Geniposide Ameliorated Dexamethasone-Induced Cholesterol Accumulation in Osteoblasts by Mediating the GLP-1R/ABCA1 Axis

Background: Overexposure to glucocorticoid (GC) produces various clinical complications, including osteoporosis (OP), dyslipidemia, and hypercholesterolemia. Geniposide (GEN) is a natural iridoid compound isolated from Eucommia ulmoides. Our previous study found that GEN could alleviate dexamethasone (DEX)-induced differentiation inhibition of MC3T3-E1 cells. However, whether GEN protected against Dex-induced cholesterol accumulation in osteoblasts was still unclear. Methods: DEX was used to induce rat OP. Micro-CT data was obtained. The ALP activity and mineralization were determined by the staining assays, and the total intracellular cholesterol was determined by the ELISA kits. The protein expression was detected by western blot. Results: GEN ameliorated Dex-induced micro-structure damages and cell differentiation inhibition in the bone trabecula in rats. In MC3T3-E1 cells, Dex enhanced the total intracellular cholesterol, which reduced the activity of cell proliferation and differentiation. Effectively, GEN decreased DEX-induced cholesterol accumulation, enhanced cell differentiation, and upregulated the expression of the GLP-1R/ABCA1 axis. In addition, inhibition of ABAC1 expression reversed the actions of GEN. Treatment with Exendin9-39, a GLP-1R inhibitor, could abrogate the protective activity of GEN. Conclusions: GEN ameliorated Dex-induced accumulation of cholesterol and inhibition of cell differentiation by mediating the GLP-1R/ABCA1 axis in MC3T3-E1 cells.