Chronic Kidney Disease-Mineral Bone Disorder in the Elderly Peritoneal Dialysis Patient

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.

Review of Isoflavones and Their Potential Clinical Impacts on Cardiovascular and Bone Metabolism Markers in Peritoneal Dialysis Patients

Cardiovascular disease is the most important cause of mortality in patients with chronic kidney disease, including patients undergoing peritoneal dialysis. Oxidative stress, systemic and vascular inflammation, and lipid abnormalities are important causes of cardiovascular disease in these patients. Bone disorders are also a common complication in dialysis patients and can lead to bone fractures, decreased quality of life, vascular calcification, cardiovascular disease, and increased mortality. Studies in non-uremic populations have shown that soy isoflavones have beneficial effects on oxidative stress, inflammation, lipid abnormalities, and markers of bone metabolism; however, very few studies in this field have been conducted with peritoneal dialysis patients. This paper reviews the key data regarding the effects of soy isoflavones on cardiovascular disease and bone markers and discusses the role of this nutraceutical in preventing and managing the complications of peritoneal dialysis.

Relationship between Residual Urine Output and Type of Dialysis with FGF23 Levels

Several studies investigated the role of fibroblast growth factor 23 (FGF23) in the regulation of renal phosphate excretion in chronic kidney disease (CKD). However, patients with residual urine output (UO) seem to control their serum phosphorus levels better. Our aim was to determine whether FGF23 levels are influenced by dialysis modality and UO. We performed a cross-sectional study in hemodialysis (HD) and peritoneal dialysis (PD) patients. The C-terminal FGF23 (cFGF23) levels were determined in plasma with a two-site enzyme-linked immunosorbent assay. The UO collection referred to an mL/day measurement. All p values were two-sided, and the statistical significance was set at p < 0.05. We enrolled 133 patients (58 HD, 75 PD, UO 70%). The median cFGF23 was significantly higher in HD vs. PD patients (p = 0.0017) and not significantly higher in patients without UO (p = 0.12). We found a negative correlation between cFGF23 and the UO volume (p = 0.0250), but the correlation was not significant when considering the type of dialysis treatment. Phosphorus (ß = 0.21677; p = 0.0007), type of dialysis (ß = −0.68392; p = 0.0003), and creatinine (ß = 0.08130; p = 0.0133) were significant and independent predictors of cFGF23 levels. In conclusion, cFGF23 was significantly higher in HD than in PD patients. We found a significant negative correlation between cFGF23 and the residual UO volume, but the correlation was not significant considering the type of dialysis. Our study reveals that dialysis modality is an independent predictor of FGF23 levels. In particular, PD is associated with lower FGF23 levels than HD.

To evaluate the relationship between serum magnesium and parathyroid hormone levels in peritoneal dialysis and hemodialysis patients

OBJECTS

This study aimed to determine the relationship between magnesium and PTH levels in peritoneal dialysis (PD) and hemodialysis (HD) patients.

METHODS

This cross-sectional study was performed on HD and PD patients in Kerman, Iran. After recording demographic and clinical data, the pre-dialysis levels of hemoglobin, 25-hydroxy vitamin D, ferritin, creatinine, calcium, phosphorus, albumin, PTH, and magnesium were measured for all patients. The P value of less than 0.05 was considered statistically significant.

RESULTS

Magnesium levels in PD patients were significantly higher than in HD patients (P < 0.001). The median PTH level in PD patients was significantly lower than in HD patients (P = 0.046). The correlation between PTH and serum magnesium levels was not significant in PD or HD patients. In the regression model, dialysis modality (PD or HD) was the only significant variable in determining serum magnesium levels (P = 0.005).

CONCLUSION

Magnesium is a neglected ion in peritoneal dialysis and hemodialysis patients. In dialysis centers that use a dialysate with standard magnesium concentration (0.5 mmol/L in HD and 0.75 mmol/L in PD), special attention is necessary to hypomagnesia and its complications because magnesium levels in PD patients were significantly higher than in HD patients. As the correlation between magnesium and PTH levels in both PD and HD patients were not significant, the association of high magnesium levels with low PTH in PD patients should be considered in terms of increasing the potential for adynamic bone disease. It seems that ordering serum magnesium in the routine tests of dialysis patients is necessary.

Estimating serum-ionized magnesium concentration in hemodialysis patients

INTRODUCTION

Cardiovascular mortality is significantly increased in kidney failure with replacement therapy (KFRT) patients, which is partly mediated by enhanced vascular calcification. Magnesium appears to have anticalcifying capabilities, and hypomagnesemia has been associated with increased mortality in KFRT patients. Ionized magnesium represents the biologically and physiologically active form. As serum ionized magnesium (Mg_ion ) is difficult to assess in clinical routine estimating equations derived from routinely assessed laboratory parameters could facilitate medical treatment.

METHODS

We developed equations to estimate serum Mg_ion using linear regression analysis in 191 hemodialysis (HD) patients. Reference test was measured ionized magnesium (Mg_ion ). As index tests, we chose estimated Mg_ion using total magnesium (Mg_tot ) and other laboratory and demographic variable candidates. Equations were internally validated, using 749 subsequent Mg_ion measurements.

FINDINGS

The median patient age was 65 years, 67.5% of the patients were male. Median (interquartile range [IQR]) measured Mg_ion was 0.64 [0.57, 0.72] mmol/L, 11 (6%) patients were hypo- (i.e., <0.45 mmol/L) and 127 (66%) were hypermagnesemic (>0.60 mmol/L). The final equation at the end of the development process included Mg_tot , serum ionized, and total calcium concentrations. In the validation dataset, bias (i.e., median difference between measured and estimated Mg_ion , -0.017 [-0.020, -0.014] mmol/L) and precision (i.e., IQR of bias 0.043 [0.039, 0.047] mmol/L) were small, 90% [88, 93] of estimated values were ±10% of measured values. The equation detected normomagnesemia with overall good diagnostic accuracy (area under the receiver-operating curve 0.91 [0.89, 0.93]).

DISCUSSION

Mg_ion can be estimated from equations containing routinely assessed laboratory variables with high accuracy and good overall performance. These equations might simplify the assessment of ionized magnesium levels in the individual hemodialysis patients and help the treating physician to guide the overall treatment.

Effects of isoflavones on bone turnover markers in peritoneal dialysis patients: a randomized controlled trial

PURPOSE

The aim of this study was to investigate the effects of soy isoflavones on serum markers of bone formation and resorption in peritoneal dialysis (PD) patients.

METHODS

In this randomized, double-blind, placebo-controlled trial, 40 PD patients were randomly assigned to either the soy isoflavone or the placebo group. The patients in the soy isoflavone group received 100 mg soy isoflavones daily for 8 weeks, whereas the placebo group received corresponding placebos. At baseline and the end of the 8th week, 7 ml of blood was obtained from each patient after a 12- to 14-h fast and serum concentrations of bone formation markers (osteocalcin and bone alkaline phosphatase), bone resorption markers [N-telopeptide and receptor activator of nuclear factor kappa B ligand (RANKL)], and osteoprotegerin as an inhibitor of bone resorption were measured.

RESULTS

Serum N-telopeptide concentration decreased significantly up to 27% in the soy isoflavone group at the end of week 8 compared to baseline (P = 0.003). Also, serum RANKL concentration reduced significantly up to 17% in the soy isoflavone group at the end of week 8 compared to baseline (P = 0.03). These bone resorption markers did not significantly change in the placebo group during the study. There were no significant differences between the two groups in mean changes of serum osteocalcin, bone alkaline phosphatase, and osteoprotegerin.

CONCLUSION

This study indicates that daily administration of 100 mg soy isoflavone supplement to PD patients reduces serum N-telopeptide and RANKL which are two bone resorption markers. CLINICALTRIALS.GOV: NCT03773029, 2018.

Mineral and bone disorder in hemodialysis patients in the Tibetan Plateau: a multicenter cross-sectional study

Background: Mineral and bone disorder (MBD) in hemodialysis patients is associated with increased morbidity and mortality. Studies on the MBD status of hemodialysis patients at high altitudes are extremely limited.

Methods: A total of 146 hemodialysis patients from 5 local hospitals across all districts with hemodialysis centers in the Tibetan Plateau were enrolled in this cross-sectional study. Parameters related to MBD, including serum phosphorus (P), calcium (Ca), and intact parathyroid hormone (iPTH) levels, were measured. The achievement of MBD goals was compared with the achievement in the Dialysis Outcomes and Practice Study (DOPPS) 3, DOPPS 4 and a multicenter study of MBD in China. Factors associated with hyperphosphatemia were examined.

Results: Altogether, 146 hemodialysis patients were recruited from the Tibetan Plateau. According to the K/DIGO guidelines, there were low achievement rates for serum Ca (40.4%), P (29.7%), and iPTH (47.1%). As for the (KDOQI) guidelines, the rates of achievement of defined targets were 38.4%, 33.7% and 16.4% for serum Ca, P and iPTH, respectively. The percentages of patients reaching the KDOQI targets for corrected Ca, P, and iPTH were significantly lower for Tibetan patients than the percentages found in DOPPS 3 (38.4% vs. 50.4%, 33.7% vs. 49.8%, and 16.4% vs. 31.4%, respectively, all p < .001) and DOPPS 4 (38.4% vs. 56.0%, 33.7% vs. 54.5%, and 16.4% vs. 35.3%, respectively, all p < .001). The percentage of patients reaching the KDOQI targets for iPTH was significantly lower in Tibet than in the plain areas of China (16.4% vs. 26.5%, p < .001). The proportion of patients with hypocalcemia was higher in Tibet than in the plain areas (44.5% vs. 19.4%, p < .001). The percentage of local patients with optimal P was significantly higher for patients with an activated vitamin D prescription than for patients without an activated vitamin D prescription (45.3% vs. 19.3%, p < .001). Age and the activated vitamin D prescription were independently associated with hyperphosphatemia.

Conclusion: The MBD status of hemodialysis patients in Tibet is far from the ideal level. High altitude is one of the possible causes of the differences found, but not the principal one. It is necessary for medical staff in Tibet to improve the detection and treatment of MBD.

Long-term effects on PTH and mineral metabolism of 1.25 versus 1.75 mmol/L dialysate calcium in peritoneal dialysis patients: a meta-analysis

Background

This study aimed to compare 1.25 and 1.75 mmol/L dialysate calcium for their effects on parathyroid hormone (PTH) and mineral metabolism in peritoneal dialysis (PD).

Methods

The PubMed, Cochrane Library, and EmBase databases were searched from inception to October 2016. Methodological quality assessment of the included studies was performed using the risk of bias tool of the Review Manager software. The meta-analysis was carried out with the Stata12.0 software. Subgroup analysis was performed by study design [randomized controlled trial (RCT) and non-RCT]. Odds ratios or standardized mean differences were used to assess the outcome measures, including intact parathyroid hormone (i-PTH) levels, serum total calcium amounts, ionized calcium levels, phosphate concentrations, and peritonitis episodes.

Results

Seven studies were enrolled in the synthesized analysis, including 4 RCTs and 3 non-RCTs. All studies compared 1.25 mmol/L and 1.75 mmol/L dialysate calcium for PD. Pooled analysis revealed that 1.75 mmol/L dialysate calcium significantly reduced i-PTH levels compared with the 1.25 mmol/L dose in PD patients. However, 1.25 mmol/L dialysate calcium was superior to the 1.75 mmol/L dose in decreasing the levels of serum total calcium and ionized calcium in PD patients. No significant differences in phosphate amounts and peritonitis episodes were observed between the two groups.

Conclusion

These findings indicated that 1.75 mmol/L dialysate calcium is more appropriate for PD patients with secondary hyperparathyroidism. Meanwhile, 1.25 mmol/L dialysate calcium is more favorable to PD patients with secondary hypercalcemia. However, further well-designed and high-quality studies are required to validate these findings.