Comparison of calcium acetate and sevelamer on vascular function and fibroblast growth factor 23 in CKD patients: a randomized clinical trial.

BACKGROUND: Fibroblast growth factor 23 (FGF-23) is a marker of endothelial dysfunction and atherosclerotic complications in patients with chronic kidney disease (CKD). Because previous studies suggested that sevelamer may exert effects on FGF-23 level and endothelial function independently of its phosphate-lowering action, we tested the effect of sevelamer versus calcium acetate on vascular function and FGF-23 levels.

STUDY DESIGN: Randomized prospective open-label trial.

SETTING & PARTICIPANTS: Patients with stage 4 CKD with hyperphosphatemia (n = 100).

INTERVENTION: An 8-week intervention with sevelamer (n = 47) and calcium acetate (n = 53).

OUTCOMES: The primary study outcome was change in flow-mediated vasodilatation in the forearm. The secondary outcome was change in FGF-23 levels.

RESULTS: Serum phosphate levels decreased in both treatment arms (P < 0.001), but more markedly in the sevelamer group (P < 0.001). Flow-mediated vasodilatation increased from 6.1% to 7.1% (P < 0.001) in sevelamer-treated patients, whereas it was unchanged in the calcium-acetate group (6.0% vs 6.0%). In a combined analysis, treatment-induced changes in flow-mediated vasodilatation were (P < 0.001) associated with simultaneous changes in FGF-23 levels (-27.1% [-33.2% to -8.8%] for the sevelamer group; 3.5% [-8.4% to 12.1%] for the calcium acetate group), as well as with C-reactive protein and fetuin A levels. These relationships were confirmed in multiple regression analysis adjusting for changes in serum phosphate levels and other factors.

LIMITATIONS: Unblinded randomized controlled study that cannot establish mechanisms of effect.

CONCLUSIONS: In hyperphosphatemic patients with stage 4 CKD, treatment with phosphate lowering induces measurable improvements in flow-mediated vasodilatation. Furthermore, independently of serum phosphate level, FGF-23 level changes induced by phosphate binders are associated with simultaneous changes in flow-mediated vasodilatation. These observations are compatible with the hypothesis that FGF-23 may contribute to vascular dysfunction in this population.