Associations of fetuin-A and osteoprotegerin with arterial stiffness and early atherosclerosis in chronic hemodialysis patients

Vascular calcification inhibitors in chronic kidney disease

BACKGROUND

Increased cardiovascular mortality due to multifactorial progressive arterial stiffness in chronic kidney disease is influenced by the disturbed balance between inducers and inhibitors of vascular calcification. The potential to enhance the protective effects of vascular calcification inhibitors through effective therapy could stimulate further research and collaboration. This systematic review aims to give a grounded overview of vascular calcification inhibitors and their serum levels in different stages of chronic kidney disease to demonstrate the dynamics during stages of declining kidney function and renal replacement therapy.

METHODS

The systematic review was registered in the PROSPERO database on August 30th, 2023 (CRD42023459169). and conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyzes (PRISMA).

RESULTS

We screened 463 articles, of which 192 were eligible, and investigated vascular calcification inhibitors or included values of their serum levels. Serum levels of fetuin-A, vitamin D, FGF-23, Klotho, osteopontin, matrix GLA protein, osteoprotegerin, magnesium, and sclerostin are demonstrated in tables and sparingly studied substances with a perspective towards better treatment options are found in Supplementary Table.

CONCLUSION

Endogenous vascular calcification inhibitors could serve the role of valuable biomarkers to detect the process earlier and estimate the effect of treatment. The serum levels presented demonstrate the dynamics in different stages in chronic kidney disease and propose practical feedback for personalized treatment strategies. Manifold possible vascular calcification inhibitors under research set a promising starting point for more effective therapeutic interventions.

The association between osteoprotegerin and arterial stiffness in a 10-year longitudinal study of patients with type 2 diabetes

Introduction: Osteoprotegerin (OPG) inhibits vascular calcification which is central to pathogenesis of arterial stiffness. However, it promotes inflammation by upregulating expression of vascular cell adhesion molecule-1(VCAM-1), thereby contributing to arterial stiffness. We investigated longitudinal association between OPG and arterial stiffness in type 2 diabetes (T2D), causality of the association and mediation by VCAM-1. Methods: This was a prospective cohort study of T2D patients (N = 1877, mean age 57.0 ± 10.8) with 10 years' follow-up. Baseline plasma OPG was measured using immunoassay. Pulse wave velocity (PWV) was assessed using applanation tonometry. We examined association between OPG and follow-up PWV using linear mixed model. One-sample Mendelian Randomization (MR) was conducted with rs1385492 as OPG-associated single nucleotide polymorphism (SNP). Results: Baseline natural log (Ln)-transformed OPG was positively associated with baseline and follow-up PWV with adjusted coefficients 0.43 (95%CI 0.05, 0.80; p = .026) and 0.51 (95%CI 0.06 to 0.97; p = .028) respectively. Genetically-predicted higher levels of plasma OPG was associated with higher last follow-up PWV with coefficient 10.81 (95%CI 2.97, 18.65; p = .007) per unit increase in LnOPG. Higher VCAM-1 accounted for 10.2% of association between LnOPG and follow-up PWV. Discussion: Baseline plasma OPG was associated with higher follow-up PWV in patients with T2D, with genetic evidence from MR. This association may be mediated, at least in part, by VCAM-1.

The Relationship of Fetuin-A with Coronary Calcification, Carotid Atherosclerosis, and Mortality Risk in Non-Dialysis Chronic Kidney Disease

Objective

This study investigated the relationship of fetuin-A with coronary calcification, carotid atherosclerosis, and mortality risk in non-dialysis chronic kidney disease (CKD).

Methods

The study included 135 adult patients with CKD at stages 3-5, who were divided into coronary artery calcification (CAC) and non-CAC groups. We excluded current smokers and individuals with diabetes mellitus, inflammatory conditions, liver diseases, acute kidney failure, chronic hemodialysis, and cancer. We conducted kidney function tests, complete blood counts, and measured serum levels of fetuin-A, tumor necrosis factor-alpha (TNF-α), high-sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), total cholesterol (TC), total triglycerides (TG), high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol. Cardiac spiral computed tomography was used to calculate the CAC score, employing the Agatston method. Carotid ultrasonography was performed to assess carotid intima-media thickness (CIMT) and to detect the presence of plaques.

Results

CAC patients had considerably higher levels of TNF-α (p<0.001), IL-6 (p<0.001), hs-CRP (p=0.006), TC, TG, parathyroid hormone (PTH) (p<0.001) and phosphorus (p<0.001) than non-CAC patients. They also had significantly lower levels of fetuin-A (p<0.001). Fetuin-A was considerably lower in CKD subgroups as CKD progressed. Fetuin-A (p=0.046), age (p=0.009), TNF-α (p=0.027), IL-6 (p=0.005), TG (p=0.002), PTH (p=0.002), and phosphorus (p=0.004) were significant predictors of CAC. CAC and fetuin-A were strong predictors of all-cause mortality and cardiovascular (CV) mortality. Fetuin-A was a significant predictor of CIMT (p=0.045).

Conclusion

Fetuin-A reliably predicted CAC and CIMT. Fetuin-A and CAC emerged as significant risk factors for all-cause and CV mortality in non-dialysis CKD.

Soluble CD14 and Osteoprotegerin Associate with Ankle-Brachial Index as a Measure of Arterial Stiffness in Patients with Mild-to-Moderate Chronic Kidney Disease in a Five-Year Prospective Study

INTRODUCTION

Vascular lesions and arterial stiffness appear at early stages of chronic kidney disease (CKD) and follow an accelerated course with disease progression, contributing to high cardiovascular mortality. There are limited prospective data on mechanisms contributing to progression of arterial stiffness in mild-to-moderate CKD (stages 2-3).

METHODS

We applied an affinity proteomics approach to identify candidates of circulating biomarkers with potential impact on vascular lesions in CKD and selected soluble cluster of differentiation 14 (sCD14), angiogenin (ANG), and osteoprotegerin (OPG) for further analysis. We studied their association with ankle-brachial index (ABI) and carotid intima-media thickness, as measures of arteriosclerosis and atherosclerosis, respectively, in 48 patients with CKD stages 2-3, who were prospectively followed and intensively treated for 5 years, and 44 healthy controls.

RESULTS

Concentrations of sCD14 (p < 0.001), ANG (p < 0.001), and OPG (p < 0.05) were higher in patients with CKD 2-3 at baseline, and sCD14 (p < 0.001) and ANG (p < 0.001) remained elevated in CKD patients at follow-up. There were positive correlations between ABI and sCD14 levels (r = 0.36, p = 0.01) and between ABI and OPG (r = 0.31, p = 0.03) at 5 years. The changes in sCD14 during follow-up correlated to changes in ABI from baseline to 5 years (r = 0.41, p = 0.004).

CONCLUSION

Elevated levels of circulating sCD14 and OPG in patients with CKD 2-3 were significantly associated with ABI, a measure of arterial stiffness. An increase in sCD14 over time in CKD 2-3 patients was associated with a corresponding increase in ABI. Further studies are needed to examine if early intensive multifactorial medication to align with international treatment targets may influence cardiovascular outcomes.

Histology and Immunohistochemistry of Radial Arteries Are Suggestive of an Interaction between Calcification and Early Atherosclerotic Lesions in Chronic Kidney Disease

Background and Objectives: recent studies suggest an implication of immune mechanisms in atherosclerotic disease. In this paper, the interaction between inflammation, calcification, and atherosclerosis on the vessel walls of patients with chronic kidney disease (CKD) is described and evaluated. Materials and Methods: patients with stage V CKD, either on pre-dialysis (group A) or on hemodialysis (HD) for at least 2 years (group B), in whom a radiocephalic arteriovenous fistula (RCAVF) was created, were included in the study. The control group included healthy volunteers who received radial artery surgery after an accident. The expressions of inflammatory cells, myofibroblasts, and vascular calcification regulators on the vascular wall were estimated, and, moreover, morphometric analysis was performed. Results: the expressions of CD68(+) cells, matrix carboxyglutamic acid proteins (MGPs), the receptor activator of nuclear factor-kB (RANK) and RANK ligand (RANKL), and osteoprotegerin (OPG), were significantly increased in CKD patients compared to the controls p = 0.02; p = 0.006; p = 0.01; and p = 0.006, respectively. In morphometric analysis, the I/M and L/I ratios had significant differences between CKD patients and the controls 0.3534 ± 0.20 vs. 0.1520 ± 0.865, p = 0.003, and 2.1709 ± 1.568 vs. 4.9958 ± 3.2975, p = 0.03, respectively. The independent variables correlated with the degree of vascular calcification were the intensity of CD34(+), aSMA(+) cells, and OPG, R² = 0.76, p < 0.0001, and, with intima-media thickness (IMT), the severity of RANKL expression R² = 0.3, p < 0.0001. Conclusion: atherosclerosis and vascular calcification in CKD seem to be strongly regulated by an immunological and inflammatory activation on the vascular wall.

The relationship between calcification inhibitor levels in chronic kidney disease and the development of atherosclerosis

Aim

We aimed to investigate the factors affecting the development of atherosclerosis and the role of calcification inhibitors fetuin-A, matrix-Gla protein (MGP), osteoprotegerin (OPG) in atherosclerosis progress.

Material and methods

The study was planned to investigate the relationship of serum OPG, MGP and fetuin-A levels with the development of atherosclerosis in the stage 2–3–4–5 chronic kidney disease (CKD) patients who did not require dialysis treatment.

Results

32 (17 female, 15 male) healthy individuals and 92 (49 females, 43 males) CKD patients were included. The mean carotid intima-media thickness (CIMT), C-reactive protein (CRP), fetuin-A, OPG and MGP of the two groups were compared statistically. In CKD patients, age, body mass index (BMI), CRP, triglyceride, urea, systolic blood pressure (SBP), fasting blood sugar have a positive linear relationship, fetuin-A, OPG, GFR have a negative linear relationship with CIMT. The mean CIMT, right CIMT, left CIMT, blood urea, CRP, urinary albumin excretion creatinine and age show a negative linear relationship with fetuin-A.

Conclusion

Fetuin-A levels begin to decline from the early stages of CKD and are significantly lower in patients with atherosclerosis as expressed with CIMT. This suggests that fetuin-A may be used as an early marker in CKD for increased cardiovascular risk. Early recognition of these risk factors is important and large-scale studies on vascular calcification inhibitors are needed.

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.

Is fetuin-A a biomarker of dialysis access dysfunction?

BACKGROUND

The arteriovenous (AV) access function of hemodialysis (HD) patients can be impaired by afferent artery stiffness due to preexisting microcalcification and by venous stenosis secondary to neointimal hyperplasia in whose development participates an upregulated local inflammatory process. Fetuin-A is a circulating potent inhibitor of vascular calcification and plays an important anti-inflammatory role. The aims of this prospective study were to investigate the relationship between baseline serum fetuin-A levels and: blood flow (Q_A) values at baseline, AV access failure (thrombosis or intervention for stenosis) during follow-up and primary unassisted AV access patency.

METHODS

We measured baseline serum fetuin-A levels and Q_A values of the AV access in 64 HD patients under routine Q_A surveillance for stenosis. Patients were classified into tertiles according to their baseline fetuin-A levels (g/L): <0.5 (tertile-1), 0.5-1.20 (tertile-2), and >1.20 (tertile-3).

RESULTS

Fetuin-A was positively correlated with Q_A (Spearman coefficient = 0.311, p = 0.012). Fourteen patients (21.9%) underwent AV access failure and they had lower fetuin-A (0.59 ± 0.32 g/L) and lower Q_A (739.4 ± 438.8 mL/min) values at baseline compared with the remaining patients (1.05 ± 0.65 g/L and 1273.0 ± 596.3 mL/min, respectively) (p = 0.027 and p < 0.001, respectively). The AV access failure rate was highest (34.8%) in tertile-1 (lowest fetuin-A level). Unadjusted Cox regression analysis showed a decrease in the risk of AV access patency loss by increasing fetuin-A concentration (hazard ratio 0.395 (95% confidence interval: 1.42-1.69), p = 0.044) but it was not confirmed in the adjusted model, although the hazard ratio was low (0.523). Kaplan-Meier analysis showed that patients in tertile-3 (highest fetuin-A concentration) had the highest primary unassisted AV access patency (λ² = 4.68, p = 0.030, log-rank test).

CONCLUSION

If our results are confirmed in further studies, fetuin-A could be used as a circulating biomarker to identify HD patients at greater risk for AV access dysfunction, who would benefit from much closer dialysis access surveillance.

The impact of cholecalciferol on markers of vascular calcification in hemodialysis patients: A randomized placebo controlled study

BACKGROUND AND AIM

Vascular calcification is an independent risk factor for cardiovascular diseases and all-cause mortality in end stage renal disease, and particularly in hemodialysis patients. Vitamin D deficiency has been shown to be associated with vascular calcification among this category of patients. Cholecalciferol or vitamin D3; the native inactivated 25-hydroxy vitamin D [25(OH)D], has been proposed to have a good impact on vascular calcification and vitamin D deficiency. However, clinical data is still limited.

METHODS AND RESULTS

A prospective, randomized, placebo-controlled study was carried out to evaluate the effect of oral cholecalciferol on vascular calcification and 25(OH)D levels in hemodialysis patients. A total of sixty eligible hemodialysis patients were randomly assigned to either a treatment group (Oral 200.000IU Cholecalciferol per month) or a placebo group, for 3 months. Serum 25-hydroxy vitamin D (25(OH)D), fetuin-A, fibroblast growth factor (FGF-23), osteoprotegerin (OPG), calcium, phosphorus, their product (CaXP) and intact parathyroid hormone (iPTH) levels, were all assessed at baseline and at the end of the study. ClinicalTrials.gov registration number: NCT03602430. Cholecalciferol significantly increased serum levels of 25(OH)D and fetuin-A in the treatment group (p-value < 0.001), while no significant difference was observed in the placebo group. Cholecalciferol administration showed no effect on either FGF-23 or OPG. None of the treatment group patients experienced any adverse effects.

CONCLUSION

Cholecalciferol was shown to be an effective, tolerable, inexpensive pharmacotherapeutic option to overcome vitamin D deficiency, with a possible modulating effect on fetuin-A, among hemodialysis patients. CLINICALTRIALS.

GOV REGISTRATION NUMBER

NCT03602430.

Osteoprotegerin is a marker of cardiovascular mortality in patients with chronic kidney disease stages 3-5

Cardiovascular disease (CVD) is the leading cause of death in patients with chronic kidney disease (CKD). Osteoprotegerin (OPG), known to regulate bone mass by inhibiting osteoclast differentiation and activation, might also play a role in vascular calcification. Increased circulating OPG levels in patients with CKD are associated with aortic calcification and increased mortality. We assessed the predictive role of OPG for all-cause and cardiovascular mortality in patients with CKD stages 3-5 over a 5-year follow-up period. We evaluated the relationship between OPG and all-cause and cardiovascular mortality in 145 CKD patients (stages 3-5) in a prospective observational follow-up study. Inflammation markers, including high-sensitivity C-reactive protein, standard echocardiography, and estimation of intima-media thickness in the common carotid artery, were assessed at baseline, and correlations with OPG levels were determined. The cutoff values for OPG were defined using ROC curves for cardiovascular mortality. Survival was assessed during follow up lasting for up to 5.5 years using Fine and Gray model. A total of 145 (89 men; age 58.9 ± 15.0 years) were followed up. The cutoff value for OPG determined using ROC was 10 pmol/L for general causes mortality and 10.08 pmol/L for CV causes mortality. Patients with higher serum OPG levels presented with higher mortality rates compared to patients with lower levels. Aalen-Johansen cumulative incidence curve analysis demonstrated significantly worse survival rates in individuals with higher baseline OPG levels for all-cause and cardiovascular mortality (p < 0.001). In multivariate analysis, OPG was a marker of general and cardiovascular mortality independent of sex, age, CVD, diabetes, and CRP levels. When CKD stages were included in the multivariate analysis, OPG was an independent marker of all-cause mortality but not cardiovascular mortality. Elevated serum OPG levels were associated with higher all-cause and cardiovascular mortality risk, independent of age, CVD, diabetes, and inflammatory markers, in patients with CKD.

Effects of fetuin-A with diverse functions and multiple mechanisms on human health

Fetuin-A (Alfa 2-Heremans-Schmid) is a glycoprotein that is mainly synthesized by hepatocytes and then released into the bloodstream. While fetuin-A, a multifunctional protein, has inhibitory effects on health in the processes of calcification, mineralization, coronary artery calcification (CAC), and kidney stone formation by various mechanisms, it has such stimulatory effects as obesity, diabetes, and tumor progression processes. Fetuin-A produces these effects on the organism mainly by playing a role in the secretion levels of some inflammatory cytokines and exosomes, preventing unwanted calcification, inhibiting the autophosphorylation of tyrosine kinase, suppressing the release of adiponectin and peroxisome proliferator-activated receptor-γ (PPARγ), activating the toll-like receptor 4 (TLR-4), triggering the phosphatidylinositol 3 (PI3) kinase/Akt signaling pathway and cell proliferation, and mimicking the transforming growth factor-beta (TGF-β) receptor. In the present review, fetuin-A was examined in a wide perspective from the structure and release of fetuin-A to its effects on health.

Soluble Klotho is associated with mortality and cardiovascular events in hemodialysis

Background

Klotho is a transmembrane protein acting as a co-receptor for FGF-23 and thus exerts clinical actions on mineral metabolism. The association of secreted Klotho with outcomes in CKD patients is unclear. This study examined the relation between plasma Klotho and cardiovascular events in dialysis patients, accounting for common and CKD-MBD related risk factors, arterial stiffness and atherosclerotic burden.

Methods

Seventy-nine chronic hemodialysis patients were observed for a median follow-up of 5.5 years. Klotho levels as well as carotid–femoral pulse wave velocity (cfPWV) and common carotid intima-media thickness (ccIMT) measurements were performed at baseline. The primary end-point was first occurrence of all-cause death, non-fatal myocardial infarction or non-fatal stroke. Secondary end-points were: (i) all-cause mortality; (ii) cardiovascular mortality; (iii) a combination of cardiovascular death, non-fatal MI, non-fatal stroke, resuscitation after cardiac arrest, coronary revascularization, heart failure hospitalization and atrial fibrillation.

Results

Cumulative freedom from the primary endpoint was 31% for the low-Klotho group (≤745 pg/ml) and 53% for the high-Klotho group (logrank p = 0.017); HR: 2.137, 95%CI 1.124–4.065. Cumulative survival was insignificantly lower (44% vs 56%, p = 0.107), but cumulative cardiovascular survival (63% vs 88%, p = 0.029) and cumulative freedom from the cardiovascular composite outcome (18% vs 45%, p = 0.009) were significantly lower in the low-Klotho group. In modelled Cox-regression analysis the association of low Klotho with the primary endpoint remained significant after stepwise adjustment for cFGF3, PTH, Ca x P product, established risk factors (age, dialysis vintage, diabetes, hypertension, smoking, history of cardiovascular disease) as well as cfPWV and ccIMT [Model 6: HR:2.759, 95%CI 1.223–6.224, p = 0.014].

Conclusions

Low Klotho is associated with cardiovascular events in hemodialysis patients, independently from factors associated with mineral-bone disease, common risk factors and intermediate outcomes, such as cfPWV and ccIMT.

Serum osteoprotegerin is an independent marker of central arterial stiffness as assessed using carotid-femoral pulse wave velocity in hemodialysis patients: a cross sectional study

Background

Cardiovascular morbidity and mortality are highly prevalent in patients with end-stage renal disease, and osteoprotegerin (OPG) may be an important link between bone loss and vascular calcification. This study was conducted to evaluate the relationship between central arterial stiffness and serum OPG levels in hemodialysis (HD) patients.

Methods

Blood samples were collected from 120 HD patients, and the carotid–femoral pulse wave velocity (cfPWV) value was measured using a validated tonometry system. The cfPWV value of > 10 m/s was used to define the high artery stiffness group. Serum OPG levels were analyzed categorically into tertiles.

Results

Of the 120 HD patients, 53 (44.2%) were defined as the high arterial stiffness group, who had higher values of systolic blood pressure (p = 0.038), serum calcium (p = 0.007), and OPG (p <  0.001) levels and a higher prevalence of diabetes mellitus (DM, p = 0.001). Increasing tertiles of serum OPG levels were significantly associated with greater height (p = 0.011), male gender (p = 0.008), higher cfPWV values (p = 0.020), and lower intact parathyroid hormone (iPTH, p = 0.049) levels. Multivariable linear regression analysis showed that cfPWV value was independently associated with DM (β = 1.83, p = 0.008) and increasing tertiles of serum OPG levels (β = 0.89 and 1.63 for tertile 2 and tertile 3, respectively, p for trend = 0.035) in HD patients. Multivariable logistic regression analysis revealed that, in addition to age, DM, low iPTH levels, and high serum calcium levels, increasing tertiles of serum OPG levels (OR = 5.34 for tertile 2; OR = 7.06 for tertile 3; p for trend = 0.002) were an independent predictor of high arterial stiffness in HD patients. Serum calcium levels positively correlated with cfPWV value only in the highest OPG tertile group (r = 0.408, p = 0.009).

Conclusion

A positive association was detected between serum OPG levels and central arterial stiffness in HD patients, and patients with high serum OPG levels may have greater influence of calcium load on central arterial stiffening.

Clinical implications of fetuin-A

Fetuin-A, also termed alpha2-Heremans-Schmid glycoprotein, is a 46kDa hepatocyte derived protein (hepatokine) and serves multifaceted functions.

The association between fetuin-A and testosterone levels and markers of arterial stiffness in Saudi subjects with type 2 diabetes mellitus

BACKGROUND

Inconsistent results have been described regarding the part of fetuin-A and testosterone in arterial stiffness in type 2 diabetes mellitus (T2DM).

AIM

To look into the links of serum fetuin-A and testosterone levels with brachial-Ankle pulse wave velocity (baPWV), a marker of arteriosclerosis and common carotid intima media thickness (ccIMT), a marker of early atherosclerosis, in diabetic Saudi men patients.

SUBJECTS AND METHODS

One hundred and fifty adult male patients with T2DM and 60 non-diabetic control subjects were enrolled from different Saudi Arabia Taif hospitals. Biochemical analysis, anthropometric measurements, blood pressure, baPWV and ccIMT were investigated.

RESULTS

Stepwise regression in diabetic patients revealed that the most important predictor of ba-PWV was serum fetuin-A followed by serum glucose and the most important predictor of ccIMT was serum fetuin-A followed by serum HDL then serum triglycerides.

CONCLUSIONS

Only fetuin-A levels not testosterone are negatively associated with early markers of atherosclerosis.

Arterial stiffness in end-stage renal disease-pathogenesis, clinical epidemiology, and therapeutic potentials

Arterial stiffness is an important risk factor for cardiovascular morbidity and mortality in patients with end-stage renal disease (ESRD). Arterial stiffness aggravates cardiovascular risk via multiple pathways, such as augmentation of aortic systolic pressure, subendocardial hypoperfusion, and excess pulsatile energy transmission from macro- to microcirculation. Pathogenesis of the arteriosclerotic process in ESRD is complex and not yet fully understood. Several factors unique to ESRD, such as mineral metabolism disturbances, vascular calcifications, formation of advanced glycation end-products, and acute and chronic volume overload, are proposed to play a particular role in the progression of arteriosclerosis in ESRD. As these and other mechanistic pathways of arterial stiffening in ESRD are elucidated, there is hope that this knowledge will be translated into novel therapeutic interventions targeting arterial stiffness. In the meantime, blood pressure (BP) lowering via strict volume control and appropriate use of antihypertensive drugs is a fundamental step in reversing accelerated arterial stiffening and modifying the cardiovascular risk profile of ESRD patients. In this article, we review the pathogenesis, clinical epidemiology, and therapies targeting arterial stiffness in ESRD, discussing recent advances and high-priority goals of future research in these important areas.

Central blood pressures in early chronic kidney disease: an analysis of CARTaGENE

Background

Vascular stiffness and advanced chronic kidney disease (CKD) are strong determinants of higher central blood pressure (BP) and are associated with high cardiovascular morbidity and mortality. Whether mild-to-moderate CKD is associated with higher central BP independently of other comorbid conditions remains uncertain.

Methods

We evaluated the central hemodynamic profile [central systolic BP, central pulse pressure (PP), augmentation index, PP amplification, augmented pressure] of Stage 3 CKD patients and compared it with participants with estimated glomerular filtration rate (eGFR) >60 mL/min/1.73 m 2 in the CARTaGENE populational cohort through propensity score matching and multivariate regression analyses.

Results

Of the 20 004 participants, 13 114 had valid pulse wave analysis and eGFRs >30 mL/min/1.73 m 2 , of which 515 had Stage 3 CKD. These 515 patients had significantly higher peripheral systolic BP (127 ± 16 versus 125 ± 15 mmHg, P = 0.01) and central PP (43.0 ± 11.4 versus 39.7 ± 10.0 mmHg, P <0.001) than the control group (eGFR >60 mL/min/1.73 m 2 ). Propensity score matching allowed the creation of 500 pairs with similar clinical characteristics. In this matched cohort, central BPs were similar in Stage 3 CKD patients compared with controls (central PP 42.9 ± 11.3 versus 43.7 ± 11.3 mmHg, P = 0.3). Multivariate analysis using data from all patients also found that the higher central hemodynamic readings found in Stage 3 CKD patients disappeared after adjusting for comorbid conditions. In a subset of 609 participants in whom albuminuria levels were measured, urine albumin excretion was not independently associated with higher central hemodynamic indices.

Conclusion

In this large cohort from the general population, early CKD and albuminuria was not independently associated with detrimental central hemodynamic parameters.

Serum osteoprotegerin in prevalent hemodialysis patients: associations with mortality, atherosclerosis and cardiac function

Background

To assess whether serum osteoprotegerin (OPG) and/or fetuin-A predict mortality and cardiovascular (CV) morbidity and mortality in hemodialysis patients.

Methods

Multicenter, observational, prospective study that included 220 hemodialysis patients followed up for up to 6 years. Serum OPG and fetuin-A levels were measured at baseline and their possible association with clinical characteristics, CV risk biomarkers, carotid ultrasonographic findings, as well as their association with overall and CV mortality and CV events were assessed.

Results

During a mean follow-up of 3.22 ± 1.91 years, there were 74 deaths (33.6%) and 86 new cardiovascular events. In the Kaplan-Meier survival analysis, the highest tertile of OPG levels was associated with higher overall mortality (p = 0.005), as well as a higher, although non-significant, incidence of CV events and CV mortality. In contrast, fetuin-A levels did not predict any of these events. OPG levels were directly associated with age, the Charlson comorbidity index (CCI), prevalent cardiovascular disease, carotid intima-media thickness, adiponectin, troponin-I and brain natriuretic peptide (BNP). OPG showed a negative correlation with left ventricular ejection fraction (LVEF) and phosphate levels. In the multivariate Cox proportional hazard analysis, all-cause mortality was associated with the highest tertile of OPG (HR:1.957, p = 0.018), age (HR:1.031, p = 0.036), smoking history (HR:2.122, p = 0.005), the CCI (HR:1.254, p = 0.004), troponin-I (HR:3.894, p = 0.042), IL-18 (HR:1.061, p < 0.001) and albumin levels (HR:0.886, p < 0.001). In the bootstrapping Cox regression analysis, the best cut-off value of OPG associated with mortality was 17.69 pmol/L (95%CI: 5.1–18.02).

Conclusions

OPG, but not fetuin-A levels, are independently associated with overall mortality, as well as clinical and subclinical atherosclerosis and cardiac function, in prevalent hemodialysis patients.

Electronic supplementary material

The online version of this article (10.1186/s12882-017-0701-8) contains supplementary material, which is available to authorized users.

Does the OPG/RANKL system contribute to the bone-vascular axis in chronic kidney disease? A systematic review

Vascular calcification (VC) is highly prevalent in patients with chronic kidney disease (CKD) and is strongly associated with cardiovascular mortality and morbidity. Accumulating evidence over the past decade has challenged the hypothesis of close interaction between bone and VC what raises the possibility of a common underlying pathophysiological mechanism. Lately, bone regulatory proteins such as: osteoprotegerin (OPG) and Receptor Activator for Nuclear Factor κB Ligand (RANKL) has attracted attention of researchers as a possible key mediators of bone-vascular calcification imbalance. The literature search was carried out using the MEDLINE/PubMed database and a combination of keywords and MeSH terms, and only papers published since January 2005 to July 2016 were selected. The search resulted in 562 potential articles. After selection according to the eligibility criteria, 107 studies fulfilled were included (102 full texts and 5 was case reports). OPG and RANKL plays essential role in the regulation of bone metabolism and may be regarded as a possible link between VC, bone and mineral metabolism in CKD patients. Further studies are required to determine the diagnostic significance of these proteins in evaluation of progression and severity of VC process in CKD patients. Finally, the efficacy and safety, especially in regard to VC, of anti-RANKL therapy in CKD patients requires well-designed prospective, randomized trials.

Emerging Human Fetuin A Assays for Biomedical Diagnostics

Human fetuin A (HFA) plays a prominent pathophysiological role in numerous diseases and pathophysiological conditions with considerable biomedical significance; one example is the formation of calciprotein particles in osteoporosis and impaired calcium metabolisms. With impressive advances in in vitro diagnostic assays during the last decade, ELISAs have become a workhorse in routine clinical diagnostics. Recent diagnostic formats involve high-sensitivity immunoassay procedures, surface plasmon resonance, rapid immunoassay chemistries, signal enhancement, and smartphone detection. The current trend is toward fully integrated lab-on-chip platforms with smartphone readouts, enabling health-care practitioners and even patients to monitor pathological changes in biomarker levels. This review provides a critical analysis of advances made in HFA assays along with the challenges and future prospects.

Calcium Phosphate Crystals from Uremic Serum Promote Osteogenic Differentiation in Human Aortic Smooth Muscle Cells

Recent study demonstrated that calcium phosphate (CaP) crystals isolated from high phosphate medium were a key contributor to arterial calcification. The present study further investigated the effects of CaP crystals induced by uremic serum on calcification of human aortic smooth muscle cells. This may provide a new insight for the development of uremic cardiovascular calcification. We tested the effects of uremic serum or normal serum on cell calcification. Calcification was visualized by staining and calcium deposition quantified. Expression of various bone-calcifying genes was detected by real-time PCR, and protein levels were quantified by western blotting or enzyme-linked immunosorbent assays. Pyrophosphate was used to investigate the effects of CaP crystals' inhibition. Finally, CaP crystals were separated from uremic serum to determine its specific pro-calcification effects. Uremic serum incubation resulted in progressively increased calcification staining and increased calcium deposition in HASMCs after 4, 8 and 12 days (P vs 0 day <0.001 for all). Compared to cells incubated in control serum, uremic serum significantly induced the mRNA expression of bone morphogenetic factor-2, osteopontin and RUNX2, and increased their protein levels as well (P < 0.05 for all). Inhibition of CaP crystals with pyrophosphate incubation prevented calcium deposition and bone-calcifying gene over-expression increased by uremic serum. CaP crystals, rather than the rest of uremic serum, were responsible for these effects. Uremic serum accelerates arterial calcification by mediating osteogenic differentiation. This effect might be mainly attributed to the CaP crystal content.

Osteoprotegerin and osteoprotegerin/TRAIL ratio are associated with cardiovascular dysfunction and mortality among patients with renal failure

PURPOSE

The high prevalence of cardiovascular morbidity and mortality among patients with chronic kidney disease (CKD) is observed especially in those undergoing dialysis. Osteoprotegerin (OPG) and its ligands, receptor activator of nuclear factor kappa-B ligand (RANKL) and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) have been associated with cardiovascular complications. Our aim was to study their role as cardiovascular risk factors in stage 5 CKD patients.

PATIENTS AND METHODS

OPG, RANKL and TRAIL concentrations were measured in 69 hemodialyzed CKD patients and 35 healthy volunteers. In CKD patients, cardiovascular dysfunction was assessed with aortic pulse wave velocity (AoPWV), carotid artery intima-media thickness (CCA-IMT), coronary artery calcium score (CACS) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) serum concentrations. Cardiovascular and overall mortality data were collected during a 7-years follow-up.

RESULTS

OPG plasma concentrations were higher in CKD patients comparing to controls. Total soluble RANKL was lower and OPG/RANKL ratio higher in patients. Soluble TRAIL concentrations did not differ between the groups and OPG/TRAIL ratio was higher in CKD patients. OPG and OPG/TRAIL positively predicted long-term mortality (all-cause and cardiovascular) in CKD patients. OPG positively correlated with AoPWV, CCA-IMT and NT-proBNP whereas OPG/TRAIL with AoPWV and NT-proBNP. Described relationships were independent of classical and non-classical cardiovascular risk factors, with exception of age.

CONCLUSIONS

Our study confirmed the role of OPG as a biomarker of cardiovascular dysfunction and a predictor of mortality in stage 5 CKD. OPG/TRAIL ratio can be proposed as a predictor of cardiovascular dysfunction and mortality.

Receptor activator of nuclear factor κB ligand/osteoprotegerin axis and vascular calcifications in patients with chronic kidney disease

Vascular calcifications are commonly observed in patients with chronic kidney disease (CKD) and contribute to the excessive cardiovascular morbidity and mortality rates observed in these patients populations. Although the pathogenetic mechanisms are not yet fully elucidated, recent evidence suggests a link between bone metabolism and the development and progression of vascular calcifications. Moreover, accumulating data indicate that receptor activator of nuclear factor κB ligand/osteoprotegerin axis which plays essential roles in the regulation of bone metabolism is also involved in extra-osseous bone formation. Further studies are required to establish the prognostic significance of the above biomarkers as predictors of the presence and severity of vascular calcifications in CKD patients and of cardiovascular morbidity and mortality. Moreover, randomized clinical trials are needed to clarify whether inhibition of osteoclast activity will protect from vascular calcifications.

Serum fetuin-A levels and abdominal aortic calcification in healthy men - The STRAMBO study

Vascular calcification results from an imbalance between increased extracellular levels of calcium and phosphate, reduced solubility, and low levels of calcification inhibitors in blood or the vascular wall. Fetuin-A is a major circulating calcification inhibitor. Rodent models of fetuin-A deficit indicate its calcification inhibiting potential. Clinical studies suggest its role as a biomarker in vascular disease. This cross-sectional study was performed in a cohort of 974 men aged ≥ 40 years (average 68 years) consisting of men holding health insurance cover with Mutuelle des Travailleurs de la Région Lyonnaise. Abdominal aortic calcification (AAC) was assessed semi-quantitatively on lateral dual energy X-ray absorptiometry (DXA) spine scans. Serum fetuin-A was measured by an immunoassay. After adjustment for confounders (age, lifestyle, body composition, health status, treatment, glomerular filtration rate [GFR], hormones, and cytokines), prevalence of severe AAC (AAC score>4) decreased with increasing fetuin-A levels (OR=0.68 per SD increase, 95% CI: 0.54-0.84, p<0.001). After adjustment for confounders, low fetuin-A and hypertension were each associated with higher odds of AAC>4. Coexistence of low serum fetuin-A levels and heavy smoking, elevated fibroblast growth factor 23 levels or low serum dickkopf-1 levels were associated with higher odds of AAC>4. Similar results were obtained for 789 men with GFR>60 mL/min/1.73 m(2). Similar results were obtained when severe AAC was defined as AAC score >3 or AAC>5. Thus, lower serum fetuin-A levels are associated with severe AAC, suggesting that poor calcification inhibitory potential contributes to vascular calcification, independently of renal impairment.

Arterial Stiffness: A Novel Risk Factor for Kidney Injury Progression?

Arterial stiffness is typical feature of vascular remodeling in chronic kidney disease (CKD). Increased arterial stiffness raises flow and pressure pulsatility and is considered the principle pathogenic mechanism of isolated systolic hypertension, left ventricular hypertrophy, and congestive heart failure. Apart from the impact of arterial stiffness on left ventricular afterload, downstream transmission of pressure pulsatility to the level of microcirculation is suggested to promote injury of other susceptible organs. This may be of particular importance for kidney injury progression, since passive renal perfusion along with low resistance and input impedance in renal microvessels make kidneys particularly vulnerable to the damaging effect of systemic pulsatile pressure. Recent studies have provided evidence that arterial stiffness culminates in elevated pulsatility and resistance in renal microvasculature, promoting structural damage of small intra-renal arterioles. Further, prospective observational studies have shown that reduced aortic compliance is closely associated with the annual rate of renal function decline and represents independent predictor of kidney injury progression to end-stage renal disease among patients with CKD. This article provides insights into the cross-talk between macrocirculation and renal microcirculation and summarizes the currently available clinical evidence linking increased arterial stiffness with kidney disease progression.

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.

Role of osteoprotegerin in vascular disorders of the end-stage renal disease patients

AIM

To assess the osteoprotegerin (OPG) relationship with cardiovascular complications in hemodialysis (HD) patients.

METHODS

The study included 87 HD patients. Clinical characteristics, ankle-arm index (AAI), OPG and mineral markers levels were recorded. Arterial intimal calcification (AIC) and arterial medial calcification (AMC) were registered.

RESULTS

OPG levels were increased in HD patients. Patients with AIC (p = 0.006)/ AMC (p = 0.01) had higher OPG levels. OPG did not have any relation with cardiovascular diseases. OPG correlated positively with age, increased HD vintage and inversely with albumin and AAI. OPG has not been a risk factor for VC or cardiovascular disease.

CONCLUSION

OPG rising could be a reaction in defense to vascular aggression, because OPG was associated with VC, but not with vascular disease.

Serum levels of fetuin-A, osteoprotegerin and osteopontin in patients with coronary artery disease: effects of statin (HMGCoA-reductase inhibitor) therapy

BACKGROUND AND OBJECTIVES

Statins (HMGCoA-reductase inhibitors) produce numerous non-lipid related, 'pleiotropic' effects. Our aim was to investigate whether simvastatin treatment affects serum levels of vascular calcification inhibitors, such as fetuin-A, osteoprotegerin (OPG) and osteopontin (OPN), in patients with coronary artery disease (CAD).

METHODS

A total of 98 statin-free patients with angiographically proven, newly diagnosed CAD were treated with simvastatin (20-40 mg daily) for 6 months to target a low-density lipoprotein (LDL) level <100 mg/dL (the statin group [SG]). Thirty-five age- and sex-matched healthy individuals without any chronic metabolic or cardiovascular disease at baseline served as a healthy control group (HCG). Clinical, anthropometrical and metabolic parameters and serum fetuin-A, OPG, OPN and high-sensitivity C-reactive protein (hsCRP) levels were assayed at baseline in all participants and after 6 months only in SG patients.

RESULTS

Compared with HCG subjects at baseline, SG patients exhibited higher serum levels of OPG (7.39 ± 2.94 pmol/L vs 2.47 ± 1.15 pmol/L, p < 0.001), OPN (60.99 ± 17.52 ng/mL vs 45.45 ± 10.26 ng/mL, p = 0.005) and hsCRP (4.66 ± 1.74 mg/L vs 1.58 ± 0.56 mg/L, p < 0.001) as well as lower serum levels of fetuin-A (0.222 ± 0.036 μg/L vs 0.839 ± 0.092 μg/L, p < 0001). Apart from significantly reducing plasma total cholesterol and LDL, simvastatin also reduced serum levels of fetuin-A (by ~62.6 %), OPG (by ~47.2 %), OPN (by ~44.6 %) and hsCRP (by ~45.3 %) (p < 0.05) in SG patients. In standard multiple regression analysis, the simvastatin-induced reduction in fetuin-A was independently associated with changes in total cholesterol (β = -0.289, p = 0.048) and LDL (β = -0.302, p = 0.032) (R (2) = 0.305, p = 0.040).

CONCLUSION

Patients with CAD showed derangements in serum levels of all vascular calcification inhibitors compared with those in healthy controls. Simvastatin treatment for 6 months significantly decreased serum fetuin-A, OPG and OPN levels, but the clinical relevance of this requires further investigation.

Relationship of apelin, procalcitonin, and fetuin-A concentrations with carotid intima-media thickness in acromegaly

Background

Acromegaly is characterized by excess growth hormone and insulin-like growth factor-1 concentrations. There is conflicting evidence as to whether acromegaly is associated with an increased risk of atherosclerosis. Apelin is an adipose tissue-derived peptide that may be associated with hyperinsulinemia. Fetuin-A is a hepatocyte produced plasma glycoprotein that has an important role as a calcification inhibitor. The aim of this study was to examine apelin, fetuin-A, and procalcitonin concentrations and to assess their relationship with carotid intima medial thickness (cIMT) in subjects with acromegaly.

Methods

Apelin, fetuin-A, and procalcitonin serum concentrations were measured in 37 (20 inactive and 17 active) subjects with acromegaly and 30 control subjects, along with carotid intima medial thickness.

Results

The concentrations of apelin, fetuin-A, and procalcitonin were increased in subjects with acromegaly. There were significant correlations between apelin, fetuin-A, and procalcitonin in subjects with acromegaly. Carotid intima medial thickness values were similar between control subjects and subjects with acromegaly.

Conclusions

Carotid intima medial thickness was not increased in subjects with acromegaly. It is possible that the increased apelin and fetuin-A concentrations observed play a protective role against the development of atherosclerosis in subjects with acromegaly.

Arterial stiffness in chronic kidney disease: an update

PURPOSE OF REVIEW

Epidemiological studies have established arterial stiffness as an important risk factor for cardiovascular events and mortality in people with chronic kidney disease (CKD) at all stages. Although much has been learned about the mechanisms that lead to arterial stiffening in CKD, many questions remain unanswered and the optimal interventions for attenuating arterial stiffness remain to be determined.

RECENT FINDINGS

Recent data have confirmed the value of arterial stiffness as a predictor of both cardiovascular and renal risk. Advanced glycation end-product accumulation and chronic cytomegalovirus infection have been identified as novel potential contributors to arterial stiffening, but fibroblast growth factor 23 has not. Genetic studies suggest that the association between chronic kidney and cardiovascular disease is a result of clinical and environmental rather than genetic factors. Treatment with angiotensin-converting enzyme inhibitor or aldosterone inhibitor improves arterial stiffness in association with lowering blood pressure, but several potential novel interventions for reducing arterial stiffness await further investigation.

SUMMARY

Arterial stiffness is increasingly recognized as an important potentially modifiable measure of subclinical vascular disease in people with CKD. The introduction of arterial stiffness into routine practice awaits research focussed on including pulse wave velocity in renal and cardiovascular risk prediction tools, as well as interventions for ameliorating arterial stiffness.

Elevated levels of plasma osteoprotegerin are associated with all-cause mortality risk and atherosclerosis in patients with stages 3 to 5 chronic kidney disease

Osteoprotegerin (OPG) regulates bone mass by inhibiting osteoclast differentiation and activation, and plays a role in vascular calcification. We evaluated the relationship between osteoprotegerin levels and inflammatory markers, atherosclerosis, and mortality in patients with stages 3-5 chronic kidney disease. A total of 145 subjects (median age 61 years, 61% men; 36 patients on hemodialysis, 55 patients on peritoneal dialysis, and 54 patients with stages 3-5 chronic kidney disease) were studied. Clinical characteristics, markers of mineral metabolism (including fibroblast growth factor-23 [FGF-23]) and inflammation (high-sensitivity C-reactive protein [hsCRP] and interleukin-6 [IL-6]), and the intima-media thickness (IMT) in the common carotid arteries were measured at baseline. Cardiac function was assessed by color tissue Doppler echocardiography. After 36 months follow-up, the survival rate by Kaplan-Meier analysis was significantly different according to OPG levels (χ²=14.33; P=0.002). Increased OPG levels were positively associated with IL-6 (r=0.38, P<0.001), FGF-23 (r=0.26, P<0.001) and hsCRP (r=0.0.24, P=0.003). In addition, OPG was positively associated with troponin I (r=0.54, P<0.001) and IMT (r=0.39, P<0.0001). Finally, in Cox analysis, only OPG (HR=1.07, 95%CI=1.02-1.13) and hsCRP (HR=1.02, 95%CI=1.01-1.04) were independently associated with increased risk of death. These results suggested that elevated levels of serum OPG might be associated with atherosclerosis and all-cause mortality in patients with chronic kidney disease.