Gene expression of BAT from GRBATKO mice exposed to cold

GRBATKO_BAT_COLDEXPOSURE Aberrant activity of the glucocorticoid (GC)/glucocorticoid receptor (GR) endocrine system has been linked to obesity-related metabolic dysfunction. Traditionally, the GC/GR axis has been believed to play a crucial role in adipose tissue formation and function in both, white (WAT) and brown adipose tissue (BAT). While recent studies have challenged this notion for WAT, the contribution of GC/GR signaling to BAT-dependent energy homeostasis remained unknown. Here, we have generated and characterized a BAT-specific GR knockout mouse (GRBATKO), for the first time allowing to genetically interrogate the metabolic impact of BAT GR. The HPA axis in GRBATKO mice was intact, as was the ability of mice to adapt to cold. BAT GR was dispensable for the adaptation to fasting-feeding cycles and the development of diet-induced obesity. In obesity, glucose and lipid metabolism, insulin sensitivity, and food intake remained unchanged, aligning with the absence of changes in thermogenic gene expression. Together, we demonstrate that the GR in UCP1-positive BAT adipocytes plays a negligible role in systemic metabolism and BAT function, thereby opposing a long-standing paradigm in the field. Gene expression of BAT from GRBATKO mice was compared to Flox control mice. RNA from a selection of brown adipose tissue was purified with RNeasy Minikit columns (Qiagen) and analyzed with RNA 6000 Nano chips and the Agilent 2100 Bioanalyzer (Agilent Technologies, Waldbronn, Germany). One-hundred nanogram of purified RNA was labeled using the Ambion WT expression kit (Invitrogen) and hybridized to an Affymetrix Mouse Gene 1.1 ST array plate (Affymetrix, Santa Clara, CA). Subsequent hybridization, washing, and scanning were carried out on an Affymetrix GeneTitan platform. Processing and analysis of raw data was performed according to published methods (Lichtenstein L, Mattijssen F, de Wit NJ, Georgiadi A, Hooiveld GJ, van der Meer R, He Y, Qi L, Köster A, Tamsma JT, et al. (2010) Angptl4 protects against severe proinflammatory effects of saturated fat by inhibiting fatty acid uptake into mesenteric lymph node macrophages. Cell Metab 12: 580–592.).