Feeding Orange Pulp Improved Bone Quality in a Rat Model of Male Osteoporosis

Oxidative stress and inflammation have been linked to bone loss. We evaluated the effects of feeding orange pulp (OP), a source of vitamin C and flavonoids, on bone quality in a rat model of male osteoporosis. One-year-old retired breeder rats (n = 43) were orchidectomized (ORX) or sham-operated (SHAM). Three days postsurgery, ORX rats were randomly assigned to treatments: ORX or ORX with 2.5% OP, 5% OP, or 10% OP. Diets were isonitrogenous, isocaloric, modified AIN-93M diets with equal fiber content. All ORX rats were fed for 4 months to the mean food intake of the SHAM group. At the end of the study blood, urine and bone samples were collected. Plasma antioxidant capacity and urinary deoxypyridinoline (DPD) were determined. Bone density, structure, and strength were assessed using dual energy X-ray absorptiometry, microcomputed tomography, and finite element analyses. ORX decreased (P < .05) antioxidant status, while OP as low as 2.5% maintained the antioxidant capacity of ORX rats comparable to that of the SHAM group. Cortical thickness at the tibial midshaft was significantly decreased by ORX and increased by OP, and urinary DPD was significantly increased by ORX and decreased by OP. In fourth lumbar trabecular cores, ORX rats had significantly reduced bone volume fraction, connectivity density, and trabecular number and increased trabecular separation. OP significantly increased bone volume fraction and trabecular number and decreased trabecular separation in ORX rats. Improvements due to OP in microarchitectural properties of vertebral bones and in cortical thickness of long bones were subtle but significant. The consistently negative impacts of ORX on bone density, structure, and strength parameters confirm the previously reported importance of testosterone for bone.