Bone Abstracts

Estrogen deficiency promotes bone loss and skeletal muscle dysfunction. Peroxisome proliferator-activated receptor (PPAR) agonists and high-impact exercise both affect musculoskeletal properties. Whereas PPARδ agonists ameliorate training response in muscle, PPARα agonists exert beneficial effects in bone and muscle. In the present study we investigated the effects of the PPARα agonist fenofibrate and high-impact jumping exercise alone and combined in ovariectomized (OVX) rats. Female Sprague–Dawley rats, 12 weeks of age, were allocated to a sham-operated group (SHAM), and four OVX groups: fenofibrate (OVX-Fen), exercise (OVX-Ex), combined fenofibrate and exercise (OVX-FenEx) and a control group (OVX-Ctr), respectively (n=12 per group). Fenofibrate (90 mg/kg per day) or vehicle (methylcellulose) were given by gavage for eight weeks. Whole body, spine and femur bone mineral density (BMD), and body composition were assessed by dual X-ray absorptiometry (DXA). Trabecular microarchitecture was analyzed using micro-computed tomography, and bone metabolism markers in plasma by immunoassays. Femoral BMD increased more in all intervention groups relative to OVX-Ctr (P<0.01), and was also normalized in the OVX-Ex and OVX-FenEx groups relative to SHAM. The BMD gain at the femur was higher in the OVX-FenEx group than in OVX-Fen and SHAM (7.4 vs 2.4 and 2.7%, P<0.05). Trabecular number was higher in the OVX-FenEx group relative to OVX-Ctr and OVX-Fen (1.79 vs 1.15 and 1.26 1/mm, P<0.05), while trabecular separation was lower in the OVX-FenEx group compared to OVX-Ctr (0.44 vs 0.63 mm, P<0.05). Higher levels of bone formation marker in plasma were observed in all intervention groups compared to OVX-Ctr (P<0.05). After the intervention, lean mass was maintained at sham level in the OVX-FenEx group, whereas all other groups had lower lean mass than SHAM (P<0.05). In conclusion, combination of fenofibrate and jumping exercise seems to increase femoral BMD more than each intervention alone, while preserving lean mass in OVX rats.