Longitudinal Analysis of Bone Metabolic Markers and Bone Mechanical Properties in STZ-Induced Diabetic Rats

<b>Background:</b> This longitudinal study examined the early effects of type 1 diabetes on bone mechanical properties and metabolic markers in mature rats, focusing on the natural progression of diabetes-induced changes without external treatments. <b>Methods</b>: Forty-eight 8-month-old male Wistar rats were divided into two groups, with one group receiving a single dose of streptozotocin (STZ, 60 mg/kg). Assessments were performed 2, 4, and 8 weeks post-administration, including serum biochemical analyses, bone marker assessments, and mechanical bone tests. The data were analyzed using two-way ANOVA to evaluate the impact of time and treatment. <b>Results</b>: At 2 weeks, diabetic rats showed increased fasting blood glucose (<i>p</i> < 0.001), decreased insulin levels (<i>p</i> = 0.03), and changes in HOMA markers (<i>p</i> < 0.001), liver enzymes (<i>p</i> < 0.001), inflammatory markers (<i>p</i> < 0.001), and bone metabolism markers (osteocalcin (<i>p</i> < 0.001), OPG (<i>p</i> = 0.006), RANKL (<i>p</i> < 0.001), and OPG/RANKL ratio (<i>p</i> < 0.001)), with initial alterations in bone geometry. By week 4, decreased body weight in the diabetic group (<i>p</i> < 0.001) led to further changes in bone geometry and initial differences in mechanical properties. At 8 weeks, significant declines in body (<i>p</i> < 0.001) and bone (<i>p</i> < 0.001) weights were observed, along with further deterioration in bone geometry and mechanical properties. <b>Conclusions</b>: The study highlights the significant impact of STZ-induced diabetes on bone health as early as two weeks post-STZ administration, with marked temporal changes in biochemical markers and mechanical properties.