Background: Obesity is considered protective for bone mass, but this view has been progressively challenged. Menopause is characterized by low bone mass and increased adiposity. Our aim was to determine how visceral and bone marrow adiposity change following ovariectomy (OVX), how they correlate with bone quality and if they are influenced by physical activity.
Methods: Five-month-old Wistar rats were OVX or sham-operated and maintained in sedentary or physically active conditions for 9 months. Visceral and bone marrow adiposity as well as bone turnover, femur bone quality and biomechanical properties were assessed.
Results: OVX resulted in higher weight, visceral and bone marrow adiposity. Visceral adiposity correlated inversely with femur Ct.Th (r = -0.63, p < 0.001), BV/TV (r = -0.67, p < 0.001), Tb.N (r = -0.69, p < 0.001) and positively with Tb.Sp (r = 0.58, p < 0.001). Bone marrow adiposity also correlated with bone resorption (r = 0.47, p < 0.01), bone formation rate (r = -0.63, p < 0.01), BV/TV (r = -0.85, p < 0.001), Ct.Th (r = -0.51, p < 0.0.01), and with higher empty osteocyte lacunae (r = 0.39, p < 0.05), higher percentage of osteocytes with oxidative stress (r = 0.64, p < 0.0.01) and lower femur maximal stress (r = -0.58, p < 0.001). Physical activity correlated inversely with both visceral (r = -0.74, p < 0.01) and bone marrow adiposity (r = -0.92, p < 0.001).
Conclusions: OVX increases visceral and bone marrow adiposity which are associated with inferior bone quality and biomechanical properties. Physical activity could contribute to reduce adipose tissue and thereby improve bone quality.
Keywords: bone quality; marrow adiposity; ovariectomy; physical activity; running wheel exercise; visceral adiposity.