Trabecular and Cortical Bone and Ossified Vessel Analysis in Rat Tibiae and Femora in a Polygenic Rat Model for Type 2 Diabetes Mellitus

Background: In type 2 diabetes mellitus (T2DM), bone and microvascular complications may be linked. Methods: The University of California Davis (UCD) polygenic T2DM and Sprague Dawley healthy control (CTL) rats (N = 48) were divided equally into diabetic and age-matched groups: (1) pre-diabetes, (2) diabetes onset, (3) early-stage T2DM, and (4) late-stage T2DM. Body mass, HbA1c, fasted blood glucose and femoral and tibial lengths were measured. Bones were scanned (μCT; 15 µm) to assess trabecular microarchitecture and density and mid-shaft cortical thickness (Ct.Th, µm), density and porosity. Ossified vessel volume (OsVV, %) and thickness (OsV.Th, µm) were also analyzed. A GLM determined significance at p < 0.05. Body mass and HbA1c were higher (p < 0.05) in all T2DM groups and blood glucose became elevated (p < 0.05) in early-stage T2DM and late-stage T2DM. Results: Tibiae and femora were longer (p < 0.05) with diabetes. Tibial bone volume was lower (p < 0.05) in pre-diabetes (4 ± 1% vs. CTL, 9 ± 2%) and late-stage T2DM (5 ± 2% vs. CTL, 8 ± 2%), and femoral bone volume was lower (p < 0.05) in pre-diabetes (7 ± 1% vs. 12 ± 4%). Cortical density (tibia) was lower (p < 0.05) in pre-diabetes and early-stage T2DM. Trabecular density in the femur was lower (p < 0.05) in all T2DM groups and cortical density was reduced (p < 0.05) in pre-diabetes, diabetes onset, and late-stage T2DM. OsVV in both bones were lower (p < 0.05) during early-stage T2DM. Tibial OsV.Th was higher (p < 0.05) in pre-diabetes (69 ± 14 µm vs. CTL, 56 ± 13 µm) and late-stage T2DM (80 ± 10 µm vs. CTL, 59 ± 13 µm) and higher (p < 0.05) in the femur at diabetes onset (58 ± 14 µm vs. CTL, 40 ± 10 µm). Conclusions: Trabecular and cortical bone varied as diabetes progressed, and the thicker ossified vessels may represent microangiopathy.