Single cell transcriptomics reveals obesity-induced endothelial and neurovascular dysfunction in brain: implications for cognitive decline

Obesity is a global pandemic and a key risk factor for several neurodegenerative diseases including Alzheimer's disease (AD), Parkinson's disease, or dementia. The neurovascular unit (NVU), essential for blood-brain barrier (BBB) integrity and comprised of endothelial cells, glial cells (microglia and astrocytes), and neurons, plays an important role in the pathogenesis of neurodegenerative diseases. However, molecular mechanisms underlying the effects of obesity on endothelial and other cells of and its contribution to neurodegeneration remains largely unknown. In this study we aimed to decipher in-dept molecular modifications induced by obesity in cells of neurovascular unit by integrative multiomics analysis of endothelial cells, neurons, microglial cells, and astrocytes from the hippocampus of ob/ob mice. Hippocampus were isolated from ob/ob and C57BL/6J male mice at 17-18 weeks of age. Gene expression profiles of cells of hippocampus were obtained using single nuclei RNA sequencing (snRNAseq) and data analyzed using in-dept bioinformatic analyses. snRNAseq and UMAP analysis revealed 19 cell types in hippocampus. Comparisons of global gene expression profiles identified different global profiles between ob/ob and WT for each of the cell types of the NVU. Statistical analyses revealed 4463 DEGs in neuronal cells, 1386 DEGs in astrocytes, 125DEGs in endothelial cells, and 155 DEGs in microglia cells, suggesting that obesity significantly impacts the expression profiles of NUV cells. Enrichment analyses revealed that these genes are involved in cellular processing like focal adhesion, cell interactions, inflammation, and metabolism. Changes in the expression in endothelial cells were positively correlated with genomic changes in other cell types, changes that we correlated with tendency in increase in BBB observed using functional MRI. Taken together, obesity exert significant cell-specific changes in global gene expression, genes that are associated with development of Alzheimer's disease or dementia. Overall design: Wild type (C57BL/6J) and ob/ob male mice were fed a standard purified diet AIN-93M, for 8 wks. Mice were sacrificed at 18 weeks of age and hippocampus was dissected from left hemisphere and then stored at -80 degree celcius. Hippocampal nuclei was isolated and single nuclei RNA sequencing was performed. Brain hippocampal endothelial cells, microglial cells, astrocytes, and neuronal cells gene expression was analyzed using a multiomic approach for differential expression of protein and non-protein coding genes, gene networks, functional pathways, and transcription factors. Blood brain barrier permeability was assessed. The Wild type data described in this study are avalilable in GSM7717249 [Samples 5,11,17, and 21].