Drug repurposing reveals Fmoc-l-leucine as an adipose thermogenesis activator in cold-exposed mice by targeting PPARγ/UCP1

Cold-induced injuries, such as hypothermia and frostbite, pose significant health risks and have limited therapeutic options. Drug repurposing using integrated bioinformatics approaches offers an effective strategy for identifying potential agents. In this study, we aimed to identify thermogenic compounds through drug repurposing and validate their efficacy in a cold-exposure animal model. Gene expression signatures from brown and inguinal white adipose tissues from cold-exposed mice (5 °C, 7 days) were obtained from transcriptomic profiles and compared with drug-induced gene expression signatures from the Library of Integrated Network-Based Cellular Signatures (LINCS) database. The top-ranked compounds predicted from cold exposure-associated transcriptomic signatures were administered to cold-exposed C57BL/6J mice. Core body temperature, lipid metabolism, and thermogenic markers were measured, and the role of PPARγ was evaluated using siRNA transfection and the antagonist T0070907 in adipocytes. LINCS screening identified five candidates with significant signature alteration, including Fmoc-l-leucine, which significantly improved cold tolerance in the cold-exposure model. Fmoc-l-leucine maintained core body temperature, reduced lipid accumulation in adipose tissue, and upregulated the expression of thermogenic genes. In addition, it promoted white adipose tissue browning (increased Ucp1, Cidea, and Dio2 expression) and mitochondrial biogenesis. PPARγ inhibition suppressed these effects, confirming its role in the efficacy of Fmoc-l-leucine. No hepato- or nephrotoxicity was observed at pharmacological doses. These findings demonstrate that drug repurposing is an effective approach for identifying agents that confer cold protection and highlight the clinical potential of Fmoc-l-leucine.