Sex differences in the single-nuclei hippocampal neurovascular unit transcriptomic response to type 2 diabetes

Dementia is a comorbidity of type 2 diabetes mellitus (T2DM) that does not affect men and women equally. The aim of this study was to understand the molecular mechanisms underlying the sex differences observed in T2DM-associated dementia. We utilized females and males of the db/db murine model, compared with sex-/age-matched wildtypes, and assessed sex divergent and in common responses. Single-nuclei RNA sequencing (snRNA seq) of hippocampi assessed the transcriptome of neurovascular unit cells: endothelial cells, microglia, astrocytes, and neurons. Cognitive function was measured by the Morris water maze. We show that the transcriptomic response to T2DM was modified by both cell type and sex. Gene ontology and pathway analyses demonstrated a greater impact of T2DM on the endothelial transcriptome in females as compared with males, with NF-κB, and integrin-mediated cell adhesion pathways specific to females. Approximately half of the pathways in microglial cells were common to both sexes, including the Ras signaling pathway. Meanwhile, most pathways altered by T2DM in astrocytes and neurons were shared between sexes, including axon guidance and MAPK signaling. Few T2DM-induced pathways were common among all studied cell types in both males and females; they were related to neurodegeneration, altered blood-brain-barrier permeability, and inflammation. Furthermore, female db/db mice exhibited earlier cognitive dysfunction than males. Thus, endothelial cells may be a key source of sex differences in T2DM-associated dementia, via mechanisms related to cell adhesion, survival, inflammation, and blood-brain-barrier permeability. Our work may provide insight for bench-to-clinic sex- and cell-specific potential therapeutic targets for T2DM-associated vascular dementia.NEW & NOTEWORTHY Utilizing single-nuclei RNA sequencing of the hippocampus in the db/db murine model, we report sex-specific and cell type-specific neurovascular unit responses to type 2 diabetes mellitus (T2DM). Sex specificity predominated in endothelial cells, characterized by a greater response in females, including altered expression of genes involved in the NF-κB inflammatory pathway. A few T2DM-induced transcriptomic responses were common to all cell types and both sexes, including differential gene expression regulating altered blood-brain-barrier permeability.