Use of magnesium as a drug in chronic kidney disease

Renal Magnesium Handling: A Comparison Between Dogs With Chronic Kidney Disease and Healthy Elderly Dogs

Chronic kidney disease (CKD) and aging are known to possibly cause a progressive reduction in glomerular filtration rate, which may be associated with an increase in fractional excretion of electrolytes due to an adaptive response of the remaining functioning nephrons. However, the behavior of magnesium excretion has not been studied in CKD and healthy elderly dogs. The objective was to evaluate the fractional excretion of magnesium (FEMg) in dogs with (CKD) compared to healthy elderly dogs. Sixteen healthy elderly dogs and 43 dogs with CKD were divided into 3 groups (CKD 2 [n = 14], CKD 3 [n = 17], CKD 4 [n = 12]), in accordance with the current International Renal Interest Society (IRIS) criteria that were used in this study. Blood samples were obtained by jugular venipuncture and urine samples were obtained by cystocentesis. The FEMg was evaluated at a single time point in both urine and blood samples. FEMg was significantly higher in dogs with CKD compared to healthy elderly dogs, especially in advanced stages. This preliminary study demonstrates that FEMg may be altered in dogs with CKD. Further research is warranted to elucidate magnesium's potential role in cardiovascular and arterial calcification in dogs with CKD as observed in humans with CKD.

Phosphate recovery from water using cellulose enhanced magnesium carbonate pellets: Kinetics, isotherms, and desorption

Phosphorus is an essential and limited nutrient that is supplied by a depleting resource, mineral phosphate rock. Eutrophication is occurring in many water bodies which provides an opportunity to recover this nutrient from the water. One method of recovery is through adsorption; this study focused on fabricating a porous and granular adsorptive material for the removal and recovery of phosphate. Magnesium carbonate was combined with cellulose in varying weight ratios (0, 5, 10, 15, 20%) to synthesize pellets, which were then calcined to increase internal surface area. Physiochemical properties such as surface area, surface morphology, elemental composition, and crystal structure of the materials were characterized using Brunauer, Emmett, and Teller (BET) surface area analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The pellet proved to be uniform in composition and an increase in BET surface area correlated with an increase in cellulose content until pellet stability was lost. Phosphate adsorption using the pellets was studied via batch kinetics and sorption isotherms. The pseudo-second-order kinetics model fits best suggesting that the adsorption occurring was chemisorption. The isotherm model that fit best was the Langmuir isotherm, which showed that the maximum equilibrium adsorption capacity increased with an increase in cellulose content between 10% and 20%. The average adsorption capacity achieved in the triplicate isotherm study was 96.4 mg g^-1 for pellets synthesized with 15% cellulose. Overall, using cellulose and subsequent calcination created an additional internal surface area for adsorption of phosphate and suggested that granular materials can be modified for efficient removal and recovery of phosphate from water.

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.

Pharmacotherapy in chronic kidney disease hyperphosphatemia – effects on vascular calcification and bone health

Hyperphosphatemia (HP) in patients with chronic kidney disease (CKD) leads to complications such as renal osteodistrophy, cardiovascular calcification and hemodynamic abnormalities, all of them having a serious impact on the survival rate and quality of life. Also, HP is a key pathogenic factor in the development of secondary hyperparathyroidism (SHPT) in CKD. Having in regard the significance of controlling serum phosphorus levels (Pi), in this paper, the needs and obstacles to successful pharmacological management of HP in CKD are presented, with an overview of major classes of phosphate binders (PBs) and other drugs affecting Pi level, such as active vitamin D sterols and calcimimetics (CMs). In addition, their effects on progression of cardiovascular calcification and bone health are elaborated. In this regard, a PubMed search was carried out to capture all abstracts and articles relevant to the topic of CKD, HP and mineral metabolism, bone disorders and vascular/valvular calcification (VC), published from January 2007 to August 2017. The search was limited to English language, with the search terms including drug name AND hyperphosphatemia or cardiovascular calcification or bone disorder. Comparative studies, clinical studies/trials and meta-analyses related to different classes/representatives of PBs, vitamin D analogues and CMs were reviewed and research data related to their efficacy and safety compared. Keywords: chronic kidney disease, hyperphosphatemia, phosphate binders, active vitamin D sterols, calcimimetics, bone disorders, cardiovascular calcification

Serum Magnesium Abnormality and Influencing Factors of Serum Magnesium Level in Peritoneal Dialysis Patients: A Single-Center Study in Northern China

BACKGROUND/AIMS

Both hypomagnesemia and hypermagnesemia have been associated with cardiovascular diseases, bone diseases, and mortality in dialysis patients. We aimed to investigate the prevalence of and influencing factors for abnormal serum Mg levels in patients on peritoneal dialysis (PD).

METHODS

A cross-sectional study in Peking University People's Hospital recorded the demographic information, clinical characteristics, and laboratory data. Data were assessed and compared with the results from 2 other studies in China.

RESULTS

Of 180 enrolled PD patients, the primary diseases were glomerulonephritis (38.3%) and diabetic nephropathy (38.3%). Mean serum Mg concentration was 1.02 ± 0.16 mmol/L; 67% had normal serum Mg concentrations, and 33% had hypermagnesemia.

CONCLUSIONS

Hypermagnesemia is likely to occur in patients with higher serum phosphate, lower intact parathyroid hormone, and lower high-sensitivity C-reactive protein levels. Serum Mg level distributions in PD patients vary throughout China, may have different potential causes (such as geographical location and dietary habits) and should be further studied.

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.

Near death by milk of magnesia

We report a case of hypermagnesemia associated with the use of milk of magnesia in a male patient with end-stage renal disease. After experiencing nausea and vomiting, he developed severe bradycardia and then asystole. Resuscitation efforts were successful; however, he developed atrial fibrillation with severe widening of the QRS and diffuse ST elevation, hypothermia, hypotension and apnoea requiring intubation. Initial diagnoses included ST-elevation myocardial infarction, cardiogenic and/or septic shock and hyperkalaemia. However, serum magnesium was later found to be >4.1 mmol/L (equivalent to >10 mg/dL). He underwent haemodialysis (HD) to remove serum magnesium with remarkable overall improvement. Severe hypermagnesemia can manifest with severe bradycardia and asystole, shock, hypothermia and respiratory failure and can mimic acute coronary syndromes complicated with cardiogenic shock or septic shock. Therefore, clinicians should be aware of this life-threatening condition in patients with significant renal dysfunction. Timely treatment with HD is highly effective and lifesaving.

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.

Magnesium in man: implications for health and disease

Magnesium (Mg(2+)) is an essential ion to the human body, playing an instrumental role in supporting and sustaining health and life. As the second most abundant intracellular cation after potassium, it is involved in over 600 enzymatic reactions including energy metabolism and protein synthesis. Although Mg(2+) availability has been proven to be disturbed during several clinical situations, serum Mg(2+) values are not generally determined in patients. This review aims to provide an overview of the function of Mg(2+) in human health and disease. In short, Mg(2+) plays an important physiological role particularly in the brain, heart, and skeletal muscles. Moreover, Mg(2+) supplementation has been shown to be beneficial in treatment of, among others, preeclampsia, migraine, depression, coronary artery disease, and asthma. Over the last decade, several hereditary forms of hypomagnesemia have been deciphered, including mutations in transient receptor potential melastatin type 6 (TRPM6), claudin 16, and cyclin M2 (CNNM2). Recently, mutations in Mg(2+) transporter 1 (MagT1) were linked to T-cell deficiency underlining the important role of Mg(2+) in cell viability. Moreover, hypomagnesemia can be the consequence of the use of certain types of drugs, such as diuretics, epidermal growth factor receptor inhibitors, calcineurin inhibitors, and proton pump inhibitors. This review provides an extensive and comprehensive overview of Mg(2+) research over the last few decades, focusing on the regulation of Mg(2+) homeostasis in the intestine, kidney, and bone and disturbances which may result in hypomagnesemia.

Magnesium prevents phosphate-induced calcification in human aortic vascular smooth muscle cells

Background

Vascular calcification (VC) is prevalent in patients suffering from chronic kidney disease. Factors promoting calcification include abnormalities in mineral metabolism, particularly high phosphate levels. Inorganic phosphate (Pi) is a classical inducer of in vitro VC. Recently, an inverse relationship between serum magnesium concentrations and VC has been reported. The present study aimed to investigate the effects of magnesium on Pi-induced VC at the cellular level using primary HAVSMC.

Methods

Alive and fixed HAVSMC were assessed during 14 days in the presence of Pi with increasing concentrations of magnesium (Mg²⁺) chloride. Mineralization was measured using quantification of calcium, von Kossa and alizarin red stainings. Cell viability and secretion of classical VC markers were also assessed using adequate tests. Involvement of transient receptor potential melastatin (TRPM) 7 was assessed using 2-aminoethoxy-diphenylborate (2-APB) inhibitor.

Results

Co-incubation with Mg²⁺ significantly decreased Pi-induced VC in live HAVSMC, no effect was found in fixed cells. At potent concentrations in Pi-induced HAVSMC, Mg²⁺ significantly improved cell viability and restored to basal level increased secretions of osteocalcin and matrix gla protein, whereas a decrease in osteopontin secretion was partially restored. The block of TRPM7 with 2-APB at 10⁻⁴ M led to the inefficiency of Mg²⁺ to prevent VC.

Conclusions

Increasing Mg²⁺ concentrations significantly reduced VC, improved cell viability and modulated secretion of VC markers during cell-mediated matrix mineralization clearly pointing to a cellular role for Mg²⁺ and 2-APB further involved TRPM7 and a potential Mg²⁺ entry to exert its effects. Further investigations are needed to shed light on additional cellular mechanism(s) by which Mg²⁺ is able to prevent VC.

Magnesium in chronic kidney disease Stages 3 and 4 and in dialysis patients

The kidney has a vital role in magnesium homeostasis and, although the renal handling of magnesium is highly adaptable, this ability deteriorates when renal function declines significantly. In moderate chronic kidney disease (CKD), increases in the fractional excretion of magnesium largely compensate for the loss of glomerular filtration rate to maintain normal serum magnesium levels. However, in more advanced CKD (as creatinine clearance falls <30 mL/min), this compensatory mechanism becomes inadequate such that overt hypermagnesaemia develops frequently in patients with creatinine clearances <10 mL/min. Dietary calcium and magnesium may affect the intestinal uptake of each other, though results are conflicting, and likewise the role of vitamin D on intestinal magnesium absorption is somewhat uncertain. In patients undergoing dialysis, the effect of various magnesium and calcium dialysate concentrations has been investigated in haemodialysis (HD) and peritoneal dialysis (PD). Results generally show that dialysate magnesium, at 0.75 mmol/L, is likely to cause mild hypermagnesaemia, results for a magnesium dialysate concentration of 0.5 mmol/L were less consistent, whereas serum magnesium levels were mostly normal to hypomagnesaemic when 0.2 and 0.25 mmol/L were used. While dialysate magnesium concentration is a major determinant of HD or PD patients' magnesium balance, other factors such as nutrition and medications (e.g. laxatives or antacids) also play an important role. Also examined in this review is the role of magnesium on parathyroid hormone (PTH) levels in dialysis patients. Although various studies have shown that patients with higher serum magnesium tend to have lower PTH levels, many of these suffer from methodological limitations. Finally, we examine the complex and often conflicting results concerning the interplay between magnesium and bone in uraemic patients. Although the exact role of magnesium in bone metabolism is unclear, it may have both positive and negative effects, and it is uncertain what the optimal magnesium levels are in uraemic patients.