Homocysteine-induced bone formation dysfunction reversed by icariin via the AKT/FOXO1 signaling pathway.

Elevated homocysteine (Hcy) is an independent osteoporosis (OP) risk factor via oxidative stress-induced bone formation dysfunction. Icariin (ICA) has ethnopharmacological bone-protective effects, but its mechanism against Hcy-induced damage remains unclear. This study aimed to confirm Hcy's causal role in OP and clarify ICA's reversal effect via the AKT/FOXO1 pathway. Mendelian randomization (MR) analyzed Hcy-OP causality. In vitro, Hcy-treated MC3T3-E1 cells (osteoblast model) were evaluated via CCK-8, ALP/alizarin red staining, MDA/SOD detection, and Western blot. Network pharmacology/molecular docking predicted key targets; PI3K inhibitor LY294002 verified the AKT pathway. In vivo, dexamethasone-induced OP mice were assessed via micro-CT, ELISA, HE staining, and Western blot/qPCR. MR confirmed elevated Hcy as an upstream OP risk factor. Hcy inhibited osteoblast function, while ICA reversed this by enhancing proliferation/differentiation (elevated ALP, osteogenic markers: BMP2/COL1/OPG/RUNX2), reducing oxidative stress (lower MDA, higher SOD), and activating AKT/FOXO1 via phosphorylation. In OP mice, ICA improved BMD/trabecular microarchitecture, elevated P1NP, reduced CTX-1, and upregulated osteogenic pathway markers. Hcy-induced bone formation dysfunction drives OP progression. ICA alleviates oxidative stress and activates AKT/FOXO1 to protect against Hcy-related OP, offering a potential therapeutic strategy.