Microarchitecture of trabecular bone in type 2 diabetic rats – Three-demensional analysis using microcomputed tomography – *
Unlike type 1 diabetes mellitus, type 2 diabetes shows a low frequency of low bone mass, and it has been questioned as a cause of osteoporosis. However, it has recently been reported that type 2 diabetes is related to the increase in a fracture risk, and the existence of the factor except for low bone mass is suggested as the mechanism. In this study, the change of microarchitecture of trabecular bone in diabetes mellitus was studied using type 2 diabetic rats, and its significance in the pathophysiology of the diabetic osteoporosis was examined. Type 2 diabetic rats (OLETF, n = 7 -ll foreachgroup) of 14, 28, 42 and 56 weeks old and control rats (LETO, n = 8 - ll for each group) of the same week old were used for the study. After the sacrifice, the fifth lumbar vertebral body (LV) , proximal tibial metaphysis (PT) , and distal tibial metaphysis (DT) were scanned by microcomputed tomography (micro-CT) with the slice thickness of 14.1-18.6 jam and the pixel size of 17.6-23.2 jum. Three-dimensional image data were analyzed by the image analysis system to evaluate trabecular bone volume fraction, trabecular thickness, number, separation and connectivity, trabecular bone pattern factor, structure model index, and degree of anisotropy. The third lumbar vertebral body was compressed to obtain the breaking force. In all week groups, body weight and blood glucose levels were higher in OLETF rats. OLETF rats showed higher values of bone volume fraction in LV at 14 weeks old and in DT at all week groups. On the other hand, at 42 and 56 weeks old OLETF rats showed lower bone volume fraction in PT. The trabecular structure of LV in OLETF rats was rod-like and less connected at 28, 42 and 56 weeks old, whereas DT in OLETF rats showed plate-like and more connected structure at all week groups. The breaking force ofLV was significantly lower in OLETF at 42 and 56 weeks old. These results indicate that the bone change in diabetes mellitus greatly varies among the skeletal sites, and suggest that, in the mechanically less loaded site like lumbar vertebra, the deterioration of trabecular microstructure is highly responsible for the decrease in bone strength. (Accepted on August 9 , 2003)
