β-Caryophyllene confers protection against type 2 diabetic osteoporosis by blocking ferroptosis via the AMPK/Nrf2 pathway.

Type 2 diabetic osteoporosis (T2DOP) is a chronic bone disorder marked by increased fracture risk and osteonecrosis, exacerbated by a persistent high-glucose and high-fat (HGHF) environment, distinguishing it from postmenopausal osteoporosis. Ferroptosis, an iron-dependent form of programmed cell death caused by lipid peroxidation, plays a crucial role in the death of bone marrow mesenchymal stem cells (BMSCs) due to glucolipotoxicity. β-Caryophyllene (BCP), a natural bicyclic sesquiterpene found in essential oils, shows extensive pharmacological promise for various diseases. This study investigated BCP's role and mechanisms in mitigating HGHF-induced ferroptosis. A murine T2DOP model was established via HGHF diet and streptozotocin (STZ) injection, while BMSCs were cultured under HGHF conditions to mimic diabetic pathology in vitro. Our findings indicated that BCP mitigated HGHF-induced ferroptosis and bone loss, as shown by decreased mitochondrial reactive oxygen species (ROS), lipid peroxidation, and malondialdehyde (MDA) levels, along with increased glutathione in vitro. BCP enhanced bone mass and increased levels of phosphorylated AMP-activated protein kinase (p-AMPK), glutathione peroxidase 4 (GPX4), and osteogenic markers in distal femurs. Mechanistically, BCP activated the AMPK/nuclear factor erythroid 2-related factor 2 (Nrf2) pathway, and AMPK knockdown via small interfering RNA (siRNA) abolished its protective effects in HGHF-exposed BMSCs. Collectively, BCP ameliorates T2DOP by inhibiting ferroptosis via AMPK/Nrf2 signaling activation and may have potential clinical applications.