Mechanism of the enterobacterial metabolite sodium butyrate mediating ferroptosis to affect osteogenic ability of BMSCs in mice with estrogen deficiency-caused osteoporosis via the PTEN/PI3K/AKT pathway.

Sodium butyrate (NaB), a major intestinal metabolite, has been suggested to protect against osteoporosis (OP). This study aimed to elucidate the mechanism by which NaB regulates ferroptosis in OP. An ovariectomy-induced mouse OP model was established, and treated with NaB or the ferroptosis inhibitor Fer-1. Bone mineral density, bone microstructure, bone formation and resorption, and ferroptosis markers were assessed. In vitro, mouse bone marrow mesenchymal stem cells (BMSCs) were treated with NaB and the ferroptosis inducer Erastin to evaluate osteogenic differentiation and ferroptosis. Phosphatase and tensin homolog (PTEN) acetylation was detected by co-immunoprecipitation, the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) pathway was evaluated by Western blot, and acetylation sites by point mutation. The role of PTEN acetylation was further validated using the p300 inhibitor C646 in vitro and in vivo. NaB treatment enhanced bone formation, suppressed ferroptosis, and promoted osteogenic differentiation in OP mice, mimicking the protective effects of Fer-1. In BMSCs, NaB promoted osteogenesis by inhibiting ferroptosis. Mechanistically, NaB induced acetylation of PTEN at K125/K128, suppressing its phosphatase activity and activating the PI3K/AKT pathway, thereby reducing ferroptosis. C646 partially abolished these effects. NaB promotes PTEN acetylation at K125/K128 to activate PI3K/AKT signaling, thereby inhibiting ferroptosis and alleviating estrogen deficiency-induced OP. These findings highlight NaB as a potential epigenetic metabolic regulator of bone metabolism.