tailieunhanh - Báo cáo khoa học: b3-Adrenoceptor knockout in C57BL/6J mice depresses the occurrence of brown adipocytes in white fat

White and brown adipocytes are usually located in distinct depots; however, in response to cold, brown adipocytes appear in white fat. This response is mediated by b-adrenoceptors but there is a controversy about the sub-type(s) involved. In the present study, we exposed to cold b3 -adrenoceptor knockout mice (b3KO) on a C57BL/6J geneticbackgroundandmeasured inwhiteadipose tissue the density of multilocular cells and the expression of the brown adipocyte marker uncoupling protein-1 (UCP1). | Eur. J. Biochem. 270 699-705 2003 FEBS 2003 doi p3-Adrenoceptor knockout in C57BL 6J mice depresses the occurrence of brown adipocytes in white fat Maria Jimenez1 Gioraio Barbatelli3. Roberta Allevi3 Saverio Cinti3. Josiane Sevdoux2 Jean-Paul Giacobino1 Patrick Muzzin1 and Frederic Preitner1 Departements de Biochimie Medicale1 et Physiologie2 Centre Medical Universitaire Geneve Switzerland 3Istituto di Morfologia Umana Normale Universita di Ancona Italy White and brown adipocytes are usually located in distinct depots however in response to cold brown adipocytes appear in white fat. This response is mediated by -adrenoceptors but there is a controversy about the sub-type s involved. In the present study we exposed to cold 3-adrenoceptor knockout mice b3KO on a C57BL 6J genetic background and measured in white adipose tissue the density of multilocular cells and the expression of the brown adipocyte marker uncoupling protein-1 UCP1 . In brown fat of b3KO mice UCP1 expression levels were normal at 24 C as well as after a 10-day cold exposure. Strikingly under both conditions in the white fat of 3KO mice the levels of UCP1 mRNA and protein as well as the density of multilocular cells were decreased. These results indicate that -adrenoceptors play a major role in the appearance of brown adipocytes in white fat and suggest that the brown adipocytes present in white fat differ from those in brown fat. Keywords adipose tissue cold exposure differentiation knockout uncoupling protein 1. Brown adipose tissue BAT and white adipose tissue WAT both play an important role in the control of energy balance in mammals. Indeed BAT is involved in the control of body temperature and body weight via nonshivering and diet-induced thermogenesis 1 2 whereas the primary function of WAT is to store and release energy. BAT function is particularly important for thermoregulation in small mammals in which the surface to volume ratio is unfavorable 1 . Moreover