White adipose tissue contributes to XXXX -independent thermogenesis.

@entity28 @entity21166 @entity19 @entity6 @entity20105 @entity4305 @entity21464
@entity21464 -adrenergic receptors (AR) are nearly exclusively expressed in brown and white adipose tissues, and chronic activation of these receptors by selective agonists has profound anti- @entity6 and anti- @entity28 effects. This study examined metabolic responses to acute and chronic @entity21166 activation in wild-type C57Bl/6 @entity19 and congenic @entity19 lacking functional uncoupling protein (UCP)1, the molecular effector of brown adipose tissue (BAT) thermogenesis. Acute activation of @entity21166 doubled metabolic rate in wild-type @entity19 and sharply elevated body temperature and BAT blood flow, as determined by laser Doppler flowmetry. In contrast, @entity21166 activation did not increase BAT blood flow in @entity19 lacking @entity4305 ( @entity4305 KO). Nonetheless, @entity21166 activation significantly increased metabolic rate and body temperature in @entity4305 KO @entity19 , demonstrating the presence of @entity4305 -independent thermogenesis. Daily treatment with the @entity21166 agonist @entity20105 (CL) for 6 days increased basal and CL-induced thermogenesis compared with naive @entity19 . This expansion of basal and CL-induced metabolic rate did not require @entity4305 expression. Chronic CL treatment of @entity4305 KO @entity19 increased basal and CL-stimulated metabolic rate of epididymal white adipose tissue (EWAT) fourfold but did not alter BAT thermogenesis. After chronic CL treatment, CL-stimulated thermogenesis of EWAT equaled that of interscapular BAT per tissue mass. The elevation of EWAT metabolism was accompanied by mitochondrial biogenesis and the induction of genes involved in lipid oxidation. These observations indicate that chronic @entity21166 activation induces metabolic adaptation in WAT that contributes to @entity21464 -AR-mediated thermogenesis. This adaptation involves lipid oxidation in situ and does not require @entity4305 expression.
