Effects of Isoliquiritigenin on Bone Metabolism and Uterus in Ovariectomized Rats

Abstract

Abstract Objectives Isoliquiritigenin (ILQ) is a phenolic compound found in licorice and is a popular dietary supplement. ILQ exhibits model-specific antioxidant, anti-inflammatory, anti-tumor, and estrogenic activities. Limited data suggest the potential of ILQ to prevent or treat osteoporosis. Therefore, this study evaluated the effects of short-duration treatment with ILQ on bone and uterine tissue in estrogen-deplete ovariectomized (ovx) rats. The uterus was important to evaluate because ILQ stimulates proliferation of MCF7 breast cancer cells through an estrogen receptor-dependent mechanism. Methods Six-week-old rats (ovx'd at 4 weeks of age) were fed diets containing 0, 100, 250 or 750 ppm ILQ (n = 5/treatment) for 1 week and sacrificed. Gene expression in femur and uterus, blood markers of global bone turnover, body composition, and uterine weight and epithelial cell height were determined. In addition, the effect of ILQ on in vitro differentiation of osteoclasts derived from bone marrow was assessed. Results Treatment resulted in a dose-dependent increase in serum ILQ with levels reaching 2.4 ± 0.2 mM in rats receiving the highest dose. ILQ did not alter serum levels of osteocalcin, a global marker of bone formation, or osteocalcin gene expression in femur. Additionally, there was little or no effect of ILQ on genes related to osteoblast differentiation or activity in femur. These largely null findings contrast with a reduction in serum CTX, a global marker of bone resorption, at all dose levels of ILQ. At the gene level, ILQ resulted in lower mRNA for genes related to osteoclast differentiation and function in femur, including Acp5 (tartrate resistant acid phosphatase), Timp2 and Mmp2, and suppressed osteoclast differentiation in vitro. ILQ had no effect on the ovx-induced increase in body weight. Ovx resulted in lower uterine weight. Treatment with ILQ at 750 ppm resulted in development of severe uterine epithelial cell hyperplasia in two of five animals. Conclusions ILQ supplementation led to reduced biochemical and gene expression markers of bone resorption in vivo and reduced osteoclast differentiation in vitro without increasing estrogen-dependent gene expression. However, the potential benefits must be weighed against potential detrimental off-target effects, including uterine hypertrophy. Funding Sources NIH [P50AT006268].