STAT1 dissociates adipose tissue inflammation from insulin sensitivity in obesity

Obesity fosters low-grade inflammation in white adipose tissue (WAT) that may contribute to the insulin resistance that characterizes type 2 diabetes mellitus (T2DM). However, the causal relationship of these events remains unclear. The established dominance of signal transducer and activator of transcription 1 (STAT1) function in the immune response suggests an obligate link between inflammation and the co-morbidities of obesity. To this end, we sought to determine how STAT1 activity in white adipocytes affects insulin sensitivity. STAT1 expression in WAT inversely correlated with fasting plasma glucose in both obese mice and humans. Metabolomic and gene expression profiling established STAT1 deletion in adipocytes (STAT1^a-KO­­­) enhanced mitochondrial function and accelerated TCA cycle flux coupled with reduced fat cell size in subcutaneous WAT depots. STAT1^a-KO reduced WAT inflammation, but insulin resistance persisted in obese mice. Rather, elimination of type I cytokine interferon gamma (IFNg) activity enhanced insulin sensitivity in diet-induced obesity. Our findings reveal a permissive mechanism that bridges WAT inflammation to whole-body insulin sensitivity.