Effects of high fat or high sucrose diets on rat femora mechanical and compositional properties.

Diets high in fat and/or sucrose decrease whole bone mechanical properties and mineralization. This study examines the impact on rat bone mechanical properties and composition of age and diets (a) low in fat, (b) high in sucrose, and (c) high in fat. Sprague-Dawley rats aged 3 weeks (weanling [W]; n = 42), 8 weeks (young [Y]; n = 42), 16 weeks (teenage [T]; n = 39) and 56 weeks (old [O]; n = 40) were randomly assigned to groups: low fat, high sucrose and high fat with n = 12-16 per group. All animals were fed a purified low-fat, high starch diet for two weeks, and fed a low fat (STD), high sucrose (HSD), or high-fat (HFD) for five additional weeks. After sacrifice, the femurs were harvested and non-osseous tissue was removed. The bones were dried at 25 degrees C for 48 hours. Length and the periosteal minimum and maximum diameter (D-min and D-max) at the mid-diaphysis of the femurs were measured with Vernier calipers. The femurs were rehydrated and tested via three-point flexure. Bones were weighed after drying at 105 degrees C (48 hours; Dry-M) and 800 degrees C (24 hours; Ash-M). Percent mineralization (%Min) was calculated as Ash-M/Dry-M X 100%. Length, D-min and D-max, Dry-M and Ash-M all significantly (p < 0.05) increased with age (W < Y < T < O) within each group. %Min and stiffness were significantly greater in [O] than in the younger femurs. No significant results were seen in any age group due to varying diet. These results indicate that five weeks of high fat or high sucrose diet feeding does not affect whole bone size, composition or mechanical properties. Whether a longer dietary period or different diet composition would elicit changes requires further study.