Lasting bone marrow defects imprinted by hyperglycemia shape the immunological characteristics of differentiated M1 and M2 macrophages

Background: Hyperglycemia in type 1 diabetes (T1D) disrupts immune function, yet it remains unclear whether hyperglycemia-induced immunological defects in the bone marrow (BM) persist in BM-derived M1 and M2 macrophages. Objective: We investigated the immunological and metabolic features of BM-derived M1 and M2 macrophages from prediabetic and diabetic non-obese diabetic (NOD) mice to determine the impact of hyperglycemic memory on polarized macrophages. Methods: Macrophages were differentiated from BM cells of prediabetic and diabetic NOD mice and subsequently polarized with lipopolysaccharide (LPS; M1 macrophages) or interleukin-4 (IL-4; M2 macrophages). Transcriptomic profiles were assessed using RNA sequencing and gene set enrichment analysis of differentially expressed genes (DEGs). In parallel, glycolysis, oxygen consumption, and cytokine production were evaluated. Results: Hyperglycemia induced pronounced transcriptomic alterations in both M1 and M2 macrophages, modifying immune and metabolic gene expression. Immune pathways, including inflammatory responses and cytokine production, were consistently suppressed in both subsets from diabetic mice compared with those from prediabetic mice. Metabolically, M1 macrophages preserved mitochondrial and glycolytic activity under diabetic conditions, whereas M2 macrophages exhibited impaired oxidative phosphorylation and glycolysis, resulting in diminished energy production. Functionally, both subsets from diabetic mice secreted lower levels of inflammatory cytokines upon stimulation relative to prediabetic counterparts. Conclusion: These findings demonstrate that hyperglycemia imprints persistent transcriptomic and functional defects in BM-derived M1 and M2 macrophages. This work provides new insights into how chronic hyperglycemia contributes to impaired host defense and dysregulated inflammation in diabetes.