Sichuan University Apr 25 2026 Obesity alters bone health not only through increased body weight but also by reshaping the bone marrow environment. Researchers show that expansion of bone marrow fat promotes immunosuppressive PD-L1 signaling, which enhances osteoclast formation and accelerates bone loss. By reducing bone marrow fat in mice, they reduced immune suppression and improved bone structure. These findings uncover a new mechanism linking metabolism, immunity, and skeletal health,