The fixed herbal drug composition “Saikokaryukotsuboreito” prevents bone loss with an association of serum IL-6 reductions in ovariectomized mice model☆

Purpose: Saikokaryukotsuboreito (SRB) is a traditional Japanese herbal medicine that has been used to treat hyperlipidemia. As some studies have shown that lipid-lowering drugs reduce osteoporosis, we investigated the effect of SRB on bone metabolism in the postmenopausal period using an ovariectomized (OVX) murine model.

Material and Methods: Fifteen aged 9 weeks female mice were divided into three groups (n=5 each). The OVX group and SRB group underwent bilateral ovariectomy, after which the OVX group was fed a normal diet and the SRB group fed a normal diet containing 2% SRB. The sham group underwent sham surgery and was then fed a normal diet. Eight weeks after surgery, all mice were sacrificed, and bone volume, bone histomorphometric parameters, and bone-associated phenotype were compared among the groups.

Results: Compared with the OVX group, the SRB group showed suppression of bone volume loss at the tibia (SRB group: 12.7±0.7%, OVX group: 9.8±0.4%; p=0.005, ANOVA) and lumbar spine (SRB group: 15.1±0.9%, OVX group: 11.3±0.1%; p=0.031, ANOVA). A significant decrease in eroded surface was also observed in SRB-treated ovariectomized mice compared with the OVX group (p=0.022, ANOVA). We also found that serum levels of interleukin (IL)-6, a primary mediator of bone resorption, in the SRB group were significantly lower than in the OVX group (SRB: 52.5±6.8pg/ml; OVX: 138.0±23.1pg/ml; p=0.011, ANOVA). However, unexpectedly, SRB did not affect estradiol and total cholesterol in ovariectomized mice.

Conclusion: SRB can prevent loss of bone volume and suppress serum IL-6 levels in this postmenopausal model and is a promising candidate for treatment of postmenopausal osteoporosis.