Tirzepatide is well known for its glucose-lowering and weight-reducing effects, primarily through central appetite suppression. However, its direct role in promoting white adipose tissue (WAT) browning and the underlying mechanisms remain unclear. We investigated Tirzepatide's direct effects on WAT in high-fat diet (HFD)-induced obese mice. RNA sequencing was performed to assess transcriptional changes in WAT. In vitro, differentiated 3T3-L1 adipocytes were treated with Tirzepatide, with or without the adenylyl cyclase inhibitor SQ22536, to explore the involvement of cAMP-dependent signaling. Tirzepatide significantly reduced body weight as well as perirenal white adipose tissue (prWAT) and inguinal white adipose tissue (ingWAT) mass, accompanied by a marked reduction in adipocyte hypertrophy in obese mice. Transcriptomic analysis revealed a coordinated upregulation of gene programs involved in thermogenesis and lipid metabolism. These molecular changes were confirmed by immunoblotting and immunohistochemistry, which showed increased expression of browning markers, including peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) and uncoupling protein 1 (UCP1), indicating a phenotypic shift of WAT toward a thermogenic state. In 3T3-L1 adipocytes, Tirzepatide activated the PGC-1α/UCP1 signaling axis in a cAMP-dependent manner, promoting white fat browning and reducing lipid droplet accumulation. The presence of SQ22536 attenuated these effects, highlighting cAMP signaling as a critical mediator of Tirzepatide's action. Collectively, these results demonstrate that Tirzepatide induces WAT browning via activation of the cAMP-PGC-1α-UCP1 signaling axis, leading to decreased lipid storage. These findings reveal a direct, adipocyte-intrinsic mechanism of action that extends Tirzepatide's therapeutic potential beyond its established effects on central appetite regulation.
