Effects of insulin-like growth factor I on alveolar bone remodeling in diabetic rats

Diabetes is a chronic hyperglycemic disorder and results in a tendency to develop osteoporosis. Furthermore, the delayed healing of tooth-extraction wounds, the activation of alveolar resorption and the suppressed formation of bone around implants are difficult for dentists to resolve. In diabetes, insulin-like growth factor I (IGF-I) appears to enhance the differentiation of osteoblasts and to activate the mineralization of bone. Hence, the aim of this study was to investigate the effects of insulin-like growth factor I on the remodeling of alveolar bone in diabetic rats.Diabetes was induced in 40 male Sprague-Dawley rats by intravenous administration of alloxan. The teeth of the rats were extracted to investigate remodeling of alveolar bone. Insulin-like growth factor I was administered, via intraperitoneal injection, to diabetic rats following tooth extraction. The remodeling of alveolar bone was determined using radiographic data, histological analyses and tetracycline fluorescence labeling.Compared with the control group, diabetes decreased alveolar bone formation. The height of alveolar bone and the bone-formation rate was significantly lower in the untreated diabetic group than in the control group or in the treated rats. Treatment with insulin-like growth factor I not only regulated abnormal blood glucose levels but also increased the height of the alveolar bone and increased the bone-formation rate relative to the results in diabetic animals. Furthermore, the expression of glucose transporter-1, the main transporter of glucose, was changed by hyperglycemia.The results suggest that insulin-like growth factor I treatment increases the volume of newly formed bone following tooth extraction and normalizes the expression of glucose transporter-1 in diabetic rats, which may play an important role in bone formation and mineralization.