Associations between the levels of sclerostin, phosphate, and fibroblast growth factor-23 and treatment with vitamin D in hemodialysis patients with low intact PTH level

The Relationship between Serum Sclerostin Levels and Bone Mineral Disorders and Vascular Calcification in Hemodialysis Patients

Background and aim of the study: Sclerostin is produced by osteocytes and has been shown to down-regulate the synthesis of many markers of bone formation by osteogenic cells. The aim of this study to investigate the relationship between serum sclerostin levels and bone mineral disorders and vascular calcification in hemodialysis patients (HD). Methods:This is a cross-sectional study of 70 patients with ESRD on regular HD for at least six months, Theodor Bilharz Research Institute, Giza, Egypt.Twenty-five subjects who matched the ages, genders, and demographics of the study patients were included as a control group.All patients and control groups included in the study underwent a full through history and clinical examination. Serum calcium, phosphorus, alkaline phosphatase and intact PTH (iPTH) levels were measured. Serum sclerostin was measured by an ELISA. Bone Mineral Densitometry Measurements BMD (g/cm2) was determined by dual-energy X-ray absorptiometry (DXA). CT scan was done to detect the presence or absence of vascular calcification and transthoracic echocardiogram to detect the presence or absence of  valvular calcification. Results:The mean seumscleostin levels was a statistically significant high in the HD patients when compared with the control group (156.8 ±121.4 Vs.29.38±0.84,  p =0.0001 ) and statistically significant high mean ALP in the HD patients when compared with the control group (147.2 ± 94.3      Vs.              38.8 ±23.4, p = 0.0001). The mean BMD  was statistically significant low in the HD patients when compared with the controls (0.839±0.086 g/ m2 Vs.1.306  ±0.153 g/ m2, p = 0.0001).The mean seumscleostin levels was statistically significant high in the HD patients with vascular and valvular  calcification  when compared with HD patients without calcification.Using spearman correlation coefficient analysis, there was  statistically significant negative correlations between serum sclerostin levels and iPTH(r=-0.362,   p =0.0021), ALP (r=-0.301, p =0.0114), and BMD (r=-0.469, p =0.0278 ), and there was a statistically significant positive correlation between serum sclerostin levels and phosphate(r=0.5829,  p =0.0001 ).Independent predictors of BMD in HD patients were determined using multi-variate regression analysis. Sclerostin levels, iPTH, ALP, and age  were found to be independent predictors of BMD. Conclusion: High sclerostin levels in patients with ESRD on HD were associated with high risk of vascular and valvularcalcification and were independent predictors of low BMD in such population.

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.

Relationship between plasma levels of sclerostin, calcium-phosphate disturbances, established markers of bone turnover, and inflammation in haemodialysis patients

PURPOSE

Data concerning the relation between increased levels of circulating sclerostin (a physiological inhibitor of bone formation) and bone turnover in patients with chronic renal failure (CRF) are limited. Therefore, the aim of this study was to evaluate associations between plasma sclerostin levels and calcium-phosphate disturbances, markers of bone turnover as well as inflammation in haemodialysis (HD) patients.

METHODS

In plasma samples obtained in 150 stable HD patients (92 men) aged 40-70 years, levels of sclerostin, fibroblast growth factor (cFGF23), osteocalcin, the N-terminal propeptide of type I procollagen, C-terminal telopeptide of the alpha chain of type I collagen (β-CTx), and inflammatory markers (IL-6 and TNF-α) in addition to routine parameters (calcium, phosphorus, parathyroid hormone-iPTH, 25-OH-D, alkaline phosphatase) were measured.

RESULTS

Plasma sclerostin concentrations were significantly higher in HD men than women (2.61 vs. 1.88 ng/mL, p < 0.01). Patients with sclerostin levels above median were characterized by lower iPTH and IL-6, but higher cFGF23 and TNF-α (significantly only in men) concentrations. Plasma sclerostin concentration positively correlated with serum 25-OH-D (τ = 0.204), phosphorus (τ = 0.1482), and TNF-α (τ = 0.183) and inversely with iPTH (τ = - 0.255), alkaline phosphatase (τ = - 0.203), IL-6 (τ =- 0.201), and β-CTx (τ = - 0.099) levels. In multivariate regression analysis, variability of sclerostin levels was explained by sex and 25-OH-D and phosphorus levels.

CONCLUSIONS

Increased circulating sclerostin levels seem to reflect slower bone turnover in HD patients. Low levels of sclerostin are associated with vitamin D deficiency and good phosphates alignment.

Serum sclerostin level might be a potential biomarker for arterial stiffness in prevalent hemodialysis patients

AIM

To explore the relationship between circulating sclerostin levels and pulse wave velocity (PWV) in prevalent hemodialysis (HD) patients.

PATIENTS & METHODS

154 HD patients were enrolled and examined for serum sclerostin level, carotid-femoral pulse wave velocity (cf-PWV), abdominal artery calcification and calcaneus bone marrow density.

RESULTS

Serum sclerostin level was significantly elevated in patients with arterial stiffness. Univariate correlation showed serum sclerostin level significantly correlated with intact parathyroid hormone level, cf-PWV and calcaneus bone marrow density. Multiple linear regression analysis in patients with parathyroid hormone ≤300 pg/ml showed that pulse pressure, logAACs and serum sclerostin level were significant independent factors for cf-PWV.

CONCLUSION

Serum sclerostin level was significantly associated with PWV in prevalent HD patients without hyperparathyroidism.

Sclerostin, TNF-alpha and Interleukin-18 Correlate and are Together with Klotho Related to Other Growth Factors and Cytokines in Haemodialysis Patients

Patients with chronic renal failure are known to have renal osteodystrophy (bone disease) and increased calcification of vessels. A new marker of bone disease, sclerostin, the two pro-inflammatory cytokines tumour necrosis factor-alpha (TNF-alpha) and interleukin-18 (IL-18), and the fibroblast growth factor-23 (FGF-23) receptor-associated marker Klotho were tested in 84 haemodialysis (HD) patients and in healthy controls. The patients had significantly higher levels of the three former markers than of the controls while Klotho was significantly higher in the controls. Low level, but significant, correlations were observed in the patient group when the levels of these four markers were compared to each other and to those of 5 cytokines and growth factors tested earlier; high-sensitive CRP (hsCRP), interleukin-6 (IL-6), hepatocyte growth factor (HGF), fibroblast growth factor-23 (FGF-23) and soluble urokinase plasminogen activator (suPAR). Ln sclerostin correlated positively to Ln hsTNF-alpha, Ln HGF and Ln suPAR. Ln hsTNF-alpha correlated positively to Ln sclerostin, Ln hsCRP, Ln IL-6, Ln FGF-23, Ln suPAR and Ln IL-18. Ln IL-18 correlated positively to Ln suPAR and Ln TNF-alpha. Ln Klotho correlated negatively to Ln hsCRP but did not correlate to Ln FGF-23. The markers studied here may be involved in the calcification of vessels seen in HD patients due to a combination of inflammation and bone disease. The mechanisms are still not fully known but may be of importance for future therapeutic possibilities in this group of patients.