Supplementary Material for: Sclerostin Declines during Hemodialysis and Appears in Dialysate

Background/Aims: Sclerostin, a soluble inhibitor of Wnt-signaling, inhibits bone formation. We assessed the impact of dialysis on serum sclerostin and whether sclerostin is detectable in effluent dialysates. Methods: In a prospective study of 54 prevalent hemodialysis patients, parameters of bone and mineral metabolism were assessed at the beginning and at the end of dialysis. In a subset of patients (n = 19) sclerostin was measured in serum at start, 1, 2, and 3 h of dialysis and in the effluent dialysate at several points in time. Results: Sclerostin serum levels decreased from median 71.4 pmol/l to 43.5 pmol/l during dialysis (p < 0.0001). In patients with high pre-dialysis sclerostin serum levels, sclerostin was detected in the dialysate. Higher Kt/V correlated with greater relative decrease of sclerostin (r = 0.467; p = 0.001). Conclusion: Sclerostin is dialysable. Furthermore, sclerostin serum levels decrease during dialysis. Whether targeting lower sclerostin levels by means of improved dialysis adequacy has direct relevance to bone disease remains to be shown.