Effects of anti-sclerostin antibody and running on bone remodeling and strength

Sclerostin antibody (Scl-Ab) represents a promising therapeutic approach to treat patients with osteoporosis. PURPOSE The aim of this study was to investigate the effects of Scl-Ab, running and a combination of both on bone formation. METHODS Sixty female Wistar rats, aged 8 months were randomly assigned to five groups (subcutaneous injections performed twice a week): (1) (Sham): sedentary rats + saline, (2) (OVX): ovariectomized rats + saline, (3) (OVX + E): OVX rats + saline + treadmill training (5 times/week, 1 h/day), (4) (OVX + E + S): OVX rats + treadmill training + 5 mg/kg Scl-Ab and (5) (OVX + S): OVX rats + 5 mg/kg Scl-Ab. After 14 weeks, body composition, whole body and femoral BMDs were determined by DXA and serum was collected for analysis of osteocalcin and NTX. Bone microarchitecture was analyzed using μCT and bone strength was assessed at the femur mid-shaft in 3-point bending. RESULTS Running exercise decreased fat mass as well as the bone resorption marker NTX relative to the non-exercised control groups, effects that were associated with a prevention of the deleterious effects of OVX on whole body and femoral BMDs. Scl-Ab increased the bone formation marker osteocalcin, which resulted in robust increases in BMD and femoral metaphyseal bone volume to levels greater than in the Sham group. OVX + S + E group did not further impact on bone mass relative to the OVX + S group. At the cortical femur diaphysis, Scl-Ab prevented the decreases in bone strength after OVX, while exercise did not affect cortical strength. CONCLUSION We suggest that while running on a treadmill can prevent some bone loss through a modest antiresorptive effect, it did not contribute to the robust bone-forming effects of Scl-Ab when combined in an estrogen ablation model.