Zoledronic acid acutely increases sclerostin serum levels in women with postmenopausal osteoporosis.

CONTEXT: Sclerostin is a circulating inhibitor of the Wnt-signaling pathway produced by osteocytes, which acts as a negative regulator of bone formation. Effects of zoledronic acid on sclerostin serum levels in postmenopausal osteoporosis are unknown.

OBJECTIVE: The purpose of this study was to evaluate sclerostin serum levels after zoledronic acid administration and correlate variations with bone turnover markers.

DESIGN AND SETTING: We conducted a prospective intervention study in an ambulatory care setting.

PARTICIPANTS AND INTERVENTION: Forty women (mean age 62.6 ± 4.9 years) with postmenopausal osteoporosis were enrolled in this study and randomized into 2 groups to receive zoledronic acid (5 mg) or placebo.

MAIN OUTCOMES MEASURES: At baseline and then at 2, 7, 30, and 360 days after zoledronic acid or placebo administration, serum levels of sclerostin, bone-specific alkaline phosphatase (BSAP), as a bone formation marker, and serum C-telopeptide of type 1 collagen (CTX), as a bone resorption marker, were measured.

RESULTS: Sclerostin serum levels increased by day 2, reached a peak at day 7 (3-fold baseline, P < .001), and then decreased at day 30 and returned near to baseline after 360 days in the zoledronic acid group. Both CTX and BSAP were reduced, and a significant negative correlation was observed between the percentage changes of sclerostin and the variation in BSAP and CTX at all time points in the zoledronic acid group (P < .05). No changes were observed in the placebo group.

CONCLUSIONS: Our data demonstrate that zoledronic acid increases sclerostin serum levels and that sclerostin could play a role in coupling bone resorption to bone formation.