Relative bone mass decreased in mice fed high dietary fat despite an increase in body mass and bone formation markers

Abstract

Osteoporosis and obesity are interrelated health disorders. Osteoblasts and adipocytes are derived from common mesenchymal stem cells and age‐related osteoporosis is associated with increased bone marrow adipogenesis. To determine whether bone mass and osteoblast number and activity are affected by dietary fat intake, six‐week‐old male C57BL/6 mice were randomly assigned to two groups (n=10–11/group) and fed either a high fat diet (HFD, 45% kcal as fat) or a low fat control diet (LFD, 10%) for 14 weeks. Bone marrow stromal cells (BMSCs) were cultured and bone architecture was evaluated by micro computed tomography. Mice fed HFD were 31% heavier (P<0.01) than those fed LFD, 41±6 vs. 31±2g, respectively. Higher numbers of alkaline phosphatase (ALP) positive colonies and calcium nodules were formed by BMSCs from HFD than from LFD mice (P<0.01). At d 14 of culture, ALP mRNA levels in BMSCs from HFD were higher (P<0.05) than from LFD mice. There were no significant differences in tibial fat‐free weight, length, and mid‐shaft diameter between the two groups (P>0.05). Although HFD increased total tibial volume by 14% as compared with LFD (2.05±0.15 vs. 1.80±0.29 mm3, respectively, P<0.05), bone volume relative to body mass decreased (8.5±1.8 vs. 11.2±3.4 mm3/kg, respectively). Our data suggest that feeding HFD results in bone resorption that exceeds any positive effect that increased body weight has on bone formation.