9-cis Retinoic acid induces the expression of the uncoupling protein-2 gene in brown adipocytes

The expression of uncoupling protein-2 (UCP2) mRNA is up-regulated during t he differentiation of brown adipocytes in primary culture. When differentia tion of brown adipocytes is impaired, UCP2 mRNA expression is down-regulate d, 9-cis Retinoic acid causes a dose-dependent induction of UCP2 mRNA level s in brown adipocytes, whereas all-trans retinoic acid has no effect. Speci fic agonists of retinoid X receptors (RXR) induce UCP2 mRNA expression, whe reas specific activators of retinoic acid receptors do not. 9-cis Retinoic acid, acting through RXR receptors, is identified as a major regulator of t he expression of the UCP2 gene in the brown fat cell. (C) 1998 Federation o f European Biochemical Societies.