To uncover novel physiological roles of the peroxisome proliferator-activated receptor (PPAR involved in maintaining energy homeostasis during energy deprivation, we have used the fluorescent differential display to compare the liver mRNA expression profiles of the wild-type (WT) and PPAR-null (KO) mice under both fed and fasted states, and isolated a novel PPAR-dependent gene which was up-regulated during fasting.