Brown adipose tissue response to cafeteria diet-feeding involves inductionof the UCP2 gene and is impaired in female rats as compared to males

Noradrenaline-dependent brown adipose tissue (BAT) thermogenesis is activat ed by the cold and excess energy intake, largely depends on the activity of the uncoupling protein 1 (UCP1), and is mediated mainly through the beta 3 -adrenoceptor (beta 3-AR). We investigated the expression of ucp2, a gene t hat encodes a putative UCP1-like uncoupling protein, along with that of ucp 1 and beta 3-ar, in the interscapular BAT (IBAT) of male and female rats ch ronically fed a cafeteria diet. After 3 months on this diet, male rats atta ined a 34% excess body mass and showed IBAT hypertrophy and increased IBAT thermogenic potential, in terms of both UCP1 and UCP2 mRNA expression (both by 1.6-fold), UCP1 protein expression (by 1.75-fold) and CDP binding to IB AT mitochondria (by 2.2-fold); female rats attained a larger excess body we ight (50%) and their IBAT, although hypertrophied, showed no signs of incre ased thermogenic potential per gram of tissue. Interestingly, the IBAT of f emale rats was already activated compared to males. Treatment of mouse brow n adipocytes in primacy culture with noradrenaline also triggered a dose-de pendent increase of the levels of UCP1 mRNA and UCP2 mRNA. Retroregulatory down-regulation of the beta 3-AR mRNA levels was found in the two models us ed. The results support a physiological. role for UCP2, along with UCP1, in rodent BAT thermogenesis.