High Phosphate Diet Changes Bone Characteristics of Mouse Femurs and Mandibles

Objectives: More than 30% of the US population consumes 2.5 times the estimated requirement of inorganic phosphate (Pi). In animal studies, a high phosphate (HP) diet has negative effects on bone health and is associated with active bone resorption in orthopedic bones. However, the effect of HP diet induced active bone modeling on jawbone characteristics has not been fully investigated. The objective of this study was to determine how a high phosphate diet alters bone characteristics in the mandible and femurs of mice.
Methods: Following IACUC approval, 30 C57BL6 mice were fed a normal phosphate (NP) diet (0.6% Pi) (n=15) or HP diet (2.0% Pi) (n=15) for 18 weeks. A femur and mandible were randomly dissected and scanned by micro-computed tomography (micro-CT) with 20 mm voxel size. Bone and teeth voxels were segmented from other voxels. Gray levels of bone voxels were converted to tissue mineral density (TMD) values using a calibration curve. Femoral cortical (CB) and trabecular (TB) bone morphological parameters were computed at 55% (CB₅₅) of the femoral length from the head and above growth plates at the distal condyle of femur, respectively. Dynamic mechanical analysis (DMA) and fracture testing of the femur were also conducted. A Student’s t-test was performed to compare all parameters between NP and HP groups.
Results: In femurs and mandibles, mineral density parameters were significantly decreased in the HP group (p<0.03). The HP femurs also had significantly smaller CB thickness (p<0.001). The DMA based stiffness and fracture strength showed that HP femurs had significantly diminished mechanical properties (p<0.05).
Conclusions: The HP diet reduced bone health of femurs and mandibles of mice, resulting in higher fracture risk of femurs.