Alterations in femoral bone histomorphometry and vitamin D metabolism in neonatal streptozotocin-induced diabetic rat

: Histomorphometric examination and histological observation of femoral bone were performed on long-standing neonatal streptozotocin-induced diabetic rats (n2STZ, n5STZ) as a human model of non-insulin-dependent diabetes mellitus. The growth and strength of femurs decreased in the STZ diabetic rats. Histomorphometric parameters such as cortical bone thickness, number of metaphysical trabeculae and percent trabecular volume of metaphysical area all significantly decreased in the STZ diabetic rats. There were no significant differences in parameters between the n2STZ and n5STZ diabetic rats. Histological findings demonstrated no significant change in the number of osteoclasts in femur nor change corresponding to osteomalacia. Bone absorption in the STZ diabetic rats appeared unchanged. The plasma calcium level did not change in the STZ diabetic rats, although their plasma phosphate or A1-p levels increased. Circulating 24, 25 (OH)2D3 was significantly lower in the STZ diabetic rats than the controls. However, 25 (OH) D3 or biologically active 1, 25 (OH)2D3 was not different between the controls and STZ diabetic rats. Osteopenia is thus present in the femurs of long-standing neonatal STZ diabetic rats, due in part to abnormal vitamin D metabolism.