Our study aimed to examine the mechanisms through which obesity induced by a high fat diet (HFD) affects uncoupling protein 1 (UCP1) expression via signal transduction and activator of transcription 5 (STAT5s).
Intravenous injection of leptin rapidly induced nuclear STAT5 DNA binding activity in jejunum of +/+ and obese (ob/ob) mice but had no effect in the diabetic (db/db) mouse that lacks the OB-Rb isoform.
Indeed, the dwarfism, elevated plasma GH, low plasma insulin-like growth factor I, and development of obesity seen in STAT5b-/- mice are all characteristics of Laron-type dwarfism, a human GH-resistance disease generally associated with a defective GH receptor.