Changes in UCP mRNA expression levels in brown adipose tissue and skeletalmuscle after feeding a high-energy diet and relationships with leptin, glucose and PPAR gamma

Brown adipose tissue and skeletal muscle are known to be important sites fo r nonshivering thermogenesis. In this context, it is accepted that uncoupli ng proteins (UCPs) are involved in such process, but little is known about the physiological regulation of these proteins as affected by the intake of a high-energy (cafeteria) diet inducing fat deposition. In this study, the UCP messenger RNA (mRNA) expression in interscapular brown adipose tissue (iBAT) and skeletal muscle was assessed to evaluate the influence of a diet ary manipulation on energy homeostasis regulation. We report a statisticall y significant increase in mRNA levels of iBAT UCP1 and UCP3 and a statistic al marginal rise in skeletal muscle UCP3 mRNA expression after feeding a hi gh-energy diet, whereas no changes in UCP2 expression were found in either tissue. Furthermore, significant positive associations between iBAT UCP1 an d UCP3 mRNA levels with serum leptin were found. Although the expression of the beta (3) adrenoceptor (beta (3)AR) was about 50% in the lean controls compared with the obese group in iBAT, no statistically significant changes were observed concerning peroxisome proliferator-activated receptor gamma2 (PPAR gamma2) mRNA levels in muscle or iBAT. We conclude that feeding a di et inducing weight and fat gain produces different outcomes on iBAT and ske letal muscle UCP mRNA expression, revealing a tissue-dependent response for the three UCPs; Results suggest that the regulation of UCP expression in b oth tissues under these specific dietary conditions may be related to lepti n circulating levels. (C) 2001 Elsevier Science Inc. All rights reserved.