Osteoporosis and diabetes mellitus

Introduction: Diabetes mellitus (DM) and osteoporotic fractures are major causes of mortality and morbidity in older subjects. Recent reports have revealed close association between fracture risk and DM types 1 and 2 (DM1 and DM2, respectively). Aim of this review is to highlight the importance of these diseases in the elderly and examine certain etiopathogenetic aspects of DM associated osteoporosis, which could be useful in management of diabetic patients.
Materials and methods: We searched the Embase and PubMed databases using diabetes, osteoporosis, and bone mineral density (BMD) as search terms and 1989-2009 as publication dates.
Discussion: The risk of fractures seems to be increased in both types of DM although DM2 seems to be associated with normal-high BMDs compared with the normal population. This apparent paradox could reflect greater bone frailty in diabetic patients that are unrelated to adipose tissue, hyperinsulinemia, deposition of advanced glycosylation end products in collagen, reduced serum IGF-1 levels, hypercalciuria, renal failure, microangiopathy, and/or inflammation. Diabetic patients' propensity to fall and multiple comorbidities might also explain their higher fracture rates. The effects of drugs that inhibit bone resorption in diabetic patients are probably similar to those obtained in nondiabetics although there is little information on this issue. In general, effective treatment of diabetes has positive effects on bone metabolism. Metformin acts directly on bone tissue, reducing AGE accumulation, and insulin has direct effects on osteoclast activity. In contrast, the thiazolidinediones seem to have negative effects since they orient mesenchymal progenitor cell differentiation toward adipose rather than bone tissue. Incretin therapy is a newer approach that appears to modify interactions between nutrition and bone turnover (e.g., postprandial suppression of bone resorption).
Conclusions: Better understanding of how diabetes and its treatment influence bone tissue could lead to more effective strategies for preventing fractures in diabetic patients. More investigation is needed to determine whether conventional osteoporotic therapy is fully effective in patients with DM.