods:

We searched for relevant articles in major bibliographic databases including MEDLINE and EMBASE. The methodological quality of interventional studies was assessed using a modified version of the Downs and Blacks criteria checklist.

Key findings:

The etiology of muscle cramps in patients receiving hemodialysis is poorly understood and there are no clear evidence-based prevention or treatment strategies. Several factors may play a role including a low concentration of serum magnesium. The prevalence of hypomagnesemia (concentration of <0.7 mmol/L) in patients receiving hemodialysis ranges from 10% to 20%. Causes of hypomagnesemia include a low dietary intake of magnesium, use of medications that inhibit magnesium absorption (eg, proton pump inhibitors), increased magnesium excretion (eg, high-dose loop diuretics), and a low concentration of dialysate magnesium. Dialysate magnesium concentrations of ≤0.5 mmol/L may be associated with a decrease in serum magnesium concentration over time. Preliminary evidence from observational and interventional studies suggests a higher dialysate magnesium concentration will raise serum magnesium concentrations and may reduce the frequency and severity of muscle cramps. However, the quality of evidence supporting this benefit is limited, and larger, multicenter clinical trials are needed to further determine if magnesium-based therapy can reduce muscle cramps in patients receiving hemodialysis. In studies conducted to date, increasing the concentration of dialysate magnesium appears to be well-tolerated and is associated with a low risk of symptomatic hypermagnesemia.

Limitations:

Few interventional studies have examined the effect of magnesium-based therapy on muscle cramps in patients receiving hemodialysis and most were nonrandomized, pre-post study designs.

Effects of parathyroidectomy on tumoral calcinosis in uremic patients with secondary hyperparathyroidism

BACKGROUND

Tumoral calcinosis (TC) is a rare disease derived from uremic secondary hyperparathyroidism (SHPT). However, parathyroidectomy (PTX) seems to be ineffective at relieving TC in some patients. In this study, we investigated the relationship between PTX and TC shrinkage.

METHODS

We retrospectively followed up nine TC patients who underwent PTX, dividing them into two groups: those with TC size reduced by > 80% were in the "effective group" (group A), and the rest in the "ineffective group" (group B).

RESULTS

We enrolled nine patients (7 men; mean age 38.6 ± 10.9 years) with SHPT-related TC. One patient with calciphylaxis was excluded due to sudden death. The efficiency of PTX in causing TC regression was 62.5% (5 patients in group A). Group A had a shorter overall duration of TC (6 [5.5, 6.0] vs. 9 [8.0, 10.0] months; P = 0.02) and higher serum levels of alkaline phosphatase (ALP; 408.0 [217.9, 1101.7] vs. 90.8 [71.0, 102.1] pg/ml; P = 0.03) and high-sensitivity C-reactive protein (hs-CRP; 82.7 [55.0, 112.4] vs. 3.1 [3.1, 4.5] mg/l; P = 0.02). Average calcium supplementation within 1 week of surgery was significantly greater in group A than in group B (96.8 [64.1, 105.3] vs. 20.1 [13.1, 32.7] g; P = 0.04). Patients in both the groups demonstrated similar serum phosphate levels before PTX, but these levels were higher in group B than in group A at follow-up times (3 months, P = 0.03; 6 months, P = 0.03).

CONCLUSIONS

The shorter duration of pre-existing TC and higher ALP levels before PTX, as well as lower serum phosphate levels after PTX, were correlated with effective SHPT-TC shrinkage.

Strategies for Phosphate Control in Patients With CKD

Hyperphosphatemia is a common complication in patients with chronic kidney disease (CKD), particularly in those requiring renal replacement therapy. The importance of controlling serum phosphate has long been recognized based on observational epidemiological studies that linked increased phosphate levels to adverse outcomes and higher mortality risk. Experimental data further supported the role of phosphate in the development of bone and cardiovascular diseases. Recent advances in our understanding of the mechanisms involved in phosphate homeostasis have made it clear that the serum phosphate concentration depends on a complex interplay among the kidneys, intestinal tract, and bone, and is tightly regulated by a complex endocrine system. Moreover, the source of dietary phosphate and the use of phosphate-based additives in industrialized foods are additional factors that are of particular importance in CKD. Not surprisingly, the management of hyperphosphatemia is difficult, and, despite a multifaceted approach, it remains unsuccessful in many patients. An additional issue is the fact that the supposedly beneficial effect of phosphate lowering on hard clinical outcomes in interventional trials is a matter of ongoing debate. In this review, we discuss currently available treatment approaches for controlling hyperphosphatemia, including dietary phosphate restriction, reduction of intestinal phosphate absorption, phosphate removal by dialysis, and management of renal osteodystrophy, with particular focus on practical challenges and limitations, and on potential benefits and harms.

Magnesium Citrate Protects Against Vascular Calcification in an Adenine-induced Chronic Renal Failure Rat Model

BACKGROUND

Hypomagnesemia was identified as a strong risk factor for cardiovascular disease in patients with chronic renal failure (CRF). However, the effects of magnesium (Mg) on vascular calcification (VC) have not been fully elucidated. Thus, we aim to determine the effects of Mg citrate (MgCit) on VC in CRF rats.

METHODS

Rats were divided into 5 groups: group 1 (normal diet), group 2 (normal diet with MgCit), group 3 (the VC model of CRF induced by 0.75% adenine and 0.9% phosphorus diet from day 1 to day 28), group 4 (group 3 treated with low-dose MgCit from day 1 to day 42), and group 5 (same as group 3 except the high-dose MgCit). All rats were killed at day 43 with collection of blood and aortas. Then, serum biochemical parameters, VC-related staining, calcium and P contents, alkaline phosphatase contents and activity, expression of alpha smooth muscle actin, and runt-related transcription factor 2 (RUNX2) in aortas were assessed.

RESULTS

Group 3 had extensive VC. The VC degree decreased in groups 4 and 5 in a dose-depended manner with reduced calcium content, P levels, alkaline phosphatase content and activity, and protein levels of RUNX2 and increased protein levels of alpha smooth muscle actin in aortas.

CONCLUSIONS

MgCit exerted a protective role in VC in adenine-induced CRF rats; thus, it may be a potential drug for the prevention of VC in patients with CRF.

A Randomized Trial of Magnesium Oxide and Oral Carbon Adsorbent for Coronary Artery Calcification in Predialysis CKD

BACKGROUND

Developing strategies for managing coronary artery calcification (CAC) in patients with CKD is an important clinical challenge. Experimental studies have demonstrated that magnesium inhibits vascular calcification, whereas the uremic toxin indoxyl sulfate aggravates it.

METHODS

To assess the efficacy of magnesium oxide (MgO) and/or the oral carbon adsorbent AST-120 for slowing CAC progression in CKD, we conducted a 2-year, open-label, randomized, controlled trial, enrolling patients with stage 3-4 CKD with risk factors for CAC (diabetes mellitus, history of cardiovascular disease, high LDL cholesterol, or smoking). Using a two-by-two factorial design, we randomly assigned patients to an MgO group or a control group, and to an AST-120 group or a control group. The primary outcome was percentage change in CAC score.

RESULTS

We terminated the study prematurely after an interim analysis with the first 125 enrolled patients (of whom 96 completed the study) showed that the median change in CAC score was significantly smaller for MgO versus control (11.3% versus 39.5%). The proportion of patients with an annualized percentage change in CAC score of ≥15% was also significantly lower for MgO compared with control (23.9% versus 62.0%). However, MgO did not suppress the progression of thoracic aorta calcification. The MgO group's dropout rate was higher than that of the control group (27% versus 17%), primarily due to diarrhea. The percentage change in CAC score did not differ significantly between the AST-120 and control groups.

CONCLUSIONS

MgO, but not AST-120, appears to be effective in slowing CAC progression. Larger-scale trials are warranted to confirm these findings.

A randomized controlled trial of different serum phosphate ranges in subjects on hemodialysis

Background

Hyperphosphataemia in dialysis subjects is associated with increased mortality. However cause and effect has not been proven, and the ideal phosphate target range is unknown despite KDOQI’s call for studies over 12 years ago. The design and conduct of a randomized controlled trial is challenging because maintaining two groups within differing target ranges of serum phosphate has not been achieved over a long follow-up of 1 year, in a trial setting, before. The SPIRiT study examines the subject acceptance, recruitment and retention rates for such a study in which subjects were randomised to two distinct serum phosphate concentrations, then titrated and maintained over 12 months.

Methods

A two center trial of 104 hemodialysis subjects randomized to lower range LRG 0.8–1.4 mmol/L or 2.5–4.3 mg/dL) and higher range (HRG 1.8–2.4 mmol/L or 5.6–7.4 mg/dL) serum phosphate groups. Two months’ titration and ten months’ maintenance phase. Interventions were non-calcium phosphate binders, self-help questionnaires, with blood tests at specified time intervals.

Results

Thirteen percent of the eligible dialysis population were successfully recruited. A mean separation by serum phosphate of 1.1 mg/dL was achieved and maintained between the groups over 10 months. Drop-out rate was 27% with mortality 10%. Nine subjects in the HRG (17.6%) and two subjects in the LRG (3.8%) died during the study, however the study was not powered to detect significant differences in outcomes.

Conclusion

Randomizing dialysis subjects to separate treatment targets for serum phosphate can achieve a clinically significant sustained separation over 12 months. A large scale longer term study is required to examine outcomes including mortality.

Trial registration

The trial registration number is ISRCTN24741445 – Date of registration 16th January, retrospectively registered.

Phosphate binders for preventing and treating chronic kidney disease-mineral and bone disorder (CKD-MBD)

BACKGROUND

Phosphate binders are used to reduce positive phosphate balance and to lower serum phosphate levels for people with chronic kidney disease (CKD) with the aim to prevent progression of chronic kidney disease-mineral and bone disorder (CKD-MBD). This is an update of a review first published in 2011.

OBJECTIVES

The aim of this review was to assess the benefits and harms of phosphate binders for people with CKD with particular reference to relevant biochemical end-points, musculoskeletal and cardiovascular morbidity, hospitalisation, and death.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Register of Studies up to 12 July 2018 through contact with the Information Specialist using search terms relevant to this review. Studies in the Register are identified through searches of CENTRAL, MEDLINE, and EMBASE, conference proceedings, the International Clinical Trials Register (ICTRP) Search Portal and ClinicalTrials.gov.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) or quasi-RCTs of adults with CKD of any GFR category comparing a phosphate binder to another phosphate binder, placebo or usual care to lower serum phosphate. Outcomes included all-cause and cardiovascular death, myocardial infarction, stroke, adverse events, vascular calcification and bone fracture, and surrogates for such outcomes including serum phosphate, parathyroid hormone (PTH), and FGF23.

DATA COLLECTION AND ANALYSIS

Two authors independently selected studies for inclusion and extracted study data. We applied the Cochrane 'Risk of Bias' tool and used the GRADE process to assess evidence certainty. We estimated treatment effects using random-effects meta-analysis. Results were expressed as risk ratios (RR) for dichotomous outcomes together with 95% confidence intervals (CI) or mean differences (MD) or standardised MD (SMD) for continuous outcomes.

MAIN RESULTS

We included 104 studies involving 13,744 adults. Sixty-nine new studies were added to this 2018 update.Most placebo or usual care controlled studies were among participants with CKD G2 to G5 not requiring dialysis (15/25 studies involving 1467 participants) while most head to head studies involved participants with CKD G5D treated with dialysis (74/81 studies involving 10,364 participants). Overall, seven studies compared sevelamer with placebo or usual care (667 participants), seven compared lanthanum to placebo or usual care (515 participants), three compared iron to placebo or usual care (422 participants), and four compared calcium to placebo or usual care (278 participants). Thirty studies compared sevelamer to calcium (5424 participants), and fourteen studies compared lanthanum to calcium (1690 participants). No study compared iron-based binders to calcium. The remaining studies evaluated comparisons between sevelamer (hydrochloride or carbonate), sevelamer plus calcium, lanthanum, iron (ferric citrate, sucroferric oxyhydroxide, stabilised polynuclear iron(III)-oxyhydroxide), calcium (acetate, ketoglutarate, carbonate), bixalomer, colestilan, magnesium (carbonate), magnesium plus calcium, aluminium hydroxide, sucralfate, the inhibitor of phosphate absorption nicotinamide, placebo, or usual care without binder. In 82 studies, treatment was evaluated among adults with CKD G5D treated with haemodialysis or peritoneal dialysis, while in 22 studies, treatment was evaluated among participants with CKD G2 to G5. The duration of study follow-up ranged from 8 weeks to 36 months (median 3.7 months). The sample size ranged from 8 to 2103 participants (median 69). The mean age ranged between 42.6 and 68.9 years.Random sequence generation and allocation concealment were low risk in 25 and 15 studies, respectively. Twenty-seven studies reported low risk methods for blinding of participants, investigators, and outcome assessors. Thirty-one studies were at low risk of attrition bias and 69 studies were at low risk of selective reporting bias.In CKD G2 to G5, compared with placebo or usual care, sevelamer, lanthanum, iron and calcium-based phosphate binders had uncertain or inestimable effects on death (all causes), cardiovascular death, myocardial infarction, stroke, fracture, or coronary artery calcification. Sevelamer may lead to constipation (RR 6.92, CI 2.24 to 21.4; low certainty) and lanthanum (RR 2.98, CI 1.21 to 7.30, moderate certainty) and iron-based binders (RR 2.66, CI 1.15 to 6.12, moderate certainty) probably increased constipation compared with placebo or usual care. Lanthanum may result in vomiting (RR 3.72, CI 1.36 to 10.18, low certainty). Iron-based binders probably result in diarrhoea (RR 2.81, CI 1.18 to 6.68, high certainty), while the risks of other adverse events for all binders were uncertain.In CKD G5D sevelamer may lead to lower death (all causes) (RR 0.53, CI 0.30 to 0.91, low certainty) and induce less hypercalcaemia (RR 0.30, CI 0.20 to 0.43, low certainty) when compared with calcium-based binders, and has uncertain or inestimable effects on cardiovascular death, myocardial infarction, stroke, fracture, or coronary artery calcification. The finding of lower death with sevelamer compared with calcium was present when the analysis was restricted to studies at low risk of bias (RR 0.50, CI 0.32 to 0.77). In absolute terms, sevelamer may lower risk of death (all causes) from 210 per 1000 to 105 per 1000 over a follow-up of up to 36 months, compared to calcium-based binders. Compared with calcium-based binders, lanthanum had uncertain effects with respect to all-cause or cardiovascular death, myocardial infarction, stroke, fracture, or coronary artery calcification and probably had reduced risks of treatment-related hypercalcaemia (RR 0.16, CI 0.06 to 0.43, low certainty). There were no head-to-head studies of iron-based binders compared with calcium. The paucity of placebo-controlled studies in CKD G5D has led to uncertainty about the effects of phosphate binders on patient-important outcomes compared with placebo.It is uncertain whether the effects of binders on clinically-relevant outcomes were different for patients who were and were not treated with dialysis in subgroup analyses.

AUTHORS' CONCLUSIONS

In studies of adults with CKD G5D treated with dialysis, sevelamer may lower death (all causes) compared to calcium-based binders and incur less treatment-related hypercalcaemia, while we found no clinically important benefits of any phosphate binder on cardiovascular death, myocardial infarction, stroke, fracture or coronary artery calcification. The effects of binders on patient-important outcomes compared to placebo are uncertain. In patients with CKD G2 to G5, the effects of sevelamer, lanthanum, and iron-based phosphate binders on cardiovascular, vascular calcification, and bone outcomes compared to placebo or usual care, are also uncertain and they may incur constipation, while iron-based binders may lead to diarrhoea.

Sucroferric oxyhydroxide for the treatment of hyperphosphatemia

INTRODUCTION

Sucroferric oxyhydroxide is a non-calcium, iron-based phosphate binder indicated for the treatment of hyperphosphatemia in patients with chronic kidney disease undergoing dialysis. Areas covered: Herein, the preclinical development and clinical data for sucroferric oxyhydroxide are reviewed, including the key data from the Phase III registration study and the latest evidence from the real-world clinical setting. Expert opinion: Sucroferric oxyhydroxide displays potent phosphate-binding capacity and clinical studies demonstrate its effectiveness for the long-term reduction of serum phosphorus levels in dialysis patients. Observational study data also show that sucroferric oxyhydroxide provides effective serum phosphorus control for hyperphosphatemic patients in the real-world clinical setting. The serum phosphorus reductions with sucroferric oxyhydroxide can be achieved with a relatively low pill burden in comparison with other phosphate binders, which may translate into better treatment adherence in clinical practice. The Phase III data also indicate that sucroferric oxyhydroxide has a favorable impact on other chronic kidney disease-related mineral bone disease parameters, including a fibroblast growth factor-23-lowering effect. Sucroferric oxyhydroxide is well tolerated and associated with low systemic iron absorption, minimizing the potential for iron accumulation or overload. These attributes render sucroferric oxyhydroxide an attractive non-calcium-containing phosphate binder for the treatment of hyperphosphatemia.

Deleting Death and Dialysis: Conservative Care of Cardio-Vascular Risk and Kidney Function Loss in Chronic Kidney Disease (CKD)

The uremic syndrome, which is the clinical expression of chronic kidney disease (CKD), is a complex amalgam of accelerated aging and organ dysfunctions, whereby cardio-vascular disease plays a capital role. In this narrative review, we offer a summary of the current conservative (medical) treatment options for cardio-vascular and overall morbidity and mortality risk in CKD. Since the progression of CKD is also associated with a higher cardio-vascular risk, we summarize the interventions that may prevent the progression of CKD as well. We pay attention to established therapies, as well as to novel promising options. Approaches that have been considered are not limited to pharmacological approaches but take into account lifestyle measures and diet as well. We took as many randomized controlled hard endpoint outcome trials as possible into account, although observational studies and post hoc analyses were included where appropriate. We also considered health economic aspects. Based on this information, we constructed comprehensive tables summarizing the available therapeutic options and the number and kind of studies (controlled or not, contradictory outcomes or not) with regard to each approach. Our review underscores the scarcity of well-designed large controlled trials in CKD. Nevertheless, based on the controlled and observational data, a therapeutic algorithm can be developed for this complex and multifactorial condition. It is likely that interventions should be aimed at targeting several modifiable factors simultaneously.

Current and potential treatment options for hyperphosphatemia

INTRODUCTION

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

AREAS COVERED

This paper reviews the most established treatment options for hyperphosphatemia, in patients with chronic kidney disease, focusing on the new inhibitors of active phosphate absorption.

EXPERT OPINION

The prevention and the treatment of hyperphosphatemia is today far to be satisfactory. Nonetheless, an extending range of phosphate binders are now available. Aluminum has potentially serious toxic risks. Calcium-based binders are very effective but can lead to hypercalcemia and/or positive calcium balance and progression of cardiovascular calcification. No long-term data are available for the new calcium acetate/magnesium combination product. Lanthanum is an effective phosphate binder, and long-term effects of tissue deposition seem clinically irrelevant. Sevelamer, appear to have profiles that would lead to pleiotropic effects and reduced progression of vascular calcification, and the main adverse events seen with these agents are gastrointestinal. Iron has a powerful capability of binding phosphate, thus numerous preparations are available, both with and without significant systemic absorption of the iron component. The inhibitors of active intestinal phosphate transport, with their very selective mechanism of action and low pill burden seem the most interesting approach; however, do not seem at present to be effective alone, in reducing serum phosphorus levels.

Magnesium Replacement to Protect Cardiovascular and Kidney Damage? Lack of Prospective Clinical Trials

Patients with advanced chronic kidney disease exhibit an increase in cardiovascular mortality. Recent works have shown that low levels of magnesium are associated with increased cardiovascular and all-cause mortality in hemodialysis patients. Epidemiological studies suggest an influence of low levels of magnesium on the occurrence of cardiovascular disease, which is also observed in the normal population. Magnesium is involved in critical cellular events such as apoptosis and oxidative stress. It also participates in a number of enzymatic reactions. In animal models of uremia, dietary supplementation of magnesium reduces vascular calcifications and mortality; in vitro, an increase of magnesium concentration decreases osteogenic transdifferentiation of vascular smooth muscle cells. Therefore, it may be appropriate to evaluate whether magnesium replacement should be administered in an attempt to reduce vascular damage and mortality in the uremic population In the present manuscript, we will review the magnesium homeostasis, the involvement of magnesium in enzymatic reactions, apoptosis and oxidative stress and the clinical association between magnesium and cardiovascular disease in the general population and in the context of chronic kidney disease. We will also analyze the role of magnesium on kidney function. Finally, the experimental evidence of the beneficial effects of magnesium replacement in chronic kidney disease will be thoroughly described.

Dietary factors and fibroblast growth factor-23 levels in young adults with African ancestry

Fibroblast growth factor-23 (FGF23), a phosphaturic hormone secreted mainly by osteocytes, maintains serum phosphate levels within a tight range by promoting phosphaturia. Previous studies have mainly focused on the link between FGF23 levels and dietary intake of phosphate, but other dietary factors may also influence FGF23 levels. This cross-sectional study pooled three populations of young adults with African ancestry (452 in Chicago, IL, USA; 477 in Victoria, Seychelles; and 482 in Kumasi, Ghana) with estimated glomerular filtration rate >80 ml/min/1.73 m² to examine the association of dietary factors based on two 24-h recalls with FGF23 levels measured using a C-terminal assay. Linear regression was used to examine the association between log-transformed FGF23 levels and quartiles of calorie-adjusted dietary factors with adjustment for covariates. In the pooled sample of 1411 study participants, the mean age was 35.2 (6.2) years and 45.3% were male. Median plasma C-terminal FGF23 values in relative units (RU)/ml were 59.5 [interquartile range (IQR) 44.1, 85.3] in the USA, 43.2 (IQR 33.1, 57.9) in Seychelles, and 34.0 (IQR 25.2, 50.4) in Ghana. With adjustment for covariates, increasing quartiles of calcium and animal protein and decreasing quartiles of vegetable protein, fiber, and magnesium intake were associated with significantly higher FGF23 levels compared to the lowest quartile. After further adjustment for dietary factors, significant trends in FGF23 levels were noted only for quartiles of calcium, fiber, and magnesium intake (P < 0.001). Dietary factors other than phosphate are associated with FGF23 levels in young adults.

Magnesium supplementation: A consideration in dialysis patients

Even though disorders of magnesium (Mg) balance are common in dialyzed patients, this cation is often neglected. Many factors interfere with serum magnesium including diet, medications (eg, antacids or phosphate binders), and the dialysis prescription. Mg supplementation may help reduce serum phosphate concentration, PTH, and interfere with vascular calcification and bone mineralization. It could also decrease the all-cause and cardiovascular mortalities, although the results of current studies are conflicting. As with many other variables that influence hard endpoints in nephrology, additional research directly targeting the role of Mg supplementation in dialyzed patients are required. Nevertheless, a current risk/benefit assessment suggests that supplementation of Mg targeting high normal serum levels may represent a plausible option to improve the outcome of dialysis patients.

The efficacy and safety of sevelamer and lanthanum versus calcium-containing and iron-based binders in treating hyperphosphatemia in patients with chronic kidney disease: a systematic review and meta-analysis

Background

It remains unclear which phosphate binders should be preferred for hyperphosphatemia management in chronic kidney disease (CKD).

Methods

We performed a systematic review and meta-analysis of randomized trials comparing sevelamer or lanthanum with other phosphate binders in CKD.

Results

Fifty-one trials (8829 patients) were reviewed. Compared with calcium-based binders, all-cause mortality was nonsignificantly lower with sevelamer {risk ratio [RR] 0.62 [95% confidence interval (CI) 0.35-1.08]} and lanthanum [RR 0.73 (95% CI 0.18-3.00)], but risk of bias was concerning. Compared with calcium-based binders, sevelamer reduced the risk of hypercalcemia [RR 0.27 (95% CI 0.17-0.42)], as did lanthanum [RR 0.12 (95% CI 0.05-0.32)]. Sevelamer reduced hospitalizations [RR 0.50 (95% CI 0.31-0.81)], but not lanthanum [RR 0.80 (95% CI 0.34-1.93)]. The presence/absence of other clinically relevant outcomes was infrequently reported. Compared with calcium-based binders, sevelamer reduced serum calcium, low-density lipoprotein and coronary artery calcification, but increased intact parathyroid hormone. The clinical relevance of these changes is unknown since corresponding clinical outcomes were not reported. Lanthanum had less favorable impact on biochemical parameters. Sevelamer hydrochloride and sevelamer carbonate were similar in three studies. Sevelamer was similar to lanthanum (three studies) and iron-based binders (three studies).

Conclusion

Sevelamer was associated with a nonsignificant reduction in mortality and significantly lower hospitalization rates and hypercalcemia compared with calcium-based binders. However, differences in important outcomes, such as cardiac events, fractures, calciphylaxis, hyperchloremic acidosis and health-related quality of life remain understudied. Lanthanum and iron-based binders did not show superiority for any clinically relevant outcomes. Future studies that fail to measure clinically important outcomes (the reason why phosphate binders are prescribed in the first place) will be wasteful.

Magnesium Counteracts Vascular Calcification: Passive Interference or Active Modulation?

Over the last decade, an increasing number of studies report a close relationship between serum magnesium concentration and cardiovascular disease risk in the general population. In end-stage renal disease, an association was found between serum magnesium and survival. Hypomagnesemia was identified as a strong predictor for cardiovascular disease in these patients. A substantial body of in vitro and in vivo studies has identified a protective role for magnesium in vascular calcification. However, the precise mechanisms and its contribution to cardiovascular protection remain unclear. There are currently 2 leading hypotheses: first, magnesium may bind phosphate and delay calcium phosphate crystal growth in the circulation, thereby passively interfering with calcium phosphate deposition in the vessel wall. Second, magnesium may regulate vascular smooth muscle cell transdifferentiation toward an osteogenic phenotype by active cellular modulation of factors associated with calcification. Here, the data supporting these major hypotheses are reviewed. The literature supports both a passive inorganic phosphate-buffering role reducing hydroxyapatite formation and an active cell-mediated role, directly targeting vascular smooth muscle transdifferentiation. However, current evidence relies on basic experimental designs that are often insufficient to delineate the underlying mechanisms. The field requires more advanced experimental design, including determination of intracellular magnesium concentrations and the identification of the molecular players that regulate magnesium concentrations in vascular smooth muscle cells.

The effect of magnesium supplementation on vascular calcification in chronic kidney disease-a randomised clinical trial (MAGiCAL-CKD): essential study design and rationale

INTRODUCTION

Chronic kidney disease (CKD) is associated with an increased risk of cardiovascular disease and mortality, which is thought to be caused by increased propensity towards vascular calcification (VC). Magnesium (Mg) inhibits phosphate-induced VC in vitro and in animal models and serum Mg is inversely associated with cardiovascular mortality in predialysis CKD and in end-stage renal disease. This paper will describe the design and rationale of a randomised double-blinded placebo-controlled multicentre clinical trial, which will investigate whether oral Mg supplementation can prevent the progression of coronary artery calcification (CAC) in subjects with predialysis CKD.

METHODS AND ANALYSIS

We will randomise 250 subjects with estimated glomerular filtration rate of 15 to 45 mL/min/1.73 m² to 12 months treatment with either slow-release Mg hydroxide 30 mmol/day or matching placebo in a 1:1 ratio. The primary end point is change in CAC score as measured by CT at baseline and after 12 months treatment. Secondary end points include change in pulse wave velocity, bone mineral density, measures of mineral metabolism and clinical end points related to cardiovascular and renal events.

ETHICS AND DISSEMINATION

This trial has been approved by the local biomedical research ethics committees and data protection agencies and will be performed in accordance with the latest revision of the Helsinki Declaration. The trial will examine for the first time the effect of increasing the uptake of a putative VC inhibitor (ie, Mg) on progression of CAC in subjects with predialysis CKD.

TRIAL REGISTRATION NUMBER

NCT02542319, pre-results.

Clinical aspects of magnesium physiology in patients on dialysis

Magnesium balance is infrequently discussed in the dialysis population, and the clinical consequences of derangements in magnesium homeostasis are incompletely understood. There is an association between hypomagnesemia and adverse outcomes including increases in cardiovascular disease and mortality, while elevated magnesium levels have also been linked with complications such as osteomalacia. In this review, we discuss the features of magnesium physiology relevant to dialysis patients and provide an updated summary of the literature linking magnesium derangements with bone disease, cardiovascular disease, sudden cardiac death, and mortality.

Effects of different phosphate lowering strategies in patients with CKD on laboratory outcomes: A systematic review and NMA

BACKGROUND

Chronic kidney disease-mineral and bone disorder (CKD-MBD), a complication of chronic kidney disease, has been linked to reduced quality and length of life. High serum phosphate levels that result from CKD-MBD require phosphate-lowering agents, also known as phosphate binders. The objective of this systematic review is to compare the effects of available phosphate binders on laboratory outcomes in patients with CKD-MBD.

METHODS

Data sources included MEDLINE and EMBASE from January 1996 to April 2016, and the Cochrane Register of Controlled Trials up to April 2016. Teams of two reviewers, independently and in duplicate, screened titles and abstracts and potentially eligible full text reports to determine eligibility, and subsequently abstracted data and assessed risk of bias in eligible randomized controlled trials (RCTs). Eligible trials enrolled patients with CKD-MBD and randomized them to receive calcium-based phosphate binders (delivered as calcium acetate, calcium citrate or calcium carbonate), non-calcium-based phosphate binders (NCBPB) (sevelamer hydrochloride, sevelamer carbonate, lanthanum carbonate, sucroferric oxyhydroxide and ferric citrate), phosphorus restricted diet (diet), placebo or no treatment and reported effects on serum levels of phosphate, calcium and parathyroid hormone. We performed Bayesian network meta-analyses (NMA) to calculate the effect estimates (mean differences) and 95% credible intervals for serum levels of phosphate, calcium and parathyroid hormone. We calculated direct, indirect and network meta-analysis estimates using random-effects models. We applied the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) approach to rate the quality of evidence for each pairwise comparison.

RESULTS

Our search yielded 1108 citations; 71 RCTs were retrieved for full review and 16 proved eligible. Including an additional 13 studies from a previous review, 29 studies that enrolled 8335 participants proved eligible; 26 trials provided data for quantitative synthesis. Sevelamer, lanthanum, calcium, iron, diet and combinations of active treatments (calcium or sevelamer or lanthanum and combination of calcium and sevelamer) resulted in significantly lower serum phosphate as compared to placebo (moderate to very low quality of evidence). We found no statistically significant differences between active treatment categories in lowering serum phosphate. Sevelamer, lanthanum and diet resulted in lower serum calcium compared to calcium (moderate quality evidence for lanthanum and diet; low quality evidence for Sevelamer). Iron, sevelamer and calcium yielded lower parathyroid hormone levels as compared to lanthanum. Meta-regression analyses did not yield a statistically significant association between treatment effect and trial duration.

DISCUSSION/CONCLUSIONS

We found few differences between treatments in impact on phosphate and differences in parathyroid hormone. Relative to calcium, sevelamer, lanthanum and diet showed significant reduction in serum calcium from baseline. Treatment recommendations should be based on impact on patient-important outcomes rather than on surrogate outcomes. Systematic review registration: PROSPERO CRD-42016032945.

Effects of Magnesium on the Phosphate Toxicity in Chronic Kidney Disease: Time for Intervention Studies

Magnesium, an essential mineral for human health, plays a pivotal role in the cardiovascular system. Epidemiological studies in the general population have found an association between lower dietary magnesium intake and an elevated risk of cardiovascular events. In addition, magnesium supplementation was shown to improve blood pressure control, insulin sensitivity, and endothelial function. The relationship between magnesium and cardiovascular prognosis among patients with chronic kidney disease (CKD) has been increasingly investigated as it is becoming evident that magnesium can inhibit vascular calcification, a prominent risk of cardiovascular events, which commonly occurs in CKD patients. Cohort studies in patients receiving dialysis have shown a lower serum magnesium level as a significant risk for cardiovascular mortality. Interestingly, the cardiovascular mortality risk associated with hyperphosphatemia is alleviated among those with high serum magnesium levels, consistent with in vitro evidence that magnesium inhibits high-phosphate induced calcification of vascular smooth muscle cells. Furthermore, a harmful effect of high phosphate on the progression of CKD is also attenuated among those with high serum magnesium levels. The potential usefulness of magnesium as a remedy for phosphate toxicity should be further explored by future intervention studies.

Electrolyte and Acid-Base Disorders in Chronic Kidney Disease and End-Stage Kidney Failure

The kidneys play a pivotal role in the regulation of electrolyte and acid-base balance. With progressive loss of kidney function, derangements in electrolytes and acid-base inevitably occur and contribute to poor patient outcomes. As chronic kidney disease (CKD) has become a worldwide epidemic, medical providers are increasingly confronted with such problems. Adequate diagnosis and treatment will minimize complications and can potentially be lifesaving. In this review, we discuss the current understanding of the disease process, clinical presentation, diagnosis and treatment strategies, integrating up-to-date knowledge in the field. Although electrolyte and acid-base derangements are significant causes of morbidity and mortality in CKD and end-stage renal disease patients, they can be effectively managed through a timely institution of combined preventive measures and pharmacological therapy. Exciting advances and several upcoming outcome trials will provide further information to guide treatment and improve patient outcomes.

Comparative Effectiveness of Phosphate Binders in Patients with Chronic Kidney Disease: A Systematic Review and Network Meta-Analysis

BACKGROUND

Chronic kidney disease-mineral and bone disorder (CKD-MBD) has been linked to poor health outcomes, including diminished quality and length of life. This condition is characterized by high phosphate levels and requires phosphate-lowering agents-phosphate binders. The objective of this systematic review is to compare the effects of available phosphate binders on patient-important outcomes in patients with CKD-MBD.

METHODS

Data sources included MEDLINE and EMBASE Trials from 1996 to February 2016. We also searched the Cochrane Register of Controlled Trials up to April 2016. Teams of two reviewers, independently and in duplicate, screened titles and abstracts and potentially eligible full text reports to determine eligibility, and subsequently abstracted data and assessed risk of bias in eligible randomized controlled trials (RCTs). Eligible trials enrolled patients with CKD-MBD, randomized them to receive calcium (delivered as calcium acetate, calcium citrate or calcium carbonate), non-calcium-based phosphate binders (NCBPB) (sevelamer hydrochloride, sevelamer carbonate, lanthanum carbonate, sucroferric oxyhydroxide and ferric citrate), phosphorus restricted diet, placebo or no treatment, and reported effects on all-cause mortality, cardiovascular mortality or hospitalization at ≥4 weeks follow-up. We performed network meta-analyses (NMA) for all cause-mortality for individual agents (seven-node analysis) and conventional meta-analysis of calcium vs. NCBPBs for all-cause mortality, cardiovascular mortality and hospitalization. In the NMAs, we calculated the effect estimates for direct, indirect and network meta-analysis estimates; for both NMA and conventional meta-analysis, we pooled treatment effects as risk ratios (RR) and calculated 95% confidence intervals (CIs) using random effect models. We used the GRADE (Grading of Recommendations, Assessment, Development and Evaluation) approach to rate the quality of evidence for each paired comparison.

RESULTS

Our search yielded 1190 citations, of which 71 RCTs were retrieved for full review and 15 proved eligible. With 13 eligible studies from a prior review, we included 28 studies with 8335 participants; 25 trials provided data for our quantitative synthesis. Results suggest higher mortality with calcium than either sevelamer (NMA RR, 1.89 [95% CI, 1.02 to 3.50], moderate quality evidence) or NCBPBs (conventional meta-analysis RR, 1.76 [95% CI, 1.21 to 2.56, moderate quality evidence). Conventional meta-analysis suggested no difference in cardiovascular mortality between calcium and NCBPBs (RR, 2.54 [95% CI, 0.67 to 9.62 low quality evidence). Our results suggest higher hospitalization, although non-significant, with calcium than NCBPBs (RR, 1.293 [95% CI, 0.94 to 1.74, moderate quality evidence).

DISCUSSION/CONCLUSIONS

Use of calcium results in higher mortality than either sevelamer in particular and NCBPBs in general (moderate quality evidence). Our results raise questions about whether administration of calcium as an intervention for CKD- MBD remains ethical. Further research is needed to explore the effects of different types of phosphate binders, including novel agents such as iron, on quality and quantity of life.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD-42016032945.

Calcium Acetate/Magnesium Carbonate and Cardiovascular Risk Factors in Chronic Hemodialysis Patients

BACKGROUND/AIM

Calcium acetate/magnesium carbonate (CaMg) is a recent phosphate binder that has been shown to have protective cardiovascular (CV) effects in animal models. The aim of this study was to evaluate the relationship between CaMg therapy and CV risk markers like pulse pressure (PP), left ventricular mass index (LVMI) and valvular calcifications compared to sevelamer or no phosphate binder (NPB) therapy in chronic hemodialysis (HD) patients.

METHODS

We performed a 48-month prospective study in 138 HD patients under hemodiafiltration with a dialysate Mg concentration of 0.5 mmol/l. Patients underwent treatment with CaMg or sevelamer for at least 36 months or NPB therapy. Demographic, clinical, biochemical and echocardiographic parameters were evaluated at baseline and after a 48-month period.

RESULTS

At the end of the study, patients who had taken CaMg showed a significant reduction in PP (p < 0.001), LVMI (p = 0.003), aortic (p = 0.004) and mitral valve calcifications (p = 0.03) compared with NPB patients. Patients under CaMg showed a significant reduction of PP (p < 0.001), LVMI (p = 0.01) and aortic valve calcifications (p = 0.02) compared to sevelamer patients. In a multivariable analysis, CaMg therapy was negatively associated with progression of LVMI (p = 0.02) and aortic valve calcifications (p = 0.01). Patients under CaMg showed higher serum Mg levels (0.93 ± 0.14 mmol/l) compared to patients under sevelamer (0.87 ± 0.13) or NPB patients (0.82 ± 0.12; p < 0.001).

CONCLUSIONS

In prevalent HD patients, the use of CaMg over 48 months was associated with a reduction of PP and LVMI and with a stabilization of aortic valve calcifications. These protective and promising results of this new phosphate binder need to be confirmed in randomized controlled studies.

Effect of parathyroid hormone on serum magnesium levels: the neglected relationship in hemodialysis patients with secondary hyperparathyroidism

Chronic kidney disease-mineral and bone disorder (CKD-MBD) is an important complication in patients with end-stage renal disease. Since recent studies have shown that magnesium (Mg) disturbance plays an important role in CKD-MBD and cardiovascular mortality, the interest on magnesium has grown recently. Although much concern focused on the effect of Mg on parathyroid hormone (PTH) levels, however, the influence of PTH on serum Mg levels is nearly unexplored. To evaluate the effect of PTH on serum Mg levels, we first described the relationship between serum Mg and PTH in secondary hyperparathyroidism. Besides, we also monitored the changes of serum Mg concentration after parathyroidectomy (PTX) in 23 patients. In our study, we found that hypermagnesemia (>2.5 mg/dL) occurred in up to 44% of cases and hypomagnesemia did not present. No statistically significant correlations were found between serum Mg levels and PTH (r = -0.143, p = 0.134). Correlation analysis and regression analysis suggested that the derangement of magnesium homeostasis was consistent with the derangement of calcium/phosphorus homeostasis. However, after PTX, serum magnesium levels dropped immediately after the surgery, minimally at the first day and gradually restored from the third day. The changes of serum Mg after surgery was positive correlated with the changes of serum phosphate (r = 0.558, p = 0.003). Taken altogether, our data suggested that the therapeutic strategies to achieve optimum serum magnesium levels in CKD-MBD should take into account the varying stages of disease development since PTH could also influence magnesium metabolism and this problem might be important in severe secondary hyperparathyroidism.

Serum Magnesium and Sudden Death in European Hemodialysis Patients

Despite suggestions that higher serum magnesium (Mg) levels are associated with improved outcome, the association with mortality in European hemodialysis (HD) patients has only scarcely been investigated. Furthermore, data on the association between serum Mg and sudden death in this patient group is limited. Therefore, we evaluated Mg in a post-hoc analysis using pooled data from the CONvective TRAnsport STudy (CONTRAST, NCT00205556), a randomized controlled trial (RCT) evaluating the survival risk in dialysis patients on hemodiafiltration (HDF) compared to HD with a mean follow-up of 3.1 years. Serum Mg was measured at baseline and 6, 12, 24 and 36 months thereafter. Cox proportional hazards models, adjusted for confounders using inverse probability weighting, were used to estimate hazard ratios (HRs) of baseline serum Mg on all-cause mortality, cardiovascular mortality, non-cardiovascular mortality and sudden death. A generalized linear mixed model was used to investigate Mg levels over time. Out of 714 randomized patients, a representative subset of 365 (51%) were analyzed in the present study. For every increase in baseline serum Mg of 0.1 mmol/L, the HR for all-cause mortality was 0.85 (95% CI 0.77–94), the HR for cardiovascular mortality 0.73 (95% CI 0.62–0.85) and for sudden death 0.76 (95% CI 0.62–0.93). These findings did not alter after extensive correction for potential confounders, including treatment modality. Importantly, no interaction was found between serum phosphate and serum Mg. Baseline serum Mg was not related to non-cardiovascular mortality. Mg decreased slightly but statistically significant over time (Δ -0.011 mmol/L/year, 95% CI -0.017 to -0.009, p = 0.03). In short, serum Mg has a strong, independent association with all-cause mortality, cardiovascular mortality and sudden death in European HD patients. Serum Mg levels decrease slightly over time.

Advances in pharmacotherapy for hyperphosphatemia in renal disease

INTRODUCTION

Hyperphosphatemia in chronic kidney disease (CKD) is considered as an independent risk factor for surrogate clinical end points like vascular calcification (VC) and bone disease, or hard clinical outcomes like cardiovascular events. Various treatment options are available for phosphate removal or reduction. Calcium-based phosphate binders (CBB) with their possible positive calcium balance became culprits for progressive VC and increased mortality risk. Non-calcium-based binders (NCBB) treatment allowed a comparable control of hyperphosphatemia with a lower risk of hypercalcemia and a slower progression of VC. Recent data have shown a 22% risk reduction in all-cause mortality with NCBB compared to CBB treatment. The appropriate timing of phosphate binder initiation in CKD patients is still unclear. Recent reports in patients with CKD stages 3b-4 showed increased VC progression when actively treated compared to placebo and a positive calcium, but no negative phosphate balance.

AREAS COVERED

This review discusses the advantages and disadvantages of the pharmacological options to treat hyperphosphatemia.

EXPERT OPINION

The use of phosphate binders is essential in preventing morbidity and mortality in dialysis patients. The choice of phosphate binder takes into account CKD stage, the presence of other components of CKD-mineral and bone disorders, concomitant therapies and drug side-effect profile.

New Conclusions Regarding Comparison of Sevelamer and Calcium-Based Phosphate Binders in Coronary-Artery Calcification for Dialysis Patients: A Meta-Analysis of Randomized Controlled Trials

Background

Sevelamer hydrochloride is used widely, but its impact upon cardiovascular calcification, cardiovascular mortality, all-cause mortality and hospitalization is not known.

Outcomes

Primary outcome was cardiovascular calcification (coronary artery calcification scores (CACS) and aortic calcification scores (ACS)). Secondary outcomes were serum characteristics, hospitalization, cardiovascular mortality and all-cause mortality. Risk ratio (RR), mean differences and standard mean difference with 95% confidence intervals (CIs) were pooled using random- or fixed-effects models.

Results

We identified 31 studies (on 23 randomized controlled trials with 4395 participants). An analysis pooling showed a significant decrease in serum levels of phosphate with calcium-based phosphate binders (CBPBs) by 0.17 mg/dL [mean difference (MD), 95% CI, 0.03, 0.31] than sevelamer. A significant difference in the change of CACS by –102.66 [MD: 95% CI, –159.51, –45.80] and ACS by –1008.73 [MD, 95% CI, –1664.75, –352.72] between sevelamer and CBPBs was observed. Prevalence of hypercalcemia (serum levels of calcium >10.2–10.5 mg/dL and >11.0 mg/dL) was significantly smaller for sevelamer (RR = 0.44, 95% CI, 0.33, 0.58; RR = 0.24, 95% CI, 0.14, 0.40). No significant difference was found in hospitalization, all-cause mortality or cardiovascular mortality.

Conclusions

This meta-analysis suggests that sevelamer benefits dialysis patients in terms of CACS, ACS and hypercalcemia.

Use of magnesium as a drug in chronic kidney disease

From chronic kidney disease (CKD) Stage 4 onwards, phosphate binders are needed in many patients to prevent the development of hyperphosphataemia, which can result in disturbed bone and mineral metabolism, cardiovascular disease and secondary hyperparathyroidism. In this review, we re-examine the use of magnesium-containing phosphate binders for patients with CKD, particularly as their use circumvents problems such as calcium loading, aluminum toxicity and the high costs associated with other agents of this class. The use of magnesium hydroxide in the 1980s has been superseded by magnesium carbonate, as the hydroxide salt was associated with poor gastrointestinal tolerability, whereas studies with magnesium carbonate show much better gastrointestinal profiles. The use of combined magnesium- and calcium-based phosphate binder regimens allows a reduction in the calcium load, and magnesium and calcium regimen comparisons show that magnesium may be as effective a phosphate binder as calcium. A large well-designed trial has recently shown that a drug combining calcium acetate and magnesium carbonate was non-inferior in terms of lowering serum phosphate to sevelamer-HCl and had an equally good tolerability profile. Because of the high cost of sevelamer and lanthanum carbonate, the use of magnesium carbonate could be advantageous and drug acquisition cost savings would compensate for the cost of introducing routine magnesium monitoring, if this is thought to be necessary and not performed anyway. Moreover, given the potential cost savings, it may be time to re-investigate magnesium-containing phosphate binders for CKD patients with further well-designed clinical research using vascular end points.

Magnesium in CKD: more than a calcification inhibitor?

Magnesium fulfils important roles in multiple physiological processes. Accordingly, a tight regulation of magnesium homeostasis is essential. Dysregulated magnesium serum levels, in particular hypomagnesaemia, are common in patients with chronic kidney disease (CKD) and have been associated with poor clinical outcomes. In cell culture studies as well as in clinical situations magnesium levels were associated with vascular calcification, cardiovascular disease and altered bone-mineral metabolism. Magnesium has also been linked to diseases such as metabolic syndrome, diabetes, hypertension, fatigue and depression, all of which are common in CKD. The present review summarizes and discusses the latest clinical data on the impact of magnesium and possible effects of higher levels on the health status of patients with CKD, including an outlook on the use of magnesium-based phosphate-binding agents in this context.

Magnesium and cardiovascular complications of chronic kidney disease

Cardiovascular complications are the leading cause of death in patients with chronic kidney disease (CKD). Abundant experimental evidence suggests a physiological role of magnesium in cardiovascular function, and clinical evidence suggests a role of the cation in cardiovascular disease in the general population. The role of magnesium in CKD-mineral and bone disorder, and in particular its impact on cardiovascular morbidity and mortality in patients with CKD, is however not well understood. Experimental studies have shown that magnesium inhibits vascular calcification, both by direct effects on the vessel wall and by indirect, systemic effects. Moreover, an increasing number of epidemiologic studies in patients with CKD have shown associations of serum magnesium levels with intermediate and hard outcomes, including vascular calcification, cardiovascular events and mortality. Intervention trials in these patients conducted to date have had small sample sizes and have been limited to the study of surrogate parameters, such as arterial stiffness, vascular calcification and atherosclerosis. Randomized controlled trials are clearly needed to determine the effects of magnesium supplementation on hard outcomes in patients with CKD.

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.