The Effect of Diabetes Mellitus, Insulin, and Thiazolidinediones on Bone Histomorphometry in Streptozotocin-induced Diabetic Postmenopausal Wistar Rats

Background: Osteoporosis is a metabolic skeletal disease with low bone mass and bone microarchitectural disorganization. Thiazolidinediones (TZD) increase insulin sensitivity through activation of peroxisome proliferator-activated receptor gamma (PPARγ). One of the most important side effects of this drugs is its effects on bone, especially in postmenopausal women. The purpose of this study was to evaluate the effect of diabetes mellitus (DM), insulin, and TZDs on bone in postmenopausal Wistar rats. Methods: Sixteen postmenopausal Wistar rats were divided into four groups: (i) control group, (ii) Streptozotocin-induced DM group without treatment, (iii) Streptozotocin-induced DM group with insulin therapy, and (iv) Streptozotocin-induced DM group receiving rosiglitazone. Pictures of the obtained samples were taken under computer-equipped photo-light microscope, and bone tissue ratios were calculated in an area of 1 mm2. In this area, trabecular thicknesses were measured from six randomly selected regions. In addition, femoral neck regions were determined by measuring the farthest distance. Results: Compared to the control group, trabecular thicknesses were decreased in the uncontrolled DM and rosiglitazone groups. In the rosiglitazone-treated group, trabecular thickness was decreased compared to the uncontrolled DM group. The histological examination of the bones showed that uncontrolled DM and rosiglitazone treatment negatively affected the osteoblast and osteocyte activity. Insulin-treated group had a similar histologic examination compared to the control group. Conclusion: Our study showed that DM had unfavorable effects on bones, and rosiglitazone further exerts this effect. However, the negative effect of DM may be neutralized with the use of insulin. Keywords: diabetes mellitus, bone, osteoporosis, bone histomorphometry, rosiglitazone, insulin, thiazolidinediones