The present study was designed to determine the effects of glucocorticoid (GC) on
bone turnover, minerals, structure, and bone mechanical properties in minipigs. Six
8-month-old Göttingen minipigs were subcutaneously injected with prednisolone (PN,
0.5 mg/kg body wt (BW)/day, 5 days/week for 26 weeks (Group GC)), 6 were treated with
vehicle alone (Group VC), and 4 were sacrificed at start of the study for baseline
controls (Group BC). The increase in BW was similar in all groups. PN significantly
reduced serum osteocalcin and urinary type-1 collagen N-telopeptide levels at 13 weeks
and thereafter, compared with baseline and control, and also reduced serum bone specific
alkaline phosphatase levels relative to baseline. At 26 weeks, the longitudinal axis
of the lumbar bone and length of femur were smaller in Group GC than Group VC. The
total cross-sectional area of femur, but not the lumbar bone, in Group GC was significantly
different from Group VC. BMD of the femur, but not L2, measured by DXA, was lower
in Group GC than in Groups BC and VC. The cortical shell structure measured by 2D-micro-CT
deteriorated and age-dependent increases in trabecular bone structure 3D micro-CT
were reduced by PN. PN also caused deterioration of the cortical structure of the
mid-femur. In L2 and femur, PN significantly reduced the ultimate load and maximum
absorption energy of the femur and L2 compared with Group VC. The structural modulus
in Group GC was lower than in Group BC. Regression analyses revealed that bone minerals,
bone structure, and chemical markers correlated with mechanical properties of L2 and
mid-femur. Our results indicate that PN reduced systemic bone formation and resorption
and suppressed the age-dependent increases in bone minerals, structure, and mechanical
properties of L2 and mid-femur. Reduced bone turnover seemed to be associated with
a reduction in mechanical properties. The growing minipig could be a suitable model
of GCs-induced osteoporosis in humans.