Effects of aging and caloric restriction on bone structure and mechanical properties.

This study examined the effects of caloric restriction on structural and material properties of tibiae and sixth lumbar vertebrae in F344BN male rats. Rats were divided into two dietary groups, ad libitum or calorie restricted. Caloric restriction commenced at 14 weeks of age, with 40% restriction and micronutrient supplementation by 16 weeks maintained until death. Rats were studied at 100% (8 months), 70% (30-35 months), and 35% (35-40 months) survival rates. Specimens were assessed using microcomputed tomography, mechanical testing, and ash analysis. A calorically restricted diet resulted in a significant decrease in total body mass when compared to ad libitum diet. Generally, direct comparisons between same-aged groups showed no significant changes in material properties, with significantly greater normalized-to-body-mass structural properties under caloric restriction. These results suggested a possible beneficial response to the calorically restricted diet where bone quality was maintained with bone quantity improved per unit body mass.