Inflammation, mineral metabolism and progressive coronary artery calcification in patients on haemodialysis

Pathophysiology and Clinical Impacts of Chronic Kidney Disease on Coronary Artery Calcification

The global prevalence of chronic kidney disease (CKD) has increased in recent years. Adverse cardiovascular events have become the main cause of life-threatening events in patients with CKD, and vascular calcification is a risk factor for cardiovascular disease. Vascular calcification, especially coronary artery calcification, is more prevalent, severe, rapidly progressive, and harmful in patients with CKD. Some features and risk factors are unique to vascular calcification in patients with CKD; the formation of vascular calcification is not only influenced by the phenotypic transformation of vascular smooth muscle cells, but also by electrolyte and endocrine dysfunction, uremic toxin accumulation, and other novel factors. The study on the mechanism of vascular calcification in patients with renal insufficiency can provide a basis and new target for the prevention and treatment of this disease. This review aims to illustrate the impact of CKD on vascular calcification and to discuss the recent research data on the pathogenesis and factors involved in vascular calcification, mainly focusing on coronary artery calcification, in patients with CKD.

IL-6 Is Associated with Progression of Coronary Artery Calcification and Mortality in Incident Dialysis Patients

INTRODUCTION

Inflammation is important in the pathogenesis of atherosclerosis. Elevated interleukin-6 (IL-6) is associated with cardiovascular events and also predicts mortality in individuals with CKD. Our goal was to determine the association between IL-6, FGF23, and high-sensitivity C-reactive protein (hsCRP) on coronary artery calcification (CAC) progression and mortality in incident dialysis patients without prior coronary events.

METHODS

A prospective cohort of incident adult dialysis participants had CAC measured by ECG-triggered multislice CT scans at baseline and at least 12 months later. Lipids, mineral metabolism markers, FGF23, and inflammatory markers, such as IL-6 and hsCRP, were measured at the baseline visit.

RESULTS

Participants in the high IL-6 tertile had the highest baseline CAC score (133.25 [10.35-466.15]) compared to the low (0.25 [0-212.2]) and intermediate (29.55 [0-182.85]) tertiles. Almost half of the participants with high IL-6 (15 of 32 [46.9%]) experienced progression of CAC compared to participants with low (8 of 32 [25%]) and intermediate (9 of 32 [28.1%]) (p = 0.05) IL-6 levels. Each log increase in IL-6 was associated with increase in death (hazard ratio 2.2, 95% CI: 1.2-3.8; p = 0.01). After adjusting for smoking, age, gender, race, diabetes, phosphate, and baseline calcium score, IL-6 (log) was associated with 2.2 times (95% CI: 1.1-4.6; p = 0.03) increase in death.

CONCLUSION

IL-6 is associated with progression of CAC and mortality in incident dialysis patients.

Gender-Related Differences in Chronic Kidney Disease-Associated Vascular Calcification Risk and Potential Risk Mediators: A Scoping Review

Vascular calcification (VC) involves the deposition of calcium apatite in vascular intima or media. Individuals of advanced age, having diabetes mellitus or chronic kidney disease (CKD) are particularly at risk. The pathogenesis of CKD-associated VC evolves considerably. The core driver is the phenotypic change involving vascular wall constituent cells toward manifestations similar to that undergone by osteoblasts. Gender-related differences are observed regarding the expressions of osteogenesis-regulating effectors, and presumably the prevalence/risk of CKD-associated VC exhibits gender-related differences as well. Despite the wealth of data focusing on gender-related differences in the risk of atherosclerosis, few report whether gender modifies the risk of VC, especially CKD-associated cases. We systematically identified studies of CKD-associated VC or its regulators/modifiers reporting data about gender distributions, and extracted results from 167 articles. A significantly higher risk of CKD-associated VC was observed in males among the majority of original investigations. However, substantial heterogeneity exists, since multiple large-scale studies yielded neutral findings. Differences in gender-related VC risk may result from variations in VC assessment methods, the anatomical segments of interest, study sample size, and even the ethnic origins of participants. From a biological perspective, plausible mediators of gender-related VC differences include body composition discrepancies, alterations involving lipid profiles, inflammatory severity, diversities in matrix Gla protein (MGP), soluble Klotho, vitamin D, sclerostin, parathyroid hormone (PTH), fibroblast growth factor-23 (FGF-23), and osteoprotegerin levels. Based on our findings, it may be inappropriate to monotonously assume that male patients with CKD are at risk of VC compared to females, and we should consider more background in context before result interpretation.

Cardiovascular Risk Factors in Peritoneal Dialysis Patients Revisited

End-stage renal disease patients are at a heightened risk of developing cardiovascular disease, with contributions from both “traditional” and “nontraditional” cardiovascular risk factors. Some of the nontraditional risk factors, such as extracellular volume overload, inflammation, and hyperphosphatemia, have also been shown to be important predictors of mortality in the dialysis population. This article provides an in-depth review of the evidence that supports the substantial contributions of nontraditional risk factors to adverse cardiovascular outcomes in chronic peritoneal dialysis patients. In addition, it provides evidence to demonstrate how loss of residual renal function may be central to the development of cardiovascular disease in the peritoneal dialysis population.

The Progression and Impact of Vascular Calcification in Peritoneal Dialysis Patients

Background

Progression of coronary artery calcification (CAC) has been described in hemodialysis patients, and severe CAC has been associated with the occurrence of cardiovascular events in this population. Little information is available regarding peritoneal patients.

Aim

To prospectively evaluate peritoneal dialysis patients in order to identify the variables associated with the rate of CAC progression, as well as to determine the impact that baseline CAC has on clinical outcomes over a 1-year follow-up period.

Methods

Using multislice coronary tomography, calcium scores were estimated at baseline and after 12 months in 49 peritoneal dialysis patients. Patients with and without CAC progression were compared with respect to clinical characteristics and biochemical variables, including lipid profile, parameters of mineral metabolism, and markers of inflammation. Cardiovascular events, hospitalizations, and all-cause mortality were recorded.

Results

At baseline, 29 patients (59%) presented CAC and a median calcium score of 234.7 (range 10.3 – 2351) Agatston units. Progression of CAC was observed in 13 patients (43%) who, in comparison with those presenting no CAC progression, were older, presented higher baseline calcium scores, and had higher mean glucose levels, lower mean high density lipoprotein cholesterol levels, and more months using low calcium peritoneal solution. We also observed a trend toward more often presenting with a history of hypertension, exhibiting more hyperphosphatemic and hyperglycemic events, and having lower albumin levels. In multiple logistic regression, only baseline calcium score was independently associated with progression of CAC. A shorter cardiovascular event-free time and a trend toward lower survival rates were observed in the group with CAC. Hospitalization event-free time did not differ between the groups.

Conclusion

Determining CAC provides important prognostic data in peritoneal dialysis patients. Baseline calcium score and disturbances in glucose, mineral, and lipid metabolism were indicative of higher risk of CAC progression in this population.

The “Heart” of Peritoneal Dialysis: Residual Renal Function

The CANUSA study originally reported the importance of total small-solute clearance in predicting survival of peritoneal dialysis (PD) patients. However, subsequent reanalysis of data from the CANUSA study clearly demonstrated that the predictive power for mortality in PD patients was largely attributable to residual renal function (RRF) and not to the dose of PD. While this should not lead to the assumption that the dose of PD is unimportant, it does clearly indicate that the contribution of residual renal clearance and PD clearance to the overall survival of PD cannot be considered equivalent. In a previous study, we also demonstrated the importance of loss of RRF in predicting a heightened risk of mortality and cardiovascular death in PD patients. In this review, we focus our discussion on the different potential mechanisms that explain the important link between RRF and cardiovascular disease and survival of PD patients. We provide evidence to explain why RRF is so important to patients receiving long-term PD treatment and why it should be regarded as the “heart” of PD.

Effect of spironolactone on the progression of coronary calcification in peritoneal dialysis patients: a pilot study

INTRODUCTION

There is evidence that aldosterone plays a role in the pathogenesis of vascular calcification. The aim of this study was to evaluate the effect of spironolactone, a mineralocorticoid receptor antagonist, on the progression of coronary calcification (CC) in peritoneal dialysis patients and to identify the factors involved in this progression.

METHODS

Thirty-three patients with a coronary calcium score (CCS) ≥ 30, detected through multi-detector computed tomography (MDCT) and expressed in Agatston units, were randomly assigned to a group receiving 25mg spironolactone per day for 12 months (spironolactone group) and a control group not receiving this drug. The primary outcome was a percentage change in CCS from baseline to end of the study (relative progression), when a further MDCT was conducted. Patients who had progression of CC were compared with those who did not progress.

RESULTS

Sixteen patients, seven in the spironolactone group and nine in the control group, concluded the study. The relative progression of the CCS was similar in both groups, 17.2% and 27.5% in the spironolactone and control groups respectively. Fifty-seven percent of the treated patients and 67% of those in the control group presented progression in the CC scores (p = 0.697). Progressor patients differed from non-progressors because they presented higher levels of calcium and low-density lipoprotein cholesterol and lower levels of albumin.

CONCLUSION

In peritoneal dialysis patients, spironolactone did not attenuate the progression of CC. However, large-scale studies are needed to confirm this observation. Disorders of mineral metabolism and dyslipidemia are involved in the progression of CC.

A Randomized Trial of Magnesium Oxide and Oral Carbon Adsorbent for Coronary Artery Calcification in Predialysis CKD

BACKGROUND

Developing strategies for managing coronary artery calcification (CAC) in patients with CKD is an important clinical challenge. Experimental studies have demonstrated that magnesium inhibits vascular calcification, whereas the uremic toxin indoxyl sulfate aggravates it.

METHODS

To assess the efficacy of magnesium oxide (MgO) and/or the oral carbon adsorbent AST-120 for slowing CAC progression in CKD, we conducted a 2-year, open-label, randomized, controlled trial, enrolling patients with stage 3-4 CKD with risk factors for CAC (diabetes mellitus, history of cardiovascular disease, high LDL cholesterol, or smoking). Using a two-by-two factorial design, we randomly assigned patients to an MgO group or a control group, and to an AST-120 group or a control group. The primary outcome was percentage change in CAC score.

RESULTS

We terminated the study prematurely after an interim analysis with the first 125 enrolled patients (of whom 96 completed the study) showed that the median change in CAC score was significantly smaller for MgO versus control (11.3% versus 39.5%). The proportion of patients with an annualized percentage change in CAC score of ≥15% was also significantly lower for MgO compared with control (23.9% versus 62.0%). However, MgO did not suppress the progression of thoracic aorta calcification. The MgO group's dropout rate was higher than that of the control group (27% versus 17%), primarily due to diarrhea. The percentage change in CAC score did not differ significantly between the AST-120 and control groups.

CONCLUSIONS

MgO, but not AST-120, appears to be effective in slowing CAC progression. Larger-scale trials are warranted to confirm these findings.

De novo Cardiac Valve Calcification after Hemodialysis in End-Stage Renal Disease Patients Predicts Future Cardiovascular Events: A Longitudinal Cohort Study

BACKGROUND

Cardiac valve calcification (CVC) in maintenance hemodialysis patients is associated with adverse cardiovascular outcomes. However, whether de novo CVC in incident hemodialysis patients predicts future cardiovascular events is unknown.

METHODS

This study included 174 patients newly receiving hemodialysis without CVC as reflected by echocardiography between January 2005 and December 2014. De novo CVC was determined with echocardiography once every 6 months until December 2016.

RESULTS

The median follow-up was 66 months (range, 19-141). De novo CVC developed in 80 out of 174 (45.98%) subjects: 58 developed aortic valve calcification (AVC) alone, 42 developed mitral valve calcification (MVC) alone, and 20 developed both AVC and MVC. The median time from baseline to de novo CVC was 46 months (range, 3-120) for AVC and 50 months (range, 13-127) for MVC. Patients who developed CVC had a higher major adverse cardiovascular events (MACE) rate than those who did not (AVC: 30/58 [51.72%] vs. 23/116 [19.83%]; MVC: 25/42 [59.52%] vs. 28/132 [21.21%]). Multivariate time-dependent Cox regression showed an association between MACE with both de novo AVC and MVC (AVC: hazard ratio [HR] 3.2, 95% confidence interval [CI] 1.55-6.63; MVC: HR 5.95, 95% CI 2.90-12.20).

CONCLUSIONS

De novo CVC is an independent risk factor for MACE in hemodialysis patients, and regular CVC screening among hemodialysis patients without preexisting CVC may be helpful to identify patients at increased risk of adverse cardiovascular outcomes.

Comparison of Limus-Eluting and Paclitaxel-Eluting Stents for Coronary Intervention in Patients with Chronic Kidney Disease

Chronic kidney disease (CKD) patients have worse adverse cardiovascular outcomes after percutaneous coronary intervention (PCI). Clinical outcomes comparing a limus-eluting stent (LES) to a paclitaxel-eluting stent (PES) in patients with CKD remain controversial.A systematic search was conducted using PubMed, EMBASE, and Cochrane Library. A pooled odds ratio (OR) and 95% confidence interval (CI) were used to calculate original data. We conducted heterogeneity, quality assessment, and publication bias analyses.A total of 17 trials involving 10,724 patients were included. No significant differences were found regarding target vessel revascularization, target lesion revascularization (TLR), stent thrombosis (ST), myocardial infarction (MI), all-cause mortality, and major adverse cardiac events (MACE) between first-generation LES implantation and PES implantation. Second-generation LES implantation was associated with lower rates of all-cause mortality (OR, 0.56; 95% CI, 0.39-0.82; P = 0.003), MACE (OR, 0.61; 95% CI, 0.38-0.97; P = 0.04), and ST (OR, 0.45; 95% CI, 0.26-0.77; P = 0.004) compared with PES implantation. In all, the long-term all-cause mortality rate was significantly lower after LES implantation than after PES implantation in patients with CKD (OR, 0.78; 95% CI, 0.66-0.93; P = 0.004). However, second-generation LES implantation resulted in a higher rate of TLR (OR, 2.23; 95% CI, 1.53-3.25; P < 0.001) than PES implantation in dialysis patients.In patients with CKD, first-generation LES and PES implantation had comparable mortality and morbidity. Second-generation LES implantation was superior to PES in reducing long-term mortality, MACE, and ST. However, PES may be more effective than LES in dialysis patients.

First-generation versus second-generation drug-eluting stents in patients with chronic kidney disease: a systematic review and meta-analysis

BACKGROUND

Chronic kidney disease (CKD) patients are associated with very high rate of adverse cardiovascular outcomes after drug-eluting stents (DES) implantation. The clinical outcomes of second-generation DES versus first-generation DES in CKD patients remain controversial.

OBJECTIVE

The aim of the current study was to perform a systematic review and meta-analysis to assess the safety and efficacy of second-generation DES versus first-generation DES in CKD patients.

METHODS

A systematical search of databases of PubMed, EMBASE, and Cochrane Library was conducted for eligible studies comparing the clinical outcomes of first-generation DES versus second-generation DES. Sirolimus-eluting and paclitaxel-eluting stents were classified as first-generation DES, and everolimus-eluting, zotarolimus-eluting, and biolimus-eluting stent (BES) were classified as second-generation DES. A pooled odds ratio (OR) and 95% confidence interval (CI) were used to summary the estimates. Heterogeneity, subgroup analysis, sensitivity analysis and publication bias were also performed.

RESULTS

We identified 14 trials involving 9,542 patients with CKD undergoing percutaneous coronary intervention. First-generation DES implantation was associated with higher risk of long-term all-cause mortality (OR, 1.31; 95% CI, 1.02-1.69; P = 0.04; I² = 0%), in stent restenosis (OR, 1.69; 95% CI, 1.14-2.49; P = 0.008; I² = 49%) and stent thrombosis (OR, 1.64; 95% CI, 1.00-2.69; P = 0.05; I² = 49%) compared with second-generation DES implantation. First-generation DES and second-generation DES showed similar efficacy in decreasing risk of repeat revascularization, myocardial infarction (MI), or major adverse cardiac events (MACE) between first-generation and second-generation DES implantation.

CONCLUSIONS

In CKD patients, the use of second-generation DES was associated with lower risk of long-term all-cause mortality, in stent restenosis and stent thrombosis as compared with first-generation DES. No differences were found regarding repeat revascularization, MI, and MACE.

Is progression of coronary artery calcification influenced by modality of renal replacement therapy? A systematic review

BACKGROUND

Progression of coronary artery calcification is an important marker for cardiovascular morbidity in end-stage renal disease patients. Therefore, we reviewed the evidence on coronary artery calcification progression in different renal replacement therapies.

METHODS

MEDLINE (PubMed), Embase and TRIP databases were searched from 1999 - 2016. Additionally, bibliographies were searched by hand and citation tracking of key publications was performed. Prospective studies were included that examined coronary artery calcification with two or more multislice computed tomography scans ≥6 months apart in patients 18-75 years old receiving any renal replacement therapy, including kidney transplantation. Reporting of separate scores for different modalities was required. Two researchers extracted data independently with pilot-tested forms and assessed the risk of bias using a validated tool.

RESULTS

We identified 29 eligible studies that assessed coronary artery calcification progression in end-stage renal disease patients, of which 19 studies evaluated haemodialysis and 8 kidney transplantation. Evidence on progression in peritoneal dialysis (three studies) and nocturnal haemodialysis (one study) was limited. Meta-analysis was not possible due to diverse reporting methods of coronary artery calcification scores and definitions of progression. Median coronary artery calcification scores were considerably higher in haemodialysis cohorts at baseline, presumably due to a generally higher age and dialysis vintage. Median coronary artery calcification progressed universally. Visual inspection suggested the least progression in kidney transplant recipients.

CONCLUSIONS

There is insufficient evidence to compare the influence of renal replacement therapies on coronary artery calcification progression. We advocate the adoption of a standardized reporting method of coronary artery calcification progression.

Activation of the mTORC1 pathway by inflammation contributes to vascular calcification in patients with end-stage renal disease

BACKGROUND

Chronic inflammation plays an important role in the progression of vascular calcification (VC). This study was designed to explore the effects and underlying mechanisms of inflammation on VC in the radial arteries of patients with end-stage renal disease (ESRD) with arteriovenostomy.

METHODS

Forty-eight ESRD patients were divided into control (n = 25) and inflammation groups (n = 23) according to plasma C-reactive protein (CRP) level. Surgically removed tissues from the radial arteries of patients receiving arteriovenostomy were used in this study. Alizarin Red S staining was used to examine calcium deposition. The expression of inflammation markers, bone structure-associated proteins and mammalian target of rapamycin complex1 (mTORC1) pathway-related proteins was assessed by immunohistochemical staining.

RESULTS

The expression of tumor necrosis factor-α (TNF-α) and monocyte chemotactic protein-1 (MCP-1) was increased in the radial arteries of the inflammation group. Additionally, Alizarin Red S staining revealed a marked increase in calcium deposition in the inflammation group compared to controls. Further analysis by immunohistochemical staining demonstrated that the deposition was correlated with the increased expression of bone-associated proteins such as bone morphogenetic proteins-2 (BMP-2) and osteocalcin and collagen I, which suggested that inflammation induces osteogenic differentiation in vascular tissues and that osteogenic cells are the main cellular components involved in VC. Interestingly, there was a parallel increase in the expression of phosphorylated mTOR (p-mTOR) and pribosomal protein S6 kinase 1 (p-S6K1) in the inflammation group. Furthermore, mTORC1 pathway-related proteins were significantly associated with the enhanced expression of bone formation biomarkers.

CONCLUSIONS

Inflammation contributed to VC in the radial arteries of ESRD patients via the induction of osteogenic differentiation in vessel walls, which could be regulated by the activation of the mTORC1 pathway.

Vascular calcification is not related to serum fetuin-A and osteopontin levels in hemodialysis patients

INTRODUCTION

Vascular calcification (VC) in hemodialysis (HD) patients is a sign of severe cardiovascular disease and can predict cardiovascular outcomes. Fetuin-A and osteopontin (OPN) inhibit VC. Serum fetuin-A levels are lower in patients with end-stage kidney disease (ESKD) and in those who are on chronic HD therapy. However, there are limited data concerning OPN in patients who are on dialysis. The aim of our study was to determine VC in HD patients, the relationship between VC and 25-OH-vitamin D, fetuin-A, and OPN levels, and independent predictors of VC.

MATERIALS AND METHODS

Ninety-three patients with ESKD on HD therapy were recruited. Among these patients, 44 were male and 49 were female. The patient group was compared with a group of 20 healthy controls of similar age and sex. A plain radiograph of the hand was taken using a mammography machine for the evaluation of VC. Serum fetuin-A, OPN, and 25-OH-vitamin D levels of both patients and controls were measured.

RESULTS

VC was detected in 45 (48.4%) HD patients. When patients were compared with healthy controls, fetuin-A levels (p < 0.029) were significantly lower in patients, whereas OPN (p < 0.000) and VC (p < 0.002) were significantly higher in the patient group. Age [odds ratio (OR) 1.036], the presence of diabetes mellitus (DM) (OR 17.527), and high parathyroid hormone (PTH) levels (OR 1.002) were independent predictors of VC in a logistic regression model including the following factors: age, the presence of DM, HD duration, and serum albumin, phosphate, PTH, 25-OH-vitamin D, fetuin-A, OPN, and calcium levels. No significant correlation was found between patients with VC and patients without VC in terms of fetuin-A, OPN, and 25-OH-vitamin D levels.

CONCLUSIONS

VC is a frequent sign in patients undergoing HD and is not related to serum fetuin-A and osteopontin levels. Age, the presence of DM, and high PTH levels were independent predictors of VC in patients undergoing HD. Further studies are warranted to understand the mechanism underlying and the factors contributing to VC.

Is Fibroblast growth factor 23 the leading cause of increased mortality among chronic kidney disease patients? A narrative review

The death rate among chronic kidney disease patients is the highest compared to other chronic diseases. 60% of these fatalities are cardiovascular. Cardiovascular calcifications and chronic inflammation affect almost all chronic kidney disease patients and are associated with cardiovascular mortality. Fibroblast growth factor 23 is associated with vascular calcification. Systemic inflammation in chronic kidney disease patients is multifactorial. The role of systemic inflammation in the pathogenesis of vascular calcification was recently reappraised. Fibroblast growth factor 23 was accused as a direct stimulus of left ventricular hypertrophy, uremic inflammation, and impaired neutrophil function. This review will discuss the underlying mechanisms that underlie the link between Fibroblast growth factor 23 and increased mortality encountered among chronic kidney disease patients.

Hyperphosphatemia and hs-CRP Initiate the Coronary Artery Calcification in Peritoneal Dialysis Patients

Background. Coronary artery calcification (CAC) contributes to high risk of cardiocerebrovascular diseases in dialysis patients. However, the risk factors for CAC initiation in peritoneal dialysis (PD) patients are not known clearly. Methods. Adult patients with baseline CaCS = 0 and who were followed up for at least 3 years or until the conversion from absent to any measurable CAC detected were included in this observational cohort study. Binary logistic regression was performed to identify the risk factors for CAC initiation in PD patients. Results. 70 patients recruited to our study were split into a noninitiation group (n = 37) and an initiation group (n = 33) according to the conversion of any measurable CAC during their follow-up or not. In univariate analysis, systolic blood pressure, serum phosphorus, fibrinogen, hs-CRP, serum creatinine, and triglycerides were positively associated with the initiation of CAC, while the high density lipoprotein and nPCR did the opposite function. Multivariate analysis revealed that hyperphosphatemia and hs-CRP were the independent risk factors for CAC initiation after adjustments. Conclusions. Hyperphosphatemia and hs-CRP were the independent risk factors for CAC initiation in PD patients. These results suggested potential clinical strategies to prevent the initiation of CAC in PD patients.

The Strategy to Prevent and Regress the Vascular Calcification in Dialysis Patients

The high prevalence of arterial calcification in end-stage renal disease (ESRD) is far beyond the explanation by common cardiovascular risk factors such as aging, diabetes, hypertension, and dyslipidemia. The finding relies on the fact that vascular and valvular calcifications are predictors of cardiovascular diseases and mortality in persons with chronic renal failure. In addition to traditional cardiovascular risk factors such as diabetes mellitus and blood pressure control, other ESRD-related risks such as phosphate retention, excess calcium, and prolonged dialysis time also contribute to the development of vascular calcification. The strategies are to reverse "calcium paradox" and lower vascular calcification by decreasing procalcific factors including minimization of inflammation (through adequate dialysis and by avoiding malnutrition, intravenous labile iron, and positive calcium and phosphate balance), correction of high and low bone turnover, and restoration of anticalcification factor balance such as correction of vitamin D and K deficiency; parathyroid intervention is reserved for severe hyperparathyroidism. The role of bone antiresorption therapy such as bisphosphonates and denosumab in vascular calcification in high-bone-turnover disease remains unclear. The limited data on sodium thiosulfate are promising. However, if calcification is to be targeted, ensure that bone health is not compromised by the treatments.

Does statins promote vascular calcification in chronic kidney disease?

BACKGROUND

In end-stage renal disease (ESRD), coronary artery calcification (CAC) and inflammation contribute to cardiovascular disease (CVD). Statins do not improve survival in patients with ESRD, and their effect on vascular calcification is unclear. We explored associations between CAC, inflammatory biomarkers, statins and mortality in ESRD.

MATERIALS AND METHODS

In 240 patients with ESRD (63% males; median age 56 years) from cohorts including 86 recipients of living donor kidney transplant (LD-Rtx), 96 incident dialysis patients and 58 prevalent peritoneal dialysis patients, associations of CAC score (Agatston Units, AUs), interleukin-6 (IL-6) with high-sensitivity C-reactive protein (hsCRP), tumour necrosis factor (TNF), use of statins and all-cause mortality were analysed. Cardiac CT was repeated in 35 patients after 1·5 years of renal replacement therapy. In vitro, human vascular smooth muscle cells (hVSMCs) were used to measure vitamin K metabolism.

RESULTS

Among 240 patients, 129 (53%) had a CAC score > 100 AUs. Multivariate analysis revealed that independent predictors of 1-SD higher CAC score were age, male gender, diabetes and use of statins. The association between CAC score and mortality remained significant after adjustment for age, gender, diabetes, CVD, use of statins, protein-energy wasting and inflammation. Repeated CAC imaging in 35 patients showed that statin therapy was associated with greater progression of CAC. In vitro synthesis of menaquinone-4 by hVSMCs was significantly impaired by statins.

CONCLUSION

Elevated CAC score is a mortality risk factor in ESRD independent of inflammation. Future studies should resolve if statins promote vascular calcification and inhibition of vitamin K synthesis in the uremic milieu.

FGF23 and inflammation

Systemic inflammation is a recognized feature in chronic kidney disease (CKD). The role of systemic inflammation in the pathogenesis of vascular calcification was recently settled. FGF23 was recently accused as a direct stimulus of systemic inflammation. This finding explains the strong association of FGF23 to vascular calcification and increased mortality among CKD.

High Serum Phosphorus Level Is Associated with Left Ventricular Diastolic Dysfunction in Peritoneal Dialysis Patients

Objectives

We initiated this study to explore the relationships of serum phosphorus level with left ventricular ultrasound features and diastolic function in peritoneal dialysis (PD) patients.

Methods

174 patients with end-stage renal disease (ESRD) receiving PD were enrolled in this retrospective observational study. Conventional echocardiography examination and tissue Doppler imaging (TDI) were performed in each patient. Clinical information and laboratory data were also collected. Analyses of echocardiographic features were performed according to phosphorus quartiles groups. And multivariate regression models were used to determine the association between serum phosphorus and Left ventricular diastolic dysfunction (LVDD).

Results

With the increase of serum phosphorus levels, patients on PD showed an increased tissue Doppler-derived E/e’ ratio of lateral wall (P < 0.001), indicating a deterioration of left ventricular diastolic function. Steady growths of left atrium and left ventricular diameters as well as increase of left ventricular muscle mass were also observed across the increasing quartiles of phosphorus, while left ventricular ejection fraction remained normal. In a multivariate analysis, the regression coefficient for E/e’ ratio in the highest phosphorus quartile was almost threefold higher relative to those in the lowest quartile group. And compared with patients in the lowest phosphorus quartile (<1.34 mmol/L) those in the highest phosphorus quartile (>1.95 mmol/L) had a more than fivefold increased odds of E/e’ ratio >15.

Conclusions

Our study showed an early impairment of left ventricular diastolic function in peritoneal dialysis patients. High serum phosphorus level was independently associated with greater risk of LVDD in these patients. Whether serum phosphorus will be a useful target for prevention or improvement of LVDD remains to be proved by further studies.

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

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

Review: Therapy for the altered mineral metabolism of chronic kidney disease: implications for vascular calcification

The development of chronic kidney disease (CKD) is associated with poor outcomes largely due an increased likelihood of adverse cardiovascular events. Many factors are playing a role in cardiovascular disease in CKD including the development of vascular calcification (VC). Studies have indeed shown that the presence of VC is associated with decreased survival among patients with CKD. The pathogenesis of VC is itself multi-factorial. LikeLy playing a significant role is the altered mineral metabolism of CKD. Management of the altered mineral metabolism in CKD is quite difficult and may also play a role in the pathogenesis of VC. In this manuscript, we will review the pathogenesis of the altered mineral metabolism of CKD, its management, and how both may play a role in the development of VC.

Factors associated with serum fetuin-A concentrations after long-term use of different phosphate binders in hemodialysis patients

Background

Fetuin-A is known as a circulating inhibitor of vascular calcification. Factors associated with serum fetuin-A concentrations after long-term use of different phosphate binders in hemodialysis patients is still uncertain.

Methods

In the post-hoc study, we analyzed serum fetuin-A and biochemical factors (Ca, P, i-PTH, hsCRP, TG, LDL-C) in 50 hemodialysis patients, who completed a 48-week, open-Label, controlled randomized parallel-group study. 23 patients received sevelamer and 27 patients received calcium carbonate.

Results

After the 48-week treatment, the sevelamer group had less serum calcium increment, less iPTH decrement, more ALK-P increment, more hsCRP decrement and more LDL-C decrement. There was no significant difference in the serum fetuin-A decrement between two groups. Decreased serum fetuin-A levels were found after 48-week treatment in both groups: from 210.61 (104.73) to 153.85 (38.64) ug/dl, P = 0.003 in sevelamer group, from 203.95 (107.87) to 170.90 (58.02) ug/mL, P =0.002 in calcium group. The decrement in serum fetuin-A (Δfetuin-A) levels was associated with ΔCa (ρ = - 0.230, P = 0.040), ΔiPTH (ρ = 0.306, P = 0.031) and Δalbumin (ρ = 0.408, P = 0.003), not associated with sevelamer use, ΔP and ΔhsCRP.

Conclusion

After long-term sevelamer or calcium carbonate treatment, both groups of maintenance HD patients had lower serum fetuin-A levels. Serum levels of increased calcium, decreased iPTH and decreased albumin were associated with the serum fetuin-A decrement.

Hyperphosphatemia as an independent risk factor for coronary artery calcification progression in peritoneal dialysis patients

Background

Coronary artery calcification (CAC) is associated with cardiovascular mortality in end-stage renal disease (ESRD) patients. The present study aimed to identify modifiable risk factors for CAC progression in peritoneal dialysis (PD) patients.

Methods

Adult patients who received regular PD for more than 6 months and underwent a series of coronary artery calcification score (CaCS) measurements by multislice spiral computed tomography (MSCT) with an interval of ≥ 6 months were included in this observational cohort study. The demographic characteristics and clinical data, including laboratory data and adequacy of PD, were collected. Curve estimation was used to fit the straight line and obtain the slope. Binary logistic regression was performed to identify the independent risk factors for CAC progression in the PD patients, and multivariate linear regression was conducted to identify factors associated with hyperphosphatemia.

Results

A total of 207 adult patients on PD (116 men, 56.0 %) with a mean age of 59.8 ± 15.9 years were recruited to this study, and 157 of them (75.8 %) received three or more CaCS assessments. The patients were divided into a slow group (n = 137) and a rapid group (n = 70) according to the linear regression slope or the average speed of development. The follow-up time was 33.0 ± 18.8 months. Multivariate logistic regression revealed that age and serum phosphate level were independent risk factors for CAC progression after adjustments. Multivariate linear regression revealed that hyperphosphatemia was associated with elevations in the transferrin and serum albumin levels and normalized protein catabolic rate (nPCR) and reductions in the hemoglobin level, residual Ccr, and PD Ccr.

Conclusions

Hyperphosphatemia is an independent risk factor for CAC progression, and the serum phosphate level may be associated with protein intake and PD adequacy. These results provide important information for the clinical management of ESRD patients.

Dysregulation of phosphate metabolism and conditions associated with phosphate toxicity

Phosphate homeostasis is coordinated and regulated by complex cross-organ talk through delicate hormonal networks. Parathyroid hormone (PTH), secreted in response to low serum calcium, has an important role in maintaining phosphate homeostasis by influencing renal synthesis of 1,25-dihydroxyvitamin D, thereby increasing intestinal phosphate absorption. Moreover, PTH can increase phosphate efflux from bone and contribute to renal phosphate homeostasis through phosphaturic effects. In addition, PTH can induce skeletal synthesis of another potent phosphaturic hormone, fibroblast growth factor 23 (FGF23), which is able to inhibit renal tubular phosphate reabsorption, thereby increasing urinary phosphate excretion. FGF23 can also fine-tune vitamin D homeostasis by suppressing renal expression of 1-alpha hydroxylase (1α(OH)ase). This review briefly discusses how FGF23, by forming a bone-kidney axis, regulates phosphate homeostasis, and how its dysregulation can lead to phosphate toxicity that induces widespread tissue injury. We also provide evidence to explain how phosphate toxicity related to dietary phosphorus overload may facilitate incidence of noncommunicable diseases including kidney disease, cardiovascular disease, cancers and skeletal disorders.

The role of fetuin-A in mineral trafficking and deposition

Calcium and phosphate are the principle ions involved in the deposition of mineral in the human body. Inhibitors of mineralisation are essential for the prevention of ectopic mineral precipitation and deposition. In the past decade, through in vitro, in vivo and clinical observation studies, we have come to appreciate the importance of fetuin-A (Fet-A), a circulating glycoprotein, in preventing ectopic calcium phosphate mineralisation. Moreover, the detection of Fet-A-containing mineral complex, termed calciprotein particles (CPPs), has provided new ways to assess an individual's calcific risk. The pathophysiological significance of CPPs in disease states is yet to be defined, but it provides an exciting avenue to further our understanding of the development of ectopic mineralisation.

Pericardial fat is associated with coronary artery calcification in non-dialysis dependent chronic kidney disease patients

Pericardial fat (PF) a component of visceral adipose tissue has been consistently related to coronary atherosclerosis in the general population. This study evaluated the association between PF and coronary artery calcification (CAC) in non-dialysis dependent chronic kidney disease (CKD) patients. This is a post-hoc cross sectional analysis of the baseline of a prospective cohort of 117 outward CKD patients without manifest coronary artery disease (age, 56.9±11.0 years, 64.1% males, 95.1% hypertensives, 25.2% diabetics, 15.5% ever smokers, CKD stage 2 to 5 with estimated glomerular filtration rate 36.8±18.1 ml/min). CAC scores, PF volume and abdominal visceral fat (AVF) areas were measured by computed tomography. The association of PF as a continuous variable with the presence of CAC was analyzed by multivariate logistic regression. CAC (calcium score >0) was present in 59.2% patients. Those presenting CAC were on average 10 years older, had a higher proportion of male gender (78.7% vs. 42.9%, p<0.001), and had higher values of waist circumference (95.9±10.7 vs. 90.2±13.2 cm, p = 0.02), PF volumes (224.8±107.6 vs. 139.1±85.0 cm³, p<0.01) and AVF areas (109.2±81.5 vs. 70.2±62.9 cm², p = 0.01). In the multivariate analysis, adjusting for age, gender, diabetes, smoking and, left ventricular concentric hypertrophy, PF was significantly associated with the presence of CAC (OR: 1.88 95% CI: 1.03–3.43 per standard deviation). PF remained associated with CAC even with additional adjustments for estimated glomerular filtration rate or serum phosphorus (OR: 1.85 95% CI: 1.00–3.42, p = 0.05). PF is independently associated with CAC in non-dialysis dependent CKD patients.

A current understanding of vascular calcification in CKD

Patients with chronic kidney disease (CKD) and end-stage renal disease (ESRD) have significant cardiovascular morbidity and mortality that is in part due to the development of vascular calcification. Vascular calcification is an active, highly regulated process that shares many similarities with normal bone formation. New discoveries related to extracellular vesicles, microRNAs, and calciprotein particles continue to reveal the mechanisms that are involved in the initiation and progression of vascular calcification in CKD. Further innovations in these fields are critical for the development of biomarkers and therapeutic options for patients with CKD and ESRD.

Association of serum phosphorus variability with coronary artery calcification among hemodialysis patients

Coronary artery calcification (CAC) is associated with increased mortality in patients on maintenance hemodialysis (MHD), but the pathogenesis of this condition is not well understood. We evaluated the relationship of CAC score (CACs) and variability in serum phosphorus in MHD patients. Seventy-seven adults on MHD at Huashan Hospital (Shanghai) were enrolled in July, 2010. CAC of all the patients were measured by computed tomography and CACs was calculated by the Agatston method at the entry of enrollment. Patients were divided into three categories according to their CACs (0∼10, 11∼400, and >400). Blood chemistry was recorded every 3 months from January 2008 to July 2010. Phosphorus variation was defined by the standard deviation (SD) or coefficient of variation (CV) and it was calculated from the past records. The ordinal multivariate logistic regression analysis was used to analyze the predictors of CAC. The mean patient age (± SD) was 61.7 years (±11.3) and 51% of patients were men. The mean CACs was 609.6 (±1062.9), the median CACs was 168.5, and 78% of patients had CACs more than 0. Multivariate analysis indicated that female gender (OR = 0.20, 95% CI = 0.07–0.55), age (OR = 2.31, 95% CI = 1.32–4.04), serum fibroblast growth factor 23 (OR = 2.25, 95% CI = 1.31–3.85), SD-phosphorus calculated from the most recent 6 measurements (OR = 2.12; 95% CI = 1.23–3.63), and CV-phosphorus calculated from the most recent 6 measurements (OR = 1.90, 95% CI = 1.16–3.11) were significantly and independently associated with CACs. These associations persisted for phosphorus variation calculated from past 7, 8, 9, 10, and 11 follow-up values. Variability of serum phosphorus may contribute significantly to CAC and keeping serum phosphorus stable may decrease coronary calcification and associated morbidity and mortality in MHD patients.

Relationship between sclerostin and cardiovascular calcification in hemodialysis patients: a cross-sectional study

Background

Sclerostin is a Wnt pathway antagonist regulating osteoblast activity and bone turnover. Here, we assessed the potential association of sclerostin with the development of coronary artery (CAC) and aortic valve calcifications (AVC) in haemodialysis (HD) patients.

Methods

We conducted a cross-sectional multi-slice computed tomography (MS-CT) scanning study in 67 chronic HD patients (59.4 ± 14.8 yrs) for measurement of CAC and AVC. We tested established biomarkers as well as serum sclerostin (ELISA) regarding their association to the presence of calcification. Fifty-four adults without relevant renal disease served as controls for serum sclerostin levels. Additionally, sclerostin expression in explanted aortic valves from 15 dialysis patients was analysed ex vivo by immunohistochemistry and mRNA quantification (Qt-RT-PCR).

Results

CAC (Agatston score > 100) and any AVC were present in 65% and in 40% of the MS-CT patient group, respectively. Serum sclerostin levels (1.53 ± 0.81 vs 0.76 ± 0.31 ng/mL, p < 0.001) were significantly elevated in HD compared to controls and more so in HD patients with AVC versus those without AVC (1.78 ± 0.84 vs 1.35 ± 0.73 ng/mL, p = 0.02). Multivariable regression analysis for AVC revealed significant associations with higher serum sclerostin. Ex vivo analysis of uraemic calcified aortic valves (n = 10) revealed a strong sclerostin expression very close to calcified regions (no sclerostin staining in non-calcified valves). Correspondingly, we observed a highly significant upregulation of sclerostin mRNA in calcified valves compared to non-calcified control valves.

Conclusion

We found a strong association of sclerostin with calcifying aortic heart valve disease in haemodialysis patients. Sclerostin is locally produced in aortic valve tissue adjacent to areas of calcification.

Serum phosphate as a risk factor for cardiovascular events in people with and without chronic kidney disease: a large community based cohort study

BACKGROUND

Serum phosphate is a known risk factor for cardiovascular events and mortality in people with chronic kidney disease (CKD), however data on the association of these outcomes with serum phosphate in the general population are scarce. We investigate this relationship in people with and without CKD in a large community-based population.

METHODS

Three groups from an adult cohort of the Quality Improvement in Chronic Kidney Disease (QICKD) cluster randomised trial (ISRCTN56023731) were followed over a period of 2.5 years: people with normal renal function (N = 24,184), people with CKD stages 1-2 (N = 20,356), and people with CKD stages 3-5 (N = 13,292). We used a multilevel logistic regression model to determine the association between serum phosphate, in these groups, and a composite outcome of all-cause mortality, cardiovascular events, and advanced coronary artery disease. We adjusted for known cardiovascular risk factors.

FINDINGS

Higher phosphate levels were found to correlate with increased cardiovascular risk. In people with normal renal function and CKD stages 1-2, Phosphate levels between 1.25 and 1.50 mmol/l were associated with increased cardiovascular events; odds ratio (OR) 1.36 (95% CI 1.06-1.74; p = 0.016) in people with normal renal function and OR 1.40 (95% CI 1.09-1.81; p = 0.010) in people with CKD stages 1-2. Hypophosphatemia (<0.75 mmol/l) was associated with fewer cardiovascular events in people with normal renal function; OR 0.59 (95% CI 0.36-0.97; p = 0.049). In people with CKD stages 3-5, hyperphosphatemia (>1.50 mmol/l) was associated with increased cardiovascular risk; OR 2.34 (95% CI 1.64-3.32; p<0.001). Other phosphate ranges were not found to have a significant impact on cardiovascular events in people with CKD stages 3-5.

CONCLUSIONS

Serum phosphate is associated with cardiovascular events in people with and without CKD. Further research is required to determine the mechanisms underlying these associations.

Oxidised LDL/LDL-cholesterol ratio and coronary artery calcification in haemodialysis patients

BACKGROUND AND AIMS

Serum malondialdehyde-modified low-density lipoprotein (MDA-LDL) and MDA-LDL/LDL-cholesterol (LDL-c) ratio are risk factors for arteriosclerosis and cardiovascular disease (CVD). However, no information is available on these parameters or their associations with coronary artery calcification (CAC) in haemodialysis (HD) patients.

METHODS AND RESULTS

Fifty-seven HD patients and 26 control subjects were included in this cross-sectional study. Serum MDA-LDL concentrations and MDA-LDL/LDL-c ratios were examined. HD patients had significantly higher MDA-LDL/LDL-c ratios than the controls (105.1 ± 27.5 vs. 81.4 ± 18.9 mU/mg, P < 0.001); however, there was no significant difference in serum MDA-LDL levels between the 2 groups. CAC scores were examined only in HD patients and their possible associations with the clinical/laboratory data were analysed. Analysis of HD patients showed that MDA-LDL/LDL-c ratio has an association with presence of CVD, CAC score, HD duration, MDA-LDL, or haemoglobin A1C. In addition, the CAC score was positively correlated with serum MDA-LDL level (P = 0.048) and MDA-LDL/LDL-c ratio (P = 0.006). Furthermore, multivariate logistic regression analysis showed that MDA-LDL/LDL-c ratio (β = 0.04, P = 0.003) and HD duration (β = 0.16, P = 0.007) were independently associated with CAC score.

CONCLUSION

The MDA-LDL/LDL-c ratio of HD patients was significantly higher than that of non-HD subjects and was independently associated with the CAC score. Therefore, this ratio could be an important risk factor for CAC in HD patients.

Progression of aortic arch calcification over 1 year is an independent predictor of mortality in incident peritoneal dialysis patients

Backgrounds and Aims

The presence and progression of vascular calcification have been demonstrated as important risk factors for mortality in dialysis patients. However, since the majority of subjects included in most previous studies were hemodialysis patients, limited information was available in peritoneal dialysis (PD) patients. Therefore, the aim of this study was to investigate the prevalence of aortic arch calcification (AoAC) and prognostic value of AoAC progression in PD patients.

Methods

We prospectively determined AoAC by chest X-ray at PD start and after 12 months, and evaluated the impact of AoAC progression on mortality in 415 incident PD patients.

Results

Of 415 patients, 169 patients (40.7%) had AoAC at baseline with a mean of 18.1±11.2%. The presence of baseline AoAC was an independent predictor of all-cause [Hazard ratio (HR): 2.181, 95% confidence interval (CI): 1.336–3.561, P = 0.002] and cardiovascular mortality (HR: 3.582, 95% CI: 1.577–8.132, P = 0.002). Among 363 patients with follow-up chest X-rays at 12 months after PD start, the proportion of patients with AoAC progression was significantly higher in patients with baseline AoAC (64.2 vs. 5.3%, P<0.001). Moreover, all-cause and cardiovascular death rates were significantly higher in the progression groups than in the non-progression group (P<0.001). Multivariate Cox analysis revealed that AoAC progression was an independent predictor for all-cause (HR: 2.625, 95% CI: 1.150–5.991, P = 0.022) and cardiovascular mortality (HR: 4.008, 95% CI: 1.079–14.890, P = 0.038) in patients with AoAC at baseline.

Conclusions

The presence and progression of AoAC assessed by chest X-ray were independently associated with unfavorable outcomes in incident PD patients. Regular follow-up by chest X-ray could be a simple and useful method to stratify mortality risk in these patients.

Dissociation between progression of coronary artery calcification and endothelial function in hemodialysis patients: a prospective pilot study

Chronic kidney disease profoundly disturbs calcium-phosphate metabolism and predisposes to premature atherosclerosis. Both coronary artery calcification (CAC) and endothelial dysfunction are common in hemodialysis (HD) patients. We hypothesized that a calcium-free phosphate binder would improve endothelial function and delay progression of vascular calcification in HD patients.

METHODS

This was a randomized parallel-group trial in HD patients comparing lanthanum carbonate (LC) with a non-LC phosphorus binders control group (non-LC) at a 1 : 1 randomization. CAC was obtained at baseline, 6, and 12 months, and endothelial function (brachial artery flow-mediated dilation - FMD) at baseline and 6 months.

RESULTS

13 patients were randomized (LC n = 7 and non-LC n = 6). CAC scores (Log ± SE) at baseline were 7.21 ± 0.62 (LC) and 6.07 ± 0.73 (control). CAC increased in the non-LC group (33 ± 17% and 77 ± 22% at 6 and 12 months), but tended to decrease in the LC group (-10 ± 11% and -2 ± 11% at 6 and 12 months). There was statistically less progression in CAC in the LC group compared to control at 6 (p = 0.002) and 12 months (p = 0.003). There was no difference between groups in FMD (p = 0.7). Markers of inflammation did not change significantly.

CONCLUSION

A slower rate of progression of CAC occurred in the LC group, independent of changes in FMD. This is the first study showing dissociation between progression of CAC and FMD in HD patients. Larger studies are warranted to elucidate the impact of different phosphate sequestration therapies on atherosclerosis in HD patients.

Vitamin d and stage 5 chronic kidney disease: a new paradigm?

Vitamin D receptor agonists (VDRA) are currently recommended for the treatment of secondary hyperparathyroidism in stage 5 CKD. They are considered to be contraindicated in the presence of low or normal (for a dialysis patient) levels of PTH due to the risk of developing adynamic bone disease, with consequent vascular calcification. However, these recommendations are increasingly at odds with the epidemiological evidence, which consistently shows a large survival advantage for patients treated with low-dose VDRAs, regardless of plasma calcium, phosphate, or PTH. A large number of pleiotropic effects of vitamin D have been described, including inhibition of renin activity, anti-inflammation, and suppression of vascular calcification stimulators and stimulation of vascular calcification inhibitors present in the uremic milieu. Laboratory studies suggest that a normal cellular vitamin D level is necessary for normal cardiomyocyte and vascular smooth muscle function. While pharmacological doses of VDRA can be harmful, the present evidence suggests that the level of 1,25-dihydroxycholecalciferol should also be more physiological in stage 5 CKD, and that widespread use of low-dose VDRA would be beneficial. A randomized controlled trial to test this hypothesis is warranted.

Vascular and valvular calcification in chronic peritoneal dialysis patients

Cardiovascular disease accounts over half of the total mortality in peritoneal dialysis (PD) patients. In addition, there is an increasing recognition of a high prevalence of vascular and valvular calcification that may contribute to the increased all-cause and cardiovascular mortality in the PD patients. Disturbed mineral metabolism in association with chronic kidney disease has been suggested as one of the major contributing factors to the increased vascular/valvular calcification in this population. In this paper, we provide an overview of the prevalence and importance of this complication in the PD patients. In addition, we review the contributing factors and some emerging mechanisms for this complication. Furthermore, we discuss some therapeutic strategies that may be useful in limiting the progression of vascular/valvular calcification in the PD population.

Cardiovascular risk in diabetic end-stage renal disease patients

Diabetes mellitus is the leading cause of end-stage renal disease (ESRD), accounting for 54% of all incident cases according to the US Renal Data System. These patients suffer an extremely high mortality rate due to the very high incidence of cardiovascular disease. A significant proportion of these patients already has established cardiovascular disease at the time of initiation of dialysis treatment. More importantly, as these patients develop progressive kidney dysfunction, they are not only subjected to traditional Framingham risk factors, but, more importantly, to a whole host of "kidney disease-related risk factors" that further accelerate the progression of cardiovascular disease and thus contribute to adverse cardiovascular outcomes. The present article provides an updated view on the multitude of traditional Framingham risk factors and kidney disease-related risk factors that diabetic ESRD patients are subjected to. A better understanding of the different cardiovascular risk factors will be fundamental to institute early detection programs, as well as to provide aggressive cardiovascular management of these patients.

Osteo-renal regulation of systemic phosphate metabolism

Impaired kidney function and subsequent skeletal responses play a critical role in disrupting phosphate balance in chronic kidney disease (CKD) patients with mineral and bone disorder (CKD-MBD). In patients with CKD-MBD, the inability of the kidney to maintain normal mineral ion balance affects bone remodeling to induce skeletal fracture and extraskeletal vascular calcification. In physiological conditions, bone-derived fibroblast growth factor 23 (FGF23) acts on the kidney to reduce serum phosphate and 1,25-dihydroxyvitamin D levels. In humans, increased bioactivity of FGF23 leads to increased urinary phosphate excretion, which induces hypophosphatemic diseases (e.g., rickets/osteomalacia). However, reduced FGF23 activity is associated with hyperphosphatemic diseases (e.g., tumoral calcinosis). In patients with CKD, high serum levels of FGF23 fail to reduce serum phosphate levels and lead to numerous complications, including vascular calcification, one of the important determinants of mortality of CKD-MBD patients. Of particular significance, molecular, biochemical and morphological changes in patients with CKD-MBD are mostly due to osteo-renal dysregulation of mineral ion metabolism. Furthermore, hyperphosphatemia can partly contribute to the development of secondary hyperparathyroidism in patients with CKD-MBD. Relatively new pharmacological agents including sevelamer hydrochloride, calcitriol analogs and cinacalcet hydrochloride are used either alone, or in combination, to minimize hyperphosphatemia and hyperparathyroidism associated complications to improve morbidity and mortality of CKD-MBD patients. This article will briefly summarize how osteo-renal miscommunication can induce phosphate toxicity, resulting in extensive tissue injuries.

Coronary Calcification and Hormones

The pathogenesis of coronary artery calcification and its role in atherogenesis has not been completely understood but is a new focus of interest in experimental and clinical research. Various bioactive substances, including hormones, have been implicated in the process of arterial calcification. This review considers the relationship between coronary artery calcification and hormones. These hormones may become therapeutic targets for the prevention of arterial calcification.

Cell biological and physicochemical aspects of arterial calcification

Processes similar to endochondral or intramembranous bone formation occur in the vascular wall. Bone and cartilage tissue as well as osteoblast- and chondrocyte-like cells are present in calcified arteries. As in bone formation, apoptosis and matrix vesicles play an important role in the initiation of vascular calcification. Recent evidence indicates that nanocrystals initially formed in the vessel wall may actively be involved in the progression of the calcification process. This review focuses on the cellular and structural similarities between bone formation and vascular calcification and discusses the initial events in this pathological mineralization process.

Effects of sodium thiosulfate on vascular calcification in end-stage renal disease: a pilot study of feasibility, safety and efficacy

BACKGROUND AND OBJECTIVES

Vascular calcification is a major contributor to morbidity and mortality in hemodialysis. The objective of this pilot study was to determine the feasibility, safety and efficacy of sodium thiosulfate (STS) in the progression of vascular calcification in hemodialysis patients.

METHODS

Chronic hemodialysis patients underwent a battery of cardiovascular tests. Those with coronary artery calcium (Agatston scores >50) received intravenous STS after each dialysis for 5 months (n = 22) and the tests were repeated. Changes in MDCT-determined calcification were assessed as the mean annualized rate of change in 3 vascular beds (coronary, thoracic and carotid arteries) and in L1-L2 vertebral bone density.

RESULTS

Although individual analyses showed coronary artery calcification progression in 14/22 subjects, there was no progression in the mean annualized rate of change of vascular calcification in the entire group. The L1-L2 vertebral bone density showed no changes. There were no correlations between rates of progression of vascular calcification and phosphorus, fetuin or C-reactive protein levels. Changes in coronary artery calcification scores correlated with those of the thoracic aorta.

CONCLUSION

STS treatment is feasible, appears safe and may decrease the rate of progression of vascular calcification in hemodialysis patients. A large, randomized, controlled trial is warranted.