Serum sclerostin in vascular calcification and clinical outcome in chronic kidney disease

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.

Higher sclerostin is associated with pulmonary hypertension in pre-dialysis end-stage kidney disease patients: a cross-sectional prospective observational cohort study

BACKGROUND

Pulmonary hypertension (PH) is a complication of chronic kidney disease (CKD) that contributes to mortality. Sclerostin, a SOST gene product that reduces osteoblastic bone formation by inhibiting Wnt/β-catenin signaling, is involved in arterial stiffness and CKD-bone mineral disease, but scanty evidence to PH. This study explored the relationship between sclerostin and PH in CKD 5, pre-dialysis end-stage kidney disease (ESKD) patients.

METHODS

This cross-sectional prospective observational cohort study included 44 pre-dialysis ESKD patients between May 2011 and May 2015. Circulating sclerostin levels were measured using an enzyme-linked immunosorbent assay. PH was defined as an estimated pulmonary artery systolic pressure > 35 mmHg on echocardiography.

RESULTS

Patients with higher sclerostin levels ≥ 218.18pmol/L had echocardiographic structural cardiac abnormalities, especially PH (P < 0.01). On multivariate logistic analysis, sclerostin over 218.19pmol/L was significantly associated with PH (odds ratio [OR], 41.14; 95% confidence interval [CI], 4.53-373.89, P < 0.01), but multivariate Cox regression analysis showed the systemic vascular calcification score over 1 point (Hazard ratio [HR] 11.49 95% CI 2.48-53.14, P = 0.002) and PH ([HR] 5.47, 95% CI 1.30-23.06, P = 0.02) were risk factors for all-cause mortality in pre-dialysis ESKD patients.

CONCLUSIONS

Serum sclerostin and PH have a positive correlation in predialysis ESKD patients. The higher systemic vascular calcification score and PH have an association to increase all-cause mortality in pre-dialysis ESKD patients.

Role of nutritional vitamin D in chronic kidney disease-mineral and bone disorder: A narrative review

Chronic kidney disease-mineral and bone disorder has complex and diverse clinical manifestations, including the simplest abnormalities of calcium, phosphorus and parathyroid hormone detected in blood, abnormalities of bone transformation and mineralization in bone, and calcification of blood vessels or other soft tissues detected on imaging. Patients with CKD-MBD combined low bone mineral density and fragility fractures are referred to as CKD-MBD with low bone mineral density. Vascular calcification refers to ectopic deposition of calcium phosphate in the blood vessel walls and heart valves. The degree of vascular calcification was inversely proportional to bone mineral density. The more severe the degree of vascular calcification, the lower the bone mineral density, and the higher the risk of death, indicating that the bone-vascular axis exists. Activation and alteration of the Wnt signaling pathway are central to the treatment of vascular diseases in uremia. Vitamin D supplementation can prevent secondary hyperparathyroidism, activate osteoblasts, relieve muscle weakness and myalgia, and reduce vascular calcification. Nutritional vitamin D may improve vascular calcification in uremia patients by regulating Wnt signaling pathway.

Sclerostin is involved in osteogenic transdifferentiation of vascular smooth muscle cells in chronic kidney disease-associated vascular calcification with non-canonical Wnt signaling

Vascular calcification is prominent in patients with chronic kidney disease (CKD) and is a strong predictor of cardiovascular mortality in the CKD population. However, the mechanism underlying CKD-associated vascular calcification remains unclear. To identify potential therapeutic targets, a 5/6 nephrectomy rat model was established by feeding of a high-phosphorous diet as the CKD group and compared with sham group rats at 4 and 16 weeks. Sequencing analyses of the rat aorta revealed 643 upregulated and 1023 downregulated genes at 4 weeks, as well as 899 upregulated and 1185 downregulated genes at 16 weeks in the CKD group compared to the sham group. Bioinformatics analyses suggested that SOST (which encodes sclerostin) and Wnt signaling are involved in CKD-associated vascular calcification. Furthermore, protein-protein interactions analysis revealed interactions between SOST, WNT5A, and WNT5B, that involved runt-related transcription factor 2 (RUNX2) and transgelin (TAGLN). SOST was increased in CKD-associated vascular calcification following reduction of the Wnt signaling, including WNT5A and WNT5B, both in vivo and in vitro. TargetScan was used to predict the microRNAs (miRNAs) targeting WNT5A and WNT5B. The expression levels of miR-542-3p, miR-298-3p, miR-376b-5p, and miR-3568 were significantly reduced, whereas that of miR-742-3p was significantly increased in calcified rat aortic vascular smooth muscle cells (VSMCs). In CKD rat aortas, the expression of miR-542-3p, miR-298-3p, miR-376b-5p, miR-3568, miR-742-3p, and miR-22-5p were significantly reduced at both 4 and 16 weeks. Altogether, owing to several assessments, potentially diagnostic and prognostic biomarkers for improving common CKD diagnostic tools were identified in this study.

Abbreviations: BUN: blood urea nitrogen; CKD: chronic kidney disease; CKD-MBD: chronic kidney disease-mineral bone disorder; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GO: the Gene Ontology; HE: hematoxylin-eosin; HRP: horseradish peroxidase; KEGG: Kyoto Encyclopedia of Genes and Genomes; MiRNAs: microRNAs; PAS: periodic acid-Schiff; RUNX2: runt-related transcription factor 2; SCr: serum creatinine; STRING: the Search Tool for the Retrieval of Interacting Genes/Proteins; TAGLN: transgelin; VSMC: vascular smooth muscle cell.

Exploring the Role of Sclerostin as a Biomarker of Cardiovascular Disease and Mortality: A Scoping Review

Sclerostin is most recognized for its role in controlling bone formation; however, it is also expressed in the heart, aorta, coronary, and peripheral arteries. Human studies have associated high circulating sclerostin levels with the presence of different cardiovascular diseases (CVD), surrogate CVD markers, and a high risk of cardiovascular events in some populations. However, this is still a matter of scientific debate, as the results have been very heterogeneous among studies. In the present review, the association between serum sclerostin levels and CVD and/or cardiovascular mortality was analyzed. For this purpose, a scoping review was performed in which articles measuring serum sclerostin levels and cardiovascular risk in patients were selected. Eleven articles answered the research question; of these articles, 8/11 evaluated the association between sclerostin and CVD, of which 4/8 found a positive association, 2/8 found a negative association, and 2/8 found no association between variables. Five (5/11) of the articles included in the study evaluated cardiovascular mortality, of which 3/5 found a positive association, 1/5 found a negative association, and 1/5 found no association between variables. In conclusion, we did not find sufficient results to be able to demonstrate an association between elevated sclerostin levels and the development of CVD and/or cardiovascular mortality in the general population due to heterogeneity in the results. However, there seems to be a tendency to consider increased sclerostin levels as a risk factor for both the development of cardiovascular events and cardiovascular mortality in specific populations. Further studies in this field will help to solve some of the inconsistencies found during this scoping review and allow for the future use of sclerostin measurement as a strategy in the prevention and diagnosis of CVD and/or cardiovascular mortality.

Association of serum klotho levels with different-staged vascular calcification status in patients with maintenance hemodialysis

Background

Vascular calcification (VC) is suggested to be associated with serum klotho levels in patients with maintenance hemodialysis (MHD), whereas there is a lack of reports on the associations of VC status in whole arteries with serum klotho contents.

Methods

One hundred forty eligible patients with MHD and a total of age-and gender-matched normal controls (NCs) were recruited. We analyzed the VC statuses of large arteries and peripheral muscular arteries by calculating the sum of scores from each artery. The levels of serum klotho were determined by ELISA. In addition, the relationship between serum klotho and VC status was evaluated using correlation analysis and regression analysis.

Results

The VC severity in MHD patients tended to be worse in comparison with NCs. Serum klotho level in patients with MHD was lower than that in the NC subjects (​P < 0.0001), which was correlated with VC scores as reflected by correlation analysis and regression analysis. Serum klotho concentrations exhibited a dynamic decline along with increased VC status stages. Subjects with higher levels of serum klotho had a higher prevalence of cardiovascular events.

Conclusion

Our study indicates serum klotho is strongly associated with VC status in a stage-dependent manner.

Relationship between Acute Respiratory Tract Infection and the Serum 25(OH) D3 Level in Chronic Kidney Disease Patients and Its Prevention and Treatment

Observational studies and randomized controlled studies propose that vitamin D plays a significant role in preventing acute respiratory tract infection (RTI); however, results are inconsistent and the optimal serum 25-hydroxyvitamin D (25-OH-D3) concentration remains unknown. This study explores the risk factors associated with acute RTI in patients with chronic kidney disease (CKD) and analyzes its correlation with serum 25-OH-D3 levels, to provide appropriate preventive treatment measures for CKD patients complicated with acute RTI. Seventy cases of CKD patients treated in the department of nephrology of Jiangxi Provincial People’s Hospital are recruited as the research objects and divided into a control group (CKD without RTI) and an observation group (CKD with RTI), with 35 cases in each group. The laboratory indexes and serum 25-OH-D3 levels are compared between the two groups. The area under the receiver operating characteristic curve (ROC) of 25-OH-D3 in the diagnosis of CKD patients complicated with RTI is 0.892, and the standard error is 0.038. The glomerular filtration rates (GFR) are $48.32\pm 9.87\text{mL}/\min$ and $50.18\pm 20.71\text{mL}/\min$ in the control group and the experimental group, respectively, with no statistical significance between the two groups ( $P>0.05$ ). The serum 25-OH-D3 content in the control group ( $35.08\pm 6.2\text{nmol}/\text{L}$ ) is dramatically higher than that in the observation group ( $20.71\pm 5.87\text{nmol}/\text{L}$ ) ( $P<0.05$ ). The proportion of patients with diabetes mellitus (DM) in the control group and observation group is 25.71% and 68.57%, respectively, with a considerable difference ( $P<0.05$ ). In the control group and the experimental group, the proportion of patients with oral vitamin D receptor agonists is 54.29% and 11.43%, respectively, and the difference is significant ( $P<0.05$ ). Results show that the serum 25-OH-D3 level is highly correlated with the occurrence of RTI in CKD patients. In addition, it is related to patients’ age, DM, and vitamin D receptor agonists.

Crosstalk between bone and other organs

Bone has long been considered as a silent organ that provides a reservoir of calcium and phosphorus, traditionally. Recently, further study of bone has revealed additional functions as an endocrine organ connecting systemic organs of the whole body. Communication between bone and other organs participates in most physiological and pathological events and is responsible for the maintenance of homeostasis. Here, we present an overview of the crosstalk between bone and other organs. Furthermore, we describe the factors mediating the crosstalk and review the mechanisms in the development of potential associated diseases. These connections shed new light on the pathogenesis of systemic diseases and provide novel potential targets for the treatment of systemic diseases.

Vascular Calcification in Chronic Kidney Disease: An Update and Perspective

Chronic kidney disease is a devastating condition resulting from irreversible loss of nephron numbers and function and leading to end-stage renal disease and mineral disorders. Vascular calcification, an ectopic deposition of calcium-phosphate salts in blood vessel walls and heart valves, is an independent risk factor of cardiovascular morbidity and mortality in chronic kidney disease. Moreover, aging and related metabolic disorders are essential risk factors for chronic kidney disease and vascular calcification. Marked progress has been recently made in understanding and treating vascular calcification in chronic kidney disease. However, there is a paucity of systematic reviews summarizing this progress, and investigating unresolved issues is warranted. In this systematic review, we aimed to overview the underlying mechanisms of vascular calcification in chronic kidney diseases and discuss the impact of chronic kidney disease on the pathophysiology of vascular calcification. Additionally, we summarized potential clinical diagnostic biomarkers and therapeutic applications for vascular calcification with chronic kidney disease. This review may offer new insights into the pathogenesis, diagnosis, and therapeutic intervention of vascular calcification.

Vitamin K Supplementation for Prevention of Vascular Calcification in Chronic Kidney Disease Patients: Are We There Yet?

Chronic Kidney Disease (CKD) patients are at high risk of presenting with arterial calcification or stiffness, which confers increased cardiovascular mortality and morbidity. In recent years, it has become evident that VC is an active process regulated by various molecules that may act as inhibitors of vessel mineralization. Matrix Gla Protein (MGP), one the most powerful naturally occurring inhibitors of arterial calcification, requires vitamin K as a co-factor in order to undergo post-translational γ-carboxylation and phosphrorylation and become biologically active. The inactive form of MGP (dephosphorylated, uncarboxylated dp-ucMGP) reflects vitamin K deficiency and has been repeatedly associated with surrogate markers of VC, stiffness, and cardiovascular outcomes in CKD populations. As CKD is a state of progressive vitamin K depletion and VC, research has focused on clinical trials aiming to investigate the possible beneficial effects of vitamin K in CKD and dialysis patients. In this study, we aim to review the current evidence regarding vitamin K supplementation in uremic patients.

Endocrine Regulation of Extra-skeletal Organs by Bone-derived Secreted Protein and the effect of Mechanical Stimulation

Bone serves as the support for body and provide attachment points for the muscles. The musculoskeletal system is the basis for the human body to complete exercise. Studies believe that bone is not only the basis for constructing structures, but also participates in the regulation of organs outside bone. The realization of this function is closely related to the protein secreted by bone. Whether bone can realize their positions in the human body is also related to their secretion. Bone-derived proteins provide a medium for the targeted regulation of bones on organs, making the role of bone in human body more profound and concrete. Mechanical stimulation effects the extra-skeletal organs by causing quantitative changes in bone-derived factors. When bone receives mechanical stimulation, the nichle of bone responds, and the secretion of various factors changes. However, whether the proteins secreted by bone can interfere with disease requires more research. In this review article, we will first introduce the important reasons and significance of the in-depth study on bone-derived secretory proteins, and summarize the locations, structures and functions of these proteins. These functions will not only focus on the bone metabolism process, but also be reflected in the cross-organ regulation. We specifically explain the role of typical bone-derived secretory factors such as osteocalcin (OCN), osteopontin (OPN), sclerostin (SOST) and fibroblast growth factor 23 (FGF23) in different organs and metabolic processes, then establishing the relationship between them and diseases. Finally, we will discuss whether exercise or mechanical stimulation can have a definite effect on bone-derived secretory factors. Understanding their important role in cross-organ regulation is of great significance for the treatment of diseases, especially for the elderly people with more than one basic disease.

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.

Changes in plasma sclerostin level associated with use of a medium cut-off dialyzer in end-stage renal disease

Background

Larger middle molecules are important substances associated with cardiovascular complications in end- stage renal disease. Unfortunately, larger middle molecules are not reliably removed by a high -flux dialyzer. A medium cut-off (MCO) membrane could effectively remove larger middle molecules. This study aimed to identify the long-term effect of the MCO membrane for changes of larger middle molecules.

Methods

Thirty-four patients were prospectively analyzed for 12 months. The enrolled patients were divided into control and MCO groups. We measured the plasma levels of growth differentiation factor 15, sclerostin, and fibroblast growth factor 23 in larger middle molecules and those of biomarkers including small solutes. Single-pool Kt/V (spKt/V) and reduction ratios also were evaluated.

Results

Plasma sclerostin did not increase significantly in patients using the MCO dialyzer (135.294 [–637.726 to 908.314], p = 0.715). And there was a significant difference in change of plasma sclerostin level between the two groups (–1,646.916 [–3,015.150 to –278.682], p = 0.033). Furthermore, a negative association between calcium and sclerostin was not observed in the MCO group (r = –0.142, p = 0.587). Solute clearance of larger middle molecules in the MCO group was significantly higher. Moreover, spKt/V values for patients in the MCO group were significantly increased without albumin loss. Values are presented as mean (95% confidence interval [CI]) or adjusted mean (95% CI).

Conclusion

The MCO dialyzer can increase dialytic adequacy and suppress the increase in plasma sclerostin level without significant albumin loss in patients with end-stage renal disease.

Sclerostin and Osteocalcin: Candidate Bone-Produced Hormones

In addition to its structural role, the skeleton serves as an endocrine organ that controls mineral metabolism and energy homeostasis. Three major cell types in bone - osteoblasts, osteoclasts, and osteocytes - dynamically form and maintain bone and secrete factors with systemic activity. Osteocalcin, an osteoblast-derived factor initially described as a matrix protein that regulates bone mineralization, has been suggested to be an osteoblast-derived endocrine hormone that regulates multiple target organs including pancreas, liver, muscle, adipose, testes, and the central and peripheral nervous system. Sclerostin is predominantly produced by osteocytes, and is best known as a paracrine-acting regulator of WNT signaling and activity of osteoblasts and osteoclasts on bone surfaces. In addition to this important paracrine role for sclerostin within bone, sclerostin protein has been noted to act at a distance to regulate adipocytes, energy homeostasis, and mineral metabolism in the kidney. In this article, we aim to bring together evidence supporting an endocrine function for sclerostin and osteocalcin, and discuss recent controversies regarding the proposed role of osteocalcin outside of bone. We summarize the current state of knowledge on animal models and human physiology related to the multiple functions of these bone-derived factors. Finally, we highlight areas in which future research is expected to yield additional insights into the biology of osteocalcin and sclerostin.

Urinary magnesium predicts risk of cardiovascular disease in Chronic Kidney Disease stage 1-4 patients

Observational studies on dietary or circulating magnesium and risk of cardiovascular disease (CVD) in Chronic Kidney Disease (CKD) stage 1-4 have reported no-to-modest inverse associations. 24 h Urinary magnesium concentration (24 h UMg), an indicator of intestinal magnesium absorption, may provide better insight into the connection of CKD progression. We examined 3179 participants aged 18-74 years with CKD stage 1-4 in the Chinese Cohort Study of Chronic Kidney Disease (C-STRIDE) study, a prospective population-based cohort study. Data were analysed using Spearman rank-order correlation coefficients for all comparisons. We also performed a time-to-event analysis of the data using the Kaplan-Meier survival model, Cox proportional hazard model and competing risk Fine and Gray subdistribution hazard model. During a median follow-up of 4.19 years (interquartile range, 3.43-5.09 years), when modelling end-stage renal disease (ESRD), CVD and death, 24 h UMg was associated with risk of CVD (HR, 1.612 (95% CI, 1.056-2.460)), while no significant association with ESRD and death endpoints could be detected. 24 h UMg risk variants display a modest association with CVD in CKD stage 1-4 patients. TRIAL REGISTRATION: ClinicalTrials.gov Identifier NCT03041987. Registered January 1, 2012. (retrospectively registered) (https://www.clinicaltrials.gov/ct2/show/NCT03041987?term=Chinese+Cohort+Study+of+Chronic+Kidney+Disease+%28C-STRIDE%29&rank=1).

Factors associated with sclerostin levels - A calcification inhibitor - In individuals with type 2 diabetes mellitus; Is autonomic neuropathy the missing link?

BACKGROUND

Sclerostin inhibits bone formation and its expression is upregulated in the vasculature during the arterial calcification process as a counterregulatory mechanism preventing further calcification. Lower extremity arterial calcification (LEAC) is common in neuropathic patients with type 2 diabetes (T2DM). Herein, we investigated for associations between plasma sclerostin levels and diabetic neuropathy as well as LEAC in subjects with T2DM.

METHODS

A total of 74 individuals with and 76 without T2DMwere recruited. Plasma sclerostin levels were measured by ELISA. Diagnosis of cardiac autonomic neuropathy (CAN) was based on the battery of the four autonomic tests, while of somatosensory peripheral neuropathy (DPN) on neuropathy symptom score and neuropathy disability score. LEAC was assessed with conventional ankle and foot x-rays.

RESULTS

Plasma sclerostin levels were higher in participants with LEAC vs. those without LEAC in both diabetes and non-diabetes cohorts (p = 0.035 and p = 0.003, respectively). In the diabetes cohort, patients with CAN, but not with DPN, had higher sclerostin levels when compared with those without CAN (p < 0.001). Multivariate analysis in the diabetes cohort demonstrated that sclerostin levels were associated positively with CAN and LEAC, while in the non-diabetes cohort there was a trend for a positive association with male gender and presence of LEAC.

CONCLUSION

Plasma sclerostin levels are increased in individuals with LEAC irrespectively of diabetes status. In addition, plasma sclerostin concentrations are associated independently with LEAC and CAN in people with T2DM.

Biomarkers of vascular calcification in serum

Over the last decades, the association between vascular calcification (VC) and all-cause/cardiovascular mortality, especially in patients with high atherogenic status, such as those with diabetes and/or chronic kidney disease, has been repeatedly highlighted. For over a century, VC has been noted as a passive, degenerative, aging process without any treatment options. However, during the past decades, studies confirmed that mineralization of the arteries is an active, complex process, similar to bone genesis and formation. The main purpose of this review is to provide an update of the existing biomarkers of VC in serum and develop the various pathogenetic mechanisms underlying the calcification process, including the pivotal roles of matrix Gla protein, osteoprotegerin, bone morphogenetic proteins, fetuin-a, fibroblast growth-factor-23, osteocalcin, osteopontin, osteonectin, sclerostin, pyrophosphate, Smads, fibrillin-1 and carbonic anhydrase II.

Associations of Serum Dickkopf-1 and Sclerostin With Cardiovascular Events: Results From the Prospective Bruneck Study

Background Dickkopf-1 and sclerostin have been implicated in atherosclerosis and vascular calcification. We aimed to quantify the association of their serum levels with incident cardiovascular disease (CVD) in the general population. Methods and Results Among 706 participants of the prospective, population-based Bruneck Study, mean±SD of serum levels were 44.5±14.7 pmol/L for dickkopf-1 and 47.1±17.5 pmol/L for sclerostin. The primary outcome was a composite CVD end point composed of ischemic or hemorrhagic stroke, transient ischemic attack, myocardial infarction, angina pectoris, peripheral vascular disease, and revascularization procedures. Over a median follow-up duration of 15.6 years, 179 CVD events occurred. For the primary CVD outcome, multivariable-adjusted hazard ratios (HRs) per SD higher level were 1.20 for dickkopf-1 (95% CI, 1.02-1.42; P=0.028) and 0.92 for sclerostin (95% CI, 0.78-1.08; P=0.286). Secondary outcome analyses revealed that the association of dickkopf-1 was primarily driven by ischemic and hemorrhagic stroke (67 events; HR, 1.37; 95% CI, 1.06-1.78; P=0.017), whereas no increase in risk was observed for transient ischemic attack (22 events; HR, 0.87; 95% CI, 0.53-1.44; P=0.593), myocardial infarction (45 events; HR, 1.10; 95% CI, 0.78-1.54; P=0.598), or for other CVD (45 events; HR, 1.25; 95% CI, 0.88-1.76; P=0.209). Conclusions In this prospective, population-based study, elevated baseline levels of dickkopf-1, but not sclerostin, were independently associated with incident cardiovascular events, which was mainly driven by stroke. Our findings support the hypothesis of a role of dickkopf-1 in the pathogenesis of CVD.

Oxidative stress contributes to vascular calcification in patients with chronic kidney disease

Vascular calcification (VC) is a major cause of mortality in patients with chronic kidney disease (CKD). While elevations in serum phosphorus contribute to VC, we provide evidence here for a major role of oxidative stress (OS) in VC pathogenesis without an apparent increase in serum phosphorus in early CKD. In a rat model for stage 5 CKD (CKD5), we observed 1) robust increases of VC and OS, 2) significant reductions of smooth muscle 22 alpha (SM22α) and calponin, and 3) upregulations in Runt-related transcription factor 2 (RUNX2) and collagen I in vascular smooth muscle cells (VSMCs). Inhibition of OS using MnTMPyP dramatically reduced these events without normalization of hyperphosphatemia. In CKD5 patients with VC (n = 11) but not in those without VC (n = 13), OS was significantly elevated. While the serum levels of calcium and phosphate were not altered in the animal model for early stage CKD (ECKD), OS, VC, SM22α, calponin, RUNX2, collagen I and NADPH oxidase 1 (NOX1) in VSMCs were all significantly changed. More importantly, serum (5%) derived from patients with ECKD (n = 30) or CKD5 (n = 30) induced SM22α and calponin downregulation, and RUNX2, collagen I, NOX1 upregulation along with a robust elevation of OS and calcium deposition in primary rat VSMCs. These alterations were all reduced by MnTMPyP, ML171 (a NOX1 inhibitor), and U0126 (an inhibitor of Erk signaling). Collectively, we provide a comprehensive set of evidence supporting an important role of OS in promoting VC development in CKD patients (particularly in those with ECKD); this was at least in part through induction of osteoblastic transition in VSMCs which may involve the Erk singling. Our research thus suggests that reductions in OS may prevent VC in CKD patients.

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.

Sclerostin levels predict cardiovascular mortality in long-term hemodialysis patients: A prospective observational cohort study

Sclerostin is a protein which is involved in bone metabolism and probably also in vessel wall function. This prospective observational cohort study evaluated the prognostic significance of sclerostin in hemodialysis (HD) patients. In total, 106 HD patients and 25 healthy controls participated in the study. HD patients were prospectively followed up for five years. Sclerostin was measured in serum using standard ELISA kits by Biomedica. Sclerostin concentrations in serum were higher in HD patients compared to the controls (89.2±40.3 pmol/l vs. 32.8±13.0 pmol/l, p<0.001). Sclerostin levels were significant for cardiovascular mortality but not for overall mortality and mortality due to infection. A higher cardiovascular risk was connected to sclerostin concentrations above the median (>84 pmol/l), HR (95 % CI): 2.577 (1.0002-10.207), p=0.04. When sclerostin was evaluated together with residual diuresis in Kaplan-Meier analysis the worst prognosis due to cardiovascular events was observed in the group with high sclerostin and zero residual diuresis compared to all other patients (p=0.007). In summary, serum sclerostin levels in HD patients were increased when compared to healthy subjects. High sclerostin levels were demonstrated as a risk factor for cardiovascular mortality. Further studies are required to clarify the pathophysiological mechanisms of sclerostin action in patients with renal failure before therapeutic measures can be established.

Pro-inflammatory Cytokines and Osteocytes

PURPOSE OF REVIEW

An elevated level of pro-inflammatory cytokines in inflammatory conditions causes bone loss and disrupts vital organ function. Osteocytes comprise > 95% of the cellular component in bone tissue, produce a range of cytokines and signaling molecules, and influence bone and other organ function. In this review, we hypothesized that an elevated level of pro-inflammatory cytokines in inflammatory conditions affects osteocyte survival and function thereby possibly amplifying inflammation, and causing bone loss and non-bone clinical complications.

RECENT FINDINGS

Several studies have reported that the elevated level of pro-inflammatory cytokines in inflammatory conditions alters osteocyte mechanosensitivity, causes osteocyte apoptosis, and modulates osteocyte-derived production of various inflammatory cytokines and signaling molecules. Cytokines and signaling molecules released from osteocytes affect surrounding bone cells and distant organ function in a paracrine and endocrine fashion. Inflammatory diseases including diabetes, chronic kidney disease, rheumatoid arthritis, and periodontitis affect osteocyte survival and function, and upregulate osteocyte-derived expression of sclerostin, RANKL, TNFα, FGF23, DKK1, and other signaling molecules.

Cardiovascular Outcomes of Romosozumab and Protective Role of Alendronate

Osteoporosis and cardiovascular diseases are major public health issues. Bone and cardiovascular remodeling share multiple biological markers and pathways. Medical intervention, such as using romosozumab, an antisclerostin antibody, improves the clinical outcome of osteoporosis. However, blocking sclerostin leads to Wnt (wingless/integrated) activation and participation in the cardiovascular remodeling process, which could potentially lead to adverse events. Based on the opposing roles of bisphosphonates and the Wnt pathway on endothelial dysfunction, lipid accumulation and calcification of the vessel walls, the combination of romosozumab and bisphosphonates could be a new therapeutic approach to reducing the risks of adverse cardiovascular events in romosozumab receivers. Visual Overview- An online visual overview is available for this article.

Relationship between serum sclerostin, vascular sclerostin expression and vascular calcification assessed by different methods in ESRD patients eligible for renal transplantation: a cross-sectional study

PURPOSE

Vascular calcification (VC) is known to be prevalent in patients with end-stage renal disease (ESRD). Sclerostin has been identified to be involved in the cross-talk between the kidney, vasculature, and bone. The aims of the present study were to evaluate vessel sclerostin expression and its correlation with VC, as well as serum sclerostin levels.

METHODS

A total of 51 adult ESRD patients undergoing living donor renal transplant (RT) were enrolled in this study. Serum sclerostin levels were measured by enzyme-linked immunosorbent assays. The thoracic aorta calcification (TAC) was measured by computed tomography (CT). The aortic calcification area index (ACAI) was used to evaluate the severity of TAC. During the RT surgery, the internal iliac arteries were collected and paraffin-embedded in 40 patients, followed by immunohistochemical staining for sclerostin expression and von Kossa-staining for vascular medial calcification degree.

RESULTS

The prevalence rate of TAC detected by CT was 58.82%. The positive rates of the internal iliac arterial calcification and vessel sclerostin expression were both 45%. Vessel sclerostin was strongly co-localized with medial calcification. Multivariate analyses revealed that only serum sclerostin was significantly associated with the presence of TAC, the severity of TAC and the positive expression of vessel sclerostin. Kappa test showed that the consistency of the two different calcification assessment methods, as well as the consistency of vessel sclerostin expression and von Kossa-staining were high. Furthermore, the cutoff points of serum sclerostin for vessel sclerostin expression, the presence of VC evaluated by CT and that evaluated by pathology were 1599.92 pg/mL, 2475.52 pg/mL, and 2116.23 pg/mL, respectively.

CONCLUSIONS

The two methods, namely CT and pathology, to evaluate VC were highly consistent. Serum sclerostin was an independent determinant of positive expression of vessel sclerostin and VC in ESRD patients eligible for RT.

Clinical advantages and disadvantages of anabolic bone therapies targeting the WNT pathway

The WNT signalling pathway is a key regulator of bone metabolism, particularly bone formation, which has helped to define the role of osteocytes - the most abundant bone cells - as orchestrators of bone remodelling. Several molecules involved in the control of the WNT signalling pathway have been identified as potential targets for the development of bone-building therapeutics for patients with osteoporosis. Several of these molecules have been investigated in animal models, but only inhibitors of sclerostin (which is produced by osteocytes) have been investigated in phase III clinical studies. Here, we review the rationale for these developments and the specificity and potential off-target actions of WNT-based therapeutics. We also describe the available preclinical and clinical studies and discuss the benefits and risks of using sclerostin inhibitors for the management of patients with osteoporosis.

Is serum sclerostin a marker of atherosclerosis in patients with chronic kidney disease-mineral and bone disorder?

PURPOSE

The complexity of chronic kidney disease-mineral and bone disorder (CKD-MBD) led to many preclinical and clinical trials. The role of sclerostin in renal pathophysiology remained unresolved, and question whether sclerostin is related to cardiovascular (CV) outcome in patients with CKD is still open. Our aim was to evaluate the possible association between serum sclerostin levels and carotid intima-media thickness (CIMT) in CV pathophysiology through various CKD stages.

METHODS

Eighty-eight patients in various CKD stages were involved in this analysis. CKD-EPI (Chronic kidney disease Epidemiology Collaboration Equation) was used to estimate glomerular filtration rate (eGFR). CKD-MBD parameters were determined in patients' serum after an overnight fasting. Early atherosclerosis was assessed by ultrasound measurement of CIMT. In order to assess the association between serum sclerostin with other CKD-MBD parameters and CIMT, correlation and regression analyses were performed.

RESULTS

Mean age was 62.84 ± 11.37 years and 56% were female. Mean values of serum sclerostin were 1.67 ± 0.44 ng/ml. Negative correlation was noticed with serum calcium and phosphate product (CaxP), alkaline phosphatase (ALP), intact parathyroid hormone (iPTH), serum creatinine, and HbA1c level. There was no association with FGF23, CIMT, and carotid atherosclerotic plaque occurence. Serum levels of sclerostin were significantly higher in female patients compared to males (p < 0.001).

CONCLUSION

Advanced CKD showed a trend of declining sclerostin levels and significantly higher CIMT levels. Serum sclerostin was not associated with CIMT. More studies are needed in order to reveal the exact role of sclerostin in the complexity of CKD-MBD pathophysiological mechanism.