Effects of 10-Hydroxy-2-decenoic Acid and 10-Hydroxydecanoic Acid in Royal Jelly on Bone Metabolism in Ovariectomized Rats: A Pilot Study

Although previous studies have demonstrated that royal jelly (RJ) may have estrogenic properties and prevent postmenopausal bone loss, the underlying mechanisms are not fully understood. This animal study aimed to investigate the effects of specific fatty acids of RJ, 10-hydroxy-2-decenoic acid (10H2DA) and 10-hydroxydecanoic acid (10HDAA), in ovariectomized rats. Ten-week-old female Wistar rats were divided into the Baseline, Sham, Ovx, Ovx + 10H2DA, and Ovx + 10HDAA groups. Rats in the Baseline group were sacrificed immediately, whereas those in the other groups were subjected to either a sham operation or bilateral ovariectomy. The animals in the Ovx + 10H2DA and Ovx + 10HDAA groups were fed diets containing 10H2DA and 10HDAA, respectively. Twelve weeks after surgery, the rats were sacrificed, and indices of bone mass and bone mechanics were analyzed. Femoral bone mineral density was significantly lower in the Ovx group than in the Sham group (p < 0.01). Administration of 10H2DA or 10HDAA did not ameliorate bone loss after ovariectomy. In addition, administration of these fatty acids diminished femur bone stiffness in ovariectomized rats (p < 0.01 and p < 0.05, respectively). These findings suggest that the favorable effects of RJ may not be exerted solely by 10H2DA or 10HDAA. However, these effects may be exhibited in combination with other RJ constituents.