201-LB: Arx and Nr2f6 Transcriptionally Regulate Visceral and Brown Fat Phenotype

Abstract

Mammals possess fat in three distinct depots- brown, subcutaneous and visceral fat depots. While brown fat contains thermogenic brown fat cells, the subcutaneous and visceral fat depots contain lipid-storing white fat cells. Excess visceral fat is associated with increased insulin resistance and type 2 diabetes, whereas the presence of brown fat corelates with lower odds of type 2 diabetes. These differences likely arise due to distinct developmental origins of brown and white fat cells. Expression of co-factors such as PRDM16 and PGC1α is limited to brown fat cells. Brown and white fat cells also have distinct sets of open chromatin. I hypothesize that epigenetic variations between brown and white fat can reveal fat depot-enriched factors that are essential to establishing fat identity and phenotype, and therefore, influence obesity and type 2 diabetes. Adipoq-NuTrap mice, that have labeled adipocytes, were used to isolate adipocyte nuclei from brown and visceral fat. ATAC-sequencing of these nuclei uncovered fat cell-specific open regions, which were then subjected to bioinformatic analysis to identify depot-enriched transcription factors. These analyses resulted in the discovery of two factors: Arx and Nr2f6. Arx is dramatically enriched in visceral gonadal fat, compared to brown and subcutaneous fat. Pathway analysis of Arx target genes reveal that Arx may regulate inflammation, cell shape and motility. Adipose-specific Arx knockout mice have lesser visceral fat and will be used to study the role of Arx in insulin tolerance and obesity. On the other hand, Nr2f6 expression is enriched in brown fat, increases with cold exposure and is dependent on PRDM16 expression. Pathway analysis of Nr2f6 target genes show that Nr2f6 regulates mitochondrial, thermogenic and lipolytic genes, genes central to brown fat function. Nr2f6 overexpression dampened thermogenic response, suggesting a novel regulatory mechanism in brown fat function. Nr2f6-null mice will be used to assess the role of Nr2f6 in brown fat function. Disclosure A. Maganti: None. J. Chi: None. P. Cohen: None. Funding American Diabetes Association (1-19-PDF-024 to A.M.)