Background: Beyond cardiac impairment, acute myocardial infarction (MI) also affects other organ systems, including the central nervous system (CNS). Clinically, MI is associated with an increased risk of cognitive decline and depression, while pathophysiological pathways remain poorly understood. MI is reported to induce neuroinflammatory responses mediated by microglia, the resident myeloid cells of the CNS. Until now, functional and metabolic consequences of microglial activation following MI remain unknown. We hypothesized that MI might induce metabolic changes in microglia that contribute to MI-mediated neuroinflammation.
Methods: Male BL6 mice underwent experimental permanent LAD ligation or sham operation. Five days post-MI, CD45-intermediate and SiglecH-positive immune cells were isolated from both cortical and subcortical brain regions by FACS sorting, followed by single-cell RNA sequencing and comprehensive metabolic assays. Metabolic assessment included mitochondrial staining for membrane potential and mitochondrial mass (MitoTracker, tetramethylrhodamine ethyl ester = TMRE) and glucose uptake evaluation (2-NBDG = 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose).
Results: Transcriptomic analysis identified microglia as the predominant immune cell population in both cortical (n = 11,581; 85.7%) and subcortical (n = 4,380; 83.5%) brain regions. Microglial subclustering revealed an increased proportion of a subpopulation defined as ‘low translational microglia’ in MI animals compared to Sham. (cortex: MI: 20.9%, Sham: 15.9%; p < 0.001, Wald H₀ test; subcortex: MI: 20.1%, Sham: 16.7%; p = 0.002). Pseudobulk differential expression analysis across all microglia identified 397 differentially expressed genes (DEGs) in cortical microglia and 302 DEGs in subcortical microglia between MI and Sham conditions. Gene Set Enrichment Analysis revealed that cortical microglia exhibited a significant downregulation of gene sets associated with translational activity after MI, including Gene Ontology terms such as "Cytoplasmic translation" (gene count: 27) and "Ribosome biogenesis" (gene count: 17). Subcortical microglia displayed reduced expression of genes involved in protein homeostasis, as indicated by downregulated terms such as "protein localization to organelle" (gene count: 16) and "protein folding" (gene count: 12). As these processes are closely linked to cellular energy status and metabolism, we then performed metabolic assays. These revealed that MI directly alters microglial metabolism, evidenced by reduced mitochondrial membrane potential (MitoTracker, TMRE) and a downward trend in glucose uptake, as measured by 2-NBDG.
Conclusion: These findings indicate that MI triggers early microglial adaptations marked by the suppression of energy-intensive processes such as translation and protein folding, which may reflect underlying metabolic constraints, consistent with altered mitochondrial function. The observed reduction in mitochondrial staining aligns with previous reports showing that neuroinflammatory activation of microglia is associated with diminished mitochondrial function and a metabolic shift away from oxidative phosphorylation. Together, our data demonstrate that MI induces transcriptional and metabolic reprogramming in microglia, highlighting a potential link between peripheral cardiovascular injury and disrupted microglial homeostasis that may contribute to MI-induced neuroinflammation and CNS dysfunction.
