In vitro induction of UCP1 mRNA in preadipocytes from rabbit considered asa model of large mammals brown adipose tissue development: importance of PPAR gamma agonists for cells isolated in the postnatal period

In mammals with a lower mass-specific metabolic rate than small laboratory rodents, the brown adipose tissue (BAT) loses its thermogenic activity afte r birth and undergoes a transformation into white adipose tissue (WAT). Rab bit is a model of these mammals of larger body mass. Preadipocytes from cer vical BAT of foetal or newborn rabbits differentiated in a chemically-defin ed medium and expressed low levels of uncoupled protein-1 (UCP1) mRNA, grea tly increased by beta 3-adrenergic or retinoic acid stimulations. On the co ntrary, preadipocytes from 1-month-old animals differentiated in the same c onditions with no detectable expression of UCP1. Peroxisome proliferator-ac tivated receptor gamma (PPAR gamma) agonists were necessary to induce UCP1 in these cells from older animals, a synergistic increase being noted in th e presence of beta 3-adrenergic agonists. In contrast to these results, pre adipocytes from perirenal WAT stimulated by PPAR gamma agonists never expre ssed UCP1. Conclusion: preadipocytes in the postnatal period are determined as brown or white preadipocytes. PPAR gamma agonists induce UCP1 expressio n in brown postnatal preadipocytes, but they are unable to trigger the gene in white preadipocytes. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.