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

ABSTRACT: 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.

ORGANISM(S): Mus musculus

PROVIDER: GSE262249 | GEO | 2024/10/30

REPOSITORIES: GEO

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Project description:The neurovascular unit (NVU) is a complex multicellular structure that helps maintain cerebral homeostasis and blood-brain barrier (BBB) integrity. While extensive evidence links NVU alterations to cerebrovascular diseases and neurodegeneration, the underlying molecular mechanisms remain unclear. Here, we use zebrafish embryos carrying a mutation in Scavenger Receptor B2, a highly conserved endolysosomal protein expressed predominantly in Radial Glia Cells (RGCs), to investigate the interplay among different NVU components. Through live imaging and genetic manipulations, we demonstrate that compromised acidification of the endolysosomal compartment in mutant RGCs leads to impaired Notch3 signaling, thereby inducing excessive neurogenesis and reduced glial differentiation. We further demonstrate that alterations to the neuron/glia balance result in impaired VEGF and Wnt signaling, leading to severe vascular defects, hemorrhages, and a leaky BBB. Altogether, our findings provide novel insights into NVU formation and function and offer new avenues for investigating diseases involving white matter defects and vascular abnormalities. The neurovascular unit (NVU) is a complex multicellular structure that helps maintain cerebral homeostasis and blood-brain barrier (BBB) integrity. While extensive evidence links NVU alterations to cerebrovascular diseases and neurodegeneration, the underlying molecular mechanisms remain unclear. Here, we use zebrafish embryos carrying a mutation in Scavenger Receptor B2, a highly conserved endolysosomal protein expressed predominantly in Radial Glia Cells (RGCs), to investigate the interplay among different NVU components. Through live imaging and genetic manipulations, we demonstrate that compromised acidification of the endolysosomal compartment in mutant RGCs leads to impaired Notch3 signaling, thereby inducing excessive neurogenesis and reduced glial differentiation. We further demonstrate that alterations to the neuron/glia balance result in impaired VEGF and Wnt signaling, leading to severe vascular defects, hemorrhages, and a leaky BBB. Altogether, our findings provide novel insights into NVU formation and function and offer new avenues for investigating diseases involving white matter defects and vascular abnormalities. The neurovascular unit (NVU) is a complex multicellular structure that helps maintain cerebral homeostasis and blood-brain barrier (BBB) integrity. While extensive evidence links NVU alterations to cerebrovascular diseases and neurodegeneration, the underlying molecular mechanisms remain unclear. Here, we use zebrafish embryos carrying a mutation in Scavenger Receptor B2, a highly conserved endolysosomal protein expressed predominantly in Radial Glia Cells (RGCs), to investigate the interplay among different NVU components. Through live imaging and genetic manipulations, we demonstrate that compromised acidification of the endolysosomal compartment in mutant RGCs leads to impaired Notch3 signaling, thereby inducing excessive neurogenesis and reduced glial differentiation. We further demonstrate that alterations to the neuron/glia balance result in impaired VEGF and Wnt signaling, leading to severe vascular defects, hemorrhages, and a leaky BBB. Altogether, our findings provide novel insights into NVU formation and function and offer new avenues for investigating diseases involving white matter defects and vascular abnormalities.

Project description:The expression of adipogenic genes is decreased in obesity and diabetes mellitus ; Samuel T. Nadler*, Jonathan P. Stoehr*, Kathryn L. Schueler*, Gene Tanimoto, Brian S. Yandell, and Alan D. Attie*,Â§ ; Departments of * Biochemistry, and Statistics and Horticulture, University of Wisconsin, Madison, WI, 53706; and Affymetrix, Inc., Santa Clara, CA 95051 ; Communicated by Neal L. First, University of Wisconsin, Madison, WI, July 13, 2000 (received for review April 3, 2000) ; Obesity is strongly correlated with type 2 diabetes mellitus, a common disorder of glucose and lipid metabolism. Although adipocytes are critical in obesity, their role in diabetes has only recently been appreciated. We conducted studies by using DNA microarrays to identify differences in gene expression in adipose tissue from lean, obese, and obese-diabetic mice. The expression level of over 11,000 transcripts was analyzed, and 214 transcripts showed significant differences between lean and obese mice. Surprisingly, the expression of genes normally associated with adipocyte differentiation were down-regulated in obesity. Not all obese individuals will become diabetic; many remain normoglycemic despite profound obesity. Understanding the transition to obesity with concomitant diabetes will provide important clues to the pathogenesis of type 2 diabetes. Therefore, we examined the levels of gene expression in adipose tissue from five groups of obese mice with varying degrees of hyperglycemia, and we identified 88 genes whose expression strongly correlated with diabetes severity. This group included many genes that are known to be involved in signal transduction and energy metabolism as well as genes not previously examined in the context of diabetes. Our data show that a decrease in expression of genes normally involved in adipogenesis is associated with obesity, and we further identify genes important for subsequent development of type 2 diabetes mellitus. Experiment Overall Design: For obesity study, lean samples include C57BL/6J lean, (C57BL/6J X BTBR) F1 and BTBR lean, obese sampples incluse C57BL/6J-ob/ob, (C57BL/6J X BTBR) F2-ob/ob and BTBR-ob/ob. All samples are subjected to Mu11K A and B arrays. Experiment Overall Design: For diabetes study, B6-ob/ob, (C57BL/6J X BTBR) F2-ob/ob low glucose, (C57BL/6J X BTBR) F2-ob/ob medium glucose, (C57BL/6J X BTBR) F2-ob/ob high glucose, and BTBR-ob/ob samples were analyzed for genes whose expression levels changes correlated with the plasma glucose levels in these mice. All samples are subjected to Mu11K A and B arrays.

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

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