Similar to previous studies, we observed significant deficits at cancellous bone sites in mice that were exposed to excessive dietary fat,

which reiterates the negative effect of HFD on bone in mice [13], [14] and [15]. The simultaneous examination of skeletally immature and mature mice in this study reveals that the HFD-associated effects on the femoral trabecular BVF are more pronounced in the younger age group. Further, the HFD tended to reduce the volumetric BMD in the distal femur of only the immature animals. Taken together, these disparate effects on bone volume and volumetric BMD between the immature and mature age groups support the controversial hypothesis of increased fracture risk in obese adolescents, but not in obese adults. Similar to this study, Ionova-Martin et al. [18] examined the effects of HFD (60% kcal fat) for 16 weeks on male C57BL/6J mice beginning Gemcitabine in vitro from 3 or 15 weeks of age,

but focused on the cortical rather than cancellous bone. The whole body BMC appeared to have a greater reduction in the young mice, but the spinal areal BMD mTOR inhibitor and cortical thickness of the femur seemed to be affected more in the older mice. The HFD apparently affected all other cortical bone properties similarly across the two age groups. Considering that Ionova-Martin et al. did not test comparisons across age groups, our observations regarding potential age-dependent effects in that study can only be based on trends. The age-dependence of HFD effects on trabecular bone that were observed in the current study may depend on anatomic site. While age and diet synergistically affected the trabecular BVF in the distal femoral metaphysis, the effects of HFD on lumbar vertebrae were equivalent in the two age groups and were less substantial than those observed GPX6 in the femur. A similar observation of anatomic site difference was observed in genetic, leptin-related mouse models of

obesity [24]. Specifically, the femoral BMC, BMD and strength were affected significantly compared to lean controls, but lumbar vertebral bone was unaffected. Considering that significant differences in the vertebrae were not observed with genetically-induced obesity, but were with HFD-induced obesity, suggests that the effects observed in the current study may be independent of body mass and are more directly associated with the excessive dietary fat and resulting metabolic syndrome. Consistent with this interpretation, more dramatic decrements in femoral bone properties were observed in the HFD-fed immature mice than in the HFD-fed mature mice despite smaller increases in body mass and hyperglycemia. In addition to the variations by anatomic site, the HFD effects on cortical bone are less pronounced than those on cancellous bone in this study and in previous studies [13] and [15]. Cao et al.