Id1 Promotes Obesity by Suppressing Brown Adipose Thermogenesis and White Adipose Browning.Obesity results from increased energy intake or defects in energy expenditure.  Brown adipose tissue (BAT) is specialized for energy expenditure, a process called adaptive thermogenesis.  Peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α) controls BAT-mediated thermogenesis by regulating the expression of Ucp1 Inhibitor of differentiation 1 (Id1) is a helix-loop-helix transcription factor that plays an important role in cell proliferation and differentiation.  We demonstrate a novel function of Id1 in BAT thermogenesis and programming of beige adipocytes in white adipose tissue (WAT).  Id1 suppresses BAT thermogenesis by binding to and suppressing PGC1α transcriptional activity.  Furthermore, brown-like differentiation is increased in Id1-deficient mouse embryonic fibroblasts. 
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