Chronic Hyperglycemia Modulates Rat Osteoporotic Cortical Bone Microarchitecture into Less Fragile Structures

Area of Science:

• Endocrinology
• Bone Biology
• Diabetology

Background:

• Diabetes mellitus, particularly type 2, is linked to impaired bone quality in postmenopausal women.
• Uncontrolled hyperglycemia is a suspected contributor to these bone health issues.
• Estrogen deficiency (menopause) exacerbates bone loss, creating a complex interplay with diabetes.

Purpose of the Study:

• To investigate the effects of chronic hyperglycemia on bone turnover, morphology, and biomechanics in female rats.
• To assess these effects in the presence and absence of estrogen (ovariectomy).

Main Methods:

• Female Wistar rats underwent sham surgery, ovariectomy (OVX), hyperglycemia induction (streptozotocin), or combined hyperglycemia and OVX (STZ+OVX).
• Evaluated bone turnover markers (PINP/CTX ratio), vertebral microarchitecture (histomorphometry), femur biomechanics (bending tests), tibia ultrastructure (SEM), and calcium levels.
• Measurements were taken 60 days post-ovariectomy.

Main Results:

• Hyperglycemic-ovariectomized rats showed a tendency for improved bone formation compared to OVX alone.
• Hyperglycemia increased tibia medullar canal size without affecting cortical thickness, unlike OVX which decreased it.
• Bones from STZ+OVX rats exhibited increased stiffness and strength, correlating with observed ultrastructural changes.

Conclusions:

• Chronic hyperglycemia induces bone morphological changes in ovariectomized rats.
• These changes positively impact the ultrastructure and mechanical properties of cortical bone.
• Findings suggest hyperglycemia may mitigate some negative effects of estrogen deficiency on bone biomechanics.