Diabetes alters macrophage identity and metabolism in tuberculosis co-infection

Diabetes is known to weaken the immune system, but how it reshapes specific immune cells in the bone marrow and during co-infection with tuberculosis is less clear. In work led by corresponding author Ranjan Kumar Nanda, researchers examined bone marrow-derived macrophages in mouse models to learn how diabetes changes these frontline immune cells and how those changes look when tuberculosis is present at the same time. The team used NA-STZ induced diabetic C57BL/6 mice alongside non-diabetic controls and infected mice with a low aerosol dose (100-120 CFU) of Mycobacterium tuberculosis H37Rv. At 3 w.p.i., total bone marrow cells were harvested and differentiated into bone marrow-derived macrophages (BMDMs). The researchers then tracked surface marker changes using flow cytometry, monitoring CD11c, CD11b and F4/80 expression. To probe deeper, they stimulated BMDMs with Mtb H37Rv lysate and carried out global transcriptome profiling. This approach let them compare how diabetes alone, tuberculosis alone, and the combined DM-TB condition each reshape macrophage identity and molecular behavior without introducing treatments not described in the study.

The study combined surface marker analysis and broad gene-expression profiling to reveal both cell-surface and metabolic changes. Flow cytometry showed that BMDMs from the DM-TB comorbid mice had lower CD11c and CD11b levels and higher F4/80 expression compared with controls. When BMDMs were stimulated with Mtb H37Rv lysate and subjected to global transcriptome profiling, distinct molecular signatures emerged. Macrophages from diabetic (DM) mice alone showed a skew toward a pro-inflammatory program, featuring perturbations in the complement response, the NF-kB pathway, and fatty acid metabolism. In contrast, macrophages from the DM-TB group displayed deregulated ceramide metabolism and amino acid metabolism. Both the DM and DM-TB macrophages, after stimulation with Mtb H37Rv lysate, showed a deregulated transcript signature that impacts the humoral response. Taken together, these methods linked specific marker shifts (CD11c, CD11b, F4/80) to broad metabolic and immune pathway changes identified by global transcriptome profiling.

The findings point to a complex picture in which diabetes reshapes macrophage differentiation and metabolism, and those changes differ when tuberculosis is also present. The dampened or altered immune signatures seen in DM-TB macrophages—lower CD11c and CD11b, higher F4/80, and shifts in ceramide and amino acid pathways—suggest that diabetes can change how bone marrow-derived macrophages respond to a tuberculosis challenge. For clinicians and researchers, these results emphasize that immune dysfunction in diabetes is not simply a stronger or weaker response but a reprogramming of cell identity and metabolic wiring. Importantly, the study highlights the need to identify novel targets for developing tailored drugs for comorbid conditions, because therapies that work in tuberculosis alone may not address the specific macrophage and metabolic disturbances present in patients with both diabetes and TB. By mapping these altered signatures, the research offers a starting point for future work to design interventions that consider both immune and metabolic changes in DM-TB.