Project description:Background: It is well recognized that obesity leads to arterial endothelial dysfunction and cardiovascular disease. However, the progression to endothelial dysfunction is not clear. Endothelial cells (ECs) adapt to the unique needs of their resident tissue and respond to systemic metabolic perturbations. We sought to better understand how obesity affects EC phenotypes in different tissues specifically focusing on mitochondrial gene expression. Methods: We performed bulk RNA sequencing (RNA-seq) and single cell RNA-seq (scRNA-seq) on mesenteric and adipose ECs isolated from normal chow (NC) and high fat diet (HFD) fed mice. Differential gene expression, gene ontology pathway, and transcription factor analyses were performed. We further investigated our hypothesis in humans using published human adipose single nuclei RNA-seq (snRNA-seq) data. Results: Bulk RNA-seq revealed higher mitochondrial gene expression in adipose ECs compared to mesenteric ECs in both NC and HFD mice. We then performed scRNA-seq and categorized EC clusters as arterial, capillary, venous, or lymphatic. HFD decreased the number of differentially expressed genes between mesenteric and adipose ECs in all subtypes, but the largest effect was seen in arterial ECs. Further analysis of arterial ECs revealed genes coding for mitochondrial oxidative phosphorylation proteins were enriched in adipose compared to mesentery under NC conditions. In HFD mice, these genes were decreased in adipose ECs becoming similar to mesenteric ECs. Transcription factor analysis revealed C/EBP and PPAR, both known to regulate lipid handling and metabolism, had high specificity scores in the NC adipose artery ECs. These findings were recapitulated in snRNA-seq data from human adipose. Conclusions: These data suggest mesenteric and adipose arterial ECs metabolize lipids differently and the transcriptional phenotype of these two vascular beds converge in obesity, in part, due to downregulation of PPARand C/EBP in adipose artery ECs. This work lays the foundation for investigating vascular bed specific adaptations to obesity.

Project description:Aims/Hypothesis. The aim of this study was to determine the potential involvement of LMO3-dependent pathways in the modulation of key functions of mature adipocytes during obesity. Methods. Based on a recently engineered hybrid rAAV serotype Rec2 shown to efficiently transduce both brown adipose tissue (BAT) and white adipose tissue (WAT), we delivered YFP or Lmo3 to epididymal WAT (eWAT) of C57Bl6/J mice on a high fat diet (HFD). The effects of eWAT transduction on metabolic parameters were evaluated 10 weeks later. To further define the role of LMO3 in insulin-stimulated glucose uptake, insulin signaling, adipocyte bioenergetics as well as endocrine function, experiments were conducted in 3T3-L1 adipocytes and newly differentiated human primary mature adipocytes, engineered for transient gain- or loss of LMO3 expression, respectively. Results. AAV transduction of eWAT results in strong and stable Lmo3 expression specifically in the adipocyte fraction over a course of 10 weeks with HFD feeding. Lmo3 expression in eWAT significantly improved glucose clearance and insulin sensitivity in diet-induced obesity, paralleled by increased serum adiponectin. On a molecular level, LMO3 expression in eWAT increased pathways indicative of adipogenesis and PPARg signaling as well as mitochondrial activity, paralleled by a suppression of adipose tissue fibrosis. In vitro, Lmo3 expression in 3T3-L1 adipocytes increased insulin-stimulated GLUT4 translocation and glucose uptake as well as mitochondrial oxidative capacity in addition to fatty acid oxidation. LMO3 overexpression promoted, while silencing of LMO3 suppressed, mitochondrial oxidative capacity in human mature adipocytes. Conclusions. LMO3 expression in visceral adipose tissue regulates multiple genes that preserve adipose tissue functionality during obesity, such as glucose tolerance, insulin sensitivity and adiponectin secretion. Together with increased PPARγ activity, these gene expression changes promote insulin-induced GLUT4 translocation, glucose uptake in addition to increased mitochondrial oxidative capacity, limiting HFD-induced adipose dysfunction. These data add LMO3 as a novel regulator improving visceral adipose tissue function during obesity.

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Loss of endothelial cell heterogeneity in arteries after obesogenic diet [scRNA-seq]

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