Lower serum magnesium is associated with cardiovascular risk factors and mortality in haemodialysis patients

Dietary magnesium supplementation in cats with chronic kidney disease: A prospective double-blind randomized controlled trial

BACKGROUND

Plasma total magnesium concentration (tMg) is a prognostic indicator in cats with chronic kidney disease (CKD), shorter survival time being associated with hypomagnesemia. Whether this risk factor is modifiable with dietary magnesium supplementation remains unexplored.

OBJECTIVES

Evaluate effects of a magnesium-enriched phosphate-restricted diet (PRD) on CKD-mineral bone disorder (CKD-MBD) variables.

ANIMALS

Sixty euthyroid client-owned cats with azotemic CKD, with 27 and 33 allocated to magnesium-enriched PRD or control PRD, respectively.

METHODS

Prospective double-blind, parallel-group randomized trial. Cats with CKD, stabilized on a PRD, without hypermagnesemia (tMg >2.43 mg/dL) or hypercalcemia (plasma ionized calcium concentration, (iCa) >6 mg/dL), were recruited. Both intention-to-treat and per-protocol (eating ≥50% of study diet) analyses were performed; effects of dietary magnesium supplementation on clinicopathological variables were evaluated using linear mixed effects models.

RESULTS

In the per-protocol analysis, tMg increased in cats consuming a magnesium-enriched PRD (β, 0.25 ± .07 mg/dL/month; P < .001). Five magnesium supplemented cats had tMg >2.92 mg/dL, but none experienced adverse effects. Rate of change in iCa differed between groups (P = .01), with decreasing and increasing trends observed in cats fed magnesium-enriched PRD and control PRD, respectively. Four control cats developed ionized hypercalcemia versus none in the magnesium supplemented group. Log-transformed plasma fibroblast growth factor-23 concentration (FGF23) increased significantly in controls (β, 0.14 ± .05 pg/mL/month; P = .01), but remained stable in the magnesium supplemented group (β, 0.05±.06 pg/mL/month; P =.37).

CONCLUSIONS AND CLINICAL IMPORTANCE

Magnesium-enriched PRD is a novel therapeutic strategy for managing feline CKD-MBD in cats, further stabilizing plasma FGF23 and preventing hypercalcemia.

The relationship between coronary artery calcification and bone metabolic markers in maintenance hemodialysis patients

BACKGROUND

To study the influencing factors for coronary artery calcification (CAC) in maintenance hemodialysis (MHD) patients and the relationship between CAC and bone metabolism markers and to attempt to find a reliable marker linking vascular calcification and bone metabolism in MHD patients.

METHODS

A total of 123 patients were enrolled. CAC was assessed by multislice spiral computed tomography (MSCT), and the CAC score (CACS) was evaluated using the Agaston method. Routine laboratory parameters, including triglycerides (TG), total cholesterol (TC), glucose (Glu), calcium (Ca), phosphorus (P), magnesium (Mg), etc., were measured. Serum markers of bone metabolism, such as alkaline phosphatase(ALP), calcitonin (CT), 25-hydroxy vitamin D [25-(OH)D], intact parathyroid hormone (iPTH), total type I procollagen amino-terminal peptide (tPINP), N-terminal mid-fragment of osteocalcin (N-MID OC), and β-type I collagen crosslinked carboxyl-terminal peptide (β-CTX), were also measured.

RESULTS

Among 123 MHD patients, 37 patients (30.08%) did not have CAC, and 86 patients (69.92%) had CAC, including 41 patients (47.67%) with mild calcification and 45 patients (52.33%) with moderate to severe calcification. Age, Body Mass Index(BMI), the prevalence of hypertension and diabetes mellitus, TC, Glu, P, and Ca×P in the calcification group were higher than those in the noncalcification group, whereas Mg, iPTH, tPINP, N-MID OC, and β-CTX were lower than those in the noncalcified group (P < 0.05). Compared with the mild calcification group (0 0.05). A logistic regression model was used to evaluate the influencing factors for CAC. The results showed that age, BMI, TC, Glu, P, and Ca×P were risk factors for CAC and its severity in MHD patients, whereas diabetes mellitus, Mg, and N-MID OC were protective factors for CAC in MHD patients. In addition, N-MID OC was a protective factor for the severity of CAC. After adjusting for the corresponding confounding factors, the results of the risk factors were consistent, and N-MID OC was still an independent protective factor for CAC and its severity.

CONCLUSIONS

Elevated serum P and Ca×P were independent risk factors for CAC in MHD patients, and serum Mg may be an independent protective factor for CAC. CAC was closely related to abnormal bone metabolism and bone metabolic markers in MHD patients. Relatively low bone turnover can promote the occurrence and development of CAC. N-MID OC may be a reliable bone metabolic marker linking vascular calcification and bone metabolism in MHD patients.

Lower serum magnesium is a predictor of left ventricular hypertrophy in patients on dialysis

PURPOSE

Left ventricular hypertrophy (LVH) represents one of the main risk factors for cardiovascular mortality in dialysis patients. Low serum magnesium Mg is related with increased mortality in general and dialysis population. Aim of our study was to evaluate the association of Mg with LVH and cardiac geometry in dialysis patients.

METHODS

Hemodialysis (HD) and peritoneal dialysis (PD) patients from nine nephrology departments were included. Echocardiographic LVH was defined by LV mass index > 95 g/m² in women and > 115 g/m² in men. Four LV geometric patterns were defined: normal, concentric remodeling, eccentric LVH and concentric LVH. Demographic and laboratory data were collected.

RESULTS

133 patients (68 HD, 65 PD) with a median age of 63 years (IQR 52-74) were studied. Mg correlated positively with creatinine, HDL and negatively with CRP levels and BMI. There were no significant differences in Mg between the modality groups. 80 patients presented LVH (43 HD and 37 PD patients). Patients with LVH were older (median age 68 vs 55 years, p < 0.001), with higher BMI (median 26.9 vs 24.7 kg/m², p = 0.009), had a history of PVD or CAD (55% vs 30.2%, p = 0.003), had higher pulse pressure (median 60 vs 50, p = 0.017), MIS score (median 5 vs 4, p = 0.011), lower albumin (median 3.5 vs 3.8 g/dl, p = 0.011) and Mg levels (median 2.1 vs 2.4 mg/dl, p < 0.001). In univariate analysis age, CVD comorbidities, pulse pressure, CRP, BMI, albumin, Mg, MIS and use of b-blockers or calcium blockers were LVH predictors. In multivariate analysis, Mg was an independent predictor of LVH, adjusted for age, MIS and b-blockers. Considering LV geometry, lower Mg levels were mainly correlated with concentric LVH.

CONCLUSION

Low serum magnesium levels seem to be an independent factor for LVH in hemodialysis and peritoneal dialysis patients.

Hypomagnesemia as a Risk Factor and Accelerator for Vascular Aging in Diabetes Mellitus and Chronic Kidney Disease

The age-old axiom that one is as old as his or her vessels are, calls for ongoing critical re-examination of modifiable risk factors of accelerated vascular ageing in chronic kidney diseases. Attempts to modulate vascular risk with cholesterol-lowering agents have largely failed in advanced chronic kidney disease (CKD). In addition to nitrogen waste products, many pathological biochemical processes also play a role in vascular calcification in chronic kidney damage. Magnesium, a cation vital for the body, may substantially reduce cardiovascular diseases' risk and progression. This narrative review aimed to address the relationship between hypomagnesemia and vascular calcification, which promotes further cardiovascular complications in diabetes, aging, and CKD. Articles with predefined keywords were searched for in the PubMed and Google Scholar databases with specific inclusion and exclusion criteria. We hypothesized that a decrease in serum magnesium levels contributes to increased vascular calcification and thereby increases cardiovascular mortality. In summary, based on existing evidence in the literature, it appears that simple and inexpensive oral magnesium supplementation may reduce the cardiovascular mortality of patients who are already severely affected by such diseases; in this context, the concept of 'normal' vs. 'ideal' serum magnesium levels should be carefully re-examined.

Preoperative hypomagnesemia as a possible predictive factor for postoperative increase of transvalvular pressure gradient in hemodialysis patients treated with transcatheter aortic valve implantation

BACKGROUND

Patients undergoing maintenance hemodialysis (HD) with severe aortic stenosis are at a high risk for bioprosthetic valve dysfunction after transcatheter aortic valve implantation (TAVI). Currently, preoperative factors that predict the occurrence of valve dysfunction after TAVI on HD patients remain to be elucidated. The aim of this study is to analyze the association between preoperative clinical factors and valve stenosis after TAVI on HD patients.

METHODS

Twenty-four of HD patients who underwent TAVI at our institution between April 2012 and January 2016 were analyzed. The mean aortic transvalvular pressure gradient (MPG) and effective orifice area index (EOAi) were assessed by serial echocardiography. Associations between preoperative clinical factors and time-series changes in MPG were examined using mixed-effects linear regression model for repeated measures.

RESULTS

Three patients developed severe structural valve deterioration with calcific valve stenosis requiring reoperation. A multivariate linear mixed-effects model showed that lower serum magnesium (sMg) levels were associated with the increase of MPG after TAVI (beta-coefficient = 0.019, p = 0.03). No correlation was observed with serum calcium, phosphorus, or intact parathyroid hormone. Time-series changes of MPG and EOAi had significant difference between lower and higher sMg group. All 3 of the patients who underwent reoperation showed lower preoperative sMgs.

CONCLUSION

Among bone-mineral metabolism markers, preoperative hypomagnesemia was associated with the increase of MPG after TAVI, suggesting that hypomagnesemia could predict post-TAVI valve dysfunction in HD patients. Further studies with larger sample sizes are warranted.

Association between hypomagnesemia and mortality among dialysis patients: a systematic review and meta-analysis

Background

Malnutrition-inflammation-atherosclerosis (MIA) syndrome is caused by the inflammatory cytokines in end stage renal disease (ESRD) patients, and MIA complex-related factors may be associated with hypomagnesemia and mortality. However, the association between serum magnesium level and mortality for dialysis patients is still not clear. Additionally, no meta-analysis has investigated the impact of serum magnesium on peritoneal dialysis and hemodialysis, separately.

Methods

We searched published studies in PubMed, Embase, Cochrane, Collaboration Central Register of Controlled Clinical Trials, and Cochrane Systematic Reviews through April 2022. Studies associated with serum magnesium and all-cause mortality or cardiovascular (CV) mortality in ESRD on kidney replacement therapy (KRT) patients were included. A hazard ratio (HR) with 95% confidence intervals (CI) was used to report the outcomes.

Results

Twenty-one studies involving 55,232 patients were included. Overall, there was a significant association between hypomagnesemia and all-cause mortality for dialysis patients (HR: 1.67, 95% CI [1.412-2.00], p < 0.001; certainty of evidence: moderate) using a mixed unadjusted and adjusted HR for analysis. There was also a significantly increased risk of CV mortality for individuals with hypomagnesemia compared with the non-hypomagnesemia group (HR 1.56, 95% CI [1.08-2.25], p < 0.001; certainty of evidence: moderate). In addition, a subgroup analysis demonstrated that hypomagnesemia was associated with a high risk of both all-cause mortality and CV mortality (all-cause mortality, HR:1.80, 95% CI [1.48-2.19]; CV mortality, HR:1.84, 95% CI [1.10-3.07]) in hemodialysis (HD) patients, but not in participants receiving peritoneal dialysis (PD; all-cause mortality, HR:1.26, 95% CI [0.84-1.91]; CV mortality, HR:0.66, 95% CI [0.22-2.00]). The systematic review protocol was prespecified and registered in PROSPERO [CRD42021256187].

Conclusions

Hypomagnesemia may be a significant risk factor for all-cause mortality and CV mortality in KRT patients, especially in those receiving hemodialysis. However, because of the limited certainty of evidence, more studies are required to investigate this association.

Associations between the serum magnesium and all-cause or cardiovascular mortality in chronic kidney disease and end-stage renal disease patients: A meta-analysis

BACKGROUND

Some studies have found that hypomagnesemia is associated with vascular calcification, atherosclerosis, and cardiovascular disease, which may lead to increased mortality in patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD) who need to maintain hemodialysis (HD). However, the conclusion of these studies remain controversial.

METHODS

Relevant literature was retrieved from the database of Cochrane library, PubMed, EMBASE, and CNKI until December 2020, without any language restrictions. The data was analyzed using the Stata 12.0 software.

RESULTS

A total of 31 studies were included, involving 205436 participants. The results showed that after multivariable adjusted, hypomagnesemia was significant associated with the risk of all-cause mortality in patients with CKD and end-stage renal disease (ESRD) (hazard ratios [HR] 1.955; 95% confidence interval (95% CI) 1.511-2.528; P = .000; hypomagnesemia vs normal magnesium or hypermagnesemia). In contrast, in patients with CKD and ESRD, hypermagnesemia was negatively correlated with all-cause mortality (HR 0.873; 95% CI 0.793-0.960; P = .005) (per unit increase). Moreover, in the adjusted model, it was observed that hypermagnesemia was significantly associated with a reduced risk of cardiovascular death (HR 0.598; 95% CI 0.094-1.102, P = .020). In addition, subgroup analysis found that hypomagnesemia was closely related to the increase of all-cause mortality in HD patients (HR 1.799; 95% CI 1.375-2.354; P = .000) (hypomagnesemia vs normal magnesium or hypermagnesemia).

CONCLUSION

Our results show that hypomagnesemia is significantly associated with cardiovascular and all-cause mortality in maintenance HD patients. Further studies should be conducted to evaluate the benefits of magnesium correction in maintenance dialysis patients with hypomagnesemia.

High Intakes of Bioavailable Phosphate May Promote Systemic Oxidative Stress and Vascular Calcification by Boosting Mitochondrial Membrane Potential-Is Good Magnesium Status an Antidote?

Chronic kidney disease is characterized by markedly increased risk for cardiovascular mortality, vascular calcification, and ventricular hypertrophy, and is associated with increased systemic oxidative stress. Hyperphosphatemia, reflecting diminished glomerular phosphate (Pi) clearance, coupled with a compensatory increase in fibroblast growth factor 23 (FGF23) secretion are thought to be key mediators of this risk. Elevated serum and dietary Pi and elevated plasma FGF23 are associated with increased cardiovascular and total mortality in people with normal baseline renal function. FGF23 may mediate some of this risk by promoting cardiac hypertrophy via activation of fibroblast growth factor receptor 4 on cardiomyocytes. Elevated serum Pi can also cause a profound increase in systemic oxidative stress, and this may reflect the ability of Pi to act directly on mitochondria to boost membrane potential and thereby increase respiratory chain superoxide production. Moreover, elevated FGF23 likewise induces oxidative stress in vascular endothelium via activation of NADPH oxidase complexes. In vitro exposure of vascular smooth muscle cells to elevated Pi provokes an osteoblastic phenotypic transition that is mediated by increased mitochondrial oxidant production; this is offset dose-dependently by increased exposure to magnesium (Mg). In vivo, dietary Mg is protective in rodent models of vascular calcification. It is proposed that increased intracellular Mg opposes Pi’s ability to increase mitochondrial membrane potential; this model could explain its utility for prevention of vascular calcification and predicts that Mg may have a more global protective impact with regard to the direct pathogenic effects of hyperphosphatemia.

Nutraceutical, Dietary, and Lifestyle Options for Prevention and Treatment of Ventricular Hypertrophy and Heart Failure

Although well documented drug therapies are available for the management of ventricular hypertrophy (VH) and heart failure (HF), most patients nonetheless experience a downhill course, and further therapeutic measures are needed. Nutraceutical, dietary, and lifestyle measures may have particular merit in this regard, as they are currently available, relatively safe and inexpensive, and can lend themselves to primary prevention as well. A consideration of the pathogenic mechanisms underlying the VH/HF syndrome suggests that measures which control oxidative and endoplasmic reticulum (ER) stress, that support effective nitric oxide and hydrogen sulfide bioactivity, that prevent a reduction in cardiomyocyte pH, and that boost the production of protective hormones, such as fibroblast growth factor 21 (FGF21), while suppressing fibroblast growth factor 23 (FGF23) and marinobufagenin, may have utility for preventing and controlling this syndrome. Agents considered in this essay include phycocyanobilin, N-acetylcysteine, lipoic acid, ferulic acid, zinc, selenium, ubiquinol, astaxanthin, melatonin, tauroursodeoxycholic acid, berberine, citrulline, high-dose folate, cocoa flavanols, hawthorn extract, dietary nitrate, high-dose biotin, soy isoflavones, taurine, carnitine, magnesium orotate, EPA-rich fish oil, glycine, and copper. The potential advantages of whole-food plant-based diets, moderation in salt intake, avoidance of phosphate additives, and regular exercise training and sauna sessions are also discussed. There should be considerable scope for the development of functional foods and supplements which make it more convenient and affordable for patients to consume complementary combinations of the agents discussed here. Research Strategy: Key word searching of PubMed was employed to locate the research papers whose findings are cited in this essay.

Low plasma magnesium concentration and future abdominal aortic calcifications in moderate chronic kidney disease

BACKGROUND

Higher plasma magnesium concentrations are associated with reduced cardiovascular disease risk in chronic kidney disease (CKD) patients. The importance of plasma magnesium concentration for vascular calcification in earlier stages of CKD remains underexplored. This study investigated whether plasma magnesium is a determinant for the presence and severity of vascular calcification in moderate CKD.

METHODS

Retrospective analysis was performed using abdominal aortic calcification (AAC) scores in 280 patients with stage 3 and 4 CKD enrolled in the MASTERPLAN trial. Lateral abdominal X-ray was used to evaluate AAC. Plasma magnesium concentration were measured over time. A zero-inflated Poisson model determined the association between plasma magnesium concentration and AAC.

RESULTS

79 out of 280 patients did not have AAC, and in patients with AAC the median calcification score was 3.5 (interquartile range: 0.0-8.6). The mean plasma magnesium concentration was 0.76 ± 0.10 mmol/L at baseline. A 0.1 mmol/L higher plasma magnesium concentration was associated with lower AAC of 0.07 point (95% CI -0.28 - 0.14). A 0.1 mmol/L higher plasma magnesium lowered the odds of detecting any AAC by 30% (OR = 0.63; 95% CI 0.29-1.37). After 1 year and 4 years (at time of X-ray) of follow-up this association was attenuated (OR = 0.93; 95% CI 0.61-1.43 and 0.93; 95% CI 0.60-1.45, respectively). None of these associations reached statistical significance.

CONCLUSIONS

Plasma magnesium concentration at baseline is not associated with the risk for future AAC. Interventions increasing magnesium to avoid vascular calcification may have greatest potential in early CKD stages prior to onset of vascular calcification.

Magnesium to prevent kidney disease-associated vascular calcification: crystal clear?

Vascular calcification is a prognostic marker for cardiovascular mortality in chronic kidney disease (CKD) patients. In these patients, magnesium balance is disturbed, mainly due to limited ultrafiltration of this mineral, changes in dietary intake and the use of diuretics. Observational studies in dialysis patients report that a higher blood magnesium concentration is associated with reduced risk to develop vascular calcification. Magnesium prevents osteogenic vascular smooth muscle cell transdifferentiation in in vitro and in vivo models. In addition, recent studies show that magnesium prevents calciprotein particle maturation, which may be the mechanism underlying the anti-calcification properties of magnesium. Magnesium is an essential protective factor in the calcification milieu, which helps to restore the mineral-buffering system that is overwhelmed by phosphate in CKD patients. The recognition that magnesium is a modifier of calciprotein particle maturation and mineralization of the extracellular matrix renders it a promising novel clinical tool to treat vascular calcification in CKD. Consequently, the optimal serum magnesium concentration for patients with CKD may be higher than in the general population.

The association between circulating magnesium and clinically relevant outcomes in patients with chronic kidney disease: A systematic review and meta-analysis

BACKGROUND & AIMS

Despite modern treatment, risk for cardiovascular disease and mortality in patients with chronic kidney disease (CKD) is unacceptably high. Observational studies have shown associations of magnesium with risk for several clinical outcomes in CKD of variable magnitude. The aim of this review is to provide a systematic overview and meta-analysis of longitudinal studies assessing the association of plasma magnesium concentration with clinically relevant outcomes in adult patients with chronic kidney disease, with a minimal follow-up of 6 months. Primary outcomes of interest were all-cause mortality, cardiovascular mortality, cardiovascular events, sudden death and hospitalisation.

METHODS

The electronic databases PubMed, Embase and The Cochrane Library were searched using terms relating to plasma magnesium and CKD patients, and two authors independently selected eligible studies. Study quality was assessed according to the Newcastle-Ottawa Scale. Results of studies with a comparable magnesium exposure and outcome measure, were pooled using a random-effects meta-regression analysis.

RESULTS

The search yielded 6156 records of which 33 studies, involving 348,059 patients, met the eligibility criteria. Finally, 22 studies could be included in the meta-analysis. Higher magnesium was associated with a lower risk for all-cause mortality (HR 0.90 [0.87-0.94] per 0.1 mmol/L increase of magnesium) and cardiovascular mortality and events (HR 0.85 [0.77-0.94] per 0.1 mmol/L).

CONCLUSIONS

Magnesium concentration is inversely associated with all-cause mortality and cardiovascular mortality and events. Therefore, increasing magnesium may improve risk in patients with chronic kidney disease. This meta-analysis forms a firm base for future prospective trials to test whether increasing plasma magnesium, indeed has beneficial effects on clinical outcomes.

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.

Prevention of hypomagnesemia in critically ill patients with acute kidney injury on continuous kidney replacement therapy: the role of early supplementation and close monitoring

Hypomagnesemia is a common electrolyte disorder in critically ill patients and is associated with increased morbidity and mortality risk. Many clinical conditions may contribute to hypomagnesemia through different pathogenetic mechanisms. In patients with acute kidney injury (AKI) the need for continuous or prolonged intermittent kidney replacement therapy (CKRT and PIKRT, respectively) may further add to other causes of hypomagnesemia, especially when regional citrate anticoagulation (RCA) is used. The basic principle of RCA is chelation of ionized calcium by citrate within the extracorporeal circuit, thus blocking the coagulation cascade. Magnesium, a divalent cation, follows the same fate as calcium; the amount lost in the effluent includes both magnesium-citrate complexes and the free fraction directly diffusing through the hemofilter. While increasing the magnesium content of dialysis/replacement solutions may decrease the risk of hypomagnesemia, the optimal concentration for the variable combination of solutions adopted in different KRT protocols has not yet been identified. An alternative and effective approach is based on including early intravenous magnesium supplementation in the KRT protocol, and close monitoring of serum magnesium levels, especially in the setting of RCA. Thus, strategies aimed at precisely tailoring both dialysis prescriptions and the composition of KRT fluids, as well as early magnesium supplementation and close monitoring, could represent a cornerstone in reducing KRT-related hypomagnesemia.

Magnesium and calciprotein particles in vascular calcification: the good cop and the bad cop

PURPOSE OF REVIEW

Vascular calcification is a major contributor to increased cardiovascular mortality in chronic kidney disease (CKD). Recently, calciprotein particles (CPP) were identified to drive the calcification process. CPP may explain the effects of high phosphate on vascular calcification. Magnesium is a promising novel therapeutic approach to halt vascular calcification, because it inhibits CPP maturation and is associated with reduced cardiovascular mortality in CKD. We aim to examine the current evidence for the role of CPP in the calcification process and to explain how magnesium prevents calcification.

RECENT FINDINGS

A recent meta-analysis concluded that reducing high phosphate levels in CKD patients does not associate with lowering cardiovascular mortality. Inhibition of CPP formation prevents phosphate-induced calcification in vitro. Consequently, delaying CPP formation and maturation may be a clinical approach to reduce calcification. Magnesium inhibits CPP maturation and vascular calcification. Clinical pilot studies suggest that magnesium is a promising intervention strategy against calcification in CKD patients.

SUMMARY

CPP induce vascular calcification and are modulated by serum phosphate and magnesium concentrations. Magnesium is a strong inhibitor of CPP maturation and therefore, a promising therapeutic approach to reduce vascular calcification in CKD. Currently, several studies are being performed to determine the clinical outcomes of magnesium supplementation in CKD.

High- and low-inpatients' serum magnesium levels are associated with in-hospital mortality in elderly patients: a neglected marker?

BACKGROUND

Altered serum magnesium (Mg) level in the human body has been hypothesized to have a role in the prediction of hospitalization and mortality; however, the reported outcomes are not conclusive.

AIMS

The present study aimed to analyze the relationship between serum Mg and in-hospital mortality (IHM) in patients admitted to the medical ward of two hospitals in the Veneto region (Italy).

METHODS

Patients > 18 years hospitalized in the medical wards of the hospitals of Vittorio Veneto and Conegliano, Italy (from January 12, 2011, through December 27, 2016) with at least one measurement of serum Mg were included in the study. A logistic regression model was used to assess the unadjusted and adjusted (by age, gender, Charlson Comorbidity index, discharge diagnosis' class) association of serum Mg and IHM.

RESULTS

In total 5024 patients were analyzed, corresponding to 6980 total admissions. The unadjusted analysis showed that IHM risk was significantly higher with 0.2 mg/dl incremental serum Mg level change from 2.4 mg/dl to 2.6, (OR 1.71 95% CI 1.55-1.89) and with 0.2 mg/dl change from serum Mg level of 1.4 mg/dl to 1.2 mg/dl, (OR 1.28 95% CI 1.17-1.40). Such results were confirmed at adjusted analysis.

DISCUSSION

Present findings have relevant implications for the clinical management of patients suffering from medical conditions, highlighting the need for analyzing Mg concentration carefully.

CONCLUSIONS

Serum Mg levels seem to be a good predictor of IHM.

Use of proton pump inhibitors is associated with an increase in adverse cardiovascular events in patients with hemodialysis: Insight from the kids registry

BACKGROUND

Proton pump inhibitors (PPIs) are known to increase the risk of mortality and cardiovascular events in the general population. However, in patients with maintenance hemodialysis, PPI effects are under investigated.

METHODS

We analyzed the risk of PPIs for cardiovascular events using the Kagoshima Dialysis (KIDS) registry, a prospective, multicenter, observational study in patients with maintenance hemodialysis in Japan.

RESULTS

In all, 531 patients were enrolled from June 2015 to December 2018. One-year follow-up data were available for 376 patients (Use of PPIs at baseline (PPI group): 217 patients and without PPIs (No PPI group): 159 patients). The incidence of a composite outcome (all-cause mortality, non-fatal myocardial infarction, or non-fatal stroke) was higher in patients in the PPI group than the No PPI group (15.2% vs. 4.4%; hazard ratio (HR): 3.65, 95% confidence interval (CI): 1.61-8.23, P = 0.002). In the multivariate analysis, even after adjustment for covariates, the use of PPIs was an independent risk factor for a composite outcome (HR: 2.38, 95% CI: 1.02-5.54, P = 0.045). We performed propensity score matching analysis as a sensitivity analysis, showing a consistent result. The incidence of bleeding showed no difference between the two groups (15.7% vs. 11.3%; HR: 1.46, 95% CI: 0.83-2.59, P = 0.19).

CONCLUSIONS

These results indicate that the use of PPIs in patients with maintenance hemodialysis might increase mortality and cardiovascular events without decreasing the risk of bleeding. Therefore, it should always be analyzed if a patient truly needs PPIs.

Long-term effects of citric acid-based bicarbonate haemodialysis on patient outcomes: a survival propensity score–matched study in western France

Background

Citric acid–based bicarbonate haemodialysis (CIT-HD) has gained more clinical acceptance over the last few years in France and is a substitute for other acidifiers [e.g. acetic acid (CH3COOH) and hydrochloric acid (HCl)]. This trend was justified by several clinical benefits compared with CH3COOH as well as the desire to avoid the consequences of the corrosive action of HCl, but a nationwide clinical report raised concerns about the long-term safety of CIT-HD. The aim of this study was to assess the long-term effects of CIT-HD exposure on patient outcomes in western France.

Methods

This is a population-based retrospective multicentre observational study performed in 1132 incident end-stage kidney disease patients in five sanitary territories in western France who started their renal replacement therapy after 1 January 2008 and followed up through 15 October 2018. Relevant data, collected prospectively with the same medical software, were anonymously aggregated for the purposes of the study. The primary goal of this study was to investigate the effects of citrate exposure on all-cause mortality. To provide a control group to CIT-HD one, propensity score matching (PSM) at 2:1 was performed in two steps: the first analysis was intended to be exploratory, comparing patients who received citrate ≤80% of the time (CIT-HD ≤80) versus those who received citrate &gt;80% of the time (CIT-HD &gt;80), while the second analysis was intended to be explanatory in comparing patients with 0% (CIT-HD0) versus 100% citrate time exposure (CIT-HD100).

Results

After PSM, in the exploratory part of the analysis, 432 CIT-HD ≤80 patients were compared with 216 CIT-HD &gt;80 patients and no difference was found for all-cause mortality using the Kaplan–Meier model (log-rank 0.97), univariate Cox regression analysis {hazard ratio [HR] 1.01 [95% confidence interval (CI) 0.71–1.40]} and multivariate Cox regression analysis [HR 1.11 (95% CI 0.76–1.61)] when adjusted for nine variables with clinical pertinence and high statistical relevance in the univariate analysis. In the explanatory part of the analysis, 316 CIT-HD0 patients were then compared with 158 CIT-HD100 patients and no difference was found using the Kaplan–Meier model (log-rank 0.06), univariate Cox regression analysis [HR 0.69 (95% CI 0.47–1.03)] and multivariate Cox regression analysis [HR 0.87 (95% CI 0.57–1.33)] when adjusted for seven variables with clinical pertinence and high statistical relevance in the univariate analysis.

Conclusions

Findings of this study support the notion that CIT-HD exposure ≤6 years has no significant effect on all-cause mortality in HD patients. This finding remains true for patients receiving high-volume online haemodiafiltration, a modality most frequently prescribed in this cohort.

Hypomagnesemia and Short-Term Mortality in Elderly Maintenance Hemodialysis Patients

Background

The relationship between magnesium and mortality in hemodialysis patients has been evaluated in several prospective studies, but few have assessed the risk of all-cause mortality in elderly hemodialysis patients. The aim of this study was to evaluate the association between magnesium levels and the risk of cardiovascular and overall mortality in elderly maintenance hemodialysis patients.

Methods

This was a retrospective study, and patients undergoing maintenance hemodialysis were screened for eligibility at a single dialysis center between July and December 2016. Patients were divided into two groups based on their magnesium levels: a low magnesium level group and a high magnesium level group. Associations between magnesium level and risk of cardiovascular and all-cause mortality were analyzed with a Cox proportional hazards regression model.

Results

In total, 413 patients were included with a median follow-up period of 12 months. We found that compared to patients with high magnesium levels, those with low magnesium levels had significantly lower levels of hemoglobin, urea, creatinine, uric acid, phosphate, potassium, chloride, albumin, and spKt/V (p < 0.05 for each parameter). There was a strong correlation between the baseline mean serum magnesium concentration 1 year prior and the concentration 1 year later (r² = 0.519, p < 0.001). After adjustment for confounding factors, multivariate Cox proportional hazards analysis showed hypomagnesemia to be an independent predictor of all-cause and cardiovascular mortality in chronic hemodialysis patients. Furthermore, subgroup analysis was performed, revealing that serum magnesium levels were still strongly associated with all-cause mortality and cardiovascular mortality in patients older than 60 years, with HR values of 0.020 (95% CI 0.001-0.415) and 0.010 (95% CI 0.000-0.491), respectively. In addition, there were still significant associations between the serum magnesium level and all-cause mortality and cardiovascular mortality in elderly dialysis patients at the 6-month follow-up visit.

Conclusion

Our study indicates that lower serum magnesium levels are strongly associated with cardiovascular and all-cause mortality in maintenance hemodialysis patients, especially in the short term and in those who are elderly. Factors affecting serum magnesium concentrations in hemodialysis patients should be investigated, and correcting hypomagnesemia may benefit elderly hemodialysis patients.

Reversal of phosphate-induced ORAI1 expression, store-operated Ca2+ entry and osteogenic signaling by MgCl2 in human aortic smooth muscle cells

In chronic kidney disease, renal phosphate retention leads to hyperphosphatemia with subsequent vascular osteogenic signaling and calcification. Osteogenic signaling involves up-regulation of the transcription factors CBFA1, MSX2, and SOX9, as well as alkaline phosphatase (ALP), an enzyme stimulating calcification by degrading the calcification inhibitor pyrophosphate. Stimulation of osteogenic signaling and calcification by phosphate donor β-glycerophosphate in human aortic smooth muscle cells (HAoSMCs) is attenuated by MgCl₂, an effect mimicked by Ca²⁺-sensing receptor agonist GdCl₃. Most recent observations revealed that the effect of β-glycerophosphate on osteogenic signaling requires ORAI1, a Ca²⁺-channel accomplishing store-operated Ca²⁺-entry (SOCE), which is stimulated by Ca²⁺-sensor STIM1. The present study explored whether ORAI1 and/or STIM1 expression and, thus, SOCE and osteogenic signaling in HAoSMCs are sensitive to MgCl₂ and/or GdCl₃. To this end, transcript levels were estimated using q-RT-PCR, protein abundance with western blotting, cytosolic Ca²⁺-concentration ([Ca²⁺]_i) by Fura-2-fluorescence, and SOCE from increase of [Ca²⁺]_i following re-addition of extracellular Ca²⁺ after store depletion with thapsigargin (1  μM). As a result, 24 h exposure to β-glycerophosphate (2 mM) significantly enhanced transcript levels of ORAI1 and STIM1 as well as SOCE, effects significantly blunted or virtually abrogated by 1.5 mM MgCl₂ and by 50  μM GdCl₃. In conclusion, MgCl₂ and GdCl₃ are powerful inhibitors of ORAI1 and STIM1 expression and store-operated Ca²⁺-entry, effects affecting osteogenic signalling in vascular smooth muscle cells.

The relationship between serum magnesium levels and mortality in non-diabetic hemodialysis patients: A 10-year follow-up study

Introduction Recently, although there are many reports showing that serum magnesium concentration is a predictor of mortality in dialysis patients, the observation periods of those reports were of short duration, typically around 12 months. Thus, we investigated this relationship over a longer follow-up period. Methods This retrospective, observational study included a total of 83 non-diabetic hemodialysis patients. The follow-up period was 120 months. Patients were divided into two groups, those with serum magnesium ≥2.5 mg/dL (Mg ≥2.5 mg/dL group) and serum magnesium <2.5 mg/dL (Mg <2.5 mg/dL group), and Kaplan-Meier analysis and Cox proportional hazards analysis were conducted. In addition to the above analysis, single and multiple regression analysis were performed at baseline to reveal the relationship between serum magnesium and clinical parameters. Findings During the follow-up period, 31 out of 83 patients died. Kaplan-Meier analysis showed a significantly higher incidence of death in the Mg <2.5 mg/dL group (log-rank test 4.951, P = 0.026). Multivariate Cox proportional hazards analysis showed a 62% decreased risk of mortality in the Mg ≥2.5 mg/dL group compared to the Mg <2.5 mg/dL group after adjustment for several confounding factors. Simple correlation coefficient analysis showed positive correlations of serum magnesium levels with serum creatinine, phosphorus, high-density lipoprotein, ankle-brachial index and KT/V, and a negative correlation with age. Multiple linear regression analysis showed that the ankle-brachial index was the only parameter that had a positive and significant correlation with the serum magnesium level. Conclusion Our study demonstrated that higher serum magnesium levels were associated with improved survival in non-diabetic hemodialysis patients.

Hypomagnesemia is not an independent risk factor for mortality in Japanese maintenance hemodialysis patients

PURPOSE

It is unclear whether hypomagnesemia is an independent risk factor or innocent bystander for mortality in maintenance hemodialysis (MHD) patients. Thus, we studied associations between hypomagnesemia and all-cause as well as cardiovascular (CV) mortality in MHD patients.

METHODS

Baseline clinical characteristics and coronary artery calcium score (CACS) of 353 Japanese MHD patients were reviewed. Three-year survival rate and mortality risk factors were assessed.

RESULTS

Median (interquartile range) age, dialysis vintage, serum magnesium (Mg), serum albumin and CACS of the subjects were 68 (60-78) years, 75 (32-151) months, 2.4 (2.2-2.7) mg/dl, 3.6 (3.3-3.8) g/dl, and 1181 (278-3190), respectively. During the 3-year period, 91 patients died. Kaplan-Meier overall 3-year survival rates were 59.0% in in patients with Mg < 2.4 mg/dl (n = 136) and 82.3% in patients with Mg ≥ 2.4 mg/dl (n = 217), (P < 0.0001). In Cox regression models not incorporating serum albumin, Mg < 2.4 mg/dl was significantly associated with 3-year all-cause death, independent of age, dialysis vintage, average ultrafiltration, Log (CACS + 1), warfarin use, serum potassium, high-sensitivity C-reactive protein (hsCRP), phosphate, uric acid, and intact parathyroid hormone [Hazard ratio (HR) 95% confidence interval (CI): 2.82 (1.31-6.29), P = 0.0078], and CV death, independent of age, dialysis vintage, Log (CACS + 1), warfarin use, serum hsCRP, and uric acid [HR (95% CI): 4.47 (1.45-16.76), P = 0.0086]. Nevertheless, associations of Mg < 2.4 mg/dl with all-cause and CV mortality were all absent in models that included serum albumin.

CONCLUSIONS

Hypomagnesemia is not an independent risk factor for mortality but is associated with malnutrition in MHD patients.

Baseline Serum Magnesium Level and Its Variability in Maintenance Hemodialysis Patients: Associations with Mortality

BACKGROUND/AIMS

The study aimed at investigating the impact of serum magnesium (Mg) baseline level and its variability on mortality in maintenance hemodialysis (MHD) patients.

METHODS

Eligible patients receiving regular MHD at Ningbo No. 2 Hospital between January 2009 and August 2016 were enrolled and follow-ups were conducted afterwards until death or transplantation. General information, laboratory results, and outcomes of subjects were collected. The relationship between baseline serum Mg level, its coefficient of variation (CV), and all-cause mortality and cardiovascular disease mortality were assessed, respectively. Subjects were divided into groups in 2 manners: by serum Mg level (lower Mg group: serum Mg <1.00 mmol/L, higher Mg group: serum Mg ≥1.00 mmol/L) and by serum Mg CV (high variation group: CV ≥0.149 mmol/L, middle variation group: 0.114 mmol/L ≤ CV < 0.149 mmol/L, and low variation group: CV <0.114 mmol/L).

RESULTS

169 MHD patients were recruited in the study, with mean serum Mg 1.00 ± 0.18 mmol/L, average age 60.20 ± 15.64 years, and median dialysis duration 37.00 (18.30, 77.97) months. During the follow-up, 69 (40.83%) patients died, 24 (34.78%) of which died due to cardiovascular disease. Comparing the two groups, patients in the lower Mg group had a higher all-cause mortality (50.00 vs. 29.33%, p = 0.007). The multivariate Cox regression analysis suggested that lower Mg level was an independent factor for all-cause mortality as well as cardiovascular mortality (HR = 13.268, 95% CI 6.234-28.237, p < 0.001; HR = 12.702, 95% CI 3.737-43.174, p < 0.001, respectively). However, there were no significant statistical differences of all-cause and cardiovascular mortality among these three groups concerning Mg variation. And in the univariate and multivariate Cox regression analysis, serum magnesium CV was not the independent factor for all-cause mortality and cardiovascular mortality.

CONCLUSIONS

The lower baseline serum magnesium level was associated with all-cause and cardiovascular mortality in MHD patients. However, the variability of magnesium level was not independently associated with the risk of death and further studies need to be conducted.

Serum magnesium, mortality, and cardiovascular disease in chronic kidney disease and end-stage renal disease patients: a systematic review and meta-analysis

BACKGROUND

Previous studies reported that magnesium deficiency was associated with vascular calcifications, atherosclerosis and cardiovascular disease, which might play an independent pathogenic role in chronic kidney disease (CKD) and end-stage renal disease (ESRD) patients. However, the results of these studies were somewhat underpowered and inconclusive.

METHODS

Literature was identified by searching PubMed, EMBASE, Web of Science and the Cochrane Central Register of Controlled Trials (CENTRAL). We included studies that investigated the association between serum magnesium with mortality risk in CKD and ESRD patients. Unadjusted and adjusted hazard ratios (HRs) with 95% confidence intervals (95% CIs) were pooled.

RESULTS

Twenty studies involving 200,934 participants were included, and the results showed that there was a strong association between hypomagnesemia and the risk of all-cause mortality in patients with CKD and ESRD (HR 1.32; 95% CI 1.19-1.47; p < 0.00001) (hypomagnesemia vs. normal magnesium or hypermagnesemia) after multivariable adjusted. On the contrary, hypermagnesemia was inversely associated with all-cause mortality in patients with CKD and ESRD (HR 0.86; 95% CI 0.79-0.94; p = 0.001) (per unit increase). Moreover, a significant association between hypermagnesemia and decreased risk of cardiovascular mortality was observed (HR 0.71; 95% CI 053-0.97, p = 0.03) in the adjusted model. In addition, subgroup analysis found that hypomagnesemia was strongly associated with increased all-cause mortality in hemodialysis patients (HR 1.29; 95% CI 1.12-1.50; p = 0.0005) (hypomagnesemia vs. normal magnesium or hypermagnesemia).

CONCLUSIONS

Our results indicate that hypomagnesemia is significantly associated with cardiovascular and all-cause mortality in patients with CKD and ESRD. Further studies evaluating benefits of magnesium correction in CKD and dialysis patients with hypomagnesemia should be performed.

Dual Roles of the Mineral Metabolism Disorders Biomarkers in Prevalent Hemodilysis Patients: In Renal Bone Disease and in Vascular Calcification

Background

Vascular calcification (VC) is highly prevalent in dialysis (HD) patients, and its mechanism is multifactorial. Most likely that systemic or local inhibitory factor is overwhelmed by promoters of VC in these patients. VC increased arterial stiffness, and left ventricular hypertrophy. Thus, the present study aimed to investigate the association of VC and myocardial remodeling and to analyze their relationship with VC promoters (fibroblast growth factor 23-FGF23, Klotho, intact parathormon-iPTH, vitamin D) in 56 prevalent HD patients (median values: age 54 yrs, HD vintage 82 months).

Methods

Besides routine laboratory analyzes, serum levels of FGF 23, soluble Klotho, iPTH, 1,25-dihydroxyvitamin D3; pulse wave velocity (PWV); left ventricular (LV) mass by ultrasound; and VCs score by Adragao method were measured.

Results

VC was found in 60% and LV concentric or eccentric hypertrophy in 50% patients. Dialysis vintage (OR 1.025, 95%CI 1.007–1.044, p=0.006) FGF23 (OR 1.006, 95% CI 0.992–1.012, p=0.029) and serum magnesium (OR 0.000, 95%CI 0.000–0.214, p=0.04) were associated with VC. Changes in myocardial geometry was associated with male sex (beta=-0.273, 95% CI -23.967 1.513, p=0.027), iPTH (beta 0.029, 95%CI -0.059–0.001, p=0.027) and vitamin D treatment (beta 25.49, 95%CI 11.325–39.667, p=0.001). Also, patients with the more widespread VC had the highest LV remodeling categories. PWV was associated patient’s age, cholesterol, diastolic blood pressure, LV mass (positively) and serum calcium (negatively), indicating potential link with atherosclerotic risk.

Conclusions

Despite to different risk factors for VC and myocardial remodeling, obtained results could indicate that risk factors intertwine in long-term treatment of HD patients and therefore careful and continuous correction of mineral metabolism disorders is undoubtedly of the utmost importance.

Magnesium: A Magic Bullet for Cardiovascular Disease in Chronic Kidney Disease?

Magnesium is essential for many physiological functions in the human body. Its homeostasis involves dietary intake, absorption, uptake and release from bone, swifts between the intra- and extracellular compartment, and renal excretion. Renal excretion is mainly responsible for regulation of magnesium balance. In chronic kidney disease (CKD), for a long time the general policy has been limiting magnesium intake. However, this may not be appropriate for many patients. The reference ranges for magnesium are not necessarily optimal concentrations, and risks for insufficient magnesium intake exist in patients with CKD. In recent years, many observational studies have shown that higher (in the high range of “normal” or slightly above) magnesium concentrations are associated with better survival in CKD cohorts. This review gives an overview of epidemiological associations between magnesium and overall and cardiovascular survival in patients with CKD. In addition, potential mechanisms explaining the protective role of magnesium in clinical cardiovascular outcomes are described by reviewing evidence from in vitro studies, animal studies, and human intervention studies with non-clinical endpoints. This includes the role of magnesium in cardiac arrhythmia, heart failure, arterial calcification, and endothelial dysfunction. Possible future implications will be addressed, which will need prospective clinical trials with relevant clinical endpoints before these can be adopted in clinical practice.

Magnesium: Are We Consuming Enough?

Magnesium is essential for maintaining normal cellular and organ function. In-adequate magnesium balance is associated with various disorders, such as skeletal deformities, cardiovascular diseases, and metabolic syndrome. Unfortunately, routinely measured serum magnesium levels do not always reflect total body magnesium status. Thus, normal blood magnesium levels eclipse the wide-spread magnesium deficiency. Other magnesium measuring methods, including the magnesium loading test, may provide more accurate reflections of total body magnesium status and thus improve identification of magnesium-deficient individuals, and prevent magnesium deficiency related complications.

Serum magnesium and cardiovascular mortality in peritoneal dialysis patients: a 5-year prospective cohort study

The aim of this study was to explore the association between serum Mg and cardiovascular mortality in the peritoneal dialysis (PD) population. This prospective cohort study included prevalent PD patients from a single centre. The primary outcome of this study was cardiovascular mortality. Serum Mg was assessed at baseline. A total of 402 patients (57 % male; mean age 49·3±14·9 years) were included. After a median of 49·9 months (interquartile range: 25·9-68·3) of follow-up, sixty-two patients (25·4 %) died of CVD. After adjustment for conventional confounders in multivariate Cox regression models, being in the lower quartile for serum Mg level was independently associated with a higher risk of cardiovascular mortality, with hazards ratios of 2·28 (95 % CI 1·04, 5·01), 1·41 (95 % CI 0·63, 3·16) and 1·62 (95 % CI 0·75, 3·51) for the lowest, second and third quartiles, respectively. A similar trend was observed when all-cause mortality was used as the study endpoint. Further analysis showed that the relationships between lower serum Mg and higher risk of cardiovascular and all-cause mortality were present only in the female subgroup, and not among male patients. The test for interaction indicated that the associations between lower serum Mg and cardiovascular and all-cause mortality differed by sex (P=0·008 and P=0·011, respectively). In conclusion, lower serum Mg was associated with a higher risk of cardiovascular and all-cause mortality in the PD population, especially among female patients.

Routine hemodialysis induces a decline in plasma magnesium concentration in most patients: a prospective observational cohort study

In hemodialysis patients, lower plasma magnesium (Mg) concentrations are associated with a higher overall and cardiovascular mortality. The optimal concentration appears to be above the reference range for the healthy population. Plasma Mg is not routinely measured after hemodialysis. Aim of this study was to determine the effect of routine hemodialysis on plasma Mg. Plasma Mg was measured in duplicate before (Mgpre) and after (Mgpost) dialysis in 6 consecutive hemodialysis sessions of 34 patients using a fixed 0.50 mmol/L dialysate Mg concentration. Mean Mgpre was 0.88 mmol/L (±0.14) and mean Mgpost was statistically significantly lower: mean intra-dialytic decline 0.10 mmol/L (95%-CI 0.06-0.13). A 0.10 mmol/L higher Mgpre was associated with a 0.03 mmol/L higher Mgpost (95%-CI 0.024-0.037). At a Mgpre of 0.74 mmol/L, Mgpost equalled Mgpre. There was an intra-dialytic decline of plasma Mg at higher Mgpre values and an increase at lower Mgpre values. In conclusion, in the majority of the hemodialysis patients, Mgpre concentrations are in the reference range of the healthy population, which may be too low for hemodialysis patients. Routine hemodialysis with the widely used 0.50 mmol/L dialysate Mg concentration, further declines magnesium in the majority of patients. Current dialysate Mg concentrations may be too low.

Current and potential therapeutic strategies for the management of vascular calcification in patients with chronic kidney disease including those on dialysis

Patients with CKD have accelerated vascular stiffening contributing significantly to excess cardiovascular morbidity and mortality. Much of the arterial stiffening is thought to involve vascular calcification (VC), but the pathogenesis of this phenomenon is complex, resulting from a disruption of the balance between promoters and inhibitors of calcification in a uremic milieu, along with derangements in calcium and phosphate metabolic pathways. Management of traditional cardiovascular risk factors to reduce VC may be influential but has not been shown to significantly improve mortality. Control of mineral metabolism may potentially reduce the burden of VC, although using conventional approaches of restricting dietary phosphate, administering phosphate binders, and use of active vitamin D and calcimimetics, remains controversial because recommended biochemical targets are hard to achieve and clinical relevance hard to define. Increasing time on dialysis is perhaps another therapy with potential effectiveness in this area. Despite current treatments, cardiovascular morbidity and mortality remain high in this group. Novel therapies for addressing VC include magnesium and vitamin K supplementation, which are currently being investigated in large randomized control trials. Other therapeutic targets include crystallization inhibitors, ligand trap for activin receptors and BMP-7. This review summarizes current treatment strategies and therapeutic targets for the future management of VC in patients with CKD.

Anion Gap as a Determinant of Ionized Fraction of Divalent Cations in Hemodialysis Patients

BACKGROUND AND OBJECTIVES

Circulating levels of anions that bind to magnesium and calcium are often altered in patients with CKD. However, it is unknown how these alterations affect the ionized fraction of magnesium and calcium.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This cross-sectional study involved patients on maintenance hemodialysis and patients not on dialysis who visited the outpatient department of nephrology. We collected whole-blood samples to measure ionized magnesium and calcium concentrations. Adjusted anion gap was calculated as an integrative index of unmeasured anions.

RESULTS

A total of 118 patients on hemodialysis and 112 patients not on dialysis were included. Although the prevalence of hypermagnesemia defined by total magnesium was much higher in patients on hemodialysis than in patients not on dialysis (69% versus 12%; P<0.001), the prevalence of hypermagnesemia defined by ionized magnesium did not differ significantly (13% versus 18%; P=0.28). Among patients on hemodialysis with high total magnesium, 83% had normal or low ionized magnesium. Consequently, the mean ionized fraction of magnesium in patients on hemodialysis was significantly lower than that in patients not on dialysis (51% versus 63%; P<0.001). Similarly, the mean ionized fraction of calcium in patients on hemodialysis was lower than that in patients not on dialysis (55% versus 56%; P<0.001). In patients on hemodialysis who had a higher adjusted anion gap than patients not on dialysis (mean [SD]: 14.1 [2.2] versus 5.1 [3.1]), the ionized fractions of magnesium and calcium were inversely associated with the adjusted anion gap. Furthermore, the anion gap significantly improved predictions of ionized magnesium and calcium in patients on hemodialysis.

CONCLUSIONS

Anions that accumulate in patients on hemodialysis contribute to the lower ionized fraction of magnesium and calcium. Equations that incorporate the anion gap provide better predictions of ionized magnesium and calcium in patients on hemodialysis.

Magnesium in Chronic Kidney Disease: Should We Care?

BACKGROUND

Magnesium (Mg) is an essential cation for multiple processes in the body. The kidney plays a major role in regulating the Mg balance. In a healthy individual, total-body Mg content is kept constant by interactions among intestine, bones and the kidneys.

SUMMARY

In case of chronic kidney disease (CKD), renal regulatory mechanisms may be insufficient to balance intestinal Mg absorption. Usually Mg remains normal; however, when glomerular filtration rate declines, changes in serum Mg are observed. Patients with end-stage renal disease on dialysis are largely dependent on the dialysate Mg concentration for maintaining serum Mg and Mg homeostasis. A low Mg is associated with several complications such as hypertension, and vascular calcification, and also associated with an increased risk for both cardiovascular disease (CVD) and non-CVD mortality. Severe hypermagnesaemia is known to cause cardiac conduction defects, neuromuscular effects and muscle weakness; a slightly elevated Mg has been suggested to be beneficial in patients with end-stage renal disease. Key Messages: The role of both low and high Mg, in general, but especially in relation to CKD and dialysis patients is discussed.

Therapeutic Interference With Vascular Calcification-Lessons From Klotho-Hypomorphic Mice and Beyond

Medial vascular calcification, a major pathophysiological process associated with cardiovascular disease and mortality, involves osteo-/chondrogenic transdifferentiation of vascular smooth muscle cells (VSMCs). In chronic kidney disease (CKD), osteo-/chondrogenic transdifferentiation of VSMCs and, thus, vascular calcification is mainly driven by hyperphosphatemia, resulting from impaired elimination of phosphate by the diseased kidneys. Hyperphosphatemia with subsequent vascular calcification is a hallmark of klotho-hypomorphic mice, which are characterized by rapid development of multiple age-related disorders and early death. In those animals, hyperphosphatemia results from unrestrained formation of 1,25(OH)₂D₃ with subsequent retention of calcium and phosphate. Analysis of klotho-hypomorphic mice and mice with vitamin D₃ overload uncovered several pathophysiological mechanisms participating in the orchestration of vascular calcification and several therapeutic opportunities to delay or even halt vascular calcification. The present brief review addresses the beneficial effects of bicarbonate, carbonic anhydrase inhibition, magnesium supplementation, mineralocorticoid receptor (MR) blockage, and ammonium salts. The case is made that bicarbonate is mainly effective by decreasing intestinal phosphate absorption, and that carbonic anhydrase inhibition leads to metabolic acidosis, which counteracts calcium-phosphate precipitation and VSMC transdifferentiation. Magnesium supplementation, MR blockage and ammonium salts are mainly effective by interference with osteo-/chondrogenic signaling in VSMCs. It should be pointed out that the, by far, most efficient substances are ammonium salts, which may virtually prevent vascular calcification. Future research will probably uncover further therapeutic options and, most importantly, reveal whether these observations in mice can be translated into treatment of patients suffering from vascular calcification, such as patients with CKD.

Serum magnesium concentrations and all-cause, cardiovascular, and cancer mortality among U.S. adults: Results from the NHANES I Epidemiologic Follow-up Study

BACKGROUND

Few studies have examined the associations of serum magnesium (Mg) concentrations with total and cause-specific mortality in a nationally representative sample of US adults. We investigate the dose-response relationships of baseline serum Mg concentrations with risk of mortalities in a large, nationally representative sample of US adults.

METHODS

We analyzed prospective data of 14,353 participants aged 25-74 years with measures of serum Mg concentrations at baseline (1971-1975) from the National Health and Nutrition Examination Survey I Epidemiologic Follow-up Study (NHEFS). Mortality data was linked through December 31, 2011. We estimated the mortality hazard ratios (HRs), for participants within serum Mg categories of <0.7, 0.7-0.74, 0.75-0.79, 0.8-0.89 (referent), 0.9-0.94, 0.95-0.99, and ≥1.0 mmol/L using weighted multivariate-adjusted Cox proportional hazards models.

RESULTS

During a median follow-up of 28.6 years, 9012 deaths occurred, including 3959 CVD deaths, 1923 cancer deaths, and 708 stroke deaths. The multivariate-adjusted HRs (95% CIs) of all-cause mortality across increasing categories of Mg were 1.34 (1.02, 1.77), 0.94 (0.75, 1.18), 1.08 (0.97, 1.19), 1.00 (referent), 1.05 (0.95, 1.16), 0.96 (0.79, 1.15), and 0.98 (0.76, 1.26). Similar trends were observed for cancer (HRs for serum Mg < 0.7: 1.39, 95% CI: 0.83, 2.32) and CVD mortality (HRs for serum Mg < 0.7: 1.28, 95% CI: 0.81, 2.02) but were not statistically significant. An elevated risk for stroke mortality was observed among participants with serum Mg < 0.70 mmol/L (HR: 2.55, 95% CI: 1.18, 5.48).

CONCLUSIONS

Very low serum Mg concentrations were significantly associated with an increased risk of all-cause mortality in US adults.

Reduced Mortality in Maintenance Haemodialysis Patients on High versus Low Dialysate Magnesium: A Pilot Study

Background: Although low magnesium levels have been associated with an increased mortality in dialysis patients, they are kept low by routinely-used dialysates containing 0.50 mmol/L magnesium. Thus, we investigated the impact of a higher dialysate magnesium concentration on mortality. Methods: 25 patients on high dialysate magnesium (HDM) of 0.75 mmol/L were 1:2 matched to 50 patients on low dialysate magnesium (LDM) of 0.50 mmol/L and followed up for 3 years with regards to all-cause and cardiovascular mortality. Patients were matched according to age, gender, a modified version of the Charlson Comorbidity Index (CCI), and smoking status. Results: During the follow-up period, five patients died in the HDM and 18 patients in the LDM group. Patients in the HDM group had significantly higher ionized serum magnesium levels than matched controls (0.64 ± 0.12 mmol/L vs. 0.57 ± 0.10 mmol/L, p = 0.034). Log rank test showed no difference between treatment groups for all-cause mortality. After adjustment for age and CCI, Cox proportional hazards regression showed that HDM independently predicted a 65% risk reduction for all-cause mortality (hazard ratio 0.35, 95% confidence interval [CI]: 0.13, 0.97). Estimated 3-year probability of death from a cardiovascular event was 14.5% (95% CI: 7.9, 25.8) in the LDM group vs. 0% in the HDM group. Log rank test found a significant group difference for cardiovascular mortality (χ² = 4.15, p = 0.042). Conclusions: Our data suggests that there might be a beneficial effect of an increased dialysate magnesium on cardiovascular mortality in chronic dialysis patients.

Hypomagnesemia and cause-specific mortality in hemodialysis patients: 5-year follow-up analysis

INTRODUCTION

The aim of this prospective study was to evaluate the association between serum magnesium (Mg) and mortality, in particular the cause-specific mortality of Mg and other risk factors in hemodialysis (HD) patients.

METHODS

We studied a cohort of 185 HD patients receiving thrice-weekly HD treatment, on a dialysate Mg concentration of 0.5 mmol/L. We stratified 3 patient groups according to the level of Mg: lower (<1.1 mmol/L), intermediate-reference (1.1 to <1.3 mmol/L), and higher (Mg >1.3 mm/L).

RESULTS

During the 5-year follow-up, 60 patients died, with cardiovascular (CV) disease as the predominant cause (73.3%). Hazard ratio (HR) for all-cause and CV mortality were 2.55 and 2.67 in the lower versus intermediate Mg group, but there was no significant association between the higher and intermediate Mg group. Univariate Cox regression analysis showed that Mg <1.1 versus 1.1-1.30 mml/L with HR 2.34, was a significant univariate predictor for increased mortality in addition to the Hb <110 g/L, Alb <40 g/L, C-reactive protein (CRP) ≥10 mg/L and brain natriuretic peptide >1,200 pg/mL. However, in the multivariate analysis only CRP ≥10 mg/L with HR 3.89 was a significant predictor of mortality. Subgroup analyses showed that among patients with CRP >10 mg/L, HR for all-cause and CV mortality of the lower versus intermediate Mg group were 1.96 and 2.39, respectively, not reaching significance for the higher versus intermediate Mg group. Conversely, there was no association between Mg level and all-cause and CV mortality within these 3 groups among patients with CRP <10 mg/L.

CONCLUSIONS

Lower serum Mg level was significantly associated with an increased all-cause and cardiovascular mortality in HD patients, especially in inflamed patients.

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.

Lower serum magnesium is associated with vascular calcification in peritoneal dialysis patients: a cross sectional study

BACKGROUND

Coronary artery calcification (CAC) is highly prevalent among dialysis patients and is associated with increased cardiovascular and all cause mortality. Magnesium (Mg) inhibits vascular calcification in animal and in-vitro studies but whether the same effect occurs in humans is uncertain.

METHODS

A single centre cross-sectional study of 80 prevalent peritoneal dialysis (PD) patients; on PD only for a minimum of 3 months. A radiologist blinded to patient status calculated their abdominal aortic calcification (AAC) scores on lateral lumbar spine radiographs, a validated surrogate for CAC.

RESULTS

Eighty patients provided informed consent and underwent lumbar spine radiography. The mean serum Mg was 0.8 mmol/L (standard deviation 0.2) and mean AAC score 8.9 (minimum 0, maximum 24). A higher serum Mg level was associated with a lower AAC score (R ² = 0.06, unstandardized coefficient [B] = -7.81, p = 0.03), and remained after adjustment for age, serum phosphate, serum parathyroid hormone, low-density lipoprotein cholesterol, smoking history, and diabetes (model adjusted R ² = 0.36, serum Mg and AAC score B = -11.44, p = 0.00). This translates to a 0.1 mmol/L increase in serum Mg being independently associated with a 1.1-point decrease in AAC score.

CONCLUSIONS

Our findings suggest that Mg may inhibit vascular calcification. If this association is replicated across larger studies with serial Mg and vascular calcification measurements, interventions that increase serum Mg and their effect on vascular calcification warrant further investigation in the PD population.

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.

Risk factors for mortality in patients undergoing hemodialysis: A systematic review and meta-analysis

BACKGROUND

No consensus exists regarding the factors influencing mortality in patients undergoing hemodialysis (HD). This meta-analysis aimed to evaluate the impact of various patient characteristics on the risk of mortality in such patients.

METHODS

PubMed, Embase, and Cochrane Central were searched for studies evaluating the risk factors for mortality in patients undergoing HD. The factors included age, gender, diabetes mellitus (DM), body mass index (BMI), previous cardiovascular disease (CVD), HD duration, hemoglobin, albumin, white blood cell, C-reactive protein (CRP), parathyroid hormone, total iron binding capacity (TIBC), iron, ln ferritin, adiponectin, apolipoprotein A1 (ApoA1), ApoA2, ApoA3, high-density lipoprotein (HDL), total cholesterol, hemoglobin A1c (HbA1c), serum phosphate, troponin T (TnT), and B-type natriuretic peptide (BNP). Relative risks with 95% confidence intervals were derived. Data were synthesized using the random-effects model.

RESULTS

Age (per 1-year increment), DM, previous CVD, CRP (higher versus lower), ln ferritin, adiponectin (per 10.0μg/mL increment), HbA1c (higher versus lower), TnT, and BNP were associated with an increased risk of all-cause mortality. BMI (per 1kg/m² increment), hemoglobin (per 1d/dL increment), albumin (higher versus lower), TIBC, iron, ApoA2, and ApoA3 were associated with reduced risk of all-cause mortality. Age (per 1-year increment), gender (women versus men), DM, previous CVD, HD duration, ln ferritin, HDL, and HbA1c (higher versus lower) significantly increased the risk of cardiac death. Albumin (higher versus lower), TIBC, and ApoA2 had a beneficial impact on the risk of cardiac death.

CONCLUSIONS

Multiple markers and factors influence the risk of mortality and cardiac death in patients undergoing HD.

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.

Oral Magnesium Supplementation in Chronic Kidney Disease Stages 3 and 4: Efficacy, Safety, and Effect on Serum Calcification Propensity-A Prospective Randomized Double-Blinded Placebo-Controlled Clinical Trial

Introduction

Chronic kidney disease (CKD) is associated with high cardiovascular morbidity and mortality. Recent evidence suggests that increases in both serum and intracellular magnesium (Mg) can slow or even prevent the development of vascular calcification seen in CKD. Serum calcification propensity (T₅₀) is a novel functional test, which is associated with all-cause mortality in CKD and measures the ability of serum to delay the formation of crystalline nanoparticles. Theoretically, increasing serum Mg should improve T₅₀ and thereby reduce the propensity towards ectopic calcification.

Methods

We conducted a randomized placebo-controlled double-blinded clinical trial to investigate the safety of 2 different doses of oral Mg supplementation in subjects with CKD stages 3 and 4 as well as their effects on intracellular Mg and T₅₀. Thirty-six subjects with CKD stages 3 and 4 were randomized to one of 3 groups (placebo, elemental Mg 15 mmol/d or elemental Mg 30 mmol/d) given as slow-release Mg hydroxide and followed for 8 weeks.

Results

Thirty-four subjects completed the trial. Intracellular Mg remained stable throughout the trial despite significant increases in both serum and urine Mg. T₅₀ increased significantly by 40 min from 256 ± 60 (mean ± SD) to 296 ± 64 minutes (95% confidence interval, 11-70, P < 0.05) in the Mg 30 mmol/d group after 8 weeks. No serious adverse events related to the study medication were reported during the study.

Discussion

Oral Mg supplementation was safe and well tolerated in CKD stages 3 and 4 and improved T₅₀, but did not increase intracellular Mg. Further studies are needed to investigate the long-term effects of Mg supplementation in CKD stage 3 and 4 and whether improvement in calcification propensity is related to clinical endpoints.

Clinical features of CKD-MBD in Japan: cohort studies and registry

Randomized controlled trials (RCTs) are essential for evidence-based medicine; however, cohort studies and registries provide an important information about risk factors and, hence, shed light on the target of laboratory parameters. The uniqueness of the current Japanese CKD-MBD guidelines lies in the lower target range of intact parathyroid hormone levels than those used in other countries, which is based on analyses of the nationwide Japan Renal Data Registry. Cohort studies were also useful in exploring risk factors of renal outcome in predialysis patients. It was revealed that low vitamin D status (very prevalent in Japan) and high fibroblast growth factor 23 (FGF23) levels predict poor renal outcome. The reported association of FGF23 levels with left ventricular hypertrophy (LVH) and heart failure observed in cohort studies may support the idea of adding the 4th component of CKD-MBD, namely, "LVH" to the three original components. When it is not feasible to conduct RCTs regarding intervention, we have no choice but to rely on observational studies with sophisticated analysis methods, such as facility-level analysis and marginal structural model minimizing indication bias. Observational studies conducted in Japan revealed that the side effects of medications for CKD-MBD, resultant compliance, and effective doses in terms of hard outcome in Japanese patients were found to be different from those in other countries. For example, the MBD-5D study confirmed the benefit of cinacalcet in terms of mortality despite its median dose of only 25 mg/day. These data are very helpful for future guidelines specific to Japanese patients with CKD.