Transcriptomic Changes of Murine Visceral Fat Exposed to Intermittent Hypoxia at Single Cell Resolution.

Abdelnaby Khalyfa,Rene Cortese,Christopher A. Bottoms,Wesley Warren,David Gozal,Jorge Andrade,Leila Kheirandish-Gozal,Edward S. Rice

doi:10.3390/ijms22010261

Abstract

Intermittent hypoxia (IH) is a hallmark of obstructive sleep apnea (OSA) and induces metabolic dysfunction manifesting as inflammation, increased lipolysis and insulin resistance in visceral white adipose tissues (vWAT). However, the cell types and their corresponding transcriptional pathways underlying these functional perturbations are unknown. Here, we applied single nucleus RNA sequencing (snRNA-seq) coupled with aggregate RNA-seq methods to evaluate the cellular heterogeneity in vWAT following IH exposures mimicking OSA. C57BL/6 male mice were exposed to IH and room air (RA) for 6 weeks, and nuclei from vWAT were isolated and processed for snRNA-seq followed by differential expressed gene (DEGs) analyses by cell type, along with gene ontology and canonical pathways enrichment tests of significance. IH induced significant transcriptional changes compared to RA across 14 different cell types identified in vWAT. We identified cell-specific signature markers, transcriptional networks, metabolic signaling pathways, and cellular subpopulation enrichment in vWAT. Globally, we also identify 298 common regulated genes across multiple cellular types that are associated with metabolic pathways. Deconvolution of cell types in vWAT using global RNA-seq revealed that distinct adipocytes appear to be differentially implicated in key aspects of metabolic dysfunction. Thus, the heterogeneity of vWAT and its response to IH at the cellular level provides important insights into the metabolic morbidity of OSA and may possibly translate into therapeutic targets.

Highlights

Sleep disordered breathing (SDB), obstructive sleep apnea (OSA), has been implicated as an important risk factor and potential cause of the metabolic syndrome [1,2,3]
To gain broader insight into the gene expression changes occurring in visceral white adipose tissue (vWAT) of mice exposed to intermittent hypoxia (IH) and room air (RA) within each cell type classification, we identified a total of 4810 differentially expressed genes (DEGs) across all cell types
Using snRNA-seq, bulk RNA-seq, and deconvolution of bulk RNA-seq to investigate the cell-type composition of tissue and heterogeneity, we clearly identified 14 cell types and among those, 3 specific subpopulations, namely macrophages, adipocytes, and endothelial cells appeared to participate in a distinct metabolic pathway

Summary

Introduction

Sleep disordered breathing (SDB), obstructive sleep apnea (OSA), has been implicated as an important risk factor and potential cause of the metabolic syndrome [1,2,3]. The visceral white adipose tissue (vWAT) has emerged as a highly active endocrine organ, [19]. It plays a key role in metabolism, which is mediated predominantly through the secretion of multiple hormones, cytokines, chemokines and other proteins, collectively referred to as adipokines [21,22]. Evidence from the obesity literature has implicated hypoxia in vWAT as a major driver of metabolic dysfunction and insulin resistance (IR) [23]. Adipose tissue is heterogeneous and comprised of multiple cell types including adipocytes, preadipocytes, endothelial cells, stromal cells, and several immune cell subtypes [24,25]. By understanding better the cellularity of adipose tissue, its variability in the population, and the individual and collective roles played by these cellular subsets in both health and disease, we should gain improved insights into the central role of vWAT in metabolic dysfunction induced by IH mimicking OSA

Methods

Findings

Discussion

Conclusion