Regulation of Lcn2 and Tac1 promoter by LEPRb mutants. HIT-T15 hamster insulinoma cells were transiently transfected with luciferase constructs driven by the rat Tac1 promoter or the rat Lcn2 promoter, along with the indicated LEPRb expression plasmids. Twenty-four hours after transfection, the cells were treated with 100 ng/ml leptin or vehicle for 24 hours in serum-free medium. Luciferase activities were determined from duplicate wells and data were normalised to β-galactosidase activities. Data are expressed as fold stimulation by leptin relative to unstimulated cells. Bars reflect means +/- SD of three independent experiments (except for FFY in the upper panel which is the mean of two).