Type 2 diabetes mellitus (T2DM) increased the risk of fragility fractures, even if it is often associated with an increase in bone density. T2DM could impact bone through several mechanisms. We evaluated the impact of diabetes on bone by measuring bone turnover, bone cells precursors and cytokines in 50 T2DM patients and 100 age and BMI matched controls. In order to evaluate the effect of T2DM on bone density (BMD), quality (TBS) and the incidence of fragility fractures we measured these parameters by DXA, in T2DM BMD was significantly higher at lumbar spine, TBS was inversely correlated with glycaemic control measured by HbA1C (R=0.35, p<0.0001), but we found no increase in the incidence of vertebral and non-vertebral fractures. Bone turnover was reduced in T2DM patients whereas osteoclast precursors in peripheral blood were significantly increased and osteoblast precursors decreased. Amongst cytokines involved in the control of bone turnover RANKL was decreased in T2DM patients, whereas there were no differences in the levels of OPG, consequently the RANKL/OPG ratio was increased in T2DM. Levels of SOST and DKK-1 were not significantly influenced by T2DM. Muscular strength and balance were significantly reduced in T2DM patients as respect to controls, with particular regard to the hand grip test and the Tinetti balance test, whereas the Timed up and Go test was not significantly different between T2DM and control. In conclusion, we observed a decreased turnover in T2DM even though osteoclast precursors were increased in peripheral blood. This result may be due to an increase in immature osteoclasts that are not recruited in bone, in fact RANKL was decreased in T2DM as respect to controls. We did not found significant difference in the incidence of fragility fracture in T2DM, this could be due to the use of controls matched for obesity and age; moreover we found no differences in TBS in diabetic patients, interestingly the bone quality seems to be worsened by the scarce glycaemic control. Muscular force and balance was impaired in T2DM, this could influence the risk of non-vertebral fragility fractures, anyway the low sample does not allow us to investigate this type of fracture.
Disclosure: The authors declared no competing interests.