42-OR: The Impact of GSNOR-Mediated Nitroso-Redox Signaling on Immuno-Metabolic Interaction in the Brown Adipose Tissue

The thermogenic function of brown adipose tissue (BAT) is tightly regulated by cellular redox status, however, the molecular mechanism underlying this regulation is largely unknown. S-nitrosoglutathione reductase (GSNOR, Adh5) is a major denitrosylase that balances intracellular nitroso-redox status. Although GSNOR dysregulation has been implicated in the pathogenesis of many chronic diseases, the pathophysiological role of GSNOR in the BAT is completely unknown. We found cold exposure increased murine BAT GSNOR while diet-induced obesity (DIO) suppressed it, indicating a potential role for GSNOR in metabolic adaptation in the BAT. Mechanistically, we found that the transcription factor heat shock factor 1 (HSF1) occupies the Adh5 promoter activating Adh5 expression, while DIO inhibited the HSF1-GSNOR axis in the BAT. Notably, administration of a HSF1 enhancer to mice with DIO significantly improved glucose intolerance and BAT mitochondrial dysfunciton. Furthermore, GSNOR deletion in the BAT (GSNOR^BKO) suppressed UCP1-dependent respiration under both thermoneutral and cold acclimation conditions, as well as elevated immune cell infiltration in the BAT. This was in part mediated by increased BAT nitrosative stress and UCP1 S-nitrosylation induced by GSNOR deletion. Moreover, GSNOR^BKO mice have worsened DIO-induced glucose intolerance and decreased UCP1-mediated oxygen consumption. In contrast, gain-of GSNOR function in the BAT improved DIO-associated glucose intolerance, increased UCP1-dependent oxygen consumption and decreased DIO-induced inflammation. These data provide novel evidence that GSNOR plays a protective role in BAT against metabolic stressors. Ultimately, insights into the mechanisms by which dysregulation of nitroso-redox signaling impairs BAT metabolic homoestasis and drives the pathologies associated with obesity are expected to accelerate the development of novel therapeutic targets for metabolic diseases.