Associations of sclerostin with carotid artery atherosclerosis and all-cause mortality in Chinese patients undergoing maintenance hemodialysis

Analysis of factors influencing vascular calcification in peritoneal dialysis patients and their impact on long-term prognosis

BACKGROUND

This study aims to investigate the influencing factors of vascular calcification in peritoneal dialysis (PD) patients and its relationship with long-term prognosis.

METHODS

This retrospective cohort study included chronic kidney disease patients undergoing peritoneal dialysis at the Peritoneal Dialysis Center of Beijing Luhu Hospital, Capital Medical University, from January 2019 to March 2019. Demographic and clinical laboratory data, including serum sclerostin (SOST), calcium (Ca), phosphate (P), serum albumin (ALB), and intact parathyroid hormone (iPTH) levels, were collected. Abdominal aortic calcification (AAC) was assessed using abdominal lateral X-ray examination to determine the occurrence of vascular calcification, and patients were divided into the AAC group and Non-AAC group based on the results.

RESULTS

A total of 91 patients were included in the study. The AAC group consisted of 46 patients, while the Non-AAC group consisted of 45 patients. The AAC group had significantly older patients compared to the non-AAC group (P < 0.001) and longer dialysis time (P = 0.004). Multivariable logistic regression analysis indicated that risk factors for vascular calcification in PD patients included dialysis time, diabetes, hypertension, and SOST. Kaplan-Meier survival analysis showed that the AAC group had a significantly higher mortality rate than the non-AAC group (χ2 = 35.993, P < 0.001). Multivariable Cox regression analysis revealed that dialysis time, diabetes and AAC were risk factors for all-cause mortality in peritoneal dialysis patients.

CONCLUSION

Longer dialysis time, comorbid diabetes, comorbid hypertension, and SOST are risk factors for vascular calcification in PD patients. Additionally, AAC, longer dialysis time, and comorbid diabetes are associated with increased risk of all-cause mortality in peritoneal dialysis patients.

New Emerging Biomarkers for Bone Disease: Sclerostin and Dickkopf-1 (DKK1)

A healthy skeleton depends on a continuous renewal and maintenance of the bone tissue. The process of bone remodeling is highly controlled and consists of a fine-tuned balance between bone formation and bone resorption. Biochemical markers of bone turnover are already in use for monitoring diseases and treatment involving the skeletal system, but novel biomarkers reflecting specific biological processes in bone and interacting tissues may prove useful for diagnostic, prognostic, and monitoring purposes. The Wnt-signaling pathway is one of the most important pathways controlling bone metabolism and consequently the action of inhibitors of the pathway such as sclerostin and Dickkopf-related protein 1 (DKK1) have crucial roles in controlling bone formation and resorption. Thus, they might be potential markers for clinical use as they reflect a number of physiological and pathophysiological events in bone and in the cross-talk with other tissues in the human body. This review focuses on the clinical utility of measurements of circulating sclerostin and DKK1 levels based on preanalytical and analytical considerations and on evidence obtained from published clinical studies. While accumulating evidence points to clear associations with a number of disease states for the two markers, and thus, the potential for especially sclerostin as a biochemical marker that may be used clinically, the lack of standardization or harmonization of the assays still hampers the clinical utility of the markers.

Sclerostin as a biomarker of cardiovascular risk in women with systemic lupus erythematosus

Cardiovascular disease is one of the main causes of death in patients with systemic lupus erythematosus (SLE). On the other hand, sclerostin is a reliable and early biomarker of vascular calcification. This study aimed to estimate the association between sclerostin and two markers of cardiovascular risk, carotid atherosclerotic plaque (CP) and carotid-femoral pulse wave velocity (PWV), in women with SLE. The presence of CP (determined by carotid artery ultrasound) and PWV were measured in 68 women with SLE and preserved renal function. None of the participants had a history of cardiovascular disease. Serum levels of sclerostin were determined using the ELISA method. Other factors associated with increased cardiovascular risk were also measured. The association between sclerostin, CP and PWV was assessed using Receiver Operating Characteristic (ROC) curves and multivariate regression models. The area under the ROC curve was 0.785 (95% confidence interval [CI] 0.662-0.871) for CP and 0.834 (95% CI 0.729-0.916) for dichotomized PWV. After adjusting for other cardiovascular risk factors, it was found that a 10-units increase in sclerostin values was associated with a 44% increase in the odds of CP (95% CI 1-105), but no adjusted association was observed between sclerostin and PWV. Predictive models included age (for both outcomes), hypertension, Framingham risk score and C-reactive protein (for PWV), but not sclerostin. Sclerostin is associated with the presence of CP in women with SLE. Further research should confirm its possible role as a biomarker of cardiovascular risk in these patients.

Joint effects of carotid plaques and renal impairment on the risk of cardiovascular disease and all-cause death in a community-based population: The Kailuan cohort study

OBJECTIVE

It is unknown whether renal impairment and atherosclerosis increase the risk of cardiovascular disease (CVD) and death. Atherosclerosis already raises the risk of CVD and all-cause death. This study investigated the joint effects of carotid plaques and renal impairment on CVD and all-cause death in community-based populations.

METHODS

The study cohort consisted of 20,416 participants from the Kailuan Study who completed a carotid plaque ultrasound in 2012. A glomerular filtration rate (GFR) of < 60 ml/min or trace semiquantitative proteinuria or higher were both considered signs of renal insufficiency. We divided them into four groups according to the presence of carotid plaque and renal impairment. These groups were categorized as no carotid plaque, estimated glomerular filtration rate (eGFR) ≥ 60 ml/min, and proteinuria < trace; no carotid plaque, eGFR < 60 ml/min, and proteinuria ≥ trace; carotid plaque, eGFR ≥ 60 ml/min and proteinuria < trace; and carotid plaque, eGFR < 60 ml/min, and proteinuria ≥ trace, respectively. We investigated the combined effect of renal impairment and carotid plaque on cardiovascular events and all-cause death in the Kailuan community-based population.

RESULT

Participants with carotid plaque, eGFR < 60 ml/min and proteinuria had a 2.88-fold higher risk of all-cause death (95% CI, 2.18-3.80), which was significantly higher than those with lone factors (HR, 1.57; 95% CI, 1.04-2.36; and HR, 1.91; 95% CI, 1.56-2.32), compared to participants with no carotid plaque, eGFR ≥ 60 ml/min and proteinuria

CONCLUSION

The joint of carotid plaques and renal impairment may further increase the risk of CVD and all-cause death compared with participants with alone factors in the age of ≥ 50 years, but not in the age of < 50 years, from a community-based study.

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Key Words

• all-cause death
• cardiovascular disease
• carotid plaque
• community-based populations
• estimated glomerular filtration rate

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Affiliation(s)

Wen Li Department of Ultrasound in Medicine, Shanghai Sixth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
Wenkun Bai Department of Ultrasound in Medicine, Shanghai Sixth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
Congliang Miao Department of Internal and Emergency Medicine, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
Shuohua Chen Department of Cardiology, Kailuan General Hospital Affiliated to North China University of Science and Technology, Tangshan, China
Xinyu Zhang Department of Ultrasound in Medicine, Shanghai Sixth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
Yanfeng Fan Department of Ultrasound in Medicine, Shanghai Sixth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
Xiao Li Department of Ultrasound in Medicine, Shanghai Sixth People’s Hospital Affiliated to Shanghai Jiao Tong University School of Medicine, Shanghai, China
Shouling Wu Department of Cardiology, Kailuan General Hospital Affiliated to North China University of Science and Technology, Tangshan, China
Xuemei Liu Department of Ultrasound in Medicine, Beijing Hospital of Traditional Chinese Medicine, Capital Medical University, Beijing, China
Jiang Hong Department of Internal and Emergency Medicine, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China

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Circulating miRNA-29b and Sclerostin Levels Correlate with Coronary Artery Calcification and Cardiovascular Events in Maintenance Hemodialysis Patients

Objective

Coronary artery calcification (CAC) is a common complication in end-stage renal disease (ESRD) patients undergoing maintenance hemodialysis (MHD), and the extent of CAC is a predominant predictor of cardiovascular outcomes in MHD patients. In this study, we sought to uncover the relationship between circulating miRNA-29b, sclerostin levels, CAC, and cardiovascular events (CVEs) in MHD patients.

Methods

This study recruited patients receiving MHD for at least three months in the Hainan General Hospital between January 2016 and June 2019, and all patients were followed up 24 months for CVEs. The serum level of sclerostin was determined by enzyme-linked immunosorbent assay (ELISA) and miRNA-29b expression by real-time qPCR (RT-qPCR). All patients received cardiac CT scans to evaluate CAC, and CAC scores were expressed in Agatston units. The MHD patients with CACs <100 were arranged into the CAC (<100) group, those with 100–400 CACs into the CAC (100–400) group, and those with CACs >400 into the CAC (>400) group. Net reclassification index (NRI) and integrated discrimination index (IDI) were calculated to assess the predictive performance of serum sclerostin level for the occurrence of CVEs.

Results

Compared with the CAC (<100) group, the CAC (>400) group had higher proportions of older patients, hypertension and diabetes mellitus patients, longer dialysis duration, higher mean arterial pressure (MAP), higher levels of high-sensitivity C-reactive protein (hs-CRP), alkaline phosphatase (ALP), and phosphate (P < 0.05). It was found that the CAC (100–400) and CAC (>400) groups exhibited higher serum levels of sclerostin but lower levels of miRNA-29b than the CAC (<100) group (P < 0.05) and the CAC (>400) group had a higher level of sclerostin and a lower level of miRNA-29b than the CAC (100–400) group (P < 0.05). The circulating level of miRNA-29b was negatively correlated with the serum level of sclerostin in MHD patients (r = −0.329, P < 0.01). The multivariate logistic regression analysis showed that hs-CRP, phosphate, sclerostin, and miRNA-29b were independent risk factors for CAC in MHD patients (P < 0.05, Table 2). ROC for prediction of CAC by sclerostin yielded 0.773 AUC with 95% CI 0.683–0.864 (P < 0.01). As depicted by Kaplan–Meier curves of CVE incidence in MHD patients according to median sclerostin (491.88 pg/mL) and median miRNA-29b (Ct = 25.15), we found that serum levels of sclerostin and miRNA-29b were correlated with the incidence of CVEs in MHD patients. When a new model was used to predict the incidence of CVEs, NRI 95% CI was 0.60 (0.16–1.03) (P < 0.05) and IDI 95% CI was 0.002 (−0.014 to 0.025) (P < 0.05), suggesting that sclerostin added into the old model could improve the prediction of the incidence of CVEs.

Conclusions

These data suggest that circulating miRNA-29b and sclerostin levels are correlated with CAC and incidence of CVEs in MHD patients. Higher sclerostin and lower miRNA-29b may serve as independent risk factors for the incidence of CVEs in MHD patients.

Cardiovascular Safety of Anti-Sclerostin Therapy in Chronic Kidney Disease

The significance of sclerostin for bone and cardiovascular health in patients with chronic kidney disease (CKD) is complex and incompletely understood. Experimental evidence suggests that anti-sclerostin therapy shows diminished efficacy on bone in the setting of CKD. Limited clinical evidence suggests that the osteoanabolic and anti-resorptive activity is attenuated, but hypocalcemia is more prevalent in patients with advanced CKD (eGFR < 30 mL/min) treated with anti-sclerostin (romosozumab) therapy as compared to patients without kidney disease. Furthermore, sclerostin is prominently expressed in uremic arteries. Whether the inhibition of sclerostin has adverse effects on cardiovascular health in CKD is currently unknown. This review summarizes the current understanding of the physiology and pathophysiology of sclerostin in CKD, with a focus on the cardiovascular safety of anti-sclerostin therapy in patients with or without CKD.

Serum sclerostin level and its relation to subclinical atherosclerosis in the polycystic ovary syndrome phenotypes: A prospective controlled study

Objective

We aim to study the relationship between atherosclerosis and serum sclerostin levels in different phenotypes of polycystic ovary syndrome (PCOS).

Materials and Methods

A total of 134 women with PCOS and 33 age-matched controls participated in this study. Women with PCOS were further divided into subgroups based on their PCOS phenotypes: phenotype A (n=35), phenotype B (n=33), phenotype C (n=31), and phenotype D (n=35). Metabolic parameters, hormonal parameters, carotid intima-media thickness (CIMT), and sclerostin levels were compared among the PCOS phenotypes.

Results

Statistically significant differences occurred among groups regarding follicle-stimulating hormone, luteinizing hormone, estradiol, total cholesterol, low-density lipoprotein, Ferriman-Gallwey score, total testosterone, and free androgen index. The mean CIMT was statistically higher in all PCOS phenotypes than in controls. In subgroup comparison, phenotypes A and B had a higher body mass index (BMI) adjusted CIMT than other phenotypes, respectively (p=0.005). Serum sclerostin levels were higher in PCOS patients than in controls. A concentration of ≥6.297 ng/mL showed a sensitivity of 56% and a specificity of 69.7% to predict PCOS. The BMI-adjusted sclerostin level was significantly higher in phenotype C (20.3±0.7 ng/mL) than in other phenotypes.

Conclusion

Patients with phenotypes A and B seem to have an increased risk for atherosclerosis. Although sclerostin was higher in PCOS patients, we could not demonstrate the relation between sclerostin and atherosclerosis in different PCOS phenotypes.

Relation of Wnt Signaling Pathway Inhibitors (Sclerostin and Dickkopf-1) to Left Ventricular Mass Index in Maintenance Hemodialysis Patients

BACKGROUND

Left ventricular hypertrophy (LVH) is common in hemodialysis (HD) patients. It predicts poor prognosis. Several inhibitors regulate Wnt canonical pathways like Dickkopf-related protein-1 (Dkk-1) and sclerostin.

OBJECTIVES

To investigate the relationship between serum sclerostin, Dkk-1, left ventricular mass (LVM), and LVM index (LVMI) in HD patients.

METHODS

This is a cross-sectional study including 65 HD patients in our HD unit. Patients were divided into two groups according to LVMI (group 1 with LVMI < 125 gm/m2 (N = 29) and group 2 with LVMI > 125 gm/m2 (N = 36)). Echocardiographic evaluation of the LVM, aortic, and mitral valves calcification (AVC and MVC) was done. Serum levels of sclerostin and Dkk-1 and patients' clinical and biochemical data were recorded.

RESULTS

Group 2 showed significantly higher age, blood pressure, AVC, and MVC and significantly lower hemoglobin, sclerostin, and Dkk-1 levels. LVM and LVMI had a significant linear negative correlation to both serum sclerostin and Dkk-1 (r = -0.329 and -0.257, P=0.01 and 0.046 for LVM; r = -0.427 and -0.324, P=0.001 and 0.012 for LVMI, resp.). Serum Dkk-1 was an independent negative indicator for LVM and LVMI in multiple regression analyses (P=0.003 and 0.041 with 95% CI = -0.963 to -0.204 and -0.478 to -0.010, resp.).

CONCLUSION

Serum sclerostin and Dkk-1 were significantly lower in HD patients with increased LVMI > 125 gm/m2, and both had a significant linear negative correlation with LVM and LVMI. Dkk-1 was a significant negative independent indicator for LVM and LVMI in HD patients.

Meta-analysis of the association between sclerostin level and adverse clinical outcomes in patients undergoing maintenance haemodialysis

BACKGROUND

Studies regarding the relationship of sclerostin (Scl) with clinical outcomes in patients undergoing maintenance haemodialysis have yielded controversial findings. This meta-analysis was performed to investigate the predictive role of Scl in this patient population.

METHODS

Several electronic medical databases (e.g. PubMed, Embase, Web of Science and Cochrane Library) were searched for eligible studies through December 20, 2019. Summary hazard ratios (HRs) with 95% confidence intervals (CIs) were calculated based on Scr level (high or low) using a random or fixed effects model.

RESULTS

From among 641 initially screened publications, 16 eligible studies were included in this meta-analysis. A high Scl level was not associated with cardiovascular events [HR = 0.8 (95% CI, 0.42-1.35)] or all-cause mortality [HR = 0.93 (95% CI, 0.56-1.54)]. There was high heterogeneity, but no evidence of publication bias. Interestingly, a high Scl level was associated with reduced cardiovascular events [HR = 0.44 (95% CI, 0.29-0.69)] in the subgroup by shorter follow-up period or all-cause mortality [pooled HR = 0.58 (95% CI, 0.36-0.91)] by shorter dialysis vintage.

CONCLUSION

This meta-analysis indicated that a high Scl level did not predict total clinical outcomes in patients undergoing maintenance haemodialysis despite survival benefits in the subgroups. The predictive role of Scl in these patients should be further evaluated in large prospective studies.

The Impact of Sclerostin Levels on Long-Term Prognosis in Patients Undergoing Coronary Angiography: A Personalized Approach with 9-Year Follow-Up

Sclerostin might play a role in atherosclerosis development. This study aimed to analyze the impact of baseline sclerostin levels on 9-year outcomes in patients without significant renal function impairment and undergoing coronary angiography. The primary study endpoint was the rate of major cardiovascular events (MACE), defined as a combined rate of myocardial infarction (MI), stroke, or death at 9 years. We included 205 patients with a mean age of 62.9 ± 0.6 years and 70.2% male. Median serum sclerostin concentration was 133.22 pg/mL (IQR 64.0–276.17). At 9 years, in the whole population, the rate of MACE was 34.1% (n = 70), MI: 11.2% (n = 23), stroke: 2.4% (n = 5), and death: 20.5% (n = 42). In the high sclerostin (>median) group, we observed statistically significant higher rates of MACE and death: 25.2% vs. 43.1% (HR 1.75, 95% CI 1.1–2.10, p = 0.02) and 14.6% vs. 26.5% (HR 1.86, 95% CI 1.02–3.41, p = 0.049), respectively. Similar relationships were observed in patients with chronic coronary syndrome and SYNTAX 0–22 subgroups. Our results suggest that sclerostin assessment might be useful in risk stratification, and subjects with higher sclerostin levels might have a worse prognosis.

The Association between the Activin A Serum Level and Carotid Intima-Media Thickness in Chronic Kidney Disease Patients

Introduction

Chronic kidney disease (CKD) is associated with high mortality rates, mainly as a result of cardiovascular complications. Meanwhile, recent studies have suggested a role of a homodimer protein called activin A in chronic kidney disease-mineral and bone disorder (CKD-MBD) conditions that may exist in the vascular calcification and osteolytic process. Ultrasound examination of the carotid intima-media thickness (cIMT) is a noninvasive method to assess vascular calcification. This study aimed to analyze the relationship between the activin A serum level and cIMT in patients with CKD at Mohammad Hoesin Hospital, Palembang, Indonesia.

Methods

We conducted a hospital-based, cross-sectional study of consecutive CKD patients at the Department of Internal Medicine, Mohammad Hoesin Hospital, from July to November 2019. The level of activin A was measured by enzyme-linked immunosorbent assay. Meanwhile, cIMT measurements were collected by B-mode ultrasound imaging.

Results

A total of 55 patients with CKD were included in this investigation. The median serum activin A level in these patients was 236.17 (116.33–283) pg/mL, while the median cIMT was 0.8 (0.6–1.45) mm. A relationship between the serum activin A level and cIMT (r  =  0.449; p = 0.001) was observed. During multivariate analysis with linear regression, triglyceride (p = 0.049), phosphate (p = 0.005), and activin A (p = 0.020) serum levels were factors associated with cIMT.

Conclusion

In this study, a relationship between the activin A serum level and cIMT in patients with CKD was identified. Vascular calcification should be screened for in all CKD patients by the measurement of cIMT.

Associations of serum sclerostin and Dickkopf-related protein-1 proteins with future cardiovascular events and mortality in haemodialysis patients: a prospective cohort study

Background

Sclerostin and Dickkopf-related protein-1 (Dkk-1) proteins are inhibitors of the canonical Wnt/β-catenin bone pathway. Sclerostin but not Dkk-1 is associated with increased arterial stiffness. This study examined the prognostic significance of sclerostin and Dkk-1 levels for cardiovascular outcomes and mortality in haemodialysis (HD) patients.

Methods

Serum sclerostin and Dkk-1 levels were measured with enzyme-linked immunosorbent assay in 80 HD patients that were followed-up for a median of 45 months. Factors that could interfere with the association of sclerostin and Dkk-1 with outcomes [including carotid–femoral pulse wave velocity (PWV), parathyroid hormone (PTH), calcium–phosphate product and others] were assessed at baseline. The primary endpoint was a combination of all-cause death, non-fatal myocardial infarction, non-fatal stroke, coronary revascularization, hospitalization for decompensated heart failure and new-onset atrial fibrillation. Secondary endpoints included cardiovascular and all-cause mortality.

Results

Cumulative freedom from the primary endpoint was significantly lower for higher tertiles of sclerostin (77.8, 69.2 and 40.7%; Tertiles 1–3, respectively; log-rank P = 0.004). The risk for the primary outcome gradually increased for higher sclerostin tertiles [Tertile 3: hazard ratio (HR) = 3.847, 95% confidence interval (CI) 1.502–9.851]. No significant association was evident between sclerostin and all-cause mortality, whereas higher sclerostin levels presented a trend towards higher risk for cardiovascular mortality. Dkk-1 levels exhibited no association with the risk of the primary or secondary endpoints. In stepwise Cox regression modelled analysis, sclerostin levels were associated with the primary outcome, independently of PTH, calcium–phosphate product, serum albumin, C-reactive protein and PWV levels (HR = 2.921, 95% CI 1.401–6.090; P = 0.004).

Conclusions

High sclerostin levels are associated with lower cumulative freedom and higher risk for a composite endpoint of cardiovascular events and mortality. Dkk-1 exhibited no association with the future risk of adverse outcomes.

Sclerostin and Vascular Pathophysiology

There is cumulating evidence for a contribution of Wnt signaling pathways in multiple processes involved in atherosclerosis and vascular aging. Wnt signaling plays a role in endothelial dysfunction, in the proliferation and migration of vascular smooth muscle cells (VSMCs) and intimal thickening. Moreover, it interferes with inflammation processes, monocyte adhesion and migration, as well as with foam cell formation and vascular calcification progression. Sclerostin is a negative regulator of the canonical Wnt signaling pathway and, accordingly, the consequence of increased sclerostin availability can be disruption of the Wnt signalling cascade. Sclerostin is becoming a marker for clinical and subclinical vascular diseases and several lines of evidence illustrate its role in the pathophysiology of the vascular system. Sclerostin levels increase with aging and persist higher in some diseases (e.g., diabetes, chronic kidney disease) that are known to precipitate atherosclerosis and enhance cardiovascular risk. Current knowledge on the association between sclerostin and vascular diseases is summarized in this review.

The relationship between sclerostin and carotid artery atherosclerosis in patients with stage 3-5 chronic kidney disease

PURPOSE

Sclerostin is an antagonist of the Wnt/β-catenin pathway. We previously reported that sclerostin is closely related to carotid artery atherosclerosis and long-term outcome in hemodialysis patients. The present study investigated the association between sclerostin, renal function, and carotid artery atherosclerosis in non-dialysis patients with stage 3-5 chronic kidney disease (CKD 3-5ND).

METHODS

A total of 140 patients with CKD 3-5ND were enrolled in this cross-sectional study. The Chronic Kidney Disease Epidemiology Collaboration equation was used to calculate estimated glomerular filtration rate (eGFR). Atherosclerotic plaques in the carotid artery were detected by B-mode Doppler ultrasound. Blood samples were collected to assess serum sclerostin levels. Unconditional logistic regression analysis was used to identify risk factors for carotid atherosclerotic plaques.

RESULTS

The median eGFR was 24.9 ml/min/1.73 m² (interquartile range [IQR] 10.0-40.3 ml/min/1.73 m²) and median serum sclerostin level was 46.76 pmol/l (IQR 30.18-67.56 pmol/l). Carotid atherosclerotic plaques were detected in 104 subjects (74.3%). There was a negative association between sclerostin level and eGFR (r =  - 0.214, p = 0.011). Unconditional logistic regression analysis revealed that sclerostin level was an independent risk factor for the occurrence of carotid plaques, with an odds ratio (95% confidence interval) of 1.026 (1.003, 1.051).

CONCLUSION

Serum sclerostin increases with declining renal function in patients with CKD 3-5ND. Sclerostin is an independent risk factor for carotid atherosclerosis.

Klotho/FGF23 and Wnt Signaling as Important Players in the Comorbidities Associated with Chronic Kidney Disease

Fibroblast Growth Factor 23 (FGF23) and Klotho play an essential role in the regulation of mineral metabolism, and both are altered as a consequence of renal failure. FGF23 increases to augment phosphaturia, which prevents phosphate accumulation at the early stages of chronic kidney disease (CKD). This effect of FGF23 requires the presence of Klotho in the renal tubules. However, Klotho expression is reduced as soon as renal function is starting to fail to generate a state of FGF23 resistance. Changes in these proteins directly affect to other mineral metabolism parameters; they may affect renal function and can produce damage in other organs such as bone, heart, or vessels. Some of the mechanisms responsible for the changes in FGF23 and Klotho levels are related to modifications in the Wnt signaling. This review examines the link between FGF23/Klotho and Wnt/β-catenin in different organs: kidney, heart, and bone. Activation of the canonical Wnt signaling produces changes in FGF23 and Klotho and vice versa; therefore, this pathway emerges as a potential therapeutic target that may help to prevent CKD-associated complications.

Sclerostin within the chronic kidney disease spectrum

Sclerostin is sometimes presented as a promising biomarker in assessing bone health both in the general population and chronic kidney disease patients. However, it is still unclear whether it has any true added value compared to existing bone biomarkers in predicting bone turnover and/or bone density in chronic kidney disease patients. A wealth of papers has been published to evaluate the association between sclerostin and vascular calcifications development or even as prognostic biomarker for mortality, but often with conflicting results. Standardization and harmonization of analytical techniques is a prerequisite to advance clinical knowledge in sclerostin.

Bone-Vascular Axis in Chronic Kidney Disease

Patients with chronic kidney disease (CKD) are at increased risk of osteoporosis and vascular calcification. Bone demineralization and vascular mineralization go often hand in hand in CKD, similar to as in the general population. This contradictory association is independent of aging and is commonly referred to as the "calcification paradox" or the bone-vascular axis. Various common risk factors and mechanisms have been identified. Alternatively, calcifying vessels may release circulating factors that affect bone metabolism, while bone disease may infer conditions that favor vascular calcification. The present review focuses on emerging concepts and major mechanisms involved in the bone-vascular axis in the setting of CKD. A better understanding of these concepts and mechanisms may identify therapeutics able to target and exert beneficial effects on bone and vasculature simultaneously.

Sclerostin: a new biomarker of CKD-MBD

The causes of the increased cardiovascular risk associated with kidney diseases partly reside in the chronic kidney disease-mineral bone disorder (CKD-MBD) syndrome. Three cardiovascular risk factors [hyperphosphatemia, vascular calcification, and elevated fibroblast growth factor 23 (FGF23)] levels have been discovered within the CKD-MBD over the last decades. In addition, sclerostin is recently presented as a new bone and vascular disease biomarker. This 22-kDa glycoprotein, secreted mainly by osteocytes, is a soluble inhibitor of the canonical Wnt pathway that has a pivotal role in bone biology and turnover. CKD patients are reported with higher levels of sclerostin, and levels decrease during dialysis. Sclerostin is associated with vascular calcification and CV risk in CKD, although data are still controversial. The question whether serum sclerostin has protective or deleterious role in CKD-MBD pathophysiology, and therefore in cardiovascular risk and overall mortality, is still open and needs to be answered. The standardization of assays and the establishment of a clear cut-off values when sclerostin starts to switch from physiological to pathophysiological role have to be another important step. Further research is needed also to define its relationship with other CKD-MBD biomarkers for future diagnostic and therapeutic strategies.