CONTEXT: Decreased bone formation due to a coupling effect limits bone mass increases after antiresorptive treatment.
OBJECTIVE: The purpose of this study was to compare the effects of 2 potent antiresorptive agents with different mechanism of action on serum levels of Wnt antagonists, sclerostin and dickkopf-1 (Dkk-1).
DESIGN: This was an interventional, parallel assignment, open-label, randomized clinical trial.
SETTING: The study was conducted at the outpatient clinics for metabolic bone diseases of 424 General Military Hospital, Thessaloniki, Greece.
PATIENTS AND INTERVENTIONS: Naive postmenopausal women with low bone mass were assigned to zoledronic acid infusion (n = 46) or denosumab injection (n = 46). One woman in the zoledronic acid group was lost to follow-up.
MAIN OUTCOME MEASURES: Serum sclerostin and Dkk-1 levels were the main outcomes. Secondary measurements were serum osteoprotegerin, receptor activator of nuclear factor κB ligand, procollagen type 1 N-terminal propeptide, and C-terminal cross-linking telopeptide of type 1 collagen.
RESULTS: Serum sclerostin levels significantly decreased in the zoledronic acid (P < .001) but increased in the denosumab group (P = .003). Dkk-1 levels significantly decreased in the zoledronic acid group (P = .006) but did not change in the denosumab group (P = .402). Serum osteoprotegerin remained essentially unchanged in either group, whereas receptor activator of nuclear factor κB ligand decreased in the zoledronic acid group (P = .004) but increased in the denosumab group (P = .037). Bone markers (procollagen type 1 N-terminal propeptide, C-terminal cross-linking telopeptide of type 1 collagen, and total serum alkaline phosphatase) decreased in both groups (all P < .001).
CONCLUSIONS: Although they both decrease bone resorption, zoledronic acid and denosumab exert opposite effects on Wnt signaling: the former decreases serum levels of both sclerostin and Dkk-1, whereas the latter increases sclerostin and does not affect Dkk-1.