Dose-response estrogen promotes osteogenic differentiation via GPR40 (FFAR1) in murine BMMSCs

Estrogen plays an essential role in bone formation, and estrogen modulation dysfunction is tightly associated with postmenopausal osteoporosis (PMOP). The underlying mechanisms of estrogen-mediated osteogenic differentiation have not been well defined. In this study, murine bone marrow mesenchymal stem cells were induced to undergo osteogenic differentiation, and gene expression analysis or GPR40 expression manipulation was performed. Bilateral ovariectomized or sham-operated C57BL/6 mice were administered GPR40 agonist (GW9508) for bone mineral density analysis. We identified GPR40, a long chain unsaturated fatty acid receptor, to be regulated by estrogen and involved in osteogenic differentiation both in vivo and in vitro. Mechanistically, the Wnt/β-catenin signaling pathway is essential for GPR40 to promote osteogenic differentiation. Furthermore, in vivo GW9508 administration rescued estrogen-deficient bone loss, indicating the essential role of the GPR40 receptor. To our knowledge, this is the first study that provides evidence for GPR40 as a positive regulator of osteogenesis and Wnt/β-catenin signaling. These results indicate that GPR40 may function as an endogenous promoter of estrogen-induced osteogenic differentiation through Wnt/β-catenin signaling activation. Therefore, as the global population of ages and the prevalence of metabolic-related disorders, especially PMOP, increases, our findings suggest that GPR40 is a key in understanding the link between bone and fat. It may also be a useful target for the treatment of bone complications in the future.