Insulin promotes bone formation in augmented maxillary sinus in diabetic rabbits

The role of insulin during the formation of bone in the augmented space of the maxillary sinus in patients with diabetes is unclear. The authors compared the differences in bone formation after maxillary sinus floor elevation in diabetic and healthy animals and evaluated the effects of insulin on osteogenesis and the differentiation and activities of the osteoblasts. 10 male Japanese white rabbits were divided into two groups after diabetic induction by a single injection of monohydrated alloxan and having maintained steady blood glucose levels. The groups included the diabetes mellitus group (DM; n = 5) and the DM + insulin group (n = 5); another five healthy rabbits comprised the control group. Maxillary sinus floor elevation was performed by grafting hydroxyapatite particles. Compared with the control group, the newly formed bone area, number of blood vessels and osteoblasts, collagen 1 content and serum osteocalcin levels were significantly decreased in DM rabbits (P < 0.01). Insulin treatment reversed the decrease in bone formation, blood vessels, osteoblasts, collagen I and serum osteocalcin (P < 0.01). Insulin treatment also promoted osteogenesis in the augmented space of the diabetic rabbits, which might have resulted from promotion of osteoblast differentiation and upregulation of neovascularization.