Glucocorticosteroid-induced osteoporosis in adult primiparous Göttingen miniature pigs: effects on bone mineral and mineral metabolism

Abstract

Information on the pathophysiology of glucocorticoid-induced osteoporosis (GIO) is limited, since its clinical picture often reflects a combined effect of glucocorticoids (GC) and the treated systemic disease (i.e., inflammation and immobility). In 50 healthy adult (30-mo-old) primiparous Göttingen minipigs, we studied the short-term (8 mo, n = 30) and long-term (15 mo, n = 10) effect of GC on bone and mineral metabolism longitudinally and cross-sectionally compared with a control group ( n = 10). All animals on GC treatment received prednisolone orally at a dose of 1.0 mg·kg body wt−1·day−1for 8 wk and thereafter at 0.5 mg/kg body wt−1·day−1. In the short term, GC reduced bone mineral density (BMD) at the lumbar spine by −47.5 ± 5.1 mg/cm3from baseline ( P < 0.001), which was greater ( P < 0.05) than the loss [not significant (NS)] in the control group of −11.8 ± 12.6 mg/cm3. Calcium absorption decreased from baseline by −2,488 ± 688 mg/7 days ( P < 0.001) compared with −1,380 ± 1,297 mg/7 days (NS) in the control group. Plasma bone alkaline phosphatase (BAP) decreased from baseline by −17.8 ± 2.2 U/l ( P < 0.000), which was significantly different ( P < 0.05) from the value of the control group of −1.43 ± 4.8 U/l. In the long term, the loss of BMD became more pronounced and bone mineral content (BMC), trabecular thickness, mechanical stability, calcium absorption, 25-hydroxyvitamin D3, 1,25-dihydroxyvitamin D3, and parathyroid hormone tended to be lower compared with the control group. There was a negative association between the cumulative dose of GC and BMD, which was associated with impaired osteoblastogenesis. In conclusion, the main outcomes after GC treatment are comparable to symptoms of GC-induced osteoporosis in human subjects. Thus the adult Göttingen miniature pig appears to be a valuable animal model for GC-induced osteoporosis.