Long‐Term High‐Fat Diet Affected Bone Marrow Microenvironment During Aging at Single‐Cell Resolution

Obesity and aging are major risk factors for diseases such as Type 2 diabetes mellitus, dementia, and osteoporosis. High-fat diet (HFD) consumption is one of the most important factors contributing to obesity. To elucidate and provide resources on how long-term HFD to aging (LHA) affects the bone marrow and solid organs, we established an LHA mice model and demonstrated that LHA caused a shift from osteogenesis to adipogenesis in the bone marrow microenvironment. Single-cell transcriptomics of bone marrow cells highlighted LHA-driven perturbations in immune cell populations with distinct metabolic adaptations to LHA. We demonstrated that bone marrow macrophages of the LHA group upregulated Chil3 and Fabp4, which are associated with inflammatory response and regulation of adipocytes. Moreover, we identified the Ptn-Sdc3 axis and Cxcl12-Cxcr4 axis between bone marrow macrophages and brain epithelial cells as possible candidates for crosstalk between bone marrow and brain in LHA mice. Our findings indicated the bone marrow microenvironment as a central hub of LHA-induced pathology, where adipogenic reprogramming and myeloid cell dysfunction collectively drive skeletal and systematic inflammation. This resource highlights therapeutic opportunities targeting bone marrow to mitigate obesity-accelerated aging.