Assessment of bone metabolism and biomechanical properties of the femur, following treatment with anastrozole and letrozole in an experimental model of menopause.

The aim of the present study was to investigate the impact of anastrozole and letrozole supplementation following surgically induced menopause on bone metabolism and biomechanical properties. A total of 45 Wistar rats underwent ovariectomy and were then randomly allocated to receive no treatment, anastrozole or letrozole. At 2 and 4 months following the initiation of the present study, the serum levels of osteoprotegerin (OPG) and receptor activator of nuclear factor-κB ligand (RANKL) were determined, and the animals were sacrificed at the end of the 4-month period to assess the biomechanical properties of the femoral bones. The applied force and the deflection of the central section were recorded during the test. Taking advantage of these quantities, the fracture force, the stiffness of the bone and the energy absorbed until fracture were determined. At 2 months following the initiation of the experimental protocol, the mean OPG levels were significantly increased in the control group compared with the anastrozole-treated group (P<0.01). Similarly, RANKL levels were significantly increased in the control rats compared with the anastrozole-treated animals (P<0.001) and animals that received letrozole (P<0.05). Notably, these trends were not observed at the end of the experiment (4 months). A biomechanical study of the femoral bones revealed significantly decreased stiffness among animals that received anastrozole (P<0.05) and letrozole (P<0.01) compared with their control counterparts. The results of the present study indicate that treatment with anastrozole and letrozole significantly increases the levels of OPG and RANKL in bone, an effect that appears to be directly associated with the biomechanical properties of bones.