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

BACKGROUND AND OBJECTIVE: 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.

MATERIAL AND METHODS: 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.

RESULTS: 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.

CONCLUSION: 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.