In vitro induction of UCP1 mRNA in preadipocytes from rabbit considered as a model of large mammals brown adipose tissue development:: importance of PPARγ 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 after birth and undergoes a transformation into white adipose tissue (WAT). Rabbit is a model of these mammals of larger body mass. Preadipocytes from cervical BAT of foetal or newborn rabbits differentiated in a chemically-defined medium and expressed low levels of uncoupled protein-1 (UCP1) mRNA, greatly increased by beta 3-adrenergic or retinoic acid stimulations. On the contrary, preadipocytes from 1-month-old animals differentiated in the same conditions with no detectable expression of UCP1. Peroxisome proliferator-activated receptor gamma (PPAR gamma) agonists were necessary to induce UCP1 in these cells from older animals, a synergistic increase being noted in the presence of beta 3-adrenergic agonists. In contrast to these results, preadipocytes from perirenal WAT stimulated by PPAR gamma agonists never expressed UCP1. Conclusion: preadipocytes in the postnatal period are determined as brown or white preadipocytes. PPAR gamma agonists induce UCP1 expression in brown postnatal preadipocytes, but they are unable to trigger the gene in white preadipocytes. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.