Leptin plays a critical role in regulating body weight, lipid metabolism, apoptosis and microvasculature of adipose tissue. To explore multiple signaling pathways of leptin action on adipose tissue, real-time PCR utilizing TaqMan low-density arrays was performed to compare mRNA expression in adipose tissue of ob/ob mice treated with vehicle or leptin (2.5 microg/d or 10 microg/d) for 14 days via subcutaneous osmotic minipumps. Of the 24 target genes selected for characterization, many were differentially expressed between control ob/ob mice and leptin-treated ob/ob mice. Increases in mRNA expression were found for hormone sensitive lipase (HSL), uncoupling protein 2 (UCP2), adrenergic receptor 3 (ADR3), mitofusin 2 (Mfn2), sirtuin 3 (Sirt3), transcription factor sterol regulatory element binding factor 1 (SREBF1), Bcl-2, Bax, Caspase 3, tumor necrosis factor alpha (TNFalpha), adiponectin and angiopoietin 2 (Ang-2). Decreases in expression were found for stearoyl-coenzyme A desaturase 1 (SCD1), fatty acid synthase (FAS), and retinol binding protein 4 (RBP4). There were no changes in expression of transcription factors involved in adipocyte differentiation (C/EBPalpha, PPARalpha, and PPARgamma). These results confirm that alterations in the expression of specific adipose tissue genes including those associated with the promotion of lipid mobilization, energy dissipation, and apoptosis may mediate leptin-induced fat loss in ob/ob mice.