The Influence of Different Degrees of Energy Restriction on Bone Parameters in Young Female Rats

The present study aimed to determine the influence of different degrees of energy restriction (ER) on the bones in young female rats. Forty female Sprague-Dawley rats (n = 40; age, 6 weeks) were randomly divided into the following five experimental groups after a 1-week acclimatization period: 0% ER, 10% ER, 20% ER, 30% ER, and 40% ER groups. The experimental period was 10.5 weeks. Statistical analysis was conducted using one-way analysis of variance, Tukey's post hoc comparison tests, and simple linear regression analysis. The body weight and fat weight showed significantly lower values above 20% ER. The bone mineral content and bone mineral density of the tibia in the 30% ER group were significantly lower than those in the 10% and 20% ER groups, and those in the 40% ER group was significantly lower than those in the 0%, 10%, and 20% ER groups. The trabecular thickness, cortical bone volume, and cortical total volume in the 40% ER group were significantly lower than those in the 0% ER group. The serum levels of parathyroid hormone, bone-specific alkaline phosphatase, and tartrate-resistant acid phosphatase significantly increased with increasing degree of ER. However, the serum levels of leptin, carboxylated osteocalcin, and carboxylated osteocalcin / uncarboxylated osteocalcin significantly decreased with increasing degree of ER. Our findings showed that 30% or 40% ER resulted in lower bone mass and 40% ER impaired bone microstructure in young female rats. However, 10% or 20% ER did not affect these parameters.