Effect of leptin on bone metabolism in rat model of traumatic brain injury and femoral fracture

Abstract

Objective To observe serum and callus leptin expression within the setting of fracture and traumatic brain injury (TBI). Methods A total of 64 male SD rats were randomized equally into 4 groups: nonoperated group, TBI group, fracture group, and fracture+TBI group. Rats were sacrificed at 2, 4, 8 and 12 weeks after fracture+TBI. Serum leptin was detected using radioimmunoassay, and callus formation was measured radiologically. Callus leptin was analyzed by immunohistochemistry. Results Serum leptin levels in the fracture group, TBI group and combined fracture+TBI group were all significantly increased compared with control group at the 2 week time-point ( P<0. 05). Serum leptin in the combined fracture+TBI group was significantly higher than that in the fracture and TBI groups at 4 and 8 weeks after injury ( P<0. 05). The percentage of leptin-positive cells in the fracture+TBI callus and callus volume were significantly higher than those in the fracture-only group ( P<0. 01). Conclusions We demonstrated elevated leptin expression within healing bone especially in the first 8 weeks in a rat model of fracture and TBI. A close association exists between leptin levels and the degree of callus formation in fractures.