Correlation of coronary artery calcification with pre-hemodialysis bicarbonate levels in patients on hemodialysis

The intermediate-conductance calcium-activated potassium channel KCa3.1 contributes to alkalinization-induced vascular calcification in vitro

OBJECTIVE

In order to find new strategies for the prevention of vascular calcification in uremic individuals especially treated by dialysis and develop novel therapeutic targets in vascular calcification, we explore the role of KCa3.1 in alkalinization-induced VSMCs calcification in vitro.

METHOD

Rat VSMCs calcification model was established by beta-glycerophosphate (β-GP, 10 mM) induction. The pH of Dulbecco's modified Eagle's medium (DMEM) was adjusted every 24 h with 10 mM HCl or 10 mM NaHCO3 . The mineralization was measured by Alizarin Red staining and O-cresolphthalein complex one method. mRNA and protein expression were detected by RT-PCR and Western blot or immunofluorescence. Ca2+ influx was measured by Elisa.

RESULT

The results indicated that alkalization induced an increase in Ca2+ influx to enhance VSMCs calcification. Furthermore, the increase of calcification was associated with the expression of KCa3.1 via advanced expression of osteoblastic differentiation markers alkaline phosphatase (ALP) and Runt-related transcription factor 2 (Runx2). Blocking KCa3.1 with TRAM-34 or shRNA vector can significantly lowered the effects of calcification in the activity of ALP and Runx2 expression.

CONCLUSION

Together all, our studies suggested that alkalinization can promote vascular calcification by upregulating KCa3.1 channel and enhancing osteogenic/chondrogenic differentiation by upregulating Runx2. The specific inhibitor TRAM-34 and KCa3.1-shRNA ameliorated VSMCs calcification by downregulating KCa3.1.

Metabolic acidosis is associated with pulse wave velocity in chronic kidney disease: Results from the KNOW-CKD Study

Metabolic acidosis is common in chronic kidney disease (CKD) and may have various deleterious consequences. Arterial stiffness in CKD patients is associated with poor cardiovascular outcomes. The present study aimed to evaluate the association between serum bicarbonate and arterial stiffness using the baseline cross-sectional data set of a large-scale Korean CKD cohort. 2,238 CKD patients were enrolled in the KoreaN Cohort Study for Outcome in Patients With Chronic Kidney Disease (KNOW-CKD) from 2011 to 2016. The present study was conducted on 1,659 patients included in this cohort with baseline serum bicarbonate and brachial-to-ankle pulse wave velocity (baPWV) data. Metabolic acidosis was defined as a serum bicarbonate level of <22 mmol/L, and baPWV was used as a surrogate of arterial stiffness. Mean serum bicarbonate was 25.8 ± 3.6 mmol/L. 210 (12.7%) patients had metabolic acidosis. baPWV was significantly higher in patients with metabolic acidosis (P < 0.001) and showed a significant inverse correlation with serum bicarbonate (Unstandardized β −16.0 cm/sec; 95% CI −20.5, −11.4; P < 0.001) in an unadjusted model, which was retained after adjustment (Unstandardized β −5.4 cm/sec; 95% CI −9.9, −1.0; P = 0.017). Metabolic acidosis was found to be associated with a high baPWV in pre-dialysis CKD patients.

Modifying Phosphate Toxicity in Chronic Kidney Disease

Phosphate toxicity is a well-established phenomenon, especially in chronic kidney disease (CKD), where hyperphosphatemia is a frequent occurrence when CKD is advanced. Many therapeutic efforts are targeted at phosphate, and comprise dietary intervention, modifying dialysis schemes, treating uncontrolled hyperparathyroidism and importantly, phosphate binder therapy. Despite all these interventions, hyperphosphatemia persists in many, and its pathological influence is ongoing. In nephrological care, a somewhat neglected aspect of treatment-when attempts fail to lower exposure to a toxin like phosphate-is to explore the possibility of "anti-dotes". Indeed, quite a long list of factors modify, or are mediators of phosphate toxicity. Addressing these, especially when phosphate itself cannot be sufficiently controlled, may provide additional protection. In this narrative overview, several factors are discussed that may qualify as either such a modifier or mediator, that can be influenced by other means than simply lowering phosphate exposure. A wider scope when targeting phosphate-induced comorbidity in CKD, in particular cardiovascular disease, may alleviate the burden of disease that is the consequence of this potentially toxic mineral in CKD.

Risks and Benefits of Sodium Polystyrene Sulfonate for Hyperkalemia in Patients on Maintenance Hemodialysis

Background

Concerns about sodium overload when using sodium polystyrene sulfonate (Na-resin) as an ion-exchange resin for the treatment of hyperkalemia led our institution to gradually shift to the use of calcium polystyrene sulfonate (Ca-resin). However, as serum potassium levels were insufficiently controlled and patients experienced constipation, we returned to using Na-resin and observed better results than previously.

Objective

As few papers have examined the potassium adsorption ability of Ca-resin compared with Na-resin, we investigated this issue within our institution.

Methods

We studied potassium adsorption in patients who switched from Ca-resin to an equivalent amount of Na-resin (change group). We also investigated the incidence of sodium loading with Na-resin, including in patients newly commencing Na-resin treatment (new start group).

Results

Mean (± standard deviation) serum potassium levels decreased significantly, from 5.5 ± 0.6 to 4.9 ± 0.6 mEq/l in the change group and from 5.9 ± 0.4 to 4.7 ± 0.6 mEq/l in the new start group. No changes were observed in blood pressure, weight gain or serum sodium levels in the change group, but serum sodium levels in the new start group increased significantly, from 137.4 ± 2.3 to 139.0 ± 2.5 mEq/l, although they remained within the normal range.

Conclusions

Our results indicate that Na-resin exhibited an advantage in treating hyperkalemia when used in small amounts. However, when prescribing an ion-exchange resin at a higher dose, physicians should select the type and amount of resin according to the sodium and/or calcium load in each case.

Cardiovascular Events in Hemodialysis Patients: Challenging against Vascular Calcification

Particularly in patients with hemodialysis, cardiovascular mortality rate is extremely high. Polyvascular diseases develop at an early stage of chronic kidney disease (CKD). Pathophysiology includes insulin resistance and/or imbalance between nitric oxide (NO) and endothelin bioavailability as well as oxidative stress. The understanding in pathophysiology of vascular calcification and strategic treatment is a critical issue to achieve favorable outcome for the patients with CKD. In this article, we aim to review the cardiovascular disease for the patients with CKD with a particular emphasis on the clinical aspects of polyvascular disease. Finally, we address to detect microcirculatory impairment and eradicate vascular calcification as early as possible prior to renal replacement therapy. (This is a translation of Jpn J Vasc Surg 2016; 25: 359-365.).

Blood Calcification Propensity, Cardiovascular Events, and Survival in Patients Receiving Hemodialysis in the EVOLVE Trial

BACKGROUND AND OBJECTIVES

Patients receiving hemodialysis are at risk of cardiovascular events. A novel blood test (T50 test) determines the individual calcification propensity of blood.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

T50 was determined in 2785 baseline serum samples of patients receiving hemodialysis enrolled in the Evaluation of Cinacalcet Therapy to Lower Cardiovascular Events (EVOLVE) trial and the T50 results were related to patient outcomes.

RESULTS

Serum albumin, bicarbonate, HDL cholesterol, and creatinine were the main factors positively/directly and phosphate was the main factor negatively/inversely associated with T50. The primary composite end point (all-cause mortality, myocardial infarction [MI], hospitalization for unstable angina, heart failure, or peripheral vascular event [PVE]) was reached in 1350 patients after a median follow-up time of 619 days. After adjustments for confounding, a lower T50 was independently associated with a higher risk of the primary composite end point as a continuous measure (hazard ratio [HR] per 1 SD lower T50, 1.15; 95% confidence interval [95% CI], 1.08 to 1.22; P<0.001). Furthermore, lower T50 was associated with a higher risk in all-cause mortality (HR per 1 SD lower T50, 1.10; 95% CI, 1.02 to 1.17; P=0.001), MI (HR per 1 SD lower T50, 1.38; 95% CI, 1.19 to 1.60; P<0.001), and PVE (HR per 1 SD lower T50, 1.22; 95% CI, 1.05 to 1.42; P=0.01). T50 improved risk prediction (integrated discrimination improvement and net reclassification improvement, P<0.001 and P=0.001) of the primary composite end point.

CONCLUSIONS

Blood calcification propensity was independently associated with the primary composite end point, all-cause mortality, MI, and PVE in the EVOLVE study and improved risk prediction. Prospective trials should clarify whether T50-guided therapies improve outcomes.

Metabolic acidosis status and mortality in patients on the end stage of renal disease

BACKGROUND AND OBJECTIVES

Uncorrected metabolic acidosis leads to higher death risk in dialysis patients. We observed the relationship between metabolic acidosis status and mortality rate in patients on renal replacement therapy during a median follow up time of 60 months.

METHODS

We studied 76 patients on an on-line hemodiafiltration. The dialysis adequacy was defined by Kt/V for urea. The Framingham risk score (FRS) points were used to determine the 10-year risk for coronary heart disease. We examined the impact of high or low serum bicarbonate concentrations on mortality rate and on 10-year risk for coronary heart disease via the Kaplan-Meier method. Cox's model was used to evaluate a combination of prognostic variables, such as dialysis adequacy defined by Kt/V for urea, age and serum bicarbonate concentrations.

RESULTS

We divided the enrolled patients in three groups according to serum bicarbonate concentrations (< 20 mmol/L, 20-22 mmol/L and > 22 mmol/L). Kaplan-Meier survival curve for the impact of serum bicarbonate concentrations on overall mortality was found significant (log-rank = 7.8, P = 0.02). The prevalence of serum bicarbonate less or more than 20 mmol/L on high FRS (> 20%) by Kaplan-Meier curve was also found significant (log-rank = 4.9, P = 0.02). Cox's model revealed the significant predictive effect of serum bicarbonate on overall mortality (P = 0.006, OR = 1.5, 95% CI = 1.12-1.98) in combination to Kt/V for urea and age.

CONCLUSION

Uncorrected severe metabolic acidosis, defined by serum bicarbonate concentrations less than 20 mmol/L, is associated with a 10-year risk for coronary heart disease more than 20% and high overall mortality in patients on renal replacement therapy.

Correlation between serum parathyroid hormone levels and coronary artery calcification in patients without renal failure

The aim of the present study was to investigate the correlation between serum parathyroid hormone (PTH) levels and coronary artery calcification (CAC) in patients without renal failure, as well as to determine independent risk factors of CAC score (CACS). A total of 157 patients who underwent coronary computed tomography angiographic examination at the 101th Hospital of the People's Liberation Army between December 2013 and February 2015 were retrospectively evaluated. The correlation between PTH levels and CACS was determined using a Pearson correlation analysis. A receiver operating characteristic (ROC) curve was drawn to determine the best cutoff PTH level for prediction of CAC. The independent association between serum PTH levels and CAC was analyzed by using a logistic regression analysis model with the response variable Be binary class. The results revealed that PTH levels in patients in the CAC group were significantly higher than those of patients in the non-calcification group. PTH levels were positively correlated with CACS (r=0.288, P<0.001). The ROC curve suggested that a PTH level of ≥31.05 pg/ml was the best cut-off point for the prediction of CAC, with a sensitivity of 80.88%, specificity of 60.67% and an area under the curve of 0.761. After including predictive factors for CAC (gender, age, smoking status, diabetes, hypertension, hyperlipidemia, body mass index, glomerular filtration rate and calcium, phosphorus, calcium-phosphorus product, magnesium, PTH, total cholesterol, low-density lipoprotein cholesterol, triglyceride, high-density lipoprotein cholesterol and C-reactive protein levels), the odds ratio of the serum PTH levels regarding the prediction of CAC was 1.050 (95% confidence interval, 1.027-1.074; P<0.001). In conclusion, the present study suggested that serum PTH levels are correlated with CAC in patients without renal failure and may thus be used as a reliable predictor of CAC.

High Parathyroid Hormone Level and Osteoporosis Predict Progression of Coronary Artery Calcification in Patients on Dialysis

Coronary artery calcifications (CACs) are observed in most patients with CKD on dialysis (CKD-5D). CACs frequently progress and are associated with increased risk for cardiovascular events, the major cause of death in these patients. A link between bone and vascular calcification has been shown. This prospective study was designed to identify noninvasive tests for predicting CAC progression, including measurements of bone mineral density (BMD) and novel bone markers in adult patients with CKD-5D. At baseline and after 1 year, patients underwent routine blood tests and measurement of CAC, BMD, and novel serum bone markers. A total of 213 patients received baseline measurements, of whom about 80% had measurable CAC and almost 50% had CAC Agatston scores>400, conferring high risk for cardiovascular events. Independent positive predictors of baseline CAC included coronary artery disease, diabetes, dialysis vintage, fibroblast growth factor-23 concentration, and age, whereas BMD of the spine measured by quantitative computed tomography was an inverse predictor. Hypertension, HDL level, and smoking were not baseline predictors in these patients. Three quarters of 122 patients completing the study had CAC increases at 1 year. Independent risk factors for CAC progression were age, baseline total or whole parathyroid hormone level greater than nine times the normal value, and osteoporosis by t scores. Our results confirm a role for bone in CKD-associated CAC prevalence and progression.

Pathophysiologic Changes in Extracellular pH Modulate Parathyroid Calcium-Sensing Receptor Activity and Secretion via a Histidine-Independent Mechanism

The calcium-sensing receptor (CaR) modulates renal calcium reabsorption and parathyroid hormone (PTH) secretion and is involved in the etiology of secondary hyperparathyroidism in CKD. Supraphysiologic changes in extracellular pH (pHo) modulate CaR responsiveness in HEK-293 (CaR-HEK) cells. Therefore, because acidosis and alkalosis are associated with altered PTH secretion in vivo, we examined whether pathophysiologic changes in pHo can significantly alter CaR responsiveness in both heterologous and endogenous expression systems and whether this affects PTH secretion. In both CaR-HEK and isolated bovine parathyroid cells, decreasing pHo from 7.4 to 7.2 rapidly inhibited CaR-induced intracellular calcium (Ca(2+)i) mobilization, whereas raising pHo to 7.6 potentiated responsiveness to extracellular calcium (Ca(2+)o). Similar pHo effects were observed for Ca(2+)o-induced extracellular signal-regulated kinase phosphorylation and actin polymerization and for L-Phe-induced Ca(2+)i mobilization. Intracellular pH was unaffected by acute 0.4-unit pHo changes, and the presence of physiologic albumin concentrations failed to attenuate the pHo-mediated effects. None of the individual point mutations created at histidine or cysteine residues in the extracellular domain of CaR attenuated pHo sensitivity. Finally, pathophysiologic pHo elevation reversibly suppressed PTH secretion from perifused human parathyroid cells, and acidosis transiently increased PTH secretion. Therefore, pathophysiologic pHo changes can modulate CaR responsiveness in HEK-293 and parathyroid cells independently of extracellular histidine residues. Specifically, pathophysiologic acidification inhibits CaR activity, thus permitting PTH secretion, whereas alkalinization potentiates CaR activity to suppress PTH secretion. These findings suggest that acid-base disturbances may affect the CaR-mediated control of parathyroid function and calcium metabolism in vivo.

Acid-base balance in uremic rats with vascular calcification

Background/Aims

Vascular calcification (VC), a major complication in humans and animals with chronic kidney disease (CKD), is influenced by changes in acid-base balance. The purpose of this study was to describe the acid-base balance in uremic rats with VC and to correlate the parameters that define acid-base equilibrium with VC.

Methods

Twenty-two rats with CKD induced by 5/6 nephrectomy (5/6 Nx) and 10 nonuremic control rats were studied.

Results

The 5/6 Nx rats showed extensive VC as evidenced by a high aortic calcium (9.2 ± 1.7 mg/g of tissue) and phosphorus (20.6 ± 4.9 mg/g of tissue) content. Uremic rats had an increased pH level (7.57 ± 0.03) as a consequence of both respiratory (PaCO₂ = 28.4 ± 2.1 mm Hg) and, to a lesser degree, metabolic (base excess = 4.1 ± 1 mmol/l) derangements. A high positive correlation between both anion gap (AG) and strong ion difference (SID) with aortic calcium (AG: r = 0.604, p = 0.02; SID: r = 0.647, p = 0.01) and with aortic phosphorus (AG: r = 0.684, p = 0.007; SID: r = 0.785, p = 0.01) was detected.

Conclusions

In an experimental model of uremic rats, VC showed high positive correlation with AG and SID.