Bone biomechanical and histomorphometrical investment in type 2 diabetic Goto-Kakizaki rats

This study was performed to characterize the bone metabolism in ten 6-month-old male Goto-Kakizaki (GK) rats, a spontaneous type 2 diabetic model, with ten age- and sex-matched non-diabetic Wistar rats as controls. The femora and the fifth lumbar vertebrae were analyzed by a dual energy X-ray absorptiometry for bone mineral density. Histomorphometrical analyses were performed on the sections from the tibia embedded in methylmethacrylate. Biomechanical characterizations were made by a three-point bending test and a compressive test on the femur and the fifth vertebral body respectively. Compared to the control rats, the bone mineral density was significantly deceased and the histomorphometrical studies showed significantly decreased trabecular bone volume, trabecular thickness and number, osteoid surface and thickness, mineralizing surface, mineral apposition rate and bone formation rate, and also a significant increase in mineralization lag time in the diabetic rats. Strength in both bones and elastic modulus of vertebral body significantly decreased in the diabetic rats as well. In addition, the serum osteocalcin levels were significantly decreased and the serum tartrate-resistant acid phosphatase activity was significantly increased. In conclusion, the 6-month-old GK diabetic rats developed osteopenia with an increased risk of fracture owing to the decreased bone formation, and might be a useful model for unraveling the effects of diabetes on bones independent of obesity frequently seen in the type 2 diabetic patients.