Diabetes causes decreased osteoclastogenesis, reduced bone formation, and enhanced apoptosis of osteoblastic cells in bacteria stimulated bone loss

The most common cause of inflammatory bone loss is periodontal disease. After bacterial insult, inflammation induces bone resorption, which is followed by new reparative bone formation. Because diabetics have a higher incidence and more severe periodontitis, we examined mechanisms by which diabetes alters the response of bone to bacterial challenge. This was accomplished with db/db mice, which naturally develop type 2 diabetes. After inoculation of bacteria osteoclastogenesis and bone resorption was measured. Both parameters were decreased in the diabetic group. Diabetes also suppressed reparative bone formation measured histologically and by the expression of osteocalcin. The impact of diabetes on new bone formation coincided with the effect of diabetes on apoptosis of bone-lining cells. Within 5 d of bacterial challenge, apoptosis declined in the wild-type animals yet remained significantly higher in the diabetic group. Thus, diabetes may cause a net loss of bone because the suppression of bone formation is greater than the suppression of bone resorption. The uncoupling of bone formation and resorption may be due in part to prolonged apoptosis of bone lining cells.