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

High Dephosphorylated-Uncarboxylated MGP in Hemodialysis patients: risk factors and response to vitamin K2, A pre-post intervention clinical trial

BACKGROUND

Vascular calcifications are highly prevalent in hemodialysis patients. Dephosphorylated-uncarboxylated MGP (dp-ucMGP) was found to increase in vitamin K-deficient patients and may be associated with vascular calcifications. Supplementation of hemodialysis patients with vitamin K2 (menaquinone-7) has been studied in Europe with a maximum 61% drop of dp-ucMGP levels. The aim of this study is to assess first the drop of dp-ucMGP in an Eastern Mediterranean cohort after vitamin K2 treatment and second the correlation between baseline dp-ucMGP and vascular calcification score.

METHODS

This is a prospective, pre-post intervention clinical trial involving 50 hemodialysis patients who received daily 360 μg of menaquinone-7 for 4 weeks. At baseline they were assessed for plasma dp-ucMGP levels and vascular calcification scores (AC-24) as well as for other demographic, clinical and biological variables. Dp-ucMGP levels were measured a second time at 4 weeks.

RESULTS

At baseline, dp-ucMGP levels were extremely elevated with a median of 3179.15 (1825.25; 4339.50) pM and correlated significantly with AC-24 (Spearman's rho = 0.43, P = 0.002). Using a bivariate regression analysis, the association between dp-ucMGP levels and AC-24 was most significant when comparing dp-ucMGP levels less than 1000 to those more than 1000 pM (P = 0.02). Dp-ucMGP levels higher than 5000 pM were significantly associated with females, patients with recent fracture and patients with lower serum albumin (respectively P = 0.02, 0.004 and 0.046). The average drop of dp-ucMGP at 4 weeks of treatment was found to be 86% with diabetics having the lowest drop rate (P = 0.01).

CONCLUSION

Vitamin K deficiency, as assessed by high dp-ucMGP levels, is profound in hemodialysis patients from the Eastern Mediterranean region and it is significantly correlated with vascular calcifications. Daily 360 μg of menaquinone-7, given for 4 weeks, effectively reduces dp-ucMGP in this population. Future studies are needed to assess the changes in vascular calcifications in hemodialysis patients treated with vitamin K2 over a longer follow-up period.

TRIAL REGISTRATION

The clinical trial was registered on clinicaltrials.gov (Identification number NCT02876354 , on August 11, 2016).

[Sucroferric oxyhydroxide, a novel iron-based phosphate binder. Which current use in dialysis patients?]

International guidelines suggest lowering elevated phosphorus level to the normal range in patients on dialysis. Among the phosphate-lowering strategies, phosphate binder is frequently used in addition to dietary phosphate restriction and an adequate dialysis strategy. However, serum phosphate concentration higher than 1.78mmol/L is observed in more than 40% of patients justifying the quest for new drugs. Sucroferric oxyhydroxide is one of the new iron-based agents and is available in France since May 2016. A recent international multicentre study showed this new drug to be as efficacious and non-inferior to sevelamer carbonate in magnitude of serum phosphate control. The serum phosphorus-lowering effect was maintained over 1year. When compared to carbonate sevelamer, the pill-burden was half with sucroferric oxyhydroxide because of its high phosphate binding capacity. As previously shown by experimental studies, no risk of iron accumulation was observed since iron absorption is negligible. Discolored feces and diarrhea were fairly frequent side effects. When diarrhea subsides, the tolerability of this new phosphate binder is excellent on a long-term basis.

Lanthanum deposition from oral lanthanum carbonate in the upper gastrointestinal tract

AIMS

Lanthanum carbonate is used as an alternative to calcium-based phosphate binders to manage hyperphosphataemia in patients with renal failure. The deposition of lanthanum within gastroduodenal mucosa of patients treated with the medication has been described, but given the relative novelty of this entity, the histiocytic deposits in the gastroduodenal mucosa can be confused with a variety of other processes, including infections and other drug-induced forms of injury.

METHODS AND RESULTS

We describe five cases of lanthanum phosphate deposition in upper gastrointestinal (GI) tract biopsies. Three cases were confirmed with scanning electron microscopy and energy dispersive X-ray analysis, including one unique patient, status post-renal transplant for polycystic kidney disease, who had last taken lanthanum 7 years prior to biopsy.

CONCLUSION

Lanthanum deposition in the upper GI tract is a mimic of other drug-related forms of GI injury, including iron pill-related gastropathy. The key to making this diagnosis is a thorough drug history and awareness of the histological features.

The Use of a Multidimensional Measure of Dialysis Adequacy-Moving beyond Small Solute Kinetics

Urea removal has become a key measure of the intensity of dialysis treatment for kidney failure. Small solute removal, exemplified by Kt/Vurea, has been broadly applied as a means to quantify the dose of thrice weekly hemodialysis. Yet, the reliance on small solute clearances alone as a measure of dialysis adequacy fails fully to quantify the intended clinical effects of dialysis therapy. This review aims to (1) understand the strengths and limitations of small solute kinetics as a surrogate marker of dialysis dose, and (2) present the prospect of a more comprehensive construct for dialysis dose, one that considers more broadly the goals of ESRD care to maximize both quality of life and survival. On behalf of the American Society of Nephrology Dialysis Advisory Group, we propose the need to ascertain the validity and utility of a multidimensional measure that moves beyond small solute kinetics alone to quantify optimal dialysis derived from both patient-reported and comprehensive clinical and dialysis-related measures.

Should nephrologists consider vascular calcification screening?

Vascular calcification (VC) has been widely discussed over the last few decades and is associated with significant morbidity and mortality among patients with chronic kidney disease. Importantly, these patients have premature and rapidly progressive calcification when compared with the general population. VC is an active and complex process that is closely regulated by a growing list of inducers and inhibitors. VC can be detected using several non-invasive modalities including plain radiography, echocardiogram and computed tomography scans. However, the usefulness of these imaging measurements to capture treatment effects may be limited. Routine screening and monitoring for progression of VC remains highly debatable.

Pharmacological Management of Secondary Hyperparathyroidism in Patients with Chronic Kidney Disease

Secondary hyperparathyroidism (SHPT) is a common complication of chronic kidney disease (CKD) and is part of the CKD-mineral bone disorder (CKD-MBD). SHPT is associated with increased risk of fracture and mortality; thus, SHPT control is recommended as kidney function declines. Effective SHPT management becomes more difficult once skeletal and cardiovascular adverse effects associated with severe SHPT have become established. However, interventional studies to lower parathyroid hormone (PTH) have so far shown inconsistent results in improving patient-centred outcomes such as mortality, cardiovascular events and fracture. Pharmacological treatment effect on PTH level is also inconsistent between pre-dialysis CKD and dialysis patients, which adds to the complexity of SHPT management. This review aims to give an overview on the pathophysiology, pharmacological and non-pharmacological treatment for SHPT in CKD including some of the limitations of current therapeutic options.

A decrease in intact parathyroid hormone (iPTH) levels is associated with higher mortality in prevalent hemodialysis patients

BACKGROUND

The mortality of dialysis patients is 10- to 100-fold higher than in the general population. Baseline serum PTH levels, and more recently, changes in serum PTH levels (ΔPTH) over time, have been associated to mortality in dialysis patients.

METHODS

We explored the relationship between ΔPTH over 1 year with mortality over the next year in a prospective cohort of 115 prevalent hemodialysis patients from a single center that had median baseline iPTH levels within guideline recommendations.

RESULTS

Median baseline iPTH levels were 205 (116.5, 400) pg/ml. ΔiPTH between baseline and 1 year was 85.2 ± 57.1 pg/ml. During the second year of follow-up, 27 patients died. ΔiPTH was significantly higher in patients who survived (+157.30 ± 25.82 pg/ml) than in those who died (+39.03 ± 60.95 pg/ml), while baseline iPTH values were not significantly different. The highest mortality (48%) was observed in patients with a decrease in ΔiPTH (ΔiPTH quartile 1, negative ΔiPTH) and the lowest (12%) mortality in quartile 3 ΔiPTH (ΔiPTH increase 101-300 pg/ml). In a logistic regression model, ΔiPTH was associated with mortality with an odds ratio (OR) of 0.998 (95% CI 0.996-0999, p = 0.038). In multivariable analysis, mortality risk was 73% and 88% lower for patients with ΔiPTH 0-100 pg/ml and 101-300 pg/ml, respectively, than for those with a decrease in ΔiPTH. In patients with a decrease in ΔiPTH, the OR for death was 4.131 (1.515-11.27)(p = 0.006).

CONCLUSIONS

In prevalent hemodialysis patients with median baseline iPTH values within the guideline recommended range, a decrease in ΔiPTH was associated with higher mortality. Further studies are required to understand the mechanisms and therapeutic implications of this observation that challenges current clinical practice.

Imaging for Vascular Calcification

Chronic decline in renal function is accompanied by deterioration of bone structure and function and progressive calcification of the vascular system. Both disease states have been linked with increased morbidity and mortality in chronic kidney disease. The severe alterations of mineral metabolism inherent with loss of renal function have an impact on vascular calcification development and progression, and several investigators have focused on ways to reduce their impact on vascular health. Imaging has contributed an important role in the assessment of vascular calcification, and the impact of various interventions aimed at curbing their progression.

Lanthanum carbonate: safety data after 10 years

Despite 10 years of post-marketing safety monitoring of the phosphate binder lanthanum carbonate, concerns about aluminium-like accumulation and toxicity persist. Here, we present a concise overview of the safety profile of lanthanum carbonate and interim results from a 5-year observational database study (SPD405-404; ClinicalTrials.gov identifier: NCT00567723). The pharmacokinetic paradigms of lanthanum and aluminium are different in that lanthanum is minimally absorbed and eliminated via the hepatobiliary pathway, whereas aluminium shows appreciable absorption and is eliminated by the kidneys. Randomised prospective studies of paired bone biopsies revealed no evidence of accumulation or toxicity in patients treated with lanthanum carbonate. Patients treated with lanthanum carbonate for up to 6 years showed no clinically relevant changes in liver enzyme or bilirubin levels. Lanthanum does not cross the intact blood-brain barrier. The most common adverse effects are mild/moderate nausea, diarrhoea and flatulence. An interim Kaplan-Meier analysis of SPD405-404 data from the United States Renal Data System revealed that the median 5-year survival was 51.6 months (95% CI: 49.1, 54.2) in patients who received lanthanum carbonate (test group), 48.9 months (95% CI: 47.3, 50.5) in patients treated with other phosphate binders (concomitant therapy control group) and 40.3 months (95% CI: 38.9, 41.5) in patients before the availability of lanthanum carbonate (historical control group). Bone fracture rates were 5.9%, 6.7% and 6.4%, respectively. After more than 850 000 person-years of worldwide patient exposure, there is no evidence that lanthanum carbonate is associated with adverse safety outcomes in patients with end-stage renal disease.

Secondary Hyperparthyroidism: Pathogenesis, Diagnosis, Preventive and Therapeutic Strategies

Uremic secondary hyperparathyroidism is a multifactorial and complex disease often present in advanced stages of chronic kidney disease. The accumulation of phosphate, the increased FGF23 levels, the reduction in active vitamin D production, and the tendency to hypocalcemia are persistent stimuli for the development and progression of parathyroid hyperplasia with increased secretion of PTH. Parathyroid proliferation may become nodular mainly in cases of advanced hyperparathyroidism. The alterations in the regulation of mineral metabolism, the development of bone disease and extraosseous calcifications are essential components of chronic kidney disease-mineral and bone disorder and have been associated with negative outcomes. The management of hyperparathyroidism includes the correction of vitamin D deficiency and control of serum phosphorus and PTH without inducing hypercalcemia. An update of the leading therapeutic tools available for the prevention and clinical management of secondary hyperparathyroidism, its diagnosis, and the main mechanisms and factors involved in the pathogenesis of the disease will be described in this review.

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.

Elemental calcium intake associated with calcium acetate/calcium carbonate in the treatment of hyperphosphatemia

Background

Calcium-based and non-calcium-based phosphate binders have similar efficacy in the treatment of hyperphosphatemia; however, calcium-based binders may be associated with hypercalcemia, vascular calcification, and adynamic bone disease.

Scope

A post hoc analysis was carried out of data from a 16-week, Phase IV study of patients with end-stage renal disease (ESRD) who switched to lanthanum carbonate monotherapy from baseline calcium acetate/calcium carbonate monotherapy. Of the intent-to-treat population (N=2520), 752 patients with recorded dose data for calcium acetate (n=551)/calcium carbonate (n=201) at baseline and lanthanum carbonate at week 16 were studied. Elemental calcium intake, serum phosphate, corrected serum calcium, and serum intact parathyroid hormone levels were analyzed.

Findings

Of the 551 patients with calcium acetate dose data, 271 (49.2%) had an elemental calcium intake of at least 1.5 g/day at baseline, and 142 (25.8%) had an intake of at least 2.0 g/day. Mean (95% confidence interval [CI]) serum phosphate levels were 6.1 (5.89, 6.21) mg/dL at baseline and 6.2 (6.04, 6.38) mg/dL at 16 weeks; mean (95% CI) corrected serum calcium levels were 9.3 (9.16, 9.44) mg/dL and 9.2 (9.06, 9.34) mg/dL, respectively. Of the 201 patients with calcium carbonate dose data, 117 (58.2%) had an elemental calcium intake of at least 1.5 g/day, and 76 (37.8%) had an intake of at least 2.0 g/day. Mean (95% CI) serum phosphate levels were 5.8 (5.52, 6.06) mg/dL at baseline and 5.8 (5.53, 6.05) mg/dL at week 16; mean (95% CI) corrected serum calcium levels were 9.7 (9.15, 10.25) mg/dL and 9.2 (9.06, 9.34) mg/dL, respectively.

Conclusion

Calcium acetate/calcium carbonate phosphate binders, taken to control serum phosphate levels, may result in high levels of elemental calcium intake. This may lead to complications related to calcium balance.

Effect of Tenapanor on Serum Phosphate in Patients Receiving Hemodialysis

Hyperphosphatemia is common among patients with CKD stage 5D and is associated with morbidity and mortality. Current guidelines recommend lowering serum phosphate concentrations toward normal. Tenapanor is a minimally absorbed small molecule inhibitor of the sodium/hydrogen exchanger isoform 3 that functions in the gut to reduce sodium and phosphate absorption. This randomized, double-blind, placebo-controlled trial assessed the effects of tenapanor on serum phosphate concentration in patients with hyperphosphatemia receiving hemodialysis. After a 1- to 3-week washout of phosphate binders, we randomly assigned 162 eligible patients (serum phosphate =6.0 to <10.0 mg/dl and a 1.5-mg/dl increase from before washout) to one of six tenapanor regimens (3 or 30 mg once daily or 1, 3, 10, or 30 mg twice daily) or placebo for 4 weeks. The primary efficacy end point was change in serum phosphate concentration from baseline (randomization) to end of treatment. In total, 115 patients (71%) completed the study. Mean serum phosphate concentrations at baseline (after washout) were 7.32-7.92 mg/dl for tenapanor groups and 7.87 mg/dl for the placebo group. Tenapanor provided dose-dependent reductions in serum phosphate level from baseline (least squares mean change: tenapanor =0.47-1.98 mg/dl; placebo =0.54 mg/dl; P=0.01). Diarrhea was the most common adverse event (tenapanor =18%-68%; placebo =12%) and frequent at the highest tenapanor doses. In conclusion, tenapanor treatment resulted in statistically significant, dose-dependent reductions in serum phosphate concentrations in patients with hyperphosphatemia receiving hemodialysis. Additional studies are required to clarify the optimal dosing of tenapanor in patients with CKD-related hyperphosphatemia.

Arterial Calcification in Diabetes Mellitus: Preclinical Models and Translational Implications

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

Vitamin D Receptor Activator Use and Cause-specific Death among dialysis Patients: a Nationwide Cohort Study using Coarsened Exact Matching

Vitamin D receptor activators (VDRA) may exert pleiotropic effects on cardiovascular disease, malignancy, and infections among dialysis patients, but recent studies have mainly focused on cardiovascular outcomes. Among 8,675 patients who started dialysis in 2007 and who survived until January 1, 2010, listed in the Renal Data Registry of the Japanese Society for Dialysis Therapy, 5,365 VDRA users were matched to 3,203 non-users based on clinically relevant variables at the end of 2009 using the coarsened exact matching procedure. Until December 31, 2011, a total of 1,128 deaths occurred, of which 468 (42%) were cardiovascular deaths, 229 (20%) were infection-related deaths, and 141 (12%) were malignancy-related deaths. Multivariable survival analyses accounting for intra-region correlation revealed that VDRA use was significantly associated with lower rates of infection- and malignancy-related deaths [subhazard ratio 0.62 (95% CI, 0.52–0.73) and 0.70 (95% CI, 0.50–0.97), respectively] but not with cardiovascular death [subhazard ratio 0.86 (95% CI, 0.72–1.04)]. Future randomized clinical trials with a sufficient sample size and an adequate follow-up period are warranted to test the clinical effectiveness of VDRA on infection and malignancy, rather than cardiovascular disease, among dialysis patients.

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.

Effects of lanthanum carbonate and calcium carbonate on fibroblast growth factor 23 and hepcidin levels in chronic hemodialysis patients

BACKGROUND

Phosphate binders have an impact on fibroblast growth factor 23 (FGF23); however, the effect of phosphate binders on serum hepcidin has not been explored. We conducted a 24-week multicenter randomized controlled trial to investigate the effects of lanthanum carbonate or calcium carbonate monotherapy on serum phosphate, FGF23, and hepcidin levels in chronic hemodialysis patients.

METHODS

Forty-six patients were recruited, and daily dietary phosphorus was controlled between 600-800 mg. Serum calcium, phosphate, albumin, alkaline phosphatase (ALP), FGF23, intact parathyroid hormone (iPTH), hepcidin, high-sensitivity CRP (hsCRP), 25(OH)D, 1,25(OH)₂D, fetuin-A, and osteopontin were checked as scheduled.

RESULTS

Twenty-five patients completed the study. Mean serum FGF23 level was significantly decreased after a 24-week treatment with lanthanum (8677.5 ± 7490.0 vs. 4692.8 ± 5348.3 pg/mL, p = 0.013, n = 13), but not with calcium (n = 12). The reduction of serum hepcidin in lanthanum group was positively correlated with the decrement of serum phosphate (r = 0.631, p = 0.021) and serum hsCRP (r = 0.670, p = 0.012) levels, respectively. Serum ALP, iPTH, vitamin D, fetuin-A, and osteopontin revealed no significant inter- or intragroup differences.

CONCLUSIONS

In summary, a decrease in serum FGF23 levels and a trend of decline in hepcidin levels were observed only in lanthanum group.

Acute calcium kinetics in haemodialysis patients

INTRODUCTION

To avoid excessive calcium loading in haemodialysis (HD) patients, current guidelines suggest a dialysate calcium concentration (dCa) of 2·5 mEq/L based on relatively stable intradialytic serum calcium levels. However, the latter do not account for possible calcium storage in acutely accessible pools. A rapidly exchangeable calcium pool located at the bone level has been previously proposed to be involved in acute (minute-to-minute) extracellular calcium regulation.

DESIGN

To evaluate the contribution of this pool in the maintenance of serum calcium levels, acute calcium buffer capacity was assessed by measuring intradialytic dialysate-sided ionized calcium mass balance (iCa_MB ) and change in extracellular fluid calcium mass in chronic HD patients using a dCa of 3·5 (n = 28) and 2·5 (n = 10) mEq/L. Serum osteocalcin, the most abundant noncollagenous bone protein, was measured before the HD session.

RESULTS

iCa_MB was invariably positive for both 2·5 and 3·5 mEq/L dCa, with a mean of 434 (±125) and 725 (±162) mg/HD, respectively (P < 0·001). Buffered intradialytic calcium load was 410 (±116) and 565 (±130) mg/HD, and acute calcium buffer capacity was 95 (±8)% and 78 (±7)% (mean values at 2·5 and 3·5 mEq/L dCa, respectively) (P < 0·001). Using 3·5 mEq/L dCa, an independent association of acute calcium buffer capacity with undercarboxylated osteocalcin (β = 0·512, P = 0·002) was demonstrated.

CONCLUSIONS

Our data strongly suggest the existence of a rapidly exchangeable calcium pool that counteracts acute serum calcium deviations in HD patients. This study provides, for the first time, experimental evidence for the involvement of bone in acute extracellular calcium regulation in vivo.

Management of phosphorus load in CKD patients

Disturbances in mineral and bone metabolism play a critical role in the pathogenesis of cardiovascular complications in patients with chronic kidney disease (CKD). The term "renal osteodystrophy" has recently been replaced with "CKD-mineral and bone disorder (CKD-MBD)", which includes vascular calcification as well as bone abnormalities. In Japan, proportions of the aged and long-term dialysis patients are increasing which makes management of vascular calcification and parathyroid function increasingly more important. There are three main strategies to manage phosphate load: phosphorus dietary restriction, administration of phosphate binder and to ensure in the CKD 5D setting, an adequate dialysis.

The role of phosphate in kidney disease

The importance of phosphate homeostasis in chronic kidney disease (CKD) has been recognized for decades, but novel insights - which are frequently relevant to everyday clinical practice - continue to emerge. Epidemiological data consistently indicate an association between hyperphosphataemia and poor clinical outcomes. Moreover, compelling evidence suggests direct toxicity of increased phosphate concentrations. Importantly, serum phosphate concentration has a circadian rhythm that must be considered when interpreting patient phosphate levels. Detailed understanding of dietary sources of phosphate, including food additives, can enable phosphate restriction without risking protein malnutrition. Dietary counselling provides an often underestimated opportunity to target the increasing exposure to dietary phosphate of both the general population and patients with CKD. In patients with secondary hyperparathyroidism, bone can be an important source of serum phosphate, and adequate appreciation of this fact should impact treatment. Dietary and pharmotherapeutic interventions are efficacious strategies to lower phosphate intake and serum concentration. However, strong evidence that targeting serum phosphate improves patient outcomes is currently lacking. Future studies are, therefore, required to investigate the effects of modern dietary and pharmacological interventions on clinically meaningful end points.

The FGF23 and Klotho system beyond mineral metabolism

FGF23 is a bone-derived hormone that acts primarily on the kidney to induce phosphaturia and suppress synthesis of 1,25-dihydroxyvitamin D₃. The unique feature of FGF23 is that it requires Klotho as an obligate co-receptor. The FGF23-Klotho system has emerged as an endocrine axis indispensable for maintaining phosphate homeostasis. Mineral and bone disorders associated with chronic kidney disease (CKD-MBD) can be viewed as a series of events triggered by a compensatory response of the FGF23-Klotho system to excess phosphate intake relative to the residual nephron number. Furthermore, the fact that disruption of the FGF23-Klotho system causes phosphate retention and a syndrome resembling aging in mammals has led to the notion that phosphate accelerates aging. The aging-like pathology caused by phosphate, or phosphatopathy, may be unique to the higher organisms having the Klotho gene and provides new insights into the molecular mechanism of aging in humans.

A critical appraisal of chronic kidney disease mineral and bone disorders clinical practice guidelines using the AGREE II instrument

BACKGROUND

Patients with chronic kidney disease mineral and bone disorders (CKD-MBD) suffer high rates of morbidity and mortality, in particular related to bone and cardiovascular outcomes. The management of CKD-MBD remains challenging. The objective of this systematic survey is to critically appraise clinical practice guidelines (CPGs) addressing CKD-MBD.

METHODS/DESIGN

Data sources included MEDLINE, EMBASE, the National Guideline Clearinghouse, Guideline International Network and Turning Research into Practice up to May 2016. Teams of two reviewers, independently and in duplicate, screened titles and abstracts and potentially eligible full text reports to determine eligibility and subsequently appraised the guidelines using the Advancing Guideline Development, Reporting and Evaluation in Health Care instrument II (AGREE).

RESULTS

Sixteen CPGs published from 2003 to 2015 addressing the diagnosis and management of CKD-MBD in adult patients (11 English, two Spanish, one Italian, one Portuguese and one Slovak) proved eligible. The National Institute for Health and Care Excellence guideline performed best with respect to AGREE II criteria; only three other CPGs warranted high scores on all domains. All other guidelines received scores of under 60% on one or more domains. Major discrepancies in recommendations were not, however, present, and we found no association between quality of CPGs which was not associated with resulting recommendations.

CONCLUSIONS

Most guidelines assessing CKD-MBD suffer from serious shortcomings using AGREE criteria although limitations with respect to AGREE criteria do not necessarily lead to inappropriate recommendations.

Analysis of the kinetics of the parathyroid hormone, and of associated patient outcomes, in a cohort of haemodialysis patients

Background

Observational studies have recently associated a decrease in serum parathyroid hormone (PTH) level with a higher rate of mortality among hemodialysis (HD) patients. Decreases in PTH level can result from medical intervention (MPD) and surgical parathyroidectomy (PTX), or may occur spontaneously, usually associated with an underlying malnutrition-inflammation syndrome (SPD). The aim of our study was to prospectively identify the incidence of decreases in PTH level in a cohort of HD patients and the frequency distribution of the different causes (MPD, PTX and SPD), as well as to evaluate the survival outcomes for each PTH group (MPD, PTX and SPD) compared to patients who did not experience a PTH decrease over the first 36 months of the study (NPD).

Methods

The 197 patients receiving HD at our center in January 2010, and meeting our eligibility criteria, were enrolled in our prospective study, and were observed for a period of 60 months. A decrease in PTH level >50 % between two successive PTH measurements obtained within an interval <3 months was defined as a significant event. MPD referred to a decrease in PTH due to an increased oral calcium intake, increased dialysate calcium concentration (DCC), increased alfacalcidol use, or use of cinacalcet therapy. A surgical 7/8 PTX was performed in young patients or in patients in whom cinacalcet therapy failed. SPD referred to a decrease in PTH related to a medical or surgical event. Baseline characteristics among patients in each group (MPD, PTX, SPD, and NPD) were evaluated using Fisher’s exact test. The 60-month survival was evaluated using Kaplan-Meier and Cox multivariable proportional hazards models. Univariate and multivariate Cox analyzes were used identify variables with mortality. The relative risk of mortality was expressed as a hazard ratio (HR).

Results

The distribution of the 197 patients forming our four study groups was 34 % in the NPD group, 35 % in the SPD group, 25 % in the MSD group and 6 % in the PTX group. Among patients in the SPD group, the main acute comorbid conditions were peripheral vascular and cardiac complications, sepsis, fractures, and cancers with an increase in serum CRP level (from 14.3 ± 18 to 132 ± 90 mg/L) and a decrease in serum albumin (from 33 ± 4.5 to 28.6 ± 4 g/L). In the MPD group, the main therapeutic change was an increase in DCC, either independently or in association with cinacalcet therapy. The median survival rate among patients was 10 months for SPD, compared to 22 months among patients in the MPD group (p < 0.001). Using multivariable Cox model and taking the NPD group as reference, the risk of mortality was lower among patients in the MPD group (HR, 0.42[0.2-0.87] p = 0.01), with survival being comparable for the SPD and NPD groups (HR, 1.3 [0.75-2.2]). No mortality was observed in the PTX group.

Conclusion

The poor outcomes associated with SPD, related to acute comorbid conditions, should not lead to undertreat secondary hyperparathyroidism whose appropriate medical or surgical therapies are associated with better outcomes.

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

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

Cardiovascular calcifications in chronic kidney disease: Potential therapeutic implications

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

Lanthanum deposition in the gastrointestinal mucosa and regional lymph nodes in dialysis patients: Analysis of surgically excised specimens and review of the literature

Lanthanum carbonate (LC) is one of the most potent phosphate binders currently used to reduce serum phosphate levels in dialysis patients with end-stage renal disease (ESRD). LC forms insoluble complexes with dietary phosphate that pass through the gastrointestinal (GI) tract with little absorption. GI lesions due to lanthanum deposition in biopsy specimens or those in endoscopic submucosal dissection (ESD) in dialysis patients have been recently identified. Here, we describe more detailed histopathological findings in the gastroduodenal mucosa and regional lymph nodes in three patients with gastric cancer. Three patients with ESRD, two elderly women and one man, underwent dialysis and were treated with LC for 3-36 months. The patients underwent laparoscopic distal gastrectomy and lymph node dissection due to gastric cancer. Many subepithelial histiocyte aggregates or small foreign body granulomas, which contained gray or brown pigments or crystal-like structures, were mostly present in non-neoplastic areas of the upper GI. Lanthanum accumulation was noted in the duodenal mucosa and the antral and body mucosae of the gastric lesser curvature. Lanthanum was also deposited in the regional lymph nodes of the three patients. Electron microscopy with energy dispersive X-ray spectroscopy confirmed lanthanum and phosphorus deposits in histiocytes. Long-term prognosis of patients and the excretion or the metabolic pathway of accumulated lanthanum remain unclear.

Design and baseline characteristics of the LANDMARK study

Background

Calcium (Ca)-based phosphate (P) binders, compared to non-Ca-based P binders, contribute to vascular calcification, which is associated with cardiovascular events.

Methods

The LANDMARK study is a multicenter, randomized, open-label, parallel comparative study of lanthanum carbonate (LC) and calcium carbonate (CC) in hemodialysis patients. Stable hemodialysis patients with intact parathyroid hormone ≤240 pg/mL meeting ≥1 of the following criteria (age >65 years, postmenopause, diabetes mellitus) were randomized into the LC and CC groups. LC group patients initially received LC 750 mg/day or the previously used dose and were titrated up to a maximum 2250 mg/day to achieve serum P levels of 3.5–6.0 mg/dL. CC group patients received CC 3 g/day or the previously used dose and were titrated to achieve the same P range. If the target serum P level was not achieved, non-Ca-based P binders (other than LC) could also be added. The primary endpoint is survival time free of cardiovascular events, including cardiovascular death, non-fatal myocardial infarction or stroke, and unstable angina.

Results

Overall, 2309 patients were allocated to the LC (N = 1154) or CC group (N = 1155). At baseline, the mean age was 68.4 years, 40.4 % were women, 55.9 % had diabetes, 18.3 % had a history of ischemic heart disease, and 13.9 % had cerebrovascular disease. A total of 184 patients (8.4 %) had undergone coronary intervention procedures. Baseline characteristics were well balanced between groups.

Conclusions

The LANDMARK study will determine whether LC, a non-Ca-based P binder, reduces cardiovascular mortality and morbidity in chronic hemodialysis patients.

CKD-Mineral Bone Disorder in Stage 4 and 5 CKD: What We Know Today?

Patients with CKD stages 4 and 5 experience biochemical derangements associated with CKD-mineral bone disorder. Some of the key abnormalities are hyperparathyroidism, hyperphosphatemia, hypocalcemia, and metabolic acidosis. We review the available treatments for these conditions and the evidence behind the treatments. We conclude that there is greater evidence for treating hyperphosphatemia than hyperparathyroidism. Treatment of metabolic acidosis in small clinical trials appears to be safe. We caution the reader about side effects associated with some of these treatments that differ in patients with CKD Stages 4 and 5 compared with patients on dialysis. The use of cinacalcet has been associated with hyperphosphatemia in patients with functioning kidneys. Activated vitamin D therapy has been associated with elevated creatinine levels, which may or may not be a reflection of true decrement in kidney function. Finally, the use of non-calcium-containing phosphate binders may be associated with improved clinical outcomes in patients; however, many more clinical trials are needed in this important area of medicine.

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.

Bone loss in chronic kidney disease: Quantity or quality?

Chronic kidney disease (CKD) patients experience bone loss and fracture because of a specific CKD-related systemic disorder known as CKD-mineral bone disorder (CKD-MBD). The bone turnover, mineralization, and volume (TMV) system describes the morphological bone lesions in renal osteodystrophy related to CKD-MBD. Bone turnover and bone volume are defined as high, normal, or low, and bone mineralization is classified as normal or abnormal. All types of bone histology related to TMV are responsible for both bone quantity and bone quality losses in CKD patients. This review focuses on current bone quantity and bone quality losses in CKD patients and finally discusses potential therapeutic measures.

Pro: cardiovascular calcifications are clinically relevant

It is increasingly acknowledged that mineral and bone disorders (MBDs) contribute to the excessively high cardiovascular (CV) disease morbidity and mortality observed in patients with chronic kidney disease (CKD). There is ongoing debate as to whether screening for CV calcification, one of the hallmarks of CKD-MBD, should be implemented in clinical practice in patients with CKD. Issues to be considered in this controversy relate to prevalence, severity, relevance, and last but not least, modifiability and reversibility of vascular and valvular calcifications in the setting of CKD. The recent expansion of the armamentarium to treat CKD-MBD (calcium-free phosphate binders and calcimimetics) creates new opportunities. Mounting experimental and clinical evidence indicates that progression of CV calcification may indeed be attenuated. Whether this will translate into better outcomes remains to be proven. We acknowledge that hard outcome data so far are limited and, overall, yielded inconclusive results. Nevertheless, in an era in which personalized medicine has gained much popularity, we consider it reasonable, awaiting the results of additional studies, to screen for CV calcification in selected individuals. This policy may help to stratify CV risk and to guide therapy. We speculate that such an approach will ultimately improve outcomes and reduce health costs.