A wide scope of biological processes, including embryonicdevelopment, cell differentiation and proliferation, immunefunction, neurogenesis, and energy metabolism, depend on thevitamin A (retinol) metabolite all-trans-retinoic acid (atRA)(1–5). atRA controls energy balance by inhibiting differentiationof pre-adipocytes into mature white adipose, regulating thefunction of white adipose cells, and by regulating whole bodylipid and carbohydrate metabolism (6–9). Dosing atRA to micefed a chow diet, which contains ample vitamin A, affords resistanceto diet-induced obesity (10, 11). Impairing atRA homeostasiscauses abnormalities in intermediary metabolism. Micewith ablated cellular retinol-binding protein 1 (encoded byRbp1), which regulates retinol homeostasis, experience glucoseintolerance from enhanced gluconeogenesis, resulting fromhyperglucagonemia, and also undergo increased adipocyte differentiation(12, 13). atRA functions through nuclear hormonereceptorsRAR, -, and - and peroxisome proliferator-activatedreceptor , which affect transcription and translation (14, 15).Genes regulated by atRA through nuclear receptors include: Pck1,which expresses phosphoenolpyruvate carboxykinase, the enzymethat catalyzes the committed step in gluconeogenesis (16); Ucp1,which expresses uncoupling protein 1, a mediator of adaptive thermogenesis(17); and inhibitors of adipogenesis, including Pref1,Klf2, and Sox9 (18). Despite the impact of atRA on energy balance,little is known about whether energy balance might regulate atRAhomeostasis.