Active vitamin D treatment in CKD patients raises serum sclerostin and this effect is modified by circulating pentosidine levels

The effect of vitamin D supplementation on serum levels of fibroblast growth factor- 23: A systematic review and meta-analysis of randomized controlled trials

Previous studies of the effect of vtamin D on serum levels of fibroblast growth factor- 23 (FGF-23) have yeilded an inconsistent findings. This systematic review and meta-analysis of randomized controlled trials (RCTs) sought to investigate the effect of vitamin D supplementation on serum levels of FGF-23. PubMed, Scopus, ISI Web of Science, and the Cochrane Library were searched, from database inception to November 2020, for RCTs that evaluated the effects of native or active vitamin D supplementation on serum levels of FGF-23 in adults. Weighted mean difference (WMD) were calculated and random effects meta-analysis was used to estimate the overall effects. Twenty-seven trials were included in the meta-analysis. Supplementation with native vitamin D (23 studies, n = 2247 participants; weighted mean difference [WMD] = 0.5 pg/mL, 95 % CI: -0.52 to 1.51, P = 0.33; I² = 29.9 %), and active vitamin D (5 studies, n = 342 participants, WMD = 29.45 pg/mL, 95 % CI: -3.9 to 62.81, P = 0.08; I² = 99.3%) had no significant effects on serum FGF-23 concentration. In subgroup analyses, supplementation with ergocalciferol (3 studies, n = 205 participants; WMD = 18.27 pg/mL, 95 % CI: 5.36-31.17, P = 0.006), and daily dosing regimens (9 studies, n = 1374 participants; WMD = 0.41 pg/mL, 95 % CI: 0.22 to 0.59, P < 0.001) increased serum FGF-23 levels compared to control. Overall, our findings revealed no significan effect of vitamin D supplementation on serum FGF-23 concentration. However, further high quality, large-scale studies are needed to better elucidate this relationship.

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.

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.

Effect of vitamin D supplementation on serum sclerostin levels in chronic kidney disease

Vitamin D deficiency, cardiovascular disease and abnormal bone mineral metabolism are common in chronic kidney disease (CKD). Abnormal bone mineral metabolism has been linked to vascular calcification in CKD. Sclerostin has emerged as an important messenger in cross talk between bone-vascular axis. We analyzed sclerostin in subjects who participated in the randomized, double blind, placebo controlled trial investigating the effect of cholecalciferol supplementation on vascular function in non-diabetic CKD stage G3-4 and vitamin D ≤ 20 ng/ml [CTRI/2013/05/003648]. Patients were randomized (1:1) to receive either two directly observed oral doses of 300,000 IU of cholecalciferol or matching placebo at baseline and 8 weeks. Of the 120 subjects enrolled, 58 in the cholecalciferol group and 59 in the placebo group completed the study. At baseline, serum levels of sclerostin were similar in both groups (cholecalciferol - median;190pg/ml, IQR;140-260 pg/ml and placebo - median;180 pg/ml, IQR; 140-240 pg/ml, p = 0.67). 16 weeks after cholecalciferol supplementation, there was no change in level of sclerostin (mean change;1.10 pg/ml, 95%CI; -27.34 to 29.34 pg/ml, p = 0.25). However, a significant decrease in sclerostin level was noted in the placebo group (mean change; -31.94 pg/ml, 95%CI; -54.76 to -9.13 pg/ml, p = 0.002). Change (Δ) in sclerostin level at 16 weeks correlated negatively with Δ eGFR (r = -0.20, p = 0.03) and positively with Δuric acid (r = 0.37, p < 0.001) but not with Δ25(OH) D (r = 0.06, p = 0.54), Δ iPTH (r = - 0.03, p = 0.78) ΔFGF23 (r = - 0.08, p = 0.38) and Δ125 (OH)₂ D (r = - 0.04, p = 0.65). In conclusion, high dose cholecalciferol supplementation did not change sclerostin levels in non-diabetic stage 3-4 CKD subjects.

Effect of Vitamin D Receptor Activation on the AGE/RAGE System and Myeloperoxidase in Chronic Kidney Disease Patients

Vitamin D receptor (VDR) activation has been reported to increase circulating levels of the advanced glycation end products (AGE) and their decoy receptor (RAGE). However, until now, the effect of VDR activation on AGE and RAGE has not been tested in the setting of a randomized, double-blind clinical trial. We have therefore analyzed the effect of VDR activation by paricalcitol on pentosidine, S100A12/ENRAGE, and RAGE and on established biomarkers of oxidative stress like myeloperoxidase in CKD patients in the PENNY trial. At baseline, human S100A12/ENRAGE, RAGE, and myeloperoxidase, but not pentosidine, were intercorrelated, and the association between S100A12/ENRAGE and myeloperoxidase (r = 0.71, P < 0.001) was the strongest among these correlations. Paricalcitol failed to modify biomarkers of the AGE/RAGE system and myeloperoxidase in unadjusted and adjusted analyses by the generalized linear model (GLM). No effect modification by other risk factors was registered. Paricalcitol does not modify biomarkers of the AGE/RAGE system and myeloperoxidase in CKD patients. The apparent increase in RAGE levels by VDR activation reported in previous uncontrolled studies is most likely due to confounding factors rather than to VDR activation per se. This trial is registered with NCT01680198.